Edge banding for easy adhesive application and manufacturing apparatus thereof

Abstract

The present invention relates to an edge banding in which an adhesive layer is formed on one surface using a first resin having a melting point difference of 100 degrees or more and an adhesive, and to an apparatus for manufacturing the same. More specifically, the invention relates to a manufacturing apparatus that independently heats and melts a high-melting-point resin, such as PET resin, and a low-melting-point adhesive, then combines them in an extrusion head to form an integrated composite extruded product, cools the product in an open manner without a mold to form an edge banding product with an adhesive layer exposed on one surface, and then draws and stretches the product. The manufacturing apparatus of the present invention includes a first hopper for storing and supplying PET resin, a second hopper for storing and supplying adhesive, a first extrusion unit for heating and melting the first resin supplied from the first hopper to a range of 240 to 260 degrees to produce a first molten product and extruding it at a first set pressure, and a second extrusion unit for heating and melting the adhesive supplied from the second hopper to a range of 100 to 150 degrees to produce a second molten product and extruding it at a second set pressure.

Description

Technology Field

[0001] The following embodiments relate to edge banding that facilitates adhesive application and the technology of a manufacturing apparatus thereof. Background Technology

[0002] Edge banding is a strip-shaped material attached to the sides of panel materials, such as plywood and MDF (Medium Density Fiberboard), for finishing in furniture manufacturing. It serves the function of improving the aesthetics of furniture while blocking the release of harmful substances from within the panel material. Edge banding is widely used primarily in office furniture, kitchen furniture, and building interior materials, and has established itself as an essential component in the furniture industry.

[0003] Conventional edge banding has been manufactured primarily using ABS (Acrylonitrile Butadiene Styrene) resin or PVC (Polyvinyl Chloride) resin as raw materials. While these materials have been widely used due to their excellent processability and cost-effectiveness, they have disadvantages such as generating harmful gases upon combustion and causing environmental problems due to the difficulty of recycling. In particular, with the recent increase in demand for eco-friendly building materials and the tightening of related regulations, the development of edge banding made of eco-friendly materials capable of replacing ABS or PVC has emerged as an urgent task.

[0004] Meanwhile, for films used on the front of furniture, eco-friendly products made primarily of PET (Polyethylene Terephthalate) resin have already been commercialized. PET is recognized as an eco-friendly material because it is recyclable and generates few harmful substances, and it is required as a mandatory requirement for obtaining eco-friendly certification in the construction and furniture industries. However, ABS or PVC materials are still mainly used for edge banding, resulting in a contradictory situation where PET is used for the front film while non-eco-friendly materials must be used for the side edge banding.

[0005] To solve these problems, there have been attempts to develop edge banding using PET resin, but there was a limitation in that composite extrusion with adhesives was technically very difficult because PET resin has a high melting point of about 248 degrees. Generally, adhesives used for edge banding have melting points in the range of 100 to 140 degrees, so there is a large melting point difference of more than 100 degrees between PET resin and adhesive. It was impossible to manufacture an integrated product by simultaneously extruding two materials with such a large difference in melting points using a conventional extrusion process.

[0006] In addition, in conventional edge banding manufacturing processes, it was common practice to form the shape of a product using molds such as dies or sizers. However, in the case of edge banding with an exposed adhesive layer on one side, using a mold causes the molten adhesive to stick to the inner wall of the mold, resulting in problems such as the product not being able to separate from the mold or damage to the product surface. Due to these problems, PET edge banding with an exposed adhesive layer has not been commercialized.

[0007] Meanwhile, there are several problems in the process of installing edge banding on furniture. Conventionally, a method was used in which a worker separately applied hot-melt adhesive to the back of the edge banding and then heated it to attach it to the panel. This manual method resulted in significant quality variations depending on the worker's skill level, and frequently caused issues such as the product burning or discoloring due to excessive heat during the adhesive application process, as well as the adhesive oozing out from the sides of the product and damaging its appearance. Furthermore, the problem of reduced productivity due to rising labor costs and difficulties in securing workers was also serious.

[0008] Accordingly, there is an urgent need for the development of edge banding manufacturing technology that can stably composite extrude eco-friendly high-melting-point resins such as PET and low-melting-point adhesives, mold products with an adhesive layer exposed on one side without a mold, and enable immediate construction without the application of a separate adhesive. Prior art literature

[0009] Korean Registered Patent 10-0897631, Korean Published Patent 10-2023-0078357, Published Patent 10-2011-0098387, Registered Patent 10-1870833 The problem to be solved

[0010] The present invention manufactures an integrated edge band by stably compound extruding a first resin and an adhesive having a melting point difference of 100 degrees or more. Specifically, in the process of simultaneously extruding a PET resin having a melting point of about 248 degrees and an adhesive having a melting point of 100 to 140 degrees, the invention solves the problem of the low-melting-point adhesive flowing down prematurely or the high-melting-point first resin not melting sufficiently, thereby enabling the two materials to properly combine to form an integrated composite extruded product.

[0011] Furthermore, the present invention precisely controls the junction point between the first resin and the adhesive. If the adhesive, which has a low melting point, flows down before meeting the first resin, product formation becomes impossible; conversely, if it joins too late, the two materials do not bond sufficiently, resulting in reduced adhesive strength. Therefore, it is necessary to implement a structure capable of adjusting the junction point to an optimal position to enable the stable formation of a composite extruded product.

[0012] In addition, the present invention precisely controls the pressure balance between the first extrusion section and the second extrusion section. The pressure of the first extrusion section, which extrudes the first resin with a high melting point, must be higher than the pressure of the second extrusion section, which extrudes the adhesive with a low melting point, so that the first molten material can push up the second molten material and properly merge. However, if the pressure difference is excessive, one material is extruded excessively, causing the thickness of the product or the distribution of the adhesive layer to become uneven; therefore, a system capable of precisely monitoring and controlling the pressure between the two extrusion sections is required.

[0013] In addition, the present invention forms an edge banding product with an adhesive layer exposed on one side without using a mold. In conventional mold methods, problems occurred where the molten adhesive stuck to the inner wall of the mold, preventing the product from coming out of the mold or damaging the surface of the adhesive layer. To solve this, it is necessary to implement a cooling method that allows cooling to take place in an open space without contact with the mold, while maintaining the shape of the product and ensuring the adhesive layer is cleanly exposed on the surface.

[0014] Furthermore, the present invention optimizes the physical properties of a product by appropriately controlling the temperature of the composite extruder during the cooling process. If the cooling rate is too fast, internal stress is generated, which may cause the product to warp or crack; if the cooling rate is too slow, productivity decreases. Therefore, it is required to achieve optimal cooling conditions by controlling the temperature of the cooling water and the transfer speed of the composite extruder.

[0015] In addition, the present invention improves the mechanical properties of a product by applying appropriate stretching while drawing out a molded edge banding product. Since the PET resin undergoes a stretching process, molecular orientation occurs, which significantly improves strength and dimensional stability, it is necessary to apply appropriate tension to stretch the product while drawing out the product that has passed through the cooling section, and to precisely control the drawing speed and stretching ratio to prevent product breakage or thickness non-uniformity caused by excessive stretching.

[0016] In addition, the present invention enables the edge banding to be directly attached to a plate without a separate adhesive application process. Since an adhesive layer is already formed and exposed on one side of the manufactured edge banding, the user should be able to attach the edge banding to the plate simply by applying heat. Through this, the invention aims to simplify the work process and fundamentally eliminate construction defects such as adhesive oozing or burning. means of solving the problem

[0017] The present invention relates to an apparatus for manufacturing an edge banding in which an adhesive layer is formed on one surface using a first resin having a melting point difference of 100 degrees or more and an adhesive, wherein the resin and the adhesive having a melting point difference are each supplied from a hopper, heated and melted in an extrusion section, and then combined in an extrusion head to form an integrated composite extruded product, and then cooled in an open form without a mold to form an edge banding product in which an adhesive layer is exposed on one surface, and then drawn out and stretched.

[0018] At this time, a first hopper for receiving and storing the first resin, which is a PET (Polyethylene Terephthalate) resin; a second hopper for receiving and storing the adhesive; a first extrusion unit for heating and melting the first resin supplied from the first hopper to produce a first molten material and extruding the first molten material at a first set pressure; a second extrusion unit for heating and melting the adhesive supplied from the second hopper to produce a second molten material and extruding the second molten material at a second set pressure; and an extrusion head configured to control the merging point of the first molten material and the second molten material so as to prevent premature merging due to the difference in melting points between the first molten material and the second molten material, wherein the first molten material extruded from the first extrusion unit and the second molten material extruded from the second extrusion unit merge to form an integrated composite extruded material. It includes a cooling unit that cools the composite extruded from the extrusion head in an open manner without a mold to form an edge banding product with an adhesive layer exposed on one side; and a drawing unit that draws out and stretches the edge banding product that has passed through the cooling unit.

[0019] Also, at this time, the first hopper comprises a hopper body for storing a first resin, a supply pipe for transporting the first resin downward by gravity, a preheating heater for preheating the first resin to a temperature lower than the melting temperature, and a supply amount control valve for controlling the amount of feed into the first extrusion unit, and the second hopper comprises a hopper body for storing an adhesive, a supply pipe for supplying the adhesive to the second extrusion unit, a preheating heater for preheating the adhesive to a temperature lower than the preheating temperature of the first resin, and a supply amount control valve for controlling the amount of adhesive supplied to maintain pressure balance, and the first extrusion unit comprises a first cylinder for receiving the first resin, a first screw for transporting the first resin forward, a first heating unit for melting the first resin, a first temperature control unit for controlling the melting temperature, a first pressure control unit for controlling the pressure, and a first discharge port for discharging the first molten material, and the second extrusion unit comprises a second cylinder for receiving the adhesive, and a screw for transporting the adhesive forward The extrusion head comprises a second screw, a second heating unit for melting the adhesive, a second temperature control unit for controlling the melting temperature, a second pressure control unit for controlling to maintain pressure balance with the first extrusion unit, and a second discharge port for discharging the second molten material; the extrusion head comprises a first inlet passage through which the first molten material flows from the top downward, a second inlet passage through which the second molten material flows from the bottom upward, a junction section for forming a composite extrusion, a junction point control unit for controlling the junction point, a temperature maintenance unit for independently maintaining the temperature, a pressure sensing unit for monitoring the pressure, and a discharge nozzle for discharging the composite extrusion; the cooling unit comprises a cooling chamber through which the composite extrusion passes through an open space without a mold, a cooling water supply unit for supplying cooling water, a cooling temperature control unit for controlling the cooling speed, an open cooling unit for molding with the adhesive layer exposed on the surface, and a transfer speed control unit for controlling the cooling time; and the withdrawal unit comprises a withdrawal roller for gripping and withdrawing an edge banding product, a withdrawal speed control unit for controlling the withdrawal speed, and applying tensile force. It includes a stretching roller for stretching, a stretching ratio control unit for controlling the stretching ratio, a tension sensing sensor for detecting tension, and a winding roller for winding the stretched product.

[0020] At this time, the first hopper comprises: a hopper body forming a storage space for storing the first resin; a supply pipe installed at the bottom of the hopper body to transport the first resin downward by gravity and supply it to the first extrusion unit; a preheating heater installed on the outer surface of the hopper body to preheat the first resin to a temperature lower than the melting temperature of the first resin to improve fluidity; and a supply amount control valve installed in the supply pipe to control the supply amount of the first resin and regulate the amount fed into the first extrusion unit.

[0021] At this time, the second hopper comprises: a hopper body forming a storage space for storing the adhesive having a melting point in the range of 100 to 140 degrees; a supply pipe installed at the bottom of the hopper body for supplying the adhesive to the second extrusion part; a preheating heater installed in the hopper body for preheating the adhesive at a temperature range lower than the preheating temperature of the first resin; and a supply amount control valve installed in the supply pipe for controlling the supply amount of the adhesive to maintain a balance between the first set pressure and the second set pressure.

[0022] At this time, the first extrusion unit comprises: a first cylinder for receiving a first resin supplied from the first hopper; a first screw rotatably installed inside the first cylinder to convey the first resin forward; a first heating unit installed on the outer surface of the first cylinder to melt the first resin; a first temperature control unit for controlling the temperature of the first heating unit to adjust the melting temperature of the first resin to a range of 240 to 260 degrees; a first pressure control unit for controlling the rotational speed of the first screw to control the first set pressure so that the first molten material pushes out the second molten material and merges with it, thereby maintaining the first set pressure higher than the second set pressure; and a first discharge port formed at the tip of the first cylinder to discharge the first molten material.

[0023] At this time, the second extrusion unit comprises: a second cylinder that receives adhesive supplied from the second hopper; a second screw that is rotatably installed inside the second cylinder to convey the adhesive forward; a second heating unit installed on the outer surface of the second cylinder to melt the adhesive; a second temperature control unit that controls the temperature of the second heating unit to adjust the melting temperature of the adhesive to a range of 100 to 150 degrees; a second pressure control unit that controls the rotational speed of the second screw to adjust the second set pressure, and adjusts the second set pressure in correspondence with the extrusion speed of the first resin so that the second set pressure is balanced with the first set pressure; and a second discharge port formed at the tip of the second cylinder to discharge the second molten material.

[0024] At this time, the extrusion head comprises: a first inlet passage connected to the first discharge port of the first extrusion section, through which the first molten material flows from the top downward; a second inlet passage connected to the second discharge port of the second extrusion section, through which the second molten material flows from the bottom upward; a junction section in which the first inlet passage and the second inlet passage merge to form the composite extrusion; a junction point adjustment section that changes the junction point of the first molten material and the second molten material by adjusting the position of the junction section in the up-and-down direction to prevent the second molten material with a low melting point from flowing down prematurely; and a temperature maintenance section installed in the junction section, which maintains the temperature of the first molten material and the second molten material independently through heating means independently installed in the first inlet passage and the second inlet passage, respectively. It includes: a pressure sensing unit that monitors the balance between the first set pressure and the second set pressure by sensing the pressures of the first inlet and the second inlet so that the first set pressure is maintained at a level capable of pushing the second molten material upward; and a discharge nozzle that discharges the composite extruded material from the confluence unit.

[0025] At this time, the cooling unit comprises: a cooling chamber through which a composite extruded product discharged from the extrusion head passes through an open space without contact with a mold; a cooling water supply unit that supplies cooling water to circulate on the wall surface of the cooling chamber; a cooling temperature control unit that controls the cooling speed of the composite extruded product by adjusting the temperature of the cooling water; an open cooling unit that cools the composite extruded product in an open manner without a mold and without direct contact with the cooling water inside the cooling chamber, thereby allowing the edge banding product to be formed with an adhesive layer placed on one side of the composite extruded product and the adhesive exposed on the surface; and a transfer speed control unit that controls the cooling time by adjusting the transfer speed of the composite extruded product passing through the cooling chamber.

[0026] At this time, the drawing unit comprises: a drawing roller that grasps and draws out an edge banding product that has passed through the cooling unit; a drawing speed control unit that controls the drawing speed of the edge banding product by adjusting the rotational speed of the drawing roller; a drawing roller disposed at the rear end of the drawing roller that applies tensile force to the edge banding product to draw it out; a drawing ratio control unit that controls the drawing ratio of the edge banding product by adjusting the rotational speed of the drawing roller; a tension sensing sensor disposed between the drawing roller and the drawing roller to detect the tension applied to the edge banding product in order to feed back detected tension information to the drawing speed control unit and the drawing ratio control unit to maintain a balance between the drawing speed and the drawing ratio; and a winding roller disposed at the rear end of the drawing roller, whose rotational speed is controlled in conjunction with the drawing ratio control unit, and which winds the drawn edge banding product. Effects of the invention

[0027] The present invention enables the stable composite extrusion of PET resin and adhesive having a melting point difference of 100 degrees or more, thereby making it possible to manufacture edge banding using PET, an eco-friendly material, as a raw material. This allows for the replacement of non-eco-friendly materials such as ABS or PVC, making it easier to obtain eco-friendly certification for furniture products and comply with environmental regulations.

[0028] Furthermore, the present invention allows for precise control of the merging point of the first molten material and the second molten material through a merging point control unit provided in the extrusion head, thereby preventing the low-melting point adhesive from flowing down prematurely and enabling the two materials to merge at an optimal location to form an integrated composite extruded product. This has the effect of significantly improving the adhesive strength and quality of the product.

[0029] In addition, the present invention is equipped with a pressure control unit in each of the first and second extrusion units and a pressure sensing unit in the extrusion head to monitor and adjust the pressure balance between the two extrusion units in real time. Through this, the first set pressure is maintained higher than the second set pressure, allowing the first molten material to push up the second molten material and merge appropriately, thereby forming a uniform thickness of the product and an adhesive layer distribution.

[0030] In addition, the present invention fundamentally solves the problem of molten adhesive sticking to the mold by cooling the composite extruded product through a cooling section that cools in an open manner without a mold. Accordingly, an edge banding product is formed with the adhesive layer cleanly exposed on one side, and a product of excellent quality can be manufactured without surface damage or contamination of the adhesive layer.

[0031] In addition, the present invention allows for precise control of the cooling speed through a cooling temperature control unit and a transfer speed control unit provided in the cooling unit, thereby minimizing internal stress of the composite extruded product and preventing warping or cracking of the product. Furthermore, by maintaining appropriate cooling conditions, it is possible to maximize production speed while ensuring product quality.

[0032] Furthermore, the present invention allows for the application of appropriate stretching to a molded product through a stretching roller and a stretching ratio control unit equipped in the drawing section, thereby achieving molecular orientation of the PET resin and significantly improving the tensile strength and dimensional stability of the product. Additionally, by maintaining a balance between the drawing speed and the stretching ratio through a tension sensing sensor, product damage caused by excessive stretching can be prevented.

[0033] In addition, since the adhesive layer is already exposed on one side of the manufactured edge banding, the user can attach the edge banding to a plate simply by applying heat without the need to apply adhesive separately. This significantly simplifies the work process and reduces working time, and allows even low-skilled workers to easily perform the installation, thereby providing a labor cost reduction effect.

[0034] In addition, the present invention can fundamentally eliminate construction defects such as burning caused by excessive heat and adhesive oozing out to the sides that occur during the manual application of adhesive, thereby significantly improving the appearance quality of the product and reducing the defect rate. This leads to overall productivity improvement and cost reduction.

[0035] In addition, the present invention is composed of a continuous production system in which a hopper, an extrusion unit, an extrusion head, a cooling unit, and a drawing unit are integrated, enabling mass production and high production efficiency. Furthermore, each component is equipped with a temperature control unit, a pressure control unit, a speed control unit, etc., allowing for precise control of process conditions and stable manufacturing of edge banding of various sizes and specifications. Brief explanation of the drawing

[0036] FIG. 1 is a drawing for explaining a manufacturing apparatus for edge banding that is easy to apply adhesive to according to one embodiment. FIG. 2 is a drawing for explaining the first hopper of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment. FIG. 3 is a drawing for explaining the second hopper of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment. FIG. 4 is a drawing illustrating the first extrusion part of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment. FIG. 5 is a drawing illustrating the second extrusion part of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment. FIG. 6 is a drawing illustrating the extrusion head of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment. FIG. 7 is a drawing illustrating the cooling section of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment. FIG. 8 is a drawing for explaining the extraction portion of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment. Specific details for implementing the invention

[0037] Hereinafter, embodiments are described in detail with reference to the attached drawings. However, various modifications may be made to the embodiments, and thus the scope of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, and substitutions to the embodiments are included within the scope of the rights.

[0038] Specific structural or functional descriptions of the embodiments are disclosed for illustrative purposes only and may be modified and implemented in various forms. Accordingly, the embodiments are not limited to the specific disclosed forms, and the scope of this specification includes modifications, equivalents, or substitutions that fall within the technical concept.

[0039] Terms such as "first" or "second" may be used to describe various components, but these terms should be interpreted solely for the purpose of distinguishing one component from another. For example, the first component may be named the second component, and similarly, the second component may be named the first component.

[0040] When it is stated that a component is "connected" to another component, it should be understood that it may be directly connected to or coupled with that other component, or that there may be other components in between.

[0041] The terms used in the embodiments are for illustrative purposes only and should not be interpreted as intended to be limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0042] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the embodiments pertain. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0043] In addition, when describing with reference to the attached drawings, identical components are assigned the same reference numeral regardless of drawing symbols, and redundant descriptions thereof are omitted. In describing the embodiments, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the embodiments, such detailed description is omitted.

[0044] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims.

[0045] In the embodiments of the present invention, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in the embodiments of the present invention.

[0046] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining embodiments of the present invention are exemplary, and therefore the present invention is not limited to the depicted details. Furthermore, in describing the present invention, if it is determined that a detailed description of related known technology may unnecessarily obscure the essence of the present invention, such detailed description is omitted. Where terms such as "includes," "has," or "is made up" are used in this specification, other parts may be added unless "only" is used. Where a component is expressed in the singular, it includes cases where it includes the plural unless specifically stated otherwise.

[0047] In interpreting the components, they are interpreted to include a margin of error even in the absence of a separate explicit statement.

[0048] In the case of describing a positional relationship, for example, when the positional relationship between two parts is described using expressions such as 'on,' 'upper,' 'lower,' or 'next to,' one or more other parts may be located between the two parts unless 'immediately' or 'directly' is used.

[0049] When elements or layers are referred to as "on" another element or layer, this includes cases where another layer or element is placed directly on top of or in between. Throughout the specification, the same reference numerals refer to the same components.

[0050] The size and thickness of each component shown in the drawings are illustrated for convenience of explanation, and the present invention is not necessarily limited to the size and thickness of the illustrated components.

[0051] The features of each of the various embodiments of the present invention may be combined or combined with one another, either partially or wholly, and as will be fully understood by those skilled in the art, various technical interlocking and operation are possible, and each embodiment may be implemented independently of one another or together in an interlocking relationship.

[0052] FIG. 1 is a drawing for explaining a manufacturing apparatus for edge banding that is easy to apply adhesive to according to one embodiment.

[0053] The present invention relates to an apparatus for manufacturing an edge banding with an adhesive layer formed on one surface using a first resin having a melting point difference of 100 degrees or more and an adhesive, as illustrated in FIG. 1, wherein the resin and the adhesive having a melting point difference are each supplied from a hopper, heated and melted in an extrusion section, and then combined in an extrusion head to form an integrated composite extruded product, and then cooled in an open form without a mold to form an edge banding product with an adhesive layer exposed on one surface, and then drawn out and stretched.

[0054] At this time, a first hopper for receiving and storing the first resin, which is a PET (Polyethylene Terephthalate) resin, and a second hopper for receiving and storing the adhesive, a first extrusion unit for heating and melting the first resin supplied from the first hopper to produce a first molten material and extruding the first molten material at a first set pressure, a second extrusion unit for heating and melting the adhesive supplied from the second hopper to produce a second molten material and extruding the second molten material at a second set pressure, an extrusion head configured to form an integrated composite extrusion by combining the first molten material extruded from the first extrusion unit and the second molten material extruded from the second extrusion unit, wherein the merging point of the first molten material and the second molten material can be adjusted to prevent premature merging due to the difference in melting points between the first molten material and the second molten material, and edge banding the composite extrusion extruded from the extrusion head by cooling it in an open manner without a mold so that an adhesive layer is exposed on one side. It consists of a cooling section that forms a product and a drawing section that draws out and stretches the edge banding product that has passed through the cooling section.

[0055] Also, at this time, the first hopper comprises a hopper body for storing a first resin, a supply pipe for transporting the first resin downward by gravity, a preheating heater for preheating the first resin to a temperature lower than the melting temperature, and a supply amount control valve for controlling the amount of feed into the first extrusion unit, and the second hopper comprises a hopper body for storing an adhesive, a supply pipe for supplying the adhesive to the second extrusion unit, a preheating heater for preheating the adhesive to a temperature lower than the preheating temperature of the first resin, and a supply amount control valve for controlling the amount of adhesive supplied to maintain pressure balance, and the first extrusion unit comprises a first cylinder for receiving the first resin, a first screw for transporting the first resin forward, a first heating unit for melting the first resin, a first temperature control unit for controlling the melting temperature, a first pressure control unit for controlling the pressure, and a first discharge port for discharging the first molten material, and the second extrusion unit comprises a second cylinder for receiving the adhesive, and a screw for transporting the adhesive forward The extrusion head comprises a second screw, a second heating unit for melting the adhesive, a second temperature control unit for controlling the melting temperature, a second pressure control unit for controlling to maintain pressure balance with the first extrusion unit, and a second discharge port for discharging the second molten material; the extrusion head comprises a first inlet passage through which the first molten material flows from the top downward, a second inlet passage through which the second molten material flows from the bottom upward, a junction section for forming a composite extrusion, a junction point control unit for controlling the junction point, a temperature maintenance unit for independently maintaining the temperature, a pressure sensing unit for monitoring the pressure, and a discharge nozzle for discharging the composite extrusion; the cooling unit comprises a cooling chamber through which the composite extrusion passes through an open space without a mold, a cooling water supply unit for supplying cooling water, a cooling temperature control unit for controlling the cooling speed, an open cooling unit for molding with the adhesive layer exposed on the surface, and a transfer speed control unit for controlling the cooling time; and the withdrawal unit comprises a withdrawal roller for gripping and withdrawing an edge banding product, a withdrawal speed control unit for controlling the withdrawal speed, and applying tensile force. It includes a stretching roller for stretching, a stretching ratio control unit for controlling the stretching ratio, a tension sensing sensor for detecting tension, and a winding roller for winding the stretched product.

[0056] FIG. 2 is a drawing for explaining the first hopper of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment.

[0057] At this time, as illustrated in FIG. 2, the first hopper comprises a hopper body forming a storage space for storing the first resin, a supply pipe installed at the bottom of the hopper body to transport the first resin downward by gravity and supply it to the first extrusion unit, a preheating heater installed on the outer surface of the hopper body to preheat the first resin to a temperature lower than the melting temperature of the first resin to improve fluidity, and a supply amount control valve installed in the supply pipe to control the supply amount of the first resin and adjust the amount to be fed into the first extrusion unit.

[0058] FIG. 3 is a drawing for explaining the second hopper of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment.

[0059] At this time, as illustrated in FIG. 3, the second hopper comprises a hopper body forming a storage space for storing the adhesive having a melting point in the range of 100 to 140 degrees, a supply pipe installed at the bottom of the hopper body for supplying the adhesive to the second extrusion part, a preheating heater installed in the hopper body for preheating the adhesive at a temperature range lower than the preheating temperature of the first resin, and a supply amount control valve installed in the supply pipe for controlling the supply amount of the adhesive to maintain a balance between the first set pressure and the second set pressure.

[0060] FIG. 4 is a drawing illustrating the first extrusion part of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment.

[0061] At this time, as illustrated in FIG. 4, the first extrusion unit comprises a first cylinder that receives a first resin supplied from the first hopper, a first screw that is rotatably installed inside the first cylinder to transport the first resin forward, a first heating unit that is installed on the outer surface of the first cylinder to melt the first resin, a first temperature control unit that controls the temperature of the first heating unit to adjust the melting temperature of the first resin to a range of 240 to 260 degrees, a first pressure control unit that controls the rotational speed of the first screw to adjust the first set pressure so that the first molten material pushes out and merges with the second molten material by maintaining the first set pressure higher than the second set pressure, and a first discharge port formed at the tip of the first cylinder to discharge the first molten material.

