Organic silicon modified natural latex high-temperature-resistant temporary protection peelable coating and preparation method thereof

Abstract

The invention discloses and provides an organic silicon modified natural latex high-temperature-resistant temporary protection peelable coating. The coating is prepared by selecting a specific organic silicon emulsion to modify natural latex, and matching with various auxiliaries such as a pH regulator, a defoaming agent, a wetting dispersant, a thickening agent, a defoaming agent and the like. And the water-based temporary protection peelable protective coating with certain temperature resistance is prepared through a special process, the temperature resistance limit of the water-based temporary protection peelable coating is improved, and the water-based temporary protection peelable coating still has good peelability after 4 hours at 150 DEG C from difficulty in peeling after 2 hours at 130 DEG C. The application scene of the water-based temporary protection peelable coating is expanded, and some specific high-temperature process links can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical coating materials and applications, and specifically relates to an organosilicon-modified natural rubber latex high-temperature resistant temporary protective strippable coating and a preparation method thereof. Background Art

[0002] With the continuous development of modern industrial technology and scientific and technological progress, many industrial parts, equipment, precision instruments, electronic equipment, etc. need temporary protection. Traditional protection measures include stickers, wrapping, plastic wrapping, oil seals, etc. Traditional protection methods have many disadvantages and are difficult to meet the fast-paced development needs of modern industry. Peelable temporary protective coatings provide an effective and direct method to solve the defects of traditional protection methods.

[0003] Peelable coating is a temporary protective coating. After application, this coating can form a temporary protective film on the surface of the substrate to be protected. This protective film can protect the substrate from bumps, fingerprint pollution, rain, aging, process, chemical corrosion, etc., and will not pollute the surface of the substrate or cause secondary damage. It has a short-term protective effect. When the protective effect needs to be terminated, the protective film can be easily peeled off.

[0004] Strippable protective coatings can be divided into two types: solvent-based and water-based. Water-based strippable protective coatings have the advantages of easy construction, good transparency, low price, safety and environmental protection, and are suitable for the protection of special-shaped parts. They are "green" products. Due to the many advantages of water-based temporary protective strippable coatings, they have been widely used in strippable temporary protection.

[0005] Water-based peelable protective coatings can be divided into acrylates, polyvinyl alcohols, polyurethanes, rubbers, etc. according to the type of resin. In order to ensure peelability, the glass transition temperature or softening point of these resins is low. After the peelable coating is applied, it may face a high temperature process in the subsequent process, such as the accelerated drying of the subsequent coating and a specific high-temperature process link, with the temperature ranging from 50℃ to 150℃. Except for rubber, all other resins in the base resin of water-based peelable coatings are thermoplastic. When the temperature rises, the molecules of these thermoplastic resins vibrate violently, and the interface effect with the protective substrate is strengthened, resulting in increased adhesion. After the high-temperature process, the peelability is significantly reduced. For example, the peelability of thermoplastic acrylic peelable coatings is significantly reduced after 90℃×2h; the peelability of polyurethane peelable coatings is also significantly reduced after 110℃×2h, and the peelability of natural latex peelable coatings is also significantly reduced after 130℃×2h.

[0006] With the continuous improvement and advancement of process and technology, the temperature faced by temporary protective strippable coatings in subsequent process will become higher and higher and more frequent. In order to adapt to the new process requirements, water-based temporary protective strippable coatings must improve their strippability after high temperatures. Summary of the invention

[0007] The main purpose of the invention is to improve the heat-resistant stripping performance of the water-based temporary protective strippable coating, and to increase the maximum tolerable temperature and time of the coating without affecting the strippability of the coating.

[0008] The present invention selects a specific organic silicon emulsion to modify the natural latex, and then adds various additives such as pH regulator, defoamer, wetting dispersant, thickener, defoamer, etc., and prepares a water-based temporary protective peelable protective coating with a certain temperature resistance through a special process, which is composed of the following components by mass percentage:

[0009]

[0010] The cellulose is any one of hydroxyethyl cellulose, methyl hydroxyethyl cellulose and methyl hydroxypropyl cellulose or a mixture of two or more of them in any proportion.

[0011] The wetting and dispersing agent is an anionic wetting and dispersing agent, including any one of carboxylates, sulfonates, sulfate esters, and phosphates, or a mixture of two or more of them in any proportion.

[0012] The anionic emulsifier is any one of alkyl sodium sulfate, alkyl polyoxyethylene sodium sulfate or sodium succinate sulfonate, or a mixture of two or more of them in any proportion.

[0013] The nonionic emulsifier is any one of modified fatty alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether, or a mixture of two or more of them in any proportion.

