Two-component polyurethane varnish, its preparation method, varnish layer and varnish products

Abstract

This application relates to a two-component polyurethane varnish, its preparation method, varnish layer, and varnish layer product. The two-component polyurethane varnish includes component A and component B. By weight, component A comprises: 8-25 parts of a first acrylic resin, 36-55 parts of a second acrylic resin, and 5-20 parts of an amino resin; both the first and second acrylic resins contain hydroxyl groups; the weight-average molecular weight (Mw) of the first acrylic resin is 10,000-20,000 Daltons, and the weight-average molecular weight (Mw) of the second acrylic resin is 2,000-9,000 Daltons. By weight, component B comprises: 70-90 parts of a polyisocyanate and 10-30 parts of a first solvent. This two-component polyurethane varnish, by interacting the first and second acrylic resins with different molecular weights and containing hydroxyl groups, and further combining them with an amino resin, can effectively improve the abrasion resistance, anti-sagging properties, appearance properties, and hardness of the two-component polyurethane varnish, while having a low VOC content.

Description

Technical Field

[0001] This application relates to the field of paints, and in particular to a two-component polyurethane varnish, its preparation method, paint layer, and paint layer products. Background Technology

[0002] The improvement of the scratch resistance of two-component polyurethane (2K-PUR) varnish mainly involves the following technical routes: (1) using polyisocyanate crosslinking agents modified with silane groups to improve the scratch resistance of polyurethane coatings; (2) using inorganic nano-silica particles and other additives to improve the scratch resistance of polyurethane coatings, but over time, the additives gradually wear away from the coating surface, resulting in a loss of scratch resistance; or grafting scratch-resistant additives onto the polymer skeleton to make them evenly distributed in the coating, minimizing the loss, but significantly increasing the cost of raw materials and limiting its application range; (3) using hyperbranched polyester resins, introducing functional monomers to synthesize resins, etc. to improve the scratch resistance of polyurethane coatings. However, traditional two-component polyurethane varnishes cannot simultaneously possess high appearance, high hardness, and high scratch resistance.

[0003] With the formal implementation of GB 24409-2020, the limit of hazardous substances in automotive coatings, the mandatory VOC standard for coatings has become more stringent. According to GB / T 38597-2020, the technical requirements for coating products with low volatile organic compound content, the VOC of automotive original two-component clear coats should be ≤420g / L, which most traditional two-component coatings cannot meet.

[0004] Therefore, it is necessary to improve traditional technologies. Summary of the Invention

[0005] Based on this, this application provides a two-component polyurethane varnish with low VOC content, good appearance, high hardness, and good scratch resistance, as well as its preparation method, varnish layer, and varnish layer products.

[0006] The technical solution to the above-mentioned technical problems in this application is as follows.

[0007] The first aspect of this application provides a two-component polyurethane varnish, characterized in that it comprises component A and component B;

[0008] By mass parts, component A comprises the following components:

[0009] 8-25 parts of the first acrylic resin;

[0010] 36-55 parts of the second acrylic resin; and

[0011] 5-20 parts of amino resin;

[0012] Both the first acrylic resin and the second acrylic resin contain hydroxyl groups; the weight-average molecular weight Mw of the first acrylic resin is 10,000 to 20,000 Daltons, and the weight-average molecular weight Mw of the second acrylic resin is 2,000 to 9,000 Daltons.

[0013] By mass parts, component B comprises the following components:

[0014] 70-90 parts of polyisocyanate; and

[0015] The first solvent is 10 to 30 parts.

[0016] In some embodiments, the two-component polyurethane varnish satisfies at least one of the following characteristics:

[0017] The mass ratio of the first acrylic resin to the second acrylic resin is 1:(2~5);

[0018] The mass ratio of the amino resin to the total mass of the first acrylic resin and the second acrylic resin is 1:(6~13).

[0019] In some embodiments, in the two-component polyurethane varnish, the monomers for preparing the first acrylic resin and the second acrylic resin each independently comprise the structure of formula (I):

[0020]

[0021] (I)

[0022] Wherein, R1 is independently H or CH3, R2 is independently an alkyl or cycloalkyl group having 2 to 20 carbon atoms, and n is an integer from 1 to 10.

[0023] In some embodiments, the two-component polyurethane varnish comprises, by weight, the monomers for preparing the first acrylic resin and the second acrylic resin, respectively, independently comprising:

[0024] 0-30 parts of hydroxyalkyl acrylate;

[0025] 10-90 parts of hydroxyalkyl methacrylate;

[0026] 5-50 parts of caprolactone-modified hydroxyethyl (meth)acrylate;

[0027] Vinyl aromatics 0-50 parts;

[0028] Other olefinic unsaturated carboxylic acids, 0-5 parts; and

[0029] 0-50 parts of alkyl esters of other olefinic unsaturated carboxylic acids.

[0030] In some embodiments, the monomers forming the first acrylic resin and the second acrylic resin, by weight, respectively, comprise:

[0031] 20-60 parts of hydroxyalkyl methacrylate;

[0032] 5-20 parts of caprolactone-modified hydroxyethyl (meth)acrylate;

[0033] Vinyl aromatics 10-30 parts;

[0034] Other olefinic unsaturated carboxylic acids, 0.5-2 parts; and

[0035] 20-30 parts of alkyl esters of other olefinic unsaturated carboxylic acids.

[0036] In some embodiments, the two-component polyurethane varnishes each independently satisfy at least one of the following characteristics:

[0037] The hydroxyalkyl acrylate includes at least one of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 3-hydroxybutyl acrylate, and 4-hydroxybutyl acrylate;

[0038] The hydroxyalkyl methacrylate includes at least one of 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 3-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate;

[0039] The caprolactone-modified (meth)acrylate hydroxyethyl ester includes at least one of hydroxyethylcaprolactone acrylate and hydroxyethylcaprolactone methacrylate;

[0040] The vinyl aromatics include styrene;

[0041] The other olefinic unsaturated carboxylic acids include acrylic acid monomers;

[0042] The other olefinic unsaturated carboxylic acids include acrylic acid;

[0043] The other alkyl esters of olefinic unsaturated carboxylic acids include alkyl acrylate monomers;

[0044] The other alkyl esters of olefinic unsaturated carboxylic acids include at least one of n-butyl methacrylate and n-butyl acrylate.

[0045] In some embodiments, in the two-component polyurethane varnish, the hydroxyl values ​​of the first acrylic resin and the second acrylic resin are independently 100 KOH / g to 200 mg KOH / g, the acid values ​​are independently 0 KOH / g to 30 mg KOH / g, and the Tg values ​​are independently -40℃ to 50℃.

[0046] In some embodiments, in the two-component polyurethane varnish, the amino resin satisfies at least one of the following characteristics:

[0047] The amino resin includes melamine compounds;

[0048] The amino resin includes at least one of hexamethoxymethyl melamine, tetramethoxymethyl benzomelamine, tetramethoxymethylurea, and butoxy / methoxy substituted melamine.

