A high-solids, ultra-weather-resistant acrylic polyurethane topcoat and its preparation method

Abstract

This invention discloses a high-solids, ultra-weather-resistant acrylic polyurethane topcoat and its preparation method. The topcoat consists of component A and component B, with a mass ratio of component A to component B of 20:(2-5). Component A includes the following components by mass: 30-45 parts acrylic resin; 2-10 parts modified resin; 2-10 parts hyperbranched polyester polyol; 25-40 parts pigments and fillers; 0-1.5 parts thixotropic agent; 0.1-10 parts dispersant; 0.1-0.5 parts defoamer; 0.01-1 part drier; and 1-10 parts mixed solvent. Component B includes the following components by mass: 70-95 parts aliphatic isocyanate polymer; 2-15 parts xylene; and 2-15 parts propylene glycol methyl ether acetate. The coating of this invention exhibits excellent weather resistance, comparable to ultra-weather-resistant fluorocarbon topcoats and polysiloxane topcoats, and possesses high mechanical strength and corrosion resistance, making it particularly suitable for coating steel structures in the South China Sea environment.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a high-solids, ultra-weather-resistant acrylic polyurethane topcoat and its preparation method. Background Technology

[0002] In recent years, strictly controlling VOC emissions during paint production and application, accelerating the development of paints that use little or no organic solvents, and transforming from traditional paints to green paints, are the development directions for the paint industry. High-solids paints, in particular, have attracted significant attention due to their ability to reduce paint usage and solvent emissions while fully utilizing existing paint production and application equipment.

[0003] Meanwhile, as the first line of defense in marine and industrial heavy-duty anti-corrosion coatings, the topcoat layer is subject to factors such as ultraviolet rays, oxygen, and moisture during use, which can cause the coating to lose its gloss, discolor, chalk, and crack. Especially in the harsh natural environment of the South China Sea, due to the special effects of high temperature, high humidity, high salinity, and high ultraviolet radiation, traditional polyurethane topcoats can no longer meet the requirements. Chalking, cracking, and other failures seriously affect its service life. Therefore, higher requirements are placed on the weather resistance of the topcoat.

[0004] Existing technologies also disclose some weather-resistant polyurethane coatings. For example, Chinese invention patent CN115584198A discloses an environmentally friendly polyurethane coating and its preparation method. This method uses low-viscosity, high-solids-content hydroxyl acrylic resin as the main substrate, compounded with modified titanium dioxide. By coating the titanium dioxide surface with silica, the catalytic degradation effect of titanium dioxide on the organic resins in the coating system is reduced, thus improving the coating's weather resistance. However, the coatings produced by this method have relatively limited color options, failing to meet market demands, and their weather resistance is comparable to traditional polyurethane coatings, offering no significant advantage.

[0005] Chinese invention patent CN116855160A discloses a method for preparing a highly weather-resistant, high-performance, and cost-effective aliphatic polyurethane coating. The coating resin is a high-solids, low-VOC polyurethane coating, composed of polymer A obtained by polymerizing monobasic acid, monobasic acid, dibasic acid, triol, modified monomer 1, modified monomer 2, and (meth)acrylate monomer 1, and polymer B obtained by polymerizing modified monomer 1, (meth)acrylate monomer 2, and styrene. The polyurethane coating prepared by this method exhibits high gloss, high fullness, high reflectivity, and excellent mechanical properties, chemical resistance, and weather resistance. However, because the phthalic anhydride and styrene content in polymer A is as high as 35%–40% of the monomers, and the styrene content in polymer B is as high as 40% of the monomers, the improvement in the coating's weather resistance is limited to some extent, failing to meet the requirements for ultra-weather resistance. Summary of the Invention

[0006] To address the issue of durability of polyurethane topcoats in the high-temperature, high-humidity, high-salt, and high-UV environment of the South China Sea, this invention provides a high-solids, ultra-weather-resistant acrylic polyurethane topcoat and its preparation method. This topcoat features high solids content, low VOCs, and excellent gloss and color retention properties.

