A rapid curing polyurea coating at low temperature and a preparation method thereof

Abstract

This invention relates to the field of coating technology, specifically to a rapid-curing polyurea coating under low-temperature conditions and its preparation method. The rapid-curing polyurea coating under low-temperature conditions comprises component A and component B. Component A, by weight, includes the following raw materials: 45-55 parts of polyisocyanate, 40-50 parts of polyether polyol, and 0.02-0.04 parts of retarder. Component B, by weight, includes the following raw materials: 40-60 parts of amino-terminated polyether, 18-20 parts of amine chain extender, 0.4-1 parts of coupling agent, and 10-20 parts of filler. The two-component polyurea coating prepared by this invention exhibits rapid curing speed and excellent mechanical properties under low-temperature conditions.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a rapid-curing polyurea coating at low temperatures and its preparation method. Background Technology

[0002] Polyurea coatings are polymer materials rapidly polymerized from isocyanate and amino compound components. Since their commercial application in the 1990s, they have been widely used in various industrial fields such as construction, municipal engineering, transportation, energy and chemical industries due to their excellent physical and mechanical properties, comprehensive protection capabilities, efficient construction characteristics and environmentally friendly solvent-free advantages. They have become the preferred protective material to replace traditional epoxy and polyurethane coatings.

[0003] Conventional two-component polyurea gels have a short curing time, can form a film in one step, and cure quickly, which can significantly shorten the construction cycle. However, in low-temperature environments, the curing time is greatly extended. A system that can cure in a few minutes may take several days at low temperatures, which seriously slows down the progress and increases costs. At the same time, low temperatures cause the viscosity of the coating components to increase dramatically, resulting in uneven mixing, poor leveling, and defects such as orange peel and pinholes. It also increases the risk of equipment failure. More importantly, low temperatures lead to incomplete curing, which reduces the mechanical properties of the coating, shortens its service life, and can also cause interlayer delamination when applying multiple layers.

[0004] However, the demand for low-temperature, rapid-curing polyurea is increasingly urgent in scenarios such as infrastructure maintenance in frigid northern regions, winter outdoor construction, and protection of wind turbine blades at high latitudes. Existing solutions mainly involve on-site insulation, material preheating, or the use of highly reactive components (such as aspartic polyurea), but these have significant limitations: on-site insulation requires substantial additional investment in equipment and energy, is greatly restricted by natural conditions, and cannot be adapted to complex scenarios; while highly reactive components can accelerate curing, they shorten the coating's pot life, increase construction requirements, and are unable to solve core issues such as incomplete curing and insufficient mechanical properties, thus limiting their application scope.

[0005] In summary, existing polyurea coatings suffer from slow curing, difficult application, and performance degradation at low temperatures, failing to meet the low-temperature protection requirements of industrial applications. Therefore, developing a polyurea coating that can cure rapidly at extreme low temperatures while maintaining ease of application has become a pressing technical challenge in the polyurea field. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to obtain a two-component polyurea coating that not only has a fast curing speed at low temperatures but also excellent mechanical properties.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a rapidly curing polyurea coating at low temperatures, comprising component A and component B. Component A, by weight, comprises the following raw materials: 45-55 parts of polyisocyanate, 40-50 parts of polyether polyol, and 0.02-0.04 parts of retarder; component B, by weight, comprises the following raw materials: 40-60 parts of amino-terminated polyether, 18-20 parts of amine chain extender, 0.4-1 parts of coupling agent, and 10-20 parts of filler.

[0008] In some embodiments, the polyisocyanate is 3,3-dimethyl-4,4-dicyclohexylmethane diisocyanate.

[0009] In some embodiments, the retarder is benzoyl chloride or phosphoric acid.

[0010] In some embodiments, the number-average molecular weight Mn of the terminal amino polyether is 200-2000.

[0011] In some embodiments, the amine chain extender is 2,5-diamino-1,3,3-trimethylcyclohexylamine.

[0012] In some embodiments, the coupling agent is a silane coupling agent.

[0013] Preferably, the silane coupling agent is KH550.