[0049] In some embodiments, in a two-component polyurethane varnish, component B satisfies at least one of the following characteristics:

[0050] The polyisocyanate includes hexylene diisocyanate oligomers;

[0051] The first solvent includes at least one of acetone, methyl ethyl ketone, cyclohexane, ethyl acetate, isobutyl acetate, 3-methoxybutyl acetate, butyl acetate, sec-butyl acetate, isopropyl acetate, ethyl 3-ethoxypropionate, methyl isobutyl ketone, methyl pentyl ketone, trimethylbenzene, tetramethylbenzene, propylene glycol methyl ether acetate, toluene, xylene, ethylbenzene, diethyl carbonate, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,3-dioxolane, and diethyl glycol.

[0052] In some embodiments, the two-component polyurethane varnish further includes, by weight, 10 to 50 parts of additives, wherein the additives include at least one of anti-sagging resin, light stabilizer, defoamer, leveling agent, catalyst, and second solvent.

[0053] In some embodiments, in a two-component polyurethane varnish, the molar ratio of hydroxyl groups in component A to isocyanate groups in component B is (0.9~1.5):1.

[0054] A second aspect of this application provides a method for preparing a two-component polyurethane varnish, comprising the following steps:

[0055] Raw materials are provided according to the components of the two-component polyurethane varnish provided in the first aspect;

[0056] The raw materials corresponding to component A are mixed to obtain component A;

[0057] The raw materials corresponding to component B are mixed to obtain component B.

[0058] The third aspect of this application provides a paint layer, the raw material of which is the two-component polyurethane varnish provided in the second aspect.

[0059] The fourth aspect of this application provides a coated article comprising the coated layer provided in the third aspect.

[0060] Compared with the prior art, the two-component polyurethane varnish of this application has the following beneficial effects:

[0061] The two-component polyurethane clear varnish of this application includes component A and component B. Component A includes a specific ratio of first acrylic resin, second acrylic resin and amino resin. Component B includes a polyisocyanate curing agent. By interacting first acrylic resin and second acrylic resin with different molecular weights and hydroxyl groups, and further coordinating with amino resin, the wear resistance, anti-sagging properties, appearance properties and hardness of the two-component polyurethane clear varnish can be effectively improved, and the VOC content is low. Detailed Implementation

[0062] Reference will now be made to detailed embodiments of the present invention, one or more of which are described below. Each example is provided for explanation and not for limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0063] Therefore, this invention is intended to cover such modifications and variations falling within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the invention are disclosed in or will be apparent from the following detailed description. It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the invention.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0065] The terms “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element preceded by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. The indefinite articles “a” and “an” preceding an element or component of the invention are not restrictive in terms of the number of elements or components (i.e., the number of times they appear). Therefore, “an” or “an” should be interpreted as including one or at least one, and singular elements or components also include plural forms, unless the quantity clearly refers only to the singular. “A plurality” means at least two, such as two, three, etc., unless otherwise expressly specified.

[0066] The weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope disclosed in the embodiments of this invention. Specifically, the weights mentioned in the embodiments of this invention can be well-known units of mass in the chemical industry, such as μg, mg, g, and kg.

[0067] Unless otherwise shown or indicated in the operational embodiments, all figures used to represent the amounts, physicochemical properties, etc., of ingredients in the specification and claims are to be understood to be adjusted by the term "about" in all cases. For example, therefore, unless stated to the contrary, the numerical parameters listed in the foregoing specification and appended claims are approximations, and those skilled in the art can appropriately modify these approximations to obtain the desired characteristics by utilizing the teachings disclosed herein. The use of numerical ranges indicated by endpoints includes all numbers within that range and any range within that range; for example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, and 5, etc.

[0068] In this application, the hydroxyl value represents the amount of potassium hydroxide (KOH) (milligrams, mg), which is equal to the molar amount of acetic acid bonded when 1g of the corresponding solid resin component is acetylated;

[0069] In this application, acid value indicates the amount of KOH (milligrams, mg) consumed to neutralize 1g of solid resin.

[0070] In this application, the Tg value represents the glass transition temperature, which is determined based on the experimental method of DIN5376 "Thermal Analysis - Dynamic Scanning Calorimetry (DSC)";

[0071] In this application, the weight-average molecular weight Mw was measured using gel permeation chromatography (GPC) with polystyrene as a standard.

[0072] One embodiment of this application provides a two-component polyurethane varnish, comprising component A and component B;

[0073] By mass parts, component A comprises the following components:

[0074] 8-25 parts of the first acrylic resin;

[0075] 36-55 parts of the second acrylic resin; and

[0076] 5-20 parts of amino resin;

[0077] Both the first acrylic resin and the second acrylic resin contain hydroxyl groups; the weight-average molecular weight Mw of the first acrylic resin is 10,000 to 20,000 Daltons, and the weight-average molecular weight Mw of the second acrylic resin is 2,000 to 9,000 Daltons.

[0078] By mass parts, component B comprises the following components:

[0079] 70-90 parts of polyisocyanate; and

[0080] The first solvent is 10 to 30 parts.

[0081] The two-component polyurethane clear varnish of this application includes component A and component B. Component A includes a specific ratio of first acrylic resin, second acrylic resin and amino resin. Component B includes a polyisocyanate curing agent. By interacting first acrylic resin and second acrylic resin with different molecular weights and hydroxyl groups, and further coordinating with amino resin, the wear resistance, anti-sagging properties, appearance properties and hardness of the two-component polyurethane clear varnish can be effectively improved, and the VOC content is low.

[0082] It is understood that, in component A, by mass parts, the first acrylic resin includes, but is not limited to, 8 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 22 parts, and 25 parts; the second acrylic resin includes, but is not limited to, 36 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 46 parts, 47 parts, 48 ​​parts, 49 parts, 50 parts, 52 parts, and 55 parts; and the amino resin includes, but is not limited to, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, and 1 part. 8 parts, 19 parts, 20 parts; In component B, by mass parts, the polyisocyanate includes, but is not limited to, 70 parts, 71 parts, 72 parts, 73 parts, 74 parts, 75 parts, 76 parts, 77 parts, 78 parts, 79 parts, 80 parts, 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts; The first solvent includes, but is not limited to, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts. In some examples, any two of these point values ​​can be used as endpoints within a range, the same applies below.

[0083] In some of these examples, in a two-component polyurethane varnish, component A comprises the following components by parts by weight:

[0084] 10-20 parts of the first acrylic resin;

[0085] 40-50 parts of the second acrylic resin; and

[0086] 5-10 parts of amino resin;

[0087] By mass parts, component B comprises the following components:

[0088] 75-85 parts of polyisocyanate; and

[0089] The first solvent is 15-25 parts.

[0090] In some of these examples, the mass ratio of the first acrylic resin to the second acrylic resin in the two-component polyurethane varnish is 1:(2~5).

[0091] It is understood that the mass ratio of the first acrylic resin to the second acrylic resin includes, but is not limited to, 1:2, 1:3, 1:4, and 1:5.

[0092] In some of these examples, the mass ratio of the amino resin to the total mass of the first acrylic resin and the second acrylic resin in the two-component polyurethane varnish is 1:(6~13).

[0093] It is understood that the mass ratio of amino resin to the total mass of the first acrylic resin and the second acrylic resin includes, but is not limited to, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, and 1:13.

[0094] In some of these examples, the total mass of the first acrylic resin and the second acrylic resin in the two-component polyurethane varnish accounts for 20% to 70% of the total mass of component A.

[0095] It is understood that the total mass of the first acrylic resin and the second acrylic resin accounts for, but is not limited to, 20%, 30%, 40%, 50%, 60%, and 70% of the total mass of component A.

