A WATER-BASED COATING COMPOSITION

Abstract

The present invention relates to a water-based coating composition, the preparation and use of the composition, a two-component coating system comprising the composition and use thereof, and an article obtained by coating with the composition or the two-component coating system. The water-based coating composition comprises a water-based UV resin; a silane-treated nanosized silicon oxide compound; and a photoinitiator; wherein per kilogram of the solid constituent of the water-based UV resin contains not less than 3 mol of ethylenically unsaturated groups, and wherein the weight ratio of the solid constituent of the nanosized silicon oxide compound to the solid constituent of the water-based UV resin is 11:20 to 73:100. The coating layer formed by the water-based coating composition of the present invention has high hardness and good adhesion, and is particularly suitable for electronic, electrical and communication equipment in the 5G field.

Claims

1. A water-based coating composition, comprising: at least a water-based UV resin; at least a silane-treated nanosized silicon oxide compound; and at least a photoinitiator; wherein per kilogram of the solid constituent of the water-based UV resin contains not less than 3 mol of ethylenically unsaturated groups, and wherein the weight ratio of the solid constituent of the nanosized silicon oxide compound to the solid constituent of the water-based UV resin is 11:20 to 73:100.

2. The water-based coating composition according to claim 1, wherein per kilogram of the solid constituent of the water-based UV resin contains not less than 3.5 mol, most preferably not less than 4 mol of ethylenically unsaturated groups.

3. The water-based coating composition according to claim 1 or 2, wherein the water-based UV resin is an aqueous UV polyurethane-acrylate dispersion.

4. The water-based coating composition according to any one of claims 1 to 3, wherein the amount of the water-based UV resin is 45% to 50% by weight, relative to the total weight of the water-based coating composition.

5. The water-based coating composition according to any one of claims 1 to 4, wherein the weight ratio of the solid constituent of the nanosized silicon oxide compound to the solid constituent of the water-based UV resin is 3:5 to 17:25.

6. The water-based coating composition according to any one of claims 1 to 5, wherein the particle size of the nanosized silicon oxide compound is 8 nm to 18 nm.

7. The water-based coating composition according to any one of claims 1 to 6, wherein the nanosized silicon oxide compound is neutral or alkaline.

8. The water-based coating composition according to any one of claims 1 to 7, wherein the amount of the photoinitiator is 0.5% to 5.0% by weight, relative to the total weight of the water-based coating composition.

9. The water-based coating composition according to any one of claims 1 to 8, wherein the water-based coating composition further comprises one or more of the following: silane coupling agents, additional aqueous polymer dispersions or emulsions, reactive diluents and additives.

10. The water-based coating composition according to claim 9, wherein the amount of the additional aqueous polymer dispersion or emulsion is not more than 50% by weight, relative to the total weight of the water-based coating composition.

11. A method for manufacturing an article, including the steps of applying the water-based coating composition according to any one of claims 1 to 10 to a substrate surface, drying and curing.

12. A two-component coating system comprising component A and component B, wherein the component A is the water-based coating composition according to any one of claims 1 to 10, and the component B is a crosslinking agent.

13. The two-component coating system according to claim 12, wherein the crosslinking agent is one or more of the following: isocyanate group-containing compounds and carbodiimides.

14. Use of the water-based coating composition according to any one of claims 1 to 10 or the two-component coating system according to claim 12 or 13 for manufacturing articles.

15. An article comprising a substrate and a coating layer formed by applying the water-based coating composition according to any one of claims 1 to 10 to the substrate or comprising a substrate and a coating layer formed by applying the two-component coating system according to claim 12 or 13 to the substrate.

16. The article according to claim 15, wherein the substrate is a PC/PMMA composite board.

17. The article according to claim 15 or 16, wherein the article is a housing for 5G products, especially a front cover or a back cover for 5G products.

Description

EXAMPLES

[0106] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs. When the definition of terms in this specification contradicts the meaning commonly understood by those skilled in the art to which the present invention belongs, the definition described herein shall apply.

[0107] Unless otherwise stated, all numerical values used in the specification and claims to express the amounts of components, reaction conditions, etc. are understood to be modified by the term “about”. Therefore, unless indicated to the contrary, the numerical parameters set forth herein are approximate values that can be varied according to the required performance that needs to be obtained.

[0108] As used herein, “and/or” refers to one or all of the mentioned elements.

[0109] As used herein, “comprising” and “including” cover the case where there are only the mentioned elements and where there are other unmentioned elements besides the mentioned elements.

