Preparation method of heat-insulating polyurethane material and synthetic leather

Abstract

This invention provides a method for preparing a thermally insulating polyurethane material and a synthetic leather. The preparation method includes: using basalt nanofibers with a diameter of 50-100 nm and a length of 1-2 μm as raw materials, and subjecting them to acid activation treatment, aminosilane coupling treatment, and carboxylation treatment to obtain carboxylated fibers; subjecting the carboxylated fibers to an esterification reaction with a small molecule diol to obtain a basalt-modified polyol with hydroxyl reaction ends; and subjecting the basalt-modified polyol as part of the hydroxyl-containing component to a polymerization reaction with a polyester polyol, diisocyanate, and a chain extender to obtain the thermally insulating polyurethane material; wherein the content of basalt nanofibers is 0.1%-5% of the total solid phase mass of the thermally insulating polyurethane material. When this thermally insulating polyurethane material is used as an intermediate layer in synthetic leather, it can improve the heat storage and insulation capacity of the synthetic leather.

Description

Technical Field

[0001] This invention relates to the field of polyurethane resin technology, specifically to a method for preparing thermal insulation polyurethane material and synthetic leather. Background Technology

[0002] Existing polyurethane synthetic leather typically consists of a base fabric, a bottom adhesive layer, an intermediate functional layer, and a surface finishing layer. When conventional polyurethane resin is used in the intermediate functional layer, although it can meet basic flexibility and film-forming requirements, its heat storage and insulation capabilities are limited. Summary of the Invention

[0003] The purpose of this invention is to overcome the problem of limited heat storage and insulation capacity of existing polyurethane synthetic leather middle layer materials, and to provide a method for preparing a heat-insulating polyurethane material and a synthetic leather containing the heat-insulating polyurethane material, which can improve the heat storage and insulation capacity of synthetic leather.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: In at least one embodiment, the present invention provides a method for preparing a thermal insulation polyurethane material, the method comprising: using basalt nanofibers with a diameter of 50-100 nm and a length of 1-2 μm as raw materials, subjecting them to acid activation treatment, aminosilane coupling treatment, and carboxylation treatment to obtain carboxylated fibers; subjecting the carboxylated fibers to an esterification reaction with a small molecule diol to obtain a basalt-modified polyol with hydroxyl reaction ends; and subjecting the basalt-modified polyol as part of the hydroxyl-containing component to a polymerization reaction with a polyester polyol, diisocyanate, and a chain extender to obtain the thermal insulation polyurethane material; wherein the content of the basalt nanofibers is 0.1%-5% of the total solid phase mass of the thermal insulation polyurethane material.

[0005] In the aforementioned design, basalt nanofibers are incorporated into the polyurethane resin. As an inorganic filler, basalt nanofibers can increase interfacial barrier properties during heat transfer within the polyurethane material and alter the heat transfer path within the continuous resin phase, thereby reducing the overall heat transfer capacity of the material and improving its thermal insulation capabilities. However, the applicant discovered that when basalt nanofibers are directly mixed into the polyurethane material, their large specific surface area makes them prone to local aggregation due to their high surface energy, leading to interfacial defects during coating, film formation, and stress application. Therefore, this solution first performs acid activation treatment on basalt nanofibers with specific physical parameters, which helps expose active sites on the fiber surface; aminosilane coupling treatment improves the bonding state between the fiber surface and the organic reaction environment; and carboxylation treatment further forms carboxyl groups on the fiber surface that can be used for esterification. Through these steps, the basalt nanofibers are transformed from a conventional dispersed reinforcing phase into a reactive modified component that can be utilized in subsequent polyurethane polymerization.

[0006] Subsequently, the carboxylated fibers were esterified with a small-molecule diol, causing the carboxyl groups on the fiber surface to react with the hydroxyl groups in the small-molecule diol, forming a structure with hydroxyl reaction ends on the fiber surface, thus obtaining a basalt-modified polyol. This basalt-modified polyol retains the inorganic fiber characteristics of basalt nanofibers while also possessing hydroxyl ends capable of participating in polyurethane polymerization. Then, through polymerization, the basalt nanofibers participate in the formation of the polyurethane material through their surface reaction ends. In this way, the relationship between the basalt nanofibers and the continuous polyurethane phase no longer relies primarily on physical contact or simple wetting, but rather forms a more stable interfacial bond during polymerization, thereby reducing the possibility of basalt nanofibers re-aggregating, settling, or forming localized defects in the resin system.

[0007] More importantly, the basalt nanofiber content is limited to 0.1%-5% of the total solid phase mass of the thermal insulation polyurethane material. In systems where basalt nanofibers are typically used as conventional inorganic fillers, higher addition amounts more readily exhibit significant physical reinforcement or thermal insulation effects. In this scheme, the basalt nanofibers, after surface reactive treatment, participate in polyurethane polymerization in the form of basalt-modified polyols. A relatively small amount of basalt nanofibers can form a relatively stable interfacial barrier and heat transfer path regulation effect in the intermediate layer. Simultaneously, the 0.1%-5% content range is beneficial for balancing heat storage and insulation capacity, dispersion stability, coating leveling, and film formation stability. Within the intermediate content range, the improvement in thermal insulation effect and mechanical properties is more pronounced.

[0008] In the preparation method disclosed in at least one embodiment, preferably, the basalt nanofibers are obtained from basalt protofibers by wet ball milling and centrifugal classification; the wet ball milling uses anhydrous ethanol as the milling medium and zirconia balls as the grinding medium, the ball-to-material mass ratio is 10:1-15:1, the ball milling speed is 400-500 rpm, and the ball milling time is 6-8 h; the centrifugal classification includes first centrifuging at 1500-2000 rpm for 10 min and taking the supernatant, then centrifuging at 8000-10000 rpm for 10-15 min and collecting the target fibers.

