Yellowing-resistant and aging-resistant polyurethane resin coating material and preparation method thereof

Abstract

The invention discloses a yellowing-resistant and aging-resistant polyurethane resin coating material and a preparation method thereof, and belongs to the technical field of polyurethane resin coating materials, and comprises the following raw materials by weight: 80-100 parts of polyether polyols, 60-80 parts of diisocyanates, 50-70 parts of butyl acetate, 5-8 parts of modified titanium dioxide, 1-2 parts of defoamers, 12-18 parts of chain extenders, 0.2-0.4 parts of ultraviolet light absorbers, and 0.1-0.2 parts of stannous octoate. The coating material is mainly made of polyether polyether and aliphatic diisocyanates, and the aliphatic diisocyanates do not contain benzene rings, thereby improving the yellowing resistance of the polyurethane resin coating material, and adding ultraviolet light absorbers and modified titanium dioxide at the same time, titanium dioxide has extremely strong ultraviolet absorption and infrared reflection characteristics, and the ultraviolet light absorber can release ultraviolet radiation in the form of heat, and the two act synergistically, and can significantly improve the anti-ultraviolet ability of the polyurethane resin coating material, thereby effectively improving the yellowing resistance and aging resistance of the polyurethane material.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane resin coating materials, and in particular relates to a yellowing-resistant and aging-resistant polyurethane resin coating material and a preparation method thereof. Background Art

[0002] With the steady growth of the national economy and the improvement of consumers' living standards, artificial leather products have gained the favor of consumers due to their special texture, gloss and comfortable feel. However, due to the special characteristics of artificial leather products, such as strong absorption, easy wrinkling and easy wear, the application of coating materials in the artificial leather industry to beautify the appearance of artificial leather and simply make artificial leather have good mechanical properties has been recognized as one of the most important processes in the artificial leather industry.

[0003] The coating on the surface of artificial leather is generally required to have good adhesion and properties such as wear resistance, heat resistance, solvent resistance, and water resistance, which can significantly improve the quality and grade of artificial leather and increase its commercial value. The commonly used materials in the coating materials used for artificial leather coating are mainly acrylic resins and polyurethane resins, which can not only improve the appearance and style of artificial leather, improve the beauty and grade of the surface of artificial leather, but also enhance the durability and comfort of artificial leather. Acrylic resins are prone to brittle cracks in winter due to their poor cold resistance, so they cannot meet the needs of high-end coatings well; polyurethane resins have high elasticity and strength, excellent wear resistance and good low-temperature compliance, and are widely used in artificial leather coatings.

[0004] Polyurethane is a block polymer formed by alternating condensation of polyols as flexible segments and diisocyanates and low molecular weight chain extenders as rigid segments. Among them, oligomeric diols constitute soft segments, and hard segments consist of polyisocyanates and chain extenders. The structure of polyurethane coatings contains urethane bonds, ester bonds, ether bonds, urea bonds, allomethyl ester bonds, biuret bonds, acylurea bonds and unsaturated fatty chains, so it has many outstanding properties, such as high tensile strength, wide hardness range, good tear strength, good chemical resistance, good heat sealing, excellent adhesion, and higher water resistance than most polymer coatings. However, like other polymer materials, polyurethane materials are prone to photo-oxidative aging such as yellowing, cracking, and decreased mechanical properties during outdoor use. During the aging process, polyurethane materials will be accompanied by yellowing, i.e. yellowing. Yellowing not only affects the appearance of polyurethane materials, but also has a warning effect on changes in its structure and performance, ultimately reducing the use value of the product.

[0005] In the prior art, in order to improve the aging resistance of polyurethane, Chinese patent application CN106009852A discloses a weather-resistant polyurethane coating, which is made of the following raw materials in parts by weight: 7-10 parts of polyamide resin, 5-8 parts of colloidal graphite powder, 8-10 parts of straw powder, 4-8 parts of barium sulfate, 11-16 parts of water-based acrylic resin, 30-44 parts of modified polyurethane resin, 4-7 parts of talc, 5-10 parts of silica sol, 7-12 parts of magnesium hydroxide, 6-10 parts of medical stone powder, 1-2 parts of antibacterial agent, 2-4 parts of pH regulator, 2-4 parts of dispersant, 4-8 parts of acrylic acid, 6-12 parts of nano-montmorillonite, and 5-8 parts of white mica powder. The beneficial effect of the invention is that the polyurethane coating of the invention has excellent weather resistance, high hardness, and good aging resistance, but the inorganic powder content added in the patent is high, and the compatibility between the materials is poor, which may lead to insufficient mechanical properties of polyurethane. In order to improve the yellowing resistance of polyurethane, Chinese patent application CN117024803A discloses a method for preparing a yellowing-resistant, highly transparent and self-repairing TPU composition film. The invention combines a light stabilizer with an antioxidant to obtain a TPU composition film with certain yellowing resistance. However, although the AM-101 used in the invention is a light stabilizer (referred to as an anti-yellowing agent in the invention), the light stabilizer easily makes the product appear gray-black. Although the influence of yellowing is avoided, the polyurethane can only be used in scenes within a specific color range, which invisibly narrows the application range of the polyurethane material.

