KR101160180B1 - Mutilayer coating for the exterior bumper of automobile - Google Patents

Abstract

The present invention provides an undercoat layer (A) formed on the surface of the substrate and formed from the undercoat composition; (B) a dry plating layer formed on the surface of the undercoat layer; And (C) a top coat layer formed on the surface of the dry plating layer and formed from a top coat composition, wherein (A) the bottom coat layer (i) has a weight average molecular weight of 200,000 to 250,000, 48 to 51% by weight of polypropylene resin having an isotactic chain mole fraction L value of 1 from 0.56 to 0.58; (ii) 46 to 48% by weight of a polypropylene resin having a weight average molecular weight of 20,000 to 40,000 and an isotactic chain mole fraction L value of 0.41 to 0.43; And (iii) 2.0 to 4.0% by weight of a polypropylene resin having a weight average molecular weight of 5,000 to 50,000 and an isotactic chain mole fraction L in the formula (1) of 0.71 to 0.73. Provide a coating.

[Equation 1]

Where T _m is the melting point of the complete crystal, T _m ⁰ is the melting point of the resin, R is the gas constant, ΔH _U is the melting enthalpy per mol of the determinable unit, and L is the mole fraction of the isotactic chain.

Polypropylene, top coat, bottom coat, paint, molded article

Description

Multilayer coating for the exterior bumper of automobile}

The present invention relates to a multilayer coating for automotive exterior bumpers, and more particularly, to a multilayer coating for automotive exterior bumpers including an undercoat layer using polypropylene exhibiting excellent adhesion to a plastic substrate.

Polyolefin resins are widely applied to automobiles, and in particular, polypropylene is inexpensive, and features sheet, film, automotive interior and exterior materials, and various molded articles due to characteristics such as moldability, chemical resistance, processing moldability, water resistance, and thermal characteristics. It is used as general purpose resin of the.

However, these polyolefin resins do not contain a polar group in the molecule and thus lack compatibility or adhesion with polar resins such as metal, glass, paper, or polyester, polyamide, polyacetal, polycarbonate, and polyacrylate. There is a difficult problem. In addition, polypropylene has high crystallinity, low surface energy, and nonpolarity, so it has almost no affinity with resins or paints having polarities such as acrylic resins, urethane resins, and vinyl oxalate resins. However, there is a problem that adhesion, printing, etc. are difficult.

Methods for solving such problems include (1) improvement of substrate: introduction of polar groups to the surface of substrate by pretreatment such as discharge treatment, flame treatment, acid treatment, etc., and (2) use of chlorinated resin: similar to substrate. (3) Use of low molecular rubber polypropylene: low molecular weight soluble poly with high compatibility with structure and substrate Coating is carried out using an acid-modified resin having a polarity by grafting unsaturated carboxylic acid such as maleic acid, fumaric acid, itaconic acid, citraconic acid or the like to propylene resin. In practice, the method (2) and (3) are often used at the same time because the adhesive force is insufficient only by the method (1).

However, in the above coating method (1), the pretreatment process complicates the process and causes problems such as excessive use of equipment, energy, and reduced productivity, and the chlorinated resin of (2) has a molar fraction L of isotactic chain. Almost one high-strength polypropylene-based resin has been used for a long time since the 1960s as a chlorine-infused resin for imparting polarity and solubility. However, the presence of chlorine has adverse effects on users, workers, and the environment It has a problem of lowering thermal stability and weather resistance and generating environmental hormones when disposing of the coated product.

In addition, the method (3) is a technique of removing chlorine in the method (2), but has the advantage of removing chlorine, but the low molecular weight polyolefin resin in rubber reduces the scratch resistance and adhesion, and the impurity of the coating due to the tag property It causes problems such as adhesion. In addition, the use of highly crystalline resins or high molecular weight resins for the improvement of scratch resistance and tag resistance reduces the paint stability, spraying properties, delays the crystallization rate, and causes the surface of the coating to become rough or teeing spray. It causes problems such as clogging of the group. As a method of suppressing the tagability, there is a method of using an organic-inorganic nucleating agent, but the use of the nucleating agent complicates the process, lowers the transparency of the formed coating film, and causes problems such as surface precipitation of the nucleating agent.

Therefore, there is a need in the market for a coating that is high in scratch resistance and adhesion without containing chlorine or a nucleating agent, and which can be coated through a sprayer without generating tag resistance, and a multilayer coating for automobile exterior bumpers including such undercoat.

It is an object of the present invention for an automotive exterior bumper including an undercoat layer having excellent adhesion to the non-polar substrates such as polyolefin resins, in particular, polypropylene substrates, excellent scratch resistance, sprayability, low tagging rate and fast crystallization rate of the painted surface. It is an object to provide a multilayer coating.

In order to achieve the above object,

(A) an undercoat layer formed on the substrate surface and formed from the undercoat composition;

(B) a dry plating layer formed on the surface of the undercoat layer; And

(C) a multi-layer coating for automobile exterior bumpers, comprising: a top coat layer formed on a surface of the dry plating layer and formed from a top coat composition,

(A) the undercoat layer is (i) 48 to 51% by weight of a polypropylene resin having a weight average molecular weight of 200,000 to 250,000 and an isotactic chain mole fraction L value of the formula (1) of 0.56 to 0.58; (ii) 46 to 48% by weight of a polypropylene resin having a weight average molecular weight of 20,000 to 40,000 and an isotactic chain mole fraction L value of 0.41 to 0.43; And (iii) 2.0 to 4.0% by weight of a polypropylene resin having a weight average molecular weight of 5,000 to 50,000 and an isotactic chain mole fraction L in the formula (1) of 0.71 to 0.73. Provide a coating.