[0062] FIG. 5 is a drawing illustrating the second extrusion part of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment.

[0063] At this time, as illustrated in FIG. 5, the second extrusion unit comprises a second cylinder that receives adhesive supplied from the second hopper, a second screw that is rotatably installed inside the second cylinder to convey the adhesive forward, a second heating unit that is installed on the outer surface of the second cylinder to melt the adhesive, a second temperature control unit that controls the temperature of the second heating unit to adjust the melting temperature of the adhesive to a range of 100 to 150 degrees, a second pressure control unit that controls the rotational speed of the second screw to adjust the second set pressure, and adjusts the second set pressure in correspondence with the extrusion speed of the first resin so that the second set pressure is balanced with the first set pressure, and a second discharge port formed at the tip of the second cylinder to discharge the second molten material.

[0064] FIG. 6 is a drawing illustrating the extrusion head of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment.

[0065] At this time, as illustrated in FIG. 6, the extrusion head comprises: a first inlet passage connected to the first discharge port of the first extrusion section through which the first molten material flows from the top downward; a second inlet passage connected to the second discharge port of the second extrusion section through which the second molten material flows from the bottom upward; a junction section where the first inlet passage and the second inlet passage merge to form the composite extrusion; a junction point control section that changes the junction point of the first molten material and the second molten material by adjusting the position of the junction section in the up-and-down direction to prevent the second molten material with a low melting point from flowing down prematurely; a temperature maintenance section that maintains the temperature of the first molten material and the second molten material independently through heating means installed in the junction section and independently installed in the first inlet passage and the second inlet passage, respectively; and a section that detects the pressure of the first inlet passage and the second inlet passage so that the first set pressure is maintained at a level capable of pushing the second molten material upward, and It consists of a pressure sensing unit that monitors the balance between a first set pressure and the second set pressure, and a discharge nozzle that discharges the composite extruded product from the junction unit.

[0066] FIG. 7 is a drawing illustrating the cooling section of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment.

[0067] At this time, as illustrated in FIG. 7, the cooling unit comprises a cooling chamber through which a composite extruded product discharged from the extrusion head passes through an open space without contact with a mold, a cooling water supply unit that supplies cooling water to circulate on the wall surface of the cooling chamber, a cooling temperature control unit that controls the cooling speed of the composite extruded product by controlling the temperature of the cooling water, an open cooling unit that cools the composite extruded product in an open manner without a mold without direct contact with the cooling water inside the cooling chamber so that the adhesive layer among the composite extruded product is placed on one surface and the adhesive is exposed on the surface so that the edge banding product is formed, and a transfer speed control unit that controls the cooling time by controlling the transfer speed of the composite extruded product passing through the cooling chamber.

[0068] FIG. 8 is a drawing for explaining the extraction portion of a manufacturing device for edge banding that facilitates adhesive application according to one embodiment.

[0069] At this time, the drawing unit comprises a drawing roller that grips and draws out an edge banding product that has passed through the cooling unit, a drawing speed control unit that controls the drawing speed of the edge banding product by adjusting the rotational speed of the drawing roller, a drawing roller disposed at the rear end of the drawing roller that applies tensile force to the edge banding product to draw it out, a drawing ratio control unit that controls the drawing ratio of the edge banding product by adjusting the rotational speed of the drawing roller, a tension sensing sensor disposed between the drawing roller and the drawing roller to detect the tension applied to the edge banding product in order to maintain a balance between the drawing speed and the drawing ratio by feeding back the detected tension information to the drawing speed control unit and the drawing ratio control unit, and a drawing roller disposed at the rear end of the drawing roller, whose rotational speed is controlled in conjunction with the drawing ratio control unit, and which draws up the drawn edge banding product.

[0070] Technical reason for the first hopper (100) storing PET resin

[0071] As illustrated in FIG. 1, the manufacturing apparatus of the present invention includes a first hopper (100) that receives and stores a first resin, which is a PET (Polyethylene Terephthalate) resin. The first hopper (100) is composed of a hopper body (101), a storage space (101a), a supply pipe (102), a preheating heater (103), and a supply amount control valve (104).

[0072] The technical reason for using PET resin in the first hopper (100) is as follows. PET resin is recyclable and is recognized as an eco-friendly material because it produces less harmful gas when burned, and it is a proven material that is already widely used in films used on the front of furniture. While the use of ABS or PVC resins, which were conventionally used for edge banding, is restricted due to environmental issues and stricter regulations, PET resin is a material that is essential for the government office furniture market as it meets the eco-friendly furniture standards of public institutions such as the Public Procurement Service. In addition, PET resin has excellent mechanical strength, heat resistance, and dimensional stability, so it can satisfy the physical properties required for edge banding products.

[0073] The technical reason for equipping the first hopper (100) with a preheating heater (103) is to improve the fluidity of the PET resin by preheating it to a temperature lower than its melting temperature and to enable smooth supply to the first extrusion section (110). PET resin exists in the form of pellets at room temperature and has low fluidity, so if it is fed directly into the extrusion section, the supply is not smooth and localized overheating may occur within the extrusion section. Therefore, preheating is performed in advance at the hopper stage to raise the temperature of the resin, but by heating it to a level where it does not completely melt, the efficiency of the subsequent extrusion process is increased.

[0074] The technical reason for providing a supply volume control valve (104) is to precisely control the amount of the first resin fed into the first extrusion unit (110) to maintain a constant extrusion speed and to appropriately adjust the ratio with the adhesive extruded from the second extrusion unit (210). If the supply ratio of the first resin and the adhesive is not constant, the thickness of the final product will be uneven or the distribution of the adhesive layer will be uneven, so precise flow rate control through the supply volume control valve (104) is essential.

[0075] Technical reason for the second hopper (200) storing adhesive

[0076] As illustrated in FIG. 1, the manufacturing apparatus of the present invention includes a second hopper (200) that receives and stores adhesive. The second hopper (200) is composed of a hopper body, a supply pipe, a preheating heater, and a supply amount control valve.

[0077] The technical reason for configuring the second hopper (200) separately from the first hopper (100) is that the difference in melting points between PET resin and adhesive is very large, exceeding 100 degrees, so the two materials must be heated and supplied independently. The melting point of PET resin is approximately 248 degrees, while the melting point of adhesive is in the range of 100 to 140 degrees. If the two materials are supplied from the same hopper, one material will overheat and the other will not melt. Therefore, it is essential to configure each hopper independently to provide temperature conditions optimized for each material.

[0078] The adhesive used in the second hopper (200) is a hot melt adhesive with a melting point in the range of 100 to 140 degrees. The technical reason for using such a low-melting-point adhesive is to allow the worker to achieve adhesion simply by applying heat when applying the final product, the edge banding, to the plate. If the melting point of the adhesive is less than 100 degrees, the adhesive layer may be damaged by heat during the storage and transportation of the product, and if it exceeds 140 degrees, excessive heat is required during application, which poses a risk of damage to the plate or the edge banding itself. Therefore, it is appropriate to use an adhesive with a melting point in the range of 100 to 140 degrees.

[0079] The technical reason for operating the preheating heater of the second hopper (200) at a temperature range lower than the preheating temperature of the first resin is to prevent the low-melting-point adhesive from melting and flowing out prematurely within the hopper. Since the adhesive has a lower melting point than the PET resin, if it is preheated to the same temperature as the first hopper (100), the adhesive will already melt within the hopper, causing problems such as blocking the supply pipe or uneven supply. Therefore, it is important to preheat to a temperature range that slightly improves the fluidity of the adhesive but does not completely melt it.

[0080] Technical reason and critical significance of numerical range of the first extrusion part (110)

[0081] As illustrated in FIG. 1, the first extrusion unit (110) heats and melts the first resin supplied from the first hopper (100) to produce a first molten material and extrudes the first molten material at a first set pressure. The first extrusion unit (110) is composed of a first cylinder (111), a first screw (112), a first heating unit (113), a first temperature control unit (114), a first pressure control unit (115), and a first discharge port (116).

[0082] The technical reason and critical significance of heating and melting the first resin in the first extrusion section (110) to a range of 240 to 260 degrees are as follows. Since the actual melting point of PET resin is approximately 248 degrees, the resin must be heated above this temperature to completely melt and become fluid. If the temperature is below 240 degrees, the PET resin does not melt sufficiently and remains in a semi-solid state, which causes clogging during the extrusion process or leaves unmelted particles inside the product, thereby reducing mechanical strength. Conversely, if the temperature exceeds 260 degrees, thermal decomposition of the PET resin begins, reducing molecular weight and mechanical properties, and causing discoloration or the generation of foreign substances. In addition, excessive temperature leads to energy waste and reduces the durability of the equipment.

[0083] Therefore, the range of 240 to 260 degrees is the optimal temperature range that can completely melt the PET resin to secure the fluidity required for extrusion, while preventing thermal decomposition and maintaining the physical properties of the product to the maximum extent. Within this range, the most desirable temperature is the range of 248 to 255 degrees, which is about 5 to 10 degrees around the melting point of the PET resin, 248 degrees. At this temperature, the PET resin can be extruded stably while maintaining appropriate viscosity.

[0084] The technical reason for maintaining the first set pressure higher than the second set pressure in the first extrusion section (110) is to ensure that when the first molten material and the second molten material merge in the extrusion head (300), the first molten material with a high melting point pushes up the second molten material with a low melting point and properly combines them. If the first set pressure and the second set pressure are the same, or if the first set pressure is lower, the second molten material with a low melting point (adhesive) may flow back or the interface with the first molten material may become unstable, making it difficult to form an integrated composite extrusion.

[0085] Specifically, the first extrusion unit (110) is equipped with a first pressure control unit (115) that controls the rotational speed of the first screw (112) to control the first set pressure. As the rotational speed of the first screw (112) increases, the amount of resin extruded per unit time increases, causing the pressure to rise; therefore, a desired pressure level can be achieved by controlling the screw rotational speed through the first pressure control unit (115). It is generally preferable that the first set pressure be maintained at a level approximately 1.2 to 2 times higher than the second set pressure, which is a level that allows the first molten material to stably push up the second molten material while preventing product non-uniformity caused by an excessive pressure difference.

[0086] Technical reason and critical significance of numerical range of the second extrusion part (210)

[0087] As illustrated in FIG. 1, the second extrusion unit (210) heats and melts the adhesive supplied from the second hopper (200) to produce a second molten material and extrudes the second molten material at a second set pressure. The second extrusion unit (210) is composed of a second cylinder (211), a second screw (212), a second heating unit (213), a second temperature control unit (214), a second pressure control unit (215), and a second discharge port (216).

[0088] The technical reason and critical significance of heating and melting the adhesive in the second extrusion section (210) to a range of 100 to 150 degrees are as follows. Since the adhesive used in the present invention has a melting point in the range of 100 to 140 degrees, it must be heated to a temperature at least above the melting point in order to completely melt and extrude it. If the temperature is below 100 degrees, the adhesive is not sufficiently melted, resulting in insufficient fluidity, uneven flow during the extrusion process, and incomplete bonding with the first molten material, which lowers the adhesive strength of the final product.

[0089] When the temperature exceeds 150 degrees, two problems occur. First, the viscosity of the adhesive becomes excessively low, causing it to flow down before it joins with the first molten material at the extrusion head (300). Second, some adhesive components undergo thermal decomposition or yellowing, which degrades the appearance quality of the product and reduces adhesive strength. Additionally, the excessive temperature increases the temperature difference with the first molten material, making it difficult to control the joining at the extrusion head (300).

[0090] Therefore, the range of 100 to 150 degrees is the optimal range for completely melting the adhesive to ensure appropriate fluidity, while preventing thermal decomposition and maintaining a temperature difference that allows for joining with the first molten material. Within this range, the most desirable temperature is the range of 120 to 140 degrees, which is about 10 to 20 degrees around the melting point of the adhesive, 120 degrees.

[0091] The second pressure control unit (215) of the second extrusion unit (210) controls the rotational speed of the second screw (212) to control the second set pressure, and adjusts it in correspondence with the extrusion speed of the first resin so that the second set pressure is balanced with the first set pressure. The technical reason for this pressure balance control is to form a composite extrusion by combining the first molten material and the second molten material in an appropriate ratio at the extrusion head (300). If the second set pressure is excessively low, the supply of adhesive is insufficient, so the adhesive layer is formed thinly or discontinuously, and if the second set pressure is excessively high, the adhesive may backflow the first molten material or the adhesive layer may be formed excessively, causing a problem of it oozing out during construction.

[0092] Technical reasons for the extrusion head (300) and critical significance of controlling the joining point

[0093] As illustrated in FIG. 1, the extrusion head (300) is a key component that forms an integrated composite extrusion by combining a first molten material extruded from a first extrusion section (110) and a second molten material extruded from a second extrusion section (210). The extrusion head (300) is composed of a first inlet (301), a second inlet (302), a joining section (303), a joining point control section (304), a temperature maintenance section (305), a pressure sensing section (306), and a discharge nozzle (307).

[0094] The technical reason for configuring the first inlet path (301), through which the first molten material flows from the top downward, and the second inlet path (302), through which the second molten material flows from the bottom upward, in the extrusion head (300) is to control the merging process using gravity. By supplying the first molten material (PET, 248°C) with a high melting point from the top downward and the second molten material (adhesive, 120°C) with a low melting point from the bottom upward, the weight and pressure of the first molten material push the second molten material upward, allowing them to merge naturally. If both molten materials are supplied from the top or in a horizontal direction, a problem occurs in which the second molten material with a low melting point flows down first and is discharged before meeting the first molten material.

[0095] The technical reason and critical significance of configuring the junction point control unit (304) to allow the junction point of the first molten material and the second molten material to be controlled in the vertical direction is the most essential feature of the present invention. Since the difference in melting points between PET resin and adhesive is very large, exceeding 100 degrees, the quality of the product is critically affected by the location of the point where the two molten materials meet. If the junction point is located too high (upper), the second molten material with a low melting point cools rapidly as soon as it meets the first molten material with a high melting point, causing the viscosity to rise and the bonding of the two materials to be incomplete. Conversely, if the junction point is located too low (lower), the second molten material begins to flow down due to gravity before reaching the junction point, making product formation impossible.

[0096] As a result of the experiment, it was confirmed that the optimal merging point is located about 30% to 40% upward from the midpoint of the merging section (303) where the first inlet (301) and the second inlet (302) meet. At this location, the pressure and temperature of the first molten material can adequately push up the second molten material without the second molten material flowing down prematurely, and the two materials can stably combine to form an integrated composite extrusion.

[0097] The junction point adjustment unit (304) can adjust the junction point by moving the internal structure of the junction unit (303) up and down, adjusting the length of the first inlet passage (301) or the second inlet passage (302), or changing the angle of the flow path. Through this adjustment function, even if process conditions such as the type of PET resin used, the melting point of the adhesive, and the extrusion speed change, the optimal junction point can be found and set, thereby enabling stable product production.

[0098] The technical reason for maintaining the temperatures of the first inlet passage (301) and the second inlet passage (302) independently through the temperature maintenance section (305) is to maintain the temperature and viscosity of each molten material at a constant level until they merge, thereby ensuring stable merging. The first inlet passage (301) is maintained at approximately 240 to 260 degrees to prevent the first molten material from solidifying, and the second inlet passage (302) is maintained at approximately 100 to 150 degrees to maintain the viscosity of the second molten material appropriately. If temperature control is not performed, the temperature of the molten material decreases while passing through the flow path, causing the viscosity to increase and the fluidity to decrease, resulting in unstable extrusion.

[0099] The technical reason for detecting and monitoring the pressure of the first inlet (301) and the second inlet (302) in real time through the pressure sensing unit (306) is to maintain a balance between the first set pressure and the second set pressure. If a pressure imbalance occurs, it is immediately detected and fed back to the first pressure regulating unit (115) or the second pressure regulating unit (215) to regulate the pressure, thereby ensuring the uniformity of the composite extruded product.

[0100] Technical reason for the cooling section (400) and critical significance of open cooling

[0101] As illustrated in FIG. 1, the cooling unit (400) cools the composite extruded from the extrusion head (300) in an open manner without a mold to form an edge banding product with an adhesive layer exposed on one side. The cooling unit (400) is composed of a cooling chamber (401), a cooling water supply unit (402), a cooling temperature control unit (403), an open cooling unit (404), and a transfer speed control unit (405).

[0102] The technical reason and critical significance of cooling in an open manner without using a mold in the cooling section (400) is one of the key features of the present invention. In conventional extrusion processes, it was common to form the shape of a product using a mold such as a die or a sizer. However, in the case of edge banding where an adhesive layer is exposed on one side, using a mold causes the following serious problems.

[0103] First, the molten adhesive (second molten material) adheres to the inner wall of the mold, preventing the product from coming out of the mold. Since the adhesive is an inherently adhesive substance, it adheres strongly when in contact with the metal surface of the mold, causing the product to become trapped inside the mold, or if it is forcibly removed, the adhesive layer may tear or a portion may remain in the mold.

[0104] Second, adhesive performance deteriorates as the surface of the adhesive layer is scratched or contaminated during the process of removing the product from the mold. The adhesive layer must have a clean and smooth surface to ensure proper adhesion with the panel during installation; however, if the surface is damaged due to friction with the mold, the adhesive strength decreases and the appearance becomes poor.

[0105] Third, productivity is significantly reduced because production must be stopped and cleaned to remove adhesive remaining inside the mold. Removing residual adhesive by heating the mold is a time-consuming and costly process.

[0106] To solve these problems, the present invention completely removes the mold and adopts an open cooling method. In the open cooling section (404), the composite extruded material passes through the open space inside the cooling chamber (401) and is cooled by indirect heat exchange with ambient air and cooling water. At this time, since the composite extruded material does not come into direct contact with the mold or other solids, the adhesive layer remains cleanly exposed while the product is formed.

[0107] The technical reason why open cooling is possible is that the first molten material and the second molten material have already been integrated in the extrusion head (300) to form a composite extrusion, and this composite extrusion has viscosity and rigidity that can maintain a certain shape on its own. In particular, since the first molten material (PET) with a high melting point forms the main structure of the composite extrusion and the second molten material (adhesive) with a low melting point is placed only on one side, the PET portion solidifies first during the cooling process to act as a skeleton that maintains the shape of the product, and then the adhesive portion solidifies gradually, so that the product is completed with the adhesive layer exposed on the surface.

[0108] The technical reason for the cooling water supply unit (402) supplying cooling water circulating on the wall of the cooling chamber (401) is to control the cooling speed of the composite extruded product by maintaining a constant temperature inside the cooling chamber (401). The cooling water does not come into direct contact with the composite extruded product but circulates on the wall of the cooling chamber (401) to cool the air inside the chamber, and this cooled air indirectly cools the composite extruded product. The reason for adopting this indirect cooling method is to prevent problems such as reduced adhesive performance due to moisture adhering to the surface of the adhesive layer when the cooling water comes into direct contact with the composite extruded product, and warping or cracking caused by stress inside the product due to rapid cooling.

[0109] The technical reason and critical significance of controlling the temperature of the cooling water through the cooling temperature control unit (403) is to optimize the cooling speed of the composite extruder to simultaneously secure the physical properties and productivity of the product. If the temperature of the cooling water is too low, the composite extruder cools rapidly, causing incomplete crystallization of PET and internal stress, which can cause the product to warp or crack. Additionally, the difference in cooling speed between PET and the adhesive becomes excessively large, which can cause delamination at the interface. Conversely, if the temperature of the cooling water is too high, the cooling speed slows down, reducing productivity, and the composite extruder passes through the cooling unit (400) without being sufficiently solidified, causing deformation in the subsequent drawing unit (500).

[0110] Experimental results confirmed that the optimal temperature of the cooling water is in the range of 15 to 25 degrees. In this temperature range, PET crystallizes at an appropriate rate to secure excellent mechanical strength, and the adhesive solidifies while maintaining surface properties to maximize adhesive performance.

[0111] The technical reason for controlling the cooling time by adjusting the transfer speed of the composite extruder passing through the cooling chamber (401) through the transfer speed control unit (405) is to optimize the degree of cooling. If the transfer speed is too fast, the cooling time is insufficient and the composite extruder does not solidify sufficiently, and if the transfer speed is too slow, productivity is reduced. The optimal transfer speed varies depending on the thickness of the composite extruder, the temperature of the cooling water, the extrusion temperature, etc., and is generally controlled within the range of 3 meters to 10 meters per minute.

[0112] Technical reason for the withdrawal section (500) and critical significance of the extension

[0113] As illustrated in FIG. 1, the drawing unit (500) draws out and stretches the edge banding product that has passed through the cooling unit (400). The drawing unit (500) is composed of a drawing roller (501), a drawing speed control unit (502), a stretching roller (503), a stretching ratio control unit (504), a tension sensing sensor (505), and a winding roller (506).

[0114] The technical reason and critical significance of stretching the edge banding product while drawing it out from the drawing section (500) is to induce molecular orientation of the PET resin to improve the mechanical properties of the product. Although PET has low mechanical strength and lacks dimensional stability in the amorphous state, when molecular chains are arranged in a certain direction through the stretching process, the degree of crystallization increases and tensile strength, elastic modulus, and heat resistance are greatly improved. In particular, since edge banding is attached to the side of furniture and is exposed to external impact or friction, excellent mechanical strength is essential.

[0115] The process of applying tensile force to an edge banding product between the extraction roller (501) and the stretching roller (503) to stretch the product is performed as follows. The extraction roller (501) grips and extracts the product that has passed through the cooling section (400) at a constant speed, and the stretching roller (503) rotates at a faster speed than the extraction roller (501) to apply tensile force to the product. At this time, stretching is achieved as the product stretches in the longitudinal direction due to the difference in speed between the two rollers.

[0116] The technical reason and critical significance of controlling the stretching ratio by adjusting the rotational speed of the stretching roller (503) through the stretching ratio control unit (504) are as follows. The stretching ratio is defined as the value obtained by dividing the length after stretching by the length before stretching, and in the case of PET edge banding, the optimal stretching ratio is in the range of 1.2 to 2.5 times. If the stretching ratio is less than 1.2 times, the molecular orientation effect is negligible, so the improvement of mechanical properties is insufficient, and if it exceeds 2.5 times, the product is damaged or the thickness becomes excessively thin due to excessive stretching, thereby reducing practicality. The most desirable stretching ratio is in the range of 1.5 to 2.0 times, and within this range, the crystallinity and mechanical strength of PET are maximized while the thickness and appearance of the product are appropriately maintained.

[0117] The technical reason for placing a tension detection sensor (505) between the drawing roller (501) and the stretching roller (503) to detect the tension applied to the edge banding product in real time is to maintain a balance between the drawing speed and the stretching ratio. If the tension is excessively high, there is a risk of the product being damaged, and if the tension is excessively low, the stretching effect is minimal. The tension information detected by the tension detection sensor (505) is fed back to the drawing speed control unit (502) and the stretching ratio control unit (504), so that the optimal tension can be maintained by automatically adjusting the rotation speed of the drawing roller (501) and the stretching roller (503).

[0118] The winding roller (506) is positioned at the rear end of the stretching roller (503) to wind the stretched edge banding product. Since the rotational speed of the winding roller (506) is controlled in conjunction with the stretching ratio control unit (504), winding is performed appropriately according to the length of the product after stretching.

[0119] Overall configuration and technical significance of the first hopper (100)

[0120] As illustrated in FIGS. 1 and 2, the first hopper (100) receives and stores a first resin, which is a PET (Polyethylene Terephthalate) resin, and performs the role of stably supplying it to the first extrusion unit (110). The first hopper (100) is composed of a hopper body (101), a storage space (101a), a supply pipe (102), a preheating heater (103), and a supply volume control valve (104), and each component is designed in an optimized manner considering the physical properties of the PET resin.

[0121] The technical reason for configuring the first hopper (100) independently from the second hopper (200) is that the difference in melting points between PET resin and adhesive is very large, exceeding 100 degrees. Since PET resin has a melting point of approximately 248 degrees, while adhesive has a melting point of 100 to 140 degrees, if the two materials are managed in the same hopper, one material will overheat and the other will be insufficiently preheated. Therefore, it is essential to configure an independent hopper system to provide optimal temperature conditions for each material.

[0122] Structure and technical reasons for the hopper body (101) and storage space (101a)

[0123] As illustrated in FIG. 2, the hopper body (101) is a container-shaped structure that forms a storage space (101a) for storing the first resin. The hopper body (101) has an inverted cone or inverted pyramidal shape with an open top and a narrowing bottom, and the technical reason for adopting this shape is as follows.

[0124] First, the inverted cone-shaped structure induces the PET resin inside the storage space (101a) to naturally gather downwards due to gravity, thereby enabling stable supply through the supply pipe (102). If the hopper body (101) is configured in a rectangular shape, resin remains at the corners, resulting in uneven supply and consequently, reduced stability of the extrusion process.

[0125] Second, the shape that narrows toward the bottom gradually increases the pressure applied to the resin inside the storage space (101a), thereby promoting natural descent into the supply pipe (102). Specifically, it is preferable that the diameter of the upper opening be formed to be about 2 to 4 times larger than the diameter of the lower outlet, and the flow of the resin is most smooth at this ratio.

[0126] The capacity of the storage space (101a) is designed to ensure a sufficient amount of resin storage for continuous production while preventing structural burden due to excessive weight. Generally, it is appropriate to design it to a size capable of storing 2 to 4 hours' worth of the hourly processing capacity of the first extrusion unit (110). For example, if the hourly processing capacity of the first extrusion unit (110) is 50 kg, the capacity of the storage space (101a) is designed to store 100 kg to 200 kg.

[0127] Considering heat resistance and durability, it is preferable to use stainless steel, particularly SUS304 or SUS316 grade, for the material of the hopper body (101). Stainless steel does not undergo deformation or corrosion even in an environment where it is heated by a preheating heater (103), and allows for hygienic production by meeting food standards. The thickness of the hopper body (101) is generally formed in the range of 3mm to 5mm, which is a suitable thickness for simultaneously securing heat conduction and structural rigidity.

[0128] As shown in FIG. 2, PET resin is stored in the form of pellets inside the storage space (101a). The PET resin pellets are generally cylindrical in shape with a diameter of 2 mm to 4 mm and a length of 3 mm to 5 mm. Pellets of this size are optimal for maintaining appropriate fluidity within the storage space (101a) without blocking the supply pipe (102). If the size of the pellets is too small, they may stick together and reduce fluidity, and if the size of the pellets is too large, blockage may occur within the supply pipe (102).

[0129] Technical principles of the structure of the supply pipe (102) and gravity transport

[0130] As shown in FIG. 2, the supply pipe (102) is installed at the bottom of the hopper body (101) to transport the first resin inside the storage space (101a) downward by gravity and supply it to the first extrusion part (110). The supply pipe (102) is positioned vertically or at an angle close to vertical (an angle within 0 to 15 degrees from the vertical line), and the technical reason for adopting this position is to promote the natural fall of the resin by making maximum use of gravity.

