High-hardness stain-resistant single-component waterborne polyurethane coating and preparation method thereof

Abstract

The invention provides a high-hardness stain-resistant single-component waterborne polyurethane coating and a preparation method thereof. The invention relates to a high-hardness stain-resistant single-component waterborne polyurethane coating, which is prepared from the following raw materials in parts by weight: 62 to 64 parts of isocyanate, 49.6 to 51.2 parts of polyether, 5 to 7 parts of chain extender, 20 to 22 parts of calcium carbonate and 2 to 2.2 parts of inorganic nano material silica sol. And the isocyanate comprises polymethylene polyphenyl polyisocyanate. According to the high-hardness stain-resistant single-component waterborne polyurethane coating, isocyanate added into the high-hardness stain-resistant single-component waterborne polyurethane coating is polymethylene polyphenyl polyisocyanate and can react with functional groups such as hydroxyl in polyether and polyglycerol to form a cross-linked structure, so that the effect of a curing agent is achieved; the cross-linked structure can significantly improve the hardness and stain resistance of the coating. In addition, polymethylene polyphenyl isocyanate also has basic properties such as good adhesion, adhesive force, strength and the like.

Description

Technical Field

[0001] The invention relates to the technical field of waterborne polyurethane coatings, and in particular to a high-hardness, stain-resistant, single-component waterborne polyurethane coating and a preparation method thereof. Background Art

[0002] Waterborne polyurethane is a new type of polyurethane system that uses water instead of organic solvents as a dispersion medium. It is also called water-dispersible polyurethane, water-based polyurethane or water-based polyurethane. Waterborne polyurethane uses water as a solvent. Waterborne polyurethane coatings are non-toxic, non-polluting, have good environmental performance, good coating dispersibility, and have good corrosion resistance and excellent wear resistance.

[0003] Compared with thermosetting coatings, some waterborne polyurethane coatings have lower hardness, which may result in their impact resistance being inferior to that of thermosetting coatings, making them unsuitable for applications requiring high hardness and high impact resistance.

[0004] Therefore, we proposed a high-hardness, stain-resistant, one-component waterborne polyurethane coating and a preparation method thereof to solve the above problems. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a high-hardness, stain-resistant, one-component water-based polyurethane coating and a preparation method thereof.

[0006] According to one aspect of the present invention, a high-hardness, stain-resistant, one-component water-based polyurethane coating is provided. Calculated by weight, the raw materials for preparing the coating include: 62 to 64 parts of isocyanate, 49.6 to 51.2 parts of polyether, 5 to 7 parts of chain extender, 20 to 22 parts of calcium carbonate, and 2 to 2.2 parts of inorganic nanomaterial silica sol; the isocyanate includes polymethylene polyphenyl polyisocyanate.

[0007] In the present invention, the isocyanate added to the high-hardness, stain-resistant, one-component waterborne polyurethane coating provided is polymethylene polyphenyl polyisocyanate, which can react with functional groups such as hydroxyl groups in polyether and polypropylene glycol to form a cross-linked structure, thereby playing the role of a curing agent. This cross-linked structure can significantly improve the hardness and stain resistance of the coating. In addition, polymethylene polyphenyl isocyanate also has good basic properties such as adhesion, adhesion and strength.

[0008] Preferably, the polyether comprises polyglycerol, and the molecular weight of the polyglycerol is 1500-1700.

[0009] The softness and elasticity of waterborne polyurethane can be increased by selecting polypropylene glycol with a molecular weight of 1500-1700. In the polymerization reaction, the hydroxyl group of polypropylene glycol can react with isocyanate to form an ester bond structure. These ester bond structures can increase the number of polyurethane branches and increase the space between molecules, thus making the polyurethane have better softness and elasticity.

[0010] Preferably, the weight ratio of isocyanate to polyether is (1.25-1.27):1.

