A kind of anti-bending polyurethane resin and preparation method thereof

Abstract

The present invention relates to a flexural polyurethane resin and a preparation method thereof, and relates to the field of polyurethane. A flexural polyurethane resin comprises the following raw materials in parts by weight: 20-25 parts of diol; 8-12 parts of castor oil; 10-15 parts of diisocyanate; 3-7 parts of cellulose acetate butyrate; 1-2 parts of hydrophilic agent; 0.5-1 parts of neutralizer; 2-3 parts of chain extender; and 50-60 parts of deionized water. When the water-based polyurethane resin prepared in the present application is used as the main raw material to prepare leather edge oil, the leather-wrapped oil edge formed has good tensile and flexural resistance.

Description

Technical Field

[0001] The invention relates to the field of polyurethane, in particular to a flexural-resistant polyurethane resin and a preparation method thereof. Background Art

[0002] Waterborne polyurethane resin is a polyurethane that uses water as a dispersion medium. It has the advantages of being environmentally friendly, low VOC emissions, and easy to clean, and meets environmental and health requirements. Waterborne polyurethane has excellent weather resistance, chemical corrosion resistance, water resistance, and abrasion resistance, and has good adhesion. It can be used as a leather finishing agent, coating, and adhesive, and is widely used in printing inks, leather, furniture, architectural decoration, and other fields.

[0003] When water-based polyurethane resin is used in the leather field, it can be used as a material for leather edge binding. Leather edge binding is a process to process the edges of leather goods to protect the edges of leather goods and increase their beauty and durability. Usually, leather edge oils of various colors are used to coat the edges of leather goods, and after drying, an oil-coated edge is formed to cover the exposed edges of the leather. Leather edge oil is made of polyurethane resin as the main raw material, combined with defoaming agents, color pastes and leveling agents.

[0004] The existing leather bag oil edges made with water-based polyurethane resin as the main raw material have poor bending and tensile resistance. Leather goods are often bent or pulled during long-term use, and the oil edges may tear or break, affecting the appearance and service life of the leather goods. Summary of the invention

[0005] In order to improve the tensile and flexural resistance of leather-wrapped oil edges prepared with water-based polyurethane resin as the main raw material, the present application provides a flexural-resistant polyurethane resin and a preparation method thereof.

[0006] The present application provides a flexural-resistant polyurethane resin and a preparation method thereof using the following technical solutions:

[0007] In a first aspect, the present application provides a flexural-resistant polyurethane resin, comprising the following raw materials in parts by weight:

[0008] 20-25 parts of diol;

[0009] 8-12 parts castor oil;

[0010] 10-15 parts of diisocyanate;

[0011] Cellulose acetate butyrate 3-7 parts;

[0012] 1-2 parts of hydrophilic agent;

[0013] Neutralizer 0.5-1 part;

[0014] 2-3 parts of chain extender;

[0015] 50-60 parts of deionized water.

[0016] By adopting the above technical scheme, castor oil is used to replace part of the polyol in the raw material of the polyurethane resin, which is beneficial to environmental protection, improves the film-forming performance, and improves the water resistance of the material; cellulose acetate butyrate is added to the raw material, which contains more hydroxyl groups and can react with the polyurethane prepolymer to form a complex three-dimensional network structure, and the crosslinking degree and hydrogen bond force in the structure are improved. When the polyurethane resin prepared is used as the raw material of leather-wrapped oil, the leather-wrapped oil edge formed during the edge sealing of leather goods is more tensile and flexural, resistant to dry and wet rubbing, and has good wear resistance, which is beneficial to extending the service life of leather goods and maintaining the appearance of leather goods.

[0017] Preferably, the acetyl content of the cellulose acetate butyrate is 13-18%, and the butyryl content is 20-28%.

