High-chemical-resistance protective coating varnish as well as preparation method and application thereof

Abstract

The invention relates to protective coating varnish with high chemical resistance as well as a preparation method and application thereof. The varnish comprises the following components: hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion, water, a wetting agent, a pH regulator, a flatting agent and a hydrophilic organic solvent, the method comprises the following steps: mixing water, a wetting agent, a flatting agent and a hydrophilic organic solvent to obtain a solution; adding a pH regulator into the solution, mixing, and regulating the pH of the solution; and adding the hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion into the solution, and mixing to obtain the protective coating varnish with high chemical resistance. Compared with the prior art, the chemical resistance is good.

Description

Technical Field

[0001] The invention belongs to the technical field of varnishes and relates to a protective coating varnish with high chemical resistance and a preparation method and application thereof. Background Art

[0002] Car interiors are mostly used outdoors, where the interior environment is relatively harsh, such as continuous high temperature, high humidity, and light. In addition, car interiors may be damaged by human factors during use, such as friction of fabrics, corrosion from detergents, and corrosion from cosmetics and sunscreens. Therefore, car OEMs will formulate relevant testing standards for car interiors, and auto parts suppliers must pass the OEM's testing standards before they can be used in the car.

[0003] In the existing automotive interior film, the parts substrate, adhesive layer, decorative layer and protective layer constitute the automotive interior surface. The protective layer is the outermost layer of the automotive interior, and its function is to protect the parts from aging in harsh environments and damage caused by human parts. Most of the existing domestic protective layer technologies use polymethyl methacrylate (PMMA) finished films or UV curing resins as the protective layer for automotive interior parts.

[0004] The existing automotive interior parts protective layer technology has the following disadvantages:

[0005] (1) The PMMA film protective layer has poor resistance to chemicals and sunscreen;

[0006] (2) The protective layer of PMMA film is not resistant to friction;

[0007] (3) The protective layer of PMMA film is brittle and is easy to break when coated and printed using a printing machine, increasing the defective rate;

[0008] (4) Most UV curing resins are solvent-based coatings, which have high volatile organic compounds (VOCs) and are not environmentally friendly.

[0009] Patent CN108192481A discloses a water-based polyurethane matte topcoat for motorcycle interior and exterior decoration and its preparation method. The coating consists of topcoat and curing agent. The topcoat includes water-based acrylic resin, pigment paste, filler, cosolvent, additive, deionized water; the curing agent includes water-based HDI isocyanate and a small amount of organic solvent; wet-on-wet two-layer spraying is used for construction, and the film is formed by baking and curing. However, the water-based acrylic resin in this patent includes a large category, and acrylic resins with different molecular weights, hydroxyl content, molecular structures, functionalities, etc. have different properties. This patent is not suitable for automotive interior protective layers that require high chemical resistance.

[0010] Patent CN110527430A discloses a modified polyvinylidene fluoride fluorocarbon coating and a preparation method thereof, including a modified polyvinylidene fluoride resin dispersion, which includes 30-45 parts of polyvinylidene fluoride resin, 5-15 parts of modifier, 0.5-1.5 parts of initiator, and 35-60 parts of solvent by weight of raw materials, and the modifier is composed of polyethylene glycol monomaleate and polyethylene glycol methacrylate in a weight ratio of 1: (0.5-1.5). However, the focus of the patent is how to make the polyvinylidene fluoride resin hydrophilic through an intermediate medium, and does not mention a mixed dispersion of multiple polymers. Moreover, the patent also cannot improve the performance of the automotive interior protective layer. Summary of the invention

[0011] The purpose of the present invention is to overcome at least one defect of the above-mentioned prior art and provide a protective coating varnish with high chemical resistance and a preparation method and application thereof. The present invention has good chemical resistance.

[0012] The purpose of the present invention can be achieved by the following technical solutions:

[0013] One of the technical solutions of the present invention is to provide a protective coating varnish with high chemical resistance, the varnish comprising the following components in parts by weight:

[0014] 8-15 parts of hydroxyl-containing polyvinylidene fluoride resin (PVDF)-polymethyl methacrylate (PMMA) aqueous polymer mixed dispersion (interpenetrating polymer network (IPN) structure, which refers to two or more polymer molecular chains cross-linked by chemical bonds to form a complex network structure), 1-3 parts of water, 0.02-0.1 parts of wetting agent, 0.01-0.1 parts of pH adjuster, 0.02-0.1 parts of leveling agent and 0.5-2 parts of hydrophilic organic solvent.

