Polyamideimide resin and coating material

Abstract

A polyamideimide resin having isocyanate groups at the terminals, wherein at least a portion of the isocyanate groups are blocked with an ether group-containing cyclic amine.

Claims

1. A coating material comprising a polyamideimide resin, a curing agent, and a solvent, wherein the polyamideimide resin has isocyanate groups at terminals, and at least a portion of the isocyanate groups are blocked with at least 0.02 mol and not more than 0.15 mol of an ether group-containing cyclic amine per 1 mol of the polyamideimide resin, wherein an amount of the curing agent is from 1 to 15 parts by mass, per 100 parts by mass of the polyamideimide resin, wherein the solvent consists essentially of the ether group-containing cyclic amine, and wherein the polyamideimide resin is produced by reacting one or more diisocyante compounds in the presence of the solvent under conditions that a molar ratio of the solvent to the one or more diisocyanate compounds ranges from 5.62 to 8.94.

2. The coating material according to claim 1, wherein the polyamideimide resin has a number average molecular weight of 12,000 to 30,000.

3. The coating material according to claim 1, wherein the curing agent comprises at least one selected from the group consisting of epoxy resins, phenol resins, melamine resins, and isocyanate compounds.

4. The coating material according to claim 2, wherein the curing agent comprises at least one selected from the group consisting of epoxy resins, phenol resins, melamine resins, and isocyanate compounds.

5. A coating material comprising a polyamideimide resin, a curing agent, and a solvent, wherein the polyamideimide resin has isocyanate groups at terminals, and at least a portion of the isocyanate groups are blocked with at least 0.02 mol and not more than 0.15 mol of an ether group-containing cyclic amine per 1 mol of the polyamideimide resin, wherein an amount of the curing agent is from 1 to 15 parts by mass, per 100 parts by mass of the polyamideimide resin, wherein the solvent comprises the ether group-containing cyclic amine, wherein the coating material comprises no co-solvent, and wherein the polyamideimide resin is produced by reacting one or more diisocyante compounds in the presence of the solvent under conditions that a molar ratio of the solvent to the one or more diisocyanate compounds ranges from 5.62 to 8.94.

6. The coating material according to claim 5, wherein the polyamideimide resin has a number average molecular weight of 12,000 to 30,000.

7. The coating material according to claim 5, wherein the curing agent comprises at least one selected from the group consisting of epoxy resins, phenol resins, melamine resins, and isocyanate compounds.

8. The coating material according to claim 6, wherein the curing agent comprises at least one selected from the group consisting of epoxy resins, phenol resins, melamine resins, and isocyanate compounds.

9. The coating material according to claim 1, wherein the amount of the curing agent is from 5 to 15 parts by mass, per 100 parts by mass of the polyamideimide resin.

10. The coating material according to claim 5, wherein the amount of the curing agent is from 5 to 15 parts by mass, per 100 parts by mass of the polyamideimide resin.

11. The coating material according to claim 1, wherein the ether group-containing cyclic amine includes a compound having a morpholine ring, a tetrahydro-1,3-oxazine ring, a tetrahydro-1,2-oxazine ring, or an oxazolidine ring.

12. The coating material according to claim 1, wherein the ether group-containing cyclic amine includes any one or more of morpholine, 4-methylmorpholine, 4-ethylmorpholine, N-formylmorpholine, and N-acetylmorpholine.

13. The coating material according to claim 1, wherein the curing agent comprises a melamine resin.

14. The coating material according to claim 1, wherein at least a portion of the isocyanate groups are blocked with at least 0.05 mol and not more than 0.15 mol of an ether group-containing cyclic amine per 1 mol of the polyamideimide resin.

15. The coating material according to claim 5, wherein at least a portion of the isocyanate groups are blocked with at least 0.05 mol and not more than 0.15 mol of an ether group-containing cyclic amine per 1 mol of the polyamideimide resin.

