A polyurethane composite coating, its preparation method and application

Abstract

The present invention belongs to the technical field of coatings, and specifically relates to a polyurethane composite coating, a preparation method thereof and an application. The polyurethane composite coating comprises the following raw materials in parts by weight: 90 - 100 parts of aqueous polyurethane resin, 1 - 5 parts of modified diatomite, 0.5 - 2 parts of dispersion aid, 1 - 3 parts of defoamer, and 0.1 - 0.3 parts of wetting agent. After acidifying the diatomite, the present invention chemically modifies it with toluene diisocyanate, and then introduces hydroxypropyl-β-cyclodextrin to obtain modified diatomite. The modified diatomite has good compatibility and interfacial bonding force with the polyurethane resin, and has good dispersibility among the components, so that the modified diatomite particles can play a role in supporting and dispersing stress, thereby slowing down the wear rate of the coating. The polyurethane composite coating can be used for leather surface treatment, improving the quality of leather materials and extending their service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and particularly relates to a polyurethane composite coating, a preparation method thereof, and an application thereof. Background Art

[0002] Polyurethane (PU) is a polymer with a repeating structural unit of urethane segments, which is made by reacting isocyanate with polyol. It has the characteristics of pollution-free, excellent mechanical properties, and easy modification, and is widely used in technical fields such as textile, leather processing, and coatings.

[0003] With the development of technology, the requirements for the performance of polyurethane coatings are also constantly increasing. Although traditional polyurethane coatings have excellent environmental protection performance, they also have problems such as poor abrasion resistance, water resistance, and corrosion resistance. For example, in the field of automotive interior materials, some automotive interiors, such as leather and synthetic leather, are easily scratched by hard objects such as keys and coins during use, and their performance may not meet the requirements. And wear-resistant composite coatings can effectively improve the scratch resistance of these materials, reduce the generation of scratches, and thus protect the integrity of the interior materials. Therefore, it is particularly important to develop a polyurethane composite coating with wear-resistant performance.

[0004] At present, there have been some studies and reports on polyurethane composite coatings. For example, by introducing inorganic nano-materials into the molecular structure of polyurethane, unique properties can be imparted to the polyurethane composite materials. However, this composite coating also faces some problems. For example, poor dispersion of inorganic materials in the polyurethane matrix will lead to deterioration of the comprehensive performance of the coating. In addition, the invention patent CN 116239752A discloses a preparation method of bio-based waterborne polyurethane. By adding lignin and a catalyst to castor oil-modified polyurethane, bio-based waterborne polyurethane with flame retardant and ultraviolet resistance characteristics is obtained. Despite these technologies, there are few reports on the research to improve the wear-resistant performance of polyurethane composite coatings.

[0005] To overcome this defect, the present invention aims to provide a polyurethane composite coating, which not only has excellent high strength but also has wear resistance, and the polyurethane composite coating can also be applied to leather surface treatment to improve the durability and environmental sustainability of materials. Summary of the Invention

[0006] The first object of the present invention is to provide a polyurethane composite coating, and the polyurethane composite coating has advantages such as high wear resistance and strong mechanical properties; the wear-resistant composite coating can significantly reduce scratches and wear caused by daily use, so as to keep the interior clean and beautiful.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A polyurethane composite coating, comprising the following raw materials in parts by weight: 90-100 parts of aqueous polyurethane resin, 1-5 parts of modified diatomaceous earth, 0.5-2 parts of dispersion aid, 1-3 parts of defoaming agent, 0.1-0.3 parts of wetting agent;

[0009] The preparation process of the modified diatomaceous earth is as follows:

[0010] (1) Add diatomaceous earth to sulfuric acid solution, heat and stir, then collect the product and calcine it to obtain pretreated diatomaceous earth;

[0011] (2) Add the pretreated diatomaceous earth obtained in step (1) to toluene, then add toluene diisocyanate, and heat and react to obtain isocyanate-modified diatomaceous earth;

[0012] (3) Add the isocyanate-modified diatomaceous earth obtained in step (2) to a solvent, then add hydroxypropyl-β-cyclodextrin and a catalyst, heat and react, and the reaction solution is purified to obtain hydroxypropyl-β-cyclodextrin-modified diatomaceous earth.

[0013] Further, the mass ratio of the diatomaceous earth to toluene diisocyanate in step (2) is 1:0.07-0.1.

