JPH09249758A - Resin composition for top coating material for automobile plastic parts and method for coating and finishing the same - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a coating film excellent in stain resistance and the like by coating on a soft plastic member such as a bumper mainly for automobile exteriors, which is a so-called above-mentioned object. To provide a resin composition for a soft top coating (top clear) that matches the above, and a coating finishing method using the resin composition. Above all, it is possible to prevent contamination and prevent contamination by simple water washing. It is to provide the technology that can be protected. SOLUTION: A so-called vinyl-based copolymer is used in which a certain amount of a specific vinyl-based monomer called a dialkylacrylamide-based monomer, which is water-soluble and oil-soluble, is used. On the other hand, by using a curing agent having reactivity with a hydroxyl group, a carboxyl group or an epoxy group, respectively, the above-mentioned effects can be obtained.
We try to maximize it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new and useful resin composition for a topcoat paint for plastic parts for automobile exteriors, and a coating finishing method therefor. More specifically, the present invention has, as essential components, a so-called amphiphilic vinyl monomer showing water solubility and oil solubility, a hydroxyl group-containing vinyl monomer, and a vinyl monomer having a functional group. A vinyl-based copolymer obtained from a monomer and the like, and a curing agent, and further, to form a coating film having a specific glass transition temperature and a specific molecular weight between crosslinks, respectively, TECHNICAL FIELD The present invention relates to a resin composition for a top coating and a coating finishing method for a plastic member for automobile exteriors.

[0002]

2. Description of the Related Art In recent years, for the purpose of reducing the weight, improving the design, and improving the productivity of automobile bodies, a part of the outer plate member is being replaced with metal from plastic.

In the coating of such plastic members, hard plastic is used for fenders and door panels. These coatings are similar to those for metal parts,
A paint that forms a so-called hard coating film is used.

On the other hand, members made of so-called soft plastics (soft plastic members) such as RIM urethane and polypropylene, which are required to have impact resistance and bending resistance, such as bumpers and fascias. A primer or a top-coat paint that forms a soft coating film is directly applied on the surface.

The problem here is, in particular, the stain resistance of a plastic member coated with a topcoat paint which forms a soft coating film. When traveling in urban areas or industrial areas, soot and dust in the atmosphere are likely to adhere, which sometimes causes black spots on the coated surface. In addition, yellow stains may occur due to pollution such as volcanic ash. All of these are factors that significantly deteriorate the appearance of the coating film.

[0006]

As described above, as long as the conventional technique is followed, it is particularly excellent in stain resistance.
The fact is that no topcoating material for flexible plastic members, which is extremely practical, especially for automobiles, has been found.

However, the inventors of the present invention have found that the plastic members for automobiles, especially soft plastics, which can improve the impact resistance and the bending resistance, and more particularly, the stain resistance can be improved. We have earnestly begun research in order to develop a paint that is suitable for painting.

[0008] Therefore, the problem to be solved by the present invention is, at first, by coating on a plastic member for automobiles, especially a soft plastic member,
In particular, the present invention provides a resin composition for a top coating, which has extremely high practicality and is capable of forming a coating film excellent in stain resistance and the like, and at the same time, a coating finishing method using the resin composition for such a top coating. Is also provided.

That is, the problem to be solved by the present invention is to protect a soft top clear coat for soft plastics such as automobile bumpers, mainly for automobile exteriors, from contamination by only simple washing with water. In a broad sense, it is possible to provide a resin composition for a topcoat paint for an automotive plastic member, and a coating finish method using the resin composition for a topcoat paint for the automotive plastic member, respectively. Especially.

[0010]

Means for Solving the Problems Accordingly, the present inventors have:
By focusing on the problems to be solved by the invention as described above, as a result of intensive studies, as a homopolymer,
Showing amphipathicity of water-soluble and oil-soluble, a specific vinyl monomer called dialkylacrylamide monomer, in a form containing a certain amount of so-called vinyl copolymer, while A coating obtained by using a curing agent having reactivity with a hydroxyl group, a curing agent having reactivity with a carboxyl group, or a curing agent having reactivity with an epoxy group, respectively,

For extremely highly practical plastic members for automobiles, especially soft plastic members, which can improve the stain resistance and the like without lowering the impact resistance and bending resistance. The present invention has been completed by finding a resin composition for a top coating, which is suitable for coating, and at the same time finding a coating finishing method for such a resin composition for a top coating for automobile plastic parts. .

That is, according to the present invention, basically, the obtained homopolymer is amphipathic of water-soluble and oil-soluble,
2 to 3 of the specific vinyl-based monomer (a-1) as described below
30% by weight, vinyl monomer having at least one functional group selected from the group consisting of hydroxyl group-containing vinyl monomer, epoxy group-containing vinyl monomer and carboxyl group-containing vinyl monomer. 5 to 50% by weight of (a-2)
And another vinylic monomer (a-3) capable of copolymerization
20 to 93% by weight of a vinyl copolymer (A) obtained by copolymerizing a mixture of monomers, and a curing agent (B).
Which has a glass transition temperature of 40 to 90 ° C. and an intercrosslinking molecular weight of 6
It is intended to provide a resin composition for an overcoating material for automobile plastic parts, which is composed of a total of 00 or less,

In addition, according to the present invention, the above-mentioned specific resin composition for a top coat paint for automobile plastic parts is finished with 2 coats and 1 bake (2C-1B) and 2 coats and 2 bake (2C-). It is also an object of the invention to provide a paint finish method comprising using as a top clear for 2B) finish, 3 coat 2 bake (3C-2B) finish and 1 coat 1 bake (1C-1B) finish.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The patent application (hereinafter referred to as the present application) is, in part, that the obtained homopolymer is an amphipathic vinyl monomer showing water solubility and oil solubility. 2 to 30% by weight of (a-1) and at least one functional group selected from the group consisting of a hydroxyl group-containing vinyl monomer, an epoxy group-containing vinyl monomer and a carboxyl group-containing vinyl monomer. Group-containing vinyl monomer (a-2)
Vinyl copolymer obtained by copolymerizing a mixture of 5 to 50% by weight of the other vinyl monomer (a-3) and 20 to 93% by weight of the other copolymerizable vinyl monomer (a-3). Polymer (A)
And a curing agent (B) as essential components, and a coating composition formed from the resin composition has a glass transition temperature of 40 to 90, respectively. There is claimed a resin composition for an overcoat paint for automobile plastic parts, which is in the range of 0 ° C and has a molecular weight between crosslinks of 600 or less.