[0096] In some of these examples, the total mass of the first acrylic resin and the second acrylic resin in a two-component polyurethane varnish accounts for 30% to 60% of the total mass of component A.

[0097] It is understood that the weight-average molecular weight (Mw) of the first acrylic resin includes, but is not limited to, 10,000 Daltons, 11,000 Daltons, 12,000 Daltons, 13,000 Daltons, 14,000 Daltons, 15,000 Daltons, 16,000 Daltons, 17,000 Daltons, 18,000 Daltons, 19,000 Daltons, and 20,000 Daltons; and the weight-average molecular weight (Mw) of the second acrylic resin includes, but is not limited to, 2,000 Daltons, 3,000 Daltons, 4,000 Daltons, 5,000 Daltons, 6,000 Daltons, 7,000 Daltons, 8,000 Daltons, and 9,000 Daltons.

[0098] In some of these examples, in a two-component polyurethane varnish, the weight-average molecular weight (Mw) of the first acrylic resin is 11,000 to 18,000 Daltons, and the weight-average molecular weight (Mw) of the second acrylic resin is 3,000 to 7,000 Daltons.

[0099] In some of these examples, in a two-component polyurethane varnish, the weight-average molecular weight (Mw) of the first acrylic resin is 12,000 to 16,000 Daltons, and the weight-average molecular weight (Mw) of the second acrylic resin is 4,000 to 7,000 Daltons.

[0100] In some of these examples, the monomers for preparing the first and second acrylic resins in the two-component polyurethane varnishes each independently comprise the structure of formula (I):

[0101]

[0102] (I)

[0103] Wherein, R1 is independently H or CH3, R2 is independently an alkyl or cycloalkyl group having 2 to 20 carbon atoms, and n is an integer from 1 to 10.

[0104] It can be understood that R2 can be an alkyl or cycloalkyl group with 2 to 20 carbon atoms, which means that the number of carbon atoms in the alkyl or cycloalkyl group includes 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20; and n includes 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

[0105] In some of these examples, n is 1, 2, 3, 4, or 5 in the two-component polyurethane varnish.

[0106] In some of these examples, the two-component polyurethane varnish comprises, by weight, the monomers for preparing the first and second acrylic resins, respectively, independently comprising:

[0107] 0-30 parts of hydroxyalkyl acrylate;

[0108] 10-90 parts of hydroxyalkyl methacrylate;

[0109] 5-50 parts of caprolactone-modified hydroxyethyl (meth)acrylate;

[0110] Vinyl aromatics 0-50 parts;

[0111] Other olefinic unsaturated carboxylic acids, 0-5 parts; and

[0112] 0-50 parts of alkyl esters of other olefinic unsaturated carboxylic acids.

[0113] It is understood that, by weight parts, hydroxyalkyl acrylate includes, but is not limited to, 0 parts, 1 part, 2 parts, 5 parts, 8 parts, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, 28 parts, and 30 parts; hydroxyalkyl methacrylate includes, but is not limited to, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, 28 parts, 30 parts, 32 parts, 35 parts, 38 parts, 40 parts, 42 parts, 45 parts, 48 ​​parts, 50 parts, 55 parts, 60 parts, 62 parts, 68 parts, 70 parts, 75 parts, 80 parts, 85 parts, and 90 parts; caprolactone-modified (meth)acrylate includes, but is not limited to, 5 parts, 10 parts, 15 parts, 18 parts, 20 parts, 25 parts, 28 parts, 30 parts, 35 parts, 38 parts, 40 parts, 45 parts, 48 ​​parts, 50 parts; vinyl aromatics including but not limited to 0 parts, 5 parts, 10 parts, 15 parts, 18 parts, 20 parts, 25 parts, 28 parts, 30 parts, 35 parts, 38 parts, 40 parts, 45 parts, 48 ​​parts, 50 parts; other olefinic unsaturated carboxylic acids including but not limited to 0 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts; alkyl esters of other olefinic unsaturated carboxylic acids including but not limited to 0 parts, 5 parts, 10 parts, 15 parts, 18 parts, 20 parts, 25 parts, 28 parts, 30 parts, 35 parts, 38 parts, 40 parts, 45 parts, 48 ​​parts, 50 parts.

[0114] In some of these examples, the two-component polyurethane varnish comprises, by weight, the monomers for preparing the first and second acrylic resins, respectively, independently comprising:

[0115] 20-60 parts of hydroxyalkyl methacrylate;

[0116] 5-20 parts of caprolactone-modified hydroxyethyl (meth)acrylate;

[0117] Vinyl aromatics 10-30 parts;

[0118] Other olefinic unsaturated carboxylic acids, 0.5-2 parts; and

[0119] 20-30 parts of alkyl esters of other olefinic unsaturated carboxylic acids.

[0120] It is understandable that the weight-average molecular weight (Mw) of the first and second acrylic resins can be controlled by adjusting parameters such as the ratio of each monomer, the type and amount of initiator.

[0121] It can also be understood that caprolactone-modified hydroxyethyl (meth)acrylate is synthesized by reacting caprolactone with hydroxyethyl (meth)acrylate through ring-opening, and it has the structure of the above formula (I).

[0122] It can be further understood that other alkyl esters of olefinic unsaturated carboxylic acids and other alkyl esters of olefinic unsaturated carboxylic acids are different from the caprolactone-modified (meth)acrylate hydroxyethyl ester and vinyl aromatics mentioned above.

[0123] In some of these examples, the hydroxyalkyl acrylate in the two-component polyurethane varnish includes at least one of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 3-hydroxybutyl acrylate, and 4-hydroxybutyl acrylate.

[0124] In some of these examples, the two-component polyurethane varnish contains hydroxyalkyl methacrylates, including at least one of 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 3-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate.

[0125] In some of these examples, the caprolactone-modified (meth)acrylate hydroxyethyl acrylate in the two-component polyurethane varnish includes at least one of hydroxyethylcaprolactone acrylate and hydroxyethylcaprolactone methacrylate.

[0126] It is understood that the CAS number of hydroxyethylcaprolactone acrylate is 110489-05-9, and its structure is as shown in the above formula (I), where R1 is H, R2 is ethyl, and n is 1; the CAS number of hydroxyethylcaprolactone methacrylate is 85099-10-1, and its structure is as shown in the above formula (I), where R1 is CH3, R2 is ethyl, and n is 1.

[0127] In some of these examples, the vinyl aromatics in the two-component polyurethane varnish include styrene.

[0128] In some of these examples, in two-component polyurethane varnishes, other olefinically unsaturated carboxylic acids include acrylic monomers.

[0129] In some of these examples, in two-component polyurethane varnishes, other olefinically unsaturated carboxylic acids include acrylic acid.

[0130] In some of these examples, in two-component polyurethane varnishes, the alkyl esters of other olefinic unsaturated carboxylic acids include alkyl acrylate monomers.

[0131] In some of these examples, the alkyl esters of other olefinic unsaturated carboxylic acids in the two-component polyurethane varnish include at least one of n-butyl methacrylate and n-butyl acrylate.

[0132] In some of these examples, the hydroxyl values ​​of the first acrylic resin and the second acrylic resin in the two-component polyurethane varnish are independently 100 KOH / g to 200 mg KOH / g.