[0014] Further, the mass ratio of the isocyanate-modified diatomaceous earth to hydroxypropyl-β-cyclodextrin in step (3) is 1:0.8-1.2, and the mass ratio of the isocyanate-modified diatomaceous earth to the catalyst is 1:0.05-0.08.

[0015] Further, the catalyst in step (3) is dibutyltin dilaurate or stannous octoate.

[0016] Further, the temperature of the heating reaction in step (2) is 50-60°C, and the time is 2-3 h.

[0017] Further, the concentration of the sulfuric acid solution in step (1) is 60-70 wt%, the heating temperature is 50-60°C, and the time is 1-2 h.

[0018] Further, the particle size of the diatomaceous earth is 20-50 µm, the SiO2 content is ≥80 wt%; the defoaming agent is polyoxypropylene glycerol ether or pentaerythritol stearate, the wetting agent is alkynediol, and the dispersion aid is sodium dodecyl sulfate.

[0019] The second object of the present invention is to provide a preparation method of a polyurethane composite coating, which is simple and efficient and helps to realize industrial production.

[0020] In order to achieve the above object, the technical solution adopted by the present invention is:

[0021] A method for preparing a polyurethane composite coating, comprising the following steps:

[0022] Weigh each raw material according to the above weight parts, mix the aqueous polyurethane resin and the modified diatomite evenly to obtain a mixed solution, and then add a dispersion aid, an antifoaming agent, and a wetting agent to the mixed solution under stirring conditions to obtain a coating, and apply it to a substrate, and obtain the product after curing.

[0023] Further, the substrate is leather or synthetic leather; the curing temperature is 75-85 °C, and the time is 5-6 h.

[0024] The third object of the present invention is to provide an application of a polyurethane composite coating in the surface treatment of automotive leather.

[0025] Compared with the prior art, the beneficial effects of the present invention are mainly as follows:

[0026] 1. In the present invention, the diatomite is acidified, and then chemically modified with toluene diisocyanate. The isocyanate group (-NCO) can react with the hydroxyl group (-OH) on the surface of the diatomite, so that the isocyanate group is introduced onto the surface of the diatomite. Under the catalysis of a catalyst, these groups further react with the hydroxypropyl group in hydroxypropyl-β-cyclodextrin to obtain modified diatomite. The modified diatomite not only retains the original porosity, but also introduces the special cavity structure and hydroxyl functional group of cyclodextrin, so that a tight interaction is formed between it and the polyurethane resin, which helps the uniform dispersion of the modified diatomite in the polyurethane resin and other components, and enables the modified diatomite particles to play a role in supporting and dispersing stress, thereby slowing down the wear rate of the coating.

[0027] 2. The polyurethane composite coating prepared by the present invention not only has excellent wear resistance, but also exhibits excellent mechanical properties and adhesion. The polyurethane composite coating can be applied to the surface treatment of leather to improve the quality of leather materials and extend their service life. Specific Embodiments

[0028] The following further describes the technical solutions of the present invention in conjunction with specific embodiments. However, those skilled in the art should understand that the following examples are only used to illustrate the present invention and should not be regarded as a limitation of the present invention. The specific conditions not specified in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are all conventional products obtained through commercial channels.

[0029] In the following examples and comparative examples, the average particle size of the diatomite is 20-50 µm, and the SiO2 content is ≥80 wt%. The solid content of the aqueous polyurethane resin (AH-1704B-2) is 30 ± 1%, and the viscosity is ≥100 mPa·s.

[0030] Example 1

[0031] A polyurethane composite coating, comprising the following raw materials in parts by weight: 95 parts of waterborne polyurethane resin, 3 parts of modified diatomaceous earth, 1 part of sodium dodecyl sulfate, 2 parts of polyoxypropylene glycerol ether, and 0.2 part of alkynediol;

[0032] The preparation process of the modified diatomaceous earth is as follows:

[0033] (1) Add diatomaceous earth to a 65wt% sulfuric acid solution, stir at 55°C for 1.5 h, then filter to collect the product. After drying, put it into a muffle furnace, heat it to 230°C at a rate of 2.5°C / min, calcine at 230°C for 35 min, and after the calcination is completed, heat it to 400°C at a rate of 2°C / min and calcine in a nitrogen atmosphere for 2 h, and pass through a 100-mesh sieve to obtain pretreated diatomaceous earth;

