Bio-based closed type non-release polyurethane-polyacrylate dispersion as well as preparation method and application thereof

Abstract

The invention discloses a bio-based closed type release-free polyurethane-polyacrylate dispersion as well as a preparation method and application thereof, the preparation method comprises the following steps: S1, mixing an acrylate monomer, isocyanate, a hydroxyl acrylate monomer and a sealing agent for reaction to obtain a mixed solution A; s2, mixing an acrylic monomer, an acrylate monomer, a vinyl monomer, an acrylamide monomer, the mixed solution A and an initiator to obtain a mixed solution B; and S3, reacting a bio-based chain extender with the mixed solution B at 50-65 DEG C, dispersing with a neutralizer, and reacting at 80-90 DEG C to obtain the bio-based closed release-free polyurethane-polyacrylate dispersion. The bio-based water-based two-component coating prepared by the method successfully solves the problems of activation period limitation, performance improvement, environmental friendliness and the like of the existing water-based two-component polyurethane coating. According to the scheme, the pot life is long, the performance reaches the level of a water-based double-component polyurethane coating, and meanwhile, the water-based double-component polyurethane coating has the remarkable environment-friendly advantage and the characteristic that the process is simplified.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and particularly relates to a bio-based closed-type non-releasing polyurethane-polyacrylate dispersion and a preparation method and application thereof. Background Art

[0002] In many application scenarios, the surface of an object needs to be protected, decorated, and given special functions by coatings. At present, most common wood coatings on the market are solvent-based coatings, which contain more than 50% of organic solvents. These solvents will evaporate into the atmosphere during the construction process, which will not only pollute the environment, but also may damage human health and bring certain safety hazards. Therefore, the water-based nature of coatings has become an important development trend in the global coatings industry. Water-based coatings are mainly divided into water-based single-component and water-based two-component polyurethane coatings. However, there is a large gap between water-based single-component coatings and traditional solvent-based coatings in terms of film properties such as water resistance, chemical resistance and hardness, which seriously limits its promotion in practical applications. In contrast, water-based two-component polyurethane coatings have excellent mechanical properties, water resistance and chemical resistance, which can be comparable to solvent-based coatings, effectively overcoming the shortcomings of single-component water-based coatings. The principle of water-based two-component polyurethane coatings is that the isocyanate group of the water-based curing agent reacts with the hydroxyl group of the water-based hydroxyl component, thereby increasing the cross-linking density of the paint film and improving the overall performance of the paint film. However, since the isocyanate group of the curing agent will also react with water, its application period is usually short, generally not exceeding 4 hours, which has become one of the key factors restricting its widespread application.

[0003] In summary, the development of a water-based two-component polyurethane coating with a long application period, especially a product based on bio-based materials, has become an important technical issue that needs to be urgently solved in the current industry. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a bio-based closed non-release polyurethane-polyacrylate dispersion and its preparation method and application. The present invention develops a water-based two-component polyurethane coating with a long application period and a repair function, focusing on bio-based materials. The preparation method uses an acrylate monomer that will subsequently participate in free radical polymerization as a solvent for the isocyanate blocking reaction, avoiding the addition of an inert solvent, and adopts a two-component design (component A contains a dispersion, and component B is a cross-linking agent, which does not react with water), so that the coating has excellent water resistance, chemical resistance, high cross-linking density, high hardness, scratch resistance, wear resistance and repair function, which is suitable for high-end wood, automobiles, metal corrosion protection and other fields, and promotes the environmental protection and high performance development of water-based coatings.

[0005] The invention also provides a bio-based closed type non-releasing polyurethane-polyacrylate dispersion.

[0006] The present invention also provides a bio-based waterborne coating.

[0007] The present invention also provides an application of the bio-based waterborne coating in the fields of wood product preparation, automobile manufacturing or anti-corrosion of metal products.

[0008] In the first aspect of the present invention, a bio-based blocked non-release polyurethane-acrylate dispersion is provided. The preparation method includes the following steps:

[0009] S1. Mix acrylate monomers, isocyanates, hydroxyacrylate monomers and blocking agents and react to obtain a mixed solution A;

[0010] S2. Mix acrylic monomers, acrylate monomers, vinyl monomers, acrylamide monomers, mixed solution A and initiators to obtain a mixed solution B;

[0011] S3. React the bio-based chain extender with the mixed solution B at 50-65 °C, then disperse it with a neutralizing agent and react at 80-90 °C to obtain a bio-based blocked non-release polyurethane-acrylate dispersion;

[0012] In step S1, the acrylate monomers include acrylate monomers without hydroxyl groups;

[0013] The blocking agents include hydroxyl-containing iminocarboxylic acid-based blocking agents;

[0014] The acrylamide monomers include acrylamide monomers containing secondary amino groups;

[0015] The bio-based chain extender includes vegetable oils containing two or more epoxy groups;

[0016] The neutralizing agent includes a tertiary amine neutralizing agent.

