A UV-curable coating composition, its preparation method and application

Abstract

This invention provides a UV-curable coating composition, its preparation method, and its application. The UV-curable coating composition of this invention comprises the following components in parts by weight: 40-60 parts of silicone-modified polyurethane acrylate, 5-30 parts of cyclic ether acrylate or its derivatives, 2-10 parts of silane coupling agent, 30-80 parts of filler, and 0.5-5 parts of photoinitiator; wherein the reaction raw materials for the silicone-modified polyurethane acrylate include the following components in parts by weight: 15-30 parts of isocyanate, 20-100 parts of hydroxyl-terminated polydimethylsiloxane, 20-100 parts of aromatic polyester polyol, and 3-15 parts of end-capping agent. By using hydroxyl-terminated polydimethylsiloxane to modify the polyurethane acrylate, and simultaneously adding cyclic ether acrylate or its derivatives as diluent monomers to the coating composition, the resulting coating exhibits high resistance to damp heat, high strength, and high elasticity.

Description

Technical Field

[0001] This invention relates to the field of photocurable coating technology, and in particular to a UV-curable coating composition, its preparation method, and its application. Background Technology

[0002] Ultraviolet (UV) curing is widely used due to its advantages such as fast curing speed, energy saving, and low pollution. Polyurethane acrylate coatings have advantages such as low odor and excellent acid and alkali resistance. However, due to the hydrophilicity of polyurethane acrylate, the coatings prepared from it have poor resistance to damp heat and acids and alkalis, which limits their application development.

[0003] Therefore, the modification of waterborne polyurethane materials has become a major research topic in recent years. Organosilicon materials, due to their unique chemical structure, exhibit excellent hydrophobic properties and low surface energy, endowing polymer coatings with superior surface properties such as good water resistance, oil resistance, and weather resistance. Furthermore, siloxane groups can undergo hydrolysis-condensation reactions in the presence of water under extremely mild conditions, requiring no catalyst and proceeding at room temperature. The resulting -Si-O-Si- bonds are very stable and form a cross-linked structure, effectively improving the material's solvent resistance and mechanical properties.

[0004] However, the hydrolysis and condensation of siloxanes must be carried out in aqueous solution, and a lot of water will inevitably remain in the product. Moreover, the condensation reaction is difficult to control stably, and the resulting oligomer has an uneven molecular weight distribution and is prone to stratification. Small molecule products are prone to migration in the coating, which affects the modification effect. Therefore, there is a need to provide a UV-curable coating that has high resistance to damp heat, high strength, and high elasticity. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing UV-curable coatings in terms of moisture and heat resistance and mechanical properties, and to provide a UV-curable coating composition that simultaneously possesses high moisture and heat resistance, high strength, and high elasticity.

[0006] Another object of the present invention is to provide a method for preparing the UV-curable coating composition.

[0007] Another object of the present invention is to provide the application of the UV-curable coating composition in the field of corrosion protection.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A UV-curable coating composition comprising the following components in parts by weight:

[0010] 40-60 parts of silicone-modified polyurethane acrylate, 5-30 parts of cyclic ether acrylate or its derivatives, 2-10 parts of silane coupling agent, 30-80 parts of filler, and 0.5-5 parts of photoinitiator;

[0011] The reaction raw materials for the organosilicon-modified polyurethane acrylate include the following components in parts by weight:

[0012] 15-30 parts isocyanate, 20-100 parts carbon hydroxyl-terminated polydimethylsiloxane, 20-100 parts aromatic polyester polyol, and 3-15 parts capping agent.

[0013] In the coating composition of the present invention, the introduction of siloxane segments into the polyurethane acrylate can significantly improve the water resistance of the cured coating. The siloxane segments have good flexibility and can also give the coating good elasticity.

[0014] This invention directly uses polydimethylsiloxane (organosilicon) to modify the polyurethane acrylate matrix, avoiding the problem of uneven molecular weight distribution caused by the hydrolysis and condensation of siloxanes. However, during the coating process, it inevitably comes into contact with moisture in the air. The siloxane segments distributed on the coating surface react with water and hydrolyze, resulting in varying molecular chain lengths in the modified polyurethane acrylate. This further leads to an uneven cross-linking network structure, affecting the mechanical properties (such as elasticity and strength) and water resistance of the coating. The uneven cross-linking network will further hydrolyze and deteriorate in high temperature and high humidity environments, destroying the integrity of the coating and causing a significant deterioration in its resistance to damp heat.

