JPH0229480A - Coating composition for coated steel sheet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a coating composition 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.

Paints for PCM are required to have properties such as press workability, hardness, moisture resistance, and solvent resistance.

Conventionally, alkyd resins, acrylic resins, or polyester resins have been used as paints for PCM. Documents using polyester resin include JP-A-54-1
6537, JP-A-54-16538, and JP-A-62-5487 (JP-A-56-167767).

In particular, Japanese Patent Publication No. 62-5467 (Japanese Unexamined Patent Publication No. 56-16
7767) discloses that a polyester resin containing a dicarboxylic acid mainly composed of aromatic dicarboxylic acids as an acid component and an alkylene oxide adduct of bisphenol A as a part of a glycol component can be used as a paint for PCM. has been done. This document describes that dimer acid can be used as an acid component other than aromatic dicarboxylic acids (although no examples are given), and that a small amount of sulfonic acid group-containing aromatic dicarboxylic acids can be used. ing.

JP-A No. 57-133166 filed by the present applicant discloses that the composition is composed of an acid component containing terephthalic acid or its ester as a main component, and a glycol component containing neopentyl glycol and polytetramethylene glycol as essential components. A resin composition for coatings is shown in which a melamine compound is blended with a polyester obtained by depolymerizing a high molecular weight polyester, but the introduction of a dimer acid, a dicarboxylic acid (or its ester) containing a sulfonic acid metal base, etc.
There is no disclosure regarding the introduction of glycol or the introduction of glycol.

JP 58-21096, also filed by the present applicant
Publication No. 0 describes an acid component whose main components are terephthalic acid (or its ester) and isophthalic acid (or its ester), a glycol component whose essential component is neopentyl glycol, and an alkali metal base of sulfonic acid and/or an alkali metal base of sulfonic acid. A polyester resin composition with excellent pigment dispersibility has been shown in which a melamine compound is blended into a linear polyester containing a polyfunctional compound having an alkali metal base of carboxylic acid as a constituent component, but regarding the introduction of dimer acid. There is no disclosure, nor is there any disclosure regarding depolymerization of this polyester.

Note that JP-A-57-25323 discloses a polyester using terephthalic acid, 5-metal isophthalic acid, and dimer acid as dicarboxylic acid components;
This document aims to improve the dyeability of polyester used as fibers, films, and other molded products, and its purpose and application are different from those of the present invention.

JP-A-58-63718 discloses a copolyester consisting of terephthalic acid (or its ester), dimer acid, poly(tetramethylene oxide) glycol, 14-butanediol and isophthalic ester containing a sulfonic acid group. However, this copolyester has high melt strength and elasticity and is intended for producing blow molded products, and its purpose and application are different from those of the present invention.

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

Point 1: PCM paints using polyester resin:
This is interesting because it improves the poor flexibility that is a drawback of alkyd resins. In particular, high molecular weight saturated polyester resins, which have recently been used as paints for PCM,
Although it has excellent processability and relatively well-balanced physical properties such as hardness, it has problems in that pigment dispersibility is not necessarily good and thick film coating is not easy.

The resin compositions described in JP-A-57-133166 and JP-A-58-210980 filed by the present applicant each have their own merits and demerits as paints for PCM, and do not necessarily meet market demands. It wasn't.

In view of these circumstances, the present invention provides a polyester paint with further improved properties as a PCM paint, that is, a PCM paint with excellent pigment dispersibility and physical properties of the coating film, and which can be made into a high solids material. It was made for that purpose.

Means for Solving the Problems The coating composition for painted steel sheets of the present invention consists of an acid component and a glycol component, each of which has an aromatic dicarboxylic acid (or its ester) as an essential component. At least a part of the acid component other than the aromatic dicarboxylic acid (or its ester) is a dimer acid, and at least a part of the acid component other than the aromatic dicarboxylic acid (or its ester) or at least a part of the glycol component is a dicarboxylic acid (or a depolymerized saturated polyester (X) with a number average molecular weight of 6,000 to 12,000, which is a depolymerized product of a high molecular weight saturated polyester, which is a glycol containing a sulfonic acid metal group (ester thereof) or a glycol containing a sulfonic acid metal group; and an alkyl etherified formaldehyde resin (Y). , especially melamine resin.

