A highly wear-resistant polyurethane material for screen plate processing and preparation method thereof

Abstract

The invention discloses a highly wear-resistant polyurethane material for screen plate processing and a preparation method thereof, belonging to the technical field of polyurethane materials, and is used to solve the technical problem in the prior art that the hardness, tensile strength, tear strength, wear resistance and flame retardancy of polyurethane materials need to be further improved. The invention specifically comprises the following components, measured by weight: 80-100 parts of modified polyurethane, 3-5 parts of NH2-rGO / MoSe2, 10-15 parts of modified nylon and 2-3 parts of auxiliary additives. The invention further improves the hardness, tensile strength, tear strength, wear resistance and flame retardancy of the polyurethane material by using hydroxyl-terminated polysiloxane, flame-retardant polyester, NH2-rGO / MoSe2 and modified nylon.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane materials, and in particular to a highly wear-resistant polyurethane material for screen plate processing and a preparation method thereof. Background Art

[0002] In industrial fields such as mining, chemical industry, and building materials, screen plates, as core components for material screening, need to withstand high-frequency vibration, material impact, and friction and wear for a long time. At the same time, they may face safety risks such as high temperature and open flames. Traditional polyurethane materials have technical problems such as hardness, toughness, wear and flame retardancy that need to be further improved due to the limitations of their molecular chain structure.

[0003] Traditional polyurethane relies on cross-linking polyether or polyester polyols with isocyanates to form a network. However, the high flexibility of the molecular chain leads to limited hardness and tensile strength. It is prone to plastic deformation or even fracture under high-frequency vibration, shortening its service life.

[0004] At the same time, the wear of traditional polyurethane is mainly due to the weak interaction force between molecular chains, and chain segment slip and interface debonding are prone to occur during friction. Although the introduction of nanofillers, such as graphene, can improve wear resistance, the uneven dispersion of the fillers or insufficient interface bonding strength leads to limited reinforcement effect and may cause a decline in mechanical properties. Most industrial scenarios require the screen plate material to have flame retardant properties. Polyurethane contains a large amount of hydrocarbon components and is a flammable material. Common flame retardant solutions, such as adding halogen flame retardants, can improve the flame retardancy level, but will lead to deterioration of the material's mechanical properties and release toxic gases during combustion, which does not meet environmental protection requirements. Halogen-free flame retardant systems, such as phosphorus-nitrogen synergistic flame retardant, have poor compatibility with polyurethane, making it difficult to achieve a balance between flame retardant efficiency and mechanical properties. In addition, the performance improvement of filled polyurethane is highly dependent on the interface bonding strength between the filler and the matrix. Traditional nylon 66 has few polar groups and is prone to phase separation when blended with polyurethane, resulting in "stratification" of the composite material and a significant decline in mechanical properties.

[0005] In summary, a solution is now proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a highly wear-resistant polyurethane material for screen plate processing and a preparation method thereof, so as to solve the technical problem in the prior art that the hardness, tensile strength, tear strength, wear resistance and flame retardancy of polyurethane materials need to be further improved.

[0007] The object of the present invention can be achieved by the following technical solution: A highly wear-resistant polyurethane material for screen plate processing, comprising the following components in parts by weight: 80-100 parts of modified polyurethane, 3-5 parts of NH2-rGO / MoSe2, 10-15 parts of modified nylon and 2-3 parts of auxiliary additives;

[0008] The auxiliary additives include the following components by weight: 8-12 parts of a curing agent, 1-2 parts of an antioxidant, and 3-5 parts of a plasticizer;

[0009] The preparation method of the modified polyurethane comprises: adding polytetramethylene glycol, hydroxyl-terminated polysiloxane, flame-retardant polyester and a catalyst into a reaction kettle containing N,N-dimethylformamide, stirring and mixing, then adding diphenylmethane diisocyanate and a chain extender, and finally adding a blocking agent after the reaction is completed, and performing post-processing to obtain the modified polyurethane;

[0010] Reaction principle:

[0011] In the preparation process of the modified polyurethane, hydroxyl-containing raw materials such as polytetramethylene glycol, hydroxyl-terminated polysiloxane, and flame-retardant polyester are first dissolved in N,N-dimethylformamide together with a dibutyltin dilaurate catalyst. After heating to 80-100°C, diphenylmethane diisocyanate is added. Under the action of the catalyst, the hydroxyl group acts as a nucleophilic reagent to attack the isocyanate group in the diphenylmethane diisocyanate, undergoing a nucleophilic addition reaction to form a carbamate bond, thereby generating an isocyanate-terminated prepolymer. Subsequently, 3,3'-dichloro-4,4'-diaminodiphenylmethane is added. At 80-100°C, the amino group of 3,3'-dichloro-4,4'-diaminodiphenylmethane reacts with the isocyanate group of the prepolymer due to its strong nucleophilicity to form a urea bond, thereby achieving molecular chain extension. Finally, a capping agent is added. The monohydroxyl group in the capping agent reacts with the remaining -NCO group to generate a stable carbamate end group, thereby terminating the chain extension, thereby obtaining the modified polyurethane.

[0012] The modified nylon preparation method comprises the following steps: adding dopamine hydrochloride and deionized water into a reactor, stirring until the dopamine hydrochloride is completely dissolved, adding hexamethylenediamine and adipic acid into the reactor, dripping sodium hydroxide solution therein until the pH is neutral, and performing post-treatment to obtain the modified nylon.

