JP2000129207A - Resin composition for coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin compsn. for coating cans, excellent in adherence to a metal, acid resistance, bending workability, and suitable for a hair dyeing chemical and a chlorine detergent. SOLUTION: This resin compsn. for coating comprises, as indispensable components, (A) a polyester resin having an imide bond in the molecular chain (polyester imide resin) wherein the content of the imide acid in the whole acidic components in the polyester resin is in the range of 10-60 wt.% and the equivalent ratio of the whole alcohols/whole acids is in the range of 1.2-2.5, and (B) a block isocyanate wherein the NCO content lies in the range of 1-30 wt.% in the block isocyanate, and is prepd. by blending 10-60 pts.wt. of the block isocyanate (B) with 100 pts.wt. of the polyester resin (A).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a polyesterimide resin as an active ingredient, and is particularly suitable for metal cans for hair dyeing agents and chlorine detergents which require acid resistance among paints for inner surfaces of cans. The present invention relates to a coating resin composition which is to be painted and has excellent acid resistance, adhesion and workability.

[0002]

2. Description of the Related Art Conventionally, polyvinyl chloride resin or epoxyphenol resin is often used for paint for the inner surface of a can. However, polyvinyl chloride resin has poor adhesion to metal as a can material. Since it is sufficient, it is necessary to coat the surface treated with an epoxy resin or the like, and there is a disadvantage that the painting process becomes complicated.

[0003] Further, as the tendency to mousse the contents of cans has become stronger, the demand for metal cans has also increased for containers containing highly acidic contents such as hair dyes and chlorine-based detergents. ing. In the field where such acid resistance is required, an epoxyphenol-based resin, a polyamideimide resin, or a polyester-based resin has been studied. However, epoxyphenol-based resins and polyamide-imide resins have the drawback that peeling or cracking of the coating film occurs during bending such as necking, and polyamide-imide resins are also expensive.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and is not only excellent in adhesion to metal and acid resistance, but also excellent in bending workability, and particularly excellent in acid resistance. It is an object of the present invention to provide a coating resin composition suitable for fields such as hair dyeing agents and chlorine-based detergents which are required to have good properties.

[0005]

Means for Solving the Problems As a result of diligent research aimed at achieving the above object, the present inventor has found that the above object can be achieved by using a resin composition described later, and has completed the present invention. It was done.

That is, the present invention relates to (A) a polyester resin having an imide bond in a molecular chain, wherein the polyester resin has an imide acid content relative to all acid components.
Those having an equivalent ratio of total alcohol / total acid in the range of 1.2 to 2.5, and (B) a blocked isocyanate whose NCO content is lower than that of the blocked isocyanate. An essential component is 1 to 30% by weight, and the blocked isocyanate (B) is blended in an amount of 10 to 60 parts by weight with respect to 100 parts by weight of the polyester resin (A). It is a resin composition for coatings characterized by becoming.

Hereinafter, the present invention will be described in detail.

The polyester resin (A) having an imide bond in the molecular chain used in the present invention can be obtained by using, for example, an imide acid represented by the following general formula.

[0009]

Embedded image (Where R represents a divalent organic group) The imidic acid of the general formula 1 can be obtained, for example, by reacting 2 mol of trimellitic anhydride with 1 mol of diamine or diisocyanate. Examples of the diamine used in this case include aromatic diamines such as 4,4'-diaminodiphenylmethane, p-phenylenediamine and m-phenylenediamine, and aliphatic diamines such as hexamethylenediamine. From the viewpoint, an aromatic diamine is preferred. There is no particular limitation on the diisocyanate, and aromatic diisocyanates such as 4,4 '
-Diphenylmethane diisocyanate, toluylene diisocyanate and the like are preferred. Although there is no particular limitation on the method for producing the imidic acid, for example, the reaction between the diamine and trimellitic anhydride is performed at a temperature of 120 to 250 ° C. in the presence of a polar solvent such as cresol, phenol, N-methylpyrrolidone and the like.
The generation of imidic acid can be confirmed by the outflow of water generated at the time of imidic acid generation.

The use rate of imidic acid in the polyester resin is limited to 10 to 60% by weight based on the total acid component of the polyester resin from the viewpoint of acid resistance and processability. If the amount used is less than 10% by weight, heat resistance and acid resistance are inferior. If it exceeds 60% by weight, imidic acid generated at the time of synthesis is insoluble in organic solvents, making production difficult and reducing the amount of imidic acid. Increasing the amount will be expensive.

As the acid component of the polyester resin having an imide bond in the molecular chain, terephthalic acid, isophthalic acid or derivatives thereof such as dimethyl terephthalic acid and dimethyl isophthalic acid can be mentioned in addition to the above-mentioned imidic acid. As the alcohol component, dihydric or higher alcohols,
For example, ethylene glycol, propylene glycol,
Neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 1,6-cyclohexanedimethanol and the like can be mentioned. Examples of the trihydric alcohol include glycerin, trimethylolpropane, pentaerythritol, tris-2-hydroxyethyl isocyanurate and the like.

