Sole based on cold pressing mold and foaming process thereof

Abstract

The invention belongs to the technical field of shoe sole manufacturing processes, and particularly relates to a shoe sole based on a cold pressing mold and a foaming process of the shoe sole. The foaming process comprises the following steps that an elastomer material is subjected to injection molding at 75-230 DEG C to form a cold blank, and the injection molding time is 300-1000 seconds; standing the cold blank at room temperature for 5-8 days; after standing is finished, the cold blank is placed in a cavity of a cold pressing mold, inert gas with the pressure of 3-20 MPa is injected, and foaming is conducted at the temperature of 65-198 DEG C; and standing for 5-10 days after foaming, and carrying out mould pressing and plasticity through an oil press to obtain a foamed product. Through the steps of cold blank standing, mold pressure stable control and the like, the shoe sole foaming ratio, pore diameter, hardness and other performance parameters are small in fluctuation, reproducibility is high, large-scale production is facilitated, and meanwhile under the condition of low cost, the shoe sole has the characteristics of being high in foaming ratio, high in resilience, uniform in internal and skin pore diameter distribution and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of shoe sole manufacturing process, and particularly relates to a shoe sole based on a cold-pressing mold and a foaming process thereof. BACKGROUND

[0002] As a key technology for preparing light-weight and high-performance elastomer products, the physical foaming process is widely used in the field of shoe sole manufacturing. The core principle is to introduce inert gas into the elastomer material to form a uniform bubble structure, thereby reducing the product density and improving the rebound performance to meet the demand for light weight and comfort of the shoe sole. At present, the physical foaming processes commonly used in shoe sole production mainly include high-pressure tank physical foaming and injection-type physical foaming. The former uses a high-pressure tank to treat the elastomer with supercritical gas, and the latter directly injection foams the elastomer mixed with gas by means of a screw.

[0003] However, the existing processes have obvious limitations in shoe sole manufacturing. The high-pressure tank physical foaming needs to be carried out in a high-pressure environment of 25 MPa-60 MPa, and the equipment is large in size and consumes a large amount of inert gas, which not only has safety hazards but also leads to high production energy consumption and high costs. Although the injection-type physical foaming process is relatively simple, the equipment construction cost is as high as 300,000-1,000,000 US dollars, and the compatibility with elastomer materials is poor, making it difficult to adapt to the foaming needs of various elastomers for shoe soles (such as TPU, TPEE, etc.). In addition, the equipment debugging period of the two processes is long (3-6 months), and the operation is difficult, which easily leads to uneven product density and fluctuation of the rebound performance of the shoe sole, affecting batch stability.

[0004] To solve the above problems, the application provides a shoe sole based on a cold-pressing mold and a foaming process thereof. SUMMARY

[0005] The purpose of the application is to provide ABCDE, which, through steps such as cold blanking and mold pressure stable control, has small fluctuations in performance parameters such as shoe sole foaming ratio, pore size, and hardness, strong reproducibility, and is beneficial to large-scale production. At the same time, under low-cost conditions, the shoe sole also has the characteristics of high foaming ratio, high rebound, and uniform pore size distribution inside and on the surface.

[0006] The technical scheme adopted by the application is as follows: A foaming process based on a cold-pressing mold, characterized by comprising the following steps: St1: injection molding an elastomer material into a cold blank at 75-230℃, and the injection molding time is 300-1000 seconds; St2: placing the cold blank at room temperature for 5-8 days; St3: After the settling period, place the cold blank into the cavity of the cold pressing mold, inject inert gas at 3-20 MPa, and foam at 65-198℃. St4: After foaming, let it stand for 5 to 10 days, and then mold it through a hydraulic press to obtain the foamed product.

[0007] In a preferred embodiment, the elastomer material in St1 is any one or more of the following materials: EVA, POE, TPU, TPEE, PEBA or other polyolefin elastomers and nylon elastomers.

[0008] In a preferred embodiment, the water content of the elastomer material is less than 500 ppm.

[0009] In a preferred embodiment, the inert gas in St3 is any one of the following gases: carbon dioxide, nitrogen, or other inert gases.

[0010] In a preferred embodiment, the foaming time in St3 is 70–180 min.

[0011] In a preferred embodiment, the foamed product has an expansion ratio of 180% to 230% and a hardness range of 25 to 55 Asker C.

[0012] In a preferred embodiment, the foamed product has a foam pore size of 100–150 μm and a skin pore size of 23–32 μm.

[0013] In a preferred embodiment, the cold pressing mold is a CMEVA mold.

[0014] A shoe sole based on a cold-pressing mold, prepared by the foaming process of a shoe sole based on a cold-pressing mold as described above, wherein the foaming ratio of the shoe sole is 180% to 230%, the hardness range is 25 to 55 Asker C, the foam pore size is 100 to 150 μm, and the surface pore size is 23 to 32 μm.

