Five-layer co-extrusion die with oblong outlet

Abstract

The application relates to the technical field of blow-filling-sealing integrated machines and discloses a five-layer co-extrusion die head with an oblong outlet, which comprises an inner main body, outer main bodies one to six which are sequentially sleeved on the outer side of the inner main body, a discharge port die plate and a thickness adjusting mechanism, five-layer independent annular flow channels are formed between the inner main body and each outer main body, the five-layer flow channels are sequentially arranged from the inside to the outside as an inner layer contact layer flow channel, an inner layer adhesive layer flow channel, an intermediate barrier layer flow channel, an outer layer adhesive layer flow channel and an outer layer protective layer flow channel, and each layer flow channel is symmetrically and balancedly arranged based on the central axis of the oblong material blank outlet. The inner layer adhesive layer, the intermediate barrier layer and the outer layer adhesive layer are combined to form a three-layer composite structure at a first superposition position, and the three-layer composite structure is extruded into an oblong material blank through the discharge port die plate. The five-layer co-extrusion die head with the oblong outlet adopts a secondary superposition structure to avoid mixed layers, the flow channel is balanced and symmetrical to ensure uniform wall thickness, and the built-in adjusting mechanism can realize independent fine adjustment of the thickness of a single layer.

Description

Technical Field

[0001] This invention relates to the technical field of blow-fill-seal integrated machines, and more particularly to an elongated oval-shaped outlet five-layer co-extrusion die. Background Technology

[0002] Blow-Fill-Seal (BFS) machines are advanced packaging equipment that integrates blow molding, filling, and sealing processes in a single aseptic environment. They are widely used in the pharmaceutical industry for injectable solutions, oral liquids, eye drops, and inhalation preparations, as well as in the food and beverage industry for high-end aseptic packaging production. This technology, with its fully enclosed molding process and extremely low risk of human intervention, is internationally recognized as one of the core technologies for pharmaceutical production with the strongest aseptic assurance capabilities, especially in demanding dosage forms such as small-volume and large-volume injections, ophthalmic preparations, and inhalation preparations. As the core molding component of the entire system, the extrusion die directly determines the geometric accuracy, wall thickness distribution, and mechanical properties and barrier characteristics of the final packaging container. However, currently available oval extrusion dies compatible with BFS machines are all single-layer structures with only a single material flow channel, capable of producing oval preforms of a single material and unable to achieve multi-layer co-extrusion composite processes. This structural limitation results in packaging products that are inadequate in key barrier properties such as oxygen barrier, moisture barrier, and light barrier. For pharmaceutical liquids and high-end beverages that are easily oxidized, easily absorb moisture, or are highly photosensitive, it is difficult to meet the stability requirements for long-term storage, significantly shortening the product shelf life and severely restricting the breadth and depth of the technology's application in the field of high-end aseptic packaging.

[0003] In the field of aseptic packaging molding equipment, specifically blow-fill-seal (BFC) machines, the application of multi-layer co-extrusion technology has lagged behind, particularly in the design of multi-layer co-extrusion dies for oblong (non-circular cross-section) billet exit structures, which still faces numerous technical bottlenecks. The special geometry of oblong billets makes the melt flow behavior at the die exit more complex. Issues such as the thickness distribution of each layer under irregular cross-sections, interlayer interface stability, and weld line control are far more difficult to address than with conventional circular billet multi-layer co-extrusion molding. Summary of the Invention

[0004] Given that the existing equipment is far less capable of multi-layer co-extrusion molding of conventional round blanks, this invention is proposed.