[0009] In the above design, wet ball milling can reduce the risk of local heat accumulation and scattering during fiber pulverization in a liquid medium, while centrifugal classification can remove excessively long fibers and coarse particles, making the collected basalt nanofibers closer to the target diameter and length range. Fibers with more stable size distribution are beneficial for subsequent acid activation, coupling, and carboxylation reactions to proceed more uniformly on the fiber surface, and also help reduce scratches, agglomeration, and local defects caused by coarse particles or long fibers during the coating process.

[0010] In the preparation method disclosed in at least one embodiment, preferably, the acid activation treatment uses 0.3-0.8 mol / L hydrochloric acid, the solid-liquid ratio of the basalt nanofibers to the hydrochloric acid is 1 g:(15-25) mL, the treatment temperature is 55-65℃, and the treatment time is 0.5-1.5 h; the aminosilane coupling treatment uses γ-aminopropyltriethoxysilane, and the amount of γ-aminopropyltriethoxysilane used is 1%-4% of the mass of the basalt nanofibers.

[0011] In the above design, acid activation treatment cleans and activates the surface of basalt nanofibers, making the subsequent aminosilane coupling treatment more stable. After hydrolysis, γ-aminopropyltriethoxysilane can form silicon-oxygen bonds on the fiber surface and improve the interaction between the fiber surface and the subsequent organic reaction environment through its organic ends. This treatment makes the formation of subsequent carboxyl sites and hydroxyl reaction ends more controllable.

[0012] In the preparation method disclosed in at least one embodiment, preferably, the aminosilane coupling treatment includes: adding the γ-aminopropyltriethoxysilane to a mixture of ethanol and water for pre-hydrolysis, wherein the volume ratio of ethanol to water is (90-98):(2-10), and the pre-hydrolysis pH is 4.5-5.0; then adding acid-activated basalt nanofibers and treating at 55-65℃ for 1.5-2.5h.

[0013] In the above design, the mixture of ethanol and water and the weakly acidic pre-hydrolysis conditions are beneficial for controlling the hydrolysis and condensation rates of silanes, reducing the ineffective consumption caused by the excessively rapid polycondensation of silanes themselves. Contacting the pre-hydrolyzed coupling agent with the acid-activated basalt nanofibers can improve the uniformity of the coupling treatment on the fiber surface, thus providing a stable surface foundation for subsequent oxidative carboxylation treatment.

[0014] In the preparation method disclosed in at least one embodiment, preferably, the carboxylation treatment uses an ammonium persulfate aqueous solution with a concentration of 35-55 g / L, and the pH is adjusted to 2.5-3.0 with dilute sulfuric acid; the solid-liquid ratio of the carboxylation treatment is 1 g:(40-60) mL, the treatment temperature is 65-75℃, and the treatment time is 90-130 min; the acid value of the carboxylated fiber is 30-50 mg KOH / g.

[0015] In the above design, the acidic ammonium persulfate system can introduce carboxyl sites onto the surface of the coupled basalt nanofibers. The acid value range is used to limit the number of carboxyl groups available for subsequent esterification reactions. Insufficient carboxyl sites result in an insufficient number of basalt-modified polyols formed by subsequent diol esterification; excessive carboxylation increases the surface reaction and washing burden on the fibers, also affecting the stability of the subsequent polymerization system. Controlling the acid value between 30-50 mg KOH / g is beneficial for balancing esterification grafting efficiency and material preparation stability.

[0016] In the preparation method disclosed in at least one embodiment, preferably, the small molecule diol includes at least one of 1,4-butanediol, neopentyl glycol, ethylene glycol, and diethylene glycol; the molar ratio of the carboxyl groups on the surface of the carboxylated fiber to the hydroxyl groups of the small molecule diol is 1:1.05-1:1.20.

[0017] In the above design, the small-molecule diol can undergo esterification with the carboxyl groups on the surface of the carboxylated fiber, while retaining the hydroxyl end that can participate in the isocyanate reaction. A moderate excess of hydroxyl groups relative to carboxyl groups is beneficial for improving the conversion degree of the carboxyl group reaction and ensuring that the resulting basalt-modified polyol retains its ability to participate in polyurethane polymerization as a hydroxyl-containing component. 1,4-Butanediol has good compatibility with the subsequent chain extension system, while neopentyl glycol, ethylene glycol, and diethylene glycol can be used to adjust the chain segment rigidity, hydrolysis resistance, or flexibility.

[0018] In the preparation method disclosed in at least one embodiment, preferably, the esterification reaction is carried out under nitrogen protection and in the presence of an organotin catalyst, at a reaction temperature of 160-180°C, for a reaction time of 2.5-3.5 h, and dehydrated under a negative pressure of 20-40 kPa; the basalt-modified polyol has a hydroxyl value of 60-120 mg KOH / g and a water content of not more than 0.10%.

[0019] In the above design, nitrogen protection helps reduce oxidation side reactions during high-temperature esterification, organotin catalysts improve the esterification efficiency between carboxyl and hydroxyl groups, and negative pressure dehydration promotes the esterification reaction and reduces residual moisture in the system. Controlling the hydroxyl value of the basalt-modified polyol to 60-120 mgKOH / g allows it to participate in the subsequent polyurethane polymerization as a hydroxyl-containing component. Maintaining the water content at no more than 0.10% helps reduce bubbles and viscosity abnormalities caused by side reactions between water and isocyanate.

[0020] In the preparation method disclosed in at least one embodiment, preferably, the polymerization reaction includes: dispersing the polyester polyol and the basalt-modified polyol in a reaction solvent after dehydration; adding diisocyanate and prepolymerizing at 75-80°C for 1.5-2 hours; adding chain extender and polymerization catalyst and reacting at 70-75°C for 3-3.5 hours; wherein the molar ratio of isocyanate groups to hydroxyl groups in the polymerization reaction is 1.03-1.12.

