Two-component transparent coating components and their preparation and application.

Abstract

DEPCT69 This invention relates to a two-component transparent coating composition and its preparation and Using that, this invention provides a two-component transparent coating element that is assembled together. With component I consisting of A) (meth) acrylic resin containing hydroxyl, B) melamine resin and C) Polyol esters are products obtained by one or more reactions that have been Select from a group containing castor oil, castor oil monoglycerides, and castor oil diglycerides. Castor oil with polyols containing primary hydroxyl radicals, and selected to contain either polybasic acid or anhydride. Component II, which includes D) polyisocyanate from which a transparent coating film is obtained. The two-component transparent coating material has molecular weights between the cross-linked regions. A 300 to 700 g / mol two-component transparent coating composition according to this invention can be made A transparent coating film is formed, resulting in an excellent finished product appearance, high hardness, and durability. Resistant to petroleum products and water;

Description

[0001] TWO-COMPONENT CLEARCOAT COMPOSITION AND PREPARATION AND USE THEREOF

[0002] Field of the invention

[0003] The present invention relates to the field of automotive coatings, and in particular relates to a two-component clearcoat composition and preparation and use thereof.

[0004] Background of the invention

[0005] Automotive coatings are applied in several layers, wherein the clearcoat film is a clear coat sprayed on a basecoat film and is mainly used for protecting the basecoat from the external environment and enhance the gloss and aesthetics of the automobile’s surface.

[0006] Clearcoat could be a one-component formulation (1 K) or two-component formulation (2K) system. For the 2K system, the clearcoat product is packaged in two barrels respectively and the formulations of the two barrels are mixed before being applied onto the basecoat. Most two- component clearcoat materials are based on polyurethane chemistry, which is derived from the use of hydroxyl-functional polyacrylate or polyester resin or polyol and isocyanate-based hardeners.

[0007] Patent Document 1 discloses a two-package clear coating composition, which can form a cured coating film which excels in all aspects of scratch resistance, acid resistance, stain resistance and finished appearance, wherein the two-package clear coating composition comprises a specific hydroxyl-containing acrylic resin, a trifunctional HMDI isocyanate compound, and a polyester polyol. Nevertheless, improvement still needs to be made in terms of aspects such as hardness and crosslinking density.

[0008] During use, automobiles will inevitably get adhered to by petroleum products such as asphalt, leaked gasoline, lubricating oil, lubricating grease and brake fluid on the road, all of which have certain dissolving and corrosive effects on the vehicle body coating films. The clearcoat film needs to have high resistance to petroleum products. Patent Document 2 discloses a crosslinked clearcoat material comprising a hydroxyl-containing acrylic resin, a castor oil, and a melamine resin. Although the clearcoat material has good finished product appearance and hardness, it has the problems of poor overall reactivity, and the resulting product has slow curing, easy shrinkage, and insufficient resistance to petroleum products and water.

[0009] Therefore, there is a need to provide a novel two-component clearcoat composition that can form a clearcoat film with excellent finished product appearance and high hardness, and resistance to petroleum products and water. Literature cited:

[0010] Patent Document 1: CN101157814 B

[0011] Patent Document 2: JP7200444 B1

[0012] Summary of the Invention

[0013] In one aspect, the present invention provides a two-component clearcoat composition comprising component I comprising

[0014] A) a hydroxyl-containing (meth)acrylic resin,

[0015] B) a melamine resin, and

[0016] C) a polyol ester which is a product obtained by reacting one or more selected from the group consisting of castor oil, castor oil monoglyceride, and castor oil diglyceride with a primary hydroxyl-containing polyol and optional polybasic acid or anhydride; and component II comprising

[0017] D) a polyisocyanate, wherein a clearcoat film obtained from the two-component clearcoat composition has a molecular weight between crosslinked sites of 300 to 700 g / mol, preferably 350 to 500 g / mol.

[0018] In another aspect, the preset invention provides articles coated with the two-component clearcoat composition of the present invention.

[0019] In another aspect, the present invention provides a method of forming a multilayer coating film, comprising

[0020] 1) optionally producing a cured first coat on a substrate;

[0021] 2) producing at least one basecoat layer on the coat obtained in step 1) by applying one or more identical or different basecoat materials; and

[0022] 3) producing at least one clearcoat layer on the topmost basecoat layer by applying one or more identical or different clearcoat materials; wherein at least one of the clearcoat materials is the two-component clearcoat composition according to the present invention; the basecoat layer and the clearcoat layer are cured separately or jointly by baking; and preferably, the basecoat layer and the clearcoat layer are jointly cured by baking after step 3).

[0023] In another aspect, the present invention provides a multilayer coating film prepared according to the method of forming a multilayer coating film according to the present invention.

[0024] It has been surprisingly found that the two-component clearcoat composition according to the present invention can form a clearcoat film with excellent finished product appearance, and high hardness, and resistance to petroleum products and water. The polyol ester used in the present invention has a specific structure and has a relatively high hydroxyl value and reactivity, has good compatibility with the hydroxyl-containing (meth)acrylic resin of the present invention, and cannot be easily separated out from the system. In the present invention, a melamine resin is used in the main component (i.e. , component I), and serves the function of effectively adjusting the rate of hardening. The various components according to the present invention cooperate synergistically with each other to obtain a clearcoat film with suitable crosslinking density, thereby achieving a balance between various properties of the clearcoat film. In some preferred embodiments of the present invention, through the selection of types of components and physical property parameters, the two-component clearcoat composition of the present invention is unexpectedly suitable for low-temperature baking; for example, when the two- component clearcoat composition of the present invention is dried at 110°C, the obtained multilayer coating film can also show good appearance, and high hardness, and resistance to petroleum products and water.

[0025] It should be noted that the above description does not disclose all embodiments of the present invention and all advantages of the present invention.

[0026] Detailed Description of the Invention

[0027] Embodiments of the present invention are described below. However, the present invention is not limited to these embodiments. The present invention is not limited to various compositions described below. Various modifications are possible within the scope of the claims. Embodiments and examples obtained by appropriately combining technical means respectively disclosed in different embodiments and examples are also included in the technical scope of the present invention. Further, all the documents described in the present specification are incorporated by reference in the present specification.

[0028] Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which the present invention belongs.

[0029] The use of the terms "a", "an", "the" and similar referents in the context of describing the present specification (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. As used in the present specification, the numerical range represented by “numerical values A B” or "numerical values A-B" refers to a range including the endpoint values A and B.

[0030] In the present specification, the use of "can" has two meanings including performing certain treatment and not performing certain treatment. In this specification, "optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

[0031] Reference throughout the present specification to "some specific / preferred embodiments", "other specific / preferred embodiments", "some specific / preferred technical solutions", "other specific / preferred technical solutions" and so forth means that a particular element (e.g., feature, structure, property, and / or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described element(s) may be combined in any suitable manner in the various embodiments.

[0032] In the present specification, the term “comprising” and any variant thereof are intended to cover non-excluding inclusions. For example, a process, method, or system, product or device comprising a series of steps or units are not limited to those listed steps or units, but may optionally further include steps or units not listed, or optionally further include other steps or units intrinsic to such process, method, product or device.

[0033] As used in the present specification, the term “polyol ester” refers to a compound having two or more hydroxyl groups wherein at least one of the hydroxyl groups is in the form of an ester.

[0034] As used in the present specification, the term “2K” or “two-component” refers to a composition comprising two components, each of which may also be a mixture of several compounds. The two components can be blended together if needed. And the two components may also be two independent packages that can be mixed on the spot for applications.

[0035] As used in the present specification, the term "acid value" refers to the mass of potassium hydroxide (KOH) in milligrams that is required to neutralize one gram of chemical substance, and is a measure of the number of carboxylic acid groups in a compound or in a mixture of compounds.

[0036] As used in the present specification, the term "hydroxyl value" refers to the mass of potassium hydroxide (KOH) in milligrams that is required to neutralize the acetic acid taken up on acetylation of one gram of a chemical substance that contains free hydroxyl groups, and is a measure of the content of free hydroxyl groups in a chemical substance.

[0037] As used in the present specification, the term "solid content" refers to a proportion of nonvolatile material contained in a coating, paint or other suspension, wherein the non-volatile material is the material left after the volatile solvent has vaporized. In the present specification, the term "(meth)acrylic resin" refers to a product obtained by polymerization of a monomer composition containing at least one monomer selected from acrylic acid and its esters, methacrylic acid and its esters.