The present invention will be explained in detail below.

<Depolymerized saturated polyester (X)> The depolymerized saturated polyester resin (X) is composed of an acid component containing an aromatic dicarboxylic acid (or its ester) as an essential component and a glycol component.

Terephthalic acid is an aromatic dicarboxylic acid.

Isophthalic acid, phthalic anhydride, phthalic acid, 1,4-naphthalic acid, 1,5-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, terephthalic acid and isophthalic acid are particularly recommended. preferable. As the aromatic dicarboxylic acid ester, an alkyl ester having about 1 to 4 carbon atoms, usually a methyl ester, is used. The proportion of the aromatic dicarboxylic acid (or its ester) in the acid component is desirably 30 mol% or more, particularly 40 mol% or more.

Acid components other than aromatic dicarboxylic acids (or esters thereof) include tetrahydrophthalic anhydride, 2,5-fulbornanedicarboxylic acid, Hett's acid, oxalic acid 1, malonic acid, dimethylmalonic acid, succinic acid, geltal acid, 2.
Examples include 2-dimethylgeltaric acid, adipic acid, dodecanedicarboxylic acid, pimelic acid, speric acid, azelaic acid, sebacic acid, 1,3-cyclohexanedicarboxylic acid (esters include alkyl esters having about 1 to 4 carbon atoms) ) is used, and its proportion in the acid component is desirably 70 mol% or less, particularly 60 mol% or less. Note that a trifunctional or more functional carboxylic acid, 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 glycol, 1,5-bentanediol, 1.6-hexanediol, 2-ethyl-1
,3-hexanediol,2,2.4-)umethyl-1
, 3-bentanediol, 1,4-cyclohexane dimetatool, polytetramethylene glycol, bisphenol A, hydrogenated bisphenol A, trimethylolethane, trimethylolpropane, glycerin, 1,3,6-hexanediol. , pentaerythritol, bisphenol dioxypropyl ether, and other trifunctional or higher functional alcohols can also be used in combination.

In the present invention, a dimer acid is used as at least a part of the acid component other than the aromatic dicarboxylic acid (or its ester).

Dimer acid is a trimerized product of unsaturated fatty acids such as oleic acid and lyluic acid, and is a mixture in which the main component is unsaturated dicarboxylic acid and small amounts of monomers and trimers. Hydrogenated products of dimer acids are also included in the scope of the present invention.

The proportion of dimer acid in the acid component is 0.1 to 70 mol%
, particularly preferably from 0.1 to 60 mol%. If the proportion of dimer acid is too small or too large, the balance of physical properties as a paint for PCM will be impaired, and the properties will also deteriorate in terms of pigment dispersibility.

Further, in the present invention, a dicarboxylic acid (or an ester thereof) containing a sulfonic acid metal base or a sulfonic acid metal base is contained as at least a part of the acid component or glycol component other than the aromatic dicarboxylic acid (or its ester). Use glycol.

A dicarboxylic acid containing a sulfonic acid metal group (or its ester) or a glycol containing a sulfonic acid metal group means that the molecule contains one or more sulfonic acid metal groups and at least two COOR groups (R is H or alkyl group)
Or it has an OH group.

Such compounds include sulfonic acid metal group-containing dicarboxylic acids (or esters thereof) such as sulfonadium phthalate, sulfokalium phthalate, sulfonodium terephthalate, sulfokalium terephthalate, sulfonium isophthalate, and sulfokalium inphthalate; 3-butene-1゜2-diol, 2-butene-1,4-diol, 2,5-dimethyl-3-hexene-2,5-diol, 15-hexadiene-3,4-diol, 2.6 −
Examples include sulfonic acid metal base-containing glycols obtained by reacting an acidic sulfite with a glycol having an unsaturated bond such as octadiene-4,5-diol.

The proportion of the dicarboxylic acid (or its ester) containing a sulfonic acid metal group or the glycol containing a sulfonic acid metal group in the acid component or glycol component is 0.1 to 5.
It is desirable that the content be mol%, particularly 0.3 to 21ymol%; too little will lead to insufficient pigment dispersibility, and too much will lead to deterioration in pigment dispersibility and water resistance.

