Supercritical polychromatic multi-density cell integrated foaming process

Abstract

The application discloses a supercritical multicolor and multi-density cell integrated foaming process, which is executed by a supercritical foaming forming machine set and comprises the following steps: an integrated multicolor shoe sole blank is prepared through multicolor injection molding, is placed into a superhigh-pressure foaming kettle, is saturated and impregnated with 28-30 MPa nitrogen gas first, and is expanded to open the gap between high molecular chains; then supercritical carbon dioxide is introduced and the pressure is increased to 35-50 MPa to continue saturation, the dissolution and penetration of the gas in different color zones are controlled by adjusting the pressure and time, and a differential saturation state is formed; after rapid pressure relief, the super-saturated gas is precipitated to form cells, and cell structures with different pore diameters and densities are formed in different color zones. The application can solve the problems that the existing process is mostly used to prepare a shoe sole in a mode of foaming and then pasting and secondary mold pressing, the process flow is long, the shoe sole is prone to delamination, glue opening and cracking during long-term use, and the service life of the product is short, and realizes integrated foaming and forming of a multicolor and multi-density shoe sole.

Description

Technical Field

[0001] This invention relates to the field of supercritical foaming molding technology for polymer materials, specifically to a supercritical multi-color, multi-density integrated foaming process. Background Technology

[0002] Currently, the mainstream manufacturing process for two-color, multi-density foamed shoe soles and similar polymer foamed products on the market adopts a single-color molding process followed by cutting and splicing to achieve a combination of multi-color appearance and dual / multi-density performance.

[0003] Existing technologies generally employ a post-bonding method for production, which involves bonding multiple components that have undergone supercritical foaming together through multiple processes, followed by secondary molding to produce the finished shoe sole. This results in a long production process and makes the product prone to delamination, glue separation, and cracking after long-term use, significantly reducing its lifespan.

[0004] Therefore, to meet current needs, a supercritical multi-color, multi-density integrated foaming process is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a supercritical multi-color, multi-density integrated foaming process. A multi-color shoe sole preform is obtained through multi-color injection molding, placed in an ultra-high pressure foaming autoclave, and first saturated with nitrogen gas at 28-30 MPa to expand the gaps between polymer chains. Then, supercritical carbon dioxide is introduced to increase the pressure to 35-50 MPa for further saturation. By adjusting the pressure and time, the dissolution and penetration of the gas in different color zones are controlled to form differentiated saturation states. After rapid depressurization, the supersaturated gas precipitates and forms pores, creating foam structures with different pore sizes and densities in different color zones, achieving integrated foaming molding of multi-color, multi-density shoe soles. This simplifies the production process and steps, eliminates the use of traditional adhesives, and allows the foamed shoe soles to be directly molded into multi-color integrated supercritical foamed finished shoe soles, solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A supercritical multi-color, multi-density integrated foaming process, wherein the process is executed by a supercritical foaming molding unit, including:

[0008] S1: Using a two-color or multi-color injection molding process, the sole blank with a multi-color partition structure is directly injection molded through multi-color injection molding equipment;

[0009] S2: Place the multi-color integrated preform into an ultra-high pressure foaming autoclave and fill the autoclave with high-pressure nitrogen;

[0010] S3: After nitrogen saturation is achieved, supercritical carbon dioxide is introduced into the reactor;

[0011] S4: After completing the dual-gas saturated impregnation, the foaming kettle is rapidly depressurized to allow the supercritical gas dissolved inside the blank to quickly precipitate and form pores, thus producing a multi-colored integrated foamed shoe sole.

[0012] Furthermore, the reaction temperature during the foaming and molding process is controlled between 20-50℃.

[0013] Furthermore, when filling the reactor with high-pressure nitrogen, the nitrogen pressure is controlled at 28-30 MPa.

[0014] Furthermore, when supercritical carbon dioxide is introduced into the reactor, the overall pressure inside the reactor is increased to 35-50 MPa.

[0015] Furthermore, when high-pressure nitrogen is introduced into the reactor, it is saturated and impregnated at a constant temperature for 2 hours; when supercritical carbon dioxide is introduced into the reactor, it is saturated and impregnated at a constant temperature for another 30-50 minutes.

[0016] Furthermore, by adjusting the pressure and saturation time of supercritical carbon dioxide, the size and density of bubbles in different regions of the green body can be controlled.

[0017] Furthermore, after rapid depressurization and foaming, a high-density structure with fine micropores is formed inside the shoe sole blank.

[0018] Furthermore, the outer layer of the blank has a low-density structure with large pores in the corresponding color area, while the inner layer of the blank has a higher density of fine pores than the outer layer. Different color zones correspond to different pore densities.

