JPH07316472A - Resin composition for powder coating material - Google Patents

Abstract

PURPOSE:To obtain the title composition which can give a semimatte or matte coating film excellent in blocking resistance and having good flexibility. CONSTITUTION:This composition comprises a polyester A mainly made from an aromatic dicarboxylic acid component and an aliphatic alcohol component, having a hydroxyl value of 1200geq/10<6>g or above and substantially gel-free, a polyester B mainly made from an aromatic dicarboxylic acid component and an aliphatic alcohol component except a Compound represented by the formula: R<1>-R-R<2> (R is a 4-18C linear aliphatic group or alicyclic group; and R<1> and R<2> are each an esterifiable group), containing 1-15mol%, based on the acid component, a compound of the formula, having a hydroxyl value of 200-1000geq/10<6>g and being substantially gel-free and an isocyanate curing agent, wherein the weight ratio of polyester A to polyester B is 70/30 to 10/90, and the difference (absolute value) between the gelling times of polyesters A and B is at least 3min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester-based resin composition for powder coating which gives a semi-matte or matte coating film.

[0002]

2. Description of the Related Art A powder coating material is non-polluting, can be used immediately after coating, does not require multi-layer coating, and is relatively inexpensive, as compared with a conventional solvent type coating material. In addition, the advantage of being able to collect and use the paint that did not adhere to the object to be coated at the time of painting was recognized, and demand has rapidly expanded in recent years as a protective decorative paint for home appliances, building materials, automobile parts, etc. is doing. By the way, if the coating is required to have gloss from an aesthetic point of view (60 degree specular gloss 90 to 10
0%) and semi matte (60 degree specular gloss of 30 to 70%) or matte (60 degree specular gloss of 30% or less) may be required.

As a resin composition for a powder coating which gives a semi-matt or matt coating, JP-A 64-1770 discloses a polyester having a hydroxyl value of 1200 geq / 10 ⁶ g or more, and a hydroxyl value of 200.
It has been proposed that a polyester and an isocyanate-based curing agent of about 1000 geq / 10 ⁶ g are used, and the difference (absolute value) in gelation time between both polyesters is 3 minutes or more. However, in the powder coating using this resin composition for powder coating,
Since the polyester with a very high functional group with a hydroxyl value of 1200 geq / 10 ⁶ g or more is used, the crosslink density of the coating film is partially increased, the flexibility of the coating film is reduced, and the workability of the coated product is reduced. There was a problem that it decreased. In order to improve the flexibility of the coating film, it is possible to copolymerize a linear aliphatic component that imparts flexibility to a polyester with a hydroxyl value of 1200 geq / 10 ⁶ g or more. Then, the glass transition point as low as about 30 to 50 ° C. is further lowered, and there is a problem that the storage stability (blocking resistance) of the resin or paint is impaired.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to provide a resin composition for powder coating which gives a semi-matt or matte coating film having excellent flexibility without impairing the blocking resistance. Is.

[0005]

The present invention is intended to solve the above-mentioned problems, and its gist is as follows.

Polyester A which is mainly composed of an aromatic dicarboxylic acid component and an aliphatic alcohol component and has a hydroxyl value of 1200 geq / 10 ⁶ g or more and which is not substantially gelled, excluding aromatic dicarboxylic acid component and the following formula Mainly composed of aliphatic alcohol component, containing 1 to 15 mol% of component consisting of compound of formula with respect to acid component, and having hydroxyl value of 200 to 1000 ge
q / 10 ⁶ g of substantially non-gelling polyester B and isocyanate curing agent, weight ratio of polyester A to polyester B 70/30 to 10/90, gelation of polyester A to polyester B Time difference (absolute value)
Is a resin composition for powder coating, which is 3 minutes or more. R ¹ -R-R ² (R is a linear aliphatic group or alicyclic group having 4 to 18 carbon atoms, R ¹
And R ² represents an ester-forming group. )

In the present invention, the hydroxyl value and the gelation time are values obtained by the following method. Hydroxyl value After acetylating the polyester, titration is performed with a potassium hydroxide methanol solution to obtain the value. Gelation time Isophorone diisocyanate curing agent blocked with ε-caprolactam (Vestagon B 1530 manufactured by Huls Co.) was mixed in an amount of functional groups equivalent to 33% by weight of titanium dioxide powder, sample amount 90 g, temperature 200 A curing curve is obtained at a temperature of ℃ by a Brabender Plasticorder (manufactured by Brabender), and the time until the inflection point is taken as the gelation time.