[0018] By adopting the above technical solution, the content of acetyl and butyryl groups can be controlled, the content of hydroxyl groups in cellulose acetate butyrate can be controlled, and the steric hindrance within the molecule can be controlled, so that after the addition of cellulose acetate butyrate, the tensile strength and dry and wet rubbing resistance of the leather-wrapped oil edge formed are excellent.

[0019] Preferably, the castor oil is a mixture of castor oil and mercaptan-modified castor oil in a mass ratio of (1.2-1.4):(0.6-0.8), and the mercaptan-modified castor oil is prepared by the following raw materials in parts by mass:

[0020] 18-22 parts of mercaptoethanol;

[0021] 5-7 parts of castor oil.

[0022] By adopting the above technical scheme, the hydroxyl value of the mercaptan-modified castor oil is increased, so that it can react more fully with diisocyanate, increase the content of the formed urethane bonds, and further increase the degree of cross-linking. By selecting castor oil and mercaptan-modified castor oil for mixing, the adhesion of the leather edge oil to the edge of the leather is enhanced, and the water resistance and tensile strength are improved.

[0023] Preferably, the diol is one or more of polytetramethylene glycol and polycarbonate glycol.

[0024] Preferably, the diisocyanate is a mixture of toluene diisocyanate and isophorone diisocyanate, and the mass ratio of the toluene diisocyanate to the isophorone diisocyanate is (0.5-0.6):(1.4-1.5).

[0025] By adopting the above technical solution, toluene diisocyanate and isophorone diisocyanate are selected for compounding, more groups are introduced into the polyurethane molecules, and the crosslinking degree of the polyurethane network is improved, which is beneficial to improving the adhesion of the leather edge oil and making the leather-wrapped oil edge more resistant to tension and bending.

[0026] Preferably, the hydrophilic agent is selected from one or more of dimethylolpropionic acid and 1,2-butanediol.

[0027] Preferably, the neutralizing agent is one or more of sodium hydroxide, triethylamine and ammonia water.

[0028] Preferably, the chain extender is one or more of ethylenediamine, N-methyldiethanolamine, and 1,6-hexanediamine.

[0029] In a second aspect, the present application provides a method for preparing a flexural-resistant polyurethane resin, comprising the following steps:

[0030] Dehydrate the diol, add castor oil and diisocyanate and mix evenly, fill with nitrogen for protection, stir and heat to 80-90°C for reaction for 2-2.5h, add hydrophilic agent and acetone, react for 1-1.5h, add acetone solution of cellulose acetate butyrate, and continue to react for 1.5-2h;

[0031] After the reaction is completed, the temperature is lowered to 35-40°C, a neutralizer is added for neutralization, deionized water is added for high-speed dispersion, and then a chain extender is added for chain extension. Finally, acetone is removed in vacuum to obtain a flexural-resistant polyurethane resin.

[0032] By adopting the above technical scheme, the preparation method of polyurethane resin is simple, the reaction conditions are mild, and the production efficiency is high.

[0033] Preferably, when castor oil is a mixture of castor oil and mercaptan-modified castor oil, the preparation steps of mercaptan-modified castor oil include:

[0034] Mercaptoethanol and castor oil react at room temperature under the action of a photoinitiator and irradiation with an ultraviolet lamp, and the obtained product is added with ethyl acetate, washed with brine and water, dried with anhydrous magnesium sulfate, and ethyl acetate is evaporated to obtain mercaptan-modified castor oil.

[0035] By adopting the technical scheme, the double bonds on castor oil are used to quickly react with thiol groups under ultraviolet light irradiation to produce TEC reaction, and the reaction conditions are simple, rapid and high in yield.

