Polyurethane block copolymerization modified polyamide material with branched structure and preparation method thereof

Abstract

The invention discloses a polyurethane block copolymerized and modified polyamide material with a branched structure and a preparation method of the polyurethane block copolymerized and modified polyamide material. The polyurethane block copolymerization modified polyamide material with the branched structure is prepared from the following components in parts by weight: 8 to 24 parts of polyol, 2 to 7 parts of polyisocyanate, 0.2 to 1 part of a cross-linking agent, 70 to 90 parts of caprolactam, 0.5 to 1 part of a catalyst and 0.5 to 1 part of a release agent, the polyol is any one or a mixture of more of polyether polyol, polyester polyol or polymer polyol. According to the preparation method, reactants are cast into a preheated mold under normal pressure to complete polymerization and molding at the same time, and the copolymerization modified polyamide material not only keeps higher strength and heat resistance of a common casting polyamide material, but also further improves the impact resistance, water resistance and dimensional stability of the material.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a polyurethane block copolymer modified polyamide material with a branched structure and a preparation method thereof. Background Art

[0002] Polyamide (PA) has the advantages of simple production process, light weight, high strength and good chemical resistance, and is widely used in the fields of electronics, electrical and automotive industries. Especially in the automotive industry, polyamide and polyamide-reinforced materials are often used in the automotive interior and exterior decoration, powertrain system to "replace aluminum with plastic, and steel with plastic" due to their high fluidity, light weight and easy processing and high specific strength. Although polyamide has many advantages, pure polyamide materials also have many shortcomings, such as easy water absorption, poor impact resistance, poor dimensional stability and thermal stability, and poor wear resistance and self-lubrication. These shortcomings limit the further promotion and application of polyamide materials.

[0003] Polyurethane (PU) is a block polymer with good flexibility and low temperature resistance. Its performance can be changed in a wide range by controlling its main chain structure, adjusting the length and distribution of the block, changing the relative molecular weight, etc. Due to the unique structural characteristics of polyurethane, a preset branched cross-linked structure can be formed through a cross-linking agent, and then combined with polyamide monomers through covalent bonds to form a block copolymer, thereby significantly improving the impact resistance, water resistance, and dimensional stability of polyamide.

[0004] Most of the existing polyurethane modified polyamide technologies use physical modification methods, that is, directly melt blending polyurethane materials and polyamide materials. The blended modified materials obtained by this method are prone to poor compatibility of the two components, resulting in serious phase separation, which affects the performance of the product. In addition, there are also a small number of methods that use chemical copolymerization modification, but usually use uncross-linked polyurethane primary prepolymers to directly initiate the polymerization of polyamide monomers. The final modified material macromolecule presents a straight-chain structure, which has limited improvement on the overall performance of the system. Summary of the invention

[0005] In view of the problems in the prior art, the present invention provides a polyurethane block copolymer modified polyamide material with a branched structure and a preparation method thereof. Chemical modification is adopted to firstly carry out branching design on the molecular structure of a polyurethane prepolymer, and then the branched polyurethane prepolymer is introduced into a polyamide system by anionic copolymerization to form a branched cross-linked block copolymer, which not only effectively improves the compatibility of polyurethane and polyamide, but also enables the obtained product to have better mechanical properties, heat resistance, impact resistance, water resistance and dimensional stability.

[0006] The first aspect of the present invention provides a polyurethane block copolymer modified polyamide material with a branched structure, comprising the following components: 8 to 24 parts by weight of polyol, 2 to 7 parts by weight of polyisocyanate, 0.2 to 1 part by weight of a crosslinking agent, 70 to 90 parts by weight of caprolactam, 0.5 to 1 part by weight of a catalyst, and 0.5 to 1 part by weight of a release agent; The polyol is any one of polyether polyol, polyester polyol or polymer polyol or a combination of several of them.

[0007] Further, the polyol is polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene adipate glycol, polyethylene adipate glycol monopropylene glycol or polyethylene adipate glycol monoacetal. Further, the molecular weight of the polyol is 1000-4000, and the functionality is 2.

[0008] The polyisocyanate is any one of toluene diisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate, 1,5-naphthalene diisocyanate, methylcyclopentane diisocyanate, dicyclohexylmethane diisocyanate, tetramethyl meta-xylylene diisocyanate or isophorone diisocyanate, or a combination of several of them.