Description

EXAMPLES

(1) A variety of examples are described below in detail, but the preferred embodiments of the invention are not limited to these examples, and of course also incorporate many embodiments other than these examples based on the scope of the present invention.

Example 1

(2) A 2-liter flask fitted with a thermometer, a stirrer and a condenser was charged with 250.3 g (1.00 mol) of 4,4′-diphenylmethane diisocyanate, 192.1 g (1.00 mol) of trimellitic anhydride and 660 g of 4-methylmorpholine, while stirring the resulting mixture, the temperature was raised to 110° C. under a stream of dry nitrogen, the mixture was reacted for about 4 hours, and the reaction was continued for a further 6 hours while holding the temperature at 160° C., thus obtaining a blocked polyamideimide resin solution (solid fraction concentration: about 40% by mass) of a resin having a number average molecular weight of 19,000. NMR measurement of the obtained polyamideimide resin confirmed that the resin was blocked with 0.02 mol of 4-methylmorpholine per 1 mol of the resin.

(3) The NMR measurement was performed under the following conditions, using a .sup.1H-NMR apparatus manufactured by Bruker Corporation.

(4) Standard: tetramethylsilane, 0 ppm

(5) Solvent: dimethyl sulfoxide-d6

(6) Frequency: 400 MHz

(7) Temperature: 23° C.±3° C.

(8) Further, for each synthesized resin, a material obtained by re-precipitation using acetone was used as the sample.

(9) The number average molecular weight of the polyamideimide resin was measured under the following conditions.

(10) GPC apparatus: Hitachi L6000

(11) Detector: Hitachi L4000 UV

(12) Wavelength: 270 nm

(13) Data processing unit: ATT 8

(14) Columns: Gelpack GL-S300MDT-5×2

(15) Column size: 8 mmø×300 mm

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

(17) Sample concentration: 5 mg/ml

(18) Injection volume: 5 μl

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

(20) Flow rate: 1.0 ml/min

Example 2

(21) A 2-liter flask fitted with a thermometer, a stirrer and a condenser was charged with 125.2 g (0.5 mol) of 4,4′-diphenylmethane diisocyanate, 132.2 g (0.5 mol) of 3,3′-dimethyl-4,4′-diisocyanatobiphenyl, 192.1 g (1.0 mol) of trimellitic anhydride and 904 g of 4-methylmorpholine, while stirring the resulting mixture, the temperature was raised to 110° C. under a stream of dry nitrogen, the mixture was reacted for about 4 hours, and the reaction was continued for a further 6 hours while holding the temperature at 160° C., thus obtaining a blocked polyamideimide resin solution of a resin having a number average molecular weight of 20,000. NMR measurement of the obtained polyamideimide resin confirmed that the resin was blocked with 0.11 mol of 4-methylmorpholine per 1 mol of the resin.

Example 3

(22) A 2-liter flask fitted with a thermometer, a stirrer and a condenser was charged with 125.2 g (0.5 mol) of 4,4′-diphenylmethane diisocyanate, 158.6 g (0.6 mol) of 3,3′-dimethyl-4,4′-diisocyanatobiphenyl, 192.1 g (1.0 mol) of trimellitic anhydride and 904 g of N-formylmorpholine, while stirring the resulting mixture, the temperature was raised to 110° C. under a stream of dry nitrogen, the mixture was reacted for about 4 hours, and the reaction was continued for a further 2 hours while holding the temperature at 160° C., thus obtaining a blocked polyamideimide resin solution of a resin having a number average molecular weight of 15,600. NMR measurement of the obtained polyamideimide resin confirmed that the resin was blocked with 0.15 mol of N-formylmorpholine per 1 mol of the resin.

Example 4

(23) A 2-liter flask fitted with a thermometer, a stirrer and a condenser was charged with 257.5 g (1.02 mol) of 4,4′-diphenylmethane diisocyanate, 192.1 g (1.0 mol) of trimellitic anhydride and 660 g of N-formylmorpholine, while stirring the resulting mixture, the temperature was raised to 110° C. under a stream of dry nitrogen, the mixture was reacted for about 4 hours, and the reaction was continued for a further 4 hours while holding the temperature at 160° C., thus obtaining a blocked polyamideimide resin solution of a resin having a number average molecular weight of 23,000. NMR measurement of the obtained polyamideimide resin confirmed that the resin was blocked with 0.06 mol of N-formylmorpholine per 1 mol of the resin.

