Polysiloxane epoxy hybrid environment-friendly coating and preparation method thereof

Abstract

The invention belongs to the technical field of coatings, and relates to a polysiloxane epoxy hybrid environment-friendly coating and a preparation method thereof. The coating belongs to an environment-friendly solvent type coating with low VOC content, modified epoxy resin is adopted as a base, auxiliaries such as a film-forming agent and a dispersing agent are added, and benzophenone and tertiary amine composite photoinitiator is supplemented, so that the prepared coating has good corrosion resistance, high temperature resistance and the like, and the coating can quickly form a film at normal temperature and under the UV illumination condition, shortens the curing period, and is suitable for large-scale popularization and application. The emission of VOC (volatile organic compounds) is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and in particular relates to a polysiloxane-epoxy hybrid environmentally friendly coating and a preparation method thereof. Background Art

[0002] With growing environmental awareness and stricter regulations, eco-friendly coatings, characterized by low pollution, low toxicity, or even non-toxicity, align with the concept of sustainable development and are evolving from a single-use coating to a multifunctional one, promising broad application prospects in diverse fields such as construction and automotive. Epoxy resins, with their outstanding adhesion and corrosion resistance, have become a research focus. Through chemical modification or compounding techniques, low-VOC coatings can be developed in various forms, including water-based, solvent-based, and powder-based systems, adapting to environmental needs and expanding their application across multiple industries.

[0003] However, traditional solvent-based epoxy coatings rely on organic solvents, which evaporate during the production, application, and curing processes, becoming a major source of VOCs. Water-based epoxy coatings, on the other hand, have negligible VOC content, but require a longer curing time. Chinese patent application number CN 106905819 A discloses a two-component water-based epoxy coating, consisting of a resin and auxiliary materials in component A and a curing agent system in component B. It uses water as the solvent and emits no VOCs, but requires 30 minutes for surface curing and 3 hours for complete drying. This long curing time prolongs the application cycle, and the uncured coating surface, in a liquid or semi-solid state, is susceptible to dust, impurities, and mechanical damage, resulting in a rough, uneven gloss, and decreased adhesion. Furthermore, with solvent-based coatings, prolonged curing times lead to the continuous volatilization of organic solvents during the curing process, which not only pollutes the environment but also poses health risks to construction workers due to prolonged exposure to volatiles from the uncured coating. Summary of the Invention

[0004] The present invention provides a polysiloxane-epoxy hybrid environmentally friendly coating and its preparation method. This coating is low in VOC and environmentally friendly, exhibiting excellent corrosion and high-temperature resistance. The coating incorporates a photoinitiator, benzophenone, and a tertiary amine co-initiator, which work synergistically to enable the colored coating to rapidly cure under ultraviolet light.

[0005] To achieve the above-mentioned object, the present invention provides a polysiloxane epoxy hybrid environmentally friendly coating, which comprises a solvent, a modified epoxy resin, a film-forming agent, a dispersant, a defoaming agent, a thickener, a pigment and a photoinitiator; the mass ratio of the solvent, the modified epoxy resin, the film-forming agent, the dispersant, the defoaming agent, the thickener, the pigment and the photoinitiator is 1: (0.3-0.6): (0.01-0.05): (0.03-0.08): (0.01-0.1): (0.05-0.2): (0.015-0.03): (0.01-0.025); the modified epoxy resin is an epoxy vinyl resin modified by vinyl-terminated polydimethylsiloxane, and its structural formula is as follows:

[0006] ,

[0007] Wherein, n is an integer between 1 and 10, and m is an integer between 20 and 100.

[0008] Preferably, the solvent is any one or more of butyl acetate and propylene glycol methyl ether acetate.

[0009] Preferably, the film-forming agent is soybean oil fatty acid methyl ester.

[0010] Preferably, the dispersant is BYK 163 dispersant.

