A method for manufacturing a supercritical foaming sole

Abstract

The invention discloses a method for manufacturing a supercritical foaming sole, and belongs to the field of shoes. The method comprises the following steps: S1: preparing modified nylon particles; S2: injecting a small embryo cold mold product; S3: loading the small embryo cold mold product into a reactor, heating the reactor, and then adding carbon dioxide into the reactor until the pressure in the reactor reaches 25-35 MPa; then circulating the carbon dioxide in the reactor, maintaining the pressure in the reactor at 25-35 MPa during the circulation process; then maintaining the temperature in the reactor at 50-100°C and the pressure at 18-32 MPa, and maintaining pressure penetration for ≤4 hours; S4: opening the reactor for pressure relief and foaming to obtain a modified nylon foaming rough mold; S5: maintaining pressure for shaping; and S6: performing secondary compression molding on the modified nylon foaming rough mold, cooling and shaping after molding, to manufacture the supercritical foaming sole. The method for manufacturing a supercritical foaming sole of the present invention has the advantages of low density, high resilience and high foaming rate.

Description

Technical Field

[0001] The invention belongs to the field of shoes, and in particular relates to a method for manufacturing a supercritical foaming sole. Background Art

[0002] Shoes are people's clothing that people wear and use every day, and the comfort of shoes depends largely on the quality of the soles. Different shoes have different sole qualities, and this article mainly explains the soles of sports shoes.

[0003] Athletic shoes are worn for outdoor activities, and their soles are required to be lightweight, highly elastic, and wear-resistant. Currently, traditional rubber soles are mostly EVA. While EVA rubber soles have a certain degree of elasticity and can meet these requirements to a certain extent, traditional EVA sole foaming technology uses chemical foaming agents to form a foamed material.

[0004] The traditional chemical foaming method uses a large amount of foaming agent and leaves a large amount of chemical residue, which is harmful to the environment and human body. In addition, its foaming effect does not fully meet the needs, and it also has disadvantages such as low foaming rate, small rebound, and easy deformation. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for manufacturing a supercritical foaming sole to overcome at least one of the above-mentioned defects in the prior art.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for manufacturing a supercritical foaming sole, comprising the following steps: S1: mixing polyamide, polyester rubber, a branching agent, an oxidant, and a plasticizer and extruding the mixture to prepare modified nylon particles; S2: performing IP injection on the modified nylon particles obtained in step S1 to obtain a small embryo cold mold product; S3: placing the small embryo cold mold product obtained in step S2 into a reactor, heating the reactor to 110° C.-130° C., then adding carbon dioxide into the reactor until the pressure in the reactor reaches 25-35 MPa, and then circulating the carbon dioxide in the reactor, maintaining the pressure in the reactor at 25-35 MPa during the circulation process. Mpa, the flow of carbon dioxide enables the small embryo cold mold product to be evenly contacted with the carbon dioxide, and then the temperature in the reactor is maintained at 50°C-100°C and the pressure is 18-32Mpa, and the pressure-maintaining penetration is ≤4h. S4: After the pressure-maintaining penetration is completed, the reactor is opened to release the pressure, and the small embryo cold mold product treated in step S3 is taken out and quickly placed in the foaming equipment for foaming to obtain a modified nylon foam rough mold. S5: The modified nylon foam rough mold obtained in step S4 is pressure-maintained and shaped. S6: The modified nylon foam rough mold after the pressure-maintaining and shaping in step S5 is subjected to secondary compression molding, and after molding, it is cooled and shaped to produce a supercritical foamed sole.

[0008] Preferably, the modified nylon particles include the following components by mass: 50-70 parts of polyamide, 20-40 parts of polyester rubber, 4-6 parts of branching agent, 1-2 parts of oxidant, and 5-8 parts of plasticizer.

[0009] Preferably, in step S2, the expansion ratio of the small embryo cold mold product is 1.85-2.30.

[0010] Preferably, in step S3, after the small embryo cold mold product is loaded into the reactor, the reactor is cleaned with 0.1-0.4 MPa carbon dioxide to exhaust the remaining air in the reactor.

[0011] Preferably, in step S3, the temperature in the reactor is maintained at 80° C., the pressure is maintained at 30 MPa, and the pressure-maintaining and penetration time is 3.5 h.

[0012] Preferably, in step S4, the foaming temperature is 100° C.-180° C., and the foaming time is 50 s-210 s.

[0013] Preferably, in step S4, the foaming equipment uses steam heating for foaming.

[0014] Preferably, in step S5, the pressure-maintaining and shaping includes the following steps: placing the modified nylon foam rough mold obtained in step S4 into a sealed pressure-maintaining tank, and filling the pressure-maintaining tank with carbon dioxide to make the pressure value in the pressure-maintaining tank reach 0.7-0.8 MPa, then maintaining the pressure for 22-26 hours and then circulating the air, while gradually discharging the carbon dioxide, filling the tube with air, and maintaining the pressure in the pressure tank at 0.7-0.8 MPa. After the carbon dioxide inside the modified nylon foam rough mold is completely replaced by air, the pressure is slowly released.

