A bio-based waterborne strippable polyurethane resin, its preparation method and application

Abstract

The embodiment of the application discloses a kind of bio-based water-based peelable polyurethane resin and its preparation method and application, belong to textile printing technical field.A kind of bio-based water-based peelable polyurethane resin, by weight fraction, its raw material is: bio-based polyol 15-20 parts, isophorone diisocyanate 20-30 parts, bio-based emulsifier 5-10 parts, 1,4-butanediol 3-5 parts, dipropylene glycol dimethyl ether 3-8 parts, dibutyl tin laurate 0.5-2 parts, double end hydroxyl poly (N-isopropyl acrylamide) 5-10 parts, triethylamine 5-10 parts, deionized water 30-50 parts, paraffin-based polyurethane microcapsule 10-15 parts.The water-based polyurethane resin of the application has good stability, strong film-forming property, the coating prepared has high cohesive strength and sufficient toughness at room temperature, can resist embroidery printing mechanical stress, is easy to remove by temperature change mechanism when peeling, and is especially suitable for processing of high-grade, easily damaged textiles such as silk, chiffon, elastic knitted fabric, etc.

Description

Technical Field

[0001] This invention relates to the field of textile printing technology, specifically to a bio-based water-based peelable polyurethane resin, its preparation method, and its application. Background Technology

[0002] In the textile and apparel industry, especially when performing intricate embroidery, appliqué, or digital printing on high-end fabrics (such as silk, chiffon, and elastic knitted fabrics), the thinness, softness, and susceptibility to deformation of the fabrics themselves make direct processing extremely prone to problems such as wrinkles, shifting, or needle hole damage, severely impacting the quality and yield of the finished product. To address this issue, a common method is to apply a temporary stabilizing backing to the back of the fabric. This backing provides necessary support and stability to the fabric during processing, ensuring the accuracy of the pattern; it is then peeled off after processing is complete.

[0003] Currently, most temporary backings widely used in the market are non-woven fabrics or paper backings coated with pressure-sensitive adhesives. While these traditional materials provide some support, they have significant drawbacks in the peeling process. Because traditional adhesives are too tightly bonded to the fabric or over-saturated, peeling requires considerable force, leading to high labor intensity for workers. Furthermore, in cases of high-density embroidery, the adhesive layer is prone to breakage, leaving adhesive particles, paper scraps, and other residues adhering to the back of the fabric. These residues not only affect the appearance and feel of the textile but may also detach during subsequent washing, contaminating the entire garment. For ultra-soft or extremely delicate fabrics, the excessive peeling force can cause the fabric itself to stretch, deform, or even be damaged, limiting its application. In addition, most existing backings are derived from petroleum-based raw materials (such as traditional polyurethane, acrylic adhesives, and non-woven fabric substrates), and their production and use processes do not align with current industry trends towards green and sustainable development. Moreover, residual microplastics or non-biodegradable paper scraps also burden the environment. Summary of the Invention

[0004] Therefore, embodiments of the present invention provide a bio-based waterborne peelable polyurethane resin, its preparation method and application, to solve the problems of excessive peeling force, easy residue, damage to fabric and poor environmental performance in the prior art when using temporary stabilizing backings for thin, soft or elastic fabrics during peeling.

[0005] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0006] According to a first aspect of the present invention, the present invention provides a bio-based waterborne peelable polyurethane resin, the raw materials of which, by weight, are: 15-20 parts of bio-based polyol, 20-30 parts of isophorone diisocyanate, 5-10 parts of bio-based emulsifier, 3-5 parts of 1,4-butanediol, 3-8 parts of dipropylene glycol dimethyl ether, 0.5-2 parts of dibutyltin laurate, 5-10 parts of hydroxyl-terminated poly(N-isopropylacrylamide), 5-10 parts of triethylamine, 30-50 parts of deionized water, and 10-15 parts of paraffin-based polyurethane microcapsules.

[0007] The functions and working principles of each raw material component are as follows:

[0008] Bio-based polyols, as flexible segments of polymers, are the main building blocks of polyurethane molecular chains. Their long molecular chain structure determines the flexibility, elongation, and low-temperature resistance of the resin film. Using bio-based sources directly reduces the product's dependence on petroleum resources from the source, which is a core manifestation of the product's green and environmentally friendly characteristics. Bio-based polyols can be obtained commercially, such as SK ECOPROL H1000 from South Korea and FH-3140 from Feihang Technology, or they can be prepared from vegetable oils through oxidation and other methods.

