Transparent polyimide copolymer, polyimide resin composition and molded article, and production method of said copolymer

Abstract

Provided are: a transparent polyimide copolymer which satisfies solvent solubility, storage stability, heat resistance, mechanical strength and thermal yellowing resistance at high levels and has excellent utility; a polyimide resin composition; a molded article; and a production method of the copolymer. The transparent polyimide copolymer is obtained by copolymerizing: (A) 4,4-oxydiphthalic dianhydride and/or 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride; and (B) at least one diamine and/or diisocyanate represented by the following Formulae (1) to (3): ##STR00001## (wherein, X represents an amino group or an isocyanate group; R.sup.1 to R.sup.8 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms; and at least one of the R.sup.1 to R.sup.8 is not a hydrogen atom).

Claims

1. A transparent polyimide copolymer obtained by copolymerizing: (A) 4,4-oxydiphthalic dianhydride; and (B) at least one diamine and/or diisocyanate represented by the following Formulae (1) or (2): ##STR00016## (wherein, X represents an amino group or an isocyanate group; R.sup.1 to R.sup.4 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms; and at least one of said R.sup.1 to R.sup.4 is not a hydrogen atom).

2. The transparent polyimide copolymer according to claim 1, having no amino group terminal.

3. The transparent polyimide copolymer according to claim 1, wherein two of said R.sup.1 to R.sup.4 in said Formula (1) or (2) of said (B) are ethyl groups and the other two are a methyl group and a hydrogen atom.

4. The transparent polyimide copolymer according to claim 1, wherein (C) second acid dianhydride and/or (D) second diamine and/or diisocyanate is/are further copolymerized.

5. A polyimide resin composition comprising the transparent polyimide copolymer according to claim 1.

6. A molded article obtained by molding the polyimide resin composition according to claim 5.

7. A method of producing a transparent polyimide copolymer, said method comprising: the oligomer production step of producing an oligomer of transparent polyimide copolymer by copolymerizing (A) 4,4-oxydiphthalic dianhydride with (B) at least one diamine and/or diisocyanate represented by the following Formulae (1) to (2): ##STR00017## (wherein, X represents an amino group or an isocyanate group; R.sup.1 to R.sup.4 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms; and at least one of said R.sup.1 to R.sup.4 is not a hydrogen atom); and the polyimide copolymer production step of producing a transparent polyimide copolymer by copolymerizing said oligomer of transparent polyimide copolymer produced in said oligomer production step with (C) second acid dianhydride and (D) second diamine and/or diisocyanate.

8. The method of producing an oligomer of transparent polyimide copolymer according to claim 7, wherein said transparent polyimide copolymer oligomer produced in said oligomer production step has an acid terminal.

9. The method of producing a transparent polyimide copolymer according to claim 7, wherein two of said R.sup.1 to R.sup.4 in said Formula (1) or (2) of said (B) are ethyl groups and the other two are a methyl group and a hydrogen atom.

Description

EXAMPLES

Example 1

(1) To a 500-mL separable four-necked flask equipped with a stainless steel anchor stirrer, a nitrogen-introducing tube and a Dean-Stark trap, 56.11 g (0.18 mol) of 4,4-oxydiphthalic anhydride (ODPA), 32.09 g (0.18 mol) of DETDA, 326.87 g of -butyrolactone (GBL), 2.85 g of pyridine and 33 g of toluene were poured, and the atmosphere in the reaction mixture was replaced with nitrogen. The reaction mixture was stirred for 30 minutes at 80 C. under nitrogen gas flow to dissolve ODPA, and the resultant was then heated to 180 C. and stirred under heating for 6 hours. Water generated by the reaction was removed from the reaction mixture as an azeotropic mixture with toluene and pyridine. After the completion of the reaction, the reaction mixture was cooled to room temperature to obtain a polyimide solution having a concentration of 20% by mass. The thus obtained polyimide copolymer had a structure represented by the following Formula (22):

(2) ##STR00009##

(3) (wherein, one of R.sup.1 to R.sup.3 is a methyl group and the other two are ethyl groups).