[0038] A two-com clearcoat com

[0039] The present invention provides a two-component clearcoat composition comprising component I comprising

[0040] A) a hydroxyl-containing (meth)acrylic resin,

[0041] B) a melamine resin, and

[0042] C) a polyol ester which is a product obtained by reacting one or more selected from the group consisting of castor oil, castor oil monoglyceride, and castor oil diglyceride with a primary hydroxyl-containing polyol and optional polybasic acid or anhydride; and component II comprising

[0043] D) a polyisocyanate; wherein in the present invention, each component of the two-component clearcoat composition may be used singly, or in combination of two or more kinds thereof at a desired ratio.

[0044] In some embodiments of the present invention, the hydroxyl-containing reactive substance in the two-component clearcoat composition consists of the component A and the component C.

[0045] The clearcoat film obtained from the two-component clearcoat composition of the present invention has a molecular weight between crosslinked sites of 300 to 700 g / mol, preferably 350 to 500 g / mol. The clearcoat film obtained from the component I and the component II excels in hardness, resistance to petroleum products, water resistance and final appearance.

[0046] <A hydroxyl-containing (meth)acrylic resin>

[0047] The component A of the present invention is a hydroxyl-containing (meth)acrylic resin and is the main film-forming resin in the two-component clearcoat composition. In some embodiments of the present invention, the hydroxyl-containing (meth)acrylic resin has a glass transition temperature (i.e., Tg) of -50°C to 50°C, preferably, -45°C to 25°C. In order to better balance the desired properties, the present invention preferably uses a hydroxyl-containing (meth)acrylic resin with a low glass transition temperature, such as -45°C to -2°C; such a hydroxyl-containing (meth)acrylic resin combined with other components of the present invention, as compared with hydroxyl-containing (meth)acrylic resins having a glass transition temperature above 0°C, form clearcoat films which not only have good crosslinking density, hardness, water resistance, and resistance to petroleum products, but also have a better appearance.

[0048] In the present invention, the glass transition temperature of the hydroxyl-containing (meth)acrylic resin is a numerical value calculated using the equations below:

[0049] 1 / Tg(K) = Z(mi / Tgi) Tg(°C) = Tg(K) - 273

[0050] Tg: Glass transition temperature of the hydroxyl-containing (meth)acrylic resin mi: Mole fraction of monomer component i

[0051] Tgi: Glass transition temperature (K) of a homopolymer of the monomer component i.

[0052] In addition, the glass transition temperatures (K) of homopolymers of monomer component i may be found, for example, in Polymer Handbook (2nd Edition) (edited by J. Brandrup et al.). As for homopolymers of the monomer that are not described in this book, the glass transition temperature can be determined by synthesizing a homopolymer of the monomer with a weight average molecular weight of about 50,000 and measuring the glass transition temperature by differential scanning calorimetry.

[0053] In some embodiments of the present invention, one or more hydroxyl-containing (meth)acrylic resins with a glass transition temperature within the aforementioned range may be directly prepared and / or selected as the component A. In other embodiments of the present invention, two or more hydroxyl-containing (meth)acrylic resins with different glass transition temperatures may be mixed as the component A as long as the glass transition temperature of the mixed component A is within the aforementioned range. In a preferred embodiment of the present invention, the component A is obtained by mixing a hydroxyl-containing (meth)acrylic resin with a glass transition temperature of 12°C to 40°C and a hydroxyl-containing (meth)acrylic resin with a glass transition temperature of -40°C to 0°C.

[0054] In the present invention, there is no particular limitation on the types of hydroxyl groups in the hydroxyl-containing (meth)acrylic resin, which, for example, include secondary hydroxyl groups, primary hydroxyl groups, etc. In some embodiments of the present invention, the hydroxyl- containing (meth)acrylic resin has a hydroxyl value of 130 to 220 mg KOH / g. A hydroxyl value within this range can impart a good crosslinking density to the clearcoat film. If the hydroxyl value is overly low, there will be a tendency of a decrease in the hardness and resistance to petroleum products and water of the clearcoat film; if the hydroxyl value is overly high, it may possibly adversely affect the appearance. In some preferred embodiments of the present invention, a hydroxyl value of the hydroxyl-containing (meth)acrylic resin of 150 to 200 mg KOH / g, more preferably 155 to 180 mg KOH / g, is conducive to obtaining a clearcoat film with good crosslinking density, hardness, resistance to petroleum products and water and appearance.

[0055] In some embodiments of the present invention, the hydroxyl-containing (meth)acrylic resin has a weight average molecular weight (Mw) of 2,000 to 10,000 g / mol, preferably 2,000 to 8,000 g / mol, and more preferably 3,000 to 6,500 g / mol. Where the weight average molecular weight is within this range, the resulting clearcoat film can achieve both the advantages of good appearance and durability.

[0056] The hydroxyl-containing (meth)acrylic resin of the present invention can be obtained, for example, by copolymerization of a hydroxyl-containing polymerizable unsaturated monomer and other copolymerizable monomers. The hydroxyl-containing polymerizable unsaturated monomer refers to a compound having at least one hydroxyl group and at least one polymerizable unsaturated bond per molecule. In some embodiments of the present invention, examples of the hydroxyl-containing polymerizable unsaturated monomer include hydroxyalkyl esters of acrylic acid or of methacrylic acid, and non-limiting examples include hydroxyalkyl (meth)acrylate with an alkyl carbon number of C1-C10 (preferably C2-C8), such as one or more selected from the group consisting of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxypentyl (meth)acrylate, hydroxyhexyl (meth)acrylate, hydroxyheptyl (meth)acrylate, and hydroxyoctyl (meth)acrylate. In other embodiments of the present invention, the hydroxyl-containing polymerizable unsaturated monomer also includes one or more selected from the group consisting of N-methylol (meth)acrylamide, allyl alcohol, and (meth)acrylates with a hydroxyl-terminated polyoxyethylene chain. Preferably, the hydroxyl- containing polymerizable unsaturated monomer includes one or more selected from the group consisting of 2-hydroxyethyl acrylate (2-HEA), 2-hydroxyethyl methacrylate (2-HEMA), 3- hydroxypropyl acrylate (3-HPA), 3-hydroxypropyl methacrylate (3-HPMA), 4-hydroxybutyl acrylate (4-HBA), 4-hydroxybutyl methacrylate (4-HBMA), 1-hydroxyethyl acrylate (1-HEA), 1- hydroxyethyl methacrylate (1-HEMA), 1- or 2-hydroxypropyl acrylate (1- or 2-HPA), 1- or 2- hydroxypropyl methacrylate (1- or 2-HPMA), 1-, 2-, or 3-hydroxybutyl acrylate (1-, 2-, or 3-HBA) and 1-, 2- or 3-hydroxybutyl methacrylate (1-, 2- or 3-HBMA); more preferably, the hydroxyl- containing polymerizable unsaturated monomer includes one or more selected from the group consisting of 4-hydroxybutyl acrylate (4-HBA), 2-hydroxyethyl acrylate (2-HEA), 2-hydroxyethyl methacrylate (2-HEMA), 1-hydroxyethyl methacrylate (1-HEMA) and 2-hydroxypropyl methacrylate (2-HPMA).

[0057] In the present invention, there is no particular limitation on the other copolymerizable monomers that can be polymerized with the hydroxyl-containing polymerizable unsaturated monomer. Examples of the other copolymerizable monomers include C1-C20 alkyl (meth)acrylate, preferably C1-C10 alkyl (meth)acrylate, such as methyl (meth)acrylate, ethyl (meth)acrylate, n- propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, stearyl (meth)acrylate and cyclohexyl methacrylate (CHMA); aromatic ring-containing polymerizable unsaturated monomers such as styrene, a-methylstyrene, vinyl toluene, benzyl (meth)acrylate, etc.; carboxyl-containing polymerizable unsaturated monomers such as (meth)acrylic acid, maleic acid, crotonic acid, p-carboxyethyl acrylate etc.; alkoxysilyl- containing polymerizable unsaturated monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, y-(meth)acryloyloxypropyltrimethoxysilane etc.; vinyl compounds such as N- vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate etc.; nitrogencontaining polymerizable unsaturated monomers such as aminoalkyl (meth)acrylate, (meth)acrylamide or derivatives thereof; carbonyl-containing polymerizable unsaturated monomers such as acrolein, acetoacetoxyethyl methacrylate, formyl styrene, vinyl alkyl ketones having 4 to 7 carbon atoms, etc.; epoxy group-containing polymerizable unsaturated monomers such as glycidyl (meth)acrylate, p-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, allyl glycidyl ether, etc; (meth)acrylate having a polyoxyethylene chain with an alkoxy group at the molecular terminal; phosphoric acid group-containing polymerizable unsaturated monomers such as 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl acid phosphate, 2-methacryloyloxypropyl acid phosphate, etc; and fluoroalkyl-containing polymerizable unsaturated monomers such as perfluoroalkyl (meth)acrylate, fluoroolefin, etc. The other copolymerizable monomers may be used singly or in combination of two or more monomers to react with the hydroxyl-containing polymerizable unsaturated monomer in the polymerization. Preferably, the other copolymerizable monomers are one or more selected from monomers with a,p-unsaturated double bonds, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylic acid, and styrene.

