A hydroxyl acrylic resin, a preparation method thereof, an environment-friendly coating and application thereof

Abstract

This application relates to a hydroxyl acrylic resin and its preparation method, as well as environmentally friendly coatings and their applications. The hydroxyl acrylic resin is prepared by solution polymerization of the following raw materials in parts by weight: 52-64 parts of acrylate monomers, 5-15 parts of UV-resistant functional monomers, 0.5-1.5 parts of chain transfer agent, 20-35 parts of environmentally friendly solvent, and 1-3 parts of initiator. Through a precise polymerization process involving multiple continuous drops, a hydroxyl acrylic resin with excellent weather resistance and corrosion resistance was successfully synthesized, solving the problems of insufficient film performance of traditional resins under high solids content conditions and decreased weather resistance due to the presence of benzene-based substances. This resin is free of benzene-based substances, exhibits excellent environmental characteristics, and when used as a key film-forming substance in coatings, it can significantly improve the coating's UV aging resistance and mechanical strength, showing broad market prospects.

Description

Technical Field

[0001] This article relates to the fields of polymer synthesis and coating technology, specifically to a hydroxyl acrylic resin with a specially designed molecular structure. Background Technology

[0002] Hydroxyl acrylic resins are key film-forming materials for preparing high-performance coatings (such as acrylic-polyurethane coatings). With increasingly stringent global environmental regulations, the coatings industry is rapidly moving towards high solids content and low volatile organic compound (VOC) content. However, traditional high-solids resin designs often achieve low viscosity by reducing molecular weight, inevitably leading to insufficient polymer chain entanglement and sacrificing the mechanical strength, density, and durability of the final coating film. On the other hand, to achieve long-term coating durability, the resin must possess excellent weather resistance, i.e., the ability to resist environmental factors such as ultraviolet radiation and humid heat. To balance cost and performance, traditional resins often incorporate styrene monomers. The benzene ring in its molecular structure is a weak point in photochemical degradation, easily causing polymer backbone breakage and yellowing under ultraviolet radiation, becoming a bottleneck restricting the coating's service life. In addition, benzene and toluene solvents used in the production process pose a serious threat to human health and environmental pollution. With increasingly stringent environmental regulations and higher market requirements for coating durability, the development of an acrylic resin that combines ultra-high weather resistance, high solids and low viscosity, and is completely free of benzene compounds has become an urgent technical need in the industry. Summary of the Invention

[0003] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of protection of this application.

[0004] The purpose of this application is to overcome the shortcomings of the prior art and provide a highly weather-resistant, environmentally friendly hydroxyl acrylic resin and its preparation method. This resin possesses excellent weather resistance potential and high solids / low viscosity characteristics, making it particularly suitable for formulating various high-performance environmentally friendly coatings. Furthermore, this resin itself contains no benzene monomers or solvents, and when used as a film-forming substance in paint formulations, it can impart weather resistance, mechanical properties, and corrosion resistance to the coating film that surpasses those of conventional products.

[0005] To achieve the above objectives, this application adopts the following technical solution: The first aspect of this application provides a hydroxyl acrylic resin, which is obtained by reacting raw materials comprising the following parts by weight: 52-64 parts of acrylate monomers, 5-15 parts of UV-resistant functional monomers, 0.5-1.5 parts of chain transfer agent, 20-35 parts of environmentally friendly solvent, and 1-3 parts of initiator.

[0006] In one exemplary embodiment, the acrylate monomer is any one or a mixture of hard monomers, soft monomers, and hydroxyl-containing functional monomers; wherein the hard monomer is selected from one or more of methacrylic acid, methyl methacrylate, ethyl methacrylate, etc.; the soft monomer is selected from one or more of butyl acrylate, butyl methacrylate, etc.; and the hydroxyl-containing functional monomer is hydroxyethyl acrylate and / or hydroxyethyl methacrylate.

[0007] In one exemplary embodiment, the acrylate monomer is a mixture of acrylate monomers.

[0008] In one exemplary embodiment, the acrylate mixed monomers are a mixture of methacrylic acid, hydroxyethyl acrylate, methyl methacrylate, butyl acrylate and butyl methacrylate, wherein, by weight, there are 0.5-0.8 parts of methacrylic acid, 9-10 parts of hydroxyethyl acrylate, 23-27 parts of methyl methacrylate, 8-10 parts of butyl acrylate and 15-16 parts of butyl methacrylate.

[0009] In one exemplary embodiment, the UV-resistant functional monomer is selected from one or more of glycidyl tert-butyl carbonate (E10P), isobornyl methacrylate (IBOMA), and cyclohexyl methacrylate (CHMA), which have large steric hindrance in their molecular structure.

[0010] In one exemplary embodiment, the chain transfer agent is selected from any one of mercaptoethanol, isooctyl mercaptoacetate, or dodecyl mercaptan; optionally, the chain transfer agent is mercaptoethanol.

[0011] In one exemplary embodiment, the environmentally friendly solvent is selected from any one or a mixture of butyl acetate, propylene glycol methyl ether acetate (PMA), propylene glycol butyl ether, etc.

