Method for integrally forming vamps and soles through injection of supercritical materials

Abstract

The invention discloses a method for integrally forming a vamp and a sole by injection of a supercritical material, which comprises the following steps of: preparing the vamp which is provided with a face part and a bottom part, stuffing a shoe tree into an inner cavity of the vamp, and opening the vamp by the shoe tree; the vamp is placed in a mold, and a gap area used for forming the shoe sole is formed between the bottom of the vamp and a cavity of the mold; before the supercritical material is injected into the mold, the supercritical material is preheated, so that the supercritical material is pre-foamed; a preheated supercritical material is injected into the mold and located in a gap area between the vamp and a mold cavity, inert gas is introduced to enable the supercritical material to be foamed, and the vamp and the shoe sole are integrally formed; and opening the mold, and taking out the integrally formed vamp and sole finished product to finish the preparation. The production efficiency is improved, and procedures and labor cost are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of shoe material preparation, in particular to a method for integrally forming a shoe upper and a shoe sole by injection molding using a supercritical material. Background Art

[0002] Existing shoe midsoles made of polymer foam beads generally proceed as follows: first, polymer particles are pre-foamed to form polymer foam beads; second, the foamed polymer foam beads are blown into a mold cavity; third, steam is introduced to heat and pressurize the mold to fuse the polymer foam beads together; finally, the mold is cooled and opened to obtain the molded shoe midsole.

[0003] The midsole and outsole are bonded together with hot-melt adhesive to form a whole. The above process involves many steps and has a low degree of automation. In addition, the preparation of the midsole through the above process requires steam heating and pressure molding. Due to the limited steam temperature and pressure, some high-melting-point polymer foam beads cannot be molded.

[0004] Chinese patent publication number CN109834901A discloses a molding process for integrally molding a shoe midsole and an outsole made of TPU foam particles, comprising the following steps: evenly applying a layer of hot melt adhesive on the fitting surface of the outsole, and then placing the adhesive-coated outsole into a mother mold of a steam molding machine; sucking the TPU foam particles into the interior of the mold and filling the entire mold, and after the molds are closed, passing high-temperature steam into the mold for steam penetration; a secondary mold closing is performed to cause the high-temperature and high-pressure steam to slightly melt the surface of the TPU foam particles, and the PU adhesive applied on the outsole is heated and melted, so that the TPU foam particles on the surface of the mold are pressurized and bonded to each other, and then bonded to the outsole below via the hot melt adhesive; the molded product is water-cooled and shaped, and after the molds are opened, an integrally molded TPU foam particle sole is obtained.

[0005] After the sole is formed, the upper and the sole are processed and formed. Currently, the upper and the sole are usually connected by sewing, which requires a special sewing process and increases labor costs. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a method for integrally forming a shoe upper and a shoe sole by injection molding using a supercritical material.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A method for integrally molding a shoe upper and a shoe sole by injection molding using a supercritical material comprises the following steps:

[0009] Prepare the shoe upper material, cut it according to the specification size and form the shoe upper with an inner cavity, wherein the shoe upper has a top and a bottom, and insert the shoe last into the inner cavity of the shoe upper, so that the shoe last can stretch the shoe upper;

[0010] The shoe upper filled with the shoe last is placed into the mold, with a gap area for forming the sole between the bottom of the shoe upper and the mold cavity;

[0011] Before injecting the supercritical material into the mold, the supercritical material is preheated to form pre-foaming of the supercritical material;

[0012] The preheated supercritical material is injected into the mold, located in the gap area between the upper and the mold cavity, and an inert gas is introduced to foam the supercritical material, so that the upper and the sole are formed into one piece;

[0013] Open the mold, take out the one-piece upper and sole products, take out the shoe last, and complete the preparation.

[0014] As a further improvement, when the supercritical material is injected into the mold for foaming, the bottom of the upper is covered and molded therein, and at the same time, the connection portion between the bottom and the upper portion is covered and molded by the supercritical material.

[0015] As a further improvement, a rubber sheet is placed on the bottom of the mold cavity. After the upper is placed in the mold, a cavity is formed between the bottom of the upper and the rubber sheet. Supercritical material is injected into the cavity. During the foaming molding process of the supercritical material, the bottom of the upper and the rubber sheet are molded as one piece.

[0016] As a further improvement, the upper material is cloth or TPU, EVA.

[0017] As a further improvement, the rubber sheet is provided with a plurality of through holes, and the supercritical material infiltrates into the through holes during the molding process.

[0018] As a further improvement, an injection molding machine is used to inject the supercritical material, and an inert gas is filled into the supercritical material injection pipeline. The supercritical material and the inert gas are transported in the same injection pipeline. The inert gas is used to pre-foam the supercritical foaming material in the injection pipeline. When the supercritical material is injected into the mold, the inert gas is simultaneously injected into the mold to accelerate the foaming of the supercritical material and complete the foaming molding within 10-40 seconds.

