Polyurethane topcoat and preparation method thereof

Abstract

The application discloses a polyurethane finish and a preparation method thereof, and belongs to the technical field of polyurethane finishes, and comprises components A and B with a mass ratio of 5-20:1; according to weight, the component A comprises 40-50 parts of a hydroxyl acrylic acid dispersion, 8-15 parts of a polyaspartic ester resin, 0.5-2 parts of a defoaming agent, 1-3 parts of a dispersing agent, 1-3 parts of a rheological auxiliary agent, 10-15 parts of pigments, 10-15 parts of fillers and 15-20 parts of a first solvent; the component B comprises 70-90 parts of an aliphatic isocyanate curing agent and 10-30 parts of a second solvent; component A is first treated, that is, the first solvent, the hydroxyl acrylic acid dispersion and the polyaspartic ester resin are dispersed, then the dispersing agent and the defoaming agent are dispersed, then the pigments and the fillers are dispersed, and finally the viscosity is adjusted; component B is then treated, that is, the curing agent and the second solvent are dispersed, and finally the component A and the component B are mixed to obtain an ultra-fast-drying polyurethane finish; compared with the prior art, the finish obtained by the application has the advantages of improved drying speed, hardness and corrosion resistance, enhanced adhesion and prolonged adaptation period.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polyurethane finish, and particularly relates to a polyurethane finish and a preparation method thereof. BACKGROUND

[0002] The polyurethane finish is suitable for engineering machinery coating, can effectively resist ultraviolet rays, rain erosion and mechanical wear, and improves the appearance durability and aesthetics of equipment. However, the traditional polyurethane finish is prone to brittle fracture in a low-temperature and humid environment, and the surface drying and drying time are significantly prolonged. When construction is carried out in a low-temperature and humid environment, the slow drying speed can cause problems such as blistering of the paint film, reduction of adhesion, and the like, which seriously affect the protective performance of the coating. In addition, the reaction activity of isocyanate in the coating system is high, which not only causes crosslinking reaction with the hydroxyl groups in the film-forming material rapidly, but also causes side reaction with moisture in the environment to generate urea polymer and release CO2 gas, resulting in pinhole and orange peel phenomena of the paint film, affecting the appearance of the paint film, and causing the viscosity of the coating to rise sharply after mixing, thereby greatly shortening the construction application period. In order to accelerate the drying speed, the existing technology adds organic tin catalyst or alcohol chain extender, which can easily cause problems such as "blistering", "false dryness", internal stress concentration, cracking, and the like, thereby damaging the comprehensive performance and service life of the paint film. SUMMARY

[0003] In view of the deficiencies of the existing polyurethane finish in terms of drying speed, application period and film performance, the present application aims to develop a new type of polyurethane finish, which can ensure rapid drying while improving the gloss, adhesion, impact resistance and good corrosion resistance of the paint film, ensure a reasonable application period, and meet the use requirements of engineering machinery in complex environments, as follows:

[0004] A polyurethane finish, comprising A component and B component, the mass ratio of the A component and the B component being 5-20:1; the A component comprises, by weight, 40-50 parts of hydroxyl acrylate dispersion, 8-15 parts of polyaspartic ester resin, 0.5-2 parts of defoaming agent, 1-3 parts of dispersing agent, 1-3 parts of rheological aid, 10-15 parts of pigment, 10-15 parts of filler, and 15-20 parts of first solvent;

[0005] The B component comprises, calculated in parts by weight, 70-90 parts of aliphatic isocyanate curing agent, 10-30 parts of second solvent; the hydroxyl acrylic dispersion is selected from one or more of BS-965, BS-960; the polyaspartic ester resin is selected from one or more of Desmophen® NH 1520, Desmophen® NH 1420 or Zhuhai Feiyang Chemical F421; the solid content of the hydroxyl acrylic dispersion is 59-66%, the hydroxyl value is 51-56 mg KOH / g, and the amino equivalent of the polyaspartic ester resin is 270-290 g / mol.

[0006] As a preferred mode, the defoaming agent is selected to be a non-silicone polymer compounded with dodecyl glyceryl itaconate; the weight ratio of the non-silicone polymer to dodecyl glyceryl itaconate is 3:1-2; the non-silicone polymer is selected from one or more of EFKA 2020, YCK-655, BYK-011.

[0007] As a preferred mode, the dispersant is selected to be a polyurethane type dispersant compounded with a dithiane type organic sulfur compound; the weight ratio of the polyurethane type dispersant to the dithiane type organic sulfur compound is 3-5:1; the polyurethane type dispersant is selected from Efka PU4061, and / or, KEPERDISP®-639, and the dithiane type organic sulfur compound is selected from 2,5-dimethyl-2,5-dihydroxy-1,4-dithiane, and / or, 2,5-dimethyl mercapto-1,4-dithiane.

[0008] As a preferred mode, the rheological aid is selected to be a polyamide wax compounded with a metal soap of oleic acid; the weight ratio of the polyamide wax to the metal soap of oleic acid is 5-10:1; the polyamide wax is selected from one or more of THIXATROL® PM 8056, THIXATROL MAX, BYK 440 RC-820, and the metal soap of oleic acid is selected to be one or more of zinc oleate, magnesium oleate, calcium oleate.

