A solventless coating and a method for preparing the same

Abstract

This invention belongs to the field of coatings and proposes a solvent-free coating and its preparation method. The raw materials include component A and component B in a mass ratio of 1:1. By mass parts, component A comprises: 45-60 parts polyester polyol, 25-35 parts polyether polyol, 6-10 parts polyaspartic acid ester resin, 2-3 parts epoxy resin, 6-8 parts titanium dioxide, 2-5 parts mica powder, 0.3-1 parts dispersant, 0.3-1 parts dehydrating agent, 0.6-1.3 parts catalyst, and 2-3 parts coupling agent. Component B consists of hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate in a mass ratio of 1.5-2:1. This polyurethane coating exhibits good aging resistance, no solvent evaporation, and is environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of coating technology and relates to a solvent-free coating and its preparation method. Background Technology

[0002] Polyurethane waterproof coatings are suitable for waterproofing various underground construction projects, such as basements and subways; they are also suitable for waterproofing railways, highways, bridges, culverts, and tunnels; and can be used for waterproofing kitchens, bathrooms, swimming pools, as well as for waterproofing gaps, pipe penetrations, and drain outlets. Additionally, it can be used for waterproofing roofs and walls of buildings. Polyurethane waterproof coatings are mainly composed of isocyanates, polyethers, and other raw materials, which undergo addition polymerization to form an isocyanate-containing prepolymer, which is then combined with catalysts, anhydrous additives, anhydrous fillers, solvents, etc. Some products also use acrylic polymer emulsions, water, defoamers, and preservatives to enhance their waterproofing and application performance.

[0003] Most single-component polyurethane waterproof coatings on the market currently work by reacting with moisture in the air to cross-link and cure, forming an elastic and dense waterproof membrane. The basic curing mechanism involves the reaction of some terminal isocyanate (-NCO) groups in the prepolymer of the coating with moisture to produce carbon dioxide gas and primary amine (-NH2) groups. The primary amine groups then rapidly react with the remaining isocyanate groups to form urea bonds, extending the chain and curing the coating. Single-component coatings are convenient to use, ready to use immediately after opening, reducing the risk of mixing errors. They dry quickly, making them suitable for rapid application and small-area repairs. However, their overall performance is generally inferior to that of two-component coatings.

[0004] Two-component polyurethane coatings achieve curing through the mixing and reaction of a base agent and a curing agent. Typically, component A consists of polyether polyols, fillers, water-absorbing agents, catalysts, and functional additives, while component B consists of polyisocyanates or prepolymers containing isocyanate groups. However, the aging resistance of existing two-component polyurethane coatings still needs improvement. Summary of the Invention

[0005] This invention proposes a solvent-free coating and its preparation method. The polyurethane coating has good aging resistance, no solvent volatilization, and is green and environmentally friendly.

[0006] The technical solution of this invention is implemented as follows:

[0007] A solvent-free coating comprising component A and component B in a mass ratio of 1:1;

[0008] By weight, component A comprises: 45-60 parts polyester polyol, 25-35 parts polyether polyol, 6-10 parts polyaspartic acid ester resin, 2-3 parts epoxy resin, 6-8 parts titanium dioxide, 2-5 parts mica powder, 0.3-1 parts dispersant, 0.3-1 parts dehydrating agent, 0.6-1.3 parts catalyst, and 2-3 parts coupling agent;

[0009] Component B consists of hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate in a mass ratio of 1.5-2:1.

[0010] The number-average molecular weight of the polyester polyol is 200-5000, the hydroxyl value is 200-300 mgKOH / g, and the viscosity at 25°C is 2500-10000 mPa·s.

[0011] The polyether polyol has a functionality of 2-3, a hydroxyl value of 25-40 mgKOH / g, and a viscosity of 500-1300 mPa.s at 25°C.

[0012] Preferably, the polyester polyol can be selected from one or more of NGPS-2320 and NGPS-260 from Zhangjiagang Nanguang Chemical Co., Ltd., or Evonik K Oxyester HS2272 from Germany.

[0013] Preferably, the polyether polyol can be selected from one or more of Shandong Lanxing Dongda DL3000D, EP-330NG, and EP-3600.