[Equation 1]

Where T _m is the melting point of the complete crystal, T _m ⁰ is the melting point of the resin, R is the gas constant, ΔH _U is the melting enthalpy per mol of the determinable unit, and L is the mole fraction of the isotactic chain.

The multilayer coating for automobile exterior bumpers of the present invention can be spray-painted on a polypropylene substrate without undergoing complicated processes such as discharge treatment, flame treatment and acid treatment, and without containing chlorine, and has excellent scratch resistance and adhesion. In addition, it is possible to complete an automobile exterior bumper having excellent physical performance such as tag property and water resistance and excellent appearance and water resistance.

The multilayer coating for automobile exterior bumpers of the present invention comprises: (A) an undercoat layer formed on a substrate surface and formed from a undercoat composition; (B) a dry plating layer formed on the surface of the undercoat layer; And (C) a top coat layer formed on the surface of the dry plating layer and formed from a top coat composition.

(A) the undercoat layer is (i) 48 to 51% by weight of a polypropylene resin having a weight average molecular weight of 200,000 to 250,000 and an isotactic chain mole fraction L value of the formula (1) of 0.56 to 0.58; (ii) 46 to 48% by weight of a polypropylene resin having a weight average molecular weight of 20,000 to 40,000 and an isotactic chain mole fraction L value of 0.41 to 0.43; And (iii) 2.0 to 4.0% by weight of a polypropylene resin having a weight average molecular weight of 5,000 to 50,000 and an isotactic chain mole fraction L in the formula (1) of 0.71 to 0.73. Provide a coating.

[Equation 1]

Where T _m is the melting point of the complete crystal, T _m ⁰ is the melting point of the resin, R is the gas constant, ΔH _U is the melting enthalpy per mol of the determinable unit, and L is the mole fraction of the isotactic chain.

In the case of polypropylene resins, the mesopentad fraction [mmmm] obtained in 13C-NMR is often used as a measure of the solubility of resins and various physical properties. Although it is used as a scale, it can be said that it is not suitable as a measure of resin design of paint materials.

Equation 1 is a modification of the equation of the freezing point drop, where L usually represents the mole fraction of the solvent in the solution. Isotactic polypropylene is a semicrystalline resin, in which a crystal part (isotactic) and an amorphous part (atactic) are mixed. Isotactic polypropylene resins can be assumed that amorphous atactic chains are mixed in the crystalline isotactic chains. In the case of polypropylene resins, heterologous monomer parts in the polymer chain structure are atactics of polypropylene. It can be assumed that the chain part is isotactic and crystalline.

Considering the atactic chain of the polyblock or polypropylene resin as the solute and the isotactic chain as the solvent, the mole fraction of the solvent at the melting point of the sample in which the crystal is completely dissolved, that is, the stereoblock polypropylene or It shows the mole fraction of the isotactic chain of polypropylene resin. Therefore, when L = 1.0, the polypropylene is a complete isotactic polypropylene, and as L approaches 1.0, a stereoblock polypropylene containing more isotactic chains having higher crystallinity is obtained. It becomes a propylene resin. In the present invention, L in the formula is referred to as the mole fraction of the isotactic chain.

The component (i), (ii), and (iii) which comprise the (A) undercoat layer of this invention are demonstrated.

It is preferable that the weight average molecular weight of (i) which is high molecular weight resin is 200,000-250,000. If the weight average molecular weight is less than 200,000, it is not preferable because the adhesive force is lowered or the tag property is generated, and if it exceeds 250,000, the stability of the paint is lowered or the sprayability is lowered to obtain a nonuniform coating film.

It is preferable that the weight average molecular weight of (ii) which is low molecular weight resin is 20,000-40,000. If the weight average molecular weight is less than 20,000, the stability of the paint is extremely good, but it causes the occurrence of the tag property, and the heat resistance of the coating film is deteriorated, which is not preferable, and if it exceeds 40,000, it means that the content of the resin component (i) is increased. In addition, the sprayability is lowered due to the fluidity drop of the paint, which is not preferable because a nonuniform coating film is obtained. If the melt viscosity of the resin (ii) is low, the occurrence of the tag property or the adhesion is reduced. If the resin (ii) is high, the spray property is lowered, making it difficult to obtain a uniform coating.

It is preferable that the weight average molecular weight of (iii) which is low molecular weight high crystalline resin is 5,000-50,000. If the weight average molecular weight is less than 5,000, it does not exhibit sufficient physical properties as a crystallization material. If the weight average molecular weight is more than 50,000, it is not preferable because it is difficult to dissolve or deteriorates tee generation, paint stability, and the like.

The polypropylene resins of (i) and (ii) constituting the (A) undercoating layer are preferably composed of only structural units derived from ordinary propylene, but contain structural units derived from less than 20 mol% of heterologous monomers. can do. However, when 20 mol% or more of heterogeneous monomers are contained, the adhesion to the polypropylene substrate is lowered or the tee generation or stability is lowered due to the presence of each HOMO resin, which is not preferable.

