JPH0436363A - Paint resin composition - Google Patents

Abstract

PURPOSE:To obtain a top coat paint resin excellent in alkali resistance, moisture resistance, and workability by incorporating an alkyl-etherified formaldehyde resin into a polyester resin formed from an aromatic dicarboxylic acid and a specified glycol component. CONSTITUTION:A polyester resin (a) formed from 100mol% aromatic dicarboxylic acid, 0-80mol% 6-10C long-chain aliphatic diol, and 100-20mol% glycol component of formula 1 (wherein R1 and R2 are each 1-4C alkyl) is mixed with an alkyl-etherified formaldehyde resin (b). The component (a) can appropriately be selected from the viewpoints of economy and physical properties; however, those made from terephthalic acid, isophthalic acid, orthophthalic acid, etc., are preferably used from the viewpoints of moisture resistance and alkali resistance. It desirable that the weight ratio of component (a) to component (b) be (95 to 60):(5 to 40).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a resin composition for Kyoto materials. More specifically, it is an object of the present invention to provide a resin composition for a top coat paint, which has excellent alkali resistance, moisture resistance, and processability.

(Conventional technology and problems to be solved) So-called pre-coated metal (PCM) such as painted steel plates is economical,
Taking advantage of its productivity and processability, it is widely used in building materials such as roofing and wall materials, outdoor equipment such as storage sheds and radiator units, and home appliances such as VTR1 audio and washing machines. The first characteristic required for painted steel sheets is excellent bending workability. Currently used paint resins include alkyd resins, acrylic resins, and epoxy resins, but they have drawbacks in processability, and high molecular weight polyesters are used in fields that require high processability. is the current situation.

Currently, the use of PCM not only in the field of building materials but also in home appliances is progressing more and more, and in particular, high molecular weight polyester resins are attracting more and more attention and being used because of the spread of PCM, which requires a high degree of processability in all kinds of home appliances. High-molecular-weight polyester, which is used as a resin for painted steel plate tops, can be used as an alternative to pre-coating from post-coating for all types of home appliances, so it is essential that it has properties such as durability that suit each application. Among these, high molecular weight polyester with excellent alkali resistance, moisture resistance, and processability has not yet been found, as it has poor performance against the corrosion of detergents in home appliances such as washing machines and dishwashers. The current situation is that there are delays, and steel plate manufacturers and the home appliance industry are demanding an immediate solution.

(Means for Solving the Problems) In view of the above-mentioned problems, the present inventors have conducted various intensive studies in order to obtain a resin composition for coatings that has excellent processability, moisture resistance, and particularly excellent alkali resistance. An aromatic dicarboxylic acid as a carboxylic acid component, a long-chain aliphatic diol having 6 to 10 carbon atoms as a glycol component, and the following general formula (I)
The present invention was accomplished by discovering that a polyester using a glycol component represented by the following significantly improves alkali resistance and provides a resin composition for coatings with excellent processability and moisture resistance. That is, the present invention uses aromatic dicarboxylic acid 100
Mol% and long chain aliphatic diol with 6 to 10 carbon atoms 0 to 80
This is a coating resin composition characterized by blending an alkyl etherified formaldehyde resin with a polyester resin consisting of 100 to 20 mol % of a glycol component represented by the following general formula (I).

The polyester resin of the present invention has, as a dicarboxylic acid component,
It consists of 100 mol% of aromatic dicarboxylic acids, and the aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, and diphenyl-p.

p'-dicarboxylic acid, diphenyl-m9m-dicarboxylic acid, diphenylmethane-p,p'-dicarboxylic acid, diphenylmethane-m,m'-dicarboxylic acid, 2.2'-
Bis(4-carboxyphenyl)propane, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl ether-p.

p'-dicarboxylic acid, diphenyl ether-m.

m'-dicarboxylic acid, diphenylsulfone-p.

p'-dicarboxylic acid, diphenylsulfone-m.

Examples include m'-dicarboxylic acids and lower alkyl ester derivatives thereof, which may be used singly or in combination of two or more. The aromatic dicarboxylic acid is appropriately selected in terms of economy and physical properties, but terephthalic acid, isophthalic acid and orthophthalic acid are preferably used in terms of moisture resistance and alkali resistance.

When aliphatic or alicyclic dicarboxylic acids are used in addition to aromatic dicarboxylic acids, alkali resistance is significantly reduced.

