Polyurethane composite coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of coatings, and particularly relates to a polyurethane composite coating as well as a preparation method and application thereof, and the polyurethane composite coating 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 a dispersing aid, 1-3 parts of a defoaming agent and 0.1-0.3 part of an impregnating compound. The preparation method comprises the following steps: acidizing diatomite, carrying out chemical modification on the diatomite by using toluene diisocynate, and introducing hydroxypropyl-beta-cyclodextrin, so as to obtain the modified diatomite. The compatibility and interface bonding force of the modified diatomite and the polyurethane resin are good, and the modified diatomite and the polyurethane resin have good dispersibility, so that the modified diatomite particles can play a role in supporting and dispersing stress, and the wear speed of the coating is slowed down. The polyurethane composite coating can be used for leather surface treatment, the quality of a leather material is improved, and the service life of the leather material is prolonged.

Description

Technical Field

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

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

[0003] With the development of science and technology, the requirements for the performance of polyurethane coatings are also constantly increasing. Although traditional polyurethane coatings have excellent environmental performance, they also have problems with poor wear 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. Wear-resistant composite coatings can effectively improve the scratch resistance of these materials, reduce the occurrence of scratches, and thus protect the integrity of interior materials. Therefore, it is particularly important to develop a polyurethane composite coating with wear resistance.

[0004] At present, there have been some studies and reports on polyurethane composite coatings. For example, by introducing inorganic nanomaterials into the molecular structure of polyurethane, unique properties can be given to polyurethane composite materials. However, this composite coating also faces some problems, such as the poor dispersibility of inorganic materials in the polyurethane matrix, which will lead to poor overall performance of the coating. In addition, invention patent CN 116239752A discloses a method for preparing a bio-based waterborne polyurethane, by adding lignin and a catalyst to castor oil-modified polyurethane, a bio-based waterborne polyurethane with flame retardant and anti-ultraviolet properties is obtained. Despite these technologies, there are few reports on research on improving the wear resistance of polyurethane composite coatings.

[0005] In order 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. The polyurethane composite coating can also be applied to leather surface treatment to improve the durability and environmental sustainability of the material. Summary of the invention

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

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: A polyurethane composite coating comprises the following raw materials in parts by weight: 90-100 parts of waterborne polyurethane resin, 1-5 parts of modified diatomaceous earth, 0.5-2 parts of dispersing aid, 1-3 parts of defoaming agent, and 0.1-0.3 parts of wetting agent; The preparation process of the modified diatomite is as follows: (1) adding diatomaceous earth to a sulfuric acid solution, heating and stirring the solution, collecting the product and calcining it to obtain pretreated diatomaceous earth; (2) adding the diatomaceous earth pretreated in step (1) into toluene, and then adding toluene diisocyanate, heating for reaction, and obtaining isocyanate-modified diatomaceous earth; (3) adding the isocyanate-modified diatomaceous earth described in step (2) into a solvent, then adding hydroxypropyl-β-cyclodextrin and a catalyst, heating to react, and purifying the reaction solution to obtain hydroxypropyl-β-cyclodextrin-modified diatomaceous earth.

[0008] Furthermore, in step (2), the mass ratio of diatomaceous earth to toluene diisocyanate is 1:0.07-0.1.

[0009] Furthermore, in step (3), the mass ratio of the isocyanate-modified diatomaceous earth to hydroxypropyl-β-cyclodextrin 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.

[0010] Furthermore, the catalyst in step (3) is dibutyltin dilaurate or stannous octoate.

[0011] Furthermore, the heating reaction temperature in step (2) is 50-60° C. and the time is 2-3 hours.

[0012] Furthermore, in step (1), the concentration of the sulfuric acid solution is 60-70wt%, the heating temperature is 50-60°C, and the heating time is 1-2h.

[0013] Furthermore, the particle size of the diatomaceous earth is 20-50µm, and the SiO2 content is ≥80wt%; the defoaming agent is polyoxypropylene glycerol ether or pentaerythritol stearate, the wetting agent is acetylene glycol, and the dispersing aid is sodium lauryl sulfate.

[0014] The second object of the present invention is to provide a method for preparing a polyurethane composite coating, which is simple and efficient and helps to achieve industrial production.

[0015] In order to achieve the above object, the technical solution adopted by the present invention is: A method for preparing a polyurethane composite coating comprises the following steps: Weigh the raw materials according to the above weight parts, mix the waterborne polyurethane resin and the modified diatomaceous earth evenly to obtain a mixed solution, and then add a dispersing aid, a defoaming agent, and a wetting agent to the mixed solution under stirring conditions to obtain a coating, which is applied to a substrate and cured to obtain the coating.

[0016] Furthermore, the substrate is leather or synthetic leather; the curing temperature is 75-85° C. and the curing time is 5-6 hours.