[0014] The defoaming agent is any one of mineral oil and silicone defoaming agents or a mixture of two or more of them in any proportion.

[0015] The vulcanizing agent is tetramethylthiuram disulfide or zinc dibutyldithiocarbamate.

[0016] The pH regulator is any one of ammonia water, dimethylethanolamine, AMP-95, and MA-95, or a mixture of two or more of them in any proportion.

[0017] The thickener is an acrylic emulsion thickener or a polyurethane thickener.

[0018] The natural latex is a natural emulsion with a solid content higher than 60%.

[0019] The organosilicon emulsion is a high temperature resistant organosilicon emulsion, and can stably exist in an alkaline system with a pH value higher than 10, and can withstand a temperature higher than 250°C for a long time.

[0020] The present invention provides a kind of organosilicon modified natural latex high temperature resistant temporary protective strippable coating, and the materials are prepared according to the above formula, and the preparation process thereof is as follows:

[0021] (1) Preparation of slurry: Deionized water is added to a pull cylinder, cellulose is slowly sprinkled in under stirring conditions, the speed is increased and dispersed for more than 30 minutes until the cellulose is completely dissolved, and then a wetting dispersant, a defoaming agent, a vulcanizing agent, titanium dioxide, talcum powder, and nano zinc oxide are added in sequence under stirring conditions, and dispersed at high speed for 60 minutes. The pH value of the system is adjusted to 10 with a pH adjuster, and the material is filtered to obtain a slurry.

[0022] (2) Preparation of coating: Add silicone emulsion to the pull cylinder, slowly add nonionic emulsifier and anionic emulsifier under stirring and stir for 30 minutes, let it stand for 4 hours, add pH adjuster under stirring until the pH value is 10, add natural latex, stir for 30 minutes, and adjust the pH value of the system to 10 with pH adjuster. Slowly add the slurry, stir evenly, add leveling agent and thickener, stir for 30 minutes, and adjust the pH value of the system to 10 with pH adjuster to obtain silicone modified natural latex high temperature resistant temporary protective strippable coating.

[0023] The base resin of the coating of the present invention is mainly natural latex. The stability of natural latex has a great relationship with the pH value. When the system pH value is lower than 10, the coating prepared by natural latex has poor stability, which easily leads to gelation during the coating preparation process. In addition, there are bacteria and enzymes in natural latex, and its pH value will gradually decrease over time, so as to cause demulsification and coagulation. For this reason, it is necessary to add ammonia or other alkalis to the natural latex to increase the pH value to more than 10 so that it can be preserved for a long time.

[0024] The silicone emulsion must be anionic or anionic / nonionic composite emulsion and be stable in a system with a pH value of 10. Cationic silicone emulsions cannot be stable in alkaline systems, and some anionic or anionic / nonionic composite silicone emulsions cannot be stable for a long time in a system with a pH value of 10.

[0025] When the amount of silicone emulsion is less than 12%, it has little effect on improving the temperature resistance of the natural latex type temporary protective stripping. When the amount is higher than 18%, the stability and stripping of the system will be affected, and the preparation stability, storage stability and stripping of the coating will deteriorate.

[0026] The coating system of the present invention is highly alkaline, with a minimum pH value of 10, and has strict requirements on the coating preparation process. Using other processes or changing the order of adding materials may lead to failure in coating preparation.

[0027] Beneficial Effects

[0028] The present invention relates to a silicone modified natural latex high temperature resistant temporary protective strippable coating and a preparation method thereof, which improves the temperature resistance limit of a water-based temporary protective strippable coating, and increases the temperature resistance limit of the water-based temporary protective strippable coating from difficult stripping after 2 hours at 130°C to good strippability after 4 hours at 150°C. The application scenarios of the water-based temporary protective strippable coating are expanded, and some specific high temperature process links can be met. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Embodiment 1:

[0031] (1) Preparation of slurry: 260 kg of deionized water was added to a pull cylinder, and 2.0 kg of hydroxyethyl cellulose and 0.4 kg of methyl hydroxypropyl cellulose were slowly sprinkled in under stirring conditions, and the rotation speed was increased to 600 rpm. The cellulose was dispersed for 35 minutes until the cellulose was completely dissolved. Then, 3 kg of sodium polyacrylate dispersant, 2.0 kg of mineral oil defoamer and 0.6 kg of silicone defoamer, 0.6 kg of tetramethylthiuram disulfide vulcanizing agent, 45 kg of titanium dioxide, 42 kg of talc, and 0.8 kg of nano zinc oxide were added in sequence under stirring conditions of 300 rpm. The mixture was dispersed at a high speed of 800 rpm for 60 minutes, and the pH value of the system was adjusted to 10 with 2.0 kg of AMP-95. The material was filtered to obtain slurry A.

