Water-based paint as well as preparation method and application thereof

Abstract

The invention discloses a water-based coating as well as a preparation method and application thereof. The water-based coating comprises the following raw materials in parts by mass: 30-55 parts of water-based acrylic resin, 5-25 parts of amino resin, 1-5 parts of a phosphate adhesion promoter, 1-10 parts of an auxiliary agent, 5-25 parts of a film-forming cosolvent and 10-40 parts of water. The number average molecular weight of the water-based acrylic resin is 6000 to 13000g / mol; the hydroxyl value of the water-based acrylic resin is 70 to 100 mgKOH / g. The high-performance water-based paint is obtained by adopting the water-based acrylic resin with specific molecular weight and hydroxyl value and combining the amino resin and the phosphate adhesion promoter, the high-performance water-based paint is high in adhesion, good in high-temperature and low-temperature circulating washing resistance and good in alkali resistance, and particularly, a coating prepared from the paint can effectively pass a dish washing machine test, so that the service life of the coating is prolonged. The water-based paint has a good application prospect in coating protection of stainless steel substrates such as stainless steel vacuum cups.

Description

Technical Field

[0001] The invention belongs to the technical field of polymers, and in particular relates to a water-based coating and a preparation method and application thereof. Background Art

[0002] Metal materials are common substrates and are often used to prepare different products. In order to protect the performance of the products, a protective coating needs to be prepared on the stainless steel substrate. The coating needs to have good adhesion on the metal substrate. With the improvement of living standards, automatic washing machines such as dishwashers have become increasingly popular. Metal products in daily life, especially kitchen and bathroom hardware products such as thermos cups, also need to be washed by automatic washing machines such as dishwashers. Therefore, higher requirements are put forward for the protective coating on the surface of stainless steel products. In addition to meeting the adhesion requirements on the stainless steel substrate, the requirements for dishwasher resistance need to be considered. From the perspective of coating performance testing, in the dishwasher washing test, the surface coating of stainless steel products such as thermos cups needs to be repeatedly subjected to high and low temperature circulating water washing (60-80℃ high pressure washing and cooling washing) and dishwashing powder (alkaline) corrosion, and conventional coatings are difficult to pass the test. At present, some studies have proposed the use of modified resin technology to solve this problem, but the coating obtained is only 10 times in the dishwasher resistance test, which does not meet the standard of more than 50 times for high-end customers. In addition, powder coatings will also encounter the problem of white spots in dishwasher tests. Summary of the invention

[0003] In order to overcome at least one of the problems existing in the above-mentioned prior art, one of the objects of the present invention is to provide a water-based coating, in which the water-based acrylic resin has a specific molecular weight and hydroxyl value, and is combined with other raw materials such as amino resin and phosphate adhesion promoter to obtain good adhesion, resistance to high and low temperature cycle water washing and alkali resistance, especially being able to effectively pass the dishwasher test.

[0004] A second object of the present invention is to provide a method for preparing the above-mentioned water-based coating.

[0005] A third object of the present invention is to provide a coating.

[0006] A fourth object of the present invention is to provide an application of the above-mentioned water-based paint or the above-mentioned coating.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The first aspect of the present invention provides a water-based coating, comprising the following raw materials in parts by weight: 30 to 55 parts of water-based acrylic resin, 5 to 25 parts of amino resin, 1 to 5 parts of phosphate adhesion promoter, 1 to 10 parts of auxiliary agent, 5 to 25 parts of film-forming cosolvent, and 10 to 40 parts of water;

[0009] The number average molecular weight of the waterborne acrylic resin is 6000 to 13000 g / mol; the hydroxyl value of the waterborne acrylic resin is 70 to 100 mgKOH / g.

[0010] Preferably, the number average molecular weight of the aqueous acrylic resin is 8000-12500 g / mol; more preferably 10000-12000 g / mol; non-limiting specific examples include 10000 g / mol, 10200 g / mol, 10500 g / mol, 10800 g / mol, 11000 g / mol, 11200 g / mol, 11500 g / mol, 11800 g / mol or 12000 g / mol.