[0019] As a further improvement, the bottom of the shoe upper is provided with a plurality of holes, into which the supercritical material penetrates during the foaming process and is formed.

[0020] As a further improvement, the bottom and the top of the shoe upper are formed by sewing with woven thread or bonding them.

[0021] The present invention has the following beneficial technical effects:

[0022] By preheating the supercritical material and introducing inert gas for foaming, pre-foaming is formed before the supercritical material is injected into the mold, reducing the molding time in the mold, achieving rapid molding, and being more stable, so that the upper and sole are molded in one piece in the mold, simplifying the complex process of traditional split production and avoiding the problem of insufficient strength in the bonding process. It has the advantages of simplifying the process flow, improving production efficiency, enhancing the connection strength between the upper and the sole, and reducing costs. DETAILED DESCRIPTION

[0023] In order to further understand the features, technical means, specific objectives and functions achieved by the present invention, the present invention is further described in detail below in conjunction with specific implementation methods.

[0024] A method for integrally molding a shoe upper and a shoe sole by injection molding using a supercritical material comprises the following steps:

[0025] Prepare the shoe upper material, cut it according to the specification size and form the shoe upper with an inner cavity, wherein the shoe upper has a top and a bottom, and insert the shoe last into the inner cavity of the shoe upper, so that the shoe last can stretch the shoe upper;

[0026] The shoe upper filled with the shoe last is placed into the mold, with a gap area for forming the sole between the bottom of the shoe upper and the mold cavity;

[0027] Before injecting the supercritical material into the mold, the supercritical material is preheated to form pre-foaming of the supercritical material;

[0028] The preheated supercritical material is injected into the mold, located in the gap area between the upper and the mold cavity. Inert gas is introduced into the injection pipeline of the supercritical material to foam the supercritical material, so that the upper and the sole are formed in one piece. That is, the inert gas and the supercritical material are transported in the same injection pipeline. There is no need to pre-foam the supercritical material separately, but pre-foaming is completed during the transportation process.

[0029] Open the mold, take out the one-piece upper and sole products, take out the shoe last, and complete the preparation. If shaping is required, perform appropriate trimming and shaping.

[0030] Supercritical materials refer to materials in a fluid state above the critical temperature and critical pressure. Specifically, polymer materials such as thermoplastic polyurethane or ethylene-vinyl acetate copolymer can be used. By adjusting the synergistic effect of temperature and pressure, the gas diffuses in the material and forms a microporous structure to achieve foaming molding. Pre-foaming refers to the initial expansion of the material before entering the mold. Specifically, heating can be used to produce a microporous structure inside the material, which helps to ensure the uniformity of the subsequent foaming process. Inert gas refers to a gas medium with stable chemical properties, such as nitrogen or carbon dioxide, which is used to promote the foaming reaction of the material in the mold and avoid oxidation. The shoe last refers to a support body that matches the shape of the inner wall of the shoe cavity. Specifically, it can be made of wood or plastic and is used to maintain the stability of the upper structure during the molding process.

[0031] Specifically, the upper is cut to form a structure with an inner cavity, which is supported by a shoe last to maintain its pre-set shape. After the mold is closed, a gap of predetermined thickness is formed between the bottom of the upper and the mold cavity. A supercritical material, preheated to a pre-foamed state, is then injected into this gap. Inert gas is simultaneously introduced to accelerate the foaming process. Within the confined space, the material expands to fill the gap and physically bond with the bottom of the upper. Once foaming is complete, the sole and upper form a seamless connection, and the shoe last can be removed from the cavity and reused.

[0032] Compared to existing technologies, which traditionally require the upper and sole to be manufactured separately and then sewn or bonded together, this solution achieves structural integration through simultaneous in-mold molding, eliminating intermediate steps. Steam molding is limited by heat transfer efficiency, while supercritical materials can achieve rapid foaming under the influence of inert gas, shortening molding time and making them suitable for materials with high melting points.

[0033] This application achieves simultaneous molding of the upper and sole, reducing production processes and equipment investment. During the molding process, the foaming pressure of the material is evenly applied to the upper, ensuring product dimensional accuracy. The supercritical material completes the foaming reaction within a sealed mold, avoiding the loss of steam heat energy in traditional processes. The sole and upper are seamlessly connected through material fusion, effectively enhancing the overall structural strength of the product.

[0034] A rubber sheet is placed on the bottom of the mold cavity. After the upper is placed in the mold, a cavity is formed between the bottom of the upper and the rubber sheet. The supercritical material is injected into the cavity. During the supercritical material foaming molding process, the bottom of the upper and the rubber sheet are molded into one piece. The rubber sheet forms the outsole of the shoe, which can play an anti-slip and wear-resistant role.

