Recycled pet modification method, and supercritical physical foamed shoe material and preparation method therefor

Abstract

The present application relates to the technical field of foamed shoe materials, and particularly provides a recycled PET modification method, and a supercritical foamed shoe material and a preparation method therefor. The recycled PET modification method comprises: S1, soaking recycled PET micropowder into an alkaline aqueous solution or an acidic aqueous solution for hydrophilization treatment to obtain hydrophilic PET powder; S2, dispersing the hydrophilic PET powder into an alcohol aqueous solution, adding an amino-containing silane coupling agent, and performing surface treatment reaction, filtering, cleaning, and drying to obtain aminated PET micropowder; and S3, reacting a mixture of a polymer diol and an aspartate ester resin with a polyisocyanate monomer to obtain a polyurethane urea prepolymer, adding the aminated PET micropowder, and continuing to react to obtain modified recycled PET. By applying the modified recycled PET of the present application to foamed shoe materials, foamed shoe materials with a good foaming effect can be obtained.

Description

A modified method for recycled PET, supercritical physical foaming shoe material and preparation method Technical Field

[0001] The present application relates to the technical field of foamed shoe materials, and in particular to a modification method of recycled PET, a supercritical physical foamed shoe material and a preparation method thereof. Background Art

[0002] PET (polyethylene terephthalate) is widely used in the production of plastic bottles. However, PET is a difficult-to-degrade material, making its recycling and reuse particularly important. Currently, there are two main methods for recycling PET: chemical, where the recycled PET undergoes alcoholysis and hydrolysis to obtain degradation products that can be reused as chemical raw materials; and physical, where the recycled PET is mechanically broken down into strips or powders, which are then blended with other materials.

[0003] Supercritical foaming shoe materials, characterized by high resilience and lightweight properties, have been widely used in running shoes and other athletic shoes, becoming a new trend in footwear. Suitable shoe materials for supercritical foaming include polymers such as ethylene-vinyl acetate copolymer (EVA), thermoplastic polyurethane (ETPU), thermoplastic polyester elastomer (TPEE), and thermoplastic nylon elastomer (PEBA).

[0004] Currently, there is no application of recycled PET powder in supercritical foaming shoe materials.

[0005] Supercritical foaming technology places high demands on polymer materials. Directly adding recycled PET powder to a polymer can reduce the material's foaming performance due to issues with the PET powder's particle size and compatibility with the polymer, preventing the production of a high-performance foamed shoe material. Even with simple surface treatments of the PET powder, such as with a silane coupling agent, the applicants have found that achieving good foaming performance is still not possible.

[0006] Summary of the Invention

[0007] In order to solve the above technical problems, the present application provides a modification method of recycled PET, a supercritical physical foaming shoe material and a preparation method.

[0008] This application adopts the following technical solutions:

[0009] A method for modifying recycled PET comprises the following steps:

[0010] S1, soaking the recycled PET micropowder in an alkaline aqueous solution or an acidic aqueous solution for hydrophilization treatment to obtain a hydrophilic PET powder;

[0011] S2, dispersing the hydrophilic PET powder described in step S1 into an alcohol aqueous solution, adding an amino-containing silane coupling agent, performing a surface treatment reaction, filtering, washing, and drying to obtain amino-treated PET micropowder;

[0012] S3. Reacting the mixture of polymer diol and aspartic acid ester resin with polyisocyanate monomer to obtain polyurethane urea prepolymer, and then adding the amino PET powder described in step S2, and continuing the reaction to obtain modified recycled PET.

[0013] Preferably, the average particle size of the recycled PET powder in step S1 is 0.1-10 μm.

[0014] Preferably, the general formula of the amino-containing silane coupling agent in step S2 is H(NH(CH2) m ) x NHCH2CH2CH2Me y Si(OR 1 ) 3-y or NH2(CH2CH2O) n NHCONHCH2CH2Si(OR 2 )3, wherein m=2-6, x=0-2, y=0-1, n=5-50, Me represents a methyl group, R 1 and R 2 independently selected from C1-C4 alkyl or C2-C4 acyl.