[0110] All percentages in the present invention are weight percentages, unless otherwise stated.

[0111] The analytical measurements of the present invention are all carried out at 23° C., unless otherwise stated.

[0112] Unless otherwise stated, the use of “a”, “an”, “an” and “the” in this specification is intended to include “at least one” or “one or more”. For example, “a component” refers to one or more components, so more than one component may be considered and may be employed or used in the implementation of the described embodiments.

[0113] The solid constituent of the dispersions was measured according to DIN-EN ISO 3251 using the HS153 moisture analyzer from Mettler Toledo. 1 gram of samples was weighed for the test.

[0114] Particle size test: The particle size of the dispersions was measured at 23° C. using laser spectroscopy after dilution with deionized water (measured using Zatasizer Nano ZS 3600 laser particle size analyzer from Malvern Instruments).

[0115] The pH value was measured at 23° C. using PB-10 pH meter from Sartorius, Germany.

[0116] Raw Materials and Reagents

[0117] Bayhydrol UV 2689/2: water-based UV resin, content of solid constituent: 41.4%, pH: 7.0 to 8.5, mole number of ethylenically unsaturated groups in per kilogram of the solid constituent of the water-based UV resin: 4 mol to 8 mol, available from Covestro Polymers (China) Co., Ltd.

[0118] Bayhydrol UV 2282: water-based UV resin, content of solid constituent: 39.6%, pH: 7.0 to 8.5, mole number of ethylenically unsaturated groups in per kilogram of the solid constituent of the water-based UV resin: less than 3 mol, available from Covestro Polymers (China) Co., Ltd.

[0119] Bayhydrol UH XP 2648: water-based UV resin, content of solid constituent: 35.6%, pH: 8.0, no ethylenically unsaturated groups, available from Covestro Polymers (China) Co., Ltd.

[0120] Dispercoll S 3030/1: aqueous dispersion of nano-silica treated with silane on the surface, content of solid constituent: 30.9%, pH: 10.5, particle size: 8 nm to 9 nm, available from Covestro Polymers (China) Co., Ltd.

[0121] Dispercoll S 2020: aqueous dispersion of nano-silica without treatment on the surface, content of solid constituent: 20.3%, pH: 3, particle size: 15 nm, available from Covestro Polymers (China) Co., Ltd.

[0122] SNOWTEX-40: aqueous dispersion of nano-silica without treatment on the surface, content of solid constituent: 40.2%, pH: 9 to 10.5, particle size: 20 nm to 25 nm, available from Nissan Chemical Industries, Ltd.

[0123] Omnirad 500: α-hydroxy ketone, surface photocuring initiator, purchased from IGM.

[0124] BYK 093: defoamer, purchased from BYK Chemical.

[0125] BYK 333: polyether modified silicone, wetting agent, purchased from BYK Chemical.

[0126] BYK 346: solution of polyether-modified siloxane, wetting agent, purchased from BYK Chemical TEGO Twin 4100: wetting agent, purchased from Evonik Industries AG.

[0127] TEGO Glide 410: wetting agent, anti-blocking agent, purchased from Evonik Industries AG.

[0128] Borchi Gel 0621: thickening agent, purchased from OMG Borchers GmbH.

[0129] Desmodur XP 2802: hydrophilically modified carbodiimide crosslinking agent, solid content: 40% by weight, NCN group content: 4.2% by weight, purchased from Covestro AG.

[0130] Bayhydur 305: polyisocyanate curing agent, water-dispersible hydrophilic aliphatic polyisocyanate based on HDI, NCO group content: 16.2% by weight, purchased from Covestro AG.

[0131] Methods for Performance Tests

[0132] 1. Conventional Adhesion

[0133] According to the national standard GB/T 9286-1998 “Cross-cut test for paints and varnishes”, the hundred grid test was carried out on the UV-cured coating. As tapes, 3M Scotch 600 was used. The evaluation method for the adhesion was based on the standards in GB/T 9286-1998 “Cross-cut test for paints and varnishes” and ASTM D 3359 “Standard method for measuring adhesion by Tape Test”, method B. Table 1 shows the evaluation criteria for conventional adhesion. The acceptable value of conventional adhesion is 5B.