Next, the present application provides, as the obtained homopolymer, 2 to 30% by weight of an amphipathic vinyl monomer (a-1) exhibiting water solubility and oil solubility, and a hydroxyl group-containing vinyl. 5 to 5 of vinyl monomers (a-2) having at least one functional group selected from the group consisting of vinyl monomers containing epoxy groups, vinyl monomers containing epoxy groups and vinyl monomers containing carboxyl groups. A vinyl-based copolymer obtained by copolymerizing a mixture of 50% by weight and another copolymerizable vinyl-based monomer (a-3) of 20 to 93% by weight ( A coating resin composition comprising A) and a curing agent (B) as essential components, and the coating film formed from the resin composition has a glass transition temperature of 40, respectively. Within the range of 90 ° C, and
A resin composition for a topcoat paint for automobile plastic parts, which has an inter-crosslinking molecular weight within a range of 600 or less, is 2 coat 1 bake finish, 2 coat 2 bake finish, 3 coat 2 bake finish and 1 coat finish, respectively. A coating finish method for automotive plastic parts is also claimed, characterized in that it is used as a top clear for a coat 1 bake finish.

In addition, in the present application, the obtained homopolymer is
As the above-mentioned vinyl-based monomer (a-1), which is amphipathic showing water solubility and oil solubility, particularly, the following general formula [I]

[0017]

Embedded image CH ₂ = CR ¹ CON (R ² ) ₂ [I]

[In the formula, R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group having 1 to 3 carbon atoms. )

A specific resin composition for a top coating material for automobile plastic parts and a coating method therefor, which uses a vinyl monomer having a dialkylacrylamide group, represented by

The present application also provides, as the above-mentioned curing agent (B), at least one selected from the group consisting of a melamine resin, a polyisocyanate compound and an acid anhydride group-containing compound as a curing agent having reactivity with a hydroxyl group. The use of a compound of the above, a specific, respectively, a resin composition for a top coating for automobile plastic parts and a coating method thereof are also claimed,

Further, in the present invention, the above-mentioned curing agent (B) is selected from the group consisting of a carboxyl group-containing acrylic resin and a carboxyl group-containing polyester resin as a curing agent having reactivity with an epoxy group. The particular use of at least one compound,
Each also claims a resin composition for a top coating material for automobile plastic parts and a coating method therefor,

Further, in the present application, the above-mentioned curing agent (B) is used.
As a curing agent having reactivity with a carboxyl group, at least one compound selected from the group consisting of an epoxy group compound and an epoxy group-containing acrylic resin is used. The claimed resin composition and its coating method are also claimed.

<< Structure >>

The resin composition for paints for automobile plastic parts and the coating finishing method using the resin composition for paints according to the present invention will be described in detail below.

First, each essential constituent component of the resin composition for paints for automobile plastic members according to the present invention will be described.

That is, the specific vinyl-based monomer component, in which the homopolymers in the vinyl-based copolymer (A) are amphipathic of water-soluble and oil-soluble, respectively, It is also a substance that has the effect of preventing the adhesion of pollutants centering on carbon, and in the unlikely event that such oil-soluble pollutants adhere, the oil-soluble pollutants can be easily removed. It is also a substance that can be removed by washing with water.

In the present invention, the above-mentioned "a homopolymer is a vinyl-based monomer which is amphipathic between water-soluble and oil-soluble" or "a homopolymer obtained is water-soluble and oil-soluble. "Vinyl monomer having amphipathicity", that is, the vinyl monomer (a-1) is a specific monomer as described below, particularly a vinyl monomer having a dialkylacrylamide group. Homopolymer (homopolymer) by itself is water-soluble and at the same time oil-soluble, that is, it is amphipathic, that is, by a vinyl polymer containing a dialkylacrylamide group. It refers to a specific monomeric compound [vinyl-based monomer (a-1)] that provides various homopolymers as typified.

The vinyl copolymer (A) is
As the name implies, of course, this vinyl monomer (a-
1), which is not a mere homopolymer of only a specific monomeric compound (monomer), but is an extension of the homopolymer, and mainly contains the vinyl monomer (a-1). The vinyl-based monomer (a-1), the functional group-containing vinyl-based monomer (a-2), and each of these (a
-1) and (a-2) and other vinyl-based monomer (a-3) copolymerizable with both monomers, so-called vinyl-based copolymer is referred to.

The most important component constituting the vinyl-based copolymer (A), which is the main component of the resin composition for paints, for the automobile plastic member according to the present invention, which has such characteristics, The so-called amphiphilic vinyl monomer (a-1) in which the homopolymer exhibits water solubility and oil solubility is not particularly limited, but is particularly representative among them. The following are general formulas [I]

[0030]

Embedded image CH ₂ = CR ¹ CON (R ² ) ₂ [I]

[Wherein R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group having 1 to 3 carbon atoms. ]

A vinyl-based monomer having a dialkyl acrylamide group represented by:
N, N-dimethylacrylamide, N, N-diethylacrylamide, N, N-dipropylacrylamide,
Examples thereof include N, N-dimethylmethacrylamide, N, N-diethylmethacrylamide, and N, N-dipropylmethacrylamide.

