JP3215300B2 - Powder paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a powder coating.
More specifically, the present invention relates to a powder coating composed of a (co) polymer having excellent molecular smoothness and excellent storage stability when formed into a powder coating because of its narrow molecular weight distribution.

[0002]

2. Description of the Related Art In recent years, with increasing interest in environmental problems, regulations on organic solvents having a large effect on the environment have been increasing. This trend is similar in the field of paints, and powder paints made of thermosetting vinyl (co) polymers are regarded as promising candidates as solvent-free paints.

[0003]

However, the conventional powder coatings made of thermosetting vinyl (co) polymers have a wide molecular weight distribution, so that the smoothness of the coating is remarkably inferior to that of the solvent type coatings. There is a problem.

The inventors of the present invention have made intensive studies on a powder coating composed of a thermosetting (co) polymer having a narrow molecular weight distribution by radical polymerization, and have reached the present invention. That is, the present invention has a glass transition point of 40 obtained by polymerizing a radical polymerizable monomer in the presence of a radical polymerization initiator and a chain transfer agent for radical polymerization represented by the following general formula (1).
It is a powder coating composed of a thermosetting (co) polymer (A) at a temperature of １００100 ° C. General formula In the formula, Q is a polyvalent organic group, A is an alkylene group having 1 to 8 carbon atoms, Z is a chain transfer group, p is 0 or 1, and m is 2 to
Represents an integer of 100, and [] may be the same or different.

The radical polymerizable monomers used for obtaining the resin for powder coatings of the present invention include the following. These may be used in combination of two or more. Glucidyl group-containing monomers; for example, glycidyl (meth) acrylate, (meth) allyl glycidyl ester and (meth) allyl glycidyl ether. Hydroxyl group-containing monomer; for example, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, polyethylene glycol (molecular weight 300)
Mono (meth) acrylate and polypropylene glycol (molecular weight 500) mono (meth) acrylate and the like. Carboxyl group-containing monomers; for example, (meth) acrylic acid, (anhydride) maleic acid, fumaric acid, (anhydride) itaconic acid, (anhydride) citraconic acid, maleic acid half-ester and fumaric acid half-ester. Aliphatic hydrocarbon monomers; for example, ethylene, propylene, isobutylene, diisobutylene, isoprene, butadiene and the like. Unsaturated nitriles; for example, acrylonitrile, methacrylonitrile and the like; (Meth) acrylic esters (alkyl group having 1 to 30 carbon atoms); for example, methyl (meth) acrylate, butyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth)
Acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, eicosyl (meth) acrylate, docosyl (meth) acrylate, etc. And hydroxypolyoxyalkylene ether mono (meth) acrylates. Aromatic hydrocarbon monomers; for example, styrene, α-methylstyrene, hydroxystyrene, chlorostyrene and the like; Fluorine-containing vinyl monomer; for example, perfluorooctylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, and the like. Nitrogen-containing vinyl monomer; for example, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth)
Acrylate, morpholinoethyl (meth) acrylate, dimethylaminoethyl chloride (meth) acrylate,
Diethylaminoethyl chloride (meth) acrylate and the like. Others; for example, vinyl-modified silicon, vinyl acetate, vinyl chloride, vinylidene chloride and the like.

[0006] Among these radically polymerizable monomers, glycidyl group-containing monomers, hydroxyl group-containing monomers and carboxyl group-containing monomers are preferred.

In the general formula (1), Q represents a residue obtained by removing OH from a polyhydric alcohol or a polyhydric phenol;
Examples of the residue include a residue obtained by removing COOH from a polyvalent carboxylic acid. Examples of the polyhydric alcohol include alkylene glycols having 2 to 8 carbon atoms (ethylene glycol, propylene glycol, 1,3- and 1,4-butanediol, 1,6
Hexanediol, neopentyl glycol, etc.),
Dihydric alcohols having a cyclic group, such as diols having 5 to 10 carbon atoms, such as diols; 3 carbon atoms, such as glycerin, trimethylolpropane, trimethylolethane, and hexanetriol;
Trivalent alcohols having 4 to 12 carbon atoms, such as pentaerythritol, methylglycoside, and diglycerin;
Polyhydric alcohols; and alcohols having higher functional groups, such as pentitol (such as adonitol, arabitol, xylitol), hexitol (such as sorbitol, mannitol, iditol, talitol, dulcitol), saccharides [sucrose, monosaccharides (glucose, mannose and the like). Glucosides such as polyols (glycols, fructose, sorbose, etc.), oligosaccharides (crehalose, lactose, raffinose, etc.);
Glycosides of alkane polyols such as glycerin, trimethylolpropane, hexanetriol); polyalkane polyols [eg, polyglycerin such as triglycerin and tetraglycerin]; polypentaerythritol (such as dipentaerythritol and tripentaerythritol); cycloalkane polyol [Tetrakis (hydroxymethyl) cyclohexanol and the like]. Further, polyvinyl alcohol having a degree of polymerization of up to 100 can be used.

