Curable fluorine containing polyimide

Abstract: A curable fluorine-containing polyimide of the formula: wherein R¹ is a group derived from an aromatic tetracarbo­ xylic acid dianhydride by the removal of two acid anhydride groups, R² is a group derived from an aromatic diamine by the removal of two amino groups, A¹ is a residue of the formula: [wherein R² is the same as defined above, and Z is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms], A² is a residue of the formula: [wherein R¹ and Z are the same as defined above], and n is a number of 0 to 90, and at least one of the groups R¹ and R² in the formula (I) contains a substituted methylene group of the formula: [wherein X is a residue of the formula: -(CH₂) p (CHF) q ( O) r (CF₂O) s (CF₂CF₂CF₂O) t R′f wherein Rf is a perfluoroalkyl group having 1 to 10 carbon atoms, R′f is a perfluoroalkyl group having 1 to 12 carbon atoms, p is an integer of 1 to 3, q is an integer of 0 to 3, r is 0 or 1, s is an integer of 0 to 5 and t is an integer of 0 to 5, and Y is the same as X or a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a fluoroalkyl group having 1 to 8 carbon atoms].

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a novel curable fluorine-containing polyimide which is useful for preparing a cured resin showing high heat- and moisture-resistance and having a low refractive index and a low dielectric constant. Description of the Related Art The following compound, for example, has been known as a curable fluorine-containing polyimide having terminal unsaturated groups: wherein D is a group derived from a diamine by the removal of two amino groups, and n is 1.0 on an average (cf. 18th International SAMPE Technical Conference, October 7 to 9, 1986, pages 710 to 721). A cured resin prepared from such a fluorine-containing polyimide may be unsatisfactorily applied on electronic or optical parts due to its inadequate moisture resistance, a high refractive index and a high dielectric constant. SUMMARY OF THE INVENTION An object of the present invention is to provide a curable fluorine-containing polyimide which is useful for preparing a cured resin showing high moisture resistance and having a low refractive index and a low dielectric constant. The present invention provides a curable fluorine-containing polyimide of the formula: wherein R¹ is a group derived from an aromatic tetracarboxylic acid dianhydride by the removal of two acid anhydride groups, R² is a group derived from an aromatic diamine by the removal of two amino groups, A¹ is a residue of the formula: [wherein R² is the same as defined above, and Z is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms], A² is a residue of the formula: [wherein R¹ and Z are the same as defined above], and n is a number of 0 to 90, and at least one of the groups R¹ and R² in the formula (I) contains a substituted methylene group of the formula: [wherein X is a residue of the formula: wherein Rf is a perfluoroalkyl group having 1 to 10 carbon atoms, R′F is a perfluoroalkyl group having 1 to 12 carbon atoms, p is an integer of 1 to 3, g is an integer of 0 to 3, r is 0 or 1, s is an integer of 0 to 5 and t is an integer of 0 to 5, and Y is the same as X or a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a fluoroalkyl group having 1 to 8 carbon atoms]. DETAILED DESCRIPTION OF THE INVENTION The present fluorine-containing polyimide includes the compounds of the following formulae: wherein R¹, R², Z and n are the same as defined above. Examples of the polyimide of the present invention are shown as follows: wherein n is the same as defined above. The present fluorine-containing polyimide has a substituted methylene group of the following formula between aromatic rings in the repeating