The amount of the above-mentioned dialkylacrylamide group monomer used as the amphipathic vinyl monomer (a-1) is within the range of 2 to 30% by weight, preferably 3 The range of ˜15% by weight is suitable, and when it is less than 2% by weight, the effects such as stain resistance are apt to be insufficiently manifested, and on the other hand, when it exceeds 30%. If the amount is too large, the coating film, in particular, the water resistance is liable to be deteriorated, which is not preferable in any case.

Then, a vinyl monomer (a-2) having a specific functional group, which is necessary for obtaining a cured coating film, is a hydroxyl group-containing vinyl monomer and an epoxy group-containing vinyl monomer, respectively. As for the body and the carboxyl group-containing vinyl-based monomer, first, only the typical hydroxyl-containing vinyl-based monomers are exemplified, 2-hydroxyethyl (meth) acrylate,
Various hydroxyalkyl (meth) acrylates such as 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate;

Various hydroxyalkyl vinyl ethers such as 2-hydroxyethyl vinyl ether or 4-hydroxyalkyl vinyl ether; or various allyl compounds such as allyl alcohol or hydroxyethyl allyl ether;

Alternatively, "Plaxel FM or FA
Monomers "[trade name of capirolactone-added monomers manufactured by Daicel Chemical Industries, Ltd.] and the like, and further obtained by addition reaction of ε-caprolactone to various monomers as listed above. And the like.

Further, only the typical epoxy group-containing vinyl monomers will be exemplified, and glycidyl (meth) acrylate, 1-methylglycidyl (meth) acrylate, aryl glycidyl ether or β. Examples thereof include -3,4-epoxycyclohexylmethanol-methacrylic acid ester compound, but of course, the examples are not intended to limit the invention.

Further, only specific examples of the above-mentioned vinyl monomer containing a carboxyl group will be given. Methacrylic acid, acrylic acid or maleic anhydride, or the above-mentioned monomer containing a hydroxyl group as mentioned above. For hydroxyl groups of the body, such as succinic anhydride or phthalic anhydride,
Examples thereof include carboxyl group-containing monomers in a form obtained by subjecting a so-called acid anhydride group-containing unsaturated compound to an addition reaction.

Then, the above-mentioned vinyl-based monomer (a-1) and functional group-containing vinyl-based monomer (a-, respectively) are listed above.
2) Other vinyl monomers (a-) that can be copolymerized with
Regarding 3), to mention only representative ones among them, methyl (meth) acrylate, ethyl (meth) acrylate, (meth)
Various monohydric alcohols having 1 to 22 carbon atoms such as propyl acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate or lauryl (meth) acrylate, and (meth) acrylic acid. Esters;

Various amide vinyl monomers such as (meth) acrylamide or N-methylolacrylamide; various aromatic vinyl monomers such as styrene, α-methylstyrene or vinyltoluene; or Various known and commonly used compounds having one or more polymerizable unsaturated bonds in one molecule, such as (meth) acrylonitrile and vinyl acetate.

In the vinyl copolymer (A) component, these (a-1), (a-2) and (a-
The content ratio of each vinyl-based monomer component 3) is based on the total weight of these monomer components. First, the main monomer (a-1) component is in the range of 2 to 30% by weight. Inside
Preferably, the range of 5 to 20% by weight is suitable,
When it is less than 2% by weight, the removability of pollutants during washing with water tends to be deteriorated. On the other hand, when it exceeds 30% by weight and too much, water resistance is inevitable. And the like tend to decrease, which is not preferable in any case.

In addition, as described above, one or more of a hydroxyl group-containing vinyl monomer, an epoxy group-containing vinyl monomer or a carboxyl group-containing vinyl monomer, respectively, The amount of the so-called functional group-containing vinyl monomer (a-2) used is 5 to 50% by weight.
The range is preferably 10 to 35%, and when the range is less than 5% by weight, the vinyl copolymer (A) having a sufficient crosslink density is inevitable. Especially because it is difficult to obtain,
When the stain resistance and the weather resistance are apt to decrease, and when the amount exceeds 50% by weight and becomes too large, the crosslinking density of the obtained vinyl copolymer (A) itself is unavoidable. It tends to be too high, and in particular, the low-temperature flexibility is extremely likely to be extremely lowered, and even when it is used as a paint, the stability is likely to be extremely lowered, which eventually leads to gelation. Because it is easy to become a place,
Either case is not preferred.

Then, these (a-1) to (a-
The copolymerization reaction of each vinyl-based monomer component 3) can be carried out in the same manner as a usual synthetic method in the case of an acrylic resin or a vinyl resin. Such as water dispersion polymerization method,
It may be carried out by various known and commonly used methods, but among others, the solution radical polymerization method is the most convenient.

As the solvents to be used at that time, only typical ones are exemplified by toluene, xylene, cyclohexane, n-hexane or octane or "Solvesso 100 or 150" (Exxon Chemical Company, USA). A variety of carbonizations such as manufactured by Aromatic Hydrocarbon Solvents) or “LAWS” (trade name of Aliphatic / Aromatic Hydrocarbon Mixed Solvents manufactured by Shell in the Netherlands) Hydrogen-based solvents;

Various ester solvents such as methyl acetate, butyl acetate, amyl acetate, ethyl ethoxy propionate or ethoxy propionate acetate; n
-Or sec-butyl alcohol or butyl cellosolve, various alcohol solvents; or various ethyl ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone or cyclohexanone.
It goes without saying that more than one kind may be used in combination.

Further, as the radical polymerization initiator, only typical ones will be exemplified. Various well-known and commonly used azo compounds represented by azobisisobutyronitrile and benzoylperoxide will be mentioned. It is known and commonly used various peroxides represented by oxides and the like.

Further, if necessary, lauryl mercaptan, octyl mercaptan, as a molecular weight regulator,
Various chain transfer agents such as 2-mercaptoethanol, octyl thioglycolate, 3-mercaptopropionic acid or α-methylstyrene dimer can also be used.