[0012] In one exemplary embodiment, the environmentally friendly solvent is a mixed environmentally friendly solvent.

[0013] In one exemplary embodiment, the mixed environmentally friendly solvent is a mixture of butyl acetate and propylene glycol methyl ether acetate, wherein, by weight, 21-23 parts of butyl acetate and 5-6 parts of propylene glycol methyl ether acetate.

[0014] In one exemplary embodiment, the initiator is selected from one or more of benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), tert-butyl peroxide (TBPB), etc.; optionally, the initiator is benzoyl peroxide.

[0015] In one exemplary embodiment, the hydroxyl acrylic resin is obtained by reacting raw materials comprising the following parts by weight: 61 parts of acrylate mixed monomers, 8 parts of UV-resistant functional monomers, 0.85 parts of chain transfer agent, 27.75 parts of mixed environmentally friendly solvents, and 2.4 parts of initiator; The acrylate mixed monomers are a mixture of 0.7 parts methacrylic acid, 9.8 parts hydroxyethyl acrylate, 25.67 parts methyl methacrylate, 9 parts butyl acrylate and 15.83 parts butyl methacrylate; the mixed environmentally friendly solvent is a mixture of 21.75 parts butyl acetate and 6 parts propylene glycol methyl ether acetate.

[0016] In one exemplary embodiment, the hydroxyl acrylic resin is obtained by reacting raw materials comprising the following parts by weight: 58 parts of acrylate mixed monomers, 12 parts of UV-resistant functional monomers, 0.85 parts of chain transfer agent, 26.55 parts of mixed environmentally friendly solvents, and 2.6 parts of initiator. The acrylate monomer mixture is a mixture of 0.67 parts methacrylic acid, 9.51 parts hydroxyethyl acrylate, 23.8 parts methyl methacrylate, 8.72 parts butyl acrylate and 15.3 parts butyl methacrylate; the environmentally friendly solvent mixture is a mixture of 21.25 parts butyl acetate and 5.3 parts propylene glycol methyl ether acetate.

[0017] In one exemplary embodiment, the hydroxyl acrylic resin is obtained by reacting raw materials comprising the following parts by weight: 59 parts of acrylate mixed monomers, 10 parts of UV-resistant functional monomers, 0.85 parts of chain transfer agent, 27.75 parts of mixed environmentally friendly solvents, and 2.4 parts of initiator. The acrylate monomer mixture is a mixture of 0.68 parts methacrylic acid, 9.65 parts hydroxyethyl acrylate, 24.25 parts methyl methacrylate, 8.85 parts butyl acrylate and 15.57 parts butyl methacrylate; the mixed environmentally friendly solvent is a mixture of 22.2 parts butyl acetate and 5.55 parts propylene glycol methyl ether acetate.

[0018] In one exemplary embodiment, the hydroxy acrylic resin has a solid content of 70±2%, a viscosity of 6000-9000 mPa·s (25±2℃), an acid value of ≤6 mg KOH / g, and an Fe-Co color number of ≤4.

[0019] The second aspect of this application provides a method for preparing the above-mentioned hydroxyl acrylic resin, comprising the following steps: a. Add a portion of environmentally friendly solvent as a base to the reactor, heat to reflux temperature under inert gas protection, and maintain the temperature; simultaneously, premix acrylate monomers and UV-resistant functional monomers, as well as a portion of initiator and chain transfer agent, to form a mixture; or A portion of environmentally friendly solvents and UV-resistant functional monomers are added to the reactor, and the mixture is heated to the reflux temperature under inert gas protection and held at that temperature. Simultaneously, acrylate monomers, a portion of initiators, and a portion of chain transfer agents are premixed to form a mixture. b. The mixture is added dropwise to the reactor at a uniform rate at the reflux temperature; c. After the addition is complete, maintain the temperature at the reflux temperature for curing; d. Add part of the initiator, part of the chain transfer agent, and part of the environmentally friendly solvent to the material in step c for the first supplementary addition; after the addition is completed, keep it at the reflux temperature; e. Add the remaining initiator, chain transfer agent, and environmentally friendly solvent dropwise for a second addition; after the addition is complete, maintain the temperature at the stated reflux temperature; f. Cool to 100±5℃, add diluted solvent and mix evenly, adjust to qualified viscosity and solid content, filter and discharge to obtain the hydroxyl acrylic resin.

[0020] In one example embodiment, when the UV-resistant functional monomer is glycidyl tert-carbonate, step a includes: adding a portion of the environmentally friendly solvent and the UV-resistant functional monomer to the reactor, heating to the reflux temperature under inert gas protection and holding at that temperature; simultaneously, premixing the acrylate monomer, a portion of the initiator, and a portion of the chain transfer agent to form a mixture.

[0021] In an exemplary embodiment, when the UV-resistant functional monomer is isobornyl methacrylate or cyclohexyl methacrylate, step a includes: adding a portion of the environmentally friendly solvent as a base material to the reactor, heating it to the reflux temperature under inert gas protection and holding it at that temperature; simultaneously, premixing the acrylate monomer and the UV-resistant functional monomer, as well as a portion of the initiator and a portion of the chain transfer agent, to form a mixture.