[0032] (2) Preparation of coating: 135 kg of organosilicon emulsion was added to a pull cylinder, 4 kg of nonylphenol polyoxyethylene ether emulsifier and 4 kg of sodium alkyl sulfate emulsifier were slowly added under stirring and stirred for 30 minutes, and then left to stand for 4 hours. 2.0 kg of MA-95 was added under stirring until the pH value was 10, and 400 kg of natural latex (solid content 61.3%) was added and stirred for 30 minutes, and the pH value of the system was adjusted to 10 with 0.2 kg of ammonia water. The slurry was slowly added and stirred evenly, and then 2 kg of leveling agent, 5 kg of acrylic emulsion thickener and 1 kg of polyurethane thickener were added and stirred for 30 minutes, and the pH value of the system was adjusted to 10 with 0.1 kg of ammonia water. The material was discharged to obtain organosilicon-modified natural latex high temperature resistant temporary protective strippable coating A.

[0033] Embodiment 2:

[0034] (1) Preparation of slurry: 240 kg of deionized water was added to a pull cylinder, and 2.2 kg of hydroxyethyl cellulose was slowly sprinkled in under stirring conditions. The rotation speed was increased to 600 rpm and dispersed for 35 minutes until the cellulose was completely dissolved. Then, 3 kg of sodium polyacrylate dispersant, 2.7 kg of silicone defoamer, 0.5 kg of tetramethylthiuram disulfide vulcanizing agent and 0.1 kg of dibutyl dithiocarbamate zinc vulcanizing agent, 43 kg of titanium dioxide, 40 kg of talc and 0.6 kg of nano zinc oxide were added in sequence under stirring conditions of 300 rpm. The mixture was dispersed at a high speed of 800 rpm for 60 minutes, and the pH value of the system was adjusted to 10 with 2.0 kg of MA-95. The material was filtered to obtain slurry B.

[0035] (2) Preparation of coating: 140 kg of organosilicon emulsion was added to a pull cylinder, and 4.2 kg of nonylphenol polyoxyethylene ether emulsifier, 2 kg of sodium alkyl sulfate and 1 kg of sodium succinate emulsifier were slowly added under stirring and stirred for 30 minutes, and then left to stand for 4 hours. Under stirring, 2.2 kg of MA-95 was added until the pH value was 10, and 430 kg of natural latex (solid content 61.5%) was added and stirred for 30 minutes. The pH value of the system was adjusted to 10 with 0.2 kg of ammonia water. The slurry was slowly added and stirred evenly, and then 2 kg of leveling agent, 5.0 kg of acrylic emulsion thickener and 1.5 kg of polyurethane thickener were added and stirred for 30 minutes. The pH value of the system was adjusted to 10 with 0.1 kg of ammonia water. The material was discharged to obtain organosilicon-modified natural latex high temperature resistant temporary protective strippable coating B.

[0036] Embodiment 3:

[0037] (1) Preparation of slurry: 248 kg of deionized water was added to a pull cylinder, and 2.3 kg of hydroxyethyl cellulose was slowly sprinkled in under stirring conditions. The rotation speed was increased to 600 rpm and dispersed for 35 minutes until the cellulose was completely dissolved. Then, 3.6 kg of sodium phosphate dispersant, 2.0 kg of mineral oil defoamer and 1.0 kg of silicone defoamer, 0.7 kg of dibutyl dithiocarbamate zinc vulcanizing agent, 50 kg of titanium dioxide, 50 kg of talc, and 0.8 kg of nano zinc oxide were added in sequence under stirring conditions of 300 rpm. The mixture was dispersed at a high speed of 800 rpm for 60 minutes, and the pH value of the system was adjusted to 10 with 2.2 kg of AMP-95. The material was filtered to obtain slurry C.

[0038] (2) Preparation of coating: 150 kg of organosilicon emulsion was added to a pull cylinder, 4.8 kg of nonylphenol polyoxyethylene ether emulsifier and 4.2 kg of sodium succinate anion emulsifier were slowly added under stirring and stirred for 30 minutes, and then left to stand for 4 hours. Then 2.1 kg of AMP-95 was added under stirring until the pH value was 10, and 460 kg of natural latex (solid content 60.8%) was added and stirred for 30 minutes. The pH value of the system was adjusted to 10 with 0.2 kg of ammonia water. The slurry was slowly added and stirred evenly, and then 3 kg of leveling agent, 4 kg of acrylic emulsion thickener and 2 kg of polyurethane thickener were added and stirred for 30 minutes. The pH value of the system was adjusted to 10 with 0.1 kg of ammonia water. The material was discharged to obtain organosilicon modified natural latex high temperature resistant temporary protective strippable coating C.

