Polyvinyl alcohol waterproof coating and preparation method thereof

Abstract

The application provides polyvinyl alcohol waterproof paint and a preparation method thereof, and belongs to the technical field of waterproof paint. The paint comprises the following components in parts 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 dispersing agent, 0.05-0.08 parts of preservative, 20-30 parts of filler and 60-80 parts of water; and the leveling agent is dopamine modified silicone oil. The specific types and the ratio of the components are controlled, so that the obtained paint has good waterproof performance, impact resistance and corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of waterproof coating technology, specifically relating to a polyvinyl alcohol waterproof coating and its preparation method. Background Technology

[0002] Coatings are broadly classified into solvent-based coatings and water-based coatings. The earliest anti-corrosion coatings were oil-soluble organic coatings, such as acrylic, polyurethane, epoxy resin, and amino coatings. Due to their superior anti-corrosion effects, they played a crucial role in protecting the base metal from corrosion, making a significant contribution to reducing economic losses and resource waste, thus becoming key products in corrosion prevention. However, solvent-based anti-corrosion coatings contain large amounts of toxic volatile organic compounds, such as benzene, aldehydes, and ketones. These toxic volatile substances have been classified as carcinogens, seriously endangering human health. Therefore, to meet the needs of green development and replace traditional solvent-based resins, toxic chromates, and lead-containing pigments, the development of water-based anti-corrosion coatings, which use water—which does not contain or release toxic and harmful substances—as a solvent and dispersant, is particularly important.

[0003] Water-based coatings are coatings that use water as a solvent or dispersion medium. Water-based coatings include three types: water-soluble coatings, water-dilutable coatings, and water-dispersible coatings. Water-soluble coatings use water-soluble resins as film-forming agents; water-dilutable coatings are made by dissolving solvent-based resins in organic solvents, and then, with the help of emulsifiers and strong mechanical stirring, dispersing the resin in water to form an emulsion, known as a post-emulsified emulsion. These coatings can be diluted with water during application; water-dispersible coatings mainly refer to coatings formulated with synthetic resin emulsions as film-forming agents.

[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, and water-based inorganic coatings. Because they do not release toxic or harmful substances, they are environmentally friendly organic coatings.

[0005] Polyvinyl alcohol (PVA) is a biodegradable, water-soluble polymer with a relatively simple chemical structure. It is non-toxic, non-carcinogenic, and one of the few water-soluble vinyl polymers. Furthermore, it exhibits good biocompatibility, making it an excellent matrix material. PVA possesses excellent film-forming properties, as well as high tensile and impact strength, and is widely used as a film and packaging material.

[0006] For example, Chinese patent CN104497662A discloses an environmentally friendly water-based coating, comprising 580-620 parts water; 64-70 parts polyvinyl alcohol; 108-115 parts titanium dioxide; 2-4 parts defoamer; 4-7 parts tributyl phosphate; 8-13 parts propylene glycol; 15-23 parts dibutyl phthalate; and 200-230 parts composite modifier. The preparation method involves heating water to 70℃-90℃, adding polyvinyl alcohol powder, and stirring until the powder dissolves. Then, tributyl phosphate, propylene glycol, and dibutyl phthalate are added and mixed evenly. Titanium dioxide and composite modifier are added to the mixture and stirred evenly. Then, defoamer is added to eliminate foam. Finally, the defoamed material is sand-milled and sieved to obtain the finished coating. This invention produces an environmentally friendly and safe coating with good waterproof and wear-resistant properties, no solvent pollution, and no cracks or fissures.

[0007] For example, patent CN103013245A discloses a water-based waterproof coating, its preparation method, and its application. The water-based waterproof coating of this invention comprises, by weight, deionized water, polyethylene glycol, melamine, a fixing agent, silica sol, polyvinyl alcohol, acrylate copolymer emulsion, a defoamer, and a whitening agent. Compared to existing technologies, this invention provides a water-based waterproof coating with excellent waterproof performance, good durability, strong ink absorption, and high-resolution printed images.

