JPS62240369A - Resin composition for powder coating compound - Google Patents

Abstract

PURPOSE:The titled composition providing a coating film having improved appearance, mechanical strength, weather resistance, stain resistance, etc., comprising a specific polyester resin, a copolymer containing both glycidyl group, etc., and a hydroxyl group and a blocked isocyanate in specific ratios, respectively. CONSTITUTION:The aimed composition consisting of (A) 60-96pts.wt. polyester having an acid value of 5-100mgKOH/g, a hydroxyl number of 5-100mgKOH/ g, 80-150 deg.C softening point and 1,000-10,000 number-average molecular weight, (B) 3-40pts.wt. copolymer which is obtained from (i) 10-95wt% one or more vinyl monomers selected from glycidyl (meth)acrylate and/or beta-methylglycidyl (meth)acrylate, (ii) 5-60wt% OH group-containing vinyl monomer and (iii) 0-85wt% other vinyl monomer, has 300-8,000 number-average molecular weight and contains both (beta-methyl)glycidyl group and OH group and (C) 1-20pts.wt. blocked isocyanate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a new and useful resin composition for powder coatings, and more specifically, it is composed of a specific polyester resin monopolymer and a blocked isocyanate. The present invention relates to a resin composition for powder coatings that is particularly excellent in physical properties, appearance, weather resistance, stain resistance, etc. of the coating film.

[Conventional technology and its limitations]

In general, powder coatings composed of a carboxyl group-containing polyester resin and a glycidyl group- and/or β-methylglycidyl group-containing acrylic resin have poor compatibility between the two resins, and furthermore, the carboxyl group and the glycidyl group and/or β-methylglycidyl group-containing acrylic resin have poor compatibility. - Due to the fast curing reaction with the methylglycidyl group, the viscosity increases rapidly from the high viscosity region when heated.Therefore, when a powder coating with such a structure is applied and baked, the melt fluidity is insufficient, thus causing The resulting cured coating film had the drawback of not exhibiting sufficient physical properties and appearance.

On the other hand, polyester resin has specific hydroxyl groups other than carboxyl groups, glycidyl groups and/or β
- In addition to improving compatibility with methylglycidyl group-containing acrylic resins, attempts were made to improve the appearance of the coating film by lowering the melt viscosity during heating by using blocked isocyanate in combination, and to improve the physical properties of the coating film through auxiliary crosslinking. However, it is still difficult to apply it to home appliances because it cannot satisfy the balance of high appearance, stain resistance, and various physical properties.

[Problems to be Solved by the Invention] The present inventors have conducted extensive research in view of the existence of such drawbacks in the prior art, and as a result, have developed a polyester resin that has both a carboxyl group and a hydroxyl group.

When (β-methyl)glycidyl (meth)acrylate and a hydroxyl group-containing vinyl monomer are used as essential monomer components and are combined with a copolymer having a specific molecular weight range and a block isocyanate.

The compatibility of these components is of course important, as is the cured coating film that can be obtained from powder coatings that combine these components.

We have completed the present invention by discovering that it has excellent physical properties and weather resistance, as well as excellent appearance and stain resistance of the coating film.

[Structure of the invention]

To summarize the present invention, the present invention includes the following as an essential component.

(A) An acid value of 5 to 100 mg KOII/g (hereinafter, units are omitted and only numbers are written), and a hydroxyl value of 5 to 100 mg KOII/g
011/U to 100 electric current (same as above), the softening point is 80 to 15
At 0℃.

and the number average molecular weight (hereinafter abbreviated as stone) is 1,000~
60 to 96 parts by weight of polyester resin to, ooo.

(B) 10-95% by weight of one or more vinyl heptamers selected from the group consisting of glycidyl acrylate (OA), glycidyl methacrylate (GMA), β-methylglycidyl acrylate (MGA) and β-methylglycidyl methacrylate (MGMA) %, 5-60% by weight of hydroxyl group-containing vinyl monomers and 0-85% by weight of other vinyl monomers.
, 3 to 40 parts by weight of a copolymer containing both a (β-methyl)glycidyl group and a hydroxyl group.

The present invention relates to a resin composition for a powder coating comprising 1 to 20 parts by weight of (C) blocked isocyanate and the above-described components (A), (B), and (C).

The configuration of the present invention will be explained in detail below.

First, the constituent components will be explained.

(i) Regarding (A) component; The polyester resin as the above-mentioned component (A) is as follows.

Each has an acid value of 5 to 100, preferably 10 to 70.

The hydroxyl value is 5 to 100, preferably 10 to 7G, the softening point is 80 to 150°C, preferably 100 to 130°C, and the stone is i, ooo to 1G, 000. Preferably 2,000 to s, oo.

