Solvent-free chemical milling protective coating and application thereof

Abstract

The invention discloses a solvent-free chemical milling protective coating which is composed of a component A and a component B. The ratio of an isocyanate functional group of the component A to an amino functional group of the component B is 0.9-1.3: 1, and the component A is composed of a prepolymer containing an isocyanate-terminated functional group and a pigment filler A; and the component B consists of primary amine or secondary amine containing at least two reactive amino groups, a pigment filler B and non-reactive interface adhesion regulation resin. The non-reactive interface adhesion regulating resin and the coating formula are used for chemical milling protection of base materials such as aluminum alloy and titanium alloy, and are beneficial to reducing interfacial tension, improving wettability of the coating to the base materials during coating, releasing residual stress of a polymerization reaction, improving interface bonding strength and improving adhesive force of a coating and the base materials; and the stability of the coating in the chemical milling process is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical coating materials and applications, and particularly relates to a solvent-free chemical milling protective coating and an application thereof. Background Art

[0002] Chemical milling technology is a technique for processing the surface of a metal substrate through chemical solution corrosion. This technology uses chemical solution corrosion to precisely remove the metal substrate in predetermined areas to achieve processing purposes such as workpiece forming and weight reduction. It has the advantages of being able to be processed in batches and having no cutting stress on the formed products. Chemical milling protective coatings are used to temporarily protect parts that do not need to be removed during the chemical milling process and are a key material for controlling forming in chemical milling processing. Chemical milling protective coatings are required to have appropriate adhesion to the surface of the metal substrate and be able to adhere well from the time the coating is completed to the time the chemical milling solution is treated, playing a role in protecting the metal substrate in areas that do not need to be milled during the chemical milling process.

[0003] Traditional chemical milling protection coatings are generally single-component coatings composed of thermoplastic elastomers, functional pigments and fillers, and organic solvents. For example, CN102010643A discloses a chemical milling protection coating that can dry at room temperature and has good chemical corrosion resistance and strippability. However, solvent-based chemical milling protection coatings have environmental protection issues. To solve this problem, a solvent-free chemical milling protection coating that forms a film through a two-component reaction has been developed. Through two-component cross-linking and curing, it has good chemical resistance and physical and mechanical properties, making it suitable for chemical milling protection. At the same time, due to its solvent-free formula design, it solves the problem of large volatile organic compound emissions of traditional chemical milling protection coatings. For example, CN114149737A discloses a coating for chemical milling protection, which is composed of a diisocyanate component A and a specific modified silicone polymer, polyether polyol, and chain extender component B. It has the characteristics of good flexibility, excellent corrosion resistance, easy stripping, no solvent volatilization, and green environmental protection. US20180187046A1 discloses a chemical-resistant strippable coating, which comprises an A component consisting of polyether, aromatic diamine, silicone elastomer particles, and polyurea, and a B component consisting of a diisocyanate containing an urethane structure and diphenylmethane diisocyanate (MDI), and can be used for chemical milling protection.

[0004] Traditional one-component solvent-based chemical milling protection coatings release large amounts of solvent during application, posing significant risks to the environment and personnel, and are therefore unfavorable to the environment. Current two-component solvent-free chemical milling protection coatings, however, suffer from high viscosity, leading to insufficient substrate wetting, uneven interfacial adhesion, and difficulty releasing residual stress during reaction. Furthermore, they are prone to localized loss of adhesion during the chemical milling process, resulting in uneven milling edges and excessive erosion, impacting molding accuracy. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a solvent-free chemical milling protective coating having uniform and good adhesion to the substrate, resistance to chemical milling solutions, and excellent mechanical properties.

[0006] A solvent-free chemical milling protective coating is composed of component A and component B, wherein the ratio of isocyanate functional groups in component A to amino functional groups in component B is 0.9 to 1.3:1, and component A is composed of the following components by weight percentage:

[0007] 40% to 100% of prepolymer containing terminal isocyanate functional groups;

[0008] Pigment and filler A 0%~60%

[0009] The B component is composed of the following components by weight percentage:

[0010] 30% to 85% of a primary or secondary amine containing at least two reactive amino groups;

[0011] Pigment and filler B 10% to 65%;

[0012] Non-reactive interface adhesion regulating resin 0.5% to 12%

[0013] Furthermore, the non-reactive interface adhesion regulating resin has a hydroxyl content of less than 0.15% and an acid value of less than 5 mgKOH / g, and is prepared by reacting a hydroxyl polyester having a molecular weight of 300 to 3500 and a hydroxyl value of 40 mgKOH / g to 120 mgKOH / g with a monoisocyanate to completely block the hydroxyl group, wherein the monoisocyanate contains at least one of a halogen, a nitro or an acryloxy substituent.

[0014] Furthermore, the ratio of the isocyanate group of the monoisocyanate to the hydroxyl group of the hydroxy polyester is 1.1 to 1.0:1.

