JPH10204332A - Thermosetting powder coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a powder coating compsn. for topcoating that is stable during its storage, exhibits excellent low-temp. meltability and low-temp. curability in its application, and can form a coating film excellent in physical properties, by making the composition contain a copolymer formed from a glycidylated monomer having a double bond, styrene, and an unsatd. monomer having no carboxyl group nor t-butyl ester group, and an aliph. dicarboxylic anhydride curing agent, and a tin-base cure catalyst. SOLUTION: The copolymer used is formed from 20-60wt.% glycidylated monomer having a double bond, 1-30wt.% styrene, and 10-79wt.% ethylenically unsatd. monomer having no carboxyl group nor t-butyl ester group. A straight- chain linear fatty acid condensate represented by formula I (wherein m is 4-20; and n>=2) is used as the curing agent. A compd. represented by formula II (wherein j+k is 2; X is a halogen, etc.; and R and R' are each an alkyl, etc.) is used as the cure catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosetting powder coating composition, and more particularly to an excellent appearance property (smoothness, sharpness, etc.) and physical properties (impact resistance, scratch resistance). , Adhesion, etc.), weather resistance and UV resistance, and chemical properties (acid resistance,
The present invention relates to a thermosetting powder coating composition which exhibits a baked coating film having solvent resistance and the like, has excellent storage stability of the coating composition, and has a low-temperature melting property / low-temperature curing property.

[0002]

[Prior art]

[Research and development trends in paint technology from the viewpoint of ecology, etc. and expectations for powder coatings] Conventionally, solvent-based coatings have been used for coating materials, and they are used in fields requiring strict quality, such as automobiles. For this purpose, paints satisfying various requirements have been developed and used.

In recent years, in the field of paint technology, from the viewpoint of local or global environmental preservation, improvement of occupational health and safety environment, prevention of fire and explosion, and resource saving, etc., solvent paint has been replaced with powder paint. Changes have been expected. And, due to historical or social demands, as the expectations for higher functionality and diversification of powder coatings grow,
Higher film performance (eg, impact resistance, acid rain resistance, etc.) comparable to solvent-based paints has been required.

[0004] However, even though the coating film performance required for powder coatings has become strict, it cannot be said that powder coatings that completely satisfy such requirements have always been put on the market.

[Technical Background of Powder Coatings in General] Specific examples of conventional powder coatings include, for example, epoxy resin and polyester resin powder coatings mainly composed of bisphenol A. However, these have problems not only in weather resistance but also in resistance to acid rain, which has been a particular problem recently, and have problems in applications intended for outdoor use such as painting of automobile bodies. .

[Technical Background of Acrylic Resin Powder Coating]
JP-A-49-34546 discloses a paint which is cured by a reaction between an acrylic resin component having a glycidyl group and an aliphatic dibasic acid as a curing agent component. However, the curing speed of the powder coating is not always sufficient, and high-temperature and long-time baking conditions are indispensable. And, the coating film formed from the powder coating material did not always have sufficient physical properties such as solvent resistance and adhesion.

Further, in such a technique without using a curing catalyst, a functional group (an acrylic resin component;
By increasing the amount of glycidyl group, curing agent component; carboxyl group), the cross-linking during coating film formation is improved,
Even if you intend to achieve low-temperature melting / low-temperature curing,
Problems similar to those described above and other problems have arisen.

Japanese Patent Application Laid-Open No. 5-112743 discloses that a monomer having at least 20% by weight of a glycidyl group
A powder coating containing a resin component containing an acrylic resin synthesized from a system containing 5 to 50% by weight of a styrene monomer is disclosed. However, when the amount of styrene exceeds 30% by weight, a problem occurs in the weather resistance of the coating film.

Japanese Patent Application Laid-Open No. 5-132634 discloses that a copolymer synthesized from a system containing a monomer having a glycidyl group and tertiary butyl acrylate or tertiary butyl methacrylate as an acrylic resin component is used as a curing agent. A technique of forming a coating film by using the same components as those described in JP-A-5-112743 and by the same curing method as in the prior art is disclosed. However, for the acrylic resin component, the third
When butyl acrylate or tertiary butyl methacrylate is used, these may cause a side reaction with other monomers having a glycidyl group during polymerization, or cause thermal decomposition during polymerization or during solvent removal during recovery, A gel, which is a product of an undesired side reaction, is likely to occur. When a coating film is formed from the powder coating composition containing such a gel-like material, unevenness tends to occur on the coating film surface.

Further, US Pat. No. 3,919,346 and US Pat. No. 3,919,347 disclose a system comprising an acrylic resin component containing a monomer having a glycidyl group and a monomer having a hydroxyl group. A method is disclosed in which the obtained copolymer is crosslinked and cured using an anhydride of dicarboxylic acid as a curing agent component. However,
In the present invention, the use of a curing agent comprising a resin component having a hydroxyl group and an anhydride of a dicarboxylic acid has resulted in poor storage stability of the paint.

[Acrylic resin-based powder coating containing a compound having an acid anhydride group as a curing agent] JP-A-50-5154
The technique disclosed in No. 2 discloses a method of curing a copolymer composed of a system containing a monomer having 5 to 20% by weight of a glycidyl group as an acrylic resin component by curing a dicarboxylic acid or a linear acid anhydride. It is a method of crosslinking and curing using an agent. However, 20% by weight of a monomer having a glycidyl group is used.
In the case of a copolymer containing the following, the crosslinked density of the obtained coating film was insufficient, and the solvent resistance and the weather resistance were poor.

Many researches and developments have been promoted for the purpose of solving the problems of the above-mentioned known techniques. U.S. Pat.
No. 1,048 and JP-B-58-2983 disclose a copolymer containing 5 to 20% by weight of a monomer having a glycidyl group, and a coating which is crosslinked and cured from an acid anhydride group. However, since these copolymers also use a copolymer containing 20% by weight or less of a monomer having a glycidyl group, the cross-linking density of the obtained coating film is insufficient, and the solvent resistance and weather resistance are not necessarily sufficient. Was.