The present invention will be described in detail below. In the resin composition of the present invention, the hydroxyl value of polyester A is 1200 geq / 10 ⁶ g or more, preferably 2000 to 5000 geq / 10 ⁶ g,
It is necessary that the hydroxyl value of polyester B is 200 to 1000 geq / 10 ⁶ g. The hydroxyl value of polyester A is 1200ge
If it is less than q / 10 ⁶ g, it is difficult to obtain a good matting effect. If the hydroxyl value of polyester B is less than 200 geq / 10 ⁶ g, the surface of the coating film tends to have large irregularities and the smoothness tends to deteriorate. On the other hand, if it exceeds 1000 geq / 10 ⁶ g,
The mechanical strength of the coating film may decrease or the matte effect may not be sufficient.

Polyesters A and B need to be substantially non-gelling polyesters. Here, "polyester which is not substantially gelled" means
This means a polyester that can be crushed by a general crusher and that can flow when melted. Gelled polyester is difficult to form into a paint, and a uniform coating film cannot be formed.

In the present invention, an isocyanate type curing agent is used. As the isocyanate-based curing agent, a blocked isophorone diisocyanate-based curing agent that does not exhibit activity at a certain temperature or lower is preferably used. Specific examples of such a curing agent include isophorone diisocyanate-based curing agent blocked by ε-caprolactam "Hurth Co.""Bestagon B 1530" or a blocking agent-free isophorone diisocyanate containing an isocyanate group. There is a hardener such as "Vestagon BF 1540" manufactured by Huls. (The use of a self-blocking type curing agent has the advantage that the blocking agent does not volatilize during the curing reaction, and there is no problem of contamination of the baking oven or baking loss.)

It is appropriate that the amount of the curing agent used is within the range of 0.8 to 1.2 times equivalent amount of functional groups, which corresponds approximately to the amount of hydroxyl groups of the polyester resin.

In the resin composition of the present invention, the blending ratio of polyesters A and B is 70:30 to 10:90 by weight, preferably 40:60 to 20:80. If the compounding ratio is out of this range, the matting effect is not sufficient.

Further, in the resin composition of the present invention, the difference (absolute value) in gelling time between polyesters A and B must be 3 minutes or more. If it is less than 3 minutes, a matte coated surface is obtained. I can't. It is preferably 5 to 15 minutes in order to obtain a highly matte coated surface (60% specular gloss of 20% or less). If the resins are out of this range, the matting effect will not be sufficient, or the mechanical strength of the coating film will decrease.

In the present invention, the degree of matting can be controlled by the hydroxyl value of polyester A, the compounding ratio of polyesters A and B, and the difference in gelling time. For example, the hydroxyl value of polyester A is about 30
00geq / 10 ⁶ g or more, the blending ratio of polyester A and B is 30:
In the case of 70, a perfect matte coating with a 60 degree specular gloss of 10 or less can be obtained by blending resins with a difference in gelation time of 6 minutes or more, and when it is about 5 minutes, a 60 degree specular surface It is possible to obtain a matte coating having a gloss of about 20%, and a semi-matt coating film having a 60 ° specular gloss of 50 to 60% when the glossiness is 3 to 4 minutes.

Further, in the resin composition of the present invention, the difference (absolute value) in acid value between polyester A and polyester B is
It is preferably 20 geq / 10 ⁶ g or more, and particularly preferably 30 geq / 10 ⁶ g or more. If the difference between the acid values of the two polyesters is too small, the 60 ° specular glossiness tends to fluctuate, and a matte coating film with stable specular gloss cannot be obtained.

