CN111234620A

CN111234620A - Aqueous soft touch coating composition and abrasion resistant coating formed therefrom

Info

Publication number: CN111234620A
Application number: CN201811435036.7A
Authority: CN
Inventors: 许升志; 刘海峰; 高思齐; 罗正松
Original assignee: PPG Coatings Tianjin Co Ltd
Current assignee: PPG Coatings Tianjin Co Ltd
Priority date: 2018-11-28
Filing date: 2018-11-28
Publication date: 2020-06-05

Abstract

The present invention provides a multilayer coating system comprising (a) a first coating layer; and (b) a second coating applied directly over at least a portion of the first coating. The first coating layer is prepared from a coating composition comprising: (1) acrylic resin; and (2) a hydroxyacrylic resin. The second coating layer is prepared from a coating composition comprising: (1) an aliphatic hydroxyl functional polyester polyurethane resin; and (2) a water-dispersible polycarbonate diol resin. The invention also provides substrates coated with the multilayer coating system.

Description

Aqueous soft touch coating composition and abrasion resistant coating formed therefrom

Technical Field

The present invention relates to a multi-layer coating system having low VOC, in particular to a multi-layer coating system comprising a first coating composition and a second coating composition. The invention also relates to substrates coated with the multilayer coating system.

Background

The traditional soft touch paint applied to 3C products (including computer products, communication products and consumer electronics products) in the current market is an oil product, the formula of the paint completely adopts solvent-containing raw materials, the VOC content reaches 600-800 g/L, and the VOC content is far beyond the national paint consumption tax free point of 420 g/L. Accordingly, there is a need in the art for waterborne soft touch coatings having low VOC content.

The invention aims to develop the water-based colored paint and the water-based elastic paint, the performance and the hand feeling of the water-based colored paint are close to the level of oil paint, the anti-fingerprint effect is even more excellent, and the VOC content of the water-based colored paint is less than 200g/L and is far lower than 420 g/L. In addition, in the traditional oily solvent construction process, the solvent is volatilized into the construction environment, the pungent smell is strong, the harm to the health of constructors is easy to cause, and the paint is flammable and explosive and requires high fireproof performance in the surrounding environment. Compared with a solvent type, the water-based paint disclosed by the invention is small in smell, small in harm to constructors, completely free of combustion supporting and safer.

Disclosure of Invention

The present invention relates to a multi-layer coating system comprising (a) a first coating layer formed from a coating composition comprising: (1) acrylic resin; and (2) a hydroxy acrylic resin; and (b) a second coating layer applied directly over at least a portion of the first coating layer, the second coating layer prepared from a coating composition comprising: (1) an aliphatic hydroxyl functional polyester polyurethane resin; and (2) a water-dispersible polycarbonate diol resin.

The present invention also relates to a coated substrate comprising: (a) a substrate; (b) a first coating layer applied over at least a portion of the substrate, the first coating layer prepared from a coating composition comprising: (1) acrylic resin; and (2) a hydroxy acrylic resin; and (c) a second coating layer applied directly over at least a portion of the first coating layer, the second coating layer prepared from a coating composition comprising: (1) an aliphatic hydroxyl functional polyester polyurethane resin; and (2) a water-dispersible polycarbonate diol resin.

Detailed Description

For purposes of the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

Moreover, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, i.e., having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

In this application, the use of the singular includes the plural and plural encompasses singular, unless expressly stated otherwise. In addition, in this application, the use of "or" means "and/or" unless explicitly stated otherwise, even though "and/or" may be explicitly used in some cases. In addition, in this application, the use of "a" or "an" means "at least one" unless explicitly stated otherwise. For example, "a" polymer, "a" coating composition, and the like, refer to one or more of any of these items.

As used herein, the term "waterborne" refers to a coating composition that comprises at least a majority of water (in an amount greater than >50 wt.%), based on the weight of total solvents in the composition.

As used herein, the term "Volatile Organic Compound (VOC)" refers to any organic compound having a boiling point of less than or equal to 250 ℃ (482 ° f) measured at standard atmospheric pressure of 101.3 kPa. Organic solvents are a typical source of VOCs.