[0034] (2) Add the pretreated diatomaceous earth obtained in step (1) to toluene, and then add 2,4-toluene diisocyanate (the mass ratio of pretreated diatomaceous earth to 2,4-toluene diisocyanate is 1:0.08). After ultrasonic stirring for 60 min, react at 55°C for 2.5 h under nitrogen protection. Then filter the reaction solution, collect the particles and wash them 3 times with absolute ethanol to remove the unreacted 2,4-toluene diisocyanate to obtain isocyanate-modified diatomaceous earth;

[0035] (3) According to the mass ratio of hydroxypropyl-β-cyclodextrin, isocyanate-modified diatomaceous earth and catalyst dibutyltin dilaurate: 1:1:0.06, add the isocyanate-modified diatomaceous earth obtained in step (2) to ethyl acetate, then add hydroxypropyl-β-cyclodextrin and dibutyltin dilaurate, and then heat to 90°C and react under nitrogen protection for 6 h. After the reaction is completed, perform vacuum distillation, and wash the product successively with acetone and ethyl acetate to obtain hydroxypropyl-β-cyclodextrin-modified diatomaceous earth.

[0036] A preparation method of a polyurethane composite coating, comprising the following steps:

[0037] Weigh each raw material according to the above parts by weight, mix the waterborne polyurethane resin and the modified diatomaceous earth evenly to obtain a mixed solution; then add sodium dodecyl sulfate, polyoxypropylene glycerol ether, and alkynediol to the mixed solution under stirring conditions to obtain a coating; coat the coating on leather and cure it at 80°C for 5.5 h to obtain the product.

[0038] Example 2

[0039] A polyurethane composite coating, comprising the following raw materials in parts by weight: 90 parts of waterborne polyurethane resin, 1 part of modified diatomaceous earth, 0.5 part of sodium dodecyl sulfate, 1 part of pentaerythritol stearate, and 0.1 part of alkynediol;

[0040] The preparation process of the modified diatomite is as follows:

[0041] (1) Add diatomite into a 60 wt% sulfuric acid solution, stir at 60 °C for 1 h, then filter to collect the product. After drying, put it into a muffle furnace, heat it to 220 °C at a rate of 2 °C / min, calcine at 220 °C for 40 min. After the calcination is completed, heat it to 350 °C at a rate of 1.5 °C / min and calcine in a nitrogen atmosphere for 3 h. Pass through a 100-mesh sieve to obtain the pretreated diatomite;

[0042] (2) Add the pretreated diatomite obtained in step (1) into toluene, and then add 2,4-toluene diisocyanate (the mass ratio of the pretreated diatomite to 2,4-toluene diisocyanate is 1:0.07). After ultrasonic stirring for 60 min, react at 50 °C for 3 h under nitrogen protection. Then filter the reaction solution, collect the particles and wash them 3 times with absolute ethanol to remove the unreacted 2,4-toluene diisocyanate to obtain isocyanate-modified diatomite;

[0043] (3) According to the mass ratio of hydroxypropyl-β-cyclodextrin, isocyanate-modified diatomite and the catalyst dibutyltin dilaurate: 1:1:0.05, add the isocyanate-modified diatomite in step (2) into toluene, add hydroxypropyl-β-cyclodextrin and stannous octoate, and then under nitrogen protection, heat to 80 °C for reaction for 7 h. After the reaction is completed, carry out vacuum distillation, and wash the product successively with acetone and ethyl acetate to obtain hydroxypropyl-β-cyclodextrin-modified diatomite.

[0044] A method for preparing a polyurethane composite coating includes the following steps:

[0045] Weigh each raw material according to the above weight parts, mix the waterborne polyurethane resin and the modified diatomite evenly to obtain a mixed solution, and then add sodium dodecyl sulfate, pentaerythritol stearate, and alkynediol under stirring conditions to obtain a coating; coat the coating on the leather and cure it at 75 °C for 6 h to obtain the product.

[0046] Example 3

[0047] A polyurethane composite coating includes the following raw materials in weight parts: 100 parts of waterborne polyurethane resin, 5 parts of modified diatomite, 2 parts of sodium dodecyl sulfate, 3 parts of polyoxypropylene glycerol ether, and 0.3 parts of alkynediol;

[0048] The preparation process of the modified diatomite is as follows:

[0049] (1) Add diatomite to a 70 wt% sulfuric acid solution, stir at 60 °C for 1 h, then filter to collect the product. After drying, place it in a muffle furnace and heat it to 240 °C at a rate of 2 °C / min. Calcinate at 240 °C for 30 min. After the calcination is completed, heat it to 450 °C at a rate of 1.5 °C / min and calcinate in a nitrogen atmosphere for 1.5 h. Pass through a 100-mesh sieve to obtain pretreated diatomite;

