JPS5847063A - Powder paint composition - Google Patents

Abstract

PURPOSE:To provide a powder paint compsn. producing a cured product with excellent corrosion resistance prepared by adding diaminodiphenyl methane to a specified modified epoxy resin. CONSTITUTION:The coating compsn. is prepared by adding diaminodiphenylmethame (B) to a modified epoxy resin (A) obtained by interaction of (1) 100pts.wt. bisphenol A type epoxy resin with an epoxy equivalent of 400-2,500 and (2) 2-8pts.wt. acrylonitrile/butadiene copolymer containing 1.6-2.4 terminal carboxyl, amino or imino groups on average per one molecule. (B) is added in such an amount that the active hydrogen of the amino group may be 1.2-1.5 equivalent per 1 equivalent of the epoxy group. By adding a hardener (B) to (A), the resultant powder paint compsn. shows a low water absorption even under highly humid conditions and produces a cured product with excellent adhesiveness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an epoxy resin powder composition that has excellent anti-corrosion properties and provides a highly damaged product.

Epoxy resin has excellent properties such as electrical insulation, heat resistance, adhesiveness, and corrosion resistance, and can be used in liquid, paste, and other forms.
Available in powder or sheet form, it is used in a variety of fields. Another reason why it is widely used is that it can be mixed in various ways and the properties of the cured product can be changed depending on the purpose of use. However, in high-temperature environments, electrical insulation, adhesion, and even corrosion resistance usually deteriorate. This is because the cured product has relatively high water permeability, and its adhesive strength decreases when it is rolled. This is considered to be because the corrosion resistance during electrical insulation deteriorates due to this effect.

− In recent years, epoxy resins have been used in fields that require a high degree of corrosion resistance, and heat-curing powder coatings are increasingly being used for rounding and factory lining due to their excellent workability during lining. It's coming. However, heat-curing powder coatings are superior to room-temperature curing liquid coatings in terms of initial properties such as mechanical strength, heat resistance, and electrical insulation properties, but their It was inferior in terms of adhesiveness and corrosion resistance. One way to improve this point is to use a powder coating containing dicyanthia as a curing agent, but in this case, the adhesion at t&humid temperature is improved, but the water absorption rate of atS is high9. It was unsatisfactory from the viewpoint of anti-corrosion performance, where the important point is to cut off water and oxygen that cause corrosion.Also, when compared to heat-curing liquid paints, it has superior mechanical strength. However, the adhesion under high environment was slightly inferior.

Taking advantage of these circumstances, the inventors of the present invention have developed a powder that can form a cured coating film with excellent corrosion resistance that does not increase the water absorption rate of the coating film even in a high-humidity environment and does not cause a decrease in adhesive strength. As a result of research into paints, we have arrived at the present invention.

Specifically, the present invention is a thermosetting epoxy resin powder composition that provides a cured product with low water absorption and good adhesion even in a high humidity environment, and which has a carboxyl group, an amino group, or an imino group at the molecular end. Used in the present invention, characterized in that diaminodiphenylmethyt is used as a curing agent for an epoxy resin modified with an acrylonitrile butadiene copolymer (hereinafter referred to as NBR) containing an average of 1.6 to 24 molecules per molecule. The epoxy resin to be used is a bisphenol epoxy resin which is the same substance at room temperature and has an equivalent of 40
0 to 2500 are used. Ebo Φ equivalent weight 400
If the temperature is below 2500, it is difficult to powder the modified resin, and if it is higher than 2500, the melting point of the modified resin will be high and the viscosity when melted in the bath will be high, making it impractical. NBR as a component for improving the adhesion properties of NBR contains 1.6 to 2.4 carboxyl groups, amino groups, or imino groups per molecule at the molecular ends,
The functional group at the end of the molecule reacts with epoxy resin 7,4 in the epoxy resin to obtain a modified epoxy resin containing an MBR component in the molecule. NBR having a molecular weight of 112,500 to 5,000 and containing acrylontrile of 10 to 30% by weight is used. A representative book is the product name Hiker 0T.
BN, High Calm TBN (both B, IF, manufactured by Gutdrich), etc.