unit: wherein X and Y are the same as defined above. When n is 0 in the formula (I), the substituted methylene group should be contained in R¹ in the formula (I-1) and in R² in the formulae (I-2) and (I-3). When n is not 0, at least one of the groups R¹ and R² in the main chain in the formula (I) should contain the substituted methylene group. The groups R¹ and R² each containing the substituted methylene group can be represented as follows, respectively: wherein X and Y are the same as defined above. The present compound may have the following groups, for example, as R¹: [wherein X and Y are the same as defined above], [wherein R³ is -O-, -CO-, -C(CH₃)₂-, -C(CF₃)₂- or -Si(CH₃)₂-], [wherein R⁴ is -C₆H₄-, -C₆H₄-O-C₆H₄- or -C₆H₄-O-C₆H₄-O-C₆H₄-], and [wherein R⁵ is -O-, -O-(CH₂)₄-O-, -O-(CH₂)₆-O-, The following groups, for example, may be present as R²: [wherein X and Y are the same as defined above], [wherein R⁶ is -O-, -CO-, -S-, -CH₂-, -C(CH₃)₂-, -C(CF₃)₂-, -SO₂-, or -Si(CH₃)₂-, and [wherein R⁷ is -O-, -SO₂-, -CH₂-, -CO-, -C(CH₃)₂- or -S-]. The present compound (I-1) can be prepared according to the following reaction scheme: When n is not 0 : When n is 0 : The present fluorine-containing polyimide compounds (I-2) and (I-3) can be prepared according to the following reaction scheme. When n is not 0 : When n is 0 : The present compounds (I-4) and (I-5), wherein n is 0, can be prepared as follows: The present fluorine-containing polyimide (I-6) can be obtained by the same way as for the production of the compound (I-2) or (I-3) but that a mixture of is used. As shown in the reaction schemes, an amide acid is prepared as an intermediate. The reaction for the preparation of the amide acid is preferably carried out for 0.1 to 5 hours at a temperature in the range of from 0 to 15 °C, in particular 20 to 100 °C in a solvent such as tetrahydrofuran, acetone, dioxane, N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, diglyme, acetonitrile, 1,3-dimethyl-2-imidazolidinone or m-xylene hexafluoride with or without benzene, toluene or xylene. Then, the amide acid is cyclodehydrated to form the present fluorine-containing polyimide. In this reaction, a dehydrating agent such as acetic anhydride, phosphorous pentoxide or conc. sulfuric acid is used. The reaction is preferably carried out in the presence of a catalyst and a base in a solvent. An oxide of an alkaline earth metal, or a carbonate, acetate, phosphate or sulfate of Fe(II) or (III), Ni(II), Mn(II) or (III), Cu(I) or (II) or Co(II) or (III) can be used as the catalyst. The base is, for example, trimethylamine, triethylamine, tributylamine or sodium acetate. The solvent previously used in the preparation of the amide acid is preferably used as such in this reaction. The dehydrating agent is usually used in a 1 to 20 times molar amount per mol of the amide acid. The catalyst and the base are added, based on the amount of the amide acid, in an amount in the range of from 1 x 10⁻² to 1 x 10 mol % and in an amount in the range of from 5 to 150 mol %, respectively. It is preferred to carry out the reaction for 2 to 24 hours at a temperature in the range of from 100 to 250 °C, in particular from 120 to 280 °C. The present fluorine-containing polyimide compounds (I-1), (I-2) and (I-3) can be cured by heating at a temperature in the range of from 200 to 500 °C, preferably from 250 to 400 °C for 0.1 to 5 hours. Prior to curing, a compound containing an ethynyl or ethylene group, such as an acrylic, styrene, vinylether or vinylester compound may be added to the present compound. To the present compounds (I-2) and (I-3), a diamine compound can also be added. In addition, a filler may be added to the fluorine-containing polyimide. The filler used is, for