Polyurethane wet-process hydrolysis-resistant resin for imitated protein shoe lining leather and preparation method of polyurethane wet-process hydrolysis-resistant resin

Abstract

The invention provides a polyurethane wet-process hydrolysis-resistant resin for imitated protein shoe lining leather as well as a preparation method and application of the polyurethane wet-process hydrolysis-resistant resin. The preparation raw materials of the polyurethane wet-process hydrolysis-resistant resin comprise the following components in parts by weight: 0.002-0.004 part of inorganic acid; 164 to 247 parts of polyhydric alcohol; 45 to 69 parts of isocyanate; 7-11 parts of small molecular alcohol; 27 to 41 parts of an auxiliary agent; and 555-833 parts of a solvent. The polyurethane wet-process hydrolysis-resistant resin has the characteristics of five-year hydrolysis resistance, thick hand feeling, high muscle forming property, good water washing property and the like, and the prepared cotton-feeling protein-imitating shoe lining leather keeps good film forming property and soft protein-imitating hand feeling, so that the product is widely applied in the aspects of softness and hydrolysis resistance.

Description

Technical Field

[0001] This invention belongs to the technical field of polyurethane materials, and particularly relates to a wet-process hydrolysis-resistant polyurethane resin for imitation protein shoe lining leather, its preparation method, and its application. Background Technology

[0002] The wet-process hydrolysis-resistant resin used for imitation protein shoe lining refers to a synthetic leather with a soft, cotton-like texture that is resistant to hydrolysis. This is achieved by first applying a prepared hydrolysis-resistant resin onto a spunlace fabric, then passing it through a scraper of a fixed thickness into water for solidification, followed by washing and drying. Finally, a layer of dry-process imitation protein skin-feel resin is applied to the surface of the wet-process base to form a hydrolysis-resistant synthetic leather with a cotton-like texture.

[0003] Currently, there are two types of resins available on the market: soft, protein-like, hydrolysis-resistant wet-process leather resins and soft, cotton-like, hydrolysis-resistant wet-process leather resins. Soft, protein-like, hydrolysis-resistant wet-process leather resins are formulated by adding a large amount of protein powder and polyvinyl alcohol to the application formula to improve the protein-like feel. This results in synthetic leather made using a wet-process technique for protein-like shoe linings. However, this method has the drawback that the resulting protein-like synthetic leather is prone to exhibiting poor surface smoothness and low peel strength. The resin used for soft, cotton-like, hydrolysis-resistant wet-process leather is designed to achieve the desired cotton-like feel by using a large amount of silicone-based softeners in the formulation. This synthetic leather is produced using a wet-process technique to mimic protein-like shoe linings. However, this method has drawbacks: the surface of the synthetic leather base is slippery after processing, making washing difficult and hindering penetration into the base fabric. Furthermore, hot-melt adhesive tape fails to adhere properly when tested for peel strength. Currently available resins for soft, protein-like, hydrolysis-resistant leather and soft, cotton-like, hydrolysis-resistant leather cannot simultaneously achieve both a protein-like effect and a cotton-like feel. This results in a bottleneck in the development of various styles for synthetic leather that cannot achieve the protein-like cotton-like feel, hindering the increase of added value in the market. Therefore, developing a polyurethane wet-process hydrolysis-resistant resin for protein-like shoe linings is essential.

[0004] Our company previously applied for an invention patent (CN120737302A) entitled "A Soft, Embossed, and Resistant Polyurethane Wet-Process Resin for Garment Leather, Its Preparation Method, and Its Application." The raw materials for preparing the polyurethane wet-process resin in this patent include the following components by weight: 0.002-0.004 parts of inorganic acid; 165-251 parts of polyester polyol; 42-64 parts of isocyanate; 7-11 parts of small molecule alcohol; 24-37 parts of additives; and 560-840 parts of solvent. The polyester polyol includes: polyester polyols in the adipic acid-ethylene glycol-1,4-butanediol system, polyester polyols in the adipic acid-phthalic acid-ethylene glycol-1,4-butanediol system, polyester polyols in the adipic acid-diethylene glycol system, and polyester polyols in the adipic acid-ethylene glycol system. Summary of the Invention

[0005] In view of the problems that existing synthetic leathers with good cotton-like feel and hydrolysis resistance are prone to slipping of the base surface and low thickness, and that insufficient washing of synthetic leather makes it difficult to test the peel strength of the product through hot melt adhesive tape, as well as the limited application range of the product, the purpose of this invention is to provide a polyurethane wet-process hydrolysis resistant resin for imitation protein shoe lining leather, its preparation method and application.

[0006] To achieve this objective, the present invention adopts the following technical solution: This invention provides a wet-process hydrolysis-resistant polyurethane resin for imitation protein shoe lining leather, the raw materials of which include the following components in parts by weight: Inorganic acid 0.002-0.004 parts; 164-247 parts of polyols; 45-69 parts of isocyanate; 7-11 parts of small molecule alcohols; 27-41 parts of auxiliary agents; Solvent 555-833 parts; Preferably, the inorganic acid is concentrated phosphoric acid.

[0007] Preferably, the polyols include polyether polyols and polyester polyols. The polyether polyols include: polyether polyols with a polytetrahydrofuran structure (denoted as PE-1) and polyether polyols with a polyoxypropylene structure. The polyether polyols with a polyoxypropylene structure include a first polyether polyol with a molecular weight range of 1800-2200 (denoted as PE-2) and a second polyether polyol with a molecular weight range of 3800-4200 (denoted as PE-3). The polyester polyols include polyester polyols of the adipic acid-1,4-butanediol-ethylene glycol system (denoted as PE-4) and polyether polyols with a polytetrahydrofuran structure (denoted as PE-5).

[0008] Preferably, the polyether polyol with the polytetrahydrofuran structure has a number average molecular weight of 1800-2200; the polyester polyol of the adipic acid-1,4-butanediol-ethylene glycol system has a number average molecular weight of 3800-4200; and the polyether polyol with the polytetrahydrofuran structure has a number average molecular weight of 800-1200.

[0009] Preferably, the polyether polyol with the polytetrahydrofuran structure and the polyether polyol with the first polyoxypropylene structure have the same molecular weight of 2000; the polyether polyol with the second polyoxypropylene structure and the polyester polyol of the adipic acid-1,4-butanediol-ethylene glycol system have a molecular weight of 4000; and the polyether polyol with the polytetrahydrofuran structure has a molecular weight of 1000.