[0017] The third object of the present invention is to provide an application of a polyurethane composite coating in the surface treatment of automobile leather.

[0018] Compared with the prior art, the beneficial effects of the present invention are mainly: 1. The present invention performs an acid treatment on diatomite and then chemically modifies it with toluene diisocyanate. The isocyanate group (-NCO) can react with the hydroxyl group (-OH) on the surface of the diatomite, thereby introducing isocyanate groups on the surface of the diatomite. Under the catalysis of the 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 it forms a close interaction with the polyurethane resin, which helps to uniformly disperse the modified diatomite in the polyurethane resin and other 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.

[0019] 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 leather surface treatment to improve the quality of leather materials and extend their service life. DETAILED DESCRIPTION

[0020] The technical scheme of the present invention is further described below in conjunction with specific embodiments. However, it should be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be regarded as limiting the present invention. The specific conditions not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are conventional products obtained through commercial channels.

[0021] In the following examples and comparative examples, the average particle size of diatomaceous earth is 20-50 µm, the SiO2 content is ≥80 wt %. The solid content of the waterborne polyurethane resin (AH-1704B-2) is 30±1%, and the viscosity is ≥100 mPa.s.

[0022] Example 1 A polyurethane composite coating comprises the following raw materials in parts by weight: 95 parts of waterborne polyurethane resin, 3 parts of modified diatomaceous earth, 1 part of sodium lauryl sulfate, 2 parts of polyoxypropylene glycerol ether, and 0.2 parts of acetylene glycol; The preparation process of the modified diatomite is as follows: (1) adding diatomaceous earth to a 65 wt % sulfuric acid solution, stirring at 55 ° C for 1.5 h, filtering and collecting the product, drying and placing in a muffle furnace, heating to 230 ° C at a rate of 2.5 ° C / min, calcining at 230 ° C for 35 min, and after calcination, heating to 400 ° C at a rate of 2 ° C / min and calcining for 2 h in a nitrogen atmosphere, and passing through a 100 mesh sieve to obtain pretreated diatomaceous earth; (2) adding the pretreated diatomaceous earth obtained in step (1) to toluene, and then adding 2,4-toluene diisocyanate (the mass ratio of the pretreated diatomaceous earth to 2,4-toluene diisocyanate is 1:0.08), stirring ultrasonically for 60 minutes, reacting at 55°C for 2.5 hours under nitrogen protection, and then filtering the reaction solution, collecting the particles and washing them with anhydrous ethanol for 3 times to remove unreacted 2,4-toluene diisocyanate, thereby obtaining isocyanate-modified diatomaceous earth; (3) According to the mass ratio of hydroxypropyl-β-cyclodextrin, isocyanate-modified diatomaceous earth and catalyst dibutyltin dilaurate: 1:1:0.06, the isocyanate-modified diatomaceous earth obtained in step (2) is added to ethyl acetate, and then hydroxypropyl-β-cyclodextrin and dibutyltin dilaurate are added. Then, under nitrogen protection, the mixture is heated to 90°C for reaction for 6 hours. After the reaction is completed, it is distilled under reduced pressure, and the product is washed with acetone and ethyl acetate in turn to obtain hydroxypropyl-β-cyclodextrin-modified diatomaceous earth.

[0023] A method for preparing a polyurethane composite coating comprises the following steps: Weigh the raw materials according to the above weight parts, mix the waterborne polyurethane resin and the modified diatomaceous earth evenly to obtain a mixed solution; then add sodium lauryl sulfate, polyoxypropylene glycerol ether and acetylene glycol to the mixed solution under stirring conditions to obtain a coating; apply the coating to leather and cure it at 80° C. for 5.5 hours to obtain the coating.

[0024] Example 2 A polyurethane composite coating comprises the following raw materials in parts by weight: 90 parts of waterborne polyurethane resin, 1 part of modified diatomaceous earth, 0.5 parts of sodium lauryl sulfate, 1 part of pentaerythritol stearate, and 0.1 parts of acetylene glycol; The preparation process of the modified diatomite is as follows: (1) adding diatomaceous earth to a 60 wt % sulfuric acid solution, stirring at 60° C. for 1 h, collecting the product by filtration, drying, placing in a muffle furnace, heating to 220° C. at a rate of 2° C. / min, calcining at 220° C. for 40 min, heating to 350° C. at a rate of 1.5° C. / min after calcination, calcining for 3 h in a nitrogen atmosphere, and filtering through a 100 mesh sieve to obtain pretreated diatomaceous earth; (2) adding the pretreated diatomaceous earth obtained in step (1) to toluene, and then adding 2,4-toluene diisocyanate (the mass ratio of the pretreated diatomaceous earth to 2,4-toluene diisocyanate is 1:0.07), stirring ultrasonically for 60 minutes, reacting at 50°C for 3 hours under nitrogen protection, and then filtering the reaction solution, collecting the particles and washing them with anhydrous ethanol for 3 times to remove unreacted 2,4-toluene diisocyanate, thereby obtaining isocyanate-modified diatomaceous earth; (3) According to the mass ratio of hydroxypropyl-β-cyclodextrin, isocyanate-modified diatomaceous earth and catalyst dibutyltin dilaurate: 1:1:0.05, the isocyanate-modified diatomaceous earth of step (2) is added to toluene, hydroxypropyl-β-cyclodextrin and stannous octoate are added, and then heated to 80°C under nitrogen protection for reaction for 7 hours. After the reaction is completed, it is distilled under reduced pressure, and the product is washed with acetone and ethyl acetate in turn to obtain hydroxypropyl-β-cyclodextrin-modified diatomaceous earth.