[0009] The cross-linking agent is any one of trimethylolpropane, triethanolamine or tetrahydroxypropylethylenediamine or a combination of the two.

[0010] The catalyst is any one or a combination of sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, sodium carbonate, sodium caprolactam salt or acetyl caprolactam.

[0011] The release agent is silicone oil, preferably any one or a combination of polydimethylsiloxane, polydiethylsiloxane, polymethylethylsiloxane, polymethylphenylsiloxane, polymethylchlorophenylsiloxane and polymethylvinylsiloxane.

[0012] The second aspect of the present invention provides a method for preparing a polyurethane block copolymer modified polyamide material having a branched structure, comprising the following steps: (1) adding polyol and polyisocyanate into a reaction kettle to react and obtain a polyurethane primary prepolymer terminated with an isocyanate group; (2) adding a crosslinking agent to the polyurethane primary prepolymer obtained in step (1) to react to obtain an isocyanate group-terminated branched crosslinked polyurethane prepolymer; (3) adding 20% ​​to 80% of molten caprolactam to the branched cross-linked polyurethane prepolymer obtained in step (2), and continuing the reaction to obtain a prepolymer component; (4) adding a catalyst to the remaining molten caprolactam and stirring the mixture to obtain a molten mixture; (5) The molten mixture of step (4) is mixed with the prepolymer component of step (3), and after stirring, poured into a mold coated with a release agent, aged, and demolded to obtain a polyurethane block copolymer modified polyamide material with a branched structure.

[0013] Preferably, in step (1), the mass content of free isocyanate groups in the polyurethane primary prepolymer is 1.5% to 6%.

[0014] Preferably, in step (1), the polyol is dehydrated before use. The dehydration treatment is preferably: add the polyol to the reaction kettle, heat it to 80-120°C, and then continue to evacuate to 0.1 MPa until all the water is removed. Preferably, the reaction temperature is 70-90°C, and the reaction time is 0.5-3h.

[0015] Preferably, in step (2), the molar ratio of NCO groups in the polyurethane primary prepolymer to OH groups in the cross-linking agent is 1.5-2.

[0016] Preferably, in step (2), the reaction temperature is 80-100° C. and the reaction time is 2-4 h.

[0017] Preferably, in step (3), the reaction temperature is 80-100° C. and the reaction time is 1-2 h.

[0018] Preferably, the caprolactam is dehydrated before use. The dehydration treatment is preferably: after the caprolactam is heated to 100-130°C in a sealed reactor to melt, vacuum is drawn to remove water for 0.5-1h until the liquid surface is calm.

[0019] Preferably, in step (4), a catalyst is added to the reaction kettle, the temperature is raised to 120-150° C., and then the vacuum is continuously drawn to 0.1 MPa until all the water is removed.

[0020] Preferably, in step (5), the stirring time is 30-90 seconds, the mold is preheated before use to a temperature of 160-180° C., the aging temperature is 120-200° C., and the aging time is 0.5-5 hours.

[0021] Compared with the prior art, the polyurethane block copolymer modified polyamide material with a branched structure provided by the present invention has the following innovative features: (1) The present invention uses polyol, polyisocyanate, crosslinking agent and caprolactam to develop a polyurethane modified polyamide material with high temperature resistance, high impact resistance, high dimensional stability and low hygroscopicity through a prepolymer modification method, and is suitable for including but not limited to automobile engine peripheral parts; (2) The polyurethane block copolymer modified polyamide material with a branched structure provided by the present invention adopts a chemical modification method, firstly, a branched cross-linked polyurethane prepolymer terminated with an isocyanate group is designed and synthesized, and the prepolymer is used as an activated initiator to initiate the ring-opening polymerization of caprolactam, and finally a block copolymer with branched cross-linking is prepared by anionic polymerization; (3) The raw materials used in the present invention for synthesizing the branched cross-linked polyurethane prepolymer terminated with isocyanate groups are of various types, so the structures and properties of different types of block copolymer materials are highly adjustable, and can also meet the requirements of the application performance of polyamide materials in different fields. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] The components and dosage are: 8 parts by weight of polypropylene glycol with a molecular weight of 2000, 2 parts by weight of carbodiimide-modified diphenylmethane diisocyanate, 0.2 parts by weight of trimethylolpropane, 90 parts by weight of caprolactam, 1 part by weight of sodium hydroxide, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Add polypropylene glycol with a molecular weight of 2000 to the reactor, heat it to 110°C and continue to evacuate to 0.1MPa until the water is completely removed, then cool it to 90°C, add carbodiimide-modified diphenylmethane diisocyanate, react for 2h, then add trimethylolpropane and continue to react at 90°C for 2h to obtain a branched cross-linked polyurethane prepolymer; take solid caprolactam and heat it to 120°C in a sealed reactor to melt, evacuate and remove water for 1h until the liquid surface is calm, and pour out half of the obtained melt. Add the branched cross-linked polyurethane prepolymer into the reactor and continue the reaction for 1 hour. Add sodium hydroxide to the remaining half of the caprolactam melt and stir evenly. Slowly heat up to 140°C and continue to evacuate to 0.1MPa until the water is completely removed. Then add all the branched cross-linked polyurethane prepolymer into the reactor and stir for 60 seconds. Pour into a mold coated with polydimethylsiloxane preheated at 180°C, put it into a vacuum drying oven at 160°C for aging for 3 hours, and demold after cooling to obtain a polyurethane block copolymer modified polyamide material.