[0010] Preferably, the isocyanate is one or more selected from diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), and dicyclohexylmethane diisocyanate (HMDI). Diphenylmethane diisocyanate (MDI) is preferred.

[0011] Preferably, the small molecule alcohol is one or more of ethylene glycol (EG), 1,4-butanediol (BDO), and diethylene glycol, serving as a chain extender. Ethylene glycol (EG) is preferred.

[0012] Preferably, the solvent is N,N-dimethylformamide (DMF), and the additive is one or more of the following: a washing aid, a stabilizer, a capping agent, and a hindered phenolic antioxidant.

[0013] Preferably, the washing aid is a polysiloxane-based softener and a polyether polyol, which can be commercially available products.

[0014] Preferably, the stabilizer is benzoic acid.

[0015] Preferably, the capping agent is methanol.

[0016] The present invention also provides a method for preparing the above-mentioned soft, cotton-feel, protein-like shoe lining leather using a wet-process hydrolysis-resistant polyurethane resin, the preparation method comprising the following steps: The first step is the preparation of intermediate A of the wet-process hydrolysis-resistant polyurethane resin: (a1) Mix polyether polyol with polytetrahydrofuran structure, polyether polyol with polyoxypropylene structure, polyester polyol with adipic acid-1,4-butanediol-ethylene glycol system, hindered phenolic antioxidant, inorganic acid, and part of the solvent, and heat the mixture. (a2) Add a portion of isocyanate to the mixture after treatment in step (a1) and react, while maintaining an R value of 1.9-2.1 and treating at a constant temperature; (a3) Add a portion of the solvent and small molecule alcohol to the mixture after step (a2) and mix, then treat at a constant temperature; (a4) Add a portion of isocyanate to the mixture after step (a3) ​​and react, then treat at a constant temperature; (a5) Add the remaining isocyanate to the mixture after step (a4) and react, keeping the R value at 0.9-1.1. Add the remaining solvent until the reaction viscosity is 10-16 Pas / 25 degrees and the liquid-solid content is 29.5%-30.5%. Then add the capping agent, stir, and cool. (a6) Add stabilizer, polysiloxane system softener and washing aid to the mixture after step (a5) and stir to obtain the polyurethane wet process hydrolysis resistant resin intermediate A.

[0017] Furthermore, the preparation steps of intermediate B of polyurethane wet-process hydrolysis-resistant resin are as follows: (b1) Mix polyether polyol with polytetrahydrofuran structure, polyether polyol with polyoxypropylene structure, polyester polyol with adipic acid-1,4-butanediol-ethylene glycol system, hindered phenolic antioxidant, inorganic acid, and part of the solvent, and heat the mixture. (b2) Add a portion of isocyanate to the mixture after treatment in step (b1) and react, while maintaining an R value of 0.4-0.6 and treating at a constant temperature; (b3) Add a portion of the solvent and small molecule alcohol to the mixture after step (b2) and mix, then treat at a constant temperature; (b4) Add a portion of isocyanate to the mixture after step (b3) and react it under constant temperature. (b5) Add the remaining isocyanate to the mixture after step (b4) and react, keeping the R value at 0.9-1.1. Add the remaining solvent until the reaction viscosity is 10-16 Pas / 25 degrees and the liquid-solid content is 29.5%-30.5%. Then add the end-capping agent, stir, and cool. (b6) Add a stabilizer to the mixture after step (b5) and stir to obtain the polyurethane wet-process hydrolysis resistant resin intermediate B.

[0018] Then comes the preparation steps of the wet-process hydrolysis-resistant polyurethane resin: (c1) Mix polyether polyol with polytetrahydrofuran structure, polyether polyol with polyoxypropylene structure, some small molecule alcohol, some hindered phenolic antioxidant, inorganic acid, and some solvent, and heat them. (c2) Add a portion of isocyanate to the mixture after step (c1) and react, while maintaining an R value of 1.5-1.7 and treating at a constant temperature; (c3) Add part of the solvent and the remaining small molecule alcohol to the mixture after step (c2) and mix, then treat at a constant temperature; (c4) Add a portion of isocyanate to the mixture after step (c3) and react it under constant temperature. (c5) Add the remaining isocyanate to the mixture after step (c4) and react, keeping the R value at 0.9-1.1. Add the remaining solvent until the reaction viscosity is 26-30 Pas / 25 degrees and the liquid-solid content is 29.5%-30.5%. Then add the end-capping agent, stir, and cool. (c6) Add stabilizer, 5% of polyurethane wet-process hydrolysis-resistant intermediate A (accounting for 5% of the total resin content), 10% of polyurethane wet-process hydrolysis-resistant intermediate B (accounting for 10% of the total resin content), polyether polyol washing aid, and the remaining hindered phenolic antioxidant to the mixture after treatment in step (c5) and stir to obtain the polyurethane wet-process hydrolysis-resistant resin.

[0019] Preferably, the preparation of the wet-process hydrolysis-resistant polyurethane resin is completed in a reaction vessel.

[0020] Preferably, in step (a1), the heating conditions are to raise the temperature to 40°C-50°C, and after heating, maintain a constant temperature and stir for 20-40 minutes. Preferably, based on the total mass of the solvent being 100%, the mass percentage of the solvent in step (a1) is 1%-2%.

[0021] Preferably, in step (a2), the constant temperature treatment is carried out at 70℃-75℃ for 1-2 hours with stirring; preferably, based on the total mass of the isocyanate as 100%, the mass percentage of the isocyanate in step (2) is 3%-4%.

[0022] Preferably, in step (a3), the constant temperature treatment condition is stirring at 70℃-75℃ for 1-2 hours; preferably, based on the total mass of the solvent as 100%, the mass percentage of the solvent in step (a3) ​​is 9%-10%; preferably, based on the total mass of the small molecule alcohol as 100%, the mass percentage of the small molecule alcohol in step (a3) ​​is 4%-5%.

[0023] Preferably, in step (a4), the constant temperature treatment condition is stirring at 70℃-75℃ for 1-2 hours; preferably, based on the total mass of the isocyanate as 100%, the mass percentage of the isocyanate in step (a4) is 1%-2%.