[0005] Therefore, the purpose of this invention is to provide a five-layer co-extrusion die with an elongated oval outlet. The purpose is to construct five independent annular flow channels by nesting the inner body and the six outer body, thus upgrading the equipment from a traditional single-layer material to a five-layer composite structure. The intermediate barrier layer can use high-barrier materials such as EVOH, which significantly improves the moisture-proof, oxygen-proof and light-proof performance of the packaged products, effectively extending the shelf life of pharmaceuticals and high-end beverages, and filling the technical gap in the field of no elongated oval five-layer co-extrusion die.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an elongated oval-shaped five-layer co-extrusion die head, comprising an inner body, and outer bodies one, two, three, four, five and six sequentially fitted on the outer side of the inner body. The outer bodies are fixedly connected by bolts and positioned by locating pins, and the inner body and the outer bodies form five independent annular flow channels. A discharge port template is provided at the discharge end of each of the outer bodies, and the discharge port template has an elongated oval material outlet; Thickness adjustment mechanisms are respectively set at the feed end of each layer of flow channel. Each set of thickness adjustment mechanisms includes an adjustment block and a fine adjustment bolt. The fine adjustment bolt passes through the side wall of the die head body and is connected to the adjustment block. The adjustment block moves along the direction perpendicular to the flow channel under the drive of the fine adjustment bolt to adjust the gap of the single layer of flow channel. The five-layer flow channel includes an inner contact layer flow channel, an inner adhesive layer flow channel, an intermediate barrier layer flow channel, an outer adhesive layer flow channel, and an outer protective layer flow channel. Each layer flow channel is arranged symmetrically and balanced with the central axis of the oblong billet outlet as the reference. The inner adhesive layer flow channel, the middle barrier layer flow channel, and the outer adhesive layer flow channel converge and overlap at the first overlapping position to form a three-layer composite structure; the inner contact layer flow channel, the three-layer composite structure, and the outer protective layer flow channel converge and overlap at the second overlapping position to form a five-layer composite structure, which is then extruded and formed through the discharge port template.

[0007] As a preferred embodiment of the oblong-shaped outlet five-layer co-extrusion die head of the present invention, wherein: the oblong-shaped billet outlet has a racetrack-shaped cross-section with arc segments at both ends and a straight segment in the middle, the length of the straight segment is matched with the cavity layout of the multi-cavity mold of the blow-fill-seal integrated machine, and the length of the billet outlet is positively correlated with the number of cavities of the blow-fill-seal integrated machine. Different lengths of billet outlet can be achieved by changing the outlet template.

[0008] As a preferred embodiment of the five-layer co-extrusion die with an elongated oval outlet according to the present invention, wherein: the length of the flow channel of each layer from the screw inlet to the billet outlet is equal, and the cross-sectional area of ​​the flow channel at the corresponding position of each layer is the same, so as to ensure that the material pressure distribution of each layer is uniform during the extrusion process.

[0009] As a preferred embodiment of the oblong-shaped five-layer co-extrusion die head of the present invention, wherein the flow channel surfaces of each of the outer body and the inner body are polished to prevent sticking.

[0010] As a preferred embodiment of the five-layer co-extrusion die head with an oblong outlet as described in this invention, the outer body one to the outer body six are combined layer by layer from top to bottom, and a sealing structure is provided between adjacent outer bodies.

[0011] As a preferred embodiment of the oblong-shaped five-layer co-extrusion die head of the present invention, wherein: an electric heating plate and a temperature sensor are installed on the outside of the die head body, and the electric heating plate and the temperature sensor are electrically connected to an external temperature control system to control the temperature of each layer of the flow channel inside the die head.

[0012] As a preferred embodiment of the oblong-shaped five-layer co-extrusion die head of the present invention, the five sets of thickness adjustment mechanisms are respectively an inner contact layer adjustment block, an inner adhesive layer adjustment block, an intermediate barrier layer adjustment block, an outer adhesive layer adjustment block, and an outer protective layer adjustment block, and each adjustment block is correspondingly arranged at the feed end of each layer flow channel.

[0013] As a preferred embodiment of the oblong-shaped five-layer co-extrusion die of the present invention, wherein: the material corresponding to the flow channel of the intermediate barrier layer is a high-barrier plastic material, the material corresponding to the flow channel of the inner contact layer is a food-grade or pharmaceutical-grade inner layer material, and the material corresponding to the flow channel of the outer protective layer is a weather-resistant protective material.

