TPU supercritical foaming material for preparing shoe sole and preparation method of TPU supercritical foaming material

Abstract

The invention relates to the field of foaming materials, in particular to a TPU supercritical foaming material for preparing shoe soles and a preparation method of the TPU supercritical foaming material. The TPU supercritical foaming material for preparing the shoe sole comprises the following raw materials in parts by weight: 80-90 parts of thermoplastic polyurethane elastomer; 8-12 parts of cellulose fiber; 1-3 parts of a nucleating agent; 2-5 parts of a cross-linking agent; wherein the thermoplastic polyurethane elastomer comprises the following raw materials in parts by weight: 40-50 parts of polyester polyol; 25 to 33 parts of diisocyanate; 14 to 24 parts of lauric acid; 7 to 12 parts of pentaerythritol; 0.02 to 0.05 part of a catalyst; 3 to 8 parts of 2, 3, 3, 4, 4-benzophenone tetracarboxylic dianhydride; and 1-3 parts of an antioxidant. The TPU supercritical foaming material prepared by the invention is good in foaming performance, small in contractility and excellent in mechanical property.

Description

Technical Field

[0001] The present invention relates to the field of foaming materials, and particularly to a TPU supercritical foaming material for preparing shoe soles and a preparation method thereof. Background Art

[0002] The performance of shoe materials and the user experience are largely determined by the performance of the midsole. The midsole material is required to be lightweight, highly resilient, shock-absorbing and low-density. Thermoplastic polyurethane elastomer, namely TPU, has good elasticity and cushioning performance, high strength, strong mechanical properties and good machining performance, etc., and has become a popular midsole material. The prepared TPU foaming material has a porous structure, and at the same time is lightweight, has good resilience and strong compression resistance, can provide structural support and buffering functions, and is suitable for the midsole of shoe materials.

[0003] Regarding the foaming method of TPU, it is divided into physical foaming and chemical foaming. Among them, the supercritical fluid foaming technology uses pollution-free nitrogen or carbon dioxide as the foaming gas, and will not produce toxic and harmful substances such as ammonia and acetophenone in traditional chemical foaming. The prepared foamed shoe materials have finer and more uniform pores and better performance, and have become the most popular technology in the field of shoe material technology.

[0004] The currently used TPU supercritical foaming materials still have the following deficiencies:

[0005] 1. The thermoplastic polyurethane elastomer has a linear structure and small melt strength, resulting in poor foaming performance of TPU and large shrinkage after foaming;

[0006] 2. The mechanical properties of the TPU foaming material are poor, affecting the comprehensive performance. Summary of the Invention

[0007] In order to improve the foaming performance of TPU and improve the mechanical properties of the TPU supercritical foaming material, the present application provides a TPU supercritical foaming material for preparing shoe soles and a preparation method thereof.

[0008] The TPU supercritical foaming material for preparing shoe soles and the preparation method provided by the present application adopt the following technical solutions:

[0009] A TPU supercritical foaming material for preparing shoe soles, comprising the following raw materials in parts by weight:

[0010] Thermoplastic polyurethane elastomer 80 - 90 parts;

[0011] Cellulose fiber 8 - 12 parts;

[0012] Nucleating agent 1 - 3 parts;

[0013] Crosslinking agent 2 - 5 parts;

[0014] Among them, the thermoplastic polyurethane elastomer comprises the following raw materials in parts by weight:

[0015] Polyester polyol: 40 - 50 parts;

[0016] Diisocyanate: 25 - 33 parts;

[0017] Lauric acid: 14 - 24 parts;

[0018] Pentaerythritol: 7 - 12 parts;

[0019] Catalyst: 0.02 - 0.05 parts;

[0020] 3,3,4,4 - Benzophenone tetracarboxylic dianhydride: 3 - 8 parts;

[0021] Antioxidant: 1 - 3 parts.

[0022] By adopting the above - mentioned technical solution, choosing to compound the thermoplastic polyurethane elastomer with cellulose fiber, the cellulose fiber has good foaming performance, thus improving the overall foaming performance. The cellulose fiber also plays a reinforcing role and synergizes with the thermoplastic polyurethane elastomer, so that the mechanical strength of the foaming material is improved.