[0035] Specifically, a rubber sheet is pre-placed at the bottom of the mold cavity. The upper, fitted with the shoe last, is then placed into the mold, creating a cavity between the upper's bottom and the rubber sheet. The preheated supercritical material is injected into this cavity, where it foams and expands under the influence of an inert gas, filling the cavity and coming into contact with the upper's bottom and the rubber sheet. During the foaming process, the material physically bonds with both the upper's bottom fibers and the rubber sheet's surface, ultimately forming an integrated structure with the upper's bottom, the rubber sheet, and the foamed material.

[0036] Compared to existing technologies, traditional soles and uppers require sewing or gluing, which results in low bond strength and complex manufacturing processes. This solution utilizes a rubber sheet and cavity design, allowing the foam material to directly wrap around the bottom of the upper and fuse to the rubber sheet during molding, eliminating the need for additional adhesives or sewing steps and streamlining the production process.

[0037] The shoe upper material is cloth or TPU, EVA.

[0038] Fabric refers to a flexible material woven from natural or synthetic fibers, specifically cotton and linen blends or polyester woven fabrics. Its porous structure enhances the breathability of the upper. TPU refers to thermoplastic polyurethane, specifically processed by injection molding, with an elastic modulus that adapts to the simultaneous deformation requirements of the upper and sole. EVA refers to ethylene-vinyl acetate copolymer, specifically processed by compression foaming, with its flexibility enhancing the bond between the upper and the foam sole.

[0039] Specifically, during the upper production process, fabric is cut and sewn to create a cavity-like structure, while TPU or EVA materials are thermoformed into a pre-set shape. When the supercritical material is injected and foamed, the gaps between the fabric fibers or the microporous structure on the TPU / EVA surface mechanically interlock with the foaming material, preventing interfacial delamination. For example, in the case of TPU, its hot-melt properties allow the bottom of the upper to form a molecular bond with the foamed sole under the high temperature environment of the mold.

[0040] Fabric materials are suitable for the breathability requirements of casual shoes, TPU materials meet the anti-deformation requirements of sports shoes, and EVA materials are suitable for the development of lightweight shoes. The selectivity of the three types of materials provides an implementation basis for different product positioning.

[0041] The rubber sheet is provided with a plurality of through holes, into which the supercritical material infiltrates during the molding process, and the bottom of the shoe upper is also provided with a plurality of holes.

[0042] Among them, the through hole refers to a hole structure that penetrates the surface of the rubber sheet, which can be formed by stamping or laser cutting. The aperture range is, for example, 0.2-2 mm, and the shape of the hole can be circular, elliptical or irregular polygonal. The through holes are evenly or gradiently distributed on the surface of the rubber sheet, and are used to form a material penetration path that penetrates the rubber sheet during supercritical material foaming.

[0043] After the supercritical material is injected into the cavity, it infiltrates into the through-holes of the rubber sheet through pressure during the foaming process. As the material cools and solidifies, the supercritical material in the through-holes forms a physical structure that interlocks with the rubber sheet and simultaneously bonds to the bottom of the upper, ultimately achieving an integrated molding of the sole, rubber sheet, and upper.

[0044] Similarly, the supercritical material will penetrate into the holes at the bottom of the upper during the foaming process, forming a stronger interlocking structure.

[0045] This application solves the problem of complex bonding process and insufficient bonding strength of traditional soles and uppers. It significantly improves the bonding stability of the soles and uppers through a physical interlocking structure, while reducing the amount of glue used and lowering production costs.

[0046] An injection molding machine is used to inject supercritical material, and an inert gas is filled into the supercritical material injection pipeline. The supercritical material and the inert gas are transported in the same injection pipeline. The inert gas is used to pre-foam the supercritical foaming material in the injection pipeline. When the supercritical material is injected into the mold, the inert gas is injected into the mold simultaneously to accelerate the foaming of the supercritical material and complete the foaming molding within 10-40 seconds.

[0047] An injection machine refers to a device used for high-pressure injection of materials. Specifically, it can be achieved by a twin-screw extruder or a plunger injection machine. It is used to achieve precise metering and delivery of supercritical materials. Inert gas refers to a gas with stable chemical properties. Specifically, it can be achieved by nitrogen or carbon dioxide. It is used to trigger the foaming reaction of the material in a closed pipeline. Pre-foaming refers to the initial expansion state formed before the material enters the mold. Specifically, it can be achieved by controlling the injection pressure and temperature of the inert gas so that the material forms a uniform microporous structure in the pipeline. Synchronous injection refers to the simultaneous entry of gas and material into the mold. Specifically, it can be achieved by a multi-channel mixing nozzle to ensure that the foaming reaction is completed quickly in the mold.

