JPH0413373B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention has excellent flexibility, adhesion, corrosion resistance,
The present invention relates to a method for producing a flexible epoxy resin for powder coatings that has good performance such as weather resistance. Epoxy resins are used in various applications such as paints, electricity, civil construction, and adhesives due to their excellent performance, and are particularly used in paints. In paint applications, the demand for powder paints has been increasing in recent years due to the increasing need for low pollution and resource conservation. This powder coating is usually obtained by heating resin components, pigments, and other additives, melting and kneading them using an extruder, etc., and then cooling and pulverizing the resulting solid material. Therefore, the resin components used are:
A resin that has good blocking resistance and low melt viscosity at storage temperature (usually room temperature) is desirable. Resins that meet these requirements include thermosetting resins such as epoxy resins and polyester resins, and thermoplastic resins such as vinyl chloride resins and polyethylene resins, but epoxy resins are used for applications that require corrosion resistance. It will be done. In applications that require this corrosion resistance, recently, temperatures ranging from room temperature to -20℃ have been
There has been a growing demand for coating films that have excellent bending workability or impact strength at low temperatures of about 1000 yen, and conventional epoxy paints are no longer able to meet these demands. The present inventors have made intensive studies to obtain an epoxy resin that can overcome these drawbacks, that is, have both corrosion resistance and flexibility, and as a result, they have discovered the present invention. That is, the present invention provides (A) a bisphenol type epoxy resin having two epoxy groups in one molecule and an epoxy equivalent of 100 to 300, and (B) an aromatic or aliphatic resin per mole of neopentyl glycol. A softening point of 80°C or higher according to the Durand mercury method, which is characterized by reacting with an acid-terminated polyester obtained by reacting a cyclic dicarboxylic acid or an anhydride of an aromatic or alicyclic dicarboxylic acid in a proportion of 1.1 to 4 moles. The present invention relates to a method for producing a flexible epoxy resin for powder coating. A typical example of the bisphenol type epoxy resin having two epoxy groups in one molecule and having an epoxy equivalent of 100 to 300 used in the present invention is a condensate of epichlorohydrin and a bisphenol compound. Can be mentioned. Examples of bisphenol compounds in this case include 2,2'-bis(4,4'-hydroxyphenyl)propane (commonly known as bisphenol A), halogenated bisphenol A,
Bis(4,4'-hydroxyphenyl)methane (commonly known as bisphenol F), bis(4,4'-hydroxyphenyl) sulfone (commonly known as bisphenol S)
can be mentioned. Preferred is bisenol A type glycidyl ether epoxy resin. In the present invention, the epoxy resin of component (A) is a bisphenol type liquid epoxy resin having an epoxy equivalent of 100 to 300, and when the epoxy equivalent is 300 or more, the flexibility of the produced epoxy resin deteriorates.
As such liquid epoxy resin, Asahi Kasei Corporation's product name AER331 (epoxy equivalent: 180~
200), AER337 (epoxy equivalent weight 225-280), etc. Aromatic dicarboxylic acids used in the present invention include, for example, phthalic acid, isophthalic acid, terephthalic acid,
and expression [However, in the formula, Z is (-CH ₂ -) _o (n: 1 to 6), -S
-,

【formula】

[Formula] or -O-. ] For example, bis(4,4'-carboxyphenyl) ether and the like can be mentioned. Examples of the alicyclic dicarboxylic acids used in the present invention include hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, methylhexahydrophthalic acid, bromohexahydrophthalic acid, methylhexahydroterephthalic acid, etc. be able to. Examples of the aromatic dicarboxylic acid anhydride used in the present invention include phthalic anhydride, bromo phthalic anhydride, and methyl phthalic anhydride. Examples of the anhydride of alicyclic dicarboxylic acid used in the present invention include hexahydrophthalic anhydride, bromohexahydrophthalic anhydride, methylhexahydrophthalic anhydride, and the like. In the present invention, the weight ratio of component (A) and component (B) is
You can choose it according to your purpose. In the present invention, diglycidyl ether of hydrogenated bisphenol is also used as component (A). Examples of this include hydrogenated 2,2'-bis(4,4'-hydroxyphenyl)propane, hydrogenated bis(4,4'-hydroxyphenyl)methane, and hydrogenated bis(4,4'-hydroxyphenyl)propane. Diglycidyl ethers such as -hydroxyphenyl) sulfone can be mentioned. The flexible epoxy resin of the present invention has two
Epoxy resin having epoxy groups or diglycidyl ether of hydrogenated bisphenol
neopentyl in the presence of a catalyst such as a tertiary amine, quaternary ammonium salt, quaternary phosphonium salt, etc. at a temperature of 80 to 200°C for a sufficient period of time, usually from about 1 to about 30 hours, to form the product. easily by reacting with an acid-terminated polyester obtained by reacting 1 mole of glycol with an aromatic or alicyclic dicarboxylic acid or an anhydride of an aromatic or alicyclic dicarboxylic acid at a ratio of 1.1 to 4 moles. That's what you get. The softening point of the obtained epoxy resin is 80°C or higher. The softening point is determined by the Durand mercury method (Shokodo Co., Ltd., "Epoxy Resin", edited by Hiroshi Kakiuchi, 1971, Vol. 6).
edition, pp. 177-178). In the present invention, the curing agent is not particularly limited, and examples of commonly used curing agents include, for example, novolac type phenolic resin, dicyandiamide, imidazoles, hydrazides, aromatic amines,
Acid anhydrides can be used. The coating film using the epoxy resin in the present invention is
It exhibits good flexibility and corrosion resistance, and also has excellent weather resistance. The use of the resin composition according to the present invention is not particularly limited, and it can be applied to a wide range of uses such as external coating of steel pipes, coating of steel bars, and electrical insulation coatings. Hereinafter, the present invention will be explained in more detail with reference to Examples. In the examples, unless otherwise specified, parts represent parts by weight. Examples 1 to 3 Diglycidyl ether of bisphenol A type AER-331R with an epoxy equivalent weight of 190 (manufactured by Asahi Kasei Corporation)
Methyltriphenylphosphonium iodide is added as a catalyst to the acid-terminated polyester obtained from neopentyl glycol and aromatic or alicyclic dicarboxylic acid, and the mixture is reacted at 140°C for about 3 to 6 hours. The results are shown in Table-1.