[0021] In the above design, the polyester polyol and basalt-modified polyol are first dehydrated and dispersed in the reaction solvent, which helps reduce water side reactions and improve the distribution of fiber-containing reactive components before polymerization. The prepolymerization stage allows the diisocyanate and hydroxyl-containing components to form a prepolymer structure, and the chain extension stage further increases the chain segments and adjusts the material's strength and flexibility. The NCO / OH molar ratio is controlled at 1.03-1.12, which helps to balance the stability of the chain segment structure and the mechanical performance after coating.

[0022] In the preparation method disclosed in at least one embodiment, preferably, the polyester polyol is polybutylene adipate polyol, the diisocyanate is diphenylmethane diisocyanate, and the chain extender is 1,4-butanediol; the reaction solvent includes N,N-dimethylformamide and toluene, and the volume ratio of N,N-dimethylformamide to toluene is (6-8):(2-4); the polymerization catalyst includes dibutyltin dilaurate, and the amount of dibutyltin dilaurate is 0.05%-0.15% of the mass of the resin solid component; the solid content of the thermal insulation polyurethane material is 50%-55%, and the viscosity at 23-27°C is 15000-30000 mPa·s.

[0023] In the above design, polybutylene adipate polyol, diphenylmethane diisocyanate, and 1,4-butanediol can form a polyurethane matrix structure suitable for use as an interlayer in synthetic leather; the mixed solvent of N,N-dimethylformamide and toluene is beneficial for balancing dissolution, dispersion, and evaporation during application; the dosage range of dibutyltin dilaurate is beneficial for controlling the polymerization rate. Matching the solids content and viscosity range with the interlayer coating application helps reduce sagging due to excessively low viscosity or leveling difficulties due to excessively high viscosity.

[0024] In at least one embodiment, the present invention also provides a synthetic leather comprising a base fabric, a bottom layer, an intermediate layer and a top layer arranged sequentially; the intermediate layer comprises a thermally insulating polyurethane material prepared by any of the above preparation methods, and the dry film thickness of the intermediate layer is 0.20-0.35 mm.

[0025] In the above design, the intermediate layer of the synthetic leather is the aforementioned heat-insulating polyurethane material, thus giving the synthetic leather excellent heat storage and insulation capabilities. An intermediate layer dry film thickness of 0.20-0.35 mm is beneficial for providing sufficient insulation performance while avoiding excessive coating thickness that could adversely affect flexibility and film-forming efficiency. The bottom layer is used to reinforce the bond with the base fabric, and the top layer provides abrasion resistance and surface protection. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are preferred embodiments of the present invention and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise expressly defined, the use of terms such as "first," "second," or "third" in the claims and description of this invention is for distinguishing different objects, not for describing a specific order.

[0028] In the claims and description of this invention, the terms "comprising," "having," and variations thereof are used to mean "including but not limited to."

[0029] The following embodiments are used to illustrate the technical solution of the present invention. Those skilled in the art can adjust the source of raw materials, conventional equipment models, and conventional post-processing methods without changing the technical concept of the present invention. Unless otherwise specified, all parts below are parts by weight, and all percentages are percentages by weight.

[0030] In this embodiment, the thermal insulation polyurethane material includes basalt nanofiber grafted and modified polyurethane resin. The total solid mass refers to the total mass of the non-volatile solid components in the thermal insulation polyurethane material, including the polyurethane resin solid component and the basalt nanofibers introduced by the basalt-modified polyol. The content of basalt nanofibers is calculated as the proportion of the mass of basalt nanofibers to the total solid mass of the thermal insulation polyurethane material.

[0031] In one embodiment, the method for preparing the thermal insulation polyurethane material includes the following steps: Basalt nanofibers with a diameter of 50-100 nm and a length of 1-2 μm were used as raw materials. After acid activation treatment, aminosilane coupling treatment and carboxylation treatment, carboxylated fibers were obtained. The carboxylated fibers were esterified with small molecule diols to obtain basalt-modified polyols with hydroxyl reaction ends. The basalt-modified polyol, as part of the hydroxyl-containing component, is polymerized with polyester polyol, diisocyanate, and chain extender to obtain the thermal insulation polyurethane material. The content of the basalt nanofibers is 0.1%-5% of the total solid mass of the thermal insulation polyurethane material.

[0032] Specifically, the preparation method of this thermal insulation polyurethane material may include the following specific steps: S10, Preparation of basalt nanofibers. Basalt protofibers were cut to 2-5 mm and dried in a hot air drying oven at 80℃ for 4 h. The dried basalt protofibers were added to a ball mill jar, anhydrous ethanol was added to form a flowable slurry, and zirconia balls were added as the grinding medium. The mass ratio of zirconia balls to basalt protofibers was controlled at 10:1-15:1. After sealing the ball mill jar, wet ball milling was performed at 400-500 rpm for 6-8 h; a 10-min pause was taken every 30 min during the ball milling process. After ball milling, the slurry was transferred to a centrifuge tube, centrifuged at 1500-2000 rpm for 10 min, and the supernatant was collected; then the supernatant was centrifuged at 8000-10000 rpm for 10-15 min, and the sediment was collected. The sediment was washed sequentially with anhydrous ethanol and deionized water, and then vacuum dried at 60-80℃ until no obvious free liquid was found, yielding basalt nanofibers with a diameter of 50-100 nm and a length of 1-2 μm.

[0033] S20, acid activation treatment. The basalt nanofibers obtained in step S10 are added to a reaction vessel equipped with stirring and temperature control. A portion of hydrochloric acid is added first, and stirring is started to disperse the fibers in the acid solution before the remaining hydrochloric acid is added. The hydrochloric acid concentration is 0.3-0.8 mol / L, and the solid-liquid ratio of basalt nanofibers to hydrochloric acid is 1 g:(15-25) mL. The system temperature is controlled at 55-65℃, and the treatment time is 0.5-1.5 h. After treatment, the fibers are separated by centrifugation or filtration, and washed several times with deionized water until the pH of the filtrate reaches 6.5-7.0. The filtrate is then vacuum dried at 80℃ for 6 h to obtain acid-activated basalt nanofibers.