[0058] The hydroxyl-containing (meth)acrylic resin of the present invention can be prepared and synthesized by a known method such as free radical polymerization. Examples of radical polymerization initiators include azo compounds, such as 2,2'-azobisisobutyronitrile, 2,2'-azobis- 2,4-dimethylvaleronitrile, etc.; organic peroxides, such as methyl ethyl ketone peroxide, cyclohexanone peroxide, 3,5,5-trimethylhexanone peroxide, benzoyl peroxide, diisopropyl peroxydicarbonate, tert-butyl peroxy-2-ethylhexanoate (TBPEH), tert-butyl peroxyneodecanoate, tert-butyl peroxylaurate, tert-butyl peroxybenzoate, tert-butyl isopropyl peroxycarbonate, etc. These radical polymerization initiators may be used singly or in combination of two or more types. The amount of the radical polymerization initiator is not particularly limited.

[0059] Examples of suitable organic solvents used for polymerization include aliphatic hydrocarbon solvents such as cyclohexane and ethylcyclohexane; aromatic hydrocarbon solvents such as toluene, xylene, ethylbenzene, and aromatic naphtha; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate and ethyl 3-ethoxypropionate; ether solvents such as dibutyl ether and tetrahydrofuran; and nitrogen-containing solvents such as acetonitrile, valeronitrile, and N,N-dimethylformamide. The organic solvent may be one type of solvent or a mixed solvent of two or more types. In some embodiments of the present invention, the hydroxyl-containing (meth)acrylic resin (based on the solid content) is used in an amount of 30 to 80 parts by weight, preferably 32 to 75 parts by weight, and more preferably 45 to 60 parts by weight, based on 100 parts by weight of the total solid content of the component I.

[0060] <Melamine resin >

[0061] The component B of the present invention is a melamine resin, which refers to a partially or fully methylolated melamine resin obtained by the reaction of melamine and an aldehyde. Nonlimiting examples of the aldehyde include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, and the like. In addition, those obtained by etherifying some or all of the methylol groups of the above methylolated melamine resins with a suitable alcohol can also be used. Non-limiting examples of the alcohol used for the etherification include one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, etc. In the present invention, the use of the melamine resin in combination with other components can not only improve the hardness and increase the crosslinking density of the clearcoat film, but also surprisingly enable adjustment of the rate of hardening of the system and solve the problems of resistance to petroleum products and control of the appearance of the clearcoat film.

[0062] The melamine resins are well known to those skilled in the art and are supplied as commercial products by many companies. Examples of suitable low molecular weight, fully etherified melamine resins are Cymel® 301 and 303 from Cytec, Luwipal® 066 from BASF, and Resimene® and Maprenal® MF from Solutia. Examples of suitable, relatively low molecular weight, highly etherified melamine resins containing free imino groups are Cymel® 325 and 327, Cymel® 202 and 203, Luwipal® 062, 018 and 014 from Cytec; Maprenal® MF 927 and 3950, VMF 3611, 3615 and 580, and Resimene® 717 and 718 from BASF; 9539 from Solutia; and Setamine® US 138 and US 146 from Akzo Resins. Examples of suitable relatively low molecular weight, partially etherified melamine resins are Luwipal® 012, 016, 015, 018 and 010 from BASF, Maprenal® MF 590 and 600 from Solutia and Setamine® US 132 and 134 from Akzo Resins. In the present invention, it is preferred to use a melamine resin etherified with a lower alcohol, in particular with methanol and / or ethanol and / or butanol as a crosslinking agent.

[0063] In some embodiments of the present invention, the melamine resin (based on the solid content) is used in an amount of 1 to 35 parts by weight, preferably 3 to 30 parts by weight, and more preferably, 5 to 20 parts by weight, based on 100 parts by weight of the total solid content of the component I.

[0064] < Polyol ester>

[0065] The component C of the present invention is a polyol ester, which is a product obtained by reacting one or more selected from the group consisting of castor oil, castor oil monoglyceride, castor oil diglyceride with a primary hydroxyl-containing polyol and optional polybasic acid or anhydride. Such polyol esters used in the present invention have higher hydroxyl values and reactivity than castor oil. In some embodiments of the present invention, the polyol esters of the present invention have excellent compatibility with the hydroxyl-containing (meth)acrylic resin, and the small molecules are not easily separated out from the system; these polyol esters, combined with other components of the present invention, can form a clearcoat film with high resistance to water and petroleum product, high hardness and good appearance.

[0066] Castor oil is a vegetable oil obtained from the seeds of the castor oil plant of the Euphorbiaceae family. It mainly comprises unsaturated fatty acids (mainly ricinoleic acid: CH3(CH2)5CH(OH) = CH(CH2)?COOH, which accounts for about 90%) and a small amount of triglycerides of saturated fatty acids (palmitic acid, stearic acid, etc.). The chemical structure of the main components of castor oil is shown as Formula (I):

[0067] Alcoholysis of castor oil with glycerol gives castor oil monoglyceride and castor oil diglyceride. Castor oil monoglyceride is also called glyceryl monoricinoleate (molecular formula: C21H40O5); castor oil diglyceride is also called glyceryl diricinoleate (molecular formula: C39H72O7).

[0068] In some embodiments of the present invention, the polyol ester of the present invention is obtained by reacting one or more of castor oil, castor oil monoglyceride and castor oil diglyceride with a primary hydroxyl-containing polyol; the reaction is a transesterification reaction. Through this transesterification reaction, the polyol ester of the present invention which contains primary hydroxyl groups and is based on ricinoleic acid and a primary hydroxyl- containing polyol is obtained. The primary hydroxyl group refers to a hydroxyl group connected to a primary carbon atom. Primary carbon atoms are carbon atoms directly connected to only one carbon atom and the carbon atoms in methane. Non-limiting examples of the primary hydroxyl-containing polyol in the present invention include one or more of ethylene glycol, propylene glycol, glycerol, trimethylolpropane, bis(trimethylolpropane), trihydroxyethylpropane, bis(trihydroxyethylpropane), pentaerythritol, bis(pentaerythritol), diglycerol, xylitol, sorbitol, galactitol, sucrose, polypropylene glycol, and polyethylene glycol. In some embodiments of the present invention, the primary hydroxyl-containing polyol is preferably a polyol containing more than 4 carbon atoms and more than two primary hydroxyl groups. Further preferably, in order to obtain better reactivity while considering the compatibility with other components in the system, the primary hydroxyl-containing polyol is one or more selected from pentaerythritol, trimethylolpropane, and sorbitol, and in some specific embodiments, may simultaneously contain a small amount of one or both of polypropylene glycol and polyethylene glycol. The conditions for the transesterification reaction can be conventional reaction conditions in the art, and it is preferred to use a catalyst to promote the reaction. The catalyst includes one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium methoxide, lead oxide, zinc oxide, and tetrabutyl titanate; preferably the catalyst is selected from tetrabutyl titanate. In some specific embodiments of the present invention, the transesterification reaction can be carried out under the protection of an inert gas at a reaction temperature of 140-250°C for 2-5 hours.