The polypropylene resin of (iii) constituting the (A) undercoating layer is also preferably composed only of structural units derived from propylene, but may contain structural units derived from less than 5 mol% of heterogeneous monomers. However, when the content of the hetero monomer is 5 mol% or more, the surface crystallization rate is lowered, so that the coating surface has a tag property or the crystallization rate of the coating film is lowered, which is not preferable because the adhesion force immediately after coating is lowered.

Examples of the hetero monomers include ethylene, 1-butene, 1-pentene, 1-hexene, 1-methyl-1-pentene, 4-methyl-1pentene, 1-heptene, 1-octene, 1-nonene, A-olefins, such as 1-decene and 1-dodecene, (meth) acrylic acid esters, such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate, dimethyl maleate, diethyl maleate, and dibutyl maleate Maleic phosphate esters, (meth) acrylic acid amides, methyl vinyl ethers, alkyl vinyl ethers such as ethyl vinyl ethers, vinyl formate, vinyl acetate, vinyl propionate, vinyl pibarate, vinyl versatic acid, and the like. Vinyl alcohols obtained by saponifying vinyl esters and vinyl esters with basic compounds, etc., 2-hydroxyethyl acrylate, glycidyl (meth) acrylate, (meth) acrylonitrile, styrene, substituted styrene, vinyl halides, Vinylidene halides, carbon monoxide, The flower of sulfur, such as and illustrated, it is also possible to use mixtures thereof. Of these, ethylene and α-olefins having 4 to 10 carbon atoms are preferable, and these may be used by copolymerizing two or more kinds.

By optimizing the resin composition obtained by acid deformation based on the difference in properties and properties of each of the resins (i), (ii) and (iii), the polypropylene coating having good adhesion, sprayability, no tagging and fast crystallization rate Construct a layer.

The molecular weight distribution (Mw / Mn) measured by gel permeation chromatography (GPC) of said (i), (ii), (iii) is 5 or less, Preferably it is 4 or less. When the molecular weight distribution (Mw / Mn) is more than 5, the teeing of the coating due to the non-uniformity of the resin, the clogging of the spray gun, and the stability of the paint may be lowered.

The inventor of the present invention has established a parameter capable of accurately expressing a polypropylene-based resin that can use isotactic chain length, which can have crystallinity that cannot be expressed by monomer chain fraction [mmmm], as an undercoat. It is shown in 1.

As the mole fraction L of the isotactic chain in Equation 1, the melting point of the polymer obtained by differential scanning calorimetry (DSC) was used. T _m is the melting point of the complete crystal, T _m ⁰ is the melting point of the resin, enthalpy value per mol% of the determinable unit ΔH _U is TM Madkuor, JE Mark, Macromol. 461K and 79kJ / mol were used with reference to Theory Simul., 7, 69 (1998), respectively.

When the hetero monomer content is 20 mol% or more in the undercoat layer, or when the molar fraction L of the isotactic chain is 0.30 or less, spraying property is good, but sufficient performance cannot be expected due to deterioration of adhesion force and generation of tagness. The reason why the polypropylene resin is used is that the polypropylene used as the substrate has poor compatibility with the polypropylene resin having a high propylene content as a polymer having a mole fraction L of the isotactic chain in Equation 1 being almost one. to be.

The adhesion mechanism between a polypropylene substrate and a paint using a polypropylene resin is known to form a co-crystal (ancaramel) between the substrate surface and the propylene chain of the coating due to heat treatment after coating the coating, erosion of the substrate surface with a solvent, and the like. If the molar fraction L of the isotactic chain is large, the adhesion to the polypropylene substrate is improved, but the solubility is poor. If the molar fraction L of the isotactic chain is small, the solubility is high, but the adhesion is poor and the film properties such as the tack resistance and scratch resistance are also bad.

The multilayer coating of the present invention may contain water or an organic solvent as a dispersion, if necessary. Possible organic solvents include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, sec-amyl alcohol, tert-amyl alcohol, 1 Alcohols such as ethyl-1-propanol, 2-methyl-1-butanol, n-hexanol, cyclohexanol, ketones such as methyl ethyl ketone, methyl isobutyl ketone, ethyl butyl ketone, cyclohexanone, benzene, toluene Aromatic hydrocarbons such as, xylene, cumene and cymene, alicyclic hydrocarbons such as cyclopentane, cyclohexane, cyclooctane, methylcyclohexane and methylcyclopentane, ethers such as tetrahydrofuran and dioxane, ethyl acetate and acetic acid esters such as -n-propyl, isopropyl acetate, -n-butyl acetate, isobutyl acetate, -sec-butyl acetate, 3-methoxybutyl acetate, methyl propionate, ethyl propionate, diethyl carbonate and dimethyl carbonate, Ethylene Glycol Monomethyl Ether, Ethylene Glycol Monoe Glycol derivatives such as ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol ethyl ether acetate, and also 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and 3-methoxy-3 Examples include methyl-1-butanol, methoxybutanol, acetonitrile, dimethylformamide, dimethylacetamide, diacetone alcohol, ethyl acetate, 1,2-dimethylglycerine, 1,3-dimethylglycerine, and trimethylglycerine. These organic solvents can be used in mixture of 2 or more types.

Among the organic solvents, ethanol, n-propanol, isopropanol, n-butanol, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethylene glycol monoethyl ether, and ethylene glycol are highly effective in promoting the aqueous phase of the resin. Monopropyl ether, ethylene glycol monobutyl ether, and diethylene glycol monomethyl ether are preferable, Among these, the organic solvent which has one hydroxyl group in a molecule | numerator is more preferable, Ethylene in the point which can resinize resin by addition of a small amount Glycol alkyl ethers are more preferred. It is preferable to set the usage-amount of the organic solvent suitably according to the optimum viscosity at the time of using the resin composition for coatings.