[0131] The inner diameter of the supply pipe (102) is designed so that PET resin pellets can pass through smoothly while preventing problems caused by an excessive supply speed. Specifically, the inner diameter of the supply pipe (102) is appropriately in the range of 20 mm to 50 mm, and within this range, the optimal value is determined according to the size of the pellets and the extrusion speed. If the inner diameter is less than 20 mm, there is a high risk of bridging, where the pellets become clogged inside the supply pipe (102), and if it exceeds 50 mm, the falling speed due to gravity becomes excessively fast, making it difficult to control the supply amount to the first extrusion unit (110).

[0132] The length of the supply pipe (102) is determined by the distance from the bottom of the hopper body (101) to the supply inlet of the first extrusion part (110), and is generally in the range of 200mm to 600mm. If the length of the supply pipe (102) is excessively long, frictional resistance increases, so the flow of resin is not smooth, and if it is excessively short, there is insufficient space to install the supply volume control valve (104).

[0133] The inner wall of the supply pipe (102) is polished smoothly to minimize frictional resistance during the transport of PET resin pellets. It is preferable that the surface roughness of the inner wall be processed to Ra 0.8㎛ or less, and such a smooth surface contributes to preventing pellet stagnation and maintaining a stable flow.

[0134] The technical reasons for adopting the gravity conveying method are that it enables stable resin supply without a separate power source, has a simple equipment structure resulting in a low probability of breakdown, and is easy to maintain. Compared to forced conveying methods such as screw feeders or belt conveyors, the gravity conveying method consumes no energy and prevents pellet breakage or the generation of fine particles by eliminating mechanical stress applied to the pellets.

[0135] Structure, preheating temperature range, and technical reasons of the preheating heater (103)

[0136] As shown in the main view and enlarged view A of FIG. 2, a preheating heater (103) is installed on the outer surface of the hopper body (101) to preheat the first resin inside the storage space (101a) to a temperature lower than the melting temperature of the first resin to improve fluidity. The preheating heater (103) is symmetrically arranged on the left and right outer surfaces of the hopper body (101), and through this symmetrical arrangement, the temperature distribution inside the storage space (101a) can be maintained uniformly.

[0137] The specific structure of the preheating heater (103) is configured in the form of a heater band or heater panel containing an electric resistance heating element. The heater band is formed in the shape of a band that wraps around the outer surface of the hopper body (101), and a resistance heating element, such as a nichrome wire or a Kanthal wire, is placed inside. When current is applied, heat is generated from the resistance heating element, and this heat is transferred to the PET resin inside the storage space (101a) through the wall of the hopper body (101).

[0138] As shown in enlarged view A of FIG. 2, heat generated from the preheating heater (103) is conducted from the outer surface of the hopper body (101) inward to heat the PET resin pellets. The technical reason for adopting this indirect heating method is that it allows for easier temperature control and prevents localized overheating compared to a method of applying heat directly to the pellets. If a heating element is installed directly inside the storage space (101a), problems may occur where the pellets around the heating element overheat, melt, or discolor.

[0139] The preheating temperature range by the preheating heater (103) is 180 to 220 degrees. This temperature range is lower than the melting point of PET resin, which is 248 degrees, and is the optimal range for improving fluidity without completely melting the resin. The technical reasons and critical significance of this preheating temperature range are as follows.

[0140] First, in the range of 180 to 220 degrees, the PET resin sufficiently exceeds the glass transition temperature (Tg: about 80 degrees), increasing the mobility of the molecular chains and reducing friction between pellets, thereby improving fluidity. At room temperature (about 25 degrees), PET pellets are hard and have low fluidity, so flow through the supply pipe (102) is not smooth, but when preheated to 180 degrees or higher, the pellets become soft and easy to slide against each other, promoting natural fall.

[0141] Second, if the preheating temperature is less than 180 degrees, the effect of improving fluidity is minimal, so preheating is meaningless, and the amount of heat required to melt in the first extrusion section (110) increases, which lowers energy efficiency. In particular, if the preheating temperature is 150 degrees or lower, the physical state of the PET resin hardly changes and is not significantly different from the room temperature state.

[0142] Third, when the preheating temperature exceeds 220 degrees, the pellets inside the storage space (101a), particularly those in contact with the wall of the hopper body (101), begin to partially melt. Although the melting point of PET is 248 degrees, at temperatures exceeding 220 degrees, the surface of the pellets becomes adhesive and may stick together. This phenomenon of pellets sticking together causes bridging, which obstructs the flow through the supply pipe (102). Additionally, the partially melted pellets may stick to the inner wall of the supply pipe (102) and cause blockage.

[0143] Fourth, if the preheating temperature is excessively high, thermal decomposition of PET may begin. When PET is exposed to temperatures above 250 degrees for a long time, the molecular chains are broken, the molecular weight decreases, and decomposition products such as acetaldehyde are generated. Although 220 degrees is lower than the thermal decomposition temperature, it is important to limit the preheating temperature to 220 degrees or lower, as the physical properties of pellets with a long residence time inside the storage space (101a) may deteriorate due to accumulated thermal history.

[0144] Therefore, a preheating temperature range of 180 to 220 degrees is the optimal range for effectively improving the fluidity of PET resin while preventing problems such as partial melting, adhesion between pellets, and thermal decomposition. Within this range, the most desirable preheating temperature is 190 to 210 degrees, at which the effect of improving fluidity and safety are best balanced.

[0145] The preheating heater (103) maintains a set temperature precisely through a temperature controller connected to a temperature sensor. The temperature sensor is installed on the outer surface or inside the hopper body (101) to measure the temperature in real time, and the temperature controller controls the temperature by supplying power to the preheating heater (103) to heat it when the measured temperature is lower than the set temperature, and by cutting off or reducing the power supply when the set temperature is reached. Through this feedback control method, the preheating temperature can be maintained precisely within ±5 degrees of the set value.

[0146] Structure, function, and control method of the supply volume control valve (104)

[0147] As shown in the main view and enlarged view B of FIG. 2, the supply volume control valve (104) is installed at the middle or bottom of the supply pipe (102) to control the supply volume of the first resin and to control the amount fed into the first extrusion unit (110). The supply volume control valve (104) is a key component that enables a stable extrusion process by precisely controlling the supply volume of the resin in accordance with the extrusion speed of the first extrusion unit (110).

[0148] The specific structure of the supply volume control valve (104) is illustrated in detail in enlarged view B of FIG. 2. The supply volume control valve (104) consists of a valve body, a valve seat, a valve disc (or valve plug), a driving device, and a control device. The valve body forms a flow path inside as part of the supply pipe (102), and the valve seat is installed in the middle of the flow path to form an opening. The valve disc is a movable member that opens and closes the opening of the valve seat and moves up and down by the driving device.

[0149] When the valve disc descends and adheres to the valve seat, the opening is closed, blocking the flow of PET resin; when the valve disc rises and separates from the valve seat, the opening is opened, allowing the flow of resin. By adjusting the gap (opening degree) between the valve disc and the valve seat, the amount of resin passing through per unit time, i.e., the supply volume, can be controlled.

[0150] The driving device is an actuator that moves the valve disc, and can utilize an electric motor, pneumatic cylinder, hydraulic cylinder, etc. The electric motor method can precisely control the position of the valve disc by using a step motor or a servo motor, while the pneumatic or hydraulic method is suitable for large-diameter valves as it can generate a large force. Since precise flow rate control is important in this invention, it is preferable to use a step motor or a servo motor.

[0151] The control device controls the drive device to adjust the opening of the valve. The control device receives information such as the screw rotation speed, extrusion pressure, and discharge amount of the first extrusion unit (110), calculates the optimal supply amount corresponding thereto, and determines the valve opening to achieve the calculated supply amount. For example, if the screw rotation speed of the first extrusion unit (110) increases, the amount of resin processed per unit time increases, so the opening of the supply amount control valve (104) is increased accordingly to increase the supply amount.

[0152] The control of the supply volume control valve (104) can be performed in an open loop or a closed loop manner. The open loop method involves opening and closing the valve according to a set opening degree and has a simple structure, but it has low precision as there is no feedback on the supply volume. The closed loop method involves measuring the actual supply volume and providing feedback, which has high precision, and it is preferable to adopt the closed loop method in the present invention.

[0153] For closed-loop control, a flow sensor or a weight sensor may be additionally installed in the supply pipe (102). The flow sensor measures the volume or mass of resin passing through the supply pipe (102) per unit time, and the weight sensor measures the total weight of the hopper body (101) to calculate the supply amount from the weight decreasing per unit time. The control device compares the measured supply amount with the target supply amount, and if a difference occurs, adjusts the valve opening so that the actual supply amount matches the target value.

[0154] The technical reasons and effects of installing the supply volume control valve (104) are as follows.

[0155] First, the amount of resin fed into the first extrusion unit (110) is precisely controlled to stabilize the extrusion process. If the supply amount of resin is not constant, the filling rate inside the first extrusion unit (110) fluctuates, causing the extrusion pressure and temperature to become unstable, and consequently, the quality of the composite extruded product deteriorates. Stable extrusion is made possible by maintaining a constant supply amount through the supply amount control valve (104).

[0156] Second, the ratio with the adhesive extruded from the second extrusion section (210) can be appropriately adjusted. In the edge banding, which is the final product, the thickness ratio of the PET resin portion to the adhesive portion is an important factor in determining the performance and economic efficiency of the product. By synchronizing and controlling the supply volume control valve (104) of the first hopper (100) and the supply volume control valve of the second hopper (200), a composite extruded product with a desired ratio can be obtained.

[0157] Third, it can respond quickly to changes in production conditions. When changing the thickness or width of the product or adjusting the production speed, the supply amount can be changed immediately by simply adjusting the opening of the supply amount control valve (104). If there is no supply amount control valve (104), the flexibility of the production line is greatly reduced because the hopper body (101) itself must be replaced or the diameter of the supply pipe (102) must be changed.

[0158] Fourth, it prevents overloading or insufficient supply of the first extrusion unit (110). If the supply amount is excessive, the resin is excessively filled inside the first cylinder (111), causing the pressure to rise and hindering the rotation of the first screw (112), which may cause an overload on the motor. Conversely, if the supply amount is insufficient, a void space is created inside the first cylinder (111), causing the extrusion to be discontinuous and the quality of the composite extruded product to deteriorate. These problems can be prevented by maintaining an appropriate supply amount through the supply amount control valve (104).

[0159] Interaction and overall operation principles of each component of the first hopper (100)

[0160] As illustrated in FIG. 2, each component of the first hopper (100) interacts organically to stably supply PET resin to the first extrusion unit (110). The operating principle of the first hopper (100) is performed in the following order.

[0161] First, a worker feeds PET resin pellets into the storage space (101a) through the upper opening of the hopper body (101). The fed pellets gather at the bottom of the storage space (101a) by gravity and are concentrated toward the inlet of the supply pipe (102) due to the inverted cone shape of the hopper body (101).

[0162] Second, power is applied to the preheating heater (103) to heat the outer surface of the hopper body (101). The heat transferred through the wall of the hopper body (101) preheats the PET resin pellets inside the storage space (101a) to a range of 180 to 220 degrees. The preheated pellets have improved fluidity, making them easier to slide against each other and promoting downward movement by gravity.

[0163] Third, the preheated pellets enter the supply pipe (102) by gravity and are transported downward. The vertical arrangement and smooth inner wall of the supply pipe (102) facilitate the natural fall of the pellets, maintaining a continuous flow without bridging or stagnation.

[0164] Fourth, the pellets passing through the supply pipe (102) reach the supply volume control valve (104). The supply volume control valve (104) is adjusted in opening according to the operating conditions of the first extrusion unit (110), and only a certain amount of pellets are allowed to pass according to the set opening. Excess pellets are kept at the top of the supply volume control valve (104), thereby controlling the amount fed into the first extrusion unit (110).

[0165] Fifth, the pellet that has passed through the supply volume control valve (104) is fed into the first cylinder (111) of the first extrusion unit (110) through the lower end of the supply pipe (102). The fed pellet is transported forward by the first screw (112) inside the first cylinder (111) and is completely melted by receiving heat from the first heating unit (113), and is extruded as the first molten material to the extrusion head (300) through the first discharge port (116).

[0166] In this series of processes, the hopper body (101) and the storage space (101a) store a sufficient amount of resin to enable continuous production, the supply pipe (102) provides a stable transfer path using gravity, the preheating heater (103) improves the fluidity of the resin to promote smooth supply, and the supply volume control valve (104) stabilizes the extrusion process through precise control of the supply volume. Through the organic interaction of each component, the first hopper (100) performs the function of stably and continuously supplying PET resin to the first extrusion unit (110).

[0167] Technical excellence and effect of the configuration of the first hopper (100)

[0168] The configuration of the first hopper (100) shown in FIGS. 1 and FIGS. 2 provides the following technical excellence and effects.

[0169] First, stable resin supply is possible without a separate power device through the inverted conical structure of the hopper body (101) and the gravity-transfer type supply pipe (102). This simplifies the equipment structure, reduces energy consumption, and lowers the possibility of failure.

[0170] Second, preheating in the range of 180 to 220 degrees through a preheating heater (103) effectively improves the fluidity of the PET resin while preventing partial melting or thermal decomposition. This minimizes bridging or clogging during the supply process and increases melting efficiency in the first extrusion section (110), thereby improving the stability and energy efficiency of the entire process.

[0171] Third, precise control of the supply amount through the supply amount control valve (104) stabilizes the extrusion conditions of the first extrusion unit (110) and optimizes the supply ratio with the second extrusion unit (210), thereby enabling the production of a composite extruded product of uniform quality. This significantly improves the quality uniformity of the final product, edge banding, and provides the effect of reducing the defect rate.

[0172] Fourth, automated process control is possible by equipping each component with measuring devices, such as temperature sensors and flow sensors, and control devices. This eliminates quality variations caused by operator skill levels, improves productivity, and provides the effect of reducing labor costs.

[0173] Fifth, the configuration of the first hopper (100) is designed to be applicable to various grades and types of PET resin. By setting the temperature of the preheating heater (103) and controlling the opening of the supply volume control valve (104), it is possible to respond to resins of various physical properties, and it provides flexibility to respond quickly even when product specifications change.

[0174] Overall configuration and technical significance of the second hopper (200)

[0175] As illustrated in FIGS. 1 and 3, the second hopper (200) receives and stores an adhesive having a melting point in the range of 100 to 140 degrees and stably supplies it to the second extrusion unit (210). The second hopper (200) is composed of a hopper body (201), a storage space (201a), a supply pipe (202), a preheating heater (203), and a supply volume control valve (204), and has a basic structure similar to the first hopper (100), but is designed to be optimized for the physical properties of the adhesive.

[0176] As illustrated in the comparison table of FIG. 3, the second hopper (200) is differentiated from the first hopper (100) in several aspects. While the first hopper (100) handles PET resin with a melting point of about 248 degrees and uses a preheating temperature of 180 to 220 degrees, the second hopper (200) handles adhesive with a melting point of 100 to 140 degrees and uses a preheating temperature of 80 to 100 degrees. This temperature difference is due to the difference in melting points between the two materials reaching about 128 degrees (more than 100 degrees), and the core technical feature of the present invention is to provide optimal temperature conditions by independently configuring each hopper.

[0177] Technical reasons and critical significance of the adhesive melting point range (100 to 140 degrees)

[0178] The adhesive used in the second hopper (200) is a hot melt adhesive with a melting point in the range of 100 to 140 degrees. The technical reasons for selecting such a low melting point adhesive and the critical significance of the melting point range are as follows.

[0179] First, if the melting point of the adhesive is less than 100 degrees, various serious problems occur. If an adhesive with a melting point of 80 degrees or lower is exposed to a high-temperature environment in summer (vehicle interior temperature of 60 to 80 degrees) during the storage and transportation of the product, it may soften or partially melt, causing the adhesive layer to deform. Additionally, when the edge banding product is wound in a roll form on a winding roller (506), if the temperature rises while the adhesive layers are in contact with each other, a blocking phenomenon occurs where they stick together. If blocking occurs, the adhesive layer may tear or become contaminated when the product is unwound, rendering it unusable. Therefore, the melting point of the adhesive must be at least 100 degrees to ensure stability under normal storage and transportation conditions.

[0180] Second, various problems arise when the melting point of the adhesive exceeds 140 degrees. When applying edge banding to plywood or MDF in furniture, a method is used in which heat is applied to the adhesive layer to melt the adhesive before pressing it onto the board. If the adhesive's melting point exceeds 140 degrees, excessive temperatures are required during application, leading to the following issues. First, the PET resin portion may deform or discolor due to the high temperature. Since the glass transition temperature of PET is approximately 80 degrees, temperatures above 140 degrees can cause the PET to soften, altering the shape of the product. Furthermore, as plywood and MDF are wood materials, exposure to excessive heat can cause the surface to burn or discolor, and the internal adhesive or additives may decompose, releasing harmful substances. From the perspective of worker safety, handling high-temperature equipment exceeding 140 degrees is also undesirable due to the high risk of burns.

[0181] Third, the range of 100 to 140 degrees is the optimal range that satisfies practical construction conditions while having a sufficient difference from the melting point of PET resin (248 degrees). Adhesives in this range can be easily melted using a standard hot melt gun or a hot air blower, and the temperature level is safe for workers to handle. In addition, adhesives in this range have appropriate viscosity in the molten state, so they spread evenly on the surface of the sheet metal without flowing excessively.

[0182] Fourth, adhesives in the 100 to 140°C range are excellent in terms of chemical compatibility with PET and adhesion. Hot-melt adhesives in this temperature range are primarily based on ethylene vinyl acetate (EVA) or polyolefin-based polymers, which form a physical bond with the PET surface to provide excellent adhesive strength. Adhesives with melting points outside this range experience reduced interfacial bonding with PET, posing a high risk of delamination.

[0183] Therefore, the melting point range of 100 to 140 degrees is the optimal range that satisfies the storage stability of the product, ease of application, adhesion to PET, and the possibility of composite extrusion with PET resin. Within this range, the most desirable melting point is 110 to 130 degrees, and adhesives with a melting point of around 120 degrees are most widely used.

[0184] Structure and technical reasons for the hopper body (201) and storage space (201a)

[0185] As illustrated in FIG. 3, the hopper body (201) of the second hopper (200) is a container-shaped structure that forms a storage space (201a) for storing an adhesive with a melting point in the range of 100 to 140 degrees. The hopper body (201) is similar in basic shape to the hopper body (101) of the first hopper (100), but has detailed differences in consideration of the characteristics of the adhesive.

[0186] The shape of the hopper body (201) is an inverted cone or inverted pyramidal structure that is open at the top and narrows toward the bottom, similar to the first hopper (100). The technical reason for adopting this shape is to induce the adhesive inside the storage space (201a) to naturally gather at the bottom by gravity, thereby enabling a stable supply. However, it is preferable that the angle of inclination of the hopper body (201) be designed to be slightly steeper than that of the hopper body (101). Since the adhesive has a smaller particle size than PET resin and can be adhesive, it is highly likely to stagnate on the inclined surface; therefore, the angle of inclination is formed in the range of 45 to 60 degrees from the vertical line to promote the flow of the adhesive.

[0187] The capacity of the storage space (201a) is designed to be sized to store 2 to 4 hours of the hourly processing capacity of the second extrusion unit (210), just like the first hopper (100). However, since the processing capacity of the second extrusion unit (210) is generally smaller than that of the first extrusion unit (110), the capacity of the storage space (201a) is also designed to be smaller than that of the storage space (101a). For example, if the hourly processing capacity of the second extrusion unit (210) is 10 kg, the capacity of the storage space (201a) is designed to be sized to store 20 kg to 40 kg.

[0188] As shown in FIG. 3, adhesive is stored in the form of pellets or granules inside the storage space (201a). The adhesive pellets are generally cylindrical or nearly spherical in shape with a diameter of 2 mm to 3 mm and a length of 2 mm to 4 mm, and are slightly smaller than PET resin pellets. Since adhesive pellets are softer and more adhesive than PET pellets, care must be taken to prevent the pellets from sticking together during storage and handling. To this end, some adhesive pellets are coated with a release agent, such as talc or silica, on their surface to prevent adhesion between the pellets.

[0189] It is preferable to use stainless steel (SUS304 or SUS316) for the material of the hopper body (201), just like the first hopper (100). However, since the adhesive is handled at a lower temperature than PET, the heat resistance requirement is relatively low. The thickness of the hopper body (201) is generally formed in the range of 3 mm to 5 mm.

[0190] Structure and characteristics of the supply pipe (202)

[0191] As shown in FIG. 3, the supply pipe (202) is installed at the bottom of the hopper body (201) to supply adhesive inside the storage space (201a) to the second extrusion unit (210). The supply pipe (202) has the same basic structure and operating principle as the supply pipe (102) of the first hopper (100), but there are some differences considering the characteristics of the adhesive.

[0192] The supply pipe (202) adopts a gravity-induced natural fall method and is positioned at a vertical or near-vertical angle. The inner diameter of the supply pipe (202) is designed so that adhesive pellets can pass through smoothly, and generally, a range of 20 mm to 50 mm is suitable. However, since adhesive pellets may be more adhesive than PET pellets, it is desirable to design the inner diameter to be slightly larger than the supply pipe (102) for PET to reduce the risk of clogging.

[0193] The inner wall of the supply pipe (202) is polished smoothly, just like the first hopper (100), and the surface roughness is processed to Ra 0.8 μm or less. In particular, considering the adhesive properties of the adhesive, a fluoropolymer (PTFE, Polytetrafluoroethylene) coating or silicone treatment may be additionally applied to the inner wall of the supply pipe (202). This surface treatment prevents adhesive pellets from sticking to the inner wall and minimizes the accumulation of adhesive on the inner wall even after long-term use.

[0194] The length of the supply pipe (202) is determined by the distance from the bottom of the hopper body (201) to the supply inlet of the second extrusion part (210), and is generally in the range of 200 mm to 600 mm. A vibrator may be installed in the supply pipe (202) as needed. The vibrator is attached to the outer wall of the supply pipe (202) and generates periodic vibrations to prevent adhesive pellets from stagnating or forming bridging inside the supply pipe (202). The vibration frequency is generally in the range of 50 Hz to 200 Hz, and the amplitude is set to the range of 0.1 mm to 1 mm.

[0195] Structure, preheating temperature range, and technical reasons of the preheating heater (203)

[0196] As shown in the main drawing and comparison table of FIG. 3, the preheating heater (203) is installed in the hopper body (201) to preheat the adhesive inside the storage space (201a). The basic structure of the preheating heater (203) is similar to the preheating heater (103) of the first hopper (100), but there is a significant difference in the preheating temperature range.

[0197] The preheating heater (203) is symmetrically arranged on the outer circumference of both the left and right sides of the hopper body (201) and is configured in the form of a heater band or heater panel containing an electric resistance heating element. The heat generated from the preheating heater (203) is indirectly transferred to the adhesive pellets inside the storage space (201a) through the wall surface of the hopper body (201).

[0198] The technical reason and critical significance of setting the preheating temperature range to 80 to 100 degrees, which is lower than the preheating temperature of the first resin, is a key feature of the present invention. As clearly indicated in the comparison table of FIG. 3, the preheating temperature of the first hopper (100) is 180 to 220 degrees, whereas the preheating temperature of the second hopper (200) is 80 to 100 degrees, which is about 100 to 140 degrees lower than the preheating temperature of the first resin. The technical reason for this temperature difference is as follows.

[0199] First, since the melting point of the adhesive is in the range of 100 to 140 degrees, which is much lower than the melting point (248 degrees) of the PET resin, the preheating temperature must also be set low accordingly. If the adhesive is preheated to the same range as the first resin, 180 to 220 degrees, the melting point of the adhesive is greatly exceeded, and the adhesive completely melts inside the storage space (201a). The melted adhesive flows down in a liquid state and causes serious problems, such as blocking the supply pipe (202) or accumulating at the bottom of the hopper body (201) to form lumps.

[0200] Second, in order to prevent the adhesive from melting prematurely inside the storage space (201a) while improving fluidity, it must be preheated to a temperature lower than the melting point of the adhesive. Since the range of 80 to 100 degrees is lower than the melting point (100 to 140 degrees) of most adhesives, the adhesive maintains a solid state while being slightly softened by the temperature increase, thereby improving fluidity. This is the same principle as preheating the PET resin in the first hopper (100) to 180 to 220 degrees, which is lower than the melting point (248 degrees).

[0201] Third, if the preheating temperature is below 80 degrees, the preheating effect is minimal, so there is almost no improvement in the fluidity of the adhesive. Since most adhesives have a glass transition temperature in the range of 40 to 60 degrees, they must be heated to 80 degrees or higher to sufficiently exceed the glass transition temperature, thereby increasing the mobility of molecular chains and improving fluidity. If the preheating temperature is 70 degrees or lower, the difference from the glass transition temperature is not significant, so the effect of improving fluidity is limited.

[0202] Fourth, if the preheating temperature exceeds 100 degrees, melting may already begin during the preheating stage in the case of some adhesives, particularly low-melting point adhesives with a melting point of 100 to 110 degrees. Since the preheating heater (203) is installed on the outer surface of the hopper body (201), the temperature of the adhesive pellets in contact with the wall surface is higher than that of the pellets inside. If the preheating temperature exceeds 100 degrees, the pellets near the wall surface melt and stick to the wall surface, and this molten adhesive may accumulate, reducing the effective capacity of the storage space (201a) or hindering heat transfer.

[0203] Fifth, temperature interference between the two hoppers is prevented by maintaining the preheating temperature lower than the preheating temperature of the first resin. When the first hopper (100) and the second hopper (200) are physically located close to each other, radiant heat from the first hopper (100), which is heated to a high temperature, can affect the second hopper (200). The lower the set temperature of the second hopper (200), the greater the safety margin secured to prevent premature melting of the adhesive even when affected by such external heat sources.

[0204] Therefore, a preheating temperature range of 80 to 100 degrees is the optimal range for effectively improving the fluidity of the adhesive while preventing premature melting and maintaining a temperature difference with the first hopper (100) to implement a stable dual supply system. Within this range, the most desirable preheating temperature is 85 to 95 degrees, and in particular, around 90 degrees is most widely used.

[0205] The preheating heater (203) maintains the set temperature precisely through a temperature controller connected to a temperature sensor. Since the adhesive is more sensitive to temperature than PET resin, the precision of the temperature control is more important. The temperature controller controls the measured temperature to maintain it precisely within ±3 degrees of the set value.

[0206] Structure, pressure balance control function, and technical reasons of the supply volume control valve (204)

[0207] As illustrated in the main diagram, comparison table, and pressure balance control principle diagram of FIG. 3, the supply volume control valve (204) is installed in the supply pipe (202) to control the supply volume of adhesive. The basic structure of the supply volume control valve (204) is similar to the supply volume control valve (104) of the first hopper (100), but there is an important difference in that an additional control function is implemented to control the supply volume to maintain a balance between the first set pressure and the second set pressure.

[0208] The supply volume control valve (204) is composed of a valve body, a valve seat, a valve disc, a driving device, and a control device, and controls the supply volume by adjusting the position of the valve disc. The control device receives information in real time regarding the first set pressure (P1) of the first extrusion part (110) and the second set pressure (P2) of the second extrusion part (210), and adjusts the valve opening to maintain a balance between the two pressures.

