Polyurethane resin and method for producing same

Abstract

The invention discloses polyurethane resin and a manufacturing method thereof. The manufacturing method of the polyurethane resin comprises a mixing step of mixing polyether glycol and polyether triol; a reaction step: adding isocyanate into the polyether glycol and the polyether triol which are mixed with each other for reaction to form a first polymer; a chain extending step of adding a chain extender to the first polymer to form a second polymer; an end-capping step: adding an end-capping agent into the second polymer to carry out an end-capping reaction and form a third polymer; and a dilution step of diluting the third polymer with a dilution solvent to form a polyurethane resin. The polyurethane resin has a hard knot ratio of 27% to 34%, a glass transition temperature of-40.2 DEG C to-44.8 DEG C, and a tensile strength of 62.5 kg / 3 cm to 68.7 kg / 3 cm. According to the polyurethane resin and the manufacturing method thereof disclosed by the invention, the problem of insufficient strength of the existing polyurethane resin applied to leather for shoes can be effectively improved.

Description

Technical Field

[0001] The present invention relates to a polyurethane resin and a method for manufacturing the same, and more particularly to a polyurethane resin applicable to shoe leather and a method for manufacturing the same. Background Art

[0002] Existing polyurethane resins applied to shoe leather have the problem of insufficient strength. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a polyurethane resin and a method for manufacturing the same, which can effectively improve the problem of insufficient strength of existing polyurethane resins applied to shoe leather in view of the deficiencies of the prior art.

[0004] To solve the above technical problem, one of the technical solutions adopted by the present invention is to provide a method for manufacturing a polyurethane resin, which includes: a mixing step of mixing a polyether diol and a polyether triol; wherein the polyether diol has a number average molecular weight between 2,000 and 3,000, and the polyether triol has a number average molecular weight between 3,000 and 6,000; a reaction step of adding an isocyanate to the mutually mixed polyether diol and polyether triol to react to form a first polymer; a chain extension step of adding a chain extender to the first polymer to form a second polymer; a capping step of adding a capping agent to the second polymer to perform a capping reaction and form a third polymer; and a dilution step of diluting the third polymer with a dilution solvent to form a polyurethane resin; wherein, based on the total weight of the polyurethane resin being 100 wt%, the content of the polyether diol is between 31.6 wt% and 40.3 wt%, the content of the polyether triol is between 14.5 wt% and 26.3 wt%, and the content of the isocyanate is between 18.3 wt% and 21.8 wt%; wherein the polyurethane resin has a hard segment ratio between 27% and 34%, and the hard segment ratio is defined as the ratio of the sum of the content of the isocyanate and the content of the chain extender to the total weight of the polyurethane resin; wherein the polyurethane resin has a glass transition temperature between -40.2 °C and -44.8 °C and a tensile strength between 62.5 kg / 3 cm and 68.7 kg / 3 cm.

[0005] Preferably, the polyurethane resin has a weight average molecular weight between 27,450 and 29,800.

[0006] Preferably, the polyether diol is polypropylene glycol, and the polyether triol is at least one selected from the group consisting of tetrahydrofuran homopolyether and glycerol; wherein, the isocyanate is at least one selected from the group consisting of diphenylmethane diisocyanate, toluene diisocyanate and isophorone diisocyanate.

[0007] Preferably, the chain extender is at least one selected from the group consisting of ethylene glycol, 1,4-butanediol and 1,6-hexanediol, and the capping agent is at least one selected from the group consisting of methyl ethyl ketoxime and dimethyl ketoxime.

[0008] Preferably, the diluting solvent is at least one selected from the group consisting of propylene glycol methyl ether acetate and propylene glycol methyl ether; wherein, the polyurethane resin has a solid content between 91% and 92%, and the solid content is defined as the weight ratio of the polyurethane resin after drying to the polyurethane resin before drying.

[0009] Preferably, the content of the chain extender is between 4.5 wt% and 6 wt%, the content of the capping agent is between 7.8 wt% and 9.9 wt%, and the content of the diluting solvent is between 7.9 wt% and 8.1 wt%.