[0015] This invention, through extensive research, has discovered that introducing alkyl groups at the ends of the main chain of organosilicon segments: 1) increases intermolecular distance, which is beneficial for the entanglement and deentanglement of silicon-oxygen segments, and helps the material to better exert its mechanical properties. 2) The introduction of alkyl groups at the ends further improves the hydrophobic properties of the silicon-oxygen segments. Furthermore, this invention further introduces cyclic ether acrylates or their derivatives as diluent monomers into the UV-curable coating. The oxygen atoms in the cyclic ether structure are exposed to the outside, thus exhibiting stronger electronegativity and greater water absorption. At the same time, the highly polar cyclic ether structure and the larger nonpolar alkyl groups repel each other. Thus, during the coating process, the highly polar diluent monomers containing cyclic ether structures preferentially adsorb moisture from the air and stay away from the silicon-oxygen segments, protecting the silicon-oxygen segments from hydrolysis and the modified polyurethane acrylate matrix from damage. After curing, a uniform and stable cross-linked coating is formed, giving the coating good resistance to damp heat, strength, and toughness.

[0016] Preferably, the carbon hydroxyl-terminated polydimethylsiloxane comprises hydroxypropyl-terminated polydimethylsiloxane.

[0017] Preferably, the number average molecular weight of the carbon hydroxyl-terminated polydimethylsiloxane is 1000-10000.

[0018] Preferably, the cyclic ether acrylate or its derivative includes at least one of glycerol methacrylate and glycerol acrylate.

[0019] Optionally, the silane coupling agent includes, but is not limited to, at least one of γ-methacryloyloxypropyltrimethoxysilane (KH-550) and γ-glycidyl etheroxypropyltrimethoxysilane (KH-560). Silane coupling agents can improve the dispersion uniformity of inorganic fillers in a polymer matrix.

[0020] Optionally, the filler includes, but is not limited to, at least one of barium sulfate, barium carbonate, and talc. These inorganic fillers can improve the mechanical strength of the coating.

[0021] Optionally, the photoinitiator includes, but is not limited to, at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, and diphenyl-(2,4,6-trimethylbenzoyl)phosphorus oxychloride.

[0022] Optionally, in the reaction raw materials for the organosilicon-modified polyurethane acrylate, the isocyanate includes, but is not limited to, at least one of toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI); the chain extender is a small molecule diol, which includes, but is not limited to, at least one of ethylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-dihydroxymethylcyclohexane, dimethyl N,N-di(2-hydroxyethyl)aminomethylphosphonate, and diethyl N,N-di(2-hydroxyethyl)aminomethylenephosphonate; the hydroxyl value of the aromatic polyester polyol is 90-220 mg KOH / g; and the end-capping agent includes, but is not limited to, hydroxyethyl acrylate.

[0023] The organosilicon-modified polyurethane acrylate described in this invention is prepared by a method comprising the following steps:

[0024] S1. According to the stated weight parts, isocyanate, carbon hydroxyl-terminated polydimethylsiloxane and aromatic polyester polyol are mixed evenly and then prepolymerized at 60-90℃ for 1-4 hours to obtain a prepolymerized mixture.

[0025] S2. Add chain extender to the prepolymer mixture obtained in step S1, mix evenly, and carry out chain extension reaction at 60-90℃ for 3-6 hours. After the chain extension reaction is completed, add end-capping agent, adjust pH to neutral, and emulsify to obtain the silicone-modified polyurethane acrylate.

[0026] Optionally, the reagents used to adjust the pH include, but are not limited to, at least one of triethylamine and ammonia.

[0027] This invention also protects a method for preparing the above-mentioned UV-curable coating composition, comprising the following steps:

[0028] The UV-curable coating composition is obtained by uniformly mixing organosilicon-modified polyurethane acrylate, cyclic ether acrylate or its derivatives, silane coupling agent, filler and photoinitiator according to the stated weight parts.

