JPH09221612A - Thermosetting polyester powder coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject new coating material capable of forming a coating film having excellent smoothness and processability by adding a powdery crystalline polyester resin to a polyester powder coating material. SOLUTION: This coating material contains (A) an amorphous polyester resin containing carboxyl group, (B) a crystalline polyester resin containing carboxyl group and/or hydroxy group and (C) an powdery acrylic crosslinking agent containing epoxy group as essential components. Preferably, >=40mol% of the resinconstituting acid component of the component B is an aromatic dicarboxylic acid and >=20mol% of the alcohol component is 1,6hexanediol. The coating material is produced e.g. by compounding about 96-50wt.% of the component A with about 4-50wt.% of the component B and compounding 20-60 pts.wt. of the component C based on 100 pts.wt. of the sum of the components A and B.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel thermosetting polyester powder coating material.

[0002]

2. Description of the Related Art Powder coatings have many characteristics such as being less pollutant than conventional solvent-based coatings, easy line management, and easy paint recovery. Therefore, it is used in many fields.

Conventionally, as a powder coating material, a thermosetting powder coating material such as a block polyisocyanate-curable polyester powder coating material and an acid-curable acrylic powder coating material has been widely used for outdoor applications. However, the polyester powder coating composition has a problem that its outdoor use is limited due to insufficient weather resistance. Further, although the acrylic powder coating material has good weather resistance, it is expensive and is rarely used in the industrial field. Further, as a powder coating obtained by improving the weather resistance of a polyester powder coating, a powder coating prepared by blending a carboxyl group-containing polyester base resin with a glycidyl group-containing vinyl polymer as a cross-linking agent is disclosed in JP-A-56-136856. It is described in the official gazette. However, the coating film obtained from the powder coating has a problem that the appearance (smoothness, gloss, etc.) and performance (processability, etc.) are not sufficient.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have found that a polyester powder coating containing a glycidyl group-containing acrylic resin as a cross-linking agent is added to a crystalline polyester. We have found that the conventional problems can be solved by adding powder resin, and have completed the present invention.

That is, the present invention provides: (A) Carboxyl group-containing non-crystalline polyester resin, (B) Carboxyl group- and / or hydroxy group-containing crystalline polyester resin, and (C) Epoxy group-containing acrylic powder cross-linking agent are contained as essential components. Thermosetting polyester powder coating, 1. In the resin component (B), 40 mol% or more of the acid component constituting the resin is an aromatic dicarboxylic acid, and 20 mol% or more of the alcohol component constituting the resin is 1,
The present invention relates to the above thermosetting polyester powder coating material, which is 6-hexanediol.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The meaning of "crystalline" in the present invention is a conventionally known term having an endothermic peak due to melting in DSC (differential scanning calorimetry) and DTA (differential thermal analysis), The peak is at 70 to 150 ° C.

Polyester resin (A) used in the present invention
Is a non-crystalline polyester resin containing a carboxyl group in the molecule, and particularly has an acid value of about 15 to 200 KOH.
mg / g, preferably 20-80 KOHmg / g, softening point about 50-150 ° C., preferably about 70-130 ° C., average molecular weight about 1000-10000, preferably about 200.
0 to 5000 is good.

The method for producing the polyester resin (A) is, for example, an acid component and alcohol so as to satisfy the above-mentioned conditions.
It can be produced by a conventionally known reaction method such as an esterification reaction, a transesterification reaction, etc., by appropriately selecting the type and mixing ratio of the component. Examples of the acid component and alcohol component constituting the polyester resin (A) include:
Acid components include terephthalic acid, isophthalic acid, their anhydrides and their lower alkyl esters, adipic acid, sebacic acid, succinic acid, maleic acid, fumaric acid,
Tetrahydrophthalic acid, hexahydrophthalic acid and their anhydrides, and the alcohol component is ethylene glycol-
, Propylene glycol, 1,3-butanediol,
1,4-butanediol, 1,6-hexanediol,
Neopentyl glycol, trimethylolethane, trimethylolpropane, glycerin, pentaerythritol
And the like are exemplified as typical ones.