[0007] In a first aspect, the present invention provides a high-solids, ultra-weather-resistant acrylic polyurethane topcoat, which is achieved by the following technical solution.

[0008] A high-solids, ultra-weather-resistant acrylic polyurethane topcoat, composed of component A and component B, wherein the mass ratio of component A to component B is 20:(2-5);

[0009] Component A comprises the following components in parts by mass:

[0010]

[0011] Component B comprises the following components in parts by weight:

[0012] 70-95 parts of aliphatic isocyanate polymer;

[0013] 2-15 parts xylene;

[0014] 2-15 parts of propylene glycol methyl ether acetate.

[0015] Furthermore, the acrylic resin is a hydroxyl acrylic resin with a solid content ≥80% and a viscosity of 4000–10000 mPa·s at 23°C, and the proportion of hydroxyl groups in the resin is 1.8–2.4%. Specifically, the acrylic resin is one or more of the following: Jianxing Resin AA-2180, Arkema Resin 854BA80, and Zhanxin Resin 2703 / 80BACX.

[0016] Furthermore, the modified resin is a polyester resin with 95% solids content and a viscosity of 4000–6000 mPa·s at 23°C, and the proportion of hydroxyl groups in the resin is 6.5%–8.5%.

[0017] Further, the synthesis method of the modified resin is as follows: 25-35 parts of 1,4-cyclohexanediethanol monomer, 15-25 parts of trimethylolpropane monomer, 25-35 parts of adipic acid monomer, 5-15 parts of trimellitic anhydride monomer, 5-15 parts of ε-caprolactone monomer, and 0.01-0.1 parts of monobutyltin oxide catalyst are mixed. Under nitrogen protection, the mixture is heated to reflux and the timing starts. After 6-8 hours, the temperature is raised to 215-220℃ and held at reflux. The mixture is dehydrated until the acid value is ≤10mg KOH / g, and then cooled to 100-120℃. A diluent composed of 3-5 parts of xylene, 1-2 parts of butyl acetate, and 1-2 parts of propylene glycol methyl ether acetate is added to obtain a polyester resin with a solid content of 95%, a viscosity of 4000-6000 mPa·s at 23℃, and a hydroxyl content of 6.5%-8.5%.

[0018] Furthermore, the hyperbranched polyester polyol has a solids content ≥70%, a viscosity of 3000–5000 mPa·s at 23°C, and a hydroxyl content of 7.2%–9.2% in the resin. Specifically, the hyperbranched polyester polyol is BASF resin Basonol HPE 1170B.

[0019] Furthermore, the pigments and fillers are selected from one or more of the following: titanium dioxide, organic yellow, carbon black, phthalocyanine blue, talc, heavy calcium carbonate, precipitated barium sulfate, and silica fume.

[0020] Furthermore, the thixotropic agent is composed of one or more of fumed silica, organobentonite, and polyamide wax. Specifically, the thixotropic agent is one or more of Evonik R 972, BYK APA and G 1958, and Haiming Sideqian PLUS. The dispersant is a high molecular weight block copolymer containing pigment affinity groups. Specifically, the dispersant is BYK 163 and Lubrizol Solsperse 32500. The defoamer is an organosilicon defoamer. Specifically, the defoamer is one or more of EFKA 2028, Deqian 6800, and BYK077. The drying agent is dibutyltin dilaurate.

[0021] Furthermore, the mixed solvent is one or more of xylene, propylene glycol methyl ether acetate, butyl acetate, propylene glycol butyl ether acetate, and mixed diesters.

[0022] Furthermore, the aliphatic isocyanate polymer is one or both of hexamethylene diisocyanate biuret and hexamethylene diisocyanate trimer, with an NCO content of 15-25%. Specifically, the aliphatic isocyanate polymer is one or more of Wanhua HT-100, Bayer Desmodur N3300, and N75.

[0023] Secondly, the present invention provides a method for preparing a high-solids, ultra-weather-resistant acrylic polyurethane topcoat, which is achieved by the following technical solution.