[0009] As a preferred mode, the aliphatic isocyanate curing agent is selected from one or more of Desmodur® N75 MPA / X, Hafotex® SH-2836, Desmodur® N75 BA, Hafotex® SH-3592.

[0010] As a preferred mode, the pigment is selected from one or more of rutile titanium dioxide, iron oxide red, carbon black, phthalocyanine blue, phthalocyanine green; the filler is selected from one or more of nano-zinc oxide, mica powder, talc powder, kaolin, bentonite.

[0011] As a preferred mode, the first solvent and the second solvent are both volatile organic solvents, and the first solvent and the second solvent are respectively selected from one or more of n-butanol, isobutyl alcohol, xylene, butyl acetate, ethylene glycol diacetate, and 1,2-propanediol.

[0012] As a preferred mode, the polyaspartic ester resin is selected from one or more of Desmophen® NH 1520, Desmophen® NH 1420, or Zhuhai Feiyang Chemical F421.

[0013] A preparation method of a polyurethane finish, comprising the following steps:

[0014] S1: first, sequentially add the first solvent, the hydroxyl acrylate dispersion, and the polyaspartic ester resin into a dispersion kettle, and disperse for 10-30 minutes;

[0015] S2: then, sequentially add the dispersant and the defoaming agent into the dispersion kettle, and disperse for 10-30 minutes;

[0016] S3: then, add the rheological aid into the dispersion kettle, and disperse for 10-30 minutes;

[0017] S4: then, sequentially add the pigment and the filler into the dispersion kettle, and disperse for 30-60 minutes, and then transfer to a grinding machine to grind to a fineness of ≤40 μm;

[0018] S5: then, use the first solvent to adjust the viscosity to 90-100 KU, and obtain component A after filtration;

[0019] S6: then, sequentially add the aliphatic isocyanate curing agent and the second solvent into the dispersion kettle, and stir until uniform, and disperse for 15-30 minutes, and obtain component B;

[0020] S7: finally, add component B into component A, mix until uniform, and obtain the polyurethane finish.

[0021] As a preferred mode, the dispersant in step S2 is a mixture obtained by dispersing a polyurethane type dispersant and a dithiane type organic sulfur compound at a weight ratio of 3-5:1 for 10-20 minutes; the defoaming agent in step S2 is a mixture obtained by dispersing a non-silicone type polymer and dodecyl glyceryl itaconate at a weight ratio of 3:1-2 for 10-20 minutes; and the rheological aid in step S3 is a mixture obtained by dispersing polyamide wax and metal oleate soap at a weight ratio of 5-10:1 for 10-20 minutes.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] 1. By using a complex of non-silicone polymer and dodecyl glyceryl itaconate as a defoaming agent, the defoaming and antifoaming effects are enhanced by destroying the bubble membrane stability, the associated network and the micropore channel formed during film formation, avoiding the problems of "foam stifling" caused by rapid surface drying and poor corrosion resistance and stability. Dodecyl glyceryl itaconate can wrap around the aliphatic isocyanate curing agent molecules, play a barrier role, hinder the direct contact of the isocyanate group of the aliphatic isocyanate curing agent with the hydroxyl group in the film-forming material, at the same time, dodecyl glyceryl itaconate can undergo controllable low-speed crosslinking with the aliphatic isocyanate curing agent, the two effects cooperate synergistically, significantly reducing the curing reaction rate between the isocyanate group and the film-forming material, thereby extending the pot life of the coating. After the coating is applied, the solvent in the wet film gradually volatilizes, the dodecyl glyceryl itaconate migrates to the surface of the paint film due to the repulsion of the hydrophilic group and the internal hydrophobic environment, the barrier wrapping the aliphatic isocyanate curing agent is broken, releasing the "shielded" isocyanate group, indirectly improving the contact efficiency of the isocyanate group and the film-forming material, effectively improving the drying speed of the polyurethane coating in a low-temperature and high-humidity environment, and forming a hydrophobic layer on the surface of the coating through the hydrophobic group of dodecyl glyceryl itaconate, improving the water resistance and corrosion resistance of the paint film. Due to its hydrophobicity, it reduces the penetration of moisture in the paint film in a humid environment, reducing the side reaction of isocyanate and water to generate CO2 from the source, inhibiting the generation of bubbles, reducing the interference of moisture on the curing process of the coating, and significantly improving the defects such as pinholes and orange peel of the paint film. In addition, dodecyl glyceryl itaconate is embedded in the curing network through intermolecular interaction, forming elastic buffer points, dispersing the internal stress generated when the film-forming material and the aliphatic isocyanate curing agent rapidly crosslink, improving the impact resistance of the paint film, effectively solving the problem of brittle cracking of traditional polyurethane paint film at low temperature; at the same time, when non-silicone polymer and dodecyl glyceryl itaconate are used in combination, the wetting performance of pigments and fillers can be improved, and the gloss of the paint film can be improved.