Particularly, Japanese Patent Publication No. 58-2983 discloses a cyclic acid anhydride (a compound having a cyclic acid anhydride group).
There is disclosed a technique relating to a powder coating composition that employs as a curing agent. Here, the cyclic acid anhydride may be aromatic or alicyclic. However, when the above-mentioned cyclic acid anhydride is used as a curing agent component, there are problems with low compatibility between the resin component / curing agent component and low crosslinking formation efficiency between the resin component / curing agent component.

[0014] EP-A-299,420 states that
Acrylic copolymer containing a glycidyl group, as a curing agent, a polyol-modified polymeric polyanhydride having an acid anhydride bond and a plurality of acid functional groups in a polymer skeleton and having substantially no halogen atom. A modified polyanhydride curing agent-containing powder coating composition is disclosed. However, when the polyol-modified polymeric polyanhydride is used as a curing agent, curing at the time of baking is insufficient, and not only physical properties of a coating film such as solvent resistance and scratch resistance are insufficient, but also storage of the coating material. Stability was also insufficient.

[0015] EP-A-695,771 discloses a technique using polyisocyanate-modified dicarboxylic acid (poly) anhydride as a curing agent for an epoxy-functional paint resin. In this case, the coating film had insufficient resistance such as weather resistance.

[Technical Background of Acrylic Resin Powder Coating Containing Curing Catalyst] JP-A-63-165463 discloses a specific glycidyl group-functional acrylic resin, aliphatic dibasic acid (anhydride) and alkyl titanate. There is disclosed a thermosetting acrylic resin powder coating composition which contains a compound as a main component and melts and hardens at a low temperature and gives a coating film having excellent hardness, impact resistance, bending resistance and the like. That is, (A) (meta)
A glycidyl group-functional acrylic resin obtained by copolymerizing an alkyl ester of acrylic acid having 1 to 14 carbon atoms and a glycidyl ester of (meth) acrylic acid as main components, (B) an aliphatic dibasic acid (preferably Is adipic acid, sebacic acid, decane diacid, muconic acid, etc.) or its linear acid anhydride, and the formula (C) Ti (OR) ₄ (R is
A thermosetting acrylic resin powder coating material containing an alkyl titanate compound represented by an alkyl group having 15 to 20 carbon atoms (eg, tetrapentadecyl titanate) as a main component is disclosed.

Here, the alkyl titanate compound has a function of catalyzing a cross-linking reaction between the resin component and the curing agent component at a low temperature when forming a coating film of the powder coating composition, and has a low melting property / low temperature curing property. It is considered to have an effect of significantly expressing sex. However, the present invention was not necessarily sufficient in terms of low-temperature meltability / low-temperature curability, storage stability, and the like.

Japanese Patent Application Laid-Open No. 8-231893 discloses a glycidyl group-containing acrylic copolymer (A), an aliphatic polycarboxylic acid (B), an aliphatic polycarboxylic acid linear anhydride (C) or Discloses a thermosetting powder coating composition containing a salt (D) of a tertiary amine compound and an organic acid and / or a tertiary amine compound (E) having a melting point of 20 ° C to 150 ° C.

However, the storage stability and the low-temperature curability of the present invention cannot be said to be sufficient with respect to the storage stability or the low-temperature curability. As disclosed in Japanese Patent Application Laid-Open No. Hei 8-231893, an aliphatic polycarboxylic acid coexists. When a salt of a tertiary amine compound and an organic acid and / or a tertiary amine compound having a melting point of 20 ° C. to 150 ° C. is used as a curing catalyst in a powder coating composition, a temperature of about 40 ° C. and a relative humidity of about 90% are used. Under storage conditions of relatively high temperature and high humidity, problems such as gelation and poor appearance of the coating film occurred due to high reactivity between glycidyl group and carboxyl group during storage. In addition, there is a problem that yellowing of the coating film becomes remarkable when the film is baked at a more severe temperature than the usual baking conditions.

[0020]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the object of the present invention is to achieve excellent stability before forming a coating film (during storage), which was difficult to achieve by the prior art. To provide a thermosetting powder coating composition capable of simultaneously exhibiting excellent coating properties and physical properties after coating film formation. It is in.

It is a further object of the present invention to provide a method capable of favorably producing such an excellent thermosetting powder coating.

[0022]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosetting powder for a top coat comprising a copolymer component (A), a curing agent component (B), and a curing catalyst component (C). The body paint composition, wherein the monomer (a-) is added to the total of 100 parts by weight of the monomers (a-1), (a-2) and (a-3).
(1) 20 to 60 parts by weight of an ethylenically unsaturated monomer having at least one glycidyl group and at least one unsaturated double bond in the molecule, and styrene 1 to 30 as a monomer (a-2). Parts by weight and monomer (a-3)
As an ethylenically unsaturated monomer 10 having neither a carboxyl group nor a tertiary butyl ester group in the molecule.
A copolymer component (A) obtained by radical polymerization in a reaction system containing -79 parts by weight, and a linear linear acid anhydride of an aliphatic divalent carboxylic acid represented by the following general formula (1). Curing agent component (B) HO- [OC (CH) mCOO] n-H (1) (m = 4 to 20, n ≧ 2, each being a natural number) and represented by the following general formula (2) (C) R _j SnX _k (2) (j and k are 0 or a natural number such that j + k = 2. X is a halogen, OH, OR ′, SR ′ or OCO
R ′. R and R 'are each independently an alkyl group or an aryl group. ) Can be achieved by a thermosetting powder coating composition for a top coat, which is characterized by containing:

Still another object of the present invention is a method for producing a thermosetting powder coating material using the composition of the present invention, wherein the method comprises at least a copolymer component (A),
A method for producing a thermosetting powder coating, comprising: a step of melt-kneading a raw material containing a curing agent component (B) and a curing catalyst component (C); and a step of cooling and pulverizing the melt-kneaded product. Can be achieved by

The present invention is characterized in that the above components (A), (B) and (C) are used in combination, that the component (A) having a specific styrene content is used, and that the specific curing catalyst component (C) It is particularly characteristic in that it is used. By controlling these compositions and composition ratios, a higher degree of action and effect can be exhibited.