[0133] It is understood that the hydroxyl values ​​of the first acrylic resin and the second acrylic resin include, but are not limited to, 100 KOH / g, 110 KOH / g, 120 KOH / g, 130 KOH / g, 140 KOH / g, 150 KOH / g, 160 KOH / g, 170 KOH / g, 180 KOH / g, 190 KOH / g, and 200 mg KOH / g.

[0134] In some of these examples, the hydroxyl values ​​of the first acrylic resin and the second acrylic resin in the two-component polyurethane varnish are independently 110 KOH / g to 190 mg KOH / g.

[0135] In some of these examples, the hydroxyl values ​​of the first acrylic resin and the second acrylic resin in the two-component polyurethane varnish are independently 130 KOH / g to 180 mg KOH / g.

[0136] In some of these examples, the acid values ​​of the first acrylic resin and the second acrylic resin in the two-component polyurethane varnish are independently 0 KOH / g to 30 mg KOH / g.

[0137] It is understood that the acid values ​​of the first and second acrylic resins include, but are not limited to, 0 KOH / g, 1 KOH / g, 5 KOH / g, 10 KOH / g, 15 KOH / g, 20 KOH / g, 25 KOH / g, and 30 mg KOH / g.

[0138] In some of these examples, the acid values ​​of the first acrylic resin and the second acrylic resin in the two-component polyurethane varnish are independently 0 KOH / g to 20 mg KOH / g.

[0139] In some of these examples, the acid values ​​of the first acrylic resin and the second acrylic resin in the two-component polyurethane varnish are independently 0 KOH / g to 10 mg KOH / g.

[0140] In some of these examples, in the two-component polyurethane varnish, the Tg values ​​of the first acrylic resin and the second acrylic resin are independently -40°C to 50°C.

[0141] It is understood that the Tg values ​​of the first acrylic resin and the second acrylic resin include, but are not limited to, -40℃, -30℃, -20℃, -10℃, 0℃, 10℃, 20℃, 30℃, 40℃, and 50℃.

[0142] In some of these examples, in the two-component polyurethane varnish, the Tg values ​​of the first acrylic resin and the second acrylic resin are independently -30°C to 40°C.

[0143] In some of these examples, the Tg values ​​of the first acrylic resin and the second acrylic resin in the two-component polyurethane varnish are independently -10°C to 30°C.

[0144] In some of these examples, the amino resin in the two-component polyurethane varnish includes melamine compounds.

[0145] In some of these examples, the amino resin in the two-component polyurethane varnish includes at least one of hexamethoxymethyl melamine, tetramethoxymethyl benzomelamine, tetramethoxymethylurea, and butoxy / methoxy combined substituted melamine.

[0146] In some of these examples, the two-component polyurethane varnish includes, by weight, component A, 5 to 30 parts of a second solvent.

[0147] It is understood that, by mass parts, the second solvent includes, but is not limited to, 5 parts, 10 parts, 20 parts, and 30 parts.

[0148] In some of these examples, the second solvent in a two-component polyurethane varnish includes an aprotic solvent.

[0149] It is understandable that aprotic solvents are chemically inert relative to other components in two-component polyurethane varnishes and do not react during curing.

[0150] In some of these examples, the second solvent in the two-component polyurethane varnish includes at least one of aromatic hydrocarbon aprotic solvents, ketone aprotic solvents, aprotic-like solvents, ester aprotic solvents, and ether aprotic solvents.

[0151] In some of these examples, aromatic hydrocarbon aprotic solvents include, but are not limited to, at least one of toluene, xylene, trimethylbenzene, Solvesso 100, Solentnaphtha®, and Hydrsol® (ARAL).

[0152] In some of these examples, ketone aprotic solvents include, but are not limited to, at least one of acetone, methyl ethyl ketone, and methyl amyl ketone.

[0153] In some of these examples, the ester aprotic solvents include, but are not limited to, at least one of ethylene glycol butyl ether acetate, ethyl acetate, butyl acetate, amyl acetate, and ethyl ethoxypropionate.

[0154] In some of these examples, ether-based aprotic solvents include, but are not limited to, at least one of diethyl ether, tetrahydrofuran, and dioxane.

[0155] In some of these examples, the second solvent in a two-component polyurethane varnish includes ethylene glycol butyl ether acetate, ethyl acetate, and trimethylbenzene.

[0156] In some of these examples, the ratio of water content in the second solvent to the total mass of the second solvent in the two-component polyurethane varnish is ≤0.5%.

[0157] It is understood that component A may also include additives commonly used in two-component polyurethane varnishes in the art, including but not limited to at least one of antioxidants, water scavengers, rheology modifiers, sag resins, light stabilizers, defoamers, leveling agents, and catalysts.

[0158] In some of these examples, the two-component polyurethane varnish further includes, by weight, 10 to 50 parts of additives, including at least one of anti-sagging resin, light stabilizer, defoamer, leveling agent and catalyst.

[0159] It is understood that, by weight, additives include, but are not limited to, 10, 20, 30, 40, and 50 parts.

[0160] In some of these examples, the two-component polyurethane varnish, by weight, includes 5-15 parts of anti-sagging resin, 1-5 parts of light stabilizer, 0.1-1 parts of defoamer, 0.1-1 parts of leveling agent, and 2-8 parts of catalyst.

[0161] It is understood that, by weight, the anti-sagging resin includes, but is not limited to, 5 parts, 8 parts, 10 parts, 12 parts, and 15 parts; the light stabilizer includes, but is not limited to, 1 part, 2 parts, 3 parts, 4 parts, and 5 parts; the defoamer includes, but is not limited to, 0.1 parts, 0.2 parts, 0.5 parts, 0.8 parts, and 1 part; the leveling agent includes, but is not limited to, 0.1 parts, 0.2 parts, 0.5 parts, 0.8 parts, and 1 part; and the catalyst includes, but is not limited to, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, and 8 parts.

[0162] It is understood that anti-sagging resins include, but are not limited to, cross-linked polymer particles, inorganic layered silicates (such as montmorillonite-type aluminum magnesium silicate, layered sodium magnesium silicate, and layered sodium magnesium fluoride lithium silicate), silica (such as Aerosile), and synthetic polymers with ionic groups and / or associative groups (such as polyvinyl alcohol, poly(meth)acrylamide, poly(meth)acrylic acid, polyvinylpyrrolidone, styrene-maleic anhydride copolymers or ethylene-maleic anhydride copolymers and their derivatives or hydrophobically modified ethoxylated urethanes or polyacrylates). At least one of the following: light stabilizers, including but not limited to at least one of ultraviolet light absorbers (UVA) and hindered amine radical scavengers (HLSA); defoamers, including but not limited to at least one of silicone oils, polyacrylates, polyurethanes, polyethers, and mineral oils; leveling agents, including but not limited to at least one of acrylic, polyester, and siloxane types; and catalysts, including but not limited to at least one of the following components blocked by sulfuric acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, dodecylbenzenesulfonic acid, acetic acid, trifluoroacetic acid, monophosphate, diester, or the corresponding amine.

[0163] In some of these examples, the anti-sagging resin in the two-component polyurethane varnish includes at least one of Setalux 81198 SS-55YA and Setal 82166 SS-64.

[0164] In some of these examples, the light stabilizer in the two-component polyurethane varnish includes at least one of Tinuvin 1130 and Tinuvin 292.