[0006] Therefore, developing a polyurethane resin coating material with excellent yellowing resistance and aging resistance is of great significance to the art. Summary of the invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a yellowing-resistant and aging-resistant polyurethane resin coating material and a preparation method thereof. The polyurethane resin coating material has good aging resistance and yellowing resistance, as well as excellent mechanical properties and has broad application prospects.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A yellowing-resistant and aging-resistant polyurethane resin coating material, comprising the following raw materials in parts by weight:

[0010] 80-100 parts of polyether polyol, 60-80 parts of diisocyanate, 50-70 parts of butyl acetate, 5-8 parts of modified titanium dioxide, 1-2 parts of defoaming agent, 12-18 parts of chain extender, 0.2-0.4 parts of ultraviolet light absorber, and 0.1-0.2 parts of stannous octoate.

[0011] Preferably, the polyether polyol is polytetramethylene ether glycol; the diisocyanate is one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate; and the chain extender is one or more of diethyltoluenediamine, 3,5-diamino-4-chlorobenzoic acid isobutyl ester, and ethylenediamine.

[0012] In the present invention, the added diisocyanate is an aliphatic diisocyanate. Since aromatic isocyanates contain benzene rings, they are easily oxidized to form quinone structures, which cause the polyurethane products to turn yellow and have poor weather resistance. Therefore, the presence of aliphatic isocyanates allows the macromolecular chains of the polyurethane coating to contain a certain amount of aliphatic hydrocarbon chemical structures, reducing the number of benzene rings in the molecular chain, thereby reducing the tendency of the polyurethane macromolecules to turn yellow due to external factors.

[0013] Preferably, the ultraviolet light absorber is one or both of 2,4-dihydroxybenzophenone and 2-hydroxy-4-n-octyloxybenzophenone; the defoaming agent is one or both of polyoxypropylene glycerol ether and pentaerythritol stearate.

[0014] In the present invention, the added ultraviolet absorber absorbs harmful ultraviolet radiation and transfers it into heat, then releases the energy in the form of heat and then recovers to the original structure, thus achieving the effect of yellowing resistance.

[0015] Preferably, the preparation method of the modified titanium dioxide comprises the following steps:

[0016] S1. Add titanium dioxide to deionized water, then add magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, urea, and sodium dodecyl sulfate, disperse by ultrasonication, and perform hydrothermal reaction. After the reaction is completed, let stand at a constant temperature, then filter, wash, dry, and calcine to obtain composite titanium dioxide;

[0017] S2, adding the composite titanium dioxide prepared in step S1 to an ethanol aqueous solution, adding vinyl triethoxysilane after uniform dispersion, stirring to react, filtering, washing, and drying after the reaction is completed to obtain vinyl titanium dioxide;

[0018] S3, adding N,N-dimethylacetamide to the vinyl titanium dioxide in step S2, and then adding 2-vinyl-4,6-diamino-1,3,5-triazine and ammonium persulfate to carry out heating reaction, filtering and washing after reacting for a period of time, drying the solid product and adding it to dimethyl sulfoxide, and then adding 1H-benzotriazole-1-carboxaldehyde to carry out constant temperature reaction, filtering, washing and drying after the reaction is completed, to obtain the modified titanium dioxide.

[0019] Preferably, the mass ratio of titanium dioxide, deionized water, magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, urea and sodium dodecyl sulfate in step S1 is 50:800-1000:38-54:18-27:48-67:10-20, the temperature of the hydrothermal reaction is 110-120°C, and the time is 10-12h; the temperature of the constant temperature standing is 70-80°C, and the time is 12-16h; the temperature of the calcination is 500-550°C, and the time is 3-4h.

[0020] In the present invention, the added modified titanium dioxide can significantly improve the aging and yellowing resistance of the polyurethane coating material. With titanium dioxide as the raw material, magnesium aluminum hydrotalcite is in situ generated on titanium dioxide by a hydrothermal method. On the one hand, the titanium dioxide can be coated to block the photoactivated points of titanium dioxide, reduce the photocatalytic activity of titanium dioxide and improve the dispersibility, thereby improving the aging resistance of the modified titanium dioxide. At the same time, the layered magnesium aluminum hydrotalcite can play a barrier role, improve the barrier performance of the modified titanium dioxide, thereby reducing the erosion of oxygen and moisture on the polyurethane coating material, and improving the aging resistance of the polyurethane. At the same time, sodium dodecyl sulfate is added during the reaction process to be inserted between the magnesium aluminum hydrotalcite layers, thereby improving the dispersibility of the composite titanium dioxide and also improving the compatibility of the composite titanium dioxide with polyurethane.