[0011] Preferably, the photoinitiator is benzophenone and a tertiary amine, the mass ratio of benzophenone to the tertiary amine is 1:(0.15-0.25), and the tertiary amine is any one or more of triethanolamine, triethylamine and dimethylethanolamine.

[0012] Preferably, the defoaming agent is liquid paraffin and hydrophobic silica, and the mass ratio of liquid paraffin to hydrophobic silica is 1:(0.1~0.2).

[0013] Preferably, the thickener is hydrogenated castor oil; the pigments are titanium dioxide and carbon black, and the mass ratio of titanium dioxide to carbon black is 1:(0.075~0.15).

[0014] The present invention also provides a method for preparing a polysiloxane epoxy hybrid environmentally friendly coating, comprising:

[0015] Step S1: bisphenol A diglycidyl ether and acrylic acid are mixed, dissolved in ethyl acetate, and a catalyst is added to react to obtain epoxy vinyl resin;

[0016] Step S2: epoxy vinyl resin and vinyl terminated polydimethylsiloxane are mixed, dissolved in ethyl acetate, and an initiator and an accelerator are added to react to obtain a modified epoxy resin;

[0017] Step S3: dispersing the modified epoxy resin in a solvent, adding a film-forming agent, a dispersant, a defoaming agent, a thickener, a pigment and a photoinitiator, and stirring in a dark environment to obtain an environmentally friendly coating.

[0018] Preferably, in step S1, the catalyst is any one or more of triethylamine, dimethylbenzylamine and tetramethylammonium bromide.

[0019] Preferably, in step S1, the reaction temperature is 60-80° C., and the reaction time is 4-6 h.

[0020] Preferably, in step S1, the mass ratio of bisphenol A diglycidyl ether, acrylic acid, ethyl acetate and catalyst is 1: (1-1.2): (3-5): (0.05-0.3).

[0021] Preferably, in step S2, the initiator is benzoyl peroxide; and the accelerator is dimethylacetamide.

[0022] Preferably, in step S2, the reaction temperature is 70-85° C., and the reaction time is 6-12 h.

[0023] Preferably, in step S2, the mass ratio of the epoxy resin, vinyl-terminated polydimethylsiloxane, ethyl acetate, initiator and accelerator is 1: (0.1-0.3): (3-5): (0.01-0.03): (0.001-0.01).

[0024] Preferably, in step S3, the stirring temperature is 55-65°C

[0025] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0026] (1) In this application, acrylic acid is reacted with bisphenol A diglycidyl ether to obtain epoxy vinyl resin, and vinyl-terminated polydimethylsiloxane and styrene are used to modify the epoxy vinyl resin to obtain a modified epoxy resin. Vinyl-terminated polydimethylsiloxane and styrene participate in the cross-linking reaction of the resin, increase the cross-linking density, and make the resin and the substrate surface more tightly bonded. At the same time, the non-polar silicon-oxygen bond in the vinyl-terminated polydimethylsiloxane structure has a certain barrier effect on polar corrosive media, which can reduce the contact between the corrosive media and the internal structure of the resin, thereby improving corrosion resistance; because the methyl groups in the vinyl-terminated polydimethylsiloxane structure are arranged outward to form a hydrophobic layer, the coating can prevent the penetration of water molecules; under the joint support of the conjugation of the benzene ring in the glycidyl ether and the flexible chain segment of the polysiloxane in the structure, the thermal motion of the molecular chain of the resin is restricted at high temperature, and the reduction of heat weakens the damage to the internal structure of the resin, which can effectively prevent the resin from softening and deforming at high temperature, thereby improving the high temperature resistance.

[0027] (2) The coating prepared in this application is based on a vinyl-terminated polydimethylsiloxane and styrene-modified epoxy vinyl resin, and a photoinitiator of a mixed system of benzophenone and tertiary amine is added. Under UV light, the coating cures rapidly, reducing VOC emissions. Benzophenone photoinitiator and tertiary amine photoinitiator auxiliary synergistically generate free radicals under light, initiating the resin cross-linking reaction. The flexible siloxane chain segments increase the movement space of the resin chain segments, reducing stress accumulation during the cross-linking process, making the reaction more thorough, and reducing small molecule residues caused by incomplete local reactions, thereby reducing VOC emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart for the preparation of polysiloxane-epoxy hybrid environmentally friendly coatings.