[0014] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This invention constructs a five-layer independent annular flow channel by nesting an inner main body with a six-layer outer main body, upgrading the equipment from a traditional single-layer material to a five-layer composite structure; the intermediate barrier layer can use high barrier materials such as EVOH, which significantly improves the moisture-proof, oxygen-proof and light-proof performance of the packaged products, effectively extending the shelf life of pharmaceutical liquids and high-end beverages, and filling the technical gap in the field of no elongated oval five-layer co-extrusion die.

[0015] 2. This invention, by setting a first and a second stacking position, pre-composite the inner adhesive layer, the middle barrier layer, and the outer adhesive layer in three layers, and then finally composites them with the inner contact layer and the outer protective layer. This decomposes the highly turbulent flow field into two low-shear convergences, significantly reducing interlayer shear stress and preventing the interface between the adhesive layer and the barrier layer from being torn or entrained. This fundamentally eliminates dead zones in the flow channel and the risk of material cross-contamination, ensuring a clear interface and uniform thickness of the five-layer material, and greatly improving the product qualification rate.

[0016] 3. This invention, by symmetrically arranging the flow channels of each layer with the central axis of the elongated blank outlet as the reference, and ensuring that the length and cross-sectional area of ​​the flow channels from the screw inlet to the outlet are completely consistent, ensures that the pressure distribution of five materials with different viscosities is uniform during the extrusion process. This effectively solves the problem of uneven thickness at both ends and skewed forming caused by uneven material distribution around the circumference when processing long and narrow bottles using traditional round blanks, and enables the wall thickness tolerance of the extruded blank to be controlled at an extremely high level.

[0017] 4. This invention allows for independent fine-tuning of the flow channel gap of any single layer by rotating the corresponding bolts. Without replacing the die head, the thickness ratio of the barrier layer, adhesive layer, or protective layer can be quickly adjusted according to the rheological properties of the material or the barrier requirements. This greatly enhances the compatibility of the die head with different polymer materials and different composite structure formulations, and reduces equipment debugging costs. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the internal flow channel structure of the elongated oval-shaped five-layer co-extrusion die of the present invention; Figure 2 This is a schematic diagram of the overall structure of the oblong-shaped five-layer co-extrusion die head of the present invention; Figure 3 This is a schematic diagram of the internal flow channel structure of the elongated oval-shaped five-layer co-extrusion die of the present invention; Figure 4 This is a schematic diagram of the material layering and secondary stacking structure of the five-layer co-extrusion die head with an elongated exit shape according to the present invention; Figure 5 This is a schematic diagram of the five-layer flow channel structure of the oblong-shaped five-layer co-extrusion die head of the present invention.

[0019] Explanation of reference numerals in the attached figures: 1. Inner body; 2. Outer body one; 3. Outer body two; 4. Outer body three; 5. Outer body four; 6. Outer body five; 7. Outer body six; 8. Discharge port template; 9. Inner contact layer adjustment block; 10. Inner adhesive layer adjustment block; 11. Intermediate barrier layer adjustment block; 12. Outer adhesive layer adjustment block; 13. Outer protective layer adjustment block; 14. Inner contact layer; 15. Inner adhesive layer; 16. Intermediate barrier layer; 17. Outer adhesive layer; 18. Outer protective layer; 19. First stacking position; 20. Second stacking position. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Example 1