[0015] Furthermore, in the hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion, the mass ratio of the acrylic acid content of polyvinylidene fluoride resin to polymethyl methacrylate (PVDF:AA) is (5-9):(1-5), and the solid hydroxyl ratio is 0.2-1%.

[0016] Furthermore, the wetting agent is selected from Evonik R420, Digo 3455, Digo 3400, the pH regulator is selected from one or more of ammonia water, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and the leveling agent is selected from Digo 346. Digo 3499, Digo One or more of 333.

[0017] As a preferred technical solution, the concentration of the pH regulator is 20-30%.

[0018] Furthermore, the hydrophilic organic solvent is selected from one or more of dipropylene glycol methyl ether acetate, ethanol, and isopropanol.

[0019] One of the technical solutions of the present invention is to provide a method for preparing the protective coating varnish with high chemical resistance, the method comprising the following steps:

[0020] S1, mixing water, a wetting agent, a leveling agent and a hydrophilic organic solvent to obtain a solution;

[0021] S2, adding a pH adjuster to the solution and mixing to adjust the pH of the solution;

[0022] S3. Add a hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion into the solution and mix to obtain a protective coating varnish with high chemical resistance.

[0023] Furthermore, in steps S1 to S3, the mixing temperature is 10-40° C., the stirring speed is 100-500 r / min, and the time is 10-30 min.

[0024] Furthermore, in step S2, the pH of the solution is adjusted to 8-9.

[0025] One of the technical solutions of the present invention is to provide an application of the highly chemical-resistant protective coating varnish, wherein the varnish is applied to the protective coating, a curing agent is added to the varnish and mixed, and the varnish is baked and cross-linked after coating to obtain a protective coating.

[0026] Furthermore, the curing agent is selected from one or more blocked isocyanates selected from blocked hexamethylene diisocyanate (blocked HDI), blocked isophorone diisocyanate (blocked IPDI), and blocked dicyclohexylmethane diisocyanate (blocked HMDI), and the mass ratio of the hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion to the curing agent is (8-15):(1.5-2).

[0027] Furthermore, the mixing temperature is 10-40°C, the stirring speed is 100-500r / min, and the time is 5-10min.

[0028] The curing temperature is 60-100° C. and the curing time is 2-10 minutes.

[0029] As a preferred technical solution, the total solid content of the curing agent and the varnish after mixing is 20-50%.

[0030] As a preferred technical solution, the coating process adopts micro-concave coating.

[0031] As a preferred technical solution, the mesh number of the coated micro-concave roller is 60-100 meshes, the drying tunnel length is 10-20m, the coating speed is 5-10m / min, and the coating thickness is 7-15μm.

[0032] As a preferred technical solution, after the protective coating is coated and cured on the release film, a decorative ink layer and a transfer adhesive layer are printed in sequence, and after ripening, they are transferred to the substrate to obtain an insert injection molding (INS) film with a protective coating on the surface.

[0033] As a preferred technical solution, the material of the release film is selected from one or more of polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP); the material of the decorative ink layer is acrylic ink; the material of the transfer adhesive layer is selected from one or more of polyester polyurethane and polyurethane acrylate; and the material of the substrate is selected from one or more of acrylonitrile-butadiene-styrene copolymer (ABS) and polycarbonate (PC).

[0034] As a preferred technical solution, the thickness of the release film is 25-75 μm, the thickness of the decorative ink layer is 2-5 μm, the thickness of the transfer adhesive layer is 2-5 μm, and the thickness of the substrate is 200-600 μm.

[0035] As a preferred technical solution, the aging temperature is 40-60°C and the time is 24-72h.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) After the film is formed, the film material itself is mostly polyvinylidene fluoride. Due to the particularity of the fluorocarbon material itself, it has excellent chemical resistance and sunscreen resistance, such as alcohol resistance and public test standard sunscreen resistance, and its wear resistance is better than that of polymethyl methacrylate material;

[0038] (2) The present invention contains a large amount of polyvinylidene fluoride, which contains a large amount of fluorine atoms. Fluorine atoms have extremely strong electronegativity and can form stable covalent bonds, thereby enhancing the stability and chemical inertness of polyvinylidene fluoride molecules. If hydroxyl groups are introduced into the molecular chain of the polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion and react with isocyanate to form urethane bonds, there will no longer be only intermolecular forces between polymer molecules, and a more dense and stable network structure will be formed between polymer molecules, which will further enhance its chemical resistance;

[0039] (3) Since the present invention contains a large amount of polyvinylidene fluoride, which is a semi-crystalline polymer, during the thermal stretching process, both the crystalline region and the amorphous region will be deformed, the amorphous region will undergo plastic deformation, the crystalline region may undergo crystal sliding and movement, and even α→β crystal transformation will occur. These are all conducive to polyvinylidene fluoride absorbing more energy during the thermal stretching process, so that the present invention exhibits greater thermal extensibility;