[0015] The technical effects achieved by this invention are as follows: This invention achieves small fluctuations in performance parameters such as foaming ratio, pore size, and hardness of the shoe sole through steps such as cold preform static setting and mold pressure stabilization control. It is highly reproducible and conducive to large-scale production. At the same time, under low-cost conditions, the foaming ratio of the shoe sole reaches 180% to 230%, and it also has characteristics such as high resilience and uniform distribution of internal and external pore size, which can meet the performance requirements of the shoe sole. This invention replaces the traditional high-pressure tank with a CMEVA cold-pressing mold, resulting in a smaller equipment size and a required pressure of only 3-20 MPa, far lower than the pressure range of 25-60 MPa in the high-pressure tank process. This significantly reduces gas consumption, thereby reducing safety risks. Furthermore, the equipment construction cost is 70% lower than the existing process, and the construction cycle for basic and auxiliary equipment is only 1-2 months, much shorter than the 3-6 months of the traditional process, making it suitable for rapid production. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0017] 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.

[0018] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0019] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in a preferred embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that mutually excludes other embodiments.

[0020] This embodiment provides a foaming process based on a cold-pressing mold, specifically: Elastomer materials are selected as raw materials and dehydrated to ensure a moisture content of ≤500ppm. The raw materials are then injection molded at 75–230℃ for 300–1000 seconds to produce cold-formed shoe soles. After cooling, the cold-formed soles are left to stand for 5–8 days. After this period, they are placed in the mold chamber of a CMEVA mold (i.e., a cold-pressed EVA mold). The mold chamber pressure is maintained at 3–20MPa using a hydraulic press, and inert gas is introduced into the chamber. Foaming is then carried out at 65–198℃ for 70–180 minutes. After foaming, the blank is removed and left to stand for 5–10 days before being molded using a traditional hydraulic press to obtain the foamed shoe sole. The foaming ratio of this foamed shoe sole is 180%–230%, the internal pore size ranges from 100–150μm, the surface pore size ranges from 23–32μm, and the hardness ranges from 25–55 Asker C.

[0021] Furthermore, the elastomer material is any one or more of the following materials: EVA, POE, TPU, TPEE, PEBA or other polyolefin elastomers and nylon elastomers; the inert gas is any one of the following gases: carbon dioxide, nitrogen or other inert gases.

[0022] By implementing the above-mentioned scheme, through steps such as cold preform settling and mold pressure stabilization control, the performance parameters of the shoe sole, such as foaming ratio, pore size, and hardness, exhibit minimal fluctuations, high reproducibility, and are conducive to large-scale production. Under low-cost conditions, the foaming ratio of the shoe sole reaches 180%–230%, and it also possesses characteristics such as high resilience and uniform pore size distribution in the internal and external layers, meeting the performance requirements of the shoe sole. At the same time, by using CMEVA cold-pressing molds instead of traditional high-pressure tanks, the equipment is smaller in size, requiring only 3–20 MPa, far lower than the pressure range of 25–60 MPa in high-pressure tank processes. This significantly reduces gas consumption, substantially lowering safety risks. Furthermore, the equipment construction cost is 70% lower than existing processes, and the construction cycle for basic and auxiliary equipment is only 1–2 months, much shorter than the 3–6 months of traditional processes, making it suitable for rapid production.

[0023] Example Example 1 TPU blends were selected as raw materials and dehydrated to a moisture content of ≤500ppm. The resulting preforms were then produced by injection molding at 170℃ for 350 seconds. After cooling, the preforms were left to stand for 5 days before being placed in the mold chamber of a CMEVA mold. A hydraulic press was used to maintain the mold chamber pressure at 10–18 MPa, and a mixture of nitrogen and carbon dioxide was injected into the mold chamber. The temperature was controlled at 170℃ for 180 minutes of foaming. After foaming, the preforms were removed and left to stand for 6 days before being shaped using a traditional hydraulic press to obtain the TPU shoe sole. This shoe sole has a foaming ratio of 210%, an internal pore size of 130μm, a surface pore size of 27μm, and a hardness of 38 Asker C. The volume ratio of nitrogen to carbon dioxide in the mixed gas is 1:1.

[0024] It should be noted that the foaming process is an existing mature technology. In this embodiment, the process flow not described in detail refers to the existing technology and will not be elaborated further here.

[0025] Example 2 TPEE blends were selected as raw materials and a cold preform for the sole was produced by injection molding at 200°C for 400 seconds. After cooling, the preform was left to stand for 6 days and then placed into the mold chamber of a CMEVA mold. The pressure in the mold chamber was maintained at 10-18 MPa by a hydraulic press, and nitrogen was injected into the mold chamber. The temperature was controlled at 160°C for 180 minutes for foaming. After foaming, the preform was removed and left to stand for 7 days before being shaped by a conventional hydraulic press to obtain the TPEE sole. The sole had a foaming ratio of 220%, an internal pore size of 140 μm, an outer pore size of 30 μm, and a hardness of 42 Asker C. The volume ratio of nitrogen to carbon dioxide in the mixed gas was 1:1.