【table】

[Table] Reference Examples 1 to 3 The resins obtained in Examples 1 to 3 were kneaded with trimellitic anhydride as a curing agent, TiO ₂ , and a flow control agent using a kneader at a temperature of 130°C in the screw part and 130°C in the die part. After that, it was ground at room temperature to obtain a powder coating. This powder coating was applied to a mild steel plate using an electrostatic coating machine and baked at 190℃ for 20 minutes to examine the coating film performance (film thickness was 100 microns). The results are shown in Table-2.

【table】

[Table] Comparative Example 1 In Reference Example 1, the same method as in Reference Example 1 was used except that bisphenol A type epoxy resin AER-664P (manufactured by Asahi Kasei Industries, Ltd.) with an epoxy equivalent of 950 was used instead of the resin in Example 1. The coating performance and film characteristics were investigated (film thickness was 100 microns). Formula AER-664P 100 parts Trimellitic anhydride 7 parts TiO ₂ 25 parts Flow regulator 1 part Coating performance Erichsen 5 mm Dupont impact value (500 g, 1/2 inch) 20 cm Adhesion 100/100 Bending property 6 mmφ passed Film properties Tensile Strength 5.5Kg/cm ² Elongation 5% Example 4 200 parts of polyester A and 0.48 parts of methyltriphenylphosphonium iodide were added to 480 parts of diglycidyl ether of hydrogenated bisphenol A having an epoxy equivalent of 240, and the mixture was heated at 140°C. The reaction was continued for 3 hours, the epoxy equivalent was 1300, and the Duran softening point was 90-93.
C. Epoxy resin A was obtained. This epoxy resin
100 parts of A, 5 parts of dicyandiamide as a hardening agent,
0.2 parts of 2-methylimidazole, 25 parts of TiO ₂ and 1 part of a flow control agent were kneaded in a kneader under the same conditions as in Reference Example 1 and pulverized to obtain a powder coating. This paint was baked at 180°C for 20 minutes in the same manner as in Reference Example 1, and the gloss retention rate was examined using a sunshine weather meter. Gloss retention rate (%) After 100 hours 90 After 300 hours 85 After 500 hours 77 Comparative example 2 In Example 4, instead of epoxy resin A, bisphenol A type epoxy resin AER-664P (Asahi Kasei Corporation) with an epoxy equivalent of 950 was used. )), and the gloss retention rate was examined in the same manner as in Example 4. Formula AER-664P 100 parts Dicyandiamide 5 parts 2-Methylimidazole 0.2 parts TiO ₂ 25 parts Flow control agent 1 part Gloss retention (%) After 100 hours 80 After 300 hours 15 (Yellowing of surface) After 500 hours Measured. figure

Claims (1)

[Scope of Claims] 1 (A) a bisphenol type epoxy resin having two epoxy groups in one molecule and an epoxy equivalent of 100 to 300; and (B) an aromatic or The softening point is 80°C according to the Durand mercury method, which is characterized by reacting with an acid-terminated polyester obtained by reacting an alicyclic dicarboxylic acid or an anhydride of an aromatic or alicyclic dicarboxylic acid in a proportion of 1.1 to 4 moles. The above is the method for producing a flexible epoxy resin for powder coating. 2. The method for producing a flexible epoxy resin for powder coatings according to claim 1, wherein the epoxy resin as component (A) is diglycidyl ether of hydrogenated bisphenol.