CN115418144B - Ultra-low alcoholysis degree polyvinyl alcohol anti-fog coating material and manufacturing method thereof - Google Patents

Abstract

The invention belongs to the technical field of fine chemical engineering, and particularly relates to an ultra-low alcoholysis degree polyvinyl alcohol anti-fog coating material and a manufacturing method thereof. The invention relates to an antifogging coating material, which comprises the following components: 15-20% of polyvinyl alcohol with ultralow alcoholysis degree, 1-10% of curing agent, 60-80% of 1, 4-dioxane, 0.01-0.5% of catalyst, 0-1.0% of auxiliary agent and 5-30% of alcoholysis degree of polyvinyl alcohol. The curing agent is selected from diisocyanate, diisocyanate oligomer and etherified amino resin; the catalyst is selected from dibutyl tin dilaurate and p-toluenesulfonic acid; the auxiliary agent is a defoaming agent and a leveling wetting agent. The antifogging coating material prepared by the invention has good antifogging effect, good water resistance and solvent resistance, and wide application range of base materials.

Description

Ultra-low alcoholysis degree polyvinyl alcohol anti-fog coating material and manufacturing method thereof

Technical field

The invention belongs to the technical field of fine chemicals, and specifically relates to an ultra-low alcoholysis degree polyvinyl alcohol anti-fog coating material and a manufacturing method thereof.

Background technique

Fogging on the surface of the material is a normal phenomenon. The reason for fogging is the temperature difference between the inside and outside of the substrate, which causes the small water droplets gathered on the surface of the substrate to refract and reflect light because they cannot cover the entire surface. Due to the massive condensation of water vapor on the material surface, atomization can cause severe light scattering and reduce the transparency of the materials, severely limiting their applications in humid environments. Currently, there are two main anti-fog strategies. One is to change the ambient temperature or surface temperature of the substrate to reduce the temperature difference. However, this method consumes a lot of energy and is not environmentally friendly, which limits its applicability. Another method of anti-fog is to apply hydrophilic or hydrophobic anti-fog treatments by changing the affinity between the solid surface and the water droplets. With the development of polymer science, polymer coatings using resin as film-forming material have attracted people's attention. The resin forms a good film layer through curing, thereby greatly extending the service life of the anti-fog coating. There are many types of anti-fog coatings, which can be roughly divided into three categories: hydrophobic anti-fog, bionic anti-fog and hydrophilic anti-fog. At present, most of the anti-fog coatings used in practice are hydrophilic anti-fog coatings, and the hydrophilic polymer route is one of its preparation methods.

Polyvinyl alcohol (PVA) is hydrophilic, non-toxic and non-polluting, and is often used to prepare anti-fog coatings or anti-fog agents. However, its water resistance is poor. Generally, glutaraldehyde, borate, boehmite, etc. need to be added for cross-linking. Even after cross-linking, there are still many hydroxyl groups remaining in the coating, which is prone to foaming and falling off in a water environment. Only use It is suitable for short-term anti-fogging in situations where water resistance requirements are not high. At present, PVA resin, adding fillers, or substrate surface pretreatment are generally used to solve the hydrophilicity and water resistance of PVA-based anti-fog coatings. For example, in patent 201210553079.1, the end groups or side groups of hydrophilic polymers including PVA are given siloxane groups so that they can chemically bond with the glass substrate. At the same time, nanoparticles are introduced to enhance the mechanical properties of the coating. In patent 201310254464.0, the base material is first hydroxylated with strong acid, then treated with 3-aminopropyltriethoxysilane, and then coated with maleic anhydride-grafted polyethylene and PVA, respectively, to obtain a PVA hydrophilic coating. In patent 201611156887.9, a primer layer containing hydroxyl acrylic resin and curing agent is first coated on the surface of the substrate, and then a topcoat layer composed of polyvinyl alcohol and nanoparticles is coated. The double-layer structural coating is cross-linked. After being soaked in an aqueous agent solution and then solidified, a super-hydrophilic anti-fog coating with a micro-nano structure on the surface was obtained. In patent 202110216754.0, a UV-curable hydrophilic semi-interpenetrating network coating was prepared using trehalose-modified polyvinyl alcohol, oligoethylene glycol dimethacrylate, benzoin dimethyl ether and deionized water. It also has anti-frost properties. In the above-mentioned patent report, the surface treatment of the substrate will complicate the preparation process of the anti-fog coating. The introduction of nanoparticles may lead to a decrease in the transparency of the coating due to poor dispersion. Modification or compounding of the resin will It is not easy to balance the relationship between adhesion, hydrophilicity and water resistance. Therefore, the preparation of hydrophilic PVA anti-fog coatings with good water resistance, good adhesion, and wide range of substrate applications still faces challenges.