[0024] A method for preparing the above-mentioned high-solids, ultra-weather-resistant acrylic polyurethane topcoat includes the following steps:

[0025] Preparation of component A:

[0026] S1. Mix the specified amounts of acrylic resin, modified resin, hyperbranched polyester polyol and mixed solvent and stir until homogeneous; then add dispersant and defoamer and stir until homogeneous; then add thixotropic agent and pigments and fillers in sequence, adjust the speed to 500-600 r / min, and stir for at least 30 min until homogeneous;

[0027] S2. Grind the product obtained in step S1 to a fineness of ≤30μm and discharge it;

[0028] S3. Add a drying agent to the product obtained in step S2 and disperse it evenly to obtain component A;

[0029] Preparation of component B:

[0030] Mix the specified amounts of aliphatic isocyanate polymer, xylene, and propylene glycol methyl ether acetate, adjust the rotation speed to 300-400 r / min, stir for at least 30 min until homogeneous, and filter through a 120-200 mesh filter to prepare component B;

[0031] Component A and component B are mixed and thoroughly mixed to prepare a high-solids, ultra-weather-resistant acrylic polyurethane topcoat.

[0032] This application has the following beneficial effects.

[0033] (1) In component A, the introduction of modified resin into acrylic resin can effectively reduce the viscosity of the resin system and further increase the solid content of the topcoat. Meanwhile, the modified resin is prepared by using 1,4-cyclohexanediethanol and trimethylolpropane as alcohol monomers, adipic acid and trimellitic anhydride as acid monomers, ε-caprolactone as a modifying monomer, and monobutyltin oxide as a catalyst, through a reasonable combination of monomers. The use of this resin not only increases the overall solid content of the coating composition but also improves the aging resistance, yellowing resistance, and chemical resistance of the coating polymer, making the coating more suitable for steel structure surfaces in harsh environments such as high temperature, high humidity, high salt, and high ultraviolet radiation in the South China Sea.

[0034] (2) In component A, the introduced hyperbranched polyester resin has a hyperbranched structure, low resin viscosity, which is convenient for developing high solids coatings, and has high hydroxyl functionality, which can significantly improve early drying speed and early hardness development, thereby improving the scratch resistance and chemical resistance of the paint film. At the same time, the resin can effectively extend the activation period and improve the leveling properties of the paint liquid.

[0035] (3) The topcoat of this invention has excellent overall performance, especially in terms of resistance to artificial aging. Its performance is far superior to traditional acrylic polyurethane topcoats and comparable to that of fluorocarbon and polysiloxane topcoats in terms of weather resistance. The VOC content is ≤250g / L and the volume solids content is ≥70%, which meets environmental protection requirements. Detailed Implementation

[0036] The present patent application will be further described below with reference to the embodiments.

[0037] Unless otherwise specified, the experimental methods used in the following preparation examples and embodiments are conventional methods; the materials and reagents used in the following preparation examples and embodiments are commercially available unless otherwise specified.

[0038] Preparation Example

[0039] The preparation method of the modified resin is as follows:

[0040] 30g of 1,4-cyclohexanediethanol monomer, 20g of trimethylolpropane monomer, 30g of adipic acid monomer, 10g of trimellitic anhydride monomer, 10g of ε-caprolactone monomer, and 0.05g of monobutyltin oxide catalyst were mixed. Under nitrogen protection, the mixture was heated to reflux and timed. After 7 hours, the temperature was raised to 220℃ and held at reflux to dehydrate until the acid value was ≤10mg KOH / g. Then, the temperature was lowered to 120℃, and a diluent composed of 4g xylene, 1g butyl acetate, and 1g propylene glycol methyl ether acetate was added to obtain a polyester resin with a solid content of 95%, a viscosity of 4000-6000 mPa·s at 23℃, and a hydroxyl content of 6.5%-8.5%.

[0041] Example 1

[0042] A method for preparing a high-solids, ultra-weather-resistant acrylic polyurethane topcoat includes the following steps:

[0043] (1) Preparation of component A: In every 100g of component A, there are 40g of AA-2180 acrylic resin, 5g of the modified resin prepared in the preparation example, 5g of Basonol HPE 1170B hyperbranched polyester polyol, 30g of titanium dioxide, 10g of talc, 0.6g of BYKAPA thixotropic agent, 1g of BYK 163 dispersant, 0.35g of EFKA 2028 defoamer, 0.05g of drying agent, and 8g of mixed solvent (i.e., 3g of xylene, 3g of propylene glycol methyl ether acetate, and 2g of mixed diester).