[0029] Figure 2 Schematic diagram of the synthesis flow line of modified epoxy resin.

[0030] Figure 3 This is a product picture of the polysiloxane epoxy hybrid environmentally friendly coating prepared in Example 2. DETAILED DESCRIPTION

[0031] The following examples are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0032] Unless otherwise specified, the reagents and equipment involved in the following examples were purchased from commercial channels.

[0033] Example 1

[0034] like Figure 1 As shown, a polysiloxane epoxy hybrid environmentally friendly coating, the preparation method of which includes:

[0035] Step S1: 10 g of bisphenol A diglycidyl ether and 10 g of acrylic acid were mixed, dissolved in 30 g of ethyl acetate, 0.5 g of triethylamine was added, and the mixture was reacted at 60° C. for 6 h to obtain an epoxy vinyl resin.

[0036] Step S2: 10 g of epoxy vinyl resin and 1 g of vinyl-terminated polydimethylsiloxane were mixed and dissolved in 30 g of ethyl acetate, 0.1 g of benzoyl peroxide and 0.01 g of dimethylacetamide were added, and the mixture was reacted at 70° C. for 12 h to obtain a modified epoxy resin, such as Figure 2 shown.

[0037] Step S3: Disperse 30 g of modified epoxy resin in 100 g of butyl acetate, add 1 g of soybean oil fatty acid methyl ester, 3 g of BYK 163 dispersant, 1 g of defoamer (0.9 g of liquid paraffin and 0.1 g of hydrophobic silica), 5 g of hydrogenated castor oil, 1.5 g of pigment (1.4 g of titanium dioxide and 0.1 g of carbon black), and 1 g of photoinitiator (0.86 g of benzophenone and 0.14 g of triethanolamine), and stir in the dark to obtain a polysiloxane-epoxy hybrid environmentally friendly coating.

[0038] Example 2

[0039] like Figure 1 As shown, a polysiloxane epoxy hybrid environmentally friendly coating, the preparation method of which includes:

[0040] Step S1: 10 g of bisphenol A diglycidyl ether and 11 g of acrylic acid were mixed, dissolved in 40 g of ethyl acetate, 1.5 g of dimethylbenzylamine was added, and the mixture was reacted at 70° C. for 5 h to obtain an epoxy vinyl resin.

[0041] Step S2: 10 g of epoxy resin and 2 g of vinyl-terminated polydimethylsiloxane were mixed and dissolved in 40 g of ethyl acetate, 0.2 g of benzoyl peroxide and 0.05 g of dimethylacetamide were added, and the mixture was reacted at 80° C. for 8 h to obtain a modified epoxy resin, such as Figure 2 shown.

[0042] Step S3, dispersing 45 g of modified epoxy resin in 100 g of propylene glycol methyl ether acetate, adding 3 g of soybean oil fatty acid methyl ester, 5 g of BYK 163 dispersant, 5 g of defoamer (4.3 g of liquid paraffin and 0.7 g of hydrophobic silica), 10 g of hydrogenated castor oil, 2 g of pigment (1.8 g of titanium dioxide and 0.2 g of carbon black), and 2 g of photoinitiator (1.6 g of benzophenone and 0.4 g of triethylamine), and stirring under light-proof conditions to obtain a polysiloxane epoxy hybrid environmentally friendly coating, such as Figure 3 shown.

[0043] Example 3

[0044] like Figure 1 As shown, a polysiloxane epoxy hybrid environmentally friendly coating, the preparation method of which includes:

[0045] Step S1: 10 g of bisphenol A diglycidyl ether and 12 g of acrylic acid were mixed, dissolved in 50 g of ethyl acetate, 3 g of tetramethylammonium bromide was added, and the mixture was reacted at 80° C. for 4 h to obtain an epoxy vinyl resin.