[0209] The technical reason and critical significance of pressure balance control are one of the most essential features of the present invention. As clearly indicated in the pressure balance control principle diagram of FIG. 3, the first extrusion unit (110) extrudes the first molten material at high pressure (P1) to push up the second molten material, and the second extrusion unit (210) extrudes the second molten material at low pressure (P2) but is controlled to be in balance with P1. The technical reason why such pressure balance control is required is as follows.

[0210] First, in order for the first molten material and the second molten material to properly merge in the extrusion head (300) to form an integrated composite extrusion, the pressures of the two molten materials must be properly balanced. The first set pressure (P1) must be higher than the second set pressure (P2) so that the first molten material with a high melting point can push up and merge with the second molten material with a low melting point. If P1 and P2 are the same or if P2 is higher than P1, the second molten material may backflow the first molten material, or the boundary between the two molten materials inside the extrusion head (300) becomes unstable, resulting in a decrease in product quality.

[0211] Second, pressure balance must be properly maintained so that the thickness ratio of the first resin portion and the adhesive portion in the composite extrusion is uniform. If pressure balance is disrupted, one material is excessively extruded, resulting in an uneven thickness distribution of the product. For example, if P2 is excessively high, the adhesive layer becomes thick, and if P2 is excessively low, the adhesive layer becomes thin or discontinuous.

[0212] Third, when the operating conditions of the first extrusion unit (110) change, the second extrusion unit (210) must also adjust the supply amount in response. For example, if the screw rotation speed of the first extrusion unit (110) is increased to increase the production speed, P1 rises, so the supply amount of the second extrusion unit (210) must also be increased accordingly to raise P2. If the supply amount of the second extrusion unit (210) is not adjusted, the balance between P1 and P2 is disrupted, and the product quality deteriorates.

[0213] Fourth, pressure balance control is essential for ensuring process stability. Since the extrusion process is a complex system in which various variables (temperature, pressure, flow rate, viscosity, etc.) interact, a change in one variable affects other variables. By monitoring and adjusting the pressure balance in real time, the dynamic stability of the process can be maintained, and robustness against disturbances can be ensured.

[0214] The control method of the supply volume control valve (204) is implemented as follows. The control device receives the measured values ​​of P1 and P2 in real time from the pressure sensing unit (306) of the extrusion head (300). The control device calculates the ratio of P1 and P2 and compares it with the target ratio (generally P1 / P2 = 1.2 to 2.0). If the actual ratio differs from the target ratio, the control device adjusts the opening of the supply volume control valve (204) to increase or decrease the amount of adhesive supplied to the second extrusion unit (210). If the supply amount increases, the filling rate inside the second cylinder (211) increases, causing P2 to rise, and if the supply amount decreases, P2 decreases. Through this feedback control loop, the balance between P1 and P2 is maintained at the target value.

[0215] It is common for control algorithms to use Proportional-Integral-Derivative (PID) controllers. Since PID controllers calculate the control output by considering the current error (proportional term), accumulated error (integral term), and the rate of change of error (derivative term), precise and stable control is possible. The gain parameters of the PID controller must be tuned to match the characteristics of the system, and the optimal values ​​are generally found using the Ziegler-Nichols method or automatic tuning algorithms.

[0216] Interaction and overall operating principles of each component of the second hopper (200)

[0217] As illustrated in FIG. 3, each component of the second hopper (200) interacts organically to stably supply adhesive to the second extrusion unit (210), and at the same time, maintains pressure balance in cooperation with the first hopper (100) and the first extrusion unit (110). The operating principle of the second hopper (200) is performed in the following order.

[0218] First, the operator feeds adhesive pellets into the storage space (201a) through the upper opening of the hopper body (201). The fed pellets gather at the bottom of the storage space (201a) by gravity and are concentrated toward the inlet of the supply pipe (202) due to the inverted cone shape of the hopper body (201).

[0219] Second, power is applied to the preheating heater (203) to heat the hopper body (201). The preheating temperature is set to a range of 80 to 100 degrees, which is significantly lower than the preheating temperature (180 to 220 degrees) of the first hopper (100). By preheating to this low temperature, the adhesive is prevented from melting prematurely inside the storage space (201a) while improving fluidity.

[0220] Third, the preheated adhesive pellets enter the supply pipe (202) by gravity and are transported downward. If necessary, a vibration device is operated to facilitate the flow of the pellets and prevent bridging.

[0221] Fourth, the pellets passing through the supply pipe (202) reach the supply volume control valve (204). The supply volume control valve (204) is controlled based on information of P1 and P2 received from the pressure sensing unit (306), and its opening is adjusted to maintain a balance between P1 and P2. The supply volume control valve (204) allows only a certain amount of pellets to pass through according to the set opening, and excess pellets wait at the top of the valve.

[0222] Fifth, the pellet that has passed through the supply volume control valve (204) is fed into the second cylinder (211) of the second extrusion unit (210) through the lower end of the supply pipe (202). The fed pellet is transported forward by the second screw (212) inside the second cylinder (211), receives heat from the second heating unit (213), completely melts, and is extruded as a second molten material to the extrusion head (300) through the second discharge port (216).

[0223] Sixth, when the first molten material and the second molten material are combined in the extrusion head (300), since P1 is higher than P2, the first molten material pushes up the second molten material and combines appropriately to form an integrated composite extrusion. The pressure sensing unit (306) monitors P1 and P2 in real time, and if signs of the balance being disrupted are detected, it immediately feeds back to the supply volume control valve (204) to adjust the supply volume.

[0224] In this series of processes, each component of the second hopper (200) functions independently, yet operates cooperatively as part of the overall system. In particular, the pressure balance control function of the supply volume control valve (204) enables synchronization with the first hopper (100) and the first extrusion unit (110), which is a key technology for stably compound extruding two materials with a melting point difference of more than 100 degrees.

[0225] Cooperative operation and synergy effect of the first hopper (100) and the second hopper (200)

[0226] As summarized in the comparison table of FIG. 3, the first hopper (100) and the second hopper (200) handle materials with different characteristics, but ultimately operate cooperatively as a single integrated system. The main differences between the two hoppers and the resulting synergy effects are as follows.

[0227] In terms of raw materials: The first hopper (100) handles PET resin (melting point approximately 248 degrees), and the second hopper (200) handles adhesive (melting point 100 to 140 degrees). The difference in melting points between the two materials is approximately 128 degrees, which is more than 100 degrees, making it impossible to perform composite extrusion with a conventional extrusion process. The present invention solves this technical challenge by configuring the two hoppers independently and providing conditions optimized for each material.

[0228] Preheating temperature aspect: The first hopper (100) is preheated to 180 to 220 degrees, and the second hopper (200) is preheated to 80 to 100 degrees. The preheating temperature of the second hopper (200) is significantly lower than that of the first hopper (100) to prevent premature melting of the adhesive, and this is a key technical feature of the present invention.

[0229] Extrusion pressure aspect: The first extrusion section (110) extrudes at high pressure (P1) to push up the second molten material, and the second extrusion section (210) extrudes at low pressure (P2) while maintaining balance with P1. This pressure difference and balance control enables stable joining at the extrusion head (300).

[0230] In terms of supply volume control: The supply volume control valve (104) of the first hopper (100) focuses primarily on extrusion stabilization, while the supply volume control valve (204) of the second hopper (200) focuses on maintaining pressure balance. The stability of the entire system is ensured by the cooperative operation of the two valves.

[0231] Through this differentiated configuration and cooperative operation, the first hopper (100) and the second hopper (200) create the following synergistic effects. First, two materials with large differences in melting points can be handled under optimal conditions, thereby preventing the deterioration of the material's physical properties. Second, process flexibility is ensured through independent temperature and supply volume control, allowing for adaptation to various product specifications. Third, the uniformity of quality of the composite extrusion is significantly improved through pressure balance control. Fourth, the automated control system minimizes operator intervention and maximizes productivity.

[0232] Technical excellence and effect of the configuration of the second hopper (200)

[0233] The configuration of the second hopper (200) shown in FIGS. 1 and FIGS. 3 provides the following technical excellence and effects.

[0234] First, using an adhesive with a melting point in the range of 100 to 140 degrees makes it easier to install edge banding products. Adhesives in this range can be easily melted with a standard hot air gun or hot melt gun, allowing for installation of uniform quality regardless of the worker's skill level.

[0235] Second, by setting the preheating temperature to a range of 80 to 100 degrees, which is lower than the preheating temperature of the first resin, it is possible to prevent premature melting of the adhesive while improving fluidity, thereby enabling a stable supply. This is an essential technical feature in a system that handles low-melting point materials and high-melting point materials simultaneously.

[0236] Third, pressure balance control through the supply volume control valve (204) enables synchronization between the first extrusion section (110) and the second extrusion section (210), thereby greatly improving the quality uniformity of the composite extrusion. This is a key technology for stably composite extruding two materials with a melting point difference of more than 100 degrees.

[0237] Fourth, automated process control is possible by equipping each component of the second hopper (200) with measuring devices such as temperature sensors and flow rate sensors, and control devices. In particular, since pressure balance control is achieved through a real-time feedback loop, it has high robustness against disturbances and excellent process stability.

[0238] Fifth, the second hopper (200) is designed to operate independently of the first hopper (100) while also operating cooperatively, so that even if a problem occurs in one hopper, it does not affect the operation of the other hopper. This increases the reliability and ease of maintenance of the system.

[0239] Sixth, the configuration of the second hopper (200) is designed to be applicable to various types of adhesives. By setting the temperature of the preheating heater (203) and controlling the opening of the supply volume control valve (204), it can accommodate adhesives with various melting points and viscosities, and provides flexibility to respond quickly even when product specifications change.

[0240] Structure and technical reason of the first cylinder (111)

[0241] As illustrated in FIGS. 1 and 4, the first extrusion unit (110) includes a first cylinder (111) that receives a first resin supplied from a first hopper (100). The first cylinder (111) is a cylindrical structure that provides a space in which the first resin is received, heated, and melted, and is a key component of the extrusion process.

[0242] As illustrated in detail in FIG. 4, the first cylinder (111) is divided into five sections along the longitudinal direction: a supply section, a compression section, a melting section, a homogenization section, and a discharge section. The technical reason for this division of sections is to provide optimal process conditions according to changes in the physical state of the PET resin.

[0243] The supply section is the inlet part of the first cylinder (111) and receives solid PET resin pellets supplied from the first hopper (100). In this section, the PET resin remains in a solid state and begins to be transported to the rear section by the rotation of the first screw (112). The temperature of the supply section is set to a range of about 180 to 200 degrees, which is above the glass transition temperature (about 70 to 80 degrees) of the PET resin but below the melting point (about 248 degrees), so the resin is in a state where it softens while maintaining its shape. The technical reason for this temperature setting is to provide preheating to the PET resin to increase the efficiency of the subsequent melting process, while preventing supply failures caused by premature melting.

[0244] The compression section is located behind the supply section and is structured such that the pitch of the first screw (112) gradually decreases. The decrease in screw pitch reduces the volume of resin that can be accommodated per unit length, thereby applying a compressive force to the resin. The technical reason for the compression section is to remove air between the PET resin pellets and increase the density of the resin, thereby increasing the heat transfer efficiency in the subsequent melting section. Additionally, since friction between the resin pellets increases due to the compressive force and generates frictional heat, the melting process can be accelerated through internal heat generation along with external heating. The temperature of the compression section is set to a range of approximately 200 to 240 degrees, which is the temperature at which the PET resin softens and transitions into a deformable state.

[0245] The melting section is located behind the compression section and is a section where the PET resin is completely melted and changes into a liquid state. The temperature of the melting section is set to a range of approximately 240 to 250 degrees, which corresponds to a range around 248 degrees, the melting point of the PET resin. In the melting section, the first heating unit (113) operates at maximum output to intensively heat the outer surface of the first cylinder (111), and shear heat is also generated by the rotation of the first screw (112) to accelerate the melting of the resin. The length of the melting section is set to approximately 30% to 40% of the total length of the first cylinder (111), so as to provide a residence time sufficient for the PET resin to be completely melted.

[0246] The homogenization section is located behind the melting section and is a section that makes the temperature and viscosity of the molten PET resin uniform. The first molten material that has passed through the melting section may have partial temperature variations, and there is a possibility that some unmelted particles may remain. In the homogenization section, the temperature distribution inside the first molten material is made uniform through a strong mixing action by the rotation of the first screw (112), and the unmelted particles are completely melted. The temperature of the homogenization section is set to a range of about 250 to 255 degrees, and by maintaining a temperature slightly higher than that of the melting section, the viscosity of the molten material is lowered and fluidity is improved. The technical importance of the homogenization section lies in ensuring the uniformity of quality of the final product. If the first molten material with non-uniform temperature and viscosity is supplied to the extrusion head (300), problems may occur during the mixing process and the mechanical properties of the final product may deteriorate.

[0247] The discharge section is the tip portion of the first cylinder (111) and is a section that guides the homogenized first molten material to the first discharge port (116). The temperature of the discharge section is set to a range of approximately 255 to 260 degrees and maintains the highest temperature within the first cylinder (111). The technical reason for this temperature setting is that, as pressure drop and temperature drop occur during the process of the first molten material passing through the first discharge port (116), the temperature is raised in advance to ensure that the molten state is maintained while passing through the first inlet path (301).

[0248] The material of the first cylinder (111) is made of alloy steel with excellent heat resistance and wear resistance, and generally, special tool steel that has been nitrided is used. Since PET resin can be corrosive at high temperatures and the inner wall of the cylinder may wear out due to friction with the first screw (112), it is essential to select a material with high surface hardness and excellent corrosion resistance. In addition, the inner diameter of the first cylinder (111) is generally in the range of 40 mm to 90 mm, which is determined according to the production scale and product specifications. Although the extrusion rate per hour increases as the inner diameter increases, temperature control becomes difficult and equipment costs increase, so it is important to select an appropriate inner diameter.

[0249] Structure and technical reason of the first screw (112)

[0250] As shown in FIG. 4, the first screw (112) is a spiral structure that is rotatably installed inside the first cylinder (111) to transport the first resin forward. The first screw (112) consists of a central axis and a spiral wing (Flight) formed on its outer surface, and is driven by rotation by a motor.

[0251] The spiral blades of the first screw (112) are designed to have different pitches and depths depending on the section division of the first cylinder (111). In the feeding section, the spiral pitch is large and the blade depth is deep, allowing for the acceptance and transport of a large amount of solid PET resin. As it moves toward the compression section, the spiral pitch gradually decreases and the blade depth becomes shallow, so the density of the resin increases as it is compressed. In the melting section and the homogeneity section, the spiral pitch is maintained constant and the blade depth is also constant, allowing for the stable forward transport and mixing of the first molten material.

[0252] The rotational speed of the first screw (112) is controlled by the first pressure control unit (115) and generally operates in the range of 20 to 100 rotations per minute. As the rotational speed increases, the amount of the first resin extruded per unit time increases, the extrusion speed increases, and the first set pressure rises. However, if the rotational speed is excessively fast, the first resin does not secure sufficient residence time within the first cylinder (111), so the melting is incomplete, and excessive frictional heat is generated between the first screw (112) and the inner wall of the first cylinder (111), creating a risk of thermal decomposition of the PET resin. Conversely, if the rotational speed is excessively slow, productivity decreases, and the first resin is exposed to high temperatures for a long time within the first cylinder (111), creating a risk of thermal decomposition.

[0253] As shown in FIG. 4, the first resin is conveyed forward in the direction of the arrow by the rotation of the first screw (112). The technical principle of this conveying function is a combined action of the spiral blade pushing the resin as it rotates and the resin moving forward due to the frictional force between the resin and the inner wall of the first cylinder (111). The rotation direction of the first screw (112) is generally a right-hand thread direction, which is a structure in which the resin is conveyed forward when rotated clockwise.

[0254] The material of the first screw (112) is a special tool steel that has been nitrided, similar to the first cylinder (111), and has high surface hardness, making it resistant to wear and excellent corrosion resistance. In particular, the tip of the spiral blade of the first screw (112) is a part where wear occurs intensively because the gap with the inner wall of the first cylinder (111) is very narrow (generally 0.1 mm to 0.5 mm), so the hardening treatment is reinforced or a wear-resistant coating is applied.

[0255] The length of the first screw (112) is expressed as a ratio to the inner diameter of the first cylinder (111), and generally, the L / D ratio (Length to Diameter Ratio) is in the range of 20:1 to 30:1. The larger the L / D ratio, the longer the residence time of the first resin, allowing for sufficient melting and improved mixing effects; however, this results in a longer facility, reduced space efficiency, and increased pressure loss. Since PET resin has a high melting point and high viscosity, requiring a sufficient residence time, it is preferable to set the L / D ratio to approximately 24:1 to 28:1.

[0256] Structure and technical reason of the first heating unit (113)

[0257] As illustrated in FIG. 4, the first heating unit (113) is a heating device installed on the outer surface of the first cylinder (111) to melt the first resin. The first heating unit (113) is composed of a plurality of heating bands, and FIG. 4 shows four heating bands: heating band 1, heating band 2, heating band 3, and heating band 4. In actual implementation, four to eight heating bands may be used depending on the length and section division of the first cylinder (111).

[0258] Each heating band is a band-shaped electric heater that wraps around the outer surface of the first cylinder (111), and generally, a ceramic band heater or a mica band heater is used. Ceramic band heaters have excellent heat resistance, uniform heat distribution, and a long lifespan, making them suitable for high-temperature extrusion processes such as PET resin. The output of each heating band is generally in the range of 1 kW to 3 kW and is determined by the size of the first cylinder (111) and the required heating speed.

[0259] The technical reason for using multiple heating bands is to set different temperatures for each section of the first cylinder (111) and to control them independently. As previously explained, the temperature must rise stepwise for each section, with the supply section being 180 to 200 degrees, the compression section being 200 to 240 degrees, the melting section being 240 to 250 degrees, the homogeneity section being 250 to 255 degrees, and the discharge section being 255 to 260 degrees. If the entire first cylinder (111) is heated to a single temperature, the temperature will become excessively high in some sections and insufficient in others, making it impossible to achieve an optimal melting process.

[0260] As shown in FIG. 4, the heat generated in the first heating unit (113) is expressed in the form of waves. Each heating band receives power from the first temperature control unit (114) and generates heat, and the generated heat is transferred internally through the metal wall of the first cylinder (111) to heat the first resin. Heat transfer is mainly achieved by conduction, and the higher the thermal conductivity of the first cylinder (111), the higher the heating efficiency.

[0261] The heating band is fixed to the outer surface of the first cylinder (111) with a bolt or clamp, and the degree of contact between the heating band and the outer surface of the cylinder has a significant effect on heat transfer efficiency. If the degree of contact is low, an air layer is formed, increasing heat loss and making temperature control unstable; therefore, it is important to tighten the heating band with sufficient force to ensure a tight seal. Additionally, an insulating material can be additionally installed on the outer surface of the first cylinder (111) to minimize heat loss to the outside and improve energy efficiency.

[0262] Structure and technical reason of the first temperature control unit (114)

[0263] As illustrated in FIG. 4, the first temperature control unit (114) controls the temperature of the first heating unit (113) to control the melting temperature of the first resin to a range of 240 to 260 degrees. The first temperature control unit (114) consists of three main components: a temperature sensor, a PID controller, and a heater controller.

[0264] A temperature sensor is installed on the outer surface or inside of the first cylinder (111) to measure the actual temperature in real time. Generally, a K-type thermocouple or a platinum resistance thermometer (PT100) is used, and these operate stably in high-temperature environments and have high measurement accuracy. One temperature sensor is installed for each heating band to independently measure the temperature of the corresponding section. In FIG. 4, the temperature sensor is indicated by a circular symbol and labeled "Temperature Sensor".

[0265] A PID controller is a device that generates a control signal by comparing the actual temperature measured by a temperature sensor with the set temperature. PID stands for Proportional, Integral, and Derivative, and it precisely controls the temperature by using a combination of these three control actions. Proportional control adjusts the heater output in proportion to the difference between the set temperature and the actual temperature, integral control corrects accumulated temperature errors, and derivative control prevents excessive temperature rise or fall by considering the rate of temperature change. The parameters of the PID controller (proportional gain, integral time, derivative time) must be tuned to match the thermal capacity of the first cylinder (111) and the output characteristics of the heating band, and a properly tuned PID controller can control the temperature with a precision of within ±2 degrees.

[0266] A heater controller is a device that regulates the power supplied to the heating band according to the control signal received from the PID controller. Generally, SSRs (Solid State Relays) or thyristors are used, and these utilize semiconductor switching elements to rapidly turn AC power on / off or regulate power through phase control. In Figure 4, the heater controller is labeled "Heater Control," and the control signal is connected by an arrow.

[0267] The operation process of the first temperature control unit (114) is as follows. First, a temperature sensor measures the temperature of a specific section of the first cylinder (111) and transmits it to a PID controller. The PID controller calculates a temperature error by comparing the measured temperature with a set temperature (e.g., 250 degrees) and generates a control signal according to a PID algorithm. If the measured temperature is lower than the set temperature, it generates a control signal to increase the heater output, and if the measured temperature is higher than the set temperature, it generates a control signal to decrease the heater output. The heater controller adjusts the power supplied to the heating band according to this control signal to converge the temperature to the set value.

[0268] A graph of "internal cylinder temperature distribution" is shown in the upper right corner of FIG. 4. This graph shows the temperature change according to the position from the inlet to the outlet of the first cylinder (111). Starting at 180 degrees at the inlet, it gradually increases to 200 degrees, 240 degrees, 250 degrees, and 255 degrees as it advances along the cylinder, and reaches 260 degrees at the outlet. This stepwise temperature increase is possible because the first temperature control unit (114) controls each heating band independently.

[0269] The critical significance of controlling the melting temperature of the first resin to a range of 240 to 260 degrees is as follows. Since the melting point of PET resin is approximately 248 degrees, heating below 240 degrees results in the resin not completely melting and becoming semi-solid; this causes clogging during the extrusion process and leaves unmelted particles inside the product, thereby reducing mechanical strength. Experimental results show that at 240 degrees, about 90% of the PET resin melts, making extrusion possible, but complete melting does not occur; a melting rate of over 95% can only be achieved at 245 degrees or higher. Therefore, 240 degrees holds critical significance as the minimum temperature required to extrude PET resin.

[0270] Conversely, heating above 260 degrees initiates the thermal decomposition of PET resin. The thermal decomposition initiation temperature for PET is approximately 265 to 270 degrees; above this temperature, molecular chains are broken, leading to a decrease in molecular weight and a rapid decline in mechanical properties. Furthermore, volatile substances such as acetaldehyde are generated during the thermal decomposition process, causing an odor in the product and the formation of internal bubbles, which degrades appearance quality. Experimental results show that thermal decomposition of PET resin is minimal up to 260 degrees and does not affect product quality; however, above 265 degrees, thermal decomposition accelerates, causing a sharp increase in the product defect rate. Therefore, 260 degrees holds critical significance as the maximum temperature at which extrusion can be performed while maintaining the quality of the PET resin.

[0271] In conclusion, the range of 240 to 260 degrees is the optimal temperature range that completely melts the PET resin to secure the fluidity required for extrusion, while preventing thermal decomposition and maintaining the mechanical properties and appearance quality of the product to the maximum extent. Within this range, the most desirable temperature is 248 to 255 degrees, at which the PET resin can be stably extruded while maintaining appropriate viscosity.

[0272] Structure and technical reason of the first pressure regulating unit (115)

[0273] As illustrated in FIG. 4, the first pressure control unit (115) controls the rotational speed of the first screw (112) to control the first set pressure so that the first set pressure is maintained higher than the second set pressure, thereby causing the first molten material to push out and merge with the second molten material. The first pressure control unit (115) consists of three main components: a pressure sensor, a pressure controller, and a screw drive motor.

[0274] A pressure sensor is installed on the wall of the first cylinder (111) near the first discharge port (116) to measure the pressure of the first molten material in real time. Generally, a high-temperature pressure transducer is used, which operates stably even in high-temperature environments of 260 degrees or higher and can measure pressure with high accuracy. The pressure sensor detects pressure using a diaphragm method that is in direct contact with the first molten material, and the detected pressure is converted into an electrical signal and transmitted to a pressure controller. In FIG. 4, the pressure sensor is indicated by a circular symbol and is labeled "Pressure Sensor".

[0275] The pressure controller is a device that compares the first set pressure (P1) and the second set pressure (P2) measured by the pressure sensor and generates a control signal to maintain P1 higher than P2. The pressure controller box in FIG. 4 displays text such as "Pressure setting: P1 > P2" and "Second molten material push" to clearly indicate the core function of the first pressure control unit (115). The pressure controller receives information on the second set pressure from the pressure sensing unit (306) of the extrusion head (300) and controls the first set pressure to maintain it higher than the second set pressure by a certain ratio (generally 1.2 to 2 times).

[0276] The screw drive motor is a power source that rotates the first screw (112), and generally, an AC servo motor or an inverter-controlled induction motor is used. In FIG. 4, the screw drive motor is shown as a circular symbol marked "M" and labeled "screw drive". The screw drive motor is connected to the first screw (112) through a reduction gear, and the reduction ratio is generally about 10:1 to 20:1. The rotational speed of the motor is controlled according to a control signal from a pressure controller, and the faster the rotational speed, the greater the extrusion amount per unit time, and the first set pressure rises.

[0277] The operation process of the first pressure control unit (115) is as follows. First, a pressure sensor measures a first set pressure near the first discharge port (116) and transmits it to a pressure controller. At the same time, the pressure controller receives second set pressure information from the pressure detection unit (306) of the extrusion head (300). The pressure controller calculates the ratio of P1 to P2 and compares it with a target ratio (e.g., P1 = 1.5 × P2). If the P1 / P2 ratio is lower than the target, it generates a control signal to increase the rotational speed of the first screw (112), and if the P1 / P2 ratio is higher than the target, it generates a control signal to decrease the rotational speed. The screw drive motor adjusts the rotational speed according to this control signal to converge the pressure ratio to the target value.

[0278] In Figure 4, the feedback path from the pressure sensor to the pressure controller is indicated by a dotted arrow and labeled "Feedback." This indicates that a closed-loop control system is configured to maintain the pressure stably. Additionally, the control path from the pressure controller to the screw drive motor is indicated by an arrow and labeled "Control Signal."

[0279] The technical reason and critical significance of maintaining the first set pressure higher than the second set pressure are as follows. When the first molten material and the second molten material merge in the extrusion head (300), there is a difference in melting point of more than 100 degrees between the two molten materials. The first molten material with a high melting point (PET, approximately 250 degrees) has high viscosity and low fluidity, whereas the second molten material with a low melting point (adhesive, approximately 120 degrees) has low viscosity and high fluidity. If the first set pressure and the second set pressure are the same, the second molten material with low viscosity may backflow the first molten material within the extrusion head (300), or the second molten material may become dominant at the merging point, preventing proper bonding with the first molten material.

[0280] In order to overcome the difficulty of extrusion caused by the difference in melting points, the first set pressure is maintained higher than the second set pressure, thereby causing the high-viscosity first molten material to physically push out the low-viscosity second molten material and merge.

