JPH0214270A - Coating composition for coating steel plate - Google Patents

Abstract

PURPOSE:To obtain the title composition copolymerized with tricycloalkane and having excellent bending workability in pressing, adhesion with face coating, corrosion resistance, moisture resistance, solvent resistance, weather resistance, etc., when used as a primer for steel plate coating. CONSTITUTION:The aimed composition obtained by blending (A) an aromatic dicarboxylic acid (e.g., terephthalic acid) with (B) a glycol (e.g., ethylene glycol) and (C) tricycloalkane expressed by the formula (X is hydroxyl group, carboxyl group, etc.; n is 0-8) so that the component C is preferably 5-25mol% and polym erizing the blend and then blending the resultant saturated polyester, preferably of 100 pts.wt. with (D) a melamine based compound such as hexamethoxymethylmelamine, preferably of 5-45wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to coating compositions, in particular primer compositions, for producing coated steel sheets, commonly referred to as PCM (pre-coated metal).

Conventional Technology Painted steel sheet (PCM) is widely used in industrial and consumer applications.

Primers for PCM are required to have properties such as press workability, adhesion to steel plates and top coats, corrosion resistance, moisture resistance, and solvent resistance.

Conventionally, alkyd resins, acrylic resins, or epoxy resins have been used as primers for PCM, and among these, epoxy resins are most commonly used.

Recently, it has been proposed to use polyester resin as a primer for PCM (for example, in Japanese Patent Application Laid-Open No. 1983-1999).
16537, JP-A-54-16538), especially JP-A-62-5467 (JP-A-56-1)
67767) discloses that a polyester resin containing a dicarboxylic acid mainly composed of aromatic dicarboxylic acids as the acid component and an alkylene oxide adduct of bisphenol A as part of the glycol component is used as a primer for PCM. Although the purpose and composition are different from the present invention, documents using tricycloalkanes as a condensation component include JP-A-58-215421 and JP-A-60 filed by the present applicant. -44559 publication. Specifically, JP-A No. 58-215421 discloses that an air-drying unsaturated polyester resin prepared by reacting tricycloalkanes, polybasic acids, polyhydric alcohols, and polyhydric alcohol allyl ethers with a filler and a vinyl monomer. (such as styrene), and JP-A-60-44559 discloses tricycloalkanes, tertiary nitrogen-containing alcohols, polybasic acids, polyhydric alcohols, and polyhydric alcohols. An unsaturated polyester resin paint is shown in which a filler and a vinyl monomer (styrene, etc.) are mixed with an air-drying unsaturated polyester resin reacted with alcohol allyl ether.

Problems to be Solved by the Invention Epoxy resins commonly used as brimers for PCM are inherently poor in flexibility, so even if the other required properties are met, this is one of the important properties. There is room for improvement in terms of bending workability during press working.

In this regard, the polyester resin described in the above-mentioned Japanese Patent Publication No. 62-5467 has well-balanced characteristics required as a primer for PCM compared to other resins, but it has poor bending workability during press processing, There is a strong desire to further improve adhesion with paint and corrosion resistance.

In view of these circumstances, the main purpose of the present invention is to provide a polyester primer with further improved characteristics as a PCM primer.

Means for Solving the Problems The coating composition for coated steel sheets of the present invention consists of an acid component whose main component is an aromatic dicarboxylic acid and a glycol component, and at least an acid component other than the aromatic dicarboxylic acid or a glycol component. A saturated polyester (X), a part of which is a tricycloalkane represented by the general formula (wherein X is a hydroxyl group, a carboxyl group, or a hydroxyalkyl group, and n is an integer of θ to 8); It consists of

The present invention will be explained in detail below.

<Saturated polyester resin (X)> The saturated polyester resin (X) is composed of an acid component containing aromatic dicarboxylic acid as a main component and a glycol component.

Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic anhydride, phthalic acid, 1,4-naphthalic acid, l,5-naphthalic acid, siphenic acid, 4,4'-oxybenzoic acid, diglycolic acid, 4,4'-sulfonyl dibenzoic acid, 2,5-naphthalene dicarboxylic acid, etc. are used, and from the viewpoint of coating film properties, it is particularly preferable to use terephthalic acid and isophthalic acid. The proportion is desirably 50 mol% or more, more preferably 70 mol% or more.

Acid components of dicarboxylic acids other than aromatic include tetrahydrophthalic anhydride, 2,5-norbornanedicarboxylic acid, Hett's acid, oxalic acid, malonic acid, dimethylmalonic acid,
Succinic acid, geltaric acid, 2,2-dimethylgeltaric acid, adipic acid, dodecanedicarboxylic acid, pimelic acid,
Speric acid, azelaic acid, sebacic acid, 1,3-cyclohexanedicarboxylic acid, etc. are mentioned, and their proportion in the acid component is preferably 50 mol% or less, and more preferably 30 mol% or less. Carboxylic acids such as trimellitic acid, pyromellitic acid, butanetetracarboxylic acid, etc. can also be used in combination.