[0025] Example 2

[0026] The components and dosage are: 16 parts by weight of polypropylene glycol with a molecular weight of 2000, 4 parts by weight of carbodiimide-modified diphenylmethane diisocyanate, 0.4 parts by weight of trimethylolpropane, 80 parts by weight of caprolactam, 1 part by weight of sodium hydroxide, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Add polypropylene glycol with a molecular weight of 2000 to the reactor, heat it to 110°C and continue to evacuate to 0.1MPa until the water is completely removed, then cool it to 90°C, add carbodiimide-modified diphenylmethane diisocyanate, react for 2h, then add trimethylolpropane and continue to react at 90°C for 2h to obtain a branched cross-linked polyurethane prepolymer; take solid caprolactam and heat it to 120°C in a sealed reactor to melt, evacuate and remove water for 1h until the liquid surface is calm, and pour out half of the obtained melt. Add the branched cross-linked polyurethane prepolymer into the reactor and continue the reaction for 1 hour. Add sodium hydroxide to the remaining half of the caprolactam melt and stir evenly. Slowly heat up to 140°C and continue to evacuate to 0.1MPa until the water is completely removed. Then add all the branched cross-linked polyurethane prepolymer into the reactor and stir for 60 seconds. Pour into a mold coated with polydimethylsiloxane preheated at 180°C, put it into a vacuum drying oven at 160°C for aging for 3 hours, and demold after cooling to obtain a polyurethane block copolymer modified polyamide material.

[0027] Example 3

[0028] The components and dosage are: 24 parts by weight of polypropylene glycol with a molecular weight of 2000, 6 parts by weight of carbodiimide-modified diphenylmethane diisocyanate, 0.6 parts by weight of trimethylolpropane, 70 parts by weight of caprolactam, 1 part by weight of sodium hydroxide, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Add polypropylene glycol with a molecular weight of 2000 to the reactor, heat it to 110°C and continue to evacuate to 0.1MPa until the water is completely removed, then cool it to 90°C, add carbodiimide-modified diphenylmethane diisocyanate, react for 2h, then add trimethylolpropane and continue to react at 90°C for 2h to obtain a branched cross-linked polyurethane prepolymer; take solid caprolactam and heat it to 120°C in a sealed reactor to melt, evacuate and remove water for 1h until the liquid surface is calm, and pour out half of the obtained melt. Add the branched cross-linked polyurethane prepolymer into the reactor and continue the reaction for 1 hour. Add sodium hydroxide to the remaining half of the caprolactam melt and stir evenly. Slowly heat up to 140°C and continue to evacuate to 0.1MPa until the water is completely removed. Then add all the branched cross-linked polyurethane prepolymer into the reactor and stir for 60 seconds. Pour into a mold coated with polydimethylsiloxane preheated at 180°C, put it into a vacuum drying oven at 160°C for aging for 3 hours, and demold after cooling to obtain a polyurethane block copolymer modified polyamide material.