Contents of the invention

The purpose of the present invention is to provide an ultra-low alcoholysis degree polyvinyl alcohol anti-fog coating material with good anti-fog performance, strong adhesion and good water resistance and a manufacturing method thereof.

The ultra-low alcoholysis degree polyvinyl alcohol (PVA) anti-fog coating material provided by the present invention has the following components:

Ultra-low alcoholysis degree PVA: 15-20%;

Curing agent: 1-10%;

1,4-dioxane: 60-80%;

Catalyst: 0.01-0.5%;

Additives: 0-1.0%;

The total amount meets 100%.

In the present invention, the alcoholysis degree range of the ultra-low alcoholysis degree PVA is 5-30%.

In the present invention, the curing agent is one of diisocyanate, diisocyanate oligomer and etherified amino resin.

Further, the curing agent described in the present invention is selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate and their biurets and trimers, permethyl etherified melamine resin, and perbutyl etherified melamine resin. , one of partially methyl etherified melamine resin and partially butylated melamine resin.

In the present invention, the catalyst is one of dibutyltin dilaurate and p-toluenesulfonic acid.

In the present invention, the auxiliary agents are defoaming agents and leveling wetting agents.

The invention also provides a method for manufacturing the above-mentioned low alcoholysis degree PVA anti-fog coating material. The specific steps are:

(1) Preparation of ultra-low alcoholysis degree PVA;

Dissolve polyvinyl acetate in tetrahydrofuran, slowly add a certain amount of sodium hydroxide methanol solution (i.e. alkali alcohol solution) for alcoholysis, and finally add dilute hydrochloric acid to adjust the pH to 6-7 to obtain ultra-low alcoholysis degree PVA. The degree of alcoholysis ranges from 5-30%;

(2) Dry the ultra-low alcoholysis degree PVA obtained in step (1), dissolve it in 1,4-dioxane, and then settle still for more than 24 hours to remove impurities and insoluble matter;

(3) Mix the ultra-low alcoholysis degree PVA solution prepared in step (2) with the curing agent according to a certain molar ratio, add catalysts and additives, and prepare ultra-low alcoholysis degree PVA anti-fog coating;

(4) Coat the coating prepared in step (3) on the transparent substrate to form a coating film, and cure the coating film;

(5) Spray the surface of the cured coating film with an alkali-alcohol solution, or soak it in an alkali-alcohol solution for a certain period of time;

(6) Rinse the surface with alkaline alcohol solution with clean water.

Further, in step (1), the molecular weight range of polyvinyl acetate used is 5000-50000g/mol.

Further, in step (1), the amount of alkali alcohol solution added is 3-35% of the polyvinyl acetate.

Further, in step (1), the alcoholysis temperature of polyvinyl acetate is 40-50°C, and the alcoholysis time is 2-4 hours.

Further, in step (4), the transparent substrate is one of polymethyl methacrylate (PMMA), polycarbonate, polyethylene terephthalate (PET) and glass.

Further, in step (4), the coating film curing condition is room temperature or heating curing.

Further, in step (5), the alkali concentration in the alkali alcohol solution sprayed or soaked is 1-10%.

Further, in step (5), the alkali in the alkali alcohol solution is sodium hydroxide.

In the present invention, polyvinyl acetate is first partially alcoholized to generate hydroxyl functional groups, which are used for cross-linking and curing of the coating film. After the cross-linked and cured coating film is post-treated with an alkali-alcohol solution, the remaining vinyl acetate groups are gradually alcoholized from the outside to the inside, forming hydroxyl groups with a certain concentration gradient distribution on the surface of the coating film, giving the coating surface good hydrophilicity. Anti-fog performance. At the same time, the unalcoholized polyvinyl acetate segment at the interface with the substrate provides good adhesion for the coating.

The ultra-low alcoholysis degree PVA anti-fog coating material of the present invention has a wide range of base materials, does not require pre-treatment of the base material, and has good anti-fog performance (after steam fumigation for 30 minutes, there is no fogging phenomenon on the surface). Excellent strength, solvent resistance (100 wipe passes with acetone) and good water resistance (no change after 24 hours of soaking).

Description of the drawings

Figure 1 shows the anti-fog performance of coating films based on ultra-low alcoholysis degree PVA resin with alcoholysis degree of 11% (left) and 17% (right) on the surface of PMMA and PET substrates.

Figure 2 shows the anti-fog performance of a coating film based on ultra-low alcoholysis PVA resin with a alcoholysis degree of 22% on the glass surface.