The thermosetting powder coating composition of the present invention is particularly useful for automobile bodies and automobile parts (aluminum wheels, wipers, pillars, door handles, fenders, bonnets, air spoilers, stabilizers, front grills, etc.). Coatings-especially topcoats (topcoats)
-Is preferably applied.

The coating film of the top coat includes appearance characteristics (smoothness, sharpness, etc.), physical characteristics (impact resistance, scratch resistance, adhesion, etc.), and chemical characteristics (acid resistance, acid rain resistance, (Solvent resistance, pitch resistance, etc.), weather resistance and UV resistance, strict quality is required, but the thermosetting powder coating composition of the present invention, despite being a powder coating, Such demands can be sufficiently satisfied.

Further, the thermosetting powder coating composition of the present invention can exhibit the above-mentioned excellent performance even when applied and baked on an aqueous undercoat.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION

[Copolymer component (A)] In the claims and specification of the present application, the copolymer may be any of a random copolymer, an alternating copolymer, a block copolymer, a graft copolymer and the like. The polymer may be linear, macrocyclic, branched, star-shaped, or three-dimensional network-shaped.

[Monomer (a-1)] In the present invention, the monomer (a-1) having a glycidyl group and an unsaturated double bond copolymerized in the copolymer component (A) includes: The compound is not particularly limited as long as it is a compound having a glycidyl group and an unsaturated double bond substantially in combination.

Specific examples of the monomer (a-1) include, for example, glycidyl acrylate, glycidyl methacrylate, β-methyl glycidyl acrylate, β-methyl glycidyl methacrylate, N-glycidyl acrylamide, allyl glycidyl ether, vinyl sulfone Glycidyl acid and the like. Among them, glycidyl acrylate and glycidyl methacrylate are preferred. These can be used alone or in combination of two or more.

The amount of the monomer (a-1) used is
20 to 60 parts by weight, preferably 25 to 50 parts by weight, based on 100 parts by weight in total of -1), (a-2) and (a-3). When the amount of the monomer (a-1) exceeds 20 parts by weight, the resulting coating film has a high crosslinking density and has good coating characteristics such as impact resistance, scratch resistance, and solvent resistance, which are preferable. When the amount of the monomer (a-1) is at most 60 parts by weight, the appearance of the coating film such as smoothness and sharpness will be good, which is preferable.

[Monomer (a-2)] Copolymer component (A)
The amount of the styrene component (monomer (a-2)) to be copolymerized therein is determined by the monomers (a-1), (a-2) and (a-
1 to 30 parts by weight, preferably 10 to 30 parts by weight, more preferably 10 to 20 parts by weight, based on 100 parts by weight in total of 3). The styrene component contributes to properties such as gloss and smoothness of the coating film and storage stability of the coating composition. If the amount of the styrene component is less than 1 part by weight, the effect due to styrene decreases, and if it exceeds 30 parts by weight, the weather resistance of the coating film tends to decrease.

[Monomer (a-3)] Copolymer component (A)
The ethylenically unsaturated monomer (a-3) which is copolymerized with the compound (a-3) is substantially different from the monomers (a-1) and (a-2), and has a carboxyl group and a tertiary butyl ester group. Any compound having no unsaturated group in the molecule and having a radically polymerizable unsaturated group can be used, and one or more compounds may be used in combination.

Specific examples of the monomer (a-3) include, for example, carboxylic esters, unsaturated hydrocarbons, nitriles, amides, etc. Among them, carboxylic esters are exemplified. Preferably, esters of primary or secondary alcohols with acrylic acid or methacrylic acid are more preferred.

Specific examples of esters of primary or secondary alcohols with acrylic acid or methacrylic acid include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, dodecyl Acrylate derivatives such as acrylate, stearyl acrylate, cyclohexyl acrylate, benzyl acrylate, phenyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, 1,4-butanediol monoacrylate, dimethylaminoethyl acrylate, methyl methacrylate, ethyl Methacrylate, propyl methacrylate, isopropyl methacrylate, Methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate,
Phenyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, 1,4-butanediol monomethacrylate, methacrylic acid derivatives such as dimethylaminoethyl methacrylate, vinyl acetate, vinyl esters such as vinyl propionate, maleic acid, Dicarboxylic acid esters such as itaconic acid, α-methylstyrene,
Unsaturated hydrocarbons such as vinyltoluene, t-butylstyrene, vinylanisole, vinylnaphthalene, divinylbenzene, chlorostyrene, etc., acrylonitrile,
Nitriles such as methacrylonitrile, amides such as acrylamide, methacrylamide, vinylamide, N-methylolacrylamide, N-methylolmethacrylamide, diacetoneacrylamide, diacetonemethacrylamide, vinyl chloride, vinylidene chloride, vinyl fluoride, monochlorotrile Halogenated ethylenically unsaturated monomers such as fluoroethylene, tetrafluoroethylene and chloroprene, ethylene, propylene, isoprene, butadiene, α-olefins or dienes having 4 to 20 carbon atoms, and alkyl vinyl ethers such as lauryl vinyl ether And ethylenically unsaturated monomers including nitrogen-containing vinyls such as vinylpyrrolidone and 4-vinylpyrrolidone. These may be used alone or in combination of two or more. Kill.

The amount of the monomer (a-3) used is
10 to 79 parts by weight, preferably 10 to 70 parts by weight, more preferably 30 to 65 parts by weight, based on 100 parts by weight of the total of -1), (a-2) and (a-3).

[Copolymerization] In the copolymerization of the copolymer component (A), generally, as a monomer (a-3), a carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, itaconic acid or the like is used. When a compound having a group is used, it is not preferred because gelation may occur during polymerization or bumps may occur on the coating film after the formation of the coating film.