In addition to the above components, the coating composition for forming the undercoating layer of the present invention may contain various substances such as surfactants, adhesion promoters, modified waxes, leveling agents, antifoaming agents, curing accelerators, pigment dispersants, ultraviolet absorbers, thickeners, weathering agents, and flame retardants. It may further include.

Examples of the surfactant include cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, fluorine-based surfactants, and reactive surfactants. Cationic surfactants include, for example, aliphatic groups having 1 to about 22 carbon atoms as quaternary ammonium compounds or aromatic alkoxy, polyoxyalkylene, alkylamido, hydroxyalkyl having from 1 to about 22 carbon atoms in the alkyl chain. , Salt-forming anions obtained from a reactor selected from aryl or alkylaryl groups and groups selected from halogen, acetate, citrate, lactate, glycolate, phosphate, nitrate, sulfate and alkylsulfate. Aliphatic groups may contain other groups such as ether bonds, ester bonds and amino groups in addition to carbon and hydrogen atoms.

As the anionic surfactant, for example, sulfate ester salts of higher alcohols, higher alkylsulfonic acids and salts thereof, higher carboxylic acids and salts thereof such as oleic acid, stearic acid and palmitic acid, alkylbenzenesulfonic acids and salts thereof, polyoxyethylene Alkyl sulfate salt, polyoxyethylene alkyl phenyl ether sulfate salt, vinyl sulfosuccinate, etc. are mentioned.

Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyethylene glycol fatty acid esters, ethylene oxide propylene oxide block copolymers, polyoxyethylene fatty acid amides, and ethylene oxide-propylene oxide copolymers. The compound which has a structure, and sorbitan derivatives, such as a polyoxyethylene sorbitan fatty acid ester, etc. are mentioned.

Lauryl betaine, lauryl dimethylamine oxide, etc. are mentioned as an amphoteric surfactant. As a reactive surfactant, such as an alkyl propenyl phenol polyethylene oxide adduct, these sulfate ester salts, allyl alkyl phenol polyethylene oxide adduct, these sulfate ester salts, allyl dialkyl phenol polyethylene oxide adduct, these sulfate ester salts, etc., The compound which has a reactive double bond is mentioned.

Preferred examples of adhesion promoters include 2- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyl Triethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3 Silanes such as -aminopropyltriethoxysilane, 3-aminopropyltriethoxysilane, N-2 (aminoethyl) -aminopropylmethyldimethoxysilane and N-2 (aminoethyl) 3-aminopropyltrimethoxysilane The coupling agent is mentioned.

A curing accelerator (or curing catalyst) may be used to shorten the coating film drying and curing time, preferably as tetramethylbutanediamine, bicyclooctane, dibutyltindilaurate, triethylenediamine and mixtures thereof. You can use the selected one.

In forming the multi-layer coating of the present invention on the surface of the substrate, by mixing the components as described above to prepare a coating composition for forming the undercoat layer, the viscosity is appropriately adjusted and then applied on the surface of the substrate (A) After forming a undercoat layer, it dries and forms a dry plating layer (B) on the surface of the dried (A) undercoat layer. (B) There is no particular limitation on the method of forming the dry plating layer, and may be formed by a general dry plating process using a vacuum evaporator. (B) The type of metal included in the dry plating layer is also not particularly limited. It can select suitably according to the physical property to provide to a coating film.

As described above, when the (B) dry plating layer is formed, a top coat layer is formed by applying a coating composition for forming a top coat layer containing an acrylic polyol resin, a curing agent, and a solvent on the surface thereof.

(C) The top coat layer applied on the surface after the dry plating process should have excellent adhesion to the deposited film for the protection of the metal deposition film, coating appearance, moisture resistance, cold / heat cycle resistance, sunscreen resistance, plasticizer performance, It should have coating properties such as wear resistance, light resistance and heat resistance. In order to obtain such a coating layer (C), the acrylic polyol resin and the acrylic polyol resin which cure the acryl polyol resin having excellent coating properties such as curing rate of the coating film, adhesion to the deposited film, smoothness and gloss, moisture resistance, coating hardness and light resistance, etc. (C) The coating composition for forming a top coat layer containing the hardening | curing agent and the solvent which can maintain compatibility and paint stability is used.

The acrylic polyol resin included as the main resin in the (C) top coat layer according to the present invention has a weight average molecular weight of 2,000 to 40,000, a hydroxyl value of 20 to 120 mg KOH, and a glass transition temperature (Tg) of 20 to 70 ° C. Is preferably. In order to improve adhesion between the deposited plating layer and the composition for forming the top coat layer, heat resistance, abrasion resistance, and the like, a relatively high molecular weight acrylic polyol resin (eg, 15,000 to 40,000) may be used. Therefore, the acrylic polyol resin having a relatively high molecular weight may be used together with the acrylic polyol resin having a relatively low molecular weight (for example, 2,000 to 15,000).

If the weight average molecular weight of the acrylic polyol resin is less than the above range, the initial drying property may be delayed and the working time may be long, and the resin viscosity may be low, so that the paint flows from the corners during painting, resulting in poor appearance and curing speed. Faster pot life can be shortened, the curing density is too high, the coating film is easily broken and the adhesion can be poor, if the above range is exceeded, the viscosity is relatively high, may cause problems such as poor coating smoothness, gloss decrease, As the molecular weight increases, the curing density is lowered, and thus the wear resistance may be poor, and the moisture resistance may be worsened.