[0022] In one exemplary embodiment, the reflux temperature is 132±2℃.

[0023] In one exemplary embodiment, in step a, the heat preservation time is 10-20 minutes; optionally, it is 15 minutes.

[0024] In one exemplary embodiment, in step b, the dripping time is 4-6 hours; optionally, it is 5 hours.

[0025] In one exemplary embodiment, in step c, the time for heat preservation and ripening is 0.5-1.5 hours; optionally, it is 1 hour.

[0026] In one exemplary embodiment, in step d, the heat preservation time is 0.5-1.5h; optionally, it is 1h.

[0027] In one exemplary embodiment, in step e, the heat preservation time is 0.3-1 h; optionally, it is 0.5 h.

[0028] In one exemplary embodiment, in steps d and e, the initiator, the chain transfer agent, and the environmentally friendly solvent are added dropwise within 15 minutes.

[0029] In one exemplary embodiment, in step a, the amount of the environmentally friendly solvent added is 82%.

[0030] In one exemplary embodiment, in step a, the amount of the initiator and the chain transfer agent added is 87.5%.

[0031] In one exemplary embodiment, in step d, the amount of the initiator and the chain transfer agent added is 8.5%; the amount of the environmentally friendly solvent added is 12%.

[0032] In one exemplary embodiment, in step e, the amount of the initiator and the chain transfer agent added is 4%; the amount of the environmentally friendly solvent added is 6%.

[0033] In one exemplary embodiment, in step f, the diluent is a mixed solvent of butyl acetate and propylene glycol methyl ether acetate in a volume ratio of 4:1.

[0034] A third aspect of this application provides a hydroxyl acrylic resin prepared by the above method.

[0035] The fourth aspect of this application provides an environmentally friendly coating, wherein the raw material of the environmentally friendly coating includes the above-mentioned hydroxyl acrylic resin as a film-forming substance.

[0036] In one exemplary embodiment, the environmentally friendly coating is a two-component acrylic polyurethane coating, and its film has at least one of the following properties: artificial weathering resistance ≥2000 hours; adhesion grade 0; pencil hardness ≥2H; and neutral salt spray resistance ≥800 hours.

[0037] The fifth aspect of this application provides an application of the aforementioned environmentally friendly coating in the fields of building exterior walls, automotive exteriors, or industrial protection.

[0038] In one exemplary embodiment, the environmentally friendly coating is used as an exterior topcoat.

[0039] Compared with existing related technologies, the beneficial effects of this application are as follows: 1. Environmental advantages of raw materials: The synthesis of hydroxyl acrylic resin in this application completely eliminates styrene monomers and benzene-based solvents such as benzene and toluene, and the product complies with green chemistry principles and the strictest environmental regulations; 2. Excellent product performance: The hydroxyl acrylic resin of this application has high solids and low viscosity characteristics, with a solids content of 70±2%, which significantly reduces the VOC content of the paint system; it has excellent stability: low acid value (≤6 mg KOH / g), light color (Fe-Co color number ≤4), and good storage stability; 3. Excellent film performance: By designing the molecular structure of the resin system and introducing a certain proportion of non-conjugated functional monomers with large steric hindrance, the steric hindrance effect can be generated by their large side group structure, which can effectively shield ultraviolet light attack and slow down the breaking rate of polymer backbone, block the electronic coupling path in the resin molecular structure, thereby reducing the formation of conjugated or oxidized structures in the coating, and giving the system excellent weather resistance.

[0040] 4. The resin provided in this application is particularly suitable for formulating architectural exterior wall coatings and automotive exterior topcoats that require extreme weather resistance, and has broad market application prospects.

[0041] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application may be realized and obtained by means of the methods described in the description. Detailed Implementation

[0042] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0043] The present application will be further described in detail below with reference to specific embodiments, but these embodiments should not be construed as limiting the present application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this invention.

[0044] The raw materials used in this application are all conventional products on the market.

[0045] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0046] Experimental methods not specified in the examples are generally performed under standard conditions or as recommended by the manufacturer.

[0047] Example 1 This embodiment of a high weather-resistant hydroxyl acrylic resin comprises the following raw materials in parts by weight: 61 parts of mixed acrylate monomers, 8 parts of glycidyl tert-carbonate, 0.85 parts of chain transfer agent, 27.75 parts of mixed environmentally friendly solvent, and 2.4 parts of initiator; The acrylate monomer mixture is a mixture of 0.7 parts methacrylic acid, 9.8 parts hydroxyethyl acrylate, 25.67 parts methyl methacrylate, 9 parts butyl acrylate and 15.83 parts butyl methacrylate; The mixed environmentally friendly solvent is a mixture of 21.75 parts butyl acetate and 6 parts propylene glycol methyl ether acetate; The chain transfer agent is mercaptoethanol; The initiator is benzoyl peroxide.