Detailed ways

Example 1

Add 204.2g tetrahydrofuran and 92.8g polyvinyl acetate into a 500mL four-neck flask, completely dissolve the polyvinyl acetate at 40°C, then slowly add 3.0g sodium hydroxide methanol solution (concentration: 5%), react for 2 hours and then add Adjust the pH to 6-7 with an appropriate amount of dilute hydrochloric acid to obtain polyvinyl alcohol with an alcoholysis degree of 11%.

4g of polyvinyl alcohol with an alcoholysis degree of 11% was dried and dissolved in 16g of 1,4-dioxane at 80°C, and left for 24 hours to precipitate to remove impurities and insoluble matter.

Take 10g of the upper layer solution, add 0.24g of hexamethylene diisocyanate trimer and 0.1g of dibutyltin dilaurate solution (concentration 1%, solvent 1,4-dioxane), stir and mix evenly, and then apply On PMMA and PET substrates, cure at 80°C for 2 hours.

Soak the coating film in 5% alkali-alcohol solution at room temperature for 1 hour. After taking it out, rinse it several times with deionized water and dry it at room temperature. The optical transmittance of the coating film is 91%.

The prepared coating film was tested for anti-fog, water resistance, and solvent resistance. The experiment showed that the coating film had a good anti-fog effect (see Figure 1). At the same time, it had good water resistance (no change after 24 hours of immersion). and solvent resistance (100 wipe passes with acetone).

Example 2

Add 201.1g tetrahydrofuran and 91.4g polyvinyl acetate into a 500mL four-neck flask. After completely dissolving the polyvinyl acetate at 40°C, slowly add 7.5g sodium hydroxide methanol solution. After 2 hours of reaction, add an appropriate amount of dilute hydrochloric acid to adjust the pH to 6-7 to obtain polyvinyl alcohol with an alcoholysis degree of 17%.

4g of polyvinyl alcohol with a degree of alcoholysis of 17% was dried and dissolved in 16g of 1,4-dioxane at 80°C, and left for 48 hours to precipitate to remove impurities and insoluble matter.

Take 10g of the solution, add 0.38g of isophorone diisocyanate trimer and 0.1g of dibutyltin dilaurate solution (concentration 1%, solvent 1,4-dioxane), stir and mix evenly, and then coat on PMMA On the base material and PET base material, cure at 80℃ for 2 hours.

Soak the coating film in 5% alkali-alcohol solution at room temperature for 1 hour. After taking it out, rinse it several times with deionized water and dry it at room temperature. The optical transmittance of the coating film is 91.5%.

The coating film was tested for anti-fog, water resistance, and solvent resistance. Experiments showed that the coating film had good anti-fog performance (see Figure 1). At the same time, it has good water resistance (no change after 24 hours of soaking) and solvent resistance (100 passes of acetone wipe).

Example 3

Add 195.9g tetrahydrofuran and 89.1g polyvinyl acetate into a 500mL four-neck flask, completely dissolve the polyvinyl acetate at 50°C, then slowly add 15.0g sodium hydroxide methanol solution (concentration: 5%), react for 2 hours and then add Adjust the pH to 6-7 with an appropriate amount of dilute hydrochloric acid to obtain PVA with an alcoholysis degree of 22%.

4g of PVA with an alcoholysis degree of 11% was dried and dissolved in 16g of 1,4-dioxane at 80°C, and left for 48 hours to precipitate to remove impurities and insoluble matter.

Take 10g of the upper solution, add 1.0g of permethyl etherified amino resin, 0.06g of p-toluenesulfonic acid, and 0.05g of leveling agent. Stir and mix evenly, then apply it on the glass substrate and cure at 160°C for 2 hours.

Spray a layer of 10% alkali alcohol solution on the surface of the cured coating film. After the methanol has evaporated, rinse it several times with deionized water and dry it at room temperature. The optical transmittance of the coating film is 90%.

The prepared coating film was tested for anti-fog, water resistance, and solvent resistance. The experiment showed that the coating film had a good anti-fog effect (see Figure 2), and at the same time, it had good water resistance (no change after 24 hours of immersion) and solvent resistance (100 wipe passes with acetone).

Among them, the test methods for water resistance, solvent resistance, anti-fog and transparency are as follows:

(1) Water resistance test

According to GB/T 1733-1993, soak the coating in water for 24 hours and conduct a water resistance test on the coating. Observe whether the coating has discoloration, blistering, wrinkling, shedding, etc.; if the coating does not swell, blister, wrinkle, turn white, or fall off, the water resistance is assessed as passing.

(2) Solvent resistance test

According to GB/T 23989-2009, wipe the coating surface back and forth one hundred times with absorbent cotton soaked in acetone. Observe whether the coating has wrinkles, peeling, etc.; if the coating does not swell, blister, wrinkle, turn white, or peel off, the solvent resistance is evaluated as passing.