As used herein, the term "emulsion" refers to a form of resin that requires the addition of an emulsifier to be emulsified in water. As used herein, the term "dispersion" refers to a form of resin that can be emulsified in water by self-emulsification without the need for additional emulsifiers.

The present invention relates to a coating system comprising at least a first coating layer and a second coating layer. As previously described, the first coating layer is prepared from a coating composition comprising an acrylic resin and a hydroxy acrylic resin.

The acrylic resin used to form the coating composition of the first coating layer has a high glass transition temperature, a high film-forming temperature. For example, the acrylic resin has a glass transition temperature of at least 80 ℃. For example, the acrylic resin has a minimum film forming temperature of at least 80 ℃. In particular, the acrylic resin may have a glass transition temperature of 80 to 100 ℃. The glass transition temperature was determined by dynamic thermo-mechanical analysis (DMA) using a TA Instruments Q800 instrument, with the parameters: frequency 10Hz, amplitude 5mm, temperature ramp-100 ℃ to 250 ℃ and Tg as determined by the peak of tan delta curve according to ASTM D7028.

As used herein, the term "minimum film forming temperature" is the lowest temperature at which a polymer emulsion can form a continuous transparent film, generally indicated by MFT. The minimum film forming temperature of the emulsion is an important application index of the emulsion. That is, below a certain temperature, after the water content of the emulsion is volatilized, the polymer particles are still in a discrete state and can not be fused into a whole, so that the emulsion can not form a continuous and uniform coating film due to the evaporation of water; at temperatures above this particular temperature, the molecules in each polymer particle will penetrate, diffuse, deform, aggregate to form a continuous transparent film after the water has evaporated. The performance and construction quality of the emulsion and the latex paint can be judged by measuring the lowest film-forming temperature of the emulsion. The MFT of the emulsion is determined by the internal architecture of the polymer particles and the glass transition temperature. The minimum film forming temperature may be determined using an MFFT-BAR minimum film forming temperature tester (RHOPOINT minimum film forming temperature tester MFFT-60/MFFT-90, UK) according to the specifications of ASTM D2354 and ISO 2115 standards.

Suitably, the acrylic resin comprises a styrene-modified acrylic resin having a number average molecular weight of about 100,000 to 120,000, and the number average molecular weight is determined by gel permeation chromatography using polystyrene as a standard. The styrene modified acrylic resin comprises styrene-based acrylic resin, wherein the content of styrene is 50-80 wt% of the styrene modified acrylic resin. The acrylic resin used to form the coating composition of the first coating layer is generally present in the form of an aqueous emulsion having a particle size in the range of 100 to 120nm, which increases the stability of the emulsion and imparts an excellent appearance to the coating.

Typically, the acrylic resin is present in the coating composition in an amount of at least about 10 wt%, suitably at least about 15 wt%, such as at least about 20 wt%, and up to about 50 wt%, suitably up to about 45 wt%, such as up to about 40 wt%, based on the weight of the coating composition forming the first coating layer. When the amount of the acrylic resin is less than 10 wt%, the hardness of the first coating layer formed from the coating composition is low, resulting in poor sanding property at the time of repair recoating and easy adhesion of sandpaper; at the same time, its adhesion to the substrate becomes poor, resulting in easy peeling of the entire paint film. When the amount of the acrylic resin is more than 50 wt%, the hardness of the first coating layer formed from the coating composition is too high, resulting in poor adhesion between the first coating layer and the second coating layer and peeling.

Many commercially available acrylic resins are useful in the present invention. For example, examples of such acrylic resins useful in the present invention include, but are not limited to: voncoat WHK-364 from DIC; carboset CR-781, Carboset PC-23 from Lubrizol; from Wanhua

6318; NeoPac from DSM^TME-123, NeoCryyl A-662, and the like; AS 2610 and AC 2508 from Alberdingk.

The hydroxy acrylic resin used to form the coating composition of the first coating layer generally has a number average molecular weight of about 4,000 to 12,000, and the number average molecular weight is determined by gel permeation chromatography using polystyrene as a standard. Suitably, the hydroxy acrylic resin has a minimum film forming temperature of about 20-60 ℃, effectively aiding the film forming properties of the overall formulation. The hydroxyl acrylic resin suitable for the invention generally has a hydroxyl value of 30-110 mgKOH/g, and the hydroxyl acrylic resin is matched with an isocyanate curing agent to improve the crosslinking density of a paint film and provide excellent flexibility, interlayer adhesion and chemical resistance.

