Polyvinyl alcohol waterproof coating and preparation method thereof

Abstract

The invention provides a polyvinyl alcohol waterproof coating and a preparation method thereof, and belongs to the technical field of waterproof coatings. The coating is prepared from the following components in parts by weight: 30 to 40 parts of waterborne acrylic emulsion, 50 to 65 parts of polyvinyl alcohol, 0.1 to 0.5 part of a defoaming agent, 0.5 to 1.0 part of a flatting agent, 5 to 10 parts of a dispersing agent, 0.05 to 0.08 part of a preservative, 20 to 30 parts of filler and 60 to 80 parts of water, the flatting agent is dopamine modified silicone oil. By controlling the specific types and proportions of the components, the obtained coating has good water resistance, impact resistance and corrosion resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of waterproof coatings, and specifically relates to a polyvinyl alcohol waterproof coating and a preparation method thereof. Background Art

[0002] Paints are divided into two categories: solvent-based paints and water-based paints. The earliest anti-corrosion paints were oil-soluble organic anti-corrosion paints, such as acrylic paints, polyurethane paints, epoxy resin paints, amino paints, etc. Due to their good anti-corrosion effects, they play a particularly important role in protecting the base metal from corrosion, and have made great contributions to reducing economic losses and waste of resources. Therefore, they have become the key products for anti-corrosion. However, solvent-based anti-corrosion paints contain a large amount of toxic volatile organic compounds, such as benzene, aldehydes, ketones, etc. These toxic volatile substances have been listed as carcinogens and seriously endanger human health. Therefore, in order to meet the needs of green development of society, it is particularly important to replace traditional solvent-based resins, toxic chromates and lead-containing pigments, and use water that does not contain and does not volatilize toxic and harmful substances as solvents and dispersants.

[0003] Water-based paint is a paint that uses water as a solvent or dispersion medium. Water-based paint includes three types: water-soluble paint, water-dilutable paint, and water-dispersible paint. Water-soluble paint is a paint that uses water-soluble resin as a film-forming material; water-dilutable paint is a solvent-based resin dissolved in an organic solvent, and then with the help of an emulsifier, the resin is dispersed in water through strong mechanical stirring to form an emulsion, which is called a post-emulsified emulsion. The resulting paint can be diluted with water during construction; water-dispersible paint mainly refers to paint formulated with synthetic resin emulsion as a film-forming material.

[0004] Water-based coatings mainly include: water-based alkyd resin coatings, water-based epoxy resin coatings, water-based polyurethane coatings, water-based acrylic coatings, water-based fluorocarbon coatings, water-based inorganic coatings, etc. Because it does not volatilize toxic and harmful substances, it is an environmentally friendly organic coating.

[0005] Polyvinyl alcohol is a biodegradable water-soluble polymer with a relatively simple chemical structure. It is non-toxic and non-carcinogenic. It is one of the few vinyl polymers that are soluble in water and has good biocompatibility. It is a good matrix material. Polyvinyl alcohol has excellent film-forming properties and high tensile strength and impact strength, and is widely used as a film material and packaging material.

[0006] For example, Chinese patent CN104497662A discloses an environmentally friendly water-based paint, including 580-620 parts of water; 64-70 parts of polyvinyl alcohol; 108-115 parts of titanium dioxide; 2-4 parts of defoamer; 4-7 parts of tributyl phosphate; 8-13 parts of propylene glycol; 15-23 parts of dibutyl phthalate; and 200-230 parts of composite modifier. The preparation method is to heat water to 70°C-90°C, add polyvinyl alcohol powder, keep warm and stir until the powder is dissolved; then add tributyl phosphate, propylene glycol and dibutyl phthalate and mix evenly; add titanium dioxide and composite modifier to the mixture and stir evenly, then add defoamer to eliminate foam; finally, sand grind the defoamed material, sieve, and obtain the finished paint. The paint of the invention is environmentally friendly and safe, has good waterproof and wear resistance, no solvent pollution, and no cracks.

[0007] For another example, patent CN103013245A discloses a water-based waterproof coating, a preparation method and its application. The main components of the water-based waterproof coating of the present invention include, by weight, deionized water, polyethylene glycol, melamine, a color fixative, silica sol, polyvinyl alcohol, an acrylic copolymer emulsion, a defoamer and a whitening agent. Compared with the prior art, the water-based waterproof coating of the present invention has good waterproof performance, good durability, strong ink absorption and high print image clarity.