[0021] Preferably, in step S2, the mass ratio of the composite titanium dioxide to vinyltriethoxysilane is 50:9-15, the temperature of the stirring reaction is 60-70° C., and the time is 2-3 h.

[0022] In the present invention, the composite titanium dioxide is reacted with vinyltriethoxysilane to introduce vinyl active groups into the composite titanium dioxide, which is beneficial to subsequent reactions.

[0023] Preferably, in step S3, the mass ratio of vinyl titanium dioxide, 2-vinyl-4,6-diamino-1,3,5-triazine, ammonium persulfate, and 1H-benzotriazole-1-carboxaldehyde is 55:6.5-11:0.5-1:7.5-12.

[0024] Preferably, the temperature of the heating reaction in step S3 is 90-100°C, the time is 1-2h, and the temperature of the isothermal reaction is 170-180°C, the time is 4-6h.

[0025] In the present invention, vinyl titanium dioxide is reacted with 2-vinyl-4,6-diamino-1,3,5-triazine, and a triazine group is introduced into titanium dioxide by a double bond addition reaction. The triazine ring in the molecular structure can absorb part of ultraviolet radiation, thereby improving the yellowing resistance of polyurethane, and at the same time, an active amino group is introduced; then, 1H-benzotriazole-1-carboxaldehyde is introduced into titanium dioxide by a Schiff base reaction, and the benzotriazole group can effectively absorb ultraviolet rays and release energy in the form of heat, thereby protecting the material from damage by ultraviolet radiation, thereby improving the aging resistance of polyurethane. Moreover, 1H-benzotriazole-1-carboxaldehyde itself has high light stability, and no significant chemical changes occur in the process of absorbing and releasing energy, so that the absorption effect of ultraviolet radiation can be exerted for a long time. 2-vinyl-4,6-diamino-1,3,5-triazine and 1H-benzotriazole-1-carboxaldehyde are reacted with each other to form a double bond addition reaction, and the triazine ring in the molecular structure can absorb part of ultraviolet radiation, thereby improving the yellowing resistance of polyurethane, and at the same time, an active amino group is introduced; then, 1H-benzotriazole-1-carboxaldehyde is introduced into titanium dioxide by a Schiff base reaction, and the benzotriazole group can effectively absorb ultraviolet rays and release energy in the form of heat, thereby protecting the material from damage by ultraviolet radiation, thereby improving the aging resistance of polyurethane. Moreover, 1H-benzotriazole-1-carboxaldehyde itself has high light stability, and no significant chemical changes occur in the process of absorbing and releasing energy, so that the absorption effect of ultraviolet radiation can be exerted for a long time. -Benzotriazole-1-formaldehyde is simultaneously connected to titanium dioxide, and the two work together to improve the yellowing resistance and aging resistance of the polyurethane coating; and, due to the residual amino group in 2-vinyl-4,6-diamino-1,3,5-triazine, it can also react with the isocyanate group in the polyurethane, thereby improving the binding performance of the modified titanium dioxide and the polyurethane, and making the polyurethane have better mechanical properties.

[0026] The present invention also protects a method for preparing the yellowing-resistant and aging-resistant polyurethane resin coating material as described above, comprising the following steps:

[0027] Add polyether polyol and butyl acetate into a reaction kettle, add diisocyanate and stannous octoate under nitrogen protection, and stir to react. When the content of NCO group reaches a predetermined content, add chain extender, defoamer, modified titanium dioxide and ultraviolet light absorber, and continue to react for 2-3 hours. After the reaction is completed, cool to obtain the yellowing-resistant and aging-resistant polyurethane resin coating material.

[0028] Preferably, the stirring reaction temperature is 80-90° C., and the stirring speed is 400-500 r / min.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The yellowing-resistant and aging-resistant polyurethane resin coating provided by the present invention uses polyether polyether and aliphatic diisocyanate as main raw materials. The aliphatic diisocyanate does not contain benzene rings, which reduces the number of benzene rings in the polyurethane macromolecular chain, thereby improving the yellowing resistance of the polyurethane resin coating. At the same time, ultraviolet absorbers and modified titanium dioxide are added. Titanium dioxide has extremely strong ultraviolet absorption and infrared reflection properties. The ultraviolet absorber can release ultraviolet radiation in the form of heat. The synergistic effect of the two can significantly improve the anti-ultraviolet ability of the polyurethane resin coating, thereby effectively improving the yellowing resistance and aging resistance of the polyurethane material.