The number average molecular weight of the vinyl copolymer (A) thus obtained is about 800 to about 2
A range of 10,000 is suitable, that is, a range of such a range is particularly suitable in terms of coating workability and coating film performance.

Next, regarding the above-mentioned curing agent (B), first, only representative representative curing agents having reactivity with a hydroxyl group will be exemplified, and amino resins and polyvalent carboxylic acids will be given. Various known and commonly used compounds such as anhydrides, polyisocyanate compounds and blocked isocyanate compounds can be used, and various curing agents can be appropriately selected and used.

The above-mentioned amino resin referred to herein is, for example, a urea resin, a melamine resin, a benzoguanamine resin and the like, which are collectively referred to.

More specifically, for example, urea, melamine or benzoguanamine compound as a main raw material component,
It refers to a compound in a form obtained by subjecting formaldehyde and an aliphatic alcohol to addition condensation (formation).

To exemplify only the particularly representative aliphatic alcohols used in the etherification at that time, methanol, ethanol, isopropanol (i-propanol) and isobutanol (i-butanol) are given. Or n-butanol and the like, which are used alone or in combination of two or more kinds.

Further, if only representative examples of the above-mentioned polyvalent carboxylic acid anhydride are to be exemplified, trimellitic anhydride, pyromellitic dianhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and het anhydride. Acid, hymic acid anhydride ["Hymic acid" is a registered trademark of Hitachi Chemical Co., Ltd. ], Maleic anhydride, itaconic anhydride, glycerol tris (trimellitate) or ethylene glycol di (trimeritate), and the like.

Further, among the above-mentioned polyisocyanate compounds, only representative ones will be exemplified, and various aromatic diisocyanates such as tolylene diisocyanate and diphenylmethane diisocyanate; hexa Such as methylene diisocyanate and trimethylhexane diisocyanate,
Various aliphatic diisocyanates; various types such as isophorone diisocyanate, methylcyclohexane-2,4 (or 2,6) -diisocyanate, 4,4′-methylenebis (cyclohexylisocyanate), 1,3- (isocyanatomethyl) cyclohexane. Alicyclic diisocyanate;

Various polyisocyanate compounds as listed above, various polyether polyols such as ethylene glycol, polyethylene glycol, polypropylene glycol or polycaprolactone polyol, and various polyhydric compounds such as trimethylolethane or trimethylolpropane. Various low molecular weight polyester resins (including oil-modified types) having alcohols, functional groups (reactive groups) that are reactive with isocyanate groups, and further hydroxyl group-containing acrylic copolymers ( That is, various addition reaction products with so-called acrylic polyols) and the like;

Isocyanate compounds having a buret structure; or 2-hydroxypropyl (meth) acrylate to hexamethylene diisocyanate and other molar adducts, or various isocyanate group-containing monomers such as isocyanate ethyl methacrylate, and various A copolymer in the form of an essential raw material component with a vinyl monomer having a copolymerizable unsaturated group;

C _{2 to} C ₈ alkylene diisocyanates, cycloalkylene diisocyanates or aralkylene diisocyanates, and C _{10 to} C ₄₀ diols, as disclosed in JP-A-61-22013, A polyisocyanate having an isocyanurate ring, which is obtained by reacting in the presence of an isocyanurate-forming catalyst, and which is soluble in a nonpolar organic solvent.

Further, by exemplifying only typical examples of the above-mentioned blocked isocyanate compound, various polyisocyanate compounds such as those mentioned above may be used in the form of a piece or an active hydrogen-containing compound. hand,
For example, it has a block form.

Used for such blocking,
As the active hydrogen group-containing compound described above, only typical ones are exemplified, and phenol,
Various phenolic compounds such as cresol; methanol,
Various alcohols such as ethanol, propanol and benzyl alcohol; various active methylene compounds such as dimethyl malonate and ethyl acetoacetate;

There are various oximes such as formaldoxime, acetoaldoxime and methylethylketoxime, and various compounds such as ε-caprolactam. These various compounds are mainly used. However, the present invention is in no way limited to these illustrative examples.

Then, the above vinyl-based copolymer (A)
As the curing agent for the epoxy group-containing copolymer which is one of the curing agents (B) for use in the present invention, a carboxyl group-containing compound is mainly used. Of these, only typical ones are exemplified. Then, the carboxyl group-containing unsaturated monomer as described above and the other copolymerizable monomer as described above are polymerized by various known and commonly used methods. As obtained by
Examples include various types of vinyl-based copolymers.

Further, polyester resins having a carboxyl group at the molecular end can also be used. The acid concentration in the carboxyl group-containing resin as the curing agent (B) is about 2.2 to about 7 mol / 1,000.
An appropriate range is g.

Then, the above vinyl-based copolymer (A)
Among them, as one of the curing agents (B) for the carboxyl group-containing copolymer, there is an epoxy group-containing compound,
Among them, only typical ones are vinyl copolymers having an epoxy group, for example, an essential raw material containing a monomer having both an epoxy group and an unsaturated group. It is a class obtained by using as a component and further polymerizing with other monomers copolymerizable with these respective monomers.