[0046] Step S2: 10 g of epoxy resin and 3 g of vinyl-terminated polydimethylsiloxane were mixed and dissolved in 50 g of ethyl acetate, 0.3 g of benzoyl peroxide and 0.1 g of dimethylacetamide were added, and the mixture was reacted at 85° C. for 6 h to obtain a modified epoxy resin, such as Figure 2 shown.

[0047] Step S3: Disperse 60 g of modified epoxy resin in 100 g of butyl acetate, add 5 g of soybean oil fatty acid methyl ester, 8 g of BYK 163 dispersant, 10 g of defoamer (8.3 g of liquid paraffin and 1.7 g of hydrophobic silica), 20 g of hydrogenated castor oil, 3 g of pigment (2.6 g of titanium dioxide and 0.4 g of carbon black), and 2.5 g of photoinitiator (2 g of benzophenone and 0.5 g of dimethylethanolamine), and stir in the dark to obtain a polysiloxane-epoxy hybrid environmentally friendly coating.

[0048] Comparative Example 1

[0049] A polysiloxane-epoxy hybrid environmentally friendly coating, the preparation method of which is different from that of Example 2 in that acrylic acid is not added in step S1.

[0050] Comparative Example 2

[0051] A polysiloxane-epoxy hybrid environmentally friendly coating, the preparation method of which is different from that of Example 2 in that vinyl-terminated polydimethylsiloxane is not added in step S2.

[0052] Comparative Example 3

[0053] A polysiloxane-epoxy hybrid environmentally friendly coating, the preparation method of which is different from that of Example 2 in that ordinary polybenzimidazole resin is used.

[0054] Comparative Example 4

[0055] A polysiloxane-epoxy hybrid environmentally friendly coating, the preparation method of which is different from that of Example 2 in that triethylamine is not added in step S3.

[0056] Performance testing:

[0057] (1) Adhesion: Apply the coating on the tinplate. After drying, place the sample on the test bench of the adhesion tester under constant temperature and humidity conditions. Tighten the adjustment bolts for fixing the sample, move the lifting rod so that the tip of the needle contacts the coating, and shake the handle evenly in a clockwise direction. The speed should be 80~100 rpm. The standard length of the circular line scratch is 7.5±0.5 cm. Move the lifting rod forward to lift the needle plate. Loosen the bolts that fix the sample, remove the sample, remove the debris on the scratch, and inspect the scratch with a magnifying glass and grade it. Take the upper side of the scratch on the sample as the inspection target and mark seven parts, namely 1, 2, 3, 4, 5, 6, and 7. They are divided into seven grades accordingly. The paint film of part 1 is intact and has the best adhesion, which is rated as level 1; the paint film of part 1 is damaged, while part 2 is intact and has the second best adhesion, which is rated as level 2. And so on. Level 7 is the worst adhesion.

[0058] (2) Impact resistance: Apply the coating to a metal substrate. After curing, fix the substrate on an impact tester. Drop a 1kg hammer from a certain height to impact the punch. Gradually increase the drop height. Test the maximum impact height at which the paint film does not crack or peel. Perform three tests at the same height.

[0059] (3) Corrosion resistance: Polish the substrate, wash it with industrial gasoline, apply the coating after drying, and after curing, immerse 2 / 3 of the substrate vertically in a 5% acid solution or alkaline solution. Check it every 24 hours to see if the paint film has blistering, cracking, or falling off.

[0060] (4) Water resistance: After coating on the substrate and curing, immerse 2 / 3 of the substrate vertically in water at a temperature of 25℃±1, and check every 24 hours to see if the paint film has peeling, blistering, etc.