[0008] However, in the presence of water, a disadvantage of films using polyvinyl alcohol as a film-forming material is that their stability is relatively poor. Therefore, it is necessary to develop a polyvinyl alcohol waterproof coating with good stability and a preparation method thereof. Summary of the invention

[0009] Based on the deficiencies of the prior art, the present invention aims to provide a polyvinyl alcohol waterproof coating with good stability and a preparation method thereof.

[0010] In order to achieve the above object, the present invention adopts the following technical solution: In one aspect, the present invention provides a polyvinyl alcohol waterproof coating, comprising the following components by weight: 30-40 parts of water-based acrylic emulsion, 50-65 parts of polyvinyl alcohol, 0.1-0.5 parts of defoaming agent, 0.5-1.0 parts of leveling agent, 5-10 parts of dispersant, 0.05-0.08 parts of preservative, 20-30 parts of filler and 60-80 parts of water.

[0011] Preferably, the polyvinyl alcohol waterproof coating comprises the following components by weight: 32-38 parts of water-based acrylic emulsion, 55-60 parts of polyvinyl alcohol, 0.2-0.4 parts of defoaming agent, 0.6-0.8 parts of leveling agent, 5-9 parts of dispersant, 0.06-0.07 parts of preservative, 22-28 parts of filler and 65-75 parts of water.

[0012] Wherein, the defoaming agent is selected from white oil.

[0013] The leveling agent is dopamine modified silicone oil, and the preparation method of the dopamine modified silicone oil is: (1) Synthesizing dopamine-modified alkoxysilane using isocyanate trimethoxysilane and dopamine hydrochloride as raw materials; The reaction formula is: (2) Dopamine-modified alkoxysilane and dimethyldimethoxysilane are co-hydrolyzed to obtain dopamine-modified silicone oil; The reaction formula is: The dispersant is a mixture of sodium cocoyl carboxyglycinate and cocamide hydroxysulfobetaine, and the mass ratio of the sodium cocoyl carboxyglycinate to cocamide hydroxysulfobetaine is 2-5:1, preferably 4:1.

[0014] The preservative is selected from isothiazolinone.

[0015] The filler is selected from one or more of nano silicon dioxide, nano titanium dioxide, nano zinc oxide, clay and boron nitride; Preferably, the filler is selected from one or more of nano silicon dioxide, nano titanium dioxide, nano zinc oxide and boron nitride; More preferably, the filler is a mixture of nano titanium dioxide and nano zinc oxide; the mass ratio of the two is 1-3:1; Further preferably, the mass ratio of the nano titanium dioxide to the nano zinc oxide is 2:1.

[0016] As some preferred implementation schemes, the mass ratio of the defoamer to the leveling agent is 1:1.5-5; preferably, the mass ratio of the defoamer to the leveling agent is 1:2-4; more preferably, the mass ratio of the defoamer to the leveling agent is 1:3.

[0017] It is well known in the art that a leveling agent has the effects of improving leveling, enhancing the smoothness of the coating surface, and enhancing the scratch resistance, and can minimize surface defects; and a defoaming agent can be used in water-based coatings to quickly remove bubbles in the system. Therefore, a leveling agent and a defoaming agent need to be used in combination to ensure that the water-based coating can have good leveling and no bubbles are generated during coating. During the implementation of the present invention, it was unexpectedly found that the dopamine-modified silicone oil described in the present invention is used as a leveling agent in combination with white oil, and the mass ratio of the two is controlled to be 1:1.5-5. The coating can have good leveling and no bubbles are generated during coating, and the resulting coating has better coating properties and stability.

[0018] As another preferred embodiment, the mass ratio of the dispersant to the filler is 1:2-5; preferably 1:3-4; and more preferably 1:3.

[0019] It is well known in the art that adding nanofillers to a polymer matrix to form an organic-inorganic hybrid polymer through chemical bonding between the polymer and the nanofillers can make the polymer have better film-forming properties and flexibility. In the present invention, a mixture of nano titanium dioxide and nano zinc oxide is used as a filler. It is unexpectedly found that adding a dispersant thereto can better mix the polymer and the filler. In the present invention, by controlling the mass ratio of the dispersant to the filler to be 1:2-6, the obtained coating has better corrosion resistance and significantly improved waterproof effect.

