POLYAMIDEIMIDE RESIN COMPOSITION AND METHOD FOR PRODUCING POLYAMIDEIMIDE RESIN

Abstract

A polyamideimide resin composition comprises a polyamideimide resin and a solvent containing a compound represented by formula (1). In the formula, R.sup.1 represents an alkyl group of 1 to 8 carbon atoms, R.sup.2 and R.sup.3 each independently represent a hydrogen atom or an alkyl group of 1 to 8 carbon atoms, and X represents an alkylene group of 1 to 8 carbon atoms.

##STR00001##

Claims

1. A polyamideimide resin composition comprising a polyamideimide resin and a solvent containing a compound represented by formula (1). ##STR00008## [In the formula, R.sup.1 represents an alkyl group of 1 to 8 carbon atoms, R.sup.2 and R.sup.3 each independently represent a hydrogen atom or an alkyl group of 1 to 8 carbon atoms, and X represents an alkylene group of 1 to 8 carbon atoms.]

2. The polyamideimide resin composition according to claim 1, wherein the polyamideimide resin has a number average molecular weight of 10,000 to 24,000 and has a degree of dispersion of 2.0 to 2.8.

3. The polyamideimide resin composition according to claim 1, wherein the polyamideimide resin has a terminal group blocked with a blocking agent containing at least one selected from the group consisting of an oxime compound, an alcohol, and a vinyl ether compound.

4. The polyamideimide resin composition according to claim 1, wherein the compound represented by formula (1) comprises at least one selected from the group consisting of 3-methoxy-N,N-dimethylpropionamide and 3-butoxy-N,N-dimethylpropionamide.

5. The polyamideimide resin composition according to claim 1, further comprising an epoxy resin.

6. The polyamideimide resin composition according to claim 1, wherein the composition is used as a coating agent for coating a surface of a metal substrate.

7. A method for producing a polyamideimide resin, comprising reacting a monomer mixture containing a diisocyanate compound and a tribasic acid anhydride or a tribasic acid halide, in a solvent containing a compound represented by formula (1). ##STR00009## [In the formula, R.sup.1 represents an alkyl group of 1 to 8 carbon atoms, R.sup.2 and R.sup.3 each independently represent a hydrogen atom or an alkyl group of 1 to 8 carbon atoms, and X represents an alkylene group of 1 to 8 carbon atoms.]

8. The method for producing a polyamideimide resin according to claim 7, wherein the reacting is performed at a temperature of 60 to 140° C.

9. The method for producing a polyamideimide resin according to claim 7, further comprising: adding a blocking agent to a reaction solution containing a polyamideimide resin obtained by reacting the monomer mixture in the solvent, to block a terminal group of the polyamideimide resin, wherein the blocking agent contains at least one selected from the group consisting of an oxime compound, an alcohol, and a vinyl ether compound.

Description

EXAMPLES

[0091] Embodiments of the present invention are described in more detail below. The present invention is not limited to the following embodiments.

1. Production of Polyamideimide Resin

[0092] The number-average molecular weight (Mn) of the polyamideimide resin manufactured in the examples and comparative examples to be described later is a value obtained by measuring under the following conditions. The degree of dispersion is calculated as a ratio (Mw/Mn) to a weight-average molecular weight (Mw) measured in the same manner as the above-mentioned number-average molecular weight (Mn).

<Measurement Conditions for Number Average Molecular Weight>

[0093] GPC apparatus: Hitachi L6000

[0094] Detector: Hitachi L 4000 Type UV

[0095] Wavelength: 270 nm

[0096] Data processing unit: ATT 8

[0097] Columns: Gelpack GL-S300MDT-5×2

[0098] Column size: 8 mmo×300 mm

[0099] Solvent: DMF/THF=1/1 (liter)+0.06 M phosphoric acid+0.06 M lithium bromide

[0100] Sample concentration: 5 mg/mL

[0101] Injection volume: 5 μL

[0102] Pressure: 49 kgf/cm.sup.2 (4.8×10.sup.6 Pa)

[0103] Flow rate: 1.0 mL/min

[0104] Column temperature: 40° C.

Example 1

[0105] 250.3 g (1.00 mole) of 4,4′-diphenylmethane diisocyanate, 192.1 g (1.00 mole) of trimellitic anhydride, and 660 g of 3-methoxy-N, N-dimethylpropionamide (DMPA) were charged into a 2-liter flask. While stirring the charged raw material, the temperature was raised to 100° C. and the temperature was maintained for 7 hours to obtain a solution containing a polyamideimide resin. The polyamideimide resin had a number average molecular weight of 18,900 and had a degree of dispersion of 2.3. To this solution, 8.7 g of methylethylketone oxime was added and reacted at 90° C. for 2 hours to obtain a solution A of a terminally blocked polyamideimide resin.