[0036] In summary, this application has the following beneficial effects:

[0037] 1. In the raw materials of polyurethane resin, castor oil is used to replace part of polyols, which is beneficial to environmental protection, improves film-forming performance, and improves the water resistance of the material; cellulose acetate butyrate is added to the raw materials, which contains more hydroxyl groups and can react with polyurethane prepolymer to form a complex three-dimensional network structure, and the crosslinking degree and hydrogen bond force in the structure are improved. When the polyurethane resin prepared in this way is used as the raw material of leather-wrapped oil, the leather-wrapped oil edge formed during the edge sealing of leather goods is more resistant to tension and bending, resistant to dry and wet rubbing, and has good wear resistance, which is beneficial to extending the service life of leather goods and maintaining the appearance of leather goods.

[0038] 2. The hydroxyl value of mercaptan-modified castor oil increases, so it can react more fully with diisocyanate, increase the content of the formed urethane bonds, and further increase the degree of cross-linking. By mixing castor oil and mercaptan-modified castor oil, the adhesion of the leather edge oil on the edge of the leather is enhanced, and the water resistance and tensile strength are improved. DETAILED DESCRIPTION

[0039] Preparation Example

[0040] Preparation Example 1

[0041] Preparation of mercaptan-modified castor oil

[0042] Put 18g of mercaptoethanol and 5g of castor oil into a round-bottom flask, add 2g of photoinitiator 1173, react at room temperature for 2h under ultraviolet light, the illumination intensity is 20mW / cm2, add 30ml of ethyl acetate to the obtained product, wash with saturated sodium chloride solution and distilled water for 3 times respectively, dry with anhydrous magnesium sulfate, and evaporate to remove the solvent to obtain thiol-modified castor oil.

[0043] Preparation Example 2

[0044] Preparation of mercaptan-modified castor oil

[0045] Put 22g of mercaptoethanol and 7g of castor oil into a round-bottom flask, add 2.5g of photoinitiator 1173, react at room temperature for 2h under ultraviolet light, the illumination intensity is 20mW / cm2, add 40ml of ethyl acetate to the obtained product, wash with saturated sodium chloride solution and distilled water for 3 times respectively, dry with anhydrous magnesium sulfate, and evaporate to remove the solvent to obtain thiol-modified castor oil.

[0046] Example

[0047] Example 1

[0048] Preparation of a flexural-resistant polyurethane resin

[0049] 20 parts of polytetrahydrofuran ether diol with a number average molecular weight of 2000 were dehydrated and placed in a three-necked flask equipped with a stirrer, a condenser and a thermometer. 8 parts of castor oil with a viscosity of 460 cps and 10 parts of isophorone diisocyanate were added to the flask and stirred evenly. Nitrogen was filled into the flask for protection, and the temperature was raised to 80°C for reaction for 2 hours under stirring.

[0050] Add 1 part of dimethylol propionic acid and a small amount of acetone, react for 1 hour, dissolve 3 parts of cellulose acetate butyrate with an acetyl content of 10% and a butyryl content of 30% in acetone to obtain an acetone solution of cellulose acetate butyrate, add it to the flask, and continue to react for 1.5 hours;

[0051] After the reaction, the temperature was lowered to 35° C., 0.5 parts of triethylamine was added for neutralization, 50 parts of deionized water were added for high-speed dispersion, and then 2 parts of ethylenediamine were added for chain extension. Finally, acetone was removed in vacuo to obtain a flexural-resistant polyurethane resin.

[0052] Example 2

[0053] Preparation of a flexural-resistant polyurethane resin

[0054] 25 parts of polycarbonate diol with a number average molecular weight of 2000 were dehydrated and placed in a three-necked flask equipped with a stirrer, a condenser and a thermometer. 12 parts of castor oil with a viscosity of 460 cps and 15 parts of toluene diisocyanate were added to the flask and stirred evenly. Nitrogen was filled into the flask for protection, and the temperature was raised to 90°C for reaction for 2.5 hours under stirring.