[0013] Reaction principle:

[0014] First, hexamethylenediamine, adipic acid and dopamine hydrochloride are dissolved in deionized water and heated to 80-90°C. Hexamethylenediamine and adipic acid are neutralized to form nylon 66 salt, and dopamine hydrochloride dissociates into cations. Then, sodium hydroxide is added dropwise to adjust the pH to neutral, so that dopamine returns to a free state. Then, under nitrogen protection, the temperature is raised to 120-150°C. The nylon 66 salt undergoes initial polycondensation to form oligomers, and dopamine is dispersed therein by physical mixing or a small amount of amidation reaction. Finally, the temperature is raised to 240-260°C. The system melts, the nylon chain grows rapidly, and the amino group of dopamine undergoes amidation reaction with the carboxyl group at the end of the nylon chain, covalently connecting to the main chain. Its catechol structure may also be oxidatively cross-linked to form branches or networks, thereby producing modified nylon.

[0015] Furthermore, the dosage ratio of the polytetramethylene ether glycol, hydroxyl-terminated polysiloxane, flame-retardant polyester, catalyst, N,N-dimethylformamide, chain extender, and end-capping agent is 100 mL: 10-20 g: 20-30 g: 1-2 mL: 300 mL: 3-5 g: 2-3 g, the added amount of the diphenylmethane diisocyanate is 0.55 times the total molar amount of oxygen-containing functional groups in the polytetramethylene ether glycol, hydroxyl-terminated polysiloxane, and flame-retardant polyester molecules, the catalyst is dibutyltin dilaurate, the chain extender is 3,3'-dichloro-4,4'-diaminodiphenylmethane, and the end-capping agent is glycidol.

[0016] Furthermore, in the preparation of the modified nylon, the usage ratio of hexamethylenediamine, adipic acid, dopamine hydrochloride and deionized water is 10 g:6 g:1 g:2 mL, and the concentration of the sodium hydroxide solution is 0.5 mol / L.

[0017] Furthermore, the preparation method of the hydroxyl-terminated polysiloxane is as follows: octamethylcyclotetrasiloxane, trifluoropropyltrimethylcyclotrisiloxane and tetramethyltetraenylcyclotetrasiloxane are added to a reactor, stirred for 30 minutes under a nitrogen atmosphere at 90°C, and then heated to 110°C, tetramethylammonium hydroxide and a capping agent H2O are added, and the reaction is continued for 3 hours. The hydroxyl-terminated polysiloxane is obtained by post-processing. The amount ratio of the octamethylcyclotetrasiloxane, trifluoropropyltrimethylcyclotrisiloxane, tetramethyltetraenylcyclotetrasiloxane, tetramethylammonium hydroxide and the capping agent H2O is 100g:50g:4g:0.01g:0.29mL.

[0018] Reaction principle:

[0019] In a nitrogen atmosphere, octamethylcyclotetrasiloxane, trifluoropropyltrimethylcyclotrisiloxane and tetramethyltetraenylcyclotetrasiloxane were added to the reactor with tetramethylammonium hydroxide as catalyst, pre-mixed at 90 ° C, and heated to 110 ° C to cause ring-opening copolymerization. The OH generated by the decomposition of the catalyst was - The ions attack the silicon atoms of the cyclosiloxane, opening the Si-O bond to initiate polymerization. The three monomers randomly open the ring to form a linear polysiloxane chain containing methyl, trifluoropropyl and vinyl side groups. The capping agent H2O then reacts with the chain end siloxy anions to generate hydroxyl capping groups, terminating chain growth. Finally, after post-treatment to remove low-boiling substances and neutralize the catalyst, hydroxyl-terminated polysiloxane is obtained.

[0020]

[0021] Furthermore, the preparation method of the flame-retardant polyester is as follows: in a nitrogen atmosphere, phthalic anhydride, diphenyl phosphate and ethylene glycol are added to a reactor, the temperature is raised to 120-140°C, the temperature is kept for reaction for 1-2 hours, the temperature is gradually raised to 180-220°C, a catalyst is added, the reaction is carried out for 3-5 hours, and the system temperature is then raised to 230-260°C and maintained for 2-4 hours to obtain the flame-retardant polyester.

[0022] Furthermore, the molar ratio of phthalic anhydride, diphenyl phosphate, ethylene glycol and catalyst is 1:1.2:0.3, and the catalyst is stannous octoate, and the amount used is 0.3%-1.0% of the total monomer mass.

[0023] Furthermore, the NH2-rGO / MoSe2 is prepared by the following steps:

[0024] A1. Add graphene oxide to anhydrous ethanol and ultrasonically disperse for 2 h. Add deionized water, acetic acid and silane coupling agent to the reactor and heat to 78 °C for 12 h to obtain NH2-rGO.