(3) Anti-fog property

Place the coating film 5cm above water vapor at 80°C and observe the fogging on the surface of the coating film.

(4) Transparency

The transmittance at a light wavelength of 550 nm was selected to evaluate the transparency.

The above are only embodiments of the present invention, but the protection scope of the present invention is not limited thereto. For those of ordinary skill in the art, improvements can be made without departing from the creative concept of the present invention. However, These all belong to the protection scope of the present invention.

Claims (4)

1. An ultra-low alcoholysis degree polyvinyl alcohol anti-fog coating material is characterized by comprising the following components:

ultra low alcoholysis degree PVA: 15-20%;

curing agent: 1-10%;

1, 4-dioxane: 60-80%;

catalyst: 0.01-0.5%;

auxiliary agent: 0-1.0%;

the total amount satisfies 100%;

the alcoholysis degree of the PVA with the ultra-low alcoholysis degree ranges from 5% to 30%;

wherein: the curing agent is one of diisocyanate, diisocyanate oligomer and etherified amino resin;

the catalyst is one of dibutyl tin dilaurate and p-toluenesulfonic acid; the auxiliary agent is a defoaming agent and a leveling wetting agent;

the polyvinyl alcohol antifogging coating material with the ultra-low alcoholysis degree is prepared by the following steps:

(1) Preparation of polyvinyl alcohol with ultra-low alcoholysis degree

Dissolving polyvinyl acetate in tetrahydrofuran, slowly adding an alkali alcohol solution for alcoholysis, and finally adding dilute hydrochloric acid to adjust the pH to 6-7 to obtain polyvinyl alcohol with ultra-low alcoholysis degree, wherein the alcoholysis degree range is 5-30%;

(2) Drying the ultra-low alcoholysis degree polyvinyl alcohol obtained in the step (1), dissolving the polyvinyl alcohol in 1, 4-dioxane, and standing and settling the polyvinyl alcohol for more than 24 hours to remove impurities and insoluble matters;

(3) Mixing the ultra-low alcoholysis degree polyvinyl alcohol solution prepared in the step (2) with a curing agent according to a certain molar ratio, and adding a catalyst and an auxiliary agent to prepare the ultra-low alcoholysis degree polyvinyl alcohol anti-fog coating;

(4) Coating the coating prepared in the step (3) on a transparent substrate to form a coating film, and curing the coating film;

(5) Spraying an alkali alcohol solution on the surface of the coating film obtained by curing, or soaking the coating film in the alkali alcohol solution for a certain time;

(6) Washing the surface alkali alcohol solution with clear water;

the alkali alcohol solution added in the step (1) accounts for 3-35% of the amount of the polyvinyl acetate;

the alcoholysis temperature of the polyvinyl acetate in the step (1) is 40-50 ℃ and the alcoholysis time is 2-4 hours.

2. A method for preparing an anti-fog coating material of ultra-low alcoholysis polyvinyl alcohol according to claim 1, which is characterized by comprising the following specific steps:

(1) Preparation of polyvinyl alcohol with ultra-low alcoholysis degree

Dissolving polyvinyl acetate in tetrahydrofuran, slowly adding an alkali alcohol solution for alcoholysis, and finally adding dilute hydrochloric acid to adjust the pH to 6-7 to obtain polyvinyl alcohol with ultra-low alcoholysis degree, wherein the alcoholysis degree range is 5-30%;

(2) Drying the ultra-low alcoholysis degree polyvinyl alcohol obtained in the step (1), dissolving the polyvinyl alcohol in 1, 4-dioxane, and standing and settling the polyvinyl alcohol for more than 24 hours to remove impurities and insoluble matters;

(3) Mixing the ultra-low alcoholysis degree polyvinyl alcohol solution prepared in the step (2) with a curing agent according to a certain molar ratio, and adding a catalyst and an auxiliary agent to prepare the ultra-low alcoholysis degree polyvinyl alcohol anti-fog coating;

(4) Coating the coating prepared in the step (3) on a transparent substrate to form a coating film, and curing the coating film;

(5) Spraying an alkali alcohol solution on the surface of the coating film obtained by curing, or soaking the coating film in the alkali alcohol solution for a certain time;

(6) Washing the surface alkali alcohol solution with clear water;

the alkali alcohol solution added in the step (1) accounts for 3-35% of the amount of the polyvinyl acetate;

the alcoholysis temperature of the polyvinyl acetate in the step (1) is 40-50 ℃ and the alcoholysis time is 2-4 hours.

3. The method according to claim 2, wherein the coating film curing condition in step (4) is room temperature or heat curing.

4. The method according to claim 2, wherein the alkali concentration in the sprayed or immersed alkali alcohol solution in step (5) is 1 to 10%; the alkali in the alkali alcohol solution is sodium hydroxide.