[0044] a. Add acrylic resin, modified resin, hyperbranched polyester polyol, and mixed solvent to the mixing tank in sequence according to the formula ratio, mix and stir evenly; then add dispersant and defoamer, stir evenly; then add thixotropic agent and pigments and fillers in sequence, adjust the speed to 500 r / min, and stir for 30 min until uniform;

[0045] b. Grind the product obtained in step a to a fineness of ≤30μm and discharge it;

[0046] c. Add a drying agent to the product obtained in step b according to the formula, and disperse evenly to obtain component A;

[0047] (2) Preparation of curing agent component B: per 100g of component B, there are 79g of aliphatic isocyanate polymer Desmodur N3300, 10g of xylene, and 11g of propylene glycol methyl ether acetate.

[0048] According to the formula ratio, add aliphatic isocyanate polymer, xylene and propylene glycol methyl ether acetate to the mixing tank in sequence, adjust the speed to 300 r / min, stir for 30 min until uniform, and filter through a 200 mesh filter to prepare curing agent component B;

[0049] (3) Mix components A and B in a mass ratio of 20:4.

[0050] Example 2

[0051] A method for preparing a high-solids, ultra-weather-resistant acrylic polyurethane topcoat, the specific preparation method is the same as in Example 1, and the components of the topcoat are as follows:

[0052] (1) Preparation of component A: In every 100g of component A, there are 35g of AA-2180 acrylic resin, 6g of the modified resin prepared in the preparation example, 9g of Basonol HPE 1170B hyperbranched polyester polyol, 27g of titanium dioxide, 3g of phthalocyanine blue, 5g of heavy calcium carbonate powder, 5g of precipitated barium sulfate, 0.6g of R 972 thixotropic agent, 3g of BYK 163 dispersant, 0.35g of 6800 defoamer, 0.05g of drying agent, and 6g of mixed solvent (i.e., 2.5g of xylene, 2.5g of propylene glycol methyl ether acetate, and 1g of mixed diester).

[0053] (2) Preparation of curing agent component B: per 100g of component B, there are 92g of aliphatic isocyanate polymer Desmodur N3300, 4g of xylene, and 4g of propylene glycol methyl ether acetate.

[0054] (3) Mix components A and B in a mass ratio of 20:4.

[0055] Example 3

[0056] A method for preparing a high-solids, ultra-weather-resistant acrylic polyurethane topcoat, the specific preparation method is the same as in Example 1, and the components of the topcoat are as follows:

[0057] (1) Preparation of component A: In every 100g of component A, there are 37g of 854BA80 acrylic resin, 8g of the modified resin prepared in the preparation example, 4g of Basonol HPE 1170B hyperbranched polyester polyol, 30g of BH4G organic yellow, 5g of heavy calcium carbonate powder, 5g of precipitated barium sulfate, 0.3g of R 972 thixotropic agent, 7.3g of BYK 163 dispersant, 0.35g of 6800 defoamer, 0.05g of drying agent, and 3g of mixed solvent (i.e., 1g of xylene and 2g of propylene glycol methyl ether acetate).

[0058] (2) Preparation of curing agent component B: per 100g of component B, there are 85g of aliphatic isocyanate polymer Desmodur N3300, 7g of xylene, and 8g of propylene glycol methyl ether acetate.

[0059] (3) Mix components A and B in a mass ratio of 20:4.