However, as long as it falls within this range, it may have a branched structure or a linear structure.

There are no particular restrictions on the method for preparing the polyester resin, and well-known and commonly used methods can be applied as they are. The above polybasic acid components can be used, as well as dihydric alcohols, trihydric alcohols and higher polyhydric alcohol components.

Therefore, only typical acid components and alcohol components constituting the polyester resin of the present invention will be listed. .

Pyromellitic acid and their anhydrides: or adipic acid, sebacic acid, succinic acid, maleic acid.

These include fumaric acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid, and their anhydrides, and alcohol components include ethylene glycol, propylene glycol, and 1,3-butanediol. , 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, bishydroxyethyl terephthalate, hydrogenated bisphenol A, ethylene oxide or propylene oxide adduct of hydrogenated bisphenol A, trimethylolethane, trimethylol Pro'glycerin, pentaerythritol and 2,2,4-trimethylpentane-1,3-diol can be used.

5 In preparing the polyester, it is of course possible to use the following epoxy group-containing compounds in combination with the acid component. 1 For example, n-butyl glycidyl ether, phenyl glycidyl ether, persatic acid glycidyl ester. Typical examples include glycide, bisphenol A type epoxy resin, and the like.

(n) Regarding component (B): Next, the copolymer containing both a (β-methyl)glycidyl group and a hydroxyl group as component (B) has a stone size of 300 to a, ooo, preferably 500. ~6,00
0, glycidyl acrylate,
One or more (β-methyl)glycidyl (
10 to 95% by weight of meth)acrylate, preferably 1
5 to 80% by weight, 5 to 60% by weight of hydroxyl group-containing vinyl monomer, preferably 7 to 50% by weight, and 0 to 85% by weight of other vinyl monomers, preferably 20 to 78% by weight. It is.

If the molecular weight of such a copolymer is lower than 300, the mechanical strength of the resulting coating film will be insufficient, and smoke will be emitted when the coating film is baked; on the other hand, if it exceeds 8,000, the resulting coating film will be In either case, it is unsuitable because not only the sharpness or smoothness of the film will be poor, but also the compatibility between the resins will be poor, and the crosslinking reaction will not proceed sufficiently, resulting in poor coating film strength. It is.

Furthermore, when the amount of (β-methyl)glycidyl (meth)acrylate is less than 10% by weight and the amount of the hydroxyl group-containing vinyl monomer is less than 5% by weight, the compatibility with the polyester resin (A) component is poor. Moreover, since the reaction with this polyester resin (A) component becomes insufficient, a good cured coating film cannot be provided.

Furthermore, if only (β-methyl)glycidyl (meth)acrylate is less than 10% by weight, the curing reaction with the polyester resin (A) component will be insufficient and good physical properties will not be obtained. -Minoga5
If the amount is less than % by weight, it becomes necessary to reduce the amount of blocked isocyanate from the viewpoint of corrosion resistance and retention of physical properties, and as a result, the effect of reducing melt viscosity by adding blocked isocyanate becomes smaller, and the appearance of the coating film is forced to deteriorate. So I don't like it.

Examples of the (β-methyl)glycidyl (meth)acrylate mentioned above include glycidyl acrylate, glycidyl methacrylate, β-methylglycidyl acrylate, and β-methylglycidyl methacrylate.

Further, examples of the above-mentioned hydroxyl group-containing vinyl monomers include mono(meth)acrylic esters and monocrotonic esters of polyhydric alcohols, allyl alcohol, and monoallyl ethers of polyhydric alcohols.

Plaxel FM, FA monomer (Daicel Chemical Industries ■
caprolactone addition monomer), hydroxyethyl vinyl ether, etc. Examples of polyhydric alcohols that can be used include ethylene glycol, polyethylene glycol,
propylene glycol, polypropylene glycol, 1
, 3-butylene gellicol, 1,4-butylene gellicol, and 1,6-hexanediol, and polyhydric alcohols such as glycerin, trimethylolpropane, trimethylolethane, and pentaerythritol.

Further, fumaric acid dihydroxyethyl ester, fumaric acid butyl hydroxyethyl ester, etc. can also be used.

In the present invention, the above-mentioned (β-methyl)glycidyl (meth)acrylate and hydroxyl group-containing vinyl 7-mer
However, other copolymerization components may also be used.
Such other vinyl monomers include (β-
Various (methyl) glycidyl (meth)acrylates and hydroxyalkyl ester (meth)acrylates
Typical examples include meth)acrylic acid ester, (meth)acrylonitrile, (meth)acrylamide, fumaric acid diester, -maleic acid diester, itaconic acid diester, and styrene. Among (meth)acrylic acid esters, cyclohexyl methacrylate, cellosolve methacrylate, and styrene are particularly suitable because they have excellent compatibility with the polyester resin (A) component.