[0014] Preferably, the hexamethylene diisocyanate-based biuret polyisocyanate has an NCO content of 21.7-22.3%.

[0015] Preferably, the hexamethylene diisocyanate-based biuret polyisocyanate can be from Wanhua Chemical. HB-100.

[0016] Preferably, the polyaspartic acid ester resin has an NH equivalent of 277 g / mol and can be F420 from Shenzhen Feiyang Junyan New Materials Co., Ltd.

[0017] Preferably, the epoxy resin is a bisphenol F type epoxy resin with an epoxy equivalent of 168-175 g / eq, and Dow Chemical's DER-354 type epoxy resin can be used.

[0018] Preferably, the coupling agent is selected from one or two of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, triethoxy[4-(trifluoromethyl)phenyl]silane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and γ-aminopropyltriethoxysilane.

[0019] Preferably, the coupling agent is triethoxy[4-(trifluoromethyl)phenyl]silane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:1.6-2.3.

[0020] Preferably, the catalyst is an organotin catalyst, selected from one or two of dibutyltin dilaurate, stannous octoate, and the organotin catalyst WCAT-S12 from Guangzhou Yourun Synthetic Materials Co., Ltd.

[0021] Preferably, the titanium dioxide has a particle size of 15-30 nm and a specific surface area of ​​30-50 m². 2 / g.

[0022] Preferably, the dehydrating agent is a molecular sieve dehydrating agent, and the D50 of the molecular sieve is 2-4 μm.

[0023] Preferably, the mica powder has a particle size of 600-800 mesh.

[0024] Preferably, component A further comprises 0.2-0.5 parts of pigment, wherein the pigment is selected from one or more of iron oxide red, chrome yellow, iron oxide yellow, iron oxide black, and molybdenum chrome red.

[0025] The present invention also provides a method for preparing the above-mentioned solvent-free coating, comprising the following steps:

[0026] Polyester polyol, polyether polyol, polyaspartic acid ester resin and epoxy resin are mixed, heated to 30-50℃ and stirred. Then titanium dioxide, mica powder, dispersant, molecular sieve dehydrating agent, catalyst and coupling agent are added and stirred again to obtain component A.

[0027] Hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate were mixed and stirred to obtain component B.

[0028] Mix component A and component B and stir to obtain solvent-free coating.

[0029] Preferably, the stirring speed is 1200-2000 r / min and the stirring time is 30-50 min.

[0030] The working principle and beneficial effects of this invention are as follows:

[0031] 1. In this invention, polyester polyol and polyether polyol are the main hydroxyl components, containing a large number of active hydroxyl groups. These hydroxyl groups can chemically react with the isocyanate groups in component B to form the molecular structure of polyurethane. Polyaspartic acid ester resin has a unique chemical structure, with significant steric hindrance on both sides of the amino groups in its molecules. This steric hindrance effect can slow down the reaction rate with isocyanate, allowing sufficient time for the coating to be applied and leveled during construction, improving the wettability of the coating to the substrate, and increasing the contact between the coating and the substrate.

[0032] In this invention, epoxy resin provides excellent adhesion, enhancing the bond between the coating and the substrate, resulting in a stronger coating. It also imparts good barrier properties, effectively preventing the penetration of water and corrosive media, protecting the substrate from corrosion, and enhancing the overall hardness and wear resistance of the coating. Furthermore, polyaspartic acid ester resin exhibits excellent light stability and weather resistance, effectively resisting aging caused by ultraviolet radiation and extending the coating's service life. Compared to epoxy resin, polyaspartic acid ester resin provides better flexibility, making the coating less prone to cracking under harsh weather and mechanical stress, maintaining surface integrity. Polyaspartic acid ester resin is typically derived from renewable resources, making it environmentally friendly and aligning with the modern coating industry's pursuit of sustainable development. The synergistic effect of epoxy resin and polyaspartic acid ester resin significantly improves weather resistance and coating adhesion, achieving an optimized balance across multiple performance indicators for this solvent-free coating.