[0048] Specifically, after the supercritical material and inert gas are mixed in the injection line, the gas pressure causes a microporous structure to form within the material. When the mixture is injected into the mold, the inert gas continuously acts on the material, causing the foaming reaction to rapidly expand within the mold cavity. By adjusting the line pressure and gas ratio, the foaming process can be completed within 10-40 seconds.

[0049] The synchronous injection of inert gas not only accelerates the foaming reaction speed, but also avoids the performance degradation of the material due to external heating. It is especially suitable for the efficient molding of high-melting-point polymers.

[0050] The bottom and the top of the shoe upper are formed by sewing with woven threads or bonding them.

[0051] Thread sewing involves sewing the bottom of the upper to the front of the shoe using sewing thread. High-strength polyester or nylon thread can be used for overlocking or double-stitching to enhance the tear resistance of the joint. Bonding molding involves bonding the bottom of the upper to the front of the shoe using adhesives. Hot melt adhesive or polyurethane adhesive can be applied locally or fully to achieve a seamless bond. Both methods allow the upper to be joined before being placed in the mold, eliminating the need for a separate sewing step.

[0052] Specifically, after the upper material is cut, the bottom and the top can be sewn together with thread using a sewing machine to form a complete upper structure with an inner cavity; or adhesive can be applied to the connection part using a gluing device, and solidified after pressing. When the connected upper is placed in the mold, the gap between its bottom and the mold cavity is used to accommodate the supercritical material. During the foaming process, the upper and the sole are combined without the need for additional sewing steps. For example, when sewing with thread, the pores formed by the stitches allow the supercritical material to penetrate and wrap around the stitches, enhancing the connection strength; when bonding is used, the adhesive layer and the supercritical material form an interpenetrating structure during the foaming process, improving the interface bonding strength.

[0053] It should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for some of the technical features therein. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for integrally forming a shoe upper and a shoe sole by injection molding using supercritical materials, characterized in that: The following steps are involved: Prepare the shoe upper material, cut it according to the specification size and form the shoe upper with an inner cavity, wherein the shoe upper has a top and a bottom, and insert the shoe last into the inner cavity of the shoe upper, so that the shoe last can stretch the shoe upper; The shoe upper filled with the shoe last is placed into the mold, with a gap area for forming the sole between the bottom of the shoe upper and the mold cavity; Before injecting the supercritical material into the mold, the supercritical material is preheated to form pre-foaming of the supercritical material; The preheated supercritical material is injected into the mold, located in the gap area between the upper and the mold cavity, and an inert gas is introduced to foam the supercritical material, so that the upper and the sole are formed into one piece; Open the mold, take out the one-piece upper and sole products, take out the shoe last, and complete the preparation.

2. The method for integrally molding a shoe upper and a shoe sole by injection molding using supercritical materials according to claim 1, characterized in that: When the supercritical material is injected into the mold for foaming, the bottom of the shoe upper is covered and molded therein, and at the same time, the connection portion between the bottom and the upper portion is covered and molded by the supercritical material.

3. The method for integrally molding a shoe upper and a shoe sole by injection molding using supercritical materials according to claim 1, characterized in that: A rubber sheet is placed on the bottom of the mold cavity. After the upper is placed in the mold, a cavity is formed between the bottom of the upper and the rubber sheet. Supercritical material is injected into the cavity. During the supercritical material foaming molding process, the bottom of the upper and the rubber sheet are formed into one piece.

4. The method for integrally molding a shoe upper and a shoe sole by injection molding using supercritical materials according to claim 1, characterized in that: The shoe upper material is cloth or TPU, EVA.

5. The method for integrally molding a shoe upper and a shoe sole by injection molding using supercritical materials according to claim 4, characterized in that: The rubber sheet is provided with a plurality of through holes, and the supercritical material infiltrates into the through holes during the molding process.

6. The method for integrally molding a shoe upper and a shoe sole by injection molding using supercritical materials according to claim 1, characterized in that: An injection molding machine is used to inject supercritical material, and inert gas is filled into the supercritical material injection pipeline. Supercritical material and inert gas are transported in the same injection pipeline. The inert gas is used to pre-foam the supercritical foaming material in the injection pipeline. When the supercritical material is injected into the mold, the inert gas is injected into the mold simultaneously to accelerate the foaming of the supercritical material and complete the foaming molding within 10-40 seconds.

7. The method for integrally molding a shoe upper and a shoe sole by injection molding using supercritical materials according to claim 1, characterized in that: The bottom of the shoe upper is provided with a plurality of holes, and the supercritical material penetrates into the holes and takes shape during the foaming process.

8. The method for integrally molding a shoe upper and a shoe sole by injection molding using supercritical materials according to claim 1, characterized in that: The bottom and the top of the shoe upper are formed by sewing with woven threads or bonding them.