[0015] Furthermore, the monoisocyanate is one or more of p-chlorophenyl isocyanate, 4-(p-chlorophenoxy)-phenyl isocyanate, 3,4-dichlorophenyl isocyanate, 3,5-dichlorophenyl isocyanate, p-bromophenyl isocyanate, p-nitrophenyl isocyanate, methacryloyloxyethyl isocyanate, acryloyloxyethyl isocyanate,

[0016] Furthermore, the hydroxy polyester is a hydroxyl-containing polymer obtained by polymerization of an excess of diol and one of lactone, dibasic acid or dibasic acid derivative.

[0017] Furthermore, the prepolymer containing terminal isocyanate functional groups has an isocyanate group content of 2.0% to 9.5%, and is prepared by reacting excess polyisocyanate with one or more of polyols or polyamines.

[0018] Furthermore, the polyol is one or more polyether diols or polyether triols with a number average molecular weight of 400 to 3000, and the polyisocyanate is one or more pure MDI, MDI-50 or MDI prepolymers.

[0019] Furthermore, the primary or secondary amine containing at least two reactive amino groups is one or more of diethyltoluenediamine, dimethylthiotoluenediamine, 4,4'-bis-sec-butylaminodiphenylmethane, 1,4-bis-sec-butylaminobenzene, and polyaspartic acid ester.

[0020] Furthermore, the pigment filler A is one or more of titanium dioxide, chrome green, carbon black, fumed silica, and talc, and the pigment filler B is one or more of titanium dioxide, chrome green, carbon black, fumed silica, and talc.

[0021] The solvent-free chemical milling protection coating can be used for chemical milling protection of substrates such as aluminum alloys and titanium alloys.

[0022] Beneficial effects

[0023] The present invention reduces interfacial tension, improves the wettability of the coating to the substrate during coating, releases residual stress from the polymerization reaction, increases interfacial bonding strength, improves adhesion between the coating and the substrate, and ensures the stability of the coating during chemical milling. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] Example 1:

[0026] Component A1 includes 95g of a prepolymer containing terminal isocyanate functional groups and having an isocyanate content of 6.5% and 5g of talc, wherein the prepolymer containing terminal isocyanate functional groups and having an isocyanate content of 6.5% is prepared by reacting excess MDI and a polyether diol having a number average molecular weight of 1000;

[0027] Component B1 includes 39.07g of polyaspartic acid ester NH-1420, 2g of fumed silica, 8g of chrome green, 20g of titanium dioxide, 20.93g of talc and 10g of a non-reactive interface adhesion regulating resin with a hydroxyl content of 0.14% and an acid value of 4.6mgKOH / g. The non-reactive interface adhesion regulating resin is prepared by reacting a hydroxyl-containing polyester with a molecular weight of 2200 and a hydroxyl value of 51mgKOH / g with methacryloyloxyethyl isocyanate, wherein the ratio of the isocyanate group of the methacryloyloxyethyl isocyanate to the hydroxyl group of the hydroxyl polyester is 1.05:1, and the hydroxyl polyester is prepared by a polymerization reaction of an excess diol and succinic acid.

[0028] During coating, the ratio of the isocyanate functional groups of component A1 to the amino functional groups of component B1 is 1.05:1.

[0029] Example 2:

[0030] The A2 component includes 90g of a prepolymer containing terminal isocyanate functional groups with an isocyanate content of 9.0% and 10g of talc. The prepolymer containing terminal isocyanate functional groups with an isocyanate content of 9.0% is prepared by reacting excess MDI-50 with a polyether triol with a number average molecular weight of 2000.

[0031] Component B2 includes 8.17g of diethyltoluenediamine, 26.63g of polyaspartic acid ester NH-1520, 3g of fumed silica, 2g of carbon black, 20g of titanium dioxide, 32.2g of talc, and 8g of a non-reactive interface adhesion regulating resin with a hydroxyl content of 0.15% and an acid value of 4.7mgKOH / g. The non-reactive interface adhesion regulating resin is prepared by reacting a hydroxyl-containing polyester with a molecular weight of 1500 and a hydroxyl value of 75mgKOH / g with p-chlorophenyl isocyanate. The ratio of isocyanate groups in the p-chlorophenyl isocyanate to hydroxyl groups in the hydroxyl polyester is 1:1. The hydroxyl polyester is prepared by polymerization of an excess of a diol with adipic acid.

[0032] During coating, the ratio of the isocyanate functional groups of component A2 to the amino functional groups of component B2 is 1.05:1.

[0033] Example 3:

[0034] Component A3 includes 100 g of a terminal isocyanate functional prepolymer with an isocyanate content of 8.4%. The terminal isocyanate functional prepolymer with an isocyanate content of 8.4% isocyanate is prepared by reacting excess MDI with a polyether diol with a number average molecular weight of 1000 and a polyether triol with a number average molecular weight of 3000.

[0035] Component B3 includes 29.52g of 4,4'-bis-sec-butylaminodiphenylmethane, 25g of titanium dioxide, 33.48g of talc and 12g of a non-reactive interface adhesion regulating resin with a hydroxyl content of 0.12% and an acid value of 4.5mgKOH / g; the non-reactive interface adhesion regulating resin is prepared by reacting a hydroxyl-containing polyester with a molecular weight of 3000 and a hydroxyl value of 37mgKOH / g with p-bromophenyl isocyanate, wherein the ratio of the isocyanate group of p-bromophenyl isocyanate to the hydroxyl group of the hydroxyl-containing polyester is 1.05:1, and the hydroxyl polyester is prepared by a polymerization reaction of an excess diol and γ-butyrolactone.