[0165] In some of these examples, the defoamer in the two-component polyurethane varnish includes VK DF-0301.

[0166] In some of these examples, the leveling agent in the two-component polyurethane varnish includes at least one of BYK 331 and BYK-3760.

[0167] In some of these examples, the catalyst in the two-component polyurethane varnish includes at least one of Nacurure 4167 and Nacurure 5528.

[0168] It is understood that polyisocyanates include, but are not limited to, at least one of aliphatic, alicyclic, or heterocyclic polyisocyanates.

[0169] In some of these examples, the polyisocyanate in the two-component polyurethane varnish includes hexyl diisocyanate (HDI) oligomers.

[0170] In some of these examples, the polyisocyanate in the two-component polyurethane varnish includes at least one of HDI dimer, HDI trimer, HDI pentamer, and HDI heptamer.

[0171] It is understandable that the first solvent has good solubility for polyisocyanate compounds but does not react with isocyanates.

[0172] In some examples, the first solvent in the two-component polyurethane varnish includes at least one selected from acetone, methyl ethyl ketone, cyclohexane, ethyl acetate, isobutyl acetate, 3-methoxybutyl acetate, butyl acetate, sec-butyl acetate, isopropyl acetate, ethyl 3-ethoxypropionate, methyl isobutyl ketone, methyl pentyl ketone, trimethylbenzene, tetramethylbenzene, propylene glycol methyl ether acetate, toluene, xylene, ethylbenzene, diethyl carbonate, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,3-dioxolane, and diethyl glycol.

[0173] In some of these examples, the molar ratio of hydroxyl groups in component A to isocyanate groups in component B in a two-component polyurethane varnish is (0.9~1.5):1.

[0174] It is understood that the molar ratio of hydroxyl groups in component A to isocyanate groups in component B includes, but is not limited to, 0.9:1, 0.92:1, 0.95:1, 0.98:1, 1:1, 1.02:1, 1.05:1, 1.08:1, 1.1:1, 1.2:1, and 1.5:1.

[0175] In some of these examples, the molar ratio of hydroxyl groups in component A to isocyanate groups in component B in a two-component polyurethane varnish is (0.95~1.25):1.

[0176] It is understandable that components A and B are stored separately; when used in combination, the molar ratio of hydroxyl groups in component A to isocyanate groups in component B can be controlled by controlling the weight ratio of components A to B.

[0177] In some of these examples, the weight ratio of component A to component B in a two-component polyurethane varnish is (2~5):1.

[0178] It is understood that the weight ratio of component A to component B includes, but is not limited to, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, and 5:1.

[0179] In some of these examples, in two-component polyurethane varnishes, the VOC content after mixing component A and component B is ≤420 g / L.

[0180] One embodiment of this application provides a method for preparing a two-component polyurethane varnish, comprising the following steps:

[0181] Step S10: Provide raw materials according to the components of the above two-component polyurethane varnish.

[0182] In some examples, step S10, the preparation of the first acrylic resin and the second acrylic resin each independently includes the following steps:

[0183] Add the third solvent to a four-necked flask equipped with a thermometer and a stirrer, and raise the temperature to the reflux temperature. After the reflux temperature stabilizes, mix the monomers that form the first or second acrylic resin, the initiator, and the third solvent, and add them dropwise to the four-necked flask while maintaining reflux.

[0184] After the reaction is complete, the solution is diluted with a fourth solvent and cooled to obtain either the first acrylic resin or the second acrylic resin.

[0185] In some of these examples, in step S10, the third solvent includes at least one of Solvesso 100 and ethyl acetate; the fourth solvent includes propylene glycol methyl ether acetate (PMA).

[0186] Step S20: Mix the raw materials corresponding to component A to obtain component A.

[0187] The first acrylic resin, the second acrylic resin, and the amino resin are mixed to obtain component A.

[0188] In some of these examples, step S20 includes the following steps:

[0189] The first acrylic resin, the second acrylic resin, the amino resin, and the additives are mixed to obtain component A.

[0190] Step S30: Mix the raw materials corresponding to component B to obtain component B.

[0191] In some of these examples, in step S30, the polyisocyanate and the first solvent are mixed to obtain component B.

[0192] In some of these examples, in step S30, mixing is carried out under nitrogen protection conditions.

[0193] One embodiment of this application provides a paint layer, the raw material of which is the above-mentioned two-component polyurethane varnish.

[0194] One embodiment of this application provides a method for preparing a paint layer, which uses the above-mentioned two-component polyurethane varnish, mixes and coats component A and component B, and then cures to obtain a paint layer.

[0195] It is understood that this application does not limit the coating method; any method applicable in the art is acceptable. Furthermore, the curing method includes, but is not limited to, baking. Further, the baking temperature is 140℃~160℃. It is understood that the baking temperature includes, but is not limited to, 140℃, 145℃, 150℃, 155℃, and 160℃.

[0196] When components A and B are mixed and cured, the hydroxyl groups of the first and second acrylic resins in component A react with the isocyanate groups of the isocyanate to form polyurethane, and the amino resin itself or with the hydroxyl and carboxyl groups of the acrylic resin undergoes a polycondensation reaction.

[0197] The coating layer formed by the above-mentioned two-component polyurethane varnish has a good appearance, high hardness, and good scratch resistance.

[0198] One embodiment of this application provides a paint layer article comprising the above-described paint layer.

[0199] In some of these examples, painted products include, but are not limited to, automobiles.

[0200] The present application will be described in further detail below with reference to specific embodiments, but the embodiments of the present application are not limited thereto.

[0201] The methacrylates used in the following examples and comparative examples were prepared as follows:

[0202] The preparation steps of acrylic resin C1 are as follows:

[0203] 45.00 parts by weight of Solvesso 100 and 15.00 parts by weight of ethyl acetate were added to a four-necked flask equipped with a thermometer and a stirrer, and the temperature was raised to the reflux temperature of 150°C. After the reflux temperature stabilized, 30.00 parts by weight of hydroxypropyl methacrylate, 10.00 parts by weight of hydroxyethyl methacrylate, 15.00 parts by weight of hydroxyethylcaprolactone acrylate, 1.00 part by weight of acrylic acid, 25.00 parts by weight of styrene monomer, 5.00 parts by weight of n-butyl methacrylate, 24.00 parts by weight of n-butyl acrylate, 2.60 parts by weight of initiator (di-tert-butyl peroxide DTBP), and 3.00 parts by weight of Solvesso 100 were uniformly added dropwise to the four-necked flask over 180 minutes. The mixture was then refluxed at 150°C for 90 minutes and cooled to room temperature. The reaction was then complete. The reaction product was diluted with propylene glycol methyl ether acetate (PMA) and cooled to 60°C to obtain acrylic resin C1 with Tg=5°C, OHV=170 mgKOH / g, Mw=13000 Daltons, and AV=8 mgKOH / g.