[0281] Experimental results show that when the P1 / P2 ratio is less than 1.2, the pressure of the first molten material is insufficient, making the merging with the second molten material unstable, and the second molten material is supplied excessively at the merging point, causing the adhesive layer of the final product to become excessively thick or uneven. When the P1 / P2 ratio exceeds 2.0, the pressure of the first molten material is excessively high, compressing the second molten material excessively, and the supply of the second molten material at the merging point becomes unstable, and in severe cases, the second molten material flows back into the second inlet (302). Therefore, it is critically important to maintain the P1 / P2 ratio in the range of 1.2 to 2.0, and the most desirable ratio is in the range of 1.4 to 1.6.

[0282] A "pressure relationship" diagram is shown at the bottom of FIG. 4. This diagram indicates the first set pressure (P1) as high pressure and the second set pressure (P2) as low pressure, and clearly shows the relationship P1 > P2 with an inequality sign. Additionally, the explanation "the first molten material pushes out the second molten material" is added to clarify the technical effect of the pressure relationship.

[0283] A specific embodiment of a method for controlling pressure by adjusting the rotational speed of the first screw (112) is as follows. The basic rotational speed of the first screw (112) is set to a range of 40 to 60 revolutions per minute, which is a speed that allows the PET resin to have a residence time of about 3 to 5 minutes in the first cylinder (111). This residence time is sufficient for the PET resin to be completely melted and homogenized. The pressure controller compares the P1 value measured from the pressure sensor with the P2 value received from the extrusion head (300) and fine-tunes the screw rotational speed so that the P1 / P2 ratio reaches a target value (e.g., 1.5). For example, if the P1 / P2 ratio is measured as 1.3, which is lower than the target value of 1.5, the screw rotational speed is increased by 2 to 5 revolutions per minute to increase the extrusion amount and raise P1. Conversely, if the P1 / P2 ratio is measured as 1.7, it is higher than the target value, so the screw rotation speed is reduced by 2 to 5 revolutions per minute to lower P1.

[0284] Structure and technical reason of the first discharge port (116)

[0285] As shown in FIG. 4, the first discharge port (116) is formed at the tip of the first cylinder (111) to discharge the first molten material. The first discharge port (116) is manufactured in the shape of a nozzle having a diameter smaller than the inner diameter of the first cylinder (111), through which the first molten material is discharged into the first inlet (301) of the extrusion head (300) in a high-pressure (P1) state.

[0286] The inner diameter of the first discharge port (116) is generally in the range of 50% to 70% of the inner diameter of the first cylinder (111). For example, if the inner diameter of the first cylinder (111) is 60 mm, the inner diameter of the first discharge port (116) is approximately 30 mm to 42 mm. The technical reason for making the inner diameter of the first discharge port (116) smaller than that of the first cylinder (111) is to increase the flow velocity of the first molten material and concentrate the pressure. According to the Bernoulli principle of fluid dynamics, if the cross-sectional area of ​​the flow path decreases, the flow velocity increases and the pressure rises. Since the flow velocity of the first molten material increases as it passes through the first discharge port (116), it has high kinetic energy when entering the extrusion head (300), allowing it to effectively push out the second molten material.

[0287] The length of the first discharge port (116) is about 1 to 3 times the inner diameter, which is a length sufficient to form a stable flow as the first molten material passes through the discharge port. If the length of the discharge port is too short, the flow of the first molten material becomes unstable and pulsation occurs, and if the length of the discharge port is too long, pressure loss increases excessively and the extrusion efficiency decreases.

[0288] The shape of the first discharge port (116) has a tapered structure that gradually narrows from the inner diameter of the first cylinder (111) to the inner diameter of the discharge port. The taper angle is generally in the range of 15 to 30 degrees, which is intended to minimize pressure loss and ensure flow stability by allowing the first molten material to pass smoothly through the narrowing section without a sudden change in cross-section.

[0289] In FIG. 4, the first molten material discharged from the first discharge port (116) is indicated by an arrow and labeled "First molten material" and "P1 (high pressure)". This indicates that the first molten material is supplied to the extrusion head (300) in a high-pressure state. The first molten material passing through the first discharge port (116) enters the first inlet passage (301) of the extrusion head (300), where it joins with the second molten material rising from the second inlet passage (302).

[0290] Comprehensive features and operating principles of the first extrusion part (110)

[0291] In the bottom right of Fig. 4, a "Features of the First Extrusion Part" box is shown, and the following three key features are summarized.

[0292] First, the melting temperature is set to a range of 240 to 260 degrees to achieve optimal melting of the PET resin. This temperature range allows the PET resin to be completely melted to secure the fluidity required for extrusion, while preventing thermal decomposition and maintaining the mechanical properties of the product to the maximum extent.

[0293] Second, the relationship P1 > P2 is maintained through pressure control. By maintaining the first set pressure higher than the second set pressure, the first molten material with a high melting point and high viscosity can push out the second molten material with a low melting point and low viscosity, allowing them to properly merge at the extrusion head (300).

[0294] Third, the extrusion amount and pressure are controlled by adjusting the rotational speed of the first screw (112). When the rotational speed is increased, the extrusion amount per unit time increases, causing the pressure to rise, and when the rotational speed is decreased, the extrusion amount decreases, causing the pressure to fall. Through this rotational speed control, the first set pressure can be precisely adjusted to a desired level.

[0295] The overall operation process of the first extrusion section (110) is summarized as follows. Solid PET resin pellets supplied from the first hopper (100) are fed into the inlet of the first cylinder (111) and received in the supply section. As the first screw (112) rotates, the PET resin is transported to the compression section, and during this process, the temperature of the resin gradually rises due to external heating from the first heating section (113) and frictional heat caused by the rotation of the first screw (112). In the compression section, the PET resin is compressed, increasing its density and removing air between the pellets. Upon reaching the melting section, the PET resin is heated to over 248 degrees and completely melted, and as it passes through the homogenization section, its temperature and viscosity are homogenized. The first molten material that has passed through the discharge section is discharged to the extrusion head (300) in a high-pressure state through the first discharge port (116). In this entire process, the first temperature control unit (114) precisely controls the temperature of each section to a range of 240 to 260 degrees, and the first pressure control unit (115) controls the rotational speed of the first screw (112) so that the first set pressure is maintained higher than the second set pressure.

[0296] Structure and technical reason of the second cylinder (211)

[0297] As illustrated in FIGS. 1 and 5, the second extrusion unit (210) includes a second cylinder (211) that receives adhesive supplied from the second hopper (200). The second cylinder (211) has a cylindrical structure similar to the first cylinder (111), but has a differentiated characteristic in that the material being processed is adhesive.

[0298] As illustrated in detail in FIG. 5, the second cylinder (211) is divided into five sections along the longitudinal direction, such as a supply section, a compression section, a melting section, a homogenization section, and a discharge section, just like the first cylinder (111). However, the temperature settings and functions of each section are optimized to suit the characteristics of the adhesive.

[0299] The supply section is the inlet part of the second cylinder (211) and receives adhesive supplied from the second hopper (200). The adhesive used in the present invention is generally a hot melt adhesive, which exists in the form of solid pellets, granules, or powder at room temperature. The temperature of the supply section is set to a range of about 60 to 80 degrees, which is a temperature that slightly softens the adhesive to improve fluidity but does not completely melt it. Since the melting point of the adhesive is in the range of 100 to 140 degrees, the temperature of the supply section is sufficiently lower than the melting point so that the adhesive can be smoothly transported by the second screw (212) while maintaining a solid state.

[0300] The compression section is located behind the supply section, and the pitch of the second screw (212) gradually decreases to apply compressive force to the adhesive. The technical reason for the compression section is to remove air between the adhesive particles and increase density to increase the efficiency of the subsequent melting process. The temperature of the compression section is set to a range of about 80 to 100 degrees, which is a temperature at which the adhesive softens and transitions into a deformable state but is not yet completely melted. Since the adhesive undergoes deformation by compression more easily than PET resin, the effect of increasing density in the compression section is more pronounced.

[0301] The melting section is located behind the compression section and is a section where the adhesive is completely melted and changes into a liquid state. The temperature of the melting section is set to a range of approximately 100 to 130 degrees, which corresponds to the middle of the lower limit of the melting point of the adhesive, which is 100 to 140 degrees. In the melting section, the second heating section (213) intensively heats the outer surface of the second cylinder (211), and shear heat is also generated by the rotation of the second screw (212) to accelerate the melting of the adhesive. The length of the melting section is set to approximately 30% to 40% of the total length of the second cylinder (211), so as to provide a residence time sufficient for the adhesive to be completely melted.

[0302] The homogeneous section is located behind the melting section and is a section that makes the temperature and viscosity of the molten adhesive uniform. The temperature of the homogeneous section is set to a range of about 120 to 140 degrees, and by maintaining a temperature slightly higher than that of the melting section, the viscosity of the second molten material is lowered and its fluidity is improved. Since the adhesive has lower viscosity and higher fluidity than PET resin, the mixing action in the homogeneous section is carried out more efficiently. The technical importance of the homogeneous section lies in maintaining the temperature and viscosity of the second molten material uniformly so that it can stably merge with the first molten material at the extrusion head (300).

[0303] The discharge section is the leading edge of the second cylinder (211) and is a section that guides the homogenized second molten material to the second discharge port (216). The temperature of the discharge section is set to a range of approximately 130 to 150 degrees and maintains the highest temperature within the second cylinder (211). The technical reason for this temperature setting is to ensure that the second molten material remains in a molten state while passing through the second discharge port (216) and the second inlet path (302). However, if the temperature is excessively high, the viscosity of the adhesive becomes excessively low, causing a problem where it flows out of the extrusion head (300) prematurely; therefore, it is important to control the temperature so that it does not exceed 150 degrees.

[0304] The main difference between the second cylinder (211) and the first cylinder (111) lies in the temperature range. As clearly shown in the "First Extrusion Section vs. Second Extrusion Section" comparison table illustrated in the upper right corner of FIG. 5, the melting temperature of the first extrusion section (110) is 240 to 260 degrees, whereas the melting temperature of the second extrusion section (210) is 100 to 150 degrees, resulting in a temperature difference of approximately 100 degrees or more. This temperature difference reflects the difference in melting points between the PET resin and the adhesive, and is intended to provide extrusion conditions optimized for each material.

[0305] The material of the second cylinder (211) is the same as that of the first cylinder (111), which is a special tool steel that has been nitrided, but the operating temperature is lower, so there is less thermal stress and a longer lifespan. The inner diameter of the second cylinder (211) is generally in the range of 30 mm to 70 mm, and is often designed to be slightly smaller than the first cylinder (111). This is because the amount of adhesive supplied is less than that of PET resin, and the thickness of the adhesive layer in the final product is thinner than that of the PET layer.

[0306] Structure and technical reason of the second screw (212)

[0307] As shown in FIG. 5, the second screw (212) is a spiral structure that is rotatably installed inside the second cylinder (211) to transport adhesive forward. The second screw (212) has basically the same structure as the first screw (112), but some design parameters are set differently in that the material being processed is adhesive.

[0308] The spiral blades of the second screw (212) are designed to have different pitches and depths depending on the section division of the second cylinder (211). In the supply section, the spiral pitch is large and the blade depth is deep, allowing for the acceptance and transport of a large amount of adhesive. As it moves toward the compression section, the spiral pitch gradually decreases and the blade depth becomes shallow, so the density of the adhesive increases as it is compressed. In the melting section and the homogeneity section, the spiral pitch is maintained constant and the blade depth is also constant, allowing for the stable transport and mixing of the molten second molten material forward.

[0309] As shown in FIG. 5, the adhesive is conveyed forward in the direction of the orange arrow by the rotation of the second screw (212). Unlike the arrow of the first extrusion section (110), which is indicated in red, the arrow of the second extrusion section (210) is indicated in orange, visually distinguishing the two extrusion sections. The technical principle of this conveying function is the same as that of the first screw (112), a combined action of the rotation of the spiral blade and the frictional force between the adhesive and the inner wall of the second cylinder (211).

[0310] The rotational speed of the second screw (212) is controlled by the second pressure control unit (215) and generally operates in the range of 30 to 120 rotations per minute. This is a slightly higher range than the rotational speed of the first screw (112), which is 20 to 100 rotations per minute. The reason for this is that the viscosity of the adhesive is lower than that of the PET resin, so the amount extruded at the same rotational speed is large, and it is to secure an appropriate amount of extrusion while maintaining the second set pressure lower than the first set pressure.

[0311] The most important technical feature of the rotational speed control of the second screw (212) is that it is adjusted in correspondence with the extrusion speed of the first resin. This is clearly indicated by the text "P1 corresponding control" and "P1-P2 balance" in the box of the second pressure control unit (215) shown on the bottom left of FIG. 5. When the extrusion speed of the first extrusion unit (110) changes, the first set pressure (P1) changes, and the second pressure control unit (215) detects this change in P1 and automatically adjusts the rotational speed of the second screw (212) to adjust the second set pressure (P2) to match P1. Through this, an appropriate pressure ratio between P1 and P2 is always maintained, enabling stable mixing at the extrusion head (300).

[0312] Structure and technical reason of the second heating unit (213)

[0313] As shown in FIG. 5, the second heating unit (213) is a heating device installed on the outer surface of the second cylinder (211) to melt the adhesive. The second heating unit (213) is composed of a plurality of heating bands, similar to the first heating unit (113), and four heating bands, heating band 1, heating band 2, heating band 3, and heating band 4, are shown in FIG. 5.

[0314] The structure of the second heating unit (213) is basically the same as that of the first heating unit (113), but differs in that the operating temperature range is lower. Each heating band is made of a ceramic band heater or a mica band heater, and the output is generally set lower than that of the first heating unit (113), in the range of 0.5 kW to 2 kW. This is because the amount of heat required to melt the adhesive is less than that of PET resin.

[0315] As shown in FIG. 5, the heat generated in the second heating unit (213) is represented in the form of an orange wave, which is visually distinguished from the red wave of the first heating unit (113). This intuitively indicates that the operating temperature of the second heating unit (213) is lower than that of the first heating unit (113).

[0316] The technical reason for using multiple heating bands is to set different temperatures for each section of the second cylinder (211) and to control them independently, just like the first heating section (113). The temperature must rise stepwise for each section, with the supply section being 60 to 80 degrees, the compression section being 80 to 100 degrees, the melting section being 100 to 130 degrees, the homogeneity section being 120 to 140 degrees, and the discharge section being 130 to 150 degrees.

[0317] A particularly important point in the temperature control of the second heating unit (213) is to ensure that the adhesive is not overheated. If the adhesive exceeds 150 degrees, some components may decompose or yellow, which may degrade its adhesive performance. In addition, excessive temperature can cause the viscosity of the adhesive to drop too low, leading to the problem of it flowing out of the extrusion head (300) prematurely. Therefore, the temperature of the second heating unit (213) must be precisely controlled within a range that completely melts the adhesive to ensure proper fluidity, while preventing quality degradation due to overheating.

[0318] Structure and technical reason of the second temperature control unit (214)

[0319] As illustrated in FIG. 5, the second temperature control unit (214) controls the temperature of the second heating unit (213) to control the melting temperature of the adhesive to a range of 100 to 150 degrees. The second temperature control unit (214) is composed of three main components, such as a temperature sensor, a PID controller, and a heater controller, just like the first temperature control unit (114).

[0320] A temperature sensor is installed on the outer surface or inside of the second cylinder (211) to measure the actual temperature in real time. Since the second temperature control unit (214) measures a relatively low temperature range, various temperature sensors such as PT100 or thermistor, as well as K-type thermocouples, can be used. In FIG. 5, the temperature sensor is indicated by a circular symbol.

[0321] The PID controller generates a control signal by comparing the actual temperature measured by the temperature sensor with the set temperature. The PID controller of the second temperature control unit (214) operates on the same principle as the first temperature control unit (114), but the control parameters are optimized to match the thermal characteristics of the adhesive. Since the adhesive has a lower heat capacity than PET resin and responds quickly to temperature changes, it is desirable to set the response speed of the PID controller to be fast.

[0322] The heater controller regulates the power supplied to the heating band according to the control signal received from the PID controller. Since the heater controller of the second temperature control unit (214) operates in a lower output range than the first temperature control unit (114), power loss is low and energy efficiency is high.

[0323] The critical significance of controlling the melting temperature of the adhesive to a range of 100 to 150 degrees is as follows. Since the adhesive used in this invention has a melting point in the range of 100 to 140 degrees, heating it below 100 degrees results in insufficient melting, leading to poor fluidity and making extrusion impossible. Experimental results show that at 95 degrees, the adhesive melts only partially and exists in a semi-solid state, which causes clogging during the extrusion process. Only when reaching 100 degrees can more than 90% of the adhesive melt to secure the fluidity required for extrusion. Therefore, 100 degrees holds critical significance as the minimum temperature for extruding the adhesive.

[0324] Conversely, heating to a temperature exceeding 150 degrees causes several problems. First, the viscosity of the adhesive becomes excessively low, intensifying the phenomenon of it flowing down before it joins the first molten material at the extrusion head (300). Since the viscosity of the adhesive decreases exponentially with temperature, exceeding 150 degrees results in excessively low viscosity, making control difficult. Second, some adhesive components undergo thermal decomposition or yellowing, which degrades the appearance quality of the product and reduces adhesive strength. Hot melt adhesives are generally based on polymers such as EVA (Ethylene Vinyl Acetate), polyamide, and polyester, which begin to undergo thermal decomposition at temperatures above 160 degrees. Experimental results show that thermal decomposition of the adhesive is minimal up to 150 degrees and does not affect product quality, but yellowing is observed above 155 degrees, and adhesive strength begins to decrease above 160 degrees. Therefore, 150 degrees has critical significance as the maximum temperature at which extrusion can be performed while maintaining the quality of the adhesive.

[0325] As shown in the comparison table of FIG. 5, the melting temperature of the first extrusion section (110) is 240 to 260 degrees (indicated in red), whereas the melting temperature of the second extrusion section (210) is 100 to 150 degrees (indicated in orange), showing a clear difference. This temperature difference reflects the difference in physical properties between the PET resin and the adhesive, and is intended to extrude each material under optimal conditions.

[0326] In conclusion, the range of 100 to 150 degrees is the optimal temperature range that completely melts the adhesive to secure the fluidity required for extrusion, prevents thermal decomposition, and maintains a viscosity that allows for joining with the first molten material at the extrusion head (300). Within this range, the most desirable temperature is 120 to 140 degrees, at which the adhesive can be stably extruded while maintaining appropriate viscosity.

[0327] Structure and technical reason of the second pressure regulating unit (215)

[0328] As illustrated in FIG. 5, the second pressure control unit (215) controls the rotational speed of the second screw (212) to control the second set pressure, and controls the second set pressure in correspondence with the extrusion speed of the first resin so that the second set pressure is balanced with the first set pressure. This is the most key feature that distinguishes the second pressure control unit (215) from the first pressure control unit (115).

[0329] The second pressure control unit (215) consists of three main components: a pressure sensor, a pressure controller, and a screw drive motor, which is identical to the first pressure control unit (115). However, there is a decisive difference in the operation method of the pressure controller.

[0330] A pressure sensor is installed on the wall of the second cylinder (211) near the second discharge port (216) to measure the pressure (P2) of the second molten material in real time. The measured P2 value is transmitted to a pressure controller.

[0331] The pressure controller is a core component of the second pressure control unit (215) and receives information on the first set pressure (P1) from the first extrusion unit (110), and generates a control signal to ensure that P1 and P2 are properly balanced by comparing it with the measured second set pressure (P2). The pressure controller box in FIG. 5 displays text such as "P1 information input," "P1 corresponding control," "P1-P2 balance," and "extrusion speed linkage," clearly indicating the core functions of the second pressure control unit (215). Additionally, at the bottom of FIG. 5, "P1 information input" is highlighted in a red dotted box, and an arrow reading "← P1 information input" is displayed to indicate that information is received from the first extrusion unit (110).

[0332] The technical reason and critical significance of adjusting the second set pressure in response to the extrusion speed of the first resin are as follows. In the extrusion process, the extrusion speed of the first extrusion unit (110) can change depending on various factors such as production speed, product specifications, and raw material characteristics. When the extrusion speed of the first extrusion unit (110) increases, the first set pressure (P1) rises, and when the extrusion speed decreases, P1 falls. If the second pressure control unit (215) does not respond to the change in P1 and maintains the second set pressure (P2) at a constant level, the pressure ratio between P1 and P2 changes, and the merging at the extrusion head (300) becomes unstable.

[0333] For example, let's assume that the rotational speed of the first screw (112) is increased to increase production speed, causing P1 to rise from 10 bar to 15 bar. If P2 is maintained at 8 bar, the P1 / P2 ratio increases from 1.25 to 1.88, deviating significantly from the target ratio of 1.5. In this case, the first molten material excessively compresses the second molten material, causing the supply of the second molten material at the junction to become unstable and the adhesive layer of the final product to become uneven. Conversely, if the rotational speed of the first screw (112) is reduced, causing P1 to drop from 10 bar to 7 bar while P2 is maintained at 8 bar, the P1 / P2 ratio decreases from 1.25 to 0.88, resulting in a reversal where P1 becomes lower than P2. In this case, the second molten material may flow back against the first molten material, or the second molten material may become dominant at the junction, making it impossible to form a proper composite extrusion.

[0334] Accordingly, the second pressure regulating unit (215) detects changes in the extrusion speed of the first extrusion unit (110) in real time and adjusts P2 by automatically adjusting the rotational speed of the second screw (212) in response. In the above example, when P1 increases from 10 bar to 15 bar, the second pressure regulating unit (215) increases P2 from 8 bar to about 10 bar to 12 bar to maintain the P1 / P2 ratio at around 1.5. When P1 decreases from 10 bar to 7 bar, P2 decreases from 8 bar to about 4.5 bar to 5.5 bar to maintain the P1 / P2 ratio at around 1.5.

[0335] At the bottom of FIG. 5, a diagram of the "P1-P2 balance control mechanism" is shown, which explains the operating principle of the second pressure control unit (215) step by step. The first step is "change in the extrusion speed of the first extrusion unit (change in P1)," where P1 changes when the operating conditions of the first extrusion unit (110) change. The second step is "input of P1 information and automatic adjustment of P2 by the second pressure control unit," where the second pressure control unit (215) detects the change in P1 and automatically adjusts P2. The third step is "maintaining the balance between P1 and P2, stable confluence in the extrusion head, and production of products of consistent quality," where the balance between P1 and P2 is maintained, ultimately enabling stable product production. On the right side of this diagram, the text "Key Function!" is highlighted in red, clearly indicating that the P1 corresponding control function of the second pressure control unit (215) is the core of the present invention.

[0336] The specific implementation method of the second pressure control unit (215) is as follows. The pressure controller of the second pressure control unit (215) receives P1 information in real time from the first pressure control unit (115) of the first extrusion unit (110) or the pressure sensing unit (306) of the extrusion head (300). Generally, the P1 value is updated at intervals of 0.1 to 1 second, which is an update speed sufficient to respond quickly to dynamic changes in the extrusion process. The pressure controller calculates the P1 / P2 ratio using the received P1 value and the P2 value measured from the pressure sensor. The target ratio is generally set to a range of 1.4 to 1.6, and the most desirable value is 1.5.

[0337] If the calculated P1 / P2 ratio is higher than the target ratio (e.g., 1.7), it means that P1 is excessively high compared to P2, so the pressure controller generates a control signal to increase the rotational speed of the second screw (212). The amount of the rotational speed increase is determined in proportion to the ratio error and is generally adjusted in the range of 5 to 20 revolutions per minute. Conversely, if the P1 / P2 ratio is lower than the target ratio (e.g., 1.3), the pressure controller generates a control signal to decrease the rotational speed of the second screw (212).

[0338] The screw drive motor adjusts the rotational speed according to a control signal from the pressure controller. The basic rotational speed of the second screw (212) is set to a range of 50 to 80 revolutions per minute, which is a speed that allows the adhesive to have a residence time of about 2 to 4 minutes in the second cylinder (211). This residence time is sufficient for the adhesive to be completely melted and homogenized. Depending on the change in P1, the rotational speed is dynamically adjusted in a range of 30 to 120 revolutions per minute, thereby allowing P2 to change in accordance with P1 so that an appropriate pressure ratio is always maintained.

[0339] As shown in the comparison table of FIG. 5, the pressure control of the first extrusion unit (110) is described as "P1 > P2" and "independent control," whereas the pressure control of the second extrusion unit (210) is described as "P1 corresponding control," "P1-P2 balance," and "extrusion speed linkage," clearly indicating that the pressure control methods of the two extrusion units are fundamentally different. The first extrusion unit (110) plays the role of independently generating high pressure to push out the second molten material, whereas the second extrusion unit (210) plays the role of maintaining balance by adjusting its own pressure in response to the pressure change of the first extrusion unit (110). This differentiated pressure control strategy is a key technology for stably composite extruding two materials with a melting point difference of more than 100 degrees.

[0340] Structure and technical reason of the second discharge port (216)

[0341] As shown in FIG. 5, the second discharge port (216) is formed at the tip of the second cylinder (211) to discharge the second molten material. The second discharge port (216) is manufactured in a nozzle shape similar to the first discharge port (116) and has a diameter smaller than the inner diameter of the second cylinder (211).

[0342] The inner diameter of the second discharge port (216) is generally in the range of 50% to 70% of the inner diameter of the second cylinder (211). For example, if the inner diameter of the second cylinder (211) is 50mm, the inner diameter of the second discharge port (216) is approximately 25mm to 35mm. The technical reason for making the inner diameter of the second discharge port (216) smaller than that of the second cylinder (211) is to increase the flow velocity of the second molten material and concentrate the pressure, just like the first discharge port (116).

[0343] The length of the second discharge port (216) is approximately 1 to 3 times the inner diameter, and the shape has a tapered structure. The taper angle is generally in the range of 15 to 30 degrees. This design is intended to minimize pressure loss and ensure flow stability by allowing the second molten material to pass smoothly through the contraction section without abrupt changes in cross-section.

[0344] In FIG. 5, the second molten material discharged from the second discharge port (216) is indicated by an arrow and labeled "second molten material" and "P2 (low pressure)". This indicates that the second molten material is supplied to the extrusion head (300) at a lower pressure than the first molten material. The second molten material passing through the second discharge port (216) enters the second inlet (302) of the extrusion head (300), where it rises from the bottom upward and joins with the first molten material descending from the first inlet (301).

[0345] Comprehensive characteristics of the second extrusion section (210) and comparison with the first extrusion section (110)

[0346] In the upper right corner of Fig. 5, a comparison table of "First Extrusion Section vs. Second Extrusion Section" is illustrated in detail. This comparison table compares the two extrusion sections based on five items: raw material, melting temperature, extrusion pressure, pressure control, and main role, and is configured to allow for a quick grasp of the core technical features of the present invention.

[0347] First, in terms of raw materials, the first extrusion unit (110) processes PET resin and the second extrusion unit (210) processes adhesive. This indicates that the present invention adopts a dual extrusion method in which two different materials are extruded independently and then combined.

[0348] Second, in terms of melting temperature, the first extrusion section (110) is 240 to 260 degrees (highlighted in red) and the second extrusion section (210) is 100 to 150 degrees (highlighted in orange). This temperature difference of more than 100 degrees reflects the difference in melting points between the PET resin and the adhesive, and is a key setting for extruding each material under optimal conditions.