[0015] Preferably, in step S2, the weight ratio of the hydrophilic PET powder to the amino-containing silane coupling agent is 1:0.001-0.1.

[0016] Preferably, the average molecular weight of the polymer diol in step S3 is 400-5000, and the polymer diol is selected from one or a combination of polyester diol, polyether diol and polybutadiene diol.

[0017] Preferably, the weight ratio of the polymer diol to the aspartic acid ester resin in the mixture in step S3 is 1:0.03-0.2.

[0018] Preferably, the ratio of the sum of the molar numbers of OH and NH to the molar number of NCO in the mixture and the polyisocyanate monomer in step S3 is 0.55-0.92:1.

[0019] Preferably, in step S3, the weight ratio of the prepolymer to the amino-modified PET powder is 1:0.1-10.

[0020] A supercritical physical foaming shoe material, comprising, by weight, (a) 100 parts of a base polymer, (b) 10-200 parts of modified recycled PET prepared by the method for modifying recycled PET described in any of the above technical solutions, and optionally one or a combination of (c) 0.3-1.5 parts of an antioxidant, (d) 0.2-2 parts of a pigment, (e) 1-3 parts of a lubricant, and (f) 0.5-2 parts of a nucleating agent;

[0021] The base polymer is selected from one or a combination of EVA, ETPU, PEBA and TPEE.

[0022] A method for preparing a supercritical physical foaming shoe material comprises: adding the raw material components of the supercritical physical foaming shoe material described in the above technical solution to a banbury mixer, forming the components, and obtaining a sample; subjecting the sample to supercritical fluid foaming to obtain a foamed sample; and further placing the foamed sample in an oven for further foaming to obtain the supercritical foaming shoe material.

[0023] In summary, this application has the following beneficial effects:

[0024] 1. This application uses polyurethane urea containing carbamate bonds and urea bonds to modify the surface of PET micropowder. There are various structures with different polarities in polyurethane urea, including ester bonds, ether bonds or carbon-carbon bonds with lower polarity, carbamate bonds with higher polarity and urea bonds with even higher polarity. The surface modification method of PET micropowder can be selected according to the different base polymers of supercritical foaming shoe materials, thereby achieving good compatibility between PET micropowder and base polymer. Even modified recycled PET can be used as a compatibilizer for different base polymers, thereby achieving good compatibility between different base polymers.

[0025] 2. In step S3 of the recycled PET modification method of the present application, when the polyurethane urea prepolymer reacts with the amino-treated PET micropowder, due to the presence of multiple amino groups on the surface of the amino-treated PET and the large molecular weight and NCO groups at both ends of the polyurethane urea prepolymer, a slight cross-linking structure exists in the modified recycled PET structure. The slight cross-linking structure does not affect the processing performance of the modified recycled PET, but can enhance the interaction between the PET micropowder and the base polymer, further improving the compatibility of the PET micropowder with the base polymer.

[0026] 3. The filling amount of PET powder in the supercritical foaming shoe material of this application can reach 30% or more, with good foaming performance. The resilience of the obtained supercritical foaming shoe material can reach 60% or more, and the density can be as low as 0.3g / cm 3 And below, the compression set can be as low as 15% and below, and the tensile strength can reach 10MPa and above. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below.

[0028] Throughout this specification, unless otherwise specified, the terms used herein should be understood as having the same meaning as commonly used in the art. Therefore, 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. In the event of any conflict, the present specification shall take precedence.

[0029] In order to solve the technical problem that the existing recycled PET micropowder is not compatible enough with polymer materials, resulting in poor foaming performance when the recycled PET micropowder is used in foamed shoe materials, on the one hand, the present application proposes a method for modifying recycled PET, comprising the following steps:

[0030] S1, soaking the recycled PET micropowder in an alkaline aqueous solution or an acidic aqueous solution for hydrophilization treatment to obtain a hydrophilic PET powder;

[0031] S2, dispersing the hydrophilic PET powder of step S1 into an alcohol aqueous solution, adding an amino-containing silane coupling agent, performing a surface treatment reaction, filtering, washing, and drying to obtain amino-treated PET micropowder;

[0032] S3. Reacting the mixture of polymer diol and aspartic acid ester resin with polyisocyanate monomer to obtain polyurethane urea prepolymer, and then adding the aminoated PET powder in step S2 to continue the reaction to obtain modified recycled PET.