For the production of a polyester resin having an imide bond in the molecular chain, the acid component and the alcohol component are restricted to the range of 1.2 to 2.5 as the equivalent ratio of total alcohol to total acid. If the corresponding amount ratio is less than 1.2, the function of the produced resin is reduced because the alcohol component is insufficient and a uniform reaction is not performed. If the corresponding ratio exceeds 2.5, the alcohol component becomes excessive, and the function of the formed resin, for example, heat resistance and acid resistance deteriorate. The heat reaction between the acid component and the alcohol component is not particularly limited as long as the reaction substantially causes an ester reaction or a transesterification reaction. For example, the reaction is carried out at a temperature of from 120 to 250 ° C. in the presence of a trace amount of an esterification catalyst such as tetraalkyl titanate, lead acetate, dibutyltin dilaurate and the like. Further, the synthesis may be carried out in the presence of a solvent such as cresol, phenol, N-methylpyrrolidone or the like according to the viscosity.

The (B) blocked isocyanates used in the present invention include aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate and toluylene diisocyanate, aliphatic diisocyanates such as hexamethylene diisocyanate, and alicyclic isocyanates such as isophorone diisocyanate. Alternatively, each isocyanurate type is used. Among them, aromatic diisocyanates are preferred in terms of heat resistance and acid resistance. The blocking agent is not particularly limited, and examples thereof include oximes such as methyl ethyl ketoxime, active methylene, and phenols. This blocked isocyanate can be used as a cross-linking agent between the remaining hydroxyl groups to the (A) polyester resin having an imide bond in the molecular chain.

The mixing ratio of the (A) polyester resin having an imide bond in the molecular chain and the (B) blocked isocyanate used in the coating resin composition of the present invention is as follows:
(A) / (B) = 100 / 10-60 (weight ratio) is preferred. (B) for the polyester resin of (A)
When the ratio of the blocked isocyanate is less than 10% by weight, the curing becomes sweet and the heat resistance and the acid resistance deteriorate. On the other hand, when the ratio of the blocked isocyanate of (B) to the polyester resin of (A) exceeds 60% by weight, the degree of crosslinking is too high, and the flexibility is poor.

Since the NCO content of the blocked isocyanate differs depending on the type of the blocking agent and the isocyanate, the mixing ratio is determined by the NCO content of the blocked isocyanate.
It is assumed that the CO content is in the range of 1 to 30% by weight.

The solvent used in the resin composition for coatings of the present invention comprises the component (A) plus the component (B) in an amount of 5 to 60% by weight of the entire resin composition. % Is desirable.

As the solvent, polar solvents such as N-methylpyrrolidone, dimethylformamide and cyclohexanone, ketone solvents such as xylene, naphtha solvents and methyl ethyl ketone, and alcohols such as isobutanol and n-isobutanol are used.

The resin composition for coatings of the present invention comprises, as essential components, a polyester resin (A) having an imide bond in the molecular chain and a blocked isocyanate (B). To the extent not necessary, and if necessary, titanium compounds, organic acid metal salts, alkoxy-modified amino resins, polyamide resins, polyimide resins, polyhydantoin resins, polysulfone resins, phenol resins, phenoxy resins, amino resins, formal resins, butyral Resins and the like can be contained at a ratio of 0.1 to 25% by weight based on the resin content. Additives such as inorganic pigments such as titanium oxide and silica, curing catalysts such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, phosphoric acid and its esterified products, surface smoothing agents, defoaming agents, dispersing agents, etc. Can be manufactured.

[0019]

The coating resin composition of the present invention is characterized in that a specific mixing ratio of blocked isocyanates to a specific polyesterimide resin having an imide bond in the molecular chain is added to the blocked isocyanate with respect to the polyesterimide resin. However, a resin composition which acts as a cross-linking agent between residual hydroxyl groups, is excellent in adhesion and acid resistance, and is excellent in bending workability is obtained.

[0020]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, “parts” means “parts by weight”.

Example 1 A stirrer, a thermometer and a Liebig condenser were attached.
In a 2 l four-necked flask, add ethylene glycol
51.3 parts of tris-2-hydroxyethyl isocyanurate (hereinafter referred to as "THEIC") 193.
0 parts, terephthalic acid (hereinafter referred to as “TPA”) 120.9
Parts, tetrabutyl titanate (hereinafter referred to as “TB
T) and 0.76 parts of xylene as a reflux solvent.
8 parts were compounded simultaneously. When the temperature is gradually increased with stirring, water from transesterification starts to be distilled out at about 190 ° C. Thereafter, the temperature was gradually raised to 230 ° C. over 5 hours. When the temperature reached 230 ° C., the mixture was diluted with 137.1 parts of N-methylpyrrolidone (hereinafter, referred to as “NMP”).