[0024] 2.The application introduces dithiane organic sulfur compounds as dispersants in combination with polyurethane dispersants, which not only improves the dispersion stability of pigments and fillers, but also improves the uniformity of the distribution of the surface stress of the paint film through the comprehensive effect of surface adsorption and steric hindrance; and through the formation of coordination bonds or hydrogen bond bridging and crosslinking network anchoring between dithiane organic sulfur compounds and polar substances in the substrate, the adhesion of the paint film is improved, so that the coating still maintains high adhesion after aging in a low-temperature and humid environment; at the same time, in a humid environment, the active groups (such as hydroxyl or mercapto groups) released by the dithiane organic sulfur compounds coordinate with the aliphatic isocyanate curing agent, which reduces the activation energy of the reaction and accelerates the curing speed of the hydroxyl acrylate dispersion and the aliphatic isocyanate curing agent, thereby improving the drying speed of the paint film in a low-temperature and high-humidity environment, avoiding the adhesion reduction caused by incomplete curing and blistering caused by water retention; the slow-release catalysis of dithiane organic sulfur compounds and the steric hindrance of polyurethane dispersants synergize to make the paint film gradiently cured, achieving the balance between construction and low-temperature fast drying, avoiding both the “blistering” caused by rapid surface closure and the “false dry” problem, and improving the mechanical properties and corrosion resistance of the paint film. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0026] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0027] The present application provides a polyurethane topcoat, which comprises A component and B component, and the mass ratio of the A component and the B component is 5-20:1.

[0028] The A component comprises, calculated by weight parts, 40-50 parts of hydroxyl acrylate dispersion, 8-15 parts of polyaspartate resin, 0.5-2 parts of defoaming agent, 1-3 parts of dispersant, 1-3 parts of rheological additive, 10-15 parts of pigment, 10-15 parts of filler, and 15-20 parts of first solvent.

[0029] The B component comprises, calculated by weight parts, 70-90 parts of aliphatic isocyanate curing agent and 10-30 parts of second solvent.

[0030] The defoaming agent is a combination of non-silicone polymers and dodecyl glyceryl itaconate.

[0031] In the present application, the hydroxyl value of the hydroxyl acrylate dispersion has a significant influence on the reactivity with the aliphatic isocyanate curing agent, a higher hydroxyl value content means more active sites for crosslinking reaction with the curing agent, which increases the crosslinking density of the paint film, thereby enhancing the hardness and wear resistance of the coating, but at the same time it will also reduce the flexibility of the coating, in order to ensure the hardness and flexibility of the coating, the hydroxyl value of the hydroxyl acrylate dispersion used in the present application is 51-56 mg KOH / g. The hydroxyl acrylate dispersion with high solid content can form a thicker coating under the same application conditions, thereby reducing the evaporation of solvent and improving the chemical resistance of the coating, but the hydroxyl acrylate dispersion with too high solid content will reduce the overall flexibility of the paint film, causing the paint film to crack when the substrate deforms, in order to ensure the chemical resistance and flexibility of the paint film, the solid content of the hydroxyl acrylate dispersion used in the present application is 59-66%, and the hydroxyl acrylate dispersion is selected from BS-965 and / or BS-960.

[0032] In the present application, the amino equivalent weight of the polyaspartic ester resin has a significant influence on the reactivity with the aliphatic isocyanate curing agent and the performance of the coating: the lower the amino equivalent weight, the more active hydrogen contained in the resin, the higher the reactivity with the aliphatic isocyanate curing agent, and the faster the curing speed, however, too high reactivity will shorten the pot life of the coating and reduce the convenience of operation; the higher the amino equivalent weight, the less active hydrogen contained in the resin, the lower the reactivity, and the slower the curing speed, thereby extending the construction time, but this may also result in slow development of the hardness and wear resistance of the coating, in order to ensure the curing speed, pot life and coating performance of the coating, the amino equivalent weight of the polyaspartic ester resin is 270-290 g / mol, and the polyaspartic ester resin is selected from one or more of Desmophen® NH 1520, Desmophen® NH 1420, Zhuhai Feiyang Chemical F421; the aliphatic isocyanate curing agent is selected from one or more of Desmodur® N75 MPA / X, Hafotex® SH-2836, Desmodur® N75 BA, Hafotex® SH-3592.

[0033] The polyaspartic ester resin and the hydroxyl acrylate dispersion are compounded in the present application to achieve low-temperature curing, but fast drying will hinder the evaporation of solvent inside the coating, leading to "blistering" or internal stress concentration, thereby affecting the mechanical strength, in addition, fast curing will also result in incomplete crosslinking reaction of the coating, especially in solvent-based systems, residual solvent or insufficiently reacted groups will also reduce the chemical corrosion resistance and long-term stability.