Polyester resin (B) used in the present invention
Is a crystalline polyester resin containing at least one selected from a carboxyl group and a hydroxy group in the molecule, and particularly, an acid value of about 20 to 200 KOHmg / g,
Preferably about 40-120 KOHmg / g, hydroxyl value about 20-100 KOHmg / g, preferably about 25-80.
KOH mg / g, melting point about 50 to 150 ° C., preferably about 70 to 140 ° C., average molecular weight about 1000 to 10,000,
It is preferably about 2000 to 5000. When the acid value is less than about 20 KOHmg / g, the processability of the coating film is reduced, and the compatibility with the polyester resin (A) is reduced to deteriorate the appearance of the coating film.
If it exceeds g, the weather resistance of the coating film decreases, which is not preferable. When the polyester resin (B) has a hydroxyl group, it is preferable to use the block polyisocyanate (D) as a crosslinking agent for the polyester resin (B). Examples of the block polyisocyanate (D) include:
Those obtained by blocking polyisocyanate (for example, isophorone diisocyanate etc.) with a blocking agent (for example, ε-caprolactam, alcohol etc.) can be preferably used. The method for producing the polyester resin (B) is, for example, a conventionally known method such as an esterification reaction, a transesterification reaction, etc. by appropriately selecting the types and mixing ratios of the acid component and the alcohol component so as to satisfy the above conditions. It can be carried out by a reaction method.

Examples of the acid component and alcohol component constituting the polyester resin (B) include those similar to the acid component and alcohol component described in the above polyester resin (A). Especially polyester resin (B)
40% by mole or more of the acid component constituting the polyester resin (B) is an aromatic dicarboxylic acid, and 20% of the alcohol component constituting the polyester resin (B).
It is preferable that the mol% or more is 1,6-hexanediol. Further, as the aromatic dicarboxylic acid, terephthalic acid and isophthalic acid are preferable. If the ratio of the acid component and the alcohol component is out of the above range, the crystallinity is lowered and the appearance of the coating film and the processability of the coating film are deteriorated, which is not preferable.

The blending ratio of the polyester resin (A) and the polyester resin (B) components is about 98 to 40% by weight, preferably about 9% by weight of the polyester resin (A) based on the total amount of both.
A range of 6 to 50% by weight, a range of about 2 to 60% by weight of the polyester resin (B), and preferably about 4 to 50% by weight is suitable. When the blending ratio of the polyester resin (A) exceeds about 98% and the polyester resin (B) falls below about 2%, the smoothness and processability of the coating film are deteriorated, while the blending ratio of the polyester resin (A) is Is less than about 40% and the polyester resin (B) is more than about 60%, the weather resistance of the coating film deteriorates, which is not preferable.

The epoxy group-containing acrylic powder crosslinking agent (C) used in the present invention has a softening point of about 50 to 150.
C., preferably in the range of about 70 to 120.degree. C., average molecular weight of about 300 to 20,000, preferably about 500 to 10,000.
Is preferred. If the softening point is less than 50 ° C, the powder coating will have poor blocking resistance, while if it exceeds 150 ° C, the fluidity of the powder coating will be poor and the coating film smoothness will be poor, such being undesirable. Further, if the average molecular weight is less than about 300, the processability of the coating film is lowered, while if it exceeds about 20,000, the smoothness of the coating film is lowered, which is not preferable. Examples of the epoxy group-containing acrylic powder crosslinking agent (C) include epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate and 3,4-epoxycyclohexylmethyl (meth) acrylate, and if necessary. And a (co) polymer obtained by a radical polymerization reaction with another radically polymerizable monomer. The blending ratio of the epoxy group-containing acrylic monomer in the (co) polymer is about 20 to
A range of 100% by weight, especially about 40-80% by weight, is preferred. Other radically polymerizable monomers include methyl (meth) acrylate, ethyl (meth) acrylate,
Propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and other (meth) acrylic acid alkyl esters, styrene and other aromatic vinyl compounds, (meth) acrylonitrile compounds And the like.

