Ethylene-vinyl acetate copolymer foaming sole material and preparation method thereof

Abstract

The invention discloses an ethylene-vinyl acetate copolymer foaming sole material and a preparation method thereof. The ethylene-vinyl acetate copolymer foaming sole material comprises the following components in percentage by weight: 35-70% of ethylene-vinyl acetate copolymer; 2%-20% of highly branched polyethylene; 5%-20% of an ethylene-octylene copolymer; 0-20% of an ethylene block copolymer; 0.4%-0.8% of a cross-linking agent; 2%-4% of a foaming agent; 2%-10% of a filling agent; 0.5%-2% of zinc oxide; 0.3% to 1.6% of zinc stearate; and 0.3%-1.2% of stearic acid. The highly branched polyethylene is polyethylene with a highly branched structure prepared by taking ethylene as a monomer and taking late transition metal as a catalyst, the branched chain structure breaks the structural regularity of a molecular main chain, and the highly branched polyethylene has excellent rebound resilience.

Description

Technical Field

[0001] The present invention relates to the technical field of shoe materials, and in particular to an ethylene-vinyl acetate copolymer (EVA) foamed sole material and a preparation method thereof. Background Art

[0002] Due to its advantages such as light weight, obvious cushioning and shock absorption effects, and good corrosion resistance, EVA foamed materials are widely used in various types of footwear products such as sports shoes, slippers, casual shoes, and beach shoes. However, during the use of EVA foamed materials, there are still problems such as poor compression set and insufficient resilience. Developing an EVA foamed sole material with low permanent compression deformation and high resilience has become an urgent problem to be solved. Summary of the Invention

[0003] Aiming at the problem that the EVA foamed sole material needs to improve its resilience, the present invention provides an ethylene-vinyl acetate copolymer foamed sole material and a preparation method thereof. Without affecting other physical properties, the resilience of the product can reach more than 70%, and the mechanical properties of the product are excellent.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] An ethylene-vinyl acetate copolymer foamed sole material, comprising the following components in weight percentages:

[0006] Ethylene-vinyl acetate copolymer: 35%-70%;

[0007] Highly branched polyethylene: 2%-20%;

[0008] Ethylene-octene copolymer: 5%-20%;

[0009] Ethylene block copolymer: 0-20%;

[0010] Crosslinking agent: 0.4%-0.8%;

[0011] Foaming agent: 2%-4%;

[0012] Filler: 2%-10%;

[0013] Zinc oxide: 0.5%-2%;

[0014] Zinc stearate: 0.3%-1.6%;

[0015] Stearic acid: 0.3%-1.2%.

[0016] Further, the mass content of vinyl acetate unit structure in the ethylene-vinyl acetate copolymer is 15-30%.

[0017] Further, the degree of branching of the highly branched polyethylene is not less than 50 branches / 1000 carbons.

[0018] Further, the degree of branching of the highly branched polyethylene is 50 - 150 branches / 1000 carbons.

[0019] Further, the degree of branching of the highly branched polyethylene is 60 - 130 branches / 1000 carbons.

[0020] Further, the weight-average molecular weight of the highly branched polyethylene is 66,000 - 518,000, and the Mooney viscosity ML(1+4) at 125 °C is 6 - 102.

[0021] Further, the crystallinity of the ethylene-octene copolymer, the highly branched polyethylene, and the ethylene block copolymer is all less than 18%; and / or the melt index of the POE < 5 g / 10 min.

[0022] Further, the filler is one or more of silicone powder, talcum powder, and calcium carbonate.

[0023] Further, the crosslinking agent is one or two of dicumyl peroxide and 1,3(1,4)-bis(tert-butylperoxyisopropyl)benzene.

[0024] Further, the blowing agent is selected from one or more of azodicarbonamide, 4,4'-oxybis(benzenesulfonylhydrazide), and N,N'-dinitrosopentamethylenetetramine.

[0025] A preparation method of an ethylene-vinyl acetate copolymer foamed sole material, comprising the following steps:

[0026] Mixing an ethylene-vinyl acetate copolymer, a highly branched polyethylene, an ethylene-octene copolymer, an ethylene block copolymer, a filler, zinc oxide, zinc stearate, and stearic acid by internal mixing, the internal mixing temperature is 100 - 108 °C, the time is 8 - 12 min, then adding a blowing agent and a crosslinking agent, and performing a second internal mixing, the internal mixing temperature is 115 - 120 °C, the time is 8 - 12 min, to obtain a mixed material;

[0027] Pelletizing the mixed material to obtain pellets;

[0028] Performing primary foaming on the pellets and then secondary foaming to obtain an ethylene-vinyl acetate copolymer foamed sole material.