[0011] Preferably, the hydroxyl value of the water-based acrylic resin is 75 to 95 mgKOH / g; more preferably 80 to 90 mgKOH / g; non-limiting specific examples include 80 mgKOH / g, 82 mgKOH / g, 84 mgKOH / g, 85 mgKOH / g, 86 mgKOH / g, 88 mgKOH / g or 90 mgKOH / g.

[0012] In some specific embodiments of the present invention, the water-based acrylic resin is selected from Qingtian R1274.

[0013] Preferably, the amino resin is selected from partially methylated amino resin; the degree of etherification of the partially methylated amino resin is 30 to 70%, and more preferably 40 to 60%.

[0014] Preferably, the methylated amino resin is selected from partially methylated melamine formaldehyde resin.

[0015] In some specific embodiments of the present invention, the amino resin is selected from allnex cymel 325.

[0016] The etherification degree of allnex cymel 325 is in the range of 40-60%. It has a better application effect when used in the coating system of the present invention, and can especially enable the obtained coating to better pass the dishwasher resistance test.

[0017] Preferably, the phosphate adhesion promoter includes polyester phosphate, epoxy phosphate or a combination thereof; further preferably, the phosphate adhesion promoter is selected from polyester phosphate.

[0018] Preferably, the phosphate adhesion promoter is selected from phosphate adhesion promoters that do not contain bisphenol A.

[0019] Preferably, the auxiliary agent includes at least one of an amine neutralizer, a wetting agent, a defoamer or a leveling agent; further preferably, the auxiliary agent includes an amine neutralizer, a wetting agent, a defoamer and a leveling agent.

[0020] Preferably, in parts by mass, the auxiliary agent includes: 1-5 parts of amine neutralizer, 0.05-2 parts of wetting agent, 0.05-2 parts of defoamer, and 0.05-3 parts of leveling agent; further preferably, in parts by mass, the auxiliary agent includes: 2-4 parts of amine neutralizer, 0.1-1 parts of wetting agent, 0.1-1 parts of defoamer, and 0.1-1.5 parts of leveling agent; further preferably, in parts by mass, the auxiliary agent includes: 2-3 parts of amine neutralizer, 0.2-0.6 parts of wetting agent, 0.2-0.6 parts of defoamer, and 0.2-0.6 parts of leveling agent.

[0021] Preferably, the amine neutralizing agent includes at least one of aqueous ammonia, N,N-dimethylethanolamine, triethylamine or triethanolamine; further preferably, the amine neutralizing agent is selected from N,N-dimethylethanolamine.

[0022] Preferably, the wetting agent comprises at least one of an acetylenic glycol compound, a modified polysiloxane, a nonionic surfactant or a fluorine-containing surfactant.

[0023] In some specific embodiments of the present invention, the wetting agent is selected from Tego 4100.

[0024] Preferably, the defoaming agent includes at least one of polydimethylsiloxane, mineral oil or acrylate defoaming agent.

[0025] In some specific embodiments of the present invention, the defoaming agent is selected from Tego 825.

[0026] Preferably, the leveling agent includes at least one of polyester-modified silicone, polyether-modified silicone or fluorocarbon-modified acrylate; further preferably, the leveling agent is selected from fluorocarbon-modified acrylate.

[0027] In some specific embodiments of the present invention, the leveling agent is selected from EFKA3772.

[0028] Preferably, the film-forming co-solvent includes at least one of ethylene glycol butyl ether, propylene glycol methyl ether or diethylene glycol butyl ether; further preferably, the film-forming co-solvent includes ethylene glycol butyl ether, diethylene glycol butyl ether or a combination thereof.

[0029] Preferably, the water-based paint comprises the following raw materials in parts by mass: 35-50 parts of water-based acrylic resin, 10-20 parts of amino resin, 2-4 parts of phosphate adhesion promoter, 3-10 parts of additives, 10-20 parts of film-forming co-solvent, and 10-35 parts of water; further preferably, the water-based paint comprises the following raw materials in parts by mass: 40-45 parts of water-based acrylic resin, 10-18 parts of amino resin, 2-3 parts of phosphate adhesion promoter, 3-5 parts of additives, 12-18 parts of film-forming co-solvent, and 20-30 parts of water.