[0034] In the construction process or curing process, air, CO2 and other gases will mix into the coating system to form a blister on the surface of the coating film, and after the paint film is dried, pinholes and orange peel phenomenon will be formed on the surface of the paint film, thereby affecting the appearance of the paint film. The present application has found that by using a non-silicone polymer and dodecyl glyceryl itaconate, the complex will be adsorbed on the gas-liquid interface, thereby reducing the stability of the bubbles. In addition, during the film forming process, the intermolecular forces of dodecyl glyceryl itaconate and the micro-pore channels formed by its arrangement provide a path for gas escape. This mechanism not only inhibits the regeneration of bubbles, but also realizes rapid defoaming, effectively solving the problems of "blistering" caused by rapid surface drying, poor corrosion resistance and stability. Dodecyl glyceryl itaconate can wrap around the aliphatic isocyanate curing agent molecules, play a barrier role, and hinder the direct contact between the isocyanate group of the aliphatic isocyanate curing agent and the hydroxyl group in the film forming material. At the same time, dodecyl glyceryl itaconate can undergo controllable low-speed crosslinking with the aliphatic isocyanate curing agent. The two effects work together to significantly reduce the curing reaction rate between the isocyanate group and the film forming material, thereby extending the pot life of the coating. After the coating is applied, the solvent in the wet film gradually evaporates. Due to the repulsion of the hydrophilic group and the internal hydrophobic environment, dodecyl glyceryl itaconate migrates to the surface of the paint film. The barrier that originally wrapped the aliphatic isocyanate curing agent is broken, releasing the "shielded" isocyanate group, indirectly improving the contact efficiency of the isocyanate group and the film forming material, effectively improving the drying speed of the polyurethane coating in a low temperature and high humidity environment. And by forming a hydrophobic layer on the surface of the coating through the hydrophobic group of dodecyl glyceryl itaconate, the water resistance and corrosion resistance of the paint film are improved. Because of its hydrophobicity, it reduces the penetration of water in the paint film in a humid environment, reducing the side reaction of isocyanate and water to generate CO2 from the source, inhibiting the generation of bubbles, reducing the interference of water on the curing process of the coating, and significantly improving the defects such as pinholes and orange peel of the paint film. In addition, dodecyl glyceryl itaconate is embedded in the curing network through intermolecular interaction, forming elastic buffer points, dispersing the internal stress generated when the film forming material and the aliphatic isocyanate curing agent rapidly crosslink, improving the impact resistance of the paint film, and effectively solving the problem of brittle fracture of traditional polyurethane paint film at low temperature; at the same time, when the non-silicone polymer and dodecyl glyceryl itaconate are used together, the wetting performance of pigments and fillers can be improved, thereby improving the gloss of the paint film.

[0035] In the topcoat system of the present application, the pigments are selected from one or more of rutile titanium dioxide, iron oxide red, carbon black, phthalocyanine blue, and phthalocyanine green; and the fillers are selected from one or more of nano-zinc oxide, mica powder, talc powder, kaolin, and bentonite.

[0036] In order to ensure that the hydroxy acrylic resin and the polyaspartic ester and the aliphatic isocyanate curing agent are crosslinked to produce low-temperature curing performance of the topcoat, meanwhile, the problem of too fast curing speed caused by the two compounds is solved, and the problem of too low curing speed of the entire film caused by the low-speed crosslinking between the dodecyl glyceryl itaconate and the aliphatic isocyanate curing agent is avoided, therefore, the weight ratio of the non-organic silicon polymer and the dodecyl glyceryl itaconate is controlled to be 3:1-2, the non-organic silicon polymer is selected from one or more of EFKA 2020, YCK-655 and BYK-011, and the dodecyl glyceryl itaconate is mainly polymerized from polyols, itaconic anhydride and glycidol or glycidol derivatives.

[0037] In the topcoat system of the present application, the dispersant is selected from the compound of the polyurethane dispersant and the dithiane organic sulfur compound. It is found through research that the introduction of the dithiane organic sulfur compound and the polyurethane dispersant compound is used, through surface adsorption and steric hindrance effect, not only the dispersion stability of the pigment and the filler is improved, but also the distribution uniformity of the film surface stress is improved, and through the coordination bond or hydrogen bond bridging and crosslinking network anchoring of the dithiane organic sulfur compound and the polar substances in the substrate, the adhesion between the film and the substrate is improved, so that the coating still maintains high adhesion after aging in a low-temperature and humid environment. It is also found that in a humid environment, the active groups released by the dithiane organic sulfur compound can act as a catalyst to accelerate the curing speed of the hydroxy acrylic dispersion and the aliphatic isocyanate curing agent, further improving the drying speed of the film in a low-temperature and high-humidity environment, avoiding the adhesion reduction caused by the water retention and incomplete curing. The slow-release catalysis of the dithiane organic sulfur compound and the steric hindrance of the polyurethane dispersant are synergistic, so that the film is gradiently cured, achieving the balance between the construction and the low-temperature and fast-drying performance, avoiding the “blistering” caused by the rapid surface closure, avoiding the “false dry” problem, and improving the mechanical properties and corrosion resistance of the film.