[0023] In the preparation of the thermoplastic polyurethane elastomer, lauric acid and pentaerythritol react to form a dibasic acid with a long alkyl chain. Choosing 3,3,4,4 - benzophenone tetracarboxylic dianhydride as the chain extender, thus enabling the TPU to form a cross - linked structure with long branched chains, enhancing the glass transition temperature and melt strength, improving the foaming performance of the thermoplastic polyurethane elastomer, and reducing the shrinkage of the foaming material. After the chain extender reacts with the diisocyanate, a benzene ring and an imide structure are introduced into the polyurethane main chain, improving the heat resistance of the TPU, and at the same time enhancing the mechanical properties such as elasticity and tensile strength. The prepared TPU supercritical foaming material has excellent mechanical properties and meets the use requirements of the midsole of shoes.

[0024] Optionally, the polyester polyol is selected from one or more of polycarbonate diol, polycaprolactone diol, poly(1,4 - butanediol adipate), and modified polyester diol.

[0025] Optionally, the polyester polyol is selected as the modified polyester diol, and the modified polyester diol comprises the following raw materials in parts by weight:

[0026] Polycarbonate diol: 40 - 50 parts;

[0027] Styrene: 7 - 13 parts;

[0028] Vinyl cyanide: 7 - 13 parts;

[0029] Azobisisobutyronitrile: 2 - 3 parts.

[0030] By adopting the above technical solution, the polycarbonate diol is modified with styrene and acrylonitrile, so that branched chains are introduced into the polyester diol, and the melt strength of the polyurethane system formed by reacting with diisocyanate is further increased, which is beneficial to the foaming performance; at the same time, the fluidity and processing performance of the polyester polyol are improved, which promotes the improvement of the mechanical properties.

[0031] Optionally, the cellulose fiber is a graft-modified cellulose fiber, and the graft-modified cellulose fiber comprises the following raw materials in parts by weight:

[0032] Cellulose fiber: 10 - 15 parts;

[0033] Ammonium persulfate: 0.5 - 1 part;

[0034] Divinylbenzene: 17 - 23 parts;

[0035] Butyl methacrylate: 6 - 10 parts.

[0036] By adopting the above technical solution, butyl methacrylate is used to modify the nanocellulose, so that the hydroxyl groups on the surface of the nanocellulose are reduced, the hydrophilicity is decreased, and the compatibility with the thermoplastic polyurethane elastomer is better, forming a uniform cross-linked network. The addition of the graft-modified cellulose fiber is also beneficial to the improvement of the tensile properties and mechanical strength of the foaming material.

[0037] Optionally, the diisocyanate is one or more of hexamethylene diisocyanate, toluene diisocyanate, and dicyclohexylmethane diisocyanate.

[0038] Optionally, the nucleating agent is one or more of nano calcium carbonate, calcium phosphate, fumed silica, and montmorillonite.

[0039] By adopting the above technical solution, the addition of the nucleating agent greatly reduces the cell size, increases the cell density, makes the cells more uniform, and better forms a closed-cell structure, ensuring the foaming effect of the foaming material.

[0040] Optionally, the cross-linking agent is one or more of dicumyl peroxide, bis(tert-butylperoxyisopropyl)benzene, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0041] By adopting the above technical solution, the cross-linking agent promotes the better cross-linking of the thermoplastic polyurethane elastomer and the cellulose fiber into a network, ensuring the high elasticity of the foaming material and reducing deformation.

[0042] The present application discloses a preparation method of a TPU supercritical foaming material for soles, comprising the following steps:

[0043] S1. Preparation of thermoplastic polyurethane elastomer: Put lauric acid, pentaerythritol and part of the catalyst into a reaction flask, introduce nitrogen for protection, heat to 190 - 210 °C for esterification reaction to generate diol;

[0044] Heat the generated diol and polyester polyol to 100 - 110 °C, stir and dehydrate under vacuum, cool to 60 - 65 °C, add diisocyanate, and slowly heat to 70 - 80 °C, stir and react to obtain a prepolymer;

[0045] Mix 3,3,4,4 - benzophenone tetracarboxylic dianhydride, the remaining catalyst and antioxidant evenly, add to the prepolymer, stir quickly and then pour into a tray, put it into an oven at 100 - 120 °C for curing for 16 - 18 h, cool to room temperature, crush with a crusher and then mold to obtain thermoplastic polyurethane elastomer;

[0046] S2. Kneading: Mix the thermoplastic polyurethane elastomer and cellulose fiber and send them into a kneader, knead at 130 - 135 °C for 20 - 30 min, add a cross - linker and a nucleating agent, and knead and blend at 125 - 130 °C until all components are evenly mixed to obtain a kneaded blend;

[0047] S3. Pressing: Use a press to press the kneaded blend into a plate and cut it;

[0048] S4. Supercritical foaming: Put the plate into an oven, preheat to 130 - 140 °C, then place the pre - heated foaming master plate into a high - temperature mold, introduce carbon dioxide gas, when the carbon dioxide gas reaches saturation in the sheet, quickly release the carbon dioxide gas in the mold to make the sheet foam quickly to obtain a TPU supercritical foaming material.