Further, the polyesters A and B preferably have a glass transition point in the range of 25 to 120 ° C, particularly 40 to 100 ° C. If the glass transition point is less than 25 ° C, a blocking phenomenon in which powdered resin is aggregated and solidified is likely to occur, or it is difficult to pulverize with a general pulverizer. On the other hand, the glass transition point is 120 ℃
If it exceeds, the kneading temperature must be increased,
There is a tendency that the curing reaction progresses when it is made into a paint, and the smoothness and mechanical strength of the coating film deteriorate.

The polyesters A and B preferably have an average degree of polymerization of 4 to 50, which facilitates powdering.

As the polyester A which is one component of the resin composition of the present invention, those obtained from the following carboxylic acid component and alcohol component are preferably used.

Carboxylic Acid Component Mainly composed of terephthalic acid and / or isophthalic acid, and if necessary, other polyvalent carboxylic acid such as phthalic acid, 2,6
-Aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, and in some cases small amounts of aliphatic dicarboxylic acids such as succinic acid, adipic acid and azelaic acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, trimellitic acid , Trivalent or higher carboxylic acids such as pyromellitic acid, and hydroxycarboxylic acids such as parahydroxybenzoic acid and tartaric acid. (The carboxylic acid component may be used as an ester-forming derivative such as a lower alkyl ester or an acid anhydride.)

Alcohol component trimethylolethane, trimethylolpropane, 3-
Mainly composed of trifunctional alcohols such as methylpentane-1,3,5-triol and glycerin, and if necessary, bifunctional alcohols such as ethylene glycol, diethylene glycol, 1,2-propanediol and neopentyl glycol. Aliphatic diol, ethylene oxide adduct of bisphenol S, and a small amount of tetrafunctional alcohol such as pentaerythritol added.

As the polyester B which is another component of the resin composition of the present invention, those obtained from the following carboxylic acid component, alcohol component and the compound represented by the above formula are preferably used.

Carboxylic Acid Component Mainly composed of terephthalic acid and / or isophthalic acid, and if necessary, other polyvalent carboxylic acid such as phthalic acid, 2,6
An aromatic dicarboxylic acid such as naphthalenedicarboxylic acid, an aliphatic dicarboxylic acid such as succinic acid, an alicyclic dicarboxylic acid such as 1,4-cyclohexanedicarboxylic acid, a small amount of trivalent or more such as trimellitic acid or pyromellitic acid Addition of hydroxycarboxylic acid such as aromatic carboxylic acid, para-hydroxybenzoic acid and tartaric acid. (The carboxylic acid component may be used as an ester-forming derivative such as a lower alkyl ester or an acid anhydride.)

Alcohol component Mainly composed of ethylene glycol and neopentyl glycol, if necessary, diethylene glycol, aliphatic diol such as 1,2-propanediol, ethylene oxide adduct of bisphenol S, small amount of trimethylolpropane, pentaerythritol, etc. With trihydric or higher alcohol.

In the compound of the formula, R has 4 to 4 carbon atoms.
It is necessary to be 18, preferably 6 to 10.
With a compound having 3 or less carbon atoms, sufficient flexibility cannot be imparted to the resin, and the effect of improving the flexibility of the coating film is not exhibited. On the other hand, in the case of a compound having 19 or more carbon atoms, the glass transition point of the resin is significantly lowered, the blocking resistance is lowered, and it is difficult to obtain it commercially.

The copolymerization amount of the compound of the formula in the polyester B is required to be 1 to 15 mol% of the acid component, preferably 2 to 13 mol%. If this amount is too small, it will not be possible to impart sufficient flexibility to the resin, and the effect of improving the flexibility of the coating film will not be sufficiently exhibited. On the other hand, if this amount is too large, the glass transition point of the resin is significantly lowered, the blocking resistance is lowered, and it becomes difficult to pulverize with a general pulverizer.