[0040] (4) The formula of the present invention belongs to a water-based system, has low volatile organic matter, is more environmentally friendly, requires a low curing temperature, and is more energy-efficient and efficient. Secondly, since the present invention contains a certain proportion of polymethyl methacrylate polymer after film formation, compared with pure polyvinylidene fluoride polymer that produces fog and has adhesion problems due to low surface tension, the present invention has higher transparency and better interlayer adhesion with ink. DETAILED DESCRIPTION

[0041] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0042] Unless otherwise specified, the equipment used in the following examples are all conventional equipment in the art; the reagents used are all commercially available products or prepared by conventional methods in the art unless otherwise specified. Anything not described in detail in the following examples can be achieved by conventional experimental means in the art.

[0043] Example:

[0044] A highly chemical-resistant protective coating varnish comprising the following components in parts by weight:

[0045] 10 parts of hydroxyl-containing polyvinylidene fluoride resin (PVDF)-polymethyl methacrylate (PMMA) aqueous polymer mixed dispersion (interpenetrating polymer network (IPN) structure, which refers to two or more polymer molecular chains cross-linked by chemical bonds to form a complex network structure) provided by Arkema, France, 2 parts of water, and Digo 3455 as a wetting agent 0.02 parts, 25% ammonia water as a pH adjuster 0.01 parts, Digo 346 as a leveling agent 0.02 parts and dipropylene glycol methyl ether acetate as a hydrophilic organic solvent 1 part;

[0046] In the hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion, the mass ratio of the acrylic acid content of the polyvinylidene fluoride resin to the acrylic acid content of the polymethyl methacrylate (PVDF:AA) is 7:3, and the solid hydroxyl ratio is 0.53%.

[0047] The preparation method of the above-mentioned highly chemical-resistant protective coating varnish comprises the following specific steps:

[0048] S1.1, by weight, 2 parts water, Digo 3455 0.02 copies, Digo 0.02 parts of 346 and 1 part of dipropylene glycol methyl ether acetate were added into a container, and stirred evenly at room temperature and 200 r / min for 10 min to obtain a solution;

[0049] S1.2, add 0.01 parts of 25% ammonia water to the solution by weight, adjust the pH of the solution to 8.5, and stir evenly at room temperature and 200 r / min for 10 minutes;

[0050] S1.3. Add 10 parts by weight of a hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion into the solution, and stir evenly at room temperature and 200 r / min for 15 minutes to obtain a protective coating varnish with high chemical resistance.

[0051] The application of the above highly chemical resistant protective coating varnish is applied to an insert injection molded (INS) film having a protective coating on the surface used as a decorative part, and the specific steps are as follows:

[0052] S2.1, by weight, Ultra305 water-based blocked hexamethylene diisocyanate (blocked HDI) was added as a curing agent in 1.5 parts to the varnish, and stirred evenly at room temperature and 200 r / min for 5 minutes. The total solid content after mixing was 30%;

[0053] S2.2, using a micro-concave coating process to coat on a polyethylene terephthalate (PET) release film with a thickness of 75 μm, using a 60-mesh micro-concave roller, a drying tunnel length of 20 m, a drying tunnel temperature of 80°C, and a coating speed of 10 m / min, and baking and cross-linking and curing on the release film for 2 minutes to obtain a protective coating with a thickness of 12 μm;

[0054] S2.3, printing a 4 μm thick one-component polyester modified acrylic ink decorative ink layer and a 2 μm thick polyurethane acrylate transfer adhesive layer on the surface of the protective coating in sequence, aging at 40° C. for 48 h, and then transferring the layers to a 400 μm thick acrylonitrile-butadiene-styrene copolymer (ABS) substrate to obtain an embedded injection molded film with a protective coating on the surface;

[0055] S2.4. The embedded injection-molded film with a protective coating on the surface is subjected to molding, punching and injection molding processes to obtain decorative parts that can be equipped with automobile door panels and instrument panels.

[0056] Comparative Example 1:

[0057] A protective coating varnish and a preparation method and application thereof are basically the same as the embodiment, except that the hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion is replaced by a hydroxyl-free polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion.

[0058] Comparative Example 2:

[0059] A protective coating varnish and a preparation method and application thereof are basically the same as Comparative Example 1, except that the mass ratio of polyvinylidene fluoride resin to polymethyl methacrylate in the hydroxyl-free polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion is replaced from 7:3 to 3:7.