[0017] According to the embodiments of the first aspect of the present invention, it has at least the following beneficial effects:

[0018] In view of the above problems existing in the existing methods for preparing polyurethane-polyacrylate dispersions and the obtained polyurethane-polyacrylate dispersions, on the one hand, the present invention provides a bio-based blocked non-release polyurethane-polyacrylate dispersion and a preparation method thereof. Using acrylate monomers as diluents, the NCO of isocyanate reacts with acrylic hydroxy esters and blocking agents to obtain a blocked isocyanate containing double bonds, which is then mixed with other monomers such as acrylic acid and acrylamide and initiators, and polymerized and chain-extended at low temperature to obtain a bio-based blocked non-release polyurethane-polyacrylate dispersion. This preparation method uses acrylate monomers that will participate in free radical polymerization later as solvents for the isocyanate blocking reaction, avoiding the addition of inert solvents; the free radical polymerization of this preparation method selects low-temperature polymerization, and the epoxy groups of vegetable oil chain extenders will not crosslink excessively with polyacrylate, thus avoiding too high viscosity of the prepolymer and being more conducive to water dispersion. The subsequent heat preservation temperature is lower than the deblocking temperature of the blocked polyurethane, which will neither cause the deblocking of the blocked polyurethane nor cause the epoxy groups of the vegetable oil chain extender and the amino groups on the polymer chain to crosslink further. Specifically, the purpose of designing the reaction temperature range in step S3 is as follows: 1. Avoid the deblocking of the blocked polyurethane: By controlling the heat preservation and crosslinking temperature within the range lower than the deblocking temperature of the blocked polyurethane, the deblocking of some blocked isocyanate groups (NCO groups) is effectively prevented. If the temperature approaches or exceeds the deblocking temperature, the deblocked isocyanate groups will react with the hydroxyl groups and water in the system, not only resulting in the release of the blocking agent, but also reducing the repair performance and stability of the product. The temperature range design of the present invention avoids this phenomenon, ensuring the stability of the blocked polyurethane and its excellent performance in subsequent applications; 2. Control side reactions: The reaction of deblocked isocyanate groups with hydroxyl groups and water will generate by-products (such as urea bonds or carbamate bonds), which will not only affect the crosslinking density and mechanical properties of the product, but also lead to the release of the blocking agent, reducing the environmental protection and safety of the product. The temperature range design of the present invention effectively inhibits the occurrence of such side reactions, improving the purity and performance of the product; 3. Avoid emulsion boiling: The upper limit of the reaction temperature range is controlled within the range far from the boiling point of water (100 °C), avoiding the phenomenon of emulsion boiling caused by too high temperature. Emulsion boiling will not only make the reaction system difficult to control, but also cause uneven dispersion of reactants, affecting the uniformity and performance of the final product. The temperature range design of the present invention ensures the stability and controllability of the reaction system, providing reliable technical support for large-scale production; 4. Optimize the crosslinking reaction: In the low-temperature stage of 50-65 °C, the bio-based chain extender (vegetable oil containing epoxy groups) and the amino groups on the polymer chain undergo preliminary crosslinking, avoiding excessive crosslinking of epoxy groups with polyacrylate, thus controlling the viscosity of the prepolymer and facilitating subsequent dispersion operations. In the high-temperature stage of 80-90 °C, the crosslinking reaction between epoxy groups and amino groups is further promoted, improving the crosslinking density and mechanical properties of the product, while ensuring that the blocked polyurethane does not deblock.

[0019] In some embodiments of the present invention, the preparation method comprises the following steps:

[0020] S1. By mass, 20 - 35 parts of acrylate monomer, 15 - 30 parts of isocyanate, and 5 - 25 parts of hydroxyacrylate monomer are reacted at 50 - 70 °C and then mixed with 5 - 20 parts of blocking agent and reacted at 70 - 90 °C to obtain a mixed solution A;

[0021] S2. 0 - 3 parts of acrylic monomer, 5 - 15 parts of acrylate monomer, 5 - 15 parts of vinyl monomer, 5 - 15 parts of acrylamide monomer, the mixed solution A, and 1 - 3 parts of initiator are mixed to obtain a mixed solution B;

[0022] S3. 5 - 20 parts of bio - based chain extender are reacted with the mixed solution B at 50 - 65 °C and then dispersed with 5 - 15 parts of neutralizer and reacted at 80 - 90 °C to obtain a bio - based blocked polyurethane - acrylate dispersion without release.

[0023] In step S1, the reaction temperature of 50 - 70 °C ensures the smooth progress of the preliminary reaction between the acrylate monomer and isocyanate, and the subsequent reaction conditions of 70 - 90 °C drive the completion of the blocking reaction through thermal activation without relying on a catalyst, avoiding the drawbacks brought by the traditional catalytic system - the introduction of a catalyst will significantly reduce the de - blocking temperature of the blocked isocyanate (NCO), resulting in the premature de - blocking of some NCO groups in the subsequent processes (such as the chain - extending or dispersion stage), and then reacting with the active amino or hydroxyl groups in the system. This side reaction will not only cause an abnormal increase in the viscosity of the prepolymer but also may lead to out - of - control cross - linking or even gelation, seriously affecting the stability and processing performance of the product.