In the case where t-butyl (meth) acrylate is usually used as the monomer (a-3) during the copolymerization of the copolymer component (A), it may be used at the time of removing the solvent or preparing the coating composition. Heating at this time causes decomposition of the t-butyl group of the copolymer component (A) to generate a carboxyl group, which is not preferable because the same problem as described above may occur.

The glass transition point (Tg) calculated from the Fox equation of the copolymer component (A) is from about 20 to about 100 ° C.
Is preferable, about 30 to about 90 ° C. is more preferable, and about 5 to about 90 ° C. is preferable.
0 to about 80C is particularly preferred. When the Tg is 20 ° C. or higher, the storage stability of the coating composition tends to be improved.

[Calculated value of glass transition point to evaluation of glass transition point (Tg) of heteropolymer] The glass transition point (Tg) of a polymer having a specific monomer composition can be obtained by calculation using the Fox equation. it can. Here, the Fox equation is for calculating the Tg of the copolymer based on the Tg of the homopolymer of the monomer for each monomer forming the copolymer, For more information, see Bullet
in of the American Physic
al Society, Series2 Volume 1 ・ 3 ・
P. 123 (1956).

The Tg of various ethylenically unsaturated monomers, which is the basis for evaluating the Tg of the copolymer according to the Fox equation, can be found, for example, in Shin Polymer Bunko, Vol. 7, Introduction to Synthetic Resins for Paints (Kitaoka By Kyozo, Polymer Publishing Association, Kyoto, 197
(4 years) The numerical values described in Table 10-2 (main raw material monomers of acrylic resin for paint) on pages 168 to 169 can be adopted.

All of the descriptions are incorporated as a part of the disclosure of the specification of the present application by citing the cited documents and the cited ranges, and by referring to the specified cited ranges, the matters or the disclosures described in the specification of the present application are described. Thus, matters or disclosures that can be directly and uniquely derived by those skilled in the art.

[Synthesis Method of Copolymer Component (A)] The method of synthesizing the copolymer component (A) is not particularly limited as long as it has substantially desired properties.

The copolymer component (A) can be synthesized by a known and publicly used ordinary method. For example, it can be prepared by a radical polymerization method including a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a bulk polymerization method. In particular, a solution polymerization method is suitably used.

[Molecular Weight of Copolymer Component (A)] Methods for adjusting the molecular weight of the copolymer component (A) include mercaptans such as dodecyl mercaptan, disulfides such as dibenzoyl sulfide, and thioglycolic acid 2- Thioglycolic acid such as ethylhexyl has 1 to 1 carbon atoms.
18 alkyl esters, a chain transfer agent of halogenated hydrocarbons such as urea tetrabromide, isopropyl alcohol,
Means such as polymerization in the presence of an organic solvent having a large chain transfer effect such as isopropylbenzene and toluene can be used.

The number average molecular weight of the copolymer component (A) is preferably from about 1,000 to about 30,000, and is preferably from about 2,000 to
About 20,000 is more preferred, and about 2,500 to about 6.0
00 is particularly preferred. When the number average molecular weight is about 1,000 or more, generally, the storage stability of the coating composition is good and preferable.

The number average molecular weight of the copolymer component (A) was evaluated by gel permeation chromatography (GPC) using polystyrene as a standard.

[Curing Agent Component (B)] In the present invention, the linear linear acid anhydride of an aliphatic dihydric carboxylic acid is substantially
A linear oligo- or polyaliphatic acid anhydride (anhydride) having a carboxyl group in the molecule, wherein at least two carboxyl groups and acid anhydride (anhydride) groups substantially exist in the molecule. It is not particularly limited as long as it has a compound, and one kind or two or more kinds can be used.

In some cases, aliphatic polycarboxylic acids such as aliphatic dihydric carboxylic acids may remain as impurities in the linear linear anhydride, but this has an adverse effect on the thermosetting powder coating composition. As long as it is not provided, it may remain.

Preferably, the linear linear anhydride of the aliphatic dihydric carboxylic acid is prepared such that the melting point is in the range of about 40 to about 150 ° C. Generally, when the melting point of the linear linear acid anhydride of aliphatic dihydric carboxylic acid is about 40 ° C. or higher, the blocking resistance of the coating composition tends to be improved. Further, generally, when the melting point of the linear linear anhydride of the aliphatic dihydric carboxylic acid is about 150 ° C. or lower, the heating fluidity of the coating tends to improve, and the resulting coating film has an appearance such as smoothness. The characteristics tend to improve.

This linear dicarboxylic acid anhydride of an aliphatic dicarboxylic acid is represented by the following general formula (1).

HO- [OC (CH2) mCOO] n-H (1) (m = 4 to 20, n ≧ 2, each being a natural number.) The upper limit of n is preferably about 20. .

Specific examples of the linear linear acid anhydride of an aliphatic dicarboxylic acid include aliphatic dihydric carboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, eicosane diacid and dodecane diacid. Examples include a linear linear condensate derived from at least one compound selected from acids by dehydration condensation. Of these, dehydrated linear linear condensates of azelaic acid, sebacic acid, dodecane diacid, and eicosane diacid are more preferred.

As the linear linear anhydride of the aliphatic dicarboxylic acid, a linear anhydride obtained by dehydration condensation of two or more aliphatic dicarboxylic acids can be used.

[Linear linear anhydride of aliphatic dihydric carboxylic acid] The term "linear linear anhydride of aliphatic divalent carboxylic acid" includes "polymeric polyanhydride", "Polymeric anhydrides containing an acid anhydride group in the polymer skeleton and containing a plurality of acid functional groups", "polyanhydrides of aliphatic carboxylic acids", "polymeric pol"
yanhydride "," polymeric po "
lynhydride containing an
hydridlinkes in the p
and "polymeric backbone" and "poly"
anhydride of alipatic ca
roxylic acids "and the like.

When a cyclic acid anhydride of a polycarboxylic acid such as succinic anhydride or phthalic anhydride is reacted with the copolymer component (A), the acid anhydride is converted into the copolymer component (A). The use of this compound is usually not preferred because it has a high probability of reacting only with the epoxy ring of the specific glycidyl group in the molecule and has a small effect of bridging a plurality of copolymer component (A) molecules.