[0026] Example 3 Polyamide (PEBA) blends were selected as raw materials. After dehydration treatment to a moisture content of ≤500ppm, the raw materials were injection molded into cold preforms at 220℃ for 450 seconds using an injection molding machine. After cooling, the preforms were left to stand for 7 days and then placed into the mold chamber of a CMEVA mold. The pressure in the mold chamber was maintained at 15-20MPa using a hydraulic press. Carbon dioxide gas was injected into the mold chamber, and the temperature was controlled at 180℃ for 180 minutes for foaming. After foaming, the preforms were removed and left to stand for 10 days before being shaped using a traditional hydraulic press to obtain the PEBA shoe sole. The shoe sole had a foaming ratio of 230%, an internal pore size of 150μm, a surface pore size of 32μm, and a hardness of 35Asker C. The volume ratio of nitrogen to carbon dioxide in the mixed gas was 1:1.

[0027] Example 4 Polyolefin elastomer (POE) blends were selected as raw materials. After dehydration treatment to a moisture content of ≤400ppm, the raw materials were injection molded into cold preforms at 100℃ for 320 seconds using an injection molding machine. After cooling, the preforms were left to stand for 5 days and then placed into the mold chamber of a CMEVA mold. The pressure in the mold chamber was maintained at 5MPa using a hydraulic press, and pure nitrogen was injected into the mold chamber. The temperature was controlled at 90℃ for 80 minutes for foaming. After foaming, the preforms were removed and left to stand for 5 days before being shaped using a conventional hydraulic press to obtain the POE shoe sole. The shoe sole had a foaming ratio of 180%, an internal pore size of 100μm, a surface pore size of 23μm, and a hardness of 45-50 Asker C.

[0028] Example 5 Nylon elastomer (PA) blends were selected as raw materials. After dehydration treatment to a moisture content of ≤350ppm, the raw materials were injection molded into cold preforms at 210℃ for 480 seconds using an injection molding machine. After cooling, the preforms were left to stand for 7 days and then placed into the mold chamber of a CMEVA mold. The pressure in the mold chamber was maintained at 14MPa using a hydraulic press. A mixture of carbon dioxide and nitrogen was injected into the mold chamber, and the temperature was controlled at 170℃ for 115 minutes for foaming. After foaming, the preforms were removed and left to stand for 9 days before being shaped using a conventional hydraulic press to obtain the PA shoe sole. The shoe sole had a foaming ratio of 225%, an internal pore size of 145μm, a surface pore size of 31μm, and a hardness of 35-40 Asker C. The volume ratio of carbon dioxide to nitrogen in the mixed gas was 1:3.

[0029] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A foaming process based on a cold-pressing mold, characterized in that: Includes the following steps: St1: The elastomer material is injection molded into a cold preform at 75-230°C for 300-1000 seconds. St2: Let the cold embryo stand at room temperature for 5 to 8 days; St3: After the settling period, place the cold blank into the cavity of the cold pressing mold, inject inert gas at 3-20 MPa, and foam at 65-198℃. St4: After foaming, let it stand for 5 to 10 days, and then mold it through a hydraulic press to obtain the foamed product.

2. The foaming process based on a cold-pressing mold according to claim 1, characterized in that: In St1, the elastomer material is any one or more of the following materials: EVA, POE, TPU, TPEE, PEBA.

3. The foaming process based on a cold-pressing mold according to claim 1, characterized in that: The water content of the elastomer material is less than 500 ppm.

4. The foaming process based on a cold-pressing mold according to claim 1, characterized in that: In St3, the inert gas is any one of the following gases: carbon dioxide, nitrogen, etc.

5. The foaming process based on a cold-pressing mold according to claim 1, characterized in that: In the St3, the foaming time is 70–180 min.

6. The foaming process based on a cold-pressing mold according to claim 1, characterized in that: The foaming ratio of the foamed product is 180% to 230%, and the hardness ranges from 25 to 55 Asker C.

7. The foaming process based on a cold-pressing mold according to claim 1, characterized in that: The foamed product has a foam pore size of 100-150 μm and a skin pore size of 23-32 μm.

8. The foaming process based on a cold-pressing mold according to claim 1, characterized in that: The cold pressing mold is a CMEVA mold.

9. A shoe sole based on a cold-pressing mold, prepared by the foaming process of a shoe sole based on a cold-pressing mold according to any one of claims 1 to 8, characterized in that: The sole has a foaming ratio of 180% to 230%, a hardness range of 25 to 55 Asker C, a foam pore size of 100 to 150 μm, and a surface pore size of 23 to 32 μm.

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