Example 2

(4) To the same apparatus as used in Example 1, 46.80 g (0.15 mol) of ODPA, 38.16 g (0.15 mol) of 4,4-diamino-3,3,5,5-tetramethyldiphenylmethane, 147.67 g of GBL, 2.39 g of pyridine and 50 g of toluene were poured, and the atmosphere in the reaction mixture was replaced with nitrogen. The reaction mixture was stirred for 30 minutes at 80 C. under nitrogen gas flow to dissolve ODPA, and the resultant was then heated to 180 C. and stirred under heating for 7 hours. Water generated by the reaction was removed from the reaction mixture as an azeotropic mixture with toluene and pyridine. After the completion of the reaction, 100 g of GBL was added when the reaction mixture was cooled to 120 C., thereby obtaining a polyimide solution having a concentration of 25% by mass. The thus obtained polyimide copolymer had a structure represented by the following Formula (23):

(5) ##STR00010##

Example 3

(6) To the same apparatus as used in Example 1, 44.70 g (0.1 mol) of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 17.83 g (0.1 mol) of DETDA, 128.44 g of GBL, 3.16 g of pyridine and 50 g of toluene were poured, and the atmosphere in the reaction mixture was replaced with nitrogen. The reaction mixture was stirred for 30 minutes at 80 C. under nitrogen gas flow to dissolve 6FDA, and the resultant was then heated to 180 C. and stirred under heating for 6 hours. Water generated by the reaction was removed from the reaction mixture as an azeotropic mixture with toluene and pyridine. After the completion of the reaction, 36.70 g of GBL was added when the reaction mixture was cooled to 120 C., thereby obtaining a polyimide solution having a concentration of 25% by mass. The thus obtained polyimide copolymer had a structure represented by the following Formula (24):

(7) ##STR00011##

(8) (wherein, one of R.sup.1 to R.sup.3 is a methyl group and the other two are ethyl groups).

Example 4

(9) To the same apparatus as used in Example 1, 32.57 g (0.105 mol) of ODPA, 12.48 g (0.07 mol) of DETDA, 100 g of GBL, 2.77 g of pyridine and 50 g of toluene were poured, and the atmosphere in the reaction mixture was replaced with nitrogen. The reaction mixture was stirred for 30 minutes at 80 C. under nitrogen gas flow to dissolve ODPA, and the resultant was then heated to 180 C. and stirred under heating for 2 hours. Water generated by the reaction was removed from the reaction mixture by azeotropic distillation with toluene.

(10) Next, after cooling the reaction mixture to 130 C., 21.03 g (0.105 mol) of 3,4-diaminodiphenyl ether (mDADE) and 40 g of GBL were added, and the resultant was stirred for 5 minutes. Then, 17.58 g (0.07 mol) of BTA and 40 g of GBL were further added, and the resulting mixture was heated to 180 C. and allowed to react for 6 hours under heating and stirring. Water generated by this reaction was removed from the reaction mixture as an azeotropic mixture with toluene and pyridine. After the completion of the reaction, 51.43 g of GBL was added when the reaction mixture was cooled to 120 C., thereby obtaining a polyimide solution having a concentration of 25% by mass. The thus obtained polyimide copolymer had a structure represented by the following Formula (25):

(11) ##STR00012##

(12) (wherein, one of R.sup.1 to R.sup.3 is a methyl group and the other two are ethyl groups).

Example 5

(13) To the same apparatus as used in Example 1, 32.57 g (0.105 mol) of ODPA, 12.48 g (0.07 mol) of DETDA, 96.91 g of N-methyl-2-pyrrolidone (NMP), 2.77 g of pyridine and 50 g of toluene were poured, and the atmosphere in the reaction mixture was replaced with nitrogen. The reaction mixture was stirred for 30 minutes at 80 C. under nitrogen gas flow to dissolve ODPA, and the resultant was then heated to 180 C. and stirred under heating for 2 hours. Water generated by the reaction was removed from the reaction mixture by azeotropic distillation with toluene.