[0021] Reference Figures 1-3This is the first embodiment of the present invention, which provides an elongated oval-shaped five-layer co-extrusion die. The elongated oval-shaped five-layer co-extrusion die includes an inner body 1 and outer bodies 2, 3, 4, 5, 6, and 7, which are sequentially fitted outside the inner body 1. Each outer body is stacked and fitted layer by layer from top to bottom along the axial direction of the inner body 1. Adjacent outer bodies are fixedly connected by multiple sets of bolts arranged at intervals along the circumference, and are positioned in both radial and circumferential directions by paired positioning pins to ensure the coaxiality between the outer bodies. The outer wall of the inner body 1 and the inner wall of each outer body are sequentially separated in the axial direction to form five independent annular flow channels that are completely continuous and non-interconnected in the circumferential direction. Each annular flow channel is arranged around the axis of the inner body 1. The discharge port template 8 is fixedly installed at the discharge end face of each outer body; the discharge port template 8 has an elongated oval material outlet that runs through its thickness direction. The cross-sectional shape of the elongated oval material outlet is racetrack-shaped, that is, it is enclosed by two semi-circular arc segments of equal radius and two parallel straight line segments connecting the endpoints of the two semi-circular arc segments. Thickness adjustment mechanisms are respectively set at the feed end positions of each layer of flow channel; each set of thickness adjustment mechanisms consists of an independent adjusting block and a fine-tuning bolt that cooperates with it; the fine-tuning bolt penetrates the side wall of the die head body radially, and its end extending into the die head body is movably connected to the adjusting block, for example, through a T-slot or ball head structure, so as to realize the conversion of rotary drive into linear displacement; when the fine-tuning bolt is rotated, the adjusting block moves reciprocally in a linear direction perpendicular to the main flow direction of the material in the flow channel, i.e., along the radial direction of the die head, under the axial drive of the fine-tuning bolt. By changing the distance between the adjusting block and the opposite side wall of the flow channel, the independent stepless adjustment of the gap size of the single layer of flow channel at this circumferential position is realized; The five flow channels, from the inside out (i.e., from the side closest to the axis of the inner main body 1 towards the outside away from that axis), are: inner contact layer 14 flow channel, inner adhesive layer 15 flow channel, intermediate barrier layer 16 flow channel, outer adhesive layer 17 flow channel, and outer protective layer 18 flow channel. The geometric center lines of each flow channel are based on the horizontal and vertical center lines of the oblong billet outlet, and are arranged in a balanced manner that is symmetrical in both the left and right and up and down within a 360° circumferential range to ensure that the material in each layer has a consistent linear velocity at the outlet. The discharge ends of the inner adhesive layer 15, the middle barrier layer 16, and the outer adhesive layer 17 flow channels intersect at the same axial position along the material flow direction inside the die head, i.e., the first superposition position 19. The three materials undergo low-shear interlayer superposition at this position to form a pre-composite structure with a three-layer structure of adhesive layer, barrier layer, and adhesive layer. The discharge ends of the inner contact layer 14 flow channels, the flow outlet of the pre-composite structure, and the discharge end of the outer protective layer 18 flow channels intersect again at another axial position closer to the discharge end along the material flow direction, i.e., the second superposition position 20. The pre-composite structure is sandwiched between the inner contact layer material and the outer protective layer material. At this position, the five layers of material are gradually layered and composited to form a five-layer composite melt with complete inner and outer functional materials and a high-barrier composite structure in the middle layer. The five-layer composite melt is then extruded through the elongated blank outlet of the discharge template 8 to form a continuous five-layer composite blank.

[0022] In the racetrack-shaped cross-section of the oblong blank outlet, the vertical distance between the two parallel straight segments, i.e., the outlet width, remains constant. The length of the straight segment between the endpoints of the two semicircular arc segments, i.e., the outlet length, matches the total length of the cavity arrangement of the multi-cavity mold of the blow-fill-seal integrated machine. The length of the straight segment at the blank outlet is linearly and positively correlated with the number of forming cavities in a single cycle of the blow-fill-seal integrated machine. That is, when the number of cavities increases, the length of the straight segment increases accordingly. By detachably replacing the outlet template 8 with different straight segment lengths, the switching of different blank outlet length specifications can be quickly achieved without replacing the entire mold head body to adapt to the production needs of molds with different numbers of cavities.

[0023] The total geometric path length of each flow channel from its respective screw feed inlet to the blank outlet end point of the discharge template 8 is equal; and at any identical axial position along the flow direction, the effective flow cross-sectional area of ​​each flow channel is the same. This setting of equal length and equal cross-sectional area ensures that the five materials with different viscosities have similar flow resistance during the extrusion process, thereby making the pressure distribution and flow velocity of each material layer uniform at the outlet.

