Preparation method of blending modified EVA supercritical foaming material

Abstract

The invention discloses a preparation method of a blending modified EVA supercritical foaming material, which comprises the following steps: step 1, weighing TPEE and EVA, and uniformly stirring through double screws to obtain a mixture; the preparation method comprises the following steps: blending the POE-g-MAH and the EPDM-g-MAH to prepare a composite compatilizer; step 2, blending the mixture obtained in the step 1, a composite compatilizer, a lubricant ST and a cross-linking agent dicumyl peroxide in an internal mixer, then granulating, and preparing small test pieces through an injection machine; 3, the small test piece is taken and placed in a reaction kettle for supercritical foaming, and a supercritical foaming test piece is obtained; step 4, taking the supercritical foaming test piece, cutting, and performing oil pressure shaping to prepare the modified EVA supercritical foaming material; the prepared foaming material is finer in cell density and high in rebound resilience, the hardness, density and compression set are obviously reduced, and the foaming material can be widely applied to the shoe material manufacturing industry.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer composites, and particularly relates to a preparation method of a blended modified EVA supercritical foaming material. BACKGROUND

[0002] With the rapid development of economy and technology, China has become the first country in shoe material manufacturing and production, with an annual production capacity of more than 3 billion pairs of shoes. The midsole is the core component of a pair of sports shoes and is the soul of sports shoes, and is the core competitiveness and foundation of major manufacturers. EVA (ethylene-vinyl acetate copolymer) soon replaced rubber as the most widely used foaming shoe material because of its light weight, obvious shock absorption effect, absorption of impact force generated during exercise, and VA component that can reduce the crystallinity of EVA, improve toughness and resilience. However, single EVA base material has poor durability, insufficient support and poor environmental weather resistance, which cannot meet the needs of high-performance foaming material products and to some extent limits its use scenarios. In order to improve the shortcomings caused by the structure of EVA, it is necessary to modify EVA to improve the comprehensive performance of EVA.

[0003] As a high-performance foaming shoe material, TPEE is a block copolymer containing polyester hard segments and polyether soft segments. The polyester hard segments impart high hardness, melting point, excellent mechanical properties and thermal stability, and the polyether soft segments impart good flexibility, resilience and processing performance to TPEE. Using TPEE to modify EVA can significantly make up for the defects of pure EVA and also control the high cost of pure TPEE. However, TPEE and EVA are thermodynamically incompatible polymers, which will cause phase separation of the material when blended, poor interfacial adhesion, and the role of TPEE cannot be fully played.

[0004] In the existing disclosed technology, Chinese patent CN117659556A discloses a modified EVA foaming material for shoe soles and a preparation method, wherein a foaming agent, a crosslinking agent, zinc oxide, POE, and glycidyl methacrylate, dicyclopentenyl acrylate, dicyclopentadiene oxyethyl acrylate, a first initiator, a second initiator, and n-dodecyl mercaptan are used. The modified EVA composite material obtained by this patent has good tensile properties and compression permanent deformation, but the types of raw materials are various, the process is complex, and the hardness of the modified material is high. Chinese patent CN118772600A discloses a high-wear-resistant TPEE supercritical foaming material and a preparation method thereof, wherein TPEE, TPU and EVA are used as the main material blend, and SEBS-g-MAH is selected as the compatibilizer to improve the compatibility and increase the wear resistance. The material obtained by this patent has good wear resistance and compression set, but the density is still large (0.25 g / cm 3It is difficult to achieve the requirement of lightweight, and the single compatibilizer used has poor heat resistance and high cost.