Of course, in addition to this, any material can be used as long as it can be copolymerized with the glycidyl (meth)acrylate.

There are no particular restrictions on the method for producing the copolymer (B) component, and any well-known and commonly used method can be applied as is, but a solution polymerization method is particularly recommended because the molecular weight can be easily adjusted.

(Quick) Regarding component (C); Furthermore, representative blocked isocyanates as component (C) are aliphatic, aromatic, or ring group isocyanates such as xylylene diisocyanate, isophorone diisocyanate, or hexamethylene diisocyanate. The free incyanate group contained in the adduct of the active hydrogen compound and the active hydrogen compound is blocked with a known and commonly used blocking agent such as methanol, isopropanol, butanol, ethyl lactate or ε-caprolactam. Typical active hydrogen compounds include various low molecular weight compounds such as ethylene glycol, butylene glycol, trimethylolpropane, glycerin, ethylene diamine or hexamethylene diamine, and various types such as polyols, polyethers, polyesters, and polyamides. Contains high molecular weight substances.

5 The present invention relates to the polyester resin (A) listed above.
component, a copolymer containing both a (β-methyl)glycidyl group and a hydroxyl group (B) component, and a blocked isocyanate (C) component in specific proportions to form a resin composition for powder coatings. However, the usage ratio of each of these ingredients (A: B: C) is 6.
0-96:3-40:1-20, preferably 60-90
It is appropriate that the ratio of epoxy groups to carboxyl groups and the ratio of hydroxyl groups to free isocyanate groups among the functional groups of each component be 0.5 to 1.5. It is desirable to keep it.

The resin composition for powder coating of the present invention thus obtained may further contain pigments or other fillers, 2
- flow modifiers such as ethylhexyl acrylate polymers or silicones, and optionally amines,
Various curing catalysts such as imidazoles or organic tin compounds, and various resins such as epoxy resins or petroleum resins can be blended to improve the physical properties of the coating film.

The resin composition for powder coating according to the present invention is kneaded using a known and commonly used kneading machine such as an extruder, and then pulverized to form a powder coating.

As the powder coating method, known and commonly used methods such as electrostatic coating or fluidized dip coating can be applied as they are.

〔Example〕

Next, the present invention will be explained in more detail with reference to Reference Examples, Examples, and Comparative Examples. In the following, parts refer to parts by weight unless otherwise specified.

Reference Example 1 [Preparation example of polyester resin (A) component] 344 parts of ethylene glycol, 1,348 parts of neopentyl glycol, 1.796 parts of dimethyl terephthalate.
and 1.8 parts of zinc acetate,
210 gradually while removing generated methanol from the system.
℃, and further added 596 parts of terephthalic acid, 740 parts of isophthalic acid, 80 parts of adipic acid, and 2 parts of dibutyltin oxide.
The temperature was raised to 40°C.

Next, the temperature of the obtained reaction product was lowered to 180°C, 136 parts of trimellitic anhydride was added, and the reaction was continued at the same temperature until the acid value was 24, the hydroxyl value was 14, and the softening point was 114°C. , and a polyester resin (A) component having an order of 4,000 was obtained. Hereinafter, this will be abbreviated as resin (A-1).

Reference Example 2 [Preparation example of polyester resin (A) component] 336 parts of ethylene glycol, 1,316 parts of neopentyl glycol, 1.752 parts of dimethyl terephthalate.
and 1.8 parts of zinc acetate,
210 gradually while removing generated methanol from the system.
After raising the temperature to ℃, 1,500 parts of terephthalic acid and 2 parts of dibutyltin oxide were added, the temperature was raised to 240℃ over 10 hours, and the reaction was continued at the same temperature until the acid value reached 15. So, the hydroxyl value is 15 and the softening point is 11.
Polyester resin with a stone size of 3,700 at 7℃ (
A) Component was obtained. Hereinafter, this will be abbreviated as resin (A-2).

Reference Example 3 [Preparation example of acrylic copolymer (B) component] 25 parts of glycidyl methacrylate, 15 parts of 2-hydroxypropyl methacrylate, 30 parts of cyclohexyl methacrylate, 10 parts of n-butyl acrylate, 20 parts of styrene. , 1 part of t-butyl perbenzoate and 0.5 part of cumene hydroperoxide was added dropwise under pressure to 100 parts of xylene heated to 150°C to polymerize. After the polymerization reaction, xylene was removed to obtain the desired polymer having a stone count of 1,500. Hereinafter, this will be abbreviated as copolymer (B-1).