[0048] The preparation method of the hydroxyl acrylic resin includes the following steps: a. Add 82% of the mixed environmentally friendly solvent and glycidyl tert-carbonate to the reactor, purge with nitrogen and heat to the reflux temperature of 132±2℃, and maintain stability for 15 min; b. Add the weighed acrylate mixed monomers and 87.5% of the initiator and chain transfer agent mixture to the monomer dropping vessel; c. The material from step b is added dropwise at a constant rate to the reaction vessel from step a at 132±2℃, and the dropping time is controlled to be 5h; d. After the addition is complete, maintain the temperature at 132±2℃ for 1 hour to mature; e. First addition: Add 8.5% of the mixture of initiator and chain transfer agent and 12% of the mixed environmentally friendly solvent to the material in step d. The addition time is 15 min, and after the addition is completed, keep it at 132±2℃ for 1 hour. f. Second addition: Add the remaining 4% of the mixture of initiator and chain transfer agent, and 6% of the mixed environmentally friendly solvent. The addition time is 15 min, and after the addition is completed, keep it at 132±2℃ for 0.5 hours. g. Cool to 100±5℃, add diluent, mix well, and then test the solid content and viscosity performance indicators, and dilute to the qualified range; wherein, the diluent is a mixed solvent of butyl acetate and propylene glycol methyl ether acetate in a volume ratio of 4:1.

[0049] In this embodiment, the performance indicators of the high weather-resistant hydroxyl acrylic resin are as follows: solid content mass fraction of 70.1%, viscosity of 6000-8000 mPa·s (25±2℃), acid value of 5.7 mg KOH / g, and color number of No. 2.

[0050] In this embodiment, the core feature of the glycidyl tert-carbon ester molecule is its highly branched C10 tert-carbon alkyl side chain. This long side chain is connected to the polymer backbone via ester bonds, forming a large and hydrophobic "protective umbrella" in space. The large tert-carbon group creates a significant physical spatial barrier around the polymer backbone, effectively blocking and scattering incident ultraviolet light, reducing the probability of ultraviolet light directly attacking the polymer backbone (especially the C-C and CH bonds), and physically delaying the initiation of photodegradation.

[0051] Example 2 This embodiment of a high weather-resistant hydroxyl acrylic resin comprises the following raw materials in parts by weight: 58 parts of mixed acrylate monomers, 12 parts of cyclohexyl methacrylate, 0.85 parts of chain transfer agent, 26.55 parts of mixed environmentally friendly solvent, and 2.6 parts of initiator; The acrylate mixed monomers are a mixture of 0.67 parts methacrylic acid, 9.51 parts hydroxyethyl acrylate, 23.8 parts methyl methacrylate, 8.72 parts butyl acrylate and 15.3 parts butyl methacrylate; The mixed environmentally friendly solvent is a mixture of 21.25 parts butyl acetate and 5.3 parts propylene glycol methyl ether acetate; The initiator is benzoyl peroxide; The chain transfer agent is mercaptoethanol.

[0052] The preparation method of the hydroxyl acrylic resin includes the following steps: a. Add 82% mixed environmentally friendly solvent to the reactor, purge with nitrogen and heat to reflux temperature of 132±2℃, and maintain stability for 15 min; b. Add the weighed mixed acrylate monomers, cyclohexyl methacrylate, and 87.5% of the mixture of initiator and chain transfer agent to the monomer dropping vessel; c. The material from step b is added dropwise at a constant rate to the reaction vessel from step a at 132±2℃, and the dropping time is controlled to be 5h; d. After the addition is complete, maintain the temperature at 132±2℃ for 1 hour to mature; e. First addition: Add 8.5% of the mixture of initiator and chain transfer agent and 12% of the mixed environmentally friendly solvent to the material in step d. The addition time is 15 min, and after the addition is completed, keep it at 132±2℃ for 1 hour. f. Second addition: Add the remaining 4% of the mixture of initiator and chain transfer agent, and 6% of the mixed environmentally friendly solvent. The addition time is 15 min, and after the addition is completed, keep it at 132±2℃ for 0.5 hours. g. Cool to 100±5℃, add diluent, mix well, and then test the solid content and viscosity performance indicators, and dilute to the qualified range; wherein, the diluent is a mixed solvent of butyl acetate and propylene glycol methyl ether acetate in a volume ratio of 4:1.

[0053] In this embodiment, the performance indicators of the high weather-resistant hydroxyl acrylic resin are as follows: solid content mass fraction of 69.2%, viscosity of 7000-9000 mPa·s (25±2℃), acid value of 5.1 mg KOH / g, and color number of 1-2.

[0054] In this embodiment, cyclohexyl methacrylate introduces a saturated six-membered ring (cyclohexyl) structure into the polymer side chain, which enhances the rigidity of the polymer chain segments. The saturated cyclohexane ring does not contain unsaturated double bonds, making it less susceptible to absorbing UV light energy and generating free radicals that initiate degradation. This rigidity not only directly contributes to the high hardness of the coating but also restricts the vibration and rotation of the polymer backbone under UV irradiation, raising the energy barrier for photochemical reactions and thus improving UV resistance.