[0010] To solve the above technical problems, another technical solution adopted by the present invention is to provide a polyurethane resin, which includes: polyether diol; wherein, the polyether diol has a number average molecular weight between 2,000 and 3,000; polyether triol; wherein, the polyether triol has a number average molecular weight between 3,000 and 6,000; isocyanate; chain extender; capping agent; and diluting solvent; wherein, based on the total weight of the polyurethane resin being 100 wt%, the content of the polyether diol is between 31.6 wt% and 40.3 wt%, the content of the polyether triol is between 14.5 wt% and 26.3 wt%, and the content of the isocyanate is between 18.3 wt% and 21.8 wt%; wherein, the polyurethane resin has a hard segment ratio between 27% and 34%, and the hard segment ratio is defined as the ratio of the sum of the content of the isocyanate and the content of the chain extender to the overall weight of the polyurethane resin; wherein, the polyurethane resin has a glass transition temperature between -40.2 °C and -44.8 °C and a tensile strength between 62.5 kg / 3 cm and 68.7 kg / 3 cm.

[0011] Preferably, the polyurethane resin has a weight average molecular weight between 27,450 and 29,800.

[0012] Preferably, the polyether diol is polypropylene glycol, the polyether triol is at least one selected from the material group consisting of tetrahydrofuran homopolyether and glycerol, and the isocyanate is at least one selected from the material group consisting of diphenylmethane diisocyanate, toluene diisocyanate and isophorone diisocyanate.

[0013] Preferably, the chain extender is at least one selected from the material group consisting of ethylene glycol, 1,4-butanediol and 1,6-hexanediol, and the capping agent is at least one selected from the material group consisting of methyl ethyl ketoxime and dimethyl ketoxime.

[0014] Preferably, the diluting solvent is at least one selected from the material group consisting of propylene glycol methyl ether acetate and propylene glycol methyl ether; wherein, the polyurethane resin has a solid content between 91% and 92%, and the solid content is defined as the weight ratio of the polyurethane resin after drying to the polyurethane resin before drying.

[0015] Preferably, based on the total weight of the polyurethane resin being 100 wt%, the content of the chain extender is between 4.5 wt% and 6 wt%, the content of the capping agent is between 7.8 wt% and 9.9 wt%, and the content of the diluting solvent is between 7.9 wt% and 8.1 wt%.

[0016] One of the beneficial effects of the present invention is that the manufacturing method of the polyurethane resin provided by the present invention can, through the technical solutions of "based on the total weight of the polyurethane resin being 100 wt%, the content of the polyether diol is between 31.6 wt% and 40.3 wt%, the content of the polyether triol is between 14.5 wt% and 26.3 wt%, and the content of the isocyanate is between 18.3 wt% and 21.8 wt%" and "the polyurethane resin has a hard segment ratio between 27% and 34%, a glass transition temperature between -40.2 °C and -44.8 °C, and a tensile strength between 62.5 kg / 3 cm and 68.7 kg / 3 cm", effectively improve the problem of insufficient strength of the existing polyurethane resin applied to shoe leather.

[0017] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the provided drawings are only for reference and illustration, and are not used to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flowchart of the manufacturing method of the polyurethane resin according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following is a description of the embodiments of the "method for manufacturing polyurethane resin" disclosed in the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. Additionally, it is stated in advance that the drawings of the present invention are only for simple schematic illustration and are not drawn according to actual dimensions. The following embodiments will further detail the related technical content of the present invention, but the disclosed content is not intended to limit the protection scope of the present invention.

[0020] It should be understood that although terms such as "first", "second", "third", etc. may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are mainly used to distinguish one component from another, or one signal from another. Additionally, the term "or" used herein should, depending on the actual situation, possibly include any one or a combination of more of the associated listed items.

[0021] [Method for Manufacturing Polyurethane Resin]

[0022] Refer to Figure 1 as shown Figure 1 is a flowchart of the method for manufacturing polyurethane resin according to an embodiment of the present invention. The embodiment of the present invention provides a method for manufacturing polyurethane resin, and the method for manufacturing polyurethane resin includes a mixing step S110, a reaction step S120, a chain extension step S130, a capping step S140, and a dilution step S150.

[0023] In the mixing step S110, a polyether diol and a polyether triol are mixed. The polyether diol has a number average molecular weight between 2,000 and 3,000, and the polyether triol has a number average molecular weight between 3,000 and 6,000. In one embodiment, the polyether diol can be, for example, polypropylene glycol, and the polyether triol can be, for example, at least one selected from the group consisting of tetrahydrofuran homopolyether and glycerol.