[0005] For foaming processes, chemical foaming is the most common foaming process for shoe materials. However, as people's requirements for shoe materials gradually increase, chemical foaming is difficult to meet the requirements of high-end shoe materials. Moreover, the chemical foaming agents used are prone to producing a lot of by-products when decomposing, resulting in products with odors and color deviations. Supercritical foaming, on the other hand, can achieve lightweight, high resilience, and durability in shoe materials. Furthermore, the CO2 and N2 used are inexpensive, the critical pressure and temperature are relatively mild, and the chemical properties are stable, making it green and environmentally friendly. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for preparing a blended modified EVA supercritical foam material, solving the problems of insufficient EVA performance, poor compatibility of TPEE and ethylene-vinyl acetate copolymer blending modification, and foaming process issues in the prior art. Directly blending TPEE and ethylene-vinyl acetate copolymer in this invention has limited effect on improving the mechanical properties of EVA. To reduce the interfacial tension between the two phases, an appropriate compatibilization method is needed to improve the mechanical properties of the blended material. Grafted POE (POE-g-MAH) is a graft copolymer of maleic anhydride and POE. This copolymer has extremely high toughening efficiency, good processing fluidity, and good dispersibility, but low upper limit of operating temperature and low compression set. Grafted EPDM (EPDM-g-MAH) has a fully saturated main chain, contains no double bonds, has a high upper limit of operating temperature, and its compression set performance is far superior to POE. However, EPDM itself has a large molecular weight, resulting in poor processing fluidity and low toughening efficiency. Therefore, this invention uses a composite compatibilizer to improve the shortcomings of a single compatibilizer and enhance the compatibility of the blend, and the two compatibilizers used are inexpensive.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a blended modified EVA supercritical foam material specifically includes the following steps:

[0009] Step 1: Weigh TPEE and EVA and stir them evenly with a twin-screw extruder to obtain a mixture; then blend POE-g-MAH and EPDM-g-MAH to prepare a composite compatibilizer.

[0010] Step 2: Take the mixture obtained in Step 1 and blend it with the composite compatibilizer, lubricant ST, and crosslinking agent dicumyl peroxide in a mixer, then granulate it and prepare small test pieces through an injection molding machine;

[0011] Step 3: Take the small test piece obtained in Step 2 and place it in the reaction vessel for supercritical foaming, then cut it into pieces to obtain super-foamed test pieces;

[0012] Step 4: Take the super-foamed sample obtained in Step 3, cut it, and perform hydraulic shaping to prepare the supercritical foamed material of TPEE modified EVA.

[0013] Furthermore, the mass ratio of TPEE to EVA mentioned in step 1 is 7:15.

[0014] Furthermore, in step 1, TPEE and EVA are stirred evenly at a temperature of 195°C using a twin-screw extruder.

[0015] Furthermore, the mass ratio of POE-g-MAH to EPDM-g-MAH in step 1 is 1:1.5.

[0016] Furthermore, in step 2, the mass ratio of the mixture, composite compatibilizer, lubricant ST, and crosslinking agent dicumyl peroxide is 1500:15-105:8:4.

[0017] Furthermore, in step 2, the internal mixer processing temperature is 115℃.

[0018] Furthermore, in step 2, the temperature of the machine gun head is 95°C, and the heating time is 400 seconds.

[0019] Furthermore, in step 3, the supercritical foaming temperature is 133℃, the pressure is 28MPa, and the holding time is 120 min.

[0020] Furthermore, the conditions for hydraulic shaping in step 4 are as follows: first, heating at a temperature of 165°C for 500 seconds, then water cooling to room temperature for 500 seconds.

[0021] The blended modified EVA supercritical foam material was prepared according to the above-mentioned preparation method.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The formulation of this invention includes a composite compatibilizer, which has high toughening efficiency, good processing fluidity, and good dispersibility, thus making up for the shortcomings of a single compatibilizer and improving the compatibility of the blended material.

[0024] 2. This invention uses high-performance elastomer TPEE to modify EVA, which improves the limitation of single EVA, increases resilience, and reduces density and compression set.

[0025] 3. This invention uses supercritical foaming technology, which makes the foamed material have a finer pore density, improves toughness and thermal shrinkage performance, overcomes the shortcomings of chemical foaming processing technology, and meets green and environmentally friendly standards. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to specific embodiments.

[0027] This invention uses EVA7470m from Taiwan Plastics Industries Co., Ltd. as the EVA base material in the blended material.

[0028] A method for preparing a blended modified EVA supercritical foam material specifically includes the following steps:

[0029] Step 1: Weigh TPEE and EVA (TPEE to EVA mass ratio of 7:15) and stir them evenly at 195℃ using a twin-screw extruder to obtain a mixture; then blend POE-g-MAH and EPDM-g-MAH (POE-g-MAH to EPDM-g-MAH mass ratio of 1:1.5) to prepare a composite compatibilizer.