[0049] By adopting the above technical solution, the plate - foaming method is selected. First, the prepared thermoplastic polyurethane elastomer is kneaded together with cellulose fiber, cross - linker and nucleating agent, pressed into a plate and then supercritically foamed. The compatibility of each component is good, the foaming efficiency is high, the cell structure is uniform and dense, and the mechanical properties and comprehensive properties of the obtained foaming material are excellent.

[0050] Optionally, when the polyester polyol is a modified polyester diol, the modified polyester diol is prepared by the following steps:

[0051] Take polycarbonate diol, styrene, acrylonitrile and azobisisobutyronitrile, mix and stir for 20 - 30 min, react at 100 - 110 °C for 1 - 2 h under a nitrogen atmosphere, and perform vacuum treatment under nitrogen bubbling to obtain a modified polyester diol.

[0052] By adopting the above technical solution, styrene and acrylonitrile graft - modify polycarbonate diol under the action of an initiator to improve the processing fluidity and mechanical strength of the polyester polyol.

[0053] Optionally, when the cellulose fiber is a graft-modified cellulose fiber, the graft-modified cellulose fiber is prepared by the following steps:

[0054] The cellulose fiber is uniformly dispersed in deionized water, stirred and heated to 65-75 °C under nitrogen protection, ammonium persulfate, divinylbenzene and butyl methacrylate are added and reacted for 2-3 h, the product is filtered out, washed repeatedly with distilled water and absolute ethanol and dried to obtain the graft-modified cellulose fiber.

[0055] By adopting the above technical scheme, ammonium persulfate is used as an initiator and divinylbenzene is used as a crosslinking agent to promote the formation of a crosslinked network of cellulose fiber and methyl methacrylate, thereby improving the mechanical strength and tensile properties.

[0056] In summary, the present application has the following beneficial effects:

[0057] The thermoplastic polyurethane elastomer is selected to be compounded with the cellulose fiber. The cellulose fiber has good foaming performance, thereby improving the overall foaming performance. The cellulose fiber also plays a reinforcing role and synergizes with the thermoplastic polyurethane elastomer, so that the mechanical strength of the foamed material is improved.

[0058] In the preparation of the thermoplastic polyurethane elastomer, lauric acid and pentaerythritol react to form a dibasic acid with a long alkyl chain, and 3,3,4,4-benzophenone tetracarboxylic dianhydride is selected as a chain extender, so that the TPU forms a crosslinked structure with long branched chains, the glass transition temperature and the melt strength are enhanced, the foaming performance of the thermoplastic polyurethane elastomer is improved, and the shrinkage of the foamed material is reduced. After the chain extender reacts with the diisocyanate, a benzene ring and an imide structure are introduced into the polyurethane main chain, so that the heat resistance of the TPU is improved, and at the same time, the mechanical properties such as elasticity and tensile strength are improved. The prepared TPU supercritical foamed material has excellent mechanical properties and meets the use requirements of the midsole of shoes. Detailed implementation mode

[0059] Preparation example

[0060] Preparation example 1

[0061] Preparation of modified polyester diol

[0062] The modified polyester diol comprises the following raw materials in parts by weight:

[0063] 40 parts of polycarbonate diol with a relative molecular mass of 2000;

[0064] 7 parts of styrene;

[0065] 13 parts of vinyl cyanide;

[0066] 2 parts of azodiisobutyronitrile.

[0067] The modified polyester diol is prepared through the following steps:

[0068] Take polycarbonate diol, styrene, acrylonitrile and azobisisobutyronitrile, mix and stir for 20 min, react at 100 °C for 1 h under a nitrogen atmosphere, and carry out vacuum treatment for 2 h under nitrogen bubbling to obtain the modified polyester diol.

[0069] Preparation Example 2

[0070] Preparation of the modified polyester diol

[0071] The modified polyester diol comprises the following raw materials in parts by weight:

[0072] 50 parts of polycarbonate diol with a relative molecular mass of 3000;

[0073] 13 parts of styrene;

[0074] 13 parts of vinyl cyanide;

[0075] 3 parts of azobisisobutyronitrile.