[0033] This application uses polyurethane urea to modify recycled PET powder. By adjusting the polymer soft segment in the polyurethane structure and the aspartic acid ester resin structure, the structure and polarity of the polyurethane urea on the surface of the modified recycled PET can be adjusted to obtain different modification results.

[0034] In the preferred technical solution of the present application, the average particle size of the regenerated PET powder in step S1 is 0.1-10 μm. The average particle size of the regenerated PET powder is too low, the difficulty of obtaining is large, and it is difficult to disperse. The excessively high average particle size will significantly affect the supercritical fluid foaming of the shoe material (the foaming pore size of the supercritical foaming shoe material is generally tens of μm), the foaming performance is poor, the stability of the foam cells is poor, and collapse is likely to occur. In the present application, the regenerated PET powder can be recovered from wastes such as PET plastic bottles and PET woven bags, or it can be directly obtained from commercially available products. Further preferably, the average particle size of the regenerated PET powder is 0.5-5 μm. For example, the average particle size can be any value of 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc.

[0035] Specifically, the alkaline aqueous solution in step S1 can be a sodium hydroxide aqueous solution, a sodium carbonate aqueous solution, or a potassium hydroxide aqueous solution with a concentration of 0.5-5wt%, and the acidic aqueous solution can be a sulfuric acid solution, a hydrochloric acid solution, a nitric acid solution, or the like with a concentration of 1-5wt%. The surface of the regenerated PET micropowder has relatively few active groups, making further modification difficult. By treating with an alkaline aqueous solution or an acidic aqueous solution, more active groups such as hydroxyl groups will be introduced to the surface of the regenerated PET micropowder. The temperature of the hydrophilization treatment can be room temperature-60°C, and the treatment time can be 5-60 minutes. If the treatment time is too short, the treatment effect will be poor, and the surface of the regenerated PET micropowder will have fewer active groups such as hydroxyl groups. If the temperature is too high or the treatment time is too long, the regenerated PET micropowder will be degraded, affecting the quality of the regenerated PET micropowder.

[0036] In this application, in step S2, an amino-containing silane coupling agent is used to react with the hydrophilic PET powder, and amino groups are grafted onto the surface of the PET powder, which can then react with the polyurethane urea prepolymer in step S3 to introduce a polyurethane urea structure onto the surface of the PET powder and modify it. In the preferred technical solution of this application, the general formula of the amino-containing silane coupling agent in step S2 is H(NH(CH2) m ) x NHCH2CH2CH2Me y Si(OR 1 ) 3-y Or amino polyethylene glycol silane coupling agent NH2(CH2CH2O) n NHCONHCH2CH2Si(OR 2 )3, wherein m=2-6, x=0-2, y=0-1, n=5-50, Me represents a methyl group, R 1 and R 2 The amino group is independently selected from C1-C4 alkyl or C2-C4 acyl. For example, the amino group-containing silane coupling agent can be 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, β-aminoethyl-γ-aminopropyltrimethoxysilane, β-aminoethyl-γ-aminopropyltrihexyloxysilane, aminopolyethylene glycol silane coupling agent, etc.

[0037] In the preferred technical solution of the present application, the weight ratio of the hydrophilic PET powder to the amino-containing silane coupling agent in step S2 is 1:0.001-0.1. Further, the weight ratio of the hydrophilic PET powder to the amino-containing silane coupling agent is 1:0.005-0.08. For example, the weight ratio can be any value of 1:0.005, 1:0.01, 1:0.015, 1:0.02, 1:0.025, 1:0.03, 1:0.035, 1:0.04, 1:0.045, 1:0.05, 1:0.055, 1:0.06, 1:0.065, 1:0.07, 1:0.075, 1:0.08, etc.

