JPH0331361A - Heat-resistant resin composition and metal plate coated with heat-resistant resin - Google Patents

Abstract

PURPOSE:To obtain a composition having excellent bending workability and processability, suitable for the protection coating of various metal plates and useful for precoat metal for automobile or domestic appliance by compounding a specific polyamide imide resin with a specific amount of a phenoxy resin. CONSTITUTION:The objective composition is produced by compounding (A) 100 pts.wt. of a polyamide imide resin produced by reacting (A1) an aromatic diisocyanate (e. g. 4,4'-diphenylmethane diisocyanate) with (A2) an aromatic tribasic acid anhydride (e. g. trimellitic anhydride) at a molar ratio (A1/A2) of 0.8-1.3 in the presence of a basic polar solvent with (B) 1-20 pts.wt. (preferably 5-10 pts. wt.) of a phenoxy resin having the structure of formula (n is integer) as a main component. The composition is applied to a metal plate (e. g. iron or aluminum plate) and baked.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heat-resistant resin composition and a heat-resistant resin-coated metal plate, and more specifically to a heat-resistant resin composition with excellent processability suitable for protective coating of various metal plates. This invention relates to a resin composition and a heat-resistant resin-coated metal plate using the same.

[Conventional technology]

Polyamide-imide resin has excellent heat resistance, chemical resistance, and solvent resistance, so it is widely used, especially in festivals for enameled wires, heat-resistant paints, and the like. However, since polyamide-imide resin has poor bendability compared to polyether sulfone, modified silicone resin, etc., there is a problem in that a metal plate obtained by coating and baking this resin has poor workability.

[Problem to be solved by the invention]

The object of the present invention is to solve the problems of the prior art and to provide a polyamide-imide resin composition that has excellent bendability and workability into metal plates obtained by coating and baking, and a heat-resistant resin-coated metal using the same. The purpose is to provide a board.

[Means to solve the problem]

The present invention relates to a polyamide-imide resin obtained by reacting an aromatic diisocyanate and an aromatic tribasic acid anhydride in the presence of a basic polar solvent, and a structure represented by the general formula I (where n is an integer). The present invention relates to a heat-resistant resin composition containing a phenoxy resin whose main component is a phenoxy resin, and a heat-resistant resin-coated metal plate obtained by coating and baking this heat-resistant resin composition on a metal plate.

As the aromatic diisocyanate used in the present invention,
4.4'-diphenylmethane diisocyanate, tolylene diisocyanate, 4.4' diphenyl ether diisocyanate, xylylene diisocyanate, 3,3'
-Diphenylmethane diisocyanate and the like. In addition to these aromatic diisocyanates, polyisocyanates such as tolylene diisocyanate and trimer of 4,4'-diphenylmethane diisocyanate, and non-aromatic diisocyanates such as hexamethylene diisocyanate can be partially used in combination. The amount used is preferably 30% by weight or less based on the aromatic diisocyanate.

The aromatic tribasic acid anhydride used in the present invention includes trimellitic anhydride. In addition to this aromatic tribasic acid anhydride, acid components include fatty acid tribasic acid anhydrides such as butanetricarboxylic anhydride, aromatic polycarboxylic acids such as terephthalic acid, isophthalic acid, and trimesic acid, adipic acid, and sebacic acid. Aliphatic polycarboxylic acids such as these can be used in combination. The amount used is preferably 50% by weight or less based on the aromatic tribasic acid anhydride.

The ratio of the aromatic diisocyanate and aromatic tribasic acid anhydride used is preferably such that the molar ratio of aromatic diisocyanate/aromatic tribasic acid anhydride is 0.8 to 1.3.

If the proportion used is outside this range, a high molecular weight polyamide-imide resin may not be obtained. If an isocyanate or acid other than aromatic diisocyanate and aromatic tribasic acid anhydride is used together, the amount used should be added to the amount used of aromatic diisocyanate or aromatic tribasic acid anhydride to ensure that it is within the above range. It is preferable to do so.

As a reaction solvent for the aromatic diisocyanate and aromatic tribasic acid anhydride, a basic polar solvent such as N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, etc. is used. If a phenolic solvent or the like is used instead of a basic polar solvent, film-forming properties will deteriorate. The amount of this solvent to be used is preferably in the range of 70 to 200 parts by weight based on 100 parts by weight of the total amount of aromatic diisocyanate and aromatic tribasic acid anhydride in terms of solution viscosity during reaction, economic efficiency, etc. . The synthesis temperature is not particularly limited, but is usually carried out in the range of 60 to 200°C, and the progress of the reaction can be confirmed by the generation of carbon dioxide gas. Optionally, basic catalysts such as triethylamine, N-methyl-morpholine, 1,8-diazabicyclo(5,4°0) undecene-7 salt may be used.

The polyamideimide resin obtained by the above method is treated with N-methyl-2-pyrrolidone,
It can also be diluted by adding basic polar solvents such as dimethylacetamide and dimethylformamide, aromatic hydrocarbons such as xylene, and ketones such as methyl ethyl ketone and methyl isobutyl ketone.

The phenoxy resin used in the present invention has the structure represented by -General I as a main component. There is no particular restriction on the molecular weight of the phenoxy resin, but usually the number average molecular weight is 20,
000 or more are used, for example, commercially available U
PKHH manufactured by CC.

Examples include YP-50 manufactured by Tobu Kasei Co., Ltd.

The amount of phenoxy resin used is 10% of polyamideimide resin.
It is preferably 1 to 20 parts by weight, especially 5 to 0 parts by weight.
10 parts by weight are preferred. If the amount used is too small, bendability may not be sufficient, whereas if the amount is too large, heat resistance, chemical resistance, and solvent resistance may deteriorate.

