Low-retraction thermoplastic polyurethane / copolymer nylon composite material foaming particle

Abstract

The invention provides a low-retraction thermoplastic polyurethane / copolymer nylon composite material foaming particle. The foaming particles are prepared from the following raw materials in parts by weight: 65-95 parts of thermoplastic polyurethane, 5-35 parts of copolymerized nylon, 1-5 parts of compatibilizer and 0.1-0.5 part of foaming promoter. The foaming particles provided by the invention limit gas in foam pores from escaping from a molecular chain region of a soft segment of the thermoplastic elastomer, and have excellent low-retraction characteristic.

Description

Technical Field

[0001] The present invention relates to the field of foaming materials, and particularly to a low-retraction thermoplastic polyurethane / copolyamide nylon composite foamed particle. Background Art

[0002] The supercritical fluid foaming method refers to a method in which a supercritical fluid is fully impregnated in a polymer resin and then, by rapidly depressurizing, micron-sized pores are formed in the polymer resin. Compared with the chemical foaming method, the supercritical fluid foaming method has the advantages of being green and environmentally friendly, having uniform cell diameters and distributions, and controllable cell densities, and thus has received great attention in recent years. Thermoplastic polyurethane (TPU), as a thermoplastic elastomer, elements such as N and O in the molecular chain can form hydrogen bond forces with gases such as carbon dioxide and nitrogen, ensuring the solubility of supercritical carbon dioxide and nitrogen in TPU. Therefore, TPU is often used as the matrix resin in supercritical fluid foaming materials. The obtained TPU foamed material retains the excellent properties of TPU and has the characteristics of light weight and high resilience, and is maturely applied in fields such as shoe materials, chip polishing pads, and rubber runways.

[0003] However, since the soft segment molecular chains in TPU still have good mobility at ambient temperature, the gas in the pores after foaming is extremely easy to escape from the soft segment molecular chain region, resulting in problems such as cell retraction, increased material density, and decreased performance.

[0004] Patent CN 111675896 A proposes a method of adding organically modified nano-montmorillonite to a thermoplastic elastomer. By forming hydrogen bond interactions between the montmorillonite and the thermoplastic elastomer, the movement of the soft segment molecular chains is fixed, and gas escape is reduced, thereby improving the problem of cell retraction of the thermoplastic elastomer. However, for this method, it is difficult to solve the problem of the dispersion of the nano-fillers in the thermoplastic elastomer.

[0005] Patent CN 107828205 A proposes adding vulcanizable crosslinked polyurethane particles to a thermoplastic elastomer, and appropriately crosslinking to improve the strength of the material, inhibit gas escape, and improve the problem of cell retraction. However, this method requires strict control of the distribution and degree of crosslinking of the crosslinking components, increasing the process complexity and production cost, and it is certain that the product stability cannot be guaranteed.

[0006] Patent CN108239385A invented a method of adding another thermoplastic resin to a thermoplastic elastomer to enhance the matrix strength of the thermoplastic elastomer, thereby reducing gas escape. However, the added thermoplastic resin has no special gas barrier effect and it is difficult to be called an efficient method.

[0007] Therefore, there is an urgent need for a method with simple process and low production cost to prepare low-retraction foamed particles that are green and environmentally friendly, have a high foaming ratio, and good resilience performance. Summary of the Invention

[0008] One of the objects of the present invention is to prepare a low-retraction thermoplastic polyurethane / copolyamide nylon composite foamed particles.

[0009] The main technical problem faced by the present invention is to restrict the escape of gas in the pores from the molecular chain region of the soft segment of the thermoplastic elastomer.

[0010] To solve the above technical problems, the inventors found that: by copolymerizing with isophthalic acid, while improving the gas barrier performance of poly(m-xylylene adipamide), the melting point of poly(m-xylylene adipamide) is reduced, enabling it to be melt-blended with TPU better. Then, a compatibilizer - polyurethane-poly(m-xylylene adipamide) (PU-b-MXD6) block copolymer is used to increase the compatibility between thermoplastic polyurethane and copolyamide nylon, so that the copolyamide nylon is uniformly dispersed in the thermoplastic polyurethane matrix. Acetoacetamide is prepared by the ammonolysis reaction of acetic anhydride, and acetic acid reacts with the hydroxyl groups on the surface of silica to graft acetoacetamide onto the surface of silica, realizing the uniform distribution of silica in the polymer matrix and increasing the solubility of carbon dioxide in the polymer. After supercritical fluid foaming treatment, the copolyamide nylon dispersed in the cell walls has excellent gas barrier performance, which can effectively prevent the gas in the pores from escaping, realizing the low-retraction performance of the thermoplastic elastomer foamed particles.