Each of the above components is condensed in an inert gas atmosphere at a temperature of about 150 to 250°C according to a conventional method, and then heated to 22°C under reduced pressure.
A high molecular weight saturated polyester is produced by polycondensation at about 0 to 280°C. Dibutyltin oxide, zinc acetate, etc. are used as the condensation reaction catalyst, and antimony triboide, germanium oxide, tetrabutyl titanate, dibutyltin oxide, etc. are used as the polycondensation reaction catalyst. It can also be added together with a catalyst.

The saturated polyester obtained by the above method is a high molecular weight saturated polyester having a number average molecular weight of about 7,000 to about 50,000.

In the present invention, a depolymerized high molecular weight saturated polyester is used. The depolymerization is performed on this high molecular weight saturated polyester at a concentration of 0.0
05-5 mol% polyol was added and the temperature was 210-2.
This can be achieved by heating and mixing at 80°C.

Through this depolymerization reaction, the number average molecular weight becomes 6000.
~12,000 depolymerized saturated polyester (X) is obtained. If the number average molecular weight is less than 6,000, the flexibility of the coating film will be impaired and it will not be able to withstand high-level bending or deep drawing. The objectives of the period cannot be fully achieved.

The polyols used in the depolymerization described in L include ethylene glycol, diethylene glycol, triethylene glycol, 1,2- or 1,3-propylene glycol, dipropylene glycol, neopentyl glycol, 1,3-14- or 2,3-butylene glycol,
Glycols such as 1.5-bentanediol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, 1,3.6-hexanediol, etc. A polyhydric alcohol of trihydric or higher hydricity is used. These can be used alone or in combination of two or more. However, considering the efficiency of depolymerization,
Usually, a trivalent or higher polyhydric alcohol is used, or a small amount of glycol is often used in combination with this.

Alkyl etherified formaldehyde resin (Y) Melamine compounds are useful as the alkyl etherified formaldehyde resin (Y).

Examples of melamine-based compounds include melamine and its derivatives, such as hexamethylolmelamine, in which most of the hydrogens in free amine groups are replaced with methylol groups, and alkoxymethylmelamines having 1 to 6 carbon atoms, i.e. - Most of the methylol groups of hexamethylolmelamine are alkoxylated, such as hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, or these Mixed etherified melamine is a combination of two types of melamine.

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.

In addition to the above, methyl ethers and butyl ethers of methylolated benzoguanamine can also be used.

The alkyl etherified formaldehyde resin (Y) may be used alone or in combination of two or more.

(Blending ratio) The blending ratio of the alkyl etherified formaldehyde resin (Y) to the weight parts of the depolymerized saturated polyester (X) ioo is preferably 5 to 45% by weight, particularly 10 to 35% by weight.Alkyl etherified formaldehyde If the blending ratio of resin (Y) is too low, the solvent resistance and stain resistance of the coating film will decrease, while if the blending ratio is too high, the coating film will become too hard and the high It cannot withstand bending or deep drawing.

<Coating method> The coating composition of the present invention comprises the above-mentioned depolymerized saturated polyester (X) and alkyl etherified formaldehyde resin (Y).
), but when painting steel plates, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, methyl cellosolve, butyl cellosolve, cellosolve acetate, butyl cellosolve acetate, calpitol, ethyl carpitol acetate are used as solvents. 1. It is used by dissolving it in a solvent such as butylcarpitol acetate, methanol, impropatol, butanol, octatool, diacetone alcohol, ethyl acetate, butyl acetate, petroleum ether, petroleum naphtha, etc. to an appropriate concentration.

In addition, in this case, extender pigments or colored pigments, that is,
Fillers such as calcium carbonate, kaolin, clay, alumina, silica, titanium oxide, talc, barium sulfate, lithopone, mica, gypsum, perlite, dolomite, red iron oxide, manganese blue bon black, iron black, ultramarine blue, chrome yellow Coloring agents such as , chrome green, aniline black, cyanine blue, phthalocyanine blue, and quinacridone red are usually added.

In addition, additives commonly used in paints, such as leveling agents (silicone, cellulose acetate butyrate, etc.), curing catalysts (p-1 luenesulfonic acid and its salts, phosphoric acid monoalkyl esters, curing catalysts for melamine resins, etc.) etc.) etc. are added as necessary.

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.