[0050] (2) Add the pretreated diatomite obtained in step (1) to toluene, and then add 2,4-toluene diisocyanate (the mass ratio of pretreated diatomite to 2,4-toluene diisocyanate is 1:0.1). After ultrasonic stirring for 60 min, react at 60 °C for 2 h under nitrogen protection. Then filter the reaction solution, collect the particles and wash them 3 times with absolute ethanol to remove the unreacted 2,4-toluene diisocyanate to obtain isocyanate-modified diatomite;

[0051] (3) According to the mass ratio of hydroxypropyl-β-cyclodextrin, isocyanate-modified diatomite and the catalyst dibutyltin dilaurate: 1:1:0.08, add the isocyanate-modified diatomite obtained in step (2) to toluene, and then add hydroxypropyl-β-cyclodextrin and stannous octoate. Under nitrogen protection, heat to 85 °C and react for 8 h. After the reaction is completed, carry out vacuum distillation, and wash the product successively with acetone and ethyl acetate to obtain hydroxypropyl-β-cyclodextrin-modified diatomite.

[0052] A method for preparing a polyurethane composite coating, comprising the following steps:

[0053] Weigh each raw material according to the above weight parts, mix the waterborne polyurethane resin and the modified diatomite evenly to obtain a mixed solution, and then add sodium dodecyl sulfate, polyoxypropylene glycerol ether, and alkynediol under stirring conditions to obtain a coating; coat the coating on the leather and cure it at 85 °C for 5 h to obtain.

[0054] Comparative Example 1

[0055] A polyurethane composite coating, comprising the following raw materials in weight parts: 95 parts of waterborne polyurethane resin, 3 parts of diatomite, 1 part of sodium dodecyl sulfate, 2 parts of polyoxypropylene glycerol ether, and 0.2 part of alkynediol.

[0056] The preparation method of the above polyurethane composite coating is the same as that of Example 1, except that the modified diatomite in Example 1 is replaced by diatomite.

[0057] Comparative Example 2

[0058] A polyurethane composite coating, comprising the following raw materials in weight parts: 95 parts of waterborne polyurethane resin, 1.5 parts of diatomite, 1.5 parts of hydroxypropyl-β-cyclodextrin, 1 part of sodium dodecyl sulfate, 2 parts of polyoxypropylene glycerol ether, and 0.2 part of alkynediol.

[0059] The preparation method of the above polyurethane composite coating is the same as that of Example 1, except that the modified diatomite in Example 1 is replaced by diatomite and hydroxypropyl-β-cyclodextrin.

[0060] Comparative Example 3

[0061] A polyurethane composite coating, comprising the following raw materials in parts by weight: 95 parts of aqueous polyurethane resin, 3 parts of modified diatomite, 1 part of sodium dodecyl sulfate, 2 parts of polyoxypropylene glycerol ether, and 0.2 part of alkynediol;

[0062] The preparation process of the modified diatomite is basically the same as that of Example 1, except that: step (3) is omitted, that is, the modified diatomite is the isocyanate-modified diatomite obtained in step (2).

[0063] The preparation method of the above polyurethane composite coating is the same as that of Example 1.

[0064] Test Example 1

[0065] In order to test the wear resistance, mechanical properties, and adhesion of the polyurethane composite coatings obtained in Examples 1 to 3 and Comparative Examples 1 to 3.

[0066] (1) According to the test standard of GB / T 1768-2006, the wear resistance of the polyurethane composite coatings obtained in Examples 1 to 3 and Comparative Examples 1 to 3 was tested, with a load of 1000, a rotation speed of 70 r / min, and 1000 wear cycles. The experimental results are shown in Table 1.

[0067] (2) Tested according to the test standard of GB / T 16777-2008; the polyurethane composite coatings obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were cut into dumbbell-shaped standard specimens, and their tensile strength and elongation at break were measured on a tensile testing machine. The tensile rate was set at 500 mm / min, and the test temperature was room temperature. The experimental results are shown in Table 1.

[0068] (3) The adhesion of the polyurethane composite coatings obtained in Examples 1 to 3 and Comparative Examples 1 to 3 was tested according to the test standard of GB / T 5210-2006. The experimental results are shown in Table 1.

[0069] Table 1

[0070]

[0071] It can be seen from the experimental results in Table 1 that the coatings prepared in Examples 1 to 3 of the present invention not only have good wear resistance, but also have excellent mechanical properties and adhesion, and can be used for leather surface treatment.