[0060] The decorative parts made of the above-mentioned inlay injection molded film with a protective coating on the surface were subjected to the Volkswagen TL226 automobile interior parts standard test, and the test results are shown in Table 1.

[0061] Table 1 Standard test performance of automobile interior decoration of the embodiments and comparative examples

[0062]

[0063] As shown in Table 1, the experimental results of the embodiment and comparative example 1 show that the hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion forms a denser network structure after reacting with the curing agent, so that in the decorative parts made of the insert injection molded film with a protective coating on the surface of the embodiment, although the thermal elongation is reduced due to the formation of a denser network between polymer molecules after the reaction of the hydroxyl group and the isocyanate, it still meets the test standard requirements, and the sunscreen corrosion resistance is significantly increased, jumping from an unqualified state to a qualified state;

[0064] The experimental results of Comparative Example 2 show that when the polyvinylidene fluoride resin component is reduced, the sunscreen corrosion resistance of the decorative parts made of the insert injection molded film with a protective coating on the surface is significantly reduced. Due to the characteristics of the fluorocarbon material itself, the chemical resistance of the polyvinylidene fluoride resin is better than that of polymethyl methacrylate. In the polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion of Comparative Example 2, the mass ratio of the acrylic acid content of the polyvinylidene fluoride resin to that of the polymethyl methacrylate is 3 / 7. The excessive proportion of polymethyl methacrylate affects the overall chemical resistance.

[0065] The experimental results of the embodiments and comparative examples show that after adding the polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion, the high and low temperature cycle, xenon lamp aging and friction resistance of the decorative parts made of the embedded injection molded film with a protective coating on the surface can meet the test standard requirements.

[0066] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A highly chemical-resistant protective coating varnish, characterized in that: The varnish comprises the following components in parts by weight: 8-15 parts of hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion, 1-3 parts of water, 0.02-0.1 parts of wetting agent, 0.01-0.1 parts of pH regulator, 0.02-0.1 parts of leveling agent and 0.5-2 parts of hydrophilic organic solvent.

2. A highly chemical-resistant protective coating varnish according to claim 1, characterized in that: In the hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion, the mass ratio of the acrylic acid content of the polyvinylidene fluoride resin to that of the polymethyl methacrylate is (5-9):(1-5), and the solid hydroxyl ratio is 0.2-1%.

3. A protective coating varnish with high chemical resistance according to claim 1, characterized in that: The wetting agent is selected from Evonik R420, Digo 3455, Digo 3400, the pH regulator is selected from one or more of ammonia water, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and the leveling agent is selected from Digo 346. Digo 3499, Digo One or more of 333.

4. A protective coating varnish with high chemical resistance according to claim 1, characterized in that: The hydrophilic organic solvent is selected from one or more of dipropylene glycol methyl ether acetate, ethanol, and isopropanol.

5. A method for preparing a protective coating varnish with high chemical resistance as claimed in any one of claims 1 to 4, characterized in that: The method comprises the following steps: S1, mixing water, a wetting agent, a leveling agent and a hydrophilic organic solvent to obtain a solution; S2, adding a pH adjuster to the solution and mixing to adjust the pH of the solution; S3. Add a hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion into the solution and mix to obtain a protective coating varnish with high chemical resistance.

6. The method for preparing a protective coating varnish with high chemical resistance according to claim 5, characterized in that: The mixing temperature in steps S1 to S3 is 10-40° C., the stirring speed is 100-500 r / min, and the time is 10-30 min.

7. The method for preparing a protective coating varnish with high chemical resistance according to claim 5, characterized in that: In step S2, the pH of the solution is adjusted to 8-9.

8. Use of a highly chemical-resistant protective coating varnish according to any one of claims 1 to 4, characterized in that: The varnish is applied to the protective coating, a curing agent is added to the varnish and mixed, and after coating, the varnish is baked for cross-linking and curing to obtain the protective coating.

9. The use of a protective coating varnish with high chemical resistance according to claim 8, characterized in that: The curing agent is selected from one or more blocked isocyanates selected from blocked hexamethylene diisocyanate, blocked isophorone diisocyanate, and blocked dicyclohexylmethane diisocyanate, and the mass ratio of the hydroxyl-containing polyvinylidene fluoride resin-polymethyl methacrylate aqueous polymer mixed dispersion to the curing agent is (8-15):(1.5-2).

10. The use of a protective coating varnish with high chemical resistance according to claim 8, characterized in that: The mixing temperature is 10-40°C, the stirring speed is 100-500r / min, and the time is 5-10min. The curing temperature is 60-100° C. and the curing time is 2-10 minutes.

Images