[0011] In the process of preparing high-hardness, stain-resistant, one-component water-based polyurethane coatings, the hardness and strength of the coatings can be effectively improved by adjusting the usage ratio of isocyanate and polyether.

[0012] Preferably, the particle size of calcium carbonate is 800-1000 mesh.

[0013] Preferably, calculated by weight, the raw materials for preparing the coating also include: 1.2 to 1.5 parts of emulsifier, 0.2 to 0.4 parts of wetting agent, 0.2 to 0.4 parts of defoaming agent, 0.8 to 1 parts of talc, 0.8 to 1 parts of titanium dioxide, 0.6 to 0.8 parts of antioxidant, 1.1 to 1.3 parts of foaming agent, and 3 to 5 parts of catalyst.

[0014] According to another aspect of the present invention, there is provided a method for preparing a high-hardness, stain-resistant, one-component waterborne polyurethane coating, comprising the following steps:

[0015] S1. Under the protection of an inert gas, preparing a polyurethane prepolymer, wherein the polyurethane prepolymer contains isocyanate and polyether;

[0016] S2. Preparing a polyurethane resin emulsion, the polyurethane resin emulsion containing a polyurethane prepolymer, a chain extender, and deionized water;

[0017] S3. Add emulsifier, wetting agent, talcum powder, titanium dioxide, antioxidant, foaming agent, catalyst, calcium carbonate, and inorganic nano-material silica sol to the polyurethane resin emulsion in sequence, filter, and obtain a high-hardness, stain-resistant, single-component water-based polyurethane coating.

[0018] Preferably, the pre-polycondensation reaction temperature in step S2 is 60-63° C., and the reaction time is 70-95 min.

[0019] Preferably, in step S3, the reaction temperature is 55-83° C., and the reaction time is 130-149 min.

[0020] Preferably, the filtration accuracy in step S3 is 220-250 meshes. DETAILED DESCRIPTION

[0021] The following is a further clear and complete description of the technical features in the technical solution provided by the present invention in conjunction with the specific implementation methods. 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 those skilled in the art without creative work are within the scope of protection of the present invention.

[0022] Example 1

[0023] This embodiment provides a high-hardness, stain-resistant, one-component waterborne polyurethane coating, and a preparation method thereof comprises the following steps:

[0024] S1. Under inert gas protection, a polyurethane prepolymer was prepared, the polyurethane prepolymer containing 62 parts by weight of isocyanate and 49.6 parts by weight of polyether; wherein the polyether comprises polypropylene glycol having a molecular weight of 1500; the weight ratio of isocyanate to polyether is 1.25:1;

[0025] S2. A polyurethane resin emulsion was prepared at a reaction temperature of 60 ° C and a reaction time of 70 min. The polyurethane resin emulsion contained a polyurethane prepolymer, 5 parts by weight of a chain extender, and deionized water; wherein the weight ratio of the polyurethane prepolymer to the deionized water was 1:1;

[0026] S3. Under the condition of a reaction temperature of 55°C, 1.2 parts by weight of emulsifier, 0.2 parts by weight of wetting agent, 0.8 parts by weight of talc, 0.8 parts by weight of titanium dioxide, 0.6 parts by weight of antioxidant, 1.1 parts by weight of foaming agent, 3 parts by weight of catalyst, 20 parts by weight of calcium carbonate with a particle size of 800, and inorganic nanomaterial silica sol are added to the polyurethane resin emulsion in sequence, the reaction time is 130 minutes, and then filtered through a 220-mesh sieve to obtain a high-hardness and stain-resistant one-component water-based polyurethane coating.