[0033] The isocyanate groups (-NCO) in hexamethylene diisocyanate-based biuret polyisocyanate can react with polyols, polyaspartic acid ester resins, and epoxy resins to form urethane bonds, thereby linking the molecules together to form the macromolecular structure of polyurethane. Its biuret structure increases the rigidity and stability of the molecule to a certain extent. The cyclic structure of dicyclohexylmethane diisocyanate provides a certain degree of rigidity to the molecule, and the presence of the cyclohexyl group gives the molecule good weather resistance and chemical resistance. Mixing the two isocyanates in a certain mass ratio can combine their respective advantages. The mass ratio of the two isocyanates affects the performance of the coating; using a mass ratio of hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate of 1.5-2:1 yields the best performance.

[0034] 2. In this invention, the dispersant enables pigments and fillers to be uniformly dispersed in the coating system, preventing agglomeration and improving the stability and coating performance of the coating; the dehydrating agent removes trace amounts of moisture from the raw materials, avoiding defects such as bubbles and blistering caused by the reaction of moisture with isocyanate to generate carbon dioxide, thus ensuring the quality of the coating; the catalyst accelerates the reaction rate of polyols and isocyanates, controlling the curing time of the coating; and the coupling agent enhances the bonding force between fillers (such as mica powder and titanium dioxide) and organic resins, thereby improving the overall mechanical properties and aging resistance of the coating.

[0035] 3. In this invention, titanium dioxide is not only a white pigment, but also absorbs ultraviolet rays, protecting the coating from photoaging, which is crucial for improving the aging resistance. Mica powder has a unique flake structure, which can form a physical shield in the coating, shielding the paint film from the damage of sunlight and ultraviolet rays, improving the aging resistance of the coating, and at the same time inhibiting the penetration of corrosive media, improving the anti-corrosion performance of the coating. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] The substances used in the following examples and comparative examples are all commercially available.

[0038] Among them, the polyester polyol NGPS-2320, with a hydroxyl value of 230±20mgKOH / g and a viscosity of 2500-4500mPa.s at 25℃, was purchased from Zhangjiagang Nanguang Chemical Co., Ltd.

[0039] The polyester polyol NGPS-260, with a hydroxyl value of 250±20mgKOH / g and a viscosity of 6000-9000mPa.s at 25℃, was purchased from Zhangjiagang Nanguang Chemical Co., Ltd.

[0040] EVONI K Oxyester HS2272, hydroxyl value 215±5mgKOH / g, viscosity 1300mPa.s, purchased from Evonik, Germany.

[0041] Polyether polyol DL3000D, functionality 2, molecular weight 3000, hydroxyl value 37-39 mgKOH / g, viscosity at 25℃ is 550-600 mPa.s, purchased from Shandong Lanxing Dongda.

[0042] Polyether polyol EP-330NG, functionality 3, molecular weight 5000, hydroxyl value 33-35 mgKOH / g, viscosity at 25℃ is 800-950 mPa.s, purchased from Shandong Lanxing Dongda.

[0043] Polyether polyol EP-3600, functionality 3, molecular weight 6000, hydroxyl value 27-29 mgKOH / g, viscosity at 25℃ is 1100-1300 mPa.s, purchased from Shandong Lanxing Dongda.

[0044] Hexamethylene diisocyanate-based biuret polyisocyanate, -NCO mass fraction 21.7–22.3%, purchased from Wanhua Chemical. HB-100.

[0045] Polyaspartic acid ester resin, NH equivalent 277 g / mol, was purchased from Shenzhen Feiyang Junyan New Material Co., Ltd. as F420.

[0046] The epoxy resin is bisphenol F type epoxy resin with an epoxy equivalent of 168-175 g / eq, and it was purchased from Dow Chemical Company of the United States as DER-354 type epoxy resin.

[0047] The dispersant YRFC-06 was purchased from Guangzhou Yourun Synthetic Materials Co., Ltd.

[0048] The titanium dioxide was purchased from Zhejiang Zhitai Nanomaterials Co., Ltd., and it is model ZT-T06H titanium dioxide with a particle size of 30nm.

[0049] The mica powder uses a particle size of 800 mesh.