[0024] In some embodiments of the present invention, the preparation method comprises the following steps:

[0025] S1. By mass, 20 - 35 parts of acrylate monomer and 15 - 30 parts of isocyanate are mixed and stirred, then heated to 50 - 70 °C, 5 - 25 parts of hydroxyacrylate monomer are added dropwise, and the addition is completed within 0.5 - 1.5 hours. Stirring is continued while maintaining the temperature for 20 - 40 minutes, then heated to 70 - 90 °C, 5 - 20 parts of blocking agent are added, and the reaction is continued while maintaining the temperature for 2 - 4 hours to form a mixed solution A for standby;

[0026] S2. By mass, 0 - 3 parts of acrylic monomer, 5 - 15 parts of acrylate monomer, 5 - 15 parts of vinyl monomer, 5 - 15 parts of acrylamide monomer, the mixed solution A, and 1 - 3 parts of initiator are mixed evenly to form a mixed solution B for standby;

[0027] S3. Add 5 - 20 parts of the bio - based chain extender into a four - necked flask equipped with a thermometer, a condenser, a stirring paddle and a constant - pressure dropping funnel. Mix and stir, and heat. When the temperature reaches 50 - 65°C, start dropping the mixture B, and finish dropping in 3.5 - 5 hours. After dropping, stir and keep warm for 30 minutes, then cool down to 40°C. Add 5 - 15 parts of the neutralizer, stir for 5 - 10 minutes, then add 250 - 400 parts of deionized water and disperse at high speed for 3 - 10 minutes. Heat up to 80 - 90°C and continue the reaction for 60 minutes. Then cool down to 40°C, filter and discharge to obtain the bio - based blocked polyurethane - acrylate dispersion without release.

[0028] In some embodiments of the present invention, the acrylate monomer is at least one of methyl methacrylate, butyl acrylate, isobornyl acrylate, cyclohexyl methacrylate and benzyl methacrylate.

[0029] In some embodiments of the present invention, the acrylic monomer is at least one of acrylic acid and methacrylic acid.

[0030] In some embodiments of the present invention, the vinyl monomer includes styrene.

[0031] In some embodiments of the present invention, the hydroxy - acrylate monomer is at least one of 2 - hydroxyethyl acrylate, 2 - hydroxypropyl acrylate, 2 - hydroxyethyl methacrylate and 2 - hydroxypropyl methacrylate.

[0032] In some embodiments of the present invention, the initiator is at least one of azodiisooctanenitrile, diisopropyl peroxydicarbonate and dicyclohexyl peroxydicarbonate.

[0033] In some embodiments of the present invention, the blocking agent is at least one of 2 - (hydroxyimino) propanoic acid and 2 - hydroxyiminocyclopentanecarboxylic acid.

[0034] In some embodiments of the present invention, the bio - based isocyanate is at least one of PDI trimer and 1,5 - pentamethylene diisocyanate.

[0035] In some embodiments of the present invention, the bio - based chain extender includes at least one of GreenSoft D special epoxy soybean oil, GreenSoft H special epoxy soybean oil and epoxy linseed oil ELO 9 - 5 TM among others.

[0036] In some embodiments of the present invention, the neutralizer is at least one of triethylamine, N,N - dimethylethanolamine and N,N - dimethylcyclohexylamine.

[0037] In a second aspect of the present invention, a bio-based closed non-release polyurethane-polyacrylate dispersion is provided, which is prepared by the described preparation method.

[0038] Advantages of the present invention: The bio-based closed non-release polyurethane-polyacrylate dispersion prepared by the present invention does not contain inert solvents; by controlling the reaction temperature, the epoxy groups of epoxidized soybean oil react step by step with the amino groups on the polymer chain, so that the prepolymer can be dispersed in water at low viscosity, making the prepolymer have better dispersion stability; after dispersion, the polymer continues to chain-extend, which can further improve the storage stability of the dispersion and also improve the performance of the final paint film; the blocking agent used is a blocking agent containing carboxyl groups, so that the blocked NCO groups are located on the periphery of the latex particles, which is more conducive to cross-linking after deblocking, and the deblocked blocking agent can be fixed by the cross-linking agent, which is more environmentally friendly and the paint film has better performance; and this preparation method has the advantages of simple operation, easy control and low cost, and can batch-prepare the bio-based closed non-release polyurethane-polyacrylate dispersion.

[0039] In a third aspect of the present invention, a bio-based waterborne coating is provided, and the preparation raw materials include the bio-based closed non-release polyurethane-polyacrylate dispersion described above.

[0040] In some embodiments of the present invention, the bio-based waterborne coating includes the following components A of the preparation raw materials in parts by weight:

[0041]

[0042] In some embodiments of the present invention, the preparation raw materials of the bio-based waterborne coating further include: component B,

[0043] Component B includes a cross-linking agent.

[0044] In some embodiments of the present invention, the cross-linking agent includes an aziridine polymer cross-linking agent.

[0045] In some embodiments of the present invention, the preparation method of the bio-based waterborne coating includes the following steps:

[0046] Premix water and a film-forming aid and add them to the bio-based closed non-release polyurethane-polyacrylate dispersion, then sequentially add an antifoaming agent, a thickening agent, a wetting agent and a neutralizing agent, disperse for 10-30 minutes, and filter to obtain component A of the bio-based waterborne coating. Component A and component B are mixed in a certain proportion before use. The addition amount of component B is 3-8% of the dispersion in component A, and the ratio of aziridine groups to carboxyl groups is 1.1-1.5.

[0047] The B component of the bio-based waterborne two-component coating includes a crosslinker that can react with carboxyl groups. The crosslinker can fix the hydroxyiminocarboxylic acid blocking agent released when the NCO is unblocked, which is more environmentally friendly and has better paint film performance. The bio-based waterborne two-component room-temperature curing coating prepared with a bio-based closed non-releasing polyurethane-polyacrylate dispersion can be repaired to a certain extent by high-temperature hot pressing if there is physical damage to the coating that has not been baked at high temperature. The bio-based waterborne two-component baking paint prepared with a bio-based closed non-releasing polyurethane-polyacrylate dispersion has better paint film performance than room-temperature curing performance, with high gloss, high transparency, excellent water and chemical resistance, high crosslinking density, high hardness, scratch resistance, wear resistance, etc. It can be used in high-end wood coatings, automotive coatings, metal anti-corrosion coatings and other industrial protective coatings.