[0030] Preferably, the water-based coating comprises the following raw materials in parts by weight: 30-55 parts of water-based acrylic resin, 5-25 parts of amino resin, 1-5 parts of phosphate adhesion promoter, 1-5 parts of amine neutralizer, 0.05-2 parts of wetting agent, 0.05-2 parts of defoamer, 0.05-3 parts of leveling agent, 5-25 parts of film-forming cosolvent, and 10-40 parts of water; further preferably, the water-based coating comprises the following raw materials in parts by weight: 35-50 parts of water-based acrylic resin, 10-20 parts of amino resin, 2-4 parts of phosphate adhesion promoter, amine neutralizer The aqueous coating comprises the following raw materials in parts by weight: 40 to 45 parts of aqueous acrylic resin, 10 to 18 parts of amino resin, 2 to 3 parts of phosphate adhesion promoter, 2 to 3 parts of amine neutralizer, 0.2 to 0.6 parts of wetting agent, 0.2 to 0.6 parts of defoaming agent, 0.2 to 0.6 parts of leveling agent, 12 to 18 parts of film-forming solvent and 20 to 30 parts of water.

[0031] The second aspect of the present invention provides a method for preparing the water-based coating described in the first aspect of the present invention, comprising the following steps: mixing water-based acrylic resin, amino resin, phosphate adhesion promoter, additives, and film-forming co-solvent, and then adding water to mix to obtain the water-based coating.

[0032] Preferably, the water-based acrylic resin, amino resin, phosphate adhesion promoter, auxiliary agent and film-forming cosolvent are mixed by high-speed mixing; the rotation speed of the high-speed mixing is 1000-1500 r / min.

[0033] Preferably, the time for mixing the water-based acrylic resin, the amino resin, the phosphate adhesion promoter, the auxiliary agent, and the film-forming cosolvent is 25 to 30 minutes.

[0034] Preferably, after the water-based acrylic resin, amino resin, phosphate adhesion promoter, auxiliary agent and film-forming cosolvent are mixed, the fineness of the mixture is detected to be ≤15 μm, and then water is added for mixing.

[0035] Preferably, the method of adding water for mixing is low-speed mixing; the rotation speed of the low-speed mixing is 500-800 r / min.

[0036] Preferably, the time for adding water and mixing is 5 to 10 minutes.

[0037] The third aspect of the present invention provides a coating, which is prepared on a stainless steel substrate by comprising the water-based coating according to the first aspect of the present invention.

[0038] In some specific embodiments of the present invention, the stainless steel substrate is selected from a stainless steel thermos cup.

[0039] The coating of the present invention has good adhesion on the stainless steel substrate, and the coating has good resistance to high and low temperature circulating water washing and alkali resistance, and can play a good protective role on the stainless steel substrate.

[0040] Preferably, the thickness of the coating is in the range of 10 to 20 μm; more preferably, in the range of 12 to 15 μm.

[0041] The fourth aspect of the present invention provides an application of the water-based paint as described in the first aspect of the present invention, or the coating as described in the third aspect of the present invention in the protection of hardware, household appliances, and building materials.

[0042] The beneficial effects of the present invention are as follows: the present invention uses a water-based acrylic resin with a specific molecular weight and hydroxyl value, combined with an amino resin and a phosphate adhesion promoter, to obtain a high-performance water-based coating with strong adhesion, good high and low temperature cycle water washing resistance, and good alkali resistance. In particular, the coating prepared by the coating can effectively pass the dishwasher test. The water-based coating is applied to the coating protection of stainless steel substrates such as stainless steel thermos cups, which can effectively solve the problem that the current water-based coating is difficult to pass the dishwasher test.