[0024] Preferably, in step (a5), the temperature is controlled at 70°C-75°C during the addition of the remaining isocyanate.

[0025] Preferably, in step (b1), the heating conditions are to raise the temperature to 40°C-50°C, and after the heating is completed, maintain the constant temperature and stir for 20-40 minutes. Preferably, based on the total mass of the solvent being 100%, the mass percentage of the solvent in step (1) is 2%-3%.

[0026] Preferably, in step (b2), the constant temperature treatment condition is stirring at 70℃-75℃ for 1-2 hours; preferably, based on the total mass of the isocyanate as 100%, the mass percentage of the isocyanate in step (b2) is 2%-3%.

[0027] Preferably, in step (b3), the constant temperature treatment condition is stirring at 70℃-75℃ for 1-2 hours; preferably, based on the total mass of the solvent as 100%, the mass percentage of the solvent in step (b3) is 3%-4%; preferably, based on the total mass of the small molecule alcohol as 100%, the mass percentage of the small molecule alcohol in step (b3) is 1%-2%.

[0028] Preferably, in step (b4), the constant temperature treatment condition is stirring at 70℃-75℃ for 1-2 hours; preferably, based on the total mass of the isocyanate as 100%, the mass percentage of the isocyanate in step (b4) is 9%-10%.

[0029] Preferably, in step (b6), the temperature is controlled at 70°C-75°C during the addition of the remaining isocyanate.

[0030] Preferably, in step (c1), the heating conditions are to raise the temperature to 40°C-50°C, and then maintain a constant temperature while stirring for 20-40 minutes after the heating is completed. Preferably, based on the total mass of the solvent being 100%, the mass percentage of the solvent in step (c1) is 19%-20%. Preferably, based on the total mass of the small molecule alcohol being 100%, the mass percentage of the small molecule alcohol in step (c1) is 11%-12%.

[0031] Preferably, in step (c2), the constant temperature treatment condition is stirring at 70℃-75℃ for 1-2 hours; preferably, based on the total mass of the isocyanate as 100%, the mass percentage of the isocyanate in step (c2) is 58%-59%.

[0032] Preferably, in step (c3), the isothermal treatment condition is stirring at 70℃-75℃ for 1-2 hours; preferably, based on the total mass of the solvent as 100%, the mass percentage of the solvent in step (c3) is 16%-17%; preferably, based on the total mass of the small molecule alcohol as 100%, the mass percentage of the small molecule alcohol in step (c3) is 68%-69%.

[0033] Preferably, in step (c4), the constant temperature treatment is carried out at 70℃-75℃ for 1-2 hours with stirring; preferably, based on the total mass of the isocyanate as 100%, the mass percentage of the isocyanate in step (4) is 19%-20%.

[0034] Preferably, in step (c5), the temperature is controlled at 70°C-75°C during the addition of the remaining isocyanate.

[0035] Thirdly, the present invention also provides a synthetic leather prepared using the above-mentioned soft, cotton-like protein-like shoe lining leather with a wet-process hydrolytically resistant polyurethane resin, or prepared using the above-mentioned method for preparing soft, cotton-like protein-like shoe lining leather with a wet-process hydrolytically resistant polyurethane resin.

[0036] Beneficial effects: (1) In the preparation of polyurethane wet-process hydrolysis resistant resin in this invention, the polyether polyol (PE-1) with polytetrahydrofuran structure, the polyether polyol (PE-2) with polyoxypropylene structure, and the polyether polyol (PE-3) with polyoxypropylene structure are selected by the main synthesis to improve the film-forming properties and firmness of the synthetic leather base surface; the water washability and high peel strength of the resin are significantly improved, and it is easier to coordinate the changes in the penetration performance of the main body on the fabric than using a single-structure polyether polyol; the resin coagulation speed is improved by using small molecule alcohol as a chain extender to make the resin more uniform while ensuring a firmer hand feel, and the temperature resistance, modulus, coagulation speed and gloss of the resin are improved by increasing the amount of chain extender, which is easier to adjust than using chain extenders with side chains; in the selection of two different structures of additives, the additives that help coagulation uniformity, water washability and improve the gloss of synthetic leather are selected, which significantly improves the gloss and softness of the synthetic leather surface.

[0037] In the preparation of the polyurethane wet-process hydrolysis-resistant resin of this invention, polyurethane resin intermediate A is synthesized by combining polytetrahydrofuran-structured polyether polyol (PE-5), adipic acid-1,4-butanediol-ethylene glycol system polyester polyol (PE-4), and polyoxypropylene structured polyether polyol (PE-3) in different proportions, along with a chain extender with good temperature resistance, a protein-like softener, and a first-step over-prepolymerization method. The resin's solidification speed, modulus, thickness retention, protein-like skin feel, and washability are significantly improved, ensuring a good combination of high peel strength and protein-like cotton feel when preparing resin for protein-like shoe lining.

[0038] In the preparation of the polyurethane wet-process hydrolysis-resistant resin of this invention, polyurethane resin intermediate B is synthesized by combining polytetrahydrofuran-structured polyether polyol (PE-1), adipic acid-1,4-butanediol-ethylene glycol system polyester polyol (PE-4), and polyoxypropylene structured polyether polyol (PE-2) in different proportions, along with a chain extender with good temperature resistance and a first-step under-polymerization method. The resin's solidification speed, modulus, thickness retention, protein-like skin feel, and washability are significantly improved, ensuring a good combination of washability and protein-like skin feel when preparing resin for protein-like shoe lining.

[0039] (4) In the preparation of the polyurethane wet process hydrolysis resistant resin of the present invention, the polyurethane resin synthesized by the same process uses 85% of the main resin and 5% of intermediate A resin and 10% of intermediate B resin to improve the 5-year hydrolysis resistance, fabric penetration, high peel strength and soft feel of the resin. The properties are relatively outstanding at the same time. It plays a key role in making polyurethane hydrolysis resistant resin for soft imitation protein shoe lining leather, which can achieve 5-year hydrolysis resistance, soft feel and high peel strength.

[0040] (5) In the preparation of the polyurethane wet-process hydrolysis resistant resin of the present invention, the washing performance and the softening performance of the resin are improved by adding polysiloxane softener at the termination of the synthesis of intermediate resin. In addition, polyether polyol is added at the termination of the synthesis of the main resin to improve the washing performance. The two are combined to achieve both washing and softening performance while reducing the amount of polysiloxane softener used, and ensuring the effect of polysiloxane softener on peel strength (polysiloxane softener has poor compatibility with polyurethane resin).