Since the present invention was made as a powder composition, M
It is necessary to react the BR and the epoxy resin in advance. The main purpose of this reaction step is to react the functional groups at the ends of NBR molecules with the epoxy groups in the epoxy resin, but it is also possible to react the epoxy groups with each other at the same time. Even if the composition is such that only a semi-solid modified epoxy resin can be obtained by the reaction between groups and epoxy groups, if the reaction conditions are selected appropriately, the reaction between the epoxy groups will also occur simultaneously, increasing the molecular weight of the modified resin and turning it into powder. A solid modified epoxy resin can be easily obtained. This reaction is usually carried out in the range of 120 to 200°C using a tertiary amine such as benzyldimethylamine, dibutyltin oxide,
This is carried out in the presence of a catalyst such as tetrabutyl titanate or triphenylphosphine. If the temperature is below 120°C, the reaction will be slow and the melt viscosity of the raw materials will be high, so the workability will be 8.
< , This is because thermal deterioration of the HBR component occurs at temperatures above 200°C.0 In order to use modified epoxy resin as a raw material for anticorrosive powder coating compositions, Epokin $II! NBR is used in 2-8 ml parts per 1100 parts by weight.

The reason for this is that the hardening machine below the line part and below the fi, zii quantity part.
〇g! This is not sufficient to suppress the decrease in adhesion (198 parts by weight or more is because the mechanical strength of the paper-cured coating film, which is soft, decreases.Also, when using a modified epoxy resin under such conditions, Diaminodiphenylmethane was the most effective in preventing the decline in adhesive strength and corrosion resistance under high humidity conditions. The primary atomyl amine (a) radical of aromatic amines, hydrogen, reacts gradually with epoxy groups at room temperature. However, it is known that secondary amino group hydrogen does not react at room temperature. When not used immediately after blending as in the present invention, modified evo medium resin 1
When using less than 1.2 equivalents of diaminodiphenyl methane per equivalent, about half the amount of diaminodiphenylmethane is used even if all the -anno group hydrogens react with the epoxy groups. Since the boxy group remains unreacted, the storage stability is poor due to the catalytic action of the amino group, and the coating film obtained after curing is poor in flexibility and toughness. If diaminodiphenylmethane is used in an amount of 1.5 or more, the storage stability will be improved and the flexibility of the cured coating will be increased, but the anticorrosion performance will be significantly lowered due to excess amino groups.

Diaminodiphenylmethane is used after being kneaded with a modified epoxy resin, as well as fillers and additives, but at this time, trace amounts of basic compounds such as tertiary amines, imidazoles, guanidines, hydrazides, or phenol,
When alcohol is used as a reaction accelerator, it can be used. The thus obtained kneaded mixture of modified epoxy tree layer and diaminodiphenylmethane is pulverized and used as a powder coating.

Powder paint is electrostatic coating method, fluid l! A cured coating film is formed by dipping and heating the coating according to a commonly known coating method. Various evaluation methods are used to evaluate the adhesion and corrosion resistance of cured coatings, but when evaluating under high humidity conditions, the typical test methods are gonometric adhesion and anodic peel testing. be. In addition, the water absorption rate and insulation resistance were evaluated in accordance with the test method for Ogoban adhesive crab DIM53151 described below.

After immersing the painted piece in warm water at 100°C for 20 hours, it is removed and subjected to 20 cycles. Thereafter, 25 goblets measuring 3m x 3m were placed in the coating film, and the adhesion state of the goblin paint film was evaluated by classifying it into five grades: GTO, . . . , GT4, in descending order of adhesion.

Cathode peel test: A13'! It was evaluated according to 'MG 8.

Drill a 5-inch hole in the center of the paint film of the paint piece and fill it with electrolyte solution (3 mm).
% saline solution) and the base steel plate, and at this time, add K1mt of electrolytic liquid, and the steel plate and w1fj! , a voltage of -67 was applied to the cell, and the electrolyte was removed for 30 days.
How much of the paint film has peeled off from the large area of the initial paint film?
w4 solid. 0 Water absorption rate: The coating film is immersed in water at 80°C for 500 hours, then removed, and the water absorption rate is calculated by determining the 1 weight increase from the initial m-weight. did.

Insulation resistance: ]1! In the second physical property where the insulation resistance of the film was measured at 1500V, the insulation resistance after being immersed in 80°C hot water for 500 hours was also measured.