[0055] Example 3 This embodiment of a high weather-resistant hydroxyl acrylic resin comprises the following raw materials in parts by weight: 59 parts of acrylate mixed monomers, 10 parts of isobornyl methacrylate, 0.85 parts of chain transfer agent, 27.75 parts of mixed environmentally friendly solvent, and 2.4 parts of initiator; The acrylate monomer mixture is a mixture of 0.68 parts methacrylic acid, 9.65 parts hydroxyethyl acrylate, 24.25 parts methyl methacrylate, 8.85 parts butyl acrylate and 15.57 parts butyl methacrylate. The mixed environmentally friendly solvent is a mixture of 22.2 parts butyl acetate and 5.55 parts propylene glycol methyl ether acetate; The initiator is benzoyl peroxide; The chain transfer agent is mercaptoethanol.

[0056] The preparation method of the hydroxyl acrylic resin includes the following steps: a. Add 82% mixed environmentally friendly solvent to the reactor, purge with nitrogen and heat to reflux temperature of 132±2℃, and maintain stability for 15 min; b. Add the weighed mixed acrylate monomers, isobornyl methacrylate, and 87.5% of the mixture of initiator and chain transfer agent to the monomer dropping vessel; c. The material from step b is added dropwise at a constant rate to the reaction vessel from step a at 132±2℃, and the dropping time is controlled to be 5h; d. After the addition is complete, maintain the temperature at 132±2℃ for 1 hour to mature; e. First addition: Add 8.5% of the mixture of initiator and chain transfer agent and 12% of the mixed environmentally friendly solvent to the material in step d. The addition time is 15 min, and after the addition is completed, keep it at 132±2℃ for 1 hour. f. Second addition: Add the remaining 4% of the mixture of initiator and chain transfer agent, and 6% of the mixed environmentally friendly solvent. The addition time is 15 min, and after the addition is completed, keep it at 132±2℃ for 0.5 hours. g. Cool to 100±5℃, add diluent, mix well, and then test the solid content and viscosity performance indicators, and dilute to the qualified range; wherein, the diluent is a mixed solvent of butyl acetate and propylene glycol methyl ether acetate in a volume ratio of 4:1.

[0057] In this embodiment, the performance indicators of the high weather-resistant hydroxyl acrylic resin are as follows: solid content mass fraction of 69.4%, viscosity of 7000-9000 mPa·s (25±2℃), acid value of 4.9 mg KOH / g, and color number of 1-2.

[0058] In this embodiment, the isoborneol group in the bicyclic backbone of isoborneol methacrylate has a large spatial volume and also has very strong rigid side chains. Its large bicyclic structure forms an extreme steric hindrance shield around the polymer backbone, which can effectively physically block the diffusion of ultraviolet light, oxygen and water molecules, thereby inhibiting the occurrence of photodegradation reactions.

[0059] Comparative Example 1 This comparative example of a high weather-resistant hydroxyl acrylic resin comprises the following raw materials in parts by weight: 67.5 parts of mixed acrylate monomers, 29.1 parts of styrene, 30 parts of mixed environmentally friendly solvents, and 2.5 parts of initiator; The acrylate mixed monomers are a mixture of 0.65 parts methacrylic acid, 12.15 parts hydroxyethyl acrylate, 5.5 parts methyl methacrylate, 15.1 parts butyl acrylate and 5 parts butyl methacrylate; The mixed environmentally friendly solvent is a mixture of 24.5 parts butyl acetate and 5.5 parts propylene glycol methyl ether acetate; The initiator is benzoyl peroxide.

[0060] The preparation method of the high weather-resistant hydroxyl acrylic resin includes the following steps: a. Add 82% mixed environmentally friendly solvent to the reactor as a base, purge with nitrogen and heat to reflux temperature of 132±2℃, and maintain stability for 15 minutes; b. Add the weighed mixed acrylate monomers, styrene, and 87.5% initiator to the monomer dropping vessel; c. The material from step b is added dropwise at a constant rate to the reaction vessel from step a at 132±2℃, and the dropping time is controlled to be 5h; d. After the addition is complete, maintain the temperature at 132±2℃ for 1 hour to mature; e. First addition: Add 8.5% of the initiator and 12% of the mixed environmentally friendly solvent to the material in step d. The addition time is 15 min. After the addition is completed, keep it at 132±2℃ for 1 hour. f. Second addition: Add the remaining 4% of the initiator and 6% of the mixed environmentally friendly solvent. The addition time is 15 min. After the addition is completed, keep it at 132±2℃ for 0.5 hours. g. Cool to 100±5℃, add diluent, mix well, and then test the solid content and viscosity performance indicators, and dilute to the qualified range; wherein, the diluent is a mixed solvent of butyl acetate and propylene glycol methyl ether acetate in a volume ratio of 4:1.

[0061] In this comparative example, the performance indicators of the high weather-resistant hydroxyl acrylic resin are as follows: solid content (mass fraction) of 70.5%, viscosity of 3000-6000 mPa·s (25±2℃), acid value of 6.8 mg KOH / g, and color number of 1-2.

