JP2000204318A - Coating resin composition for metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating resin composition for metals, good in adhesivity to the metals, having excellent flexural processability, and especially useful as a coating for the metals requiring corrosion resistance. SOLUTION: The coating resin composition for metals comprises (A) a polyesterimide resin and (B) an alkyl titanate compound. The polyesterimide resin is obtained by reacting an alcohol component with an acid component which consists mainly of a polyamic acid and a naphthalene skeleton dicarboxylic acid or its derivative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint for coating a metal surface with a polyesterimide resin as an active ingredient, and particularly to a metal can which is required to have acid resistance, such as a hair dye or a chlorine-based detergent. The present invention relates to a metal coating resin composition which is suitably applied and has excellent acid resistance, retort resistance, adhesion and workability.

[0002]

2. Description of the Related Art Polyvinyl chloride resins and epoxy phenol resins are often used for metal coating paints. It is necessary to treat the coating with an epoxy resin or the like in advance, and there is a drawback that the painting process becomes complicated.

[0003] Further, as the tendency of the contents of metal cans to become mousse becomes stronger, there is a demand for metal cans for containers containing highly acidic contents such as hair dyeing agents and chlorine-based detergents. Is getting higher. In the field where such acid resistance is required, the above-mentioned epoxyphenol-based resin is used, and a polyamideimide resin or a polyester-based resin is being studied. However, epoxyphenol-based resins and polyamide-imide resins have the drawback that peeling and coating cracking occur during bending such as necking, and polyamide-imide resins are also expensive. Also,
There is a disadvantage that the acid resistance of a general polyester resin is not sufficient.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and has excellent adhesion to metals, acid resistance and bending workability, and is useful for hair dyeing agents and chlorine-based detergents. An object of the present invention is to provide a coating resin composition for a metal suitable for a metal can.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have found that the above object can be achieved by using a resin composition having the composition described below. Is completed.

That is, the present invention relates to (A) a polyesterimide resin obtained by reacting an acid component containing a polyamic acid (polyimide precursor) and a naphthalene skeleton dicarboxylic acid or a derivative thereof with an alcohol component, and (B) an alkyl titanate. A metal coating resin composition characterized by being applied to the formation of a coating film on a metal surface. Further, the polyamic acid is contained in a proportion of 5 to 60% by weight based on the polyesterimide resin as a resin component, and the equivalent ratio of total alcohol component / total acid component in the polyesterimide resin reaction is 1.2 to 2%. 0.5, which is a coating resin composition for metals containing the above alkyl titanates in a ratio of 0.5 to 5 parts by weight based on 100 parts by weight of the polyesterimide resin.

Hereinafter, the present invention will be described in detail.

The polyamic acid in the molecular chain used in the present invention 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, for example, 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. The diisocyanate is not particularly limited, and is preferably an aromatic diisocyanate, for example, 4,4'-diphenylmethane diisocyanate, toluylene diisocyanate and the like.

The method for producing the polyamic acid is not particularly limited. For example, the reaction between diamine and trimellitic anhydride is carried out at a temperature of 120 ° C. to 250 ° C. in the presence of a polar solvent such as cresol, phenol, N-methylpyrrolidone. Done.
The generation of the polyamic acid can be confirmed by distilling off water generated during the generation of the polyamic acid. The amount of the polyamic acid used is desirably limited to the range of 5 to 60% by weight in the resin from the viewpoint of acid resistance and processability. If it is less than 5% by weight, the acid resistance is poor, and if it exceeds 60% by weight, the production becomes difficult because the polyamic acid produced during the synthesis is insoluble in the organic solvent.