[0034] S30, aminosilane coupling treatment is performed. γ-aminopropyltriethoxysilane is added to a mixture of ethanol and water at a volume ratio of (90-98):(2-10). The pH of the pre-hydrolysis system is adjusted to 4.5-5.0 with glacial acetic acid, and the mixture is stirred for 30 min for pre-hydrolysis. The amount of γ-aminopropyltriethoxysilane used is 1%-4% of the mass of the basalt nanofibers. The acid-activated basalt nanofibers obtained in step S20 are added to the pre-hydrolyzed silane solution, ultrasonically dispersed for 10-20 min, and then the system temperature is controlled at 55-65℃ and stirred for 1.5-2.5 h. After treatment, the fibers are collected by centrifugation or filtration, washed with ethanol, and then vacuum dried at 80℃ for 8-12 h to obtain aminosilane-coupled fibers.

[0035] S40, carboxylation treatment. The aminosilane-coupled fibers obtained in step S30 are added to an ammonium persulfate aqueous solution with a concentration of 35-55 g / L, and the pH of the system is adjusted to 2.5-3.0 with dilute sulfuric acid. The solid-liquid ratio of the aminosilane-coupled fibers to the ammonium persulfate aqueous solution is 1 g:(40-60) mL. After stirring, the system temperature is controlled at 65-75℃, and the treatment is carried out for 90-130 min. After the reaction is completed, the fibers are collected by centrifugation or filtration, washed with deionized water until the washing solution is neutral, and then vacuum dried at 60℃ for 12 h to obtain carboxylated fibers. The acid value of the obtained carboxylated fibers is 30-50 mgKOH / g.

[0036] S50, Preparation of Basalt-Modified Polyol. Based on the acid value of the carboxylated fiber obtained in step S40, the molar amount of carboxyl groups is calculated. The carboxylated fiber and a small-molecule diol are added to an esterification reaction vessel equipped with a stirrer, thermometer, condenser, and vacuum dehydration interface. The molar ratio of carboxyl groups on the surface of the carboxylated fiber to hydroxyl groups of the small-molecule diol is 1:1.05-1:1.20. The small-molecule diol is at least one selected from 1,4-butanediol, neopentyl glycol, ethylene glycol, and diethylene glycol. Nitrogen gas is introduced into the reaction vessel to replace the air, and an organotin catalyst is added. The amount of organotin catalyst is 0.05%-0.10% of the total mass of the carboxylated fiber and the small-molecule diol. Under nitrogen protection, the system is heated to 160℃ and reacted for 1 h, then heated to 175℃ and reacted for 2-2.5 h. During the reaction, the absolute pressure of the system is controlled at 20-40 kPa to remove generated water and some free small-molecule diol. The esterification reaction endpoint was defined as an acid value not exceeding 8 mgKOH / g, or an acid value change of less than 0.5 mgKOH / g within 30 minutes. After the reaction, the mixture was cooled under nitrogen protection to obtain basalt-modified polyols with hydroxyl groups. The obtained basalt-modified polyols had hydroxyl values ​​of 60-120 mgKOH / g and a water content not exceeding 0.10%.

[0037] S60, proceed with the polymerization reaction. The polyester polyol and the basalt-modified polyol obtained in step S50 are added to a polymerization reactor equipped with stirring, temperature control, vacuum, and nitrogen protection, and dehydrated at 100-110℃ and -0.09 MPa for 1-2 h. After dehydration, the temperature is lowered, and the polyester polyol and basalt-modified polyol are dispersed in a reaction solvent, which includes N,N-dimethylformamide and toluene, with a volume ratio of N,N-dimethylformamide to toluene of 7:3. The molar amount of hydroxyl groups in each hydroxyl-containing component is calculated based on its mass and hydroxyl value, and the molar amount of isocyanate groups in the diisocyanate is calculated based on its mass and NCO content, so that the molar ratio of isocyanate groups to hydroxyl groups in the polymerization reaction is 1.03-1.12.

[0038] Under nitrogen protection, diisocyanate was added to the polymerization reactor and prepolymerized at 75-80℃ for 1.5-2 h. Subsequently, a chain extender and polymerization catalyst were added, and the reaction was carried out at 70-75℃ for 3-3.5 h. The polyester polyol was polybutylene adipate polyol, the diisocyanate was diphenylmethane diisocyanate, the chain extender was 1,4-butanediol, and the polymerization catalyst included dibutyltin dilaurate. The amount of dibutyltin dilaurate was 0.05%-0.15% of the resin solids component mass. After the reaction, the solid content was adjusted by the reaction solvent to obtain the thermal insulation polyurethane material. The solid content of this thermal insulation polyurethane material was 50%-55%, and the viscosity at 25℃ was 15000-30000 mPa·s; the content of basalt nanofibers was 0.1%-5% of the total solid phase mass of the thermal insulation polyurethane material.

[0039] Furthermore, this embodiment also relates to a synthetic leather comprising a base fabric, a bottom layer, a middle layer, and a top layer arranged sequentially. The base fabric is made of polyester microfiber nonwoven or knitted fabric with a thickness of 0.6-1.2 mm. First, a bottom coating liquid is applied to the surface of the base fabric. The bottom coating liquid comprises 100 parts of ordinary polyurethane resin, 30-60 parts of N,N-dimethylformamide, and 0.1-0.5 parts of a leveling agent. After coating, it is dried at 80°C for 2-3 minutes to form a bottom layer with a dry film thickness of 0.05-0.12 mm. Then, the aforementioned thermal insulation polyurethane material is used as the main resin of the intermediate layer coating liquid. 0-30 parts of N,N-dimethylformamide are added to 100 parts of the thermal insulation polyurethane material to adjust the application viscosity. The intermediate layer coating liquid is then applied to the substrate, with a wet film thickness of 0.35-0.55 mm. It is then dried sequentially at 80℃ for 3 min, 100℃ for 3 min, and 120℃ for 2 min, forming an intermediate layer with a dry film thickness of 0.20-0.35 mm. Subsequently, a topcoat liquid is applied to the surface of the intermediate layer. The topcoat liquid comprises 100 parts of polyurethane topcoat resin, 3-8 parts of colorant, 0.5-2 parts of abrasion-resistant additive, and 0.1-0.5 parts of leveling agent. After application, it is dried at 100-130℃ for 5-8 min, forming a topcoat with a dry film thickness of 0.03-0.08 mm, thus obtaining synthetic leather.