In addition, if a small amount is used in combination with an unsaturated dicarboxylic acid such as maleic anhydride, maleic acid, itaconic anhydride, itaconic acid, or fumaric acid, no problem will arise.

Glycol components include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,2- or 1,3-propylene glycol, dipropylene glycol, polypropylene glycol, neopentyl glycol, 1,3-11.4-
or 2゜3-butylene gellicol, 1,5-bentanediol, 1,6-hexanediol, 2-ethyl-1
, 3-hexanediol, 2,2.4-1-limethyl-1
, 3-bentanediol, 1,4-cyclohexane dimetatool, etc., and tri- or higher functional alcohols such as trimethyl a-lethane, trimethylolpropane, glycerin, pentaerythritol, and bisphenol dioxypropyl ether can also be used together. .

In the present invention, it is important to use a tricycloalkane represented by the general formula as at least a part of the acid component other than the aromatic dicarboxylic acid or the glycol component. However, in the formula, X is hydroxyl, a carboxyl group, or a hydroxyalkyl group, and n is an integer of O to 8.

Among the tricycloalkanes of the above formula, one in which n=0, that is, tricyclodecane as exemplified below, is practical, considering the ease of acquisition.

The tricycloalkane represented by the general formula (I) is classified into dicarboxylic acid type and glycol type depending on the type of X.

The content of tricycloalkane in the saturated polyester (X) is such that it is at least 5 mol %, in particular 7 to 25 mol %, based on the total amount of acid component and glycol component. When the content of tricycloalkane is too low, the effect of improving metal adhesion, corrosion resistance, etc. of the resulting primer composition is insufficient.

The saturated polyester (X) is produced by condensing the above-mentioned components in a conventional manner at a temperature of about 150 to 250°C under an inert gas atmosphere, and then polycondensing them at a temperature of about 220 to 270°C under reduced pressure. The ratio of the acid component to the glycol component is approximately equimolar, but either one may be used in slight excess.

Melamine Compound (Y)> As the melamine compound (Y), melamine and its derivatives, such as M
l! ll amino groups in which most of the hydrogens have been replaced with methylol groups, and alkoxymethylmelamines having 1 to 6 carbon atoms, i.e., those in which most of the methylol groups of the above-mentioned hexamethylolmelamine are alkoxylated, such as hexaethoxymethylmelamine. , hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, or a mixed etherified melamine that is a combination of two of these.

Alkoxymethylmelamine, for example, in the case of hexamethoxymethylmelamine, is obtained by etherifying hexamethylolmelamine obtained by reacting melamine and formaldehyde with methanol, and most of it becomes methoxymethyl groups.

Furthermore, if necessary, a methyl ether or a butyl ether of methylolated benzoguanamine can also be used in combination.

The melamine compounds (Y) may be used alone or in combination of two or more.

<Blending ratio> The blending ratio of the melamine compound (Y) to 100 parts by weight of the saturated polyester (X) is preferably 5 to 45% by weight, particularly 10 to 35% by weight. If the blending ratio is too small, the solvent resistance and stain resistance of the coating film will decrease;
) is too large, the coating film becomes too hard and cannot withstand the high degree of bending and deep drawing during press working.

<Coating method> The primer composition of the present invention is composed of a mixture of the above-mentioned saturated polyester (X) and melamine compound (Y). isobutyl ketone,
Cyclohexanone, isophorone, methyl cellosolve, butyl cellosolve, cellosolve acetate, butyl cellosolve acetate, carpitol, ethyl carpitol acetate, butyl carpitol acetate, methanol, impropatol, butanol, octatool, diacetone alcohol, ethyl acetate, butyl acetate, petroleum ether , dissolved in a solvent such as petroleum naphtha to an appropriate concentration. In addition, fillers commonly used in paints (calcium carbonate, kaolin clay, alumina, silica, titanium oxide, talc, barium sulfate, lithopone, mica, gypsum, perlite, dolomite, etc.) and colorants (red iron , manganese blue, carbon black, iron black, ultramarine blue, chrome yellow, chrome green, aniline black, cyanine blue, etc.), rust preventive pigments (strontium chromate, etc.), leveling agents (silicone, cellulose acetate butyrate, etc.), curing catalysts (p-toluenesulfonic acid and its salt, phosphoric acid monoalkyl ester, curing catalyst for melamine resin, etc.) and the like are mixed and used.