[0062] Comparative Example 2 This comparative example of a high weather-resistant hydroxyl acrylic resin comprises the following raw materials in parts by weight: 67.5 parts of mixed acrylate monomers, 30 parts of mixed environmentally friendly solvents, and 2.5 parts of initiator; The acrylate monomer mixture is a mixture of 0.7 parts methacrylic acid, 9.5 parts hydroxyethyl acrylate, 30.1 parts methyl methacrylate, 9.78 parts butyl acrylate and 17.42 parts butyl methacrylate. The mixed environmentally friendly solvent is a mixture of 24.5 parts butyl acetate and 5.5 parts propylene glycol methyl ether acetate; The initiator is benzoyl peroxide.

[0063] The preparation method of the high weather-resistant hydroxyl acrylic resin includes the following steps: a. Add 82% mixed environmentally friendly solvent to the reactor as a base, purge with nitrogen and heat to reflux temperature of 132±2℃, and maintain stability for 15 minutes; b. Add the weighed acrylate mixed monomers and 87.5% of the initiator to the monomer dropping vessel; c. The material from step b is added dropwise at a constant rate to the reaction vessel from step a at 132±2℃, and the dropping time is controlled to be 5h; d. After the addition is complete, maintain the temperature at 132±2℃ for 1 hour to mature; e. First addition: Add 8.5% of the initiator and 12% of the mixed environmentally friendly solvent to the material in step d. The addition time is 15 min. After the addition is completed, keep it at 132±2℃ for 1 hour. f. Second addition: Add the remaining 4% of the initiator and 6% of the mixed environmentally friendly solvent. The addition time is 15 min. After the addition is completed, keep it at 132±2℃ for 0.5 hours. g. Cool to 100±5℃, add diluent, mix well, and then test the solid content and viscosity performance indicators, and dilute to the qualified range; wherein, the diluent is a mixed solvent of butyl acetate and propylene glycol methyl ether acetate in a volume ratio of 4:1.

[0064] In this comparative example, the performance indicators of the high weather-resistant hydroxyl acrylic resin are as follows: solid content (mass fraction) of 70.0%, viscosity of 40000-60000 mPa·s (25±2℃), acid value of 9.6 mg KOH / g, and color number of 1-2.

[0065] Comparative Example 3 The composition of the high weather-resistant hydroxyl acrylic resin raw material described in this comparative example is the same as that in Example 1. The only difference is the experimental production process. The preparation method used in this comparative example includes the following steps: a. Add 82% of the mixed environmentally friendly solvent and glycidyl tert-carbonate as a base to the reactor and mix evenly. Purge with nitrogen and heat to the reflux temperature of 132±2℃, and maintain stability for 15 minutes. b. Add the weighed acrylate mixed monomers and 91.5% of the initiator and chain transfer agent mixture to the monomer dropping vessel; c. The material from step b is added dropwise at a constant rate to the reaction vessel from step a at 132±2℃, and the dropping time is controlled to be 5h; d. After the addition is complete, maintain the temperature at 132±2℃ for 1 hour to mature; e. Add 8.5% of the mixture of initiator and chain transfer agent and 18% of the mixed environmentally friendly solvent to the material in step d. The dripping time is 15 min. After the dripping is completed, keep it at 132±2℃ for 1 hour. f. Cool to 100±5℃, add diluent, mix well, and then test the solid content and viscosity performance indicators, and dilute to the qualified range; wherein, the diluent is a mixed solvent of butyl acetate and propylene glycol methyl ether acetate in a volume ratio of 4:1.

[0066] In this comparative example, the performance indicators of the high weather-resistant hydroxyl acrylic resin are as follows: solid content (mass fraction) of 68.2%, viscosity of 4000-6000 mPa·s (25±2℃), acid value of 6.5 mg KOH / g, and color number of 1-2.

[0067] test: 1. A clear varnish was prepared by mixing the high weather-resistant hydroxyl acrylic resin prepared in Examples 1-3 and Comparative Example 3 with an aliphatic isocyanate curing agent, BYK-052n defoamer, and LHP-96 leveling agent. The mixture was diluted with an environmentally friendly solvent to a suitable viscosity for spraying. The varnish was then evenly sprayed onto a treated tinplate surface (the surface was wiped with alcohol, dried, sanded smooth, and then cleaned thoroughly to ensure it was free of foreign matter). The surface was allowed to stand in a constant temperature and humidity chamber for 5 minutes to level, and then dried in an oven at 120℃ for 1 hour, with the film thickness controlled at 23±3 μm. After drying, the film was cured at room temperature, and the relevant properties were tested. The results are shown in Table 1 below.

[0068] Table 1 The multi-step, continuous dropwise addition and fractional replenishment of the precise polymerization process employed in this application, compared to the simplified process used in Comparative Example 3, has a decisive impact on the final resin and coating film properties. Although only one less initiator was added, the resin viscosity and properties measured in the comparative example showed a sharp decline compared to the example. This indicates that the process in Comparative Example 3 cannot ensure sufficient reaction and molecular structure regularity, resulting in excessive residual monomers and uneven molecular weight distribution in the resin, ultimately damaging the curing network and overall mechanical properties of the coating film.