Example 2

[0106] 250.3 g (1.00 mole) of 4,4′-diphenylmethane diisocyanate, 192.1 g (1.00 mole) of trimellitic anhydride, and 660 g of 3-methoxy-N,N-dimethylpropionamide (DMPA) were charged into a 2-liter flask. While stirring the charged raw material, the temperature was raised to 100° C. and the temperature was maintained for 7.5 hours to obtain a solution containing a polyamideimide resin. The polyamideimide resin had a number average molecular weight of 19,700 and had a degree of dispersion of 2.4. To this solution, 6.1 g of ethanol and 4.3 g of butyl vinyl ether were added and reacted at 80° C. for 2 hours to obtain a solution B of a polyamideimide resin having blocked ends.

Example 3

[0107] 150.2 g (0.6 mole) of 4,4-Diphenylmethane diisocyanate, 105.7 g (0.4 mole) of 3,3′-dimethyl-4,4′-diisocyanatobiphenyl, 192.1 g (1.0 mole) of trimellitic anhydride, and 672 g of 3-methoxy-N,N-dimethylpropionamide (DMPA) were charged into 2-liter flask. While stirring the charged raw material, the temperature was raised to 100° C., the temperature was maintained, and the reaction was performed for 7.5 hours to obtain a solution containing a polyamideimide resin. The polyamideimide resin had a number average molecular weight of 18,300 and had a degree of dispersion of 2.2. To this solution 8.7 g of methyl ethyl ketone oxime and 4.3 g of butyl vinyl ether were added and reacted at 80° C. for 2 hours to obtain a solution C of a polyamideimide resin with blocked ends.

Comparative Example 1

[0108] 250.3 g (1.00 mole) of 4,4′-diphenylmethane diisocyanate, 192.1 g (1.00 mole) of trimellitic anhydride, and 660 g of N-methyl-2-pyrrolidone (NMP) were charged into 2-liter flask. While stirring the charged raw material, the temperature was raised to 125° C. in about 3 hours, and the temperature was maintained and the reaction was performed for 6 hours to obtain a solution D containing a polyamideimide resin. The polyamideimide resin had a number average molecular weight of 18,200 and had a degree of dispersion of 1.8.

Comparative Example 2

[0109] 250.3 g (1.00 mole) of 4,4′-diphenylmethane diisocyanate, 192.1 g (1.00 mole) of trimellitic anhydride, and 660 g of N-ethyl-2-pyrrolidone (NEP) were charged into 2-liter flask. While stirring the charged raw material, the temperature was raised to 135° C. in about 3 hours, and the temperature was maintained and the reaction was performed for 8 hours to obtain a solution E containing a polyamideimide resin. The polyamideimide resin had a number average molecular weight of 27,900 and had a degree of dispersion of 1.6.

Comparative Example 3

[0110] 150.2 g (0.6 mole) of 4,4′-diphenylmethane diisocyanate, 69.7 g (0.4 mole) of mixed toluene diisocyanate (Coronate T-60), 192.1 g (1.00 mole) of trimellitic anhydride, and 660 g of γ-butyrolactone GBL) were charged into 2-liter flask. While stirring the charged raw material, the temperature was raised to 135° C. in about 3 hours, and the temperature was maintained and the reaction was performed for 8 hours to obtain a polyamideimide resin solution F. The polyamideimide resin had a number average molecular weight of 24,300 and had a degree of dispersion of 1.6.

Comparative Example 4

[0111] 250.3 g (1.00 mole) of 4,4′-diphenylmethane diisocyanate, 192.1 g (1.00 mole) of trimellitic anhydride, and 660 g of N,N-dimethylacetamide (DMAC) were charged into 2-liter flask. While stirring the charged raw material, the temperature was raised to 135° C. in about 3 hours, and the temperature was maintained and the reaction was performed for 8 hours to obtain a solution G of a polyamideimide resin. The polyamideimide resin had a number average molecular weight of 23,900 and had a degree of dispersion of 1.6.

<2> Preparation and Evaluation of Coating Agents

(Preparation of Coating Agent)

[0112] Epoxy resin was added to and mixed with solutions A-G of the resin obtained in Examples 1 to 3 and Comparative Examples 1 to 4, respectively, to prepare a polyamideimide resin composition (coating agent).

[0113] The same solvent as the polymerization solvent used in the production of the polyamideimide resin was added, if necessary, so that the content of the polyamideimide resin was 25% by mass with respect to the total mass of the coating agent. In addition, the epoxy resin used for the preparation of the above coating agent was Epomic (registered trade mark) R-140, manufactured by Mitsui Chemicals, Inc., which is a diglycidyl etherate of 2,2-bis (4-hydroxyphenyl) propane with epichlorohydrin, and was added in an amount so that the epoxy resin concentration in the coating agent was about 4 wt % (that is, with respect to 100 parts by mass of the solution containing 25 mass % of the polyamideimide resin, 4.25 parts by mass of the epoxy resin was added).

(Evaluation of the Coating Film)

[0114] A coating film was formed by using each of the coating agents prepared previously, and characteristics of the coating film were evaluated as follows.