The terms “anhydride”, “anhydride group”, “anhydride bond” and “polyanhydride” used in the specification of the present application include “MARUZ”.
EN Polymer Dictionary-Concise Encyclop
edia of PolymerScience an
d Engineering (Kroschwitz
Ed., Translated by Tatsuta Mita, Maruzen, Tokyo, 1994) "・ 99
The concept of each word described in the section of “Polyanhydride” on pages 6 to 998 is also included.

All of the descriptions are incorporated as a part of the disclosure of the specification of the present application by specifying the cited documents and the cited ranges, and by referring to the specified cited ranges, the matters or disclosures described in the specification of the present application are described. Thus, matters or disclosures that can be directly and uniquely derived by those skilled in the art.

In the early 1980's when polyanhydride was actively researched and developed on biodegradable bio (medical) polymer materials and application of the materials to drug delivery systems, researchers at MIT were active. And came to the spotlight.

The linear linear acid anhydride of an aliphatic dicarboxylic acid can be synthesized, for example, by a method such as melt polycondensation, solution polycondensation, and interfacial polycondensation.

The amount of the linear dianhydride of the aliphatic dihydric carboxylic acid to be used is based on 1 equivalent of the glycidyl group in the copolymer component (A) and the linear linear anhydride of the aliphatic dihydric carboxylic acid. Of the carboxyl group and the acid anhydride group present in the molecule of about 0.1.
5 to about 2.0 equivalents are preferred, and about 0.7 to about 1.2 equivalents are more preferred. When the amount of the linear linear acid anhydride of the aliphatic dihydric carboxylic acid is within the above range, the resulting coating film has good appearance, and has excellent properties such as solvent resistance, impact resistance, and weather resistance. I have.

[Curing Catalyst Component (C)] The curing catalyst component (C) can be used in combination with the copolymer component (A) and the curing agent component (B) without impairing the storage stability of the paint. Compared with the case where (C) is not used, there is no particular limitation as long as the paint baking conditions can be obtained at a lower temperature, in a shorter time and with good coating properties.

In the present invention, the curing catalyst component (C) comprises:
The following general formula (2): R _j SnX _k (2) (j and k are 0 or a natural number such that j + k = 2. X is halogen, OH, OR ′, SR ′ or OCO
R ′. R and R 'are each independently an alkyl group or an aryl group. ), One or more of which can be used. When R and R ′ are alkyl groups, the number of carbon atoms is 6 to
About 18 is preferable.

Preferred specific examples of the above compounds include:
For example, stannous hexanoate, stannous octoate, stannous laurate, stannous stearate, stannous 2-ethylhexanoate, stannous chloride, stannous bromide Tin salts and the like.

Particularly preferred examples include stannous hexanoate, stannous octoate, stannous laurate, stannous stearate and the like.

As another specific example of the curing catalyst, for example,
Examples thereof include quaternary ammonium salts, phosphonium salts, phosphines, imidazoles, amines, and melamine-based compounds. Depending on the mode of the powder coating composition, these compounds may be used to improve the storage stability of the powder coating composition or the coating film. There may be a problem regarding characteristics (appearance such as smoothness).

On the other hand, the curing catalyst component (C) used in the present invention hardly exhibits a curing acceleration effect during storage of the powder coating, and the storage stability (chemical stability) of the powder coating is good. In the baking temperature range of the powder coating at 100 ° C. or higher, the effect of accelerating the curing is remarkably exhibited.

The amount of the curing catalyst component (C) used is generally 1% of the total of the copolymer component (A) and the curing agent component (B).
The amount is preferably about 0.005 to about 3 parts by weight, more preferably about 0.01 to about 2 parts by weight, based on 00 parts by weight. When the amount of the curing catalyst component (C) used is 3 parts by weight or less, the storage stability of the coating composition is generally good, the curing reaction is performed at an appropriate speed, the smoothness of the coating film, and the storage stability of the coating. Sex is maintained.

[Characteristics of Curing Catalyst Component (C)] The curing catalyst component (C) has a storage stability of the paint even under high temperature and humidity conditions, particularly at a temperature of 40 ° C. and a relative humidity of 90% or more. It is characteristic in that it is not damaged and that the curing acceleration effect is remarkably exhibited when the temperature reaches the baking temperature range of the paint. As a curing catalyst, a tertiary amine or a metal salt of a carboxylic acid, such as sodium octanoate or calcium stearate, as disclosed in JP-A-5-112743 and JP-A-5-132634, is used as the component (A) and When used in combination with (B), it is difficult to satisfy both low-temperature meltability / low-temperature curability and storage stability.

[Additives] In the present invention, various additives usually added to paints can be used.

For example, the powder coating composition of the present invention may contain a synthetic resin composition including an epoxy resin, a polyester resin, a polyamide, and the like, and a natural resin including a cellulose or a cellulose derivative. Alternatively, a coating film appearance or coating film properties can be improved by blending a semi-synthetic resin composition.

For example, in the powder coating of the present invention, pigments, flow regulators, thixotropic agents (thixotropic regulators), charge regulators, surface regulators, gloss-imparting agents, anti-blocking agents may be appropriately added according to the purpose. Further, additives such as a plasticizer, an ultraviolet absorber, an anti-bake agent, and an antioxidant may be blended.

[About kneading of powder coating composition] Components (A) and (B) or components (A), (B) and (C)
The temperature of the material to be kneaded when mechanically kneading the composition containing is not particularly limited as long as a substantially uniform powder coating composition can be prepared.

As the melt kneading apparatus, a heating roll machine, a heating kneader, an extruder (extruder) and the like are usually used.

Specific examples of the method of blending the thermosetting powder coating composition of the present invention include a roll machine, a kneader machine, a mixer (Banbury type, transfer type, etc.), a calendar facility, an extruder (extruder) and the like. Kneaders and kneaders are appropriately combined, and the conditions of each step (temperature, melting or non-melting, rotation speed, vacuum atmosphere, inert gas atmosphere, etc.) are appropriately set and mixed sufficiently uniformly. After that, a method of obtaining a powder coating composition in a uniform fine powder state by a pulverizer can be adopted, but the method is not limited thereto.