[0050] The dehydrating agent was purchased from Zhengzhou Chaorong Nanomaterials Co., Ltd., specifically the CR-1273 molecular sieve with a particle size D50 of 2-4 μm.

[0051] Example 1

[0052] A method for preparing a solvent-free coating includes the following steps:

[0053] A. Material preparation:

[0054] Prepare components A and B with a mass ratio of 1:1;

[0055] By weight, component A comprises: 45 parts polyester polyol NGPS-2320, 35 parts polyether polyol EP-330NG, 10 parts polyaspartic acid ester resin, 2.5 parts epoxy resin, 6 parts titanium dioxide, 5 parts mica powder, 0.3 parts dispersant, 1 part dehydrating agent, 0.6 parts catalyst dibutyltin dilaurate, 1 part triethoxy[4-(trifluoromethyl)phenyl]silane, and 2 parts γ-(2,3-epoxypropoxy)propyltrimethoxysilane;

[0056] Component B consists of hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate in a mass ratio of 1.8:1.

[0057] B. Mix polyester polyol, polyether polyol, polyaspartic acid ester resin, and epoxy resin, heat to 40°C, stir at 1200 r / min for 30 min, then add titanium dioxide, mica powder, dispersant, molecular sieve dehydrating agent, catalyst, triethoxy[4-(trifluoromethyl)phenyl]silane, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and stir again at 1500 r / min for 40 min to obtain component A;

[0058] C. Mix hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate, stir at a speed of 1200 r / min for 30 min to obtain component B;

[0059] D. Mix components A and B, stir at a speed of 800 r / min for 20 min, and the solvent-free coating is obtained.

[0060] Example 2

[0061] A method for preparing a solvent-free coating includes the following steps:

[0062] A. Material preparation:

[0063] Prepare components A and B with a mass ratio of 1:1;

[0064] By mass, component A comprises: 60 parts polyester polyol NGPS-260, 30 parts polyether polyol DL3000D, 6 parts polyaspartic acid ester resin, 2 parts epoxy resin, 8 parts titanium dioxide, 2 parts mica powder, 1 part dispersant, 0.3 parts dehydrating agent, 1.3 parts catalyst stannous octoate, and 2 parts 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane;

[0065] Component B consists of hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate in a mass ratio of 2:1.

[0066] B. Mix polyester polyol, polyether polyol, polyaspartic acid ester resin, and epoxy resin, heat to 30°C, stir at 800 r / min for 20 min, then add titanium dioxide, mica powder, dispersant, molecular sieve dehydrating agent, catalyst, and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, stir again at 800 r / min for 20 min to obtain component A;

[0067] C. Mix hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate, stir at 800 r / min for 20 min to obtain component B;

[0068] D. Mix components A and B, stir at a speed of 800 r / min for 30 min, and the solvent-free coating is obtained.

[0069] Example 3

[0070] A method for preparing a solvent-free coating includes the following steps:

[0071] A. Material preparation:

[0072] Prepare components A and B with a mass ratio of 1:1;

[0073] By weight, component A comprises: 50 parts polyester polyol EVONI K Oxyester HS2272, 25 parts polyether polyol EP-3600, 10 parts polyaspartic acid ester resin, 3 parts epoxy resin, 8 parts titanium dioxide, 5 parts mica powder, 0.8 parts dispersant, 0.5 parts dehydrating agent, 1 part catalyst WCAT-S12 (Guangzhou Yourun Synthetic Materials Co., Ltd.), 2.5 parts γ-aminopropyltriethoxysilane, and 0.3 parts iron oxide red;

[0074] Component B consists of hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate in a mass ratio of 1.5:1.

[0075] B. Mix polyester polyol, polyether polyol, polyaspartic acid ester resin, and epoxy resin, heat to 50°C, stir at 1000 r / min for 30 min, then add titanium dioxide, mica powder, dispersant, molecular sieve dehydrating agent, catalyst, γ-aminopropyltriethoxysilane, and iron oxide red, and stir again at 900 r / min for 40 min to obtain component A;

[0076] C. Mix hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate, stir at 1000 r / min for 30 min to obtain component B;

[0077] D. Mix components A and B, stir at a speed of 1000 r / min for 20 min, and the solvent-free coating is obtained.