Typically, the hydroxyacrylic resin is present in the coating composition in an amount of at least about 10 wt.%, suitably at least about 15 wt.%, such as at least about 20 wt.%, and up to about 50 wt.%, suitably up to about 45 wt.%, such as up to about 40 wt.%, based on the weight of the coating composition forming the first coating layer. When the amount of the hydroxyl acrylic resin is less than 10% by weight, the crosslinking density of the first coating film formed from the coating composition is too low, resulting in poor adhesion to the upper coating film and poor chemical resistance, hardness and RCA abrasion resistance. When the amount is more than 50% by weight, the crosslinking density of the first coating layer formed from the coating composition is too high, resulting in poor adhesion to the upper coating film.

Many commercially available hydroxyacrylic resins are useful in the present invention. For example, examples of such polyurethane resins useful in the present invention include, but are not limited to: UC 84, AC2597, AC2598, AC2592, AC31 and AC3669 from Alberdingk; bayhydrol A2845 XP and Bayhydrol U XP 2755 from Covestro; WD-551, WD-554, WD-555, and WD-556 from DIC; from Allnex

VSM 6299W/42WA, SM 6817W, Setaqua 6510, Setaqua 6516, Setaqua 6520, and Setaqua 6522; from DSMs

XK-110、

XK-103 and

XK-102; antkote 2033 and Antkote2042 from wanhua; WPA-4402, WPA-4403 and WPA-4407 from Huigao; carboset 451 and Carboset 452 from Lubrizol.

The coating composition used to form the first coating layer also includes a thickener. Preferably, an alkali-soluble anionic thickener is used, which is an acid-containing crosslinked acrylic emulsion copolymer. Such thickeners swell rapidly in the emulsion particles when diluted with water and neutralized with alkali. The polyacrylic acid type thickener is effective in improving low shear rate viscosity, so that the formed coating has high shear dilution characteristics, thereby ensuring excellent workability and avoiding fat edges. Typically, the thickener is present in the coating composition in an amount of about 0.5 to 2 wt%, based on the weight of the coating composition forming the first coating layer.

Many commercially available thickeners are useful in the present invention. For example, examples of such thickeners useful in the present invention include, but are not limited to: rheolate 150, Rheolate175 from Element; from Basf

DS6256、

HV 30; ACRYSOL from Dow^TMASE-60, TT-935, UCAR POLYPHONE T-900 and T-901.

The coating composition used to form the first coating layer also includes various adjuvants and cosolvents useful in aqueous systems, including, but not limited to, surfactants, rheology adjuvants, ethers and amine cosolvents, and the like.

As previously described, the second coating is applied directly over at least a portion of the first coating. The second coating is prepared from a coating composition comprising an aliphatic hydroxyl functional polyester polyurethane resin and a water dispersible polycarbonate diol resin.

The aliphatic hydroxyl functional polyester polyurethane resin of the coating composition for forming the second coating layer adopts a long-chain linear structure in which the number of carbon atoms of the aliphatic group is about 15 to 25. Suitably, the aliphatic hydroxyl functional polyester polyurethane resin has a ratio of polyester groups to polyurethane groups of about 1:1 to about 2. Suitably, the aliphatic hydroxyl functional polyester polyurethane resin may have a number average molecular weight of about 8,000 to 10,000, and the number average molecular weight is determined by gel permeation chromatography using polystyrene as a standard. The aliphatic hydroxyl functional polyester polyurethane resin is generally present in the form of an aqueous dispersion having a particle size in the range of 120 to 150nm, which increases the stability of the dispersion and imparts an excellent appearance to the coating. Also, the aliphatic hydroxyl functional polyester polyurethane resin in the form of an aqueous dispersion may have a solid content of about 40 to 60 wt%, such as 50 wt%. The aliphatic hydroxyl functional polyester polyurethane resin in the form of an aqueous dispersion may be completely free of VOCs.