[0038] In order to balance the construction performance such as sag resistance, drying time, leveling property and low-temperature and fast-drying performance, and improve the dispersion stability of the pigment and the filler and the adhesion and corrosion resistance of the film, the weight ratio of the polyurethane dispersant and the dithiane organic sulfur compound is 3-5:1, the polyurethane dispersant is selected from Efka PU4061 and / or KEPERDISP®-639, and the dithiane organic sulfur compound is selected from 2,5-dimethyl-2,5-dihydroxy-1,4-dithiane and / or 2,5-dimethyl mercapto-1,4-dithiane.

[0039] In the present application, rheological aids are compounded with polyamide wax and metal soap of oleic acid. The polyamide wax can swell in the solvent and form a network structure between molecules. The carboxylate of the metal soap of oleic acid can be adsorbed on the surface of the pigment to form a negatively charged layer on the surface of the pigment. Through the dual mechanisms of "charge stabilization + network locking", not only the aggregation of pigments and fillers is prevented, the settling of pigments and fillers is avoided, the stability of the paint in the storage stage is improved, but also the anti-sagging performance of the paint and the gloss of the coating are improved. Through the formation of a dense protective layer and the inhibition of the corrosion of pigments and fillers, the hardness, wear resistance and corrosion resistance of the paint are enhanced. The weight ratio of the polyamide wax to the metal soap of oleic acid is 5-10:1. The polyamide wax is selected from one or more of PM8056, THIXATROL MAX, BYK 440 RC-820. The metal soap of oleic acid is selected from one or more of zinc oleate, magnesium oleate, calcium oleate.

[0040] In the present application, the first solvent and the second solvent are volatile organic solvents. The first solvent and the second solvent are respectively selected from one or more of n-butanol, isobutyl alcohol, xylene, butyl acetate, ethylene glycol diacetate, 1,2-propanediol.

[0041] A preparation method of a polyurethane finish, comprising the following steps:

[0042] S1: first, the first solvent, the hydroxyl acrylate dispersion and the polyaspartic ester resin are sequentially put into a dispersion kettle and dispersed for 10-30 minutes;

[0043] S2: then, the dispersant and the defoaming agent are sequentially put into the dispersion kettle and dispersed for 10-30 minutes;

[0044] S3: then, the rheological aid is put into the dispersion kettle and dispersed for 10-30 minutes;

[0045] S4: then, the pigments and the fillers are sequentially put into the dispersion kettle and dispersed for 30-60 minutes, and then transferred to a grinding machine for grinding to a fineness of ≤40 μm;

[0046] S5: then, the viscosity is adjusted to 90-100 KU using the first solvent, and then filtered to obtain component A;

[0047] S6: then, the aliphatic isocyanate curing agent and the second solvent are sequentially put into the dispersion kettle, uniformly stirred and dispersed for 15-30 minutes to obtain component B;

[0048] S7: finally, component B is added to component A and uniformly mixed to obtain the polyurethane finish.

[0049] The dispersant in step S2 is a mixture obtained by dispersing a polyurethane dispersant and a dithiane organic sulfur compound at a weight ratio of 3-5:1 for 10-20 minutes.

[0050] The defoaming agent in step S2 is a mixture obtained by dispersing a non-silicone polymer and dodecyl glyceryl itaconate at a weight ratio of 3:1 to 2 for 10 to 20 minutes.

[0051] The rheological aid in step S3 is a mixture obtained by dispersing a polyamide wax and a metal soap of oleic acid at a weight ratio of 5 to 10:1 for 10 to 20 minutes. Example 1

[0052] The present example provides a polyurethane finish, which comprises an A component and a B component, and the mass ratio of the A component to the B component is 5:1.

[0053] The A component comprises, calculated by weight parts, 40 parts of a hydroxy acrylic dispersion, 8 parts of a polyaspartic ester resin, 0.5 parts of a defoaming agent, 1 part of a dispersing agent, 1 part of a rheological aid, 10 parts of a pigment, 10 parts of a filler, and 15 parts of a first solvent.

[0054] The B component comprises, calculated by weight parts, 70 parts of an aliphatic isocyanate curing agent and 10 parts of a second solvent.

[0055] A method for preparing a polyurethane finish:

[0056] First step: 12 parts of n-butanol (first solvent) and 40 parts of BS-965 (hydroxy acrylic dispersion), 8 parts of Desmophen® NH 1520 (polyaspartic ester resin) are sequentially put into a dispersing kettle and dispersed for 10 minutes.

[0057] Second step: a mixture obtained by dispersing 0.75 parts of Efka PU4061 (polyurethane type dispersing agent) and 0.25 parts of 2,5-dimethyl-2,5-dihydroxy-1,4-dithiane (dithiane type organic sulfur compound) for 10 minutes, and a mixture obtained by dispersing 0.3 parts of EFKA 2020 (non-silicone polymer) and 0.2 parts of dodecyl glyceryl itaconate for 10 minutes are sequentially put into the dispersing kettle and dispersed for 10 minutes.

[0058] Third step: a mixture obtained by dispersing 0.9 parts of THIXATROL® PM 8056 (polyamide wax) and 0.1 parts of zinc oleate (metal soap of oleic acid) for 10 minutes is put into the dispersing kettle and dispersed for 10 minutes.