[0019] Furthermore, the multi-color integrated preform is a two- or three-color or more integrated injection molding structure with clear boundaries between each color area.

[0020] Furthermore, the various colored areas of the sole blank are a continuous structure without any seams.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. Through multi-color integrated molding process, multi-color and multi-density synchronous integrated molding is achieved, completely eliminating the later cutting, bonding and splicing processes, simplifying the production process, shortening the production cycle, reducing production energy consumption and labor costs, and greatly improving production efficiency; moreover, the color boundaries are regular, without misalignment or color mixing defects, and the multi-color appearance is still complete and clear after foaming, and the appearance texture and integration are far superior to traditional spliced ​​products.

[0023] 2. The products obtained by this process have a continuous structure with no splicing interface, eliminating the risk of delamination, glue separation, or cracking. They have strong structural integrity, stable mechanical properties, excellent bending resistance and fatigue resistance, and significantly improved product service life.

[0024] 3. This process precisely matches multi-color zones with multi-density cell structures. Different color zones correspond to cell structures of different sizes and densities. The cell gradient is controllable and can be adapted to the performance requirements of different parts of the sole. The process is highly adaptable and can be compatible with the production of two-color and multi-color sole products. The process parameters are stable and controllable, and the batch consistency of products is good, making it suitable for large-scale industrial production. Attached Figure Description

[0025] Figure 1 This is a flow chart of the supercritical multicolor multi-density integrated foaming process of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] To address the common problem of current manufacturing technologies that rely on post-bonding, which involves multiple supercritical foaming processes to bond together and then perform a secondary molding process to produce the finished sole, resulting in a long production flow and a high risk of delamination, glue separation, and cracking with long-term use, significantly reducing product lifespan, please refer to [link to relevant documentation]. Figure 1 This embodiment provides the following technical solution:

[0028] A supercritical multi-color, multi-density integrated foaming process, wherein the process is executed by a supercritical foaming molding unit, including:

[0029] S1: The shoe sole blank with a multi-color partition structure is directly injection molded using a two-color or multi-color injection molding process and a multi-color injection molding equipment; the reaction temperature of the foaming molding process is controlled between 20-50℃.

[0030] S2: Place the multi-color integrated green body into an ultra-high pressure foaming kettle, fill the kettle with high-pressure nitrogen, control the nitrogen pressure to 28-30MPa, and saturate impregnate at a constant temperature for 2 hours to allow the nitrogen to penetrate evenly into the polymer matrix of each color area of ​​the green body.

[0031] S3: After nitrogen saturation is completed, supercritical carbon dioxide is introduced into the reactor to increase the overall pressure inside the reactor to 35-50 MPa. The reactor is then kept at a constant temperature for 30-50 minutes to continue saturation impregnation. This increases the overall pressure inside the reactor, allowing the carbon dioxide to penetrate deeply into the green body. By adjusting the pressure and saturation time of the supercritical carbon dioxide, the size and density of the pores in different areas of the green body can be controlled, achieving integrated molding of multi-color zones corresponding to different pore densities on the same product.

[0032] S4: After completing the dual-gas saturated impregnation, the foaming kettle is rapidly depressurized, causing the supercritical gas dissolved inside the blank to quickly precipitate and form pores, producing a multi-color integrated foamed shoe sole. After rapid depressurization and foaming, a high-density structure with fine small pores is formed inside the shoe sole blank; a low-density structure with large pores is formed in the corresponding color areas of the outer layer of the blank; the density of the fine pore areas in the inner layer of the blank is higher than that in the outer layer, with different color zones corresponding to different pore densities, simultaneously achieving a multi-color appearance and multi-density performance; each color area of ​​the shoe sole blank is a continuous integrated structure without seams; the multi-color integrated blank is a two- or three-color integrated injection molding structure with clear boundaries between each color area, without color mixing or misalignment defects, and maintains a complete multi-color zone shape after foaming.

[0033] The supercritical foaming molding unit consists of a multi-color injection molding machine, an ultra-high pressure closed foaming kettle, a high-pressure gas proportioning and conveying module, a constant temperature control module, and a rapid pressure relief control module, which work together to perform the following operations:

[0034] The shoe sole blank with a multi-color partition structure is directly injection molded by multi-color injection molding equipment. The multi-color integrated blank is placed into an ultra-high pressure sealed foaming kettle. High pressure nitrogen is injected into the kettle through a high pressure gas ratio delivery module, so that the nitrogen can be evenly penetrated into the polymer matrix of each color area of ​​the blank.