[0009] Isophorone diisocyanate (IPDI), as the rigid hard segment of the polymer, is the main diisocyanate monomer. IPDI has an alicyclic structure, which imparts excellent mechanical strength, abrasion resistance, hydrolysis resistance, and light stability to the resin. Its moderate reactivity facilitates process control during production.

[0010] Bio-based emulsifiers, with their built-in hydrophilic groups, are key to achieving the waterborne transformation of polyurethane. During the reaction, they are incorporated into the polyurethane chain, giving the polymer itself hydrophilicity, allowing it to disperse in water under shear force and form a stable emulsion. Using bio-based emulsifiers further enhances the overall bio-based content and environmental friendliness of the product. Bio-based emulsifiers can be commercially available, such as M-30 from Anhui Jingcheng New Materials and GLU-CE from Xi'an Ruixi Biotechnology, or prepared from bio-based polyols through saponification reactions.

[0011] 1,4-Butanediol, a small molecule chain extender. It is crucial for balancing resin peelability and processing strength, ensuring the coating has sufficient support before peeling.

[0012] Dipropylene glycol dimethyl ether is an environmentally friendly solvent. It can efficiently dissolve polyols containing acid groups, ensuring that the prepolymerization reaction proceeds uniformly and completely.

[0013] Dibutyltin laurylate is a highly efficient catalyst. It can selectively catalyze the reaction between -NCO and -OH, significantly accelerating the synthesis and chain extension rate of polyurethane prepolymers, reducing reaction temperature, shortening the production cycle, and ensuring complete reaction.

[0014] The chemical formula of hydroxyl-terminated poly(N-isopropylacrylamide) (HO-PNIPAM-OH) is as follows:

[0015] Hydroxyl value: 55-59 mg KOH / g, acid value: ≤1 mg KOH / g, viscosity: 65000-68000 mpa.s / 40℃. The hydroxyl groups at both ends allow it to be incorporated into the polyurethane backbone as a polyol, facilitating the construction of a compatible cross-linking network. While controlling the cross-linking density of the coating to balance mechanical strength, the synergistic effect of the terminal hydroxyl groups and PNIPAM segments optimizes interfacial bonding strength and peel efficiency. Simultaneously, the introduction of thioether bonds (-S-), ester groups (-OOC-), and terminal hydroxyl groups (-OH) regulates the LCST of the PNIPAM segments to 50-55℃. At low temperatures, it hydrophilically expands to enhance the interfacial bonding between the coating and the fabric, while at high temperatures, it rapidly dehydrates and shrinks, generating significant shrinkage stress. This force is one of the core driving forces for actively "pushing open" the coating-fabric interface and is key to achieving heat-triggered, low-peel-force peeling.

[0016] Triethylamine is a neutralizing agent. It reacts with the carboxyl group (-COOH) on bio-based emulsifier molecules to form ammonium carboxylate salts (-COO). - NH + This process imparts good water dispersibility to the polyurethane prepolymer. Only after neutralization with triethylamine can the prepolymer be successfully emulsified in water under high shear.

[0017] Deionized water is the dispersion medium. It constitutes the aqueous system of the final product, replacing organic solvents, and is safe, environmentally friendly, and pollution-free. The amount of water used determines the solid content and viscosity of the final resin.

[0018] Paraffin-based polyurethane microcapsules, with a polyurethane outer shell protecting the paraffin core material, ensure its stability during processing and storage. When the temperature rises to the paraffin phase transition temperature (≥50℃), the paraffin melts. Under peel stress, the liquid paraffin seeps out from the microcapsules, forming a lubricating film at the interface between the coating and the fabric, significantly reducing peel force. This works synergistically with the shrinkage stress of PNIPAM to achieve easy and complete peeling under heated conditions.

[0019] The resin coating of this invention provides excellent mechanical support during processing, and after processing, it can achieve a fast, complete, and near-zero residue peeling effect with extremely low peeling force, effectively protecting the structure and performance of high-end fabrics.