[0076] The modified polyester diol is prepared through the following steps:

[0077] Take polycarbonate diol, styrene, acrylonitrile and azobisisobutyronitrile, mix and stir for 30 min, react at 110 °C for 2 h under a nitrogen atmosphere, and carry out vacuum treatment for 3 h under nitrogen bubbling to obtain the modified polyester diol.

[0078] Preparation Example 3

[0079] Preparation of the graft-modified cellulose fiber

[0080] The graft-modified cellulose fiber comprises the following raw materials in parts by weight:

[0081] 10 parts of cellulose fiber;

[0082] 0.5 part of ammonium persulfate;

[0083] 17 parts of divinylbenzene;

[0084] 6 parts of butyl methacrylate.

[0085] The graft-modified cellulose fiber is prepared through the following steps:

[0086] Disperse the cellulose fiber evenly in 40 parts of deionized water, stir and heat to 65 °C under nitrogen protection, add ammonium persulfate, divinylbenzene and butyl methacrylate and react for 2 h, filter out the product and wash it repeatedly with distilled water and absolute ethanol, and place it in an oven to dry at 80 °C for 12 h to obtain the graft-modified cellulose fiber.

[0087] Preparation Example 4

[0088] Preparation of Grafted Modified Cellulose Fiber

[0089] The grafted modified cellulose fiber comprises the following raw materials in parts by weight:

[0090] Cellulose fiber: 15 parts;

[0091] Ammonium persulfate: 1 part;

[0092] Divinylbenzene: 23 parts;

[0093] Butyl methacrylate: 10 parts.

[0094] The grafted modified cellulose fiber is prepared by the following steps:

[0095] The cellulose fiber is uniformly dispersed in 50 parts of deionized water, stirred and heated to 75°C under nitrogen protection, ammonium persulfate, divinylbenzene and butyl methacrylate are added and reacted for 3 h, the product is taken out by filtration and washed repeatedly with distilled water and absolute ethanol, and then placed in an oven and dried at 80°C for 12 h to obtain the grafted modified cellulose fiber.

[0096] Example

[0097] Example 1

[0098] Preparation of TPU Supercritical Foaming Material for Sole

[0099] The TPU supercritical foaming material for sole comprises the following raw materials in parts by weight:

[0100] Thermoplastic polyurethane elastomer: 80 parts;

[0101] Cellulose fiber: 8 parts;

[0102] Nucleating agent: 1 part, and the nucleating agent is selected as nano calcium carbonate;

[0103] Crosslinking agent: 2 parts, and the crosslinking agent is selected as dicumyl peroxide;

[0104] The thermoplastic polyurethane elastomer comprises the following raw materials in parts by weight:

[0105] Polyester polyol: 40 parts, specifically selected as polycaprolactone diol with a relative molecular mass of 2000;

[0106] Diisocyanate: 25 parts, specifically selected as hexamethylene diisocyanate;

[0107] Lauric acid: 14 parts;

[0108] Pentaerythritol: 7 parts;

[0109] 0.02 parts of catalyst, and the catalyst is dibutyltin dilaurate;

[0110] 3 parts of 3,3,4,4-benzophenone tetracarboxylic dianhydride;

[0111] 1 part of antioxidant, specifically antioxidant 1010 is selected.

[0112] The TPU supercritical foaming material is prepared by the following steps:

[0113] S1. Preparation of thermoplastic polyurethane elastomer: Put lauric acid, pentaerythritol and 0.005 parts of catalyst into a reaction flask, introduce nitrogen for protection, heat to 190 °C for esterification reaction for 3 h to generate diol;

[0114] Heat the generated diol and polyester polyol to 100 °C, stir and dehydrate under vacuum for 1.5 h, cool to 60 °C, add diisocyanate, slowly heat to 70 °C, and stir and react for 2 h to obtain a prepolymer;

[0115] Mix 3,3,4,4-benzophenone tetracarboxylic dianhydride, the remaining 0.015 parts of catalyst and antioxidant evenly, add the prepolymer, stir quickly and pour it into a tray, put it into an oven at 100 °C for curing for 16 h, cool to room temperature, crush it with a crusher and then perform molding to obtain a thermoplastic polyurethane elastomer;

[0116] S2. Kneading: Mix the thermoplastic polyurethane elastomer and cellulose fiber and send them into a kneader, knead at 130 °C for 20 min, add a crosslinking agent and a nucleating agent, and knead and blend at 125 °C until all components are evenly mixed to obtain a kneaded blend;