[0008] However, in the presence of water, films using polyvinyl alcohol as the film-forming substance have a drawback: poor stability. Therefore, it is necessary to develop a polyvinyl alcohol waterproof coating with good stability and its preparation method. Summary of the Invention

[0009] In view of the shortcomings of the existing technology, the present invention aims to provide a polyvinyl alcohol waterproof coating with good stability and its preparation method.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: On one hand, the present invention provides a polyvinyl alcohol waterproof coating, comprising the following components by weight: The ingredients are: 30-40 parts water-based acrylic emulsion, 50-65 parts polyvinyl alcohol, 0.1-0.5 parts defoamer, 0.5-1.0 parts leveling agent, 5-10 parts dispersant, 0.05-0.08 parts preservative, 20-30 parts filler, and 60-80 parts water.

[0011] Preferably, the polyvinyl alcohol waterproof coating comprises the following components by weight: The composition includes 32-38 parts of water-based acrylic emulsion, 55-60 parts of polyvinyl alcohol, 0.2-0.4 parts of defoamer, 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] The defoamer mentioned above 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 as follows: (1) Synthesize dopamine-modified alkoxysilane using isocyanate-based 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 hydroxysulfonate betaine, wherein the mass ratio of sodium cocoyl carboxyglycinate to cocamide hydroxysulfonate betaine 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-silica, nano-titanium dioxide, nano-zinc oxide, clay, and boron nitride; Preferably, the filler is selected from one or more of nano-silica, 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; More preferably, the mass ratio of the nano-titanium dioxide to the nano-zinc oxide is 2:1.

[0016] As some preferred embodiments, 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; and even more preferably, the mass ratio of the defoamer to the leveling agent is 1:3.

[0017] As is well known in the art, leveling agents can improve leveling properties, enhance the smoothness of the coating surface, and improve scratch resistance, thereby minimizing surface defects. Defoamers, used in water-based coatings, can quickly remove air bubbles from the system. Therefore, leveling agents and defoamers need to be used in combination to ensure that water-based coatings achieve good leveling properties without generating air bubbles. In the course of implementation, this invention unexpectedly discovered that using the dopamine-modified silicone oil described in this invention as a leveling agent in combination with white oil, and controlling the mass ratio of the two to 1:1.5-5, can achieve good leveling properties without generating air bubbles during coating, resulting in coatings with better coatability 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 known in the art that adding nanofillers to a polymer matrix can form an organic-inorganic hybrid polymer through chemical bonding between the polymer and the nanofiller, which can give the polymer better film-forming properties and flexibility. In this invention, a mixture of nano-titanium dioxide and nano-zinc oxide is used as a filler. It was unexpectedly discovered that adding a dispersant can better mix the polymer and the filler. By controlling the mass ratio of dispersant to filler to 1:2-6, this invention can make the resulting coating have better corrosion resistance and significantly improved waterproofing.

[0020] The present invention also provides a method for preparing the above-mentioned polyvinyl alcohol waterproof coating, comprising the following steps: (1) Heat water to 80-90℃ and add polyvinyl alcohol. Keep warm and stir until completely dissolved. Then add water-based acrylic emulsion and stir evenly to obtain a mixture. (2) Add filler and dispersant to the mixture and continue stirring until uniform. Then add defoamer, leveling agent and preservative and mix until uniform. Then sieve to obtain the polyvinyl alcohol waterproof coating.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, dopamine-modified silicone oil is used as a leveling agent and is used in combination with white oil. The mass ratio of the two is controlled to be 1:1.5-5, which can ensure that the coating has good leveling properties and does not produce bubbles during application. The resulting coating has better coatability and stability. (2) In this invention, a mixture of nano titanium dioxide and nano zinc oxide is used as filler. It was unexpectedly discovered that adding a dispersant can better mix the polymer and filler. By controlling the mass ratio of dispersant to filler to 1:2-6, this invention makes the coating have better corrosion resistance and significantly improves the waterproof effect. (3) By controlling the specific types and proportions of the components, the present invention enables the coating to have good waterproof, impact-resistant and corrosion-resistant properties. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; and the materials and reagents used are commercially available unless otherwise specified.