[0020] The present invention also provides a method for preparing the polyvinyl alcohol waterproof coating, comprising the following steps: (1) After heating water to 80-90°C, add polyvinyl alcohol, stir while keeping warm until completely dissolved, then add water-based acrylic emulsion and stir evenly to obtain a mixture; (2) Add the filler and dispersant to the mixture and continue to stir evenly, then add the defoamer, leveling agent and preservative, mix evenly, and sieve to obtain the polyvinyl alcohol waterproof coating.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses dopamine-modified silicone oil as a leveling agent, which is used in combination with white oil, and the mass ratio of the two is controlled to be 1:1.5-5, so that the coating can have good leveling properties and will not generate bubbles during coating, and the obtained coating has better coating properties and stability; (2) The present invention uses a mixture of nano titanium dioxide and nano zinc oxide as a filler. It is unexpectedly found that adding a dispersant thereto can better mix the polymer and the filler. The present invention controls the mass ratio of the dispersant to the filler to be 1:2-6, so that the obtained coating has better corrosion resistance and significantly improved waterproof effect; (3) The present invention controls the specific types and proportions of the components so that the resulting coating has good waterproof, impact resistance and corrosion resistance. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial channels.

[0024] Basic Example: A method for preparing dopamine-modified silicone oil comprises the following steps: (1) Synthesizing dopamine-modified alkoxysilane using isocyanate trimethoxysilane and dopamine hydrochloride as raw materials; The reaction formula is: (2) Dopamine-modified alkoxysilane and dimethyldimethoxysilane are co-hydrolyzed to obtain dopamine-modified silicone oil; The reaction formula is: Specifically: (1) Preparation of dopamine-modified alkoxysilane: (1.1) Weigh dopamine hydrochloride and dried DMF in a mass ratio of 1:1.5, stir to dissolve, and obtain a mixed solution; add dry triethylamine (with a molar ratio of 3.5:1 to dopamine) to the mixed solution, stir, and filter to remove the precipitate to obtain a clear solution; (1.2) adding the clear solution obtained in step (1) into a reactor, heating and stirring under nitrogen protection, the reaction temperature is 60°C, and isocyanate trimethoxysilane (with a molar ratio of 1.5:1 to dopamine) is added dropwise to the clear solution for 20 minutes. After the addition is completed, the reaction is continued for 5.5 hours. After the reaction is completed, DMF, triethylamine and unreacted siloxane are removed to obtain dopamine-modified alkoxysilane; (2) Preparation of dopamine-modified silicone oil: Add dimethyldimethoxysilane, triethylamine and deionized water to the dopamine-modified alkoxysilane obtained in step (1.2), heat to 70°C under nitrogen protection, then gradually heat to 100°C (heating rate of 10°C / 20min), and react for 5 hours. After the reaction, cool to 70°C, remove water and low-boiling substances, heat to 120°C, react for 8 hours, remove low-boiling substances such as DMF after the reaction, and obtain dopamine-modified silicone oil.

[0025] Example 1 A polyvinyl alcohol waterproof coating and a preparation method thereof, comprising the following components by weight: 30 parts of water-based acrylic emulsion, 50 parts of polyvinyl alcohol, 0.1 parts of white oil, 0.5 parts of leveling agent, 4 parts of sodium cocoyl carboxyglycinate, 2 parts of cocamide hydroxysulfobetaine, 0.05 parts of isothiazolinone, 10 parts of nano titanium dioxide, 10 parts of nano zinc oxide and 60 parts of water.

[0026] The leveling agent is dopamine-modified silicone oil (prepared according to the method described in the basic example).

[0027] The preparation method of polyvinyl alcohol waterproof coating comprises the following steps: (1) After heating water to 85°C, add polyvinyl alcohol, keep the temperature and stir until it is completely dissolved, then add the aqueous acrylic emulsion and stir evenly to obtain a mixture; (2) Add the filler and dispersant to the mixture and continue to stir evenly, then add the defoamer, leveling agent and preservative, mix evenly, and sieve to obtain the polyvinyl alcohol waterproof coating.

[0028] Example 2 A polyvinyl alcohol waterproof coating and a preparation method thereof, comprising the following components by weight: 40 parts of water-based acrylic emulsion, 65 parts of polyvinyl alcohol, 0.5 parts of white oil, 0.8 parts of leveling agent, 7.5 parts of sodium cocoyl carboxyglycinate, 1.5 parts of cocamide hydroxysulfobetaine, 0.08 parts of isothiazolinone, 22.5 parts of nano titanium dioxide, 7.5 parts of nano zinc oxide and 80 parts of water.

