Preparation method and application of solvent-free anti-aging waterborne polyurethane

Abstract

The invention discloses a preparation method of solvent-free anti-aging waterborne polyurethane, which is characterized by comprising the following preparation steps: (1) controlling the moisture content of polyhydric alcohol to be less than 0.03%; (2) mixing the polyol dried in the step (1) with isocyanate for reaction; (3) after the reaction in the step (2) is sufficient, adding a first hydrophilic chain extender, a second hydrophilic chain extender and a catalyst, uniformly mixing, and reacting to obtain a waterborne polyurethane prepolymer; (4) adding a light stabilizer into the waterborne polyurethane prepolymer in the step (3), neutralizing with an alkaline aqueous solution, and emulsifying until the pH value is neutral or weakly alkaline; and (5) carrying out a chain extension reaction on the solution system obtained in the step (4) and a compound containing two or more amino groups to obtain the solvent-free waterborne polyurethane. The invention has the beneficial effects that the finished product resin prepared by the invention has the following properties: high solid content (52-55%), low viscosity (3200-3800 (mPa.s, 25 DEG C)) and high hydrolysis resistance (1200-1500 H (50 DEG C, RH 95%)).

Description

Technical Field

[0001] The invention relates to the technical field of leather, and in particular to a preparation method and application of solvent-free aging-resistant waterborne polyurethane. Background Art

[0002] Solvent-based polyurethane has long been criticized for causing environmental pollution, and low-solid resins also greatly increase transportation costs. The high solid content of water-based polyurethane has always been a common problem in the industry. In terms of performance, polyurethanes all have serious aging problems. At the same time, acetone-based polyurethanes have problems such as high energy consumption and difficult recycling during the desolventizing process. Under long-term light, humidity, and heat conditions, the molecular chains of polyurethane molecules will crack or harden, causing the polyurethane to denature, thereby affecting the polyurethane product. For example, if the solid content of foamed polyurethane used in synthetic leather is too low, the dry film will be thin after coating, and workers will need to apply it multiple times, which is cumbersome. Secondly, the aging of polyurethane will cause the foamed resin to collapse and rebound poorly, making the product unqualified. As the requirements for synthetic leather increase frequently, reducing energy consumption and costs, the requirements for hydrolysis resistance are also higher.

[0003] CN 115260436 A in the prior art discloses a high-solid solvent-free waterborne polyurethane resin and a preparation method thereof. The high-solid solvent-free waterborne polyurethane resin is prepared from the following raw materials in parts by weight: 100-200 parts of polyol, 1-2 parts of antioxidant, 1-2 parts of light stabilizer, 40-70 parts of isocyanate, 0.5-3 parts of chain extender, 3-5 parts of neutralizer, 150-300 parts of deionized water, 4-7 parts of hydrophilic chain extender, and 550 parts of post-chain extender. The high-solid solvent-free waterborne polyurethane resin prepared by the invention not only does not contain any organic solvents but also has excellent performance in terms of alkali resistance, temperature resistance, stability, elongation at break, and breaking strength.

[0004] In summary, in order to solve the problems of the prior art, the present invention provides a preparation method and application of a solvent-free, aging-resistant waterborne polyurethane. The preparation method advances the phase transition point and increases the solid content through molecular design, particle size distribution stacking, and hydrophilic ratio control, thereby producing a waterborne foamable polyurethane with high solid content (52-55%), low viscosity (3200-3800 (mPa·s, 25°C)), and high hydrolysis resistance (1200-1500H (50°C, RH95%)). Summary of the Invention

[0005] The present invention aims to provide a preparation method and application of a solvent-free, aging-resistant waterborne polyurethane. The preparation method advances the phase transition point and increases the solid content through molecular design, particle size distribution and stacking, and hydrophilic ratio regulation, thereby producing a waterborne foamable polyurethane with high solids (52-55%), low viscosity (3200-3800 (mPa·s, 25°C)), and high hydrolysis resistance (1200-1500H (50°C, RH95%)).