[0041] (6) In the later extended applications of soft, cotton-feel imitation protein shoe lining leather, it was found that the synthetic leather made by the large impregnation process and the peeling process has a significant effect on the surface smoothness, cotton-feel and other properties, which increases the added value of the synthetic leather. Detailed Implementation

[0042] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand... The embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0043] The raw materials used in the embodiments and comparative examples of this invention are as follows: PE-1 (polyether polyol with polytetrahydrofuran structure): molecular weight 2000 (manufacturer: Hyosung Group (Jiaxing) Co., Ltd., model: PTMG-2000); PE-17 (polyether polyol with polytetrahydrofuran structure): molecular weight 1000 (manufacturer: same as above, model: PTMG-1000); PE-2 (a polyether polyol with a first polyoxypropylene structure): molecular weight 2000 (manufacturer: Shandong Lanxing Dongda Co., Ltd., model: DP-2000D); PE-3 (a polyether polyol with a second polyoxypropylene structure): molecular weight 4000 (manufacturer: Wanhua Chemical (Ningbo) Rongwei Polyurethane Co., Ltd., model: PPG-4000); PE-4 (adipic acid-1,4-butanediol-ethylene glycol system polyester polyol): molecular weight 4000; PE-5 (polyether polyol with a polytetrahydrofuran structure): molecular weight 1000 (manufacturer: Dalian Chemical Industry Co., Ltd., Taiwan, China; model: PTMG-1000) PE-6 (a polyester polyol based on adipic acid-1,4-butanediol system): molecular weight 4000; Hindered phenolic antioxidant: ROX-13TP (Manufacturer: Double Bond Chemical Co., Ltd., Taiwan, China; Model: Antioxidant 1330); Detergents: Polysiloxane softener: XP-300 (manufacturer: Guangzhou Sloco Polymer Co., Ltd., model: 8818F2) and polyether polyol: XP-600 (manufacturer: Shandong Lanxing Dongda Co., Ltd., model: EP-3600).

[0044] Of the raw materials used in this invention, PE-4 and PE-6 were prepared in the laboratory, while the others were commercially available products.

[0045] Example 1: A wet-process hydrolysis-resistant polyurethane resin for imitation protein shoe lining leather, the raw materials for which are prepared include the following components: PE-1: 71g, PE-2: 29g, PE-3: 81g, PE-4: 3g, PE-5: 2g; Hindered phenolic antioxidant ROX-13TP: 0.2g, concentrated phosphoric acid: 0.003g, ethylene glycol: 8.4g, DMF: 625g, MDI: 51.3g, methanol: 0.25g, benzoic acid: 0.45g, polysiloxane softener XP-300: 6.8g, polyether polyol XP-600: 22.3g.

[0046] The above-mentioned wet-process hydrolysis-resistant polyurethane resin preparation method is as follows.

[0047] The first step is the preparation of intermediate A of the wet-process hydrolysis-resistant polyurethane resin: (a1) Mix polyether polyol PE-5 with polytetrahydrofuran structure, polyether polyol with second polyoxypropylene structure accounting for 6% (100% calculation) of the total amount of PE-3, polyester polyol of adipic acid-1,4-butanediol-ethylene glycol system accounting for 60% (100% calculation) of the total amount of PE-4, hindered phenolic antioxidant accounting for 5% (100% calculation) of the total amount of ROX-23TP, inorganic acid accounting for 30% (100% calculation) of the total amount of concentrated phosphoric acid, and a portion of the solvent accounting for 1.5% (100% calculation) of the total amount of DMF, and heat the mixture. (a2) Add 3.2% (calculated as 100%) of the isocyanate to the mixture after treatment in step (a1) and react it while keeping the R value at 1.9-2.1 and treating at a constant temperature; (a3) Add 0.8% of the total solvent and 5.2% (calculated as 100%) of the small molecule alcohol to the mixture after treatment in step (a2), mix, and treat at a constant temperature; (a4) Add 1.5% of the total isocyanate to the mixture after step (a3) ​​and react at a constant temperature; (a5) Add the remaining isocyanate (0.2% of the total amount) to the mixture after step (a4) and react, keeping the R value at 0.9-1.1. Add the remaining solvent until the reaction viscosity is 10-16 Pas / 25 degrees and the liquid-solid content is 29.5%-30.5%. Then add the end-capping agent, stir, and cool. (a6) Add stabilizer, polysiloxane system softener and washing aid to the mixture after step (a5) and stir to obtain the polyurethane wet process hydrolysis resistant resin intermediate A.

[0048] Furthermore, the preparation steps of intermediate B of polyurethane wet-process hydrolysis-resistant resin are as follows: (b1) Mix 10.9% (100% calculation) of polytetrahydrofuran structured polyether polyol in PE-1, 37.6% (100% calculation) of first polyoxypropylene structured polyether polyol in PE-2, 40% of the total amount of adipic acid-1,4-butanediol-ethylene glycol system polyester polyol, 15% of the total amount of hindered phenolic antioxidant, 30% of the total amount of inorganic acid, and 2.5% of the total amount of solvent, and heat the mixture. (b2) Add a portion of isocyanate to the mixture after treatment in step (b1) to react at a total amount of 2.3%, and keep the R value at 0.4-0.6 and treat at a constant temperature; (b3) Add 3.2% of the solvent and 11.2% of the small molecule alcohol to the mixture after step (b2) and mix, then treat at a constant temperature; (b4) Add 9.1% of the total isocyanate to the mixture after step (b3) and react it at a constant temperature; (b5) Add the remaining isocyanate (0.4% of the total amount) to the mixture after step (b4) and react, keeping the R value at 0.9-1.1. Add the remaining solvent until the reaction viscosity is 10-16 Pas / 25 degrees and the liquid-solid content is 29.5%-30.5%. Then add the end-capping agent, stir, and cool. (b6) Add a stabilizer to the mixture after step (b5) and stir to obtain the polyurethane wet-process hydrolysis resistant resin intermediate B.