Further, the polyester resin of the present invention may consist of 0 to 80 mol% of a long-chain aliphatic diol with a carbon atom number of 6 to 10 as a glycol component and 100 to 20 mol% of a glycol component represented by the following general formula (1). Required. Examples of long-chain aliphatic glycols having 6 to 10 carbon atoms include hexanediol, heptanedione, octanediol, nonanediol, and dodecanediol, and those represented by the general formula (I)
The glycol components represented by are neopentyl glycol, 2,2'-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2'-di- Examples include n-butyl-1,3-propanediol. If the content of the long-chain aliphatic glycol having 6 to 10 carbon atoms exceeds 80 mol % in the polyester resin of the present invention, the hardness of the alkali-resistant cured coating film will decrease and the object of the present invention will not be achieved.

The polyester resin of the present invention consists essentially of dicarboxylic acid and glycol, but by using a small amount of trifunctional or higher functional polycarboxylic acid or/and polyol,
Furthermore, alkali resistance and moisture resistance can be improved. Examples of trifunctional or higher-functional polycarboxylic acids that can be used for this purpose include aromatic polycarboxylic acids such as trimellitic acid and pyromellitic acid, and aliphatic carboxylic acids such as butanetetracarboxylic acid. Examples of the above polyols include aliphatic polyols such as glycerin, trimethylolpropane, and pentaerythritol, in an amount of 10 mol% or less, preferably 1 mol% to
It can be used in a range of 5 mol%.

The polyester resin of the present invention has a reduced viscosity of 0.3 to 0.
7. The number average molecular weight is preferably 5.000 to 25.000.

Examples of the alkyl etherified formaldehyde resin used in the present invention include formaldehyde or paraformaldehyde that has been alkyl etherified with an alcohol having 1 to 4 carbon atoms such as methanol, ethanol, n-propatol, 1so-propatol, and n-butanol. and urea, N, N'-ethylene urea, dicyandiamide, aminotriazine, etc., specifically methoxylated methylol urea, methoxylated methylol-N, N'-ethylene urea, methoxylated methylol dicyandiamide, Examples include methoxylated methylol melamine, methoxylated methylol benzoguanamine, butoxylated methylol melamine, butoxylated methylol benzoguanamine.

In the coating resin composition of the present invention, the ratio of the polyester resin to the alkyl etherified formaldehyde resin is 95%.
-60:5-40 (weight ratio) is preferable. If the proportion of the polyester resin exceeds 95% by weight, the desired alkali resistance and hardness will be insufficient, which is undesirable. Moreover, if it is less than 60% by weight, processability will be poor, which is not preferable. In the coating resin composition of the present invention, as a curing catalyst 1)-
) Luenesulfonic acid, phosphoric acid monoalkyl ester, p
- Amine salts of toluenesulfonic acid may be added. The amount of catalyst used is 0 for the formaldehyde resin.
~5% by weight.

Further, the resin composition for paint of the present invention is used in a form dissolved in an organic solvent. As an organic solvent, e.g. evaluene, xylene, Tsurpetz-100, Tsurpetz 1150, ethyl acetate, butyl acetate, methyl cellosolve, butyl cellosolve, methyl cellosolve acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, ethylene glycol acetate, etc. It is selected appropriately considering the evaporation rate.

The paint resin composition of the present invention may contain extender pigments such as titanium oxide, talc, barium sulfate, etc., known colorants, surface smoothing agents, antifoaming agents, thixotropic agents, etc., depending on the purpose and use. In addition, other synthetic resins such as epoxy resins and vinyl chloride resins can also be blended within a range that does not impair the purpose of the present invention.

The coating resin composition of the present invention is produced by a known dispersion and cross-mixing method using a roll kneader, a medium disperser, and the like. The coating composition of the present invention can be applied by conventional methods such as roll coater, curtain coater, and spray coating, and the drying and baking temperature can be selected as appropriate, but it is usually applied at 150 to 270°C for 10 seconds to 20 seconds.
It's a minute.

(Examples) Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

In the examples, the term "part" simply indicates part by weight, and the term "%" indicates weight %. Each measurement item was measured according to the following method.

(1) Reduced viscosity 77 sp/c (d(!/g
) Dissolve 0.1 g of polyester in 25 cc of phenol/tetrachloroethane (volume ratio 6/4) mixed solvent,
Measured at °C.