[0006] To achieve the above objectives, the following technical solutions are adopted: A method for preparing a solvent-free, aging-resistant waterborne polyurethane comprises the following steps: (1) Dehydrate 300-600 parts of polyol in a vacuum at 100-120°C and a negative pressure of less than 0.095 for 0.5-2 hours to control the water content of the polyol to be less than 0.03%; (2) The dried polyol prepared in step (1) is mixed with 70 to 120 parts of isocyanate, and the mixture is heated to 80°C to 100°C and reacted for 1 to 3 hours; (3) After the reaction in step (2) is fully completed, 2-5 parts of No. 1 hydrophilic chain extender, 5-15 parts of No. 2 hydrophilic chain extender, and 0.02-0.05 parts of catalyst are added and mixed evenly. The reaction time is 2-4 hours to obtain a waterborne polyurethane prepolymer. Among them, No. 1 and No. 2 hydrophilic chain extenders and catalysts have been dried, and the moisture content is less than 0.03%; (4) neutralizing the waterborne polyurethane prepolymer in step (3) with an alkaline aqueous solution after adding a light stabilizer, and then emulsifying until the pH value reaches neutral or weak alkaline; (5) The solution system obtained in step (4) is subjected to a post-chain extension reaction with a compound containing two or more amino groups, and the reaction is carried out at a constant temperature of 50 to 60° C. for 1 to 2 hours, and then the temperature is lowered to room temperature. The final emulsion obtained is filtered to obtain a solvent-free waterborne polyurethane.

[0007] As a further improvement of this solution, in S1, the polyol is any one or more of polytetramethylene glycol and polypropylene glycol with a number average molecular weight of 2000 to 3000.

[0008] As a further improvement of this solution, in S2, the isocyanate is any one or more of isophorone diisocyanate, dicyclohexane diisocyanate, and hexamethylene diisocyanate.

[0009] As a further improvement of this solution, in S3, The first hydrophilic chain extender and the second hydrophilic chain extender are any one or more of dimethylol propionic acid, dimethylol butyric acid, Pasto N120, and PEG1000; The No. 1 hydrophilic chain extender, No. 2 hydrophilic chain extender and catalyst are all dried, and the moisture content is less than 0.03%. As a further improvement of this solution, in S4, The base is any one or more of triethylamine, diethanolamine, triethanolamine, sodium hydroxide, sodium bicarbonate, sodium acetate, and ammonia water; Water is deionized water; Moreover, during the emulsification process, the solid content of the system is 50~55%.

[0010] As a further improvement of this solution, the catalyst is any one or more of Maitu MC710, stannous octoate, and organic bismuth.

[0011] As a further improvement of this solution, the neutralizing agent is any one or more of triethylamine, sodium hydroxide, and ammonia water.

[0012] A method for applying solvent-free aging-resistant waterborne polyurethane, comprising: 100 parts of the solvent-free, aging-resistant waterborne polyurethane prepared by the method for preparing the solvent-free, aging-resistant waterborne polyurethane according to any one of claims 1 to 7 Thickener TA-450 4~5 parts Color paste M103 0.5 parts 2 parts of leveling agent V-248 3 parts of foaming agent STA 3 parts of foam stabilizer EP112; The above raw materials are stirred at high speed, foamed 1.3-1.5 times, prepared into slurry, and directly coated on the stretch fabric, and then dried in an oven at 120℃.

[0013] The anti-collapse genuine leather for automobile interior decoration of the present invention has the following beneficial effects: The waterborne polyurethane of the present invention uses only deionized water as the solvent throughout the entire process, and no organic solvent is added during the synthesis process, thereby eliminating the need for subsequent organic solvent removal steps, reducing production costs, and being more environmentally friendly. The finished resin prepared by the present invention has high solid content, low viscosity, solid content of 50-55%, and low transportation cost; 3) The properties of the finished resin prepared by the present invention are as follows: high solid (52-55%), low viscosity (3200-3800 (mPa·s, 25°C)), and high hydrolysis resistance (1200-1500H (50°C, RH95%)); 4) The finished resin obtained by the present invention has uniform and fine pores after foaming, and a smooth surface after coating and drying. In addition, the addition of a directionally compounded light stabilizer during the synthesis can further improve the aging resistance and comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the surface image of the coating of Example 3 of the present invention (large cells and rough surface); Figure 2 This is the surface image of the coating of Comparative Example 1 of the present invention (large cells and rough surface); Figure 3 This is a surface diagram of the coating of Comparative Example 4 of the present invention (large cells and rough surface); Figure 4 This is a scanning electron microscope image of the cross section of the coating of Comparative Example 4 of the present invention (the cells are large, sparse and uneven); Figure 5 This is a scanning electron microscope image of the cross section of the coating of Comparative Example 1 of the present invention (cells of different sizes); Figure 6 This is a scanning electron microscope image of the cross section of the coating of Comparative Example 4 of the present invention (the cells are small and evenly distributed); DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described below with reference to the embodiments and accompanying drawings: The names, sources, specifications and models of the raw materials used in the following examples.