[0024] Basic Example: A method for preparing dopamine-modified silicone oil, comprising the following steps: (1) Synthesize dopamine-modified alkoxysilane using isocyanate-based 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 alkoxysilanes: (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 dried triethylamine (molar ratio of 3.5:1 to dopamine) to the mixed solution, stir, filter to remove the precipitate, and obtain a clear solution; (1.2) Add the clear solution obtained in step (1) into the reactor, heat and stir under nitrogen protection, the reaction temperature is 60℃, add isocyanate-based trimethoxysilane (molar ratio with dopamine is 1.5:1) dropwise into the clear solution, the dropwise addition time is 20 minutes, after the dropwise addition is completed, continue the reaction for 5.5 hours, after the reaction is completed, remove DMF, triethylamine and unreacted siloxane to obtain dopamine modified alkoxysilane; (2) Preparation of dopamine-modified silicone oil: Dimethyldimethoxysilane, triethylamine, and deionized water were added to the dopamine-modified alkoxysilane obtained in step (1.2). The mixture was heated to 70°C under nitrogen protection, and then gradually increased to 100°C (heating rate of 10°C / 20 min) for 5 hours. After the reaction, the temperature was lowered to 70°C to remove water and low-boiling substances. The temperature was then raised to 120°C and reacted for 8 hours. After the reaction, low-boiling substances such as DMF were removed to obtain dopamine-modified silicone oil.

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

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

[0027] The preparation method of polyvinyl alcohol waterproof coating includes the following steps: (1) Heat water to 85°C and add polyvinyl alcohol. Keep warm and stir until completely dissolved. Then add water-based acrylic emulsion and stir evenly to obtain a mixture. (2) Add filler and dispersant to the mixture and continue stirring until uniform. Then add defoamer, leveling agent and preservative and mix until uniform. Then sieve to obtain the polyvinyl alcohol waterproof coating.

[0028] Example 2 A polyvinyl alcohol waterproof coating and its preparation method, comprising the following components by weight: The composition includes 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 cocoamide hydroxysulfonate betaine, 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 examples).

[0030] Preparation method of polyvinyl alcohol waterproof coating: (1) Heat water to 85°C and add polyvinyl alcohol. Keep warm and stir until completely dissolved. Then add water-based acrylic emulsion and stir evenly to obtain a mixture. (2) Add filler and dispersant to the mixture and continue stirring until uniform. Then add defoamer, leveling agent and preservative and mix until uniform. Then sieve to obtain the polyvinyl alcohol waterproof coating.

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

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

[0033] Preparation method of polyvinyl alcohol waterproof coating: (1) Heat water to 85°C and add polyvinyl alcohol. Keep warm and stir until completely dissolved. Then add water-based acrylic emulsion and stir evenly to obtain a mixture. (2) Add filler and dispersant to the mixture and continue stirring until uniform. Then add defoamer, leveling agent and preservative and mix until uniform. Then sieve to obtain the polyvinyl alcohol waterproof coating.

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

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

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

[0037] Comparative Example 4 The difference from Example 3 is that the mass ratio of dispersant to filler is 1:1, that is, 12.8 parts of oil-based carboxyglycinate sodium, 3.2 parts of cocamidoyl hydroxysulfonate betaine, 10.5 parts of nano titanium dioxide, and 5.5 parts of nano zinc oxide, while other components and contents remain unchanged.