[0011] To achieve the above invention object, the technical solutions adopted by the present invention are as follows:

[0012] A kind of low-retraction thermoplastic polyurethane / copolyamide nylon composite foamed particles, calculated by weight, the raw materials of the foamed particles comprise the following components:

[0013] 65 - 95 parts of thermoplastic polyurethane,

[0014] 5 - 35 parts of copolyamide nylon,

[0015] 1 - 5 parts of compatibilizer,

[0016] 0.1 - 0.5 parts of co-foaming agent.

[0017] In one embodiment of the present invention, the melting point of the thermoplastic polyurethane is 180 - 240 °C, preferably 190 - 210 °C.

[0018] In one embodiment of the present invention, the copolyamide nylon is polymerized from m-xylylenediamine and an acid component, and the acid component is adipic acid and aromatic diacid; preferably, the molar ratio of adipic acid to aromatic diacid is (80 - 97) : (3 - 20).

[0019] In one embodiment of the present invention, the relative viscosity of the prepared copolyamide nylon is 2.5 - 3.0, preferably 2.5 - 2.8.

[0020] In one embodiment of the present invention, the prepared copolyamide has a melting point of 215-237 °C, preferably 215-232 °C.

[0021] Exemplarily, a preparation method of the copolyamide is as follows: Add m-xylylenediamine, adipic acid, isophthalic acid, water, and sodium hypophosphite into a reaction kettle for prepolymerization reaction. After the prepolymerization reaction is completed, raise the temperature and maintain the gauge pressure inside the kettle. Then heat the temperature inside the kettle and release it to atmospheric pressure. Continue the reaction as the pressure decreases; add nitrogen, and obtain the copolyamide by water-cooling and pelletizing the melt. It is well known that the process for preparing the copolyamide itself is the prior art in this field.

[0022] In one embodiment of the present invention, the compatibilizer is a block copolymer formed by isocyanate-terminated polyurethane PU and amino-terminated poly(m-xylylene adipamide) MXD6.

[0023] Exemplarily, a preparation method of the block copolymer is as follows: a. Preparation of diisocyanate-terminated PU oligomer: Add dimethylmethane diisocyanate and butanediol into a reaction kettle and heat for reaction. Cool, dry, and pulverize to prepare the diisocyanate-terminated PU oligomer. b. Preparation of diamino-terminated MXD6 oligomer: Add m-xylylenediamine, adipic acid, and water into a reaction kettle and heat for reaction; after completion, release the pressure to atmospheric pressure, and obtain the diamino-terminated MXD6 oligomer by cooling, drying, and pulverizing the high-temperature melt. c. Preparation of the block copolymer: Put the diisocyanate-terminated PU oligomer and adipic acid into the reaction kettle containing the diamino-terminated MXD6 oligomer, raise the temperature, evacuate, and react to obtain the PU and MXD6 block copolymer (PU-b-MXD6), and obtain the block copolymer pellets by water-cooling, pelletizing, and drying. It is well known in the art that the above process itself is a common process for block copolymers.

[0024] In one embodiment of the present invention, the co-foaming agent is acetylacetamide-grafted modified silica obtained by reacting silica with acetylacetamide; preferably, the mass ratio of ammonium acetylacetate to silica is 1.5-2.5:1.

[0025] Exemplarily, a preparation method of the modified silica of the present invention is as follows: a. Add acetic anhydride, ammonium acetate, and water, stir for reaction, and obtain the acetylacetamide powder by cooling, suction filtration, and drying; b. Add toluene and acetylacetamide, raise the temperature, and then add silica for reaction. Transfer the solution, and obtain the acetylacetamide-modified silica by cooling, suction filtration, and drying.