Further, di- and triethanolamines; alkylamines having 2 to 20 carbon atoms, 2 to 6 carbon atoms
Alkylene diamines such as ethylenediamine, propylenediamine, hexamethylenediamine, polyalkylenepolyamines such as aliphatic amines such as diethylenetriamine and triethylenetetramine, aniline, phenylenediamine, diaminotoluene, xylylenediamine, and aromatic compounds such as methylenedianiline and diphenyletherdiamine Alicyclic amines such as aliphatic amines, isophoronediamine, cyclohexylenediamine and dicyclohexylmethanediamine; and alkylene oxide adducts such as aminoethylpiperazine.

Examples of polyhydric phenols include monocyclic polyhydric phenols such as pyrogallol, hydroquinone, and phloroglucin; bisphenols such as bisphenol A and bisphenolsulfone; condensates of phenol and formaldehyde (novolak); and polyphenols.

Examples of the polyvalent carboxylic acid include divalent carboxylic acids [(1) aliphatic dicarboxylic acids having 2 to 20 carbon atoms (maleic acid, fumaric acid, succinic acid, adipic acid, sebacic acid, malonic acid, azelaic acid, (2) an alicyclic dicarboxylic acid having 8 to 20 carbon atoms (such as cyclohexanedicarboxylic acid and methylmedic acid); and (3) an aromatic dicarboxylic acid having 8 to 20 carbon atoms (phthalic acid). Acid, isophthalic acid, terephthalic acid, toluenedicarboxylic acid, naphthalenedicarboxylic acid, etc.);
(4) Alkyl or alkenyl succinic acids having a hydrocarbon group having 4 to 35 carbon atoms in the side chain (such as isododecenyl succinic acid and n-dodecenyl succinic acid)], trivalent or higher carboxylic acids [(1) carbon number 7-20 aliphatic polycarboxylic acids (1,2,4-butanetricarboxylic acid, 1,2,5
-Hexanetricarboxylic acid, 1,3-dicarboxyl-
2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, etc.); (2) carbon number 9-20
Alicyclic polycarboxylic acids (e.g., 1,2,4-cyclohexanetricarboxylic acid); (3) aromatic polycarboxylic acids having 9 to 20 carbon atoms (1,2,4-benzenetricarboxylic acid, 1,2,5 -Benzenetricarboxylic acid, 2,5,7
-Naphthalenetricarboxylic acid and 1,2,4-naphthalenetricarboxylic acid, pyromellitic acid, benzophenonetetracarboxylic acid, etc.)]. Further, a polymer of an unsaturated polycarboxylic acid having a polymerization degree of up to 100 can be mentioned.

In the general formula (1), Z is SH,
SR, SSR, CX ₃ (R is an alkyl, aryl, aralkyl, alkoxy, aryloxy or cycloalkyl group having 1 to 20 carbon atoms, which may be substituted with a halogen atom, an alkyl group, a cyano group, or a nitro group. Represents a chlorine atom, a bromine atom.) And the like. Of these, SH is preferred.

In the general formula (1), p is 0 when Q is a polyhydric alcohol or polyhydric phenol residue, and p is 1 when Q is a polycarboxylic acid residue. In the general formula (1), m is preferably 2 to 8. Also, p is 0
It is preferred that

The chain transfer agent represented by the general formula (1) is
Is SH, for example, it can be manufactured by the following method. Chain transfer agent 1 (when p is 0) The terminal of an alkylene glycol ether of a polyhydric alcohol is chlorinated with thionyl chloride or the like, and then reacted with an alkali hydrosulfide. Further, the ω-mercapto-alkyl alcohol and the polyhydric alcohol are etherified. Specific examples of the chain transfer agent include ethylene glycol-di-2-mercaptoethyl ether, trimethylolpropane-tri-2-mercaptoethyl ether, and pentaerythritol-tetra-2-mercaptoethyl ether.

Chain transfer agent 2 (when p is 1) ω-mercapto-alkyl alcohol is esterified with a polycarboxylic acid. Specific examples of the chain transfer agent include maleic acid-di-2-mercaptoethyl ester, fumaric acid-di-2-mercaptoethyl ester, adipic acid-di-2-mercaptoethyl ester, and terephthalic acid-di-
2-mercaptoethyl ester and the like.