TABLE-US-00001 TABLE 1 Evaluation criteria for conventional adhesion Conventional adhesion Description 5B The cutting edge is completely smooth without falling off 4B The coating layer falls partly off at the intersection of cuts, but the affected area is not significantly greater than 5% 3B The coating layer falls off at the intersection and/or along the edge of cuts. The affected area is significantly greater than 5%, but not significantly greater than 15% 2B The coating layer falls partly or completely off in large fragments along the edge of cuts, and/or partly or completely on different parts of the grids. The affected area is significantly greater than 15%, but not significantly greater than 35% 1B The coating layer falls partly or completely off in large fragments along the edge of cuts, and/or on some or all of the grids. The affected area is significantly greater than 35%, but not significantly greater than 65%. 0B The falling off degree exceeds that under 1B.

[0134] 2. Pencil Hardness

[0135] According to the national standard GB/T 6739-1996 “Determination of film hardness by pencil test”, MITSUBISHI UNI pencil was used and mounted on a dedicated pencil hardness tester. The load applied to the pencil tip was 1 kg, and the angle between the pencil and the horizontal plane was 45°. The pencil was pushed to slide forward about 10 mm long, and 5 lines in total was drawn in different positions. Then the pencil traces were wiped with an eraser, and the coating surface were evaluated for scratches. It is required that no more than 1 scratch is left on the coating surface. A pencil hardness of not less than 3H is considered acceptable.

[0136] 3. Water-Boiling Adhesion

[0137] A film with the UV-cured coating layer was completely immersed in hot water at 80° C. for 30 minutes, taken out and gently dried by absorbing the moisture on the surface. The change in the appearance of the coating layer was evaluated and the hundred grid test was carried out. Methods and criteria for evaluating the adhesion are the same as that for the conventional adhesion. Water-boiling adhesion ≥4B is regarded as acceptable.

[0138] Table 2 shows the composition of the water-based coating compositions or two-component coating systems of Examples and Comparative Examples, and the results of performance tests for the coating layers formed by the coating compositions or two-component coating systems.

[0139] Method for Preparing the Water-Based Coating Compositions of Comparative Examples 1-5, 7, 9-11 and Examples 1-2

[0140] According to the content of the components shown in Table 2, the resin, the photoinitiator, the optional aqueous nano-silica dispersion, the optional additives and deionized water were added to a container and stirred until all components were dispersed uniformly. The compositions of Examples and Comparative Examples were obtained.

[0141] Method for Preparing the Two-Component Coating Systems of Comparative Examples 6, 8 and Examples 3-4

[0142] Preparation of component A: According to the content of the components shown in Table 2, the resin, the photoinitiator, the optional aqueous nano-silica dispersion, the optional additives and deionized water were added to a container and stirred until all components were dispersed uniformly.

[0143] Component A and component B were mixed and stirred at 200-500 rpm for 5 min to 10 min. After mixing, a 200-mesh filter screen was used for filtering. The two-component coating systems of Examples and Comparative Examples were obtained and ready for use.

[0144] Method for Preparing Coating Layers

[0145] The water-based coating compositions or the two-component coating systems were roller coated evenly on the PMMA surface of PC/PMMA films with a dry film thickness of about 8 μm to 15 μm. The coating layers were dried in an oven at 60° C. to 80° C. for about 5 minutes. A UV device of M-40-2×1-URS-TR-SS type from IST was used for curing (the curing dosage was measured by using EIT UV Power Pack II dosimeter). The coating layers were cured by passing through the UV device only once at a continuous curing rate of 5 m/min and a radiation intensity of about 600 mJ/cm.sup.2 to 800 mJ/cm.sup.2.