[0026] In one embodiment of the present invention, the raw materials of the foamed particles further comprise an antioxidant, and the antioxidant is one or more selected from antioxidant H10, antioxidant 168, antioxidant 1076, antioxidant 264, antioxidant 1098, and antioxidant 1010. Preferably, it is a compounding system of antioxidant H10 and antioxidant 1098 in a mass ratio of 2:1.

[0027] In one embodiment of the present invention, the raw materials of the foamed particles further comprise a lubricant, and the lubricant is one or more of calcium stearate, silicone oil, and paraffin wax. Preferably, it is calcium stearate.

[0028] As is well known in the art, to provide physical properties and processing performance, the raw materials of the foamed ions may further comprise an antioxidant, a lubricant, etc. For example, 0.1 - 0.5 parts of an antioxidant and 0.1 - 0.5 parts of a lubricant.

[0029] Another object of the present invention is to provide a method for preparing thermoplastic polyurethane / copolyamide composite foamed particles.

[0030] A method for preparing thermoplastic polyurethane / copolyamide composite foamed particles, wherein the foamed particles are the above-mentioned foamed particles, and the preparation method is: preparing a thermoplastic polyurethane / copolyamide composite; foaming the composite by intermittent autoclave supercritical carbon dioxide foaming method to obtain the target foamed particles.

[0031] In one embodiment of the present invention, the step of preparing the thermoplastic polyurethane / copolyamide composite is: blending thermoplastic polyurethane, copolyamide, compatibilizer, co - blowing agent, and other additives in a blender, and then feeding the blend into a screw extruder for preparation; preferably, the rotation speed of the blender in the blending step is 30 - 50 rpm, and the blending time is 5 - 10 min; preferably, the temperature of the screw of the extruder is 240 - 250 °C, and the screw rotation speed is 100 - 120 rpm.

[0032] In one embodiment of the present invention, the foaming temperature is 120 - 150 °C, the foaming pressure is 15 - 20 MPaG, and the saturation time is 3 - 6 h.

[0033] In one embodiment of the present invention, the cell diameter of the foamed particles obtained by foaming is 50 - 300 μm, preferably 150 - 200 μm.

[0034] Another object of the present invention is to provide a use of the thermoplastic polyurethane / copolyamide composite foamed particles.

[0035] Use of a thermoplastic polyurethane / copolyamide nylon composite foamed particle, where the foamed particle is the above-mentioned foamed particle or the foamed particle prepared by the above-mentioned preparation method, and the foamed particle is used in the fields of sole manufacturing and chemical mechanical polishing pad manufacturing.

[0036] Compared with the prior art, the positive effects of the present invention are as follows:

[0037] 1) By introducing a copolymerization unit into MXD6 nylon, the melting point of the nylon material is reduced, enabling its processing window to coincide with that of thermoplastic polyurethane.

[0038] 2) The introduction of copolyamide nylon greatly reduces the shrinkage rate of the foamed particles, enabling the foamed particles to maintain the initial foaming ratio unchanged for a long time.

[0039] 3) The co-foaming agent significantly increases the foaming ratio of the foamed particles, and the cell size is uniform without defects. Description of the Drawings

[0040] Figure 1 SEM image of the internal cell structure of the thermoplastic polyurethane / copolyamide nylon composite foamed particle prepared in Example 6. Detailed Embodiments

[0041] The following further illustrates the present invention through specific examples. The examples described in the present invention are only for the purpose of illustrating the present invention and do not limit the scope of the present invention.

[0042] Testing Methods:

[0043] (1) Number average molecular weight test: It is tested through a gel permeation chromatography (GPC) system, and the equipment model is WATERS1515.

[0044] (2) Relative viscosity test: Accurately weigh 0.5 g of polyurethane / copolyamide nylon composite particles into a 50 ml volumetric flask, add 96% sulfuric acid, dissolve at 80 °C to prepare a 0.1 g / ml solution, and measure the relative viscosity at 25 °C through a fully automatic Ubbelohde viscometer. Equipment model: IV 6000.

[0045] (3) Scanning electron microscopy (SEM) test of the internal cell structure of the thermoplastic polyurethane / copolyamide nylon composite foamed particle: The thermoplastic polyurethane / copolyamide nylon composite foamed particle is brittle fractured in liquid nitrogen, and then sputter-coated with gold and observed under a scanning electron microscope (JSG-5900LV, Japan) for the cross-section.