[0117] S3. Tablet pressing: Press the kneaded blend into a sheet with a tablet press and cut it;

[0118] S4. Supercritical foaming: Put the sheet into an oven, preheat to 130 °C, then place the preheated foaming master sheet into a high-temperature mold, the temperature of the high-temperature mold is 140 °C, the pressure of carbon dioxide gas in the mold is 16 MPa, introduce carbon dioxide gas, and when the carbon dioxide gas reaches saturation in the sheet, quickly release the carbon dioxide gas in the mold to make the sheet quickly foam to obtain the TPU supercritical foaming material.

[0119] Example 2

[0120] Preparation of TPU supercritical foaming material for sole

[0121] The TPU supercritical foaming material for sole preparation includes the following raw materials in parts by weight:

[0122] 90 parts of thermoplastic polyurethane elastomer;

[0123] 12 parts of cellulose fiber;

[0124] 3 parts of nucleating agent, and the nucleating agent is selected as 2 parts of fumed silica and 1 part of montmorillonite;

[0125] 5 parts of crosslinking agent, and the crosslinking agent is selected as di-tert-butyl peroxyisopropylbenzene;

[0126] The thermoplastic polyurethane elastomer comprises the following raw materials in parts by weight:

[0127] 50 parts of polyester polyol, specifically 30 parts of polycarbonate diol with a relative molecular mass of 2000 and 20 parts of poly(1,4-butanediol adipate) with a relative mass of 2400;

[0128] 33 parts of diisocyanate, specifically toluene diisocyanate;

[0129] 24 parts of lauric acid;

[0130] 12 parts of pentaerythritol;

[0131] 0.05 part of catalyst, and the catalyst is selected as dibutyltin dilaurate;

[0132] 8 parts of 3,3,4,4-benzophenone tetracarboxylic dianhydride;

[0133] 3 parts of antioxidant, specifically 1 part of antioxidant 1076 and 2 parts of antioxidant 168.

[0134] The TPU supercritical foaming material is prepared by the following steps:

[0135] S1. Preparation of thermoplastic polyurethane elastomer: Place lauric acid, pentaerythritol and 0.01 part of catalyst in a reaction flask, introduce nitrogen for protection, heat to 210 °C for esterification reaction for 3 h to generate diol;

[0136] Heat the generated diol and polyester polyol to 110 °C, stir and dehydrate under vacuum for 2 h, cool to 65 °C, add diisocyanate, slowly heat to 80 °C, and stir and react for 2 h to obtain a prepolymer;

[0137] Mix 3,3,4,4-benzophenone tetracarboxylic dianhydride, the remaining 0.04 part of catalyst and antioxidant evenly, add to the prepolymer, stir quickly and then pour into a tray, place in an oven at 120 °C for curing for 18 h, cool to room temperature, crush with a crusher and then mold to obtain the thermoplastic polyurethane elastomer;

[0138] S2. Internal mixing: Mix the thermoplastic polyurethane elastomer and cellulose fiber and send them into an internal mixer, internally mix at 135 °C for 30 min, add the crosslinking agent and nucleating agent, and internally mix and blend at 130 °C until all components are evenly mixed to obtain an internally mixed blend;

[0139] S3. Pressing: Use a press to press the kneaded blend into a sheet and then cut it.

[0140] S4. Supercritical foaming: Place the sheet in an oven and preheat it to 140 °C. Then, place the preheated foaming masterbatch into a high-temperature mold. The temperature of the high-temperature mold is 140 °C, the pressure of carbon dioxide gas in the mold is 16 MPa. Introduce carbon dioxide gas. When the carbon dioxide gas reaches saturation in the sheet, quickly release the carbon dioxide gas in the mold to make the sheet foam rapidly, obtaining the TPU supercritical foaming material.