[0020] Furthermore, the preparation method of the bihydroxyl-terminated poly(N-isopropylacrylamide) includes the following steps:

[0021] (1) 2-(dodecyltrithiocarbonate)-2-methylpropionic acid and ethylene glycol in a molar ratio of 2:1 were esterified at 80-90°C in the presence of p-toluenesulfonic acid and toluene. After neutralization, washing with water, drying and vacuum distillation, bis[2-(dodecyltrithiocarbonate)-2-methylpropionic acid]ethylene glycol ester was obtained.

[0022] (2) 60-80 parts of N-isopropylacrylamide monomer, 2-4 parts of bis[2-(dodecyltrithiocarbonate)-2-methylpropionic acid] ethylene glycol ester from step (1), 0.1-0.3 parts of azobisisobutyronitrile and 60-80 parts of 1,4-dioxane were subjected to RAFT polymerization under inert gas protection. After precipitation with diethyl ether, washing and drying, the bistrithioester end-group polymer was obtained. The RAFT polymerization reaction conditions were: 70-90℃, 8-12h.

[0023] (3) Dissolve the bis(trithioester) end-group polymer from step (2) in 3-5 parts of tetrahydrofuran, add 10-15 parts of n-butylamine, and carry out the end-group aminolysis reaction under inert gas protection. The conditions for the end-group aminolysis reaction are: 40-60℃, 5-7h.

[0024] (4) Add 15-17 parts of hydroxyethyl acrylate and 0.1-0.3 parts of azobisisobutyronitrile to the reaction solution in step (3), and carry out the mercapto-olefin click reaction under inert gas protection. After purification by ether precipitation, washing and drying, the double-hydroxyl-terminated poly(N-isopropylacrylamide) is obtained. The conditions for the mercapto-olefin click reaction are: 65-85℃, 6-8h.

[0025] Furthermore, the core material of the paraffin-based polyurethane microcapsule is low-temperature paraffin, and the phase transition temperature of low-temperature paraffin is 50-60℃.

[0026] Furthermore, the preparation method of the bio-based polyol includes the following steps:

[0027] (1) Mix 15-20 parts of vegetable oil with 5-10 parts of formic acid at 40-60℃ for 10-30 min, add 5-8 parts of hydrogen peroxide and react for 10-30 min, then raise the temperature to 60-80℃ and continue the reaction for 3-5 h to obtain epoxidized vegetable oil;

[0028] (2) Mix 4-6 parts of ring-opening agent, 10-15 parts of deionized water and 5-8 parts of sulfuric acid and heat to 65-85°C. Add the epoxidized vegetable oil obtained in step (1) and heat to 80-90°C for 30-60 minutes. Then add 3-5 parts of sodium bicarbonate to neutralize the reaction system. After cooling to room temperature, the precipitate is discarded. Remove excess methanol and water by vacuum distillation to obtain the bio-based polyol.

[0029] Furthermore, the vegetable oil is selected from one or more of fenugreek oil, jatropha oil, and castor oil;

[0030] The ring-opening agent is selected from one or more of methanol, ethanol, and propanol.

[0031] Furthermore, the preparation method of the bio-based emulsifier includes:

[0032] The bio-based polyol was saponified in the presence of sodium hydroxide and ethanol. After acid neutralization, the organic phase was extracted, dried, and distilled under reduced pressure to obtain the carboxylated dimer hydroxystearic acid product, which is the bio-based emulsifier.

[0033] Furthermore, the mass ratio of sodium hydroxide, ethanol and bio-based polyol is 5-8:3-5:15-20, and the saponification reaction conditions are 70-90℃ for 3-5 hours.

[0034] According to a second aspect of the present invention, the present invention provides a method for preparing a bio-based waterborne peelable polyurethane resin as described in any of the preceding claims, the method comprising:

[0035] Mix bio-based polyol, bio-based emulsifier, hydroxyl-terminated poly(N-isopropylacrylamide), 1,4-butanediol and dipropylene glycol dimethyl ether, and stir at 55-65℃ for 0.5-1h.

[0036] Heat to 80-95℃, add isophorone diisocyanate, and stir for 0.5-1 hour;

[0037] Add dibutyltin laurylate and stir for 3-4 hours;

[0038] Cool to 40℃, add triethylamine, and stir for 0.5-1 h to obtain polyurethane prepolymer;

[0039] Add paraffin-based polyurethane microcapsules and stir for 0.5-1 hour;

[0040] After adding deionized water and dispersing at high speed, the bio-based waterborne peelable polyurethane resin is obtained.