[0014] In some embodiments, the method for preparing the filler includes the following steps: (1) Add mica powder to an ethanol solution and stir at 350-450 rpm at 35-45℃. At the same time, add γ-methacryloyloxypropyltriethoxysilane to adjust the pH and continue stirring for 2-3 hours. Filter, wash and dry to obtain silane-modified mica powder. (2) Under nitrogen protection, the silane-modified mica powder, initiator and 4-vinylaniline obtained in step (1) are added to toluene and reacted at 65-75℃ for 1-2 hours. Then, silicon micropowder is added and stirred at room temperature for 20-30 minutes. The mixture is then filtered, washed and dried to obtain the filler.

[0015] This invention involves surface-treating mica powder with a specific silane coupling agent, followed by a free radical copolymerization reaction with 4-vinylaniline and the double bonds on the filler surface. This is then combined with silica powder to form a composite filler system. The introduction of amino groups into the filler allows them to react with polyisocyanates in component A during the curing reaction, generating urea bonds. This makes the filler itself a crosslinking point, participating in the reaction. These additional reaction points increase the overall crosslinking density of the system, providing more nucleation centers and reaction sites for the curing reaction, thus accelerating the overall curing process to some extent and compensating for the loss of reaction rate at low temperatures. By grafting organic copolymer layers, the filler surface is made organic, enhancing its interfacial bonding with the polyurea matrix, eliminating interfacial defects, and allowing for smoother movement of polymer chain segments at the interface, which is beneficial for uniform curing. Furthermore, the introduction of benzene ring structures provides a modulus gradient transition layer between the rigid filler and the flexible matrix, effectively buffering stress concentration and significantly improving the coating's toughness and impact resistance. The aniline structure, after being chemically grafted onto the mica powder surface, has its UV absorption function "anchored" in the coating, unlike small-molecule UV absorbers which migrate, volatilize, or are extracted, affecting the coating's mechanical properties. In addition, the layered structure of mica flakes and microsilica particles form a "flake-particle" geometric complementarity. Horizontally, the mica flakes provide a continuous barrier; vertically, and between the flakes, the microsilica particles provide point-like support and filling. This synergy not only enhances the coating's mechanical properties under static conditions but also ensures its structural stability under dynamic temperature changes and stress.

[0016] In some embodiments, the mass ratio of the mica powder to γ-methacryloyloxypropyltriethoxysilane is 1:(0.05-0.2).

[0017] In some embodiments, the mass ratio of silane-modified mica powder, 4-vinylaniline and silicon micropowder in step (2) is 1:(0.03-0.1):(0.2-0.6).

[0018] A second aspect of this invention provides a method for preparing a rapidly curing polyurea coating at low temperatures, comprising the following steps: S1. Heat the polyisocyanate and retarder to 40-50℃, then add the polyether polyol, and then heat to 80-90℃. React for 1.5-2.5 hours, seal and store for later use to obtain component A. S2. Stir the terminal amino polyether and filler at room temperature for 30-60 min, then add amine chain extender and coupling agent and stir at 400-500 rpm for 50-60 min to obtain component B. S3. When using, mix component A and component B in the specified proportions to obtain a polyurea coating that cures rapidly at low temperatures.

[0019] In some embodiments, the mass ratio of component A to component B is 1:(1.2-2).

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention prepares a two-component polyurea coating by means of polyisocyanate, polyether polyol, amino-terminated polyether, chain extender and other additives, which can be rapidly cured under low temperature conditions and has excellent mechanical properties.

[0021] (2) This invention constructs a reactive composite filler system by subjecting mica powder to specific silane coupling treatment and introducing 4-vinylaniline for free radical copolymerization, and then combining it with silica micropowder. The amino groups grafted on the surface of the filler can participate in curing and serve as crosslinking points to improve the low-temperature reaction rate; at the same time, the organic copolymer layer eliminates interface defects, and the benzene ring structure provides a modulus gradient to buffer stress, significantly enhancing the toughness of the coating. In addition, the flake mica and spherical silica micropowder form a "flake-particle" geometric complementary structure, which synergistically improves the mechanical stability and density of the coating. Detailed Implementation

[0022] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0023] In the following examples and comparative examples, the compounds and related reagents used were all commercially available. The polyether polyol was polypropylene glycol with Mn=2000; the amino-terminated polyether was polyetheramine D400; the mica powder was wet-processed mica powder with an average particle size of 20 μm; and the silica powder had an average particle size of 10 μm.