[0141] Example 3

[0142] Preparation of TPU Supercritical Foaming Material for Soles

[0143] The TPU supercritical foaming material for soles comprises the following raw materials in parts by weight:

[0144] 85 parts of thermoplastic polyurethane elastomer;

[0145] 10 parts of cellulose fiber;

[0146] 2 parts of nucleating agent, and the nucleating agent is selected as calcium phosphate;

[0147] 3 parts of crosslinking agent, and the crosslinking agent is selected as 2 parts of diisopropylbenzene peroxide and 1 part of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane;

[0148] The thermoplastic polyurethane elastomer comprises the following raw materials in parts by weight:

[0149] 45 parts of polyester polyol, specifically selected as polycarbonate diol with a relative molecular mass of 2000;

[0150] 28 parts of diisocyanate, specifically selected as 20 parts of toluene diisocyanate and 8 parts of dicyclohexylmethane diisocyanate;

[0151] 19 parts of lauric acid;

[0152] 9 parts of pentaerythritol;

[0153] 0.04 part of catalyst, and the catalyst is selected as dibutyltin dilaurate;

[0154] 6 parts of 3,3,4,4-benzophenone tetracarboxylic dianhydride;

[0155] 2 parts of antioxidant, specifically selected as antioxidant 168.

[0156] The TPU supercritical foaming material is prepared through the following steps:

[0157] S1. Preparation of thermoplastic polyurethane elastomer: Put lauric acid, pentaerythritol and 0.01 part of catalyst into a reaction flask, introduce nitrogen for protection, heat to 200 °C for esterification reaction for 3 h to generate diol;

[0158] Heat the generated diol and polyester polyol to 105 °C, stir and dehydrate under vacuum for 2 h, cool to 63 °C, add diisocyanate, slowly heat to 75 °C, and stir and react for 2 h to obtain a prepolymer;

[0159] Mix 3,3,4,4-diphenylmethane tetracarboxylic dianhydride, the remaining 0.03 part of catalyst and antioxidant evenly, add to the prepolymer, quickly stir and then pour into a tray, put it into an oven at 110 °C for curing for 17 h, cool to room temperature, crush with a crusher and then mold to obtain thermoplastic polyurethane elastomer;

[0160] S2. Kneading: Mix the thermoplastic polyurethane elastomer and cellulose fiber and send them into a kneader, knead at 132 °C for 25 min, add a crosslinking agent and a nucleating agent, and knead and blend at 128 °C until all components are evenly mixed to obtain a kneaded blend;

[0161] S3. Pressing: Use a press to press the kneaded blend into a sheet and cut it;

[0162] S4. Supercritical foaming: Put the sheet into an oven, preheat to 135 °C, then place the preheated foaming master sheet into a high-temperature mold, the temperature of the high-temperature mold is 140 °C, the pressure of carbon dioxide gas in the mold is 16 MPa, introduce carbon dioxide gas, when the carbon dioxide gas reaches saturation in the sheet, quickly release the carbon dioxide gas in the mold to make the sheet quickly foam to obtain a TPU supercritical foaming material.

[0163] Example 4

[0164] The difference between the TPU supercritical foaming material of this example and that of Example 1 is only that: the polyester polyol in the raw materials for preparing the thermoplastic polyurethane elastomer is different.

[0165] In this example, the polyester polyol is the modified polyester diol prepared in Preparation Example 1.

[0166] The remaining steps are the same as those in Example 1.

[0167] Example 5

[0168] The difference between the TPU supercritical foaming material of this example and that of Example 1 is only that: the polyester polyol in the raw materials for preparing the thermoplastic polyurethane elastomer is different.

[0169] In this example, the polyester polyol is the modified polyester diol prepared in Preparation Example 2.

[0170] All the other steps are the same as those in Example 1.

[0171] Example 6

[0172] The difference between the TPU supercritical foaming material of this example and that of Example 1 lies only in that the cellulose fiber in the raw material components is different.

[0173] In this example, the cellulose fiber is the graft-modified cellulose fiber prepared in Preparation Example 3.

[0174] All the other steps are the same as those in Example 1.

[0175] Example 7

[0176] The difference between the TPU supercritical foaming material of this example and that of Example 1 lies only in that the cellulose fiber in the raw material components is different.

[0177] In this example, the cellulose fiber is the graft-modified cellulose fiber prepared in Preparation Example 4.

[0178] All the other steps are the same as those in Example 1.

[0179] Example 8

[0180] The difference between the TPU supercritical foaming material of this example and that of Example 1 lies in that the polyester polyol in the raw materials for preparing the thermoplastic polyurethane elastomer is different, and the cellulose fiber in the raw material components is different.

[0181] In this example, the polyester polyol is the modified polyester diol prepared in Preparation Example 1, and the cellulose fiber is the graft-modified cellulose fiber prepared in Preparation Example 4.

[0182] Comparative Example

[0183] Comparative Example 1

[0184] The difference between the TPU supercritical foaming material of this comparative example and that of Example 1 lies only in that no cellulose fiber is added to the raw material components.

