Graphene modified EVA supercritical foaming sole or slipper and preparation method thereof

Abstract

The invention provides a graphene modified EVA supercritical foaming sole or slipper and a preparation method thereof, and belongs to the technical field of foaming materials. The foaming material is prepared from the following raw materials: an ethylene-vinyl acetate copolymer, modified graphene, stearic acid, zinc stearate and a cross-linking agent. Through the supercritical foaming process, the prepared foamed sole or slipper is higher in strength and lighter in material; the modified graphene, the thermoplastic elastomer and the EVA are compounded, so that the foaming material is endowed with more excellent flexibility and slow rebound resilience, and after the foaming material is made into a sole material, under the condition of long-time use, the sole has good rebound resilience and is softer, and the plantar pressure can be obviously reduced.

Description

Technical Field

[0001] The invention relates to the technical field of foaming materials, and in particular to a graphene-modified EVA supercritical foaming sole or slipper and a preparation method thereof. Background Art

[0002] Shoes are a necessity in human life, and with the continuous development of human civilization, the types of shoes are also constantly enriched, such as casual shoes, sports shoes, canvas shoes, ski shoes, sandals, slippers, medical shoes, safety shoes and other types of shoes. As the sole materials for these shoes, natural materials or synthetic materials such as leather, rubber, polyvinyl chloride and polyurethane are widely used. From the perspective of lightweight, polyurethane materials have been widely used because of their advantages over other materials such as low density and bending resistance. However, with the development of modernization, people's requirements for soles are getting higher and higher. Ordinary polyurethane soles have the limitations of the material itself. When they are deformed, the rebound speed is fast, which will produce a reaction force on the human foot. For example, after falling from a height, the human foot will feel pain or even be injured when it lands on the ground. This is caused by the too fast rebound. Some people use soft materials that are easier to deform to make soles, but this will cause the deformation to remain for a long time after being subjected to force, causing the material itself to deform and form a depression. After a long time, the restoring force is lost. After a person falls from a height, the foot will feel pain or be injured because there is no deformation when it lands on the ground. Summary of the invention

[0003] The object of the present invention is to provide a graphene-modified EVA supercritical foaming sole or slipper and a preparation method thereof, so as to solve the above-mentioned technical problems.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a graphene-modified EVA supercritical foaming sole or slipper, which is prepared from the following raw materials in parts by mass:

[0006]

[0007]

[0008] Furthermore, the thermoplastic elastomer comprises one or more of Hybrar5127, L609 and S1611.

[0009] Furthermore, the preparation method of the modified graphene comprises the following steps:

[0010] dispersing graphene oxide in water to obtain a graphene dispersion;

[0011] N-aminoethyl-γ-aminopropyltriethoxysilane is mixed into a graphene dispersion under heating conditions, and then natural latex and acetic acid solution are added in sequence, mixed, filtered, and dried to obtain modified graphene.

[0012] Furthermore, the mass ratio of N-aminoethyl-γ-aminopropyltriethoxysilane to graphene oxide is 0.8-2:2; the mass ratio of graphene oxide to natural latex is 1:1-2, the amount of acetic acid solution added is 20-30% of the volume of the graphene dispersion; and the heating temperature is 70-90°C.

[0013] Furthermore, the cross-linking agent comprises one or more of di-tert-butyl diisopropylbenzene peroxide, trimethylolpropane and triethanolamine.

[0014] The present invention also provides a method for preparing a graphene-modified EVA supercritical foaming sole or slipper, comprising the following steps:

[0015] 1) adding ethylene-vinyl acetate copolymer, thermoplastic elastomer and modified graphene according to their weight fractions for twin-screw melt blending to obtain a blend, wherein the temperature of the twin-screw is 160-200° C.;

[0016] 2) adding stearic acid and zinc stearate to the blend and kneading them, then adding a cross-linking agent and continuing kneading for 3 to 5 minutes, granulating and cooling the uniformly mixed mixture to obtain graphene-modified EVA supercritical foaming particles;

[0017] 3) pouring the graphene-modified EVA supercritical foamed granules into a molding mold, hot-pressing and cooling them in a flat vulcanizer to obtain a supercritical foamed billet;

[0018] 4) placing the supercritical foaming blank into a supercritical foaming reactor, injecting 10-30 MPa supercritical nitrogen, maintaining temperature and pressure at 80-200° C. for 1-5 hours, and instantly releasing the pressure to obtain graphene-modified EVA supercritical foaming soles or slippers.