[0048] In some embodiments of the present invention, the film-forming aid includes at least one of propylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether and dipropylene glycol butyl ether.

[0049] In some embodiments of the present invention, the defoaming agent includes at least one of a polyether siloxane copolymer defoaming agent and a modified polysiloxane copolymer solution.

[0050] In some embodiments of the present invention, the polyether siloxane copolymer defoamer includes at least one of TEGO-800, TEGO-805, TEGO-815 and TEGO-825.

[0051] In some embodiments of the present invention, the modified polysiloxane copolymer solution includes at least one of BYK-019 and BYK-020.

[0052] In some embodiments of the present invention, the thickener includes at least one of a nonionic polyurethane associative thickener, a hydrophobically modified alkali-swellable associative thickener, an alkali-swellable non-associative thickener, and a nonionic associative thickener.

[0053] In some embodiments of the present invention, the nonionic polyurethane associative thickener comprises RM-8W.

[0054] In some embodiments of the present invention, the hydrophobically modified alkali-swellable associative thickener includes TT-935.

[0055] In some embodiments of the present invention, the alkali-swellable non-associative thickener comprises ASE-60.

[0056] In some embodiments of the present invention, the nonionic associative thickener includes at least one of TEGO ViscoPlus 3000, TEGO ViscoPlus 3030, and TEGO ViscoPlus 3060.

[0057] In some embodiments of the present invention, the wetting agent includes at least one of polyether siloxane copolymer, nonionic organic surfactant, and polyether-modified polysiloxane solution.

[0058] In some embodiments of the present invention, the polyether siloxane copolymer includes TEGO-245.

[0059] In some embodiments of the present invention, the nonionic organic surfactant includes TEGO-500.

[0060] In some embodiments of the present invention, the polyether-modified polysiloxane solution includes BYK-346.

[0061] In some embodiments of the present invention, the aziridine polymer crosslinking agent is one or more of HD100, HD105, and HD110 from Kanglejia Company;

[0062] In the fourth aspect of the present invention, there is provided the application of the bio-based waterborne two-component coating in the fields of wood product preparation, automobile manufacturing, or anti-corrosion of metal products. Detailed Embodiments

[0063] In order to make the technical solutions of the present invention clearer and more understandable to those skilled in the art, the following examples are listed for illustration. It should be noted that the following examples do not limit the scope of protection required by the present invention.

[0064] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial channels or can be obtained by existing known methods.

[0065] The following examples are further defined. The acrylate monomers are one or several of methyl methacrylate, butyl acrylate, isobornyl acrylate, cyclohexyl methacrylate, and / or benzyl methacrylate from Sanmu Company;

[0066] The acrylic monomers are acrylic acid or methacrylic acid from Sanmu Company;

[0067] The vinyl monomer is styrene from Sanmu Company;

[0068] The hydroxyacrylate monomer is one of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate from Changxing Company;

[0069] The initiator is one of 2,2'-azobis(2-methylbutyronitrile) from Shanghai Titan Company, diisopropyl peroxydicarbonate from Wuhan Karnox Company, and dicyclohexyl peroxydicarbonate.

[0070] The bio-based isocyanate is the PDI trimer from Covestro One of CQ N 7300 and 1,5-pentamethylene diisocyanate Stabio PDI of Mitsui & Co., Ltd.;

[0071] The blocking agent is one of 2-(hydroxyimino)propionic acid and 2-hydroxyiminocyclopentanecarboxylic acid;

[0072] The bio-based chain extender is GreenSoft D special epoxy soybean oil, GreenSoft H special epoxy soybean oil, and epoxy linseed oil ELO of Xingbang High Polymer Materials Co., Ltd. 9-5 TM One of them; the neutralizing agent is triethylamine, N,N-dimethylethanolamine, or N,N-dimethylcyclohexylamine of Dow Chemical Company.

[0073] The defoaming agent is one or more of polyether silicone copolymer defoaming agents TEGO-800, TEGO-805, TEGO-815, TEGO-825 of TEGO company and modified polysiloxane copolymer solutions BYK-019, BYK-020 of BYK company;

[0074] The thickener is one or more of nonionic polyurethane associative thickener RM-8W, hydrophobic modified alkali-swellable associative thickener TT-935, alkali-swellable non-associative thickener ASE-60 of DOW company and nonionic associative thickeners TEGOViscoPlus 3000, TEGO ViscoPlus 3030, TEGO ViscoPlus 3060 of TEGO company;

[0075] The wetting agent is one or more of polyether silicone copolymer TEGO-245, nonionic organic surfactant TEGO-500 of TEGO company and polyether-modified polysiloxane solution BYK-346 of BYK company;

[0076] The basic performance test includes: the hydroxyl and isocyanate group concentrations are obtained by theoretical calculation, and the hydroxyl and isocyanate group concentrations are the ratios of the amounts of substances of the hydroxyl and isocyanate groups to the mass of the emulsion or coating solids, with the unit of mol / 100g. The film performance is tested with reference to GB / T23999-2009 "Waterborne Wood Coatings for Interior Decoration and Refurbishment", and the gloss, hardness, water resistance, dry heat resistance, and alcohol resistance are tested.