Comparative Example 1

(24) A 2-liter flask fitted with a thermometer, a stirrer and a condenser was charged with 250.3 g (1.0 mol) of 4,4′-diphenylmethane diisocyanate, 192.1 g (1.0 mol) of trimellitic anhydride and 660 g of N-methyl-2-pyrrolidone, while stirring the resulting mixture, the temperature was raised to 140° C. under a stream of dry nitrogen, and the mixture was then reacted for about 6 hours, thus obtaining a polyamideimide resin solution of a resin having a number average molecular weight of 22,000.

(25) <Adhesion>

(26) The resin solutions obtained in the above examples and comparative example were each applied to a substrate (aluminum sheet JIS H 4000, thickness: 1 mm, unpolished) and then baked at 270° C. for 30 minutes to prepare a coated sheet having a coating film thickness of about 20 μm, and the initial adhesion was then measured.

(27) The adhesion was measured in accordance with the old JIS K 5400 (%, cross-cut retention rate). In other words, a cutter knife was used to insert 1×1 mm square grid cuts in the test surface, thus forming 100 grid squares. A mending tape #810 (manufactured by 3M Corporation) was pressed strongly onto the grid squares, the tape was then peeled gradually away, and the state of the grid squares was inspected, with the number of retained squares among the 100 squares being calculated as a percentage. This peel test was performed 5 times, and the number of retained squares was counted for each test.

(28) <Storage Stability>

(29) Each of the obtained resin solutions was left to stand at 40° C. for 6 months, with the viscosity measured before and after the storage period, and the change in viscosity was investigated. The viscosity was measured in accordance with JIS C 2103 using a B-type rotational viscometer at 25° C., using a No. 4 rotor and a rotational rate of 12 rpm.

(30) <Mechanical Properties>

(31) Each of the above resin solutions was applied to a glass plate, subjected to heat-curing at 270° C. for 30 minutes, and then peeled from the glass plate to prepare a coating film having a film thickness of about 20 μm, a width of 10 mm and a length of 60 mm.

(32) Using a tensile tester “Autograph AGS-5kNG” manufactured by Shimadzu Corporation, a tensile test was performed under conditions including a chuck separation of 20 mm and a tensile speed of 5 mm/minute, and the tensile strength, the elastic modulus, and the elongation percentage were determined.

(33) The results of the above evaluations are shown in Table 1. Each adhesion result represents the average value obtained across the 5 tests.

(34) TABLE-US-00001 TABLE 1 Comparative Example 1 Example 2 Example 3 Example 4 Example 1 Adhesion Cross-cut retention rate, % 100 100 100 100 100 Storage 40° C., 6 months, change in +51 +22 +24 +23 +120 stability viscosity Mechanical Strength (MPa) 115 133 151 121 106 properties Elastic modulus (GPa) 3.3 3.9 4.6 3.1 2.5 Elongation percentage (%) 8 7 8 9 14

(35) Based on Table 1, it is evident that the coating films obtained using the blocked polyamideimide resins of the examples have a higher elastic modulus compared with the coating film obtained using the unblocked polyamideimide resin of the comparative example. Further, the resin solutions of the examples exhibited considerably superior storage stability compared with the resin solution of the comparative example.

(36) This Application is related to the subject matter disclosed in prior Japanese Application 2015-243133 filed on Dec. 14, 2015, the entire contents of which are incorporated by reference herein.

(37) It should be noted that, in addition to the embodiments already described, various modifications and alterations may be made to these embodiments without departing from the novel advantageous features of the present invention. Accordingly, it is intended that all such modifications and alterations are included within the scope of the appended claims.