[0024] Unless otherwise specified, the post-processing steps such as "washing", "drying", and "filtration" used below are routine operations for those skilled in the art, and can be selected according to actual operation.

[0025] Preparation Example 1 The preparation method of filler-1 includes the following steps: (1) Add 100g of mica powder to 2000ml of 95wt% ethanol solution, stir at 400rpm at 40℃, add 10g of γ-methacryloyloxypropyltriethoxysilane, adjust the pH to 4.5 with acetic acid and continue stirring for 2.5h, filter, wash and dry to obtain silane modified mica powder. (2) Under nitrogen protection, 100g of silane-modified mica powder obtained in step (1), 0.07g of benzoyl peroxide and 7g of 4-vinylaniline were added to 2000ml of toluene and reacted at 70℃ for 1.5h. Then, 45g of silicon micropowder was added and stirred at room temperature for 25min. The mixture was then filtered, washed and dried to obtain filler-1.

[0026] Preparation Example 2 The preparation method of filler-2 is the same as that of preparation example 1, except that the amount of γ-methacryloyloxypropyltriethoxysilane added in step (1) is 21g.

[0027] Preparation Example 3 The preparation method of filler-3 is the same as that of preparation example 1, except that the amount of 4-vinylaniline added in step (2) is 11g.

[0028] Preparation Example 4 The preparation method of filler-4 is the same as that of preparation example 1, except that 4-vinylaniline in step (2) is replaced with 3-butene-1-amine in equal amounts.

[0029] Preparation Example 5 The preparation method of filler-5 is the same as that of preparation example 1, except that the amount of silicon micro powder added in step (2) is 65g.

[0030] Preparation Example 6 The preparation method of filler-6 includes the following steps: (1) Add 100g of mica powder to 2000ml of 95wt% ethanol solution, stir at 400rpm at 40℃, add 10g of γ-methacryloyloxypropyltriethoxysilane, adjust the pH to 4.5 with acetic acid and continue stirring for 2.5h, filter, wash and dry to obtain silane modified mica powder. (2) Under nitrogen protection, 100g of silane-modified mica powder obtained in step (1), 0.07g of benzoyl peroxide and 7g of 4-vinylaniline were added to 2000ml of toluene and reacted at 70℃ for 1.5h. The mixture was then filtered, washed and dried to obtain filler-6.

[0031] Example 1 A rapid-curing polyurea coating at low temperatures comprises component A and component B. Component A, by weight, comprises the following raw materials: 50 parts of 3,3-dimethyl-4,4-dicyclohexylmethane diisocyanate, 45 parts of polyether polyol, and 0.03 parts of benzoyl chloride. Component B, by weight, comprises the following raw materials: 50 parts of amino-terminated polyether, 19 parts of 2,5-diamino-1,3,3-trimethylcyclohexylamine, 0.7 parts of KH550, and 15 parts of filler-1.

[0032] The method for preparing a rapidly curing polyurea coating at low temperatures in this embodiment includes the following steps: S1. Heat 3,3-dimethyl-4,4-dicyclohexylmethane diisocyanate and benzoyl chloride to 45°C, then add polyether polyol, then heat to 85°C and react for 2 hours. Seal and store for later use to obtain component A. S2. Stir the terminal amino polyether and filler-1 at room temperature for 45 min, then add 2,5-diamino-1,3,3-trimethylcyclohexylamine and KH550 and stir at 450 rpm for 55 min to obtain component B. S3. When using, mix component A and component B at a mass ratio of 1:1.6 to obtain a polyurea coating that cures rapidly at low temperatures.