(1) Adhesion

[0115] After each coating agent was applied to the surface of an aluminum substrate (A 1050P, thickness 1 mm, dimensions 50 mm×100 mm, unpolished), the aluminum substrate was put into a dryer and pre-dried at 80° C. for 30 minutes. Then, the aluminum substrate was subjected to heat curing at 230° C. for 30 minutes to form a coating film (test sample A) having a film thickness of 35 μm. As a comparison of the curing temperatures, a coating agent was applied in the same manner as described above, and the coating agent was placed in a dryer and pre-dried at 80° C. for 5 minutes, and then heat-cured at 150° C. for 60 minutes to form a coating film (test sample B) having a film thickness of 35 μm on the aluminum substrate.

[0116] The initial adhesion of the coating film to the aluminum substrate of the test samples A and B prepared as described above was evaluated as follows.

[0117] Adhesion was measured according to the old JIS K 5400 standard (cross-cut remaining %). That is, a 1×1-mm square grid cut was made in the coating film surface (test surface) by using a cutter knife, and 100 grid patterns were formed. Mending tape #810 (manufactured by 3M Co., Ltd.) was strongly crimped to the grid part, and after slowly peeling the tape, the state of the grid was observed. These peeling tests were performed five times, and the number of residual masses was counted for each peeling test, and the mean value was calculated. Table 1 shows the average of the remaining mass (%) out of the 100 masses.

(2) Pencil Hardness

[0118] Two types of test samples were prepared in the same manner as the test samples A and B that were prepared to evaluate the adhesion, and a pencil hardness test for the coating film was performed in accordance with the pencil scratch test of the old JIS K 5400 standard. The surface of the coating film after the test was visually observed to evaluate the presence of scratches. The pencil hardness at which clear scratches were observed is shown in Table 1.

(3) Bending Test

[0119] A test sample was prepared in the same manner as the test sample A that was prepared for evaluating the adhesion, and a bending test was performed. A test sample was wound around a rod having a predetermined diameter, and the coating surface was visually observed to evaluate the presence of cracks. The diameters of the bars with clear cracks are shown in Table 1.

(4) Solvent Resistance (Curability)

[0120] After each coating agent was applied to the surface of an iron plate (SPCC-SB, thickness of 0.5 mm, dimensions of 20 mm×50 mm), it was put into a dryer and pre-dried at 80° C. for 30 minutes. Then, it was heated and cured at 150° C. for 60 minutes to form a coating film having a thickness of 15 μm on the iron plate. The test sample thus obtained was set in an ultrasonic cleaner while immersed in N-methylpyrrolidone (NMP) adjusted to a temperature of 20 to 30° C. and left for 1 hour. After 1 hour, the test samples were removed, washed with acetone and dried, and then the mass of the test samples was measured. Next, the coating film residual ratio (%) was calculated from the difference in the mass of the test sample from before and after the immersion, and the curability was evaluated. Table 1 shows the remaining percentages of the coating films.

TABLE-US-00001 TABLE 1 Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 1 Example 2 Example 3 Example 4 Components of Coating Agent A B C D E F G (Solution of PAI Resin) PAI Resin Number-average 18,900 19,700 18,300 18,200 27,900 24,300 23,900 molecular weight (Mn) Weight-average 44,200 47,400 40,000 32,500 45,200 40,000 38,400 molecular weight(Mw) Degree of dispersion 2.3 2.4 2.2 1.8 1.6 1.6 1.6 (Mw/Mn) Solvent (Polymerization Solvent) DMPA DMPA DMPA NMP NEP GBL DMAC Adhesion Curing temperature 100 100 100 100 98 88 87 (%) 230° C. Curing temperature 100 100 100 100 65 72 60 150° C. Pencil Hardness Curing temperature 2H 2H 2H 2H 2H 2H 2H 230° C. Curing temperature 2H 2H 2H 2H 2H  H  H 150° C. Bending Test Curing temperature 2 mm 2 mm 2 mm 3 mm 3 mm 3 mm 3 mm 230° C. Solvent Resistance Curing temperature 96 92 98 78 71 25 43 (Remaining % of 150° C. Coating Film)

[0121] As can be seen from the results shown in Table 1, when 3-methoxy-N,N-propionamide is used in the production of a polyamideimide resin (Examples 1 to 3), a polyamideimide resin having a smaller Mn and having a greater degree of dispersion than a polyamideimide resin obtained by using a typical conventional polar solvent shown as a comparative example is obtained. Further, by forming the coating agent using the solution of the polyamideimide resin, excellent solvent resistance (hardenability) can be obtained even when low-temperature curing at 150° C. is employed, and excellent coating film characteristics such as adhesion can be obtained as in the case of high-temperature curing at 230° C. (see Examples 1 to 3). On the other hand, in Comparative Examples 2 to 4, the adhesion of the coating film is low, and particularly the adhesion at the time of low-temperature curing is remarkably reduced. The bending property and solvent resistance (curability) of the coating film were inferior to those of Comparative Examples 1 to 4.