[0031] (2) The yellowing-resistant and aging-resistant polyurethane resin coating provided by the present invention is added with modified titanium dioxide, and magnesium aluminum hydrotalcite is in situ generated on titanium dioxide by a hydrothermal method. On the one hand, the titanium dioxide can be coated to block the photoactivated points of titanium dioxide, reduce the photocatalytic activity of titanium dioxide and improve the dispersibility, thereby improving the aging resistance of the modified titanium dioxide. At the same time, the layered magnesium aluminum hydrotalcite can play a barrier role, improve the barrier performance of the modified titanium dioxide, thereby reducing the erosion of oxygen and moisture on the polyurethane coating material, and improving the aging resistance of the polyurethane; then, the composite titanium dioxide is reacted with sodium dodecyl sulfate, and the sodium dodecyl sulfate is inserted into the interlayer of the magnesium aluminum hydrotalcite, thereby improving the dispersibility of the composite titanium dioxide and also improving the compatibility of the composite titanium dioxide with polyurethane; then, the composite titanium dioxide is vinylized, which is beneficial to subsequent reactions; finally, the vinyl titanium dioxide is reacted with 2-vinyl-4,6-diamino-1,3,5-triazine, 1H -benzotriazole-1-carboxaldehyde is reacted to graft 2-vinyl-4,6-diamino-1,3,5-triazine and 1H-benzotriazole-1-carboxaldehyde onto titanium dioxide. The introduced benzotriazole and triazine have good ultraviolet attraction performance. Through the transfer of intramolecular hydrogen bonds or cis-trans isomerization, harmful ultraviolet radiation is absorbed and transferred into heat, protecting the material from damage by ultraviolet radiation, thereby improving the aging resistance of polyurethane. In addition, 1H-benzotriazole-1-carboxaldehyde itself has high light stability and does not undergo significant chemical changes in the process of absorbing and releasing energy, so it can absorb ultraviolet radiation for a long time. The two work together to improve the yellowing resistance and aging resistance of polyurethane coating materials. In addition, since the residual amino group in 2-vinyl-4,6-diamino-1,3,5-triazine can also react with the isocyanate group in polyurethane, the combination performance of modified titanium dioxide and polyurethane is improved, so that polyurethane has better mechanical properties.

[0032] (3) The yellowing-resistant and aging-resistant polyurethane resin coating provided by the present invention contains no fluorocarbon substrate in the raw materials and additives added, thereby avoiding the problem that the polyurethane resin coating is difficult to degrade, has bioaccumulation and multi-toxicity due to fluorocarbon materials, and is beneficial to environmental protection. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] In the present invention, the titanium dioxide is rutile titanium dioxide with a particle size of 200-300 nm; the polytetramethylene ether glycol is purchased from Shandong Suihua Biotechnology Co., Ltd. with a molecular weight of 2000 Example 1

[0035] A yellowing-resistant and aging-resistant polyurethane resin coating material, comprising the following raw materials:

[0036] 90 g of polytetramethylene ether glycol, 70 g of isophorone diisocyanate, 60 g of butyl acetate, 7 g of modified titanium dioxide, 1.5 g of polyoxypropylene glycerol ether, 15 g of ethylenediamine, 0.3 g of 2,4-dihydroxybenzophenone, and 0.15 g of stannous octoate.

[0037] Wherein, the preparation method of the modified titanium dioxide comprises the following steps:

[0038] S1. Add 50 g of titanium dioxide to 900 g of deionized water, then add 46 g of magnesium nitrate hexahydrate, 22.5 g of aluminum nitrate nonahydrate, 57.6 g of urea, and 15 g of sodium dodecyl sulfate, and perform ultrasonic dispersion for 15 min. Perform hydrothermal reaction at 115 ° C for 11 h. After the reaction is completed, stand at a constant temperature of 75 ° C for 14 h, then filter, wash, dry, and calcine at 500 ° C for 4 h to obtain composite titanium dioxide;

[0039] S2, adding 50g of the composite titanium dioxide in step S1 to 800g of ethanol aqueous solution (the mass fraction of ethanol is 75%), adding 13.3g of vinyl triethoxysilane after uniform dispersion, reacting at 65°C for 2.5h, filtering, washing and drying after the reaction is completed to obtain vinyl titanium dioxide;

[0040] S3, add 55g of vinyl titanium dioxide in step S2 to 900mL of N,N-dimethylacetamide, then add 9.6g of 2-vinyl-4,6-diamino-1,3,5-triazine and 0.8g of ammonium persulfate, react at 95°C for 1.5h, then filter and wash, dry the solid product and add it to 900mL of dimethyl sulfoxide, then add 10.3g of 1H-benzotriazole-1-carboxaldehyde, react at a constant temperature of 175°C for 5h, filter, wash and dry after the reaction is completed, to obtain the modified titanium dioxide.