[0041] According to a third aspect of the present invention, the present invention provides the application of the bio-based water-based peelable polyurethane resin as described in any of the preceding claims as a temporary stable substrate in fine embroidery, appliqué embroidery or digital printing on fabrics, said fabrics including silk, chiffon, and elastic knitted fabrics.

[0042] The embodiments of the present invention have the following advantages:

[0043] 1. This invention constructs a thermosensitive synergistic system by combining hydroxyl-terminated poly(N-isopropylacrylamide) and paraffin-based polyurethane microcapsules. Under heated conditions (e.g., drying or ironing during finishing processes at temperatures ≥50°C), the two exhibit a significant synergistic effect. Specifically, the poly(N-isopropylacrylamide) molecular chains undergo rapid dehydration and shrinkage, changing from hydrophilic to hydrophobic. This volumetric phase change generates significant internal stress within the coating, greatly weakening the adhesion between the coating and the fabric and providing initial impetus for coating peeling. Furthermore, the paraffin core material in the paraffin-based polyurethane microcapsules releases liquid paraffin upon heating. This paraffin acts as an excellent lubricant at the interface between the coating and the fabric, further significantly reducing the peeling force of the coating.

[0044] 2. The waterborne polyurethane resin provided by this invention exhibits good stability and strong film-forming properties. The resulting coating possesses high cohesive strength and toughness at room temperature, capable of withstanding the mechanical stress during embroidery and printing processes; and upon peeling, it becomes extremely easy to remove through the aforementioned temperature-dependent mechanism. It is particularly suitable for processing high-end, fragile textiles such as silk, chiffon, and elastic knitted fabrics.

[0045] 3. This invention uses bio-based polyols (such as those derived from castor oil and corn sugar) and bio-based emulsifiers, which significantly reduces the product's dependence on petroleum-based resources and is in line with the trends of green chemistry and sustainable development in the industry. Detailed Implementation

[0046] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] The preparation method of bio-based polyols is as follows: 15 parts fenugreek oil and 5 parts formic acid are mixed and reacted at 40℃ for 10 min. 8 parts of 10% hydrogen peroxide are added and reacted for 30 min. The temperature is raised to 60℃ and the reaction continues for 5 h to obtain epoxidized vegetable oil. 4 parts methanol, 10 parts deionized water and 5 parts 1 mol / L sulfuric acid are poured into a beaker and continuously stirred and heated to the boiling point of methanol. Then, the epoxidized vegetable oil is added to the mixture, the temperature is raised to 80℃ and the reaction continues for 30 min. After the reaction is completed, the pH of the system is adjusted to 7 with sodium bicarbonate, cooled to room temperature, and the solid and liquid phases are separated. The obtained liquid phase is removed by vacuum distillation to remove excess methanol and water to obtain bio-based polyols.

[0048] The preparation method of the bio-based emulsifier is as follows: saponification of the bio-based polyol using sodium hydroxide solution. Specifically, in a round-bottom flask equipped with a condenser, 15 parts of bio-based polyol are mixed with 3 parts of ethanol and 5 parts of sodium hydroxide, and the mixture is refluxed for 5 hours. After neutralizing the product with 1 mol / L hydrochloric acid solution, the organic layer is extracted with dichloromethane, washed with sodium chloride solution, dried with anhydrous magnesium sulfate to remove the organic solvent, and finally the carboxylated dihydroxystearic acid product, i.e., the bio-based emulsifier, is obtained.