[0069] 2. The high weather-resistant hydroxyl acrylic resins prepared in Examples 1-3 and Comparative Examples 1-2 were used to prepare two-component acrylic polyurethane topcoat products according to the formulation, and the relevant properties were tested. The results are shown in Table 2.

[0070] Table 2 Based on Table 2, a comprehensive analysis of the performance data of the two-component topcoats in Examples 1-3 and Comparative Examples 1-2, particularly their aging resistance and chemical resistance, strongly verifies that the introduction of functional monomers with large steric hindrance is the core mechanism for achieving the coating's superior weather resistance. In Comparative Example 1, the conjugated photosensitive effect of the benzene ring structure has a strong absorption effect on ultraviolet light, which causes the coating to show severe chalking and loss of gloss after 800 hours. The performance of Comparative Example 2 shows that the resin molecules that lack a specific large steric hindrance structure design have excessively high viscosity, which seriously affects the application and construction performance of the paint products. On the other hand, although their weather resistance is relatively stable in the early stage, the performance of the board surface declines sharply after a certain period of time, which also fails to meet the needs of high-end applications.

[0071] The three functional monomers with different structures used in Examples 1-3 all successfully enabled the coatings to exceed 2000 hours of artificial weathering resistance, with optimal levels of chalking, discoloration, and gloss loss. They collectively possess large side groups that construct effective physical and chemical barriers at the polymer molecular scale, preventing the formation of conjugated systems.

[0072] In summary, compared with existing related technologies, the beneficial effects of this application are as follows: 1. Environmental advantages of raw materials: The synthesis of hydroxyl acrylic resin in this application completely eliminates styrene monomers and benzene-based solvents such as benzene and toluene, and the product complies with green chemistry principles and the strictest environmental regulations; 2. Excellent product performance: The hydroxyl acrylic resin of this application has high solids and low viscosity characteristics, with a solids content of 70±2%, which significantly reduces the VOC content of the paint system; it has excellent stability: low acid value (≤6 mg KOH / g), light color (Fe-Co color number ≤4), and good storage stability; 3. Excellent film performance: By designing the molecular structure of the resin system and introducing a certain proportion of non-conjugated functional monomers with large steric hindrance, the steric hindrance effect can be generated by their large side group structure, which can effectively shield ultraviolet light and slow down the breaking rate of the polymer backbone, blocking the coupling path of electrons in the resin molecular structure, thereby reducing the formation of conjugated or oxidized structures in the coating, and giving the system excellent weather resistance.

[0073] 4. The resin provided in this application is particularly suitable for formulating architectural exterior wall coatings and automotive exterior topcoats that require extreme weather resistance, and has broad market application prospects.

[0074] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A hydroxyl acrylic resin, obtained by reacting raw materials comprising the following parts by weight: 52-64 parts of acrylate monomers, 5-15 parts of UV-resistant functional monomers, 0.5-1.5 parts of chain transfer agent, 20-35 parts of environmentally friendly solvent, and 1-3 parts of initiator; The hydroxy acrylic resin has a solid content of 70±2%, a viscosity of 6000-9000 mPa·s (25±2℃), an acid value ≤6mg KOH / g, and an Fe-Co color number ≤4.

2. The hydroxyl acrylic resin according to claim 1, wherein, The acrylate monomer is any one or a mixture of hard monomers, soft monomers, and hydroxyl-containing functional monomers; the hard monomer is selected from one or more of methacrylic acid, methyl methacrylate, and ethyl methacrylate; the soft monomer is selected from one or more of butyl acrylate and butyl methacrylate; the hydroxyl-containing functional monomer is hydroxyethyl acrylate and / or hydroxyethyl methacrylate; and / or The UV-resistant functional monomer is selected from one or more of glycidyl tert-carbonate, isobornyl methacrylate, and cyclohexyl methacrylate; and / or The chain transfer agent is selected from any one of mercaptoethanol, isooctyl mercaptoacetate, or dodecyl mercaptan; and / or The environmentally friendly solvent is selected from any one or a mixture of butyl acetate, propylene glycol methyl ether acetate, and propylene glycol butyl ether; and / or The initiator is selected from any one or more of benzoyl peroxide, azobisisobutyronitrile, and tert-butyl peroxide.

3. The hydroxyl acrylic resin according to claim 1 or 2, wherein, The acrylate monomers are mixed acrylate monomers; and / or The chain transfer agent is mercaptoethanol; and / or The environmentally friendly solvent is a mixed environmentally friendly solvent; and / or The initiator is benzoyl peroxide.