[0041] A method for preparing a yellowing-resistant and aging-resistant polyurethane resin coating material comprises the following steps:

[0042] Add polytetramethylene ether glycol and butyl acetate into a reaction kettle, add isophorone diisocyanate and stannous octoate under nitrogen protection, and stir to react at 85°C and 450r / min. When the content of NCO group reaches 10%, add ethylenediamine, polyoxypropylene glycerol ether, modified titanium dioxide and 2,4-dihydroxybenzophenone, and continue to react for 2.5 hours. After the reaction is completed, cool to obtain the yellowing-resistant and aging-resistant polyurethane resin coating material. Example 2

[0043] A yellowing-resistant and aging-resistant polyurethane resin coating material, comprising the following raw materials:

[0044] 80 g of polytetramethylene ether glycol, 60 g of dicyclohexylmethane diisocyanate, 50 g of butyl acetate, 5 g of modified titanium dioxide, 1 g of pentaerythritol stearate, 12 g of diethyltoluenediamine, 0.2 g of 2-hydroxy-4-n-octyloxybenzophenone, and 0.1 g of stannous octoate.

[0045] Wherein, the preparation method of the modified titanium dioxide comprises the following steps:

[0046] S1. Add 50 g of titanium dioxide to 800 g of deionized water, then add 38.4 g of magnesium nitrate hexahydrate, 18.8 g of aluminum nitrate nonahydrate, 48 g of urea, and 10 g of sodium dodecyl sulfate, and ultrasonically disperse for 10 min. Hydrothermally react at 110 ° C for 12 h. After the reaction is completed, stand at a constant temperature of 70 ° C for 16 h, then filter, wash, dry, and calcine at 500 ° C for 4 h to obtain composite titanium dioxide;

[0047] S2, adding 50g of the composite titanium dioxide in step S1 to 800g of ethanol aqueous solution (the mass fraction of ethanol is 70%), adding 9.5g of vinyl triethoxysilane after uniform dispersion, reacting at 60°C for 3h, filtering, washing and drying after the reaction is completed to obtain vinyl titanium dioxide;

[0048] S3, add 55g of vinyl titanium dioxide in step S2 to 900mL of N,N-dimethylacetamide, then add 6.9g of 2-vinyl-4,6-diamino-1,3,5-triazine and 0.5g of ammonium persulfate, react at 90°C for 2h, then filter and wash, dry the solid product, add it to 900mL of dimethyl sulfoxide, then add 7.5g of 1H-benzotriazole-1-carboxaldehyde, react at a constant temperature of 170°C for 6h, filter, wash and dry after the reaction is completed, to obtain the modified titanium dioxide.

[0049] A method for preparing a yellowing-resistant and aging-resistant polyurethane resin coating material comprises the following steps:

[0050] Add polytetramethylene ether glycol and butyl acetate into a reaction kettle, add dicyclohexylmethane diisocyanate and stannous octoate under nitrogen protection, and stir to react at 80°C and 400r / min. When the content of NCO group reaches 10%, add diethyltoluenediamine, pentaerythritol stearate, modified titanium dioxide and 2-hydroxy-4-n-octyloxybenzophenone, and continue to react for 3 hours. After the reaction is completed, cool to obtain the yellowing-resistant and aging-resistant polyurethane resin coating material. Example 3

[0051] A yellowing-resistant and aging-resistant polyurethane resin coating material, comprising the following raw materials:

[0052] 100 g of polytetramethylene ether glycol, 80 g of hexamethylene diisocyanate, 70 g of butyl acetate, 8 g of modified titanium dioxide, 2 g of polyoxypropylene glycerol ether, 18 g of 3,5-diamino-4-chlorobenzoic acid isobutyl ester, 0.4 g of 2,4-dihydroxybenzophenone, and 0.2 g of stannous octoate.