(14) Next, after cooling the reaction mixture to 130 C., 45.41 g (0.105 mol) of bis[4-(3-aminophenoxy)phenyl]sulfone (mBAPS) and 100 g of NMP were added, and the resultant was stirred for 5 minutes. Then, 17.64 g (0.07 mol) of BTA and 40 g of NMP were further added, and the resulting mixture was heated to 180 C. and allowed to react for 6 hours under heating and stirring. Water generated by this reaction was removed from the reaction mixture as an azeotropic mixture with toluene and pyridine. After the completion of the reaction, 67.69 g of NMP was added when the reaction mixture was cooled to 120 C., thereby obtaining a polyimide solution having a concentration of 25% by mass. The thus obtained polyimide copolymer had a structure represented by the following Formula (26):

(15) ##STR00013##

(16) (wherein, one of R.sup.1 to R.sup.3 is a methyl group and the other two are ethyl groups).

Example 6

(17) A titanium dioxide dispersion was obtained by mixing 10 parts of titanium dioxide (TIPAQUE R-830, manufactured by Ishihara Sangyo Kaisha, Ltd.) and 10 parts of GBL and stirring the resulting mixture to homogeneity. To this titanium dioxide dispersion, 50 parts of the transparent polyimide varnish obtained in Example 4 was added, and the resultant was stirred to homogeneity under vacuum degassing. The resulting white composition was strained through a 400-mesh polyethylene filter to remove coarse particles, thereby obtaining a white ink containing 80 parts of titanium dioxide with respect to 100 parts of the transparent polyimide resin.

Comparative Example 1

(18) To the same apparatus as used in Example 1, 35.31 g (0.12 mol) of BPDA, 21.39 g (0.12 mol) of DETDA, 209.50 g of NMP, 1.90 g of pyridine and 50 g of toluene were poured, and the atmosphere in the reaction mixture was replaced with nitrogen. The reaction mixture was stirred for 30 minutes at 80 C. under nitrogen gas flow to dissolve BPDA, and the resultant was then heated to 180 C. and stirred under heating for 6 hours. Water generated by the reaction was removed from the reaction mixture as an azeotropic mixture with toluene and pyridine. After the completion of the reaction, the reaction mixture was cooled to 120 C., thereby obtaining a polyimide solution having a concentration of 20% by mass. The thus obtained polyimide copolymer had a structure represented by the following Formula (27):

(19) ##STR00014##

(20) (wherein, one of R.sup.1 to R.sup.3 is a methyl group and the other two are ethyl groups).

Comparative Example 2

(21) To the same apparatus as used in Example 1, 22.62 g (0.1 mol) of cyclohexane-1,2,4,5-tetracarboxylic dianhydride (H-PMDA), 23.80 g (0.1 mol) of 3,3-dimethylmethylenedicyclohexylamine, 221.06 g of NMP, 3.16 g of pyridine and 50 g of toluene were poured, and the atmosphere in the reaction mixture was replaced with nitrogen. Under nitrogen gas flow, the reaction mixture was heated to 180 C. and stirred under heating for 5 hours. Water generated by the reaction was removed from the reaction mixture as an azeotropic mixture with toluene and pyridine. After the completion of the reaction, the reaction mixture was cooled to room temperature, thereby obtaining a polyimide solution having a concentration of 15% by mass. The thus obtained polyimide copolymer had a structure represented by the following Formula (28):

(22) ##STR00015##

Comparative Example 3

(23) A titanium dioxide dispersion was obtained by mixing 10 parts of titanium dioxide (TIPAQUE R-830, manufactured by Ishihara Sangyo Kaisha, Ltd.) and 10 parts of NMP and stirring the resulting mixture to homogeneity. To this titanium dioxide dispersion, 83 parts of the fully alicyclic polyimide varnish obtained in Comparative Example 2 and 42 parts of NMP as a diluent were added, and the resultant was stirred to homogeneity under vacuum degassing. The resulting white composition was strained through a 400-mesh polyethylene filter to remove coarse particles, thereby obtaining a white ink containing 80 parts of titanium dioxide with respect to 100 parts of the fully alicyclic polyimide resin.