[0049] Then comes the preparation steps of the wet-process hydrolysis-resistant polyurethane resin: (c1) Mix 89.1% of the total amount of polytetrahydrofuran-structured polyether polyol in PE-1, 62.4% of the total amount of polyether polyol in the first polyoxypropylene structure in PE-2, 11.8% of the total amount of small molecule alcohol, 80% of the total amount of hindered phenolic antioxidants, 40% of the total amount of inorganic acid, and 19.4% of the total amount of solvent, and then heat the mixture. (c2) Add 58.9% of the total isocyanate to the mixture after step (c1) and react, keeping the R value at 1.5-1.7 and treating at a constant temperature; (c3) Add 16.6% of the solvent and 71.8% of the remaining small molecule alcohol to the mixture after step (c2) and mix, then treat at a constant temperature; (c4) Add 19.6% of the total isocyanate to the mixture after step (c3) and react it at a constant temperature; (c5) Add the remaining isocyanate, which accounts for 3.8% of the total amount, to the mixture after step (c4) and react, while keeping the R value at 0.9-1.1. Add the remaining solvent until the reaction viscosity is 26-30 Pas / 25 degrees and the liquid-solid content is 29.5%-30.5%. Then add the end-capping agent, stir, and cool down. (c6) Add stabilizer, 5% of polyurethane wet-process hydrolysis-resistant intermediate A (accounting for 5% of the total resin content), 10% of polyurethane wet-process hydrolysis-resistant intermediate B (accounting for 10% of the total resin content), polyether polyol washing aid, and the remaining hindered phenolic antioxidant to the mixture after treatment in step (c5) and stir to obtain the polyurethane wet-process hydrolysis-resistant resin.

[0050] Example 2: A wet-process hydrolysis-resistant polyurethane resin for imitation protein shoe lining leather, the raw materials for which are prepared include the following components: PE-1: 71g, PE-2: 55g, PE-3: 55g, PE-4: 3g, PE-5: 2g; Hindered phenolic antioxidant ROX-13TP: 0.2g, concentrated phosphoric acid: 0.003g, ethylene glycol: 8.4g, DMF: 625g, MDI: 51.3g, methanol: 0.25g, benzoic acid: 0.45g, polysiloxane softener XP-300: 6.8g, polyether polyol XP-600: 22.3g.

[0051] The above-mentioned wet-process hydrolysis-resistant polyurethane resin preparation method is as follows.

[0052] The first step is the preparation of intermediate A of the wet-process hydrolysis-resistant polyurethane resin: (a1) Mix polyether polyol PE-5 with polytetrahydrofuran structure, polyether polyol with second polyoxypropylene structure accounting for 6% (100% calculation) of the total amount of PE-3, polyester polyol of adipic acid-1,4-butanediol-ethylene glycol system accounting for 60% (100% calculation) of the total amount of PE-4, hindered phenolic antioxidant accounting for 5% (100% calculation) of the total amount of ROX-23TP, inorganic acid accounting for 30% (100% calculation) of the total amount of concentrated phosphoric acid, and a portion of the solvent accounting for 1.5% (100% calculation) of the total amount of DMF, and heat the mixture. (a2) Add 3.2% (calculated as 100%) of the isocyanate to the mixture after treatment in step (a1) and react it while keeping the R value at 1.9-2.1 and treating at a constant temperature; (a3) Add 0.8% of the total solvent and 5.2% (calculated as 100%) of the small molecule alcohol to the mixture after treatment in step (a2), mix, and treat at a constant temperature; (a4) Add 1.5% of the total isocyanate to the mixture after step (a3) ​​and react at a constant temperature; (a5) Add the remaining isocyanate (0.2% of the total amount) to the mixture after step (a4) and react, keeping the R value at 0.9-1.1. Add the remaining solvent until the reaction viscosity is 10-16 Pas / 25 degrees and the liquid-solid content is 29.5%-30.5%. Then add the end-capping agent, stir, and cool. (a6) Add stabilizer, polysiloxane system softener and washing aid to the mixture after step (a5) and stir to obtain the polyurethane wet process hydrolysis resistant resin intermediate A.

[0053] Furthermore, the preparation steps of intermediate B of polyurethane wet-process hydrolysis-resistant resin are as follows: (b1) Mix 10.9% (100% calculation) of polytetrahydrofuran structured polyether polyol in PE-1, 37.6% (100% calculation) of first polyoxypropylene structured polyether polyol in PE-2, 40% of the total amount of adipic acid-1,4-butanediol-ethylene glycol system polyester polyol, 15% of the total amount of hindered phenolic antioxidant, 30% of the total amount of inorganic acid, and 2.5% of the total amount of solvent, and heat the mixture. (b2) Add a portion of isocyanate to the mixture after treatment in step (b1) to react at a total amount of 2.3%, and keep the R value at 0.4-0.6 and treat at a constant temperature; (b3) Add 3.2% of the solvent and 11.2% of the small molecule alcohol to the mixture after step (b2) and mix, then treat at a constant temperature; (b4) Add 9.1% of the total isocyanate to the mixture after step (b3) and react it at a constant temperature; (b5) Add the remaining isocyanate (0.4% of the total amount) to the mixture after step (b4) and react, keeping the R value at 0.9-1.1. Add the remaining solvent until the reaction viscosity is 10-16 Pas / 25 degrees and the liquid-solid content is 29.5%-30.5%. Then add the end-capping agent, stir, and cool. (b6) Add a stabilizer to the mixture after step (b5) and stir to obtain the polyurethane wet-process hydrolysis resistant resin intermediate B.

[0054] Then comes the preparation steps of the wet-process hydrolysis-resistant polyurethane resin: (c1) Mix 89.1% of the total amount of polytetrahydrofuran-structured polyether polyol in PE-1, 62.4% of the total amount of polyether polyol in the first polyoxypropylene structure in PE-2, 11.8% of the total amount of small molecule alcohol, 80% of the total amount of hindered phenolic antioxidants, 40% of the total amount of inorganic acid, and 19.4% of the total amount of solvent, and then heat the mixture. (c2) Add 58.9% of the total isocyanate to the mixture after step (c1) and react, keeping the R value at 1.5-1.7 and treating at a constant temperature; (c3) Add 16.6% of the solvent and 71.8% of the remaining small molecule alcohol to the mixture after step (c2) and mix, then treat at a constant temperature; (c4) Add 19.6% of the total isocyanate to the mixture after step (c3) and react it at a constant temperature; (c5) Add the remaining isocyanate, which accounts for 3.8% of the total amount, to the mixture after step (c4) and react, while keeping the R value at 0.9-1.1. Add the remaining solvent until the reaction viscosity is 26-30 Pas / 25 degrees and the liquid-solid content is 29.5%-30.5%. Then add the end-capping agent, stir, and cool down. (c6) Add stabilizer, 5% of polyurethane wet-process hydrolysis-resistant intermediate A (accounting for 5% of the total resin content), 10% of polyurethane wet-process hydrolysis-resistant intermediate B (accounting for 10% of the total resin content), polyether polyol washing aid, and the remaining hindered phenolic antioxidant to the mixture after treatment in step (c5) and stir to obtain the polyurethane wet-process hydrolysis-resistant resin.