TABLE-US-00002 TABLE 2 the composition of coating compositions or two-component coating systems of Examples and Comparative Examples, and the results of performance tests thereof Composition/g Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 1 Ex. 2 Ex. 3 Bayhydrol UV 2689/2 77.0 77.0 77.0 77.0 77.0 77.0 77.0 Bayhydrol UV 2282 Bayhydrol UH XP 2648 Omnirad 500 1.0 1.0 1.0 1.0 1.0 1.0 1.0 BYK 093 1.0 1.0 1.0 1.0 1.0 1.0 1.0 BYK 333 0.3 0.3 0.3 0.3 0.3 0.3 0.3 BYK 346 0.8 0.8 0.8 0.8 0.8 0.8 0.8 TEGO Twin 4100 0.5 0.5 0.5 0.5 0.5 0.5 0.5 TEGO Glide 410 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Borchi Gel 0621 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Deionized water 15.7 15.7 15.7 15.7 15.7 15.7 15.7 Dispercoll S 3030/1 61.6 69.3 61.6 61.6 46.2 53.9 SNOWTEX-40 Dispercoll S 2020 Desmodur XP 2802 3.1 Bayhydur 305 2.5 Weight ratio 3:5 17:25 3:5 3:5 0 9:20 53:100 Results of performance tests Appearance of glossy glossy glossy glossy glossy glossy glossy coating layers Conventional adhesion 5B 5B 5B 5B 4B 5B 5B Pencil hardness 3H 3H 3H 3H 2H <2H 3H Water-boiling adhesion 5B 5B 4B 5B 0B 3B 0B Composition/g Comp. Comp. Comp. Comp. Comp. Comp. Comp. Comp. Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Bayhydrol UV 77.0 77.0 77.0 77.0 77.0 77.0 77.0 2689/2 Bayhydrol UV 77.0 2282 Bayhydrol UH 12.5 12.5 XP 2648 Omnirad 500 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 BYK 093 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 BYK 333 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 BYK 346 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 TEGO Twin 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 4100 TEGO Glide 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 410 Borchi Gel 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0621 Deionized 15.7 15.7 15.7 15.7 15.7 15.7 15.7 15.7 water Dispercoll S 77.0 115.5 46.2 46.2 46.2 59.3 3030/1 SNOWTEX-40 47.3 Dispercoll S 93.7 2020 Desmodur XP 2802 Bayhydur 305 2.3 2.5 Weight ratio 3:4 113:100 9:20 9:20 9:20 3:5 3:5 3:5 Results of performance tests Appearance of slightly whitish glossy glossy glossy matt grainy glossy coating layers foggy Conventional 5B 5B 4B 4B 1B 4B / 0B adhesion Pencil <2H <2H <2H <2H <2H <2H / <2H hardness Water-boiling 5B 5B 0B 0B 0B 1B / 0B adhesion Note: The weight ratio refers to that of the solid constituent of the nanosized silicon oxide compound to the solid constituent of the water-based UV resin.

[0146] The water-based coating compositions or two-component coating systems of Examples 1˜4 of the present invention had good conventional adhesion, water-boiling adhesion and pencil hardness. Among them, Example 3-4 were two-component coating systems and contained a curing agent of polyisocyanate type and a curing agent of carbodiimide type respectively. As can be seen from the results of performance tests in Table 2, high pencil hardness, conventional adhesion and water-boiling adhesion can be achieved by adding different curing agents.

[0147] The composition of Comparative Example 1 contained no silane-treated nanosized silicon oxide compound, so that the conventional adhesion, the water-boiling adhesion and the pencil hardness of the coating layers prepared by the composition were unacceptable.

[0148] The weight ratios of the solid constituent of the nanosized silicon oxide compound to the solid constituent of the water-based UV resin of the coating compositions or coating systems of Comparative Examples 2-3, 6-8 were less than 11:20. The weight ratios of the solid constituent of the nanosized silicon oxide compound to the solid constituent of the water-based UV resin of the coating compositions of Comparative Examples 4-5 were greater than 73:100. The coating layers formed by the above coating compositions or coating systems failed to show a combination of good conventional adhesion, water-boiling adhesion and pencil hardness.

[0149] Compared with that in Example 1, an aqueous alkaline dispersion of nano-silica without treatment by silane was used in Comparative Example 9, and an aqueous acidic dispersion of nano-silica without treatment by silane was used in Comparative Example 10. The coating layer prepared by the water-based coating composition of Comparative Example 9 showed unacceptable conventional adhesion, water-boiling adhesion and pencil hardness. The coating layer formed by the water-based coating composition of Comparative Example 10 was grainy, i.e. had macroscopic small particles on the surface. That means the components of the composition were incompatible with each other, so that no performance tests could be carried out.

[0150] Compared with that in Example 1, the resin Bayhydrol UV 2282 was used in Comparative Example 11. The mole number of ethylenically unsaturated groups per kilogram of the solid constituent of Bayhydrol UV 2282 was less than 3.0 mol. The coating layer prepared by the composition containing said resin showed unacceptable conventional adhesion, water-boiling adhesion and pencil hardness.

[0151] Those skilled in the art can easily understand that the present invention is not limited to the foregoing specific details. The present invention can be implemented in other specific forms without departing from the spirit or main characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as illustrative rather than restrictive. The scope of the present invention should be indicated by the claims rather than the foregoing descriptions. Therefore any changes, as long as they fall into the meaning and scope of the claims, should be regarded as belonging to the present invention.