The mixing ratio of the above-mentioned cross-linking agent (C) component is about 10 to 100 parts by weight, particularly about 20 parts by weight per 100 parts by weight of the total amount of polyester resin (A) and polyester (B).
The range of -60 parts by weight is preferred. If the blending ratio of the cross-linking agent (C) component is less than about 10 parts by weight, the workability and weather resistance of the coating film will deteriorate, and if it exceeds about 100 parts by weight, the smoothness of the coating film,
It is not preferable because the workability is deteriorated.

When the cross-linking agent (D) component is used, the (block) isocyanate group of the cross-linking agent (D) component is about 0.5 to the hydroxyl group of the polyester resin (B) component. It can be added in an amount of 1.5 equivalents, preferably about 0.6 to 1.1 equivalents.

In the present invention, an organic coloring pigment, an inorganic coloring pigment, a filler and the like can be blended, if necessary, in addition to the components (A) to (D). In particular, since the polyester resin (B) component used in the present invention has good dispersibility in the pigment, the filler, etc., the smoothness, gloss, processability, etc. of the coating film are better than those not blended. Excel.

In the present invention, in addition to the above, a curing catalyst, an ultraviolet stabilizer, an ultraviolet absorber, a fluidity adjusting agent,
Anti-repellent agent and the like can be added.

The powder coating material of the present invention is prepared, for example, by a conventional method, for example, by blending a polyester resin, a curing agent and, if necessary, other components and dry blending them with a mixer, followed by heating, melt-kneading and cooling. It can be produced by coarse pulverization, fine pulverization and filtration.

The powder coating material of the present invention is obtained by powder coating an object to be coated and baking it (for example, at a temperature of about 170 ° C. for about 30 minutes and at about 200 ° C. for about 15 minutes) to form a cured coating film. You can As the material to be coated, a conventionally known material can be used without any particular limitation as long as it is a material capable of electrostatic powder coating. Examples of the object to be coated include metals, metals subjected to surface treatment, glasses, and those obtained by coating these materials with paint.

The electrostatic powder coating is preferably carried out by a method known per se, such as electrostatic powder coating or triboelectric powder coating. The coating thickness is not particularly limited, but is about 20 μm.
Suitable ranges are from m to 150 μm, especially from about 30 μm to 100 μm.

[0020]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 A carboxyl group-containing non-crystalline polyester resin (average molecular weight: about 6600, softening temperature: 112 ° C., acid value: 26 KOHm)
g / g, terephthalic acid / neopentyl glycol / 1,
6-Hexanediol = 62.8 / 31.4 / 5.8 weight ratio) 90 g, carboxyl group-containing crystalline polyester resin (average molecular weight about 3000, melting point 130 ° C., acid value 10)
0KOHmg / g, terephthalic acid / isophthalic acid / 1,
6-hexanediol = 55.5 / 9 / 35.5 weight ratio, "100 mol% of aromatic dicarboxylic acid as an acid component and 100 mol% of 1,6-hexanediol as an alcohol component") 10 g , Epoxy group-containing acrylic powder cross-linking agent (glycidyl methacrylate / methyl methacrylate = 35/65 “weight ratio” average molecular weight about 1700, softening point about 98 ° C., epoxy equivalent 485) 31.1 g and titanium dioxide (Type CR-95, trade name, manufactured by Ishihara Sangyo Co., Ltd.) 60 g of the compound was dry blended (Henschel mixer), melt-mixed and dispersed (biaxial extruder).
Kneading machine), cooling, coarse pulverization, fine pulverization (atomizer), and filtration were carried out to produce the thermosetting polyester powder coating material of Example 1.