[0077] Example 1

[0078] A bio-based blocked non-releasing polyurethane-polyacrylate dispersion 1 is prepared by the following steps:

[0079] S1. Mix 7.2 parts by mass of methyl methacrylate, 25 parts by mass of butyl acrylate and 22.5 parts by mass of PDI trimer, stir, and then heat to 60°C. Dropwise add 5.7 parts by mass of 2-hydroxyethyl acrylate over 1 hour. After dropping, continue stirring at 60°C for 30 minutes, then heat to 90°C, add 10 parts by mass of 2-(hydroxyimino)propanoic acid, and continue reacting at 90°C for 2.5 hours to form a mixed solution A1 for standby;

[0080] S2. Mix 0.5 part by mass of acrylic acid, 14 parts by mass of isobornyl acrylate, 6.3 parts by mass of styrene, 6.2 parts by mass of N-tert-butylacrylamide, mixed solution A1, and 2 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) uniformly to form a mixed solution B1 for standby;

[0081] S3. Add 9.1 parts by mass of GreenSoft D to a four-necked flask equipped with a thermometer, a condenser, a stirring paddle and a constant pressure dropping funnel, mix and stir, and heat. When the temperature reaches 60°C, start dropping mixed solution B1 over 4 hours. After dropping, stir and keep the temperature for 30 minutes, then cool to 40°C, add 7.4 parts by mass of N,N-dimethylethanolamine, stir for 5 minutes, then add 290 parts by mass of deionized water and disperse at high speed for 3 minutes, heat to 80°C, continue reacting for 60 minutes, cool to 40°C, filter and discharge to obtain the bio-based blocked non-releasing polyurethane-polyacrylate dispersion 1.

[0082] After the bio-based blocked non-releasing polyurethane-polyacrylate dispersion is formulated into the bio-based waterborne coating 1, the addition amount of the crosslinking agent HD-100 during use is 5% of the dispersion 1.

[0083] Example 2

[0084] A bio-based blocked non-releasing polyurethane-polyacrylate dispersion 2 is prepared by the following steps:

[0085] S1. Mix 12 parts by mass of methyl methacrylate, 18.5 parts by mass of butyl acrylate and 18.7 parts by mass of 1,5-pentamethylene diisocyanate, stir, and then heat to 65°C. Dropwise add 15.8 parts by mass of 2-hydroxypropyl acrylate over 1 hour. After dropping, continue stirring at 65°C for 30 minutes, then heat to 85°C, add 17.3 parts by mass of 2-hydroxyiminocyclopentanecarboxylic acid, and continue reacting at 85°C for 3.5 hours to form a mixed solution A2 for standby;

[0086] S2. Mix 1 part by mass of methacrylic acid, 8.5 parts by mass of cyclohexyl methacrylate, 11 parts by mass of styrene, 6 parts by mass of N-ethylacrylamide, mixed solution A2, and 2.5 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) uniformly to form a mixed solution B2 for standby;

[0087] S3. Add 10.9 parts of GreenSoftH into a four-necked flask equipped with a thermometer, a condenser, a stirring paddle and a constant-pressure dropping funnel, mix and stir, and heat. When the temperature reaches 60 °C, start to dropwise add the mixture B2, and finish dropping in 4 hours. After dropping, stir and keep warm for 30 minutes, cool down to 40 °C, add 13.5 parts of N,N-dimethylcyclohexylamine, stir for 5 minutes, then add 339.25 parts of deionized water and disperse at high speed for 3 minutes, heat up to 80 °C, continue to react for 60 minutes, cool down to 40 °C, filter and discharge to obtain the bio-based blocked non-release polyurethane-polyacrylate dispersion 2.

[0088] After the bio-based blocked non-release polyurethane-polyacrylate dispersion is formulated into the bio-based waterborne coating 2, the addition amount of the crosslinking agent HD-105 during use is 5% of the dispersion 2.

[0089] Comparative Example 1

[0090] A bio-based blocked non-release polyurethane-polyacrylate dispersion 3. The difference between this comparative example and the examples lies in increasing the temperature of free radical polymerization, and it is prepared by the following steps:

[0091] S1. By mass, mix and stir 7.2 parts of methyl methacrylate, 25 parts of butyl acrylate and 22.5 parts of PDI trimer, then heat up to 60 °C, dropwise add 5.7 parts of 2-hydroxyethyl acrylate, finish dropping in 1 hour, continue to stir at 60 °C for 30 minutes, heat up to 90 °C, add 10 parts of 2-(hydroxyimino)propanoic acid, and continue to react at 90 °C for 2.5 hours to form the mixture A3 for standby;

[0092] S2. By mass, mix 0.5 part of acrylic acid, 14 parts of isobornyl acrylate, 6.3 parts of styrene, 6.2 parts of N-tert-butylacrylamide, the mixture A1, and 2 parts of azobisisoheptonitrile evenly to form the mixture B3 for standby;

[0093] S3. Add 9.1 parts of GreenSoft D into a four-necked flask equipped with a thermometer, a condenser, a stirring paddle and a constant-pressure dropping funnel, mix and stir, and heat. When the temperature reaches 90 °C, start to dropwise add the mixture B3, finish dropping in 4 hours, after dropping, stir and keep warm for 30 minutes, cool down to 40 °C, add 7.4 parts of N,N-dimethylethanolamine, stir for 5 minutes, then add 290 parts of deionized water and disperse at high speed for 3 minutes, filter and discharge to obtain the bio-based blocked non-release polyurethane-polyacrylate dispersion 3.

[0094] After the bio-based blocked non-release polyurethane-polyacrylate dispersion is formulated into the bio-based waterborne coating 3, the addition amount of the crosslinking agent HD-100 during use is 5% of the dispersion 3.