[0046] (4) Density test of the thermoplastic polyurethane / copolyamide nylon composite foamed particle: It is tested through a density balance, and the equipment model is JA3003J.

[0047] (5) The foaming ratio of the thermoplastic polyurethane / copolyamide nylon composite foamed particles is calculated by formula (1):

[0048]

[0049] ρ in the formula polymer refers to the density of the polymer particles before foaming, and ρ foam refers to the density of the particles after foaming.

[0050] The following materials were used in the following examples:

[0051] Thermoplastic polyurethane: Grade: Elastollan 1164D, thermoplastic polyether-based polyurethane, melting point 194 °C, manufacturer: BASF.

[0052] Thermoplastic polyurethane: Grade: Elastollan 1174D, thermoplastic polyether-based polyurethane, melting point 201 °C, manufacturer: BASF.

[0053] Thermoplastic polyurethane: Grade: Texin 250, thermoplastic polyether-based polyurethane, melting point 191 °C, manufacturer: Bayer.

[0054] Adipic acid: industrial grade, Huafeng Chemical Co., Ltd.

[0055] m-Xylylenediamine: industrial grade, Mitsubishi Chemical Corporation, Japan.

[0056] Isophthalic acid: industrial grade, Beijing InnoChem Science & Technology Co., Ltd.

[0057] Diphenylmethane diisocyanate: industrial grade, Wanhua Chemical Group Co., Ltd.

[0058] 1,4-Butanediol: industrial grade, Jiangsu Runfeng Synthetic Technology Co., Ltd.

[0059] Acetic anhydride: industrial grade, Beijing InnoChem Science & Technology Co., Ltd.

[0060] Acetamide: industrial grade, Beijing InnoChem Science & Technology Co., Ltd.

[0061] Antioxidant: industrial grade, Beijing InnoChem Science & Technology Co., Ltd.

[0062] Lubricant: industrial grade, Beijing InnoChem Science & Technology Co., Ltd.

[0063] Fumed silica: industrial grade, Beijing InnoChem Science & Technology Co., Ltd.

[0064] Concentrated sulfuric acid: industrial grade, Beijing InnoChem Science & Technology Co., Ltd.

[0065] Prepare Example 1

[0066] The copolyamide nylon is prepared according to the following steps.

[0067] 1928 g of m-xylylenediamine, 2031 g of adipic acid, 70 g of isophthalic acid, 2666 g of water, and 6 g of sodium hypophosphite are added to a 10 L reaction kettle. After purging with nitrogen three times, the temperature is raised to 190 °C and maintained for 1 h for prepolymerization reaction. After the prepolymerization reaction is completed, the temperature is raised to 240 °C. During this period, the opening of the pressure relief valve is adjusted to maintain the gauge pressure in the kettle at 1.3 MPaG. Then the temperature in the kettle is heated to 250 °C, and the pressure in the kettle is released to atmospheric pressure. Then, the reaction system is evacuated to reduce the gauge pressure to below 100 KPa, and the reaction continues for 1 h; nitrogen is added to make the gauge pressure in the kettle reach 40 KPa, and the melt is granulated by water cooling to obtain copolyamide nylon (MXD6I-1). The number-average molecular weight of the prepared copolyamide nylon is 25063 g / mol, the molecular weight distribution is 2.06, the relative viscosity is 2.5, and the melting point is 232 °C.

[0068] Prepare Example 2

[0069] The copolyamide nylon is prepared according to the following steps.

[0070] 1928 g of m-xylylenediamine, 1969 g of adipic acid, 141 g of isophthalic acid, 2666 g of water, and 6 g of sodium hypophosphite are added to a 10 L reaction kettle. After purging with nitrogen three times, the temperature is raised to 200 °C and maintained for 1 h for prepolymerization reaction. After the prepolymerization reaction is completed, the temperature is raised to 250 °C. During this period, the opening of the pressure relief valve is adjusted to maintain the gauge pressure in the kettle at 1.5 MPaG. Then the temperature in the kettle is heated to 260 °C, and the gauge pressure in the kettle is released to atmospheric pressure. Then, the reaction system is evacuated to reduce the gauge pressure to below 100 KPaG, and the reaction continues for 0.75 h; nitrogen is added to make the gauge pressure in the kettle reach 40 KPaG, and the melt is granulated by water cooling to obtain copolyamide nylon (MXD6I-2). The number-average molecular weight of the prepared copolyamide nylon is 25517 g / mol, the molecular weight distribution is 2.68, the relative viscosity is 2.8, and the melting point is 224 °C.