When the cured coating film obtained from the powder coating composition of the present invention was evaluated based on the above-mentioned adhesion evaluation method and anticorrosion performance evaluation method, it showed excellent values.1 The powder coating of the present invention has excellent corrosion resistance. It can be called a powder coating.

Next, the details of the present invention will be explained with reference to Examples.0 (Assembly of rubber-modified epoxy resin) 100 parts by weight of epoxy resin trade name Epicote φ1002 manufactured by Yuka Shell Epoxy Co., Ltd., B, and IP.

Liquid rubber manufactured by Gutdrich, part name CTBN1300×
Parts by weight of each of 1.3.6.7.10 of 8 were mixed and stirred at 150°C for 3 hours in the presence of 0.2 parts by weight of triphenylphosphine to obtain modified epoxy resin (A) (B) (
0) (D) A modified epoxy resin of class 511 of (1) was obtained.

In addition, 1001 parts of epoxy resin trade name Epicote φ1004 manufactured by Yuka Shell Epoxy Co., Ltd. and the above OTBM were added.
Four parts of 1300X8 were mixed and stirred at 150°C for 3 hours in the presence of 0.2 parts of triphenylphosphine, followed by 4 parts of modified epoxy F11 fat (F).

Example 1-4 Rubber-modified epoxy resin and diaminosyphaermethane, 1
1! Titanium chloride and Modaflow, a flow regulator manufactured by Monnant Co., Ltd. (trade name), were blended as shown in Table 1, and then approximately 90%
Grinding and classification after mixing #1 at 0℃ (145 mesh pass)
A powder coating was obtained.

The resulting powder coating was preheated to 1230℃ #:, 3.2X
100Xl'0O)Ill was electrostatically sprayed onto a sandblasted steel plate (average thickness 3-4μ) and after mourning, 230
9. Heat at ℃ for 5 minutes to prepare a painted piece with blood having a film thickness of 300 to 350 μm. For painted pieces, the value of the coating film is determined in advance, and then the water absorption rate and insulation resistance c1j are determined. Three pieces were prepared: one for layer force dfli and one for #N peeling evaluation. The test results for each item Vc2 are shown in Table 1 along with #C performance conditions, and it is clear that the water absorption rate is low and there is no low adhesive strength or cathode peeling #! ! Even in trials, I got good results.

Comparative Example 1 A powder coating consisting of EBOKI 7-oil manufactured by Yuka Shell Epoxy Co., Ltd. (trade name: Epicote Fyo 1004) and dicyandiamide was prepared with the formulation shown in Table 1, and tested on the same machine as in Example 1. It became clear that the water absorption rate of the fallen membrane was high and the shielding force was decreased, and that there was a problem with the anticorrosion performance of No. 11.2 in the presence of scratches.

Comparative Example 2.3 A powder containing rubber-modified epoxy Slim (A), (K) and diaminodiphenylmethane was used in the formulation shown in Table 1, and 5! A: Created and tested using the same procedure as Example 1. I did it.

In the case of Comparative Example 2, the I4 pole delamination test and silkworm force enhancement were omitted.ζ
In the case of Comparative Example 3, the long-term properties were inferior to those of the Examples and could not be put to practical use.

Comparative Example 4.5 In the case of Comparative Example 4, powder paint was prepared in the same manner as in Example 1 using 8 fl (0) of rubber-modified epoxy resin and a powder paint with a different amount of diaminodiphenylmethane. It is inferior in body retention properties and punch resistance, and in the case of Comparative Example 5, anticorrosion performance is decreased.

Claims (1)

[Claims] One molecule of carboxyl group, amino group, or imino group is added at the molecular end to 100 parts by weight of a bisphenol epoxy resin having an epoxy fi content of 400 to 2,500, with an average of 1.
Diaminodiphenylmethane is added to 1 equivalent of epoxy group of modified epoxy 6M resin obtained by reacting 2 to 8 parts by weight of an acrylonitrile butadiene copolymer containing 6 to 2.4 parts by weight in advance, and the activity of the amino group is Hydrogen 1.2-1.
An anticorrosive epoxy resin powder coating composition, characterized in that it contains an anticorrosive epoxy resin powder coating composition in an amount of 5 equivalents.