[0024] In the reaction step S120, isocyanate is added to the polyether diol and the polyether triol which are mixed with each other to carry out a reaction to form a first polymer. Specifically, in the reaction step S120, the temperature of the reaction tank containing the polyether diol and the polyether triol can be first raised to between about 40°C and 60°C (preferably about 50°C), and then the isocyanate and a small amount of bismuth carboxylate catalyst are added and the temperature is raised to between about 60°C and 80°C (preferably about 70°C) and reacted for about 1.5 hours. In one embodiment, the isocyanate can be at least one selected from the group consisting of diphenylmethane diisocyanate, toluene diisocyanate, and isophorone diisocyanate.

[0025] In the chain extension step S130, a chain extender is added to the first polymer to form a second polymer. Specifically, after adding the chain extender and reacting with the first polymer for about 1.5 hours, the temperature is lowered to between 35°C and 55°C (preferably about 45°C). In one embodiment, the chain extender can be at least one selected from the group consisting of ethylene glycol, 1,4-butanediol, and 1,6-hexanediol.

[0026] In the capping step S140, a capping agent is added to the second polymer to carry out a capping reaction and form a third polymer. The reaction time of the capping step S140 can be about 1 hour to ensure the completion of the capping reaction. In one embodiment, the capping agent can be at least one selected from the group consisting of methyl ethyl ketoxime and dimethyl ketoxime.

[0027] In the dilution step S150, the third polymer is diluted with a dilution solvent to form a polyurethane resin. In one embodiment, the dilution solvent is at least one selected from the group consisting of propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether. The polyurethane resin has a solid content between 91% and 92%, and the solid content is defined as the weight ratio of the polyurethane resin after drying to the polyurethane resin before drying. If the manufacturing method of the polyurethane resin does not include the dilution step S150, the finally prepared polyurethane resin will have the problem of too high viscosity and difficult processing.

[0028] Based on the total weight of the polyurethane resin being 100 wt%, the content of the polyether diol is between 31.6 wt% and 40.3 wt%, the content of the polyether triol is between 14.5 wt% and 26.3 wt%, the content of the isocyanate is between 18.3 wt% and 21.8 wt%, the content of the chain extender is between 4.5 wt% and 6 wt%, the content of the capping agent is between 7.8 wt% and 9.9 wt%, and the content of the dilution solvent is between 7.9 wt% and 8.1 wt%.

[0029] It is worth mentioning that in the polyurethane resin, the content of the polyether diol is higher than that of the polyether triol. In other words, other polyurethane resins with a content of polyether diol lower than that of polyether triol are not suitable for comparison with the polyurethane resin in the present invention. In addition, the dosage of the chain extender is within a specific range so that the weight average molecular weight of the polyurethane resin can be increased and it has higher strength. Specifically, the polyurethane resin can have a weight average molecular weight between 27,450 and 29,800. In the polyurethane resin, the functional group crosslinking degree in the main chain structure of the polyurethane resin can be adjusted by the long-chain polyether triol, thereby enhancing the strength and solvent resistance of the polyurethane resin.

[0030] The polyurethane resin has a hard segment ratio between 27% and 34%, and the hard segment ratio is defined as the ratio of the sum of the content of the isocyanate and the content of the chain extender to the total weight of the polyurethane resin. The hard segment ratio of the polyurethane resin is controlled within a specific range so that the polyurethane resin can have a higher glass transition temperature. Accordingly, the strength of the polyurethane resin can be enhanced and it can have excellent low-temperature flex resistance.

[0031] The polyurethane resin has a glass transition temperature between -40.2 °C and -44.8 °C, a tensile strength between 62.5 kg / 3 cm and 68.7 kg / 3 cm, and a viscosity between 34,650 cps and 37,400 cps.

[0032] [Polyurethane Resin]

[0033] The embodiment of the present invention also provides a polyurethane resin. The polyurethane resin can be obtained, for example, by performing the manufacturing method of the aforementioned polyurethane resin, but the present invention is not limited thereto.

[0034] The polyurethane resin contains polyether diol, polyether triol, isocyanate, capping agent and diluting solvent. Based on the total weight of the polyurethane resin being 100 wt%, the content of the polyether diol is between 31.6 wt% and 40.3 wt%, the content of the polyether triol is between 14.5 wt% and 26.3 wt%, the content of the isocyanate is between 18.3 wt% and 21.8 wt%, the content of the chain extender is between 4.5 wt% and 6 wt%, the content of the capping agent is between 7.8 wt% and 9.9 wt%, and the content of the diluting solvent is between 7.9 wt% and 8.1 wt%.