[0071] Prepare Example 3

[0072] The copolyamide nylon is prepared according to the following steps.

[0073] 1928 g of m-xylylenediamine, 1845 g of adipic acid, 282 g of isophthalic acid, 2666 g of water, and 6 g of sodium hypophosphite were added to a 10 L reaction kettle. After purging with nitrogen three times, the temperature was raised to 210 °C and maintained for 1 h for prepolymerization reaction. After the prepolymerization reaction was completed, the temperature was raised to 260 °C. During this period, the opening of the pressure relief valve was adjusted to maintain the gauge pressure in the kettle at 1.5 MPaG. Then, the temperature in the kettle was heated to 270 °C, and the pressure in the kettle was released to atmospheric pressure. Then, the system was evacuated to reduce the gauge pressure of the reaction system to below 100 KPaG and reacted for another 1 h; nitrogen was introduced to make the gauge pressure in the kettle reach 40 KPaG, and the melt was pelletized by water cooling to obtain copolyamide (MXD6I-3). The number-average molecular weight of the prepared copolyamide was 26092 g / mol, the molecular weight distribution was 2.43, the relative viscosity was 2.6, and the melting point was 215 °C.

[0074] Prepare Example 4

[0075] The copolyamide was prepared according to the following steps.

[0076] 1928 g of m-xylylenediamine, 2093 g of adipic acid, 2666 g of water, and 6 g of sodium hypophosphite were added to a 10 L reaction kettle. After purging with nitrogen three times, the temperature was raised to 200 °C and maintained for 1 h for prepolymerization reaction. After the prepolymerization reaction was completed, the temperature was raised to 250 °C. During this period, the opening of the pressure relief valve was adjusted to maintain the gauge pressure in the kettle at 1.5 MPaG. Then, the temperature in the kettle was heated to 260 °C, and the pressure in the kettle was released to atmospheric pressure. Then, the system was evacuated to reduce the gauge pressure of the reaction system to below 100 KPaG and reacted for 0.75 h; nitrogen was introduced to make the gauge pressure in the kettle reach 40 KPaG, and the melt was pelletized by water cooling to obtain nylon (MXD6). The number-average molecular weight of the prepared copolyamide was 24990 g / mol, the molecular weight distribution was 2.21, the relative viscosity was 2.5, and the melting point was 237 °C.

[0077] Prepare Example 5

[0078] The compatibilizer - PU-b-MXD6 block copolymer was prepared according to the following steps.

[0079] a. Preparation of diisocyanate-terminated PU oligomer: 3692 g of dimethylmethane diisocyanate (MDI) and 1059 g of butanediol (BDO) were added to a 10 L reaction kettle. After purging with nitrogen three times, the temperature was raised to 70 °C and reacted for 3 h. The high-temperature melt was cooled by water cooling, dried, and pulverized to prepare the diisocyanate-terminated PU oligomer. The number-average molecular weight of the prepared diisocyanate-terminated PU oligomer was 1583.58519 g / mol, and the concentration of terminal isocyanate groups was 1.26 mmol / g.

[0080] b. Preparation of diamine-terminated MXD6 oligomer: Add 2356 g of m-xylylenediamine, 2070 g of adipic acid, and 2666 g of water into a 10 L reaction kettle. Replace the air with nitrogen three times, heat up to 200 °C and keep it for 1 h to complete the prepolymerization reaction. After completion, release the pressure to atmospheric pressure, and obtain the diamine-terminated MXD6 oligomer through cooling, drying, and pulverizing of the high-temperature melt. The number-average molecular weight of the prepared diamine-terminated MXD6 oligomer is 1250 g / mol, and the terminal amino group content is 1.59 mmol / g;

[0081] c. Preparation of block copolymer: Put 2984 g of diisocyanate-terminated PU oligomer and 62 g of adipic acid into the reaction kettle containing diamine-terminated MXD6 oligomer. After replacing the air with nitrogen 3 times, heat up to 210 °C, evacuate to make the gauge pressure of the reaction system drop below 100 KPaG, and react for 60 min to obtain the PU and MXD6 block copolymer (PU-b-MXD6). Then, through water cooling, pelletizing, and drying, obtain the block copolymer pellets. The number-average molecular weight of this block copolymer is 20925 g / mol, and the mass fraction of MXD6 is 50%.