In the production of the above compound, for example, a cyclic ether and a cyclic lactone can be co-added,
In the case of co-addition, either random co-addition or block co-addition may be used. Examples of the cyclic ether include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, and styrene oxide. Examples of the cyclic thioether include episulfide, and examples of the cyclic imine include ethylene imine. These can be co-added, and when co-added, either random co-addition or block co-addition may be used. Of these, preferred are cyclic ethers, and more preferred are ethylene oxide, propylene oxide and mixtures thereof. Examples of the cyclic lactone include ε-caprolactone and δ-valerolactone, and examples of the cyclic lactam include ε-caprolactam. These can be co-added, and when co-added, either random co-addition or block co-addition may be used.

As long as the above conditions are satisfied, the structure can be arbitrarily selected depending on the properties of the desired polymer. For example, in the case of Compound 1, the cyclic ether to be added is preferably propylene oxide in order to obtain a styrene resin.

The amount of the chain transfer agent used in the present invention is usually from 0.01 to 20% by weight, preferably from 0.1 to 10%, particularly preferably from 0.1 to 5%, based on the monomer. is there.

Known initiators can be used as the polymerization initiator. Examples of the initiator include water-soluble azo initiators (such as azobisamidinopropane (salt) and azobiscyanovalerate (salt)) and oil-soluble azo initiators. Initiators (azobiscyanovaleronitrile, azobisisobutyronitrile, azobiscyclohexanecarbonitrile, etc.), water-soluble peroxides (hydrogen peroxide, peracetic acid, etc.), oil-soluble peroxides (benzoyl peroxide, cumene Hydroxyperoxide, etc.) and inorganic peroxides (ammonium persulfate, sodium persulfate, etc.). A redox initiator system may be formed by the peroxide and the reducing agent as described above. Examples of the reducing agent include bisulfites (sodium bisulfite, potassium bisulfite,
Ammonium bisulfite, etc.), tertiary amines (dimethylaminobenzoic acid (salt), dimethylaminoethanol, etc.), amine complexes of transition metal salts (pentamethylenehexamine complex of cobalt (III) chloride, diethylenetriamine complex of copper (II) chloride) Etc.). Further, an azo initiator, a peroxide initiator, or a redox initiator may be appropriately used in combination. The amount of the polymerization initiator is usually 0.01 to 10% by weight, preferably 0.05 to 5% by weight, based on the radical polymerizable monomer.

In the method for producing the polymer of the present invention, the polymerization method may be any of solution polymerization, emulsion polymerization, suspension and bulk polymerization. In the case of solution polymerization, water,
Alcohols (methanol, ethanol, isopropanol, etc.), ketones (acetone, methyl isobutyl ketone, etc.), ethers (tetrahydrofuran, etc.), aliphatic hydrocarbons (hexane, heptane, etc.), aromatic hydrocarbons (toluene, xylene) Etc.), halogenated solvents (such as ethylene dichloride) and mixtures thereof.

The polymerization temperature is usually 50 to 300 ° C.,
Preferably it is 100-250 degreeC. For solution polymerization,
Examples of the temperature include a temperature lower than the boiling point of the polymerization solution under normal pressure, a boiling point of the polymerization solution under normal pressure, and a temperature higher than the boiling point of the polymerization solution under pressure. When a dispersion medium, an emulsifier, a dispersant, or the like is used, there is no particular limitation, and known materials can be used.

The number average molecular weight of the polymer obtained by the production method of the present invention is usually 1,000 to 500,000, preferably 3,000 to 500,000. The molecular weight distribution is usually 1.20 to 3.00, preferably 1.20 to 2.0.
50. Although the molecular weight distribution differs depending on the polymerization system, it is much narrower than when the chain transfer agent of the present invention is not used. Here, the molecular weight distribution means (weight average molecular weight / number average molecular weight).

The resin used in the powder coating of the present invention has a crosslinkable functional group such as a glycidyl group, a hydroxyl group or a carboxyl group in a molecule, and is heated by using a curing agent or self-crosslinked by heating. It is three-dimensionalized and hardened by hardening. The glass transition point (Tg) of the resin used in the powder coating of the present invention is usually 40 ° C to 100 ° C.
° C, preferably between 45 and 80 ° C. T
When the g is lower than 40 ° C, the storage stability of the powder coating becomes poor, and when the g is higher than 100 ° C, the smoothness of the coating film deteriorates.
In addition, the resin melt index (JIS K 721)
0, test temperature 125 ° C, test load 2.16kgf)
Usually, it is in the range of 1 to 35. The melt viscosity of the resin at 125 ° C. is generally 10 to 5000 cps, preferably 100 to 2000 cps. If it is less than 10 cps, the storage stability of the powder coating becomes poor, and the
If it exceeds ps, the effect of improving the smoothness of the coating film is not obtained.