[0019] Furthermore, in the step 3), the temperature of the hot pressing molding is 150-170° C., and the time of the hot pressing molding is 200-400 seconds.

[0020] Beneficial effects of the present invention:

[0021] The modified graphene of the present invention chemically covalently modifies graphene oxide by N-aminoethyl-γ-aminopropyltriethoxysilane, thereby increasing the adhesion between graphene oxide and thermoplastic elastomer molecules, improving the toughness and elasticity of the thermoplastic elastomer, and the addition of the modified graphene gives the foamed sole or slippers characteristics such as higher strength, ultra-light weight and multi-sized pore structures.

[0022] The EVA material and the thermoplastic elastomer in the present invention can significantly improve the performance of both after compounding, so that the foam material has better flexibility and slow rebound performance. The foam material is used as a sole material or a slipper material, which can significantly reduce the pressure on the sole of the foot when the user walks for a long time. DETAILED DESCRIPTION

[0023] The present invention provides a graphene-modified EVA supercritical foaming sole or slipper, which is prepared from the following raw materials in parts by mass:

[0024]

[0025] In the present invention, the amount of the ethylene-vinyl acetate copolymer added is preferably 48 to 55 parts by mass, and more preferably 50 to 53 parts by mass.

[0026] In the present invention, the mass content of VA in the ethylene-vinyl acetate copolymer is 18-23%, and the EVA with this VA content can maintain a certain flexibility and also have moderate resilience. In the present invention, EVA is preferably Celanese 2020 or TAISOX7350F from the United States.

[0027] In the present invention, the amount of the thermoplastic elastomer added is preferably 11 to 14 parts by mass, and more preferably 12 to 13 parts by mass.

[0028] In the present invention, the amount of modified graphene added is preferably 2 to 4 parts by mass, and more preferably 3 parts.

[0029] In the present invention, the amount of stearic acid added is preferably 0.8 to 1.2 parts by mass, and more preferably 0.9 to 1.0 parts by mass.

[0030] In the present invention, the added amount of zinc stearate is preferably 0.8 to 1.8 parts by mass, and more preferably 1 to 1.5 parts by mass.

[0031] In the present invention, the amount of the cross-linking agent added is preferably 3 to 4 parts by mass, and more preferably 3.5 parts by mass.

[0032] In the present invention, the thermoplastic elastomer comprises one or more of Hybrar5127, L609 and S1611, preferably Hybrar5127.

[0033] In the present invention, the preparation method of the modified graphene comprises the following steps:

[0034] dispersing graphene oxide in water to obtain a graphene dispersion;

[0035] N-aminoethyl-γ-aminopropyltriethoxysilane is mixed into a graphene dispersion under heating conditions, and then natural latex and acetic acid solution are added in sequence, mixed, filtered, and dried to obtain modified graphene.

[0036] In the present invention, the concentration of the graphene dispersion is 15 to 30 g / L, preferably 20 to 25 g / L, and more preferably 22 to 24 g / L.

[0037] In the present invention, the mass ratio of N-aminoethyl-γ-aminopropyltriethoxysilane to graphene oxide is 0.8 to 2:2, preferably 1.0 to 1.5:1, and more preferably 1:1;

[0038] The mass ratio of graphene oxide to natural latex is 1:1-2, preferably 1:1.5; the amount of acetic acid solution added is 20-30% of the volume of the graphene dispersion, preferably 22-28%, and more preferably 25%; the heating temperature is 70-90°C, preferably 80°C.

[0039] In the present invention, the cross-linking agent comprises one or more of di-tert-butyl diisopropylbenzene peroxide, trimethylolpropane and triethanolamine, preferably di-tert-butyl diisopropylbenzene peroxide.