[0016] Polytetramethylene ether glycol Korea Hyosung Co., Ltd. Industrial Grade Polypropylene glycol Shandong Bluestar Dongda industrial grade Isophorone diisocyanate Wanhua Chemical Industrial Grade Hexamethylene diisocyanate Wanhua Chemical Industrial Grade Stannous octanoate Aladdin analytical grade T~9 MC710 Momentive Industrial Grade Dimethylolpropionic acid, analytical grade, Sinopharm Chemical Reagent Co., Ltd. Dihydroxymethylbutyric acid, analytical grade, Sinopharm Chemical Reagent Co., Ltd. Polyethylene glycol (analytical grade) from Sinopharm Chemical Reagent Co., Ltd. N120 Pasto Chemical Industrial Grade Triethylamine, analytical grade, Sinopharm Chemical Reagent Co., Ltd. Dimethylethanolamine, analytical grade, Sinopharm Chemical Reagent Co., Ltd. Ethylenediamine (Analytical Grade) Sinopharm Chemical Reagent Co., Ltd. Isophorone diamine (analytical grade) from Sinopharm Chemical Reagent Co., Ltd. Light stabilizer Tianjin Li'anlong New Materials Co., Ltd. Industrial grade Example 1 Step 1: First, add 400 parts of polytetramethylene ether glycol (PTMG2000), 8 parts of N120 (hydrophilic chain extender No. 2) and 200 parts of polypropylene glycol (PPG3000) into a 1000ml four-necked flask with an electric stirrer, a thermometer, a constant pressure funnel and a vacuum pump. Then turn on the electric stirrer for stirring, turn on the oil bath to heat up, turn on the positive vacuum pump to vacuum the four-necked flask. When the thermometer on the four-necked flask reaches 110°C and the vacuum pressure is ≤-0.095MPa, start timing, and maintain the temperature at 100°C~110°C and the pressure ≤-0.095MPa for vacuum dehydration for 1.5h.

[0017] Step 2: Lower the oil bath temperature. When the thermometer reaches 75°C, add 4 parts of DMPA (dimethylolpropionic acid), a hydrophilic chain extender. Slowly add 85 parts of isophorone diisocyanate via a constant pressure funnel. Stir thoroughly after addition and begin heating. When the temperature reaches 90°C, start the timer and continue the reaction at this temperature for 2 hours. Then, cool the mixture to 75°C and add 0.03 parts of catalyst MC710. Stir for 5 minutes, then raise the temperature to 80°C and start the timer. Maintain the temperature for 2 hours. Then, titrate the mixture until the -NCO content reaches the designed value. This will yield a solvent-free waterborne polyurethane prepolymer.

[0018] Step 3: Add 1 part each of the two light stabilizers (UV-328 + UV-531) to the prepolymer and react at 60°C for 10 minutes. Immediately transfer the resulting prepolymer to an emulsifier to obtain a prepolymer. Then, add 3 parts of triethylamine to the prepolymer and stir for 5 minutes. After the prepolymer is completely neutralized, increase the stirring speed to 2500 rpm, quickly add 313g of deionized water, and stir at high speed for 5 minutes.

[0019] Step 4: Slowly add an amine solution diluted with 10g of deionized water to (3), wherein the post-chain extender is hydrazine hydrate and ethylenediamine, 3.8 parts of hydrazine hydrate and 6.2 parts of ethylenediamine. After the addition, stir at high speed for 10 minutes, reduce the stirring speed to 800r / min, and stir for 5 minutes. Then transfer it to a 1000ml three-necked flask equipped with a thermometer and a stirring device, turn on the stirring device and oil bath, and heat it while stirring. When the temperature reaches 60℃, maintain this temperature for 1h, turn off the oil bath and start cooling. When the temperature drops to room temperature, filter the emulsion to obtain waterborne polyurethane.