[0027] Example 2

[0028] This embodiment provides a high-hardness, stain-resistant, one-component waterborne polyurethane coating, and a preparation method thereof comprises the following steps:

[0029] S1. Under inert gas protection, a polyurethane prepolymer was prepared, wherein the polyurethane prepolymer contained 63 parts by weight of isocyanate and 50 parts by weight of polyether; wherein the polyether comprises polypropylene glycol having a molecular weight of 1600; the weight ratio of isocyanate to polyether is 1.26:1;

[0030] S2. A polyurethane resin emulsion was prepared at a reaction temperature of 63 ° C for 83 min, wherein the polyurethane resin emulsion contained a polyurethane prepolymer, 6 parts by weight of a chain extender, and deionized water; wherein the weight ratio of the polyurethane prepolymer to the deionized water was 1:1;

[0031] S3. Under the condition of a reaction temperature of 69°C, 1.4 parts by weight of emulsifier, 0.3 parts by weight of wetting agent, 0.9 parts by weight of talcum powder, 0.9 parts by weight of titanium dioxide, 0.7 parts by weight of antioxidant, 1.2 parts by weight of foaming agent, 4 parts by weight of catalyst, 21 parts by weight of calcium carbonate with a particle size of 900, and inorganic nanomaterial silica sol are added to the polyurethane resin emulsion in sequence, the reaction time is 140 minutes, and then filtered through a 235-mesh sieve to obtain a high-hardness and stain-resistant one-component water-based polyurethane coating.

[0032] Example 3

[0033] This embodiment provides a high-hardness, stain-resistant, one-component waterborne polyurethane coating, and a preparation method thereof comprises the following steps:

[0034] S1. Under inert gas protection, a polyurethane prepolymer was prepared, the polyurethane prepolymer containing 64 parts by weight of isocyanate and 51.2 parts by weight of polyether; wherein the polyether comprises polypropylene glycol having a molecular weight of 1700; the weight ratio of isocyanate to polyether is 1.27:1;

[0035] S2. A polyurethane resin emulsion was prepared at a reaction temperature of 61°C for 95 min, wherein the polyurethane resin emulsion contained a polyurethane prepolymer, 7 parts by weight of a chain extender, and deionized water; wherein the weight ratio of the polyurethane prepolymer to the deionized water was 1:1;

[0036] S3. Under the condition of a reaction temperature of 69°C, 1.5 parts by weight of emulsifier, 0.4 parts by weight of wetting agent, 1 part by weight of talcum powder, 1 part by weight of titanium dioxide, 0.8 parts by weight of antioxidant, 1.3 parts by weight of foaming agent, 5 parts by weight of catalyst, 22 parts by weight of calcium carbonate with a particle size of 1000, and inorganic nanomaterial silica sol are added to the polyurethane resin emulsion in sequence. The reaction time is 149 minutes, and then the mixture is filtered through a 250-mesh sieve to obtain a high-hardness and stain-resistant one-component water-based polyurethane coating.

[0037] Comparative Example 1

[0038] Comparative Example 1 is a common coating on the market.

[0039] Test Case

[0040] 1. Test subjects

[0041] In this test example, the high-hardness, stain-resistant, one-component water-based polyurethane coatings prepared in Examples 1 to 3 and the common coating on the market in Comparative Example 1 were used as test objects to conduct relevant performance tests.

[0042] 2. Test content

[0043] (1) Hardness test

[0044] Before the test, the high-hardness, stain-resistant, one-component waterborne polyurethane coatings prepared in Examples 1 to 3 and the common coatings on the market in Comparative Example 1 were applied to the test board and left for one month, and were protected from being washed by rain. After the test board was left for one month, the hardness of the coating film formed by the coating was evaluated by scratching the test board with a pencil.

[0045] 3. Test results

[0046] Table 1 Related performance test results of high hardness and stain-resistant one-component waterborne polyurethane coating

[0047] A B C D Coating area / m2 1 1 1 1 Coating process / layer 2 2 2 2 Scratch speed 1cm / s 1cm / s 1cm / s 1cm / s Pencil hardness 6H 6H 6H 6H Paint surface damage A little damage A little damage A little damage More damage

[0048] The relevant performance test results of the high-hardness, stain-resistant, one-component waterborne polyurethane coatings provided in Examples 1 to 3 and the coating provided in Comparative Example 1 are shown in Table 1.