[0038] The specific operation of step S2 of the present application may be, but does not represent a limitation of the present application: ultrasonically disperse 1-5 parts by weight of hydrophilic PET powder into 100 parts by weight of an alcohol aqueous solution (composed of anhydrous ethanol and water in a volume ratio of 8:2-9:1), add an aminosilane coupling agent, stir at room temperature for 0.5-1 hour, heat to 50-70°C and continue to react for 1-2 hours, collect the solid, wash with anhydrous ethanol, and dry at 50-100°C to obtain.

[0039] In the preferred technical solution of the present application, the average molecular weight of the polymer diol in step S3 is 400-5000, and the polymer diol can be selected from one or more combinations of polyester diol, polyether diol (such as polyethylene glycol, polypropylene glycol, polyethylene glycol polypropylene glycol copolymer, polytetramethylene glycol, etc.) and polybutadiene diol. Further, the average molecular weight of the polymer diol is 500-4000, for example, the number average molecular weight can be any value among 500, 600, 800, 1000, 1200, 1500, 1800, 200, 2200, 2500, 2800, 3000, 3200, 3500, 3700, 4000, etc.

[0040] In a preferred embodiment of the present invention, the weight ratio of the polymer diol to the aspartic acid ester resin in the mixture in step S3 is 1:0.03-0.2. For example, the weight ratio of the polymer diol to the aspartic acid ester resin can be any value including 1:0.03, 1:0.05, 1:0.08, 1:0.1, 1:0.12, 1:0.15, 1:0.17, and 1:0.2.

[0041] In the present application, the aspartic acid ester resin may have a structure of:

[0042] Wherein, R can be a C1-C18 alkyl group, a polyether segment, etc., and X is the structure of the corresponding diprimary amine compound after removing two primary amine groups. Aspartic acid ester resin can be obtained by reacting a diprimary amine compound with a maleic acid diester or a fumaric acid diester through a Michael addition reaction. Specifically, the diprimary amine compound corresponding to X can be 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, isophoronediamine, 1,6-hexanediamine, 2-methyl-1,5-pentanediamine, 3-methyl-1,5-pentanediamine, 1-methyl-2,4-cyclohexanediamine, 1,3-cyclohexanedimethylamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 1,3-cyclopentanediamine, o-diaminomethylcyclopentane, polyetheramine D-230, polyetheramine D-400, polyetheramine D-2000, polyetheramine ED-600, polyetheramine ED-900, polyetheramine T-403, polyetheramine T-5000, polyetheramine ED-2300, double-terminated amino polyethylene glycol, etc. Aspartic acid ester resin can maintain a reaction rate with polymer diols that is close to that of polyisocyanate monomers, and can also introduce highly polar urea bonds. The R group can also be adjusted to achieve different polarities or compatibility with different polymers.

[0043] In the preferred technical solution of the present application, the ratio of the sum of the moles of OH and NH to the moles of NCO in the mixture and the polyisocyanate monomer in step S3 is 0.55-0.92:1. Using the above technical solution, NCO is in excess, and an isocyanate-terminated polyurethane urea prepolymer can be obtained. For example, the ratio of the sum of the moles of OH and NH to the moles of NCO can be any value among 0.55:1, 0.58:1, 0.6:1, 0.63:1, 0.65:1, 0.7:1, 0.73:1, 0.75:1, 0.77:1, 0.8:1, 0.82:1, 0.85:1, 0.88:1, 0.8:1, 0.9:1, 0.92:1, etc.

[0044] In the preferred technical solution of the present application, the weight ratio of the prepolymer to the amino-treated PET powder in step S3 is 1:0.1-10. Further, the weight ratio of the prepolymer to the amino-treated PET powder is 1:0.3-5. For example, the weight ratio can be any value of 1:0.3, 1:0.5, 1:0.8, 1:1, 1:1.3, 1:1.5, 1:1.7, 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3, 1:3.3, 1:3.5, 1:3.7, 1:4, 1:4.2, 1:4.5, 1:4.7, 1:5, etc.