[0095] Comparative Example 2

[0096] A bio-based closed-type non-release polyurethane-polyacrylate dispersion 4. The difference between this comparative example and the example lies in canceling the final heat preservation and crosslinking. It is prepared by the following steps:

[0097] S1. By mass, mix 7.2 parts of methyl methacrylate, 25 parts of butyl acrylate and 22.5 parts of PDI trimer, stir and heat to 60°C, dropwise add 5.7 parts of hydroxyethyl acrylate, finish dropping in 1 hour, continue to stir at 60°C for 30 minutes, heat to 90°C, add 10 parts of 2-(hydroxyimino)propanoic acid, and continue to react at 90°C for 2.5 hours to form a mixed solution A4 for standby;

[0098] S2. By mass, mix 0.5 part of acrylic acid, 14 parts of isobornyl acrylate, 6.3 parts of styrene, 6.2 parts of N-tert-butylacrylamide, mixed solution A4, and 2 parts of azobisisoheptonitrile evenly to form a mixed solution B4 for standby;

[0099] S3. Add 9.1 parts of GreenSoft D to a four-necked flask equipped with a thermometer, a condenser, a stirring paddle and a constant pressure dropping funnel, mix and stir and heat. When the temperature reaches 60°C, start to dropwise add the mixed solution B4, finish dropping in 4 hours. After dropping, stir and keep warm for 30 minutes, cool to 40°C, add 7.4 parts of N,N-dimethylethanolamine, stir for 5 minutes, then add 290 parts of deionized water and disperse at high speed for 3 minutes, and filter and discharge to obtain the bio-based closed-type non-release polyurethane-polyacrylate dispersion 4.

[0100] After the bio-based closed-type non-release polyurethane-polyacrylate dispersion is formulated into a bio-based waterborne coating 4, the addition amount of the crosslinking agent HD-100 during use is 5% of the dispersion 4.

[0101] Comparative Example 3

[0102] A bio-based closed-type non-release polyurethane-polyacrylate dispersion 5. The difference between this comparative example and the example is that the acrylamide monomer is a primary amine. It is prepared by the following steps:

[0103] S1. By mass, mix 7.2 parts of methyl methacrylate, 25 parts of butyl acrylate and 22.5 parts of PDI trimer, stir and heat to 60°C, dropwise add 5.7 parts of hydroxyethyl acrylate, finish dropping in 1 hour, continue to stir at 60°C for 30 minutes, heat to 90°C, add 10 parts of 2-(hydroxyimino)propanoic acid, and continue to react at 90°C for 2.5 hours to form a mixed solution A5 for standby;

[0104] S2. By mass, mix 0.5 part of acrylic acid, 14 parts of isobornyl acrylate, 6.3 parts of styrene, 1.73 parts of acrylamide, mixed solution A5, and 2 parts of azobisisoheptonitrile evenly to form a mixed solution B5 for standby;

[0105] S3. Add 9.1 parts of GreenSoft D into a four-necked flask equipped with a thermometer, a condenser, a stirring paddle and a constant-pressure dropping funnel, mix and stir, and heat. After the temperature reaches 60 °C, start dropping the mixed liquid B5, and finish dropping it in 4 hours. After dropping, stir and keep warm for 30 minutes, cool down to 40 °C, add 7.4 parts of N,N-dimethylethanolamine, stir for 5 minutes, then add 278.6 parts of deionized water and disperse at high speed for 3 minutes, heat up to 80 °C, continue the reaction for 60 minutes, cool down to 40 °C, filter and discharge to obtain the bio-based blocked non-release polyurethane-polyacrylate dispersion 5.

[0106] After the bio-based blocked non-release polyurethane-polyacrylate dispersion is formulated into the bio-based waterborne coating 5, the addition amount of the crosslinking agent HD-100 during use is 5% of the dispersion 5.

[0107] Comparative Example 4

[0108] A bio-based blocked non-release polyurethane-polyacrylate dispersion 6. The difference between this comparative example and the examples is that the blocked isocyanate does not contain double bonds, and it is prepared by the following steps:

[0109] S1. By mass, mix and stir 7.2 parts of methyl methacrylate, 25 parts of butyl acrylate and 15 parts of PDI trimer, then heat up to 90 °C, add 10 parts of 2-(hydroxyimine)propanoic acid, and continue to react at 90 °C for 2.5 hours to form the mixed liquid A6 for standby;

[0110] S2. By mass, mix 0.5 part of acrylic acid, 14 parts of isobornyl acrylate, 6.3 parts of styrene, 6.2 parts of N-tert-butylacrylamide, the mixed liquid A6, and 2 parts of azobisisoheptonitrile evenly to form the mixed liquid B6 for standby;

[0111] S3. Add 9.1 parts of GreenSoft D into a four-necked flask equipped with a thermometer, a condenser, a stirring paddle and a constant-pressure dropping funnel, mix and stir, and heat. After the temperature reaches 60 °C, start dropping the mixed liquid B6, and finish dropping it in 4 hours. After dropping, stir and keep warm for 30 minutes, cool down to 40 °C, add 7.4 parts of N,N-dimethylethanolamine, stir for 5 minutes, then add 256.8 parts of deionized water and disperse at high speed for 3 minutes, heat up to 80 °C, continue the reaction for 60 minutes, cool down to 40 °C, filter and discharge to obtain the bio-based blocked non-release polyurethane-polyacrylate dispersion 6.