[0078] Example 4

[0079] A method for preparing a solvent-free coating includes the following steps:

[0080] A. Material preparation:

[0081] Prepare components A and B with a mass ratio of 1:1;

[0082] By weight, component A comprises: 45 parts polyester polyol NGPS-2320, 35 parts polyether polyol EP-330NG, 10 parts polyaspartic acid ester resin, 2.5 parts epoxy resin, 6 parts titanium dioxide, 5 parts mica powder, 0.3 parts dispersant, 1 part dehydrating agent, 0.6 parts catalyst dibutyltin dilaurate, and 3 parts γ-(2,3-epoxypropoxy)propyltrimethoxysilane;

[0083] Component B consists of hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate in a mass ratio of 1.8:1.

[0084] B. Mix polyester polyol, polyether polyol, polyaspartic acid ester resin, and epoxy resin, heat to 40°C, stir at 1200 r / min for 30 min, then add titanium dioxide, mica powder, dispersant, molecular sieve dehydrating agent, catalyst, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and stir again at 1500 r / min for 40 min to obtain component A;

[0085] C. Mix hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate, stir at a speed of 1200 r / min for 30 min to obtain component B;

[0086] D. Mix components A and B, stir at a speed of 800 r / min for 20 min, and the solvent-free coating is obtained.

[0087] Example 5

[0088] A method for preparing a solvent-free coating includes the following steps:

[0089] A. Material preparation:

[0090] Prepare components A and B with a mass ratio of 1:1;

[0091] By weight, component A comprises: 45 parts polyester polyol NGPS-2320, 35 parts polyether polyol EP-330NG, 10 parts polyaspartic acid ester resin, 2.5 parts epoxy resin, 6 parts titanium dioxide, 5 parts mica powder, 0.3 parts dispersant, 1 part dehydrating agent, 0.6 parts catalyst dibutyltin dilaurate, and 3 parts triethoxy[4-(trifluoromethyl)phenyl]silane;

[0092] Component B consists of hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate in a mass ratio of 1.8:1.

[0093] B. Mix polyester polyol, polyether polyol, polyaspartic acid ester resin, and epoxy resin, heat to 40°C, stir at 1200 r / min for 30 min, then add titanium dioxide, mica powder, dispersant, molecular sieve dehydrating agent, catalyst, and triethoxy[4-(trifluoromethyl)phenyl]silane, stir again at 1500 r / min for 40 min to obtain component A;

[0094] C. Mix hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate, stir at a speed of 1200 r / min for 30 min to obtain component B;

[0095] D. Mix components A and B, stir at a speed of 800 r / min for 20 min, and the solvent-free coating is obtained.

[0096] Comparative Example 1

[0097] A method for preparing a solvent-free coating includes the following steps:

[0098] A. Material preparation:

[0099] Prepare components A and B with a mass ratio of 1:1;

[0100] By mass, component A comprises: 45 parts polyester polyol NGPS-2320, 35 parts polyether polyol EP-330NG, 12.5 parts polyaspartic acid ester resin, 6 parts titanium dioxide, 5 parts mica powder, 0.3 parts dispersant, 1 part dehydrating agent, 0.6 parts catalyst dibutyltin dilaurate, 1 part triethoxy[4-(trifluoromethyl)phenyl]silane, and 2 parts γ-(2,3-epoxypropoxy)propyltrimethoxysilane;

[0101] Component B consists of hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate in a mass ratio of 1.8:1.

[0102] B. Mix polyester polyol, polyether polyol, and polyaspartic acid ester resin, heat to 40°C, stir at 1200 r / min for 30 min, then add titanium dioxide, mica powder, dispersant, molecular sieve dehydrating agent, catalyst, triethoxy[4-(trifluoromethyl)phenyl]silane, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and stir again at 1500 r / min for 40 min to obtain component A;

[0103] C. Mix hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate, stir at a speed of 1200 r / min for 30 min to obtain component B;

[0104] D. Mix components A and B, stir at a speed of 800 r / min for 20 min, and the solvent-free coating is obtained.