Typically, the aliphatic hydroxyl-functional polyester polyurethane resin is present in the coating composition in an amount of at least about 10 wt.%, suitably at least about 15 wt.%, such as at least about 20 wt.%, and up to about 40 wt.%, suitably up to about 35 wt.%, such as up to about 30 wt.%, based on the weight of the coating composition forming the second coating layer. When the amount of the resin is less than 10% by weight, the second coating layer formed from the coating composition feels too sticky, is deteriorated in slipperiness, and is deteriorated in fingerprint resistance. When the amount is more than 40 wt%, the scratch resistance and hardness of the second coating layer formed from the coating composition are deteriorated.

Many commercially available aliphatic hydroxyl functional polyester polyurethane resins are useful in the present invention. For example, examples of aliphatic hydroxyl functional polyester polyurethane resins useful in the present invention include, but are not limited to: from Covestor

U XP2757、

U XP 2698, Bayhydrol U355, Bayhydrol UH340/1 and DLC-F; matt300 from Alberdingk; sancure PC-55, 2060C from Lubrizol; NeoRez R-1000, NeoRez R-1010 from DSM; WSL-250 from DIC; PD-802, PD-804 from Stahl; w6110 from Mitsui; WPU-2501, WPU-2502 and the like from comet valley chemical industry; from Wanhua

6512 and

6110 of; PU40, PU471, PU 980, PU461 from Lamberti, etc.

The water dispersible polycarbonate diol resin of the coating composition for forming the second coating layer contains a sulfonate hydrophilic group and is directly dispersible in water. Suitably, the water dispersible polycarbonate diol has a number average molecular weight of 800 to 1,000 and a hydroxyl value of 90 to 110mg KOH/g, and the number average molecular weight is determined by gel permeation chromatography using polystyrene as a standard. Generally, the water dispersible polycarbonate diol resin is a transparent 100% solids content material, completely free of VOCs. The water dispersible polycarbonate diol has an average particle diameter of 100 to 130nm when dispersed in water, and such a range of particle diameter increases the stability of the dispersion and gives a coating excellent in appearance.

Typically, the water dispersible polycarbonate diol resin is present in the coating composition in an amount of at least about 10 wt.%, suitably at least about 15 wt.%, such as at least about 20 wt.%, and up to about 40 wt.%, suitably up to about 35 wt.%, such as up to about 30 wt.%, based on the weight of the coating composition forming the second coating layer. When the amount of the resin is less than 10% by weight, scratch resistance, abrasion resistance, chemical resistance and hardness of a second coating layer formed from the coating composition are deteriorated. When the amount is more than 40% by weight, the second coating layer formed from the coating composition feels sticky and is not easily matted and a desired film thickness is obtained.

Many commercially available water dispersible polycarbonate diol resins are usable in the present invention. For example, examples of the water dispersible polycarbonate diol resin useful in the present invention include, but are not limited to: 6665W from chang; PCDX-103 from Asahi Kasei; PU 98D from Lamberti; HUX-516S and HUX-564 from Adaka; UW-3039E, UW-1077 and UW-2001A from UBE and the like.

The coating composition used to form the first and second coating layers also comprises, as a curing agent, an isocyanate group-containing component that reacts with the aliphatic hydroxyl-functional polyester polyurethane and the hydroxyl acrylate to form a coating film. As used herein, the term "isocyanate group-containing component" and similar terms include isocyanates, polyisocyanates, and cyclic trimers of polyisocyanates.

Suitable isocyanates include isophorone diisocyanate, 1, 3-or 1, 4-cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, tetraalkylxylylene diisocyanates such as m-tetramethylxylylene diisocyanate, p-phenylene diisocyanate, polymethylene polyphenyl isocyanates, diphenyl pentamethyl diisocyanate, 2, 6-toluene diisocyanate, dianisidine diisocyanate, ditoludine diisocyanate, naphthalene-1, 4-diisocyanate, bis (4-isocyanatophenyl) methane, 4' -diphenylpropane diisocyanate, hexamethylene diisocyanate, and, where appropriate, trimers of the above, for example, the isocyanate trimer of hexamethylene diisocyanate.