The resin used in the powder coating material of the present invention is three-dimensionally cured by heating using a curing agent or by self-crosslinking by heating. You. When using a curing agent, the curing agent may be selected according to the type of the crosslinkable functional group. When a typical curing agent is exemplified, when the functional group is a hydroxyl group, an amino resin such as hexamethoxymethylmelamine, or ε
-A typical example is a blocked polyisocyanate such as isophorone diisocyanate blocked with caprolactam.If the functional group is a carboxyl group, a typical example is a polyepoxy compound, and the functional group is a glycidyl group. In some cases, a polycarboxylic acid such as dodecane diacid or an acid anhydride thereof is typical.

When this resin is used as a powder coating, 5 to 30 parts by weight of a curing agent and, if necessary, 20 to 40 parts by weight of a pigment such as titanium oxide are melt-mixed with 100 parts by weight of the resin. After cooling, the mixture is pulverized by a pulverizer to obtain a powder coating. The powder coating thus obtained is applied to a metal object using an electrostatic coating machine, and baked at 120 to 200 ° C.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be further described below with reference to examples, but the present invention is not limited to these examples. Parts in the examples are parts by weight. The method of measuring the number average molecular weight and the molecular weight distribution by GPC is as follows. Model: HLC-8120 (manufactured by Tosoh) Column: TSK gel Super H4000 + TSK gel Super H3000 + TSK gel Super H2000 (all manufactured by Tosoh) Column temperature: 40 ° C. Detector: RI solvent: tetrahydrofuran Sample concentration: 0.25 weight % Injection amount: 10 μl Standard: polystyrene Also, each test method is as follows. 1) Glass transition point measurement device: DSC20, SS manufactured by Seiko Electronic Industry Co., Ltd.
C / 580 Conditions: ASTM (D3418-2) Method 2) Measurement of Melt Viscosity Apparatus: RHEOMAT RM-18 manufactured by METTLER
0 Temperature: 125 ° C SHARE RATE (1 / SEC): 60 3) Measurement of MI value Apparatus: Melt indexer manufactured by Tester Sangyo Co., Ltd. Conditions: 125 ° C, 2160g 4) Evaluation of smoothness Powder on zinc phosphate treated steel sheet After painting and baking, film thickness 40
Visual determination of painted surface of ~ 60μ. ：: good ×: bad 5) Judgment of storage stability 50 g of powder coating material was placed in a cylinder having a diameter of 3 cm and left at 30 ° C. for one week to check for the occurrence of blocking substances. ○: No blocking material ×: With blocking material

[0026]

【Example】

(Production of chain transfer agent) Production Example 1 150 parts of triethylene glycol was charged into a reaction vessel,
At 80 ° C., 262 parts of thionyl chloride was added dropwise with stirring over 2 hours. After maintaining the same temperature for 1 hour, 500 parts of a 30% aqueous sodium hydrosulfide solution was added dropwise over 3 hours.
After maintaining at the same temperature for 1 hour, the temperature was returned to room temperature, liquid separation was performed, and ethylene glycol di-2-mercaptoethyl ether 18
0 parts were obtained. This is designated as chain transfer agent A.

Preparation Example 2 In the same manner as in Preparation Example 1, pentaerythritol-tetra-
2-Mercaptoethyl ether was obtained. This is designated as chain transfer agent B.

Example 1 In a mixed solution of 480 parts of xylene and 20 parts of the chain transfer agent A, glycidyl methacrylate / methyl methacrylate / styrene / 2-ethylhexyl acrylate (25% by weight /
A mixture of 2,000 parts of 33% by weight / 40% by weight / 2% by weight) and 20 parts of the chain transfer agent A, and 10 parts of dibutyl peroxide were subjected to drop polymerization at 170 ° C. for 3 hours. Devolatilize at normal pressure while raising the temperature to 180 ° C;
Was switched to reduced pressure, and devolatilization was performed under reduced pressure for 2 hours. The glass transition point of the obtained resin is 65.
C., MI value (125 ° C., 2160 g) was 10, the number average molecular weight was 7,000, and the molecular weight distribution was 1.6.