[0035] After nitrogen saturation is completed, supercritical carbon dioxide is continued to be introduced into the reactor through the high-pressure gas proportioning and delivery module to increase the overall pressure inside the reactor to 35-50MPa. The constant temperature control module is kept in working state to continue constant temperature saturation impregnation for 30-50 minutes, so that carbon dioxide can achieve deep penetration inside the green body.

[0036] After completing the dual-gas saturated impregnation, the foaming kettle is rapidly depressurized through the rapid depressurization control module, causing the supercritical gas dissolved inside the blank to quickly precipitate and form pores. Differentiated cell structures with different densities are formed in different color areas of the blank, resulting in multi-color, multi-density integrated foamed shoe sole products.

[0037] Example 1

[0038] The steps of the supercritical multi-color, multi-density integrated foaming process are as follows:

[0039] The shoe sole blank is injection molded using a two-color injection molding process. The two color areas of the blank are a continuous whole structure with no splicing gaps.

[0040] Place the two-color integrated preform into an ultra-high pressure foaming kettle, close the kettle seal, fill the kettle with nitrogen, control the pressure inside the kettle to be stable at 28MPa, and saturate impregnate at a constant temperature for 2 hours.

[0041] After nitrogen saturation is completed, maintain a constant temperature and continuously inject supercritical carbon dioxide into the reactor to increase the overall pressure inside the reactor to 35 MPa. Continue saturation impregnation at a constant temperature for 30 minutes.

[0042] After saturation, the foaming kettle is quickly and fully depressurized, and the supercritical gas dissolved inside the blank is rapidly released to form pores, thus producing a two-color integrated foamed shoe sole.

[0043] The finished product obtained in this embodiment has two color areas with different densities of cell structure. The outer layer corresponding to the color area has a coarse cell thickness of 2mm, while the inner layer has a higher density of fine cell area. The two colors are clearly separated, with no color mixing or layering.

[0044] Example 2

[0045] The difference between this embodiment and Embodiment 1 is that the supercritical carbon dioxide pressure is increased to 38 MPa, the saturation time is maintained at 30 minutes, and the remaining process steps and parameters are the same as in Embodiment 1.

[0046] The finished product obtained in this embodiment has complete two-color partitioning, more obvious differences in cell density between different color areas, and a coarse cell thickness of 2.9mm in the outer layer corresponding to the color area, resulting in better cushioning performance.

[0047] Example 3

[0048] The difference between this embodiment and Embodiment 1 is that the supercritical carbon dioxide pressure is increased to 42 MPa, the saturation time is maintained at 30 minutes, and the remaining process steps and parameters are the same as in Embodiment 1.

[0049] The finished product obtained in this embodiment has a greater gradient of cell density in different color areas, and the outer layer corresponding to the color area has a coarse cell thickness of 4.5mm. The product has outstanding lightweight effect and better softness.

[0050] Comparison Example

[0051] A control experiment was set up, with nitrogen pressure and saturation time, and carbon dioxide pressure and saturation time kept exactly the same as in Example 1. The reaction temperature was set to be below 20°C and above 50°C, respectively, and foaming molding experiments were conducted.

[0052] The experimental results show that when the reaction temperature exceeds the range of 20~50℃, the gas penetration inside the green body is uneven, the cell formation in different color areas is disordered, the density difference is uncontrollable, and problems such as local cell collapse and color boundary deformation are likely to occur, resulting in a significant reduction in the product qualification rate. This verifies the rationality and optimization of the 20~50℃ process temperature range of the present invention.

[0053] Group Nitrogen pressure / saturation time Carbon dioxide pressure Carbon dioxide saturation time Process temperature Molding effect / performance characteristics Example 1 28MPa / 2h 35MPa 30min 20-50℃ The two colors are clear and without layering; the outer layer has coarse pores with a thickness of 2mm, while the inner layer has fine pores and high density. Example 2 28MPa / 2h 38MPa 30min 20-50℃ The dual-color design is complete, with a coarse outer layer of 2.9mm thick foam, providing excellent cushioning performance. Example 3 28MPa / 2h 42MPa 30min 20-50℃ It features a large cell density gradient, with an outer layer of coarse cells 4.5mm thick, making it lightweight and flexible. Comparative Example 28MPa / 2h 35MPa 30min <20 or >50℃ Disordered cell structure, uncontrolled density, prone to collapse, color boundary deformation, and low pass rate.

