High-solid low-viscosity resin based on glycidyl tertiary carboxylic ester, preparation method and polyurethane coating

Abstract

The invention discloses a high-solid low-viscosity resin based on glycidyl tertiary carboxylic ester, a preparation method and application of the high-solid low-viscosity resin in a polyurethane coating, and belongs to the technical field of polymer synthesis. The high-solid low-viscosity resin based on glycidyl tertiary carboxylic ester is characterized in that the high-solid low-viscosity resin based on glycidyl tertiary carboxylic ester comprises the following raw materials: glycidyl tertiary carboxylic ester, polybasic acid and a catalyst; the molar ratio of the glycidyl tertiary carboxylic ester to the polybasic acid is 1: (0.9-1.1), and the polybasic acid is at least one of dimethylolpropionic acid and dimethylolbutyric acid. The invention aims to provide hydroxyl resin with high solid content, low viscosity, high reaction activity and high crosslinking potential.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polymer synthesis, in particular to a glycidyl tertiary carbonate-based high-solid low-viscosity resin, a preparation method thereof and a polyurethane coating. BACKGROUND

[0002] With the enhancement of environmental awareness and the increasing strictness of environmental regulations, the paint industry is facing great challenges and changes. Reducing the content of volatile organic compounds (VOC) in the paint system has become the main direction of industry development, which not only helps to reduce environmental pollution, but also protects people's health. High solid content paint, as one of the effective ways to achieve low VOC emission, has received extensive attention and research. It can reduce the amount of organic solvent used while meeting the performance requirements, thereby reducing VOC emissions. At the same time, the performance of the coating, such as drying speed, hardness, chemical resistance and weather resistance, directly affects the application range and service life of the coating, so the performance requirements for the resin are also increasing.

[0003] In the prior art, in order to meet the basic performance requirements of the paint, traditional hydroxyl acrylic resin or polyester resin is usually used. These resins have a wide range of applications in the paint industry and have certain advantages, such as good film-forming property and chemical corrosion resistance. When it is necessary to increase the solid content of the paint, the formula and synthesis process of the resin are often adjusted to achieve this goal. However, this method has certain limitations. In actual operation, the traditional hydroxyl acrylic resin or polyester resin often has a sharp increase in viscosity when increasing the solid content. In order to ensure the construction performance of the paint, a large amount of organic solvent must be added to reduce the viscosity, which undoubtedly increases the VOC emissions. In addition, in order to improve the performance of the coating, the crosslinking density and functional group activity of the resin are often considered. Generally speaking, resins containing primary hydroxyl groups have high reactivity, which is beneficial to rapid curing, and increasing the hydroxyl functionality of the resin can increase the crosslinking density of the coating, thereby improving the hardness and resistance of the coating. However, in actual application, it is very difficult to simultaneously achieve high solid content, low viscosity, high reactivity and high functionality, and the existing resin system cannot meet these performance requirements.

[0004] The prior art has obvious defects. The traditional hydroxyl acrylic resin or polyester resin has a sharp increase in viscosity when increasing the solid content, which brings great difficulties to the construction and application of the paint. In order to ensure the smooth progress of the construction, a large amount of organic solvent must be added to reduce the viscosity, which not only increases the cost, but also leads to a large amount of VOC emissions, which does not meet the environmental protection requirements. Moreover, it is difficult to find a resin that can simultaneously have the characteristics of high solid content, low viscosity, high reactivity and high functionality, which cannot meet the demand of the modern paint industry for high-performance and environmentally friendly coatings. SUMMARY

[0005] The present application provides a glycidyl tertiary carbonate-based high-solid low-viscosity resin, a preparation method thereof and a polyurethane coating.

[0006] The first aspect of the present application is to provide a glycidyl tertiary carbonate-based high-solid low-viscosity resin, which adopts the following technical solution: A glycidyl tertiary carbonate-based high-solid low-viscosity resin, the high-solid low-viscosity resin has the following molecular structure: Or ; Wherein R1, R2, R3 are branched alkyl of tertiary carbonic acid.

[0007] In a preferred embodiment, the raw material of the high-solid low-viscosity resin comprises glycidyl tertiary carbonate, polybasic acid and catalyst. Wherein the polybasic acid is at least one of dimethylol propanoic acid and dimethylol butanoic acid.

[0008] In a preferred embodiment, the molar ratio of the glycidyl tertiary carbonate to the polybasic acid is 1: (0.9-1.1).