[0040] The present invention also provides a method for preparing a graphene-modified EVA supercritical foaming sole or slipper, comprising the following steps:

[0041] 1) adding ethylene-vinyl acetate copolymer, thermoplastic elastomer and modified graphene according to their weight fractions for twin-screw melt blending to obtain a blend, wherein the temperature of the twin-screw is 160-200° C.;

[0042] 2) adding stearic acid and zinc stearate to the blend and kneading them, then adding a cross-linking agent and continuing kneading for 3 to 5 minutes, granulating and cooling the uniformly mixed mixture to obtain graphene-modified EVA supercritical foaming particles;

[0043] 3) pouring the graphene-modified EVA supercritical foamed granules into a molding mold, hot-pressing and cooling them in a flat vulcanizer to obtain a supercritical foamed billet;

[0044] 4) placing the supercritical foaming blank into a supercritical foaming reactor, injecting 10-30 MPa supercritical nitrogen, maintaining the temperature and pressure at 80-200° C. for 1-5 hours, and instantly releasing the pressure to obtain graphene-modified EVA supercritical foaming soles or slippers.

[0045] In the present invention, in step 3), the temperature of hot pressing is 150-170°C, preferably 155-165°C, more preferably 160°C, and the time of hot pressing is 200-400s, preferably 250-350s, more preferably 300s.

[0046] In the present invention, in the step 4), the pressure of supercritical nitrogen is 10-30 MPa, preferably 15-25 MPa, the supercritical temperature is 80-200°C, preferably 140-160°C, and more preferably 150°C; the supercritical time is 1-5 hours, preferably 2-4 hours, and more preferably 3 hours.

[0047] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0048] Example 1

[0049] A method for preparing a graphene-modified EVA supercritical foaming sole or slipper comprises the following steps:

[0050] raw material:

[0051]

[0052] 1) adding ethylene-vinyl acetate copolymer (2020), thermoplastic elastomer Hybrar5127 and modified graphene according to their weight fractions for twin-screw melt blending to obtain a blend, wherein the temperature of the twin-screw is 180° C.;

[0053] 2) adding stearic acid and zinc stearate to the blend and kneading at 120° C., then adding diisopropyl di-tert-butyl peroxide and continuing kneading for 5 min, granulating and cooling the uniformly mixed mixture to obtain graphene-modified EVA supercritical foaming particles;

[0054] 3) pouring the graphene-modified EVA supercritical foamed particles into a foaming mold, hot pressing and molding at 160° C. on a flat vulcanizer, and obtaining a foamed blank after cooling;

[0055] 4) placing the foamed green sheet into a supercritical foaming reactor, injecting 15 MPa supercritical nitrogen, maintaining the pressure at 140° C. for 4 hours, and then releasing the pressure instantly to obtain a graphene-modified EVA supercritical foamed sole or slipper.

[0056] Preparation of modified graphene:

[0057] Dispersing 20 g of graphene oxide in water to obtain a graphene dispersion with a mass concentration of 20 g / L;

[0058] 18 g of N-aminoethyl-γ-aminopropyltriethoxysilane was mixed into the above graphene dispersion at 70° C., and then 25 g of natural latex and 200 mL of 15 wt % acetic acid solution were added in sequence, mixed, filtered, and dried to obtain modified graphene.

[0059] Example 2

[0060] A method for preparing a graphene-modified EVA chemical foaming sole or slipper comprises the following steps:

[0061] raw material:

[0062]

[0063] 1) adding ethylene-vinyl acetate copolymer (TAISOX7350F), thermoplastic elastomer L609 and modified graphene according to their weight fractions for twin-screw melt blending to obtain a blend, and the temperature of the twin-screw is 180° C.;

[0064] 2) adding stearic acid and zinc stearate to the blend and kneading at 120° C., then adding trimethylolpropane and continuing kneading for 5 minutes, granulating and cooling the uniformly mixed mixture to obtain graphene-modified EVA supercritical foaming particles;

[0065] 3) pouring the graphene-modified EVA supercritical foamed particles into a molding mold, hot pressing and molding at 160° C. on a flat vulcanizer, and obtaining a foamed blank after cooling;

[0066] 4) placing the foamed green sheet into a supercritical foaming reactor, injecting 20 MPa supercritical nitrogen, maintaining heat and pressure at 160° C. for 2 hours, and then releasing the pressure instantly to obtain a graphene-modified EVA supercritical foamed sole or slipper.

[0067] The preparation of modified graphene is the same as in Example 1.