4. The hydroxyl acrylic resin according to claim 3, wherein, The acrylate monomer mixture is a mixture of methacrylic acid, hydroxyethyl acrylate, methyl methacrylate, butyl acrylate, and butyl methacrylate, wherein, by weight, 0.5-0.8 parts methacrylic acid, 9-10 parts hydroxyethyl acrylate, 23-27 parts methyl methacrylate, 8-10 parts butyl acrylate, and 15-16 parts butyl methacrylate; and / or The mixed environmentally friendly solvent is a mixture of butyl acetate and propylene glycol methyl ether acetate, wherein, by weight, butyl acetate comprises 21-23 parts and propylene glycol methyl ether acetate comprises 5-6 parts.

5. The hydroxyl acrylic resin according to claim 4, wherein, The hydroxyl acrylic resin is obtained by reacting the following raw materials in parts by weight: 61 parts of acrylate mixed monomers, 8 parts of UV-resistant functional monomers, 0.85 parts of chain transfer agent, 27.75 parts of mixed environmentally friendly solvents, and 2.4 parts of initiator. The acrylate mixed monomers are a mixture of 0.7 parts methacrylic acid, 9.8 parts hydroxyethyl acrylate, 25.67 parts methyl methacrylate, 9 parts butyl acrylate, and 15.83 parts butyl methacrylate; the mixed environmentally friendly solvent is a mixture of 21.75 parts butyl acetate and 6 parts propylene glycol methyl ether acetate. or The hydroxyl acrylic resin is obtained by reacting the following raw materials in parts by weight: 58 parts of acrylate mixed monomers, 12 parts of UV-resistant functional monomers, 0.85 parts of chain transfer agent, 26.55 parts of mixed environmentally friendly solvents, and 2.6 parts of initiator. The acrylate monomer mixture is a mixture of 0.67 parts methacrylic acid, 9.51 parts hydroxyethyl acrylate, 23.8 parts methyl methacrylate, 8.72 parts butyl acrylate, and 15.3 parts butyl methacrylate; the environmentally friendly solvent mixture is a mixture of 21.25 parts butyl acetate and 5.3 parts propylene glycol methyl ether acetate. or The hydroxyl acrylic resin is obtained by reacting the following raw materials in parts by weight: 59 parts of acrylate mixed monomers, 10 parts of UV-resistant functional monomers, 0.85 parts of chain transfer agent, 27.75 parts of mixed environmentally friendly solvents, and 2.4 parts of initiator. The acrylate monomer mixture is a mixture of 0.68 parts methacrylic acid, 9.65 parts hydroxyethyl acrylate, 24.25 parts methyl methacrylate, 8.85 parts butyl acrylate and 15.57 parts butyl methacrylate; the mixed environmentally friendly solvent is a mixture of 22.2 parts butyl acetate and 5.55 parts propylene glycol methyl ether acetate.

6. A method for preparing a hydroxyl acrylic resin according to any one of claims 1 to 5, wherein, Includes the following steps: a. Add a portion of the environmentally friendly solvent as a base material to the reactor, heat it to the reflux temperature under inert gas protection, and maintain the temperature; Simultaneously, acrylate monomers and UV-resistant functional monomers, along with some initiators and some chain transfer agents, are premixed to form a mixture; or Some environmentally friendly solvents and UV-resistant functional monomers are added to the reactor, and the temperature is raised to the reflux temperature and held under inert gas protection. Simultaneously, acrylate monomers, along with some initiators and some chain transfer agents, are premixed to form a mixture; b. The mixture is added dropwise to the reactor at a uniform rate at the reflux temperature; c. After the addition is complete, maintain the temperature at the reflux temperature for curing; d. Add a portion of the initiator, a portion of the chain transfer agent, and a portion of the environmentally friendly solvent to the material from step c for the first replenishment; after the addition is complete, keep the material at the reflux temperature. e. Add the remaining initiator, chain transfer agent, and environmentally friendly solvent dropwise for a second addition; after the addition is complete, maintain the temperature at the reflux temperature; f. Cool to 100±5℃, add diluted solvent and mix evenly, adjust to qualified viscosity and solid content, filter and discharge to obtain the hydroxyl acrylic resin.

7. The method according to claim 6, wherein, The reflux temperature is 132±2℃; and / or In step a, the heat preservation time is 10-20 minutes; and / or In step b, the dripping time is 4-6 hours; and / or In step c, the heat preservation and maturation time is 0.5-1.5 hours; and / or In step d, the heat preservation time is 0.5-1.5 hours; and / or In step e, the heat preservation time is 0.3-1h.

8. The method according to claim 6 or 7, wherein, In steps d and e, the initiator, the chain transfer agent, and the environmentally friendly solvent are added dropwise within 15 minutes.

9. An environmentally friendly coating, wherein the raw material of the environmentally friendly coating comprises the hydroxy acrylic resin of any one of claims 1 to 5, or the hydroxy acrylic resin prepared by the method of any one of claims 6 to 8; Optionally, the environmentally friendly coating is a two-component acrylic polyurethane coating, and its film has at least one of the following properties: artificial weathering resistance ≥2000 hours; adhesion grade 0; pencil hardness ≥2H; and neutral salt spray resistance ≥800 hours.

10. The application of the environmentally friendly coating of claim 9 in the fields of building exterior walls, automotive exteriors, or industrial protection.

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