POLYIMIDE FOR SPACECRAFT, POLYIMIDE FILM FOR SPACECRAFT, AND SPACECRAFT MEMBER INCLUDING SAME

Abstract

Provided are a polyimide film that, when applied as a material for a spacecraft, exhibits excellent resistance to atomic oxygen derived from an oxygen molecule which is an atmospheric residual component and generates a small amount of outgas compound upon heating; and a polyimide used in the polyimide film. A polyimide for a spacecraft, the polyimide containing a diamine-derived structural unit and an aromatic acid dianhydride-derived structural unit, wherein the polyimide contains, as the diamine-derived structural unit, at least a structural unit derived from a silicon-containing diamine represented by the following formula (1) (provided that the silicon-containing diamine has a number average molecular weight of 500 or less), and a proportion of the structural unit derived from the silicon-containing diamine is 5 to 100 mol % relative to the entire diamine-derived structural unit. (In the formula, RI and R2 are each independently a divalent aliphatic hydrocarbon group having 3 to 20 carbons, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are each independently a monovalent aliphatic hydrocarbon group having 1 to 3 carbons, and m is 1 or 2.)

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Claims

1. A polyimide for a spacecraft, the polyimide comprising a diamine-derived structural unit and an aromatic acid dianhydride-derived structural unit, wherein the polyimide comprises, as the diamine-derived structural unit, at least a structural unit derived from a silicon-containing diamine represented by the following formula (1) (provided that the silicon-containing diamine has a number average molecular weight of 500 or less), and a proportion of the structural unit derived from the silicon-containing diamine is 5 to 100 mol % relative to the entire diamine-derived structural unit: ##STR00005## (wherein R.sup.1 and R.sup.2 are each independently a divalent aliphatic hydrocarbon group having 3 to 20 carbons, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are each independently a monovalent aliphatic hydrocarbon group having 1 to 3 carbons, and m is 1 or 2).

2. The polyimide for a spacecraft according to claim 1, wherein the polyimide comprises, as the aromatic acid dianhydride-derived structural unit, at least a structural unit derived from one or more selected from 1,2,4,5-tetracarboxylic dianhydride, 3,3,4,4-diphenyl ether tetracarboxylic dianhydride, 3,3,4,4-diphenyl sulfone tetracarboxylic dianhydride, and 3,3,4,4-biphenyltetracarboxylic dianhydride.

3. The polyimide for a spacecraft according to claim 1, wherein the polyimide further comprises, as the diamine-derived structural unit, one or more selected from 2,2-bis (4-aminophenoxyphenyl) propane and 9,9-bis (4-aminophenyl) fluorene.

4. A polyimide film for a spacecraft, the polyimide film comprising the polyimide for a spacecraft described in claim 1 in an amount of 90 wt. % or more.

5. The polyimide film for a spacecraft according to claim 4, wherein an amount of a cyclic siloxane generated by heat treatment at 180 C. for 0.5 hours under a nitrogen gas stream is 1 g or less per g of the film.

6. The polyimide film for a spacecraft according to claim 4, wherein a weight reduction rate in an irradiation area is 0.5 wt. % or less by irradiation with atomic oxygen under vacuum and under conditions of 20 C., a film thickness of 25 m, and an irradiation dose of 1.010.sup.20 to 2.010.sup.21 atoms/cm.sup.2.

7. A material for a spacecraft, the material comprising the polyimide film for a spacecraft described in claim 4.

8. A solar battery panel structure for a low-earth-orbit satellite, the solar battery panel structure comprising the polyimide film for a spacecraft described in claim 4.

9. A laminated film comprising the polyimide film for a spacecraft described in claim 4 and a metal film laminated on the polyimide film.

10. A thermal blanket for a low-earth-orbit satellite, the thermal blanket comprising the laminated film described in claim 9.

11. An artificial satellite comprising the thermal blanket described in claim 10 on a surface or inside of an airframe of the artificial satellite.

Description

EXAMPLE 1

[0097] Acid dianhydride DSDA (0.11 mol), 200 g of N-methyl-2-pyrrolidone (NMP), and 200 g of xylene were placed in a 1000-ml separable flask and mixed at room temperature. Silicon-containing diamine A (0.085 mol) was then added dropwise using a dropping funnel. This reaction solution was ice-cooled under stirring, and aromatic diamine BAPP (0.025 mol) was added thereto. The mixture was stirred at room temperature for 2 hours to prepare a polyimide precursor solution. The mole ratio (a/b) of the acid dianhydride (a) to the total amount of the diamines (b) was set 1.0. The temperature of the polyimide precursor solution was raised to 190 C., and the solution was heated and stirred for 20 hours to prepare a solution of polyimide having a weight average molecular weight (Mw) of 20000. The polyimide solution was applied onto a release film, dried to form a film, and the release film was peeled off to produce a polyimide film. The physical properties of the polyimide film were as follows: a glass transition temperature Tg of 150 C. and a tensile elastic modulus E of 1.75 GPa.

[0098] The results of the AO resistance test and the outgas test performed on the produced polyimide film are shown in Table 3.

EXAMPLES 2 TO 11 AND COMPARATIVE EXAMPLES 1 TO 7

[0099] A polyimide precursor solution was prepared in the same manner as in Example 1 except that the acid dianhydride (a) and the diamine (b) were changed to the compositions shown in Tables 1 and 2, and then a polyimide film was produced. The numerals in Tables 1 and 2 indicate the ratio of the amount of the acid dianhydride or diamine used (mol) to the amount of the acid dianhydride used (mol).