Next, diaminodiphenylmethane (hereinafter referred to as "diaminodiphenylmethane")
95.5 parts of "DAM") and 185.0 parts of trimellitic anhydride (hereinafter referred to as "TMA") were added, and the temperature was gradually raised from 120 ° C, and the reaction was allowed to proceed from 180 ° C to 210 ° C for 4 hours. When the temperature reached 210 ° C, the pressure was reduced to 300 mmHg to remove water and unreacted substances. The reaction is performed at 280 ° C by hot plate method.
The gelation was terminated when the gelation time reached 20 seconds.

Next, the above reaction solution was diluted with 173.6 parts of NMP, and at 100 ° C. or lower, 29.3 parts of blocked isocyanate A (obtained by blocking the isocyanurate type of tolylene diisocyanate with phenol), and 468.0 parts of a cresol-blocked diisocyanate diluted with NMP (40%). After dissolving for 1 hour, the mixture was diluted with 369.0 parts of methyl ethyl ketone (hereinafter referred to as “MEK”) at 80 ° C. or lower. Then, 12.9 parts of TBT, 10.0 parts of alkyl titanate, and 4.0 parts of a fluorine-based surface smoothing agent were added dropwise after dilution with 80.4 parts of NMP, 55.6 parts of cyclohexanone, and 100.0 parts of MEK. 30
After stirring for minutes, the mixture was filtered to obtain a polyesterimide resin.

Example 2 Using the same apparatus as in Example 1, 49.6 parts of EG, THEI
C186.5 parts, TPA116.9 parts, TBT0.73 as catalyst
And 3.7 parts of xylene as a reflux solvent. 190 ℃ when the temperature is gradually increased with stirring
Water from the transesterification starts to distill about. Thereafter, the temperature was gradually raised to 230 ° C. over 5 hours. 230 ° C
When reached, the mixture was diluted with 132.6 parts of NMP.

Next, 92.3 parts of DAM and 178.9 parts of TMA
The temperature was gradually raised from 0 ° C., and the reaction was carried out from 180 ° C. to 210 ° C. for 4 hours. When the temperature reached 210 ° C, the pressure was reduced to 300 mmHg to remove water and unreacted substances. The reaction was terminated when the gel time at 280 ° C. by the hot plate method reached 20 seconds.

Next, the above reaction mixture was diluted with 496.4 parts of NMP, and the block isocyanate C (4,4 '
Phenol-blocked diaminodiphenylmethane) 282.8 parts and 405.8 parts of MEK
Dissolved for hours. Thereafter, 12.4 parts of TBT, 10.0 parts of alkyl titanate, and 4.0 parts of a fluorine-based surface smoothing agent were added to NMP.
After dilution with 100.0 parts and 100.0 parts of MEK, the mixture was added dropwise. After stirring for 30 minutes, the mixture was filtered to obtain a polyesterimide resin.

Comparative Example 1 A commercially available polyamideimide resin was obtained and used as a comparative example.

With respect to the coating resin compositions of Examples 1 and 2 and Comparative Example, the results of bending workability, wet heat resistance test, and acid resistance test are shown in Table 1. In each case, the present invention was excellent, and the effects of the present invention could be confirmed. Preparation of a test piece and a test method were performed as follows.

Preparation of Test Specimens The coating resin composition was coated on an aluminum plate with a bar coater # 38.
And heat-cured at 260 ° C for 5 minutes.
A test piece having a thickness of about 10 to 15 μm was used. Bendability After the test piece was bent at 180 degrees, it was treated in boiling water for 90 minutes, and the bent portion was observed with a loupe to evaluate the presence or absence of cracks in the coating film. ○: good without cracks, x: cracks. Moisture / heat resistance PCT (pressure cooker test) 120 ° C x 2 at
After 24 hours at 100% humidity and 100% humidity, the appearance was observed. ○: good, x: marked whitening or blistering. Acid resistance Acid resistance spot test Acetic acid was dropped on the test piece, left at room temperature for 90 minutes, and the appearance was observed. ○: good, x: marked whitening or blistering. Acid resistance Acid resistance solution test The test piece was immersed in a 10% acetic acid solution, boiled for 60 minutes, and the appearance was observed. ○: good, x: marked whitening or blistering.

[0030]

[Table 1]

[0031]

As apparent from the above description and Table 1, the coating resin composition of the present invention has good adhesion to metals and acid resistance, and further has good bending life. It is suitable as a paint in a field requiring acid resistance and the like.

Claims (1)

[Claims] 1. A polyester resin having an imide bond in its molecular chain, wherein the polyester resin has an imide acid content in the range of 10 to 60% by weight with respect to all acid components, / Equivalent ratio of all acids is 1.2 ~
2.5) and (B) a blocked isocyanate having an NCO content of 1 to 30% by weight based on the blocked isocyanate as an essential component. The block isocyanate of (B) is 10 to 60 parts by weight based on 100 parts by weight of the base resin.
A resin composition for coatings, which is blended in a ratio of parts by weight.