[0009] In a preferred embodiment, the number average molecular weight of the high-solid low-viscosity resin is 600-900 g / mol, the hydroxyl value is 390-450 mgKOH / g, the solid content is 85-95%, and the viscosity is 800-2500 mPa·s (25℃).

[0010] By adopting the above technical solution, the present application generates a low molecular weight and high branching structure through precise ring-opening addition of glycidyl tertiary carbonate and dimethylol acid, and effectively reduces the viscosity of the resin by using the large steric hindrance effect of tertiary carbonate. The viscosity of the resin can still be maintained within the suitable processing range of 1000-2000 mPa·s under the condition of about 90% high solid content. Moreover, the obtained numerical value of the present application accurately contains two primary hydroxyl groups and one secondary hydroxyl group on each molecular chain, which has higher functionality and primary hydroxyl group ratio compared to traditional resins. The resin has high reactivity with isocyanate and can form a highly cross-linked network structure, thereby effectively solving the problem of viscosity increase of high solid content coating, and due to the high solid content, it is easier to configure a coating with VOC content lower than 300 g / L or even lower, which can better meet the environmental protection requirements.

[0011] In a preferred embodiment, the catalyst is one of stannous octoate and tetrabutylammonium bromide.

[0012] In a preferred embodiment, the catalyst is used in an amount of 0.05-1% of the total mass of the glycidyl ester of versatic acid and the polybasic acid.

[0013] The second aspect of the present application is to provide a preparation method of the high-solid low-viscosity resin based on glycidyl ester of versatic acid as described above, comprising the following steps: S1, adding the polybasic acid and the catalyst into a solvent, stirring and mixing, and heating; S2, adding the glycidyl ester of versatic acid dropwise and controlling the reaction temperature; S3, after the dropwise addition is completed, keeping the reaction until the epoxy groups are completely reacted, cooling, and filtering to obtain the high-solid low-viscosity resin.

[0014] Further preferably, the solvent is an ester, a ketone, an aromatic hydrocarbon, or a mixture thereof, such as ethyl acetate, propylene glycol methyl ether acetate, methyl isobutyl ketone, toluene, etc.

[0015] In a preferred embodiment, the temperature of the step S1 and the step S2 is 100-120℃.

[0016] By adopting the technical scheme, the preparation method of the present application is a one-step ring-opening addition reaction, the raw materials are easy to obtain, the process conditions are mild, and the industrial production is easy, and the small molecule by-products do not need to be removed by post-treatment.

[0017] The third aspect of the present application is to provide a polyurethane coating, comprising an A component and a B component, the A component at least comprising the high-solid low-viscosity resin as described above, and the B component at least comprising a polyisocyanate curing agent.

[0018] In a preferred embodiment, the equivalent ratio of the hydroxyl groups and the isocyanate groups in the A component and the B component is 1: (0.9-1.2).

[0019] By adopting the technical scheme, the high-solid low-viscosity resin obtained by the present application is applied to the polyurethane coating, and due to the high activity of the resin, the isocyanate groups react rapidly to form a dense crosslinked network, so that the hardness, wear resistance, solvent resistance, and hydrolysis resistance of the coating are effectively improved, the tertiary carbonate structure in the resin further improves the hydrophobicity and weather resistance of the coating, in addition, the high reactivity of the resin and the isocyanate groups makes the drying rate of the coating significantly improved.

[0020] In summary, the present application has the following beneficial effects: 1. The high-solid low-viscosity resin has a specific repeating unit structure, can realize high solid content and low viscosity, solves the problem of rapid increase in viscosity when increasing the solid content of traditional resins, reduces the amount of organic solvent used, reduces VOC emissions, makes it easier to prepare a coating with a VOC content of less than 300g / L or even lower, and meets the environmental protection requirements; 2. The high solid low viscosity resin contains two primary hydroxyl groups and one secondary hydroxyl group on each molecular unit, which helps to improve the reactivity and functionality of the resin, facilitates fast curing, increases the crosslinking density of the coating, and improves the hardness and resistance of the coating. 3. The number average molecular weight, hydroxyl value, solid content and viscosity of the high solid low viscosity resin are within a specific range, which can balance the application performance and coating performance of the coating.

[0021] 4. The synthesis process of the high solid low viscosity resin is simple, the raw materials are easy to obtain, the process conditions are mild, and the industrial production is easy, and there is no need for post-treatment to remove small molecular by-products. DETAILED DESCRIPTION

[0022] The application will be further described in detail below in combination with examples. All reagents not specified by the manufacturer are conventional reagent products that can be obtained by purchase.