[0185] All the other steps are the same as those in Example 1.

[0186] Comparative Example 2

[0187] The difference between the TPU supercritical foaming material of this comparative example and that of Example 1 lies only in that lauric acid and pentaerythritol are not added to the raw materials for preparing the thermoplastic polyurethane elastomer.

[0188] All the other steps are the same as those in Example 1.

[0189] Comparative Example 3

[0190] The difference between the TPU supercritical foaming material of this comparative example and that of Example 1 is only that: in the raw materials for preparing the thermoplastic polyurethane elastomer, 1,4-butanediol with equal mass is used to replace 3,3,4,4-benzophenone tetracarboxylic dianhydride.

[0191] The remaining steps are the same as those in Example 1.

[0192] Performance testing

[0193] The TPU supercritical foaming materials prepared in Examples 1-8 and Comparative Examples 1-3 were subjected to performance testing, and the test results are shown in Table 1.

[0194] Tensile strength: It was determined by referring to the method in GB / T 6344-2008 "Determination of Tensile Strength and Elongation at Break of Flexible Cellular Plastics".

[0195] Elasticity: It was measured by referring to Method A in GB / T 6670-2008 "Determination of Rebound Resilience of Flexible Cellular Plastics by the Falling-Ball Method" to obtain the rebound rate.

[0196] Tear resistance: The tear strength was determined by referring to the method in GB / T 10808-2006 "Determination of Tear Strength of Cellular Rubbers and Thermoplastic Elastomers".

[0197] Table 1

[0198]

[0199]

[0200] It can be seen from Table 1 that the TPU supercritical foaming material prepared according to the formula of this application has excellent mechanical properties, and good resilience and tear resistance. Through the mutual cooperation of raw material components, the foaming performance of the foaming material is good, the cell structure is uniform, dense in size, and the permanent compression set is small.

[0201] Compared with Example 1, in Examples 4-5, modified polyester diol was selected as the raw material of the thermoplastic polyurethane elastomer. The polycarbonate diol was modified by styrene and acrylonitrile, so that a branched structure was introduced into the soft segment of the polyurethane, increasing the melt strength and improving the mechanical properties of the synthesized TPU at the same time.

[0202] Compared with Example 1, in Examples 6-7, graft-modified cellulose fiber was selected as the raw material of the TPU supercritical foaming material. It was modified by butyl methacrylate to improve the compatibility and crosslinking of the system, which was beneficial to the improvement of the tensile strength and mechanical properties of the TPU supercritical foaming material.

[0203] In Comparative Example 1, compared with Example 1, nano-cellulose was not added, and the performance of the foaming material decreased significantly. The nano-cellulose has excellent foaming performance and also plays a role in reinforcing the thermoplastic polyurethane elastomer.

[0204] In Comparative Example 2, compared with Example 1, pentaerythritol and lauric acid were not added to the raw materials of the thermoplastic polyurethane elastomer. The polyurethane molecular chain lacked branches, resulting in a decrease in the crosslinking degree of the polyurethane, and the foaming performance and mechanical strength were affected.

[0205] In Comparative Example 3, compared with Example 1, 1,4-butanediol was selected as the chain extender in the raw materials of the thermoplastic polyurethane elastomer, and the performance of the foaming material decreased. This shows that the chain extender 3,3,4,4-benzophenone tetracarboxylic dianhydride can introduce benzene rings and imides into the polyurethane structure, which plays a promoting role in elasticity and mechanical properties.

[0206] The specific embodiments are only explanations of the present application and do not limit the present application. After reading this specification, those skilled in the art can make modifications that do not contribute creatively to the specific embodiments 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 TPU supercritical foaming material for preparing a shoe sole, characterized in that: The invention comprises the following raw materials in parts by weight: 80-90 parts of thermoplastic polyurethane elastomer; 8-12 parts of cellulose fiber; 1-3 parts of nucleating agent; 2-5 parts of cross-linking agent; The thermoplastic polyurethane elastomer comprises the following raw materials in parts by weight: 40-50 parts of polyester polyol; 25-33 parts of diisocyanate; 14-24 parts of lauric acid; Pentaerythritol 7-12 parts; Catalyst 0.02-0.05 parts; 3, 3,4,4-benzophenonetetracarboxylic dianhydride 3-8 parts; 1-3 parts of antioxidants.