[0035] The polyether diol has a number average molecular weight between 2,000 and 3,000, and the polyether triol has a number average molecular weight between 3,000 and 6,000. In one embodiment, the polyether diol is polypropylene glycol, the polyether triol is at least one selected from the group consisting of tetrahydrofuran homopolyether and glycerol, and the isocyanate is at least one selected from the group consisting of diphenylmethane diisocyanate, toluene diisocyanate, and isophorone diisocyanate.

[0036] In one embodiment, the chain extender is at least one selected from the group consisting of ethylene glycol, 1,4-butanediol, and 1,6-hexanediol, and the capping agent is at least one selected from the group consisting of methyl ethyl ketoxime and dimethyl ketoxime.

[0037] In one embodiment, the diluting solvent is at least one selected from the group consisting of propylene glycol methyl ether acetate and propylene glycol methyl ether, the polyurethane resin has a solid content between 91% and 92%, and the solid content is defined as the weight ratio of the polyurethane resin after drying to the polyurethane resin before drying.

[0038] The polyurethane resin has a hard segment ratio between 27% and 34%, and the hard segment ratio is defined as the ratio of the sum of the content of the isocyanate and the content of the chain extender to the total weight of the polyurethane resin.

[0039] The polyurethane resin has a glass transition temperature between -40.2 °C and -44.8 °C, a tensile strength between 62.5 kg / 3 cm and 68.7 kg / 3 cm, and a viscosity between 34,650 cps and 37,400 cps. The polyurethane resin has a weight average molecular weight between 27,450 and 29,800.

[0040] [Experimental data test]

[0041] Hereinafter, the content of the present invention will be described in detail with reference to Examples 1 to 4 and Comparative Examples 1 to 3. However, the following examples are only for helping to understand the present invention, and the scope of the present invention is not limited to these examples.

[0042] Example 1: The polyurethane resin contains 31.6 wt% of polyether diol, 26.3 wt% of polyether triol, 20 wt% of isocyanate, 5.3 wt% of chain extender, 8.7 wt% of capping agent, and 8.1 wt% of diluting solvent.

[0043] Demonstration Example 2: The polyurethane resin contains 34.3 wt% of polyether diol, 21.6 wt% of polyether triol, 21.2 wt% of isocyanate, 6 wt% of chain extender, 8.9 wt% of capping agent, and 8 wt% of diluting solvent.

[0044] Demonstration Example 3: The polyurethane resin contains 37.9 wt% of polyether diol, 23.5 wt% of polyether triol, 18.3 wt% of isocyanate, 4.5 wt% of chain extender, 7.8 wt% of capping agent, and 8 wt% of diluting solvent.

[0045] Demonstration Example 4: The polyurethane resin contains 40.3 wt% of polyether diol, 14.5 wt% of polyether triol, 21.8 wt% of isocyanate, 5.6 wt% of chain extender, 9.9 wt% of capping agent, and 7.9 wt% of diluting solvent.

[0046] Comparative Example 1: The polyurethane resin contains 24.6 wt% of polyether diol, 48.9 wt% of polyether triol, 11.7 wt% of isocyanate, 1.7 wt% of chain extender, 5.2 wt% of capping agent, and 7.9 wt% of diluting solvent.

[0047] Comparative Example 2: The polyurethane resin contains 22.6 wt% of polyether diol, 44.9 wt% of polyether triol, 14.8 wt% of isocyanate, 3.1 wt% of chain extender, 6.7 wt% of capping agent, and 7.9 wt% of diluting solvent.

[0048] Comparative Example 3: The polyurethane resin contains 26.8 wt% of polyether diol, 38.4 wt% of polyether triol, 16.3 wt% of isocyanate, 3.6 wt% of chain extender, 7.3 wt% of capping agent, and 7.6 wt% of diluting solvent.

[0049] The component ratios, glass transition temperature, tensile strength, low-temperature flex resistance, solvent resistance, viscosity, solid content, and weight-average molecular weight of the polyurethane resins in Demonstration Examples 1 to 4 and Comparative Examples 1 to 3 are as shown in Table 1 below, and the relevant test methods are described as follows.