[0204] The preparation steps of acrylic resin C2 are as follows:

[0205] To a four-necked flask equipped with a thermometer and stirrer, add 17.50 parts by weight of Solvesso 100 and 12.00 parts by weight of ethyl acetate, and raise the temperature to reflux temperature of 150°C. After the reflux temperature stabilizes, mix 22.00 parts by weight of hydroxypropyl methacrylate, 6.50 parts by weight of hydroxyethyl ester caprolactone acrylic acid, 0.65 parts by weight of acrylic acid, 13.00 parts by weight of styrene monomer, 7.00 parts by weight of n-butyl methacrylate, 15.50 parts by weight of n-butyl acrylate, 3.00 parts by weight of initiator (dapteramyl peroxide DTAP), and 3 parts by weight of Solvesso 100 uniformly in a beaker. Add this mixture dropwise uniformly to the four-necked flask over 180 minutes, then reflux at 150°C for 90 minutes, and finally cool to room temperature. The reaction is complete. The reaction product was diluted with propylene glycol methyl ether acetate (PMA) and cooled to 60°C to obtain acrylic resin C2 with Tg=4°C, OHV=150 mgKOH / g, Mw=5500 Daltons, and AV=8 mgKOH / g.

[0206] Adjust the proportions of each monomer and prepare acrylic resin C3 according to the above method. Its Tg=4℃, OHV=140mgKOH / g, Mw=18000 Daltons, and AV=7mgKOH / g.

[0207] Adjust the proportions of each monomer and prepare acrylic resin C4 according to the above method. Its Tg=-1℃, OHV=160mgKOH / g, Mw=3000 Daltons, and AV=8mg KOH / g.

[0208] Acrylic resin C5 was prepared according to the above method, with Tg=5℃, OHV=150mgKOH / g, Mw=11000 Daltons, and AV=6.5mg KOH / g.

[0209] Acrylic resin C6 was prepared according to the above method, with Tg=3℃, OHV=135mgKOH / g, Mw=7000 Daltons, and AV=7.5mg KOH / g.

[0210] The preparation steps of acrylic resin C7 are as follows:

[0211] To a four-necked flask equipped with a thermometer and stirrer, add 30.00 parts by weight of Solvesso 100 and 20.00 parts by weight of ethyl acetate, and raise the temperature to reflux temperature of 150°C. After the reflux temperature stabilizes, mix 35.00 parts by weight of hydroxypropyl methacrylate, 10.00 parts by weight of hydroxyethyl acrylate, 24.00 parts by weight of isobornyl acrylate, 1.00 part by weight of acrylic acid, 28.00 parts by weight of styrene monomer, 1.00 part by weight of isobutyl acrylate, 6.00 parts by weight of DTAP, and 5 parts by weight of Solvesso 100 evenly in a beaker. Add this mixture dropwise evenly to the four-necked flask over 180 minutes. Then, reflux at 150°C for 90 minutes, and cool to room temperature. The reaction is complete. The reaction product was diluted with propylene glycol methyl ether acetate (PMA) and cooled to 60°C to obtain hydroxyl-functionalized polyacrylic acid resin C7, with Tg=35°C, OHV=140mgKOH / g, Mw=4000 Daltons, and AV=8 mg KOH / g.

[0212] Example 1

[0213] (1) Component A

[0214] In a container equipped with a stirrer, under stirring conditions, 10 kg of acrylic resin C1, 50 kg of acrylic resin C2, 10 kg of Cymel 325 (amino resin), 10 kg of Setal 82166 SS-64 (anti-sagging resin), 0.3 kg of VK DF-0301 (defoamer), 0.3 kg of Nacure 4167 (acid catalyst), 3 kg of Nacure 5528 (acid catalyst), 1.5 kg of Tinuvin 1130 (UV absorber), 0.8 kg of Tinuvin 292 (light stabilizer), 0.2 kg of BYK 331 (leveling agent), 0.4 kg of BYK-3760 (leveling agent), 3 kg of n-butyl acetate, and 2.5 kg of trimethylbenzene were added sequentially and stirred until homogeneous to obtain polyurethane varnish component A; the mass ratio of amino resin to the total mass of acrylic resin C1 and acrylic resin C2 was 1:6.

[0215] (2) Polyurethane varnish component B

[0216] In a container equipped with a stirrer, under nitrogen protection, 80 kg of Desmodur N3300 (isocyanate curing agent), 10 kg of n-butyl acetate, and 10 kg of Solvesso 100 were added sequentially and stirred until homogeneous to obtain component B of the polyurethane varnish.

[0217] Example 2

[0218] (1) Polyurethane varnish component A

[0219] In a container equipped with a stirrer, under stirring conditions, 15 kg of acrylic resin C1, 45 kg of acrylic resin C2, 10 kg of Cymel 238, 10 kg of Setalux 81198 SS-55 YA, 0.3 kg of VK DF-0301, 0.3 kg of Nacure 4167, 3 kg of Nacure 5528, 1.5 kg of Tinuvin 1130, 0.8 kg of Tinuvin 292, 0.2 kg of BYK 331, 0.4 kg of BYK-3760, 3 kg of n-butyl acetate, and 2.5 kg of trimethylbenzene were added sequentially and stirred until homogeneous to obtain polyurethane varnish component A.

[0220] (2) Polyurethane varnish component B

[0221] In a container equipped with a stirrer, under nitrogen protection, 80 kg of Desmodur N3300, 10 kg of n-butyl acetate, and 10 kg of Solvesso 100 were added sequentially and stirred until homogeneous to obtain component B of the polyurethane varnish.

[0222] Example 3

[0223] (1) Polyurethane varnish component A

[0224] In a container equipped with a stirrer, under stirring conditions, 20 kg of acrylic resin C1, 40 kg of acrylic resin C2, 10 kg of Cymel 238, 10 kg of Setal 82166 SS-64, 0.3 kg of VK DF-0301, 0.3 kg of Nacure 4167, 3 kg of Nacure 5528, 1.5 kg of Tinuvin 1130, 0.8 kg of Tinuvin 292, 0.2 kg of BYK 331, 0.4 kg of BYK-3760, 3 kg of n-butyl acetate, and 2.5 kg of tricresylbenzene were added sequentially and stirred until homogeneous to obtain polyurethane varnish component A.

[0225] (2) Polyurethane varnish component B

[0226] In a container equipped with a stirrer, under nitrogen protection, 60 kg of Desmodur N3300, 20 kg of Desmodur N3900, 10 kg of n-butyl acetate, and 10 kg of Solvesso 100 were added sequentially and stirred until homogeneous to obtain component B of the polyurethane varnish.

[0227] Example 4

[0228] (1) Polyurethane varnish component A

[0229] In a container equipped with a stirrer, under stirring conditions, 15 kg of acrylic resin C1, 45 kg of acrylic resin C2, 8 kg of Cymel 238, 2 kg of Cymel 325, 10 kg of Setalux 81198 SS-55 YA, 0.3 kg of VKDF-0301, 0.3 kg of Nacure 4167, 3 kg of Nacure 5528, 1.5 kg of Tinuvin 1130, 0.8 kg of Tinuvin292, 0.2 kg of BYK 331, 0.4 kg of BYK-3760, 3 kg of n-butyl acetate, and 2.5 kg of trimethylbenzene were added sequentially to obtain polyurethane varnish component A.

[0230] (2) Polyurethane varnish component B

[0231] In a container equipped with a stirrer, under nitrogen protection, 80 kg of Desmodur N3900, 10 kg of n-butyl acetate, and 10 kg of Solvesso 100 were added sequentially and stirred until homogeneous to obtain component B of the polyurethane varnish.