As the coating method, various methods such as a spray coating method, a roll coating method, a flow coating method, an electrostatic coating method, an electrodeposition coating method, and a dip coating method are employed.

Function and Effects of the Invention The PCM primer composition of the present invention has better properties required for a PCM primer (bending workability during press working, adhesion to steel plate and top coat, corrosion resistance, moisture resistance) than conventional ones. It has a well-balanced combination of properties (durability, solvent resistance).

The adhesion with the top coat is also less dependent on baking conditions, which is advantageous in terms of work. It also has good weather resistance, so it can be used as a top coat.

Example Next, the present invention will be further explained with reference to Examples.

Hereinafter, "part" and "%" refer to reflective gloss retention rate (%)
Except for , all figures are expressed on a weight basis.

(Production of saturated polyester (X)) Production Example 1 In a two-piece reaction vessel equipped with a stirrer, a rectification column, a nitrogen inlet tube, a vacuum device, and a thermometer, 290.7 parts of terephthalic acid, 290.7 parts of isophthalic acid, Ethylene glycol 271J
Tricyclodecane dimethylol 17 represented by the following formula
1.9 parts, di-n-butyltin oxide 0.2 parts, and antimony trioxide 0.3 parts, and heated from 150°C to 220°C.
The esterification reaction was carried out over a period of 5 hours. followed by 30
The pressure was reduced to 1 mmHg over several minutes, and then 0.1-0.
Polycondensation reaction was carried out at 250-260° C. for 2 hours under reduced pressure of 8+smHg. As a result, a pale yellow transparent saturated polyester (X-1) was obtained.

Production Example 2 A saturated polyester (
X-2) was manufactured.

Production Example 3 Saturated polyester (X-3) was produced in the same manner as Production Example 1 using terephthal m/isophthalic acid as the acid component and ethylene glycol/neopentyl glycol/tricyclodecane dimethylol of the following formula as the glycol component. did.

Production Example 4 A saturated polyester (
X-4) was produced.

Preparation Example 5 of a 1:1 mixture with saturated polyester ( X-5) was produced.

Production Example 6 Terephthalic acid/isophthalic acid/tricyclodecanedicarboxylic acid used in Production Example 5 as the acid component, ethylene glycol/neopentyl glycol/ as the glycol component
Using tricyclodecane dimethylol used in Production Example 3, saturated polyester (x-e
) was manufactured.

Comparative Production Example 1 Using terephthalic acid/isophthalic acid/sebacic acid as the acid component and 2 moles of ethylene oxide adduct of ethylene glycol/bisphenol A (New Ball BPE-20 manufactured by Sanyo Chemical Industries, Ltd.) as the glycol component,
Saturated polyester (X-a) was prepared in the same manner as in Production Example 1.
was manufactured.

Comparative Production Example 2 Using terephthalic acid/isophthalic acid as the acid component and propylene oxide 4.4 mole adduct of ethylene glycol/bisphenol A (Uniol DB-500 manufactured by NOF Corporation) as the glycol component, the following Production Example 1 was carried out.
A saturated polyester (x-b) was produced in the same manner as above.

The compositions and reduced viscosities of the saturated polyesters obtained in Production Examples 1 to 6 and Comparative Production Examples 1 to 2 are as follows.
They are summarized in the table.

However, the reduced viscosity was measured at 30° C. by dissolving 0.10 g of saturated polyester in a mixed solvent 251 of phenol and tetrachloroethane in a ratio of 6 to 4.

<Preparation of primer> Example 1 The saturated polyester (X-t) obtained in Production Example 1 was mixed with cyclohexanone/Tsurpetz #150 (aromatic solvent manufactured by Esso Standard Oil)/isophorone = 50/30/
20 (weight ratio) to make a solution with a resin content of 40%, and using this solution, each component was mixed according to the following formulation, and dispersed and kneaded for 1 hour in a disper to obtain a primer composition for PCM. was prepared.

Example 2 A 40% solution of the saturated polyester (X-2) obtained in Production Example 2 was used instead of the 40% solution of the saturated polyester (X-1), and Sumitomo Chemical Co., Ltd. 9 was used as the melamine compound (Y). Sumimaru M504C manufactured by the company (96% non-volatile content)
) was used in the same manner as in Example 1 except that 15 parts of PCM
A primer composition was prepared.

Example 3 A 40% solution of the saturated polyester (X-3) obtained in Production Example 3 was used instead of the 40% solution of the saturated polyester (X-1), and the melamine compound (Y) was manufactured by Hiki Carbide T Co., Ltd. Karatsuku MS-11 manufactured by Co., Ltd. (non-volatile content 60
PC was carried out in the same manner as in Example 1 except that 15 parts of %) were used.
A primer composition for M was prepared.