[0015] Preferably, in step S6, the modified nylon foam rough mold is placed in a mold, and the modified nylon foam rough mold is subjected to secondary steam compression molding.

[0016] Preferably, the polyester rubber is a high molecular block polymer of polyester hard segments and aliphatic polyether soft segments.

[0017] The beneficial effects of the present invention are:

[0018] 1. Adding polyester rubber to polyamide, combined with the assistance of branching agents, oxidants, and plasticizers to achieve compatible mixing of polyester rubber and polyamide, combined with subsequent injection of small embryo cold mold products with the required foaming ratio, and subsequent treatment of the small embryo cold mold products, the resulting soles have low density, high resilience, high foaming rate, and low specific gravity.

[0019] 2. The foaming equipment uses steam heating and foaming. The high-temperature steam has strong penetrability and can quickly fill the foaming equipment. It can also be evenly coated around the small embryo cold mold product, so that the small embryo cold mold product can be evenly heated to ensure the foaming effect. DETAILED DESCRIPTION

[0020] Example 1

[0021] A method for manufacturing a supercritical foaming sole provided in this embodiment includes the following steps:

[0022] S1: 50 parts polyamide, 40 parts polyester rubber, 4 parts branching agent, 1 part oxidant, and 5 parts plasticizer are mixed and extruded through an extrusion pelletizer to produce modified nylon pellets. The addition of plasticizer affects the diffusion properties of carbon dioxide in the system, increasing the diffusion coefficient and enhancing foaming. Polyester rubber is a high-molecular-weight block polymer composed of polyester hard segments and aliphatic polyether soft segments.

[0023] S2: The modified nylon particles obtained in step S1 are subjected to IP injection to obtain a small embryo cold mold product with a foaming ratio of 1.85.

[0024] S3: Place the small cold mold product obtained in step S2 into a reactor. Use low-pressure carbon dioxide (0.1-0.4 MPa) to purge the reactor and expel any remaining air. Heat the reactor to 110°C using a hot water circulation system. Then, add carbon dioxide until the pressure inside the reactor reaches 30 MPa.

[0025] Experiments show that when the pressure of carbon dioxide exceeds 7.38 MPa and the temperature exceeds 31.1°C, it reaches a supercritical state. Like other supercritical fluids, supercritical carbon dioxide possesses strong solvating power and excellent mass transfer properties. Its surface tension is zero, and it possesses exceptional permeability, allowing it to penetrate into small cold molds. Furthermore, carbon dioxide is an inert gas and will not chemically react with the extracted substances. It is also non-toxic, residue-free, environmentally friendly, and readily available at low cost.

[0026] The supercritical carbon dioxide is then circulated in the reactor, maintaining the pressure at 25 MPa. This flow of supercritical carbon dioxide ensures uniform contact between the small embryo cold mold product and the carbon dioxide, ensuring more complete contact. The pressurization process is gradual. The reactor temperature is maintained at 80°C, the pressure at 30 MPa, and the pressure is maintained for 3.5 hours. This ensures that the supercritical carbon dioxide fully penetrates the micropores of the small embryo cold mold product. This 3.5-hour holding time is set because after 3.5 hours of penetration, the small embryo cold mold product does not show any significant changes.

[0027] S4: After the pressure-maintaining infiltration is complete, the reactor is opened to release the pressure. The small cold mold product treated in step S3 is removed and quickly placed in a foaming apparatus for foaming at a temperature of 100°C for 180 seconds, yielding a modified nylon foam rough mold. The foaming apparatus of this embodiment utilizes steam heating for foaming. The high-temperature steam has strong penetrability, rapidly filling the foaming apparatus and evenly coating the small cold mold product, ensuring uniform heating of the small cold mold product and ensuring a foaming effect.

[0028] S5: The modified nylon foam rough mold obtained in step S4 is subjected to pressure-maintaining shaping to prevent the modified nylon foam rough mold from drying out and cracking. The pressure-maintaining shaping includes the following steps:

[0029] The modified nylon foaming rough mold obtained in step S4 is placed in a sealed pressure-maintaining tank, and carbon dioxide is filled into the pressure-maintaining tank until the pressure inside the pressure-maintaining tank reaches 0.7 MPa. After maintaining the pressure for 24 hours, air is circulated, and air is filled into the tube while gradually releasing the carbon dioxide. At the same time, the pressure inside the pressure-maintaining tank is maintained at 0.7 MPa. After the carbon dioxide inside the modified nylon foaming rough mold is completely replaced by air, the pressure is slowly released. A foam rough mold product with low density, high resilience, and high foaming rate can be produced.

[0030] S6: The modified nylon foam rough mold after pressure holding and shaping in step S5 is subjected to secondary compression molding. Specifically, the modified nylon foam rough mold is placed in a mold, and the modified nylon foam rough mold is subjected to secondary steam compression molding. After molding, it is cooled and shaped to produce a supercritical foam sole.