[0082] Preparation Example 6

[0083] Prepare a foaming aid - modified silica according to the following steps.

[0084] a. Add 855 g of acetic anhydride, 645 g of ammonium acetate, and 1500 g of water into a 5 L four-necked flask. Start stirring, set the rotation speed at 50 rpm, react for 1 h, and obtain the acetoacetamide powder through cooling, suction filtration, and drying.

[0085] b. Add 1500 g of toluene and 87.5 g of acetoacetamide into a 5 L flask, heat up to 80 °C, then add 50 g of silica, and react for 10 h. Transfer the solution to a beaker, and obtain the acetoacetamide-modified silica (SiO2-1) through cooling, suction filtration, and drying.

[0086] Preparation Example 6

[0087] Prepare a foaming aid - modified silica according to the following steps.

[0088] a. Add 855 g of acetic anhydride, 645 g of ammonium acetate, and 1500 g of water into a 5 L four-necked flask. Start stirring, set the rotation speed at 50 rpm, react for 1 h, and obtain the acetoacetamide powder through cooling, suction filtration, and drying.

[0089] b. Add 1500 g of toluene and 100 g of acetoacetamide into a 5 L flask, heat up to 80 °C, then add 50 g of silica, and react for 10 h. Transfer the solution to a beaker, and obtain the acetoacetamide-modified silica (SiO2-2) through cooling, suction filtration, and drying.

[0090] Example 1

[0091] The TPU / copolyamide nylon composite foamed particles were prepared according to the following method:

[0092] (1) Preparation steps of TPU / copolyamide nylon blend particles: 9.5 kg of thermoplastic polyurethane (BASF, Elastollan 1160D), 0.5 kg of copolyamide nylon (MXD6I-1), 100 g of compatibilizer PU-b-MXD6, 10 g of auxiliary foaming agent (SiO2-1), 10 g of antioxidant (antioxidant H10), and 10 g of paraffin were mixed by a blender at a rotation speed of 30 rpm and a temperature of 30 °C for 5 min, and then the mixture was fed into a screw extruder. The temperatures of each section of the extruder were 240 °C, 245 °C, 250 °C, and 245 °C, the head temperature was 245 °C, and the rotation speed was 100 rpm. Extrusion granulation was carried out to obtain TPU / copolyamide nylon blend particles.

[0093] (2) Preparation steps of TPU / copolyamide nylon composite foamed particles: The TPU / copolyamide nylon blend particles prepared in step (1) were put into a high-temperature and high-pressure reaction kettle, heated to 150 °C, and pressurized with carbon dioxide to 15 MPaG, and the saturation time was 3 h. After the saturation process was completed, rapid pressure relief was carried out to obtain TPU / copolyamide nylon composite foamed particles.

[0094] Example 2

[0095] The TPU / copolyamide nylon composite foamed particles were prepared according to the following method:

[0096] (1) Preparation steps of TPU / copolyamide nylon blend particles: 6.5 kg of thermoplastic polyurethane (BASF, Elastollan 1174D), 3.5 kg of copolyamide nylon (MXD6I-2), 500 g of compatibilizer PU-b-MXD6-2, 50 g of auxiliary foaming agent (SiO2-2), 20 g of antioxidant (antioxidant 1098), and 20 g of calcium stearate were mixed by a blender at a rotation speed of 50 rpm and a temperature of 25 °C for 10 min, and then the mixture was fed into a screw extruder. The temperatures of each section of the extruder were 245 °C, 250 °C, 250 °C, and 245 °C, the head temperature was 245 °C, and the rotation speed was 120 rpm. Extrusion granulation was carried out to obtain TPU / copolyamide nylon blend particles.

[0097] (2) Preparation steps of TPU / copolyamide nylon composite foamed particles: The TPU / copolyamide nylon blend particles prepared in step (1) were put into a high-temperature and high-pressure reaction kettle, heated to 120 °C, and pressurized with carbon dioxide to 20 MPaG, and the saturation time was 6 h. After the saturation process was completed, rapid pressure relief was carried out to obtain TPU / copolyamide nylon composite foamed particles.