One embodiment of the compounding and kneading step of adding an additive and the like to the powder coating composition of the present invention is as follows. The thermosetting powder coating composition of the present invention may contain, if necessary, an antiblocking agent and a surface conditioning agent. Agents, plasticizers, charge control agents, pigments, fillers,
Additives such as a bulking agent are added, and the mixture is sufficiently melt-kneaded in a range of about 40 to about 130 ° C., cooled, and then uniformly ground to an appropriate particle size (usually, about 100 mesh or less) to obtain a powder coating. .

[Coating Method and Baking Method] The powder coating obtained by pulverization is applied to an object to be coated, heated and thermally cured to form a coating film.

Specific examples of the method of applying the thermosetting powder coating composition of the present invention include known coating methods such as an electrostatic coating method and a fluid immersion method.

When the thermosetting powder coating composition of the present invention is used as an overcoat,
In the case of using not only a conventional solvent-type paint but also a water-based paint, the paint film of the present invention has excellent properties in the film after baking, as in the case of using the solvent-type paint.

That is, an aqueous undercoat (including pigment and / or metal powder) is applied and dried for a predetermined time, and then the thermosetting powder coating composition of the present invention is coated with the undercoat by the method described above. And heat-cured by heating to form a coating film.

The baking of the thermosetting powder coating composition of the present invention is usually carried out at a temperature in the range of 100 to 200 ° C. Preferably about 100 to about 160 ° C, more preferably about 1
At a temperature of 20 to about 150 ° C, usually about 10 to about 60
By performing the reaction for a period of one minute, a crosslinking reaction between the copolymer component (A) and the curing agent component (B) can be performed. After baking,
By cooling to room temperature, a coating film having excellent properties can be obtained.

The coating method to which the thermosetting powder coating composition of the present invention can be applied is also applied to an automobile body or an automobile part. In particular, it is very useful as a top coat for the body of an automobile or an automobile part.

[Concept of the word "derivative"] The concept of the word "derivative" used in the claims and the specification of the present application means that a hydrogen atom of a specific compound is replaced by another atom or an atomic group Z. Includes

Here, Z is a monovalent hydrocarbon group containing at least one carbon atom. More specifically, Z is an aliphatic group, an alicyclic group having a substantially low aromaticity, or a combination thereof. Group, or a residue in which these are linked by a hydroxyl group, a carboxyl group, an amino group, nitrogen, silicon sulfur, phosphorus, etc., and among these, particularly those having an aliphatic structure in a narrow sense. preferable.

Z is the same as described above, except that a hydroxyl group, an alkyl group, a cycloalkyl group, an allyl group, an alkoxyl group, a cycloalkoxyl group, an allyloxyl group, a halogen (F, Cl, Br, etc.) group is substituted. It may be a group.

By appropriately selecting these substituents, it is possible to control various properties of a coating film formed by the powder coating composition of the present invention.

[Concept of the term "storage stability"] The concept of the term "storage stability" used in the specification of the present application includes physical stability (blocking resistance) and chemical Includes stability (solid phase resistance).

[0088]

Examples Examples, production examples and embodiments described below are as follows.
The purpose is to assist understanding of the contents of the present invention, and the description does not limit the present invention in any way. In the description, “parts” and “%” are values by weight unless otherwise specified.

[Production Example 1] Production of copolymer component (A) 66.7 parts of xylene was charged into a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet tube, and cooled to reflux temperature. The temperature was raised while stirring. After reaching the reflux temperature, the monomers shown in Table 1 and t-butyl-peroxy-2-ethylhexanoate (trade name: Perbutyl O, manufactured by NOF Corporation) as a polymerization initiator were added for 5 hours. After that, the mixture was further kept for 1 hour, and then 0.5 part of perbutyl O was added dropwise at 100 ° C. and kept for 2 hours. The solvent was removed from the obtained polymerization solution to obtain a copolymer component (A-1).

Further, as shown in Table 1, various copolymer components (A-2) to (A-5) were obtained by changing the type and composition of the monomers.

Various physical properties of the copolymer were measured by the following methods. (1) Glass transition temperature (Tg); based on monomer composition,
It was obtained by calculation according to the Fox equation. (2) Number average molecular weight (Mn): Measured by GPC using polystyrene as a standard.

[0092]

[Table 1] Legend: ST: Styrene MMA: Methyl methacrylate nBMA: n-butyl methacrylate iBMA: iso-butyl methacrylate GMA: glycidyl methacrylate PB-O: t-butyl-peroxy-2-ethylhexanoate.

[Production Example 2] Production of linear linear anhydride of aliphatic divalent carboxylic acid 1 mol of dodecane diacid and 0.8 mol of acetic anhydride were charged into a reaction vessel, and the temperature was raised to 150 ° C. The reaction was carried out for 5 hours while removing generated acetic acid by a vacuum line so that acetic anhydride did not flow out of the system. Thereafter, the mixture was immediately cooled, and a white solid was recovered to obtain a linear linear anhydride of dodecane diacid. The melting point of this compound was 73 to 82 ° C.

Further, a linear linear anhydride of sebacic acid was also produced in the same manner using sebacic acid, and the melting point was 7
2-81 ° C was obtained. Further, other carboxylic acid linear anhydrides were produced in the same manner.