[0023] The reaction formula of dihydroxypropionic acid and glycidyl versatate is as follows: . Example 1

[0024] A preparation method of a high solid low viscosity resin based on glycidyl versatate, comprising the following steps: S1, 67.1g (0.5mol) of dimethylol propionic acid, 0.1g of stannous octoate catalyst and 21.1g of butyl acetate are added to a four-necked flask, protected by nitrogen, stirred and heated to 110℃; S2, 122.5g (0.5mol) of glycidyl versatate is placed in a dropping funnel and slowly added within 2h, the reaction temperature is controlled between 100-120℃, after the addition is completed, the reaction is continued at 120℃ for 4h; S3, after the ring acid value is reduced to below 5mgKOH / g, the reaction is stopped, the temperature is reduced to below 50℃, the material is filtered out, a light yellow transparent resin solution is obtained, and the solid content is 90.5%, the viscosity is 1850mPa·s (25℃), the hydroxyl value is 425mgKOH / g, and the number average molecular weight Mn of the resin is 620. Example 2

[0025] A preparation method of a high solid low viscosity resin based on glycidyl versatate, comprising the following steps: S1, 67.1g (0.5mol) of dimethylol propionic acid, 0.1g of stannous octoate catalyst and 21.1g of butyl acetate are added to a four-necked flask, protected by nitrogen, stirred and heated to 110℃; S2, 122.5 g (0.5 mol) of glycidyl ester of tertiary carbonic acid was placed in a dropping funnel and slowly added dropwise within 2 h, controlling the reaction temperature at 100-120°C, after the addition was completed, the reaction was continued at 120°C for 5 h; S3, after the ring acid value was reduced to below 5 mgKOH / g, the reaction was stopped, the temperature was reduced to below 50°C, the product was filtered out, a light yellow transparent resin solution was obtained, and the solid content was 89.6%, the viscosity was 1569 mPa·s (25°C), the hydroxyl value was 429 mgKOH / g, and the number average molecular weight Mn of the resin was 720. Example 3

[0026] A preparation method of a high-solid low-viscosity resin based on glycidyl ester of tertiary carbonic acid, comprising the following steps: S1, 73.7 g (0.55 mol) of dimethylol propionic acid, 0.1 g of stannous octoate catalyst and 21.1 g of butyl acetate were added to a four-necked flask, protected by nitrogen, stirred and heated to 100°C; S2, 122.5 g (0.5 mol) of glycidyl ester of tertiary carbonic acid was placed in a dropping funnel and slowly added dropwise within 2 h, controlling the reaction temperature at 100-120°C, after the addition was completed, the reaction was continued at 120°C for 3 h; S3, after the ring acid value was reduced to below 5 mgKOH / g, the reaction was stopped, the temperature was reduced to below 50°C, the product was filtered out, a light yellow transparent resin solution was obtained, and the solid content was 90.3%, the viscosity was 1986 mPa·s (25°C), the hydroxyl value was 416 mgKOH / g, and the number average molecular weight Mn of the resin was 860. Example 4

[0027] A preparation method of a high-solid low-viscosity resin based on glycidyl ester of tertiary carbonic acid, which is different from example 1 in that equal molar dimethylol butyric acid is used instead of dimethylol propionic acid, and the others are the same as example 1, and the light yellow transparent resin solution obtained is detected, and the solid content is 90.1%, the viscosity is 1350 mPa·s (25°C), the hydroxyl value is 408 mgKOH / g, and the number average molecular weight Mn of the resin is 898. Comparative Example 1

[0028] A preparation method of a high solid and low viscosity resin based on glycidyl ester of versatic acid, which is different from example 1 in that the molar ratio of glycidyl ester of versatic acid to dihydroxy acrylic acid is 1:0.7, i.e. glycidyl ester of versatic acid is 122.5g (0.5mol), dimethylol propionic acid is 47g (0.35mol), and the others are the same as example 1. The obtained transparent resin solution is detected to have a solid content of 80%, a viscosity of 690mPa·s (25℃), a hydroxyl value of 362mgKOH / g, and a number average molecular weight Mn of the resin of 465. Comparative example 2

[0029] A preparation method of a high solid and low viscosity resin based on glycidyl ester of versatic acid, which is different from example 1 in that the molar ratio of glycidyl ester of versatic acid to dihydroxy acrylic acid is 1:1.3, i.e. glycidyl ester of versatic acid is 122.5g (0.5mol), dimethylol propionic acid is 87.2g (0.65mol), and the others are the same as example 1. The obtained light yellow transparent resin solution is detected to have a solid content of 95.1%, a viscosity of 3625mPa·s (25℃), a hydroxyl value of 564mgKOH / g, and a number average molecular weight Mn of the resin of 424.