[0112] After the bio-based blocked non-release polyurethane-polyacrylate dispersion is formulated into the bio-based waterborne coating 6, the addition amount of the crosslinking agent HD-100 during use is 5% of the dispersion 6.

[0113] Comparative Example 5

[0114] A bio-based closed non-releasing polyurethane-polyacrylate dispersion 7, the difference between this comparative example and the embodiment is that the free radical polymerization temperature is too high, and the closed polyurethane is unblocked during the free radical polymerization stage, which is prepared by the following steps:

[0115] S1. In parts by mass, 7.2 parts of methyl methacrylate, 25 parts of butyl acrylate and 22.5 parts of PDI trimer were mixed and stirred, and the temperature was raised to 60°C, 5.7 parts of hydroxyethyl acrylate were added dropwise, and the mixture was dripped over 1 hour, and the mixture was stirred at 60°C for 30 minutes, and the mixture was heated to 90°C, 10 parts of 2-(hydroxyimino)propionic acid were added, and the mixture was reacted at 90°C for 2.5 hours to form a mixed solution A7 for standby use;

[0116] S2. In parts by mass, 0.5 parts of acrylic acid, 14 parts of isobornyl acrylate, 6.3 parts of styrene, 6.2 parts of N-tert-butylacrylamide, a mixed solution A7, and 2 parts of azobisisoheptanenitrile were mixed to form a mixed solution B7 for standby use;

[0117] S3. Add 9.1 parts of GreenSoft D to a four-necked flask equipped with a thermometer, a condenser, a stirring paddle and a constant pressure dropping funnel, stir and heat, and start to drip the mixed solution B7 when the temperature reaches 140°C. The mixture is dripped in 4 hours. After the dripping is completed, stir and keep warm for 30 minutes, cool to 40°C, add 7.4 parts of N,N-dimethylethanolamine, stir for 5 minutes, add 290 parts of deionized water and disperse at high speed for 3 minutes, heat to 80°C, continue to react for 60 minutes, cool to 40°C, and filter the material to obtain a bio-based closed-type non-release polyurethane-polyacrylate dispersion 7.

[0118] After the bio-based closed non-releasing polyurethane-polyacrylate dispersion is formulated into the bio-based water-based coating 7, the addition amount of the crosslinking agent HD-100 is 5% of the dispersion 7 when used.

[0119] Test Example 1

[0120] Test Example A bio-based water-based coating was prepared. The bio-based closed non-releasing polyurethane-polyacrylate dispersion was prepared in the examples and comparative examples. The specific steps were as follows:

[0121] The bio-based waterborne coating component A is composed of the following components in parts by weight:

[0122]

[0123] The preparation method of the bio-based waterborne coating is as follows: Add the bio-based blocked non-releasing polyurethane-polyacrylate dispersion into a stirring kettle with a rotation speed of 700 revolutions per minute. Premix water, dipropylene glycol butyl ether and dipropylene glycol methyl ether and then add them into the stirring kettle. Sequentially add TEGO-800, RM-8W, and TEGO-245, disperse for 20 minutes, filter and discharge to obtain the component A of the bio-based waterborne coating. Component A and component B (aziridine crosslinking agent) are mixed in a certain proportion before use.

[0124] Two groups of paint films were prepared with the bio-based waterborne coating. Group A was only dried at 50 °C for 2 hours, and group B was baked at 135 °C for 30 minutes after being dried at 50 °C for 2 hours. Their performances are shown in Table 1 and Table 2 respectively.

[0125] The test standards are as follows:

[0126] Appearance of the coating film: Visual inspection;

[0127] Pencil hardness: GB / T 6739-2006;

[0128] Gloss of the coating film / (60°, %): GB / T 9754-2007;

[0129] Water resistance (25 °C, 24 h): GB / T 4893.1-2020;

[0130] Dry heat resistance (70 ± 2 °C, 15 h): GB / T 4893.3-2020;

[0131] Ethanol resistance (50%, 1 h): GB / T 4893.1-2020;

[0132] Scratch repair: Film was prepared on tinplate. Use a blade to draw a "×" on the surface of the coating film to ensure that the coating film is penetrated. Set the iron at 150 °C and press for 10 minutes. Immerse the scratched area in water for 24 h and observe whether it rusts;

[0133] Table 1. Parameters of bio-based blocked non-releasing polyurethane-polyacrylate dispersion and performance parameters of bio-based waterborne coating under room temperature curing

[0134] project Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Appearance Slightly transparent Slightly transparent cream Slightly transparent cream Slightly transparent cream Unblockable NCO concentration, 0.084 0.089 0.084 0.084 0.087 0.095 0.084 Hydroxyl concentration, mol / 100g 0.042 0.045 0.042 0.042 0.044 0.047 0.042 Bio-based content% 21.1 17.4 21.1 21.1 21.9 18.8 21.1 Store at 50℃ for 30 days No abnormality No abnormality Layering Layering Layering Slightly Layering Applicable period, h 24 24 24 24 24 24 24 Wet film appearance Semi-transparent Semi-transparent cream Slightly transparent cream Slightly transparent cream Pencil hardness 2H 2H 2H HB 2H H H Coating gloss / (60°,%) 96 95 92 85 88 93 92 Water resistance (25℃, 24h) Level 5 Level 5 Level 5 Level 4 Level 5 Level 4 Level 3 Dry heat resistance (70±2℃, 15min) Level 4 Level 4 Level 4 Level 3 Level 4 Level 4 Level 4 Ethanol resistance (50%, 1h) Level 4 Level 4 Level 4 Level 4 Level 4 Level 4 Level 3 Scratch Repair No rust No rust No rust No rust No rust No rust rust