Reference Example 4 [Preparation example of acrylic copolymer (B) component] In the same manner as in Reference Example 3, 20 parts of β-methylglycidyl methacrylate, 20 parts of 2-hydroxyethyl methacrylate, and 20 parts of ethyl cellosolve methacrylate were prepared.
1 part, 20 parts of methyl methacrylate, and 20 parts of styrene were polymerized.

A polymer having 1,600 stones was obtained. Hereinafter, this will be abbreviated as copolymer (B-2).

Reference Example 5 [Preparation example of acrylic copolymer (B) component] 25 parts of glycidyl methacrylate, 15 parts of 2-hydroxypropyl methacrylate, 50 parts of cyclohexyl methacrylate, 10 parts of n-butyl acrylate, azobisisobutyro 4.5 parts of nitrile.

The mixture was added dropwise to 100 parts of xylene under normal pressure and polymerized while refluxing.

0.3 parts of azobisisobutyronitrile was further added and polymerized at 90°C. After the polymerization reaction, xylene was removed and the stones were
, 100 of the desired polymer was obtained. Hereinafter, this will be referred to as a copolymer (
It is abbreviated as B-3).

Examples 1 to 5 The components shown in Table 1 were triblended, then kneaded using an extruder, cooled, and then pulverized to obtain various powder coatings. Thereafter, the powder coating was applied to a zinc phosphate treated steel plate and baked at 180° C. for 20 minutes to obtain a cured coating.

The various performances of each of the coating films thus obtained were investigated. The results are shown in Table 1.

Reference Example 6 (Example of Preparation of Acrylic Copolymer for Comparison) In the same manner as in Reference Example 3, 40 parts of glycidyl methacrylate, 20 parts of methyl methacrylate, 20 parts of ethyl cellosolve methacrylate, and 20 parts of styrene were polymerized. A polymer containing no hydroxyl groups and having a stone count of 1,500 was obtained. Hereinafter, this will be abbreviated as copolymer (B'-1).

Reference Example 7 (Example of preparation of acrylic copolymer for comparison) In the same manner as in Reference Example 3, 25 parts of glycidyl methacrylate, 20 parts of cyclohexyl methacrylate, n
-20 parts of butyl methacrylate and 35 parts of styrene were polymerized to obtain a polymer containing 1,600 stones and containing no hydroxyl groups. Hereinafter, this will be abbreviated as copolymer (B'-2).

Reference Example 8 (Example of preparation of acrylic copolymer for comparison) In the same manner as in Reference Example 3, 7 parts of glycidyl methacrylate, 3 parts of 2-hydroxyethyl methacrylate,
25 parts of ethyl cellosolve methacrylate, 25 parts of methyl methacrylate, and 40 parts of styrene were polymerized to obtain a polymer having a density of 1,600 per stone and low in both glycidyl groups and hydroxyl groups. Hereinafter, this will be abbreviated as copolymer (B'-3).

Comparative Examples 1-3 Same as Examples 1-5 except that the acrylic copolymer was changed and the blending ratio was changed as shown in Table 1 according to the amount of functional groups in the copolymer. A control powder coating was prepared, a cured coating was obtained, and the performance of the coating was then investigated. The results are shown in Table 1.

Comparative Example 4 A paint similar to that of Comparative Example 1 was prepared using the same polyester resin and coheavy metal at the compounding ratio as shown in Example 1, and various performances of the cured coating were examined. The results are shown in Table 1.

As shown in Table 1, the coating films obtained from the resin composition for powder coatings of the present invention were superior in appearance, mechanical strength, weather resistance, etc., compared to those of the comparative examples. I know that there is.

(Margin below)

Claims (1)

[Scope of Claims] Essential components include (A) an acid value of 5 to 100 mgKOH/g, a hydroxyl value of 5 to 100 mgKOH/g, and a softening point of 80 to 150°C;
and 60 to 96 parts by weight of a polyester resin with a number average molecular weight of 1,000 to 10,000, (B) glycidyl (meth)acrylate and/or β
- 10 to 95% by weight of one or more vinyl monomers selected from the group consisting of methylglycidyl (meth)acrylate
, a copolymer containing both a glycidyl group and/or a β-methylglycidyl group and a hydroxyl group with a number average molecular weight of 300 to 8000 obtained from 5 to 60% by weight of a hydroxyl group-containing vinyl monomer and 0 to 85% by weight of other vinyl monomers. A resin composition for a powder coating, comprising 3 to 40 parts by weight of a polymer and 1 to 20 parts by weight of (C) a blocked isocyanate.