[0040] To further illustrate the functional effects of the synthetic leather using the above-prepared thermal insulation polyurethane material as the intermediate layer in this embodiment, the following examples and comparative examples are provided.

[0041] In the following examples and comparative examples, the basalt fiber used was commercially available continuous basalt fiber roving, grade GBF-1, manufactured by Zhejiang Shijin Basalt Fiber Co., Ltd., cut to 2-5 mm before use; alternatively, commercially available chopped basalt fiber yarn could be used as the fiber source. Anhydrous ethanol, hydrochloric acid, dilute sulfuric acid, and ammonium persulfate were commercially available analytical grade reagents. γ-aminopropyltriethoxysilane was silane coupling agent KH-550, grade SG-Si 1100, manufactured by Nanjing Shuguang Chemical Group Co., Ltd. 1,4-Butanediol was BASF 1,4-Butanediol industrial grade; neopentyl glycol could be BASF NPG solid product. Polybutylene adipate polyol was T-44 polyester polyol from Huada Chemical Group Co., Ltd., a polyester polyol based on 1,4-butanediol and adipic acid, with a molecular weight of approximately 2000, a hydroxyl value of 53-59 mgKOH / g, and a moisture content of less than 0.03%. The diisocyanate used was WANNATE MDI-50F from Wanhua Chemical Group Co., Ltd. Dibutyltin dilaurate was used with Evonik DABCO T-12 or KOSMOS T-12 N. N,N-dimethylformamide and toluene were commercially available industrial grade or analytical grade products.

[0042] The common polyurethane resin used for the base and top layers is a commercially available polyurethane resin for synthetic leather. The leveling agent, colorant, and abrasion-resistant additives are commercially available synthetic leather coating additives. In the examples, these additives are used only in the preparation of the synthetic leather base or top layer.

[0043] Example 1 In this embodiment, a thermal insulation polyurethane material with a basalt nanofiber content of 2.00% of the total solid phase mass of the thermal insulation polyurethane material was prepared, and the material was used as the intermediate layer of synthetic leather.

[0044] Basalt protofibrils were cut to 2-5 mm and dried at 80℃ for 4 h. The dried basalt protofibrils were then added to a ball mill jar, anhydrous ethanol was added to form a flowable slurry, and zirconia balls were added at a mass ratio of 12:1 to the basalt protofibrils. Wet milling was performed at 450 rpm for 6 h, with a 10-min pause every 30 min. After milling, the slurry was transferred to a centrifuge tube, centrifuged at 1800 rpm for 10 min and collected the supernatant, then centrifuged at 9000 rpm for 12 min and collected the precipitate. The precipitate was washed with anhydrous ethanol and deionized water and then vacuum dried at 70℃ to obtain basalt nanofibers with a diameter of 50-100 nm and a length of 1-2 μm.

[0045] Basalt nanofibers were added to 0.5 mol / L hydrochloric acid at a solid-liquid ratio of 1 g: 20 mL and stirred at 60 °C for 1 h. After treatment, the fibers were collected, washed with deionized water until the pH of the filtrate was 6.5-7.0, and then vacuum dried at 80 °C for 6 h to obtain acid-activated basalt nanofibers.

[0046] KH-550 was added to a mixture of ethanol and water at a volume ratio of 95:5. The pH was adjusted to 4.5-5.0 with glacial acetic acid, and the mixture was stirred for pre-hydrolysis for 30 min. The amount of KH-550 used was 2% of the mass of the basalt nanofibers. The acid-activated basalt nanofibers were added to the pre-hydrolyzed KH-550 solution, ultrasonically dispersed for 15 min, and then stirred at 60℃ for 2 h. After treatment, the fibers were collected, washed with ethanol, and vacuum dried at 80℃ for 12 h to obtain aminosilane-coupled fibers.

[0047] Aminosilane-coupled fibers were added to a 45 g / L ammonium persulfate aqueous solution, and the pH was adjusted to 2.5-3.0 with dilute sulfuric acid. The solid-liquid ratio was 1 g:50 mL, and the mixture was stirred at 70 °C for 110 min. After treatment, the fibers were collected, washed with deionized water until the washing solution was neutral, and then vacuum dried at 60 °C for 12 h to obtain carboxylated fibers. The acid value of the carboxylated fibers was measured to be 38.6 mg KOH / g.

[0048] The molar amount of carboxyl groups was calculated based on the acid value of the carboxylated cellulose. Carboxylated cellulose and 1,4-butanediol were added to an esterification reaction vessel at a carboxyl to hydroxyl molar ratio of 1:1.05. Dibutyltin dilaurate was added, with the amount being 0.08% of the total mass of the carboxylated cellulose and 1,4-butanediol. Nitrogen gas was introduced into the reaction vessel, and the temperature was raised to 160℃ for 1 h, then raised to 175℃ for 2 h, while maintaining the absolute pressure of the system at 20-40 kPa for dehydration. After the acid value reached no higher than 8 mg KOH / g, the temperature was lowered under nitrogen protection to obtain basalt-modified polyol. The obtained basalt-modified polyol had a hydroxyl value of 80-110 mg KOH / g and a water content no higher than 0.08%.