[0061] (5) High temperature resistance: Apply the coating to the metal substrate and place it in a forced air drying oven at 80-100°C for 24 hours after curing. After the specified time, remove the test panel from the oven or high-temperature furnace and allow it to cool to room temperature. Inspect the test panel and compare it with an unheated test panel prepared under the same conditions to see if there is any change in the color of the coating or any other damage to the coating.

[0062] (6) Drying time test: Coating was applied on a glass substrate with a coating thickness of 50 μm and a coating temperature of 25 ± 2 °C. The substrate was then placed in a drying oven with a relative humidity of 50 ± 5% and a temperature of 25 ± 2 °C. The coating curing time was recorded. Coating was applied on a glass substrate under the same environmental conditions. The substrate was placed in a drying oven equipped with a UV mercury lamp at a temperature of 25 ± 2 °C and a mercury lamp power of 200 mW / cm 2 , irradiate the substrate and record the coating curing time.

[0063] Table 1 Test data of coating wear resistance, impact resistance and adhesion performance

[0064]

[0065] According to the data in Table 1, the impact resistance of the coatings prepared in Examples 1 to 3 is higher than 40 cm, and the adhesion is all level 1; while the impact resistance of the coatings prepared in Comparative Examples 1 to 4 is significantly lower than that in Examples 1 to 3, and the adhesion level is also lower than that in Examples 1 to 3.

[0066] Table 2 Test data of corrosion resistance and water resistance of coating

[0067]

[0068] As shown in Table 2, the coatings prepared in Examples 1 to 3 showed no signs of blistering, cracking or falling off in acidic or alkaline environments, and no blistering, wrinkling or falling off occurred in water; the coating prepared in Comparative Example 1 fell off in acidic, alkaline and water; the coating prepared in Comparative Example 2 cracked in an acidic environment, blistered in an alkaline environment, and fell off in water; the coating prepared in Comparative Example 3 fell off in acidic, alkaline and water environments; the coating prepared in Comparative Example 4 blistered in acidic, alkaline and water, but did not blister, crack or fall off in water.

[0069] Table 3 Test results of coating high temperature resistance

[0070]

[0071] As shown in the data in Table 3, after the coatings prepared in Examples 1 to 3 and Comparative Example 4 were placed at high temperature for 24 hours, the coatings did not show any cracks, peeling or powdering, and the color did not change; the coatings prepared in Comparative Examples 1 and 2 cracked at high temperature, and showed gloss loss and slight fading; the coating prepared in Comparative Example 3 fell off and powdered at high temperature, and the coating lost gloss and faded significantly.

[0072] Table 4 Determination of coating drying time

[0073]

[0074] According to the data in Table 4, the coatings prepared in Examples 1 to 3 dried at 25±2°C for less than 45 h; the coating prepared in Comparative Example 1 dried at 25±2°C for 52 h, which was slightly higher than that in Examples 1 to 3; the coatings prepared in Comparative Examples 2 to 4 cured for more than 100 h, and the coatings in Comparative Examples 3 and 4 dried for more than 150 h.

[0075] The coatings prepared in Examples 1 through 3 dried significantly faster under UV illumination than those without UV illumination, all within 15 minutes. The coating in Comparative Example 1 dried slightly longer under UV illumination, at 25.7 minutes. The coatings prepared in Comparative Examples 2 through 4 dried faster under UV illumination than those in Comparative Examples 3 and 4, with drying times exceeding 60 minutes, significantly longer than those in the other groups. Compared to the coatings without UV illumination, the drying times of these coatings under UV illumination were significantly shorter.

[0076] In summary, acrylic acid is reacted with bisphenol A diglycidyl ether to obtain epoxy vinyl resin, and then vinyl-terminated polydimethylsiloxane is introduced to modify the epoxy vinyl resin to obtain a modified epoxy resin. By using this modified epoxy resin and adding other auxiliary materials, the mechanical properties, corrosion resistance and water resistance of the coating can be improved. Combined with the composite photoinitiator system of benzophenone and tertiary amine, it can be quickly and thoroughly cured under light.