[0055] Add 2 parts of dihydroxymethylpropionic acid and a small amount of acetone, react for 1.5 hours, dissolve 7 parts of cellulose acetate butyrate with an acetyl content of 20% and a butyryl content of 18% in acetone to obtain an acetone solution of cellulose acetate butyrate, add it to the flask, and continue to react for 2 hours;

[0056] After the reaction is completed, the temperature is lowered to 40°C, 1 part of ammonia water is added for neutralization, 60 parts of deionized water are added for high-speed dispersion, and then 3 parts of N-methyldiethanolamine are added for chain extension. Finally, acetone is removed in vacuum to obtain a flexural-resistant polyurethane resin.

[0057] Example 3

[0058] Preparation of a flexural-resistant polyurethane resin

[0059] 22 parts of polycarbonate diol with a number average molecular weight of 2000 were dehydrated and placed in a three-necked flask equipped with a stirrer, a condenser and a thermometer. 10 parts of castor oil with a viscosity of 460 cps and 12 parts of isophorone diisocyanate were added to the flask and stirred evenly. Nitrogen was filled into the flask for protection, and the temperature was raised to 85°C for reaction for 2.5 hours under stirring.

[0060] 1.5 parts of 1,2-butanediol and a small amount of acetone were added, and the reaction was continued for 1 hour. 5 parts of cellulose acetate butyrate having an acetyl content of 20% and a butyryl content of 22% were dissolved in acetone to obtain an acetone solution of cellulose acetate butyrate, which was added to the flask, and the reaction was continued for 2 hours.

[0061] After the reaction is completed, the temperature is lowered to 35° C., 1 part of triethylamine is added for neutralization, 55 parts of deionized water are added for high-speed dispersion, and then 2 parts of 1,6-hexanediamine are added for chain extension. Finally, acetone is removed in vacuum to obtain a flexural-resistant polyurethane resin.

[0062] Example 4

[0063] Preparation of a flexural-resistant polyurethane resin

[0064] The difference between this embodiment and embodiment 1 is that in the raw material of the flexural-resistant polyurethane resin, the acetyl content of cellulose acetate butyrate is 13%, and the butyryl content is 28%.

[0065] Example 5

[0066] Preparation of a flexural-resistant polyurethane resin

[0067] The difference between this embodiment and embodiment 1 is that in the raw material of the flexural-resistant polyurethane resin, the acetyl content of cellulose acetate butyrate is 18%, and the butyryl content is 20%.

[0068] Example 6

[0069] Preparation of a flexural-resistant polyurethane resin

[0070] The difference between this embodiment and embodiment 1 is that in the raw materials of the flexural-resistant polyurethane resin, castor oil is a mixture of castor oil and thiol-modified castor oil prepared in Preparation Example 1, wherein castor oil is 4.8 parts and thiol-modified castor oil prepared in Preparation Example 1 is 3.2 parts.

[0071] Example 7

[0072] Preparation of a flexural-resistant polyurethane resin

[0073] The difference between this embodiment and embodiment 1 is that in the raw materials of the flexural-resistant polyurethane resin, castor oil is a mixture of castor oil and thiol-modified castor oil obtained in Preparation Example 2, wherein castor oil is 5.6 parts and thiol-modified castor oil obtained in Preparation Example 1 is 2.4 parts.

[0074] Example 8

[0075] Preparation of a flexural-resistant polyurethane resin

[0076] The difference between this embodiment and embodiment 1 is that in the raw materials of the fold-resistant polyurethane, the diisocyanate is a mixture of toluene diisocyanate and isophorone diisocyanate, wherein the toluene diisocyanate is 2.5 parts and the isophorone diisocyanate is 7.5 parts.

[0077] Example 9

[0078] Preparation of a flexural-resistant polyurethane resin

[0079] The difference between this embodiment and embodiment 1 is that in the raw materials of the fold-resistant polyurethane, the diisocyanate is a mixture of toluene diisocyanate and isophorone diisocyanate, wherein toluene diisocyanate is 3 parts and isophorone diisocyanate is 7 parts.