[0045] On the other hand, the present application also proposes a supercritical physical foaming shoe material, the raw material components, by weight, comprising (a) 100 parts of a base polymer, (b) 10-200 parts of modified recycled PET prepared by the modified method of recycled PET described in any of the above technical solutions, and optionally (c) 0.3-1.5 parts of an antioxidant, (d) 0.2-2 parts of a pigment, (e) 1-3 parts of a lubricant, and (f) 0.5-2 parts of a nucleating agent, or a combination thereof;

[0046] The base polymer is selected from one or a combination of EVA, ETPU, PEBA and TPEE. In this application, the base polymer can be directly obtained from commercial products.

[0047] The modified recycled PET obtained in this application can be directly mixed with the base polymer material of shoe materials (especially midsoles) to obtain shoe materials that can be directly foamed with supercritical fluids, and the foaming performance is good. The polyurethane urea on the surface of the modified recycled PET in this application contains multiple polymer segments of different polarities, and there is a slight cross-linking structure between the polymer segments, which can produce good compatibility with different base polymers and even serve as a compatibilizer for base polymers of different polarities, allowing multiple base polymers of different polarities to be mixed and used, increasing the degree of freedom in the design of foamed shoe materials.

[0048] On the other hand, the present application also proposes a method for preparing supercritical physical foaming shoe materials, comprising: adding the raw material components of the supercritical physical foaming shoe materials in the above technical scheme to a banbury mixer, forming, and obtaining a shoe material sample; subjecting the shoe material sample to supercritical fluid foaming to obtain a foamed sample; and placing the foamed sample in an oven for further foaming to obtain a supercritical foaming shoe material.

[0049] In the above-mentioned preparation method of supercritical physical foaming shoe materials, the molding can be carried out by injection molding or compression molding, etc., and the material is pre-molded into the preset shape of the foamed shoe material, and then foamed. In order to avoid the melting of PET micropowder, the temperature during the molding process is preferably not more than 200°C. The operation of supercritical fluid foaming can be: the shoe material sample is placed in a high-pressure reactor and sealed, a supercritical fluid (supercritical CO2 or supercritical N2, etc.) is introduced and pressurized to a saturated state, a pressure of 8-30MPa, a temperature of 40-65°C, a holding time of 12-36h, and then the supercritical fluid is quickly released within 1-2s to obtain a pre-foamed shoe material. The operation of continuing foaming can be: the pre-foamed sample is then placed in a constant temperature device for foaming to obtain a foamed shoe material, the foaming temperature is 80-120°C, and the foaming time is 0.1-5min.

[0050] The technical solution of the present application is described in detail below with reference to the following examples and comparative examples. Unless otherwise specified, the parts in the following examples and comparative examples are parts by weight.

[0051] Example 1-6 Preparation of modified recycled PET

[0052] Example 1

[0053] At room temperature, 1 part of recycled PET powder with an average particle size of 2 μm was immersed in 3 parts of 1 wt% NaOH aqueous solution for 30 min for hydrophilization treatment, filtered, washed with purified water 3 times, and dried in a vacuum oven at 60°C overnight to obtain hydrophilic PET powder.

[0054] 3 parts of the above hydrophilic PET powder were ultrasonically dispersed into 100 parts of anhydrous ethanol aqueous solution with a water content of 15% by volume, 0.15 parts of 3-aminopropyltrimethoxysilane were added, and the mixture was stirred at room temperature for 1 hour. The temperature was raised to 55°C and the reaction was continued for 1.5 hours. The solid was collected and washed twice with anhydrous ethanol, and dried in a vacuum oven at 60°C overnight to obtain amino-modified PET micropowder.