[0053] Wherein, the preparation method of the modified titanium dioxide comprises the following steps:

[0054] S1. Add 50g of titanium dioxide to 1000g of deionized water, then add 54g of magnesium nitrate hexahydrate, 26.3g of aluminum nitrate nonahydrate, 67g of urea, and 20g of sodium dodecyl sulfate, and ultrasonically disperse for 20min. Hydrothermally react at 120°C for 10h. After the reaction is completed, stand at a constant temperature of 80°C for 12h, then filter, wash, dry, and calcine at 550°C for 3h to obtain composite titanium dioxide;

[0055] S2, adding 50g of the composite titanium dioxide in step S1 to 800g of ethanol aqueous solution (the mass fraction of ethanol is 80%), adding 15g of vinyl triethoxysilane after uniform dispersion, reacting at 70°C for 2h, filtering, washing and drying after the reaction is completed to obtain vinyl titanium dioxide;

[0056] S3, adding 55g of vinyl titanium dioxide in step S2 to 900mL of N,N-dimethylacetamide, then adding 1g of 2-vinyl-4,6-diamino-1,3,5-triazine and 1g of ammonium persulfate, reacting at 100°C for 1h, then filtering and washing, drying the solid product, adding it to 900mL of dimethyl sulfoxide, then adding 12g of 1H-benzotriazole-1-carboxaldehyde, and reacting at a constant temperature of 180°C for 4h. After the reaction is completed, filtering, washing and drying are performed to obtain the modified titanium dioxide.

[0057] A method for preparing a yellowing-resistant and aging-resistant polyurethane resin coating material comprises the following steps:

[0058] Add polytetramethylene ether glycol and butyl acetate into a reaction kettle, add hexamethylene diisocyanate and stannous octoate under nitrogen protection, and stir to react at 90°C and 500r / min. When the content of NCO group reaches 10%, add 3,5-diamino-4-chlorobenzoic acid isobutyl ester, modified titanium dioxide and 2,4-dihydroxybenzophenone, and continue to react for 2h. After the reaction is completed, cool to obtain the yellowing-resistant and aging-resistant polyurethane resin coating material. Comparative Example 1

[0059] A yellowing-resistant and aging-resistant polyurethane resin coating material, comprising the following raw materials:

[0060] 90 g of polytetramethylene ether glycol, 70 g of isophorone diisocyanate, 60 g of butyl acetate, 7 g of modified titanium dioxide, 1.5 g of polyoxypropylene glycerol ether, 15 g of ethylenediamine, 0.3 g of 2,4-dihydroxybenzophenone, and 0.15 g of stannous octoate.

[0061] Wherein, the preparation method of the modified titanium dioxide comprises the following steps:

[0062] S1. Add 50 g of titanium dioxide to 800 g of ethanol aqueous solution (the mass fraction of ethanol is 75%), and after uniform dispersion, add 13.3 g of vinyl triethoxysilane, and react at 65°C for 2.5 h. After the reaction is completed, filter, wash, and dry to obtain vinyl titanium dioxide;

[0063] S2. Add 55 g of vinyl titanium dioxide in step S1 to 900 mL of N,N-dimethylacetamide, then add 9.6 g of 2-vinyl-4,6-diamino-1,3,5-triazine and 0.8 g of ammonium persulfate, react at 95° C. for 1.5 h, then filter and wash, dry the solid product, add it to 900 mL of dimethyl sulfoxide, then add 10.3 g of 1H-benzotriazole-1-carboxaldehyde, and react at a constant temperature of 175° C. for 5 h. After the reaction is completed, filter, wash and dry to obtain the modified titanium dioxide.

[0064] A method for preparing a yellowing-resistant and aging-resistant polyurethane resin coating material comprises the following steps:

[0065] Add polytetramethylene ether glycol and butyl acetate into a reaction kettle, add isophorone diisocyanate and stannous octoate under nitrogen protection, and stir to react at 85°C and 450r / min. When the content of NCO group reaches 10%, add ethylenediamine, polyoxypropylene glycerol ether, modified titanium dioxide and 2,4-dihydroxybenzophenone, and continue to react for 2.5 hours. After the reaction is completed, cool to obtain the yellowing-resistant and aging-resistant polyurethane resin coating material.

[0066] Compared with Example 1, this comparative example did not generate magnesium aluminum hydrotalcite in situ on titanium dioxide. Comparative Example 2

[0067] A yellowing-resistant and aging-resistant polyurethane resin coating material, comprising the following raw materials:

[0068] 90 g of polytetramethylene ether glycol, 70 g of isophorone diisocyanate, 60 g of butyl acetate, 7 g of modified titanium dioxide, 1.5 g of polyoxypropylene glycerol ether, 15 g of ethylenediamine, 0.3 g of 2,4-dihydroxybenzophenone, and 0.15 g of stannous octoate.