[0055] Example 3: A wet-process hydrolysis-resistant polyurethane resin for imitation protein shoe lining leather, the raw materials for which are prepared include the following components: PE-1: 71g, PE-2: 29g, PE-3: 70g, PE-4: 14g, PE-5: 2g; Hindered phenolic antioxidant ROX-13TP: 0.2g, concentrated phosphoric acid: 0.003g, ethylene glycol: 8.4g, DMF: 625g, MDI: 51.3g, methanol: 0.25g, benzoic acid: 0.45g, polysiloxane softener XP-300: 6.8g, polyether polyol XP-600: 22.3g.

[0056] The above-mentioned wet-process hydrolysis-resistant polyurethane resin preparation method is as follows.

[0057] The first step is the preparation of intermediate A of the wet-process hydrolysis-resistant polyurethane resin: (a1) Mix polyether polyol PE-5 with polytetrahydrofuran structure, polyether polyol with second polyoxypropylene structure accounting for 6% (100% calculation) of the total amount of PE-3, polyester polyol of adipic acid-1,4-butanediol-ethylene glycol system accounting for 60% (100% calculation) of the total amount of PE-4, hindered phenolic antioxidant accounting for 5% (100% calculation) of the total amount of ROX-23TP, inorganic acid accounting for 30% (100% calculation) of the total amount of concentrated phosphoric acid, and a portion of the solvent accounting for 1.5% (100% calculation) of the total amount of DMF, and heat the mixture. (a2) Add 3.2% (calculated as 100%) of the isocyanate to the mixture after treatment in step (a1) and react it while keeping the R value at 1.9-2.1 and treating at a constant temperature; (a3) Add 0.8% of the total solvent and 5.2% (calculated as 100%) of the small molecule alcohol to the mixture after treatment in step (a2), mix, and treat at a constant temperature; (a4) Add 1.5% of the total isocyanate to the mixture after step (a3) ​​and react at a constant temperature; (a5) Add the remaining isocyanate (0.2% of the total amount) to the mixture after step (a4) and react, keeping the R value at 0.9-1.1. Add the remaining solvent until the reaction viscosity is 10-16 Pas / 25 degrees and the liquid-solid content is 29.5%-30.5%. Then add the end-capping agent, stir, and cool. (a6) Add stabilizer, polysiloxane system softener and washing aid to the mixture after step (a5) and stir to obtain the polyurethane wet process hydrolysis resistant resin intermediate A.

[0058] Furthermore, the preparation steps of intermediate B of polyurethane wet-process hydrolysis-resistant resin are as follows: (b1) Mix 10.9% (100% calculation) of polytetrahydrofuran structured polyether polyol in PE-1, 37.6% (100% calculation) of first polyoxypropylene structured polyether polyol in PE-2, 40% of the total amount of adipic acid-1,4-butanediol-ethylene glycol system polyester polyol, 15% of the total amount of hindered phenolic antioxidant, 30% of the total amount of inorganic acid, and 2.5% of the total amount of solvent, and heat the mixture. (b2) Add a portion of isocyanate to the mixture after treatment in step (b1) to react at a total amount of 2.3%, and keep the R value at 0.4-0.6 and treat at a constant temperature; (b3) Add 3.2% of the solvent and 11.2% of the small molecule alcohol to the mixture after step (b2) and mix, then treat at a constant temperature; (b4) Add 9.1% of the total isocyanate to the mixture after step (b3) and react it at a constant temperature; (b5) Add the remaining isocyanate (0.4% of the total amount) to the mixture after step (b4) and react, keeping the R value at 0.9-1.1. Add the remaining solvent until the reaction viscosity is 10-16 Pas / 25 degrees and the liquid-solid content is 29.5%-30.5%. Then add the end-capping agent, stir, and cool. (b6) Add a stabilizer to the mixture after step (b5) and stir to obtain the polyurethane wet-process hydrolysis resistant resin intermediate B.

[0059] Then comes the preparation steps of the wet-process hydrolysis-resistant polyurethane resin: (c1) Mix 89.1% of the total amount of polytetrahydrofuran-structured polyether polyol in PE-1, 62.4% of the total amount of polyether polyol in the first polyoxypropylene structure in PE-2, 11.8% of the total amount of small molecule alcohol, 80% of the total amount of hindered phenolic antioxidants, 40% of the total amount of inorganic acid, and 19.4% of the total amount of solvent, and then heat the mixture. (c2) Add 58.9% of the total isocyanate to the mixture after step (c1) and react, keeping the R value at 1.5-1.7 and treating at a constant temperature; (c3) Add 16.6% of the solvent and 71.8% of the remaining small molecule alcohol to the mixture after step (c2) and mix, then treat at a constant temperature; (c4) Add 19.6% of the total isocyanate to the mixture after step (c3) and react it at a constant temperature; (c5) Add the remaining isocyanate, which accounts for 3.8% of the total amount, to the mixture after step (c4) and react, while keeping the R value at 0.9-1.1. Add the remaining solvent until the reaction viscosity is 26-30 Pas / 25 degrees and the liquid-solid content is 29.5%-30.5%. Then add the end-capping agent, stir, and cool down. (c6) Add stabilizer, 5% of polyurethane wet-process hydrolysis-resistant intermediate A (accounting for 5% of the total resin content), 10% of polyurethane wet-process hydrolysis-resistant intermediate B (accounting for 10% of the total resin content), polyether polyol washing aid, and the remaining hindered phenolic antioxidant to the mixture after treatment in step (c5) and stir to obtain the polyurethane wet-process hydrolysis-resistant resin.