Specific examples of the compound represented by the formula include the following compounds. Aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, pimelic acid, suberic acid, dodecanedioic acid, tetradecanedioic acid and hexadecanedioic acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1, Aliphatic diols such as 5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,10-decanediol and 1,18-octadecanediol.

The compound of formula needs to be incorporated into polyester B. As a result, the flexibility of the entire coating material can be supplemented and the blocking resistance can be maintained at a level at which there is no practical problem. (The compound of formula is polyester A
However, the glass transition point of the polyester A is too low and the blocking resistance of the entire coating cannot be maintained. )

The polyesters A and B are produced by subjecting the above-mentioned components to an esterification reaction or a transesterification reaction and a polycondensation reaction by a conventional method, and depolymerizing them with a polyhydric alcohol as required. You can At this time, a catalyst may be used.

The resin composition for powder coating material of the present invention can be prepared by kneading the above polyesters A and B and the curing agent at 70 to 150 ° C. using a kneader or roll.

A curing catalyst, a leveling agent, a pigment and other additives may be added to the resin composition of the present invention, if necessary.

[0031]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. The characteristic values were measured by the following methods. Copolymerization Amount of Compound of Formula It was determined by gas chromatography after methanolysis. Average degree of polymerization Determined by gel permeation chromatography. Hydroxyl value Determined by the method described above. The acid value was determined by dissolving in dioxane and titrating with a potassium hydroxide-methanol solution. Glass transition point It was measured at a temperature rising rate of 10 ° C./min using a DSC-20 type differential scanning calorimeter manufactured by Seiko Instruments Inc. Gelation time It was determined by the method described above. 60 degree specular gloss Measured according to JIS K 5400. Impact resistance: Measured according to JIS K 5400 using a ball with a diameter of 1/2 inch and 500 g. It was measured according to Erichsen JIS K 5400 and evaluated in the following two stages. ○: 7 mm or more ×: less than 7 mm Blocking resistance 10 cm x 3 for a coating composition that passed through a 140 mesh sieve
Fill a cmφ test tube to a height of 5 cm and place in a 40 ° C incubator.
After standing for 72 hours, the state of blocking was observed and evaluated in the following two stages. ○: No blocking ×: With blocking

Reference Examples 1 and 2 <Preparation of Polyester A> The raw material compounds of Table 1 were charged in the amounts (parts by weight) shown in Table 1 into a stainless steel reaction can equipped with a stirrer, and heated and stirred at 230 ° C. to produce The formed water was continuously removed from the reaction system. Subsequently, the degree of vacuum was kept at 800 hPa for 3 hours to obtain polyester resins 1A and 2A.

Reference Example 3 <Preparation of Polyester A> The raw material compounds of Table 1 were charged in the amounts (parts by weight) shown in Table 1 into a stainless steel reaction can equipped with a stirrer, and heated and stirred at 260 ° C. to generate water. Was continuously removed from the reaction system. Subsequently, 0.584 parts by weight of antimony trioxide was added as a polycondensation reaction catalyst, the pressure reduction degree was maintained at 1.5 to 0.5 hPa, and the temperature was adjusted to 2 at 280 ° C.
After carrying out polycondensation reaction for a long time to obtain a polyester having a high degree of polymerization, the temperature is lowered to 270 ° C., and the compounds described in the column of depolymerization in Table 1 are added in the amounts (parts by weight) shown in Table 1 and sealed. The depolymerization reaction was performed below to obtain polyester resin 3A.

Reference Example 4 <Preparation of Polyester A> The raw material compounds of Table 1 were charged in the amounts (parts by weight) shown in Table 1 into a stainless steel reaction can equipped with a stirrer, 0.88 parts by weight of zinc acetate was added, and the mixture was heated at 230 ° C. The mixture was heated and stirred at, and the produced methanol was continuously removed from the reaction system. Subsequently, the decompression degree is 800 hPa
After being kept for 3 hours, a polyester resin 4A was obtained.