[0025] Reaction principle:

[0026] First, graphene oxide was ultrasonically dispersed in anhydrous ethanol. The polarity of ethanol and the mechanical action of ultrasound destroyed its agglomeration to form a stable suspension. Deionized water, acetic acid, and γ-aminopropyltriethoxysilane were then added to the system. The acidic environment provided by the acetic acid catalyzed the hydrolysis of the silane coupling agent, converting its ethoxy groups into silanol groups. The silanol groups then underwent a condensation reaction with the hydroxyl and carboxyl groups on the graphene oxide surface, forming silicon-oxygen bonds through dehydration, and grafting amino groups onto the graphene oxide surface. At the same time, the ethanol in the system exerted a weak reducing property at acidity and 78°C, promoting the deoxygenation and reduction of graphene oxide, forming NH2-rGO with both amino activity and reducing properties.

[0027] A2. NH2-rGO and Na2MoO4·2H2O were added to deionized water. After ultrasonic treatment for 30 minutes, Se solution and hydrazine hydrate were added. The mixture was stirred at 20-30°C for 1 hour. The mixed solution was then transferred to a polytetrafluoroethylene-lined hydrothermal reactor and the reaction was maintained at 200°C for 24 hours. NH2-rGO / MoSe2 was obtained after post-treatment.

[0028] Reaction principle:

[0029] First, NH2-rGO and Na2MoO4·2H2O were ultrasonically dispersed in deionized water, and the protonated amino groups on the surface of NH2-rGO were used to adsorb MoO4. 2- , then add Se solution and hydrazine hydrate, hydrazine hydrate reduces Se to Se 2-At the same time, Mo(VI) was pre-reduced to Mo(IV); after being transferred to a hydrothermal reactor and heated to 200°C, Mo(IV) and Se 2- The reaction generates layered MoSe2 nanosheets, which grow uniformly on the surface of NH2-rGO through the anchoring effect of amino groups to obtain NH2-rGO / MoSe2.

[0030] Furthermore, in step A1, the amount ratio of the graphene oxide, anhydrous ethanol, deionized water, acetic acid and silane coupling agent is 0.25 g:25 mL:3 mL:0.25 mL:1 g, and the silane coupling agent is γ-aminopropyltriethoxysilane; in step A2, the amount ratio of the NH2-rGO, Na2MoO4·2H2O, deionized water and Se solution is 1 g:3 g:20 mL:20 mL, and the Se solution is composed of Se and N2H4·H2O in a ratio of 0.41 g:15 mL.

[0031] The present invention also proposes a method for preparing a highly wear-resistant polyurethane material for screen plate processing: adding modified polyurethane to an internal mixer, melting the modified polyurethane at 90-110°C, then adding NH2-rGO / MoSe2 and reacting for 15-20 minutes, and finally adding modified nylon and auxiliary additives, heating to 250-260°C and reacting for 10-20 minutes to obtain a polyurethane material.

[0032] The present invention has the following beneficial effects:

[0033] 1. In the present invention, first, the hydroxyl-terminated polysiloxane significantly improves the molecular chain flexibility of the polyurethane by introducing siloxane bonds and fluoroalkyl side chains. The low glass transition temperature of the siloxane bond gives the material excellent low-temperature toughness, and the strong hydrophobicity and low surface energy of the trifluoropropyl group effectively reduce the friction between the molecular chains, thereby improving the elongation at break of the polyurethane. Secondly, after the hydroxyl-terminated polysiloxane is blended with polytetramethylene ether glycol, it is cross-linked by isocyanate groups to form a "rigid-flexible block" network structure, which improves the hardness, tensile strength and tear strength of the material. Finally, the flame-retardant polyester uses a phosphorus-nitrogen synergistic flame retardant mechanism to improve the mechanical properties while giving the material flame retardant properties. The phosphate groups in the molecular chain decompose to form phosphoric acid and metaphosphoric acid during combustion, promoting the formation of a carbon layer and inhibiting the release of combustible gases. The phthalic anhydride skeleton enhances the density of the carbon layer, improves the vertical burning grade and limiting oxygen index of the polyurethane material, and also improves the tensile strength and tear strength of the material, so that the material can withstand the high-frequency vibration load of the sieve plate and meet the fire safety requirements of industrial scenarios.

[0034] 2. The two-dimensional lamellar structure of the amino-reduced graphene oxide (NH2-rGO) of the present invention is tightly bonded to the polyurethane chain segments through hydrogen bonds to form a nano-scale reinforcing filler. The surface amino groups react with the isocyanate groups of the polyurethane to form urea bonds, which effectively inhibit filler agglomeration and interface debonding, and reduce the plastic deformation of the matrix. MoSe2 nanosheets are embedded between the rGO sheets as "molecular bearings", and the layered slip characteristics are used to reduce the friction coefficient and reduce the interfacial energy loss. At the same time, its Se atoms form a strong interaction with the π electron conjugated system of rGO to prevent the nanosheets from falling off during wear. In addition, the conjugated structure of NH2-rGO / MoSe2 can also improve the thermal conductivity of the material, quickly dissipate the heat generated by friction, avoid material softening caused by local overheating, and further extend the service life of the screen plate.