[0030] The high solid and low viscosity resin solutions obtained in the above examples and comparative examples are applied to polyurethane coatings, specifically as follows. Application example 1

[0031] A preparation method of a polyurethane varnish, which comprises the following steps: Preparation of component A: 100g of the resin solution obtained in example 1 is taken, 0.5g of a leveling agent, 0.2g of a defoaming agent, and 0.5g of an organic tin catalyst are added, and the viscosity is adjusted to 40g of propylene glycol methyl ether acetate under stirring to disperse uniformly; Component B: HDI trimer (NCO content is 22%) is used; Paint preparation: A and B components are weighed and mixed according to the equivalent ratio of NCO:OH of 1.2:1, and after aging for 15min, they are sprayed on a treated tin plate with a wet film thickness of about 100μm, and dried at room temperature. Application example 2

[0032] A preparation method of a polyurethane varnish, which is different from application example 1 in that the equivalent ratio of NCO:OH is 0.9:1, and the others are the same as example 1. Application example 3

[0033] A preparation method of a polyurethane varnish, which is different from application example 1 in that the resin solution is the resin solution obtained in example 2, and the others are the same as application example 1. Application example 4

[0034] A method for preparing a polyurethane varnish, which is different from that of application example 1 in that the resin solution is the resin solution obtained in example 3, and the others are the same as in application example 1. Application example 5

[0035] A method for preparing a polyurethane varnish, which is different from that of application example 1 in that the resin solution is the resin solution obtained in example 4, and the others are the same as in application example 1. Application example 6

[0036] A method for preparing a polyurethane varnish, which is different from that of application example 1 in that the resin solution is the resin solution obtained in comparative example 1, and the others are the same as in application example 1. Application example 7

[0037] A method for preparing a polyurethane varnish, which is different from that of application example 1 in that the resin solution is the resin solution obtained in comparative example 2, and the others are the same as in application example 1. Comparative example

[0038] A method for preparing a polyurethane varnish, which is different from that of application example 1 in that the resin solution obtained in example 1 is replaced by a commercially available general-purpose high-solid hydroxyl acrylic resin, the solid content of the high-solid hydroxyl acrylic resin is 70%, the hydroxyl value is about 120 mgKOH / g, the functionality is 4, and the main functional group is secondary hydroxyl group, and the others are the same as in application example 1. Performance test

[0039] The construction viscosity, VOC content, coating surface drying time, coating drying time, coating hardness, solvent resistance, water resistance and acid resistance of the polyurethane varnish obtained in the above application example were tested, and the test results are shown in Table 1.

[0040] The construction viscosity was tested by using a coating-4 cup and the time required for testing at 25°C.

[0041] Solvent resistance test: A cotton ball dipped in methyl ethyl ketone was used to wipe the surface of the paint film back and forth under a pressure of 500g, and the number of wipes before the paint film was damaged (such as wrinkling and dissolution) was recorded.

[0042] Water resistance test: After the dried sample was immersed in water for 240h, the paint film surface was observed for bubbles, rust and loss of gloss.

[0043] Acid resistance test: After the dried sample was immersed in 10wt% sulfuric acid for 48h, the paint film surface was observed for bubbles, peeling and discoloration.