The heat-resistant resin composition of the present invention may contain, in addition to the polyamideimide resin and phenoxy resin, various curing agents, catalysts, and appearance modifiers depending on the application.

By coating and baking the heat-resistant resin composition of the present invention on a metal plate, a heat-resistant resin-coated metal plate with excellent bendability and workability can be obtained. There are no particular restrictions on the coating method, and spray coating, brush coating, roller coating, etc. are performed depending on the shape of the object to be coated. The baking temperature is preferably in the range of 150 to 450°C, and heating is performed for a long time if the temperature is low, and for a short time if the temperature is high. There is no particular limit to the coating thickness, but it is usually 3.
~30μm coated. Further, there is no particular restriction on the metal plate of the base material, and aluminum, iron, stainless steel, copper, etc. are used, and iron and aluminum are particularly preferred. To improve the level of adhesion, it can be blasted, chemically surface treated, or primed with various primers.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

Note that "inverted part" refers to parts by weight.

Example 1 250 g of 4.4′-diphenylmethane diisocyanate
, 192 g of l-limellitic anhydride and N-methyl-
663 g of 2-pyrrolidone was charged into a No. 22 flask, and the temperature was raised to 130'C over about 4 hours while stirring, and then kept at 130'C for 3 hours to obtain a polyamideimide resin. Then, 200 g of xylene was added to obtain a polyamideimide resin solution. The non-volatile content of this solution (200
'c-2h) is 35% by weight, and the viscosity is 51 poise (
30"C).

To 300 g of this polyamide-imide resin solution, 5.25 g (5 parts per 100 parts of polyamide-imide resin) of phenoxy resin PKHH (manufactured by UCC) was added, and the heat-resistant resin composition was heated and stirred until uniform. Obtained.

Example 2 To 300 g of the polyamideimide resin solution obtained in Example 1,
Phenoxy resin YP-50 (manufactured by Tobu Kasei Co., Ltd.) 10.5g
(10 parts to 100 parts of polyamide-imide resin) was added, and the mixture was heated and stirred until uniform, to obtain a heat-resistant resin composition.

Example 3 4.41-diphenylmethane diisocyanate 262.
5g, trimellitic anhydride 172.8g.

17.4 g of Sebacin M and 679 g of N-methyl-2-pyrrolidone were charged into 21 flasks, the temperature was raised to 125° C. over about 4 hours with stirring, and then 125 g of N-methyl-2-pyrrolidone was charged.
The mixture was kept warm at 5'C for 2 hours to obtain a polyamideimide resin. Then, 212 g of xylene was added to obtain a polyamideimide resin solution. Non-volatile content of this solution (200°C-2
h) was 35% by weight.

To 300 g of this polyamide-imide resin solution, add 7.88 g of phenoxy resin PKHH (polyamide-imide resin 1
00 parts) was added thereto, and the mixture was heated and stirred until uniform, to obtain a heat-resistant resin composition.

Comparative Example 1 The polyamide-imide resin solution obtained in Example 1 was used as a heat-resistant resin composition.

<Test Example> Using the heat-resistant resin compositions obtained in Examples 1 to 3 and Comparative Example 1, a heat-resistant resin-coated metal plate was produced under the trial production conditions shown in Table 1, and its characteristics were measured.

The results are shown in Table 2.

Table 1 Table 2 *1: Conducted according to JIS BO202.

*2: Bending test A painted metal plate is bent with the painted side facing outward. Then,
Sandwich the same metal plate used for painting inside and
Crush for 5 seconds at 0 kg/cd and observe with a 10x magnifying glass to see if any cracks occur in the coating. The test was conducted by increasing the number of metal plates sandwiched together until no cracks occurred, and the number of metal plates at the time no cracks occurred was expressed. (For example, if a crack occurs in one sheet, write it as 1T. If a crack occurs in 13 sheets, write it as 3T.) *3: Adhesion after heating and deteriorating at 200°C for 50 hours (crosscut residual rate, %) * 4: Rub the paint film surface with gauze impregnated with methyl ethyl ketone and observe changes in the appearance of the paint film (100 times of rubbing)
.

From Table 2, the resin coated plates obtained in Examples 1 to 3 are as follows:
It is shown that the bendability is significantly improved compared to the coated plate obtained in Comparative Example 1.

〔Effect of the invention〕

According to the heat-resistant resin composition of the present invention, a heat-resistant resin-coated metal plate with excellent bendability and workability can be obtained.

Moreover, this metal plate has excellent heat resistance, solvent resistance, and chemical resistance, so it can be used in fields where harsh processing is required.
For example, it is particularly useful for pre-coated metals for automobiles, home appliances, etc., materials for cans, etc.

Claims (1)

[Claims] 1. A polyamide-imide resin obtained by reacting an aromatic diisocyanate and an aromatic tribasic acid anhydride in the presence of a basic polar solvent, and the general formula I ▲There are mathematical formulas, chemical formulas, tables, etc. ▼ A heat-resistant resin composition containing a phenoxy resin whose main component is a structure represented by (where n is an integer). 2. The heat-resistant resin composition according to claim 1, wherein the phenoxy resin is contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of the polyamide-imide resin. 3. The heat-resistant resin composition according to claim 1 or 2, wherein the aromatic tribasic acid anhydride is trimellitic anhydride. 4. The heat-resistant resin composition according to claim 1, wherein the ratio of aromatic diisocyanate/aromatic tribasic acid anhydride is 0.8 to 1.3. 5. A heat-resistant resin-coated metal plate obtained by coating and baking the heat-resistant resin composition according to claims 1 to 4 on a metal plate. 6. The heat-resistant resin-coated metal plate according to claim 5, wherein the metal plate is made of iron or aluminum.