[0029] Example 4

[0030] The components and dosage are: 16 parts by weight of polyethylene adipate diol with a molecular weight of 2000, 4 parts by weight of carbodiimide-modified diphenylmethane diisocyanate, 1 part by weight of trimethylolpropane, 80 parts by weight of caprolactam, 1 part by weight of sodium hydroxide, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Add polyethylene adipate glycol with a molecular weight of 2000 to the reactor, heat it to 110°C and continue to evacuate to 0.1MPa until the water is completely removed, then cool it to 90°C, add carbodiimide-modified diphenylmethane diisocyanate, react for 2h, then add trimethylolpropane and continue to react at 90°C for 4h to obtain a branched cross-linked polyurethane prepolymer; take solid caprolactam and heat it to 120°C in a sealed reactor to melt, evacuate and remove water for 1h until the liquid surface is calm, and pour the resulting molten body into Half of it was added to the reactor of branched cross-linked polyurethane prepolymer and the reaction was continued for 1 hour. Sodium hydroxide was added to the remaining half of the caprolactam melt and stirred evenly. The temperature was slowly raised to 140°C and the vacuum was continuously evacuated to 0.1MPa until the water was completely removed. After that, all of it was added to the reactor of branched cross-linked polyurethane prepolymer and stirred for 60 seconds. The mixture was poured into a mold coated with polydimethylsiloxane preheated at 180°C and placed in a vacuum drying oven at 160°C for aging for 3 hours. The polyurethane block copolymer modified polyamide material was obtained after being cooled and demolded.

[0031] Example 5

[0032] The components and dosage are: 16 parts by weight of polytetramethylene glycol with a molecular weight of 2000, 4 parts by weight of carbodiimide-modified diphenylmethane diisocyanate, 0.4 parts by weight of trimethylolpropane, 80 parts by weight of caprolactam, 1 part by weight of sodium hydroxide, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Add polytetramethylene glycol with a molecular weight of 2000 to the reactor, heat it to 110°C and continue to evacuate to 0.1MPa until the water is completely removed, then cool it to 90°C, add carbodiimide-modified diphenylmethane diisocyanate, react for 2h, then add trimethylolpropane and continue to react at 90°C for 2h to obtain a branched cross-linked polyurethane prepolymer; take solid caprolactam and heat it to 120°C in a sealed reactor to melt, evacuate and remove water for 1h until the liquid surface is calm, and pour out the obtained melt. Half of it was added into the reactor of branched cross-linked polyurethane prepolymer and the reaction was continued for 1 hour. Sodium hydroxide was added into the remaining half of the caprolactam melt and stirred evenly. The temperature was slowly raised to 140°C and the vacuum was continuously evacuated to 0.1MPa until all the water was completely removed. After that, all of it was added into the reactor of branched cross-linked polyurethane prepolymer and stirred for 60 seconds. The mixture was poured into a mold coated with polydimethylsiloxane preheated at 180°C and placed in a vacuum drying oven at 160°C for aging for 3 hours. The polyurethane block copolymer modified polyamide material was obtained after being cooled and demolded.

[0033] Example 6

[0034] The components and dosage are: 17 parts by weight of polypropylene glycol with a molecular weight of 2000, 3 parts by weight of toluene diisocyanate, 0.4 parts by weight of trimethylolpropane, 80 parts by weight of caprolactam, 1 part by weight of sodium hydroxide, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Add polypropylene glycol with a molecular weight of 2000 to the reactor, heat it to 110°C and continue to evacuate to 0.1MPa until the water is completely removed, then cool it to 90°C, add toluene diisocyanate, react for 2h, then add trimethylolpropane and continue to react at 90°C for 2h to obtain a branched cross-linked polyurethane prepolymer; take solid caprolactam and heat it to 120°C in a sealed reactor to melt, evacuate to remove water for 1h until the liquid surface is calm, pour out half of the melt and add branched cross-linked polyurethane prepolymer; The reaction was continued in the reactor of the branched cross-linked polyurethane prepolymer for 1 hour. Sodium hydroxide was added to the remaining half of the caprolactam melt and stirred evenly. The temperature was slowly raised to 140°C and the vacuum was continuously evacuated to 0.1MPa until the water was completely removed. After that, all of it was added to the reactor of the branched cross-linked polyurethane prepolymer and stirred for 60 seconds. The mixture was poured into a mold coated with polydimethylsiloxane preheated at 180°C and placed in a vacuum drying oven at 160°C for aging for 3 hours. The polyurethane block copolymer modified polyamide material was obtained after being cooled and demolded.