[0098] Example 3

[0099] The TPU / co-nylon composite foam particles were prepared as follows:

[0100] (1) Preparation steps of TPU / copolymer nylon blend particles: 7.5 kg of thermoplastic polyurethane (Bayer, Texin250), 2.5 kg of copolymer nylon (MXD6I-3), 300 g of compatibilizer PU-b-MXD6, 30 g of auxiliary foaming agent (SiO2-2), 50 g of antioxidant (antioxidant H10 and antioxidant 1098 are compounded in a mass ratio of 2:1), and 50 g of calcium stearate are mixed in a blender at a speed of 40 rpm and a temperature of 25°C for 8 min, and then the mixture is fed to a screw extruder. The temperatures of each section of the extruder are 240°C, 245°C, 250°C, and 245°C, the head temperature is 245°C, and the speed is 100 rpm. The TPU / copolymer nylon blend particles are obtained by extrusion granulation.

[0101] (2) Preparation of TPU / co-nylon composite foam particles: The TPU / co-nylon blend particles prepared in step (1) are placed in a high-temperature and high-pressure reactor, and the temperature is raised to 130° C., carbon dioxide is introduced and the pressure is increased to 18 MPaG, and the saturation time is 5 hours. After the saturation process is completed, the pressure is quickly released to obtain TPU / co-nylon composite foam particles.

[0102] Comparative Example 1

[0103] Compared with Example 3, the nylon material added in this comparative example was not subjected to copolymerization chemical modification.

[0104] The TPU / nylon composite foam particles were prepared as follows:

[0105] Preparation steps of TPU / copolymer nylon blend particles: 7.5kg of thermoplastic polyurethane (Bayer, Texin250), 2.5kg of nylon (MXD6), 300g of compatibilizer PU-b-MXD6, 30g of auxiliary foaming agent (SiO2-2), 50g of antioxidant (antioxidant H10 and antioxidant 1098 are compounded in a mass ratio of 2:1), and 50g of calcium stearate are mixed in a blender at a speed of 40rpm and a temperature of 25°C for 8min, and then the mixture is fed to a screw extruder. The temperatures of each section of the extruder are 240°C, 245°C, 250°C, and 245°C, the head temperature is 245°C, the speed is 100rpm, and TPU / copolymer nylon blend particles are obtained by extrusion granulation.

[0106] (2) Preparation steps of TPU / co-nylon composite foam particles: According to step (2) of Example 3, the above-mentioned TPU / co-nylon blend particles are prepared into foam particles.

[0107] Comparative Example 2

[0108] Compared with Example 3, the foaming aid added in this comparative example was not graft-modified.

[0109] Prepare TPU / copolyamide nylon composite foamed particles according to the following method:

[0110] (1) Preparation steps of TPU / copolyamide nylon blend particles: The preparation steps of TPU / copolyamide nylon blend particles: Mix 7.5 kg of thermoplastic polyurethane (Bayer, Texin 250), 2.5 kg of copolyamide nylon (MXD6I-3), 300 g of compatibilizer PU-b-MXD6, 50 g of antioxidant (compound of antioxidant H10 and antioxidant 1098 with a mass ratio of 2:1), and 50 g of calcium stearate in a mixer at a rotation speed of 40 rpm and a temperature of 25°C for 8 minutes, and then feed the mixture into a screw extruder. The temperatures of each section of the extruder are 240°C, 245°C, 250°C, 245°C, the temperature of the die head is 245°C, and the rotation speed is 100 rpm. Extrusion granulation is carried out to obtain TPU / copolyamide nylon blend particles.

[0111] (2) Preparation steps of TPU / copolyamide nylon composite foamed particles: Prepare the above TPU / copolyamide nylon blend particles into foamed particles according to step (2) of Example 3.

[0112] Carry out relevant tests on the foamed particles prepared by each scheme, and the test results are shown in Table 1:

[0113] Table 1 Test results of examples and comparative examples

[0114]

[0115] It can be seen from the density and foaming ratio results at the initial and stable stages shown in Table 1 for the examples and comparative examples that the copolyamide nylon introduced in the present invention effectively prevents the escape of gas in the thermoplastic polyurethane foamed particles under the action of the amphiphilic block copolymer, thereby improving the shrinkage problem of the TPU foamed particles.