[0135] Table 2. Parameters of bio-based blocked non-releasing polyurethane-polyacrylate dispersion and performance parameters of bio-based waterborne coating under baking curing

[0136]

[0137]

[0138] As can be seen from the above table, compared with Comparative Example 1 and Example 1, the polymerization temperature in the free radical polymerization stage increased from 60 °C to 90 °C, and the crosslinking degree of the prepolymer and the crosslinking agent in the free radical polymerization stage increased significantly, resulting in too high viscosity of the prepolymer, poor dispersion stability, and further resulting in milky white appearance and poor storage stability; compared with Comparative Example 2 and Example 1, due to the cancellation of the 80 °C heat preservation crosslinking process at the end, the crosslinking density of the polymer decreased, and there were residues of some secondary amino groups and epoxy groups. Therefore, the film hardness was low and the resistance of the room temperature cured film was poor. Compared with Comparative Example 3 and Example 1, since the reaction activity of primary amine was significantly higher than that of secondary amine, the bio-based crosslinking agent reacted faster with primary amine, and the viscosity of the prepolymer increased significantly, resulting in milky white appearance of the dispersion and poor storage stability; compared with Comparative Example 4 and Example 1, since the blocked isocyanate had no double bond groups, it was not incorporated into the polymer main chain, resulting in poor storage stability and low hardness of the room temperature cured film. Compared with Comparative Example 5 and Example 1, the free radical polymerization temperature was higher than the deblocking temperature of the blocked isocyanate. Therefore, the blocked isocyanate was deblocked and crosslinked in the free radical polymerization stage, resulting in too high viscosity of the prepolymer, poor dispersion stability and storage stability. From Examples 1 and 2, it can be known that the present invention discloses a preparation method of a bio-based blocked polyurethane-polyacrylate dispersion, and the film made of the prepared bio-based waterborne coating has the advantages of high hardness, good water and chemical resistance, high crosslinking density, scratch resistance, wear resistance, etc., and can be applied to high-grade wood coatings, automotive coatings, metal anti-corrosion coatings and other industrial protective coatings.

[0139] The above has described the embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A preparation method of a bio-based closed and non-releasing polyurethane-polyacrylate dispersion, characterized in that, The preparation method includes the following steps: S1. Mix acrylate monomer, isocyanate, hydroxyacrylate monomer and a blocking agent and react to obtain a mixed solution A; S2. Mix acrylic monomer, acrylate monomer, vinyl monomer, acrylamide monomer, mixed solution A and an initiator to obtain a mixed solution B; S3. React a bio-based chain extender with the mixed solution B at 50-65 °C, then disperse it with a neutralizing agent and react at 80-90 °C to obtain a bio-based blocked non-release polyurethane-polyacrylate dispersion; The acrylate monomer described in step S1 includes acrylate monomers without hydroxyl groups; The blocking agent includes hydroxylimine carboxylic acid-based blocking agents; The acrylamide monomer includes acrylamide monomers containing secondary amino groups; The bio-based chain extender includes vegetable oils containing two or more epoxy groups; The neutralizing agent includes tertiary amine neutralizing agents.

2. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: S1. By mass, react 20-35 parts of acrylate monomer, 15-30 parts of isocyanate, 5-25 parts of hydroxyacrylate monomer at 50-70 °C, then mix with 5-20 parts of a blocking agent and react at 70-90 °C to obtain a mixed solution A; S2. Mix 0-3 parts of acrylic monomer, 5-15 parts of acrylate monomer, 5-15 parts of vinyl monomer, 5-15 parts of acrylamide monomer, mixed solution A and 1-3 parts of an initiator to obtain a mixed solution B; S3. React 5-20 parts of a bio-based chain extender with the mixed solution B at 50-65 °C, then disperse it with 5-15 parts of a neutralizing agent and react at 80-90 °C to obtain a bio-based blocked non-release polyurethane-polyacrylate dispersion.

3. The preparation method according to claim 1, characterized in that, The acrylate monomer includes at least one of methyl methacrylate, butyl acrylate, isobornyl acrylate, cyclohexyl methacrylate and benzyl methacrylate.

4. The preparation method according to claim 1, characterized in that, The acrylic monomer includes at least one of acrylic acid and methacrylic acid.

5. The preparation method according to claim 1, characterized in that, The blocking agent includes at least one of 2-(hydroxyimine)propionic acid and 2-hydroxyimine cyclopentanecarboxylic acid.

6. The preparation method according to claim 1, wherein The neutralizing agent includes at least one of triethylamine, N,N-dimethylethanolamine and N,N-dimethylcyclohexylamine.

7. A bio-based closed-type non-release polyurethane-polyacrylate dispersion, characterized in that, Prepared by the preparation method according to any one of claims 1-6.

8. A bio-based waterborne coating, characterized in that, The preparation raw materials include the bio-based blocked non-release polyurethane-polyacrylate dispersion according to claim 7.

9. The bio-based waterborne coating according to claim 8, characterized in that, Component A of the preparation raw materials includes the following parts by weight: 60-80 parts of bio-based blocked non-release polyurethane-polyacrylate dispersion; 10. Application of a bio-based waterborne two-component coating according to claim 8 or 9 in the fields of wood product preparation, automobile manufacturing or anti-corrosion of metal products.

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