The acrylic polyol resin is preferably contained in 20 to 70% by weight per 100% by weight of the composition for forming the top coat layer. If the content is less than 20% by weight, the curing rate is lowered, adhesion with the deposited plating layer is poor, moisture resistance is lowered, and the corrosion of the deposition plated layer can be promoted, and the curing density can be lowered to lower the wear resistance. have. On the other hand, if the content exceeds 70% by weight, the coating film is easily broken, adhesion with the deposited plating layer is poor, and the use of a hardener may increase, thereby increasing the paint price.

Preferred examples of the acryl polyol resin include copolymerized acryl polyol resins with an acrylic compound represented by CH ₂ = CR ₁ COOR ₂ , a hydroxyl group-containing acrylic compound represented by CH ₂ = CR ₃ COO-R ₄ OH, and a vinyl monomer. Ternary copolymer resin is mentioned. R ₁ and R ₃ represent a hydrogen atom or a methyl group, R ₂ represents a hydrogen atom or a monovalent substituted or unsubstituted aliphatic hydrocarbon group having 1 to 6 carbon atoms, and R ₄ represents a divalent substituted or unsubstituted carbon atom having 1 to 6 carbon atoms. Aliphatic hydrocarbon group. Examples of the substituted or unsubstituted aliphatic hydrocarbon group having 1 to 6 carbon atoms include an aliphatic hydrocarbon group having 1 to 6 carbon atoms substituted or unsubstituted or substituted with an alkyl or alkoxy group having 1 to 4 carbon atoms, specifically methyl, ethyl, propyl, Butyl, isobutyl, hexyl, ethylhexyl, methoxyethyl group and the like, but is not limited thereto.

Examples of the general formula CH ₂ = CR ₁ COOR ₂ are acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, Butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, hexyl acrylate, hexyl methacrylate, and the like. Examples of the general formula CH ₂ = CR ₃ COO-R ₄ OH include 2-hydroxyethyl acrylate. , 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, and the like. In addition, examples of the vinyl monomers include styrene and vinyltoluene.

As a curing agent for curing the acrylic polyol resin, a polyisocyanate capable of reacting with hydroxyl groups in the resins and curing at room temperature or forcing is preferably used. Specifically, 1 or more types are selected and used out of homopolymers or modified bodies of hexamethylene diisocyanate and isophorone diisocyanate which are excellent in coating film appearance and light resistance.

In the present invention, the polyisocyanate curing agent is preferably used in an amount such that the equivalent ratio of the hydroxyl group and the polyisocyanate group in the acrylic polyol resin and the polyester polyol resin is 1: 0.8 to 1: 1.2. When the amount of the polyisocyanate curing agent used is less than or above the above range, the curing may not be sufficient or the curing may occur excessively, thereby preventing the desired coating film properties from being obtained.

The solvent is used to maintain the thickness of the coating film and to improve the coating workability, and includes non-polar solvents such as n-heptane, toluene, xylene, petroleum compounds and n-hexane; Ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monoethyl ether acetate, dibasic ester, 3-methoxy butyl acetate, amyl acetate, butyl glycol acetate, methyl ethyl ketone, methyl isobutyl ketone, acetone, diiso Polar solvents such as butyl ketone, isophorone and cyclohexanone; And the mixture of the nonpolar solvent and the polar solvent can be appropriately selected and used in accordance with the properties and volatilization rate of the resin. There is no particular restriction on the amount of solvent used. However, when the solvent is used too much, it is difficult to meet the specified coating thickness in terms of workability, and appearance defects may occur due to the flow of the paint, and when used in a small amount, spray workability of the paint, coating film leveling, etc. It is difficult to expect improvement in appearance quality. Preferably, 10 to 30% by weight of the solvent is used per 100% by weight of the total top layer forming composition.

In addition to the above components, the (C) top coat layer of the present invention may further include additives such as synthetic waxes, leveling agents, and antifoaming agents, curing accelerators, and the like as described in the composition for forming the bottom coat layer.

Synthetic wax usable for the top coat layer (C) of the present invention serves to reduce the hardening shrinkage stress of the top coat film and to promote adhesion with the metal deposition layer. Improves. As the synthetic wax, a synthetic wax prepared from polyethylene, polypropylene, polyamide, polytetrafluoroethylene, or a mixture thereof is preferable, and liquid wax dispersed in powder or solvent may be used. As a property, the synthetic wax whose average particle size is 5-15 micrometers, a softening point is 60 degreeC-150 degreeC, and an acid value is 5 mgKOH / g or less is preferable.

The synthetic wax is preferably contained 0.1 ~ 7.0% by weight of the composition for forming the top coat layer, if the content of the synthetic wax is less than 0.1% by weight is not desirable to improve the wear resistance and adhesion promoting effect, if the weight exceeds 7.0% by weight It is not preferable because the transparency of the resin can be made poor and the coating film smoothness can be inhibited.

The coating amount of the coating material for forming the multi-layer coating of the present invention can be appropriately adjusted, and in order to appropriately control, the coating material suitable for the desired thickness of the upper and lower coating films is appropriately selected while appropriately selecting the apparatus used for the coating and its use conditions. It is preferable to adjust and use with a density | concentration and a viscosity.