[0035] 3. In the present invention, the amino group of dopamine reacts with the isocyanate group of polyurethane to form a urea bond, and the catechol structure oxidizes and self-polymerizes to form a polydopamine cross-linked network, which covalently anchors the nylon chain segments and the polyurethane molecular chains, thereby improving the interfacial shear strength of the composite material. This strong interfacial effect is directly reflected in the tensile strength and tear strength. In addition, the nitrogen element in the modified nylon and the phosphorus element in the flame-retardant polyester form a "nitrogen-phosphorus synergistic" mechanism. During combustion, the nitrogen element promotes carbonization and inhibits the release of combustible gases, and the phosphorus element enhances the stability of the carbon layer, so that the vertical combustion level of the material can stably reach V0 level, significantly improving the flame retardant properties of the material. DETAILED DESCRIPTION

[0036] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] In the present invention, polytetramethylene ether glycol is selected from Jining Sunbright Biotechnology Co., Ltd., CAS No. 25190-06-1, product molecular weight 2000±50, active ingredient content ≥99.5%, model PTMG, product No. J30633;

[0038] In the present invention, dibutyltin dilaurate is selected from Shandong Qiyuan Chemical Co., Ltd., with a CAS number of 77-58-7, an active ingredient content of 18%, and a flash point of 226.7°C;

[0039] In the present invention, graphene oxide is selected from Shanghai Xiangtian Nanomaterial Co., Ltd., with a specification of Go-01, an active ingredient content of 99.9%, a product number of Go, and a model number of XT-Go.

[0040] Example 1

[0041] This embodiment provides a method for preparing a highly wear-resistant polyurethane material for screen plate processing, comprising the following steps:

[0042] S1. Preparation of hydroxyl-terminated polysiloxane

[0043] Weigh: 100g octamethylcyclotetrasiloxane, 50g trifluoropropyltrimethylcyclotrisiloxane and 4g tetramethyltetraenylcyclotetrasiloxane are added to the reactor, stirred for 30min under a nitrogen atmosphere at 90°C, and then heated to 110°C. 0.01g tetramethylammonium hydroxide and 0.29mL capping agent H2O are added, and the reaction is continued for 3h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, 50mL deionized water is added to the reactor, stirred and dispersed for 20min, and allowed to stand. The upper layer liquid is washed three times with deionized water and then transferred to a rotary evaporator with a water bath temperature of 80°C. Low boiling substances are evaporated under reduced pressure to obtain hydroxyl-terminated polysiloxane.

[0044] S2. Preparation of flame-retardant polyester

[0045] Weigh: 5g of phthalic anhydride, 2g of diphenyl phosphate and 3g of ethylene glycol are added to a reactor. In a nitrogen atmosphere, the temperature is raised to 120°C. After the reaction is kept warm for 1 hour, the temperature is gradually raised to 180°C. 0.1g of stannous octoate is added as a catalyst and the reaction is carried out for 3 hours. The system temperature is then raised to 230°C and maintained for 2 hours. After the material is discharged while hot, it is cooled and solidified, and crushed to obtain flame-retardant polyester.

[0046] S3. Preparation of modified polyurethane

[0047] Weigh: 100 mL of polytetramethylene glycol, 10 g of hydroxyl-terminated polysiloxane, 20 g of flame-retardant polyester and 1 mL of dibutyltin dilaurate are added to a reactor containing 300 mL of N,N-dimethylformamide and stirred. After heating to 80 ° C, the amount of diphenylmethane diisocyanate added is calculated as 0.55 times the total molar amount of oxygen-containing functional groups in polytetramethylene glycol, hydroxyl-terminated polysiloxane and flame-retardant polyester, and added to the reactor. After keeping the temperature for 2 hours, 3 g of diphenylmethane diisocyanate is added. 3,3'-dichloro-4,4'-diaminodiphenylmethane, add 2g of end-capping agent glycidyl ether to the reactor, keep warm and react for 40min, reduce the temperature of the reactor to room temperature, add 1500mL of deionized water to the reactor, stir and disperse for 30min, filter, wash the filter cake with purified water 3 times and then dry it, transfer the filter cake to a drying oven at 70℃, dry it to constant weight, and obtain modified polyurethane.

[0048] S4. Preparation of NH2-rGO / MoSe2

[0049] Weigh: 0.25g of graphene oxide was added to 25mL of anhydrous ethanol and ultrasonically dispersed for 2h. 3mL of deionized water, 0.25mL of acetic acid and 1g of γ-aminopropyltriethoxysilane were added to the reactor and the temperature was raised to 78℃ for reaction for 12h. After the reaction was completed, the temperature of the reactor was lowered to room temperature. The product was washed once with ethanol and then washed three times with deionized water. Finally, it was transferred to a vacuum drying oven and dried at 60℃ for 12h to obtain NH2-rGO.

[0050] Se and N2H4·H2O were mixed uniformly at a ratio of 0.41 g:15 mL to obtain a Se solution for later use;

[0051] Weigh: 1g NH2-rGO and 3g Na2MoO4·2H2O were added to 20mL deionized water. After ultrasonic treatment for 30min, 20mL Se solution was added and stirred at 20℃ for 1h. The mixed solution was then transferred to a polytetrafluoroethylene-lined hydrothermal reactor and maintained at 200℃ for 24h. After the reaction was completed, it was cooled to room temperature and transferred to a vacuum drying oven. It was dried at 60℃ for 12h to obtain NH2-rGO / MoSe2.