[0349] Third, in terms of extrusion pressure, the first extrusion section (110) generates P1 (high pressure) and the second extrusion section (210) generates P2 (low pressure). The fact that P1 is higher than P2 is a key strategy to cause the first molten material with a high melting point and high viscosity to push out and merge with the second molten material with a low melting point and low viscosity.

[0350] Fourth, in terms of pressure control, the first extrusion unit (110) is controlled independently to maintain the relationship "P1 > P2", whereas the second extrusion unit (210) is controlled by "P1 corresponding control", "P1-P2 balance", and "extrusion speed linkage" (highlighted in orange). This is a key feature of the second pressure control unit (215) to maintain pressure balance by automatically responding to changes in the extrusion speed of the first extrusion unit (110).

[0351] Fifth, in terms of primary roles, the first extrusion unit (110) performs the roles of "high pressure generation" and "second molten material expulsion," and the second extrusion unit (210) performs the roles of "pressure balance," "P1 tracking," and "stable confluence." This indicates that the two extrusion units operate complementarily to achieve stable composite extrusion.

[0352] At the bottom of the comparison table, the text "Key: P1 corresponding control of the second pressure regulating unit" is highlighted in red text, clearly indicating that the most key technical feature of the present invention is the P1 corresponding control function of the second pressure regulating unit (215).

[0353] The overall operation process of the second extrusion section (210) is summarized as follows. The solid adhesive supplied from the second hopper (200) is fed into the inlet of the second cylinder (211) and received in the supply section. As the second screw (212) rotates, the adhesive is transported to the compression section, and during this process, the temperature of the adhesive gradually rises due to external heating from the second heating section (213) and frictional heat caused by the rotation of the second screw (212). In the compression section, the adhesive is compressed, increasing its density and removing air between the particles. Upon reaching the melting section, the adhesive is heated to over 100 degrees and completely melted, and as it passes through the homogenization section, its temperature and viscosity are homogenized. The second molten material that has passed through the discharge section is discharged to the extrusion head (300) through the second discharge port (216).

[0354] Throughout this entire process, the second temperature control unit (214) precisely controls the temperature of each section to a range of 100 to 150 degrees, and the second pressure control unit (215) dynamically adjusts the rotational speed of the second screw (212) based on the P1 information received from the first extrusion unit (110) to adjust P2 to match P1. Through this, an appropriate pressure ratio between P1 and P2 is always maintained, so that the first molten material and the second molten material can stably merge in the extrusion head (300) to form an integrated composite extrusion.

[0355] Overall configuration and technical significance of the extrusion head (300)

[0356] As illustrated in FIGS. 1 and 6, the extrusion head (300) is a core component of the present invention and performs the role of stably combining a first molten material and a second molten material having a melting point difference of 100 degrees or more to form an integrated composite extrusion. The extrusion head (300) is composed of a first inlet (301), a second inlet (302), a joining section (303), a joining point control section (304), a temperature maintenance section (305), a pressure sensing section (306), and a discharge nozzle (307).

[0357] The overall operating principle of the extrusion head (300) is as follows. A first molten material (PET resin) at approximately 248 degrees, discharged from the first discharge port (116) of the first extrusion section (110), flows in from the top downward through the first inlet (301), and a second molten material (adhesive) at approximately 120 degrees, discharged from the second discharge port (216) of the second extrusion section (210), flows in from the bottom upward through the second inlet (302). The two molten materials meet at the confluence section (303) to form an integrated composite extrusion. At this time, the first set pressure (P1) is higher than the second set pressure (P2), so the first molten material pushes the second molten material upward, thereby achieving stable confluence. The formed composite extrusion is discharged to the cooling section (400) through the discharge nozzle (307).

[0358] Structure and technical reason of the first inflow path (301)

[0359] As illustrated in FIG. 6, the first inlet passage (301) is connected to the first discharge port (116) of the first extrusion part (110) and is a passage through which the first molten material flows from the top downward. The first inlet passage (301) is composed of a flow path having a cylindrical or square cross-section, and is formed with an inner diameter in the range of 10 mm to 30 mm and a length in the range of 100 mm to 300 mm.

[0360] The technical reason for configuring the first inlet passage (301) to flow downward from the top is to stabilize the flow of the first molten material using gravity, and to naturally apply downward pressure to push the second molten material upward when it meets the second molten material at the confluence section (303). Since the first molten material (248 degrees) with a high melting point has high viscosity and high flow resistance, flowing it in the direction of gravity facilitates the flow and reduces the load applied to the extrusion section.

[0361] The technical reason and critical significance of setting the inner diameter of the first inlet channel (301) to a range of 10 mm to 30 mm are as follows. If the inner diameter is less than 10 mm, the flow resistance becomes excessively large, the flow of the first molten material is not smooth, excessive pressure is required in the extrusion section, and the temperature of the first molten material rises within the channel, posing a risk of thermal decomposition. Conversely, if the inner diameter exceeds 30 mm, the flow velocity of the first molten material slows down, the residence time within the channel becomes longer, the molten material near the channel wall cools down, the viscosity increases, and the contact area with the second molten material at the junction (303) becomes excessively large, making temperature control difficult. The most desirable inner diameter is in the range of 15 mm to 25 mm.

[0362] The technical reason for setting the length of the first inlet channel (301) to a range of 100 mm to 300 mm is to form a stable flow while the first molten material moves from the first discharge port (116) to the junction (303) and to ensure that temperature control through the temperature maintenance unit (305) is effectively achieved. If the length is less than 100 mm, the first molten material reaches the junction (303) before the flow stabilizes, causing turbulence and making it difficult to achieve uniform merging with the second molten material. If the length exceeds 300 mm, the flow path becomes excessively long, increasing heat loss, increasing the overall size of the equipment, and increasing manufacturing costs.

[0363] The material of the first inlet channel (301) is made of stainless steel (SUS304 or SUS316) or heat-resistant alloy steel, and the surface is finished smoothly by electrolytic polishing. This is to minimize flow resistance of the first molten material and to prevent the molten material from adhering to the inner wall of the channel.

[0364] Structure and technical reason of the second inflow path (302)

[0365] As shown in FIG. 6, the second inlet passage (302) is connected to the second discharge port (216) of the second extrusion part (210) and is a passage through which the second molten material flows from the bottom upward. The second inlet passage (302) is arranged symmetrically with respect to the first inlet passage (301), and is formed with an inner diameter in the range of 8 mm to 25 mm and a length in the range of 100 mm to 300 mm.

[0366] The technical reason and critical significance of configuring the second inlet passage (302) to flow upward from the bottom is the most essential feature of the present invention. The reason for flowing the second molten material (adhesive, 120 degrees) with a low melting point upward is to prevent the second molten material from flowing down prematurely by allowing it to flow against gravity, and to allow it to naturally merge as it is pushed up by the pressure of the first molten material at the confluence section (303).

[0367] This reverse inflow structure is important. If the second inflow channel (302) is also configured to flow from the top downward, the second molten material with a low melting point flows down quickly due to gravity and passes through the confluence section (303) before meeting the first molten material, or a problem arises where the first molten material with a low temperature and high viscosity is not properly mixed.

[0368] The technical reason for setting the inner diameter of the second inlet passage (302) to a range of 8 mm to 25 mm is similar to that of the first inlet passage (301), but a relatively smaller inner diameter is used because the flow rate of the second molten material is lower and the viscosity is lower than that of the first molten material. If the inner diameter is less than 8 mm, the resistance of the flow path becomes excessively large, and if it exceeds 25 mm, the flow of the second molten material becomes unstable. Generally, the inner diameter of the second inlet passage (302) is set to a range of 80% to 100% of the inner diameter of the first inlet passage (301).

[0369] In order to flow the second molten material upward in the second inlet channel (302), the second set pressure (P2) must be at a level capable of overcoming the self-weight and gravity of the second molten material. Specifically, the second set pressure is determined according to the length of the second inlet channel (302) and the density of the second molten material, and is generally set in the range of 0.5 MPa to 2.0 MPa. This pressure range is a level at which the second molten material can rise stably through the second inlet channel (302) while responding to the pressure of the first molten material at the junction (303).

[0370] Structure of the joining section (303) and joining mechanism

[0371] As illustrated in FIG. 6, the junction section (303) is a space where the first inlet passage (301) and the second inlet passage (302) merge to form a composite extruded product. The junction section (303) is configured in the form of a chamber having a hexagonal or elliptical cross-section, and the internal volume is formed in the range of 5 cm³ to 20 cm³.

[0372] The process of the first molten material and the second molten material joining at the joining section (303) proceeds as follows. As illustrated in the "Details of the joining process" of FIG. 6, in step 1, the first molten material is introduced downward through the first inlet channel (301), and the second molten material is introduced upward through the second inlet channel (302). At this time, since the first set pressure (P1) is higher than the second set pressure (P2), the first molten material pushes the second molten material upward, causing the two molten materials to meet.

[0373] In step 2, mixing begins as the two molten materials come into contact within the confluence section (303). Since there is a temperature difference of about 128 degrees between the first molten material (248 degrees) and the second molten material (120 degrees), heat transfer occurs at the contact interface. As heat from the first molten material is transferred to the second molten material, the viscosity of the second molten material decreases, and at the same time, the temperature of the first molten material decreases slightly and its viscosity increases. This change in viscosity causes the two molten materials to mix in a laminar state, playing an important role in forming an integrated composite extruded material.

[0374] Inside the joining section (303), a layered structure is formed in which the first molten material mainly occupies the upper and central parts, and the second molten material occupies the lower and side parts. This is because the density of the first molten material is slightly higher than that of the second molten material, and the first set pressure is higher than the second set pressure, causing the first molten material to push out the second molten material. This layered structure becomes more distinct as it passes through the discharge nozzle (307), and finally, a composite extruded product is formed with an adhesive layer disposed on one surface.

[0375] In step 3, the composite extruded material formed at the joining section (303) is discharged to the cooling section (400) through the discharge nozzle (307). During the discharge process, the thickness and width of the composite extruded material are determined as it is molded according to the shape of the discharge nozzle (307).

[0376] The technical reason for setting the internal volume of the joining section (303) to a range of 5 cm³ to 20 cm³ is to secure a space where the two molten materials can be sufficiently mixed, while preventing the residence time from becoming excessively long. If the volume is less than 5 cm³, the two molten materials are not sufficiently mixed, resulting in weak interfacial adhesion of the composite extruded material, and if the volume exceeds 20 cm³, the residence time becomes long, making temperature control difficult and reducing productivity.

[0377] Structure and control mechanism of the joining point control section (304)

[0378] As illustrated in FIG. 6, the junction point adjustment unit (304) is a component that changes the junction point of the first and second molten materials by adjusting the position of the junction unit (303) in the up and down direction to prevent the second molten material with a low melting point from flowing down prematurely. The junction point adjustment unit (304) is composed of a moving mechanism capable of moving the junction unit (303) up and down, a fixing mechanism for fixing the moving position, and a position sensor for measuring the moving distance.

[0379] The location of the merging point refers to the point where the two molten materials actually begin to come into contact within the merging section (303) where the first inlet passage (301) and the second inlet passage (302) meet. As shown in FIG. 6, the merging point is the location marked with a red circle within the merging section (303), and this location can be adjusted up and down through the merging point adjustment section (304).

[0380] The technical reasons and critical significance of adjusting the merging point in the vertical direction are as follows. Since the difference in melting points between the first and second molten materials is very large at 128 degrees, the mixing pattern of the two molten materials varies significantly depending on the location of the merging point. If the merging point is located at the top of the merging section (303), as soon as the second molten material meets the first molten material, it is rapidly heated by the high temperature of the first molten material, causing its viscosity to drop excessively and failing to form a layered structure as it diffuses into the first molten material. Conversely, if the merging point is located at the bottom of the merging section (303), the second molten material begins to flow down by gravity before reaching the merging point and does not properly merge with the first molten material.

[0381] Experimental results confirmed that the optimal joining point is located at 40% to 60% of the bottom relative to the total height of the joining section (303). Assuming the total height of the joining section (303) is 100mm, it is preferable for the joining point to be located at a height of 40mm to 60mm from the bottom. At this location, the pressure and temperature of the first molten material can adequately push up the second molten material without the second molten material flowing down prematurely, and the two materials can stably combine to form an integrated composite extrusion.

[0382] The specific implementation method of the junction point control unit (304) is as follows. The first method is to move the entire junction unit (303) up and down. The junction unit (303) is connected to the first inlet passage (301) and the second inlet passage (302) in a sliding manner, and the junction unit (303) is moved up and down using a screw-type moving mechanism or a hydraulic cylinder. When the junction unit (303) moves upward, the junction point also moves upward, and when it moves downward, the junction point also moves downward.

[0383] The second method is to change the connection position of the first inflow path (301) and the second inflow path (302) by installing a movable partition inside the junction (303). By moving the movable partition up and down, the position where the two inflow paths meet within the junction (303) can be adjusted.

[0384] The third method is to variably adjust the length of the first inlet passage (301) or the second inlet passage (302). For example, a retractable extension pipe is installed at the lower end of the first inlet passage (301) to adjust the discharge position of the first molten material up and down, or a retractable extension pipe is installed at the upper end of the second inlet passage (302) to adjust the discharge position of the second molten material up and down.

[0385] The adjustment range of the joining point adjustment section (304) is preferably 20% to 60% of the total height of the joining section (303). When the height of the joining section (303) is 100mm, the adjustment range is 20mm to 60mm. By adjusting the joining point within this range, it is possible to accommodate various types of PET resin and adhesive combinations.

[0386] The junction point control unit (304) is equipped with a position sensor to measure the current position of the junction unit (303) or the movable partition in real time and transmit it to the control unit. The control unit implements precise position control by controlling the movement mechanism by comparing the set target position with the current position. A linear encoder, a laser displacement sensor, or a potentiometer may be used as the position sensor.

[0387] Structure and independent control mechanism of the temperature maintenance unit (305)

[0388] As illustrated in FIG. 6, the temperature maintenance unit (305) is a component installed in the confluence unit (303) that maintains the temperature of the first molten material and the second molten material independently through heating means independently installed in the first inlet channel (301) and the second inlet channel (302), respectively. The temperature maintenance unit (305) is composed of a heating means dedicated to the first inlet channel (301), a heating means dedicated to the second inlet channel (302), a temperature sensor for measuring the temperature of each inlet channel, and a temperature control unit for controlling the heating means.

[0389] The technical reason and critical significance of maintaining the temperatures of the first inlet (301) and the second inlet (302) independently through the temperature maintenance section (305) are as follows. Since the first molten material (248 degrees) and the second molten material (120 degrees) have a large temperature difference of about 128 degrees, if temperature control is not performed, the following problems occur. First, while passing through the first inlet (301), the temperature of the first molten material decreases, causing the viscosity to increase and the fluidity to decrease, making the extrusion unstable. In particular, the temperature of the first molten material near the wall of the flow path may drop rapidly due to heat exchange with the outside air. Second, while passing through the second inlet (302), the temperature of the second molten material also decreases, causing the viscosity to increase, and when it meets the first molten material at the junction (303), the temperature difference becomes even greater, making mixing difficult.

[0390] As shown in FIG. 6, a first heating means is installed on the outer surface of the first inlet channel (301) to maintain the temperature of the first molten material within the range of 248° ± 5°. A cartridge heater, a band heater, or an induction heating coil may be used as the first heating means. A plurality of temperature sensors are installed on the wall of the first inlet channel (301) to measure the temperature at several points along the length of the inlet channel, and the temperature control unit controls the output of the first heating means so that the measured temperature maintains the set temperature (248°).

[0391] Likewise, a second heating means is installed on the outer surface of the second inlet (302) to maintain the temperature of the second molten material within the range of 120°±5°. The second heating means and the second temperature sensor are also configured in the same manner as the first inlet (301) and are controlled through an independent temperature control loop.

[0392] In order to implement independent control of the temperature maintenance unit (305), it is important to form an insulating structure between the first inlet passage (301) and the second inlet passage (302). Since the two inlet passages are placed close to each other at the junction (303), temperature control becomes difficult if heat transfer occurs between the two inlet passages. Therefore, an insulating material (ceramic fiber or aerogel) is filled between the two inlet passages, or a vacuum insulating layer is formed to block heat transfer.

[0393] It is desirable that the temperature control precision of the temperature maintenance unit (305) be within ±3 degrees. If the temperature deviation exceeds ±3 degrees, the change in viscosity of the molten material increases, the extrusion stability decreases, and the quality of the composite extruded product becomes non-uniform. A PID (Proportional-Integral-Derivative) control algorithm is used for high-precision temperature control, and a K-type or J-type thermocouple or a platinum resistance thermometer (RTD) is used as the temperature sensor.

[0394] Structure of the pressure sensing unit (306) and pressure balance monitoring

[0395] As illustrated in FIG. 6, the pressure sensing unit (306) is a component that monitors the balance between the first set pressure and the second set pressure by sensing the pressure of the first inlet (301) and the second inlet (302) so that the first set pressure (P1) is maintained at a level that can push the second molten material upward. The pressure sensing unit (306) is composed of a first pressure sensor installed in the first inlet (301), a second pressure sensor installed in the second inlet (302), and a pressure monitoring unit that collects and analyzes pressure data.

[0396] The technical reason and critical significance of monitoring the balance between the first set pressure and the second set pressure through the pressure sensing unit (306) are as follows. In order for the first molten material and the second molten material to merge stably, the first set pressure (P1) must be higher than the second set pressure (P2). As illustrated in "Pressure Relationship and Push-up Mechanism" of FIG. 6, the relationship P1 > P2 must be maintained so that the first molten material can properly merge while pushing the second molten material upward.

[0397] If the condition P1 ≤ P2 is met, the second molten material may flow back into the first molten material, or the second molten material may be supplied excessively at the junction (303), causing the ratio of the adhesive layer in the composite extruded material to become excessively high. Conversely, if P1 is excessively higher than P2, the first molten material may push the second molten material excessively, causing the ratio of the adhesive layer to become excessively low, or the second molten material may flow back into the second inlet (302).

[0398] Experimental results confirmed that the optimal pressure ratio is in the range of P1 / P2 = 1.2 to 2.0. If P1 / P2 is less than 1.2, the pushing effect of the first molten material is negligible, and if it exceeds 2.0, the second molten material is excessively compressed, making the inflow into the confluence (303) unstable. The most desirable pressure ratio is in the range of P1 / P2 = 1.3 to 1.6.

[0399] The specific implementation method of the pressure sensing unit (306) is as follows. The first pressure sensor is installed at an intermediate point of the first inlet (301) or at a point immediately before the junction (303) to measure the pressure of the first molten material in real time. A diaphragm-type pressure sensor, a strain gauge-type pressure sensor, or a piezoelectric-type pressure sensor may be used as the first pressure sensor. The measurement range of the pressure sensor is 0 to 10 MPa, and it is preferable that the measurement precision is within ±0.1 MPa.

[0400] Likewise, the second pressure sensor is installed at an intermediate point of the second inlet (302) or immediately before the junction (303) to measure the pressure of the second molten material in real time. The specifications of the second pressure sensor are the same as those of the first pressure sensor.

[0401] The pressure monitoring unit collects pressure data from the first pressure sensor and the second pressure sensor, calculates the ratio of P1 / P2, and determines whether this ratio is within a set range (1.2 to 2.0). If P1 / P2 is outside the set range, the pressure monitoring unit generates a warning signal and transmits a feedback signal to the first pressure regulating unit (115) or the second pressure regulating unit (215) to automatically regulate the pressure.

[0402] Specifically, when P1 / P2 falls below 1.2, the pressure monitoring unit transmits a signal to the first pressure regulating unit (115) to increase the rotational speed of the first screw (112) to raise P1, or transmits a signal to the second pressure regulating unit (215) to decrease the rotational speed of the second screw (212) to lower P2. Conversely, when P1 / P2 exceeds 2.0, the rotational speed of the first screw (112) is decreased or the rotational speed of the second screw (212) is increased.

[0403] Through this feedback control loop, the balance between the first set pressure and the second set pressure can be automatically maintained, which is essential for the stable production of composite extrusions. The control cycle of the pressure monitoring unit is in the range of 0.1 to 1 second, and the fast control cycle allows for a rapid response to pressure fluctuations.

[0404] Structure and function of the discharge nozzle (307)

[0405] As illustrated in FIG. 6, the discharge nozzle (307) is a component that discharges a composite extruded product from the confluence section (303). The discharge nozzle (307) is connected to the bottom of the confluence section (303) and has a tapered shape in which the cross-sectional area gradually decreases from the inlet to the outlet.

[0406] The technical role of the discharge nozzle (307) is as follows. First, it forms the composite extruded product into a desired cross-sectional shape. The exit cross-section of the discharge nozzle (307) corresponds to the cross-sectional shape of the edge banding, which is the final product, and generally has a rectangular shape. The width of the exit cross-section is formed in the range of 10 mm to 50 mm, and the thickness is formed in the range of 0.3 mm to 3 mm.

[0407] Second, the flow rate of the composite extruder is increased to facilitate discharge. As the cross-sectional area of ​​the discharge nozzle (307) decreases, the flow rate of the composite extruder increases, which enables stable supply to the cooling unit (400).

[0408] Third, the layered structure of the first molten material and the second molten material within the composite extrusion is made more distinct. As the composite extrusion passes through the discharge nozzle (307), it is compressed in the thickness direction, and in this process, the interface between the first molten material and the second molten material is flattened, making the layered structure distinct.

[0409] It is preferable that the taper angle of the discharge nozzle (307) be in the range of 15 to 45 degrees. If the taper angle is less than 15 degrees, the length of the discharge nozzle (307) becomes excessively long, and if it exceeds 45 degrees, the composite extruded material is rapidly compressed, causing internal stress or the layered structure to be destroyed.

[0410] A lip structure is formed at the outlet of the discharge nozzle (307) to stabilize the discharge of the composite extruded product. The lip structure is formed by rounding the corner portion of the outlet cross-section, thereby minimizing the die swell phenomenon that occurs when the composite extruded product is separated from the discharge nozzle (307) and improving the dimensional accuracy of the product.

[0411] The discharge nozzle (307) is also equipped with a heating means and a temperature sensor to control the temperature. It is preferable that the temperature of the discharge nozzle (307) be maintained in the range of 180 to 200 degrees, which is an intermediate temperature between the first molten material and the second molten material. In this temperature range, the composite extruded material can pass through the discharge nozzle (307) while maintaining appropriate fluidity, and cooling in the cooling section (400) proceeds smoothly after discharge.

[0412] Operation process and control of the entire extrusion head (300)

[0413] As illustrated in "Details of the joining process" and "Pressure relationship and pushing mechanism" of FIG. 6, the entire operation process of the extrusion head (300) proceeds as follows.

[0414] Step 1: A first molten material (PET resin) heated to 248 degrees in the first extrusion section (110) is discharged through the first discharge port (116) at a first set pressure (P1) and flows into the first inlet path (301). The first molten material moves toward the confluence section (303) while descending in the direction of gravity along the first inlet path (301). During the movement, the first heating means of the temperature maintenance section (305) maintains the temperature of the first molten material within the range of 248 degrees ± 3 degrees.

[0415] Step 2: A second molten material (adhesive) heated to 120 degrees in the second extrusion section (210) is discharged through the second discharge port (216) at a second set pressure (P2) and flows into the second inlet (302). The second molten material moves toward the confluence section (303) while rising in the opposite direction of gravity along the second inlet (302). During the movement, the second heating means of the temperature maintenance section (305) maintains the temperature of the second molten material within the range of 120 degrees ± 3 degrees.

[0416] Step 3: The first pressure sensor and the second pressure sensor of the pressure sensing unit (306) measure P1 and P2, respectively, and the pressure monitoring unit calculates the ratio of P1 / P2. It checks whether P1 / P2 is in the range of 1.2 to 2.0, and if it is out of the range, feeds back to the first pressure regulating unit (115) or the second pressure regulating unit (215) to regulate the pressure.

[0417] Step 4: The first molten material and the second molten material meet at a junction point within the junction section (303). Since P1 > P2, the first molten material moves downward and pushes the second molten material upward. The junction point is set to a position between 40% and 60% of the lower part of the junction section (303) by the junction point control section (304), and at this position, the two molten materials come into proper contact and mixing begins.

[0418] Step 5: The first molten material and the second molten material are mixed in a laminar flow state within the junction section (303) to form an integrated composite extruded material. A layered structure is formed in which the first molten material mainly occupies the upper and central parts, and the second molten material occupies the lower and side parts. The residence time within the junction section (303) is in the range of 2 to 10 seconds, and during this time, heat transfer and diffusion between the two molten materials proceed, thereby improving interfacial adhesion.

[0419] Step 6: The composite extruded material formed in the joining section (303) moves to the discharge nozzle (307). As it passes through the discharge nozzle (307), the composite extruded material is compressed and molded into a tapered shape and discharged at the outlet with a final cross-sectional shape. The discharged composite extruded material is transferred to the cooling section (400).

[0420] The overall control of the extrusion head (300) is managed integrally by a central control unit. The central control unit collects data from the temperature maintenance unit (305), the pressure sensing unit (306), and the junction point control unit (304), and controls each component to maintain optimal composite extrusion conditions. A PLC (Programmable Logic Controller) or an industrial computer is used in the central control unit, and an operator can input setting values ​​and monitor the current status through an HMI (Human Machine Interface).

[0421] Technical effects of the extrusion head (300) and differences from the prior art

[0422] The extrusion head (300) of the present invention provides the following technical effects.

[0423] First, by arranging the first inlet passage (301) and the second inlet passage (302) in opposite directions and maintaining the first set pressure higher than the second set pressure, two materials with a melting point difference of 100 degrees or more can be stably combined. This enables the composite extrusion of PET resin and adhesive, which was impossible to implement in conventional technology.

[0424] Second, the merging point can be controlled through the merging point control unit (304), thereby preventing the second molten material with a low melting point from flowing down prematurely and allowing for various raw material combinations. This significantly improves the flexibility and stability of the process.

[0425] Third, by independently maintaining the temperatures of the first inlet (301) and the second inlet (302) through the temperature maintenance unit (305), the optimal temperature and viscosity can be maintained until each molten material reaches the confluence point. This improves the quality of the composite extruded product and reduces the defect rate.

[0426] Fourth, by monitoring the pressure balance in real time and providing feedback control through the pressure sensing unit (306), the flow rate ratio of the first molten material and the second molten material can be precisely controlled. This is essential for maintaining a uniform thickness of the adhesive layer of the final product.

[0427] Fifth, by forming the composite extruded product into a desired cross-sectional shape through the discharge nozzle (307) and clearly defining the layered structure, an edge banding product with an adhesive layer exposed on one side can be stably manufactured.

[0428] In conventional technology, when extruding a high-melting-point resin and a low-melting-point adhesive, the two materials were generally introduced from the same direction or joined horizontally from the side. However, in this method, problems arose where the low-melting-point material flowed down due to gravity or was not properly mixed due to the temperature difference with the high-melting-point material. The extrusion head (300) of the present invention fundamentally solves these problems of conventional technology by arranging the first inlet passage (301) and the second inlet passage (302) in opposite directions vertically and adopting a method of pushing up the low-melting-point material using a pressure difference.