[0044] Table 1 Performance test results of polyurethane varnish Item Viscosity / sec VOC content g / L Tack-free time / min Through-dry time / h Pencil hardness Resistance to solvent / number Water resistance Acid resistance Example 1 20 250 45 6 H 220 No bubble No rust No gloss loss No change in paint film Example 2 20 260 45 6 H 230 No bubble No rust No gloss loss No change in paint film Example 3 19 255 45 6 H 220 No bubble No rust No gloss loss No change in paint film Example 4 21 258 45 6 H 225 No bubble No rust No gloss loss No change in paint film Example 5 19 262 45 6 H 230 No bubble No rust No gloss loss No change in paint film Example 6 18 298 120 16 B 50 Bubble, rust, slight gloss loss Bubble, rust in paint film Example 7 26 286 146 22 F 30 Bubble, rust, slight gloss loss Bubble, rust in paint film Comparative Example 22 520 65 8 F 45 No bubble No rust Slight gloss loss Bubble, rust in paint film The test results of Table 1 are combined: When the high-solid and low-viscosity resin obtained by the embodiments of the present application is applied to polyurethane coatings, the VOC content of the polyurethane varnish calculated in Application Examples 1-5 is much lower than the VOC content of the polyurethane coating obtained by using the hydroxyl acrylic resin in the Comparative Example, and the hardness and the solvent resistance, water resistance and acid resistance of the paint film are all superior to those in the Comparative Example, which further indicates that the resin obtained by the present application solves the problem of viscosity increase when increasing the solid content of the traditional hydroxyl acrylic resin or polyester resin, and the VOC content of the varnish prepared by using the resin obtained by the present application is lower, which can better meet the environmental protection requirements.

[0045] When the molar ratio of glycidyl ester of versatic acid to dimethylol propionic acid is not within the range defined by the present application, the viscosity of the resin solution obtained by Comparative Example 1 is low, and the hydroxyl value content is also low, the solid content of the resin solution obtained by Comparative Example 2 is high, and the viscosity is also high, when the resin solutions obtained by Comparative Examples 1-2 are applied to polyurethane varnish, the VOC content of the polyurethane varnish calculated in Application Examples 6-7 is higher than that in Application Example 1, and the tack-free time and the dry time are significantly increased, the hardness is significantly reduced, and the solvent resistance, water resistance and acid resistance are all significantly reduced compared with Application Example 1, which further indicates that by optimizing the molar ratio of glycidyl ester of versatic acid to dimethylol propionic acid, a resin solution with high solid content, low viscosity and high hydroxyl value content can be obtained, which can reduce the VOC emission in the varnish when applied to polyurethane varnish, and also can be better applied.

[0046] The embodiments of the specific embodiment are the preferred embodiments of the present application, and do not limit the protection scope of the present application, so: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A high-solids, low-viscosity resin based on glycidyl tert-carbonate, characterized in that, The high-solids, low-viscosity resin has the following molecular structure: or , R1, R2, and R3 are branched alkyl groups of tertiary carbonate.

2. The high-solids, low-viscosity resin based on glycidyl tert-carbonate according to claim 1, characterized in that: The high-solids, low-viscosity resin raw materials include glycidyl tert-carbonate, polybasic acids, and catalysts. The polyacid is at least one of dimethylolpropionic acid and dimethylolbutyric acid.

3. The high-solids, low-viscosity resin based on glycidyl tert-carbonate according to claim 2, characterized in that: The molar ratio of the glycidyl tert-carbonate to the polybasic acid is 1:(0.9-1.1).

4. The high-solids, low-viscosity resin based on glycidyl tert-carbonate according to claim 3, characterized in that: The high-solids, low-viscosity resin has a number-average molecular weight (Mn) of 600-900 g / mol, a hydroxyl value of 390-450 mg KOH / g, a solid content of 85-95%, and a viscosity of 800-2500 mPa·s (25℃).

5. The high-solids, low-viscosity resin based on glycidyl tert-carbonate according to claim 2, characterized in that: The catalyst is one of stannous octoate and tetrabutylammonium bromide.

6. The high-solids, low-viscosity resin based on glycidyl tert-carbonate according to claim 2, characterized in that: The amount of catalyst used is 0.05-1% of the total mass of glycidyl tert-carbonate and polybasic acid.

7. A method for preparing a high-solids, low-viscosity resin based on glycidyl tert-carbonate as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Add the polybasic acid and catalyst to the solvent, stir and mix, and then heat. S2. Add glycidyl tert-carbonate dropwise and control the reaction temperature; S3. After the addition is complete, keep the reaction at a constant temperature until the epoxy groups have completely reacted. Then cool down, filter, and obtain a high-solids, low-viscosity resin.

8. The method for preparing a high-solids, low-viscosity resin based on glycidyl tert-carbonate according to claim 7, characterized in that: The temperature for both steps S1 and S2 is 100-120℃.

9. A polyurethane coating, comprising component A and component B, characterized in that: Component A includes at least the high-solids, low-viscosity resin as described in any one of claims 1-6, and component B includes at least a polyisocyanate curing agent.

10. A polyurethane coating according to claim 9, characterized in that: The equivalence ratio of hydroxyl groups to isocyanate groups in components A and B is 1:(0.9-1.2).

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