(24) <Film-Forming Property>

(25) The polyimide copolymers obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were each coated on a silicon wafer by a spin coating method and then pre-dried for 10 minutes on a 120 C. hot plate. The resulting pre-dried film was detached from the silicon wafer, fixed on a stainless steel frame and subsequently dried at 180 C. for 30 minutes and then at 250 C. for 1 hour. As for the evaluation of the film-forming property, an evaluation was given when the film could not maintain a film shape by itself when detached from the silicon wafer after the pre-drying at 120 C.; an evaluation was given when the film was so brittle that it could not maintain a film shape after the drying at 250 C.; and an evaluation was given when the film was able to maintain a film shape by itself even after the completion of the drying at 250 C. The results thereof are shown in Tables 1 and 2.

(26) It is noted here that, since the polyimide copolymer obtained in Comparative Example 2 could not maintain a film shape under the film-forming conditions for the evaluation of film-forming property, a film formed under the following conditions was used for the below-described evaluations. Specifically, the polyimide copolymer obtained in Comparative Example 2 was coated on a silicon wafer by a spin coating method and then pre-dried for 10 minutes on a 120 C. hot plate. The resulting pre-dried film was detached from the silicon wafer, fixed on a stainless steel frame and subsequently dried at 200 C. for 1 hour.

(27) <Measurement of Thickness>

(28) For the films that were prepared for the evaluation of film-forming property, the thickness was measured. The measurement was performed using ABC Digimatic Indicator (manufactured by Mitutoyo Corporation). The results thereof are shown in Tables 1 and 2.

(29) <Glass Transition Temperature>

(30) For the films that were prepared for the evaluation of film-forming property, the glass transition temperature was measured. The measurement was performed using DSC6200 (manufactured by Seiko Instruments Inc.). Each film was heated to 500 C. at a heating rate of 10 C./min, and the midpoint glass transition temperature was adopted as the glass transition temperature of the film. The results thereof are shown in Tables 1 and 2.

(31) <5% Thermal Weight Loss Temperature>

(32) For the films that were prepared for the evaluation of film-forming property, the 5% thermal weight loss temperature was measured. The measurement was performed using TG/DTA6200 (manufactured by Seiko Instruments Inc.). As for the heating condition, each film was heated at a rate of 10 C./min, and the temperature at which the mass was reduced by 5% was measured. The results thereof are shown in Tables 1 and 2.

(33) <Mechanical and Physical Properties>

(34) The films prepared for the evaluation of film-forming property were each processed into a test piece of 100 mm in length10 mm in width, and the tensile elastic modulus, tensil strength and elongation were measured using a creep meter (RE2-33005B, manufactured by Yamaden Co., Ltd.). Each film was measured 5 times, and the data showing the maximum value in tensile strength was adopted. The chuck distance was 50 mm and the tensile rate was 5 mm/sec.

(35) <Total Light Transmittance>

(36) For the films that were prepared for the evaluation of film-forming property, the total light transmittance was measured in accordance with JIS K7361. The measurement was performed using a haze meter NDH4000 (manufactured by Nippon Denshoku Industries Co., Ltd.). The results thereof are shown in Tables 1 and 2.

(37) <Haze>

(38) For the films that were prepared for the evaluation of film-forming property, the haze was measured in accordance with JIS K7136. The measurement was performed using a haze meter NDH4000 (manufactured by Nippon Denshoku Industries Co., Ltd.). The results thereof are shown in Tables 1 and 2.

(39) <Color Difference b-Value>

(40) For the films that were prepared for the evaluation of film-forming property, the color difference b-value was measured. The measurement was performed using a color difference meter CR-5 (manufactured by Konica Minolta, Inc.). The results thereof are shown in Tables 1 and 2.