[0080] Example 10

[0081] Preparation of a flexural-resistant polyurethane resin

[0082] The difference between this embodiment and embodiment 1 is that: in the raw material of the folding-resistant polyurethane, the acetyl content in the cellulose acetate butyrate is 13%, and the butyryl content is 28%;

[0083] The castor oil is a mixture of castor oil and the mercaptan-modified castor oil obtained in Preparation Example 1, wherein the castor oil is 4.8 parts and the mercaptan-modified castor oil obtained in Preparation Example 1 is 3.2 parts;

[0084] The diisocyanate is a mixture of toluene diisocyanate and isophorone diisocyanate, wherein the toluene diisocyanate is 3 parts and the isophorone diisocyanate is 7 parts.

[0085] Comparative Example

[0086] Comparative Example 1

[0087] Preparation of a flexural-resistant polyurethane resin

[0088] The difference between this comparative example and Example 1 is that the raw materials of the flexural-resistant polyurethane resin include: 28 parts of polytetramethylene glycol, 10 parts of isophorone diisocyanate, 1 part of dihydroxymethylpropionic acid, 3 parts of cellulose acetate butyrate, 0.5 parts of triethylamine, 2 parts of ethylenediamine and 50 parts of deionized water.

[0089] Comparative Example 2

[0090] Preparation of a flexural-resistant polyurethane resin

[0091] The difference between this comparative example and Example 1 is that cellulose acetate butyrate is not added to the raw material of the flexural-resistant polyurethane resin.

[0092] Performance Test The polyurethane resin prepared in Examples 1-10 and Comparative Examples 1-2 was used to prepare leather edge oil. The raw materials of the leather edge oil included: 60 parts of polyurethane resin; 6 parts of color paste; 2 parts of defoaming agent; and 1 part of leveling agent.

[0093] The edges of leather goods are painted with leather edge oil, which is then dried to form an oil-covered leather edge. The tensile strength, folding fastness, and resistance to dry and wet rubbing of the oil-covered leather edge are then tested.

[0094] 1. Tensile strength

[0095] The tensile strength was measured according to method 6.2 of QB / T 2710-2005 “Determination of tensile strength and elongation of leather in physical and mechanical tests”, and the test results of tensile strength were recorded in Table 1.

[0096] 2. Folding fastness

[0097] The test was carried out in accordance with QB / T 2712-2005 “Determination of folding fastness of leather in physical and mechanical tests”, and the number of folding times was recorded in Table 1.

[0098] 3. Resistance to dry and wet friction

[0099] The test was conducted according to the method of 5.11 Surface Color Fastness in QB / T 1646-2007 Polyurethane Synthetic Leather, and the results were recorded in Table 1.

[0100] Table 1

[0101]

[0102]

[0103] The performance test of the flexural resistant polyurethane resin prepared in Example 1 was carried out, and the test results are recorded in Table 2.

[0104] Table 2

[0105] index Solid content pH Viscosity Appearance result 45％ 8 55mPa.s milky

[0106] Result analysis:

[0107] According to Table 1 and Table 2, the polyurethane resin prepared according to the formula of the present application can form a complex three-dimensional network structure, with high crosslinking degree and hydrogen bonding force, and the low viscosity of the polyurethane resin is more convenient for subsequent processing, and the strong fluidity is convenient for forming a film and adhering to the edge of the leather. When the polyurethane resin is used for leather hemming, the leather hemming oil edge formed has good tensile strength, folding fastness and dry and wet rubbing resistance, which is conducive to extending the service life of the leather and maintaining the appearance.

[0108] According to Examples 4-5, after further limiting the butyryl and acetyl contents of cellulose acetate butyrate, the steric hindrance within the molecule is controlled by controlling the hydroxyl content of cellulose acetate butyrate, and when the polyurethane is modified, the crosslinking of the polyurethane system can be made denser, thereby improving the overall performance of the oil-covered leather edge.