[0055] Under nitrogen protection, a mixture of 1 part of dried and dehydrated polycarbonate diol (number average molecular weight 1000) and 0.1 part of dried and dehydrated aspartic acid ester resin (obtained by reacting 4,4'-diaminodicyclohexylmethane and diethyl maleic anhydride in a molar ratio of 1:2) and IPDI were added to a reaction vessel at a molar ratio of NH and OH and to NCO of 0.8:1, and stirred at room temperature until the NCO group reached a preset value to obtain a polyurethane urea prepolymer. 1.1 parts of the above-mentioned amino PET powder were added, and the stirring reaction was continued for 2 hours to obtain a modified recycled PET.

[0056] Example 2

[0057] The difference between Example 2 and Example 1 is that in Example 1, in the step of reacting the polyurethane urea prepolymer with the amino-modified PET powder, the amount of the amino-modified PET powder was adjusted from 1.1 parts to 0.22 parts, while the remaining steps remained unchanged.

[0058] Example 3

[0059] The difference between Example 3 and Example 1 is that in Example 1, in the step of reacting the polyurethane urea prepolymer with the amino-treated PET fine powder, the amount of the amino-treated PET fine powder was adjusted from 1.1 parts to 3.3 parts, while the remaining steps remained unchanged.

[0060] Example 4

[0061] At room temperature, 1 part of recycled PET powder with an average particle size of 1 μm was immersed in 5 parts of a 2 wt% NaOH aqueous solution for 20 min for hydrophilization. The resulting powder was filtered, washed with purified water three times, and dried in a vacuum oven at 60°C overnight to obtain a hydrophilic PET powder.

[0062] 5 parts of the above hydrophilic PET powder were ultrasonically dispersed into 100 parts of anhydrous ethanol aqueous solution with a water content of 15% by volume, 0.1 parts of β-aminoethyl-γ-aminopropyltrimethoxysilane were added, and the mixture was stirred at room temperature for 1 hour. The temperature was raised to 55°C and the reaction was continued for 1.5 hours. The solid was collected and washed twice with anhydrous ethanol, and dried in a vacuum oven at 60°C overnight to obtain amino-modified PET powder.

[0063] Under nitrogen protection, a mixture of 1 part of dried and dehydrated polypropylene glycol (number average molecular weight 1500) and 0.05 parts of dried and dehydrated aspartic acid ester resin (obtained by reacting 4,4'-diaminodicyclohexylmethane and dioctyl maleic anhydride in a molar ratio of 1:2) and HMDI were added to a reaction vessel at a molar ratio of NH and OH to NCO of 0.85:1, and stirred at room temperature until the NCO group reached a preset value to obtain a polyurethane urea prepolymer. Then, 3 parts of the above-mentioned aminoated PET powder were added, and the stirring reaction was continued for 2 hours to obtain modified recycled PET.

[0064] Example 5

[0065] The difference between Example 5 and Example 4 is that in Example 4, the aspartic acid ester resin is adjusted from 0.05 parts to 0.12 parts. The other steps remain unchanged.

[0066] Example 6

[0067] Under nitrogen protection, a mixture of 1 part of dried and dehydrated polypropylene glycol (number average molecular weight 1500) and 0.18 parts of dried and dehydrated aspartic acid ester resin (obtained by reacting 4,4'-diaminodicyclohexylmethane and dioctyl maleic anhydride in a molar ratio of 1:2) and HMDI were added to a reaction vessel at a molar ratio of NH and OH to NCO of 0.65:1, and stirred at room temperature until the NCO group reached a preset value to obtain a polyurethane urea prepolymer. 4.5 parts of the aminoated PET powder in Example 4 were added, and the stirring reaction was continued for 2 hours to obtain a modified recycled PET.

[0068] Example 7-17 Preparation of supercritical foaming shoe materials

[0069] Example 7

[0070] The foamed shoe material consists of 100 parts of ETPU, 50 parts of the modified recycled PET of Example 1, 1 part of antioxidant 1010 and 0.6 parts of nano-silicon dioxide with an average particle size of 30 nm.