[0030] Step 2: Take the mixture obtained in Step 1 and mix it with the composite compatibilizer, lubricant ST, and crosslinking agent dicumyl peroxide (the mass ratio of the mixture, composite compatibilizer, lubricant ST, and crosslinking agent dicumyl peroxide is 1500:15-105:8:4) in an internal mixer. The mixing temperature is 115℃. Then, granulate the mixture and prepare small test pieces through an injection molding machine. The temperature of the injection molding machine gun head is 95℃ and the heating time is 400s.

[0031] Step 3: Take the small test piece obtained in Step 2 and place it in the reactor for supercritical foaming. The supercritical foaming temperature is 133℃, the pressure is 28MPa, and the holding time is 120 min. Then cut the test piece to obtain the super-foamed test piece.

[0032] Step 4: Take the super-foamed sample obtained in Step 3, cut it, and perform hydraulic pressing to prepare the supercritical foamed material of TPEE modified EVA. The hydraulic pressing conditions are: first heat at 165℃ for 500s, then water cool to room temperature for 500s.

[0033] Example 1

[0034] Step 1: TPEE and EVA are stirred evenly at 195°C using a twin-screw extruder at a mass ratio of 7:15 to obtain a mixture; POE-g-MAH and EPDM-g-MAH are blended at 125°C at a mass ratio of 1:1.5 to obtain the composite compatibilizer POE-g-MAH / EPDM-g-MAH.

[0035] Step 2: The mixture obtained in Step 1 is mixed and modified with composite compatibilizer, lubricant ST, and crosslinking agent dicumyl peroxide at a mass ratio of 1500:15:8:4 at 115°C. Then, the mixture is granulated and small test pieces are prepared by injection molding machine with the injection gun head temperature at 95°C and the heating time at 400s.

[0036] Step 3: The small test piece prepared in Step 2 is foamed at a temperature of 133℃, a pressure of 28MPa, and a holding time of 120 min. The resulting test piece is then cut into long sections. Width Height is 25cm 25cm 1cm.

[0037] Step 4: Heat the small sample obtained in Step 3 at 165℃ for 500s, and then cool it to room temperature for 500s to prepare the supercritical foaming material of TPEE modified EVA.

[0038] Example 2

[0039] Step 1: TPEE and EVA are stirred evenly at 195°C using a twin-screw extruder at a mass ratio of 7:15 to obtain a mixture; POE-g-MAH and EPDM-g-MAH are blended at 125°C in a ratio of 1:1.5 to obtain the composite compatibilizer POE-g-MAH / EPDM-g-MAH.

[0040] Step 2: The mixture obtained in Step 1 is mixed and modified with composite compatibilizer, lubricant ST, and crosslinking agent dicumyl peroxide at a mass ratio of 1500:45:8:4 at 115°C. Then, the mixture is granulated and small test pieces are prepared by injection molding machine. The temperature of the injection molding machine gun head is 95°C and the heating time is 400s.

[0041] Step 3: The small test piece prepared in Step 2 is foamed at a temperature of 133℃, a pressure of 28MPa, and a holding time of 120 min. The resulting test piece is then cut into long sections. Width Height is 25cm 25cm 1cm.

[0042] Step 4: Heat the small sample obtained in Step 3 at 165℃ for 500s, and then cool it to room temperature for 500s to prepare the supercritical foaming material of TPEE modified EVA.

[0043] Example 3

[0044] Step 1: TPEE and EVA are stirred evenly at 195°C using a twin-screw extruder at a mass ratio of 7:15 to obtain a mixture; POE-g-MAH and EPDM-g-MAH are blended at 125°C in a ratio of 1:1.5 to obtain the composite compatibilizer POE-g-MAH / EPDM-g-MAH.

[0045] Step 2: The mixture obtained in Step 1 is mixed and modified with composite compatibilizer, lubricant ST, and crosslinking agent dicumyl peroxide at a mass ratio of 1500:75:8:4 at 115°C. Then, the mixture is granulated and small test pieces are prepared by injection molding machine with the injection gun head temperature at 95°C and the heating time at 400s.