example, calcium carbonate, silica, alumina, titania, aluminium hydroxide, aluminium silicate, zirconium silicate, zircon, glass, talc, mica, graphite, aluminium, copper or iron in a powder or short fibrous form. The present fluorine-containing polyimide can be molded by, for example, compression or transfer molding. The molding may be easily carried out by the addition of the filler. It is also possible to coat the present compound as a varnish on a substrate. The present fluorine-containing polyimide can be suitably used as a heat- and moisture-resistant material in, for example, a matrix resin for an aerospace structural material; a base resin for a heat resistant adhesive and a conductive adhesive; a rigid or flexible printed board material; a sealing agent for electric parts such as a semiconductor device; a passivation film; an interlayer insulating film; an α-ray blocking film; a protecting film on a surface against an external force; an insulating and reinforcing material for wire bonding parts; a masking material for ion implantation and lift-off; an oriented film for a liquid crystal display device; a sealing and protecting coating agent for optical parts such as a glass fiber and LED; and a protecting film for a solar battery. PREFERRED EMBODIMENTS OF THE INVENTION The invention is further illustrated by the following Examples. Example 1 To a stirred mixture of the compound (32.89 g; 0.04 mol) of the formula: with N-methylpyrrolidone (NMP; 60 ml) in a 200 ml three necked flask, a solution of 1,3-bis(3-aminophenoxy)benzene (APB; 5.85 g; 0.02 mol) in NMP (15 ml) was slowly dropwise added at a room temperature. After stirring for one hour at 50 °C, 3-aminophenylacetylene (APA; 5.04 g; 0.043 mol) in NMP (6 ml) was added and heated. Then, benzene was added and heated under reflux for 20 hours at 140 °C with removing water by a Dean-Stark condenser. The reaction solution was cooled to the room temperature and poured into ethyl alcohol to precipitate a reaction product. The reaction product was filtered and washed three times with ethyl alcohol to remove NMP. Then, ethyl alcohol was distilled off under a reduced pressure. After drying for 24 hours at 80 °C under a reduced pressure, the compound of the formula: wherein n is 1.0 on an average, was obtained. Yield: 32.43 g (0.015 mol; 77 %). The value n was calculated by a quantitative analysis of terminal acetylene according to L. Barnes, Jr., Anal. Chem., 31 (3), 405 (1959). ¹H-NMR (CDCl₃/TMS) δ [ppm]: 8.1 - 6.7 (m, 32H), 3.11 (s, 2H), 3.0 - 1.6 (broad, 8H). ¹⁹F-NMR CDCl₃/TFA) δ [ppm]: - 13.1 (s, 6F), 2.1 (t, 6F), 35.7 (broad, 4F), 43.0 (broad, 12F), 44.1 (broad, 8F), 47.3 (broad, 4F). IR, ν [cm⁻¹]: 3300, 1780, 1725, 1585, 1480, 1430, 1375, 1240, 1200, 1170, 1140, 1100, 1010, 980, 910, 870, 840, 790, 740, 720, 710. Example 2 In a 200 ml three necked flask, a mixture of the compound (41.12 g; 0.05 mol) of the formula: with APA (6.44 g; 0.055 mol) and NMP (70 ml) was stirred for one hour at 50 °C and then further heated. Then, to the mixture, toluene was added and heated under reflux for 15 hours at 140 °C with removing water by a Dean-Stark condenser. The reaction solution was cooled to a room temperature and poured into ethyl alcohol to precipitate a reaction product. The reaction product was filtered and washed three times with ethyl alcohol to remove NMP. Then, ethyl alcohol was distilled off under a reduced pressure. After drying for 24 hours at 80 °C under a reduced pressure, the compound of the formula: was obtained. Yield: 34.30 g (0.034 mol; 67 %). ¹H-NMR (CDCl₃/TMS) δ [ppm]: 8.1 - 7.2 (m, 14H), 3.11 (s, 2H), 3.0 - 1.6 (broad, 4H). ¹⁹F-NMR (CDCl₃/TFA) δ [ppm]: - 13.1 (s, 3F), 2.1 (t, 3F), 35.8 (broad, 2F), 43.1 (broad, 6F), 44.0 (broad, 