[0071] The above raw materials were added to an internal mixer and mixed, then injection molded at 190°C to produce shoe material samples. The shoe material samples were then placed in a sealed autoclave, where supercritical CO2 was introduced and pressurized to saturation at 22 MPa and 52°C for 21 hours. The supercritical fluid was then rapidly released within 2 seconds to produce pre-foamed shoe material. The pre-foamed sample was then placed in a constant temperature apparatus at 100°C for 2 minutes to produce the foamed shoe material.

[0072] Example 8

[0073] The difference between Example 8 and Example 7 is that in Example 7, 100 parts of TPU was adjusted to a combination of 80 parts of TPU and 20 parts of TPEE. The other steps remained unchanged.

[0074] Example 9

[0075] The difference between Example 9 and Example 7 is that in Example 7, the modified recycled PET in Example 1 is replaced by an equal weight of the modified recycled PET in Example 2. The remaining steps remain unchanged.

[0076] Example 10

[0077] The difference between Example 10 and Example 7 is that in Example 7, the modified recycled PET in Example 1 is replaced by an equal weight of the modified recycled PET in Example 3. The remaining steps remain unchanged.

[0078] Example 11

[0079] The difference between Example 11 and Example 7 is that in Example 7, the modified recycled PET in Example 1 is adjusted from 50 parts to 15 parts. The other steps remain unchanged.

[0080] Example 12

[0081] The difference between Example 12 and Example 7 is that in Example 7, the modified recycled PET in Example 1 is adjusted from 50 parts to 100 parts. The other steps remain unchanged.

[0082] Comparative Example 1

[0083] The difference between Comparative Example 1 and Example 7 is that in Example 7, the modified recycled PET is replaced by an equal weight of the untreated recycled PET powder in Example 1. The remaining steps remain unchanged.

[0084] Comparative Example 2

[0085] The difference between Comparative Example 2 and Example 7 is that in Example 7, the modified recycled PET is replaced by an equal weight of the amino-treated PET powder in Example 1. The remaining steps remain unchanged.

[0086] Comparative Example 3

[0087] The difference between Comparative Example 3 and Example 7 is that in Example 7, the modified recycled PET is replaced by 15 parts of the amino-treated PET powder in Example 1. The remaining steps remain unchanged.

[0088] Example 13

[0089] The foamed shoe material consists of 100 parts of ETPU and 70 parts of the modified recycled PET of Example 4.

[0090] Supercritical foaming was carried out according to the supercritical foaming method of Example 7.

[0091] Example 14

[0092] The difference between Example 14 and Example 13 is that in Example 13, 100 parts of TPU are replaced by a combination of 70 parts of ETPU and 30 parts of EVA (vinyl acetate content 18%). The other steps remain unchanged.

[0093] Example 15

[0094] The difference between Example 15 and Example 14 is that in Example 14, the modified recycled PET in Example 4 is replaced by an equal weight of the modified recycled PET in Example 5. The remaining steps remain unchanged.

[0095] Example 16

[0096] The difference between Example 16 and Example 14 is that in Example 14, the modified recycled PET in Example 4 is replaced by an equal weight of the modified recycled PET in Example 6. The remaining steps remain unchanged.

[0097] Example 17

[0098] The difference between Example 17 and Example 13 is that in Example 13, 100 parts of TPU are replaced by a combination of 60 parts of ETPU, 20 parts of TPEE, and 20 parts of EVA (vinyl acetate content 18%). The remaining steps remain unchanged.

[0099] Comparative Example 4

[0100] The foamed shoe material is composed of 70 parts of ETPU and 30 parts of EVA (vinyl acetate content 18%).

[0101] Supercritical foaming was carried out according to the supercritical foaming method of Example 7.

[0102] Comparative Example 5

[0103] The foamed shoe material is composed of 60 parts of ETPU, 20 parts of TPEE and 20 parts of EVA (vinyl acetate content 18%).

[0104] Supercritical foaming was carried out according to the supercritical foaming method of Example 7.

[0105] The performance tests and results of the foamed shoe materials of Examples 7-17 and Comparative Examples 1-5 are shown in Table 1 below.