The automobile plastic member according to the present invention prepared by using the vinyl copolymer (A) and the curing agent (B) as essential film-forming components, respectively, as described above. A curing catalyst can be added to the resin composition for a top coating composition for use in the resin composition. Among them, only a typical catalyst as a reaction catalyst of a carboxyl group and an epoxy group can be used. Methylammonium fluoride, tetramethylammonium bromide, trimethylbenzylammonium hydroxide, 2-hydroxypyridine, trimethylammonium methoxide, phenyltrimethylammonium chloride, phenyltrimethylammonium bromide, phenyltrimethylammonium hydroxide, phenyltrimethylan Niumuyo - iodide, phenyl trimethyl ammonium bromide, phosphonium Foko link Russia chloride sodium salt,

Stearyl ammonium bromide, tetra-n-butylammonium hydroxide, tetra-n-butylammonium phosphate, tetra-n
-Dodecyl ammonium trichloride, tetraethyl ammonium hydroxide, tetraethyl ammonium tetrafluoroborate, acetylcholine bromide, alkyldimethylbenzyl ammonium chloride, benzyl choline bromide, benzyl-n-butyl ammonium bromide, betaine, butyryl chloride, bis (tetra Various quaternary ammonium salts, such as -n-butylammonium) dichromate or trimethylvinylammonium bromide;

Or allyltriphenylphosphonium chloride, n-amyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, bromomethyltriphenylphosphonium bromide, 2-dimethylaminoethyltriphenylphosphonium bromide , Ethoxycarbonylphosphonium bromide, n-heptyltriphenylphosphonium bromide, methyltriphenylphosphonium bromide, tetrakis (hydroxymethyl) phosphonium sulfate or tetraphenylphosphonium bromide, and various phosphonium salts And so on.

Further, as a reaction catalyst for the curing agent (B) with the hydroxyl group in the hydroxyl group-containing vinyl copolymer (A) as one of the vinyl copolymer (A), various acid catalysts can be used. Various known and conventional compounds can be used.

Then, each of the cured coating films obtained from the resin composition for coating material according to the present invention has a glass transition temperature of about 40 ° C. to about 90 ° C. It is important to adjust the molecular weight between crosslinks of the coating film to be about 600 or less. That is, in the present invention, if any one of these requirements is lacking, the object of the present invention cannot be achieved.

In the present invention, the above-mentioned glass transition temperature means the isolated coating film as "V" of a vibron dynamic viscoelasticity measuring device.
IBRON DDV-IIEA type "[product of Toyo Bordwin Co., Ltd.], the frequency was 110 Hz, and the heating rate was 3 C / min. In the case where the glass transition temperature is lower than about 40 ° C., the stain resistance is apt to be remarkably deteriorated. On the other hand, when the glass transition temperature is higher than about 90 ° C., too high. Inevitably, the low-temperature physical properties and the like, especially the low-temperature flexibility, are extremely likely to be deteriorated, which is not preferable in any case.

The term "molecular weight between crosslinks" used above means the high temperature elastic modulus measured by using the above-mentioned apparatus and is applied to the following rubber viscoelasticity theoretical formula such as Flory. This is to refer to the theoretical calculation value of the obtained form, and when it exceeds about 600 and becomes too large, the stain resistance is apt to be remarkably lowered, and in any case, it is not preferable. .

That is, the molecular weight between crosslinks (hereinafter abbreviated as Mc) is

[0072]

## EQU1 ## Mc = 3.rho.RT / E '

[However, R in the equation is 8.13 × 10 ⁷
erg / Kmol is a constant, and
E ′ is the high temperature elastic modulus (minimum elastic modulus), T is the temperature (K) at which the minimum elastic modulus is exhibited, and ρ is the density (g / cm) of the sample coating film. ]

It is a value calculated based on the following equation.

In the resin composition for coating material according to the present invention,
Of a cured coating film obtained using this resin composition of the present invention,
First, the adjustment of the glass transition temperature is mainly based on the usage of the various vinyl-based monomer (a-3) components as described above, and the adjustment of the other inter-crosslinking molecular weight is mainly as described above. This can be achieved by adjusting the blending amount of various vinyl monomer (a-2) components.

The thus-obtained topcoat resin composition for automobile plastic parts according to the present invention contains various known and conventional additives such as leveling agents and ultraviolet absorbers, and plasticizers. It is also possible to add various resins such as polyester resin and mix them.

Furthermore, the coating finishing method according to the present invention is
For example, the intended multilayer coating film can be formed by the 2-coat 1-bake (2C-1B) method, the 2-coat 2-bake (2C-2B) method, or the overcoat method. However, through such a coating finishing method, in forming a target laminated coating film, that is, in carrying out the coating finishing method according to the present invention, as a coating resin composition for a base coat,
It is not particularly limited as long as it can form a coating film, that is, it can form a cured coating film. For example, a composition of a hydroxyl group-containing resin and a melamine resin; a composition of a hydroxyl group-containing resin and a polyisocyanate compound;

A composition of a hydroxyl group-containing resin and a block polyisocyanate compound; a composition of a carboxyl group-containing resin and an epoxy group-containing resin; or a hydrolyzed silyl group-containing resin, and Further, it is a combination system of two or more of these, and further, a composition in a form in which pigments of at least one kind of organic pigment, inorganic pigment or metal pigment are also mixed.

The coating method for the so-called base coat paint based on each of these base coat resin compositions is not particularly limited, and various well-known and conventional means are appropriately selected. However, it is preferable to use a bell type or RE
It can be carried out by various electrostatic coating such as A or air spray coating. When these various coating methods are used, the paint to be used at that time is usually, for example, Ford Cup No. In 4,
It is suitable to dilute to a viscosity within the range of about 12 to 35 seconds before coating.

The coating film thickness in that case is, for example, in the case of clear coating, a range of about 20 to about 80 micrometers (μm), preferably 30 to 50 μm.

The paint based on the resin composition for a topcoat paint for automobile plastic parts according to the present invention may be applied directly to a plastic part, or may be previously subjected to solvent vapor degreasing, polishing, It is safe to coat the surface-treated plastic member by various known and commonly used means such as acid treatment or corona discharge, but in particular, the above-mentioned surface treatment is applied in advance. It is desirable that the shaped plastic member is further coated with a primer or the like.

This coating composition based on the resin composition for a top coating composition according to the present invention is particularly suitable for coating the surface of a plastic member of the class used in the outer plate portion of an automobile body. is there. That is, as compared with the conventional type soft coating film-forming coating material, this coating material based on the resin composition for a top coating material of the present invention has, in particular, impact resistance and bending resistance that are equal to or more than that. And, moreover,
In particular, it is particularly desirable to apply it to the above-mentioned soft plastic member because it is possible to further improve the stain resistance and the like, and especially the removability by washing with water.