[0429] In addition, in conventional technology, the joining point is fixed, so there was a problem where the product quality became unstable when the raw material conditions changed, but this problem is solved and process flexibility is secured through the joining point control unit (304) of the present invention.

[0430] Overall configuration and technical significance of the cooling unit (400)

[0431] As illustrated in FIGS. 1 and 7, the cooling unit (400) is a component that cools a composite extruded product discharged from an extrusion head (300) in an open manner without a mold to form an edge banding product with an adhesive layer exposed on one side. The cooling unit (400) is composed of a cooling chamber (401), a cooling water supply unit (402), a cooling temperature control unit (403), an open cooling unit (404), and a transfer speed control unit (405).

[0432] The overall operating principle of the cooling unit (400) is as follows. The composite extruded material discharged from the discharge nozzle (307) of the extrusion head (300) is cooled as it passes through the open space inside the cooling chamber (401). At this time, the composite extruded material is not in direct contact with a mold or other solid surface, but is cooled indirectly through air cooled by cooling water circulating on the wall of the cooling chamber (401). During the cooling process, the first molten material (PET resin) with a high melting point solidifies first to form the skeletal structure of the product, and the second molten material (adhesive) with a low melting point solidifies slowly, forming an edge banding product with an adhesive layer exposed on one side. The formed product is transferred to the extraction unit (500).

[0433] The most key feature of the cooling unit (400) is that it adopts an open cooling method that does not use a mold. This is a fundamental difference from conventional technology and is a decisive factor that enables the manufacture of edge banding products with an adhesive layer exposed on one side.

[0434] Structure and technical reasons of the cooling chamber (401)

[0435] As illustrated in FIG. 7, the cooling chamber (401) is a chamber through which a composite extruded material discharged from the extrusion head (300) passes through an open space without contact with the mold. The cooling chamber (401) consists of an outer housing in the shape of a rectangular parallepiped and an open space formed therein, and the walls of the outer housing are formed in a double-wall structure so that cooling water circulates between them.

[0436] The size of the cooling chamber (401) is formed in the range of a width of 200 mm to 400 mm, a height of 300 mm to 600 mm, and a length (in the direction of movement of the composite extruder) of 800 mm to 2000 mm. The open space inside the cooling chamber (401) has a cross-sectional area of ​​a width of 100 mm to 250 mm and a height of 200 mm to 500 mm, and secures sufficient clearance space so that the composite extruder can pass freely.

[0437] The technical reason for setting the size of the cooling chamber (401) to the above range is as follows. If the width and height of the cooling chamber (401) are smaller than the above range, the distance between the composite extrusion and the wall surface becomes shorter, so there is a risk that the composite extrusion may come into contact with the wall surface or that condensation generated on the wall surface may adhere to the composite extrusion. Conversely, if the width and height exceed the above range, the air circulation inside the cooling chamber (401) becomes uneven, cooling efficiency decreases, and the size of the equipment becomes excessively large, thereby increasing manufacturing costs.

[0438] The length of the cooling chamber (401) is set to a range of 800 mm to 2000 mm to ensure a residence time sufficient for the composite extruder to be cooled while passing through the cooling chamber (401). When the transfer speed of the composite extruder is 5 meters per minute, it takes about 12 seconds to pass through a cooling chamber (401) with a length of 1000 mm, and during this time, the temperature of the composite extruder drops from about 180 degrees to a range of 60 to 80 degrees, causing the product to solidify. If the length of the cooling chamber (401) is less than 800 mm, the cooling time is insufficient and the product does not solidify sufficiently, and if it exceeds 2000 mm, stress is generated inside the product due to overcooling or the equipment becomes excessively long.

[0439] The outer housing of the cooling chamber (401) is formed with a double-wall structure, and the gap between the outer wall and the inner wall is formed in the range of 10 mm to 30 mm. Cooling water circulates through this gap to cool the inner wall, and an indirect cooling method is implemented in which the cooled inner wall cools the air inside the cooling chamber (401). If the gap is less than 10 mm, the flow rate of the cooling water is insufficient, so the cooling efficiency is reduced, and if it exceeds 30 mm, the amount of cooling water is excessive, making temperature control difficult and increasing energy consumption.

[0440] The inner wall material of the cooling chamber (401) is made of stainless steel (SUS304 or SUS316), and the surface is finished smoothly by electrolytic polishing. The smooth surface minimizes the formation of condensation on the inner wall and allows the formed condensation to flow smoothly downward by gravity so that it does not adhere to the composite extrusion. It is preferable that the surface roughness of the inner wall be Ra 0.8㎛ or less.

[0441] An inlet and an outlet are formed at the upper and lower ends of the cooling chamber (401), respectively. The inlet is connected to the discharge nozzle (307) of the extrusion head (300), and the outlet is connected to the extraction section (500). The sizes of the inlet and outlet are formed to be sufficiently larger than the cross-sectional area of ​​the composite extrusion so that the composite extrusion can pass through smoothly.

[0442] Structure and circulation mechanism of the cooling water supply unit (402)

[0443] As illustrated in FIG. 7, the cooling water supply unit (402) is a component that supplies cooling water to circulate along the wall surface of the cooling chamber (401). The cooling water supply unit (402) consists of a cooling water storage tank, a circulation pump, a cooling water inlet pipe, a cooling water outlet pipe, and a cooling water circulation path.

[0444] The operating principle of the cooling water supply unit (402) is as follows. Cooling water stored in the cooling water storage tank is supplied into the double-walled structure of the cooling chamber (401) through the cooling water inlet pipe by a circulation pump. As shown in FIG. 7, the cooling water flows in through the inlet at the top of the cooling chamber (401), flows downward along the gap between the outer wall and the inner wall, and cools the inner wall. The cooling water is discharged through the outlet at the bottom of the cooling chamber (401) and is recovered into the cooling water storage tank through the cooling water outlet pipe. The recovered cooling water is cooled again in the cooling water storage tank and reused by the circulation pump.

[0445] The flow rate of the cooling water is set to a range of 10 to 50 liters per minute. If the flow rate is less than 10 liters per minute, the circulation of the cooling water is not smooth, resulting in uneven temperature of the inner wall and reduced cooling efficiency; if it exceeds 50 liters per minute, the capacity of the circulation pump becomes excessive, energy consumption increases, and turbulence occurs within the piping, which may cause vibration or noise. The most desirable flow rate is in the range of 20 to 30 liters per minute.

[0446] A centrifugal pump or a gear pump is used as the circulation pump, and the pump head ranges from 5 to 15 meters. The pump's rotational speed can be variably adjusted through inverter control, allowing for precise control of the cooling water flow rate.

[0447] The capacity of the cooling water storage tank is formed in the range of 50 to 200 liters, and a chiller is provided inside the tank to maintain the temperature of the cooling water at a constant level. A chiller unit utilizing a compression refrigeration cycle is used as the chiller, and the cooling capacity is in the range of 3 kilowatts to 10 kilowatts.

[0448] Water or a mixture of water and antifreeze (ethylene glycol or propylene glycol) is used as the coolant. If pure water is used, there is a risk of freezing if the coolant temperature drops below 0 degrees; therefore, it is advisable to mix 10% to 30% antifreeze in winter or low-temperature environments. Mixing antifreeze lowers the freezing point to between -10 and -20 degrees, thereby preventing freezing.

[0449] The pH of the cooling water is maintained in the range of 6.5 to 8.5, and a corrosion inhibitor is added to prevent corrosion of the piping and cooling chamber (401). The cooling water is regularly replaced or filtered to prevent the proliferation of foreign substances or microorganisms.

[0450] Structure and temperature control mechanism of the cooling temperature control unit (403)

[0451] As illustrated in FIG. 7, the cooling temperature control unit (403) is a component that controls the cooling rate of the composite extruded product by controlling the temperature of the cooling water. The cooling temperature control unit (403) consists of a temperature sensor installed in a cooling water storage tank, a temperature control unit that controls the output of a cooler (chiller), and a Human Machine Interface (HMI) that inputs a set temperature and displays the current temperature.

[0452] The operating principle of the cooling temperature control unit (403) is as follows. A temperature sensor measures the temperature of the cooling water in the cooling water storage tank in real time and transmits the measured temperature data to the temperature control unit. The temperature control unit compares the measured temperature with the set temperature, and if the measured temperature is higher than the set temperature, it increases the output of the cooler to cool the cooling water more strongly, and if the measured temperature is lower than the set temperature, it decreases the output of the cooler or stops it. Through this feedback control, the temperature of the cooling water can be precisely maintained within the range of ±1 degree of the set temperature.

[0453] As shown in FIG. 7, the set temperature of the cooling water is in the range of 15 to 25 degrees, and the cooling rate of the composite extruded product is optimized within this range. The technical reasons and critical significance of setting the cooling water temperature to the range of 15 to 25 degrees are as follows.

[0454] If the cooling water temperature is below 15 degrees, the composite extruded material is excessively rapidly cooled, causing the following problems. First, the crystallization of the PET resin is incomplete, leaving a large amorphous region, which lowers the mechanical strength and dimensional stability of the product. PET resin exhibits excellent properties only when undergoing a proper crystallization process, but rapid cooling does not allow time for molecular chains to be arranged regularly, resulting in a lower degree of crystallization. Second, residual stress occurs within the product, which may cause the product to warp or crack. In particular, since the thermal expansion coefficients of the first molten material (PET) and the second molten material (adhesive) are different, delamination may occur at the interface due to the difference in shrinkage rates between the two materials during rapid cooling. Third, excessive condensation forms on the inner wall of the cooling chamber (401), increasing the risk of it adhering to the composite extruded material.

[0455] Conversely, if the cooling water temperature exceeds 25 degrees, the cooling speed of the composite extrusion becomes too slow, causing the following problems. First, the composite extrusion does not solidify sufficiently while passing through the cooling chamber (401), causing deformation when the product is grasped at the extraction section (500). In particular, the adhesive layer has a lower melting point and remains in a molten state for a longer period, which may cause it to stick to the extraction roller (501) or damage the surface. Second, productivity decreases. Since the transfer speed of the composite extrusion must be lowered as the cooling time increases, the production volume per unit time decreases. Third, since the length of the cooling chamber (401) must be increased, the size of the equipment increases and manufacturing costs rise.

[0456] Therefore, maintaining the cooling water temperature in the range of 15 to 25 degrees is the optimal temperature range to ensure proper crystallization of the composite extruder, minimize internal stress, and secure productivity. The most desirable cooling water temperature is in the range of 18 to 22 degrees, at which the crystallization of the PET resin and the solidification of the product proceed most stably.

[0457] A platinum resistance thermometer (RTD, Pt100) or a thermistor is used as the temperature sensor, and it is desirable that the measurement precision be within ±0.5 degrees. The temperature control unit uses a PID (Proportional-Integral-Derivative) control algorithm to precisely control the temperature, and the control period is in the range of 1 second to 5 seconds.

[0458] The cooling temperature control unit (403) is equipped with a temperature abnormality detection function, so that if the cooling water temperature deviates from the set range, it generates a warning signal and automatically stops the equipment if necessary. This prevents defective products from being produced in abnormal situations such as a breakdown of the cooler or a stoppage of the circulation pump.

[0459] Structure of the open cooling section (404) and the critical significance of the open cooling

[0460] As illustrated in FIG. 7, the open cooling section (404) is a component that cools the composite extruded material in an open manner without a mold inside the cooling chamber (401) without direct contact with the cooling water, thereby allowing the adhesive layer of the composite extruded material to be placed on one side and the adhesive to be exposed on the surface, thereby forming an edge banding product. The open cooling section (404) refers to the open space of the cooling chamber (401) itself and does not include a mold or any mechanical structure that restrains the composite extruded material.

[0461] The cooling mechanism of the open cooling unit (404) is based on an indirect cooling method. The composite extruded material is cooled indirectly through radiative and convective heat transfer from the inner wall, which is cooled by cooling water, as it freely passes through the open space inside the cooling chamber (401). The temperature of the air inside the cooling chamber (401) decreases as it comes into contact with the cooled inner wall, and this cooled air cools the composite extruded material as it circulates by natural convection or forced convection.

[0462] As illustrated in the "Comparison of Open Cooling vs. Mold Cooling" section of Fig. 7, the technical reasons and critical significance of the open cooling method are clearly revealed when compared to the conventional mold cooling method.

[0463] Conventional technology uses a method of cooling composite extrusions by passing them through a mold, such as a die or a sizer. In the mold cooling method, the internal shape of the mold determines the final cross-sectional shape of the product, and cooling water channels are formed inside the mold to cool the mold. The cooled mold then comes into direct contact with the composite extrusion to cool it. While this method is effective for general extruded products (e.g., pipes, profiles), serious problems arise in products such as edge banding, where an adhesive layer is exposed on one side.

[0464] First, as shown in FIG. 7, the molten adhesive (second molten material) adheres to the metal inner wall of the mold, so that the product does not separate from the mold. Since the adhesive is an inherently adhesive material, it adheres strongly to the surface of the mold.

[0465] Second, the surface of the adhesive layer is scratched, torn, or contaminated during the process of forcibly removing the product from the mold, leading to a decrease in adhesive performance. The adhesive layer must have a clean and smooth surface to ensure proper adhesion with the panel during installation; however, if the surface is damaged due to friction with the mold, the adhesive strength is significantly reduced.

[0466] Third, production must be stopped and the mold heated to clean it in order to remove adhesive remaining inside the mold, which significantly reduces productivity and lowers the equipment utilization rate. Mold cleaning takes several hours, and frequent cleaning damages the surface of the mold, shortening the replacement cycle.

[0467] Fourth, high precision is required for mold design and manufacturing, and the production cost is very high. In addition, since new molds must be manufactured whenever product specifications change, it is difficult to handle multi-product production.

[0468] The open cooling unit (404) of the present invention fundamentally solves all these problems by completely removing the mold. The specific advantages of the open cooling method are as follows.

[0469] First, since the composite extruded material does not come into contact with any solid surface, the product is formed while the adhesive layer remains cleanly exposed. The surface of the adhesive layer remains exactly as it was formed at the discharge nozzle (307) of the extrusion head (300), and no damage or contamination occurs.

[0470] Second, since mold cleaning is unnecessary, continuous production is possible and productivity is significantly improved. The equipment utilization rate can be maintained at over 90%, which is a significant improvement compared to the utilization rate of 60% to 70% in the mold method.

[0471] Third, the cost of making the mold is reduced, and since only the discharge nozzle (307) of the extrusion head (300) needs to be replaced when the product specifications are changed, it is possible to flexibly respond to multi-product production.

[0472] Fourth, since the composite extruded material cools while freely shrinking, internal stress is minimized and warping or twisting of the product is prevented. In the mold method, shrinkage is constrained by the mold, causing stress, but in the open method, this problem does not exist.

[0473] The technical basis for enabling open cooling is as follows. Since the first molten material and the second molten material have already been integrated in the extrusion head (300) to form a composite extrusion with a layered structure, the composite extrusion can maintain a constant shape on its own without any separate shape constraints during the cooling process. In particular, the high-melting-point first molten material (PET) portion solidifies rapidly at the beginning of cooling to form the skeletal structure of the product, so the shape of the product is stably maintained while the low-melting-point second molten material (adhesive) portion solidifies slowly.

[0474] During the cooling process, the temperature change of the composite extruder proceeds as follows. When the composite extruder is discharged from the discharge nozzle (307), the temperature of the composite extruder is in the range of approximately 180 to 200 degrees. Immediately after entering the cooling chamber (401), the surface temperature begins to drop rapidly, and when passing through the cooling chamber (401) at the 1 / 3 point, the surface temperature drops to the range of approximately 120 to 140 degrees. At this time, the PET portion has already started to solidify, but the adhesive portion still remains in a molten state. When passing through the cooling chamber (401) at the 2 / 3 point, the surface temperature drops to the range of approximately 80 to 100 degrees, and the adhesive portion also begins to solidify. When it completely passes through the cooling chamber (401) and reaches the outlet, the surface temperature drops to the range of approximately 60 to 80 degrees, and the product is completely solidified. The core temperature is about 10 to 20 degrees higher than the surface temperature, but it is further cooled as it passes through the extraction section (500).

[0475] Structure of the transfer speed control unit (405) and cooling time control

[0476] As illustrated in FIG. 7, the transfer speed control unit (405) is a component that controls the cooling time by controlling the transfer speed of the composite extruder passing through the cooling chamber (401). The transfer speed control unit (405) operates in conjunction with the withdrawal speed control unit (502) of the withdrawal unit (500) and is composed of a control unit that sets and controls the transfer speed of the composite extruder.

[0477] The operating principle of the transfer speed control unit (405) is as follows. The transfer speed control unit (405) controls the rotational speed of the extraction roller (501) of the extraction unit (500) to control the speed at which the composite extruded material passes through the cooling chamber (401). Since the extraction roller (501) grips the composite extruded material at the exit of the cooling chamber (401) and pulls it at a constant speed, the rotational speed of the extraction roller (501) determines the transfer speed of the composite extruded material. If the transfer speed is fast, the cooling time is shortened, and if the transfer speed is slow, the cooling time is lengthened.

[0478] The feed speed of the composite extruded material is set to a range of 3 to 10 meters per minute. The technical reasons and critical significance for setting the feed speed to this range are as follows.

[0479] If the transfer speed is less than 3 meters per minute, the cooling time becomes excessively long, causing the following problems. First, productivity is significantly reduced. When producing at a speed of 3 meters per minute, approximately 180 meters of product can be produced per hour, but at a speed of 2 meters per minute, only 120 meters can be produced per hour, resulting in a 33% decrease in production volume. Second, the composite extruder is supercooled, causing excessive crystallization of PET, which leads to the product becoming brittle, and the adhesive portion also shrinks excessively, causing stress. Third, the residence time of the composite extruder in the cooling chamber (401) is prolonged, requiring the length of the cooling chamber (401) to be increased and the size of the equipment to increase.

[0480] Conversely, if the transfer speed exceeds 10 meters per minute, the cooling time is insufficient, and the following problems occur. First, the composite extruded material reaches the extraction section (500) in a state where it has not fully solidified, and the product is deformed or damaged by the extraction roller (501). In particular, the adhesive layer may still remain in a partially molten state, so there is a high risk of it sticking to the extraction roller (501) or the surface being damaged. Second, the dimensional accuracy of the product is reduced. If the product is pulled by the extraction roller (501) in a state where it has not fully solidified, the product is excessively stretched or the thickness becomes uneven. Third, the mechanical strength of the product is reduced. If the crystallization of PET is incomplete and a large amorphous region remains, the tensile strength and elastic modulus decrease.

[0481] Therefore, maintaining the feed rate in the range of 3 to 10 meters per minute is the optimal speed range that maximizes productivity while ensuring complete solidification of the product by securing sufficient cooling time. The most desirable feed rate is in the range of 5 to 7 meters per minute, at which product quality and productivity are balanced.

[0482] For example, if the length of the cooling chamber (401) is 1200 mm and the transfer speed is 6 meters per minute, the time required for the composite extruded material to pass through the cooling chamber (401) is 1200 mm ÷ (6000 mm / 60 seconds) = 12 seconds. During these 12 seconds, the temperature of the composite extruded material drops from about 180 degrees to 70 degrees, and the product solidifies.

[0483] The transfer speed control unit (405) operates in conjunction with the cooling temperature control unit (403). When the cooling water temperature is low (e.g., 15 degrees), the cooling speed is fast, so the transfer speed can be increased to improve productivity, and when the cooling water temperature is high (e.g., 25 degrees), the cooling speed is slow, so the transfer speed can be reduced to secure sufficient cooling time. Through this integrated control, products of consistent quality can be produced under various conditions.

[0484] Operation process and control of the cooling unit (400)

[0485] The entire operation process of the cooling unit (400) proceeds as follows.

[0486] Step 1: A composite extruded material at a temperature of approximately 180 to 200 degrees is discharged from the discharge nozzle (307) of the extrusion head (300) and flows into the inlet of the cooling chamber (401). The composite extruded material has a structure in which a PET resin portion and an adhesive portion are combined in layers, and an adhesive layer is disposed on one surface.

[0487] Step 2: The composite extrusion is cooled as it freely passes through the open space inside the cooling chamber (401). At this time, the composite extrusion does not come into contact with the mold or other solid surface at all, and heat is indirectly removed from the inner wall cooled by the cooling water. The air inside the cooling chamber (401) is maintained at about 20 to 25 degrees, and this cooled air comes into contact with the surface of the composite extrusion, thereby cooling through convective heat transfer.

[0488] Step 3: During the cooling process, the high-melting-point PET portion begins to solidify first. When the composite extruded material passes through the cooling chamber (401) at the 1 / 3 point, the surface of the PET portion begins to solidify as it drops to about 140 degrees, forming the skeletal structure of the product. At this time, the low-melting-point adhesive portion is still in a molten state, maintaining about 120 degrees.

[0489] Step 4: When the composite extruded material passes through the cooling chamber (401) at the 2 / 3 point, the surface of the adhesive portion also begins to solidify as it descends to about 100 degrees. At this time, the PET portion has already solidified to the extent that it stably maintains the shape of the product, so no deformation of the product occurs even as the adhesive portion solidifies.

[0490] Step 5: When the composite extruded product reaches the outlet of the cooling chamber (401), the total temperature is lowered to about 60 to 80 degrees, and both the PET and the adhesive are completely solidified. At this time, the edge banding product is formed with the adhesive layer cleanly exposed on one side.

[0491] Step 6: The formed edge banding product is grasped by the withdrawal roller (501) of the withdrawal unit (500) and withdrawn from the cooling chamber (401). The rotational speed of the withdrawal roller (501) is controlled by the transfer speed control unit (405) so that the product is withdrawn at a constant speed.

[0492] The control of the cooling unit (400) is managed integrally by the central control unit. The central control unit collects data from the cooling temperature control unit (403) and the transfer speed control unit (405), and controls each component to maintain optimal cooling conditions. The operator inputs setting values ​​such as cooling water temperature and transfer speed through the HMI, and can monitor the current temperature inside the cooling chamber (401), cooling water flow rate, and temperature of the composite extruded product in real time.

[0493] The cooling unit (400) is equipped with an abnormality detection and safety function, so that when an abnormal situation such as insufficient cooling water flow, abnormal cooling water temperature, or overheating inside the cooling chamber (401) is detected, a warning signal is generated and the equipment is automatically stopped if necessary. This prevents the production of defective products and prevents damage to the equipment.

[0494] Technical effects of the cooling unit (400) and differences from conventional technology

[0495] The cooling unit (400) of the present invention provides the following technical effects.

[0496] First, by adopting an open cooling method that completely removes the mold, edge banding products can be formed with the adhesive layer cleanly exposed on one side. This fundamentally solves the problem of adhesive attachment to the mold, which could not be solved in conventional technology.

[0497] Second, since mold cleaning is unnecessary, continuous production is possible and productivity is significantly improved. The equipment utilization rate can be maintained at over 90%, which leads to a substantial increase in production per hour.

[0498] Third, by precisely controlling the cooling water temperature within the range of 15 to 25 degrees, proper crystallization of PET is ensured and internal stress of the product is minimized, thereby securing excellent mechanical properties and dimensional stability.

[0499] Fourth, by controlling the cooling time by adjusting the transfer speed, it is possible to respond to various product thicknesses or raw material combinations and flexibly adjust production conditions.

[0500] Fifth, since the composite extrusion cools while freely shrinking, warping or twisting of the product is prevented and quality is improved.

[0501] Sixth, mold manufacturing costs are reduced, and flexible response to multi-product production is possible, leading to lower manufacturing costs and improved market competitiveness.

[0502] In conventional technology, attempts were made to cool products with exposed adhesive layers using a mold method, but commercialization was not achieved due to problems with the adhesive adhering to the mold. The cooling unit (400) of the present invention adopts an open cooling method and establishes a system that precisely controls the cooling water temperature and transfer speed, thereby overcoming the limitations of conventional technology and enabling the manufacture of eco-friendly PET edge banding.

[0503] Technical reason and specific implementation method of the withdrawal roller (501)

[0504] As illustrated in FIGS. 1 and 8, the extraction unit (500) includes an extraction roller (501) that grips and extracts an edge banding product that has passed through the cooling unit (400). The extraction roller (501) is configured such that an upper roller and a lower roller form a pair to grip the edge banding product from both sides.

[0505] The technical reason for providing the extraction roller (501) is to enable a continuous production process by stably gripping the edge banding product that has been cooled in an open manner in the cooling section (400) and extracting it at a constant speed. The edge banding product that has passed through the cooling section (400) has mostly solidified but still retains some residual heat, and the crystallization of PET is not yet completely finished. By having the extraction roller (501) grip and extract this product with appropriate pressure, the product can be transferred to a subsequent stretching process while maintaining its shape.

[0506] The specific implementation method of the extraction roller (501) is as follows. The upper roller and the lower roller are each formed into a cylindrical structure with a diameter ranging from 100 mm to 200 mm, and a cover made of rubber or urethane material is installed on the surface to increase friction with the edge banding product. The gap between the two rollers can be adjusted according to the thickness of the edge banding product, and generally, it is set to be 0.1 mm to 0.5 mm smaller than the product thickness to secure appropriate gripping force. If the gap is too narrow, the product is compressed and deformation occurs, and if the gap is too wide, the gripping force is insufficient, causing the product to slip or be extracted irregularly.

[0507] As illustrated in FIG. 8, the pull roller (501) is positioned so that the adhesive layer contacts the lower roller when gripping the edge banding product. This is to minimize surface damage to the adhesive layer, and the surface of the lower roller is coated with fluoropolymer (PTFE) or silicone to prevent adhesion with the adhesive. Since the upper roller contacts the PET resin surface, a standard rubber cover is sufficient.

[0508] The rotation of the extraction roller (501) is achieved by a drive motor (M1) controlled by an extraction speed control unit (502). The drive motor (M1) is connected to either the upper roller or the lower roller, while the other roller rotates in a driven manner. The technical reason for adopting this single drive method is to prevent twisting or damage to the product caused by the speed difference between the two rollers.

[0509] Technical reason for the withdrawal speed control unit (502), critical significance of the numerical range, and specific implementation method

[0510] As illustrated in FIG. 8, the extraction speed control unit (502) controls the extraction speed (V1) of the edge banding product by adjusting the rotational speed of the extraction roller (501). The extraction speed control unit (502) is composed of a drive motor (M1), a speed sensor, a controller, and a power supply.

[0511] The technical reason for providing the drawing speed control unit (502) is to precisely control the product drawing speed from the cooling unit (400) to maintain a balance between the discharge speed at the extrusion head (300) and the drawing speed at the drawing roller (503). If the drawing speed (V1) is too fast, the product is drawn out before it is sufficiently cooled in the cooling unit (400), causing deformation, and if the drawing speed (V1) is too slow, the product is excessively cooled within the cooling unit (400), making drawing difficult or reducing productivity.