[0068] Example 3

[0069] A method for preparing a graphene-modified EVA supercritical foaming sole or slipper comprises the following steps:

[0070] raw material:

[0071]

[0072]

[0073] 1) adding ethylene-vinyl acetate copolymer (TAISOX7350F), thermoplastic elastomer S1611 and modified graphene according to their weight fractions for twin-screw melt blending to obtain a blend, wherein the temperature of the twin-screw is 200° C.;

[0074] 2) adding stearic acid and zinc stearate to the blend and kneading at 120° C., then adding trimethylolpropane and continuing kneading for 3 minutes, granulating and cooling the uniformly mixed mixture to obtain graphene-modified EVA supercritical foaming particles;

[0075] 3) pouring the graphene-modified EVA supercritical foamed particles into a molding mold, hot pressing and molding at 160° C. on a flat vulcanizer, and obtaining a foamed blank after cooling;

[0076] 4) placing the foamed green sheet into a supercritical foaming reactor, injecting 25 MPa supercritical nitrogen, maintaining heat and pressure at 150° C. for 1.5 hours, and then releasing the pressure instantly to obtain a graphene-modified EVA supercritical foamed sole or slipper.

[0077] The preparation of modified graphene is the same as in Example 1.

[0078] Example 4

[0079] A method for preparing a graphene-modified EVA supercritical foaming sole or slipper comprises the following steps:

[0080] raw material:

[0081]

[0082] 1) adding ethylene-vinyl acetate copolymer (2020), thermoplastic elastomer L609 and modified graphene according to their weight fractions for twin-screw melt blending to obtain a blend, wherein the temperature of the twin-screw is 200° C.;

[0083] 2) adding stearic acid and zinc stearate to the blend and kneading at 120° C., then adding trimethylolpropane and continuing kneading for 3 minutes, granulating and cooling the uniformly mixed mixture to obtain graphene-modified EVA supercritical foaming particles;

[0084] 3) pouring the graphene-modified EVA supercritical foamed particles into a molding mold, hot pressing and molding at 160° C. on a flat vulcanizer, and obtaining a foamed blank after cooling;

[0085] 4) The foamed blank is placed in a supercritical foaming reactor, supercritical nitrogen is injected at 30 MPa, and after heat and pressure maintenance at 155° C. for 1 hour, the pressure is released instantly to obtain a graphene-modified EVA supercritical foamed sole or slipper.

[0086] The preparation of modified graphene is the same as in Example 1.

[0087] Comparative Example 1

[0088] The raw materials for preparation of this comparative example are the same as those in Example 1, except that no modified graphene is added;

[0089] The preparation method is the same as that of Example 1.

[0090] Comparative Example 2

[0091] The raw materials for preparation of this comparative example are the same as those in Example 1, except that the thermoplastic elastomer is replaced by styrene-butadiene rubber;

[0092] The preparation method is the same as that of Example 1.

[0093] Comparative Example 3

[0094] The raw materials for preparation of this comparative example are the same as those in Example 1, except that EVA is changed to EVA7320M (VA content 28%);

[0095] The preparation method is the same as that of Example 1.

[0096] The materials obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were made into shoe soles of size 40 with a thickness of 5 cm, and slow rebound tests and stress deformation tests were carried out.

[0097] 1. Thickness deformation rate: The manufactured soles were subjected to pressure tests of 0.5 kPa, 1.5 kPa, 2.5 kPa, 3.5 kPa and 4.5 kPa to test their thickness deformation rate. The test results are shown in Table 1 below.

[0098] Deformation rate = (original thickness - thickness after deformation) / original thickness.

[0099] Table 1 Test results

[0100]

[0101]

[0102] 2. Thickness deformation recovery time: Apply external force to the manufactured sole to make it deform with a thickness deformation rate of 20%, then remove the external force and record the time taken for recovery. The same sole was tested 100 times, and the time at the 1st, 10th, 50th and 100th times was recorded. The test results are shown in Table 2 below.

[0103] Table 2 Test results

[0104] project 1st time 10th 50th The 100th Example 1 5s 10s 10s 11s Example 2 5s 8s 8s 10s Example 3 8s 11s 11s 12s Example 4 6s 9s 9s 11s Comparative Example 1 2s 2s 3s 20s Comparative Example 2 2s 3s 3s 31s Comparative Example 3 3s 3s 20s No reply

[0105] It can be seen from the above test results that the deformation rate of the sole made of the foam material of the present invention under different pressures is moderate, and it has the characteristics of slow rebound. When the force is 0.5-1.5kPa, its deformation rate is 0.5-3%, and when the force is increased to 2.5-4.5kPa, its deformation rate can reach 10-20%, thereby playing a role in buffering absorption capacity, and consumers will not be too soft during normal wearing. It can be seen from the data in Table 2 that when no modified graphene is added to Comparative Example 1, it shows high rebound performance in the first 50 tests, but with the increase of the number of experiments, the rebound performance of the material decreases significantly; although the styrene-butadiene rubber used in Comparative Example 2 has high rebound performance, it also cannot meet the requirements of long-term and multiple use; Comparative Example 3 uses EVA7320M, and the VA content is 28%. The softness of the material decreases significantly, and the rebound performance decreases after multiple uses, and it cannot meet the use requirements of the sole material.