Reference Example 5 <Preparation of Polyester B> The raw material compounds of Table 1 were charged in the amounts (parts by weight) shown in Table 1 into a stainless steel reaction can equipped with a stirrer, 0.88 parts by weight of zinc acetate was added, and the mixture was heated at 230 ° C. The mixture was heated and stirred at, and the produced methanol was continuously removed from the reaction system. Subsequently, the temperature was raised to 280 ° C. and the degree of vacuum was kept at 1.5 to 0.5 hPa for 1 hour to obtain polyester resin 5B.

Reference Examples 6 to 11 <Preparation of Polyester B> The raw material compounds of Table 1 were charged in the amounts (parts by weight) shown in Table 1 into a stainless steel reaction can equipped with a stirrer, and heated and stirred at 260 ° C. to produce The formed water was continuously removed from the reaction system. Subsequently, 0.584 parts by weight of antimony trioxide was added as a polycondensation reaction catalyst, the pressure reduction degree was maintained at 1.5 to 0.5 hPa, and the temperature was adjusted to 2 at 280 ° C.
After carrying out polycondensation reaction for a long time to obtain a polyester having a high degree of polymerization, the temperature is lowered to 270 ° C., and the compounds described in the column of depolymerization in Table 1 are added in the amounts (parts by weight) shown in Table 1 and sealed. The depolymerization reaction was performed below to obtain polyester resins 6B to 11B.

The characteristic values of each polyester resin are shown in Table 2.

[0038]

[Table 1]

[0039]

[Table 2]

Examples 1 to 6 and Comparative Examples 1 to 6 Polyester resins and curing agents shown in Table 3; "Vestagon B 1530" manufactured by Huls, or "Vestagon BF manufactured by Huls.
1540 ", leveling agent;" Acronal 4F "manufactured by BASF
(Butyl polyacrylate compound), benzoin, curing catalyst; "Stann OMF" manufactured by Sansha Kisei Co., Ltd. (organotin compound), epoxy resin; "Epototo YD" manufactured by Toto Kasei
014 ”, titanium dioxide and precipitated barium sulphate in the proportions shown in Table 3, dry-blended with Mitsui Miike Seisakusho FM 10B type Henschel mixer, and then 90-110 using a Buss PR-46 type co-kneader. Melt kneading at ℃, cooling,
After crushing, it was separated by a wire mesh of 140 mesh to obtain a powder coating. The obtained powder coating material was electrostatically coated on a zinc phosphate-treated steel plate to a film thickness of 50 to 60 μm and baked at 200 ° C. for 20 minutes. The results of evaluation of coating film performance are shown in Table 3.

[0041]

[Table 3]

[0042]

Industrial Applicability According to the present invention, there is provided a resin composition for powder coatings which provides a semi-matt or matt coating film having excellent blocking resistance and good flexibility.

Claims (3)

[Claims] 1. A polyester A comprising an aromatic dicarboxylic acid component and an aliphatic alcohol component as main components and having a hydroxyl value of 1200 geq / 10 ⁶ g or more and not substantially gelled, an aromatic dicarboxylic acid component and the following formula: Mainly composed of an aliphatic alcohol component except for, containing 1 to 15 mol% of a component consisting of a compound of the formula with respect to an acid component, and having a hydroxyl value of 200 to 1000.
geq / 10 ⁶ g of substantially non-gelling polyester B
And an isocyanate curing agent, polyester A
A resin composition for powder coatings, wherein the weight ratio of the polyester B to the polyester B is 70/30 to 10/90, and the difference (absolute value) in gelling time between the polyester A and the polyester B is 3 minutes or more. R ¹ -R-R ² (R is a linear aliphatic group or alicyclic group having 4 to 18 carbon atoms, R ¹
And R ² represents an ester-forming group. ) 2. The polyester A is mainly composed of a terephthalic acid component and / or an isophthalic acid component and a trimethylolpropane component, and the polyester B is a terephthalic acid component and / or an isophthalic acid component and an ethylene glycol component and / or neo. The resin composition for powder coating according to claim 1, which is mainly composed of a pentyl glycol component. 3. The resin composition for powder coating according to claim 1 or 2, wherein the isocyanate curing agent is a blocked isophorone diisocyanate compound.