■ Flexibility (workability) 3T is a test in which a painted steel plate is bent 180° and cracks that occur at the bend are determined. No cracks occur when three sheets of the same thickness are sandwiched and bent at the bend. Show that.

■Pencil hardness test Cut the tip of lead''* (JIS standard E rhombus pencil) at a right angle,
Draw on the painted surface at a 45° inclination and display at the softest hardness that will not cause damage.

(4) Moisture-resistant coated plates were provided with base grains specified in JIS G 3312 8.6, and 50 copies were left in air at 2°C and a humidity of 98% or higher for 240 hours, and then a peeling test was performed using cellophane tape.

(2) Alkali resistance It was immersed in a 5% NaOH aqueous solution at room temperature for 24 hours, and abnormalities in appearance were determined.

Production Example 1 916 parts of inphthalic acid, 355 parts of orthophthalic acid, 15.4 parts of trimellitic anhydride, 6 parts of neopentyl glycol
66 parts of hexanediol, 1133 parts of hexanediol, and 0.82 parts of tetrabutyl titanate were charged into a reaction vessel.
The humidity was raised to 0°C over 4 hours to carry out an esterification reaction.

Next, the pressure was reduced to 1m+sHg over 30 minutes, and further 0.1
The polycondensation reaction was carried out at 250 to 270° C. for 1 hour under a reduced pressure of 0.3 mm·g. The obtained resin (A) had a reduced viscosity of 0.
It was 37. In the same manner, various polyesters (
B) to (H) were synthesized. The results are shown in Table 1.

Examples and Comparative Examples 100 parts of each of the polyester resins (A) to (D) were mixed with a cyclohexanone/Tsurupez '150 mixed solvent (weight ratio: 50
150) was dissolved in 100 parts, and the nonvolatile content was adjusted to 50%.

200 parts of the above polyester resin solution, methyl etherified methylolmelamine (trade name: Sumimaru M-408.
Nonvolatile content 80%, manufactured by Sumitomo Chemical Co., Ltd.) 31.3 parts, titanium oxide (trade name: CR-930 manufactured by Ishihara Sangyo ■) 100 parts
part, p-) 0.25 part of luenesulfonic acid, surface smoothing agent (
0.5 part of Polyflow (trade name: Polyflow-S1 manufactured by Kyoeisha Yushi ■) was blended and shaken and kneaded for 6 hours using a bead disperser to prepare resin compositions 0) to aV) for coatings of the present invention, respectively.

Coating compositions M were obtained in exactly the same manner using polyester resins (E) to (H). The obtained coating composition was applied to a galvanized iron plate (JISG3302) with a thickness of 0.3 fins.
It was coated using a bar coater and baked at 230°C for 60 seconds. The coating thickness was about 20-. The coating performance of the obtained coated board is shown in Table 2.

It can be seen that the coating composition for coated steel sheets of the present invention has extremely excellent alkali resistance compared to the case where conventional high molecular weight polyester is used.

(Effects of the present invention) The resin composition for coating of the present invention includes an aromatic dicarboxylic acid as a polyester resin noccarboxylic acid component, a long-chain aliphatic diol having 6 to 10 carbon atoms as a glycol component, and a long-chain aliphatic diol represented by the general formula (I) above. Because it uses a glycol component, it has excellent processability and moisture resistance, and in particular, it has significantly better acid resistance than when conventional high molecular weight polyester resins are used.

It is of great industrial significance that the coating resin composition of the present invention has achieved high processability, moisture resistance, and alkali resistance. The resin composition for paint of the present invention takes advantage of the advantages described in L, and can be widely used as a top coat for painted steel plates, especially for home appliances such as washing machines and dishwashers, which require alkali resistance and moisture resistance. Of course, it can also be used as a paint for metals, plastics, and paper.

Claims (1)

[Claims] 100 mol% aromatic dicarboxylic acid and 6 to 10 carbon atoms
0 to 80 mol% of a long-chain aliphatic diol and 100 to 20 mol% of a glycol component represented by the following general formula (I)
1. A resin composition for paint, characterized in that an alkyl etherified formaldehyde resin is blended into a polyester resin consisting of the following. ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(I) [In the formula, R_1 and R_2 are each an alkyl group having 1 to 4 carbon atoms. ]