[0060] Comparative Example 1: The preparation process is basically the same as that of Example 1, except that 1.36g of 1,4-butanediol is used instead of 0.94g of ethylene glycol in the chain extender of intermediate B.

[0061] Comparative Example 2: The preparation process is basically the same as that of Example 1, except that 0.64g of 2-methyl-1,3-propanediol is used instead of 0.44g of ethylene glycol in the chain extender of intermediate A.

[0062] Comparative Example 3: The preparation process is basically the same as that of Example 1, except that the polyester polyol (PE-6) of the adipic acid-1,4-butanediol system is used instead of the polyester polyol (PE-4) of the adipic acid-1,4-butanediol-ethylene glycol system.

[0063] Comparative Example 4: The preparation process is basically the same as that of Example 1, except that a polyether polyol with a molecular weight of 1000 (denoted as PE-17) is used instead of a polyether polyol with a molecular weight of 2000 (PE-1) in the polytetrahydrofuran structure.

[0064] The raw materials and contents of the polyurethane wet-process hydrolysis-resistant resins of Examples 1-3 and Comparative Examples 1-4 are shown in Table 1, in g.

[0065] Table 1

[0066] The polyurethane wet-process hydrolysis-resistant resins described in Examples 1-3 and Comparative Examples 1-4 were respectively prepared into soft, cotton-like protein-like shoe lining leather according to the following steps: 100g of the synthesized polyurethane resin was added to a plastic bottle, along with 10g of mica powder, 1g of oily black paste, and 80g of DMF solvent, and stirred at 3000 rpm. -1The mixture is dispersed evenly at a high stirring speed, and then allowed to stand to degas before use. The leather base fabric is soaked in a 50% DMF aqueous solution to remove surface impurities, then pressed with a water press, and then ironed until semi-dry. A 0.2mm thick feeler gauge is then placed on the back of the base fabric. A small amount of the prepared slurry is poured onto the front of the spunlace fabric and scraped onto it. It is then placed in water to fully solidify, followed by washing and drying to make a wet-process base. After that, a 15-mil thick dry-process imitation protein skin-feel fabric is attached to obtain the soft cotton-feel imitation protein shoe lining leather of Examples 1-3 and the soft cotton-feel imitation protein shoe lining leather of Comparative Examples 1-4.

[0067] The soft, cotton-like protein-like shoe lining leathers of Examples 1-3 and Comparative Examples 1-4 were subjected to the following performance tests, and the evaluation criteria are as follows: Thickness: After spreading the resin coating at a fixed caliper at 100 micrometers, a thickness of 0.3mm or more is considered excellent, while a thickness of less than 0.1mm is considered poor.

[0068] Peel strength: A peel strength of 3KG after drying at 110℃ is considered excellent; if it does not reach 3KG, it is considered poor.

[0069] Feel: Excellent: After drying at 110℃, it should feel soft and tender; Poor: If it does not feel soft and tender, it should feel good.

[0070] 5-year hydrolysis resistance: Excellent results are achieved when the peel strength remains unchanged after soaking in a 10% NaOH aqueous solution for 24 hours, followed by washing off the NaOH and drying; poor results are achieved when the peel strength decreases significantly after soaking.

[0071] Water washing: After 15 passes of water washing roller compression, a smooth surface is considered excellent; an uneven surface is considered poor. The results are shown in Table 2.

[0072] Table 2 Sample Name thickness Peel strength feel 5-year hydrolysis resistance Water wash Example 1 excellent excellent excellent excellent excellent Example 2 excellent Difference Difference excellent excellent Example 3 excellent Difference excellent Difference excellent Comparative Example 1 Difference Difference excellent excellent excellent Comparative Example 2 excellent Difference excellent excellent Difference Comparative Example 3 Difference excellent Difference excellent Difference Comparative Example 4 Difference excellent Difference excellent Difference As shown in Table 2, Example 1 has excellent comprehensive performance, including 5-year hydrolysis resistance, high thickness, high peel strength, good softness, good surface smoothness, and outstanding washability.

[0073] The comparison between Example 1 and the comparative example shows that the use of two polyurethane intermediates with different properties produced by different processes and polyol structural combinations, when added to the main polyurethane resin, can improve the thickness retention, softness, and especially the performance in terms of water washing and surface smoothness of the product compared to using only a single process to produce polyurethane resin.

[0074] A comparison of Examples 1 and 3 shows that selecting a polyester polyol with a specific adipic acid-1,4-butanediol-ethylene glycol structure and a molecular weight of 4000 can improve the washability and maintain 5-year hydrolysis resistance of synthetic leather products, while also enhancing their softness and suppleness. A comparison of Examples 1 and Comparative Example 4 shows that selecting a polyether polyol with a specific molecular weight of 2000 can improve the film-forming properties and washability of the synthetic leather base surface. All techniques not specifically mentioned above refer to existing technologies.

[0075] Compared to the prior art invention in the background, the technical problems and application scenarios of this application are completely different. The prior art invention (i.e., the previously analyzed "soft embossed garment leather polyurethane wet-process resin") clearly states that the technical problem it aims to solve is that "existing synthetic leather is prone to stiffness and poor temperature resistance after high-temperature embossing, and the thickness retention rate of synthetic leather before and after embossing is low," and its application scenario focuses on the high-temperature embossing process of garment leather. In contrast, the technical problem that this application (a soft, protein-like skin-feeling shoe and bag leather wet-process resin) aims to solve is that "existing cotton-feeling hydrolysis-resistant synthetic leather is prone to slippery surface and low thickness, and due to insufficient washing, the peel strength of synthetic leather is difficult to test using hot melt adhesive tape," and its application scenario focuses on the protein-like skin feel and hydrolysis resistance of shoe lining leather and bag leather. There are significant differences in performance requirements between garment leather and shoe lining / bag leather: garment leather focuses more on embossing molding and softness, while shoe lining and bag leather focus more on hydrolysis resistance, peel strength, and protein-like skin feel.