In the present invention, the paint drying is not particularly limited, but may be performed in a wide temperature range of about 0 to 250 ° C., and when the heat resistance of the substrate is not high enough, about 0 to 200 ° C. is more practical. Moreover, drying time depends also on drying temperature, the thickness of a coating film, etc., and is not specifically limited, Usually, it can be made into the range of 5 second-120 minutes. If it is the temperature of 50-150 degreeC, the favorable coating film will be obtained about 5 second-about 3 minutes, and about 30 to 120 minutes at room temperature.

It provides a multilayer coating of the present invention and a molded article produced using the multilayer coating. According to the present invention, it is possible to provide a multilayer coating and a molded article having excellent physical properties such as adhesion, storage stability and pigment dispersibility of the coating film, and excellent appearance and water resistance, no tag, and excellent scratch resistance.

Example

Subfloor  Preparation of Coating Composition for Formation

In this embodiment, the polypropylene resin for forming the undercoating layer was polymerized as follows. As the polymerization catalyst for obtaining polypropylene resin having various molecular weights, three kinds of homogeneous / heterogeneous catalysts were used. As the heterogeneous catalyst, a chromium-based catalyst used for examining the physical properties of the polypropylene-based resin illustrated by TiCl ₃ / AlEt ₂ Cl (E. Albizzati, Macromol. Symp. 89.73 (1995)) and Shin et al.

The preparation of the metallocene-based catalyst synthesized bis (2-phenylindenyl) -ziruconium dichloride and bis (2- (bis-3,5-trifluorom-ethylphenyl) indenyl) -ziruconium dichloride according to Waymouth's method. Using these catalysts, a plurality of polypropylene resins were polymerized while introducing hydrogen for molecular weight control, or by varying polymerization conditions by controlling polymerization temperature and monomer concentration.

For polymerization, 0.4 L to 1 L of toluene and organoaluminum (manufactured by Tosoakuzo Co., Ltd.) were added to a 3 L autoclave in which nitrogen was substituted at room temperature (25 ° C). After the addition of hydrogen to the polymerization of the low molecular weight polypropylene, a certain amount of propylene gas was introduced, and then heteropolymers were slowly added in the copolymerization, and a predetermined catalyst / external donor-toluene solution was added to raise the temperature to a predetermined temperature. Reacted. After reacting for 1 to 6 hours, ethanol was introduced to terminate the polymerization. The obtained reactant was introduced into an ethanol-hydrochloric acid solution to precipitate a polymer, and the solvent and resin were separated, and the resulting polymer was dried for 7 hours in a reduced pressure dryer to obtain a polypropylene resin. Each polypropylene resin was put together in Table 1.

Run Monomer catalyst Polymerization temperature
(℃) Hydrogen
(MPa) One P Cr 90 0.1 2 P Cr 70 0.05 3 P Cr 70 0.01 4 P + E Cr 70 - 5 P + E Cr 70 0.03 6 P + B Cr 70 - 7 P + B Cr 70 0.03 8 P Zr 40 - Monomers; P = propylene, E = Ethylene, B = 1-Butene.

Next, the effectiveness of the index L of this invention is demonstrated by comparing the mesopentad fraction and the mole fraction L of an isotactic chain in polypropylene resin.

Molecular weight and molecular weight distribution were obtained using SSC-7700 HT-GPC (manufactured by Senshu Science Co., Ltd.). The measurement was carried out at 140 ° C. using o-dichlorobenzene in the solvent and polystyrene in the standard sample.

The molar fraction L of the isotactic chain was DSC820 (manufactured by METTLER CORPORATION), and the measurement was calculated using a value obtained by carrying out a temperature increase rate of 20 ° C / min in the range of 20 to 220 ° C.

Run Mw / 10 ⁴ Mw / Mn L value One 1.5 2.3 0.72 2 4.5 2.6 0.71 3 4.6 2.1 0.77 4 23 3.1 0.57 5 3.5 3.3 0.42 6 18 3.0 0.47 7 3.3 3.7 0.45 8 36 2.8 0.66

In Table 2, it can be seen that L of Run 2 is 0.71, L of Run 3 is 0.77, and higher than L value of Run 2. In addition, L of Run 6 is 0.47 and L of Run 7 is 0.45, which is higher than Run 6.

Polymerized Polypropylene system  Resin Maleic anhydride  transform

100 g of the copolymer of Table 1 was introduced into a 3L stainless steel reactor equipped with a thermometer and a stirring rod, and 500 g of xylene was injected, and heated to 140 ° C for dissolution. It was dripped slowly over 3 hours, and reaction was performed again for 3 hours. After completion of the reaction, the reaction solution was added dropwise to 2 L of acetone to crystallize, and then washed and dried three times to obtain an acid-modified polypropylene resin.

The acid amount of acid-modified resin was measured by permeation method using Nicolet iS10 FT-IR Spectrometer. After the Interferogram, which is the time dominant spectrum, is obtained by using the Michelson Interferometer, the Fourier transform is used to obtain the frequency dominant spectrum. FT-IR is complementary to other spectroscopy methods, such as NMR, because it has many advantages in terms of time and sensitivity in obtaining spectrum compared to conventional dispersive IR.

As a result of measurement of each spectrum (Scans: 32, resolution: 4 cm ^-1 ), peaks derived from the carbonyl group of maleic acid and the CH ₃ of polypropylene were detected at 1785 cm ^-1 and 1167 cm ^-1 , respectively.