[0025] A method for preparing a polyurethane composite coating comprises the following steps: Weigh the raw materials according to the above weight parts, mix the waterborne polyurethane resin and modified diatomaceous earth evenly to obtain a mixed solution, and then add sodium lauryl sulfate, pentaerythritol stearate and acetylene glycol under stirring conditions to obtain a coating; apply the coating on leather and cure it at 75°C for 6 hours to obtain the coating.

[0026] Example 3 A polyurethane composite coating comprises the following raw materials in parts by weight: 100 parts of waterborne polyurethane resin, 5 parts of modified diatomaceous earth, 2 parts of sodium lauryl sulfate, 3 parts of polyoxypropylene glycerol ether, and 0.3 parts of acetylene glycol; The preparation process of the modified diatomite is as follows: (1) adding diatomaceous earth to a 70 wt % sulfuric acid solution, stirring at 60° C. for 1 h, collecting the product by filtration, drying, placing in a muffle furnace, heating to 240° C. at a rate of 2° C. / min, calcining at 240° C. for 30 min, heating to 450° C. at a rate of 1.5° C. / min after calcination, calcining in a nitrogen atmosphere for 1.5 h, and filtering through a 100 mesh sieve to obtain pretreated diatomaceous earth; (2) adding the pretreated diatomaceous earth obtained in step (1) to toluene, and then adding 2,4-toluene diisocyanate (the mass ratio of the pretreated diatomaceous earth to 2,4-toluene diisocyanate is 1:0.1), stirring ultrasonically for 60 minutes, reacting at 60°C for 2 hours under nitrogen protection, and then filtering the reaction solution, collecting the particles and washing them with anhydrous ethanol for 3 times to remove unreacted 2,4-toluene diisocyanate, thereby obtaining isocyanate-modified diatomaceous earth; (3) According to the mass ratio of hydroxypropyl-β-cyclodextrin, isocyanate-modified diatomaceous earth and catalyst dibutyltin dilaurate: 1:1:0.08, the isocyanate-modified diatomaceous earth obtained in step (2) is added to toluene, and then hydroxypropyl-β-cyclodextrin and stannous octoate are added. Under nitrogen protection, the mixture is heated to 85°C for reaction for 8 hours. After the reaction is completed, the mixture is distilled under reduced pressure and the product is washed with acetone and ethyl acetate in turn to obtain hydroxypropyl-β-cyclodextrin-modified diatomaceous earth.

[0027] A method for preparing a polyurethane composite coating comprises the following steps: Weigh the raw materials according to the above weight parts, mix the waterborne polyurethane resin and modified diatomaceous earth evenly to obtain a mixed solution, and then add sodium lauryl sulfate, polyoxypropylene glycerol ether and acetylene glycol under stirring conditions to obtain a coating; apply the coating on leather and cure it at 85°C for 5 hours to obtain the coating.

[0028] Comparative Example 1 A polyurethane composite coating comprises the following raw materials in parts by weight: 95 parts of waterborne polyurethane resin, 3 parts of diatomaceous earth, 1 part of sodium lauryl sulfate, 2 parts of polyoxypropylene glycerol ether, and 0.2 parts of acetylene glycol.

[0029] The preparation method of the polyurethane composite coating is the same as that of Example 1, except that the modified diatomaceous earth in Example 1 is replaced by diatomaceous earth.

[0030] Comparative Example 2 A polyurethane composite coating comprises the following raw materials in parts by weight: 95 parts of waterborne polyurethane resin, 1.5 parts of diatomaceous earth, 1.5 parts of hydroxypropyl-β-cyclodextrin, 1 part of sodium lauryl sulfate, 2 parts of polyoxypropylene glycerol ether, and 0.2 parts of acetylene glycol.

[0031] The preparation method of the polyurethane composite coating is the same as that of Example 1, except that the modified diatomaceous earth in Example 1 is replaced by diatomaceous earth and hydroxypropyl-β-cyclodextrin.