In one aspect, the molar ratio of isocyanate groups in the isocyanate group-containing component to hydroxyl groups in the aliphatic hydroxyl-functional polyester polyurethane resin is in the range of 1.5 to 2:1, where the molar ratio balances the combination of performance and appearance requirements.

In one aspect, the molar ratio of isocyanate groups in the isocyanate group-containing component to hydroxyl groups in the hydroxyacrylic resin is in the range of 1.3 to 2:1, where the molar ratio meets the requirements of reaction rate and resin pot life.

The coating composition used to form the second coating layer also includes a thickener. Polyether polyurethane associative thickeners are preferably used. Such thickeners are highly effective viscosity aids in the low to medium shear rate range that provide strong shear thinning properties to balance film formation (film building) and fat edge (fat edge). Typically, the thickener is present in the coating composition in an amount of about 1 to 2 wt%, based on the weight of the coating composition forming the second coating layer.

Many commercially available thickeners are useful in the present invention. For example, examples of such thickeners useful in the present invention include, but are not limited to: WT-105A, 299 from Element; from Basf

PU 1191; RM-12W from Dow; 3060 from Evonik; BORCHI GEL 0620 from Borchers, and the like.

The coating composition used to form the second coating layer also contains various adjuvants and cosolvents useful in aqueous systems, including, but not limited to, leveling agents, defoamers, surfactants, wetting dispersants, matting agents, and the like.

The coating system of the present invention can be applied to a wide variety of substrates known to the coatings industry. For example, the coating system can be applied to automotive substrates, industrial substrates, aircraft and aircraft parts, marine substrates and parts, such as ships and boats and on-shore and off-shore facilities, storage tanks, windmills, nuclear power plants, packaging substrates, wood flooring and furniture, apparel, electronic equipment, including housings and circuit boards, glass and transparencies, sports equipment, including golf balls, stadiums, buildings, bridges, and the like. The substrate may be metallic or non-metallic, for example. Metal substrates include, but are not limited to, tin, steel (including electrogalvanized steel, cold rolled steel, hot dip galvanized steel, etc.), aluminum alloys, zinc-aluminum alloys, steel coated with zinc-aluminum alloys, and aluminized steel. Non-metallic substrates include polymers, plastics, polyesters, polyolefins, polyamides, celluloses, polystyrenes, polyacrylics, polyethylene naphthalates, polypropylenes, polyethylenes, nylons, EVOH, polylactic acid, other "green" polymer substrates, polyethylene terephthalate (PET), polycarbonates, polycarbonate acrylonitrile butadiene styrene (PC/ABS), polyamides, wood, veneers, wood composites, particle board, medium density fiberboard, cement, stone, glass, paper, cardboard, textiles, synthetic and natural leather, and the like.

The substrate may also comprise a metallized plastic substrate. As used herein, "metallized plastic substrate" refers to a substrate formed from both plastic and metal. For example, the metallized plastic substrate may comprise a plastic material comprising a metal material incorporated into the plastic material and/or coated on at least a portion of the plastic material.

In particular, substrates include, but are not limited to, Polycarbonate (PC), acrylonitrile-2-butadiene-2-styrene terpolymer (ABS) + polycarbonate, polycarbonate + Glass Fibers (GF), and Carbon Fibers (CF).

The coating system is particularly useful when applied at least partially over consumer electronics products. For example, the coatings of the present invention may be applied to substrates found on notebook computers, tablet computers, keyboards, mobile phones, other handheld electronic devices, and the like. Based on the foregoing, the invention also includes an electronic or electronic component having a surface at least partially coated with a coating as described herein. It should be understood that the consumer electronic product may be formed from any of the aforementioned materials, such as a metallized plastic.

During application of the coating system, a coating composition forming a first coating layer is applied to at least a portion of the substrate and cured with thermal dehydration at a temperature of 50 to 80 ℃ to form the first coating layer. And then applying a coating composition forming a second coating layer on at least a portion of the first coating layer, and curing at a temperature of 50 to 80 ℃ by thermal dehydration to form the second coating layer.