[0049] The preparation method of hydroxyl-terminated poly(N-isopropylacrylamide) is as follows: 72.8 parts of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid are mixed with 6.2 parts of ethylene glycol, 0.5 parts of p-toluenesulfonic acid, and 200 parts of toluene. The mixture is reacted at 90°C for 1.5 h under nitrogen protection. The mixture is then neutralized with sodium bicarbonate solution, washed with water, and the organic phase is dried. Toluene is removed by vacuum distillation to obtain bis[2-(dodecyltrithiocarbonate)-2-methylpropionic acid]ethylene glycol ester (as a RAFT chain transfer agent). Using 80 parts of N-isopropylacrylamide monomer, 2 parts of bis[2-(dodecyltrithiocarbonate)-2-methylpropionic acid]ethylene glycol ester, and 0.1 parts of azobisisobutyronitrile as initiators, the mixture is reacted with 60 parts of anhydrous 1,4-dioxane. In a cyclic solvent, the reaction was carried out at 70°C for 12 h under nitrogen protection. After the reaction, the product was precipitated with diethyl ether, washed, and dried to obtain a bis(trithioester) end-group polymer. The polymer was then dissolved in 3 parts of tetrahydrofuran, and 10 parts of n-butylamine were added. The reaction was carried out at 50°C for 6 h to obtain a dithiol intermediate. Finally, 15 parts of hydroxyethyl acrylate and 0.1 parts of azobisisobutyronitrile catalyst were added, and the reaction was carried out at 70°C for 8 h. The end groups were converted to hydroxyl groups through a mercapto-olefin click reaction. After the reaction, the system was cooled to room temperature, and 5 parts of diethyl ether were added under stirring to precipitate the product. The solid and liquid were separated, the solid product was collected, and washed with diethyl ether 2-3 times. Then, it was dried under vacuum to constant weight to obtain a hydroxyl-terminated poly(N-isopropylacrylamide). The hydroxyl value was 57 mg KOH / g, the acid value was ≤1 mg KOH / g, the viscosity was 68000 mpa.s / 40°C, and the minimum critical dissolution temperature was 50°C.

[0050] Paraffin-based polyurethane microcapsules: The core material is low-temperature paraffin, and the shell material is polyurethane. The phase transition temperature of low-temperature paraffin is 50-60℃. You can choose PCM-A-62 from Donglin Polymer Materials, PCM-70 from Shengbang Plastics, or MDH-PCM from Rushang New Energy Technology.

[0051] Example 1

[0052] This embodiment provides a bio-based waterborne peelable polyurethane resin, the preparation method of which is as follows:

[0053] 15 parts of bio-based polyol, 5 parts of bio-based emulsifier, 5 parts of hydroxyl-terminated poly(N-isopropylacrylamide), 3 parts of 1,4-butanediol, and 3 parts of dipropylene glycol dimethyl ether were mixed and stirred at 60°C for 1 hour. The temperature was raised to 90°C, 20 parts of isophorone diisocyanate were added, and the mixture was stirred for 0.5 hours. 0.5 parts of dibutyltin laurylate were added, and the mixture was stirred for another 3 hours. The temperature was lowered to 40°C, and 5 parts of triethylamine were added and stirred for 1 hour to obtain a polyurethane prepolymer. 10 parts of paraffin-based polyurethane microcapsules were added and stirred for 0.5 hours. Finally, 30 parts of deionized water were added, and the mixture was dispersed at high speed to obtain a bio-based waterborne peelable polyurethane resin.

[0054] Example 2

[0055] This embodiment provides a bio-based waterborne peelable polyurethane resin, the preparation method of which is as follows:

[0056] 18 parts of bio-based polyol, 6 parts of bio-based emulsifier, 9 parts of hydroxyl-terminated poly(N-isopropylacrylamide), 4 parts of 1,4-butanediol, and 6 parts of dipropylene glycol dimethyl ether were mixed and stirred at 60°C for 1 hour. The temperature was then raised to 90°C, 25 parts of isophorone diisocyanate were added, and the mixture was stirred for 0.5 hours. 1 part of dibutyltin laurylate was added, and the mixture was stirred for 3 hours. The temperature was lowered to 40°C, and 8 parts of triethylamine were added, and the mixture was stirred for 1 hour to obtain a polyurethane prepolymer. 12 parts of paraffin-based polyurethane microcapsules were added, and the mixture was stirred for 0.5 hours. Finally, 35 parts of deionized water were added, and the mixture was dispersed at high speed to obtain a bio-based waterborne peelable polyurethane resin.

[0057] Example 3

[0058] This embodiment provides a bio-based waterborne peelable polyurethane resin, the preparation method of which is as follows:

[0059] 20 parts of bio-based polyol, 10 parts of bio-based emulsifier, 10 parts of hydroxyl-terminated poly(N-isopropylacrylamide), 5 parts of 1,4-butanediol, and 8 parts of dipropylene glycol dimethyl ether were mixed and stirred at 60°C for 1 hour. The temperature was then raised to 90°C, 30 parts of isophorone diisocyanate were added, and the mixture was stirred for 0.5 hours. 1 part of dibutyltin laurate was added and the mixture was stirred for 3 hours. The temperature was lowered to 40°C, and 10 parts of triethylamine were added and stirred for 1 hour to obtain a polyurethane prepolymer. 15 parts of paraffin-based polyurethane microcapsules were added and stirred for 0.5 hours. Finally, 40 parts of deionized water were added, and the mixture was dispersed at high speed to obtain a bio-based waterborne peelable polyurethane resin.