After calculating the area of each of the two peaks obtained, the CI (Carbonyl Index) corresponding to maleic acid strain was calculated using the following equation with reference to the literature. In addition, the acid-modified polyethylene has a carbonyl group of maleic acid and a terminal CH ₃ of the polyethylene main chain at 1783 cm ⁻¹ and 1378 cm ⁻¹ , respectively. Derived peaks were detected, and the acid strain was calculated using the following calculation formulas with reference to the literature.

* Acid-modified polypropylene resin

Table 3 shows the calculation results of each acid-modified resin.

Run C.I ingredient One 2.8 C-1 2 2.6 C-2 3 2.4 C-3 (B) 4 2.9 A-1 5 1.6 B-1 6 2.2 A-2 7 1.8 B-2 8 3.3 A-3 (B)

Example  One

1-1. Subfloor  formation

After introducing 56 g of a mixed solvent of methylcyclohexane: methyl ethyl ketone = 9: 1 into a four-necked flask equipped with a stirrer and a thermometer, 5.0 g of component A-1 resin of Table 3, 4.7 g of B-1 resin, and C After introducing 0.3 g of -1 resin and dissolving it at 70 degreeC for 4 hours, the solvent dispersion of the resin for polypropylene high-viscosity coating was obtained by returning to room temperature. The solvent dispersion of the coating resin was diluted with a mixed solvent of hexane: methyl ethyl ketone = 9: 1 so that the value measured by the Pod Cup No. 4 at 25 ° C. was 13 ± 1 second to obtain a coating composition for forming a bottom layer. After washing the surface of each polypropylene plate (6 × 10 cm) with isopropyl alcohol cleanly, the coating composition for forming an undercoat layer of Examples and Comparative Examples was applied so as to have a thickness of 20 μm after drying, and dried at 80 ° C. for 20 minutes. The undercoat layer was formed.

1-2. Dry Plating Layer  formation

The undercoating layer was dried and a dry plating layer was formed by using a vacuum evaporator (Al (aluminum) deposition, manufactured by Korea Vacuum).

1-3. Top floor  formation

As a top coat, 98.8 g of acrylic polyol resin (R5640, KCC Co., Ltd.), 50 g of hardener polyisocyanate (R6603, KCC Co., Ltd.), 10 g of toluene, 26 g of xylene, 14 g of butyl acetate, leveling agent (BYK 331, BYK production) 1.0g, defoamer (BYK 065, BYK production) 0.2g was mixed to prepare a coating composition for forming a top coat layer. The coating layer-forming composition was coated on the plated layer so that the coating layer had a thickness of 30 μm, and dried at 75 ° C. for 50 minutes to form a top coat layer.

Comparative example  One

The same procedure as in Example 1 was carried out except that 5.0 g of component A-1 resin, 4.7 g of B-1 resin, and 0.3 g of C-1 resin were changed to 10 g of A-1 resin (alone).

Comparative example  2

The same procedure as in Example 1 was carried out except that 5.0 g of the component A-1 resin, 4.7 g of the B-1 resin, and 0.3 g of the C-1 resin were changed to 10 g of the B-1 resin (alone).

Comparative example  3

It carried out by the same method as Example 1 except having changed 5.0 g of component A-1 resin of Table 3, 4.7 g of B-1 resin, and 0.3 g of C-1 resin into 10 g (alone) of C-1 resin.

Comparative example  4

In the same manner as in Example 1, except that 5.0 g of component A-1 resin, 4.7 g of B-1 resin, and 0.3 g of C-1 resin were changed to 5 g of A-2 resin and 5 g of B-2 resin. Was carried out.

Comparative example  5

Example except that 5.0 g of component A-1 resin of Table 3, 4.7 g of B-1 resin, and 0.3 g of C-1 resin were changed to 9.5 g of A-3 (non) resin and 0.5 g of C-2 resin. It carried out by the same method as 1.

Comparative example  6

5.0 g of component A-1 resin, 4.7 g of B-1 resin, and 0.3 g of C-1 resin were changed to 5 g of A-1 resin, 4.7 g of B-1 resin, and 0.3 g of C-3 (non) resin. Except that was carried out in the same manner as in Example 1.

Comparative example  7

5.0 g of component A-1 resin, 4.7 g of B-1 resin, and 0.3 g of C-1 resin were changed to 5 g of A-3 (non) resin, 4.7 g of B-2 resin, and 0.3 g of C-1 resin. Except that was carried out in the same manner as in Example 1.

Table 4 summarizes the components and the compounding ratios of the resins used in Example 1 and Comparative Examples 1-7.

ingredient Compounding ratio (% by weight) Example 1

A-1 50 B-1 47 C-1 3 Comparative Example 1 A-1 100 Comparative Example 2 B-1 100 Comparative Example 3 C-1 100 Comparative Example 4 A-2 50 B-2 50 Comparative Example 5 A-3 (B) 95 C-2 5 Comparative Example 6 A-1 50 B-1 47 C-3 (B) 3 Comparative Example 7 A-3 (B) 50 B-2 47 C-1 3

Performance Evaluation and Results

Spray  evaluation

Iwata sprayer (W-101) the atomization pressure 4kg / cm ^2, in Example 1, in comparison example, each of the coating film by applying the samples, and the atomization of the resulting homogeneous ◎ 1-7, the atomizing can be obtained a non-uniform coating film (Triangle | delta), and if it is not atomized, it was represented by x.