[0106] The density and mechanical properties of the graphene-modified EVA supercritical foamed soles or slippers obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were tested, and the results are shown in Table 3 below.

[0107] Table 3 Performance test of Examples 1 to 4 and Comparative Examples 1 to 3

[0108]

[0109] The test results in Table 3 show that the EVA foamed soles or slippers obtained by adding modified graphene in the present invention have lower density, improved strength, and moderate material hardness, which makes up for the defects of low hardness and poor wear resistance of the EVA material itself.

[0110] As can be seen from the above embodiments, the present invention provides a graphene-modified EVA supercritical foamed sole or slipper and a preparation method thereof. The present invention uses a supercritical nitrogen foaming process to make the prepared foamed sole or slipper stronger and lighter; the compounding of modified graphene, thermoplastic elastomer and EVA in the present invention gives the foaming material better flexibility and slow rebound performance, and the made sole or slipper has good resilience and is softer when used for a long time, which can significantly reduce the pressure on the sole of the foot.

[0111] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A graphene-modified EVA supercritical foaming sole or slipper, characterized in that: Prepared from the following raw materials in parts by weight:

2. The graphene-modified EVA supercritical foaming sole or slipper according to claim 1, characterized in that: The thermoplastic elastomer comprises one or more of Hybrar5127, L609 and S1611.

3. The graphene-modified EVA supercritical foaming sole or slipper according to claim 1 or 2, characterized in that: The preparation method of the modified graphene comprises the following steps: dispersing graphene oxide in water to obtain a graphene dispersion; N-aminoethyl-γ-aminopropyltriethoxysilane is mixed into a graphene dispersion under heating conditions, and then natural latex and acetic acid solution are added in sequence, mixed, filtered, and dried to obtain modified graphene.

4. The graphene-modified EVA supercritical foaming sole or slipper according to claim 3, characterized in that: The mass ratio of N-aminoethyl-γ-aminopropyltriethoxysilane to graphene oxide is 0.8-2:2; the mass ratio of graphene oxide to natural latex is 1:1-2; the amount of acetic acid solution added is 20-30% of the volume of the graphene dispersion; and the heating temperature is 70-90°C.

5. The graphene-modified EVA supercritical foaming sole or slipper according to claim 1 or 4, characterized in that: The cross-linking agent comprises one or more of di-tert-butyl diisopropylbenzene peroxide, trimethylolpropane and triethanolamine.

6. The method for preparing the graphene-modified EVA supercritical foaming soles or slippers according to any one of claims 1 to 5, characterized in that: The following steps are involved: 1) adding ethylene-vinyl acetate copolymer, thermoplastic elastomer and modified graphene according to their weight fractions for twin-screw melt blending to obtain a blend, wherein the temperature of the twin-screw is 160-200° C.; 2) adding stearic acid and zinc stearate to the blend and kneading at 120-130° C. for 2-5 min, then adding a crosslinking agent and continuing kneading for 3-5 min, granulating and cooling the uniformly mixed mixture to obtain graphene-modified EVA supercritical foamed granules; 3) pouring the graphene-modified EVA supercritical foamed granules into a molding mold, hot-pressing and cooling them in a flat vulcanizer to obtain a supercritical foamed billet; 4) placing the supercritical foaming blank into a supercritical foaming reactor, injecting 10-30 MPa supercritical nitrogen, maintaining the temperature and pressure at 80-200° C. for 1-5 hours, and instantly releasing the pressure to obtain graphene-modified EVA supercritical foaming soles or slippers.

7. The method for preparing the graphene-modified EVA supercritical foaming soles or slippers according to claim 6, characterized in that: In the step 3), the temperature of the hot pressing molding is 150-170° C., and the time of the hot pressing molding is 200-400 seconds.

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