[0043] Specifically, compared with the prior art, the present invention has the following advantages:

[0044] 1. The present invention adopts a water-based acrylic resin with a number average molecular weight of 6000-13000 g / mol and a hydroxyl value of 70-100 mgKOH / g. A large molecular weight of the resin can effectively improve the anti-sagging performance of the coating, and improve the wetting and spreading of the wet film on the substrate, which is helpful to improve the adhesion; however, too high a molecular weight will lead to a high dilution ratio, reduce the construction solid content, and cause the dry film to have no film thickness after curing, and the fullness will be poor; therefore, the water-based acrylic resin within the specific molecular weight range of the present invention is selected, and its surface drying is faster, which can meet the anti-sagging requirements and obtain better fullness. In addition, the higher the hydroxyl value of the water-based acrylic resin, the higher the cross-linking degree and the better the performance; however, too high a hydroxyl value will cause it to remain in the coating without complete reaction, and the hydrophilic functional groups contained in the resin will cause the coating performance to decrease, and at the same time cause the coating to become brittle; too low a hydroxyl value will cause insufficient cross-linking, and the coating will not reach the required strength; the water-based acrylic resin within the specific hydroxyl value range of the present invention is selected to obtain a coating with good mechanical properties and adhesion.

[0045] 2. Both phosphate adhesion promoters and silane coupling agent adhesion promoters can improve the adhesion of the coating on the stainless steel substrate, improve the impact resistance, and improve the boiling resistance after adding; however, relatively speaking, in the coating system of the present invention, the effect of using phosphate adhesion promoters is better than that of silane coupling agent adhesion promoters in terms of stainless steel boiling resistance. At the same time, the polyester phosphate used in the present invention has a lower reaction temperature than epoxy phosphate, a higher crosslinking density, and better dishwasher resistance test performance; and polyester phosphate does not contain bisphenol A, which can better meet the requirements of food safety and export restrictions. DETAILED DESCRIPTION

[0046] The content of the present invention is further described in detail below through specific examples. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the principles set forth in the present invention all belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific data exemplified below. The raw materials, reagents or devices used in the following examples and comparative examples, unless otherwise specified, can all be obtained from conventional commercial sources, or can be obtained by existing known methods.

[0047] It should be noted that the specific information of some raw materials used in the examples and comparative examples of the present invention are as follows:

[0048] Water-based acrylic resin: number average molecular weight is 11000g / mol, hydroxyl value is 85mgKOH / g, brand is Qingtian R1274;

[0049] Partially methylated amino resin: Brand A is Cymel 325 from Allnex;

[0050] Brand B is Yuanbang 5625A;

[0051] Polyester phosphate: brand name is Longhai 2504;

[0052] Epoxy phosphate: brand name is Changxing 4901-B-72;

[0053] Leveling agent EFKA3772: fluorocarbon modified acrylate;

[0054] Wetting agent: brand Tego 4100;

[0055] Defoaming agent: brand Tego 825;

[0056] Amine neutralizer: N,N-dimethylethanolamine;

[0057] Film-forming co-solvent: ethylene glycol butyl ether and diethylene glycol butyl ether, the mass ratio of the two is 1:1.

[0058] Examples 1 to 5 and Comparative Examples 1 to 8

[0059] Examples 1 to 5 and Comparative Examples 1 to 8 each provide a water-based coating, the specific raw materials are shown in Table 1 and Table 2, and the specific preparation method is as follows:

[0060] The other raw materials except deionized water are blended, and then dispersed at a high speed of 1000-1500 r / min for 25-30 minutes. After the fineness is detected to be ≤15 μm, deionized water is added, and then mixed at a low speed of 500-800 r / min for 5-10 minutes to obtain the water-based coating.

[0061] Table 1 Raw materials and their dosages of Examples 1 to 5 and Comparative Examples 1 to 4 (dosage units are parts by mass)

[0062]

[0063]

[0064] Table 2 Raw materials and dosage of comparative examples 5 to 8 (dosage units are parts by mass)

[0065]

[0066] Performance Testing

[0067] The water-based coatings of Examples 1 to 5 and Comparative Examples 1 to 8 were sprayed to form panels, and the specific steps were as follows:

[0068] First, the water-based coatings of Examples 1 to 5 and Comparative Examples 1 to 8 were diluted to a 25-second spraying time, sprayed on the stainless steel substrate, and the dry film was controlled between 12 and 15 μm. They were baked and cured at 150 degrees for 20 minutes, and then taken out and cooled for 1 hour before the following performance tests were performed:

[0069] Adhesion: measured according to GB / T 9286-2021; Grade 0 is qualified;

[0070] Hardness: Determined according to GB / T 6739-2022; 2H is qualified;

[0071] Impact performance: measured according to GB / T 1732-2020; 50kg·cm is qualified;

[0072] Dishwasher test: Using Haier EYW101286BKTU1 dishwasher high-power mode, 100 times is qualified.