The acid component of the polyester imide resin (A) used in the present invention includes, in addition to the above-mentioned polyamic acid, naphthalene skeletons such as 2,6-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid dimethyl ester. A dicarboxylic acid component is used. Terephthalic acid, isophthalic acid or a derivative thereof may be mixed in a small amount.
(A) As an alcohol component of the polyesterimide resin, for example, tris-2-hydroxyethyl isocyanurate is mainly used, and ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, Dihydric alcohols such as 1,6-cyclohexanedimethanol, for example,
A tri- or higher-valent alcohol such as glycerin or trimethylolpropane may be used in combination.

In producing the polyesterimide resin, the equivalent ratio of the acid component to the alcohol component is preferably such that the ratio of total alcohol / total acid is 1.2 to 2.5. If the equivalent 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. On the other hand, if the equivalent ratio exceeds 2.5, the alcohol component becomes excessive, and the function of the resulting resin, for example, the acid resistance, deteriorates.

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, in the presence of an esterification catalyst such as tetraalkyl titanate, lead acetate, dibutyltin dilaurate, etc.
It is performed at a temperature of 50 ° C. 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) alkyl titanates used in the present invention are used as a crosslinking agent between the remaining hydroxyl groups of the polyesterimide resin, and include, for example, tetrabutyl titanate, tetraisopropyl titanate, tetra (2-ethyl) octyl titanate. And the like.

The mixing ratio of the (A) polyesterimide resin and the (B) alkyl titanates used in the present invention is as follows:
It is preferable that (A) / (B) = 100 / 0.5 to 5 (weight ratio). The ratio of the alkyl titanates (B) to the polyesterimide resin (A) is 0.5% by weight.
If it is less than the above, the curing becomes sweet and the acid resistance becomes poor. If the ratio of the alkyl titanate (B) to the polyester imide resin (A) exceeds 5% by weight, the compatibility between the polyester imide resin and the alkyl titanate deteriorates, and the coating properties deteriorate, which is not preferable.

The metal coating resin composition of the present invention comprises (A)
The polyesterimide resin and the (B) alkyl titanates are essential components, but as far as the object of the present invention is not adversely affected, and if necessary, a titanium compound, a metal salt of an organic acid, an alkoxy-modified amino resin, a polyamide resin, A polyimide resin, a polyhydantoin resin, a polysulfone resin, a phenol resin, a phenoxy resin, an amino resin, a formal resin, a butyral resin, and the like can be contained at a ratio of 0.1 to 25% by weight based on the resin component.
In addition, inorganic pigments such as titanium oxide and silica, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, phosphoric acid and its esterification catalyst, surface smoothing agent, defoaming agent, dispersant and other additives are added and blended. can do.

[0016]

The resin composition for metal coating of the present invention comprises (A) a polyesterimide resin obtained by reacting an acid component having a naphthalene skeleton as a main component with an alcohol component, and (B) an alkyl titanate compound. By doing so, it was possible to obtain a metal coating resin composition having excellent adhesiveness and acid resistance and excellent bending workability.

[0017]

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 Ethylene glycol (hereinafter referred to as “ethylene glycol”) was placed in a 2 L four-necked flask equipped with a stirrer, a thermometer, and a Liebig condenser.
67.0 parts of tris-2-hydroxyethyl isocyanurate (hereinafter referred to as THEIC), 228.0 parts, 2,6-naphthalenedicarboxylic acid dimethyl ester (hereinafter referred to as NDCM) 22
1.4 parts, tetrabutyl titanate (hereinafter, referred to as a catalyst)
0.93 part of this was referred to as TBT) and 4.7 parts of Naphtha No. 2 as a reflux solvent were simultaneously added. When the temperature is gradually increased while stirring, methanol from the transesterification starts to be distilled out at about 160 ° C. Thereafter, the temperature was raised to 200 ° C. over 4 hours. When the temperature reached 200 ° C., the mixture was diluted with 169.3 parts of N-methylpyrrolidone (hereinafter referred to as NMP). Next, the temperature was lowered to 120 ° C. or lower, and 117.5 parts of diaminodiphenyl ether (hereinafter, referred to as DDE) and 225.4 parts of trimellitic anhydride (hereinafter, referred to as TMA) were added.
From 180 ° C to 210 ° C over 4 hours. When the temperature reaches 210 ° C, 300 mmH
g, to remove water, methanol and unreacted materials.
The reaction was terminated when the gelling time at 280 ° C. by the hot plate method became 20 seconds, then diluted with 234.2 parts of NMP, and 336.1 parts of methyl ethyl ketone (hereinafter referred to as MEK) at 80 ° C. or lower. Diluted. Next, T
16.7 parts of BT, 9.9 parts of alkyl titanate, and 3.98 parts of a fluorine-based surface smoothing agent were diluted with a mixed solvent of 266.1 parts of NMP and 200.0 parts of MEK, and then added dropwise to the flask. After stirring at 50 ° C. for 30 minutes, the mixture was filtered to obtain a polyesterimide resin.