[0059] Fourth step: 10 parts of rutile titanium dioxide (pigment) and 10 parts of mica powder (filler) are sequentially put into the dispersing kettle and high-speed dispersed for 30 minutes, and then transferred to a grinding machine for grinding to a fineness of ≤40 μm.

[0060] Fifth step: adjust the viscosity to 90 KU using 3 parts of n-butanol (first solvent), and obtain component A after filtration;

[0061] Sixth step: sequentially add 70 parts of Desmodur® N75 MPA / X (aliphatic isocyanate curing agent) and 10 parts of isobutanol (second solvent) into the dispersion kettle, stir uniformly, and disperse for 15 minutes to obtain component B;

[0062] Seventh step: add component B to component A, and the mass ratio of component A to component B is 5:1, and obtain the polyurethane finish after uniform mixing. Example 2

[0063] The present embodiment provides a polyurethane finish, which comprises component A and component B, and the mass ratio of component A to component B is 10:1;

[0064] The component A comprises, by weight parts, 45 parts of hydroxyl acrylic dispersion, 10 parts of polyaspartic ester resin, 1.3 parts of defoaming agent, 2 parts of dispersant, 1.1 parts of rheological aid, 12 parts of pigment, 12 parts of filler, and 16 parts of first solvent;

[0065] The component B comprises, by weight parts, 80 parts of aliphatic isocyanate curing agent and 20 parts of second solvent.

[0066] A method for preparing a polyurethane finish:

[0067] First step: sequentially add 14 parts of xylene (first solvent), 45 parts of BS-960 (hydroxyl acrylic dispersion), and 10 parts of Desmophen® NH 1420 (polyaspartic ester resin) into the dispersion kettle, and disperse for 30 minutes;

[0068] Second step: sequentially add the mixture obtained by dispersing 1.6 parts of KEPERDISP®-639 (polyurethane type dispersant) and 0.4 parts of 2,5-dimethylmercapto-1,4-dithiane (dithiane type organic sulfur compound) for 20 minutes, and the mixture obtained by dispersing 0.8 parts of YCK-655 (non-silicone type polymer) and 0.5 parts of dodecyl glyceryl itaconate for 20 minutes into the dispersion kettle, and disperse for 30 minutes;

[0069] Third step: add the mixture obtained by dispersing 0.5 parts of THIXATROL MAX (polyamide wax), 0.5 parts of RC-820 (polyamide wax), and 0.1 parts of magnesium oleate (metallic soap of oleic acid) for 10 minutes into the dispersion kettle, and disperse for 30 minutes;

[0070] Fourth step: 6 parts of iron oxide red (pigment), 6 parts of phthalocyanine blue (pigment), and 12 parts of nano zinc oxide (filler) are sequentially put into a dispersion kettle, dispersed for 60 minutes, and then transferred to a grinding machine to grind to a fineness of ≤40 μm;

[0071] Fifth step: 2 parts of xylene (first solvent) are used to adjust the viscosity to 100 KU, and after filtration, component A is obtained;

[0072] Sixth step: 80 parts of Hafotex® SH-2836 (aliphatic isocyanate curing agent) and 20 parts of xylene (second solvent) are sequentially put into a dispersion kettle, stirred uniformly, and dispersed for 30 minutes to obtain component B;

[0073] Seventh step: component B is added to component A, and the mass ratio of component A to component B is 10:1, and after uniform mixing, the polyurethane finish is obtained. Example 3

[0074] The present application provides a polyurethane finish, which comprises component A and component B, and the mass ratio of component A to component B is 20:1.

[0075] The component A comprises, by weight parts, 50 parts of hydroxy acrylic dispersion, 15 parts of polyaspartic ester resin, 2 parts of defoaming agent, 3 parts of dispersing agent, 3 parts of rheological aid, 15 parts of pigment, 15 parts of filler, and 20 parts of first solvent;

[0076] The component B comprises, by weight parts, 90 parts of aliphatic isocyanate curing agent and 30 parts of second solvent.

[0077] A preparation method of a polyurethane finish:

[0078] First step: 18 parts of ethylene glycol diacetate (first solvent), 25 parts of BS-960 (hydroxy acrylic dispersion), 25 parts of BS-965 (hydroxy acrylic dispersion), 7 parts of Desmophen® NH 1520 (polyaspartic ester resin), and 8 parts of Zhuhai Feiyang Chemical F421 (polyaspartic ester resin) are sequentially put into a dispersion kettle and dispersed for 30 minutes;

[0079] Second step: a mixture obtained by dispersing 1.5 parts of Efka PU4061 (polyurethane dispersant), 1 part of KEPERDISP®-639 (polyurethane dispersant) and 0.3 parts of 2,5-dimethyl-2,5-dihydroxy-1,4-dithiane (dithiane organic sulfur compound), 0.2 parts of 2,5-dimethylmercapto-1,4-dithiane (dithiane organic sulfur compound) for 20 minutes, and a mixture obtained by dispersing 0.5 parts of YCK-655 (non-silicone polymer), 1 part of BYK-011 (non-silicone polymer) and 0.5 parts of dodecyl glyceryl itaconate for 20 minutes, were sequentially added into a dispersing kettle and dispersed for 30 minutes;