[0232] Example 5

[0233] The example is basically the same as Example 1, except that in Example 5, the acrylic resin C1 (Mw=13000 Daltons) in Example 1 is replaced with an equal mass of acrylic resin C3 (Mw=18000 Daltons), and the acrylic resin C2 (Mw=5500 Daltons) is replaced with an equal mass of acrylic resin C4 (Mw=3000 Daltons).

[0234] Example 6

[0235] The example is basically the same as Example 1, except that in Example 6, the acrylic resin C1 (Mw=13000 Daltons) in Example 1 is replaced with an equal mass of acrylic resin C5 (Mw=11000 Daltons), and the acrylic resin C2 (Mw=5500 Daltons) is replaced with an equal mass of acrylic resin C6 (Mw=7000 Daltons).

[0236] Example 7

[0237] The example is basically the same as Example 1, except that in Example 7, the amount of acrylic resin C1 added is 11 kg, the amount of acrylic resin C2 added is 54 kg, the amount of amino resin Cymel 325 added is 5 kg, and the mass ratio of amino resin to the total mass of acrylic resin C1 and acrylic resin C2 is 13:1.

[0238] Comparative Example 1

[0239] (1) Polyurethane varnish component A

[0240] In a container equipped with a stirrer, 60 kg of acrylic resin C1, 10 kg of Cymel 238, 10 kg of Setalux 81198 SS-55 YA, 0.3 kg of VK DF-0301, 0.3 kg of Nacure 4167, 3 kg of Nacure 5528, 1.5 kg of Tinuvin 1130, 0.8 kg of Tinuvin 292, 0.2 kg of BYK 331, 0.4 kg of BYK-3760, 3 kg of n-butyl acetate, and 2.5 kg of tricresylbenzene were added sequentially under stirring conditions to obtain polyurethane varnish component A.

[0241] (2) Polyurethane varnish component B

[0242] In a container equipped with a stirrer, under nitrogen protection, 80 kg of Desmodur N3300, 10 kg of n-butyl acetate, and 10 kg of Solvesso 100 were added sequentially and stirred until homogeneous to obtain component B of the polyurethane varnish.

[0243] Comparative Example 2

[0244] (1) Polyurethane varnish component A

[0245] In a container equipped with a stirrer, 25 kg of acrylic resin C1, 45 kg of acrylic resin C2, 10 kg of Setal 82166 SS-64, 0.3 kg of VK DF-0301, 0.3 kg of Nacure 4167, 3 kg of Nacure 5528, 1.5 kg of Tinuvin 1130, 0.8 kg of Tinuvin 292, 0.2 kg of BYK 331, 0.4 kg of BYK-3760, 3 kg of n-butyl acetate, and 2.5 kg of tricresylbenzene were added sequentially under stirring conditions to obtain polyurethane varnish component A.

[0246] (2) Polyurethane varnish component B

[0247] In a container equipped with a stirrer, under nitrogen protection, 80 kg of Desmodur N3300, 10 kg of n-butyl acetate, and 10 kg of Solvesso 100 were added sequentially and stirred until homogeneous to obtain component B of the polyurethane varnish.

[0248] Comparative Example 3

[0249] (1) Polyurethane varnish component A

[0250] In a container equipped with a stirrer, 60 kg of acrylic resin C7, 10 kg of Cymel 238, 10 kg of Setalux 81198 SS-55 YA, 0.3 kg of VK DF-0301, 0.3 kg of Nacure 4167, 3 kg of Nacure 5528, 1.5 kg of Tinuvin 1130, 0.8 kg of Tinuvin 292, 0.2 kg of BYK 331, 0.4 kg of BYK-3760, 3 kg of n-butyl acetate, and 2.5 kg of tricresylbenzene were added sequentially under stirring conditions to obtain polyurethane varnish component A.

[0251] (2) Polyurethane varnish component B

[0252] In a container equipped with a stirrer, under nitrogen protection, 80 kg of Desmodur N3300, 10 kg of n-butyl acetate, and 10 kg of Solvesso 100 were added sequentially and stirred until homogeneous to obtain component B of the polyurethane varnish.

[0253] Comparative Example 4

[0254] (1) Polyurethane varnish component A

[0255] In a container equipped with a stirrer, 60 kg of acrylic resin C2, 10 kg of Cymel 325, 10 kg of Setalux 81198 SS-55 YA, 0.3 kg of VK DF-0301, 0.3 kg of Nacure 4167, 3 kg of Nacure 5528, 1.5 kg of Tinuvin 1130, 0.8 kg of Tinuvin 292, 0.2 kg of BYK 331, 0.4 kg of BYK-3760, 3 kg of n-butyl acetate, and 2.5 kg of tricresylbenzene were added sequentially under stirring conditions to obtain polyurethane varnish component A.

[0256] (2) Polyurethane varnish component B

[0257] In a container equipped with a stirrer, under nitrogen protection, 80 kg of Desmodur N3300, 10 kg of n-butyl acetate, and 10 kg of Solvesso 100 were added sequentially and stirred until homogeneous to obtain component B of the polyurethane varnish.

[0258] Comparative Example 5

[0259] The comparison is basically the same as Example 1, except that the acrylic resin C1 (Mw=13000 Daltons) in Example 1 is replaced with an equal mass of acrylic resin C6 (Mw=7000 Daltons).

[0260] Comparative Example 6

[0261] The comparison is basically the same as Example 1, except that in Comparative Example 6, the amount of acrylic resin C1 added is 50 kg and the amount of acrylic resin C2 added is 10 kg.

[0262] Comparative Example 7

[0263] The comparison is basically the same as Example 1, except that Component B is removed in Comparative Example 7 and an amino resin is used as the curing agent.

[0264] The components and proportions of the polyurethane varnishes provided in each embodiment and comparative example are shown in Table 1.

[0265] Table 1

[0266] C1 to C7 refer to acrylic resins C1 to C7, respectively, and Mw is in Daltons.

[0267] According to the coating methods known to those skilled in the art, the intermediate coat and color paint of Xiangjiang Kansai were sequentially coated on the electrophoretic ED plate, and the clear varnish samples of the above-mentioned embodiments or comparative examples were coated respectively (component A and component B were mixed at a weight ratio of 3.5:1). According to the test plate preparation and evaluation methods known to those skilled in the art, the coating parameters, coating workability and coating film performance were evaluated respectively.

[0268] Scratch resistance is tested by measuring the scratch resistance of the dry surface, and the method is as follows:

[0269] 1. Experimental equipment and model: SDL ATLAS M238BB Model CM-5 rubbing color fastness tester;

[0270] 2. Sandpaper for the experiment: 2400 mesh, round, 30mm diameter SiC adhesive-backed sandpaper;

[0271] 3. Experimental procedures and result evaluation:

[0272] 3.1 Mark the scratch test location and 3 gloss measurement locations on the test plate. Divide the scratch test location into 4 equal parts for gloss measurement.

[0273] 3.2 Use a gloss meter to measure the gloss at the marked location and record the 20° gloss G0.

[0274] 3.3 Set the number of wipes to 15;

[0275] 3.4 When attaching the sandpaper to the instrument, it is not allowed to be attached crookedly, wrinkled, or otherwise abnormal.

[0276] 3.5 Place the sample on the operating table with the test surface facing up, hold the sample firmly with both hands, and do not allow the sample to shake or move during the test;

[0277] 3.6 Start the test. After the test, use a gloss meter to measure the gloss at the marked gloss position and record the 20° gloss G1.