[0069] In other specific embodiments of the present invention, the polyol ester of the present invention is a product obtained by reacting one or more of castor oil, castor oil monoglyceride and castor oil diglyceride with a primary hydroxyl-containing polyol and polybasic acid or anhydride. By adding polybasic acid or anhydride as a modifier, the reaction system involves not only the esterification of polybasic acid or anhydride with a primary hydroxyl-containing polyol, but also the esterification of castor oil monoglyceride and castor oil diglyceride with polybasic acid or anhydride, and the transesterification of primary hydroxyl-containing polyol with castor oil. The polyol ester synthesized by this method is a ricinoleic acid-based polyester polyol, which contains hydroxyl groups, ester groups and long-chain alkyl groups, and has good compatibility with the hydroxyl-containing (meth)acrylic resin of the present invention. In order to obtain better reactivity, preferably, the polyol ester of the present invention contains primary hydroxyl groups. The polybasic acid or anhydride is preferably a polybasic acid or anhydride with C4-C12 carbon atoms. Non-limiting examples of the polybasic acid include one or more of glutaric acid, adipic acid, phthalic acid, and isophthalic acid. In some preferred embodiments of the present invention, the anhydride is an anhydride with a cyclic structure, such as one or more of phthalic anhydride, hexahydrophthalic anhydride, and o-phthalic anhydride. In some embodiments of the present invention, the polybasic acid or anhydride can be added to the reaction system together with one or more of castor oil, castor oil monoglyceride and castor oil diglyceride, and a primary hydroxyl-containing polyol for a polycondensation reaction. In other embodiments of the present invention, one or more of castor oil, castor oil monoglyceride and castor oil diglyceride are first subjected to a transesterification reaction with a primary hydroxyl-containing polyol to obtain a product of alcoholysis of castor oil, and then a polybasic acid or anhydride is added to carry out a polycondensation reaction. The transesterification reaction is as described above. The conditions for the polycondensation reaction can also be conventional reaction conditions in the art. It is preferred to use a catalyst to promote the reaction. The catalyst includes one or more of tetrabutyl titanate, tetraisopropyl titanate, tetraisobutyl titanate, tin tetrachloride and diethylamine. Preferably, the catalyst is selected from tetrabutyl titanate. In some specific embodiments of the present invention, the polycondensation reaction can be carried out under the protection of an inert gas at a reaction temperature of 140 to 250°C for 2 to 5 hours.

[0070] In some embodiments of the present invention, the polyol ester of the present invention has a hydroxyl value of 180 to 500 mg KOH / g. If the hydroxyl value is too low, the reactivity will be low, and the clearcoat layer will cure slowly and shrink easily; if the hydroxyl value is too high, it will easily lead to insufficient reaction of hydroxyl groups, which will adversely affect the water resistance of the clearcoat film and may also cause cracking of the clearcoat film. In order to obtain a clearcoat film with various excellent properties, the hydroxyl value of the polyol ester is further preferably 200 to 450 mg KOH / g. In order to make the clearcoat film achieve higher hardness, and resistance to petroleum products and water and better appearance, the hydroxyl value of the polyol ester is more preferably 240 to 400 mg KOH / g.

[0071] In some embodiments of the present invention, the polyol ester of the present invention has a weight average molecular weight of 1 ,000 to 3,000 g / mol, and further preferably 1 ,200 to 2,800 g / mol.

[0072] In some embodiments of the present invention, in order to improve the compatibility with other components of the present invention, the polyol ester of the present invention has a polymer dispersity index (PDI) of above 1.5, further preferably above 1.8, and more preferably above 2.0.

[0073] In some embodiments of the present invention, the polyol ester is present in an amount of 5 to 35 parts by weight, based on 100 parts by weight of the total solid content of the component I. In some specific embodiments of the present invention, in order to obtain a clearcoat film with better resistance to petroleum products and water and / or better appearance, the polyol ester preferably is present in an amount of 8 to 20 parts by weight.

[0074] <Polyisocyanate>

[0075] The component D of the present invention is a polyisocyanate, which acts as a crosslinking agent. The polyisocyanate is a collective term for compounds containing two or more isocyanate groups (this is understood by the person skilled in the art to mean free isocyanate groups of the general structure -N=C=O) in the molecule and includes monomeric polyisocyanates and / or oligomeric polyisocyanates. The simplest and most important representatives of these polyisocyanates are diisocyanates. They have the general structure O=C=N-R-N=C=O where R typically represents aliphatic, cycloaliphatic and / or aromatic radicals. Examples of the polyisocyanate of the present invention include aliphatic polyisocyanates, cycloaliphatic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates and derivatives of these polyisocyanates. These may be used individually or in combination of two or more types. Examples of the polyisocyanate of the present invention include one or more of propylene diisocyanate, butylene diisocyanate, hexylene diisocyanate, pentylene diisocyanate, hexamethylene diisocyanate (HDI), 2,2,4- and / or 2,4,4-trimethylhexamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, 1,8-diisocyanato-4-(isocyanatomethyl)octane, dimer fatty acid diisocyanate, methyl 2,6- diisocyanatohexanoate, 1 ,3-cyclopentene diisocyanate, 1 ,4-cyclohexane diisocyanate, 1,3- cyclohexane diisocyanate, isophorone diisocyanate, methyl-2,4-cyclohexane diisocyanate, 1,4- or 1,3-bis(isocyanatomethyl)cyclohexane, methyl-2,6-cyclohexane diisocyanate, diphenylmethane diisocyanate (MDI), polymeric MDI, 3,3'-dimethyldiphenyl diisocyanate, m- tetramethylxylene diisocyanate, 1,3-phenylene diisocyanate, 1 ,4-phenylene diisocyanate, 4,4'- diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4- or 2,6-toluene diisocyanate, 4,4'- toluidine diisocyanate, biuret forms of these compounds and oligomeric isocyanates. In a preferred embodiment, the polyisocyanate is an aliphatic polyisocyanate and / or a cycloaliphatic polyisocyanate, such as hexamethylene diisocyanate (HDI) and / or isophorone diisocyanate (I PDI). In a preferred embodiment, the polyisocyanate is an oligomeric isocyanate compound, such as an isocyanate dimer, an isocyanate trimer, etc. In a specific embodiment, the polyisocyanate is a trimer of HDI. The polyisocyanate can be obtained by reacting an excess isocyanate with water or a polyol (such as ethylene glycol, propylene glycol, 1 ,3-butanediol, hexanediol, etc.) or by reacting an isocyanate with itself. The polyisocyanates used in the present invention are commercially available. Commercial suppliers include Bayer, BASF and Asahi Kasei Corporation, and suitable polyisocyanates are sold under trade names such as Desmodur, Duranate, Tolonate and Basonate.

[0076] In some embodiments of the present invention, the polyisocyanate has an NCO content of preferably 10%-30%, further preferably 15%-25%.

[0077] In some preferred embodiments of the present invention, the polyisocyanate of the present invention is an unblocked polyisocyanate. Compared with blocked polyisocyanates, the use of unblocked polyisocyanates of the present invention contributes to the achievement of low- temperature baking.

[0078] The content of the polyisocyanate is not particularly limited. From the perspective of better promoting the curing reaction, the molar equivalent ratio (NCO / OH) of the isocyanate groups of the polyisocyanate to the total hydroxyl groups of the component A and the component C of the present invention is (0.8-1.5): 1 , preferably (0.9-1.3): 1.

[0079] <Other components>

[0080] The two-component clearcoat composition of the present invention further comprises a solvent and other components that are optionally co-used as needed, such as curing catalysts, rheology control agents, ultraviolet absorbers, light stabilizers, pigments, defoamers, leveling agents, antioxidants, film-forming agents, surface conditioners, etc.

[0081] The two-component clearcoat composition of the present invention may be water-based or organic solvent-based. Examples of organic solvents include one or more of acetone, toluene, xylene, ethyl acetate, butyl acetate, isopropyl alcohol, n-butanol, 2-ethylhexanol and ethyl 3- ethoxypropionate. Water and organic solvents can be used in combination. The water is not particularly limited and may be ion exchange water. In some specific embodiments of the present invention, the two-component clearcoat composition is organic solvent-based.