[0060] Comparative Example 1

[0061] This comparative example provides a polyurethane resin, which differs from Example 1 only in that it does not use paraffin-based polyurethane microcapsules. Specifically, its preparation method is as follows:

[0062] 15 parts of bio-based polyol, 5 parts of bio-based emulsifier, 5 parts of hydroxyl-terminated poly(N-isopropylacrylamide), 3 parts of 1,4-butanediol and 3 parts of dipropylene glycol dimethyl ether were mixed and stirred at 60°C for 1 hour. The temperature was raised to 90°C, 20 parts of isophorone diisocyanate were added and stirred for 0.5 hours, 0.5 parts of dibutyltin laurylate were added and stirred for 3 hours. The temperature was lowered to 40°C and 5 parts of triethylamine were added and stirred for 1 hour to obtain a polyurethane prepolymer. Finally, 30 parts of deionized water were added and dispersed at high speed (600 rpm) to obtain a bio-based waterborne peelable polyurethane resin.

[0063] Comparative Example 2

[0064] This comparative example provides a polyurethane resin, which differs from Example 1 only in that it does not use hydroxyl-free poly(N-isopropylacrylamide). Specifically, its preparation method is as follows:

[0065] 15 parts of bio-based polyol, 5 parts of bio-based emulsifier, 3 parts of 1,4-butanediol and 3 parts of dipropylene glycol dimethyl ether were mixed and stirred at 60°C for 1 hour. The temperature was raised to 90°C, 20 parts of isophorone diisocyanate were added and stirring was continued for 0.5 hours. 0.5 parts of dibutyltin laurylate were added and stirred for 3 hours. The temperature was lowered to 40°C and 5 parts of triethylamine were added and stirred for 1 hour to obtain a polyurethane prepolymer. 10 parts of paraffin-based polyurethane microcapsules were added and stirred for 0.5 hours. Finally, 30 parts of deionized water were added and dispersed at high speed (600 rpm) to obtain a bio-based waterborne peelable polyurethane resin.

[0066] Comparative Example 3

[0067] This comparative example provides a polyurethane resin, which differs from Example 1 only in that it does not use hydroxyl-terminated poly(N-isopropylacrylamide) and paraffin-based polyurethane microcapsules. Specifically, its preparation method is as follows:

[0068] 15 parts of bio-based polyol, 5 parts of bio-based emulsifier, 3 parts of 1,4-butanediol and 3 parts of dipropylene glycol dimethyl ether were mixed and stirred at 60°C for 1 hour; the temperature was raised to 90°C, 20 parts of isophorone diisocyanate were added and stirred for 0.5 hours, 0.5 parts of dibutyltin laurylate were added and stirred for 3 hours; the temperature was lowered to 40°C and 5 parts of triethylamine were added and stirred for 1 hour to obtain a polyurethane prepolymer; finally, 30 parts of deionized water were added and dispersed at high speed (600 rpm) to obtain a bio-based waterborne peelable polyurethane resin.

[0069] Performance testing

[0070] (1) Membrane preparation: The polyurethane resins of Examples 1-3 and Comparative Examples 1-3 were coated or scraped onto release paper and dried at 100°C for 3 minutes to form a uniform polyurethane film with a dry film thickness of about 0.1 mm.

[0071] (2) Preparation of composite sample: The above-mentioned dried polyurethane film and 120D chiffon fabric were hot-pressed together at 105℃ and 0.5MPa pressure for 30 seconds to form a composite sample. The sample was then equilibrated for 24 h under standard temperature and humidity (23±2℃, 50±10%RH) conditions before testing.

[0072] (3) Mechanical property test: According to GBT1040.3-2006, the mechanical properties of the polyurethane films of Examples 1-3 and Comparative Examples 1-3 were tested at room temperature. The tensile speed was 20 mm / min until the sample broke. Three parallel samples were tested in each group, and the average value was taken. The test results are shown in Table 1.