[0060] Comparative Example 1

[0061] A method for preparing an acrylic polyurethane topcoat, the specific preparation method is the same as in Example 1, and the components of the topcoat are as follows:

[0062] (1) Preparation of component A: per 100g of component A, there are 41g of AA-2180 acrylic resin, 9g of Basonol HPE 1170B hyperbranched polyester polyol, 27g of titanium dioxide, 3g of phthalocyanine blue, 5g of heavy calcium carbonate powder, 5g of precipitated barium sulfate, 0.6g of R 972 thixotropic agent, 3g of BYK163 dispersant, 0.35g of 6800 defoamer, 0.05g of drying agent, and 6g of mixed solvent (i.e., 2.5g of xylene, 2.5g of propylene glycol methyl ether acetate, and 1g of mixed diester).

[0063] (2) Preparation of curing agent component B: per 100g of component B, there are 72g of aliphatic isocyanate polymer Desmodur N3300, 14g of xylene, and 14g of propylene glycol methyl ether acetate.

[0064] (3) Mix components A and B in a mass ratio of 20:4.

[0065] Comparative Example 2

[0066] A method for preparing an acrylic polyurethane topcoat, the specific preparation method is the same as in Example 1, and the components of the topcoat are as follows:

[0067] (1) Preparation of component A: In every 100g of component A, there are 40g of AA-2180 acrylic resin, 8g of the modified resin prepared in the preparation example, 30g of titanium dioxide, 10g of talc, 0.6g of BYKAPA thixotropic agent, 1g of BYK 163 dispersant, 0.35g of EFKA2028 defoamer, 0.05g of drying agent, and 10g of mixed solvent (i.e., 4g of xylene, 4g of propylene glycol methyl ether acetate, and 2g of mixed diester).

[0068] (2) Preparation of curing agent component B: Each 100g of component B contains 74g of aliphatic isocyanate polymer Desmodur N3300, 13g of xylene, and 13g of propylene glycol methyl ether acetate.

[0069] (3) Mix components A and B in a mass ratio of 20:4.

[0070] Comparative Example 3

[0071] Three products from CNOOC Changzhou Coatings & Chemicals Research Institute Co., Ltd.—acrylic polyurethane topcoat, fluorocarbon topcoat, and polysiloxane topcoat—were used as comparative examples.

[0072] Coating performance testing

[0073] The acrylic polyurethane topcoats prepared in Examples 1-3, and the conventional acrylic polyurethane topcoats, fluorocarbon topcoats, and polysiloxane topcoats in Comparative Examples 1-2 and 3, were respectively tested as follows:

[0074] Volumetric solids content: determined according to GB / T 9272-2007;

[0075] VOC content: determined according to GB / T 23985-2009;

[0076] Actual strength: determined according to Method A of GB / T 1728-1979;

[0077] Pencil hardness: determined according to GB / T 6739-2006;

[0078] Flexibility: determined according to GB / T 1731-1993, the test plate is tinplate, and the coating thickness is 20±3μm;

[0079] Impact test: According to GB / T 1732-1993, the test plate is tinplate, and the film thickness is 20±3μm;

[0080] Pull-off adhesion test: according to GB / T 5210-2006, the test plate is a sandblasted steel plate, and the film thickness is 320±20μm;

[0081] Acid and alkali resistance: determined by immersion method in GB / T 9274-1988;

[0082] Salt spray resistance test: determined according to GB / T 1771-2007;

[0083] Artificial weathering resistance test: determined according to GB / T 1865-2009.

[0084] The test results are shown in Table 1.

[0085] Table 1

[0086]

[0087]

[0088] The above experimental results show that the acrylic polyurethane topcoat of the present invention has excellent mechanical properties and chemical resistance, especially in terms of weather resistance, which has a significant advantage over traditional acrylic polyurethane topcoats and is comparable in performance to ultra-weather resistant topcoats, fluorocarbon topcoats and polysiloxane topcoats.