[0036] During coating, the ratio of the isocyanate functional groups of component A3 to the amino functional groups of component B3 is 1.05:1.

[0037] Comparative Example:

[0038] A solvent-free chemical milling protection coating consists of component A and component B. Component A includes 90g of a prepolymer containing terminal isocyanate functional groups with an isocyanate content of 9.0% and 10g of talc. Component B includes 8.17g of diethyltoluenediamine, 26.63g of polyaspartic acid ester NH-1520, 3g of fumed silica, 2g of carbon black, 20g of titanium dioxide, and 40.2g of talc. During application, the ratio of isocyanate groups to amino groups in the two components is 1.05:1.

[0039] The coatings of the above examples and comparative examples were applied to aluminum alloy substrates respectively, and after drying, the performance was tested and shown in the following table.

[0040]

[0041]

[0042] From the performance test results, it can be seen that the comparative example without the non-reactive interface adhesion regulating resin has problems such as a large etching ratio and an uneven milling line, while the present invention solves this problem. In addition, the present invention meets the requirements of the chemical milling process specifications and has good strippability after the chemical milling process is completed.

[0043] The present disclosure has been described using the aforementioned embodiments. However, the aforementioned embodiments are merely exemplary embodiments of the present disclosure. It should be noted that the disclosed embodiments do not limit the scope of the present disclosure. On the contrary, modifications and alterations made without departing from the spirit and scope of the present disclosure are within the scope of patent protection of the present disclosure.

Claims

1. A solvent-free chemical milling protective coating, characterized by: The invention is composed of component A and component B, wherein the ratio of the isocyanate functional group of component A to the amino functional group of component B is 0.9 to 1.3:1, and the component A is composed of the following components by weight percentage: 40% to 100% of prepolymer containing terminal isocyanate functional groups; Pigment and filler A0%~60% The B component is composed of the following components by weight percentage: 30% to 85% of a primary or secondary amine containing at least two reactive amino groups; Pigment and filler B 10% to 65%; The non-reactive interface adhesion regulating resin is 0.5% to 12%.

2. The solvent-free chemical milling protective coating according to claim 1, characterized in that: The non-reactive interface adhesion regulating resin has a hydroxyl content of less than 0.15% and an acid value of less than 5 mgKOH / g. It is prepared by reacting a hydroxyl polyester having a molecular weight of 300 to 3500 and a hydroxyl value of 40 mgKOH / g to 120 mgKOH / g with a monoisocyanate to completely block the hydroxyl group. The monoisocyanate contains at least one of a halogen, a nitro or an acryloxy substituent.

3. The solvent-free chemical milling protective coating according to claim 2, characterized in that: The ratio of the isocyanate group of the monoisocyanate to the hydroxyl group of the hydroxy polyester is 1.1 to 1.0:

1.

4. The solvent-free chemical milling protective coating according to claim 2, characterized in that: The monoisocyanate is one or more of p-chlorophenyl isocyanate, 4-(p-chlorophenoxy)-phenyl isocyanate, 3,4-dichlorophenyl isocyanate, 3,5-dichlorophenyl isocyanate, p-bromophenyl isocyanate, p-nitrophenyl isocyanate, methacryloyloxyethyl isocyanate, and acryloyloxyethyl isocyanate.

5. The solvent-free chemical milling protective coating according to claim 2, characterized in that: The hydroxy polyester is prepared by polymerization reaction of excess diol with one of lactone, dibasic acid or dibasic acid derivatives, wherein the dibasic acid is one or more of succinic acid, adipic acid and sebacic acid.

6. The solvent-free chemical milling protective coating according to claim 1, characterized in that: The isocyanate content of the prepolymer containing terminal isocyanate functional groups is 2.0% to 9.5%, and the prepolymer is prepared by reacting excess polyisocyanate with one or more of polyols or polyamines.

7. The solvent-free chemical milling protective coating according to claim 6, characterized in that: The polyol is one or more polyether diols or polyether triols with a number average molecular weight of 400 to 3000, and the polyisocyanate is one or more pure MDI, MDI-50 or MDI prepolymers.

8. The solvent-free chemical milling protective coating according to claim 1, characterized in that: The primary or secondary amine containing at least two reactive amino groups is one or more of diethyltoluenediamine, dimethylthiotoluenediamine, 4,4'-bis-sec-butylaminodiphenylmethane, 1,4-bis-sec-butylaminobenzene, and polyaspartic acid ester.

9. The solvent-free chemical milling protective coating according to claim 1, characterized in that: The pigment filler A is one or more of titanium dioxide, chrome green, carbon black, fumed silica, and talc powder; the pigment filler B is one or more of titanium dioxide, chrome green, carbon black, fumed silica, and talc powder.

10. An application of the solvent-free chemical milling protective coating according to claims 1-9, characterized in that: The coating can be used for chemical milling protection of substrates such as aluminum alloys and titanium alloys.

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