[0035] Example 7

[0036] The components and dosage are: 17 parts by weight of polypropylene glycol with a molecular weight of 2000, 3 parts by weight of hexamethylene diisocyanate, 0.4 parts by weight of triethanolamine, 80 parts by weight of caprolactam, 1 part by weight of sodium hydroxide, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Add polypropylene glycol with a molecular weight of 2000 to the reactor, heat it to 110°C and continue to evacuate to 0.1MPa until the water is completely removed, then cool it to 90°C, add hexamethylene diisocyanate, react for 2h, then add triethanolamine and continue to react at 90°C for 2h to obtain a branched cross-linked polyurethane prepolymer; take solid caprolactam and heat it to 120°C in a sealed reactor to melt, evacuate and remove water for 1h until the liquid surface is calm, pour out half of the melt and add branched cross-linked polyurethane prepolymer; The reaction was continued in the reactor of the branched cross-linked polyurethane prepolymer for 1 hour. Sodium hydroxide was added to the remaining half of the caprolactam melt and stirred evenly. The temperature was slowly raised to 140°C and the vacuum was continuously evacuated to 0.1MPa until the water was completely removed. After that, all of it was added to the reactor of the branched cross-linked polyurethane prepolymer and stirred for 60 seconds. The mixture was poured into a mold coated with polydimethylsiloxane preheated at 180°C and placed in a vacuum drying oven at 160°C for aging for 3 hours. The polyurethane block copolymer modified polyamide material was obtained after being cooled and demolded.

[0037] Example 8

[0038] The components and dosage are: 16 parts by weight of polypropylene glycol with a molecular weight of 2000, 4 parts by weight of carbodiimide-modified diphenylmethane diisocyanate, 0.6 parts by weight of tetrahydroxypropylethylenediamine, 80 parts by weight of caprolactam, 1 part by weight of sodium caprolactam salt, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Add polypropylene glycol with a molecular weight of 2000 to the reactor, heat it to 110°C and continue to evacuate to 0.1MPa until the water is completely removed, then cool it to 90°C, add carbodiimide-modified diphenylmethane diisocyanate, react for 2h, then add tetrahydroxypropylethylenediamine and continue to react at 90°C for 3h to obtain a branched cross-linked polyurethane prepolymer; take solid caprolactam and heat it to 120°C in a sealed reactor to melt, evacuate to remove water for 1h until the liquid surface is calm, pour out half of the obtained melt and add The mixture was added into the reactor of the branched cross-linked polyurethane prepolymer and continued to react for 1 hour. Sodium caprolactam salt was added to the remaining half of the caprolactam melt and stirred evenly. The temperature was slowly raised to 140°C and the vacuum was continuously evacuated to 0.1 MPa until all the water was completely removed. After that, all the mixture was added into the reactor of the branched cross-linked polyurethane prepolymer and stirred for 60 seconds. The mixture was poured into a mold coated with polydimethylsiloxane which was preheated at 180°C and placed in a vacuum drying oven at 160°C for maturation for 3 hours. The polyurethane block copolymer modified polyamide material was obtained after being cooled and demolded.

[0039] Example 9

[0040] The components and dosage are: 14 parts by weight of polypropylene glycol with a molecular weight of 1000, 6 parts by weight of isophorone diisocyanate, 0.6 parts by weight of trimethylolpropane, 80 parts by weight of caprolactam, 1 part by weight of sodium hydroxide, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Add polypropylene glycol with a molecular weight of 1000 to the reactor, heat it to 100°C and continue to evacuate to 0.1MPa until the water is completely removed, then cool it to 90°C, add isophorone diisocyanate, react for 2h, then add trimethylolpropane and continue to react at 90°C for 3h to obtain a branched cross-linked polyurethane prepolymer; take solid caprolactam and heat it to 120°C in a sealed reactor to melt, evacuate and remove water for 1h until the liquid surface is calm, pour out half of the obtained melt and add branched The reaction was continued in the reactor of the cross-linked polyurethane prepolymer for 1 hour. Sodium hydroxide was added to the remaining half of the caprolactam melt and stirred evenly. The temperature was slowly raised to 140°C and the vacuum was continuously evacuated to 0.1 MPa until all the water was completely removed. After that, all of it was added to the reactor of the branched cross-linked polyurethane prepolymer and stirred for 60 seconds. The mixture was poured into a mold coated with polydimethylsiloxane preheated at 180°C and placed in a vacuum drying oven at 160°C for aging for 3 hours. The polyurethane block copolymer modified polyamide material was obtained after cooling.