Example 2 Using the same apparatus as in Example 1, the same reaction was carried out. The compounding ratio of Example 2 is as follows. EG67.0
Parts, THEIC 227.7 parts, NDCM 221.2 parts,
0.93 parts of TBT, 4.7 parts of Naphtha-2, NMP16
9.1 parts of diaminodiphenylmethane (hereinafter referred to as D
AM) (116.2 parts), TMA (225.16 parts), NMP (233.3 parts), MEK (337.0 parts), and then TBT (16.7 parts), alkyl titanate (9.9 parts), fluorine surface smoothing agent (3.98) Department, NMP26
A solution of 8.3 parts and 200.0 parts of MEK was added dropwise to obtain a polyesterimide resin.

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

Using the coating resin compositions of Examples 1 and 2 and Comparative Example 1, coating film tests shown in Table 1 were conducted. The test method is as follows.

A test piece was prepared by applying the coating resin composition once to an aluminum plate with a bar coater # 38,
Heat-cured at 0 ° C for 5 minutes, and the film thickness is 10m to 15m
Was about to be.

The bending workability was determined by bending the test piece at 180 degrees, treating the test piece in boiling water for 90 minutes, observing the bent work portion with a magnifying glass, and determining the presence or absence of cracks in the coating film.
○: good, x: cracks.

The moisture and heat resistance is as follows: PCT (pressure cooker test) 120 ° C. × 2 atm × humidity 100% × 2
After 4 hours, the appearance was observed. ○: good, x: marked whitening or blistering.

In the acetic acid spot test, acetic acid was dropped on a test piece, allowed to stand at room temperature for 90 minutes, and the appearance was observed.
○: good, x: marked whitening or blistering.

In the acetic acid dissolution test, the test piece was immersed in a 10% acetic acid solution, boiled for 120 minutes, and the appearance was observed. ○: good, x: marked whitening or blistering.

[0027]

[Table 1]

[0028]

As is apparent from the above description and Table 1, the metal coating resin composition of the present invention is excellent in metal adhesion, acid resistance, bending workability, and is required to have acid resistance. It is suitable as a metal coating in the field.

Claims (4)

[Claims] 1. A polyester imide resin obtained by reacting (A) an acid component containing a polyamic acid and a naphthalene skeleton dicarboxylic acid or a derivative thereof with an alcohol component, and (B) an alkyl titanate as essential components, A paint resin composition for metals, which is used for forming a coating film. 2. The metal coating resin composition according to claim 1, wherein the polyamic acid in the polyesterimide resin (A) is contained in a proportion of 5 to 60% by weight based on the polyesterimide resin (A). 3. The equivalent ratio of total alcohol component / total acid component in the polyesterimide resin reaction of (A) is 1.2.
The coating resin composition for a metal according to claim 1, wherein the composition is in the range of 2.5 to 2.5. 4. The method according to claim 1, wherein (B) the alkyl titanate is (A)
0.5 parts per 100 parts by weight of the polyesterimide resin
4. The coating resin composition for metal according to claim 1, which is blended in an amount of about 5 parts by weight.