4F), 47.3 (broad, 2F). IR, ν [cm⁻¹]: 3300, 1780, 1720, 1600, 1580, 1480, 1430, 1370, 1230, 1200, 1170, 1140, 1100, 1005, 970, 785, 740, 710, 700. Example 3 In a 200 ml three necked flask, a mixture of the compound (43.56 g; 0.07 mol) of the formula: with APA (8.79 g; 0.075 mol) and NMP (80 ml) was stirred for one hour at 50 °C and then further heated. Then, to the mixture, toluene was added and heated under reflux for 20 hours at 140 °C with removing water by a Dean-Stark condenser. The reaction solution was cooled to a room temperature and poured into ethyl alcohol to precipitate a reaction product. The reaction product was filtered and washed three times with ethyl alcohol to remove NMP. Then, ethyl alcohol was distilled off under a reduced pressure. After drying for 24 hours at 80 °C under a reduced pressure, the compound of the formula: was obtained. Yield: 41.33 g (0.050 mol; 72 %). ¹H-NMR (CDCl₃/TMS) δ [ppm]: 8.1 - 7.2 (m, 14H), 3.12 (s, 2H), 3.0 - 1.6 (broad, 4H). ¹⁹F-NMR (CDCl₃/TFA) δ [ppm]: - 13.3 (s, 3F), 2.3 (t, 3F), 35.2 (broad, 2F), 45.2 (broad, 2F), 47.3 (broad, 2F). IR, ν [cm⁻¹] : 3300, 1780, 1720, 1600, 1570, 1540, 1480, 1430, 1370, 1235, 1200, 1170, 1140, 1100, 1010, 970, 870, 790, 740, 710, 700. Example 4 In a 200 ml three necked flask, a mixture of the compound (41.30 g; 0.06 mol) of the formula: with APA (7.73 g; 0.066 mol) and NMP (70 ml) was stirred for one hour at 50 °C and then further heated. Then, to the mixture, toluene was added and heated under reflux for 15 hours at 140 °C with removing water by a Dean-Stark condenser. The reaction solution was cooled to a room temperature and poured into ethyl alcohol to precipitate a reaction product. The reaction product was filtered and washed three times with ethyl alcohol to remove NMP. Then, ethyl alcohol was distilled off under a reduced pressure. After drying for 24 hours at 80 °C under a reduced pressure, the compound of the formula: was obtained. Yield: 39.69 g (0.045 mol; 75 %). ¹H-NMR CDCl₃/TMS) δ [ppm]: 8.1 - 7.1 (m, 14H), 3.11 (s, 2H), 3.0 - 1.6 (broad, 4H). ¹⁹F-NMR (CDCl₃/TMS) δ [ppm]: - 12.2 (s, 3F), 2.9 (t, 3F), 3.1 (broad, 2F), 4.7 (d, 3F), 51.3 (broad, 1F), 52.8 (s, 2F). IR, ν [cm⁻¹]: 3300, 1780, 1720, 1600, 1570, 1480, 1430, 1370, 1230, 1200, 1160, 1005, 970, 840, 750. Example 5 To a stirred mixture of the compound (35.62 g; 0.05 mol) of the formula: with m-xylene hexafluoride (m-XHF; 150 ml) In a 500 ml four necked frask, a solution of maleic anhydride (12.7 g; 0.13 mol) in m-XHF (150 ml) was slowly dropwise added at 50 °C and then stirred for 30 minutes at the same temperature. Then, benzyltrimethylammonium chloride (BTMAC; 0.5 g), Ni(OAc)₂·4H₂O (0.5 g) and conc. sulfuric acid (1.2 ml) were added to the reaction mixture and heated under reflux for 10 hours with removing water by a Dean-Stark condenser. An organic phase was neutralized with an aqueous Na₂CO₃ solution, washed two times with an aqueous NaCl solution and dried over anhydrous Na₂SO₄. Then, m-XHF was distilled off under a reduced pressure to obtain the compound of the formula: Yield: 28.10 g (0.032 mol; 64 %). ¹H-NMR (CDCl₃/TMS) δ [ppm]: 7.43 (s, 8H), 6.88 (s, 4H), 3.0 - 1.5 (broad, 4H). ¹⁹F-NMR CDCl₃/TFA) δ [ppm]: - 12.8 (s, 3F), 2.2 (t, 3F), 35.9 (broad, 2F), 43.1 (broad, 6F), 43.7 (broad, 4F), 47.3 (broad, 2F). IR, ν [cm⁻¹]: 3500, 1720, 1610, 1520, 1400, 1380, 1200, 1140, 1060, 1020, 1000, 970, 950, 830, 700. Example 6 To a stirred mixture of the compound (35.62 g; 0.05 mol) of the formula: with m-XHF (150 ml) in a 500 ml four necked frask, a solution of 5-norbornene-2,3-dicarboxylic anhydride (21.3 g; 0.13 mol) in m-XHF was slowly dropwise added at 50 °C and then stirred for 30 minutes at the same temperature. Then, BTMAC (0.5 g), Ni(OAc)₂·4H₂O (0.5 g) and conc. sulfuric acid (1.2 ml) were added to the reaction mixture and heated under reflux for 10 hours with removing water by a Dean-Stark condenser. An organic phase was neutralized with an aqueous Na₂CO₃ solution, washed two times with an aqueous NaCl solution and dried over anhydrous Na₂SO₄. Then, m-XHF was distilled off under a reduced pressure to obtain the compound of the formula: Yield: 34.66 g (0.035 mol; 69 %). ¹H-NMR (CDCl₃/TMS) δ [ppm]: 7.25 (q, 8H), 6.23 (s, 4H), 3.43 (m, 8H), 3.1 - 1.6 (broad, 4H), 1.7 (q, 4H). ¹⁹F-NMR (CDCl₃/TMS) δ [ppm]: - 13.0 (s, 3F), 2.2 (t, 3F), 35.8 (broad, 2F), 43.1 (broad, 6F), 44.0 (broad, 4F), 47.4 (broad, 2F). IR, ν [cm⁻¹]: 3400, 1710, 1510, 1375, 1200, 1170, 1140, 1000, 820, 720, 700. Example 7 A 50 % by weight solution of the present fluorine-containing polyimide of Example 1 in NMP was casted on a stainless steel plate and heated for 20 minutes at 80 °C, 20 minutes at 150 °C and then one hour at 250 °C to form a cured resin. The obtained resin was subjected to the following examinations. As a comparison, a fluorine-containing polyimide of the formula: wherein n is 1.0 on an average, was used. (i) Water absorption A specimen (76.2 mm x 25.4 mm x 50 µm) of the cured resin was dried for 24 hours at 50 ± 3 °C, cooled in a desiccator and then weighed (W₁). The specimen was immersed in distilled water at 23 ± 1 °C for 24 hours. Then, after wiping water off, the specimen was weighed (W₂). The water absorption (A) of the resin was calculated as follows: (ii) Refractive index A refractive index of the cured resin was measured at 23 °C by using an Abbe refractometer. The results are shown in the following Table 1. Resin Water absorption Refractive index (n D ²³) Example 1 0.25 1.468 Comparison 1.4 1.617 It was found that the refractive index of the present compound of Example 1 approximated to that of quartz (n D ²³ = 1.46).

Claims: A curable fluorine-containing polyimide of the formula: wherein R¹ is a group derived from an aromatic tetracarboxylic acid dianhydride by the removal of two acid anhydride groups, R² is a group derived from an aromatic diamine by the removal of two amino groups, A¹ is a residue of the formula: [wherein R² is the same as defined above, and Z is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms], A² is a residue of the formula: [wherein R¹ and Z are the same as defined above], and n is a number of 0 to 90, and at least one of the groups R¹ and R² in the formula (I) contains a substituted methylene group of the formula: [wherein X is a residue of the formula: wherein Rf is a perfluoroalkyl group having 1 to 10 carbon atoms, R′F is a perfluoroalkyl group having 1 to 12 carbon atoms, p is an integer of 1 to 3, q is an integer of 0 to 3, r is 0 or 1, s is an integer of 0 to 5 and t is an integer of 0 to 5, and Y is the same as X or a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a fluoroalkyl group having 1 to 8 carbon atoms]. The polyimide according to claim 1, which is a compound selected from the group consisting of the compounds of the formulae: wherein R¹, R², Z and n are the same as defined above. The polyimide according to claim 2, wherein, when n is 0 in the formula (I), the substituted methylene group should be contained in R¹ in the formula (I-1) and in R² in the formulae (I-2) and (I-3). The polyimide according to claim 2, wherein, when n is not 0, at least one of the groups R¹ and R² in the main chain in the formula (I) should contain the substituted methylene group.

Inventors: KOBAYASHI TSUTOMU, KUBO MOTONOBU, KOBAYASHI, TSUTOMU, KUBO, MOTONOBU
Applicants: DAIKIN IND LTD, DAIKIN INDUSTRIES, LIMITED
Application year: 1989
Main classification: C07D207
IPC codes: C07D209, C07D207, C07D487, C07D403, C08G73