[0033] Example 2 A rapid-curing polyurea coating at low temperatures comprises component A and component B. Component A, by weight, comprises the following raw materials: 45 parts of 3,3-dimethyl-4,4-dicyclohexylmethane diisocyanate, 40 parts of polyether polyol, and 0.02 parts of benzoyl chloride. Component B, by weight, comprises the following raw materials: 40 parts of amino-terminated polyether, 18 parts of 2,5-diamino-1,3,3-trimethylcyclohexylmethylamine, 0.4 parts of KH550, and 10 parts of filler-1.

[0034] The method for preparing a rapidly curing polyurea coating at low temperatures in this embodiment includes the following steps: S1. Heat 3,3-dimethyl-4,4-dicyclohexylmethane diisocyanate and benzoyl chloride to 40°C, then add polyether polyol, and then heat to 80°C. React for 2.5 hours, seal and store for later use to obtain component A. S2. Stir the terminal amino polyether and filler-1 at room temperature for 30 min, then add 2,5-diamino-1,3,3-trimethylcyclohexylamine and KH550 and stir at 400 rpm for 60 min to obtain component B. S3. When using, mix component A and component B at a mass ratio of 1:1.2 to obtain a polyurea coating that cures rapidly at low temperatures.

[0035] Example 3 A rapid-curing polyurea coating at low temperatures comprises component A and component B. Component A, by weight, comprises the following raw materials: 55 parts of 3,3-dimethyl-4,4-dicyclohexylmethane diisocyanate, 50 parts of polyether polyol, and 0.04 parts of benzoyl chloride. Component B, by weight, comprises the following raw materials: 60 parts of amino-terminated polyether, 20 parts of 2,5-diamino-1,3,3-trimethylcyclohexylamine, 1 part of KH550, and 20 parts of filler-1.

[0036] The method for preparing a rapidly curing polyurea coating at low temperatures in this embodiment includes the following steps: S1. Heat 3,3-dimethyl-4,4-dicyclohexylmethane diisocyanate and benzoyl chloride to 50°C, then add polyether polyol, and then heat to 90°C. React for 1.5 hours, seal and store for later use to obtain component A. S2. Stir the terminal amino polyether and filler-1 at room temperature for 60 min, then add 2,5-diamino-1,3,3-trimethylcyclohexylamine and KH550 and stir at 500 rpm for 50 min to obtain component B. S3. When using, mix component A and component B at a mass ratio of 1:2 to obtain a polyurea coating that cures rapidly at low temperatures.

[0037] Example 4 A rapid curing polyurea coating under low temperature conditions and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that filler-1 is replaced with filler-2 in equal amounts.

[0038] Example 5 A rapid curing polyurea coating at low temperature and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that filler-1 is replaced with filler-3 in equal amounts.

[0039] Example 6 A rapid curing polyurea coating under low temperature conditions and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that filler-1 is replaced with filler-4 in equal amounts.

[0040] Example 7 A rapid curing polyurea coating at low temperature and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that filler-1 is replaced with filler-5 in equal amounts.

[0041] Example 8 A rapid curing polyurea coating at low temperature and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that filler-1 is replaced with filler-6 in equal amounts.

[0042] Example 9 A rapid-curing polyurea coating at low temperatures and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that filler-1 is replaced in equal amounts with a mixture of mica powder and silica powder, with a mass ratio of 1:0.45.

[0043] Performance testing For the low-temperature rapid-curing polyurea coatings prepared in each embodiment, the heating temperature of component A and component B was set to 60°C using a polyurea spraying device, and the pipeline was insulated at 60°C. During spraying, the dynamic pressure of components A and B was 1900-2000 PSI, the static pressure was 2400-2500 PSI, and the polyurea coating thickness was 0.15-0.20 mm, with a range of 0.05 mm. The surface drying time at 0°C and 40% relative humidity, and the tensile strength and elongation at break after 48 hours of curing under standard curing conditions were tested according to standard GB / T23446-2009.