[0049] Polybutylene adipate polyol and the aforementioned basalt-modified polyol were added to a polymerization reactor and dehydrated at 105℃ and -0.09 MPa for 1.5 h. After dehydration, a mixed solvent of N,N-dimethylformamide and toluene was added, with a volume ratio of N,N-dimethylformamide to toluene of 7:3. The molar amount of hydroxyl groups was calculated based on the hydroxyl values ​​of the polybutylene adipate polyol and the basalt-modified polyol, and WANNATE MDI-50F was weighed according to an NCO / OH molar ratio of 1.08. Nitrogen gas was introduced into the polymerization reactor, and WANNATE MDI-50F was added, and prepolymerization was carried out at 75-80℃ for 1.5-2 h; subsequently, 1,4-butanediol and DABCO T-12 were added, and the reaction was carried out at 70-75℃ for 3-3.5 h. The amount of DABCO T-12 was 0.10% of the mass of the resin solids component. The amount of solvent was adjusted to achieve a resin solid content of approximately 52% and a viscosity of 20,000-25,000 mPa·s at 25°C. The content of basalt nanofibers was controlled by the amount of basalt-modified polyol added, ensuring that the basalt nanofibers accounted for 2.00% of the total solid phase mass of the thermal insulation polyurethane material.

[0050] A polyester microfiber nonwoven fabric with a thickness of approximately 0.8 mm was used as the base fabric. A bottom coating solution was applied to the base fabric, comprising 100 parts of ordinary polyurethane resin, 45 parts of N,N-dimethylformamide, and 0.3 parts of a leveling agent. After coating, it was dried at 80°C for 2.5 min to form a bottom layer with a dry film thickness of 0.08-0.10 mm. 100 parts of the thermal insulation polyurethane material prepared in this embodiment and 15 parts of N,N-dimethylformamide were mixed to prepare an intermediate layer coating solution. This solution was applied to the bottom layer, resulting in a wet film thickness of 0.45 mm. The solution was then sequentially dried at 80°C for 3 min, 100°C for 3 min, and 120°C for 2 min to form an intermediate layer with a dry film thickness of 0.28-0.35 mm. Subsequently, a surface coating liquid is applied, which includes 100 parts of polyurethane surface layer resin, 5 parts of color paste, 1 part of abrasion-resistant additive, and 0.3 parts of leveling agent. After coating, it is dried at 120℃ for 6 minutes to form a surface layer with a dry film thickness of 0.05-0.06 mm, thus obtaining synthetic leather.

[0051] Example 2 The difference between this embodiment and Example 1 is that the amounts of basalt-modified polyol and polybutylene adipate polyol added in the polymerization reaction are adjusted so that the content of basalt nanofibers is 0.10% of the total solid phase mass of the thermal insulation polyurethane material. The amount of diisocyanate added is still calculated based on the actual molar amount of hydroxyl groups and the NCO / OH molar ratio of 1.08. The remaining steps are the same as in Example 1.

[0052] Example 3 The difference between this embodiment and Example 1 is that the amounts of basalt-modified polyol and polybutylene adipate polyol added in the polymerization reaction are adjusted so that the content of basalt nanofibers is 4.95% of the total solid phase mass of the thermal insulation polyurethane material. The amount of diisocyanate added is still calculated based on the actual molar amount of hydroxyl groups and the NCO / OH molar ratio of 1.08. The remaining steps are the same as in Example 1.

[0053] In other embodiments, 1,4-butanediol in the esterification reaction can be wholly or partially replaced by neopentyl glycol, ethylene glycol, or diethylene glycol. When replacing, the molar amount of carboxyl groups is still calculated based on the acid value of the carboxylated fiber, and the molar ratio of carboxyl groups to hydroxyl groups of the small molecule diol is controlled to be 1:1.05-1:1.20. The amount of diisocyanate added in the polymerization reaction is recalculated based on the actual hydroxyl value and NCO content.

[0054] Comparative Example 1 This comparative example prepared a polyurethane material without basalt nanofibers. Basalt-modified polyols were not added during the polymerization reaction; instead, polybutylene adipate polyol, WANNATE MDI-50F, and 1,4-butanediol were used. The amount of diisocyanate added was calculated based on an NCO / OH molar ratio of 1.08. The polymerization temperature, reaction time, catalyst dosage, solid content, viscosity window, and preparation conditions for the synthetic leather bottom layer, intermediate layer, and top layer were all the same as in Example 1.

[0055] Comparative Example 2 This comparative example prepared a 2.00% physically mixed basalt fiber polyurethane material. The basalt nanofibers obtained according to step S10 of Example 1 were directly added to the polyurethane polymerization system without acid activation, aminosilane coupling, carboxylation, or esterification. The content of basalt nanofibers was 2.00% of the total solid mass of the polyurethane material. Polybutylene adipate polyol, WANNATE MDI-50F, and 1,4-butanediol were used in the polymerization reaction, and the amount of diisocyanate added was calculated based on an NCO / OH molar ratio of 1.08. The polymerization temperature, reaction time, catalyst dosage, solid content, viscosity window, and preparation conditions for the synthetic leather bottom layer, intermediate layer, and top layer were all the same as in Example 1.

[0056] Comparative Example 3 This comparative example prepared conventional PU synthetic leather for comparison of its thermal performance with the synthetic leather of Example 1. This comparative example did not include basalt nanofibers or basalt-modified polyols. A polyester microfiber nonwoven fabric with a thickness of approximately 0.8 mm was used as the base fabric. A bottom coating solution was applied to the base fabric, comprising 100 parts of ordinary polyurethane resin, 45 parts of N,N-dimethylformamide, and 0.3 parts of leveling agent. After coating, it was dried at 80°C for 2.5 min to form a bottom layer with a dry film thickness of 0.08-0.10 mm. Subsequently, a conventional PU intermediate layer coating solution was prepared, comprising 100 parts of ordinary polyurethane resin for synthetic leather and 15 parts of N,N-dimethylformamide. This solution was applied to the bottom layer, resulting in a wet film thickness of 0.45 mm, and then sequentially dried at 80°C for 3 min, 100°C for 3 min, and 120°C for 2 min to form an intermediate layer with a dry film thickness of 0.28-0.35 mm. Next, a surface coating liquid is applied to the surface of the intermediate layer. The surface coating liquid includes 100 parts of polyurethane surface layer resin, 5 parts of color paste, 1 part of wear-resistant additive and 0.3 parts of leveling agent. After coating, it is dried at 120℃ for 6 minutes to form a surface layer with a dry film thickness of 0.05-0.06 mm, thus obtaining conventional PU synthetic leather.