[0082] In some embodiments of the present invention, the two-component clearcoat composition of the present invention may optionally comprise a curing catalyst. The curing catalyst includes carboxylates of tin, zinc, titanium, lead, iron, bismuth, barium and zirconium; non-metallic catalysts such as tertiary amines, 1,4-diazabicyclo[2.2.2]octane (DABCO) and diazabicycloundecene; phosphorus-containing catalysts such as substituted phosphonic acid monoesters, phosphonic acid diesters, diphosphonic acid diesters (preferably selected from acyclic phosphonic acid diesters, cyclic phosphonic acid diesters, acyclic diphosphonic acid diesters, and cyclic diphosphonic acid diesters) and / or amine adducts thereof (preferably amine-blocked phosphoric acid ethylhexyl esters and amine-blocked phosphoric acid phenyl esters); sulfonic acid catalysts such as dodecylbenzenesulfonic acid (DDBSA), dinonylnaphthalene disulfonic acid (DNNSA) and p-toluenesulfonic acid (p-TSA); and blocked sulfonic acid catalysts such as blocked DDBSA, blocked DNNSA or blocked p-TSA. Sulfonic acid catalysts and phosphorus-containing catalysts are preferably used to ensure the stability and durability of the coating system. In some preferred embodiments of the present invention, an amine-blocked phosphoric acid catalyst is preferred as it shows high catalytic efficiency and stable and controllable effects on the appearance and performance of the clearcoat film. The curing catalyst is used in an amount of 0.01 to 2 parts by weight, preferably 0.05 to 1 part by weight, based on 100 parts by weight of the total solid content of the component I.

[0083] In some embodiments of the present invention, the two-component clearcoat composition of the present invention may optionally comprise a rheology control agent. Conventionally known rheology control agents can be used, and examples thereof include clay minerals (for example, metal silicates and montmorillonites), (meth)acrylics, polyolefins (for example, polyethylene, polypropylene, etc.), amides (higher fatty acid amides, polyamides, etc.), polycarboxylic acids, cellulose (including various derivatives such as nitrocellulose, acetyl cellulose, cellulose ether, etc.), urethane (a polymer and / or an oligomer or the like having a urethane structure in the molecule), and urea (a polymer and / or an oligomer having a urea structure in the molecule). The rheology control agent (based on the solid content) is used in an amount of 8 to 35 parts by weight, preferably 10 to 30 parts by weight, based on 100 parts by weight of the total solid content of the component I.

[0084] In some embodiments of the present invention, the two-component clearcoat composition of the present invention may further optionally comprise conventionally known ultraviolet absorbers, such as benzotriazole absorbers, triazine absorbers, salicylic acid absorbents, benzophenone absorbers, etc. These may be used individually or in combination of two or more types.

[0085] In some embodiments of the present invention, the two-component clearcoat composition of the present invention may further optionally comprise conventionally known light stabilizers such as hindered amine light stabilizers and the like. Examples of hindered amine light stabilizers include acylated hindered amines, amino ether-based hindered amines, and the like.

[0086] In some embodiments of the present invention, the two-component clearcoat composition of the present invention may further optionally comprise pigments such as colorants, antirust pigments, etc., which may be contained in an amount not substantially detrimental to the transparency of the formed coating film.

[0087] Those skilled in the art can choose to add other adjuvants such as defoamers, leveling agents, antioxidants, film-forming agents, surface conditioners, etc. as needed, and can determine the amount thereof according to actual applications. In some embodiments of the present invention, the weight ratio (based on solid content) of the component I and the component II of the two-component clearcoat composition of the present invention is (1-5): 1 , preferably (1.5-3.5):1.

[0088] Articles coated with the two-component clearcoat composition

[0089] Application of the two-component clearcoat composition of the present invention may be carried out by using any method known in the art, such as an air sprayer, an electrostatic air sprayer, a roll coater, a flow coater or a dip coater or a brush coater or a bar coater or an applicator. Spray coating is preferred in the present invention.

[0090] There is no limit to the thickness of the clearcoat film obtained by applying the two-component clearcoat composition of the present invention, but the thickness of the dried clearcoat film is preferably in the range of 10 pm to 150 pm, more preferably in the range of 30 pm to 60 pm. The clearcoat film obtained from the two-component clearcoat composition of the present invention has a molecular weight between crosslinked sites of 300 to 700 g / mol. The molecular weight between crosslinked sites (MC) refers to the average molecular weight of a chain segment between two adjacent crosslinked sites. The smaller the average molecular weight between two adjacent crosslinked sites is, the more crosslinked sites there are and the greater the crosslinking density is. In the present invention, if the molecular weight between crosslinked sites is too low, the mechanical properties such as tensile properties of the coating film will be affected, and cracking will easily occur during the hardening process, resulting in poor appearance of the clearcoat film; if the molecular weight between crosslinked sites is too high, the crosslinking density will be insufficient, thereby resulting in a decrease in the hardness, and resistance to petroleum products and water. In some embodiments of the present invention, in order to balance the various properties required for the clearcoat film, the molecular weight between crosslinked sites is preferably 310 to 500 g / mol, and further preferably 350 to 500 g / mol.

[0091] Examples of substrates to be coated with the two-component clearcoat composition of the present invention include inorganic and organic materials such as metal, wood, glass, cloth, plastic, foam, elastomer, paper, ceramic, concrete, gypsum board, etc., and metal substrates are preferred. These substrate materials may or may not undergo pretreatment.

[0092] The present invention also provides articles coated with the two-component clearcoat composition of the present invention. Examples of coated articles obtained or obtainable include metal articles, structural materials, wood articles, plastic articles, rubber articles, paper articles, ceramic articles, glass articles, etc., and more specifically include automobiles and automobile parts (for example, vehicle bodies, bumpers, spoilers, mirrors, wheels, interior decorative parts and the like, which are made of a variety of materials), metal sheets such as steel sheets, bicycles, bicycle parts, materials used on roads (for example guard rails, traffic signs, sounddeadening walls and the like), materials used in tunnels (for example side wall panels and the like), ships, railway rolling stock, aircraft, furniture, musical instruments, household electrical appliance, building materials, containers, office accessories, sports accessories, toys and the like. Preferred coated articles of the present invention are automobiles and automobile parts.

[0093] A method of forming a multilayer coating film

[0094] The present invention further provides a method of forming a multilayer coating film, comprising

[0095] 1) optionally producing a cured first coat on a substrate;

[0096] 2) producing at least one basecoat layer on the coat obtained in step 1) by applying one or more identical or different basecoat materials; and

[0097] 3) producing at least one clearcoat layer on the topmost basecoat layer by applying one or more identical or different clearcoat materials; wherein at least one of the clearcoat materials is the two-component clearcoat composition according to the present invention; the basecoat layer and the clearcoat layer are cured separately or jointly by baking; and preferably, the basecoat layer and the clearcoat layer are jointly cured by baking after step 3).

[0098] In this method, a multilayer coating film system is built on a substrate. According to the present invention, the substrate is preferably selected from the group consisting of metal substrates, plastics, glass and ceramics, and more particularly selected from metal substrates. The metal substrates mainly include substrates containing or consisting of, for example, iron, aluminum, copper, zinc, magnesium and alloys thereof and steel in any of a variety of forms and compositions. Particularly preferred substrates are steel substrates, in particular those typical steel substrates used in the field of automobile industry. Prior to step 1) of the method of the present invention, the metal substrate can be pretreated in a conventional manner, for example, by washing. Suitable plastic substrates are in principle substrates comprising or consisting of (i) polar plastics, such as polycarbonate, polyamide, polystyrene, styrene copolymers, polyesters, polyphenyl ethers, and blends of these plastics, (ii) reactive plastics, such as PUR-RIM, SMC and BMC, and (iii) polyolefin substrates of the polyethylene and polypropylene types with a high rubber content, such as PP-EPDM, and also surface-activated polyolefin substrates. The plastics may also be fiber-reinforced, more particularly using carbon fibers and / or metal fibers. Before step (1) of the method of the present invention, the plastic substrate may also be pretreated, more particularly by cleaning in order to improve the adhesion of the first coat. Moreover, it is also possible to use those which contain both metallic and plastic fractions as substrates. Substrates of this kind are, for example, vehicle bodies containing plastic parts.

[0099] Step 1) In step 1) of this method, a cured first coat may be produced on a substrate by applying a coating material to the substrate and optionally subsequently curing.

[0100] The coating material in step 1) may be an electrophoretic coating material. The first coat is preferably a cured electrocoat with a thickness in the range of, for example, 8 pm to 20 pm.