[0076] Secondly, the core of the prior art invention lies in the use of polyester polyols entirely, compounded through five different polyester polyols with varying structures and molecular weights (adipic acid-ethylene glycol-1,4-butanediol system, adipic acid-phthalic acid-ethylene glycol-1,4-butanediol system, hexanediol-diethylene glycol-ethylene glycol system, adipic acid-diethylene glycol system, and adipic acid-ethylene glycol system) to improve the embossing resilience and hand feel of garment leather. The present application, however, breaks through the limitations of a pure polyester system, creatively constructing a composite system of polyether polyols and polyester polyols: this application simultaneously uses polyether polyols with a polytetrahydrofuran structure (PE-1, PE-5) and polyether polyols with a polyoxypropylene structure (PE-2, PE-3), combined with a polyester polyol (PE-4) of the adipic acid-1,4-butanediol-ethylene glycol system, and finely classifies the molecular weights of these polyols (different molecular weight levels such as 2000, 4000, and 1000). This composite design of polyether and polyester is the material basis for endowing the resin with excellent hydrolysis resistance and a protein-like feel—the introduction of polyether polyol significantly improves the resin's hydrolysis resistance, which is something that polyester polyol cannot achieve. The pure polyester system in the prior art, due to the inherent hydrolysis of its ester bonds, simply cannot achieve the "5-year hydrolysis resistance" required by this application. Regarding the preparation process, the prior art only uses one intermediate for blending, while this application designs two intermediates, A and B, synthesized using different R-value strategies (intermediate A uses an over-prepolymerization method with an R-value of 1.9-2.1, and intermediate B uses an under-prepolymerization method with an R-value of 0.4-0.6), and blends them with the main resin. Simultaneously, in the final stage of the main resin synthesis in this application, a polysiloxane softener and a polyether polyol washing aid are added to synergistically achieve a balance between a protein-like feel and excellent washing performance.

[0077] Example 1 of this application achieved an "excellent" rating in thickness, peel strength, hand feel, 5-year hydrolysis resistance, and washability, achieving a perfect combination of "5-year hydrolysis resistance," "soft and tender feel," and "protein-like skin feel." The achievement of "5-year hydrolysis resistance" is a direct result of the introduction of a specific polyether polyol system in this application, which is unattainable by the pure polyester system in the prior art. Furthermore, through the synergistic effect of the "dual intermediate" process and the polysiloxane softener and polyether polyol wash aid, this application overcomes the contradiction in the prior art where it is difficult to simultaneously achieve a protein-like effect with peel strength and washability—the test results of Comparative Examples 1 to 4 show that changing any key component or process parameter in this application will lead to a significant decrease in one or more properties. For example, when polyester polyol (PE-6) of the adipic acid-1,4-butanediol system was used to replace PE-4 of this application (Comparative Example 3), although the peel strength remained excellent, the hand feel and washability both became "poor"; when polyether polyol of 1000 molecular weight was used to replace PE-1 of 2000 molecular weight of this application (Comparative Example 4), the thickness, hand feel, and washability all became "poor". These comparative data fully demonstrate that the technical solution of this application is a carefully designed and optimized overall solution, with close synergistic relationships between the components and process steps. The resulting comprehensive performance improvement is unexpected and cannot be derived from the simple components and processes disclosed in the prior application.

[0078] The technical means disclosed in this invention are not limited to those described above, but also include technical solutions composed of any combination of the above technical features. The above descriptions are specific embodiments of this invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

Claims

1. A wet-process hydrolysis-resistant polyurethane resin for imitation protein shoe lining leather, characterized in that, The raw materials for preparation include the following components in parts by weight: Inorganic acid 0.002-0.004 parts; 164-247 parts of polyols; 45-69 parts of isocyanate; 7-11 parts of small molecule alcohols; 27-41 parts of auxiliary agents; The solvent comprises 555-833 parts, wherein the polyol includes polyether polyol and polyester polyol, wherein the polyether polyol includes: polyether polyol with a polytetrahydrofuran structure and polyether polyol with a polyoxypropylene structure, wherein the polyether polyol with a polyoxypropylene structure includes a first polyoxypropylene structure polyether polyol with a molecular weight range of 1800-2200 and a second polyoxypropylene structure polyether polyol with a molecular weight range of 3800-4200; and the polyester polyol includes polyester polyol of the adipic acid-1,4-butanediol-ethylene glycol system and polyether polyol with a polytetrahydrofuran structure.

2. The polyurethane for imitation protein shoe lining as described in claim 1, characterized in that, The inorganic acid is concentrated phosphoric acid.

3. The polyurethane for imitation protein shoe lining as described in claim 1, characterized in that, The molecular weight range of the polyether polyol with the polytetrahydrofuran structure is 1800-2200; the molecular weight range of the polyester polyol in the adipic acid-1,4-butanediol-ethylene glycol system is 3800-4200; and the molecular weight range of the polyether polyol with the polytetrahydrofuran structure is 800-1200.

4. The polyurethane for imitation protein shoe lining as described in claim 1, characterized in that, The isocyanate is one or more of diphenylmethane diisocyanate, dimethyl diphenylmethane diisocyanate, and toluene diisocyanate.

5. The polyurethane for imitation protein shoe lining as described in claim 1, characterized in that, The small molecule alcohol is one or more of ethylene glycol, 1,4-butanediol, and diethylene glycol.

6. The polyurethane for imitation protein shoe lining as described in claim 1, characterized in that, The solvent is N,N-dimethylformamide, and the additive is one or more of the following: a washing aid, a stabilizer, a capping agent, and a hindered phenolic antioxidant.

7. The polyurethane for imitation protein shoe lining as described in claim 6, characterized in that, The washing aid is a polyether polyol and polysiloxane system softener, the stabilizer is benzoic acid, and the capping agent is methanol.

8. The method for preparing polyurethane for imitation protein shoe lining leather according to any one of claims 1-7, characterized in that, The process includes the following steps: First, prepare polyurethane wet-process hydrolysis-resistant resin intermediate A; then, prepare polyurethane wet-process hydrolysis-resistant resin intermediate B; finally, prepare polyurethane wet-process hydrolysis-resistant resin by using polyurethane wet-process hydrolysis-resistant resin intermediate A (5% of the total resin content) and polyurethane wet-process hydrolysis-resistant resin intermediate B (10% of the total resin content) as components.

9. A synthetic leather, characterized in that, It is prepared using the polyurethane for imitation protein shoe lining leather according to any one of claims 1-7, or prepared using the method for preparing polyurethane for imitation protein shoe lining leather according to claim 8.

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