[0029] Further, the pelletizing temperature is controlled at 80 - 95 °C; the temperature of the primary foaming is 180 °C, the time is 300 - 500 s; the temperature of the secondary foaming is 180 °C, the time is 400 - 600 s; the cooling time is 400 - 600 s.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] The highly branched polyethylene of the present invention uses ethylene as a monomer and a late transition metal as a catalyst to prepare polyethylene with a highly branched structure. The branched chain structure breaks the structural regularity of the molecular main chain and has excellent resilience. Moreover, when the Mooney viscosity is the same, the highly branched polyethylene has a higher molecular weight; the highly branched polyethylene has branched chains of different lengths, which can form C-C cross-linking bonds of different lengths between the molecular main chains during peroxide vulcanization, effectively avoiding stress concentration, thereby endowing the whole with higher mechanical properties. After adding highly branched polyethylene rubber to the ethylene-vinyl acetate copolymer, the material has high resilience and maintains good mechanical properties. The density of the ethylene-vinyl acetate copolymer foamed sole material of the present invention is 0.16 - 0.17 g / cm 3 , the hardness is 40 - 47 C, the resilience performance is 66 - 71%, the tear strength is 3.4 - 3.7 N / mm, the tensile strength is 3.9 - 4.5 MPa, and the compression set is 19.8 - 22.1%. Detailed Embodiments

[0032] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the disclosure of the present invention can be understood more thoroughly and comprehensively.

[0033] An ethylene-vinyl acetate copolymer (EVA) foamed sole material of the present invention comprises the following components in weight percentages:

[0034] Ethylene-vinyl acetate copolymer (EVA): 35% - 70%;

[0035] Highly branched polyethylene: 2% - 20%;

[0036] Ethylene-octene copolymer (POE): 5% - 20%;

[0037] Ethylene block copolymer (OBC): 0 - 20%;

[0038] Crosslinking agent: 0.4% - 0.8%;

[0039] Foaming agent: 2% - 4%;

[0040] Filler: 2% - 10%;

[0041] Zinc oxide: 0.5% - 2%;

[0042] Zinc stearate: 0.3% - 1.6%.

[0043] Stearic acid: 0.3% - 1.2%.

[0044] The mass content of vinyl acetate unit structure in the EVA is 15-30%.

[0045] The highly branched polyethylene is a kind of ethylene homopolymer with a degree of branching of not less than 50 branches / 1000 carbons. It is mainly made of ethylene as raw material and prepared by solution polymerization with (α-diimine) nickel / palladium as the catalyst.

[0046] Furthermore, the degree of branching of the highly branched polyethylene is 50-150 branches / 1000 carbons.

[0047] Furthermore, the degree of branching of the highly branched polyethylene is 60-130 branches / 1000 carbons.

[0048] Furthermore, the weight-average molecular weight of the highly branched polyethylene is 66,000-518,000, and the Mooney viscosity ML(1+4) at 125°C is 6-102.

[0049] Preferably, the crystallinity of the POE, highly branched polyethylene and OBC is all lower than 18%;

[0050] The melt index of the POE is <5 g / 10 min.

[0051] The filler is one or more of silicone powder, talcum powder and calcium carbonate.

[0052] The crosslinking agent is one or two of dicumyl peroxide (DCP) and 1,3(1,4)-bis(tert-butylperoxyisopropyl)benzene (BIBP).

[0053] The blowing agent is selected from one or more of azodicarbonamide (AC), 4,4-oxybis(benzenesulfonylhydrazide) (OBSH) and N,N'-dinitrosopentamethylenetetramine.

[0054] The preparation method of the EVA foamed sole material includes the following steps:

[0055] (1) Weighing materials: According to the formula, weigh the EVA, POE, highly branched polyethylene, ethylene block copolymer, crosslinking agent, blowing agent, filler, zinc oxide, zinc stearate and stearic acid.