[0100] The results of the AO resistance test and the outgas test performed on the produced polyimide films are shown in Tables 3 and 4.

EXAMPLE 12

[0101] Acid dianhydride PMDA (0.11 mol) and 400 g of N-methyl-2-pyrrolidone (NMP) were placed in a 1000-ml separable flask and mixed at room temperature. Next, silicon-containing diamine A (0.033 mol) was added dropwise using a dropping funnel. The reaction solution was ice-cooled under stirring, and aromatic diamine BAPP (0.077 mol) was added thereto. The mixture was stirred at room temperature for 2 hours to prepare a polyimide precursor solution. The mole ratio (a/b) of the acid dianhydride (a) to the total amount of the diamines (b) was 1.0. The polyimide precursor solution was applied onto a release film, dried and heated in an oven at 200 C. for 20 minutes for imidization, and then the release film was peeled off to produce a polyimide film. The physical properties of the polyimide film were as follows: a glass transition temperature Tg of 250 C. and a tensile elastic modulus E of 2.40 GPa. The results of the AO resistance test and the outgas test performed on the produced polyimide film are shown in Table 3.

EXAMPLES 13 TO 15

[0102] A polyimide precursor solution was prepared in the same manner as in Example 12 except that the acid dianhydride (a) and the diamine (b) were changed to the compositions shown in Table 1, and then a polyimide film was produced. The numerals in Table 1 indicate the ratio of the amount of the acid dianhydride or diamine used (mol) to the amount of the acid dianhydride used (mol).

[0103] The results of the AO resistance test and the outgas test performed on the produced polyimide films are shown in Table 3.

TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Acid dianhydride DSDA 1 1 1 Acid dianhydride ODPA 1 1 1 1 Acid dianhydride BPDA 1 1 1 1 Acid dianhydride PMDA 1 1 1 1 Silicon-containing diamine A 0.77 0.6 0.3 0.77 0.3 0.77 0.3 0.77 0.3 0.77 0.3 0.3 0.77 0.3 0.77 Aromatic diamine BAPP 0.23 0.4 0.7 0.23 0.7 0.23 0.7 0.7 0.23 Aromatic diamine BAFL 0.23 0.7 0.23 0.7 0.7 0.23 Note: The numerals in the table indicate the mole ratio relative to acid dianhydride.

TABLE-US-00002 TABLE 2 Comparative Example 1 2 3 4 5 6 7 Acid dianhydride 1 1 1 1 1 1 DSDA Acid dianhydride 1 ODPA Silicon-containing 0.77 0.77 0.77 diamine B Silicon-containing 0.77 diamine C Silicon-containing 0.77 diamine D Silicon-containing 0.77 diamine E Silicon-containing 0.77 diamine F Aromatic diamine 0.23 0.23 0.23 0.23 0.23 0.23 BAPP Aromatic diamine 0.23 BAFL Note: The numerals in the table indicate the mole ratio relative to acid dianhydride.

TABLE-US-00003 Example 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 AO irradiation dose 3 3 3 6 6 6 1 1 1 3 3 3 3 3 3 [atoms/cm.sup.2] 10.sup.20 10.sup.20 10.sup.20 10.sup.20 10.sup.20 10.sup.20 10.sup.21 10.sup.21 10.sup.21 10.sup.20 10.sup.20 10.sup.20 10.sup.20 10.sup.20 10.sup.20 Mass reduction rate 0.17 0.16 0.15 0.19 0.19 0.17 0.17 0.24 0.21 0.14 0.16 0.19 0.17 0.28 0.17 [%] before and after irradiation Change rate [%] of 3 3.2 1.1 3.9 3.1 3.1 0 1 4.2 2.3 1.5 1.2 1.8 1.3 1.8 solar absorptance before and after irradiation Change rate [%] of 0.2 0.5 0.2 0.3 0 1.2 0.7 1 0.7 0.6 0.3 0.1 0.3 0 0.4 normal infrared emittance before and after irradiation Outgas test result Good Good Good Good Good Good Good Good Good Good Good Good Good Good Good

TABLE-US-00004 TABLE 4 Comparative Example 1 2 3 4 5 6 7 AO irradiation dose 3 3 3 6 6 6 1 [atoms/cm.sup.2] 10.sup.20 10.sup.20 10.sup.20 10.sup.20 10.sup.20 10.sup.20 10.sup.21 Mass reduction rate [%] 0.43 0.62 0.53 0.75 0.85 0.93 0.73 before and after irradiation Outgas test result Poor Poor Poor Poor Poor Poor Poor

[0104] As is clear from the results of the Examples and the Comparative Examples, the polyimide film for a spacecraft of the present invention exhibits a small mass reduction due to AO irradiation, a small change in solar absorptance due to AO irradiation, and a small change in normal infrared emittance due to AO irradiation. Further, the polyimide film for a spacecraft of the present invention generated a small amount of outgas upon heating.

[0105] That indicates that the polyimide film for a spacecraft of the present invention is suitable as a member of a spacecraft (e.g., an artificial satellite or a space station) used in a low-altitude orbit, such as a solar battery panel structure for a low-earth-orbit satellite or a thermal blanket for a low-earth-orbit satellite.

INDUSTRIAL APPLICABILITY

[0106] The polyimide film for a spacecraft of the present invention can be suitably used as a member for a spacecraft in particular.