[0101] Step 2)

[0102] The concept of basecoat materials in the present invention also includes primer materials. The basecoat material in step 2) is preferably a water-based colored basecoat material. Suitable water-based colored basecoat materials are commercially available, for example from BASF N- 3000 N6. The basecoat materials corresponding to respective basecoat layers may be the same or different. Two or more basecoat layers may be prepared using the same basecoat material, or one or more basecoat layers may be prepared using one or more other basecoat materials. The basecoat layer may be cured separately or cured jointly with the clearcoat layer by baking. In some embodiments of the present invention, the basecoat layer is cured separately at a baking temperature (or curing temperature) of 100°C to 250°C, preferably 110°C to 160°C, for 10 to 45 min. In other embodiments of the present invention, the basecoat layer is jointly cured with the clearcoat layer by baking, in step 2), the basecoat layer is preferably not exposed to a temperature above 100°C for more than 1 minute, and particularly preferably, in step 2) the basecoat layer is not exposed to a temperature above 100°C at all; in a specific embodiment of the present invention, a low temperature, such as 60 to 80°C, is used to flashdry the basecoat material. Each basecoat film obtained after curing has a thickness greater than 4 pm. Preferably, the thickness of the basecoat film obtained after curing is in the range of 12 pm to 18 pm.

[0103] Step 3)

[0104] At least one of the clearcoat materials in step 3) is the two-component clearcoat composition of the present invention. In some embodiments of the present invention, the clearcoat materials may also include other different clearcoat materials, but in order to ensure the performance of the coating film, it is preferred to use the two-component clearcoat composition of the present invention as the top clearcoat material. It is further preferred that the clearcoat layer of the present invention only comprises a layer obtained by applying the two-component clearcoat composition of the present invention. The clearcoat layer can be cured alone or cured jointly with the basecoat layer by baking. In some embodiments of the present invention, the clearcoat layer is cured separately at a baking temperature (or curing temperature) of 80°C to 160°C, preferably 110°C to 130°C, for 10 to 45 min. In other embodiments of the present invention, the basecoat layer and the clearcoat layer are jointly cured by baking at a baking temperature (or curing temperature) of 110°C to 160°C for 10 to 45 minutes. In some preferred embodiments of the present invention, low-temperature baking can be realized in the present invention. For the both processes of separate curing and joint bake-curing, the baking temperature is preferably 110°C to 130°C. Even if the curing temperature is low, the multilayer coating film obtained by the present invention can still have good comprehensive properties.

[0105] Each clearcoat film obtained after curing has a thickness of 15 pm to 80 pm, preferably 20 pm to 65 pm, particularly preferably 30 pm to 60 pm.

[0106] The two-component clearcoat composition of the present invention can be suitable for different coating processes and has wide applicability.

[0107] In another aspect, the present invention further provides a multilayer coating film prepared by the method of forming a multilayer coating film according to the present invention. The obtained multilayer coating film not only has excellent finished product appearance but also has high hardness and resistance to petroleum products and water. In some preferred embodiments of the present invention, the multilayer coating film comprises one or two basecoat films and only one clearcoat film.

[0108] Embodiments

[0109] The following embodiments serve to illustrate the present invention in more detail.

[0110] Embodiment 1

[0111] A two-component clearcoat composition comprising component I comprising

[0112] A) a hydroxyl-containing (meth)acrylic resin,

[0113] B) a melamine resin, and

[0114] C) a polyol ester which is a product obtained by reacting one or more selected from the group consisting of castor oil, castor oil monoglyceride, and castor oil diglyceride with a primary hydroxyl-containing polyol and optional polybasic acid or anhydride; and component II comprising

[0115] D) a polyisocyanate, wherein a clearcoat film obtained from the two-component clearcoat composition has a molecular weight between crosslinked sites of 300 to 700 g / mol, preferably 350 to 500 g / mol.

[0116] Embodiment 2 The two-component clearcoat composition according to Embodiment 1 , wherein the component A has a glass transition temperature of -50°C to 50°C, preferably -45°C to 25°C, more preferably -40°C to -2°C.

[0117] Embodiment 3

[0118] The two-component clearcoat composition according to Embodiment 1 or 2, wherein the component A has a hydroxyl value of 130 to 220 mg KOH / g, preferably 150 to 200 mg KOH / g.

[0119] Embodiment 4

[0120] The two-component clearcoat composition according to any one of Embodiments 1-3, wherein the component C has a hydroxyl value of 180 to 500 mg KOH / g, preferably 200 to 450 mg KOH / g, more preferably 240 to 400 mg KOH / g.

[0121] Embodiment 5

[0122] The two-component clearcoat composition according to any one of Embodiments 1-4, wherein the component C has a weight average molecular weight of 1 ,000 to 3,000 g / mol.

[0123] Embodiment 6

[0124] The two-component clearcoat composition according to any one of Embodiments 1-5, wherein the component C has a polymer dispersity index (PDI) of above 1.5.

[0125] Embodiment 7

[0126] The two-component clearcoat composition according to any one of Embodiments 1-6, wherein the primary hydroxyl-containing polyol is a polyol containing more than 4 carbon atoms and more than two primary hydroxyl groups.

[0127] Embodiment 8

[0128] The two-component clearcoat composition according to any one of Embodiments 1-7, wherein the molar equivalent ratio (NCO / OH) of the isocyanate groups of the component D to the total hydroxyl groups of the component A and the component C is (0.8-1.5):1, preferably (0.9-1.3): 1.

[0129] Embodiment 9

[0130] The two-component clearcoat composition according to any one of Embodiments 1-8, wherein the component C is present in an amount of 5 to 35 parts by weight, preferably 8 to 20 parts by weight, based on 100 parts by weight of the total solid content of the component I.

[0131] Embodiment 10

[0132] The two-component clearcoat composition according to any one of Embodiments 1-9, wherein the component B is present in an amount of 1 to 35 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the total solid content of the component I.

[0133] Embodiment 11

[0134] An article coated with the two-component clearcoat composition according to any one of Embodiments 1-10.

[0135] Embodiment 12

[0136] A method of forming a multilayer coating film, comprising

[0137] 1) optionally producing a cured first coat on a substrate;

[0138] 2) producing at least one basecoat layer on the coat obtained in step 1) by applying one or more identical or different basecoat materials; and

[0139] 3) producing at least one clearcoat layer on the topmost basecoat layer by applying one or more identical or different clearcoat materials; wherein at least one of the clearcoat materials is the two-component clearcoat composition according to any one of Embodiments 1-10; the basecoat layer and the clearcoat layer are cured separately or jointly by baking; and preferably, the basecoat layer and the clearcoat layer are jointly cured by baking after step 3).

[0140] Embodiment 13

[0141] The method of forming a multilayer coating film according to Embodiment 12, wherein the temperature for baking the clearcoat layer is 80°C to 160°C; and preferably, the temperature for baking the clearcoat layer is 110°C to 130°C.

[0142] Embodiment 14

[0143] The method of forming a multilayer coating film according to Embodiment 11 or 12, wherein the basecoat material is a water-based colored basecoat material.

[0144] Embodiment 15

[0145] A multilayer coating film prepared by the method of forming a multilayer coating film according to any one of Embodiments 11-14.

[0146] The present invention will be explained in more detail below with reference to the Examples, but it should be understood that the present invention is not limited thereto.

[0147] In the Examples, the coating film thickness refers to the thickness of the cured dry film.

[0148] Test methods:

[0149] Solid content (%)

[0150] The solid content was determined according to DIN EN ISO 3251 (date: June, 2008).

[0151] One gram of the sample was weighed into a pre-dried aluminum foil, dried in a drying oven at 125°C for 60 minutes, cooled in a desiccator, and then reweighed. The residue, relative to the total amount of the sample employed, corresponds to the solid content or non-volatile fraction.

[0152] Solid mass = sample mass x solid content (%)

[0153] Dry film thickness

[0154] The dry film thickness was determined according to DIN EN ISO 2808: 2007-05 (date: May, 2007), method 12A - magnetic induction gauge, using the FMP20 instrument from Helmut- Fischer Corporation.

[0155] Acid value and hydroxyl value

[0156] The acid value was determined according to DIN EN ISO 2114 (date: June, 2002). The hydroxyl value was determined according to DIN53240-2 (date: November, 2007). Molecular weight

[0157] The number average molecular weight, weight average molecular weight, and PDI were determined and calculated according to DIN 55672-1 (date: August, 2007).

[0158] Glass transition temperature (Tg)

[0159] The glass transition temperature was calculated using the method described above in the specification of the present invention.