[0041] Example 10

[0042] The components and dosage are: 17 parts by weight of polypropylene glycol with a molecular weight of 4000, 3 parts by weight of carbodiimide-modified diphenylmethane diisocyanate, 0.2 parts by weight of trimethylolpropane, 80 parts by weight of caprolactam, 0.5 parts by weight of sodium ethoxide, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Add polypropylene glycol with a molecular weight of 4000 to the reactor, heat it to 120°C and continue to evacuate to 0.1MPa until the water is completely removed, then cool it to 90°C, add carbodiimide-modified diphenylmethane diisocyanate, react for 2h, then add trimethylolpropane and continue to react at 90°C for 2h to obtain a branched cross-linked polyurethane prepolymer; take solid caprolactam and heat it to 120°C in a sealed reactor to melt, evacuate and remove water for 1h until the liquid surface is calm, and pour out half of the obtained melt. Add the branched cross-linked polyurethane prepolymer into the reactor and continue the reaction for 1 hour. Add sodium ethanol to the remaining half of the caprolactam melt and stir evenly. Slowly heat up to 140°C and continue to evacuate to 0.1MPa until the water is completely removed. Then add all the branched cross-linked polyurethane prepolymer into the reactor and stir for 60 seconds. Pour into a mold coated with polydimethylsiloxane preheated at 180°C, put it into a vacuum drying oven at 160°C for aging for 3 hours, and demold after cooling to obtain a polyurethane block copolymer modified polyamide material.

[0043] Comparative Example 1 The components and dosage of the monomer casting polyamide material are: 100 parts by weight of caprolactam, 0.5 parts by weight of sodium hydroxide, 0.5 parts by weight of toluene diisocyanate, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Solid caprolactam is heated to 120°C in a sealed reactor and melted, and then vacuumed to remove water for 1 hour until the liquid surface is calm. Sodium hydroxide is added and stirred evenly, and then the temperature is slowly raised to 140°C and vacuumed to 0.1MPa until all the water is removed. Toluene diisocyanate is then added, stirred for 30 seconds, and poured into a mold coated with polydimethylsiloxane preheated at 180°C, and placed in a vacuum drying oven at 160°C for aging for 3 hours. After cooling, demolding is performed to obtain a monomer casting polyamide material.

[0044] Comparative Example 2 The components and dosage of the polyurethane block copolymer modified polyamide material are: 16 parts by weight of polypropylene glycol with a molecular weight of 2000, 4 parts by weight of carbodiimide modified diphenylmethane diisocyanate, 80 parts by weight of caprolactam, 1 part by weight of sodium hydroxide, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Add polypropylene glycol with a molecular weight of 2000 to the reactor, heat it to 110°C and continue to evacuate to 0.1MPa until the water is completely removed, then cool it to 90°C, add carbodiimide modified diphenylmethane diisocyanate, react for 2h to obtain a polyurethane prepolymer; take solid caprolactam and heat it to 120°C in a sealed reactor to melt it, evacuate and remove water for 1h until the liquid surface is calm, pour out half of the obtained melt and add it to the reactor of the polyurethane prepolymer to continue to react for 1h, add sodium hydroxide to the remaining half of the caprolactam melt and stir evenly, slowly heat it to 140°C and continue to evacuate to 0.1MPa until the water is completely removed, then add all of it to the reactor of the polyurethane prepolymer, stir for 60s, pour it into a mold coated with polydimethylsiloxane preheated at 180°C, put it in a vacuum drying oven at 160°C for aging for 3h, and demold it after cooling to obtain a polyurethane block copolymer modified polyamide material.

[0045] Comparative Example 3 The components and dosage of the polyurethane block copolymer modified polyamide material are: 16 parts by weight of polypropylene glycol with a molecular weight of 2000, 4 parts by weight of carbodiimide modified diphenylmethane diisocyanate, 0.4 parts by weight of trimethylolpropane, 80 parts by weight of caprolactam, 1 part by weight of sodium hydroxide, and 1 part by weight of polydimethylsiloxane. The specific preparation steps are as follows: Add polypropylene glycol with a molecular weight of 2000 to the reactor, heat it to 110°C and continue to evacuate to 0.1MPa until the water is completely removed, then cool it to 90°C, add trimethylolpropane and carbodiimide modified diphenylmethane diisocyanate successively, react for 2h to obtain a polyurethane prepolymer; take solid caprolactam and heat it to 120°C in a sealed reactor to melt, evacuate and remove water for 1h until the liquid surface is calm, pour out half of the obtained melt and add it to the reactor of the polyurethane prepolymer to continue to react for 1h, add sodium hydroxide to the remaining half of the caprolactam melt and stir evenly, slowly heat it to 140°C and continue to evacuate to 0.1MPa until the water is completely removed, then add all of it to the reactor of the polyurethane prepolymer, stir for 60s, pour it into a mold coated with polydimethylsiloxane preheated at 180°C, put it in a vacuum drying oven at 160°C for aging for 3h, and demold it after cooling to obtain a polyurethane copolymer modified polyamide material.