[0044] The test results are shown in Table 1: Table 1

[0045] As shown in Table 1, the polyurea coatings of Examples 1-3 exhibit short surface drying times, rapid curing, and excellent mechanical properties under low-temperature conditions. A comparison of the data from Example 4 and Example 1 reveals that the change in the ratio of mica powder and γ-methacryloyloxypropyltriethoxysilane may lead to an increase in the number of double bonds grafted onto the mica powder surface, resulting in excessive cross-linking, increased surface drying time, higher tensile strength, and decreased elongation at break. A comparison of the data from Examples 5 and 7 and Example 1 indicates that the change in the ratio of silane-modified mica powder, 4-vinylaniline, and silica powder may be due to the introduction of… The addition of a large amount of rigid structure and rigid filler leads to a decrease in the elongation at break of the coating. As can be seen from the comparison between Example 6 and Example 1, replacing 4-vinylaniline with an equal amount of 3-butene-1-amine reduces the compatibility between the aliphatic chain and the mica sheet structure, resulting in a decrease in the mechanical properties of the coating. As can be seen from the comparison between Example 8 and Example 1, without the addition of silica powder, the number of rigid particles is reduced, the space for molecular chain movement is increased, and the mechanical properties of the coating decrease. As can be seen from the comparison between Example 9 and Example 1, using unmodified mica powder results in poor compatibility with polyurea resin, and both tensile strength and elongation at break decrease.

[0046] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A rapidly curing polyurea coating at low temperatures, characterized in that, The product comprises component A and component B. Component A, by weight, includes the following raw materials: 45-55 parts of polyisocyanate, 40-50 parts of polyether polyol, and 0.02-0.04 parts of retarder. Component B, by weight, includes the following raw materials: 40-60 parts of amino-terminated polyether, 18-20 parts of amine chain extender, 0.4-1 parts of coupling agent, and 10-20 parts of filler.

2. The rapidly curing polyurea coating under low-temperature conditions according to claim 1, characterized in that, The polyisocyanate is 3,3-dimethyl-4,4-dicyclohexylmethane diisocyanate.

3. The rapidly curing polyurea coating under low-temperature conditions according to claim 1, characterized in that, The retarder is benzoyl chloride or phosphoric acid.

4. The rapidly curing polyurea coating under low-temperature conditions according to claim 1, characterized in that, The number-average molecular weight (Mn) of the terminal amino polyether is 200-2000.

5. The rapidly curing polyurea coating under low-temperature conditions according to claim 1, characterized in that, The amine chain extender is 2,5-diamino-1,3,3-trimethylcyclohexylamine.

6. The rapidly curing polyurea coating under low-temperature conditions according to claim 1, characterized in that, The method for preparing the filler includes the following steps: (1) Add mica powder to an ethanol solution and stir at 350-450 rpm at 35-45℃. At the same time, add γ-methacryloyloxypropyltriethoxysilane to adjust the pH and continue stirring for 2-3 hours. Filter, wash and dry to obtain silane-modified mica powder. (2) Under nitrogen protection, the silane-modified mica powder obtained in step (1), the initiator, and 4-vinylaniline are reacted at 65-75℃ for 1-2 hours, and then silicon micro powder is added and stirred at room temperature for 20-30 minutes. The mixture is then filtered, washed, and dried to obtain the filler.

7. The rapidly curing polyurea coating under low-temperature conditions according to claim 6, characterized in that, The mass ratio of mica powder to γ-methacryloxypropyltriethoxysilane is 1:(0.05-0.2).

8. The rapidly curing polyurea coating under low-temperature conditions according to claim 6, characterized in that, The mass ratio of silane-modified mica powder, 4-vinylaniline and silica powder in step (2) is 1:(0.03-0.1):(0.2-0.6).

9. A method for preparing a rapidly curing polyurea coating under low-temperature conditions according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Heat the polyisocyanate and retarder to 40-50℃, then add the polyether polyol, and then heat to 80-90℃. React for 1.5-2.5 hours, seal and store for later use to obtain component A. S2. Stir the terminal amino polyether and filler at room temperature for 30-60 min, then add amine chain extender and coupling agent and stir at 400-500 rpm for 50-60 min to obtain component B. S3. When using, mix component A and component B in the specified proportions to obtain a polyurea coating that cures rapidly at low temperatures.

10. The method for preparing a rapidly curing polyurea coating under low-temperature conditions according to claim 9, characterized in that, The mass ratio of component A to component B is 1:(1.2-2).

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