[0106] Drop ball rebound: tested according to the method of GB / T6670-2008.

[0107] Density: tested using KW-300A microcomputer electronic density meter.

[0108] Tensile strength: tested according to the method of GB / T528-2008.

[0109] Compression set: tested according to ASTM 3574, test conditions: 50% compression rate, 23°C, 22h.

[0110] Table 1

[0111] From the results in Table 1 above, it can be seen that the modified recycled PET obtained by the modification method of recycled PET of the present application is used for supercritical foaming shoe materials. The shoe materials have good foaming performance and the performance of the shoe materials after foaming is good. In addition, it can also promote the compatibility of different base polymer materials.

[0112] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for modifying recycled PET, characterized in that: The following steps are involved: S1, soaking the recycled PET micropowder in an alkaline aqueous solution or an acidic aqueous solution for hydrophilization treatment to obtain a hydrophilic PET powder; S2, dispersing the hydrophilic PET powder described in step S1 into an alcohol aqueous solution, adding an amino-containing silane coupling agent, performing a surface treatment reaction, filtering, washing, and drying to obtain amino-treated PET micropowder; S3, reacting the mixture of polymer diol and aspartic acid ester resin with polyisocyanate monomer to obtain polyurethane urea prepolymer, and then adding the amino PET powder described in step S2, continuing the reaction to obtain modified recycled PET.

2. The method for modifying recycled PET according to claim 1, characterized in that: The average particle size of the recycled PET powder in step S1 is 0.1-10 μm.

3. The method for modifying recycled PET according to claim 1, characterized in that: The general formula of the amino-containing silane coupling agent in step S2 is H(NH(CH2) m ) x NHCH2CH2CH2Me y Si(OR 1 ) 3-y or NH2(CH2CH2O) n NHCONHCH2CH2Si(OR 2 )3, wherein m=2-6, x=0-2, y=0-1, n=5-50, Me represents methyl, R 1 and R 2 independently selected from C1-C4 alkyl or C2-C4 acyl.

4. The method for modifying recycled PET according to claim 1, characterized in that: The weight ratio of the hydrophilic PET powder to the amino-containing silane coupling agent in step S2 is 1:0.001-0.

1.

5. The method for modifying recycled PET according to claim 1, characterized in that: The average molecular weight of the polymer diol in step S3 is 400-5000, and the polymer diol is selected from one or a combination of polyester diol, polyether diol and polybutadiene diol.

6. The method for modifying recycled PET according to claim 1, characterized in that: The weight ratio of the polymer diol to the aspartic acid ester resin in the mixture in step S3 is 1:0.03-0.

2.

7. The method for modifying recycled PET according to claim 1, characterized in that: The ratio of the sum of the molar numbers of OH and NH to the molar number of NCO in the mixture and the polyisocyanate monomer in step S3 is 0.55-0.92:

1.

8. The method for modifying recycled PET according to claim 1, characterized in that: The weight ratio of the prepolymer to the amino PET powder in step S3 is 1:0.1-10.

9. A supercritical physical foaming shoe material, characterized in that: The raw material components, measured by weight, include (a) 100 parts of a base polymer, (b) 10-200 parts of a modified recycled PET prepared by the method for modifying recycled PET according to any one of claims 1 to 8, and optionally (c) 0.3-1.5 parts of an antioxidant, (d) 0.2-2 parts of a pigment, (e) 1-3 parts of a lubricant, and (f) 0.5-2 parts of a nucleating agent, or a combination thereof; The base polymer is selected from one or a combination of EVA, ETPU, PEBA and TPEE.

10. A method for preparing a supercritical physical foaming shoe material, characterized in that: include: Adding the raw material components of the supercritical physical foaming shoe material of claim 9 into a mixer and kneading, forming, and obtaining a sample; The sample is subjected to supercritical fluid foaming to obtain a foamed sample; the foamed sample is then placed in an oven for further foaming to obtain the supercritical foamed shoe material.

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