[0105] Comparative Example 2

[0106] A method for preparing a solvent-free coating includes the following steps:

[0107] A. Material preparation:

[0108] Prepare components A and B with a mass ratio of 1:1;

[0109] By weight, component A comprises: 45 parts polyester polyol NGPS-2320, 35 parts polyether polyol EP-330NG, 10 parts polyaspartic acid ester resin, 2.5 parts epoxy resin, 6 parts titanium dioxide, 5 parts mica powder, 0.3 parts dispersant, 1 part dehydrating agent, 0.6 parts catalyst dibutyltin dilaurate, 1 part triethoxy[4-(trifluoromethyl)phenyl]silane, and 2 parts γ-(2,3-epoxypropoxy)propyltrimethoxysilane;

[0110] Component B is hexamethylene diisocyanate-based biuret polyisocyanate;

[0111] B. Mix polyester polyol, polyether polyol, polyaspartic acid ester resin, and epoxy resin, heat to 40°C, stir at 1200 r / min for 30 min, then add titanium dioxide, mica powder, dispersant, molecular sieve dehydrating agent, catalyst, triethoxy[4-(trifluoromethyl)phenyl]silane, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and stir again at 1500 r / min for 40 min to obtain component A;

[0112] C. Mix components A and B, stir at 800 r / min for 20 min to obtain solvent-free coating.

[0113] The impact resistance, abrasion resistance, artificial weathering resistance and adhesion of the coating were tested according to HG / T5177 2017, and the results are shown in Table 1.

[0114] Table 1

[0115]

[0116]

[0117] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solvent-free coating, characterized in that, The raw materials consist of component A and component B in a mass ratio of 1:1; By weight, component A comprises: 45-60 parts polyester polyol, 25-35 parts polyether polyol, 6-10 parts polyaspartic acid ester resin, 2-3 parts epoxy resin, 6-8 parts titanium dioxide, 2-5 parts mica powder, 0.3-1 parts dispersant, 0.3-1 parts dehydrating agent, 0.6-1.3 parts catalyst, and 2-3 parts coupling agent; Component B consists of hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate in a mass ratio of 1.5-2:

1. The number-average molecular weight of the polyester polyol is 200-5000, the hydroxyl value is 200-300 mgKOH / g, and the viscosity at 25°C is 2500-10000 mPa·s. The polyether polyol has a functionality of 2-3, a hydroxyl value of 25-40 mgKOH / g, and a viscosity of 500-1300 mPa.s at 25°C. The NCO content of the hexamethylene diisocyanate-based biuret polyisocyanate is 21.7% to 22.3%. The coupling agent is triethoxy[4-(trifluoromethyl)phenyl]silane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:1.6-2.3; The titanium dioxide has a particle size of 15-30 nm and a specific surface area of ​​30-50 m². 2 / g; The mica powder has a particle size of 600-800 mesh.

2. The solvent-free coating according to claim 1, characterized in that, The catalyst is an organotin catalyst, selected from one or both of dibutyltin dilaurate and stannous octoate.

3. The solvent-free coating according to claim 1, characterized in that, The dehydrating agent is a molecular sieve dehydrating agent, and the D50 of the molecular sieve is 2-4 μm.

4. The solvent-free coating according to claim 1, characterized in that, Component A also includes 0.2-0.5 parts of pigment, which is selected from one or more of iron oxide red, chrome yellow, iron oxide yellow, iron oxide black, and molybdenum chrome red.

5. The method for preparing a solvent-free coating as described in claim 1, characterized in that, Includes the following steps: Polyester polyol, polyether polyol, polyaspartic acid ester resin and epoxy resin are mixed, heated to 30-50℃ and stirred. Then titanium dioxide, mica powder, dispersant, molecular sieve dehydrating agent, catalyst and coupling agent are added and stirred again to obtain component A. Hexamethylene diisocyanate-based biuret polyisocyanate and dicyclohexylmethane diisocyanate were mixed and stirred to obtain component B. Mix component A and component B and stir to obtain solvent-free coating.

6. The method for preparing a solvent-free coating according to claim 5, characterized in that, The stirring speed is 800-1500 r / min and the stirring time is 20-50 min.

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