[0054] Table 1. Reference Table for Examples and Comparative Examples

[0055] The beneficial effects achieved by the above are as follows: Through multi-color integrated molding technology, multi-color and multi-density simultaneous integrated molding is realized, completely eliminating post-processing cutting, bonding, and splicing, simplifying the production process, shortening the production cycle, reducing energy consumption and labor costs, and significantly improving production efficiency. Furthermore, the color boundaries are regular, without misalignment or color mixing defects, and the multi-color appearance remains complete and clear after foaming, with an appearance and texture far superior to traditional spliced ​​products. Secondly, the product has a continuous overall structure without splicing interfaces, eliminating the risk of delamination, glue separation, and cracking. It has strong structural integrity, stable mechanical properties, excellent bending resistance and fatigue resistance, and a significantly extended product lifespan. Simultaneously, it precisely achieves the corresponding matching of multi-color zones and multi-density cell structures. Different color areas correspond to different sizes and densities of cell structures, and the cell gradient is controllable, adapting to the performance requirements of different parts of the shoe sole. The process is highly adaptable, compatible with the production of two-color and multi-color shoe soles, with stable and controllable process parameters, good batch consistency, and suitability for large-scale industrial production.

[0056] Working principle: A continuous multi-colored shoe sole preform is produced through a two-color or multi-color injection molding process. The preform is placed in an ultra-high pressure foaming autoclave and first impregnated with nitrogen gas at a constant temperature of 28-30 MPa, allowing the nitrogen to penetrate evenly into the polymer matrix and open the gaps between the material molecular chains. Then, supercritical carbon dioxide is introduced to increase the autoclave pressure to 35-50 MPa and continue to maintain a constant temperature saturation. By controlling the carbon dioxide pressure and saturation time, the amount of gas dissolved and the penetration depth in different color areas of the preform are controlled, forming differentiated gas saturation states. Finally, the pressure is rapidly released, and the supersaturated gas instantly precipitates and nucleates, forming a cell structure with different pore sizes and densities in different color areas of the preform. This achieves the integrated molding of multi-color areas with different densities of cells in the same product, completing the integrated preparation of multi-color, multi-density foamed shoe soles without splicing.

[0057] It should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0058] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A supercritical multi-color, multi-density integrated foaming process, characterized in that, The process is performed by a supercritical foaming molding unit and includes: S1: Using a two-color or multi-color injection molding process, the sole blank with a multi-color partition structure is directly injection molded through multi-color injection molding equipment; S2: Place the multi-color integrated preform into an ultra-high pressure foaming autoclave and fill the autoclave with high-pressure nitrogen; S3: After nitrogen saturation is achieved, supercritical carbon dioxide is introduced into the reactor; S4: After completing the dual-gas saturated impregnation, the foaming kettle is rapidly depressurized to allow the supercritical gas dissolved inside the blank to quickly precipitate and form pores, thus producing a multi-colored integrated foamed shoe sole.

2. The supercritical multi-color, multi-density integrated foaming process according to claim 1, characterized in that, The reaction temperature during the foaming molding process is controlled between 20-50℃.

3. The supercritical multi-color, multi-density integrated foaming process according to claim 1, characterized in that, In S2, when high-pressure nitrogen is introduced into the reactor, the nitrogen pressure is controlled to be 28-30 MPa.

4. The supercritical multi-color, multi-density integrated foaming process according to claim 3, characterized in that, In S3, when supercritical carbon dioxide is introduced into the reactor, the overall pressure inside the reactor is increased to 35-50 MPa.

5. The supercritical multi-color, multi-density integrated foaming process according to claim 4, characterized in that, When high-pressure nitrogen is introduced into the reactor, it is saturated and impregnated at a constant temperature for 2 hours; when supercritical carbon dioxide is introduced into the reactor, it is saturated and impregnated at a constant temperature for 30-50 minutes.

6. The supercritical multi-color, multi-density integrated foaming process according to claim 1, characterized in that, By adjusting the pressure and saturation time of supercritical carbon dioxide, the size and density of the bubbles in different regions of the green body can be controlled.

7. The supercritical multi-color, multi-density integrated foaming process according to claim 1, characterized in that, In S4, after rapid depressurization and foaming, a high-density structure with fine small pores is formed inside the shoe sole blank.

8. The supercritical multi-color multi-density integrated foaming process according to claim 7, characterized in that, The outer layer of the blank has a low-density structure with large pores in the corresponding color area, while the inner layer of the blank has a higher density of fine pores than the outer layer. Different color zones correspond to different pore densities.

9. The supercritical multi-color multi-density integrated foaming process according to claim 8, characterized in that, Multi-color integrated preforms are two- or three-color or more integrated injection molding structures with clear boundaries between each color area.

10. The supercritical multi-color, multi-density integrated foaming process according to claim 9, characterized in that, The various colored areas of the sole blank are a continuous structure without any seams.

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