Example 4 PCM primer was prepared in the same manner as in Example 1, except that the 40% solution of saturated polyester (X-4) obtained in Production Example 4 was used instead of the 40% solution of saturated polyester (X-t). A composition was prepared.

Example 5 A process for PCM was carried out in the same manner as in Example 1, except that the 40% solution of saturated polyester (X-5) obtained in Production Example 5 was used in place of the 40% solution of saturated polyester (X-1). A primer composition was prepared.

Example 6 PCM primer was prepared in the same manner as in Example 1, except that the 40% solution of saturated polyester (X-6) obtained in Production Example 6 was used instead of the 40% solution of saturated polyester (X-1). A composition was prepared.

Comparative Example 1 For PCM in the same manner as in Example 1, except that the 40% solution of saturated polyester (X-a) obtained in Comparative Production Example 1 was used instead of the 40% solution of saturated polyester (X-1). A primer composition was prepared.

Comparative Example 2 For PCM in the same manner as in Example 1, except that the 40% solution of saturated polyester (x-b) obtained in Comparative Production Example 2 was used instead of the 40% solution of saturated polyester (X-1). A primer composition was prepared.

Comparative example 3 A commercially available epoxy resin paint for PCM was used.

<Coating test> The PCM primer composition prepared above was coated with a thickness of 0.3
The dry explosion film thickness is 17 to 20 on the zinc phosphate treated mild steel plate (Bonde #144 treated plate made by Nippon Test Panel Co., Ltd.).
The final temperature of the mild steel plate is 23.
Baking was performed using a hot air dryer for 60 seconds at 0°C.

The physical properties of the coating film of the obtained coated steel plate (PCM) were measured by the method described below. The results are shown in Table 2 below.

<Measurement of coating film properties> Engineering E 60°-so” reflective gloss retention was measured.

11 next day 1 Measured according to JIS K-5400.

Sandwich a mild steel plate of the same thickness as the test piece between the bent parts that have been bent to a 2φ mandrel, and use a vise to perform final scissor bending, and determine the number of plates that can be sandwiched until no cracks appear in the bent part. Processability was evaluated. nT for the case of n sheets
It was expressed as To judge the folding rack, the folded part should be 30
This was done by observing with a magnifying glass.

The methyl ethyl ketone coated surface was wrapped 100 times at 20° C. with gauze impregnated with methyl ethyl ketone, and the condition of the coated surface was observed.

Measurement was performed according to JIS K-5400 (11! Water spray test).

``Chochu'' L (After being immersed in standing boiling water for 2 hours, the 60°-60° reflective gloss retention rate was measured.

The top coat was scratched with a coin after 1 day, and evaluated as O1Δ, × based on the degree of peeling required.

○: Very strong! A: Requires a peeling force Δ: Slightly strong ′A: Requires a punching force ×: Peels with a light peeling force Sakakami Gojaku top coated board 7, thickness 0.2m layer, [1] 5 layers, length 5
Bonding the 0-layer steel plate using epoxy resin adhesive,
A T-peel peel test (pulling speed: 5 mm/5 in) was conducted to measure peel strength (5 kg/am).

1--Tightness with No. ゛- From the top of the PCM primer composition coating layer obtained in 1-, apply and bake a polyester resin paint with the composition shown in C.
A peel test was conducted in the same manner as above, and the peel strength was measured.

(As the polyester resin mentioned above, a condensate having a composition of Te1/phthalic acid/isophthalic acid/sebacic acid/ethylene glycol/neopentyl glycol and an original viscosity of 0.7 dl/g is used.) Patent applicant Nippon Gosei Chemical Industry Co., Ltd. Co., Ltd. Representative Patent Attorney Masaru Oishi Table 1 TPA, IPA, SbA, EG, NPC, Terephthalic acid.

Isophthalic acid.

Sebacic acid.

ethylene glycol.

Neopentyl glycol.

Claims (1)

[Scope of Claims] 1. Consisting of an acid component whose main component is an aromatic dicarboxylic acid and a glycol component, and at least a part of the acid component other than the aromatic dicarboxylic acid or the glycol component has the general formula ▲ mathematical formula, chemical formula, There are tables, etc. ▼ (I) A saturated polyester (X) which is a tricycloalkane represented by (wherein, Y) A coating composition for painted steel plates. 2. The composition according to claim 1, wherein the proportion of aromatic dicarboxylic acid in the acid component is 50 mol% or more. 3. The composition according to claim 1, wherein the amount of tricycloalkane introduced into the saturated polyester (X) is at least 5 mol% of the total amount of the acid component and the glycol component.