[0029] The application of the UV-curable coating composition in the field of corrosion protection is also within the scope of protection of this invention. It should be noted that, in practical use, the UV-curable coating composition requires cross-linking and curing under the action of light and a photoinitiator to obtain a dense coating and achieve its anti-corrosion function.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] This invention uses carbon hydroxyl-terminated polydimethylsiloxane to modify polyurethane acrylates, and simultaneously adds cyclic ether acrylates or their derivatives to the coating composition as diluent monomers. Under the combined action of the two, the resulting coating has high resistance to damp heat, high strength, and high elasticity. Detailed Implementation

[0032] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further describe the invention below. However, these embodiments do not limit the invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, all reagents and materials used in this invention are commercially available.

[0033] Diluting monomer (cyclic ether acrylates or their derivatives): Glyceryl methacrylate, commercially available;

[0034] Silane coupling agent: KH-550, commercially available;

[0035] Filler: Ultrafine barium sulfate powder, purchased from Hebei Huihao Environmental Protection Technology Co., Ltd.;

[0036] Photoinitiator: Photoinitiator 184, commercially available;

[0037] Organosilicon-modified polyurethane acrylate: The organosilicon-modified polyurethane acrylate in the embodiments of this invention was prepared in-house. The formulation (raw materials and amounts) is shown in Table 1, and it was prepared according to the following method:

[0038] S1. After uniformly mixing isocyanate, carbon hydroxyl-terminated polydimethylsiloxane, and aromatic polyester polyol, a prepolymerization reaction was carried out at 90°C for 2 hours to obtain a prepolymer mixture.

[0039] S2. Add chain extender to the prepolymer mixture obtained in step S1, mix evenly, carry out chain extension reaction at 80°C for 4 hours, add end-capping agent, then adjust pH to neutral with triethylamine, stir and emulsify to obtain the organosilicon modified polyurethane acrylate.

[0040] Carbon hydroxyl-terminated polydimethylsiloxane:

[0041] 1#: Hydroxypropyl-terminated polydimethylsiloxane OF1300, with a number average molecular weight of 4000 and a hydroxyl content of 0.7-1.0%, was purchased from Nanjing Xisibo Organosilicon Co., Ltd.

[0042] 2#: Bi-hydroxyl-terminated long-chain alkyl silicone oil, IOTA-8865H, with a number average molecular weight of 4000, a hydroxyl content of 0.8%, and a viscosity of 1500-2500 mPa·s at 25℃, purchased from Anhui Aiyota Silicone Oil Co., Ltd.

[0043] Silyl hydroxyl-terminated polydimethylsiloxane: hydroxyl polysiloxane F-1.5, with a viscosity of 1500 mPa·s at 25℃, was purchased from Jiangsu Kexing New Materials Co., Ltd.

[0044] Aromatic polyester polyol: PF-1205B, hydroxyl value 110±10mgKOH / g, acid value 1.5-2.0mgKOH / g, purchased from Qingdao Ruinuo Chemical Co., Ltd.;

[0045] Isocyanate: Toluene diisocyanate (TDI), commercially available;

[0046] Chain extender: 1,4-Butanediol, commercially available;

[0047] Capping agent: Hydroxyethyl acrylate, commercially available;

[0048] Table 1. Formulation of Organosilicon-Modified Polyurethane Acrylate Raw Materials (parts by weight)

[0049]

[0050] Examples 1-6, Comparative Examples 1-2

[0051] A series of UV-curable coating compositions are provided, prepared by a method comprising the following steps:

[0052] According to the formula in Table 2, the silicone-modified polyurethane acrylate, cyclic ether acrylate or its derivatives, silane coupling agent, filler, and photoinitiator are stirred and mixed evenly to obtain the UV-curable coating composition.

[0053] Table 2 UV-curable coating compositions (parts by weight)

[0054]

[0055] Performance testing

[0056] The properties of the UV-curable coating compositions obtained in the above embodiments and comparative examples were characterized. The UV-curable coating compositions prepared in the above embodiments and comparative examples were uniformly coated onto a rock slab, with a coating amount controlled at 50 g / m². UV curing was then performed in a benchtop UV curing machine (medium-pressure mercury column, H lamp, 120 watts / cm²), with the UVC curing dose controlled at 0.1 joules / cm². The cured coatings were then subjected to the following performance tests:

[0057] 1. 180° peel force (N / 25mm): Tested according to standard GB / T 2792-2014, the results are shown in Table 3;

[0058] 2. Moisture and heat resistance test: The test was conducted according to the method in the standard GB-T 1740-2007. The time (h) for coating failure (blistering or cracking) was observed under the conditions of (47±1)℃ and (97±2)RH%. The test results are shown in Table 3.