[0046] Step 3: The small test piece prepared in Step 2 is foamed at a temperature of 133℃, a pressure of 28MPa, and a holding time of 120 min. The resulting test piece is then cut into long sections. Width Height is 25cm 25cm 1cm.

[0047] Step 4: Heat the small sample obtained in Step 3 at 165℃ for 500s, and then cool it to room temperature for 500s to prepare the supercritical foaming material of TPEE modified EVA.

[0048] Example 4

[0049] Step 1: Weigh TPEE and EVA at a mass ratio of 7:15 and stir them evenly at 195℃ using a twin-screw extruder to obtain a mixture; then blend POE-g-MAH and EPDM-g-MAH at a ratio of 1:1.5 at 125℃ to obtain the composite compatibilizer POE-g-MAH / EPDM-g-MAH.

[0050] Step 2: The mixture obtained in Step 1 is mixed and modified with composite compatibilizer, lubricant ST, and crosslinking agent dicumyl peroxide at a mass ratio of 1500:105:8:4 at 115°C. Then, the mixture is granulated and prepared into small test pieces by injection molding machine. The temperature of the injection molding machine gun head is 95°C and the heating time is 400s.

[0051] Step 3: The small test piece prepared in Step 2 is foamed at a temperature of 133℃, a pressure of 28MPa, and a holding time of 120 min. The resulting test piece is then cut into long sections. Width Height is 25cm 25cm 1cm.

[0052] Step 4: Heat the small sample obtained in Step 3 at 165℃ for 500s, and then cool it to room temperature for 500s to prepare the supercritical foaming material of TPEE modified EVA.

[0053] Example 5

[0054] Step 1: TPEE and EVA are stirred evenly at 195°C using a twin-screw extruder at a mass ratio of 7:15 to obtain a mixture; POE-g-MAH and EPDM-g-MAH are blended at 125°C in a ratio of 1:1.5 to obtain the composite compatibilizer POE-g-MAH / EPDM-g-MAH.

[0055] Step 2: The mixture obtained in Step 1 is mixed and modified with composite compatibilizer, lubricant ST, and crosslinking agent dicumyl peroxide at a mass ratio of 1500:135:8:4 at 115°C. Then, it is granulated and small test pieces are prepared by injection molding machine with the temperature of the injection gun head at 95°C and the heating time at 400s.

[0056] Step 3: The small test piece prepared in Step 2 is foamed at a temperature of 133℃, a pressure of 28MPa, and a holding time of 120 min. The resulting test piece is then cut into long sections. Width Height is 25cm 25cm 1cm.

[0057] Step 4: Heat the small sample obtained in Step 3 at 165℃ for 500s, and then cool it to room temperature for 500s to prepare the supercritical foaming material of TPEE modified EVA.

[0058] Comparative example

[0059] Step 1: TPEE and EVA are mixed at 195°C using a twin-screw extruder at a mass ratio of 7:15 to obtain a homogeneous mixture.

[0060] Step 2: The mixture obtained in Step 1 is mixed and modified with lubricant ST and crosslinking agent dicumyl peroxide at a mass ratio of 1500:8:4 at 115°C. Then, it is granulated and small test pieces are prepared by injection molding machine with the temperature of the injection gun head at 95°C and the heating time at 400s.

[0061] Step 3: The small test piece prepared in Step 2 is foamed at a temperature of 133℃, a pressure of 28MPa, and a holding time of 120 min. The resulting test piece is then cut into long sections. Width Height is 25cm 25cm 1cm.

[0062] Step 4: Heat the small sample obtained in Step 3 at 165℃ for 500 seconds, then cool it to room temperature with water for 500 seconds.

[0063] The foamed material was prepared.

[0064] The foamed materials prepared in Examples 1-5 and the comparative examples were subjected to tests for resilience, hardness, density, and compression set.

[0065] Table 1. Comparison of springback between Examples 1-5 and Comparative Examples

[0066]

[0067] As shown in Table 1, compared with the foamed materials without the composite compatibilizer POE-g-MAH / EPDM-g-MAH, the rebound of Examples 1-5 is significantly improved, indicating that the rebound performance of the foamed materials prepared by the present invention is improved, that is, the compatibility of the foamed materials is significantly increased.