It should be understood that the first coating layer may be applied to the substrate as a primer layer and the second coating layer may be applied over the first coating layer as a topcoat layer. As used herein, "primer coating" refers to a base coating that can be deposited onto a substrate in order to prepare a surface for application of a protective or decorative coating. Further, "topcoat" refers to a top coat deposited over another coating, such as a primer, to provide a protective and/or decorative layer.

The second coating layer can also be applied as a transparent top coat layer. As used herein, "clear coat" refers to a coating that is at least substantially transparent or completely transparent. The term "substantially transparent" refers to a coating wherein the surface on the other side of the coating is at least partially visible to the naked eye when viewed through the coating. The term "substantially transparent" refers to a coating wherein the surface on the other side of the coating is substantially visible to the naked eye when viewed through the coating. It should be understood that the transparent topcoat layer may include a colorant, such as a pigment, provided that the colorant does not interfere with the desired transparency of the transparent topcoat layer. Alternatively, the transparent topcoat layer is free of colorants, such as pigments (i.e., uncolored).

The coating compositions of the present invention can be applied by any method standard in the art, such as electrocoating, spraying, electrostatic spraying, dipping, roll coating, brushing, and the like, and then cured to form a coating. The first coating of the present invention can be applied to a dry film thickness of 5 microns to 15 microns. In addition, the second coating of the present invention can be applied to a dry film thickness of 20 microns to 60 microns.

Examples

The following examples are provided to further illustrate the invention but are not to be construed as limiting the invention to the details set forth in the examples. All parts and percentages in the following examples, as well as throughout the specification, are by weight unless otherwise indicated.

Example 1.

The # 1 coating system of the present invention was prepared according to tables 1-2 below.

Primer composition # 1 was prepared from the components listed in table 1.

TABLE 1.1# primer composition

The # 1 varnish composition was prepared from the components listed in table 2.

TABLE 2.1# varnish compositions

Components	Weight percent of
		Aliphatic hydroxy-functional polyester polyurethane, WPU-2502	30
Water dispersible polycarbonate diol 6665W	30
		Organic silicon leveling agent, Tego 410	1.00
Silicone antifoams, Byk 024	0.50
		Organosilicon levelling agent, Byk 348	0.40
Organosilicon wetting dispersant, Tego 752w	0.50
		Modified Matt powder, Tosoh E-1011	7.00
Element 299 as a polyurethane-associated thickener	0.10
		Deionized water	30.5
Total of	100

Hardener, Covestro 2487/1	70
		Diluent	30

Example 2.

The # 2 coating system of the present invention was prepared according to tables 3-4 below.

The # 2 primer composition was prepared from the components listed in table 3.

TABLE 3.2# primer composition

The # 2 varnish composition was prepared from the components listed in table 4.

TABLE 4.2# varnish compositions

Example 3.

The 3# coating system of the present invention was prepared according to tables 5-6 below.

The # 3 primer composition was prepared from the components listed in table 5.

TABLE 5.3# primer composition

The # 3 varnish composition was prepared from the components listed in table 6.

TABLE 6.3# varnish compositions

The components listed in tables 1 to 6, except hardener and diluent, were weighed and stirred in a container for about 15 minutes or at room temperature until homogeneous. The hardener and diluent were then added and mixed for five minutes prior to spraying to ensure adequate mixing of all components. The coating mixture was sprayed within two hours of mixing of all components.

EXAMPLE 4 application and evaluation of Multi-layer coatings

The substrate (ABS + PC) was subjected to pretreatment including wiping and electrostatic dust removal. The primer compositions prepared in examples 1-3 were then sprayed by hand or machine (including shuttle, robot, automated line) to form a first coating. Baking the coating at 60-80 ℃ for about 20-30 minutes to obtain a coating with a dry film thickness of 5-15 microns. The varnish compositions prepared in examples 1-3 were then sprayed on top of this first coating by hand or by machine (including shuttle, robot, automated line) to form a second coating. And (3) enabling the formed coating to flash dry and flow for 3-10 minutes at room temperature, and then baking the coating for about 20-30 minutes at the temperature of 60-80 ℃ to obtain the coating with the dry film thickness of 20-60 micrometers. Finally, the coated substrate was baked at a temperature of 60-80 ℃ for about 6-8 hours to produce a test panel.