[0072] Combined with the experimental data of Comparative Example 1, it can be seen that after replacing the modified diatomite prepared in the present invention with ordinary diatomite, the wear resistance of Comparative Example 1 is the worst, which may be due to the poor compatibility between diatomite and polyurethane resin and the uneven dispersion therein. Combined with the experimental data of Comparative Example 2, it can be seen that after replacing the modified diatomite with diatomite and hydroxypropyl-β-cyclodextrin, the wear resistance of the coating is inferior to that of Example 1, and the mechanical properties also decrease. Combined with the experimental data of Comparative Example 3, it can be seen that after not adding hydroxypropyl-β-cyclodextrin during the preparation of the modified diatomite, the wear resistance and mechanical properties of the polyurethane composite coating also decrease, which shows the importance of hydroxypropyl-β-cyclodextrin in the modified diatomite.

[0073] The modified diatomite prepared in the present invention can effectively improve the wear resistance and mechanical properties of the coating. This is because compared with ordinary diatomite, the modified diatomite in the present invention not only retains the original porosity, but also introduces the special cavity structure and hydroxyl functional groups of cyclodextrin, so that a strong interaction is formed between it and polyurethane resin, which helps the modified diatomite to be uniformly dispersed in polyurethane resin and other components. The modified diatomite particles can play a role in supporting and dispersing stress, thereby slowing down the wear rate of the coating. Therefore, after interacting with polyurethane resin and other components, the prepared coating can exhibit excellent wear resistance, mechanical properties and adhesion, and can be used for leather surface treatment.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. The basic principles and main features of the present invention have been described in the above with specific implementation schemes. On the basis of the present invention, some modifications or replacements can be made, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the present invention claimed.

Claims

1. A polyurethane composite coating, characterized in that, It comprises the following raw materials in parts by weight: 90 - 100 parts of waterborne polyurethane resin, 1 - 5 parts of modified diatomite, 0.5 - 2 parts of dispersion aid, 1 - 3 parts of defoamer, and 0.1 - 0.3 parts of wetting agent; The preparation process of the modified diatomite is as follows: (1) Add diatomite into sulfuric acid solution, heat and stir for treatment, then collect the product for calcination to obtain pretreated diatomite; (2) Add the pretreated diatomite obtained in step (1) into toluene, then add toluene diisocyanate, and heat for reaction to obtain isocyanate - modified diatomite; (3) Add the isocyanate - modified diatomite obtained in step (2) into a solvent, then add hydroxypropyl - β - cyclodextrin and a catalyst, and heat for reaction. The reaction solution is purified to obtain the modified diatomite; The mass ratio of the pretreated diatomite to toluene diisocyanate in step (2) is 1:0.07 - 0.1; The mass ratio of the isocyanate - modified diatomite to hydroxypropyl - β - cyclodextrin in step (3) is 1:0.8 - 1.2, and the mass ratio of the isocyanate - modified diatomite to the catalyst in step (3) is 1:0.05 - 0.08; The catalyst in step (3) is dibutyltin dilaurate or stannous octoate.

2. The polyurethane composite coating according to claim 1, characterized in that, The temperature of the heating reaction in step (2) is 50 - 60 °C, and the time is 2 - 3 h.

3. A polyurethane composite coating according to claim 1, characterized in that, The concentration of the sulfuric acid solution in step (1) is 60 - 70 wt%, the heating temperature is 50 - 60 °C, and the time is 1 - 2 h.

4. A polyurethane composite coating according to claim 1, wherein The particle size of the diatomite is 20 - 50 µm, and the SiO₂ content is ≥80 wt%; The defoamer is polyoxypropylene glycerol ether or pentaerythritol stearate; The wetting agent is alkynediol, and the dispersion aid is sodium dodecyl sulfate.

5. A method for preparing a polyurethane composite coating, characterized in that, It comprises the following steps: Weigh each raw material according to the parts by weight described in claim 1, mix the waterborne polyurethane resin and the modified diatomite evenly to obtain a mixed solution, then add the dispersion aid, defoamer, and wetting agent to the mixed solution under stirring conditions to obtain a coating. Coat the coating on a substrate and cure it to obtain the product.

6. The preparation method of the polyurethane composite coating according to claim 5, characterized in that, The substrate is leather or synthetic leather; The curing temperature is 75 - 85 °C, and the time is 5 - 6 h.

7. The application of the polyurethane composite coating as described in claim 1 in the surface treatment of automotive leather.

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