[0056] (2) Kneading: First, heat the inner cavity temperature of the internal mixer to between 80-85°C. Then, put the EVA, POE, highly branched polyethylene, ethylene block copolymer and other materials (excluding the crosslinking agent and blowing agent) into the internal mixer for kneading. The kneading temperature is controlled at 100-108°C and the time is 8-12 min. Then add the blowing agent and crosslinking agent, start the internal mixer for the second kneading, the kneading temperature is controlled at 115-120°C and the time is 8-12 min, and the mixture is obtained.

[0057] (3) Granulation. After kneading, the mixed material is added to a two-roll mill and pressed into a thin sheet. The uniformly mixed material is poured into a granulator for granulation to obtain granular material. The granulation temperature is controlled at 80 - 95 °C.

[0058] (4) Foaming: The granulated material is poured into a foaming mold for primary foaming, then secondary foaming and cooling are carried out to obtain the finished product.

[0059] Among them, the temperature of the primary foaming is 180 °C, and the time is 300 - 500 s; the temperature of the secondary foaming is 180 °C, and the time is 400 - 600 s; the cooling time is 400 - 600 s.

[0060] The following are specific examples.

[0061] Example 1

[0062] The present invention provides an EVA foamed sole material, comprising the following components in weight percentages: EVA: 62%, highly branched polyethylene: 5%, POE: 10%, OBC: 10%, dicumyl peroxide (DCP): 0.6%, azodicarbonamide (AC): 2.6%, talcum powder: 6%, zinc oxide: 1.4%; zinc stearate: 1.4%, stearic acid: 1.0%. The mass content of vinyl acetate unit structure in the EVA is 15%. The degree of branching of the highly branched polyethylene is 60 branches / 1000 carbons.

[0063] Its preparation method comprises the following steps:

[0064] 1. Weighing: Accurately weigh EVA, POE, highly branched polyethylene, OBC, dicumyl peroxide, azodicarbonamide, talcum powder, zinc oxide, zinc stearate, stearic acid.

[0065] 2. Kneading: First, heat the inner cavity temperature of the internal mixer to between 80 - 85 °C. Then, put the EVA, POE, highly branched polyethylene, OBC and other materials (excluding dicumyl peroxide and azodicarbonamide) into the internal mixer for kneading. The kneading temperature is controlled at 100 - 108 °C, and the time is 10 min. Then add the blowing agent and crosslinking agent, start the internal mixer for the second kneading, and the kneading temperature is controlled at 115 - 120 °C, and the time is 10 min to obtain the mixed material.

[0066] 3. Granulation: After kneading, the mixed material is added to a two-roll mill and pressed into a thin sheet. The uniformly mixed material is poured into a granulator for granulation to obtain granular material. The granulation temperature is controlled at 80 - 95 °C.

[0067] 4. Heat the mold to 180°C, pour the prepared pellets into the foaming mold, conduct the first foaming with a foaming temperature of 180°C and a time of 350 s. Then conduct the second foaming with a foaming temperature of 180°C and a time of 500 s, and cool for 500 s to obtain the finished product.

[0068] Example 2

[0069] The present invention provides an EVA foamed sole material, comprising the following components in parts by weight: EVA: 57%, highly branched polyethylene: 10%, POE: 10%, OBC: 10%, dicumyl peroxide (DCP): 0.6%, azodicarbonamide (AC): 2.6%, talcum powder: 6%, zinc oxide: 1.4%, zinc stearate: 1.4%, stearic acid: 1.0%. The mass content of vinyl acetate unit structure in the EVA is 30%. The degree of branching of the highly branched polyethylene is 130 branches / 1000 carbons.

[0070] Its preparation method comprises the following steps:

[0071] 1. Weighing: Accurately weigh EVA, POE, highly branched polyethylene, OBC, dicumyl peroxide, azodicarbonamide, talcum powder, zinc oxide, zinc stearate, stearic acid.

[0072] 2. Kneading: First, heat the inner cavity temperature of the internal mixer to between 80 - 85°C. Then, put the EVA, POE, highly branched polyethylene, OBC and other materials (excluding dicumyl peroxide and azodicarbonamide) into the internal mixer for kneading, control the kneading temperature at 100 - 108°C and the time at 10 min, then add the foaming agent and crosslinking agent, start the internal mixer for the second kneading, control the kneading temperature at 115 - 120°C and the time at 10 min to obtain the mixed material.

[0073] 3. Pelletizing: After kneading, add the mixed material into a two-roll mill and press it into a thin sheet. Pour the uniformly mixed material into a pelletizer for pelletizing to obtain pellets. Control the pelletizing temperature at 80 - 95°C.