Effects of the invention The coating composition for PCM of the present invention has a P
It has a good balance of properties required as a paint for commercials (bending workability during press working, adhesion to steel plates, moisture resistance, and solvent resistance).

Further, since dimer acid and a dicarboxylic acid (or its ester) containing a sulfonic acid metal group or a glycol containing a sulfonic acid metal group are introduced as constituent components, an effect of excellent pigment dispersibility is also achieved. Furthermore, −
Since the high molecular weight saturated polyester resin obtained by the reaction of the above components is depolymerized until the number average molecular weight becomes 6,000 to 12,000, high solids can be produced without impairing the above properties, and thick film coating is possible. It also has the effect of making it easier.

As described above, the paint of the present invention has both the characteristics required as a paint for PCM.

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

Hereinafter, "parts" and "%" are expressed on a weight basis, except for 1 reflection gloss (%) and gloss retention (%).

<Production of depolymerized saturated polyester (X)> Production Example 1 Stirrer 1. In a reaction vessel equipped with a rectification column, nitrogen introduction tube, vacuum device, and thermometer, 199.4 parts of terephthalic acid, 99.7 parts of isophthalic acid, 182.0 parts of sebacic acid, 242.1 parts of ethylene glycol, and neopentyl were added. glycol 6
2.5 parts of dimer acid (manufactured by Harima Kasei Kogyo Co., Ltd., Haridimer #300), 43.8 parts of sulfoisophthalic acid dimethyl ester Na salt, and 410.2 parts of moro-butyltin oxa as a reaction catalyst. 0.3 part of antimony trioxide was charged, and an esterification reaction was carried out from 150°C to 220°C over 5 hours. Next, the pressure was reduced to 1 nusHg over 30 minutes, and then Q, l ~ Q,
Polycondensation reaction was carried out at 230 to 250° C. for 2 hours under reduced pressure of 8 mmHH.

After that, the reaction system was returned to normal pressure with nitrogen gas, 8.4 parts of trimethylolpropane was charged, and 2
The depolymerization reaction was carried out for an hour.

As a result, a pale yellow transparent depolymerized saturated polyester resin was obtained.

The composition of this depolymerized saturated polyester resin was analyzed by NMR1 atomic absorption, gas chromatography, and the like. Also GPC (gel permeation chromatography)
The molecular weight was measured by

The results are shown in Table 1.

Production Examples 2 to 7 According to Production Example 1, depolymerized saturated polyesters having the compositions and molecular weights shown in Table 1 were produced.

Comparative Production Examples 1 to 3 According to Production Example 1, depolymerized saturated polyesters having the compositions and molecular weights shown in Table 1 were produced. A high molecular weight saturated polyester without depolymerization was also produced. The results are also shown in Table 1.

Comparative Production Example 1 lacks both dimer acid and sulfoisophthalic acid dimethyl ester Na salt, Comparative Production Example 2
Comparative Production Example 3 is a case in which depolymerization is not performed.

The meanings of the abbreviations in Table 1 are as follows, and the unit of composition in the table is "mole".

Acid component molecule PA is terephthalic acid IPA, isophthalic acid SbA, sebacic acid DA, dimer acid H-DA is hydrogenated dimer acid SIPMJi, Na salt of sulfoisophthalic acid dimethyl ester glycol component EC is ethylene glycol NPC is neopentyl glycol S-1,48G is depolymerized with Na salt of sulfo-1,4-butanediol TPM is depolymerized with trimethylolpropane PE is depolymerized with pentaerythritol Molecular weight Mn is number average molecular weight i is the weight average molecular weight Mw/Mn, which is the ratio of both (preparation of paint) Examples 1 to 7, Comparative Examples 1 to 3 Aromatic solvent) was dissolved in a mixed solvent with a weight ratio of 50/20/30 to make a solution with a resin content of 40%. Using this solution, each component was mixed according to the following recipe and dispersed in a disper for 1 hour. By kneading, paint compositions for PCM (white enamel paint and black enamel paint) were prepared.

In the above white enamel paint formulation, carbon black (MA manufactured by Mitsubishi Kasei Corporation) was used instead of 50 parts of titanium dioxide.
loo) using 4 parts.

<Coating test) 100 parts of the above white enamel paint and black enamel paint) 24
A gray paint was prepared by mixing the two parts with a dispenser for 1 minute.