[0160] Synthesis Examples 1-6

[0161] To a four-necked flask provided with a stirrer, a thermometer, a cooling tube and a nitrogen gas inlet, 60 parts by weight of a solvent (Ac-1) were added under nitrogen gas, and the temperature therein was raised to 155°C. After the temperature reached 155°C, monomers (Am) and 3 parts by weight of a polymerization initiator (Ab) were added dropwise into the flask over two hours, wherein the composition and ratios of the monomers (Am) are shown in Table 1. Then, the product was aged at 155°C for three hours while nitrogen gas was introduced, and then the product was cooled to room temperature and was diluted with a solvent (Ac-2), thereby obtaining acrylic resins (A) having a solid content of 60%. The property parameters of the obtained acrylic resins (A) are also shown in Table 1.

[0162] Table 1 wherein,

[0163] St: styrene;

[0164] 2-EHA: 2-ethylhexyl acrylate;

[0165] CHMA: cyclohexyl methacrylate;

[0166] MMA: methyl methacrylate;

[0167] AA: acrylic acid;

[0168] HEMA: hydroxyethyl methacrylate;

[0169] 4-HBA: 4-hydroxybutyl acrylate; solvent (Ac-1): butyl acetate; solvent (Ac-2): ethyl 3-ethoxypropionate; polymerization initiator (Ab): tert-butyl peroxy (2-ethylhexanoate).

[0170] Examples of preparation and synthesis of polyol esters (C):

[0171] Synthesis Examples 7-8

[0172] To a four-necked flask provided with a heater, a stirrer, a thermometer, a reflux condenser and a water separator, castor oil (C1), primary hydroxyl-containing polyol (C2), and the catalyst tetrabutyl titanate (the amount of addition thereof was 0.5 wt% of the mass of castor oil) at molar ratios shown in Table 2 were added. The temperature therein was raised to 220°C with stirring under nitrogen gas, kept constant for three hours and reduced gradually to 150°C to obtain polyol esters of the present invention (C-1 to C-2). Synthesis Examples 9-11

[0173] To a four-necked flask provided with a heater, a stirrer, a thermometer, a reflux condenser and a water separator, castor oil (C1) and primary hydroxyl-containing polyol (C2) at molar ratios

[0174] 5 shown in Table 2 below were added, and polybasic acid or anhydride (C3) was added according to the molar ratio as shown in Table 2. The temperature was raised to 220°C at a rate of 20°C / hour. After 3 hours of heat preservation, when the acid value was about 10 mg KOH / g, the temperature was reduced to 180°C and the flask was vacuumized. When the acid value was less than or equal to 1.5 mg KOH / g, polyol esters of the present invention (C-3 to C-5) were 0 obtained.

[0175] Synthesis Example 12

[0176] Castor oil (C1) served as a comparative example to be used (C-6). 5

[0177] The parameters of the obtained polyol esters (C-1 to C-5) and castor oil (C-6) are also shown in Table 2.

[0178] Table 2 0 wherein castor oil (C1): manufactured by Itoh Oil Chemicals Co., Ltd., refined castor oil, weight average molecular weight: 1,510 g / mol; 5 primary hydroxyl-containing polyol (C2): primary hydroxyl-containing polyol (C2-1): pentaerythritol, weight average molecular weight: 136 g / mol, primary hydroxyl-containing polyol (C2-2): trimethylolpropane, weight average molecular weight: 0 134 g / mol, primary hydroxyl-containing polyol (C2-3): glycerol, weight average molecular weight: 92 g / mol, and primary hydroxyl-containing polyol (C2-4): sorbitol, weight average molecular weight: 182 g / mol; polybasic acid or anhydride (C3): polybasic acid or anhydride (C3-1): phthalic anhydride, weight average molecular weight: 148 g / mol, and polybasic acid or anhydride (C3-2): hexahydrophthalic anhydride, weight average molecular weight: 154 g / mol.

[0179] Preparation of two-component clearcoat compositions

[0180] Examples 1-11 and Comparative Examples 1-4

[0181] Those hydroxyl-containing (meth)acrylic resins (A) (all having a solid content of 60%) and polyol esters (C) obtained in the above Preparation and Synthesis Examples 1-12 and other starting materials as given in Table 3 (melamine (B), a curing catalyst (E), a rheology control agent (F)) were mixed at the mixing ratios as shown in Table 3 using a rotary blade-type agitator to obtain components I; and polyisocyanates (D) were prepared according to the amounts given in Table 3 so as to obtain components II, thereby obtaining two-component clearcoat compositions (CC- 1 to CC-15).

[0182] The component I and the component II of each of CC-1 to CC-15 were mixed and the mixtures were stirred evenly. The viscosity of the mixtures was adjusted by addition of ethyl acetate to 25 seconds using Ford cup No. 4 at 20°C. Then various test plates were prepared according to the following conditions.

[0183] Preparation of PP plates for use in terms of molecular weight (MC) between crosslinked sites

[0184] Test pieces with a width of 10 mm and a length of 70 mm were manufactured and subjected to dynamic viscoelasticity measurement (storage elastic modulus E) under the following conditions, and the MC was measured according to Equation (II): equipment: the dynamic viscoelasticity measurement equipment RSA3; measurement mode: resonance-free forced vibration method; heating rate: 3.0°C / min; interval of measurement: 12 / min; frequency: 1.0 Hz; temperature range: -50 to 200°C;

[0185] Equation (II): MC=(293x1.05) / (log((E / 3),10)-7).

[0186] The evaluation standards were as follows:

[0187] O: 350 to 500 g / mol

[0188] A: 300 to 349 or 500 to 700 g / mol

[0189] X : Below 299 or above 701 for use in terms of

[0190] A zinc phosphate-treated low carbon steel plate was coated with cationic electrodeposition coating material (product name “CathoGuard 800", produced by BASF Coatings) by electrostatic deposition and baked at 175°C for 25 minutes to obtain an electrodeposition coated plate (referred to as “electrodeposited plate") with a dry film thickness of 20 pm.

[0191] Subsequently, the electrodeposited plate was coated with a first basecoat material (Waterborne Gray Basecoat / Primer, produced by BASF Coatings) using a rotary atomization type bell coater (product name “Metallic bell G1-COPES bell”, manufactured by ABB) at a temperature of 25°C and a relative humidity of 75% so that the dry film thickness was 15 pm. The obtained plate was then allowed to stand at room temperature for 5 minutes and then coated with a second basecoat material (Lava Red waterborne Glitter Basecoat, produced by BASF Coatings) so that the dry film thickness was 12 pm. The plate was then allowed to stand for 5 minutes at room temperature and then subjected to flash evaporation at 80°C for 10 minutes. After allowing the plate to cool to 25°C, a clearcoat material (selected from one of CC-1 to CC-15 respectively) was applied to the plate to provide a dry film thickness of 45 pm. Following this coating, the plate was allowed to stand at room temperature for 10 minutes and then baked horizontally at 140°C for 30 minutes so as to obtain test plates with multilayer coating films (Example 1-11 and Comparative Example 1-4).

[0192] The basecoat materials, the process of spray coating and the baking temperatures were changed:

[0193] A zinc phosphate-treated low carbon steel plate was coated with cationic electrodeposition coating material (product name “CathoGuard 800", produced by BASF Coatings) by electrostatic deposition and baked at 175°C for 25 minutes to obtain an electrodeposition coated plate (referred to as “electrodeposited plate") with a dry film thickness of 20 pm.

[0194] The electrodeposited plate was coated with a first basecoat material (Waterborne White Basecoat / Primer, produced by BASF Coatings) using a rotary atomization type bell coater (product name “Metallic bell G1-COPES bell”, manufactured by ABB) at a temperature of 25°C and a relative humidity of 75% so that the dry film thickness was 15 pm. The obtained plate was then allowed to stand at room temperature for 10 minutes, baked horizontally at 140°C for 30 minutes, and then coated with a second basecoat material (Bright White Waterborne Basecoat, produced by BASF Coatings) so that the dry film thickness was 12 pm. The plate was then allowed to stand for 10 minutes and then baked horizontally at 140°C for 30 minutes. After allowing the plate to cool to 25°C, a clearcoat material (selected from one of CC-1, CC-7, CC-13 and CC-15 respectively) was applied to the plate to provide a dry film thickness of 45 pm. Following this coating, the plate was allowed to stand at room temperature for 10 minutes and then baked horizontally at 110°C for 30 minutes so as to obtain test plates with multilayer coating films that correspond to Examples 12 and 13 and Comparative Examples 5 and 6.

[0195] The obtained test plates were subjected to the following coating film performance tests, results of which are shown in Table 3.

[0196] Hardness:

[0197] The hardness was evaluated according to pencil hardness with reference to the GB / T 6739- 2006 standard.