Comparative Example 1 A resin was obtained in the same manner as in Example 1 except that no chain transfer agent A was used. The glass transition point of the obtained resin is 65 ° C.
The MI value (125 ° C., 2160 g) was 10, the number average molecular weight was 7,000, and the molecular weight distribution was 2.1.

Example 2 In a mixed solution of 480 parts of xylene and 40 parts of a chain transfer agent B, glycidyl methacrylate / methyl methacrylate / styrene / 2-ethylhexyl acrylate (23% by weight /
A mixture of 2,000 parts (30% by weight / 40% by weight / 7% by weight), 40 parts of a chain transfer agent B, and 10 parts of dibutyl peroxide were subjected to drop polymerization at 170 ° C. for 3 hours. Devolatilize at normal pressure while raising the temperature to 180 ° C;
Was switched to reduced pressure, and devolatilization was performed under reduced pressure for 2 hours. The glass transition point of the obtained resin is 50.
C., MI value (125 ° C., 2160 g) was 15, number average molecular weight was 5,000, and molecular weight distribution was 1.6.

Comparative Example 2 A resin was obtained in the same manner as in Example 2 except that no chain transfer agent B was used. The glass transition point of the obtained resin is 50 ° C.,
The MI value (125 ° C., 2160 g) was 15, the number average molecular weight was 5,000, and the molecular weight distribution was 2.0.

Comparative Example 3 A resin was obtained in the same manner as in Example 1, except that 20 parts of lauryl mercaptan and 20 parts (total of 40 parts) were used instead of the chain transfer agent A. The glass transition point of the obtained resin is 5
At 0 ° C., the MI value (125 ° C., 2160 g) was 10, the number average molecular weight was 5,000, and the molecular weight distribution was 2.3.

Test Examples Using the resins obtained in Examples 1 and 2 and Comparative Examples 1 to 3, the following tests were respectively performed. Dodecane 2 in 100 parts of resin
20 parts of acid is dry-blended, 1 part of coating surface adjuster is added,
After kneading using a heating kneader at 100 ° C., 20-150
It was pulverized to μ to obtain a cruier powder coating. The obtained powder coating was electrostatically coated on a zinc phosphate treated steel sheet using an electrostatic powder coating machine, and baked at 150 ° C. for 20 minutes with a circulating drier. Table 1 shows the test results.

[0034]

Table 1 Test results ------------------------------------------------------------------------------------------- Resin Smoothness Storage stability ---------------------- −−−−−−−−−−−−−−− Example 1 ○ ○ Example 2 ○ ○ −−−−−−−−−−−−−−−−−−−−−−−−−− Comparative Example 1 × ○ Comparative Example 2 ○ × Comparative Example 3 × × −−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0035]

The powder coating comprising the (co) polymer (A) of the present invention improves the smoothness of a coating film without deteriorating storage stability. Accordingly, it is possible to improve the problems of the conventional powder coating, to promote the replacement of the solvent-based coating which has been delayed because of its poor smoothness, and to greatly expand its use.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takao Saito 11-11, Hitotsubashi-Honcho, Higashiyama-ku, Kyoto Examiner, Sanyo Chemical Industries Co., Ltd. Toshiyasu Kimura (56) References JP-A-61-87767 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C09D 157/10 C09D 5/03 C08F 2/38-2/42

Claims (6)

(57) [Claims] A glass transition point obtained by polymerizing a radically polymerizable monomer in the presence of a radical polymerization initiator and a chain transfer agent for radical polymerization represented by the following general formula (1) is 40 to 100. A powder coating composed of a thermosetting (co) polymer (A) at a temperature of ° C. General formula In the formula, Q is a polyvalent organic group, A is an alkylene group having 1 to 8 carbon atoms, Z is a chain transfer group, p is 0 or 1, and m is 2 to
Represents an integer of 100, and [] may be the same or different. 2. The powder coating according to claim 1, wherein Z is SH in the general formula (1). 3. The powder coating according to claim 1, wherein p is 0 in the general formula (1). 4. The (co) polymer (A) contains at least one selected from the group consisting of a glycidyl group-containing monomer, a hydroxyl group-containing monomer and a carboxyl group-containing monomer as a constituent unit. Powder coating material according to any one of 1 to 3. 5. The (co) polymer (A) has a number average molecular weight of 1,000 to 500,000 and a molecular weight distribution of 1.
The powder coating according to any one of claims 1 to 4, which is 2 to 3.0. 6. A resin composition for powder coatings comprising the (co) polymer (A) according to claim 1 and a curing agent.