[0073] Table 3 Performance test results of Examples 1 to 5 and Comparative Examples 1 to 8

[0074] Adhesion hardness Impact performance (kg·cm) Dishwasher test (times) Dilution ratio (%) Example 1 Level 0 2H 50 155 30 Example 2 Level 0 2H 50 140 30 Example 3 Level 0 2H 50 150 30 Example 4 Level 0 2H 50 110 45 Example 5 Level 0 2H 50 160 55 Comparative Example 1 Level 0 2H 50 130 35 Comparative Example 2 Level 0 2H 50 120 35 Comparative Example 3 Level 0 2H 50 125 35 Comparative Example 4 Level 0 2H 50 115 35 Comparative Example 5 Level 1 2H 50 20 25 Comparative Example 6 Level 0 3H 40 45 70 Comparative Example 7 Level 1 3H 40 35 60 Comparative Example 8 Level 0 2H 50 30 55

[0075] As can be seen from Table 3, Examples 1 to 5 and Comparative Examples 1 to 4 can all meet the requirements of 100 dishwasher test; by comparing Examples 1 to 5 with Comparative Examples 1 to 4, it can be seen that by using different amino resins as cross-linking agents, Allnex Cymel 325 is slightly better than Yuanbang 5625A in dishwasher resistance test (for example, Example 1 is better than Example 3); the use of polyester phosphate adhesion promoter is better than epoxy phosphate adhesion promoter, and the number of dishwasher resistance tests is more (for example, Comparative Example 1 is better than Comparative Example 3); the coating with a relatively high amount of amino resin has correspondingly better dishwasher resistance (for example, Example 1 is better than Example 2).

[0076] It can be seen from Examples 1 to 5 and Comparative Examples 5 to 8 that when other components and dosages are the same and only the number average molecular weight or hydroxyl value of the waterborne acrylic resin is changed, Comparative Example 5 uses a waterborne acrylic resin with a number average molecular weight of 4000 g / mol and a hydroxyl value of 60 mgKOH / g. The result after curing is: the dishwasher test is only 20 times, and the stainless steel adhesion is level 1; and because the resin molecular weight is low, the dilution ratio is very low, which will increase the paint cost and it is easy to sag. Comparative Example 6 uses a waterborne acrylic resin with a number average molecular weight of 15000 g / mol and a hydroxyl value of 110 mgKOH / g. The result after curing is: the dilution ratio is very high, resulting in low construction solid content and poor fullness. Although the dishwasher test is improved, the impact performance is reduced. Comparative Example 7 uses a waterborne acrylic resin with a hydroxyl value of 11000 g / mol and a hydroxyl value of 120 mgKOH / g. The result after curing is: the adhesion is reduced, not as good as the adhesion of the embodiment, and the impact performance is reduced. Comparative Example 8 uses a water-based acrylic resin with a weight of 11000 g / mol and a hydroxyl value of 60 mgKOH / g. The results after curing are: adhesion and impact resistance meet the requirements, but the dishwasher test does not meet the requirements.

[0077] The embodiment of the present invention adopts a water-based acrylic resin with a number average molecular weight of 6000-13000 g / mol and a hydroxyl value of 70-100 mgKOH / g. A large molecular weight of the resin can effectively improve the anti-sagging performance of the coating, and improve the wetting and spreading of the wet film on the substrate, which is helpful to improve the adhesion; however, too high a molecular weight will lead to a high dilution ratio, reduce the construction solid content, and cause the dry film to have no film thickness after curing, and the fullness will be poor; therefore, the water-based acrylic resin within the specific molecular weight range of the present invention is selected, and its surface drying is faster, which can meet the anti-sagging requirements and obtain better fullness. In addition, the higher the hydroxyl value of the water-based acrylic resin, the higher the cross-linking degree and the better the performance; however, too high a hydroxyl value will cause it to remain in the coating without complete reaction, and the hydrophilic functional groups contained in the resin will cause the coating performance to decrease, and at the same time cause the coating to become brittle; too low a hydroxyl value will cause insufficient cross-linking, and the coating will not reach the required strength; selecting a water-based acrylic resin within the specific hydroxyl value range of the present invention can obtain a coating with good mechanical properties and adhesion.