[0052] S5. Preparation of modified nylon

[0053] Weigh: 1g dopamine hydrochloride and 2mL deionized water are added to a nitrogen-protected reactor, the reactor is heated to 80°C, stirred until the dopamine hydrochloride is completely dissolved, 10g hexamethylenediamine and 6g adipic acid are added to the reactor, stirred for 20min, 0.5mol / L sodium hydroxide solution is added dropwise to the reactor until the pH is neutral, the reactor is sealed, the reactor heat exchange medium is heated to 120°C, and the reaction is kept warm for 0.5h, the reactor heat exchange medium is heated to 240°C again, and the reaction is kept warm for 3h. After the reaction is completed, the material is discharged while hot, the reactant is cooled to room temperature, crushed, and the product is washed 3 times with deionized water, transferred to a vacuum drying oven, and dried at 80°C for 12h to obtain modified nylon.

[0054] S6. Preparation of polyurethane material

[0055] The auxiliary additives consist of 8 parts of curing agent, 1 part of antioxidant and 3 parts of plasticizer;

[0056] Weigh 80 parts of modified polyurethane into an internal mixer, melt the modified polyurethane at 90-110°C, then add 3 parts of NH2-rGO / MoSe2 and react for 15 minutes, finally add 10 parts of modified nylon and 2 parts of auxiliary additives, heat to 240°C and react for 10 minutes, and discharge to obtain a polyurethane material.

[0057] Example 2

[0058] This embodiment provides a method for preparing a highly wear-resistant polyurethane material for screen plate processing, comprising the following steps:

[0059] S1. Preparation of hydroxyl-terminated polysiloxane

[0060] Weigh: 100g octamethylcyclotetrasiloxane, 50g trifluoropropyltrimethylcyclotrisiloxane and 4g tetramethyltetraenylcyclotetrasiloxane are added to the reactor, stirred for 30min under a nitrogen atmosphere at 90°C, and then heated to 110°C. 0.01g tetramethylammonium hydroxide and 0.29mL capping agent H2O are added, and the reaction is continued for 3h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, 50mL deionized water is added to the reactor, stirred and dispersed for 25min, and allowed to stand. The upper layer liquid is washed three times with deionized water and then transferred to a rotary evaporator with a water bath temperature of 85°C. Low boiling substances are evaporated under reduced pressure to obtain hydroxyl-terminated polysiloxane.

[0061] S2. Preparation of flame-retardant polyester

[0062] Weigh: 5g of phthalic anhydride, 2g of diphenyl phosphate and 3g of ethylene glycol are added to a reactor. In a nitrogen atmosphere, the temperature is raised to 120°C. After the reaction is kept warm for 1 hour, the temperature is gradually raised to 180°C. 0.1g of stannous octoate is added as a catalyst and the reaction is carried out for 3 hours. The system temperature is then raised to 230°C and maintained for 2 hours. After the material is discharged while hot, it is cooled and solidified, and crushed to obtain flame-retardant polyester.

[0063] S3. Preparation of modified polyurethane

[0064] Weigh: 100 mL of polytetramethylene glycol, 15 g of hydroxyl-terminated polysiloxane, 25 g of flame-retardant polyester and 1.5 mL of dibutyltin dilaurate and add them to a 300 mL The reaction kettle was stirred with N,N-dimethylformamide, and the temperature was raised to 90°C. The amount of diphenylmethane diisocyanate added was calculated as 0.55 times the total molar amount of the oxygen-containing functional groups in the polytetramethylene ether glycol, hydroxyl-terminated polysiloxane and flame-retardant polyester, and the mixture was added to the reactor. After the reaction was kept warm for 2.5 hours, 4 g of 3,3'-dichloro-4,4'-diaminodiphenylmethane was added thereto. 2.5 g of the blocking agent glycidyl ether was added to the reactor, and the reaction was kept warm for 50 minutes. The temperature of the reactor was lowered to room temperature, 1500 mL of deionized water was added to the reactor, and the mixture was stirred and dispersed for 40 minutes. The mixture was filtered, and the filter cake was washed three times with purified water and then dried. The filter cake was then transferred to a drying oven at 75°C and dried to constant weight to obtain a modified polyurethane.

[0065] S4. Preparation of NH2-rGO / MoSe2

[0066] Weigh: 0.25g of graphene oxide was added to 25mL of anhydrous ethanol and ultrasonically dispersed for 2h. 3mL of deionized water, 0.25mL of acetic acid and 1g of γ-aminopropyltriethoxysilane were added to the reactor and the temperature was raised to 78℃ for reaction for 12h. After the reaction was completed, the temperature of the reactor was lowered to room temperature. The product was washed once with ethanol and then washed three times with deionized water. Finally, it was transferred to a vacuum drying oven and dried at 60℃ for 12h to obtain NH2-rGO.

[0067] Se and N2H4·H2O were mixed uniformly at a ratio of 0.41 g:15 mL to obtain a Se solution for later use;

[0068] Weigh: 1g NH2-rGO and 3g Na2MoO4·2H2O were added to 20mL deionized water. After ultrasonic treatment for 30min, 20mL Se solution was added and stirred at 25℃ for 1h. The mixed solution was then transferred to a polytetrafluoroethylene-lined hydrothermal reactor and maintained at 200℃ for 24h. After the reaction was completed, it was cooled to room temperature and transferred to a vacuum drying oven. It was dried at 60℃ for 12h to obtain NH2-rGO / MoSe2.