[0074] 4. Heat the mold to 180°C, pour the prepared pellets into the foaming mold, conduct the first foaming with a foaming temperature of 180°C and a time of 350 s. Then conduct the second foaming with a foaming temperature of 180°C and a time of 400 - 600 s, and cool for 500 s to obtain the finished product.

[0075] Example 3

[0076] The present invention provides an EVA foamed sole material, which comprises the following components in percentage by weight: EVA: 52%, highly branched polyethylene: 15%, POE: 10%, OBC: 10%, dicumyl peroxide (DCP): 0.6%, azodicarbonamide (AC): 2.6%, talcum powder: 6%, zinc oxide: 1.4%, zinc stearate: 1.4%, stearic acid: 1.0%. The mass content of vinyl acetate unit structure in the EVA is 20%. The degree of branching of the highly branched polyethylene is 100 branches / 1000 carbons.

[0077] Its preparation method comprises the following steps:

[0078] 1. Weighing materials: Weigh accurately EVA, POE, highly branched polyethylene, OBC, dicumyl peroxide, azodicarbonamide, talcum powder, zinc oxide, zinc stearate, and stearic acid.

[0079] 2. Kneading: First, heat the inner cavity temperature of the internal mixer to between 80 - 85°C. Then, put the EVA, POE, highly branched polyethylene, OBC and other materials (excluding dicumyl peroxide and azodicarbonamide) into the internal mixer for kneading. Control the kneading temperature at 100 - 108°C and the time at 10 min. Then add the blowing agent and crosslinking agent, start the internal mixer for the second kneading, control the kneading temperature at 115 - 120°C and the time at 10 min to obtain the mixed material.

[0080] 3. Pelletizing: After kneading, add the mixed material into a two-roll open mill and press it into a thin sheet. Pour the uniformly mixed material into a pelletizer for pelletizing to obtain pellets. Control the pelletizing temperature at 80 - 95°C.

[0081] 4. Heat the mold to 180°C, pour the made pellets into the foaming mold for the first foaming, with the foaming temperature at 180°C and the time at 350 s. Then conduct the second foaming, with the foaming temperature at 180°C and the time at 500 s, and cool for 500 s to obtain the finished product.

[0082] Example 4

[0083] The present invention provides an EVA foamed sole material, which comprises the following components in percentage by weight: EVA: 47%, highly branched polyethylene: 20%, POE: 10%, OBC: 10%, dicumyl peroxide (DCP): 0.6%, azodicarbonamide (AC): 2.6%, talcum powder: 6%, zinc oxide: 1.4%, zinc stearate: 1.4%, stearic acid: 1.0%. The mass content of vinyl acetate unit structure in the EVA is 25%. The degree of branching of the highly branched polyethylene is 80 branches / 1000 carbons.

[0084] Its preparation method comprises the following steps:

[0085] 1. Weighing: Accurately weigh EVA, POE, hyperbranched polyethylene, OBC, dicumyl peroxide, azodicarbonamide, talcum powder, zinc oxide, zinc stearate, and stearic acid.

[0086] 2. Kneading: First, heat the inner cavity temperature of the internal mixer to between 80 - 85 °C. Then, put the EVA, POE, hyperbranched polyethylene, OBC, and other materials (excluding dicumyl peroxide and azodicarbonamide) into the internal mixer for kneading. The kneading temperature is controlled at 100 - 108 °C for 10 minutes. Then add the blowing agent and crosslinking agent, and start the internal mixer for the second kneading. The kneading temperature is controlled at 115 - 120 °C for 10 minutes to obtain the mixed material.

[0087] 3. Pelletizing: After kneading, add the mixed material into a two-roll mill and press it into a thin sheet. Pour the uniformly mixed material into a pelletizer for pelletizing to obtain pellets. The pelletizing temperature is controlled at 80 - 95 °C.

[0088] 4. Heat the mold to 180 °C, pour the made pellets into the foaming mold for the first foaming. The foaming temperature is 180 °C and the time is 350 s. Then conduct the second foaming. The foaming temperature is 180 °C and the time is 500 s, and then cool for 500 s to obtain the finished product.