[0020] Step 5: Application of Waterborne Polyurethane. The polyurethane obtained in Step 5 was foamed and stabilized in a high-speed mixer using 3% STA foaming agent, 3% EP112 foam stabilizer, and 2% V-248 leveling agent. Then, it was thickened to 35,000 mPa·s using 4% TA450 thickener. The mixture was then applied directly to the stretch fabric and dried in an oven at 120°C.

[0021] In this embodiment 1: The raw materials (parts by mass) are as follows: 400 parts of polytetramethylene glycol (PTMG2000), 200 parts of polypropylene glycol (PPG3000), 85 parts of isophorone diisocyanate, 4 parts of DMPA (hydrophilic chain extender No. 1), 8 parts of N120 (hydrophilic chain extender No. 2), 0.03 parts of MC710 catalyst, 2 parts of light stabilizer (1 part of UV-328 + 1 part of UV-531), 3 parts of triethylamine, and 10 parts of post-chain extender (6.2 parts of ethylenediamine + 3.8 parts of hydrazine hydrate). Comparative Example 1 Comparative Example 1: Preparation process and steps according to Example 1 • Variable: Single component hydrophilic chain extender, only DMPA (no second chain extender N120), no light stabilizer • Raw materials (parts by weight): 400 parts of PTMG2000, 200 parts of PPG3000, 85 parts of isophorone diisocyanate, 12 parts of DMPA (excess of one component), 0.03 parts of MC710 catalyst, light stabilizer, 3 parts of triethylamine, 10 parts of post-chain extender (ethylenediamine (6.2 parts) + hydrazine hydrate (3.8 parts)).

[0022] Comparative Example 2 Comparative Example 2: Preparation process and steps according to Example 1 • Variant: Adding acetone as solvent (conventional process) + single light stabilizer (UV-521) • Raw materials (parts by weight): 400 parts of PTMG2000, 200 parts of PPG3000, 85 parts of isophorone diisocyanate, 4 parts of DMPA, 8 parts of N120, 200 parts of acetone, 0.03 parts of MC710 catalyst, 2 parts of light stabilizer (UV-521), 3 parts of triethylamine, 10 parts of post-chain extender Example 2 With reference to the preparation method of Example 1, the formula of each step is selected as follows: 420 parts PTMG3000, 180 parts PPG2000, 100 parts hexamethylene diisocyanate, 3 parts DMPA, 12 parts PEG1000 (hydrophilic chain extender), 0.04 parts stannous octoate, 1.5 parts light stabilizer (single UV-328), 2 parts sodium hydroxide, 8 parts post-chain extender (isophorone diamine). Example 3 (High Hydrolysis Resistance Modification) Referring to the preparation method of Example 1, the formula for each step is selected as follows: 300 parts of PTMG2000, 300 parts of PPG3000, 90 parts of isophorone diisocyanate, 2 parts of DMPA, 13 parts of N120, 0.05 parts of organic bismuth catalyst, 2 parts of light stabilizer (UV-531 + hindered amine compound), 4 parts of triethylamine, and 12 parts of post-chain extender (diethylenetriamine).

[0023] Comparative Example 3 (No Aging Resistance Modification) • Variable: Omit the light stabilizer • Raw materials (parts by weight): Refer to the preparation method and formulation components of Example 3, except for the light stabilizer. • Disadvantage: Reduced aging resistance. Comparative Example 4 • Variable: Reduce the amount of polyol and increase the amount of deionized water • Variables: Reduce polyol dosage, increase deionized water • Raw materials (parts by mass): 300 parts of PTMG2000, 300 parts of PPG3000, 90 parts of isophorone diisocyanate, 2 parts of DMPA, 13 parts of N120, 0.05 parts of organic bismuth catalyst, 2 parts of light stabilizer (hindered amine), and 4 parts of triethylamine.