[0073] (4) Peel strength test: According to FZ / T 80007.1-2023 (test method for peel strength of fused lining garments), the peel strength and peel residue of the composite sample at different temperatures were tested. The results are shown in Table 2 below.

[0074] Table 1 Mechanical properties of polyurethane membranes

[0075]

[0076] The results showed that the tensile strengths of Examples 1-3 were 16.7 MPa, 15.2 MPa, and 14.8 MPa, respectively, all significantly higher than those of Comparative Examples 1-3 (14.0 MPa, 12.6 MPa, and 9.7 MPa, respectively). This indicates that the samples containing both hydroxyl-terminated poly(N-isopropylacrylamide) and paraffin-based polyurethane microcapsules exhibit superior mechanical strength. This improvement in mechanical properties stems from the synergistic reinforcement mechanism of the bifunctional PNIPAM and the microcapsules. PNIPAM participates in the chain extension and cross-linking of the polyurethane network through its terminal hydroxyl groups, acting as a chemical cross-linking point to improve the overall density and integrity of the network. Simultaneously, its molecular chains physically entangle with the polyurethane matrix, further restricting chain slippage, thus jointly contributing to the improvement of material rigidity and strength. The paraffin-based polyurethane microcapsules, acting as a rigid filler, are uniformly dispersed in the matrix, effectively transferring and dispersing external stress, hindering the propagation of microcracks, and exhibiting the classic particle reinforcement effect. The synergistic effect of both components results in a reinforcement efficiency exceeding the simple superposition of single components, with Example 1 showing the best performance.

[0077] Table 2 Peel performance of polyurethane film

[0078]

[0079] Note: Excellent indicates peel force > 10N; Good indicates 1N < peel force < 10N; Poor indicates peel force < 1N.

[0080] The results showed that, in terms of peel strength and residual properties, at room temperature of 25°C, the peel strength of Examples 1-3 and Comparative Examples 1-2 was excellent (>10N), with only slight adhesive residue. Although Comparative Example 3 also had excellent peel strength, it showed obvious adhesive marks. Under heating conditions of 50°C, the peel strength of Examples 1-3 dropped sharply to poor (<1N), and complete peeling was still possible. The peel strength of Comparative Examples 1-2 dropped to good (1N < peel strength < 10N), with partial breakage and residue during peeling. The peel strength of Comparative Example 3 remained excellent, but obvious adhesive marks remained.

[0081] In summary, this invention employs a system combining hydroxyl-terminated poly(N-isopropylacrylamide) and paraffin-based polyurethane microcapsules. The two components work synergistically, not only enhancing the mechanical strength of the film and improving the coating's abrasion resistance and structural stability during embroidery, printing, and other processing, but also achieving a performance switch between room-temperature adhesion and heat-sensitive peeling through temperature control. This meets the processing requirements of embroidery, printing, and other applications. At 50°C, a peel force of <1N allows for complete peeling of the entire sheet, avoiding damage to the fabric. This invention shows promising application prospects in the processing of high-end, fragile textiles.

[0082] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A bio-based aqueous strippable polyurethane resin, characterized in that, By weight, the raw materials are: 15-20 parts of bio-based polyol, 20-30 parts of isophorone diisocyanate, 5-10 parts of bio-based emulsifier, 3-5 parts of 1,4-butanediol, 3-8 parts of dipropylene glycol dimethyl ether, 0.5-2 parts of dibutyltin laurylate, 5-10 parts of hydroxyl-terminated poly(N-isopropylacrylamide), 5-10 parts of triethylamine, 30-50 parts of deionized water, and 10-15 parts of paraffin-based polyurethane microcapsules. The preparation method of the bio-based polyol includes the following steps: (1) Mix 15-20 parts of vegetable oil with 5-10 parts of formic acid at 40-60℃ for 10-30 min, add 5-8 parts of hydrogen peroxide and react for 10-30 min, then raise the temperature to 60-80℃ and continue the reaction for 3-5 h to obtain epoxidized vegetable oil; (2) Mix 4-6 parts of ring-opening agent, 10-15 parts of deionized water and 5-8 parts of sulfuric acid and heat to 65-85°C. Add the epoxidized vegetable oil obtained in step (1) and heat to 80-90°C for 30-60 min. Then add 3-5 parts of sodium bicarbonate to neutralize the reaction system. After cooling to room temperature, the precipitate is discarded. Remove excess methanol and water by vacuum distillation to obtain the bio-based polyol. The chemical formula of the hydroxyl-terminated poly(N-isopropylacrylamide) is as follows: , hydroxyl number 55-59 mg KOH / g, acid number < 1 mg KOH / g, viscosity 65000-68000 mpa.s / 40°C, LCST 50-55°C; The core material of the paraffin-based polyurethane microcapsules is low-temperature paraffin, and the phase transition temperature of low-temperature paraffin is 50-60℃.