[0029] The leveling agent is dopamine-modified silicone oil (prepared according to the method described in the basic example).

[0030] Preparation method of polyvinyl alcohol waterproof coating: (1) After heating water to 85°C, add polyvinyl alcohol, keep the temperature and stir until it is completely dissolved, then add the aqueous acrylic emulsion and stir evenly to obtain a mixture; (2) Add the filler and dispersant to the mixture and continue to stir evenly, then add the defoamer, leveling agent and preservative, mix evenly, and sieve to obtain the polyvinyl alcohol waterproof coating.

[0031] Example 3 A polyvinyl alcohol waterproof coating and a preparation method thereof, comprising the following components by weight: 35 parts of water-based acrylic emulsion, 55 parts of polyvinyl alcohol, 0.2 parts of white oil, 0.6 parts of leveling agent, 6.4 parts of sodium cocoyl carboxyglycinate, 1.6 parts of cocamide hydroxysulfobetaine, 0.06 parts of isothiazolinone, 16 parts of nano titanium dioxide, 8 parts of nano zinc oxide and 70 parts of water.

[0032] The leveling agent is dopamine-modified silicone oil (prepared according to the method described in the basic example).

[0033] Preparation method of polyvinyl alcohol waterproof coating: (1) After heating water to 85°C, add polyvinyl alcohol, keep the temperature and stir until it is completely dissolved, then add the aqueous acrylic emulsion and stir evenly to obtain a mixture; (2) Add the filler and dispersant to the mixture and continue to stir evenly, then add the defoamer, leveling agent and preservative, mix evenly, and sieve to obtain the polyvinyl alcohol waterproof coating.

[0034] Comparative Example 1 The difference from Example 3 is that the leveling agent is replaced by silicone oil, and the other components and contents remain unchanged.

[0035] Comparative Example 2 The difference from Example 3 is that the mass ratio of the defoamer to the leveling agent is 1:1, that is, 0.4 parts of white oil and 0.4 parts of leveling agent, and the other components and contents remain unchanged.

[0036] Comparative Example 3 The difference from Example 3 is that the mass ratio of the defoamer to the leveling agent is 1:7, that is, 0.1 part of white oil and 0.7 part of leveling agent, and the other components and contents remain unchanged.

[0037] Comparative Example 4 The difference from Example 3 is that the mass ratio of the dispersant to the filler is 1:1, namely, 12.8 parts of sodium oleyl carboxyglycinate, 3.2 parts of cocamide hydroxysulfobetaine, 10.5 parts of nano titanium dioxide, and 5.5 parts of nano zinc oxide, and the other ingredients and contents remain unchanged.

[0038] Performance Testing 1) Waterproof test The waterproof performance of the coated specimen is measured by measuring the contact angle between the coated specimen and deionized water. The larger the contact angle, the better the waterproof performance. The test results are shown in Table 1 below.

[0039] Table 1 According to the test results in Table 1 above, the coatings prepared in Examples 1-3 of the present invention have better waterproof effects. In Comparative Examples 1-3, changing the type of leveling agent or changing the mass ratio of the defoaming agent to the leveling agent will affect the fluidity of the coating and the bubble elimination effect, thereby affecting the waterproofness of the coating. In Comparative Example 4, changing the mass ratio of the dispersant and the filler will affect the full mixing of the polymer and the filler, thereby affecting the film-forming property of the coating, thereby reducing the waterproof effect of the coating.

[0040] 2) Impact strength Referring to the test method of standard GB / T 1732-2020, the coated specimen is fixed on the storage table with the face upward, the weight is fixed at the required height, the weight is released, and the weight is vertically hit on the specimen. The impact strength of the coating is evaluated at the maximum height where no cracks, wrinkles or peeling of the coating are observed. The test results are shown in Table 2 below.

[0041] Table 2 According to the test results in Table 2 above, the coatings prepared in Examples 1-3 of the present invention have better impact resistance. In Examples 1-3, changing the type of leveling agent or changing the mass ratio of the defoaming agent and the leveling agent will affect the fluidity of the coating and the bubble elimination effect, thereby affecting the impact resistance of the coating. In Example 4, changing the mass ratio of the dispersant and the filler affects the full mixing of the polymer and the filler, thereby affecting the film-forming property of the coating, thereby reducing the impact resistance of the coating.