[0069] S5. Preparation of modified nylon

[0070] Weigh: 1g dopamine hydrochloride and 2mL deionized water are added to a nitrogen-protected reactor, the reactor is heated to 85°C, stirred until the dopamine hydrochloride is completely dissolved, 10g hexamethylenediamine and 6g adipic acid are added to the reactor, stirred for 25min, 0.5mol / L sodium hydroxide solution is added dropwise to the reactor until the pH is neutral, the reactor is sealed, the reactor heat exchange medium is heated to 140°C, and the reaction is kept warm for 0.5h, the reactor heat exchange medium is heated to 250°C again, and the reaction is kept warm for 4h. After the reaction is completed, the material is discharged while hot, the reactant is cooled to room temperature, crushed, and the product is washed 3 times with deionized water, transferred to a vacuum drying oven, and dried at 80°C for 12h to obtain modified nylon.

[0071] S6. Preparation of polyurethane material

[0072] The auxiliary additives consist of 10 parts of curing agent, 1 part of antioxidant and 4 parts of plasticizer;

[0073] Weigh 90 parts of modified polyurethane in parts by weight and add them into an internal mixer. Melt the modified polyurethane at 100°C, then add 4 parts of NH2-rGO / MoSe2 and react for 17 minutes. Finally, add 12 parts of modified nylon and 2 parts of auxiliary additives, heat to 250°C and react for 15 minutes, then discharge to obtain a polyurethane material.

[0074] Example 3

[0075] This embodiment provides a method for preparing a highly wear-resistant polyurethane material for screen plate processing, comprising the following steps:

[0076] S1. Preparation of hydroxyl-terminated polysiloxane

[0077] Weigh: 100g octamethylcyclotetrasiloxane, 50g trifluoropropyltrimethylcyclotrisiloxane and 4g tetramethyltetraenylcyclotetrasiloxane are added to the reactor, stirred for 30min under a nitrogen atmosphere at 90°C, and then heated to 110°C. 0.01g tetramethylammonium hydroxide and 0.29mL capping agent H2O are added, and the reaction is continued for 3h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, 50mL deionized water is added to the reactor, stirred and dispersed for 30min, and allowed to stand. The upper layer liquid is washed three times with deionized water and then transferred to a rotary evaporator with a water bath temperature of 90°C. Low boiling substances are evaporated under reduced pressure to obtain hydroxyl-terminated polysiloxane.

[0078] S2. Preparation of flame-retardant polyester

[0079] Weigh: 5g of phthalic anhydride, 2g of diphenyl phosphate and 3g of ethylene glycol are added to a reactor. In a nitrogen atmosphere, the temperature is raised to 120°C. After the reaction is kept warm for 1 hour, the temperature is gradually raised to 180°C. 0.1g of stannous octoate is added as a catalyst and the reaction is carried out for 3 hours. The system temperature is then raised to 230°C and maintained for 2 hours. After the material is discharged while hot, it is cooled and solidified, and crushed to obtain flame-retardant polyester.

[0080] S3. Preparation of modified polyurethane

[0081] Weigh: 100 mL of polytetramethylene glycol, 20 g of hydroxyl-terminated polysiloxane, 30 g of flame-retardant polyester and 2 mL of dibutyltin dilaurate are added to a reactor containing 300 mL of N, N-dimethylformamide and stirred. After heating to 100 ° C, the amount of diphenylmethane diisocyanate added is calculated as 0.55 times the total molar amount of oxygen-containing functional groups in polytetramethylene glycol, hydroxyl-terminated polysiloxane and flame-retardant polyester, and added to the reactor. After keeping the temperature for 3 hours, 5 g of diphenylmethane diisocyanate is added. 3,3'-dichloro-4,4'-diaminodiphenylmethane, add 3g of end-capping agent glycidyl ether to the reactor, keep warm and react for 60min, reduce the temperature of the reactor to room temperature, add 1500mL of deionized water to the reactor, stir and disperse for 50min, filter, wash the filter cake with purified water three times and then dry it, transfer the filter cake to a drying oven at 80℃, dry it to constant weight, and obtain modified polyurethane.

[0082] S4. Preparation of NH2-rGO / MoSe2

[0083] Weigh: 0.25g of graphene oxide was added to 25mL of anhydrous ethanol and ultrasonically dispersed for 2h. 3mL of deionized water, 0.25mL of acetic acid and 1g of γ-aminopropyltriethoxysilane were added to the reactor and the temperature was raised to 78℃ for reaction for 12h. After the reaction was completed, the temperature of the reactor was lowered to room temperature. The product was washed once with ethanol and then washed three times with deionized water. Finally, it was transferred to a vacuum drying oven and dried at 60℃ for 12h to obtain NH2-rGO.

[0084] Se and N2H4·H2O were mixed uniformly at a ratio of 0.41 g:15 mL to obtain a Se solution for later use;

[0085] Weigh: 1g NH2-rGO and 3g Na2MoO4·2H2O were added to 20mL deionized water. After ultrasonication for 30min, 20mL Se solution was added and stirred at 30℃ for 1h. The mixed solution was then transferred to a polytetrafluoroethylene-lined hydrothermal reactor and maintained at 200℃ for 24h. After the reaction was completed, it was cooled to room temperature and transferred to a vacuum drying oven. It was dried at 60℃ for 12h to obtain NH2-rGO / MoSe2.