Examples 2 to 6 The thermosetting polyester powder coating materials of Examples 2 to 6 were produced in the same manner as in Example 1 with the formulations shown in Table 1.

Comparative Example 1 A thermosetting polyester powder coating composition of Comparative Example 1 was produced in the same manner as in Example 1 except that the formulation shown in Table 1 was used.

[0024]

[Table 1]

In Table 1, the compounding amount is g, and the hydroxyl group-containing crystalline polyester resin and the block polyisocyanate have the following meanings.

Hydroxyl group-containing crystalline polyester resin: average molecular weight 2600, melting point 114 ° C., hydroxyl value 46
KOH mg / g, terephthalic acid / 1,6-hexanediol / 1,4-butanediol = 60.5 / 13.5 /
26 weight ratio, aromatic dicarboxylic acid 100 as the acid component
Mol%, 1,6-hexanedio-as the alcohol component
28 mol% block polyisocyanate: ε-caprolactam block isophorone diisocyanate compound Carboxyl group-containing amorphous polyester resin, carboxyl group-containing crystalline polyester resin and hydroxyl group used in Examples and Comparative Examples The results of DSC (differential scanning calorimetry) measurement of the contained crystalline polyester resin are shown in FIG. As is clear from FIG. 1, the carboxyl group-containing crystalline polyester resin has an endothermic peak (melting point) due to crystallinity at 130 ° C., and the hydroxy group-containing crystalline polyester resin has an endothermic peak due to crystallinity at 114 ° C. It has a melting point. Further, the peak appearing at 63 ° C. of the carboxyl group-containing amorphous polyester resin is due to a measurement error or due to a glass transition point and does not show crystallinity.

Table 2 shows the results of coating film performance tests of Examples and Comparative Examples.

[0028]

[Table 2]

In Table 2, the test was conducted as follows.

Preparation of coated plate: A zinc phosphate-treated steel plate was electrostatically powder coated to a film thickness of about 60 μm, and 180 ° C.
What was baked for 20 minutes was used as a test.
In Table 1, the coating film appearance, specular reflectance, and smoothness were tested by the following methods.

Appearance of coating film: The surface of the coating film was visually observed and evaluated. ◎ indicates that there was no abnormality such as smoothness and shrinkage at all, and は indicates that there was some abnormality such as smoothness and shrinkage but was good. Is markedly inferior with abnormalities such as smoothness and shrinkage.

Specular reflectance: 60 of JIS K-5400
The degree of specular gloss was measured.

Impact resistance: According to JIS K-5400 DuPont type impact resistance test, weight 500g, hammer core diameter 1/2
The maximum weight height that does not cause damage to the coating under the condition of inch is displayed. The maximum is 50 cm.

Flex resistance: Flex resistance tester (diameter 10 m
The test was performed according to JIS K-5400 using a m, 6 mm core rod).は: No cracks and peeling, Δ: Cracking and peeling were observed and X: Cracking and peeling were observed and markedly inferior.

[0035]

EFFECTS OF THE INVENTION The thermosetting polyester powder coating composition of the present invention exhibits remarkable effects such that a coating film having excellent smoothness and processability can be formed.

[Brief description of drawings]

FIG. 1 is a chart in which the polyester resin used in Examples and Comparative Examples was measured by DSC (Differential Scanning Calorimetry) to check for crystallinity.

Claims (2)

[Claims] 1. A carboxyl group-containing non-crystalline polyester resin, (B) carboxyl group- and / or hydroxy group-containing crystalline polyester resin, and (C) epoxy group-containing acrylic powder crosslinking agent are contained as essential components. A thermosetting polyester powder coating characterized by the following. 2. In the resin component (B), 40 mol% or more of the acid component constituting the resin is an aromatic dicarboxylic acid,
The thermosetting polyester powder coating composition according to claim 1, wherein 20 mol% or more of the alcohol component constituting the resin is 1,6-hexanediol.