[0050] Glass transition temperature test: Take 5 mg of the sample and place it on a differential scanning calorimeter (model: TADSC25), and perform analysis with a heating rate of 20 °C / min and a temperature range of -90 °C to 150 °C.

[0051] Tensile strength test: Measured with a universal tensile testing machine (manufacturer: SHIMADZU, model: AG-X).

[0052] Low-temperature flex resistance test: The test sample (4.5 cm * 7 cm) is installed on a flex resistance testing machine (model GT-7006-V50), and 30,000 flex tests are carried out at an angle of 22.5°, a frequency of 100 times / minute, and a temperature of -30°C. Then, observe whether there is damage (wrinkling and cracking) on the surface of the test piece. No damage is recorded as O, and damage is recorded as X.

[0053] Solvent resistance test: Take a sample (5 cm * 8 cm) and soak it completely in dimethylformamide (DMF) for 3 minutes, and observe whether there is dissolution on the surface of the test piece. No dissolution is recorded as O, and dissolution is recorded as X.

[0054] Viscosity test: Measured with a viscometer (brand: BROOKFIELD, model: DV-E).

[0055] Solid content test: Take 2 mg of the sample and place it in a pre-weighed container, and dry it in an oven (brand: Chenghui, model: STD-45B) at a temperature of 110°C for 3 h. Then, weigh the weight of the solid sample and calculate the solid content. Solid content (wt%) = (weight of solid sample / weight of sample) × 100.

[0056] Weight-average molecular weight test: Measured with a gel permeation analyzer (brand: SHIMADZU, model: LC-40XR).

[0057] [Table 1 Component ratio formulations and physical and chemical property test results of the demonstration examples and comparative examples]

[0058]

[0059]

[0060] [Discussion of test results]

[0061] In Demonstration Examples 1 to 4, the content of polyether diol is between 31.6 wt% and 40.3 wt%, the content of polyether triol is between 14.5 wt% and 26.3 wt%, and the content of isocyanate is between 18.3 wt% and 21.8 wt%. Therefore, the polyurethane resin can meet the requirements of a viscosity between 20,000 cps and 40,000 cps and a tensile strength greater than 60 kg / 3 cm.

[0062] In the polyurethane resins of Comparative Examples 1 to 3, due to the relatively low content of polyether diol, the relatively high content of polyether triol, and the relatively low content of isocyanate, the viscosity of the polyurethane resin is relatively low and the tensile strength is relatively low.

[0063] [Beneficial effects of the examples]

[0064] One of the beneficial effects of the present invention is that the manufacturing method of the polyurethane resin provided by the present invention can, through the technical solution of "based on the total weight of the polyurethane resin being 100 wt%, the content of the polyether diol is between 31.6 wt% and 40.3 wt%, the content of the polyether triol is between 14.5 wt% and 26.3 wt%, and the content of the isocyanate is between 18.3 wt% and 21.8 wt%" and "the polyurethane resin has a hard segment ratio between 27% and 34%, a glass transition temperature between -40.2 °C and -44.8 °C, and a tensile strength between 62.5 kg / 3 cm and 68.7 kg / 3 cm", effectively improve the problem of insufficient strength of the existing polyurethane resin applied to shoe leather.

[0065] The content disclosed above is only the preferred feasible embodiment of the present invention, and does not limit the patent scope of the present invention. Therefore, all equivalent technical changes made by using the description and drawings of the present invention are included in the patent scope of the present invention.

Claims

1. A method for producing a polyurethane resin, characterized in that: The method for producing the polyurethane resin comprises: A mixing step of mixing a polyether diol and a polyether triol; wherein the polyether diol has a number average molecular weight between 2,000 and 3,000, and the polyether triol has a number average molecular weight between 3,000 and 6,000; A reaction step of adding isocyanate to the polyether diol and the polyether triol mixed with each other to react to form a first polymer; a chain extension step, adding a chain extender to the first polymer to form a second polymer; an end-capping step, adding an end-capping agent to the second polymer to perform an end-capping reaction and form a third polymer; and a dilution step of diluting the third polymer with a dilution solvent to form a polyurethane resin; wherein, based on the total weight of the polyurethane resin being 100wt%, the content of the polyether diol is between 31.6wt% and 40.3wt%, the content of the polyether triol is between 14.5wt% and 26.3wt%, and the content of the isocyanate is between 18.3wt% and 21.8wt%; wherein the polyurethane resin has a hardness ratio between 27% and 34%, wherein the hardness ratio is defined as the ratio of the sum of the content of the isocyanate and the content of the chain extender to the overall weight of the polyurethane resin; The polyurethane resin has a glass transition temperature between -40.2°C and -44.8°C and a tensile strength between 62.5kg / 3cm and 68.7kg / 3cm.