[0086] S5. Preparation of modified nylon

[0087] Weigh: 1g dopamine hydrochloride and 2mL deionized water are added to a nitrogen-protected reactor, the reactor is heated to 90°C, stirred until the dopamine hydrochloride is completely dissolved, 10g hexamethylenediamine and 6g adipic acid are added to the reactor, stirred for 30min, 0.5mol / L sodium hydroxide solution is added dropwise to the reactor until the pH is neutral, the reactor is sealed, the reactor heat exchange medium is heated to 150°C, and the reaction is kept warm for 1h, the reactor heat exchange medium is heated to 260°C again, and the reaction is kept warm for 5h. After the reaction is completed, the material is discharged while hot, the reactant is cooled to room temperature, crushed, and the product is washed 3 times with deionized water, transferred to a vacuum drying oven, and dried at 80°C for 12h to obtain modified nylon.

[0088] S6. Preparation of polyurethane material

[0089] The auxiliary additives consist of 12 parts of curing agent, 2 parts of antioxidant and 5 parts of plasticizer;

[0090] Weigh by weight: 100 parts of modified polyurethane are added to an internal mixer, the modified polyurethane is melted at 110°C, then 5 parts of NH2-rGO / MoSe2 are added and reacted for 20 minutes, finally 15 parts of modified nylon and 3 parts of auxiliary additives are added, the temperature is raised to 260°C, the reaction is carried out for 20 minutes, and the material is discharged to obtain a polyurethane material.

[0091] Comparative Example 1

[0092] The difference between this comparative example and Example 3 is that in step S1, trifluoropropyltrimethylcyclotrisiloxane is not added.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 3 is that step S2 is omitted and flame-retardant polyester is not added in S3.

[0095] Comparative Example 3

[0096] The difference between this comparative example and Example 3 is that step S4 is eliminated and NH2-rGO / MoSe2 in step S6 is replaced by graphene oxide.

[0097] Comparative Example 4

[0098] The difference between this comparative example and Example 3 is that in step S5, dopamine hydrochloride is not added.

[0099] Performance testing:

[0100] The hardness, tensile strength, tear strength, and relative volume wear of a highly wear-resistant polyurethane material for sieve plate processing prepared in Examples 1-3 and Comparative Examples 1-4 were measured with reference to the standard GB / T 33091-2016 "Polyurethane Sieve Plate";

[0101] The vertical burning rating of a highly wear-resistant polyurethane material for screen plate processing prepared in Examples 1-3 and Comparative Examples 1-4 was determined with reference to the standard T / SHPTA 015-2021 "Flame Retardant Thermoplastic Polyurethane Elastomer Cable Material". The specific test results are shown in Table 1 below:

[0102] Table 1-Performance test data of the sample

[0103]

[0104] Data Analysis:

[0105] The data in Table 1 above are compared and analyzed. The highly wear-resistant polyurethane material for screen plate processing prepared by the present invention has a hardness of 95.7 Shore A, a tensile strength of 52.3 MPa, a tear strength of 95.8 MPa, and a relative volume wear of 8.4 mm. 3 , the vertical combustion level is V0;

[0106] Comparative Example 1-2 Compared with Example 3, the hydroxyl-terminated polysiloxane is blended with polytetramethylene glycol by introducing siloxy bonds and trifluoropropyl side chains, and then cross-linked by isocyanate groups to form a "rigid-flexible block" network structure, thereby improving the material hardness to 95.7 Shore A, tensile strength to 52.3 MPa, and tear strength to 95.8 MPa. At the same time, the flame-retardant polyester improves the vertical flammability rating from V2 to V0 through a phosphorus-nitrogen synergistic flame retardant mechanism;

[0107] Comparative Example 3 Compared with Example 3, in the NH2-rGO / MoSe2 nanohybrid filler, the two-dimensional sheets of NH2-rGO are combined with the polyurethane segments through hydrogen bonds to form urea bonds to inhibit agglomeration. The MoSe2 nanosheets act as "molecular bearings" to reduce the friction coefficient to 0.21, and the relative volume wear is as low as 8.4 mm³, which is more than 40% lower than that of traditional polyurethane. In addition, the conjugated structure improves thermal conductivity and avoids local overheating.

[0108] Compared with Example 3, in Comparative Example 4, the modified nylon forms a urea bond through the reaction of the amino group of dopamine with the isocyanate group of polyurethane, and the catechol structure is oxidized and self-polymerized to form a cross-linked network, which increases the tensile strength and tear strength to 52.3 MPa and 95.8 MPa. At the same time, the nitrogen element and the phosphorus element of the flame-retardant polyester form a "nitrogen-phosphorus synergism", ensuring that the vertical burning grade stably reaches the V0 level.