The so-called soft plastic member used as a bumper or a fascia is itself
It has material properties that can withstand impact and deformation due to collisions at low temperatures, and as a coating film to be applied to such members, it has flexibility at low temperatures that does not impair these coating material properties. Is required to be present.
That is, the elongation at 20 ° C. is 5% or more, preferably 1
It is required to be 0% or more. Of course, in the case of the conventional paint, if the elongation is set to this level, the stain resistance is remarkably inferior. In addition, it is very difficult to remove the contaminants by washing the contaminated coating film with water or waxing.

[0084]

EXAMPLES Next, the present invention will be described more specifically with reference examples, examples and comparative examples. However, the present invention is by no means limited to only these illustrative examples. Absent. In the following, all parts and percentages are by weight unless otherwise specified.

Reference Example 1 [Preparation Example of Vinyl Copolymer (A) Containing Component (a-1) and Hydroxyl Group]

A four-necked flask equipped with a thermometer, a cooling tube, a stirrer and a nitrogen gas introducing tube was charged with 500 parts of xylene and 300 parts of n-butyl acetate and heated to 90 ° C. , N-dimethylacrylamide 100
Parts, 160 parts of n-butyl acrylate, 1 part of styrene
60 parts, 360 of 2-ethylhexyl methacrylate
Part, 20 parts of acrylic acid and 200 parts of 4-hydroxybutyl methacrylate,

A mixture of 200 parts of xylene, 30 parts of azobisisobutyronitrile (AIBN) and 50 parts of tert-butylperoxy-2-ethylhexanoate was added dropwise over 5 hours. .

After completion of the dropping, the reaction was continued by maintaining the same temperature for 5 hours to give a nonvolatile content of 50.8% and a Gardner viscosity at 25 ° C. (hereinafter, referred to as
Abbreviated as viscosity. ) Is A, and the number average molecular weight is 5,
A solution of the target copolymer of 000 was obtained. Hereinafter, this is abbreviated as resin (A-1).

Reference Example 2 [Preparation Example of Vinyl Copolymer (A) Containing Component (a-1) and Carboxyl Group]

100 of N, N-diethyl acrylamide
Parts, 150 parts of methacrylic acid, 130 parts of styrene and 380 parts of n-butyl acrylate, 200 parts of ethyl acrylate and 40 parts of n-butyl methacrylate.
Parts, 200 parts of xylene, 30 parts of azobisisobutyronitrile (AIBN) and ter.
t-butylperoxy-2-ethylhexanoate 5
Except that a mixture consisting of 0 parts was used.

By carrying out the reaction in the same manner as in Reference Example 1, a solution of the target copolymer having a nonvolatile content of 50.8%, a viscosity of LM and a number average molecular weight of 5,000 was obtained. Obtained. Hereinafter, this is abbreviated as resin (A-2).

Reference Example 3 [Preparation example of vinyl resin (A) containing component (a-1) and epoxy group]

To 200 parts of glycidyl methacrylate,
Further, 220 parts of styrene, 200 parts of n-butyl acrylate, 7 parts of 4-hydroxybutyl methacrylate.
4 parts and 156 parts of 2-ethylhexyl acrylate, N, N-dimethylacrylamide and 1 part of xylene.
A mixture of 50 parts, 15 parts of AIBN and 50 parts of tert-butylperoxy-2-ethylhexanoate was added to 400 parts of xylene and 160 parts of butanol in advance. The temperature is raised to 125 ° C., the solution is added dropwise over 5 hours, and the reaction is carried out to obtain a solution of the objective resin having a nonvolatile content of 60%, a viscosity of B, and a number average molecular weight of 6,000. It was Hereinafter, this is abbreviated as resin (A-3).

Reference Example 4 [(a-1) Component, Vinyl Copolymer (A) Containing Carboxyl Group and Hydroxyl Group]
Preparation Example]

100 of N, N-diethyl acrylamide
Parts, methacrylic acid 150 parts, styrene 130 parts, n
A mixture of 360 parts of butyl acrylate, 200 parts of ethyl acrylate and 60 parts of 4-hydroxybutyl acrylate, 200 parts of xylene, 30 parts of azobisisobutyronitrile (AIBN) and t
tert-butyl peroxy-2-ethylhexanoate and a mixture consisting of 50 parts of

By carrying out the reaction in the same manner as in Reference Example 1, a solution of the target copolymer having a nonvolatile content of 50.2%, a viscosity of AB and a number average molecular weight of 8,500 was obtained. Obtained. Hereinafter, this is abbreviated as resin (A-4).

Reference Example 5 [Preparation Example of Vinyl Copolymer (A) Containing Component (a-1) and Hydroxyl Group]

A four-necked flask equipped with a thermometer, a cooling tube, a stirrer and a nitrogen gas introducing tube was charged with 500 parts of xylene and 300 parts of n-butyl acetate and heated to 90 ° C., 100 parts of N, N-dipropyl acrylamide, 160 parts of n-butyl acrylate, 160 parts of styrene, 3 parts of 2-ethylhexyl methacrylate
A mixture consisting of 60 parts, 20 parts of acrylic acid and 200 parts of β-hydroxyethyl acrylate,

A mixture of 200 parts of xylene, 30 parts of azobisisobutyronitrile (AIBN) and 50 parts of tert-butylperoxy-2-ethylhexanoate was added dropwise over 5 hours. .

After the completion of the dropping, the reaction was continued by maintaining the same temperature for 5 hours, whereby the nonvolatile content was 50.8%, the viscosity was C, and the number average molecular weight was 5,
A solution of the target copolymer of 700 was obtained. Hereinafter, this is abbreviated as resin (A-5).