Immediately after preparation, this gray paint was coated on a tin plate with a thickness of 0.3 mm using a bar coater to a dry film thickness of 17 to 20 g.
The coated plate was coated so as to have a coating thickness of m, immediately subjected to a rubbing test, and then baked at 180°C to obtain a coated plate 1.

Further, after storing this gray paint at 50° C. for 5 days, coating was performed in the same manner as above to obtain coated plate 2.

Painting 1'' L1 The above white enamel paint was applied to a 0.3cm thick zinc phosphate treated mild steel plate (Bonde #144 treated plate manufactured by Japan Test Panel Company) with a dry film thickness of 17 to 21 JLm. It was coated using a reverse coater so that the mild steel plate reached a final temperature of 220°C, and was baked in a hot air dryer for 90 seconds.

<Evaluation> The above coating composition and the obtained coated steel sheet (PCM) were evaluated for pigment dispersibility, measurement of non-volatile content, and measurement of physical properties of the coating film using the methods described below. The results are shown in Table 2 below.

The degree of color separation in the rubbing test portions of Painted Board 1 and Painted Board 2 was visually determined.

(2) The color difference (color difference ΔE given by the following formula from the Lab value) of coated plate 1 and coated plate 2 was measured using a color difference meter, and those with a small color difference ΔE were judged to have good pigment dispersibility.

ΔE = (L+ −LZ)” ” (a+ −aZ)
`` '' (b+ -b2)2 The non-volatile content of the paint was determined when the viscosity (20°C) measured with #4 food cup was 60 seconds.

Note that dilution was performed with isophorone.

Le E 60°-60° reflective gloss was measured.

The coated surface of the coated steel plate was measured in accordance with JIS K-5400 using a high-grade pencil specified in JIS S-6006.

(Pressure T-bending) A mild steel plate with the same thickness as the test piece is placed between the bent portion of the 2φ mandrel, and the final scissor bending is performed using a vise until no cracks appear in the bent portion. Workability was evaluated based on the number of sandwiched plates. nT for the case of n sheets
It was expressed as

The top coated surface of the 32 bases of the horsetail was heated to 20°C with gauze impregnated with pheasant roll for 10 minutes.
It was wrapped 0 times and the condition of the coated surface was observed.

After being immersed in boiling water for 2 hours, the 60°-60° reflective gloss was measured and expressed as the gloss retention rate (%) relative to before immersion in boiling water.

Patent applicant Nippon Gosei Kagaku Kogyo Co., Ltd. - Processor tj
TF document (spontaneous) 1. Indication of the incident 1986 Patent fi1i No. 178758 Address 9-6 Nozaki-cho, Kita-ku, Osaka Name (410) B Honsei Kagaku T Gyo Co., Ltd. Representative Masaru Ohashi 4, Agent Person: 533 Address: Oshiro Building, 1-19-11 Higashinakajima, Higashiyodoyo-ku, Osaka (Telephone number: 06-323-0038) Name: (8788) Patent attorney Seibu Oishi 5, details of the invention in the specification subject to amendment Explanation column 6, content of amendment

Claims (1)

[Scope of Claims] 1. Consists of an acid component whose essential component is an aromatic dicarboxylic acid (or its ester) and a glycol component, and at least a part of the acid component other than the aromatic dicarboxylic acid (or its ester) is a dimer. A dicarboxylic acid (or an ester thereof) containing a sulfonic acid metal base or a part of the acid component other than the aromatic dicarboxylic acid (or its ester) or at least a part of the glycol component containing a sulfonic acid metal base. A coating composition for coated steel plates comprising a depolymerized saturated polyester (X) having a number average molecular weight of 6,000 to 12,000, which is a depolymerized product of a high molecular weight saturated polyester, which is a glycol, with a polyol, and an alkyl etherified formaldehyde resin (Y). 2. Claim 1, wherein the proportion of dimer acid in the acid component in the depolymerized saturated polyester (X) is 0.1 to 50 mol%.
Compositions as described. 3. The ratio of the dicarboxylic acid (or its ester) containing a sulfonic acid metal base or the glycol containing a sulfonic acid metal base to the acid component or glycol component in the depolymerized saturated polyester (X) is 0.1 to 5 moles. %
The composition according to claim 1.