[0080] Third step: a mixture obtained by dispersing 2.5 parts of RC-820 and 0.5 parts of calcium oleate (oleic acid metal soap) for 10 minutes was added into a dispersing kettle and dispersed for 30 minutes;

[0081] Fourth step: 15 parts of phthalocyanine green (pigment), 8 parts of talc (filler), and 7 parts of kaolin (filler) were sequentially added into a dispersing kettle and dispersed for 60 minutes, and then transferred to a grinder to grind to a fineness of ≤40 μm;

[0082] Fifth step: 2 parts of ethylene glycol diacetate (first solvent) were used to adjust the viscosity to 100 KU, and then A component was obtained after filtration;

[0083] Sixth step: 45 parts of Desmodur® N75 BA (aliphatic isocyanate curing agent), 45 parts of Hafotex® SH-3592 (aliphatic isocyanate curing agent), and 30 parts of 1,2-propanediol (second solvent) were sequentially added into a dispersing kettle, stirred uniformly, and dispersed for 30 minutes to obtain B component;

[0084] Seventh step: B component was added to A component, and the mass ratio of A component to B component was 20:1, and then the polyurethane topcoat was obtained after uniform mixing.

[0085] Comparative Example 1

[0086] The preparation method of this comparative example was the same as that of Example 1, except that an equal amount of non-silicone polymer EFKA 2020 was used to replace dodecyl glyceryl itaconate.

[0087] Comparative Example 2

[0088] The preparation method of this comparative example was the same as that of Example 1, except that an equal amount of polyurethane dispersant Efka PU4061 was used to replace 2,5-dimethyl-2,5-dihydroxy-1,4-dithiane.

[0089] Comparative Example 3

[0090] The comparative example was prepared in the same manner as example 1, except that an equal amount of polyamide wax THIXATROL® PM 8056 was used instead of zinc oleate.

[0091] Comparative example 4

[0092] The comparative example was prepared in the same manner as example 1, except that the weight ratio of non-silicone polymer to dodecyl glyceryl itaconate was 4:1.

[0093] Comparative example 5

[0094] The comparative example was prepared in the same manner as example 1, except that an equal amount of BS-8170 with a solid content of 70% and a hydroxyl value of 70 mg KOH / g was used instead of the hydroxyl acrylate dispersion BS-965, an equal amount of polyaspartic ester resin F220 with an amino equivalent weight of 230 g / mol was used instead of the polyaspartic ester resin Desmophen® NH 1520, an equal amount of non-silicone polymer EFKA 2020 was used instead of dodecyl glyceryl itaconate, an equal amount of polyurethane type dispersant Efka PU4061 was used instead of 2,5-dimethyl-2,5-dihydroxy-1,4-dithiane, and an equal amount of polyamide wax THIXATROL® PM 8056 was used instead of zinc oleate.

[0095] The polyurethane topcoat prepared in examples 1-3 and comparative examples 1-5 was subjected to performance testing (product implementation standard combined with “HG / T 2454-2014 Solvent-based polyurethane coatings (two components)”), and the test results are shown in Table 1:

[0096] Table 1 Performance testing indicators of the coating and performance testing results of the polyurethane topcoat

[0097]

[0098] The test results in Table 1 show that the polyurethane topcoat obtained in examples 1-3 meets the technical requirements of type II exterior topcoat 2 product in the standard “HG / T 2454-2014 Solvent-based polyurethane coatings (two components)”.

[0099] Compared with comparative example 1, example 1 uses a non-silicone polymer compounded with dodecyl glyceryl itaconate, which improves the gloss of the paint film, speeds up the drying speed in a low-temperature and high-humidity environment, enhances the impact resistance, water resistance, and corrosion resistance of the paint film, reduces defects such as blistering, pinholes, and orange peel, and prolongs the pot life of the coating.

[0100] Compared with Comparative Example 2, Example 1 uses a specific ratio of polyurethane dispersant and dithiane organic sulfur compound to compound, which enhances the adhesion of the paint film and improves the drying speed of the paint film in a low-temperature and high-humidity environment, realizes the balance of construction and low-temperature fast drying, and significantly improves the corrosion resistance of the paint film.

[0101] Compared with Comparative Example 3, Example 1 uses a specific ratio of polyamide wax and metal soap of oleic acid, which not only improves the sag resistance of the coating and the gloss of the coating, but also improves the hardness and corrosion resistance of the coating.

[0102] Compared with Comparative Example 4, Example 1 controls the weight ratio of non-silicone polymer and dodecyl glyceryl itaconate in the range of 3:1~2, which not only further improves the gloss of the paint film, speeds up the drying speed in a low-temperature and high-humidity environment, but also enhances the impact resistance, water resistance and corrosion resistance of the paint film, further reduces the occurrence of blistering of the paint film, and prolongs the pot life of the coating.