Reference Example 6 [Preparation Example of Carboxyl Group-Containing Vinyl Copolymer (B)] In a four-necked flask equipped with a thermometer, a cooling tube, a stirrer and a nitrogen gas introducing tube, 500 parts of xylene and n- were added. Charge 300 parts of butanol, raise the temperature to 125 ° C,
A mixture of 250 parts of methacrylic acid, 200 parts of styrene, 350 parts of n-butyl methacrylate and 200 parts of n-butyl acrylate,

A mixture of 200 parts of xylene, 30 parts of AIBN and 50 parts of tert-butylperoxy-2-ethylhexanoate was added dropwise over 5 hours, and after the addition, the same amount was obtained. By allowing the reaction to continue by holding at temperature for 5 hours,
A solution of the target copolymer having a nonvolatile content of 50.8%, a viscosity of VW and a number average molecular weight of 3,500 was obtained. Hereinafter, this is abbreviated as resin (B-1).

Reference Example 7 [Preparation Example of Epoxy Group-Containing Vinyl Resin (B-2)] "Cyclomer M-100" [of alicyclic epoxy group-containing polymerizable monomer manufactured by Daicel Chemical Industries, Ltd.] Product name] 2
Non-volatile by carrying out the polymerization reaction in the same manner as in Reference Example 4, except that 20 parts, and further 250 parts of styrene, 250 parts of n-butyl acrylate and 280 parts of 2-ethylhexyl acrylate were used. A solution of the target resin having a content of 60%, a viscosity of T, and a number average molecular weight of 3,500 was obtained. Hereinafter, this is abbreviated as resin (B-2).

Reference Example 8 [Example of Preparation of Vinyl Copolymer (A) Containing Component (a-1) and Hydroxyl Group]

A four-necked flask equipped with a thermometer, a cooling tube, a stirrer and a nitrogen gas introducing tube was charged with 500 parts of xylene and 300 parts of n-butyl acetate and heated to 90 ° C., N, N-dimethylacrylamide 4
00 parts, 100 parts of styrene, 330 parts of 2-ethylhexyl methacrylate, 20 parts of acrylic acid and β-
A mixture of 150 parts of hydroxyethyl acrylate,

A mixture of 200 parts of xylene, 30 parts of azobisisobutyronitrile (AIBN) and 50 parts of tert-butylperoxy-2-ethylhexanoate was added dropwise over 5 hours. .

After the completion of dropping, the reaction was continued by maintaining the same temperature for 5 hours, whereby the nonvolatile content was 51.0%, the viscosity was G, and the number average molecular weight was 6,
A solution of the target copolymer of 300 was obtained. Hereinafter, this is abbreviated as resin (A-6).

Reference Example 9 [Preparation Example of Hydroxyl Group-Containing Vinyl Copolymer] In a four-necked flask equipped with a thermometer, a cooling tube, a stirrer and a nitrogen gas introducing tube, 500 parts of xylene and n-acetic acid were added.
After charging 300 parts of butyl and heating up to 90 ° C., 200 parts of n-butyl methacrylate, 200 parts of n-butyl acrylate, 100 parts of styrene, 330 parts of 2-ethylhexyl methacrylate, of acrylic acid 20 parts and 15 of β-hydroxyethyl acrylate
A mixture of 0 parts,

A mixture of 200 parts of xylene, 30 parts of azobisisobutyronitrile (AIBN) and 50 parts of tert-butylperoxy-2-ethylhexanoate was added dropwise over 5 hours. .

After completion of the dropping, the reaction was continued at the same temperature for 5 hours to give a non-volatile content of 51.0%, a viscosity of I, and a number average molecular weight of 6,
A solution of the target copolymer of 700 was obtained. Hereinafter, this is abbreviated as resin (C-1).

Examples 1 to 5 As shown in Table 1, first, by using the various resins obtained in Reference Examples 1 to 5 and Reference Examples 8 and 9, for convenience, 7 types of clear paints ( Clear coat)
Was prepared.

Next, by using each of the predetermined clear coat paints (clear coat) and various base coat paints (base coats) as will be described later, five different paint finishing methods are carried out for convenience. did.

In the table, the compounding composition ratio for the clear coat paint (clear coat) and the type of the base coat paint (base coat) to be combined with the clear coat paint (clear coat) are shown together. , And the different coating finishing methods to be implemented.

However, in the table, each of the three types of base coat paints (base coats) to be combined is selected from the following three types. People use abbreviations such as "Paint finish method".

As shown below, the base coat paint A is abbreviated as “BC-1”, the base coat paint B is abbreviated as “BC-2”, and the base coat paint C is abbreviated. Is abbreviated as "BC-3".

That is, the above base coat paint A (BC
-1) include "Acridic WJ-100" [trade name of hydroxyl group-containing acrylic resin manufactured by Dainippon Ink and Chemicals, Inc.] and "Super Beckamine L-117-".
60 "(trade name of melamine resin manufactured by the same company) and" aluminum paste 7160NS "[trade name of aluminum paste manufactured by Toyo Aluminum Co., Ltd.],
A so-called metallic base coat paint obtained by using "Fastgen Super Red BN" [trade name of red pigment manufactured by Dainippon Ink and Chemicals, Inc.], in which aluminum is used. PWC is 1
3% and the PWC of the red pigment is 15%.