The samples were tested for various performance indicators according to the tests in table 7 below. Table 7 compares the properties of the inventive coating systems # 1, # 2, # 3 and two commercially available products, which are products mainly used in automotive interiors and the general household appliance market.

TABLE 7 test results

As can be seen from the above table, the coating system of the present invention is superior in all respects to the existing commercial products. The pencil hardness of the coating system can reach H level or even 2H, which is obviously higher than the pencil hardness level F of the existing commercial products (pencil hardness: 2H > H > F > HB > B). Thus, the coating system of the present invention has excellent scratch resistance. Also, for RCA abrasion resistance, the test results for the coating system of the present invention can reach at least 150, and even 200 cycles, comparable to, and even superior to, the levels that can be achieved with prior art solvent-based soft touch coating compositions of superior performance. In general, with respect to an aqueous coating composition, the RCA abrasion resistance is improved and the feel and workability of the coating may be deteriorated. The coating system provided by the invention can provide high RCA wear resistance and ensure the hand feeling and the application property of the coating.

While particular aspects of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims

1. A multi-layer coating system comprising:

(a) a first coating layer formed from a coating composition comprising:

(1) acrylic resin; and

(2) a hydroxy acrylic resin; and

(b) a second coating layer applied directly over at least a portion of the first coating layer, the second coating layer prepared from a coating composition comprising:

(1) an aliphatic hydroxyl functional polyester polyurethane resin; and

(2) a water-dispersible polycarbonate diol resin.

2. The multi-layer coating system of claim 1, wherein said acrylic resin has a glass transition temperature of at least 80 ℃.

3. The multi-layer coating system of claim 1, wherein the acrylic resin comprises a styrene modified acrylic resin having a number average molecular weight of about 100,000 to 120,000.

4. The multi-layer coating system of claim 1, wherein said hydroxy acrylic resin has a hydroxyl number of 30 to 110 mgKOH/g.

5. The multilayer coating system of claim 1, wherein the hydroxy acrylic resin has a number average molecular weight of 4,000 to 12,000.

6. The multi-layer coating system of claim 1, wherein the hydroxyacrylic resin has a minimum film formation temperature of about 20 to 60 ℃.

7. The multi-layer coating system of claim 1, wherein the coating composition forming the first coating layer further comprises an alkali-soluble anionic thickener.

8. The multi-layer coating system of claim 7, wherein the alkali-soluble anionic thickener is a polyacrylic acid-type thickener.

9. The multi-layer coating system of claim 1, wherein the aliphatic hydroxy-functional polyester polyurethane resin has a number average molecular weight of 8,000 to 10,000, and the water dispersible polycarbonate diol resin has a number average molecular weight of 800 to 1,000.

10. The multi-layer coating system of claim 1, wherein the coating composition forming the second coating layer further comprises a polyester polyurethane associative thickener.

11. The multi-layer coating system of claim 1, wherein the coating composition forming the first and second coating layers further comprises an isocyanate group-containing component.

12. The multi-layer coating system of claim 11, wherein the molar ratio of isocyanate groups in the isocyanate group-containing component to hydroxyl groups in the aliphatic hydroxyl-functional polyester polyurethane resin is in the range of 1.5 to 2: 1.

13. The multilayer coating system of claim 11, wherein the molar ratio of isocyanate groups in the isocyanate group-containing component to hydroxyl groups in the hydroxyacrylic resin is from 1.3 to 2: 1.

14. A coated substrate comprising:

(a) a substrate;

(b) a first coating layer applied over at least a portion of the substrate, the first coating layer prepared from a coating composition comprising:

(1) acrylic resin; and

(2) a hydroxy acrylic resin; and

(c) a second coating layer applied directly over at least a portion of the first coating layer, the second coating layer prepared from a coating composition comprising:

(1) an aliphatic hydroxyl functional polyester polyurethane resin; and

(2) a water-dispersible polycarbonate diol resin.

15. The coated substrate of claim 14, wherein the substrate comprises a substrate formed from: polycarbonate, acrylonitrile-2-butadiene-2-styrene terpolymer + polycarbonate, polycarbonate + glass fiber and carbon fiber.