[0089] Example 5

[0090] The present invention provides an EVA foamed sole material, which includes the following components in weight percentages: EVA: 35%, hyperbranched polyethylene: 20%, POE: 20%, OBC: 8.6%, dicumyl peroxide (DCP): 0.4%, azodicarbonamide (AC): 4%, a mixture of talcum powder and calcium carbonate with a mass ratio of 1:1: 10%, zinc oxide: 0.5%, zinc stearate: 0.3%, stearic acid: 1.2%. The mass content of vinyl acetate unit structure in the EVA is 25%. The degree of branching of the hyperbranched polyethylene is 50 branches / 1000 carbons.

[0091] Its preparation method includes the following steps:

[0092] 1. Weighing: Accurately weigh EVA, POE, hyperbranched polyethylene, OBC, dicumyl peroxide, azodicarbonamide, talcum powder, zinc oxide, zinc stearate, and stearic acid.

[0093] 2. Kneading: First, heat the temperature inside the internal mixer to between 80 - 85°C. Then, put the EVA, POE, highly branched polyethylene, OBC and other materials (excluding dicumyl peroxide and azodicarbonamide) into the internal mixer for kneading. Control the kneading temperature at 100 - 108°C for 8 minutes. Then add the blowing agent and crosslinking agent, start the internal mixer for the second kneading, control the kneading temperature at 115 - 120°C for 10 minutes to obtain the mixed material.

[0094] 3. Pelletizing: After kneading, add the mixed material into a two-roll mill and press it into a thin sheet. Pour the uniformly mixed material into a pelletizer for pelletizing to obtain pellets. Control the pelletizing temperature at 80 - 95°C.

[0095] 4. Heat the mold to 180°C, pour the made pellets into the foaming mold for the first foaming. The foaming temperature is 180°C and the time is 450 s. Then conduct the second foaming. The foaming temperature is 180°C and the time is 550 s, and then cool for 450 s to obtain the finished product.

[0096] Example 6

[0097] The present invention provides an EVA foamed sole material, which comprises the following components in weight percentages: EVA: 70%, highly branched polyethylene: 2%, POE: 5%, OBC: 14.3%, 1,3(1,4)-bis(tert-butylperoxyisopropyl)benzene (BIBP): 0.8%, 4,4-oxybisbenzenesulfonyl hydrazide (OBSH): 2%, calcium carbonate: 2%, zinc oxide: 2%, zinc stearate: 1.6%, stearic acid: 0.3%. The mass content of vinyl acetate unit structure in the EVA is 30%. The degree of branching of the highly branched polyethylene is 150 branches / 1000 carbons.

[0098] Its preparation method comprises the following steps:

[0099] 1. Weighing: Accurately weigh EVA, POE, highly branched polyethylene, OBC, dicumyl peroxide, azodicarbonamide, talcum powder, zinc oxide, zinc stearate, stearic acid.

[0100] 2. Kneading: First, heat the temperature inside the internal mixer to between 80 - 85°C. Then, put the EVA, POE, highly branched polyethylene, OBC and other materials (excluding dicumyl peroxide and azodicarbonamide) into the internal mixer for kneading. Control the kneading temperature at 100 - 108°C for 12 minutes. Then add the blowing agent and crosslinking agent, start the internal mixer for the second kneading, control the kneading temperature at 115 - 120°C for 10 minutes to obtain the mixed material.

[0101] 3. Granulation: After kneading, the mixed material is added to a two-roll mill and pressed into a thin sheet. The uniformly mixed material is poured into a granulator for granulation to obtain granular materials. The granulation temperature is controlled at 80 - 95 °C.

[0102] 4. Heat the mold to 180 °C, pour the granulated materials into the foaming mold, conduct the first foaming with a foaming temperature of 180 °C and a time of 500 s. Then conduct the second foaming with a foaming temperature of 180 °C and a time of 600 s, and cool for 600 s to obtain the finished product.

[0103] Example 7

[0104] The present invention provides an EVA foamed sole material, comprising the following components in weight percentages: EVA: 70%, highly branched polyethylene: 10%, POE: 8.5%, dicumyl peroxide (DCP): 0.5%, N,N'-dinitrosopentamethylenetetramine: 3%, silicone powder: 5%, zinc oxide: 1%, zinc stearate: 1%, stearic acid: 1.0%. The mass content of vinyl acetate unit structure in the EVA is 18%. The degree of branching of the highly branched polyethylene is 120 branches / 1000 carbons.