[0049] The pencil hardness of the high-hardness, stain-resistant, one-component water-based polyurethane coatings of Examples 1 to 3 is all 6H, and although the pencil hardness of the common coating on the market in Comparative Example 1 is not clearly marked with a specific value (but in the comparative context it can be understood as being lower than 6H or significantly different from 6H, because "more damage" is mentioned below), it can be inferred from the description that its hardness may be lower than or equal to 6H, but in actual performance it is not as good as Examples 1 to 3.

[0050] The coatings of Examples 1 to 3 were only slightly damaged after the pencil hardness test, indicating that the coating films formed by these coatings have high hardness and scratch resistance. The coating of Comparative Example 1 was more damaged after the test, indicating that its scratch resistance was relatively poor.

[0051] Based on the above analysis, it can be concluded that the high-hardness, stain-resistant, one-component water-based polyurethane coatings prepared in Examples 1 to 3 performed well in pencil hardness test and scratch resistance, and were significantly better than the common coatings on the market in Comparative Example 1. These coatings have high hardness and good stain resistance, and are suitable for occasions requiring high hardness protection. At the same time, from Examples 1 to 3, although the amount of isocyanate, polyether, reaction temperature, reaction time, and the amount of additives changed, they did not significantly affect the hardness of the coating, indicating that the preparation method has good stability and applicability within a certain range.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the technical solutions of the present invention can be modified or equivalently replaced, but these modifications or replacements are all within the protection scope of the present invention.

Claims

1. A high-hardness, stain-resistant, one-component waterborne polyurethane coating, characterized in that: Calculated by weight, the raw materials for preparing the coating include: 62-64 parts of isocyanate, 49.6-51.2 parts of polyether, 5-7 parts of chain extender, 20-22 parts of calcium carbonate, and 2-2.2 parts of inorganic nanomaterial silica sol; The isocyanate includes polymethylene polyphenyl polyisocyanate.

2. The high-hardness, stain-resistant, one-component waterborne polyurethane coating according to claim 1, characterized in that: The polyether includes polyglycerol, and the molecular weight of the polyglycerol is 1500-1700.

3. The high-hardness, stain-resistant, one-component waterborne polyurethane coating according to claim 1, characterized in that: The weight ratio of the isocyanate to the polyether is (1.25-1.27):

1.

4. The high-hardness, stain-resistant, one-component waterborne polyurethane coating according to claim 1, characterized in that: The particle size of the calcium carbonate is 800-1000 meshes.

5. The high-hardness, stain-resistant, one-component waterborne polyurethane coating according to claim 1, characterized in that: Calculated by weight, the raw materials for preparing the coating also include: 1.2 to 1.5 parts of emulsifier, 0.2 to 0.4 parts of wetting agent, 0.2 to 0.4 parts of defoaming agent, 0.8 to 1 parts of talcum powder, 0.8 to 1 parts of titanium dioxide, 0.6 to 0.8 parts of antioxidant, 1.1 to 1.3 parts of foaming agent, and 3 to 5 parts of catalyst.

6. A method for preparing a high-hardness, stain-resistant, one-component waterborne polyurethane coating as claimed in claims 1 to 5, characterized in that: The following steps are involved: S1. Under inert gas protection, preparing a polyurethane prepolymer, wherein the polyurethane prepolymer contains the isocyanate and the polyether; S2. preparing a polyurethane resin emulsion, the polyurethane resin emulsion containing the polyurethane prepolymer, the chain extender, and deionized water; S3. Add the emulsifier, the wetting agent, the talcum powder, the titanium dioxide, the antioxidant, the foaming agent, the catalyst, the calcium carbonate, and the inorganic nanomaterial silica sol to the polyurethane resin emulsion in sequence, filter, and obtain a high-hardness, stain-resistant, single-component water-based polyurethane coating.