[0024] The flow channel surfaces of each outer body and inner body 1 are coated with polytetrafluoroethylene or electrochemically polished to reduce the adhesion and friction coefficient of molten material on the flow channel wall, and avoid material retention and decomposition. Example 2

[0025] Reference Figures 1-5This is the second embodiment of the present invention. The difference between this embodiment and the first embodiment is that the outer body 1 2, outer body 2 3, outer body 3 4, outer body 4 5, outer body 5 6 and outer body 6 7 are assembled and packaged layer by layer from top to bottom in the vertical direction; annular sealing grooves are provided on the mating surfaces of two adjacent outer bodies, and high-temperature resistant elastic sealing rings, such as fluororubber O-rings or metal hollow O-rings, are embedded in the annular sealing grooves to prevent material in each layer of the flow channel from flowing through and leaking under the action of interlayer pressure difference.

[0026] Multiple electric heating plates and multiple temperature sensors are fixedly installed on the outer wall of the die head body. The electric heating plates are cast aluminum or cast copper heaters that are attached to the outer circumference of each outer body. The temperature sensors are thermocouples, with their sensing ends inserted into the die head body near the flow channel of each layer. The electric heating plates and temperature sensors are electrically connected to an external temperature control system, such as a PID temperature controller or a programmable logic controller, through wires. The temperature control system independently controls the power of each electric heating plate based on the real-time temperature signal fed back by the temperature sensor, thereby independently and accurately controlling the temperature of each flow channel area inside the die head within its respective preset process temperature range.

[0027] The thickness adjustment mechanisms are named inner contact layer adjustment block 9, inner adhesive layer adjustment block 10, intermediate barrier layer adjustment block 11, outer adhesive layer adjustment block 12, and outer protective layer adjustment block 13, respectively. Each set of adjustment blocks is an arc-shaped block structure, and its curvature is consistent with the circumferential curvature of the flow channel. Each adjustment block is only set in a local circumferential area of ​​the annular feed end of each flow channel, rather than being set around the entire circumference, in order to adjust the local thickness in the width direction of the billet outlet.

[0028] The material connected to the 16 channels of the intermediate barrier layer is a high-barrier plastic material; the material connected to the 14 channels of the inner contact layer is a food-grade or pharmaceutical-grade inner layer material; and the material connected to the 18 channels of the outer protective layer is a weather-resistant protective material.

[0029] The remaining structure is the same as that in Example 1.

[0030] Based on embodiments 1-2, the working principle of the present invention is as follows: During operation, five different materials are independently fed by five extrusion screws, corresponding to the inner contact layer 14 flow channel, the inner adhesive layer 15 flow channel, the intermediate barrier layer 16 flow channel, the outer adhesive layer 17 flow channel, and the outer protective layer 18 flow channel; among them, the three materials of the inner adhesive layer 15, the intermediate barrier layer 16, and the outer adhesive layer 17 first converge at the first stacking position 19 to complete the three-layer low-shear pre-composite, forming a three-layer composite structure. This pre-composite then converges again with the two materials of the inner contact layer 14 and the outer protective layer 18 at the second stacking position 20, completing the step-by-step layered composite of the five layers of materials; the composite five layers of materials enter the balanced flow channel symmetrically arranged with the central axis of the elongated billet outlet as the reference, and after pressure stabilization and buffering... The elongated oval material blank is evenly conveyed to the outlet template 8. During the entire extrusion process, the operator can rotate the corresponding fine-tuning bolts to drive the inner contact layer adjustment block 9, inner adhesive layer adjustment block 10, intermediate barrier layer adjustment block 11, outer adhesive layer adjustment block 12, and outer protective layer adjustment block 13 to move along the direction perpendicular to the flow channel, and independently adjust the gap size of any layer of the flow channel, thereby achieving precise fine-tuning of the thickness of a single layer of material. At the same time, the electric heating plate and temperature sensor installed on the outside of the die head body are used to accurately control the internal temperature of the die head, ensuring that each layer of material is always in the best melting state. Finally, an elongated oval five-layer composite material blank with clear layers, distinct interfaces, uniform wall thickness, and excellent barrier performance is continuously and stably extruded, and supplied to the blow-fill-seal integrated machine to complete the subsequent blow molding, filling, and sealing processes.