[0059] 3. Salt spray resistance test: The test was conducted in accordance with the standard ASTM B117-19, and the corrosion level was recorded after 48 hours of exposure in the test chamber.

[0060] 4. Impact resistance test: The test was conducted in accordance with the standard GB / T 1732-2020, and the test results are shown in Table 3.

[0061] Table 3 Performance test results of the coating

[0062]

[0063] The results above show that:

[0064] The UV-curable coating composition prepared by this invention exhibits excellent performance after UV curing. Specifically, the 180° peel strength is above 25 N / 25 mm, meeting application requirements; the damp heat resistance at (47±1)℃ and (97±2)RH% conditions is above 2000 h; no corrosion is observed after 48 h of exposure in a salt spray test chamber; and the impact strength is above 50 kg·cm / cm. 2 above.

[0065] Comparative Example 1 uses a silicone resin with hydroxyl-terminated ends to modify polyurethane acrylate, and the main molecular chain does not contain alkyl groups; in Comparative Example 2, the diluent containing a cyclic ether structure was replaced with a diluent conventional in the art, and the performance of the cured coating deteriorated significantly.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A UV-curable coating composition, characterized in that, The components include the following weights: 40-60 parts of silicone-modified polyurethane acrylate, 5-30 parts of cyclic ether acrylate or its derivatives, 2-10 parts of silane coupling agent, 30-80 parts of filler, and 0.5-5 parts of photoinitiator; The cyclic ether acrylates or their derivatives include at least one of glycerol methacrylate and glycerol acrylate. The reaction raw materials for the silicone-modified polyurethane acrylate include the following components in parts by weight: The composition includes 15-30 parts isocyanate, 20-100 parts carbon hydroxyl-terminated polydimethylsiloxane, 20-100 parts aromatic polyester polyol, 5-20 parts chain extender, and 3-15 parts end-capping agent; wherein the end-capping agent includes hydroxyethyl acrylate.

2. The UV-curable coating composition according to claim 1, characterized in that, The hydroxyl-terminated polydimethylsiloxane includes hydroxypropyl-terminated polydimethylsiloxane.

3. The UV-curable coating composition according to claim 1, characterized in that, The number average molecular weight of the carbon hydroxyl-terminated polydimethylsiloxane is 1000-10000.

4. The UV-curable coating composition according to claim 1, characterized in that, The silane coupling agent includes at least one of γ-methacryloxypropyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane.

5. The UV-curable coating composition according to claim 1, characterized in that, The filler includes at least one of barium sulfate, barium carbonate, and talc.

6. The UV-curable coating composition according to claim 1, characterized in that, The photoinitiator includes at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, and diphenyl-(2,4,6-trimethylbenzoyl)phosphorus oxychloride.

7. The UV-curable coating composition according to claim 1, characterized in that, The isocyanate includes at least one of toluene diisocyanate and diphenylmethane diisocyanate; And / or, the hydroxyl value of the aromatic polyester polyol is 90-220 mgKOH / g; And / or, the chain extender is a small molecule diol, which includes at least one of ethylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-dihydroxymethylcyclohexane, dimethyl N,N-di(2-hydroxyethyl)aminomethylphosphonate, and diethyl N,N-di(2-hydroxyethyl)aminomethylenephosphonate.

8. A method for preparing the UV-curable coating composition according to any one of claims 1-7, characterized in that, Includes the following steps: The UV-curable coating composition is obtained by uniformly mixing organosilicon-modified polyurethane acrylate, cyclic ether acrylate or its derivatives, silane coupling agent, filler and photoinitiator according to the stated weight parts. The organosilicon-modified polyurethane acrylate is prepared by a method comprising the following steps: S1. According to the stated weight parts, isocyanate, carbon hydroxyl-terminated polydimethylsiloxane and aromatic polyester polyol are mixed evenly and then prepolymerized at 60-90℃ for 1-4 hours to obtain a prepolymerized mixture; S2. Add chain extender to the prepolymer mixture obtained in step S1, mix evenly, and carry out chain extension reaction at 60-90℃ for 3-6 hours. After the chain extension reaction is completed, add end-capping agent, adjust pH to neutral, and emulsify to obtain the silicone-modified polyurethane acrylate.

9. The use of the UV-curable coating composition according to any one of claims 1-7 in the field of corrosion protection.

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