[0109] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A highly wear-resistant polyurethane material for screen plate processing, characterized in that: The invention comprises the following components in parts by weight: 80-100 parts of modified polyurethane, 3-5 parts of NH2-rGO / MoSe2, 10-15 parts of modified nylon and 2-3 parts of auxiliary additives; The auxiliary additives include the following components in parts by weight: 8-12 parts of a curing agent, 1-2 parts of an antioxidant, and 3-5 parts of a plasticizer; The preparation method of the modified polyurethane comprises: adding polytetramethylene glycol, hydroxyl-terminated polysiloxane, flame-retardant polyester and a catalyst into a reaction kettle containing N,N-dimethylformamide, stirring and mixing, then adding diphenylmethane diisocyanate and a chain extender, and finally adding a blocking agent after the reaction is completed, and performing post-processing to obtain the modified polyurethane; The modified nylon preparation method comprises: adding dopamine hydrochloride and deionized water into a reactor, stirring until the dopamine hydrochloride is completely dissolved, adding hexamethylenediamine and adipic acid into the reactor, dripping sodium hydroxide solution therein until the pH is neutral, and post-treating to obtain the modified nylon; The preparation method of the hydroxyl-terminated polysiloxane is as follows: octamethylcyclotetrasiloxane, trifluoropropyltrimethylcyclotrisiloxane and tetramethyltetraenylcyclotetrasiloxane are added to a reaction kettle, stirred for 30 minutes under a nitrogen atmosphere at 90°C, and then heated to 110°C, tetramethylammonium hydroxide and a capping agent H2O are added, and the reaction is continued for 3 hours, followed by post-treatment to obtain the hydroxyl-terminated polysiloxane; The flame-retardant polyester is prepared by adding phthalic anhydride, diphenyl phosphate and ethylene glycol to a reactor in a nitrogen atmosphere, heating the reactor to 120-140°C, maintaining the temperature for reaction for 1-2 hours, then gradually heating the reactor to 180-220°C, adding a catalyst, reacting the reactor for 3-5 hours, and then increasing the system temperature to 230-260°C and maintaining the temperature for 2-4 hours to obtain the flame-retardant polyester. The NH2-rGO / MoSe2 is prepared by the following steps: A1. Add graphene oxide to anhydrous ethanol and ultrasonically disperse for 2 h. Add deionized water, acetic acid and silane coupling agent to the reactor and heat to 78 °C for 12 h to obtain NH2-rGO. A2. NH2-rGO and Na2MoO4·2H2O were added to deionized water, ultrasonicated for 30 min, and then Se solution was added. The mixture was stirred at 20-30°C for 1 h. The mixed solution was then transferred to a polytetrafluoroethylene-lined hydrothermal reactor and maintained at 200°C for 24 h. NH2-rGO / MoSe2 was obtained by post-treatment.

2. The highly wear-resistant polyurethane material for screen plate processing according to claim 1, characterized in that: In the preparation of the modified polyurethane, the dosage ratio of the polytetramethylene ether glycol, hydroxyl-terminated polysiloxane, flame-retardant polyester, catalyst, N,N-dimethylformamide, chain extender, and end-capping agent is 100 mL:10-20 g:20-30 g:1-2 mL:300 mL:3-5 g:2-3 g, the added amount of the diphenylmethane diisocyanate is 0.55 times the total molar amount of oxygen-containing functional groups in the polytetramethylene ether glycol, hydroxyl-terminated polysiloxane, and flame-retardant polyester molecules, the catalyst is dibutyltin dilaurate, the chain extender is 3,3'-dichloro-4,4'-diaminodiphenylmethane, and the end-capping agent is glycidol.

3. The highly wear-resistant polyurethane material for screen plate processing according to claim 1, characterized in that: In the preparation of the modified nylon, the usage ratio of hexamethylenediamine, adipic acid, dopamine hydrochloride and deionized water is 10g:6g:1g:2mL, and the concentration of the sodium hydroxide solution is 0.5mol / L.

4. The highly wear-resistant polyurethane material for screen plate processing according to claim 1, characterized in that: The usage ratio of the octamethylcyclotetrasiloxane, trifluoropropyltrimethylcyclotrisiloxane, tetramethyltetraenylcyclotetrasiloxane, tetramethylammonium hydroxide and the capping agent H2O is 100 g:50 g:4 g:0.01 g:0.29 mL.

5. The highly wear-resistant polyurethane material for screen plate processing according to claim 1, characterized in that: The mass ratio of the phthalic anhydride, diphenyl phosphate, ethylene glycol and catalyst is 5:2:3:0.1, and the catalyst is stannous octoate.

6. The highly wear-resistant polyurethane material for screen plate processing according to claim 1, characterized in that: In step A1, the amount ratio of the graphene oxide, anhydrous ethanol, deionized water, acetic acid and silane coupling agent is 0.25 g:25 mL:3 mL:0.25 mL:1 g, and the silane coupling agent is γ-aminopropyltriethoxysilane; in step A2, the amount ratio of the NH2-rGO, Na2MoO4·2H2O, deionized water and Se solution is 1 g:3 g:20 mL:20 mL, and the Se solution is obtained by uniformly mixing Se and N2H4·H2O in a ratio of 0.41 g:15 mL.

7. The method for preparing a highly wear-resistant polyurethane material for screen plate processing according to any one of claims 1 to 6, characterized in that: The preparation method of the highly wear-resistant polyurethane material for screen plate processing comprises: adding modified polyurethane into an internal mixer, melting the modified polyurethane at 90-110° C., then adding NH2-rGO / MoSe2 and reacting for 15-20 minutes, finally adding modified nylon and auxiliary additives, heating to 240-260° C. and reacting for 10-20 minutes, and discharging to obtain the polyurethane material.

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