[0198] The hardness was evaluated according to the following standards:

[0199] O: HB and above

[0200] A: B

[0201] X : 2B and below

[0202] Appearance (LW and SW):

[0203] The appearance of dried and cured clearcoat was evaluated by its surface texture, which was measured by a BYK wave-scan device. Surface texture was a mixture of various textures, ranging from very fine to very coarse. BYK wave-scan dually measured the surface textures at different scale levels, which was differentiated into six categories, identified by wavelength (Du, Wa, Wb, Wc, Wd, We). Based on these measured data, LW and SWwere calculated by the equipment and denote the appearance level of the paint. Lower LW and SW values represent a better performance in appearance. LWwas mainly determined by the clearcoat film, while SW was determined not only by the clearcoat film, but also by the substrate and the basecoat.

[0204] LW was evaluated according to the following standards:

[0205] O: 0<LW<5

[0206] A: 5<LW<10

[0207] X : LW>10

[0208] SWwas evaluated according to the following standards:

[0209] O: 5<SW<25 A: 3<SW<5, 25<SW<30 X : SW<3, SW >30

[0210] Resistance to petroleum products:

[0211] Preparation of E10 petroleum alcohol solution:

[0212] No. 93 gasoline and ethanol were mixed at a mass ratio of 9:1, and the mixed solution was an E10 test solution.

[0213] A sufficient amount of the E10 solution was poured into a glass tank and the test temperature was adjusted to 40°C ± 2°C. Two thirds of the test plate was immersed in E10. The test plate can be immersed in a vertical position for 1 hour using a suitable holder. The immersed test plate was at least 30 mm away from the inner wall of the tank, and the test plates were 30 mm apart from each other. In order to reduce the loss of the E10 solution due to evaporation, the container shall be covered.

[0214] When the end of the specified immersion period was reached, the test plate was taken out, and the surface thereof was wiped with a filter paper to remove the residual liquid. The change in L of the coating film of the test plate was immediately checked using a colorimeter before and after immersion.

[0215] The resistance to petroleum products was evaluated according to the following standard:

[0216] O: AL<0.3 (Good)

[0217] A: 0.3<AL<0.8 (There is slight discoloration, but it does not hinder use)

[0218] X : AL>0.8 (There is serious discoloration and the coating film cannot be used).

[0219] Water resistance:

[0220] The test plate was immersed in warm water at 40°C for 240 hours, taken out and dried at 20°C for 12 hours. Then, the multilayer coating film on the test plate was crosscut with a cutter to the depth reaching the substrate, to form a grid of one hundred 2 mm*2 mm squares. Next, adhesive cellophane tape was attached to the surface thereof and rapidly peeled off at 20°C and the condition of the remaining crosscut coating film was examined.

[0221] The water resistance was evaluated according to the following standards:

[0222] O: One hundred squares of the coating film remained, and no chipping of the cut edges was caused.

[0223] A: One hundred squares of the coating film remained but chipping of the cut edges was observed.

[0224] X : The number of the remaining squares was not more than 99. Table 3

[0225]

[0226]

[0227] wherein: melamine resin (B): CYMEL™ 202, manufactured by allnex Corporation, solid content = 100% polyisocyanate (D-1): DURANATE ™ TPA-100, manufactured by Asahikasei Corporation, solid content = 100%, NCO% = 23.1 polyisocyanate (D-2): DURANATE ™ TKA-100, manufactured by Asahikasei Corporation, solid content = 100%, NCO% = 21.7

[0228] Curing Catalyst (E):

[0229] E-1 : NACURE 5076, manufactured by King Industries Corporation

[0230] E-2: CYCAT 4045, manufactured by allnex Corporation

[0231] E-3: NACURE 4167, manufactured by King Industries Corporation

[0232] E-4: DURAPHOS BAP, manufactured by Solvay Corporation

[0233] Rheology control agent (F):

[0234] To a four-necked flask provided with a stirring device, a thermometer, a cooling tube and a nitrogen gas inlet, 60 parts by weight of a solvent (Ac-1) were added under nitrogen gas, and the temperature therein was raised to 155°C. After the temperature reached 155°C, 34 parts by weight of butyl acrylate, 21 parts by weight of hydroxyethyl acrylate, 39 parts by weight of styrene, 2 parts by weight of methacrylic acid, and 2 parts by weight of di-tert-butyl hydroperoxide as a polymerization initiator were added to the flask over two hours.

[0235] Subsequently, the product was aged at 155°C for three hours while nitrogen gas was introduced, and then the product was cooled to room temperature and was diluted with a solvent so as to obtain a rheology control agent (F) having a solid content of 60%.

[0236] As can be seen from Table 3, only the two-component clearcoat compositions that meet the requirements of the present invention can form clearcoat films with excellent finished appearance, and high hardness, and resistance to petroleum products and water. Moreover, in some preferred embodiments, the two-component clearcoat compositions of the present invention, even if subjected to low-temperature bake curing, can still form clearcoat films with good comprehensive properties.

Claims

DEPCT691. A two-component transparent coating composition consisting of component I, which includes A) meth) hydroxyl-containing acrylic resin, B) melamine resin, and C) polyol ester, which is a product obtained by one or more reactions of a selected group consisting of castor oil, castor oil monoglycerides, and castor oil diglycerides with a primary hydroxyl-containing polyol and selected to contain polybacid acid or anhydride; and component II, which includes D) polyisocyanate, from which the transparent coating film is obtained.

1. A two-component transparent coating composition with a crosslinked molecular weight of 300 to 700 g / mol, commonly 350 to 500 g / mol.

2. A two-component transparent coating composition according to claim 1, characterized by component A having a glass transition temperature of -50°C to 50°C, commonly -45°C to 25°C, and even more commonly -40°C to -2°C.

3. A two-component transparent coating composition according to claim 1 or 2, characterized by component A having a hydroxyl value of 130 to 220 mg.

1. A commonly used hydroxyl concentration (KOH / g) of 150 to 200 mg KOH / g.

4. A two-component transparent coating composition according to any one of claims 1 to 3, characterized by the C component having a hydroxyl concentration of 180 to 500 mg KOH / g, commonly 200 to 450 mg KOH / g, and more commonly 240 to 400 mg KOH / g.

5. A two-component transparent coating composition according to any one of claims 1 to 4, characterized by the C component having a weight-average molecular weight of 1,000 to 3,000 g / mol.

6. A two-component transparent coating composition according to any one of claims 1 to 5, characterized by the C component having a weight-average molecular weight of 1,000 to 3,000 g / mol.

7. A two-component transparent coating composition according to any of the claims 1 through 6, characterized by the primary hydroxyl polyol being a polyol with more than 4 carbon atoms and more than 2 primary hydroxyl groups.

8. A two-component transparent coating composition according to any of the claims 1 through 7, characterized by the equivalent molar ratio (NCO₃ / OH₂) of the isocyanate groups of component D to the total hydroxyl groups of components A and C being (0.8-1.5):1, preferably (0.9-1.5).3):

19. A two-component transparent coating composition pursuant to any one of Reputations 1 through 8, which is characterized in which component C is present in an amount of 5 to 35 parts by weight, preferably 8 to 20 parts by weight, based on 100 parts by weight of the total solids of component I.

10. A two-component transparent coating composition pursuant to any one of Reputations 1 through 9, which is characterized in which component B is present in an amount of 1 to 35 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the total solids of component I.

11. An object coated with a two-component transparent coating composition pursuant to any one of Reputations 1 through 10. 12.Methods for the formation of multilayer coatings comprising: 1) selection for the production of a primary coating that is hardened on a substrate; 2) production of at least one primer layer on the coating obtained in step 1) by applying one or more identical or different primer materials; and 3) production of at least one clear coating layer on the top primer layer by applying one or more identical or different clear coating materials, where at least one of the clear coating materials is a two-component clear coating component according to any of the claims 1 through 10; the primer and clear coatings are hardened separately or together by curing, and in a preferred manner, the primer and clear coatings are hardened together by curing after step 3).

13. Methods for the formation of multilayer coatings according to claim 12, which are characterized by curing temperatures for clear coatings of 80°C to 160°C, and in a preferred manner, curing temperatures for clear coatings of 110°C to 130°C. 14.A method for creating multilayer coatings under claim 12 or 13, which is characterized by the primer being a water-based primer; 15. Multilayer coatings prepared by any of the multilayer coating methods under claims 12 through 14;