[0116] When TPU is directly blended with pure MXD6 with a high melting point (Comparative Example 1), even if a block copolymer compatibilizer is added, due to the too large difference in the processing windows of the two, the mixing effect is poor, and high-ratio foamed particles cannot be obtained.

[0117] When unmodified silica is used as a foaming aid in the blend (Comparative Example 3), the solubility of carbon dioxide in the polymer is low, so the foaming ratio of the foamed particles is low.

[0118] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the method of the present invention, several improvements and supplements can still be made, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A kind of low-retraction thermoplastic polyurethane / copolyamide nylon composite foam particles, characterized in that, By weight parts, the raw materials of the foamed particles comprise the following components: 65 - 95 parts of thermoplastic polyurethane, 5 - 35 parts of copolyamide, 1 - 5 parts of compatibilizer, 0.1 - 0.5 part of auxiliary foaming agent.

2. The expanded particles according to claim 1, characterized in that, The melting point of the thermoplastic polyurethane is 180 - 240 °C, preferably 190 - 210 °C.

3. The expanded particles according to claim 1 or 2, characterized in that, The copolyamide is polymerized from metaxylylenediamine and an acid component, and the acid component is adipic acid and aromatic diacid; Preferably, the molar ratio of adipic acid to aromatic diacid is (80 - 97):(3 - 20); And / or, the relative viscosity of the prepared copolyamide is 2.5 - 3.0, preferably 2.5 - 2.8; And / or, the melting point of the prepared copolyamide is 215 - 237 °C, preferably 215 - 232 °C.

4. The expanded particles according to any one of claims 1 to 3, characterized in that, The compatibilizer is a block copolymer formed by isocyanate - terminated polyurethane PU and amino - terminated poly(m - xylylene adipamide) MXD6.

5. The expanded particles according to any one of claims 1-4, characterized in that, The auxiliary foaming agent is silica graft - modified with acetoacetamide obtained by the reaction of silica and acetoacetamide; Preferably, the mass ratio of ammonium acetoacetate to silica is 1.5 - 2.5:

1.

6. The expanded particles according to any one of claims 1-5, characterized in that, The raw materials of the foamed particles further comprise an antioxidant, and the antioxidant is one or more selected from antioxidant H10, antioxidant 168, antioxidant 1076, antioxidant 264, antioxidant 1098, antioxidant 1010, preferably a compounding system of antioxidant H10 and antioxidant 1098 with a mass ratio of 2:1; And / or, the raw materials of the foamed particles further comprise a lubricant, and the lubricant is one or more of calcium stearate, silicone oil, paraffin wax, preferably calcium stearate.

7. A method for preparing thermoplastic polyurethane / copolyamide composite foamed particles, wherein the foamed particles are the foamed particles according to any one of claims 1-7, characterized in that, The preparation method is: preparing a thermoplastic polyurethane / copolyamide composite material; foaming the composite material by batch autoclave supercritical carbon dioxide foaming method to obtain the target foamed particles.

8. The preparation method according to claim 7, characterized in that, The steps for preparing the thermoplastic polyurethane / copolyamide composite material are: blending thermoplastic polyurethane, copolyamide, compatibilizer, auxiliary foaming agent and other additives in a mixer, and then feeding the blend into a screw extruder for preparation; Preferably, in the blending step, the rotation speed of the mixer is 30 - 50 rpm and the blending time is 5 - 10 min; Preferably, the screw temperature of the extruder is 240 - 250 °C and the screw rotation speed is 100 - 120 rpm; And / or, the foaming temperature is 120 - 150 °C, the foaming pressure is 15 - 20 MPaG, and the saturation time is 3 - 6 h; And / or, the cell diameter of the foamed particles obtained by foaming is 50 - 300 μm, preferably 150 - 200 μm.

9. Use of a thermoplastic polyurethane / copolyamide composite material foamed particle, wherein the foamed particle is the foamed particle according to any one of claims 1 - 6, or the foamed particle prepared by the preparation method according to claim 7 or 8, and the foamed particle is used in the fields of sole manufacturing and chemical mechanical polishing pad manufacturing.

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