[0103] Compared with Comparative Example 5, Example 1 uses non-silicone polymer and dodecyl glyceryl itaconate as defoaming agent, polyurethane dispersant and dithiane organic sulfur compound as dispersant, and polyamide wax and metal soap of oleic acid as rheological additive, realizes the synergistic effect of multiple additives, obtains fast-drying polyurethane topcoat, effectively improves the corrosion resistance, adhesion and gloss of the paint film, and prolongs the pot life.

[0104] The above is only a specific embodiment of the present disclosure, which enables those skilled in the art to understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to these embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A polyurethane topcoat, characterized in that: The invention comprises component A and component B, wherein the mass ratio of component A to component B is 5-20:1; the component A comprises, calculated by weight, 40-50 parts of hydroxy acrylic dispersion, 8-15 parts of polyaspartic acid resin, 0.5-2 parts of defoamer, 1-3 parts of dispersant, 1-3 parts of rheological additive, 10-15 parts of pigment, 10-15 parts of filler, and 15-20 parts of solvent; The B component includes, calculated by weight, 70-90 parts of an aliphatic isocyanate curing agent and 10-30 parts of a solvent; the hydroxylated acrylic dispersion is selected from BS-965 and / or BS-960; the solid content of the hydroxylated acrylic dispersion is 59-66%, the hydroxyl value is 51-56 mg KOH / g, and the amino equivalent of the polyaspartic acid ester resin is 270-290 g / mol; the defoamer is a compound of a non-silicone polymer and dodecylglycerol itaconate, and the weight ratio of the non-silicone polymer to dodecylglycerol itaconate is 3:1-2; the non-silicone polymer is selected from one or more of EFKA 2020, YCK-655, and BYK-011; the dispersant is a compound of a polyurethane dispersant and a dithiane organic sulfur compound, and the polyurethane dispersant is selected from Efka PU4061, and / or, KEPERDISP®-639, the dithiane organic sulfur compound is selected from 2,5-dimethyl-2,5-dihydroxy-1,4-dithiane, and / or, 2,5-dimethylmercapto-1,4-dithiane.

2. A polyurethane topcoat according to claim 1, characterized in that, The weight ratio of the polyurethane dispersant to the dithiane organic sulfur compound is 3 to 5:

1.

3. A polyurethane topcoat according to claim 1, characterized in that, The rheological modifier is a compound of polyamide wax and oleic acid metal soap; the weight ratio of the polyamide wax to the oleic acid metal soap is 5 to 10:1; the polyamide wax is selected from one or more of THIXATROL® PM 8056, THIXATROL MAX, BYK 440, and RC-820, and the oleic acid metal soap is selected from one or more of zinc oleate, magnesium oleate, and calcium oleate.

4. A polyurethane topcoat according to claim 1, characterized in that, The aliphatic isocyanate curing agent is selected from one or more of Desmodur® N75 MPA / X, Hafotex® SH-2836, Desmodur® N75 BA, and Hafotex® SH-3592.

5. A polyurethane topcoat according to claim 1, characterized in that, The pigment is selected from one or more of rutile titanium dioxide, red iron oxide, carbon black, phthalocyanine blue, and phthalocyanine green; and the filler is selected from one or more of nano zinc oxide, mica powder, talc, kaolin, and bentonite.

6. A polyurethane topcoat according to claim 1, characterized in that: The solvent is a volatile organic solvent, and the solvent is selected from one or more of n-butanol, isobutanol, xylene, butyl acetate, ethylene glycol diacetate, and 1,2-propylene glycol.

7. A polyurethane topcoat according to claim 1, characterized in that, The polyaspartic acid ester resin is selected from one or more of Desmophen® NH 1520, Desmophen® NH 1420, and Zhuhai Feiyang Chemical F421.

8. A method for preparing the polyurethane topcoat according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: First, add the solvent, hydroxylated acrylic dispersion, and polyaspartic acid ester resin into the dispersion kettle in sequence and disperse for 10 to 30 minutes; S2: Add the dispersant and defoamer into the dispersion kettle in sequence and disperse for 10 to 30 minutes; S3: Add the rheological additive into the dispersion kettle and disperse for 10 to 30 minutes; S4: Add pigment and filler into the dispersion kettle in sequence, disperse for 30-60 minutes, and grind to a fineness of ≤40μm in a grinder; S5: Adjust the viscosity to 90-100 KU using a solvent, and obtain component A after filtration; S6: Then, the aliphatic isocyanate curing agent and the solvent are sequentially added into the dispersion kettle, stirred evenly, and dispersed for 15 to 30 minutes to obtain component B; S7: Finally, add component B to component A and mix evenly to obtain the polyurethane topcoat.

9. The method for preparing a polyurethane topcoat according to claim 8, wherein: The dispersant in step S2 is a mixture obtained by dispersing a polyurethane dispersant and a dithiane organic sulfur compound in a weight ratio of 3 to 5:1 for 10 to 20 minutes; the defoamer in step S2 is a mixture obtained by dispersing a non-silicone polymer and dodecylglycerol itaconate in a weight ratio of 3:1 to 2 for 10 to 20 minutes; the rheological additive in step S3 is a mixture obtained by dispersing polyamide wax and oleic acid metal soap in a weight ratio of 5 to 10:1 for 10 to 20 minutes.

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