[0278] 3.7 An experiment is conducted three times. If any result deviates from the average by more than 10%, that result must be discarded and the experiment repeated. If two results deviate from the average by 10%, the plate must be remade and the experiment repeated.

[0279] 3.8 Calculate the light retention rate = G1 / G0 * 100%

[0280] 4. Other requirements:

[0281] 4.1 Before testing, the sample should be kept at a temperature of (23±2)℃ and a relative humidity of (50±5)% for at least 24 hours.

[0282] 4.2 The experimental conditions were: temperature (23±2)℃ and relative humidity (50±5)%.

[0283] 4.3 Carefully observe the experimental process for any abnormal phenomena and record them.

[0284] 4.4 The surface of the test sample shall not have defects such as particles or scratches that may affect the measurement results.

[0285] VOC: GB 38597-2009; Pencil hardness: GB / T 6739-2006; Horizontal long wave value L and vertical long wave value L: BYK orange peel tester; Sagging performance: GB / T 9264-2012.

[0286] The test results are shown in Table 2.

[0287] Table 2

[0288]

[0289] As shown in Table 2, compared with the comparative examples, the polyurethane varnishes provided in each embodiment have better overall performance in terms of appearance, hardness, and scratch resistance, with Example 1 showing relatively better overall performance. However, compared to Example 1, Comparative Example 1 did not add low molecular weight acrylic resin C2, and the mass of acrylic resin C1 was 60 kg. The large amount of C1 resin introduced caused difficulties in horizontal flow, leading to a deterioration in the horizontal appearance (long-wavelength L value). Comparative Example 2 did not add amino resin, and the mass of acrylic resin C1 and acrylic resin C2 increased by 5 kg each, resulting in a significant decrease in pencil hardness. Comparative Example 3 replaced acrylic resin C1 and acrylic resin C2 with 60 kg of low molecular weight acrylic resin C7 without hydroxyethylcaprolactone acrylate monomer, resulting in a significant decrease in scratch resistance and anti-sagging properties. Comparative Example 4 did not add high molecular weight acrylic resin C1, and the mass of acrylic resin C2 containing only hydroxyethylcaprolactone (meth)acrylate monomer was 60 kg. Kg, resulting in a significant decrease in its anti-sagging performance; Comparative Example 5 replaced acrylic resin C1 in Example 1 with an equal mass of acrylic resin C6. Due to the decrease in molecular weight, its anti-sagging performance was significantly lower than that of Example 1; Comparative Example 6 added 50 kg of acrylic resin C1 and 10 kg of acrylic resin C2. Due to the large amount of C1 resin introduced, the sagging performance was greatly improved, but it brought difficulties in horizontal flow, and the long wavelength L value of the horizontal plate was too high, resulting in the deterioration of the coating appearance; Comparative Example 7 removed the B component containing the crosslinking group isocyanate group compared to Example 1 and used amino resin as the crosslinking agent, resulting in insufficient crosslinking reaction and a decrease in coating hardness. At the same time, due to the lack of urethane bonds, the chain elasticity in the coating molecules was insufficient, resulting in a decrease in scratch resistance.

[0290] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0291] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A two-component polyurethane clearcoat, characterized in that, Includes component A and component B; By mass parts, component A comprises the following components: 8-25 parts of the first acrylic resin; 36-55 parts of the second acrylic resin; and 5-20 parts of amino resin; Both the first acrylic resin and the second acrylic resin contain hydroxyl groups; the weight-average molecular weight Mw of the first acrylic resin is 10,000 to 20,000 Daltons, and the weight-average molecular weight Mw of the second acrylic resin is 2,000 to 9,000 Daltons. By mass parts, component B comprises the following components: 70-90 parts of polyisocyanate; and 10-30 parts of the first solvent; The monomers for preparing the first acrylic resin and the second acrylic resin each independently comprise the structure of the following formula (I): （Ⅰ） Wherein, R1 is independently H or CH3, R2 is ethyl, and n is 1.

2. The two-component polyurethane varnish as described in claim 1, characterized in that, The mass ratio of the first acrylic resin to the second acrylic resin is 1:(2~5).

3. The two-component polyurethane varnish as described in claim 1, characterized in that, The mass ratio of the amino resin to the total mass of the first acrylic resin and the second acrylic resin is 1:(6~13).

4. The two-component polyurethane varnish as described in claim 1, characterized in that, By mass fraction, the monomers for preparing the first acrylic resin and the second acrylic resin each independently comprise: 0-30 parts of hydroxyalkyl acrylate; 10-90 parts of hydroxyalkyl methacrylate; Preparation of monomers of formula (I) 5~50 parts; Vinyl aromatics 0-50 parts; 0-5 parts acrylic acid; and 0-50 parts of (meth)acrylate n-butyl ester.

5. The two-component polyurethane varnish as described in claim 4, characterized in that, The hydroxyalkyl acrylate includes at least one of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 3-hydroxybutyl acrylate, and 4-hydroxybutyl acrylate.

6. The two-component polyurethane varnish as described in claim 4, characterized in that, The hydroxyalkyl methacrylate includes at least one of 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 3-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate.

7. The two-component polyurethane varnish as described in claim 4, characterized in that, The vinyl aromatics include styrene.

8. The two-component polyurethane varnish as described in claim 1, characterized in that, The hydroxyl values ​​of the first acrylic resin and the second acrylic resin are independently 100 mg KOH / g to 200 mg KOH / g, the acid values ​​are independently 0 mg KOH / g to 30 mg KOH / g, and the Tg values ​​are independently -40℃ to 50℃.

9. The two-component polyurethane varnish according to any one of claims 1 to 8, characterized in that, The polyisocyanate includes hexanediisocyanate oligomers.

10. The two-component polyurethane varnish according to any one of claims 1 to 8, characterized in that, The first solvent includes at least one of acetone, methyl ethyl ketone, cyclohexane, ethyl acetate, 3-methoxybutyl acetate, butyl acetate, isopropyl acetate, ethyl 3-ethoxypropionate, methyl isobutyl ketone, methyl pentyl ketone, trimethylbenzene, tetramethylbenzene, propylene glycol methyl ether acetate, toluene, xylene, ethylbenzene, diethyl carbonate, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,3-dioxolane, and diethyl ethylene glycol.

11. The two-component polyurethane varnish according to any one of claims 1 to 8, characterized in that, Based on parts by weight, component A further includes 10 to 50 parts of additives, which include at least one of anti-sagging resin, light stabilizer, defoamer, leveling agent, catalyst, and second solvent.

12. The two-component polyurethane varnish according to any one of claims 1 to 8, characterized in that, In the two-component polyurethane varnish, the molar ratio of hydroxyl groups in component A to isocyanate groups in component B is (0.9~1.5):

1.

13. A method for preparing a two-component polyurethane varnish, characterized in that, Includes the following steps: The raw materials are provided according to the components of the two-component polyurethane varnish as described in any one of claims 1 to 12; The raw materials corresponding to component A are mixed to obtain component A; The raw materials corresponding to component B are mixed to obtain component B.

14. A paint layer, characterized in that, The raw material for the paint layer is the two-component polyurethane varnish as described in any one of claims 1 to 12.

15. A painted product, characterized in that, It includes the paint layer as described in claim 14.

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