2. The TPU supercritical foaming material for preparing a shoe sole according to claim 1, characterized in that: The polyester polyol is selected from one or more of polycarbonate diol, polycaprolactone diol, poly 1,4-butylene glycol adipate, and modified polyester diol.

3. The TPU supercritical foaming material for preparing a shoe sole according to claim 2, characterized in that: The polyester polyol is a modified polyester diol, and the modified polyester diol comprises the following raw materials in parts by weight: 40-50 parts of polycarbonate diol; Styrene 7-13 parts; 7-13 parts of vinyl nitrile; 2-3 parts of azobisisobutyronitrile.

4. The TPU supercritical foaming material for preparing a shoe sole according to claim 1, characterized in that: The cellulose fiber is selected from grafted modified cellulose fiber, and the grafted modified cellulose fiber includes the following raw materials in parts by weight: 10-15 parts of cellulose fiber; 0.5-1 part of ammonium persulfate; 17-23 parts of divinylbenzene; Butyl methacrylate 6-10 parts.

5. The TPU supercritical foaming material for preparing a shoe sole according to claim 1, characterized in that: The diisocyanate is selected from one or more of hexamethylene diisocyanate, toluene diisocyanate, and dicyclohexylmethane diisocyanate.

6. The TPU supercritical foaming material for preparing a shoe sole according to claim 1, characterized in that: The nucleating agent is selected from one or more of nano calcium carbonate, calcium phosphate, fumed silica, and montmorillonite.

7. The TPU supercritical foaming material for preparing a shoe sole according to claim 1, characterized in that: The crosslinking agent is selected from one or more of dicumyl peroxide, di-tert-butyl peroxycumene, and 2,5-dimethyl-2,5-bis(tert-butyl peroxide)hexane.

8. The method for preparing a TPU supercritical foaming material for preparing a shoe sole according to any one of claims 1 to 7, characterized in that: The steps include: S1. Preparation of thermoplastic polyurethane elastomer: lauric acid, pentaerythritol and part of the catalyst are placed in a reaction bottle, nitrogen is introduced for protection, and the reaction is heated to 190-210°C for esterification reaction to generate diol; The generated diol and polyester polyol are heated to 100-110°C, stirred and dehydrated under vacuum, cooled to 60-65°C, diisocyanate is added, the temperature is slowly raised to 70-80°C, stirred and reacted to obtain a prepolymer; 3,3,4,4-benzophenonetetracarboxylic dianhydride, the remaining catalyst and antioxidant are mixed evenly, added to the prepolymer, stirred rapidly, poured into a tray, placed in an oven at 100-120°C for aging for 16-18h, cooled to room temperature, crushed with a crusher and then molded to obtain a thermoplastic polyurethane elastomer; S2. Banburying: The thermoplastic polyurethane elastomer and cellulose fiber are mixed and sent into a banbury mixer, and banburying is performed at 130-135° C. for 20-30 min. A crosslinking agent and a nucleating agent are added, and the mixture is banburying at 125-130° C. until the components are uniformly mixed to obtain a banburying blend; S3 tableting: using a tablet press to press the kneaded blend into a sheet and cut; S4. Supercritical foaming: Place the sheet into an oven and preheat it to 130-140°C. Then place the preheated foamed mother board into a high-temperature mold and introduce carbon dioxide gas. When the carbon dioxide gas reaches saturation in the sheet, quickly release the carbon dioxide gas in the mold to make the sheet foam quickly and obtain TPU supercritical foaming material.

9. The method for preparing a TPU supercritical foaming material for preparing a shoe sole according to claim 8, characterized in that: When the polyester polyol is a modified polyester diol, the modified polyester diol is prepared by the following steps: Take polycarbonate diol, styrene, acrylonitrile and azobisisobutyronitrile, mix and stir for 20-30 minutes, react at 100-110° C. for 1-2 hours under nitrogen environment, and vacuum treat under nitrogen bubbling to obtain modified polyester diol.

10. The method for preparing a TPU supercritical foaming material for preparing a shoe sole according to claim 8, characterized in that: When the cellulose fiber is selected from grafted modified cellulose fibers, the grafted modified cellulose fibers are prepared by the following steps: The cellulose fibers were uniformly dispersed in deionized water, stirred and heated to 65-75°C under nitrogen protection, and ammonium persulfate, divinylbenzene and butyl methacrylate were added to react for 2-3 hours. The product was filtered out and repeatedly washed with distilled water and anhydrous ethanol and dried to obtain grafted modified cellulose fibers.

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