[0089] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high-solids, ultra-weather-resistant acrylic polyurethane topcoat, characterized in that: It consists of component A and component B, with a mass ratio of component A to component B of 20:(2-5); Component A comprises the following components in parts by mass: 30-45 parts of acrylic resin; 2-10 parts of modified resin; 2-10 parts of hyperbranched polyester polyol; 25-40 parts of pigments and fillers; Thixotropic agent 0-1.5 parts; Dispersant 0.1-10 parts; Defoamer 0.1-0.5 parts; Drying agent 0.01-1 part; Mixed solvent 1 to 10 parts; Component B comprises the following components in parts by weight: 70-95 parts of aliphatic isocyanate polymer; 2-15 parts xylene; 2-15 parts of propylene glycol methyl ether acetate; The modified resin is synthesized as follows: 25-35 parts of 1,4-cyclohexanediethanol monomer, 15-25 parts of trimethylolpropane monomer, 25-35 parts of adipic acid monomer, 5-15 parts of trimellitic anhydride monomer, 5-15 parts of ε-caprolactone monomer, and 0.01-0.1 parts of monobutyltin oxide catalyst are mixed. Under nitrogen protection, the mixture is heated to reflux and the timing starts. After 6-8 hours, the temperature is raised to 215-220℃ and held at reflux. The mixture is dehydrated until the acid value is ≤10mg KOH / g. Then, the temperature is lowered to 100-120℃, and a diluent composed of 3-5 parts of xylene, 1-2 parts of butyl acetate, and 1-2 parts of propylene glycol methyl ether acetate is added to obtain a polyester resin with a solid content of 95%, a viscosity of 4000-6000 mPa·s at 23℃, and a hydroxyl content of 6.5%-8.5%. The solid content of the hyperbranched polyester polyol is ≥70%, the viscosity at 23℃ is 3000~5000mPa·s, and the proportion of hydroxyl groups in the resin is 7.2%~9.2%.

2. The high-solids, ultra-weather-resistant acrylic polyurethane topcoat according to claim 1, characterized in that: The acrylic resin is a hydroxyl acrylic resin with a solid content of ≥80% and a viscosity of 4000~10000mPa·s at 23℃, and the proportion of hydroxyl groups in the resin is 1.8~2.4%.

3. The high-solids, ultra-weather-resistant acrylic polyurethane topcoat according to claim 1, characterized in that: The pigments and fillers are selected from one or more of the following: titanium dioxide, organic yellow, carbon black, phthalocyanine blue, talc, heavy calcium carbonate, precipitated barium sulfate, and silica fume.

4. The high-solids, ultra-weather-resistant acrylic polyurethane topcoat according to claim 1, characterized in that: The thixotropic agent is composed of one or more of fumed silica, organobentonite, and polyamide wax; the dispersant is a high molecular weight block copolymer containing pigment affinity groups; the defoamer is an organosilicon defoamer; and the drying agent is dibutyltin dilaurate.

5. The high-solids, ultra-weather-resistant acrylic polyurethane topcoat according to claim 1, characterized in that: The mixed solvent is several of xylene, propylene glycol methyl ether acetate, butyl acetate, propylene glycol butyl ether acetate, and mixed diesters.

6. The high-solids, ultra-weather-resistant acrylic polyurethane topcoat according to claim 1, characterized in that: The aliphatic isocyanate polymer is one or two of hexamethylene diisocyanate biuret and hexamethylene diisocyanate trimer, with an NCO content of 15-25%.

7. A method for preparing a high-solids, ultra-weather-resistant acrylic polyurethane topcoat according to any one of claims 1-6, characterized in that: Includes the following steps: Preparation of component A: S1. Mix the specified amounts of acrylic resin, modified resin, hyperbranched polyester polyol and mixed solvent and stir until homogeneous; then add dispersant and defoamer and stir until homogeneous; then add thixotropic agent and pigments and fillers in sequence, adjust the speed to 500-600 r / min, and stir for at least 30 min until homogeneous; S2. Grind the product obtained in step S1 to a fineness of ≤30μm and discharge it; S3. Add a drying agent to the product obtained in step S2 and disperse it evenly to obtain component A; Preparation of component B: Mix the specified amounts of aliphatic isocyanate polymer, xylene, and propylene glycol methyl ether acetate, adjust the rotation speed to 300-400 r / min, stir for at least 30 min until homogeneous, and filter through a 120-200 mesh filter to prepare component B; Component A and component B are mixed and thoroughly mixed to prepare a high-solids, ultra-weather-resistant acrylic polyurethane topcoat.

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