Scratch resistance  evaluation

After the dried coating body was allowed to stand at room temperature for 24 hours, water and sand (50/50) were rubbed uniformly on the coating film, and then the state of the coating film and the glossiness retention rate were determined. (Circle) when glossiness retention rate is 80 or more, (circle) when glossiness retention rate is 70 or more and less than 80, (triangle | delta), and glossiness retention rate are 60 or more and less than 70, and it displayed as x when glossiness retention rate was less than 60.

Adhesion  evaluation

Examples and Comparative Examples The respective coating materials were applied and dried at 80 ° C. for 20 minutes. After the dried coating body was allowed to stand at room temperature for 1 hour and 24 hours, 100 cross cuts of 1 × 1 mm were produced and the cello tape peeling test was carried out. (Triangle | delta) if it is / 100 or more and less than 10/100, and it showed with x when the peeling number was 10/100 or more.

Tagness  evaluation

Examples and Comparative Examples The respective coating materials were applied and dried at 80 ° C. for 20 minutes. After allowing the dry coating to stand at room temperature for 1 hour, the OPP film (12 × 20 cm) is placed on the upper surface of the coating body, and the iron plate (12 × 20 cm) weighing 2 kg is placed on the top of the OPP for 30 minutes, and then the steel plate is angled at 90 °. When the OPP at the bottom rises up with the iron plate, ◎, the OPP is moved, and if there is no movement of the coating body, the coating body moves or is separated from the OPP.

Water resistance rating

Examples and Comparative Examples The respective coating materials were applied and dried at 80 ° C. for 20 minutes. If the dried coating body is allowed to stand at room temperature for 24 hours, and there is no blister in the coating film after being immersed in water at 40 ° C. for 10 days, ◎, if there are 5 or less blisters in an area of 5 × 5 cm, ○, (Triangle | delta) when the number was 20 or less, and it was set as x when 20 or more.

Spray Scratch resistance Adhesion Tagness Water resistance 1h 24h Example 1 ◎ ○ ○ ◎ ◎ ◎ Comparative Example 1 × △ △ ◎ ◎ ◎ Comparative Example 2 ◎ × × × × × Comparative Example 3 ◎ ○ × △ ◎ × Comparative Example 4 ◎ △ × △ ○ × Comparative Example 5 × ◎ ◎ ◎ ○ ○ Comparative Example 6 ○ △ △ ○ × ○ Comparative Example 7 × ◎ ○ ◎ ◎ ◎

Referring to Table 5, it was found that in Example 1, the spraying property of the paint was excellent, and the scratch resistance of the prepared coating film was excellent, and the adhesion, tag, and water resistance were good.

In Comparative Example 1, the high molecular weight resin alone was not atomized and the coating was uneven. In the high temperature storage test, a thickening phenomenon was observed. It became.

In Comparative Example 3, the low molecular weight high crystalline resin alone produced a large amount of tee at low temperature storage properties, and due to the uneven coating, a decrease in adhesion occurred. Delays in speed caused problems in adhesion and water resistance.

Comparative Example 5 had problems in thickening and spraying property due to the large molecular weight of component A, and Comparative Example 6 had problems in tagability because it did not contain a high molecular weight resin (component A). 7, the molar fraction L value of the isotactic chain of component C was 0.77, and since the tee generation amount was large, spray property fell and the coating film obtained was nonuniform.

Therefore, by using the multilayer coating of the present invention, spray coating is possible without going through a process such as discharge treatment, flame treatment or acid treatment of a polypropylene substrate, and does not contain chlorine, and has excellent scratch resistance and adhesion. It can be seen that there is an excellent effect having no tagability.

Claims (4)

(A) an undercoat layer formed on the substrate surface and formed from the undercoat composition; (B) a dry plating layer formed on the surface of the undercoat layer; And (C) a multi-layer coating for automobile exterior bumpers, comprising: a top coat layer formed on a surface of the dry plating layer and formed from a top coat composition, (A) the undercoat layer is (i) 48 to 51% by weight of a polypropylene resin having a weight average molecular weight of 200,000 to 250,000 and an isotactic chain mole fraction L value of the formula (1) of 0.56 to 0.58; (ii) 46 to 48% by weight of a polypropylene resin having a weight average molecular weight of 20,000 to 40,000 and an isotactic chain mole fraction L value of 0.41 to 0.43; And (iii) 2.0 to 4.0% by weight of a polypropylene resin having a weight average molecular weight of 5,000 to 50,000 and an isotactic chain mole fraction L in the formula (1) of 0.71 to 0.73. coating. [Equation 1]

Where T _m is the melting point of the complete crystal, T _m ⁰ is the melting point of the resin, R is the gas constant, ΔH _U is the melting enthalpy per mol of the determinable unit, and L is the mole fraction of the isotactic chain. According to claim 1, wherein the polypropylene resin of (i), (ii), (iii) each of ethylene, 1-butene, 1-pentene, 1-hexene, 1-methyl-1-pentene, 4-methyl -1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 1-dodecene multilayer coating for automotive exterior bumper, characterized in that it comprises at least one monomer selected from the group consisting of. The multilayer coating of claim 1, wherein the topcoat layer (C) comprises an acrylic polyol resin, a curing agent, and a solvent. According to claim 3, wherein the acrylic polyol resin has a weight average molecular weight of 2,000 to 40,000, the hydroxyl group 20 ~ 120 mg KOH, the glass transition temperature (Tg) based on solids, characterized in that the vehicle exterior bumper Multi-layer coating.