[0046] The materials of Examples 1 to 11 and Comparative Examples 1 to 3 were subjected to performance tests. Performance test: The cast samples were standard samples, and the hardness, tensile strength, heat deformation temperature, notched impact strength, water absorption and shrinkage were tested according to national standards GB / T 2411-2008, GB / T 1040-2022, GB / T 1634.1-2019, GB / T 1842-2008, GB / T 1034-2008 and GB / T 17037.4-2003. The results are shown in Table 1.

[0047] Table 1 Material properties of embodiments and comparative examples

Claims

1. A polyurethane block copolymer modified polyamide material with a branched structure, comprising the following components: 8 to 24 parts by weight of polyol, 2 to 7 parts by weight of polyisocyanate, 0.2 to 1 part by weight of a crosslinking agent, 70 to 90 parts by weight of caprolactam, 0.5 to 1 part by weight of a catalyst, and 0.5 to 1 part by weight of a release agent; The polyol is any one of polyether polyol, polyester polyol or polymer polyol or a combination of several of them.

2. The polyurethane block copolymer modified polyamide material with a branched structure according to claim 1, characterized in that: The polyol is polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene adipate glycol, polyethylene adipate glycol monopropylene glycol or polyethylene adipate glycol monoacetal.

3. The polyurethane block copolymer modified polyamide material with a branched structure according to claim 1, characterized in that: The polyisocyanate is any one of toluene diisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate, 1,5-naphthalene diisocyanate, methylcyclopentane diisocyanate, dicyclohexylmethane diisocyanate, tetramethyl meta-xylylene diisocyanate or isophorone diisocyanate, or a combination of several of them.

4. The polyurethane block copolymer modified polyamide material with a branched structure according to claim 1, characterized in that: The cross-linking agent is any one of trimethylolpropane, triethanolamine or tetrahydroxypropylethylenediamine or a combination of the two.

5. The polyurethane block copolymer modified polyamide material with a branched structure according to claim 1, characterized in that: The catalyst is any one or a combination of sodium hydroxide, potassium hydroxide, sodium methoxide, sodium ethoxide, sodium carbonate, sodium caprolactam salt or acetyl caprolactam.

6. The polyurethane block copolymer modified polyamide material with a branched structure according to claim 1, characterized in that: The release agent is silicone oil, preferably any one or a combination of polydimethylsiloxane, polydiethylsiloxane, polymethylethylsiloxane, polymethylphenylsiloxane, polymethylchlorophenylsiloxane and polymethylvinylsiloxane.

7. A method for preparing a polyurethane block copolymer modified polyamide material with a branched structure according to any one of claims 1 to 6, comprising the following steps: (1) adding polyol and polyisocyanate into a reaction kettle to react and obtain a polyurethane primary prepolymer terminated with an isocyanate group; (2) adding a crosslinking agent to the polyurethane primary prepolymer obtained in step (1) to react to obtain an isocyanate group-terminated branched crosslinked polyurethane prepolymer; (3) adding 20% ​​to 80% of molten caprolactam to the branched cross-linked polyurethane prepolymer obtained in step (2), and continuing the reaction to obtain a prepolymer component; (4) adding a catalyst to the remaining molten caprolactam and stirring the mixture to obtain a molten mixture; (5) The molten mixture of step (4) is mixed with the prepolymer component of step (3), and after stirring, poured into a mold coated with a release agent, aged, and demolded to obtain a polyurethane block copolymer modified polyamide material with a branched structure.

8. The preparation method according to claim 7, characterized in that: In step (1), the free isocyanate group mass content of the polyurethane primary prepolymer is 1.5% to 6%.

9. The preparation method according to claim 7, characterized in that: The molar ratio of NCO groups in the polyurethane primary prepolymer to OH groups in the crosslinking agent is 1.5~2.

10. The preparation method according to claim 7, characterized in that: In step (1), the reaction temperature is 70-90°C; in step (2), the reaction temperature is 80-100°C; in step (3), the reaction temperature is 80-100°C.

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