[0069] Wherein, the preparation method of the modified titanium dioxide comprises the following steps:

[0070] S1. Add 50 g of titanium dioxide to 900 g of deionized water, then add 46 g of magnesium nitrate hexahydrate, 22.5 g of aluminum nitrate nonahydrate, 57.6 g of urea, and 15 g of sodium dodecyl sulfate, and perform ultrasonic dispersion for 15 min. Perform hydrothermal reaction at 115 ° C for 11 h. After the reaction is completed, stand at a constant temperature of 75 ° C for 14 h, then filter, wash, dry, and calcine at 500 ° C for 4 h to obtain composite titanium dioxide;

[0071] S2, adding 50g of the composite titanium dioxide in step S1 to 800g of ethanol aqueous solution (the mass fraction of ethanol is 75%), adding 13.3g of vinyl triethoxysilane after uniform dispersion, reacting at 65°C for 2.5h, filtering, washing and drying after the reaction is completed to obtain vinyl titanium dioxide;

[0072] S3. Add 900 mL of N,N-dimethylacetamide to 55 g of vinyl titanium dioxide in step S2, and then add 9.6 g of 2-vinyl-4,6-diamino-1,3,5-triazine and 0.8 g of ammonium persulfate, react at 95° C. for 1.5 h, and then filter, wash, and dry to obtain the modified titanium dioxide.

[0073] A method for preparing a yellowing-resistant and aging-resistant polyurethane resin coating material comprises the following steps:

[0074] Add polytetramethylene ether glycol and butyl acetate into a reaction kettle, add isophorone diisocyanate and stannous octoate under nitrogen protection, and stir to react at 85°C and 450r / min. When the content of NCO group reaches 10%, add ethylenediamine, polyoxypropylene glycerol ether, modified titanium dioxide and 2,4-dihydroxybenzophenone, and continue to react for 2.5 hours. After the reaction is completed, cool to obtain the yellowing-resistant and aging-resistant polyurethane resin coating material.

[0075] Compared with Example 1, in this comparative example, 1H-benzotriazole-1-carboxaldehyde is not grafted onto the modified titanium dioxide. Comparative Example 3

[0076] A yellowing-resistant and aging-resistant polyurethane resin coating material, comprising the following raw materials:

[0077] 90 g of polytetramethylene ether glycol, 70 g of isophorone diisocyanate, 60 g of butyl acetate, 7 g of modified titanium dioxide, 1.5 g of polyoxypropylene glycerol ether, 15 g of ethylenediamine, 0.3 g of 2,4-dihydroxybenzophenone, and 0.15 g of stannous octoate.

[0078] Wherein, the preparation method of the modified titanium dioxide comprises the following steps:

[0079] S1. Add 50 g of titanium dioxide to 900 g of deionized water, then add 46 g of magnesium nitrate hexahydrate, 22.5 g of aluminum nitrate nonahydrate, 57.6 g of urea, and 15 g of sodium dodecyl sulfate, and perform ultrasonic dispersion for 15 min. Perform hydrothermal reaction at 115 ° C for 11 h. After the reaction is completed, stand at a constant temperature of 75 ° C for 14 h, then filter, wash, dry, and calcine at 500 ° C for 4 h to obtain composite titanium dioxide;

[0080] S2, adding 50g of the composite titanium dioxide in step S1 to 800g of ethanol aqueous solution (the mass fraction of ethanol is 75%), adding 13.3g of vinyl triethoxysilane after uniform dispersion, reacting at 65°C for 2.5h, filtering, washing and drying after the reaction is completed to obtain vinyl titanium dioxide;

[0081] S3. Evenly mix 55 g of vinyl titanium dioxide and 10.3 g of 1H-benzotriazole-1-carboxaldehyde in step S2 to obtain the modified titanium dioxide.

[0082] A method for preparing a yellowing-resistant and aging-resistant polyurethane resin coating material comprises the following steps:

[0083] Add polytetramethylene ether glycol and butyl acetate into a reaction kettle, add isophorone diisocyanate and stannous octoate under nitrogen protection, and stir to react at 85°C and 450r / min. When the content of NCO group reaches 10%, add ethylenediamine, polyoxypropylene glycerol ether, modified titanium dioxide and 2,4-dihydroxybenzophenone, and continue to react for 2.5 hours. After the reaction is completed, cool to obtain the yellowing-resistant and aging-resistant polyurethane resin coating material.

[0084] Compared with Example 1, in this comparative example, 2-vinyl-4,6-diamino-1,3,5-triazine is not implanted on the modified titanium dioxide.