2. The bio-based waterborne peelable polyurethane resin according to claim 1, characterized in that, The preparation method of the bihydroxyl-terminated poly(N-isopropylacrylamide) includes the following steps: (1) 2-(dodecyltrithiocarbonate)-2-methylpropionic acid and ethylene glycol in a molar ratio of 2:1 were esterified at 80-90°C in the presence of p-toluenesulfonic acid and toluene. After neutralization, washing with water, drying and vacuum distillation, bis[2-(dodecyltrithiocarbonate)-2-methylpropionic acid]ethylene glycol ester was obtained. (2) 60-80 parts of N-isopropylacrylamide monomer, 2-4 parts of bis[2-(dodecyltrithiocarbonate)-2-methylpropionic acid] ethylene glycol ester from step (1), 0.1-0.3 parts of azobisisobutyronitrile and 60-80 parts of 1,4-dioxane were subjected to RAFT polymerization under inert gas protection. After precipitation with diethyl ether, washing and drying, the bistrithioester end-group polymer was obtained. The RAFT polymerization reaction conditions were: 70-90℃, 8-12h. (3) Dissolve the bis(trithioester) end-group polymer from step (2) in 3-5 parts of tetrahydrofuran, add 10-15 parts of n-butylamine, and carry out the end-group aminolysis reaction under inert gas protection. The conditions for the end-group aminolysis reaction are: 40-60℃, 5-7h. (4) Add 15-17 parts of hydroxyethyl acrylate and 0.1-0.3 parts of azobisisobutyronitrile to the reaction solution in step (3), and carry out the mercapto-olefin click reaction under inert gas protection. After purification by ether precipitation, washing and drying, the double-hydroxyl-terminated poly(N-isopropylacrylamide) is obtained. The conditions for the mercapto-olefin click reaction are: 65-85℃, 6-8h.

3. The bio-based waterborne peelable polyurethane resin according to claim 1, characterized in that, The vegetable oil is selected from one or more of fenugreek oil, jatropha oil, and castor oil. The ring-opening agent is selected from one or more of methanol, ethanol, and propanol.

4. The bio-based waterborne peelable polyurethane resin according to claim 1, characterized in that, The preparation method of the bio-based emulsifier includes: The bio-based polyol was saponified in the presence of sodium hydroxide and ethanol. After acid neutralization, the organic phase was extracted, dried, and distilled under reduced pressure to obtain the carboxylated dimer hydroxystearic acid product, which is the bio-based emulsifier.

5. The bio-based waterborne peelable polyurethane resin according to claim 4, characterized in that, The mass ratio of sodium hydroxide, ethanol and bio-based polyol is 5-8:3-5:15-20, and the saponification reaction conditions are 70-90℃ for 3-5 hours.

6. The method for preparing the bio-based waterborne peelable polyurethane resin according to any one of claims 1-5, characterized in that, The method includes: Mix bio-based polyol, bio-based emulsifier, hydroxyl-terminated poly(N-isopropylacrylamide), 1,4-butanediol and dipropylene glycol dimethyl ether, and stir at 55-65℃ for 0.5-1h. Heat to 80-95℃, add isophorone diisocyanate, and stir for 0.5-1 hour; Add dibutyltin laurylate and stir for 3-4 hours; Cool to 40℃, add triethylamine, and stir for 0.5-1 h to obtain polyurethane prepolymer; Add paraffin-based polyurethane microcapsules and stir for 0.5-1 hour; After adding deionized water and dispersing at high speed, the bio-based waterborne peelable polyurethane resin is obtained.

7. The application of the bio-based waterborne peelable polyurethane resin according to any one of claims 1-5 as a temporary stable backing in fine embroidery, appliqué embroidery, or digital printing on fabrics, characterized in that, The fabrics include silk, chiffon, and elastic knitted fabrics.

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