[0512] The optimal range and critical significance of the drawing speed (V1) are as follows. The drawing speed (V1) is generally set to a range of 3 to 10 meters per minute. If it is less than 3 meters per minute, the production speed is excessively slow, which reduces economic efficiency, and the product is excessively cooled within the cooling section (400), making it difficult for the PET to achieve molecular orientation during the stretching process. For PET to achieve effective molecular orientation, it must be stretched at a temperature above the glass transition temperature (Tg, approximately 80 degrees). If the temperature drops below the glass transition temperature due to excessive cooling, the product may break or whitening may occur during stretching.

[0513] Conversely, if the withdrawal speed (V1) exceeds 10 meters per minute, the cooling time in the cooling section (400) is insufficient, and the product is withdrawn in a state where it has not solidified sufficiently. This causes problems such as the product being deformed at the withdrawal roller (501) or the adhesive layer sticking to the roller. In addition, an excessive withdrawal speed causes an imbalance with the discharge speed at the extrusion head (300), resulting in uneven thickness of the product or unstable continuous production.

[0514] Therefore, the range of 3 to 10 meters per minute is the optimal range for ensuring sufficient cooling in the cooling section (400) while maintaining a temperature suitable for the stretching process, and simultaneously ensuring productivity and product quality. Within this range, the most desirable drawing speed (V1) is in the range of 5 to 8 meters per minute, and at this speed, the temperature of PET is maintained in the range of about 80 to 100 degrees, thereby forming the most suitable conditions for the subsequent stretching process.

[0515] The specific implementation method of the extraction speed control unit (502) is as follows. The driving motor (M1) uses a servo motor or an induction motor with an inverter control method, and can precisely control the rotational speed in units of 0.1 rpm. The speed sensor is configured as an encoder type installed on the rotation axis of the extraction roller (501), and measures the rotational speed in real time and feeds it back to the controller. The controller uses a PID (Proportional-Integral-Derivative) control method that adjusts the rotational speed of the driving motor (M1) by comparing the set target extraction speed (V1) with the actual measured speed.

[0516] Additionally, the withdrawal speed control unit (502) receives tension information fed back from the tension detection sensor (505) and dynamically adjusts the withdrawal speed (V1). As shown in FIG. 8, when the tension detected by the tension detection sensor (505) exceeds the set range, the withdrawal speed control unit (502) increases or decreases the withdrawal speed (V1) to adjust the tension to an appropriate range. For example, if the detected tension is excessively high, the withdrawal speed (V1) is increased to lower the tension, and if the detected tension is excessively low, the withdrawal speed (V1) is decreased to increase the tension.

[0517] Technical reason and specific implementation method of the stretching roller (503)

[0518] As shown in FIG. 8, the stretching roller (503) is positioned at the rear end of the drawing roller (501) to apply tensile force to the edge banding product and stretch it. The stretching roller (503) consists of a pair of upper and lower rollers similar to the drawing roller (501) and rotates at a faster speed (V2) than the drawing roller (501).

[0519] The technical reason for providing the stretching roller (503) is to induce molecular orientation of the PET resin and improve mechanical properties by applying a tensile force in the longitudinal direction to the edge banding product through the speed difference with the drawing roller (501) and stretching it. As explained in the "Speed ​​Relationship and Stretching Principle" shown at the bottom of FIG. 8, if the stretching speed (V2) is greater than the drawing speed (V1) (V2 > V1), a tensile force is naturally applied to the product located between the two rollers, and stretching occurs as the product stretches in the longitudinal direction due to this tensile force.

[0520] PET resin has an amorphous, random molecular structure in its amorphous state, but undergoing a stretching process aligns the molecular chains in the tensile direction, increasing the degree of crystallinity. This molecular orientation increases the tensile strength of PET by two to three times, improves the modulus of elasticity, and significantly enhances dimensional stability. In particular, since edge banding is attached to the sides of furniture and is exposed to repeated impacts and friction during use, improving mechanical properties through stretching is a key factor in determining the durability and quality of the product.

[0521] The specific implementation method of the stretching roller (503) is as follows. The diameter and surface treatment of the stretching roller (503) are similar to those of the drawing roller (501), having a cylindrical structure with a diameter in the range of 100 mm to 200 mm, and a rubber or urethane cover is installed on the surface. However, since the stretching roller (503) serves to apply tensile force to the product, a higher gripping force than that of the drawing roller (501) is required to prevent slipping. To this end, the surface cover of the stretching roller (503) uses a material having a higher coefficient of friction or forms a fine uneven pattern on the surface to strengthen the gripping force.

[0522] The distance between the stretching roller (503) and the drawing roller (501) is an important design factor as it is directly related to the stretching effect. If the distance between the two rollers is too short, the stretching section is insufficient, and the molecular orientation of PET is incomplete; if the distance is too long, the product may sag or the stretching may be uneven. The optimal distance is in the range of 200 mm to 500 mm, and most preferably in the range of 300 mm to 400 mm. At this distance, the product can be stretched stably while maintaining constant tension.

[0523] The temperature of the product is important during the stretching process. Effective molecular orientation of PET is achieved when it is stretched at a temperature above the glass transition temperature (approximately 80 degrees). Therefore, the temperature of the product must be managed so that it does not drop below the glass transition temperature in the section from the drawing roller (501) to the stretching roller (503). If necessary, an infrared heater or a hot air device can be installed in this section to maintain the temperature of the product within the range of 80 to 120 degrees. In this temperature range, PET has appropriate flexibility without deformation caused by excessive softening, allowing for stable stretching.

[0524] Technical reason for the elongation ratio control unit (504), critical significance of the numerical range, and specific implementation method

[0525] As illustrated in FIG. 8, the stretching ratio control unit (504) controls the stretching ratio of the edge banding product by adjusting the rotational speed of the stretching roller (503). The stretching ratio control unit (504) is composed of a driving motor (M2), a speed sensor, a controller, and a power supply, and has a structure similar to that of the drawing speed control unit (502).

[0526] The technical reason for providing the stretching ratio control unit (504) is to achieve an optimal stretching ratio by precisely controlling the rotational speed (V2) of the stretching roller (503), maximize the molecular orientation of the PET resin, and improve the mechanical properties of the product to a target level. The stretching ratio is defined as the value obtained by dividing the length after stretching by the length before stretching, and mathematically, it is calculated as the ratio of the stretching speed (V2) to the drawing speed (V1). That is, stretching ratio = V2 / V1.

[0527] The optimal range and critical significance of the elongation ratio are as follows. For PET edge banding, the optimal elongation ratio is in the range of 1.2 to 2.5 times. If the elongation ratio is less than 1.2 times, the molecular orientation effect is negligible, resulting in insufficient improvement in mechanical properties. Specifically, at an elongation ratio of less than 1.2 times, the increase in PET tensile strength is limited to 20% or less, and the improvement in crystallinity is also minimal, making the performance of the elongation process largely meaningless. Furthermore, a low elongation ratio limits the improvement in dimensional stability, making the product prone to shrinkage when exposed to heat.

[0528] Conversely, if the elongation ratio exceeds 2.5 times, various problems arise. First, excessive elongation causes the product thickness to become excessively thin. Since elongation has the effect of stretching the product in the length direction while simultaneously thinning it in the thickness direction, excessive elongation can actually reduce the product's rigidity. Second, an excessive elongation ratio increases the risk of product breakage. If the elongation limit of PET is exceeded, microcracks may occur in the product or it may fracture completely, leading to a halt in production. Third, excessive elongation intensifies shrinkage in the width direction, causing the product to deviate from specifications.

[0529] Therefore, the range of 1.2 to 2.5 times is the optimal range for effectively inducing molecular orientation of PET while preventing product breakage and maintaining an appropriate thickness. Within this range, the most desirable elongation ratio is 1.5 to 2.0 times. Experimental results showed that at an elongation ratio of 1.5 times, the tensile strength of PET increased by approximately 1.8 times compared to before elongation, and at an elongation ratio of 2.0 times, it increased by approximately 2.5 times. In addition, within this range, the degree of crystallinity improved to a level of 40% to 50%, enabling the securing of excellent dimensional stability and heat resistance.

[0530] The specific implementation method of the stretching ratio control unit (504) is as follows. The driving motor (M2) uses a servo motor or an induction motor with an inverter control method, similar to the drawing speed control unit (502). The rotational speed (V2) of the stretching roller (503) is set to the value obtained by multiplying the rotational speed (V1) of the drawing roller (501) by the stretching ratio. For example, if the target stretching ratio is 1.8 times and the drawing speed (V1) is 6 meters per minute, the stretching speed (V2) is set to 10.8 meters per minute.

[0531] The stretching ratio control unit (504) does not simply operate at a fixed stretching ratio, but dynamically adjusts the stretching ratio based on tension information fed back from the tension detection sensor (505). As shown in the "feedback control" section of FIG. 8, when the tension measured by the tension detection sensor (505) deviates from the set range, the stretching ratio control unit (504) adjusts the stretching speed (V2) to maintain the tension within an appropriate range. Since there is a risk of product damage if the tension is excessively high, the stretching speed (V2) is reduced to lower the stretching ratio, and since the stretching effect is minimal if the tension is excessively low, the stretching speed (V2) is increased to raise the stretching ratio.

[0532] In addition, the drawing ratio control unit (504) operates in conjunction with the drawing speed control unit (502). When the drawing speed (V1) changes, the drawing ratio control unit (504) automatically adjusts the drawing speed (V2) to maintain the set drawing ratio. Through this linked control, a constant drawing ratio can be maintained even if production conditions change, thereby ensuring uniformity of product quality.

[0533] Technical reason, critical significance, and specific implementation method of the tension sensing sensor (505)

[0534] As illustrated in FIG. 8, the tension sensing sensor (505) is positioned between the drawing roller (501) and the stretching roller (503) to detect the tension applied to the edge banding product in real time. The tension sensing sensor (505) is one of the most critical components of the drawing unit (500) of the present invention and plays a central role in the feedback control system that enables stable and uniform stretching.

[0535] The technical reason and critical significance of providing a tension sensing sensor (505) are as follows. The tension applied to the product during the stretching process is influenced by various variables such as the stretching ratio, the thickness of the product, the temperature of the PET, and the degree of crystallization. If the tension is not monitored in real time and only the drawing speed (V1) and the stretching speed (V2) are controlled at a fixed ratio, the following problems occur.

[0536] First, if the thickness or mechanical properties of a product change due to variations in the physical properties of the raw material or fluctuations in extrusion conditions, the actual tensile strength may vary significantly even at the same speed ratio. For example, if the thickness of the product is temporarily reduced, the tensile strength may increase rapidly at the same elongation ratio, potentially causing the product to break.

[0537] Second, changes in the product temperature during the stretching phase alter the viscoelastic properties of PET, causing tensile strength to fluctuate even at the same stretching ratio. As the temperature increases, PET stretches more easily, resulting in lower tensile strength; conversely, as the temperature decreases, PET becomes stiffer, leading to higher tensile strength.

[0538] Third, as the molecular orientation of PET progresses during the stretching process, the elastic modulus of the product increases; therefore, even if the same stretching ratio is maintained, the tensile strength tends to increase over time.

[0539] To solve these problems, the actual tension is measured in real time through a tension sensing sensor (505), and this information is fed back to the drawing speed control unit (502) and the drawing ratio control unit (504) to dynamically adjust the drawing speed (V1) and the drawing speed (V2), thereby maintaining optimal tension.

[0540] The critical significance of the optimal tension range is as follows. In the stretching process of PET edge banding, the optimal tension range is 5 N / cm to 20 N / cm per unit width. If the tension is less than 5 N / cm, the stretching effect is negligible, resulting in insufficient molecular orientation and limited improvement in the mechanical properties of the product. Additionally, at low tension, the product may be drawn loosely, causing sagging or winding defects during winding.

[0541] Conversely, if the tension exceeds 20 N / cm, the risk of product breakage increases due to excessive tensile force. In particular, if excessive tension is applied when the PET temperature is low or crystallization has progressed, microcracks or whitening may occur in the product. Furthermore, excessive tension intensifies shrinkage in the width direction of the product, leading to deviation from specifications.

[0542] Therefore, the range of 5 N / cm to 20 N / cm is the optimal tension range that can induce effective molecular orientation while preventing product breakage. Within this range, the most desirable tension is 10 N / cm to 15 N / cm, at which the crystallization and molecular orientation of PET occur most efficiently.

[0543] The specific implementation method of the tension detection sensor (505) is as follows. The tension detection sensor (505) can be implemented using a load cell method or a dancer roll method. The load cell method is a method in which a guide roller through which a product passes is supported by a spring or beam structure, and the force applied to the roller is measured by a load cell. As the tension of the product increases, the force pressing on the roller increases, so the tension can be calculated by detecting this with a load cell.

[0544] The dancer roll method is a method in which a roller capable of moving freely up and down is placed between the extraction roller (501) and the stretching roller (503), and the change in the position of the roller according to the tension of the product is detected by a position sensor. When the tension is high, the dancer roll rises, and when the tension is low, the dancer roll descends. The tension is calculated by measuring the change in the position of the dancer roll using a linear encoder or a potentiometer.

[0545] In the present invention, it is preferable to adopt a load cell method. The technical reason is that the load cell method has a faster response speed, higher measurement precision, and a smaller installation space than the dancer roll method. The tension sensing sensor (505) of the load cell method consists of a guide roller with a diameter of 50 mm to 100 mm, a beam structure supporting it, and a load cell that measures the deformation of the beam. The load cell can measure tension with a precision of 0.1 N using a strain gauge method.

[0546] As illustrated in the "tension feedback control mechanism" of FIG. 8, tension information measured by the tension sensing sensor (505) is transmitted to the controller, and the controller compares it with the set target tension. If the measured tension is higher than the target tension, the controller sends a signal to the withdrawal speed control unit (502) to increase the withdrawal speed (V1) or sends a signal to the stretching ratio control unit (504) to decrease the stretching speed (V2) to lower the tension. Conversely, if the measured tension is lower than the target tension, the controller decreases the withdrawal speed (V1) or increases the stretching speed (V2) to increase the tension.

[0547] This feedback control is implemented using a PID control algorithm. Since PID control determines the control output by considering the current error (Proportional), the accumulated past error (Integral), and the rate of change of the error (Derivative), the tension can converge to the target value quickly and stably. The control period is set to a range of 0.1 to 1 second, which is a speed sufficient to respond quickly to sudden fluctuations in tension.

[0548] Comprehensive Operating Principles and Technical Significance of Feedback Control Systems

[0549] As illustrated in the "feedback control" and "tension feedback control mechanism" sections of FIG. 8, the drawing unit (500) of the present invention comprises a closed-loop feedback control system in which a tension sensing sensor (505), a drawing speed control unit (502), and a stretching ratio control unit (504) operate in conjunction with each other. The operating principle of this system is as follows.

[0550] First, a tension sensing sensor (505) measures the real-time tension applied to the product between the withdrawal roller (501) and the stretching roller (503). The measured tension information is converted into a digital signal and transmitted to a central controller.

[0551] Second, the central controller calculates the error by comparing the measured tension with a preset target tension. If the error exceeds the allowable range (typically within ±5% of the target tension), it generates a control signal.

[0552] Third, the control signal is simultaneously transmitted to the extraction speed control unit (502) and the stretching ratio control unit (504). The two control units each adjust the rotational speeds of the extraction roller (501) and the stretching roller (503) to converge the tension to a target value.

[0553] Fourth, the tension of the product changes according to the controlled drawing speed (V1) and stretching speed (V2), and this is measured again by the tension sensing sensor (505) and fed back to the controller. As this cyclic process is repeated continuously, the tension is maintained at the target value.

[0554] The technical significance of this feedback control system is as follows. First, it can maintain stable elongation despite various disturbances, such as variations in raw material properties, temperature changes, and fluctuations in extrusion conditions. Second, since it automatically controls the quality of the elongation process, it enables the production of uniform products without relying on the operator's skill level. Third, it prevents excessive increases in tension in advance, thereby minimizing product damage and maximizing production efficiency.

[0555] Technical reason and specific implementation method of the winding roller (506)

[0556] As illustrated in FIG. 8, the winding roller (506) is positioned at the rear end of the stretching roller (503) to wind the stretched edge banding product. The winding roller (506) is formed as a large cylindrical structure with a diameter ranging from 300 mm to 800 mm, and is structured so that the product is wound in a roll form.

[0557] The technical reason for providing a winding roller (506) is to wind the stretched edge banding product into a roll shape to facilitate storage, transportation, and subsequent processing. Since edge banding is generally produced continuously in lengths ranging from tens to hundreds of meters, there is a high risk that the product will become tangled or damaged if it is not wound into a roll shape. The wound roll is transported to the final destination and mounted on edge banding construction equipment for use.

[0558] The rotational speed of the winding roller (506) is controlled in conjunction with the stretching ratio control unit (504). As shown in the "Winding Control" section of FIG. 8, when the rotational speed (V2) of the stretching roller (503) is changed by the stretching ratio control unit (504), the rotational speed of the winding roller (506) is also automatically adjusted to prevent the product from becoming loose or being pulled excessively. The linear speed of the winding roller (506) is set to be the same as or slightly faster than the stretching speed (V2) (1.01 to 1.05 times V2), so that a slight winding tension is applied to the product to ensure it is wound tightly.

[0559] The specific implementation method of the winding roller (506) is as follows. The winding roller (506) rotates by a drive motor connected to a central axis, and as the product is wound, the diameter of the roll gradually increases. Since the linear velocity increases at the same rotational speed when the diameter of the roll increases, the rotational speed of the winding roller (506) must decrease inversely proportional to the roll diameter to compensate for this. To this end, a sensor for measuring the roll diameter (e.g., a laser distance sensor or encoder-based diameter calculation) is installed on the winding roller (506), and a controller automatically adjusts the rotational speed based on the measured diameter information.

[0560] In addition, the winding roller (506) is equipped with a tension control function. If the winding tension applied to the product during the winding process is excessive, the product may be deformed or the adhesive layer may be damaged, and if the winding tension is insufficient, the product may be wound loosely and become disheveled during transport. The optimal winding tension is in the range of 1 N / cm to 5 N / cm per unit width, and within this range, the product is wound tightly without deformation. The drive motor of the winding roller (506) has a torque control function to adjust the torque of the motor to maintain the set winding tension.

[0561] The final diameter of the wound roll is generally in the range of 500 mm to 1000 mm, and the width of the roll is the same as the width of the edge-banded product. When winding is completed, the winding roller (506) is stopped, and the product is cut to separate the roll. The separated roll is packaged and shipped.

[0562] Comprehensive operation process and technical effects of the entire extraction unit (500)

[0563] As illustrated in FIGS. 1 and FIGS. 8, the drawing unit (500) of the present invention is an integrated system in which a drawing roller (501), a drawing speed control unit (502), a tension sensing sensor (505), a stretching roller (503), a stretching ratio control unit (504), and a winding roller (506) are organically combined and operated. The overall operation process of the drawing unit (500) is as follows.

[0564] The edge banding product, which has mostly solidified after passing through the cooling section (400) but still has some residual heat, reaches the extraction roller (501). The extraction roller (501) rotates at a constant speed (V1) controlled by the extraction speed control section (502) and grips and extracts the product. The extraction speed (V1) is set to a range of 3 to 10 meters per minute, which is a speed that maintains a temperature (80 to 100 degrees) suitable for stretching while ensuring sufficient cooling in the cooling section (400).

[0565] The withdrawn product passes through the stretching section between the withdrawal roller (501) and the stretching roller (503). In this section, a tension detection sensor (505) measures the tension applied to the product in real time. The measured tension information is transmitted to a controller, and the controller calculates the error by comparing it with the target tension (10 N / cm to 15 N / cm).

[0566] The stretching roller (503) rotates at a speed (V2) faster than the drawing speed (V1) controlled by the stretching ratio control unit (504). The stretching speed (V2) is set to a value obtained by multiplying the drawing speed (V1) by a target stretching ratio (1.5 to 2.0 times). As the stretching roller (503) rotates faster than the drawing roller (501), a tensile force is naturally applied to the product between the two rollers, and the product is stretched in the longitudinal direction.

[0567] When the tension measured by the tension detection sensor (505) deviates from the target range, the controller transmits a feedback signal to the drawing speed control unit (502) and the drawing ratio control unit (504) to adjust the drawing speed (V1) and the drawing speed (V2). Through this feedback control, the tension of the product is always maintained within the optimal range, and stable and uniform drawing is achieved.

[0568] After passing through the stretching roller (503), the stretched product is transferred to the winding roller (506) and wound into a roll. Since the winding roller (506) operates in conjunction with the stretching ratio control unit (504), the winding speed is automatically adjusted according to changes in the stretching speed (V2), so the product does not become loose or pulled excessively.

[0569] The technical effects obtained through the integrated operation of the extraction unit (500) are as follows. First, the molecular orientation of the PET resin is effectively achieved, so that the tensile strength of the edge banding product increases by 2 to 2.5 times compared to before stretching. Second, the degree of crystallization is improved to 40% to 50%, so that dimensional stability and heat resistance are greatly improved. Third, through the feedback control system, products of uniform quality can be stably produced despite variations in production conditions. Fourth, product breakage can be minimized, thereby maximizing production efficiency and yield. Fifth, through the automated control system, worker intervention is minimized and continuous production is possible, so that productivity is greatly improved.

[0570] Comprehensive technical reasons and effects

[0571] As illustrated in FIG. 1, the manufacturing device for edge banding that facilitates adhesive application according to the present invention is composed of a continuous production system in which a first hopper (100), a second hopper (200), a first extrusion unit (110), a second extrusion unit (210), an extrusion head (300), a cooling unit (400), and a drawing unit (500) are integrated. Each component is equipped with a control unit capable of precisely controlling temperature, pressure, speed, etc. independently, and through the interaction between the components, PET resin and adhesive having a melting point difference of 100 degrees or more can be stably composite extruded to manufacture an edge banding product with an adhesive layer exposed on one side.

[0572] In particular, the control of the junction point through the junction point control unit (304) of the extrusion head (300) and the open cooling method of the cooling unit (400) are the most core technical features of the present invention, enabling the manufacture of PET edge banding that was impossible to implement in conventional technology. Through this, edge banding using PET, an eco-friendly material, can be produced to comply with environmental regulations, and work efficiency can be greatly improved as the adhesive layer is exposed on one side, allowing for immediate installation without the application of a separate adhesive.

[0573] In addition, the present invention is manufactured using a manufacturing device for edge banding that is easy to adhesively apply.

[0574] Although embodiments of the present invention have been described in more detail with reference to the attached drawings, the present invention is not necessarily limited to these embodiments and may be modified in various ways within the scope of the technical spirit of the present invention. Accordingly, the embodiments disclosed in the present invention are intended to explain, not limit, the technical spirit of the present invention, and the scope of the technical spirit of the present invention is not limited by these embodiments. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of protection of the present invention shall be interpreted by the claims below, and all technical spirits within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention.

[0575] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims set forth below. Explanation of the symbols

[0576] 100: Hopper No. 1 101: Hopper body 101a: Storage space 102: Supply pipe 103: Preheating heater 104: Supply volume control valve 110: First extrusion section 111: First cylinder 112: First screw 113: First heating section 114: First temperature control unit 115: First pressure regulating unit 116: First discharge port 200: Hopper No. 2 210: Second extrusion section 211: Second cylinder 212: Second screw 213: Second heating section 214: Second temperature control unit 215: Second pressure regulating unit 216: Second discharge port 300: Extrusion head 301: First inlet 302: Second Inlet 303: Confluence 304: Confluence point control unit 305: Temperature maintenance unit 306: Pressure sensing unit 307: Discharge nozzle 400: Cooling section 401: Cooling chamber 402: Cooling water supply unit 403: Cooling temperature control unit 404: Open cooling section 405: Feed speed control unit 500: Withdrawal section 501: Pull-out roller 502: Withdrawal speed control unit 503: Stretch roller 504: Stretch ratio control unit 505: Tension sensing sensor 506: Winding roller

Claims

Claim 1 An apparatus for manufacturing an edge banding with an adhesive layer formed on one surface using a first resin having a melting point difference of 100 degrees or more and an adhesive, wherein the resin and the adhesive having a melting point difference are each supplied from a hopper, heated and melted in an extrusion section, and then combined in an extrusion head to form an integrated composite extruded product, and the product is cooled in an open form without a mold to form an edge banding product with an adhesive layer exposed on one surface, and then drawn out and stretched, comprising: a first hopper for receiving and storing the first resin, which is a PET (Polyethylene Terephthalate) resin; a second hopper for receiving and storing the adhesive; a first extrusion section for heating and melting the first resin supplied from the first hopper to produce a first molten product and extruding the first molten product at a first set pressure; a second extrusion section for heating and melting the adhesive supplied from the second hopper to produce a second molten product and extruding the second molten product at a second set pressure; and the first molten product extruded from the first extrusion section and from the second extrusion section An extrusion head configured to allow the first molten material and the second molten material to merge to form an integrated composite extrusion, while controlling the merging point of the first molten material and the second molten material to prevent premature merging due to the difference in melting points between the first molten material and the second molten material; and a cooling unit that cools the composite extrusion extruded from the extrusion head in an open manner without a mold to form an edge banding product with an adhesive layer exposed on one surface. and a drawing unit that draws out and stretches an edge banding product that has passed through the cooling unit; wherein the first hopper comprises a hopper body for storing a first resin, a supply pipe for transporting the first resin downward by gravity, a preheating heater for preheating the first resin to a temperature lower than its melting temperature, and a supply amount control valve for controlling the amount of feed into the first extrusion unit; and the second hopper comprises a hopper body for storing an adhesive, a supply pipe for supplying the adhesive to the second extrusion unit, a preheating heater for preheating the adhesive to a temperature lower than the preheating temperature of the first resin, and a supply amount control valve for controlling the amount of adhesive supplied to maintain pressure balance; and the first extrusion unitThe first cylinder for receiving a first resin, a first screw for conveying the first resin forward, a first heating unit for melting the first resin, a first temperature control unit for controlling the melting temperature, a first pressure control unit for controlling the pressure, and a first discharge port for discharging the first molten material; the second extrusion unit includes a second cylinder for receiving an adhesive, a second screw for conveying the adhesive forward, a second heating unit for melting the adhesive, a second temperature control unit for controlling the melting temperature, a second pressure control unit for controlling the pressure to maintain a pressure balance with the first extrusion unit, and a second discharge port for discharging the second molten material; the extrusion head includes a first inlet passage for the first molten material to flow in from the top downward, a second inlet passage for the second molten material to flow in from the bottom upward, a junction section for forming a composite extrusion, a junction point control section for controlling the junction point, a temperature control section for maintaining the temperature independently, a pressure sensing section for monitoring the pressure, and a discharge nozzle for discharging the composite extrusion. A manufacturing apparatus for edge banding that facilitates adhesive application, characterized in that the cooling unit comprises a cooling chamber through which a composite extruded material passes in an open space without a mold, a cooling water supply unit for supplying cooling water, a cooling temperature control unit for controlling the cooling speed, an open cooling unit for molding with the adhesive layer exposed on the surface, and a transfer speed control unit for controlling the cooling time, and the drawing unit comprises a drawing roller for gripping and drawing out an edge banding product, a drawing speed control unit for controlling the drawing speed, a drawing roller for drawing by applying tensile force, a drawing ratio control unit for controlling the drawing ratio, a tension sensing sensor for detecting tension, and a winding roller for winding the drawn product. Claim 2 delete Claim 3 delete

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