[0031] Example 2:

[0032] The difference between this embodiment and embodiment 1 is that:

[0033] In the process of preparing the modified nylon particles, the amount of polyester rubber added is greater than 30% and less than or equal to 35% (accounting for the total weight).

[0034] Example 3:

[0035] The difference between this embodiment and embodiment 1 is that:

[0036] In the process of preparing the modified nylon particles, the amount of polyester rubber added is greater than 25% and less than or equal to 30% (accounting for the total weight).

[0037] Example 4:

[0038] The difference between this embodiment and embodiment 1 is that:

[0039] In the process of preparing the modified nylon particles, the amount of polyester rubber added is greater than 20% and less than or equal to 25% (accounting for the total weight).

[0040] Example 5:

[0041] The difference between this embodiment and embodiment 1 is that:

[0042] In the process of preparing the modified nylon particles, the amount of polyester rubber added is less than or equal to 20% (accounting for the total weight).

[0043] Table 1 shows the performance indicators of Examples 1-5. From these data results, it can be seen that as the amount of polyester rubber added in the formula decreases, the specific gravity of the sole product will become lower and lower, and the rebound relative to the polyester rubber reaches a peak when the addition amount is 30%.

[0044] Table 1 Performance indicators of Examples 1-5

[0045]

[0046] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, it should be understood by those skilled in the art that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for making a supercritical foaming sole, characterized in that: The following steps are involved: S1: polyamide, polyester rubber, a branching agent, an oxidant, and a plasticizer are mixed and extruded to prepare modified nylon particles, wherein the polyester rubber is a high molecular block polymer of polyester hard segments and aliphatic polyether soft segments; The modified nylon particles include the following components in parts by mass: Polyamide 50-70 parts; Polyester rubber 20-40 parts; 4-6 parts of grafting agent; 1-2 parts of oxidant; 5-8 parts of plasticizer; S2: IP injection molding the modified nylon particles obtained in step S1 to obtain a small embryo cold mold product, wherein the foaming ratio of the small embryo cold mold product is 1.85-2.30; S3: The small embryo cold mold product obtained in step S2 is placed in a reactor, and the reactor is heated to 110° C.-130° C., and then carbon dioxide is added to the reactor until the pressure in the reactor reaches 25-35 MPa, and then the carbon dioxide is circulated in the reactor. During the circulation process, the pressure in the reactor is maintained at 25-35 MPa. The flow of carbon dioxide allows the small embryo cold mold product to be uniformly contacted with the carbon dioxide. Then, the temperature in the reactor is maintained at 50° C.-100° C. and the pressure is maintained at 18-32 MPa. The pressure penetration is maintained for ≤4 hours. S4: After the pressure-maintaining infiltration is completed, the reactor is opened to release the pressure, and the small cold mold product treated in step S3 is taken out and quickly placed in a foaming equipment for foaming to obtain a modified nylon foam rough mold; S5: Pressure-maintaining and shaping the modified nylon foam rough mold obtained in step S4; S6: performing secondary compression molding on the modified nylon foam rough mold after pressure holding and shaping in step S5, cooling and shaping after molding to produce a supercritical foamed sole.

2. The method for making a supercritical foaming sole according to claim 1, wherein: In step S3, after the small cold mold product is loaded into the reactor, the reactor is cleaned with 0.1-0.4 MPa carbon dioxide to exhaust the remaining air in the reactor.

3. The method for making a supercritical foaming sole according to claim 1, wherein: In step S3, the temperature in the reactor is maintained at 80° C., the pressure is maintained at 30 MPa, and the pressure-maintaining and penetration time is 3.5 h.

4. The method for making a supercritical foaming sole according to claim 1, wherein: In step S4, the foaming temperature is 100° C.-180° C., and the foaming time is 50 s-210 s.

5. The method for making a supercritical foaming sole according to claim 1, wherein: In step S4, the foaming equipment uses steam to heat and foam.

6. The method for making a supercritical foaming sole according to claim 1, characterized in that: In step S5, pressure maintaining and shaping includes the following steps: The modified nylon foam rough mold obtained in step S4 is placed in a sealed pressure-maintaining tank, and carbon dioxide is filled into the pressure-maintaining tank to make the pressure value in the pressure-maintaining tank reach 0.7-0.8 MPa. After maintaining the pressure for 22-26 hours, air circulation is performed. While gradually discharging the carbon dioxide, air is filled into the tube while maintaining the pressure in the pressure tank at 0.7-0.8 MPa. After the carbon dioxide inside the modified nylon foam rough mold is completely replaced by air, the pressure is slowly released.

7. The method for making a supercritical foamed sole according to claim 1, wherein: In step S6, the modified nylon foam rough mold is placed in a mold, and the modified nylon foam rough mold is subjected to secondary steam compression molding.

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