Further, the base coat paint B (BC-
As 2), "Beckolite M-6015" [trade name of hydroxyl group-containing polyester resin manufactured by Dainippon Ink and Chemicals, Inc.] and "Super Beckamine L-117".
-60 "and carbon black,
It has a PWC of 5%,

Further, the base coat paint C (BC-
As 3), styrene: n-butyl methacrylate:
n-butyl acrylate: methacrylic acid: 2-hydroxypropyl methacrylate = 10: 40: 43: 2: 5
(Part by weight ratio), and a hydroxyl group-containing vinyl copolymer emulsion having a nonvolatile content of 40%, and "Cymel C-325" [manufactured by Mitsui Cyanamid Co., Ltd.,
Product name of methyl etherified melamine resin], “Primal ASE-60” (product name of acrylic emulsion made by Rohm and Haas Company, USA), and “Aluminum paste WZ7160” [made by Toyo Aluminum Co., Ltd.] , A trade name of aluminum paste] and a so-called metallic base coat paint,

In the case of Examples 1 to 5, 2C-1
It is said that the coating film was formed by the B finishing method, and in the cases of Comparative Examples 1 and 2, 2C-
It is said that the coating film was formed by the 1B finishing method. However, the baking conditions are all 140 ° C.
Then, it was made equal to the fixed condition of 20 minutes.

[0120]

[Table 1]

<< Footnotes in Table 1 >> All numerical values in the table mean parts by weight.

L-117 ... "Super Beckamine
L-117-60 "

[0123]

[Table 2]

[0124]

[Table 3]

<< Footnote in Table 2 >> Gloss ………………………… 60 degree specular reflectance (%)

Impact resistance: DuPont type concave impact test (1/2 inch notch, load = 500 g)

Scratch resistance: 5% on felt
The gloss retention (%) of the coating film after being impregnated with cleanser water of a concentration and being rubbed by applying a load of 1 kg for 30 reciprocations was indicated.

Water resistance …………………………………………………………………………………………………………………………………………………….

Weather resistance …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… ••• Displayed.

Carbon stain resistance: Carbon is wetted with water (30%), applied on a coating film, dried at 70 ° C. for 30 minutes, and washed with water. The degree of contamination of the coating film was measured by a color difference meter and displayed as a color difference value (ΔD).

Actual exposure pollution property ……………… From June to September in the summer, at a complex in Takasago, Takaishi City, Osaka Prefecture, the film was exposed horizontally and washed with water, before and after exposure. The degree of contamination was measured by a color difference meter and displayed as a color difference value (ΔD).

Low temperature flexibility ... coating film at -20 ° C
Stored in the low temperature bath for 2 hours and then 3 /
Perform a bending test with an 8-inch mandrel,
The presence or absence of cracks on the coated surface was visually evaluated and judged.

[0133]

[Table 4]

[0134]

EFFECT OF THE INVENTION The resin composition for a top coating material for an automobile plastic member and the coating finishing method according to the present invention are particularly suitable for an automobile plastic member.
It is a resin composition for top-coat paint, which is suitable for coating for soft plastic parts, and it is also a coating finishing method, improving impact resistance and bending resistance, etc., and especially improving stain resistance. It will be easy to know that it is a resin composition for a top-coat paint that can be made extremely highly practical and a coating finishing method.

As long as the resin composition for a topcoat paint according to the present invention is used, or if the coating finish method according to the present invention is followed, it is unlikely that oil-soluble pollutants will adhere. Even in such a case, the oil-soluble contaminant can be removed by a simple washing with water.

That is, if the resin composition for a top coating composition for automobile plastic parts according to the present invention is used, and if the coating finishing method according to the present invention is performed using the resin composition for a coating composition, An extremely highly practical automobile that can improve stain resistance and the like without lowering impact resistance and flex resistance, and can be removed by simple water washing. It is possible to provide a plastic member for use, especially a soft plastic member.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location // C08F 220/26 MML C08F 220/26 MML 220/32 MMP 220/32 MMP 220/56 MNC 220 / 56 MNC C09D 133/24 PFW C09D 133/24 PFW

Claims (6)

[Claims] 1. The homopolymer obtained is 2 of an amphipathic vinyl monomer (a-1) which exhibits water solubility and oil solubility.
To 30% by weight, and a vinyl-based monomer having at least one functional group selected from the group consisting of a hydroxyl-containing vinyl-based monomer, an epoxy group-containing vinyl-based monomer, and a carboxyl group-containing vinyl-based monomer. 5 to 50% by weight of the body (a-2) and another vinyl-based monomer (a- that can be copolymerized)
3) A vinyl copolymer (A) obtained by copolymerizing a mixture of monomers of 20 to 93% by weight and a curing agent (B) are contained as essential components. And a coating composition formed from the resin composition has a glass transition temperature of 40.
To 90 ° C., and the inter-crosslinking molecular weight is 60.
A resin composition for a topcoat paint for automobile plastic parts, which is in the range of 0 or less. 2. The above-mentioned homopolymer obtained is an amphipathic vinyl monomer (a) which exhibits water solubility and oil solubility.
-1) is represented by the following general formula [I]: CH ₂ ═CR ¹ CON (R ² ) ₂ [I] [wherein R ¹ represents a hydrogen atom or a methyl group,
R ² is an alkyl group having 1 to 3 carbon atoms. The composition according to claim 1, which is a vinyl-based monomer having a dialkylacrylamide group represented by the formula (1). 3. The above-mentioned curing agent (B) is at least one compound selected from the group consisting of a melamine resin, a polyisocyanate compound and an acid anhydride group-containing compound as a curing agent having reactivity with a hydroxyl group. Yes, claim 1
A composition according to claim 1. 4. The curing agent (B) is at least one selected from the group consisting of a carboxyl group-containing acrylic resin and a carboxyl group-containing polyester resin as a curing agent having reactivity with an epoxy group. The composition of claim 1 which is a compound of 5. The above-mentioned curing agent (B) is at least one compound selected from the group consisting of an epoxy group compound and an epoxy group-containing acrylic resin as a curing agent having reactivity with a carboxyl group, The resin composition for paint according to claim 1. 6. The resin composition for coating composition according to claim 1, wherein 2 coat 1 bake finish, 2 coat 2 bake finish, 3 coat 2 bake finish and 1 coat 1
A coating finishing method for automobile plastic parts, which is used as a top clear for bake finishing.