[0024] Referring to the preparation method and formulation components of Example 3, the light stabilizer is only a hindered amine. It can be seen from Examples 1 to 3 and Comparative Examples 1 to 4 that the products prepared in Examples 1 to 3 are relatively better. Among the performance test results of Examples 1 to 3, Example 3 has the best comprehensive performance: the product of the present invention does not use organic solvents throughout the entire process, and is environmentally friendly and pollution-free; through the directional selection of monomers, the compounding of light stabilizers, and the selection and design of chain extenders, the finished resin has high solid and low viscosity, and has good aging resistance and xenon lamp resistance after application.

[0025] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent transformations made using the present invention are within the scope of patent protection of the present invention.

Claims

1. A method for preparing a solvent-free, aging-resistant waterborne polyurethane, characterized in that: The method comprises the following preparation steps: (1) vacuum dehydrating 300-600 parts of polyol at 100°C-120°C and negative pressure of less than 0.095 for 0.5-2 hours to control the water content of the polyol to be less than 0.03%; (2) mixing the dried polyol obtained in step (1) with 70 to 120 parts of isocyanate, heating the mixture to 80° C. to 100° C., and reacting the mixture for 1 to 3 hours; (3) After step (2) is fully reacted, 2-5 parts of No. 1 hydrophilic chain extender, 5-15 parts of No. 2 hydrophilic chain extender, and 0.02-0.05 parts of catalyst are added and mixed evenly. The reaction time is 2-4 hours to obtain a waterborne polyurethane prepolymer. Among them, No. 1 and No. 2 hydrophilic chain extenders and catalysts have been dried and the moisture content is less than 0.03%; (4) adding a light stabilizer to the waterborne polyurethane prepolymer in step (3), neutralizing it with an alkaline aqueous solution, and then emulsifying it until the pH value reaches neutral or weak alkaline; (5) The solution system obtained in step (4) is subjected to a post-chain extension reaction with a compound containing two or more amino groups, and the reaction is carried out at a constant temperature of 50 to 60° C. for 1 to 2 hours, and then the temperature is lowered to room temperature. The final emulsion obtained is filtered to obtain a solvent-free waterborne polyurethane.

2. The method for preparing the solvent-free aging-resistant waterborne polyurethane according to claim 1, characterized in that: In S1, the polyol is any one or more of polytetramethylene glycol and polypropylene glycol with a number average molecular weight of 2000 to 3000.

3. The method for preparing the solvent-free aging-resistant waterborne polyurethane according to claim 1, characterized in that: In S2, the isocyanate is any one or more of isophorone diisocyanate, dicyclohexane diisocyanate, and hexamethylene diisocyanate.

4. The method for preparing the solvent-free aging-resistant waterborne polyurethane according to claim 1, wherein: In S3, The first hydrophilic chain extender and the second hydrophilic chain extender are any one or more of dimethylol propionic acid, dimethylol butyric acid, Pasto N120, and PEG1000; The No. 1 hydrophilic chain extender, the No. 2 hydrophilic chain extender and the catalyst are all dried, and the moisture content is less than 0.03%.

5. The method for preparing the solvent-free aging-resistant waterborne polyurethane according to claim 1, wherein: In S4, The base is any one or more of triethylamine, sodium hydroxide, and ammonia water; Water is deionized water; Moreover, during the emulsification process, the solid content of the system is 50-55%.

6. The method for preparing solvent-free aging-resistant waterborne polyurethane according to claim 1, characterized in that: In S3, the catalyst is any one or more of Maitu MC710, stannous octoate, and organic bismuth.

7. The method for preparing solvent-free aging-resistant waterborne polyurethane according to claim 1, characterized in that: The neutralizing agent is any one or more of triethylamine, sodium hydroxide, and ammonia water.

8. A method for applying a solvent-free, aging-resistant waterborne polyurethane, characterized in that: include 100 parts of the solvent-free, aging-resistant water-based polyurethane prepared by the method for preparing the solvent-free, aging-resistant water-based polyurethane according to any one of claims 1 to 7; Thickener TA-450 4-5 parts; Color paste M103 0.5 parts; 2 parts of leveling agent V-248; 3 parts of foaming agent STA; 3 parts of foam stabilizer EP112; The above raw materials are stirred at high speed, foamed 1.3-1.5 times, prepared into slurry, and directly coated on the stretch fabric, and then dried in an oven at 120℃.

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