[0057] Performance tests were conducted on the above embodiments and comparative examples. The performance test items are shown below: Solid content test: Weigh about 1.0 g of resin sample and dry it in an oven at 105℃ until constant weight. The percentage of the residual mass after drying to the initial sample mass is taken as the solid content.

[0058] Viscosity test: The resin sample was placed at a constant temperature of 25°C and tested using a rotational viscometer. The readings were recorded under the conditions of rotor No. 4 and 12 rpm.

[0059] Acid value test: Weigh the dried carboxylated fiber sample, disperse it in a mixed solvent of neutral ethanol and toluene, titrate it to the phenolphthalein endpoint with KOH ethanol standard solution, and perform blank correction.

[0060] Hydroxyl value test: The hydroxyl value of basalt-modified polyols was determined using the acetic anhydride-pyridine method. Moisture content was determined using the Karl Fischer method.

[0061] Mechanical property testing: The synthetic leathers obtained in the examples and comparative examples were conditioned for 24 hours at 23°C and 50% relative humidity. Tensile strength was determined according to the method for tensile strength testing in GB / T 46469-2025 "Physical and Mechanical Tests of Leather - Determination of Tensile Strength and Elongation"; tear strength was determined according to GB / T 45711.2-2025 "Determination of Tear Strength of Leather - Part 2: Bilateral Tear". At least 5 samples were taken from each group of samples, and the average value of the samples in the same batch was recorded.

[0062] Thermal conductivity test: Cut synthetic leather samples of the same thickness into flat specimens that match the test fixture, and adjust them for 24 h in an environment of 23℃ and 50% relative humidity. The thermal conductivity is determined by heat flow meter method according to GB / T 10295-2008. During the test, the test area, thickness direction and clamping state of each sample are kept consistent.

[0063] Thermal resistance test: Cut synthetic leather samples of the same thickness into flat specimens, conditioned them in an environment of 23℃ and 50% relative humidity for 24 h, and conduct thermal resistance test according to GB / T 11048-2018; the base fabric side and the surface layer side of the specimen should be aligned during the test.

[0064] Heat preservation time test: Cut the synthetic leather sample of the same thickness into 100 mm × 100 mm samples and place them on a 45℃ constant temperature hot plate so that the temperature of the test point at the center of the sample reaches 40℃; after removing the heat source, record the time required for the temperature of the test point at the center of the sample to drop to 30℃ in an environment of 23℃, which is the heat preservation time.

[0065] Alkali resistance test: The synthetic leather sample was placed in a 10% NaOH aqueous solution and soaked at 25°C for 24 h. After being taken out, it was rinsed with deionized water and dried. The appearance was observed and the tensile strength retention rate after soaking was tested.

[0066] Storage stability test: The resin sample was sealed and placed in an environment of 25°C for 7 days. The sedimentation, gelation and stratification were observed, and the viscosity change rate before and after placement was recorded according to the viscosity test method described above.

[0067] In the above tests, the examples and comparative examples used the same base fabric, the same total thickness, the same intermediate layer thickness, the same drying regime, and the same test direction.

[0068] The mechanical property test results of the examples and comparative examples are shown in the table below.

[0069]

[0070] Compared to Comparative Example 1, Example 1 showed improved tensile strength and tear strength. While both Example 1 and Comparative Example 2 had a basalt nanofiber content of 2.00%, Example 1 used carboxylated fibers esterified with a small-molecule diol to form a basalt-modified polyol, which was then used as a hydroxyl-containing component in the polyurethane polymerization. Comparative Example 2 added basalt nanofibers to the polyurethane system via physical mixing. In Example 2, the basalt nanofiber content was 0.10%, resulting in improved tensile strength and tear strength compared to Comparative Example 1. In Example 3, the basalt nanofiber content was 4.95%, and the tensile strength and tear strength remained higher than both Comparative Example 1 and Comparative Example 2. The mechanical properties of Example 1 were higher than those of Examples 2 and 3, indicating that in this embodiment, when the basalt nanofiber content was controlled within the preferred range, the thermal insulation polyurethane material exhibited higher tensile strength and tear strength in the coated film state.

[0071] The test results of the thermal performance of synthetic leather are shown in the table below:

[0072] The thermal performance test results show that the thermal conductivity of the synthetic leathers in Examples 2, 1, and 3 is lower than that in Comparative Example 3, while the thermal resistance and heat preservation time are higher. This indicates that within the corresponding example range, using heat-insulating polyurethane material in the intermediate layer of synthetic leather can improve the heat storage and insulation performance of the synthetic leather. Among them, Example 1 has the lowest thermal conductivity and the highest thermal resistance and heat preservation time, indicating that the heat preservation effect is more obvious when the basalt nanofiber content is at an optimal level. Compared with Comparative Example 2, both Example 1 and Comparative Example 2 have a basalt nanofiber content of 2.00%, but Example 1 uses carboxylated fibers and small molecule diols to esterify and form basalt-modified polyols, and uses this basalt-modified polyol as a hydroxyl-containing component in polyurethane polymerization; Comparative Example 2 uses a physical mixing method to add basalt nanofibers. The thermal conductivity of Example 1 is lower than that of Comparative Example 2, while the thermal resistance and heat preservation time are higher, indicating that the above reaction combination method is beneficial to improving the dispersion and interfacial bonding state of basalt nanofibers in the intermediate layer, thereby enabling the synthetic leather to obtain a more stable heat storage and insulation effect.

[0073] The results of the alkali resistance and storage stability tests are shown in the table below.