[0031] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An oblong outlet five-layer co-extrusion die comprising an inner body (1), characterized in that: Outer body one (2), outer body two (3), outer body three (4), outer body four (5), outer body five (6) and outer body six (7) are sequentially fitted on the outside of the inner body (1). The outer bodies are fixedly connected by bolts and positioned by positioning pins. The inner body (1) and the outer bodies form five independent annular flow channels. The discharge port template (8) is set at the discharge end of each of the outer bodies, and the discharge port template (8) has an elongated (racetrack-shaped) material outlet; Thickness adjustment mechanisms are respectively set at the feed end of each layer of flow channel. Each set of thickness adjustment mechanisms includes an adjustment block and a fine adjustment bolt. The fine adjustment bolt passes through the side wall of the die head body and is connected to the adjustment block. The adjustment block moves along the direction perpendicular to the flow channel under the drive of the fine adjustment bolt to adjust the gap of the single layer of flow channel. The five-layer flow channel includes an inner contact layer (14) flow channel, an inner adhesive layer (15) flow channel, an intermediate barrier layer (16) flow channel, an outer adhesive layer (17) flow channel and an outer protective layer (18) flow channel. Each layer of flow channel is arranged symmetrically and balanced with the central axis of the oblong billet outlet as the reference. The inner adhesive layer (15) flow channel, the middle barrier layer (16) flow channel and the outer adhesive layer (17) flow channel converge and overlap at the first overlapping position (19) to form a three-layer composite structure; the inner contact layer (14) flow channel, the three-layer composite structure and the outer protective layer (18) flow channel converge and overlap at the second overlapping position (20) to form a five-layer composite structure, which is extruded and formed by the discharge port template (8).

2. The oblong outlet five-layer co-extrusion die of claim 1, wherein: The oblong material outlet has a racetrack-shaped cross section with arc segments at both ends and a straight segment in the middle. The length of the straight segment matches the cavity layout of the multi-cavity mold of the blow-fill-seal machine. The length of the material outlet is positively correlated with the number of cavities of the blow-fill-seal machine. Different length specifications of material outlet can be achieved by changing the outlet template (8).

3. The oblong outlet five-layer co-extrusion die of claim 1, wherein: The lengths of the flow channels in each layer from the screw inlet to the billet outlet are equal, and the cross-sectional areas of the flow channels in each layer are the same at corresponding positions, so as to ensure that the material pressure distribution in each layer is uniform during the extrusion process.

4. The oblong outlet five-layer co-extrusion die of claim 1, wherein: The flow channel surfaces of each of the outer body and the inner body (1) are polished to prevent sticking.

5. The oblong outlet five-layer co-extrusion die of claim 1, wherein: The outer body 1 (2) to the outer body 6 (7) are assembled layer by layer from top to bottom, and a sealing structure is provided between adjacent outer bodies.

6. The oblong outlet five-layer co-extrusion die of claim 1, wherein: An electric heating plate and a temperature sensor are installed on the outside of the die head body. The electric heating plate and the temperature sensor are electrically connected to an external temperature control system to control the temperature of each flow channel inside the die head.

7. The oblong outlet five-layer co-extrusion die of claim 1, wherein: The five sets of thickness adjustment mechanisms are inner contact layer adjustment block (9), inner adhesive layer adjustment block (10), middle barrier layer adjustment block (11), outer adhesive layer adjustment block (12) and outer protective layer adjustment block (13), and each adjustment block is set at the feed end of each layer channel.

8. The oblong outlet five-layer co-extrusion die of claim 1, wherein: The material connected to the flow channel of the intermediate barrier layer (16) is a high-barrier plastic material, the material connected to the flow channel of the inner contact layer (14) is a food-grade or pharmaceutical-grade inner layer material, and the material connected to the flow channel of the outer protective layer (18) is a weather-resistant protective material.

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