[0068] Table 2. Hardness comparison between Examples 1-5 and Comparative Examples

[0069]

[0070] As shown in Table 2, compared with the foamed material without the composite compatibilizer POE-g-MAH / EPDM-g-MAH, the hardness of Examples 1-5 is significantly reduced, indicating that the flexibility of the foamed material prepared by the present invention is improved.

[0071] Table 3. Density comparison between Examples 1-5 and Comparative Examples

[0072]

[0073] As shown in Table 3, compared with the POE-g-MAH / EPDM-g-MAH foamed material without composite compatibilizer, the densities of Examples 1-5 are significantly reduced. This is because the compatibility of the foamed material increases significantly after the addition of the compatibilizer, and the cell structure is more refined during foaming.

[0074] Table 4 Comparison of compression set of Examples 1-5 and Comparative Examples

[0075]

[0076] As shown in Table 4, compared with the foamed materials without the composite compatibilizer POE-g-MAH / EPDM-g-MAH, the compression set of Examples 1-5 was reduced. This indicates that after using POE-g-MAH for compatibilization, the cross-linked network structure of EVA and TPEE is more tightly bonded, and the ability to resist permanent deformation and toughness are significantly improved.

[0077] The above description of the present invention represents only some embodiments, but the present invention is not limited to the above examples. The above embodiments are illustrative and not restrictive. All specific extensions using the materials and methods of the present invention, without departing from the spirit and scope of the claims, are within the protection scope of the present invention.

Claims

1. A method for preparing a blended modified EVA supercritical foam material, characterized in that, Specifically, the implementation steps include the following: Step 1: Weigh TPEE and EVA and stir them evenly with a twin-screw extruder to obtain a mixture; then blend POE-g-MAH and EPDM-g-MAH to prepare a composite compatibilizer. Step 2: Take the mixture obtained in Step 1 and blend it with the composite compatibilizer, lubricant ST, and crosslinking agent dicumyl peroxide in a mixer, then granulate it and prepare small test pieces through an injection molding machine; Step 3: Take the small test piece obtained in Step 2 and place it in the reaction vessel for supercritical foaming, then cut it into pieces to obtain super-foamed test pieces; Step 4: Take the super-foamed sample obtained in Step 3, cut it, and perform hydraulic shaping to prepare the supercritical foamed material of TPEE modified EVA.

2. The method for preparing a blended modified EVA supercritical foaming material according to claim 1, characterized in that, The mass ratio of TPEE to EVA mentioned in step 1 is 7:

15.

3. The method for preparing a blended modified EVA supercritical foaming material according to claim 1, characterized in that, In step 1, TPEE and EVA are mixed evenly using a twin-screw extruder at a temperature of 195°C.

4. The method for preparing a blended modified EVA supercritical foaming material according to claim 1, characterized in that, The mass ratio of POE-g-MAH to EPDM-g-MAH in step 1 is 1:1.

5.

5. The method for preparing a blended modified EVA supercritical foaming material according to claim 1, characterized in that, In step 2, the mass ratio of the mixture, composite compatibilizer, lubricant ST, and crosslinking agent dicumyl peroxide is 1500:15-135:8:

4.

6. The method for preparing a blended modified EVA supercritical foaming material according to claim 1, characterized in that, In step 2, the internal mixer processing temperature is 115℃.

7. The method for preparing a blended modified EVA supercritical foaming material according to claim 1, characterized in that, In step 2, the temperature of the machine gun head is 95℃ and the heating time is 400s.

8. The method for preparing a blended modified EVA supercritical foaming material according to claim 1, characterized in that, In step 3, the supercritical foaming temperature is 133℃, the pressure is 28MPa, and the holding time is 120 min.

9. The method for preparing a blended modified EVA supercritical foaming material according to claim 1, characterized in that, The conditions for hydraulic shaping in step 4 are as follows: first, heat to 165℃ for 500s, then cool to room temperature for 500s.

10. The blended modified EVA supercritical foam material prepared by the method for preparing a blended modified EVA supercritical foam material according to any one of claims 1-9.

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