[0105] Its preparation method comprises the following steps:

[0106] 1. Weighing: Accurately weigh EVA, POE, highly branched polyethylene, dicumyl peroxide, azodicarbonamide, talcum powder, zinc oxide, zinc stearate, and stearic acid.

[0107] 2. Kneading: First, heat the inner cavity temperature of the internal mixer to between 80 - 85 °C. Then, put the EVA, POE, highly branched polyethylene, OBC and other materials (excluding dicumyl peroxide and azodicarbonamide) into the internal mixer for kneading. The kneading temperature is controlled at 100 - 108 °C and the time is 10 min. Then add the foaming agent and crosslinking agent, start the internal mixer for the second kneading, and control the kneading temperature at 115 - 120 °C and the time at 12 min to obtain the mixed material.

[0108] 3. Granulation: After kneading, the mixed material is added to a two-roll mill and pressed into a thin sheet. The uniformly mixed material is poured into a granulator for granulation to obtain granular materials. The granulation temperature is controlled at 80 - 95 °C.

[0109] 4. Heat the mold to 180 °C, pour the granulated materials into the foaming mold, conduct the first foaming with a foaming temperature of 180 °C and a time of 400 s. Then conduct the second foaming with a foaming temperature of 180 °C and a time of 500 s, and cool for 400 s to obtain the finished product.

[0110] Example 8

[0111] The present invention provides an EVA foamed sole material, which comprises the following components in percentage by weight: EVA: 41%, highly branched polyethylene: 15%, POE: 10%, OBC: 20%, dicumyl peroxide (DCP): 0.6%, azodicarbonamide (AC): 3.4%, talcum powder: 8%, zinc oxide: 1%, zinc stearate: 0.5, stearic acid: 0.5%. The mass content of vinyl acetate unit structure in the EVA is 25%. The degree of branching of the highly branched polyethylene is 140 branches / 1000 carbons.

[0112] Its preparation method comprises the following steps:

[0113] 1. Weighing materials: Accurately weigh EVA, POE, highly branched polyethylene, OBC, dicumyl peroxide, azodicarbonamide, talcum powder, zinc oxide, zinc stearate, and stearic acid.

[0114] 2. Kneading: First, heat the inner cavity temperature of the internal mixer to between 80 - 85°C. Then, put the EVA, POE, highly branched polyethylene, OBC and other materials (excluding dicumyl peroxide and azodicarbonamide) into the internal mixer for kneading. Control the kneading temperature at 100 - 108°C and the time at 10 min. Then add the blowing agent and crosslinking agent, start the internal mixer for the second kneading, control the kneading temperature at 115 - 120°C and the time at 8 min to obtain the mixture.

[0115] 3. Pelletizing: After kneading, add the mixture into a two-roll open mill and press it into a thin sheet. Pour the uniformly mixed materials into a pelletizer for pelletizing to obtain pellets. Control the pelletizing temperature at 80 - 95°C.

[0116] 4. Heat the mold to 180°C, pour the made pellets into the foaming mold for the first foaming, with the foaming temperature at 180°C and the time at 300 s. Then conduct the second foaming, with the foaming temperature at 180°C and the time at 400 s, and cool for 600 s to obtain the finished product.

[0117] Comparative Example 1

[0118] This comparative example provides an EVA foamed sole material, which comprises the following components in parts by weight: EVA: 59%, POE: 10, OBC: 10, dicumyl peroxide (DCP): 0.6, azodicarbonamide (AC): 2.6%, talcum powder: 6%, zinc oxide: 1.4%, zinc stearate: 1.4%, stearic acid: 1.0%.

[0119] Its preparation method comprises the following steps:

[0120] 1. Weighing: Accurately weigh EVA, POE, OBC, dicumyl peroxide, azodicarbonamide, talcum powder, zinc oxide, zinc stearate, and stearic acid.

[0121] 2. Kneading: First, heat the inner cavity temperature of the internal mixer to between 80 - 85°C. Then, put the EVA, POE, OBC and other materials (excluding dicumyl peroxide and azodicarbonamide) into the internal mixer for kneading. The kneading temperature is controlled at 100 - 108°C for 10 minutes. Then add the blowing agent and cross-linking agent, start the internal mixer for the second kneading, and control the kneading temperature at 115 - 120°C for 10 minutes to obtain the mixed material.

[0122] 3. Pelletizing: After kneading, add the mixed material into a two-roll open mill and press it into a thin sheet. Pour the uniformly mixed material into a pelletizer for pelletizing to obtain pellets. The pelletizing temperature is controlled at 80 - 95°C.