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A polysiloxane epoxy hybrid environmentally friendly coating, characterized in that: The coating comprises a solvent, a modified epoxy resin, a film-forming agent, a dispersant, a defoamer, a thickener, a pigment and a photoinitiator; the mass ratio of the solvent, the modified epoxy resin, the film-forming agent, the dispersant, the defoamer, the thickener, the pigment and the photoinitiator is 1: (0.3-0.6): (0.01-0.05): (0.03-0.08): (0.01-0.1): (0.05-0.2): (0.015-0.03): (0.01-0.025); the modified epoxy resin is an epoxy vinyl resin modified by vinyl-terminated polydimethylsiloxane, and its structural formula is as follows: ， Wherein, n is an integer between 1 and 10, and m is an integer between 20 and 100.

2. A polysiloxane epoxy hybrid environmentally friendly coating according to claim 1, characterized in that: The solvent is any one or more of butyl acetate and propylene glycol methyl ether acetate; the film-forming agent is soybean oil fatty acid methyl ester; the dispersant is BYK 163 dispersant; the photoinitiator is benzophenone and a tertiary amine, the mass ratio of benzophenone to tertiary amine is 1:(0.15-0.25), and the tertiary amine is any one or more of triethanolamine, triethylamine and dimethylethanolamine.

3. The polysiloxane epoxy hybrid environmentally friendly coating according to claim 1, characterized in that: The defoaming agent is liquid paraffin and hydrophobic silica, and the mass ratio of the liquid paraffin to the hydrophobic silica is 1: (0.1-0.2).

4. The polysiloxane epoxy hybrid environmentally friendly coating according to claim 1, characterized in that: The thickener is hydrogenated castor oil; the pigments are titanium dioxide and carbon black, and the mass ratio of titanium dioxide to carbon black is 1:(0.075-0.15).

5. The method for preparing a polysiloxane epoxy hybrid environmentally friendly coating according to any one of claims 1 to 4, characterized in that: include: Step S1: bisphenol A diglycidyl ether and acrylic acid are mixed, dissolved in ethyl acetate, and a catalyst is added to react to obtain epoxy vinyl resin; Step S2: epoxy vinyl resin and vinyl terminated polydimethylsiloxane are mixed, dissolved in ethyl acetate, and an initiator and an accelerator are added to react to obtain a modified epoxy resin; Step S3: dispersing the modified epoxy resin in a solvent, adding a film-forming agent, a dispersant, a defoaming agent, a thickener, a pigment and a photoinitiator, and stirring in a dark environment to obtain an environmentally friendly coating.

6. The method for preparing a polysiloxane epoxy hybrid environmentally friendly coating according to claim 5, characterized in that: In step S1, the catalyst is any one or more of triethylamine, dimethylbenzylamine and tetramethylammonium bromide; the reaction temperature is 60-80° C., and the reaction time is 4-6 h.

7. The method for preparing a polysiloxane epoxy hybrid environmentally friendly coating according to claim 5, characterized in that: In step S1, the mass ratio of bisphenol A diglycidyl ether, acrylic acid, ethyl acetate and catalyst is 1: (1-1.2): (3-5): (0.05-0.3).

8. The method for preparing a polysiloxane epoxy hybrid environmentally friendly coating according to claim 5, characterized in that: In step S2, the initiator is benzoyl peroxide; the accelerator is dimethylacetamide; the reaction temperature is 70-85° C., and the reaction time is 6-12 h.

9. The method for preparing a polysiloxane epoxy hybrid environmentally friendly coating according to claim 5, characterized in that: In step S2, the mass ratio of the epoxy resin, vinyl-terminated polydimethylsiloxane, ethyl acetate, initiator and accelerator is 1: (0.1-0.3): (3-5): (0.01-0.03): (0.001-0.01).

10. The method for preparing a polysiloxane epoxy hybrid environmentally friendly coating according to claim 5, characterized in that: In step S3, the stirring temperature is 55-65°C.

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