[0078] Phosphate adhesion promoters and silane coupling agent adhesion promoters can both improve the adhesion of the coating on the stainless steel substrate, while improving the impact resistance, and both have improvements in boiling resistance after addition; however, relatively speaking, in the coating system of the present invention, the effect of using phosphate adhesion promoters is better than that of silane coupling agent adhesion promoters in terms of stainless steel boiling resistance. At the same time, the polyester phosphate used in the embodiment of the present invention has a lower reaction temperature than epoxy phosphate, a higher crosslinking density, and better dishwasher resistance test performance; and polyester phosphate does not contain bisphenol A, which can better meet the requirements of food safety and export restrictions.

[0079] In summary, the present invention uses a water-based acrylic resin with a specific molecular weight and hydroxyl value, combined with an amino resin and a phosphate adhesion promoter to obtain a high-performance water-based coating with strong adhesion, good resistance to high and low temperature cycle water washing, and good alkali resistance. In particular, the coating prepared using the coating can effectively pass the dishwasher test. The water-based coating has good application prospects in the coating protection of stainless steel substrates such as stainless steel thermos cups.

Claims

1. A water-based paint, characterized in that: The invention comprises the following raw materials in parts by weight: 30 to 55 parts of water-based acrylic resin, 5 to 25 parts of amino resin, 1 to 5 parts of phosphate adhesion promoter, 1 to 10 parts of auxiliary agent, 5 to 25 parts of film-forming cosolvent, and 10 to 40 parts of water; The number average molecular weight of the waterborne acrylic resin is 6000 to 13000 g / mol; the hydroxyl value of the waterborne acrylic resin is 70 to 100 mgKOH / g.

2. The water-based paint according to claim 1, characterized in that: The amino resin is selected from partially methylated amino resin; The etherification degree of the partially methylated amino resin is 30-70%.

3. The water-based paint according to claim 1, characterized in that: The phosphate adhesion promoter is selected from phosphate adhesion promoters that do not contain bisphenol A.

4. The water-based paint according to claim 1, characterized in that: The auxiliary agent includes at least one of an amine neutralizer, a wetting agent, a defoaming agent or a leveling agent.

5. The water-based paint according to claim 1, characterized in that: In parts by mass, the auxiliary agent includes: 1 to 5 parts of an amine neutralizer, 0.05 to 2 parts of a wetting agent, 0.05 to 2 parts of a defoaming agent, and 0.05 to 3 parts of a leveling agent.

6. The water-based paint according to claim 4 or 5, characterized in that: The amine neutralizer includes at least one of aqueous ammonia, N,N-dimethylethanolamine, triethylamine or triethanolamine; and / or, the wetting agent comprises at least one of an acetylenic glycol compound, a modified polysiloxane, a nonionic surfactant or a fluorine-containing surfactant; and / or, the defoaming agent comprises at least one of polydimethylsiloxane, mineral oil or acrylate defoaming agent; And / or, the leveling agent includes at least one of polyester-modified silicone, polyether-modified silicone or fluorocarbon-modified acrylate.

7. The water-based paint according to claim 1, characterized in that: The film-forming auxiliary solvent includes at least one of ethylene glycol butyl ether, propylene glycol methyl ether or diethylene glycol butyl ether.

8. A method for preparing a water-based coating as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: The water-based acrylic resin, amino resin, phosphate adhesion promoter, auxiliary agent and film-forming cosolvent are mixed, and then water is added for mixing to obtain the water-based coating.

9. A coating, characterized in that: The invention is prepared by coating the water-based coating according to any one of claims 1 to 7 on a stainless steel substrate.

10. Use of the water-based paint according to any one of claims 1 to 7, or the coating according to claim 9, in the protection of hardware, household appliances, and building materials.

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