[0042] 3) Corrosion resistance test The salt spray resistance test was carried out with reference to GB / T 1771-2007. The test time was 1200h. The test results are shown in Table 3 below.

[0043] Table 3 According to the test results in Table 3 above, the paint coatings prepared in Examples 1-3 of the present invention have better corrosion resistance. In Comparative Examples 1-3, changing the type of leveling agent or changing the mass ratio of the defoaming agent and the leveling agent will affect the fluidity of the coating and the bubble elimination effect, thereby affecting the corrosion resistance of the coating; in Comparative Example 4, changing the mass ratio of the dispersant and the filler will affect the full mixing of the polymer and the filler, thereby affecting the film-forming property of the coating, thereby reducing the corrosion resistance of the coating.

[0044] The present invention adopts dopamine modified silicone oil as a leveling agent, which is used in combination with white oil, and the mass ratio of the two is controlled to be 1:1.5-5, so that the coating can have good leveling property and no bubbles are generated during coating, and the obtained coating has better coating property and stability; a mixture of nano titanium dioxide and nano zinc oxide is adopted as a filler, and it is unexpectedly found that adding a dispersant therein can better mix the polymer and the filler, and the present invention controls the mass ratio of the dispersant and the filler to be 1:2-6, so that the obtained coating has better cold and heat resistance and chemical stability, and the waterproof effect is also significantly improved; in summary, the present invention controls the specific types and ratios of the components so that the obtained coating has good waterproof, impact resistance and corrosion resistance.

[0045] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A polyvinyl alcohol waterproof coating, characterized in that: The components are as follows by weight: 30-40 parts of water-based acrylic emulsion, 50-65 parts of polyvinyl alcohol, 0.1-0.5 parts of defoamer, 0.5-1.0 parts of leveling agent, 5-10 parts of dispersant, 0.05-0.08 parts of preservative, 20-30 parts of filler and 60-80 parts of water; The leveling agent is dopamine modified silicone oil, and its preparation method is as follows: (1) Synthesizing dopamine-modified alkoxysilane using isocyanate trimethoxysilane and dopamine hydrochloride as raw materials; (2) Dopamine-modified alkoxysilane and dimethyldimethoxysilane are co-hydrolyzed to obtain dopamine-modified silicone oil.

2. The polyvinyl alcohol waterproof coating according to claim 1, characterized in that: The composition comprises the following components by weight: 32-38 parts of water-based acrylic emulsion, 55-60 parts of polyvinyl alcohol, 0.2-0.4 parts of defoaming agent, 0.6-0.8 parts of leveling agent, 5-9 parts of dispersant, 0.06-0.07 parts of preservative, 22-28 parts of filler and 65-75 parts of water.

3. The polyvinyl alcohol waterproof coating according to claim 1, characterized in that: The defoaming agent is selected from white oil.

4. The polyvinyl alcohol waterproof coating according to claim 1, characterized in that: The dispersant is a mixture of sodium cocoyl carboxyglycinate and cocamide hydroxysulfobetaine, and the mass ratio of the two is 2-5:

1.

5. The polyvinyl alcohol waterproof coating according to claim 4, characterized in that: The dispersant is a mixture of sodium cocoyl carboxyglycinate and cocamide hydroxysulfobetaine, and the mass ratio of the two is 4:

1.

6. The polyvinyl alcohol waterproof coating according to claim 1, characterized in that: The filler is selected from one or more of nano silicon dioxide, nano titanium dioxide, nano zinc oxide, clay and boron nitride.

7. The polyvinyl alcohol waterproof coating according to claim 6, characterized in that: The filler is a mixture of nano titanium dioxide and nano zinc oxide; the mass ratio of the two is 1-3:

1.

8. The polyvinyl alcohol waterproof coating according to claim 1, characterized in that: The mass ratio of the defoamer to the leveling agent is 1:1.5-5.

9. The polyvinyl alcohol waterproof coating according to claim 1, characterized in that: The mass ratio of the dispersant to the filler is 1:2-5.

10. The method for preparing the polyvinyl alcohol waterproof coating according to any one of claims 1 to 9, characterized in that: The steps include: (1) After heating water to 80-90°C, add polyvinyl alcohol, keep warm and stir until it is completely dissolved, then add water-based acrylic emulsion and stir evenly to obtain a mixture; (2) Add the filler and dispersant to the mixture and continue to stir evenly, then add the defoamer, leveling agent and preservative, mix evenly, and sieve to obtain the polyvinyl alcohol waterproof coating.

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