[0038] Performance testing 1) Waterproofing test The waterproofing performance of a specimen coated with paint is measured by the contact angle between the paint and deionized water. A larger contact angle indicates better waterproofing 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 this invention have better waterproofing effects. In Comparative Examples 1-3, changing the type of leveling agent or the mass ratio of defoamer and leveling agent will affect the fluidity of the coating and the elimination of bubbles, thereby affecting the waterproofing of the coating. In Comparative Example 4, changing the mass ratio of dispersant and filler will affect the full mixing of polymer and filler, thereby affecting the film-forming properties of the coating and thus reducing the waterproofing effect of the coating.

[0040] 2) Impact resistance Following the test method of standard GB / T 1732-2020, the coated specimen was fixed upwards on a platform, and a weight was fixed at the required height. The weight was then released, and the specimen was struck vertically. The impact resistance of the coating was evaluated based on the maximum height from which no cracks, wrinkles, or peeling of the coating were 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 this invention have better impact resistance. In Comparative Examples 1-3, changing the type of leveling agent or the mass ratio of defoamer and leveling agent will affect the fluidity of the coating and the elimination of bubbles, thereby affecting the impact resistance of the coating. In Comparative Example 4, changing the mass ratio of dispersant and filler will affect the full mixing of polymer and filler, thereby affecting the film-forming properties of the coating and thus reducing the impact resistance of the coating.

[0042] 3) Corrosion resistance test Salt spray resistance test was conducted in accordance with GB / T 1771-2007 for 1200 hours. The test results are shown in Table 3 below.

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

[0044] This invention utilizes dopamine-modified silicone oil as a leveling agent, used in combination with white oil, and controls the mass ratio of the two to be 1:1.5-5. This allows the coating to achieve good leveling properties without generating bubbles during application, resulting in a coating with better coatability and stability. Using a mixture of nano-titanium dioxide and nano-zinc oxide as a filler, it was unexpectedly discovered that adding a dispersant further improves the mixing of the polymer and filler. By controlling the mass ratio of dispersant to filler to be 1:2-6, this invention results in a coating with better resistance to cold and heat, chemical stability, and significantly improved waterproofing. In summary, this invention, by controlling the specific types and proportions of the components, produces a coating with excellent waterproofing, impact resistance, and corrosion resistance.

[0045] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A polyvinyl alcohol waterproof coating, characterized in that: It comprises the following components by weight: The composition includes 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 a dopamine-modified silicone oil, which is prepared by the following method: (1) Synthesize dopamine-modified alkoxysilane using isocyanate-based trimethoxysilane and dopamine hydrochloride as raw materials; (2) Dopamine-modified alkoxysilane and dimethyldimethoxysilane are co-hydrolyzed to obtain dopamine-modified silicone oil; The defoamer mentioned is selected from white oil; The filler is a mixture of nano-titanium dioxide and nano-zinc oxide; the mass ratio of the two is 1-3:

1. The mass ratio of the defoamer to the leveling agent is 1:1.5-5; The mass ratio of the dispersant to the filler is 1:2-5.

2. The polyvinyl alcohol waterproof coating according to claim 1, characterized in that: The product 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 defoamer, 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 dispersant is a mixture of sodium cocoyl carboxyglycinate and cocamide hydroxysulfonate betaine, with a mass ratio of 2-5:

1.

4. The polyvinyl alcohol waterproof coating according to claim 3, characterized in that: The dispersant is a mixture of sodium cocoyl carboxyglycinate and cocamide hydroxysulfonate betaine in a mass ratio of 4:

1.

5. The method for preparing the polyvinyl alcohol waterproof coating according to any one of claims 1-4, characterized in that: Includes the following steps: (1) Heat water to 80-90℃ and add polyvinyl alcohol. Keep warm and stir until completely dissolved. Then add water-based acrylic emulsion and stir evenly to obtain a mixture. (2) Add filler and dispersant to the mixture and continue stirring until uniform. Then add defoamer, leveling agent and preservative and mix until uniform. Then sieve to obtain the polyvinyl alcohol waterproof coating.

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