(41) <Whiteness and Yellowness>

(42) The varnishes obtained in Example 6 and Comparative Example 3 were each coated on a polyimide film (KAPTON 200EN) by a spin coating method, and the thus coated polyimide film was fixed on a stainless steel frame and dried in a 120 C. incubator for 10 minutes and then at 200 C. for 1 hour, thereby obtaining an 18 m-thick film of white polyimide on KAPTON 200EN. For each of the thus obtained films, the whiteness and yellowness were measured in accordance with ASTM E313-73 using a color difference meter CR-5 (manufactured by Konica Minolta, Inc.). Further, as a thermal yellowing resistance test, after measuring the initial whiteness and yellowness, the whiteness and yellowness were also measured for the film that was allowed to float in a 260 C. solder bath for 10 seconds and the film that was left to stand for 5 hours in a 200 C. incubator so as to verify the thermal yellowing resistance. The results thereof are shown in Table 3.

(43) In the present invention, the thermal yellowing resistance was evaluated based on the change in the whiteness and yellowness values before and after the heat treatment. Specifically, the film of interest was subjected to a 10-second heat treatment in a 260 C. solder bath or a 5-hour heat treatment in a 200 C. incubator, and the whiteness and yellowness were measured before and after the heat treatment. As for the whiteness, a larger value indicates a higher whiteness of the subject coating film, and a higher whiteness after the heat treatment means that the whiteness was better maintained even after the heat treatment. Further, a smaller numerical difference between before and after the heat treatment indicates superior thermal yellowing resistance. As for the yellowness, a larger value indicates a stronger yellowish tone, and a larger value after the heat treatment means a stronger yellowish tone of the subject coating film. Further, a larger numerical difference between before and after the heat treatment indicates inferior thermal yellowing resistance.

(44) TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Storage stability Thickness (m) 23 23 21 21 32 Glass transition temperature ( C.) 339 312 353 310 273 5% weight loss temperature ( C.) 510 520 512 445 466 Film-forming property Tensile elastic modulus (GPa) 1.71 2.41 1.76 2.22 2.22 Tensil strength (MPa) 94 107 85 98 115 Elongation (%) 17 11 9 41 13 Total light transmittance (%) 89 88 91 88 88 Haze (%) 0.28 0.2 0.19 0.18 0.57 Color difference b-value 2.63 2.74 1.32 2.31 3.69

(45) TABLE-US-00002 TABLE 2 Comparative Comparative Example 1 Example 2 Storage stability Thickness (m) 28 21 Glass transition temperature ( C.) 500 or higher 231 5% weight loss temperature ( C.) 523 443 Film-forming property Tensile elastic modulus (GPa) 2.01 2.78 Tensil strength (MPa) 115 101 Elongation (%) 10 9 Total light transmittance (%) 81 91 Haze (%) 0.45 0.24 Color difference b-value 27.91 1.52

(46) TABLE-US-00003 TABLE 3 Comparative Example 6 Example 3 Whiteness (%) Initial 69.89 51.14 Solder 69.63 (0.26) 45.80 (5.34) 260 C./10 s 200 C./5 h 65.56 (4.33) 25.15 (25.99) Yellowness (%) Initial 0.06 5.11 Solder 0.09 (+0.03) 7.79 (+2.68) 260 C./10 s 200 C./5 h 1.52 (+1.46) 14.71 (+9.60)
*The values in parentheses indicate the difference from the respective initial whiteness or yellowness values.

(47) According to Tables 1 to 3, the polyimide copolymers of the present invention exhibited excellent heat resistance with a glass transition temperature of 270 C. or higher while maintaining high transparency with a total light transmittance of 85% or higher. Moreover, because of the excellent heat resistance, the polyimide copolymers of the present invention also have excellent resistance to yellowing caused by the drying step of distilling off the solvents and long-term exposure to a high-temperature environment and thus show a characteristic feature of not impairing the color tone of a coloring agent or the like.