[0123] 4. Heat the mold to 180°C, pour the made pellets into the foaming mold for the first foaming. The foaming temperature is 180°C and the time is 350 s. Then conduct the second foaming with a temperature of 180°C and a time of 500 s, and cool for 500 s to obtain the finished product.

[0124] Take the products of Examples 2 - 4 and Comparative Example 1 respectively for relevant tests. The test items include density, hardness, resilience, tear strength, tensile strength, and compression deformation.

[0125] Table 1 Performance test results of samples prepared in Examples and Comparative Examples

[0126]

[0127]

[0128] As can be seen from Table 1, high-branched polyethylene was not added in Comparative Example 1, and the resilience performance was poor. The EVA foamed sole material prepared with EVA, high-branched polyethylene, POE, EVA, and ethylene block copolymer as the main raw materials in the present invention has significantly improved resilience and good mechanical properties.

[0129] The above is only an illustration of the best embodiment of the present invention, but it should not be construed as a limitation of the claims. The present invention is not limited to the above embodiments, and its specific structure allows for changes. Any changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

[0130] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. An ethylene-vinyl acetate copolymer foamed sole material, characterized in that: The composition comprises the following weight percentages: Ethylene-vinyl acetate copolymer: 35%-70%; Highly branched polyethylene: 2%-20%; Ethylene-octene copolymer: 5%-20%; Ethylene block copolymer: 0-20%; Cross-linking agent: 0.4%-0.8%; Foaming agent: 2%-4%; Fillers: 2%-10%; Zinc oxide: 0.5%-2%; Zinc stearate: 0.3%-1.6%; Stearic acid: 0.3%-1.2%.

2. The ethylene-vinyl acetate copolymer foamed sole material according to claim 1, characterized in that: The mass content of vinyl acetate unit structure in the ethylene-vinyl acetate copolymer is 15-30%.

3. The ethylene-vinyl acetate copolymer foamed sole material according to claim 1, characterized in that: The branching degree of the highly branched polyethylene is not less than 50 branches / 1000 carbons.

4. The ethylene-vinyl acetate copolymer foamed sole material according to claim 1, characterized in that: The weight average molecular weight of the highly branched polyethylene is 66,000 to 518,000, and the Mooney viscosity ML (1+4) at 125° C. is 6 to 102.

5. The ethylene-vinyl acetate copolymer foamed sole material according to claim 1, characterized in that: The crystallinity of the ethylene-octene copolymer, the highly branched polyethylene and the ethylene block copolymer is lower than 18%; and / or the POE melt index is less than 5g / 10min.

6. The ethylene-vinyl acetate copolymer foamed sole material according to claim 1, characterized in that: The filler is one or more of silicone powder, talcum powder and calcium carbonate.

7. The ethylene-vinyl acetate copolymer foamed sole material according to claim 1, characterized in that: The cross-linking agent is one or both of dicumyl peroxide and 1,3(1,4)-bis(tert-butylperoxyisopropyl)benzene.

8. The ethylene-vinyl acetate copolymer foamed sole material according to claim 1, characterized in that: The foaming agent is selected from one or more of azodicarbonamide, 4,4-oxodibenzenesulfonylhydrazide and N,N'-dinitrosopentamethylenetetramine.

9. A method for preparing an ethylene-vinyl acetate copolymer foamed sole material according to any one of claims 1 to 8, characterized in that: The following steps are involved: The ethylene-vinyl acetate copolymer, the highly branched polyethylene, the ethylene-octene copolymer, the ethylene block copolymer, the filler, the zinc oxide, the zinc stearate and the stearic acid are banburying at a temperature of 100-108° C. for 8-12 min, and then a foaming agent and a crosslinking agent are added, and the second banburying is performed at a temperature of 115-120° C. for 8-12 min to obtain a mixture; granulating the mixed material to obtain granules; The pellets are foamed once and then foamed twice to obtain an ethylene-vinyl acetate copolymer foamed sole material.

10. The method for preparing the ethylene-vinyl acetate copolymer foamed sole material according to claim 9, characterized in that: The granulation temperature is controlled at 80-95°C; the temperature of the primary foaming is 180°C and the time is 300-500s; the temperature of the secondary foaming is 180°C and the time is 400-600s; and the cooling time is 400-600s.

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