[0039] Technical Effects of the Invention

[0040] The products of Examples 1-3 were brush-coated on substrates of the same specifications, and then baked at 150° C. for 2 h, 3 h, and 4 h, respectively, and then subjected to peelability tests. The results are as follows:

[0041] Test items Example 1 Example 2 Example 3 Coating thickness 60μm 60μm 60μm Temperature resistance 150℃×2h 150℃×3h 150℃×4h Heat resistance after peeling Easy to peel Easy to peel Easy to peel

[0042] It can be seen from the above table that the present invention has achieved good technical effects.

[0043] The present disclosure has been described by the above-mentioned relevant embodiments, but the above-mentioned embodiments are only examples for implementing the present disclosure. It must be pointed out that the disclosed embodiments do not limit the scope of the present disclosure. On the contrary, changes and modifications made without departing from the spirit and scope of the present disclosure are all within the scope of patent protection of the present disclosure.

Claims

1. A silicone-modified natural rubber latex high temperature resistant temporary protective strippable coating, characterized in that: Calculated by mass percentage, it is composed of the following components:

2. The organosilicon-modified natural rubber latex high temperature resistant temporary protective strippable coating according to claim 1, characterized in that: The cellulose is any one of hydroxyethyl cellulose, methyl hydroxyethyl cellulose and methyl hydroxypropyl cellulose or a mixture of several of them in any proportion.

3. The organosilicon-modified natural rubber latex high temperature resistant temporary protective strippable coating according to claim 1, characterized in that: The wetting and dispersing agent is an anionic wetting and dispersing agent, and the anionic wetting and dispersing agent is any one of carboxylates, sulfonates, sulfate ester salts, and phosphates, or a mixture of several of them in any proportion.

4. The organosilicon-modified natural rubber latex high temperature resistant temporary protective strippable coating according to claim 1, characterized in that: The anionic emulsifier is any one of alkyl sodium sulfate, alkyl polyoxyethylene sodium sulfate, and sodium succinate sulfonate, or a mixture of several of them in any proportion.

5. The organosilicon-modified natural rubber latex high temperature resistant temporary protective strippable coating according to claim 1, characterized in that: The nonionic emulsifier is any one of modified fatty alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether, or a mixture of two or more of them in any proportion.

6. The organosilicon-modified natural rubber latex high temperature resistant temporary protective strippable coating according to claim 1, characterized in that: The defoaming agent is any one of mineral oil and silicone defoaming agents or a mixture of several of them in any proportion; the vulcanizing agent is tetramethylthiuram disulfide or zinc dibutyl dithiocarbamate.

7. The organosilicon-modified natural rubber latex high temperature resistant temporary protective strippable coating according to claim 1, characterized in that: The pH regulator is any one of ammonia water, dimethylethanolamine, AMP-95 and MA-95, or a mixture of several of them in any proportion.

8. The organosilicon-modified natural rubber latex high temperature resistant temporary protective strippable coating according to claim 1, characterized in that: The thickener is any one of acrylic emulsion thickeners or polyurethane thickeners or a mixture of several of them in any proportion; the solid content of the natural latex is ≥60%.

9. The organosilicon-modified natural rubber latex high temperature resistant temporary protective strippable coating according to claim 1, characterized in that: The organosilicon emulsion is a high temperature resistant organosilicon emulsion, and can stably exist in an alkaline system with a pH value higher than 10, and has a long-term temperature resistance higher than 250°C.

10. A method for preparing the high temperature resistant temporary protective strippable coating of organosilicon modified natural rubber latex according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) Preparation of slurry: Deionized water is added to a pull cylinder, cellulose is slowly sprinkled in under stirring conditions, the speed is increased and dispersed for more than 30 minutes until the cellulose is completely dissolved, and then a wetting dispersant, a defoaming agent, a vulcanizing agent, titanium dioxide, talcum powder, and nano zinc oxide are added in sequence under stirring conditions, and dispersed at high speed for 60 minutes. The pH value of the system is adjusted to 10 with a pH adjuster, and the material is filtered to obtain a slurry. (2) Preparation of coating: Add silicone emulsion to the pull cylinder, slowly add nonionic emulsifier and anionic emulsifier under stirring and stir for 30 minutes, let it stand for 4 hours, add pH adjuster under stirring until the pH value is 10, add natural latex, stir for 30 minutes, and adjust the pH value of the system to 10 with pH adjuster. Slowly add the slurry, stir evenly, add leveling agent and thickener, stir for 30 minutes, and adjust the pH value of the system to 10 with pH adjuster to obtain silicone modified natural latex high temperature resistant temporary protective strippable coating.

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