2. The method for producing a polyurethane resin according to claim 1, characterized in that: The polyurethane resin has a weight average molecular weight between 27,450 and 29,800.

3. The method for producing a polyurethane resin according to claim 1, wherein: The polyether diol is polypropylene glycol, and the polyether triol is at least one selected from the material group consisting of tetrahydrofuran homopolyether and polypropylene glycol; wherein the isocyanate is at least one selected from the material group consisting of diphenylmethane diisocyanate, toluene diisocyanate and isophorone diisocyanate.

4. The method for producing a polyurethane resin according to claim 1, wherein: The chain extender is at least one selected from the group consisting of ethylene glycol, 1,4-butanediol and 1,6-hexanediol, and the end-capping agent is at least one selected from the group consisting of methyl ethyl ketone oxime and dimethyl ketone oxime.

5. The method for producing a polyurethane resin according to claim 1, wherein: The dilution solvent is at least one selected from the material group consisting of propylene glycol methyl ether acetate and propylene glycol methyl ether; wherein the polyurethane resin has a solid content between 91% and 92%, and the solid content is defined as the weight ratio of the polyurethane resin after drying to the polyurethane resin before drying.

6. The method for producing a polyurethane resin according to claim 1, characterized in that: Based on 100 wt % of the total weight of the polyurethane resin, the content of the chain extender is between 4.5 wt % and 6 wt %, the content of the end capping agent is between 7.8 wt % and 9.9 wt %, and the content of the dilution solvent is between 7.9 wt % and 8.1 wt %.

7. A polyurethane resin, characterized in that The polyurethane resin comprises: Polyether diol; wherein the polyether diol has a number average molecular weight between 2,000 and 3,000; Polyether triol; wherein the polyether triol has a number average molecular weight between 3,000 and 6,000; Isocyanates; Chain extenders; a capping agent; and diluent; wherein, based on the total weight of the polyurethane resin being 100wt%, the content of the polyether diol is between 31.6wt% and 40.3wt%, the content of the polyether triol is between 14.5wt% and 26.3wt%, and the content of the isocyanate is between 18.3wt% and 21.8wt%; wherein the polyurethane resin has a hardness ratio between 27% and 34%, wherein the hardness ratio is defined as the ratio of the sum of the content of the isocyanate and the content of the chain extender to the overall weight of the polyurethane resin; The polyurethane resin has a glass transition temperature between -40.2°C and -44.8°C and a tensile strength between 62.5kg / 3cm and 68.7kg / 3cm.

8. The polyurethane resin according to claim 7, characterized in that The polyurethane resin has a weight average molecular weight between 27,450 and 29,800.

9. The polyurethane resin according to claim 7, characterized in that The polyether diol is polypropylene glycol, the polyether triol is at least one selected from the material group consisting of tetrahydrofuran homopolyether and polypropylene glycol, and the isocyanate is at least one selected from the material group consisting of diphenylmethane diisocyanate, toluene diisocyanate and isophorone diisocyanate.

10. The polyurethane resin according to claim 7, characterized in that The chain extender is at least one selected from the group consisting of ethylene glycol, 1,4-butanediol and 1,6-hexanediol, and the end-capping agent is at least one selected from the group consisting of methyl ethyl ketone oxime and dimethyl ketone oxime.

11. The polyurethane resin according to claim 7, characterized in that The dilution solvent is at least one selected from the material group consisting of propylene glycol methyl ether acetate and propylene glycol methyl ether; wherein the polyurethane resin has a solid content between 91% and 92%, and the solid content is defined as the weight ratio of the polyurethane resin after drying to the polyurethane resin before drying.

12. The polyurethane resin according to claim 8, characterized in that Based on 100 wt % of the total weight of the polyurethane resin, the content of the chain extender is between 4.5 wt % and 6 wt %, the content of the end capping agent is between 7.8 wt % and 9.9 wt %, and the content of the dilution solvent is between 7.9 wt % and 8.1 wt %.

Images