[0085] The yellowing-resistant and aging-resistant polyurethane resin coating materials prepared in Examples 1-3 and Comparative Examples 1-3 were poured into a preheated tetrafluoroethylene mold, dried in a vacuum drying oven at 80°C to form a film, and a test sample was obtained for performance testing, wherein the tensile strength and elongation at break were tested according to the Determination of Tensile Properties of Plastics Part 3: Test Conditions for Films and Sheets GB / T1040.3-2006 "Determination of Tensile Properties of Plastics Part 3: Test Conditions for Films and Sheets", and the tensile rate was 50 mm / min; aging resistance test: an ultraviolet light weathering artificial aging test was carried out according to GB / T 23987-2009 standard, with an irradiation wavelength of 340 nm, a temperature of 50°C, and a time of 240 h, and the yellowing index was tested according to HG / T 3862-2006 "Plastic Yellowness Index Test Method", and the tensile strength retention rate and elongation at break retention rate of the aged sample were tested, and the test results are shown in Table 1 below:

[0086] Table 1 Properties of each group of polyurethane resin coating materials

[0087]

[0088] As can be seen from Table 1 above, compared with Comparative Examples 1-3, Examples 1-3 have better mechanical properties, lower yellowing index and higher mechanical property retention rate, indicating that the polyurethane resin coating material prepared by the present invention has excellent mechanical properties, yellowing resistance and aging resistance, and has good application prospects.

[0089] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A yellowing-resistant and aging-resistant polyurethane resin coating material, characterized in that: By weight, it includes the following raw materials: 80-100 parts of polyether polyol, 60-80 parts of diisocyanate, 50-70 parts of butyl acetate, 5-8 parts of modified titanium dioxide, 1-2 parts of defoamer, 12-18 parts of chain extender, 0.2-0.4 parts of ultraviolet light absorber, 0.1-0.2 parts of stannous octoate; The preparation method of the modified titanium dioxide comprises the following steps: S1. Add titanium dioxide to deionized water, then add magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, urea, and sodium dodecyl sulfate, disperse by ultrasonication, and perform hydrothermal reaction. After the reaction is completed, let stand at a constant temperature, then filter, wash, dry, and calcine to obtain composite titanium dioxide; S2, adding the composite titanium dioxide prepared in step S1 to an ethanol aqueous solution, adding vinyl triethoxysilane after uniform dispersion, stirring to react, filtering, washing, and drying after the reaction is completed to obtain vinyl titanium dioxide; S3, adding N,N-dimethylacetamide to the vinyl titanium dioxide in step S2, and then adding 2-vinyl-4,6-diamino-1,3,5-triazine and ammonium persulfate, heating reaction, filtering and washing after a period of reaction, drying the solid product and adding it to dimethyl sulfoxide, and then adding 1H-benzotriazole-1-carboxaldehyde, and reacting at a constant temperature, filtering, washing and drying after the reaction is completed, to obtain the modified titanium dioxide; The mass ratio of titanium dioxide, deionized water, magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, urea, and sodium dodecyl sulfate in step S1 is 50:800-1000:38-54:18-27:48-67:10-20, the temperature of the hydrothermal reaction is 110-120° C., and the time is 10-12 h; the temperature of the constant temperature standing is 70-80° C., and the time is 12-16 h; the temperature of the calcination is 500-550° C., and the time is 3-4 h; In step S2, the mass ratio of the composite titanium dioxide to vinyl triethoxysilane is 50:9-15, the stirring reaction temperature is 60-70° C., and the time is 2-3 hours; In step S3, the mass ratio of vinyl titanium dioxide, 2-vinyl-4,6-diamino-1,3,5-triazine, ammonium persulfate, and 1H-benzotriazole-1-carboxaldehyde is 55:6.5-11:0.5-1:7.5-12; the temperature of the heating reaction is 90-100°C, the time is 1-2h, and the temperature of the constant heat reaction is 170-180°C, and the time is 4-6h.

2. The yellowing-resistant and aging-resistant polyurethane resin coating material according to claim 1, characterized in that: The polyether polyol is polytetramethylene ether glycol; the diisocyanate is one or more of isophorone diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate; and the chain extender is one or more of diethyltoluenediamine, 3,5-diamino-4-chlorobenzoic acid isobutyl ester, and ethylenediamine.

3. The yellowing-resistant and aging-resistant polyurethane resin coating material according to claim 1, characterized in that: The ultraviolet light absorber is one or two of 2,4-dihydroxybenzophenone and 2-hydroxy-4-n-octyloxybenzophenone; the defoamer is one or two of polyoxypropylene glycerol ether and pentaerythritol stearate.

4. A method for preparing the yellowing-resistant and aging-resistant polyurethane resin coating material according to any one of claims 1 to 3, characterized in that: The following steps are involved: Add polyether polyol and butyl acetate into a reaction kettle, add diisocyanate and stannous octoate under nitrogen protection, and stir to react. When the content of NCO group reaches a predetermined content, add chain extender, defoamer, modified titanium dioxide and ultraviolet light absorber, and continue to react for 2-3 hours. After the reaction is completed, cool to obtain the yellowing-resistant and aging-resistant polyurethane resin coating material.

5. The preparation method according to claim 4, characterized in that: The stirring reaction temperature is 80-90°C, and the stirring speed is 400-500r / min.

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