[0109] According to Examples 6-7, when castor oil is a mixture of castor oil and mercaptan-modified castor oil, the hydroxyl value can be further increased, the reaction is more complete, and the adhesion, water resistance, tensile strength, flexural strength, and wet and dry rubbing resistance of the oil-covered leather edge are enhanced.

[0110] According to Examples 7-8, when the diisocyanate is selected from phenyl diisocyanate and isophorone diisocyanate, the comprehensive performance of the leather edge is better.

[0111] According to Comparative Examples 1-2, in Comparative Example 1, castor oil was not added to the raw material of the polyurethane resin, and in Comparative Example 2, cellulose acetate butyrate was not added to the raw material of the polyurethane resin. The tensile strength, folding fastness, and dry and wet rubbing resistance of the oil-covered edge of the leather were all reduced. It can be seen that when castor oil and cellulose acetate butyrate are used in a synergistic combination, the mechanical strength and mechanical properties of the polyurethane can be improved.

[0112] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A flexural-resistant polyurethane resin, characterized in that: The invention comprises the following raw materials in parts by weight: 20-25 parts of diol; 8-12 parts castor oil; 10-15 parts of diisocyanate; Cellulose acetate butyrate 3-7 parts; 1-2 parts of hydrophilic agent; Neutralizer 0.5-1 part; 2-3 parts of chain extender; 50-60 parts of deionized water; The castor oil is a mixture of castor oil and mercaptan-modified castor oil in a mass ratio of (1.2-1.4):(0.6-0.8), and the mercaptan-modified castor oil is prepared by the following raw materials in mass parts: 18-22 parts of mercaptoethanol; 5-7 parts of castor oil.

2. The flexural-resistant polyurethane resin according to claim 1, characterized in that: The cellulose acetate butyrate has an acetyl content of 13-18% and a butyryl content of 20-28%.

3. The flexural-resistant polyurethane resin according to claim 1, characterized in that: The diol is selected from one or more of polytetramethylene glycol and polycarbonate glycol.

4. The flexural-resistant polyurethane resin according to claim 1, characterized in that: The diisocyanate is a mixture of toluene diisocyanate and isophorone diisocyanate, and the mass ratio of the toluene diisocyanate to the isophorone diisocyanate is (0.5-0.6):(1.4-1.5).

5. The flexural-resistant polyurethane resin according to claim 1, characterized in that: The hydrophilic agent is dimethylol propionic acid.

6. The flexural-resistant polyurethane resin according to claim 1, characterized in that: The neutralizing agent is selected from one or more of sodium hydroxide, triethylamine and ammonia water.

7. The flexural-resistant polyurethane resin according to claim 1, characterized in that: The chain extender is selected from one or more of ethylenediamine, N-methyldiethanolamine, and 1,6-hexanediamine.

8. The method for preparing a flexural-resistant polyurethane resin according to any one of claims 1 to 7, characterized in that: The following steps are involved: Dehydrate the diol, add castor oil and diisocyanate and mix evenly, fill with nitrogen for protection, stir and heat to 80-90°C for reaction for 2-2.5h, add hydrophilic agent and acetone, react for 1-1.5h, add acetone solution of cellulose acetate butyrate, and continue to react for 1.5-2h; After the reaction is completed, the temperature is lowered to 35-40°C, a neutralizer is added for neutralization, deionized water is added for high-speed dispersion, and then a chain extender is added for chain extension. Finally, acetone is removed in vacuum to obtain a flexural-resistant polyurethane resin.

9. The method for preparing a flexural-resistant polyurethane resin according to claim 8, characterized in that: When the castor oil is a mixture of castor oil and mercaptan-modified castor oil, the preparation steps of the mercaptan-modified castor oil include: Mercaptoethanol and castor oil react at room temperature under the action of a photoinitiator and irradiation with an ultraviolet lamp, and the obtained product is added with ethyl acetate, washed with brine and water, dried with anhydrous magnesium sulfate, and ethyl acetate is evaporated to obtain mercaptan-modified castor oil.

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