[0032] Comparative Example 3 A polyurethane composite coating comprises the following raw materials in parts by weight: 95 parts of waterborne polyurethane resin, 3 parts of modified diatomaceous earth, 1 part of sodium lauryl sulfate, 2 parts of polyoxypropylene glycerol ether, and 0.2 parts of acetylene glycol; The preparation process of the modified diatomite is substantially 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).

[0033] The preparation method of the above polyurethane composite coating is the same as that of Example 1.

[0034] Test Example 1 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.

[0035] (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 at a load of 1000 and a rotation speed of 70 r / min. The number of wears was 1000 times. The experimental results are shown in Table 1.

[0036] (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 to 500 mm / min and the test temperature was room temperature. The experimental results are shown in Table 1.

[0037] (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 test results are shown in Table 1.

[0038] Table 1 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.

[0039] Combined with the experimental data of Comparative Example 1, it can be seen that after the modified diatomaceous earth prepared by the present invention is replaced with ordinary diatomaceous earth, the wear resistance of Comparative Example 1 is the worst, which may be due to the poor compatibility of diatomaceous earth with polyurethane resin and uneven dispersion therein. Combined with the experimental data of Comparative Example 2, it can be seen that after the modified diatomaceous earth is replaced with diatomaceous earth and hydroxypropyl-β-cyclodextrin, the wear resistance of the coating is not as good as that of Example 1, and the mechanical properties are also reduced. Combined with the experimental data of Comparative Example 3, it can be seen that after hydroxypropyl-β-cyclodextrin is not added during the preparation of modified diatomaceous earth, the wear resistance and mechanical properties of the polyurethane composite coating also decrease, which illustrates the importance of hydroxypropyl-β-cyclodextrin in modified diatomaceous earth.

[0040] The modified diatomite prepared by 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 of the present invention not only retains the original porosity, but also introduces the special cavity structure and hydroxyl functional group of cyclodextrin, so that it forms a close interaction with the polyurethane resin, thereby facilitating the uniform dispersion of the modified diatomite in the polyurethane resin and other 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. Therefore, after interacting with the polyurethane resin and other components, the prepared coating can show excellent wear resistance, mechanical properties and adhesion, and can be used for leather surface treatment.

[0041] 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 above with specific implementation schemes. On the basis of the present invention, some modifications or replacements may be made thereto, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of protection claimed by the present invention.

Claims

1. A polyurethane composite coating, characterized in that: The invention comprises the following raw materials in parts by weight: 90-100 parts of waterborne polyurethane resin, 1-5 parts of modified diatomaceous earth, 0.5-2 parts of dispersing aid, 1-3 parts of defoaming agent and 0.1-0.3 parts of wetting agent; The preparation process of the modified diatomite is as follows: (1) adding diatomaceous earth to a sulfuric acid solution, heating and stirring the solution, collecting the product and calcining it to obtain pretreated diatomaceous earth; (2) adding the diatomaceous earth pretreated in step (1) into toluene, and then adding toluene diisocyanate, heating for reaction, and obtaining isocyanate-modified diatomaceous earth; (3) adding the isocyanate-modified diatomaceous earth described in step (2) into a solvent, then adding hydroxypropyl-β-cyclodextrin and a catalyst, heating to react, and purifying the reaction solution to obtain the modified diatomaceous earth.

2. A polyurethane composite coating according to claim 1, characterized in that: The mass ratio of the pretreated diatomaceous earth to toluene diisocyanate in step (2) is 1:0.07-0.

1.

3. A polyurethane composite coating according to claim 1, characterized in that: In step (3), the mass ratio of the isocyanate-modified diatomaceous earth to hydroxypropyl-β-cyclodextrin 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.

4. A polyurethane composite coating according to claim 1, characterized in that: The catalyst in step (3) is dibutyltin dilaurate or stannous octoate.

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

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

7. The polyurethane composite coating according to claim 1, characterized in that: The particle size of the diatomaceous earth is 20-50µm, and the SiO2 content is ≥80wt%; the defoaming agent is polyoxypropylene glycerol ether or pentaerythritol stearate; the wetting agent is acetylene glycol, and the dispersing aid is sodium dodecyl sulfate.

8. A method for preparing a polyurethane composite coating, characterized in that: The following steps are involved: Weigh the raw materials according to the weight parts of claim 1, mix the waterborne polyurethane resin and the modified diatomaceous earth evenly to obtain a mixed solution, then add a dispersing aid, a defoaming agent and a wetting agent to the mixed solution under stirring conditions to obtain a coating, apply the coating to a substrate, and obtain the coating after curing.

9. The method for preparing the polyurethane composite coating according to claim 8, characterized in that: The substrate is leather or synthetic leather; the curing temperature is 75-85° C. and the curing time is 5-6 hours.

10. Use of the polyurethane composite coating as claimed in claim 1 in the surface treatment of automobile leather.

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