[Evaluation of Performance] The powder coatings obtained in Examples and Comparative Examples described later were evaluated by the following methods. (1) Smoothness Observe the appearance of the coating film,
も の indicates a slightly uneven surface, and × indicates a poor smoothness. (2) Sharpness Using a DOI meter (Paul N. Gardner), GM91
The coating film was evaluated according to No. 013. DOI value is 90
A film having a sharpness of 100 or more was evaluated as ◎ as a coating film having excellent clarity, a film having a value of 70 or more and less than 90 was evaluated as 、, and a film having less than 70 was evaluated as a coating film having poor clarity. (3) Gloss The gloss was measured (60 ° gloss). (4) Impact resistance test (DuPont impact test) It was carried out in accordance with JIS K5400 6.13.3.
The weight of the weight adopted here is 500 g. The numerical value of the evaluation result was indicated by the drop height at which cracks and peeling occurred in the coating film. (5) Adhesion Measured with an Erichsen tester and measured when the coating film peels off
(mm). (6) Solvent resistance The coating film surface is reciprocated 50 times with gauze impregnated with xylol.
Observation was performed after the rubbing. ◎ indicates no trace, ○ indicates a slight trace, and × indicates a trace. (7) Scratch resistance The coating film surface was subjected to a scratch test using a 0.3% cleanser suspension to rub with a brush, and the gloss value was evaluated before and after the friction to calculate the gloss retention. . 60% gloss retention
The above samples were evaluated as ◎ as a scratch-resistant coating film, and 50 to 60% were evaluated as ○, 40 to 50% as Δ, and less than 50% as a non-scratch coating film. (8) Weather resistance test A 4000 hour acceleration test was performed using a QUV tester, and the gloss (60 °) of the coating film before and after the acceleration test was measured.
The gloss retention (%) was determined. The gloss retention was calculated by the following equation. Gloss persistence (%) = (60 ° gloss after accelerated test) ÷
(60 ° glossiness before accelerated test) × 100 ◎ for gloss retention of 80% or more, を for 70-80%, Δ for 60-70%, × for less
And (9) Storage stability test of powder coating material (blocking resistance test) The powder coating material was visually and finger-touched to observe the blocking state after storage at a temperature of 40 ° C and a relative humidity of 90% for 14 days. As a result, ◎ indicates that there is no abnormality at all,
Inferior was rated as x. (10) Storage stability test of powder coating (solid phase resistance test) After storing the powder coating under the above conditions, 10 mmφ, 0.3 g
Was prepared and adhered on a plate, then kept vertically, and the dripping state of the pellet when baked at 140 ° C. for 30 minutes was measured. Those hanging over 150 mm or more are evaluated as ◎ as powder coatings having excellent solid phase resistance, and 100 to 150 mm are evaluated as 、, and those below are evaluated as ×.
And (11) Yellowing resistance test of paint film A powder paint is applied on a white acrylic base coat,
The yellowing state of the coating film when baked at 40 ° C. for 30 minutes or 150 ° C. for 60 minutes is measured by a colorimeter (Tokyo Denshoku Co., Ltd.)
Was calculated with respect to a white acrylic base coat not subjected to powder coating (ΔE = delta E). The smaller the value, the better the yellowing resistance of the coating film.

<Examples 1 to 8 and Comparative Examples 1 to 13> [Preparation of powder coating material] The copolymer component (A), the curing agent component (B) and the curing catalyst component (C) are shown in Tables 2 and 3. -3, and 100 parts of the total of the components (A) and (B) were mixed with Residmix RL-4 (trade name, manufactured by Mitsui Toatsu Chemicals, low viscosity acrylic resin, flow modifier). , Trade name Tinuvin 144 (manufactured by Ciba Geigy, light stabilizer),
After adding 1 part of each of benzoin (an anti-bake agent) and 2 parts of Tinuvin 900 (trade name, an ultraviolet absorber manufactured by Ciba Geigy) and mixing them sufficiently uniformly, the mixture was mixed using a twin-screw extruder. The mixture was melt-kneaded under the condition of 60 ° C., cooled, finely pulverized by a pulverizer, and a section having passed through a 150-mesh sieve was recovered to prepare a powder coating.

[Preparation of base treated steel sheet] A 0.8 mm thick matte steel sheet treated with zinc phosphate is coated with a polyester-melamine cross-linked black paint to a thickness of 20 µm, and then baked to prepare a base treated steel sheet. did.

[Preparation, coating and baking of test plate] The powder coating obtained by the method of the present invention and the powder coating obtained by the comparative example were
Electrostatic coating was performed on the base-treated steel sheet so that the film thickness became 60 to 70 μm, and baking was performed at 140 ° C. for 30 minutes to obtain a test plate.

The results of evaluation of the powder coatings and coating films formed in Examples 1 to 8 are shown in Tables 4 and 6. Tables 5 and 7 show the evaluation results of the powder coatings and the coating films formed in Comparative Examples 1 to 13 related thereto.

The powder coatings of Examples 1 to 8 shown in Table 2 are within the scope of the present invention, and include the type of the curing agent component (B) and the type and weight of the curing catalyst component (C). , And these results indicate excellent appearance, physical properties and weather resistance of the coating film, and excellent storage stability of the coating composition.

Comparative Examples 1 and 3 are examples in which a curing catalyst was not used. In this case, the baking of the coating film was insufficient, and the physical properties and weather resistance of the coating film were inferior.

Comparative Examples 1 and 2 are examples in which an aliphatic divalent carboxylic acid was used as a curing agent. In this case, the appearance and scratch resistance were poor.

Comparative Example 4 is an example using a copolymer containing no styrene. In this case, the appearance of the coating film and the storage stability of the coating material are inferior.

Comparative Example 5 is a case where the copolymer contains an excessive amount of styrene. In this case, the weather resistance of the coating film is inferior.

Comparative Example 6 was a case where the glycidyl group of the copolymer was out of the range of the present invention. Since the glycidyl group was too small, the physical properties of the coating film and the weather resistance were poor.

Comparative Example 7 is an example in which an aromatic acid anhydride was used as a curing agent. In this case, various performances were inferior.

Comparative Examples 8 and 9 are examples in which a metal salt of a carboxylic acid other than the present invention was used as a curing catalyst. In this case, the coating film was inferior in scratch resistance and weather resistance.

Comparative Examples 10 and 11 are examples in which an amine compound or a salt thereof outside the present invention was used as a curing catalyst.
In this case, the storage stability of the coating and the yellowing resistance during overheating are inferior.