[0074]

[0075] The above results indicate that the thermal insulation polyurethane material obtained in Example 1 forms a stable coating layer in the intermediate layer of synthetic leather. After alkali-resistant treatment, the synthetic leather did not exhibit blistering, delamination, or obvious cracking; after the resin was sealed and placed, no obvious sedimentation, gelation, or delamination occurred, and the viscosity change rate was within the workable range.

[0076] The foregoing description of the specifications and embodiments is intended to explain the scope of protection of this invention, but does not constitute a limitation on the scope of protection of this invention. Modifications, equivalent substitutions, or other improvements to the embodiments of this invention or a portion thereof that can be obtained by those skilled in the art through logical analysis, reasoning, or limited experimentation, based on the teachings of this invention or the foregoing embodiments, in conjunction with common knowledge, general technical knowledge, and / or existing technology, should all be included within the scope of protection of this invention.

Claims

1. A method for preparing a thermal insulation polyurethane material, characterized in that, Includes the following steps: Basalt nanofibers with a diameter of 50-100 nm and a length of 1-2 μm were used as raw materials. After acid activation treatment, aminosilane coupling treatment and carboxylation treatment, carboxylated fibers were obtained. The carboxylated fibers were esterified with small molecule diols to obtain basalt-modified polyols with hydroxyl reaction ends. The basalt-modified polyol, as part of the hydroxyl-containing component, is polymerized with polyester polyol, diisocyanate, and chain extender to obtain the thermal insulation polyurethane material. The content of the basalt nanofibers is 0.1%-5% of the total solid mass of the thermal insulation polyurethane material.

2. The method for preparing the thermal insulation polyurethane material as described in claim 1, characterized in that, The basalt nanofibers are obtained from basalt protofibers through wet ball milling and centrifugal classification. The wet ball milling uses anhydrous ethanol as the milling medium and zirconia balls as the grinding medium, with a ball-to-material mass ratio of 10:1-15:1, a milling speed of 400-500 rpm, and a milling time of 6-8 h. The centrifugal classification includes first centrifuging at 1500-2000 rpm for 10 min and collecting the supernatant, then centrifuging at 8000-10000 rpm for 10-15 min and collecting the target fibers.

3. The method for preparing the thermal insulation polyurethane material as described in claim 1, characterized in that, The acid activation treatment uses 0.3-0.8 mol / L hydrochloric acid, the solid-liquid ratio of the basalt nanofibers to the hydrochloric acid is 1 g:(15-25) mL, the treatment temperature is 55-65℃, and the treatment time is 0.5-1.5 h; the aminosilane coupling treatment uses γ-aminopropyltriethoxysilane, and the amount of γ-aminopropyltriethoxysilane used is 1%-4% of the mass of the basalt nanofibers.

4. The method for preparing the thermal insulation polyurethane material as described in claim 3, characterized in that, The aminosilane coupling treatment includes: adding the γ-aminopropyltriethoxysilane to a mixture of ethanol and water for pre-hydrolysis, wherein the volume ratio of ethanol to water is (90-98):(2-10), and the pre-hydrolysis pH is 4.5-5.0; then adding acid-activated basalt nanofibers and treating at 55-65℃ for 1.5-2.5 h.

5. The method for preparing the thermal insulation polyurethane material as described in claim 1, characterized in that, The carboxylation treatment uses an ammonium persulfate aqueous solution with a concentration of 35-55 g / L, and the pH is adjusted to 2.5-3.0 with dilute sulfuric acid; the solid-liquid ratio of the carboxylation treatment is 1 g:(40-60) mL, the treatment temperature is 65-75℃, and the treatment time is 90-130 min; the acid value of the carboxylated fiber is 30-50 mgKOH / g.

6. The method for preparing the thermal insulation polyurethane material as described in claim 1, characterized in that, The small molecule diol includes at least one of 1,4-butanediol, neopentyl glycol, ethylene glycol, and diethylene glycol; the molar ratio of the carboxyl groups on the surface of the carboxylated fiber to the hydroxyl groups of the small molecule diol is 1:1.05-1:1.

20.

7. The method for preparing the thermal insulation polyurethane material as described in claim 1, characterized in that, The esterification reaction is carried out under nitrogen protection and in the presence of an organotin catalyst at a temperature of 160-180℃ for 2.5-3.5 h, and dehydrated under a negative pressure of 20-40 kPa. The basalt-modified polyol has a hydroxyl value of 60-120 mgKOH / g and a water content of no more than 0.10%.

8. The method for preparing the thermal insulation polyurethane material as described in claim 1, characterized in that, The polymerization reaction includes: The polyester polyol and the basalt-modified polyol were dehydrated and dispersed in the reaction solvent; Add diisocyanate and prepolymerize at 75-80℃ for 1.5-2 h; Add chain extender and polymerization catalyst, and react at 70-75℃ for 3-3.5 h; In the polymerization reaction, the molar ratio of isocyanate groups to hydroxyl groups is 1.03-1.

12.

9. The method for preparing the thermal insulation polyurethane material as described in claim 8, characterized in that, The polyester polyol is polybutylene adipate polyol, the diisocyanate is diphenylmethane diisocyanate, and the chain extender is 1,4-butanediol; the reaction solvent includes N,N-dimethylformamide and toluene, and the volume ratio of N,N-dimethylformamide to toluene is (6-8):(2-4); the polymerization catalyst includes dibutyltin dilaurate, and the amount of dibutyltin dilaurate is 0.05%-0.15% of the mass of the resin solid component; the solid content of the thermal insulation polyurethane material is 50%-55%, and the viscosity at 23-27℃ is 15000-30000 mPa·s.

10. A synthetic leather, characterized in that, It includes a base fabric, a bottom layer, an intermediate layer and a top layer arranged in sequence; the intermediate layer contains a thermal insulation polyurethane material prepared by the preparation method according to any one of claims 1 to 9, and the dry film thickness of the intermediate layer is 0.20-0.35 mm.

Images