Comparative Example 12 is an example in which tetrapentadecyl titanate was used as a component of a paint, and the storage stability of the paint was poor.

Comparative Example 13 is an example in which dibutyltin dilaurate, which is out of the range of the present invention, was used as a curing catalyst. The curing promotion was insufficient, and the solvent resistance and the scratch resistance were poor.

[0111]

[Table 2] [Legend] DDA anhydride: dehydrated condensate of dodecane diacid sephacinic anhydride: dehydrated condensate of sebacic acid SO: stannous octoate SS: stannous stearate

[0112]

[Table 3] Legend: DDA: Dodecane diacid DDA anhydride: Dehydrated condensate of dodecane diacid Terephthalic anhydride: Dehydrated condensate of terephthalic acid SO: Stannous octoate DSO: Sodium octoate CS: Calcium stearate M -2HT: ARMEEN M-2HT (amine based catalyst, manufactured by Lionax Corporation) DBU-Fa: DBU formate (1,8-diaza-bicyclo acid [5,4,0] undecene-7 and formed from formic acid Amine salt) TPT: Tetrapentadecyl titanate DTL: Dibutyltin dilaurate

[0113]

[Table 4]

[0114]

[Table 5]

[0115]

[Table 6]

[0116]

[Table 7]

[0117]

According to the present invention, excellent stability before coating film formation (during storage) and excellent stability during coating film formation, which were difficult to achieve with the prior art relating to powder coatings. Further, it is possible to provide a thermosetting powder coating composition capable of simultaneously exhibiting excellent coating film properties and physical properties after coating film formation.

The thermosetting powder coating composition of the present invention is particularly useful for automobile bodies and automobile parts (aluminum wheels, wipers, pillars, door handles, fenders, bonnets, air spoilers, stabilizers, front grills, etc.). Coatings-especially topcoats (topcoats)
-Is preferably applied.

The coating film of the top coat includes appearance characteristics (smoothness, sharpness, etc.), physical characteristics (impact resistance, scratch resistance, adhesion, etc.), and chemical characteristics (acid resistance, acid rain resistance, (Solvent resistance, pitch resistance, etc.), weather resistance and UV resistance, strict quality is required, but the thermosetting powder coating composition of the present invention, despite being a powder coating, Such demands can be sufficiently satisfied.

Further, the thermosetting powder coating composition of the present invention can exhibit the above-mentioned excellent performance even when applied and baked on an aqueous undercoat paint.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08G 59/36 C08G 59/36 59/42 59/42 59/68 59/68 C09D 157/06 C09D 157/06 (C08F 220 / 12 220: 32 212: 08) (72) Inventor Tsuyoshi Matsumoto 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Within Mitsui Chemicals, Inc. (72) Inventor Eiichi Kawasaki Lumiere Hill, Beppu City, Oita Prefecture H-88

Claims (8)

[Claims] 1. A thermosetting powder coating composition for a top coat, comprising a copolymer component (A), a curing agent component (B), and a curing catalyst component (C). Total 1 of bodies (a-1), (a-2) and (a-3)
20 parts by weight of an ethylenically unsaturated monomer having at least one glycidyl group and at least one unsaturated double bond in the molecule as the monomer (a-1), 1 to 30 parts by weight of styrene as a monomer (a-2), and ethylenically unsaturated monomer having neither a carboxyl group nor a tertiary butyl ester group as a monomer (a-3) A copolymer component (A) obtained by radical polymerization in a reaction system containing 10 to 79 parts by weight of a monomer; a linear linear acid anhydride of an aliphatic divalent carboxylic acid represented by the following general formula (1): (B) HO- [OC (CH) mCOO] n-H (1) (m = 4 to 20, n ≧ 2, each of which is a natural number) and the following general formula ( curing catalyst component containing a compound represented by 2) (C) R _j S X _k (2) (j and k, the j + k = 2, 0 or a natural number .X is halogen, OH, OR ', SR' or OCO
R ′. R and R 'are each independently an alkyl group or an aryl group. A) a thermosetting powder coating composition for a top coat, which comprises: 2. An equivalent ratio between a functional group present in the molecule of the copolymer of the copolymer component (A) and a functional group present in the molecule of the curing agent of the curing agent component (B) is a copolymer weight. Carboxyl groups and acid anhydrides (anhydrides) present in the curing agent molecule per one equivalent of glycidyl groups present in the molecules of the coalescing
The thermosetting powder coating composition according to claim 1, wherein the total of the groups is 0.5 to 2.0 equivalents. 3. The curing catalyst component (C) is contained in an amount of 0.005 to 3 parts by weight with respect to a total of 100 parts by weight of the copolymer component (A) and the curing agent component (B). 3. The thermosetting powder coating composition according to 2. 4. A linear linear anhydride of an aliphatic dihydric carboxylic acid represented by the general formula (1) is (b-1) azelaic acid, (b-2) sebacic acid, or (b-3) The heat according to any one of claims 1 to 3, which is a compound derived by dehydration condensation from at least one compound selected from the group consisting of eicosane diacid and (b-4) dodecane diacid. Curable powder coating composition. 5. A curing catalyst comprising a compound represented by the general formula (2), wherein (c-1) stannous hexanoate, (c-
2) At least one catalyst selected from the group consisting of stannous octoate, (c-3) stannous laurate, and (c-4) stannous stearate. The thermosetting powder coating composition according to any one of claims 1 to 4. 6. The heat according to claim 1, wherein the linear linear anhydride of the aliphatic dihydric carboxylic acid represented by the general formula (1) has a melting point of 40 to 150 ° C. Curable powder coating composition. 7. A method for producing a thermosetting powder coating material using the composition according to claim 1, comprising at least a copolymer component (A), a curing agent component (B) and a curing catalyst. A method for producing a thermosetting powder coating, comprising: a step of melt-kneading a raw material containing the component (C); and a step of cooling and pulverizing the melt-kneaded material. 8. The method according to claim 7, wherein the melt-kneading step is performed at a temperature of 40 to 130 ° C.