JP4214531B2 - Soluble end-modified imide oligomer and varnish and cured product thereof - Google Patents

Description

  TECHNICAL FIELD The present invention relates to terminal-modified imide oligomers and varnishes and cured products thereof, and particularly relates to materials for members that can be used in a wide range of fields that require easy moldability and high heat resistance, including aircraft and space industry equipment. .

Aromatic polyimide is a polymer-based material that has the highest level of heat resistance and is excellent in mechanical properties and electrical properties, and is therefore used as a material in a wide range of fields.
On the other hand, aromatic polyimide is generally poor in processability, and is not particularly suitable for use as a matrix resin for melt molding or fiber reinforced composite materials. For this reason, an imide oligomer having a terminal modified with a thermal crosslinking group has been proposed. Among them, an imide oligomer having a terminal modified with 4- (2-phenylethynyl) phthalic anhydride is considered to have an excellent balance of moldability, heat resistance, and mechanical properties. For example, Patent Document 1, Patent Document 2, and Non-Patent Document It is introduced in Patent Document 1 and Non-Patent Document 2. Patent Document 1 aims to provide a terminal-modified imide oligomer having excellent heat resistance and mechanical properties of the cured product and high practicality, and 2,3,3 ′, 4′-biphenyl. A terminal-modified imide oligomer obtained by reacting tetracarboxylic dianhydride, an aromatic diamine compound and 4- (2-phenylethynyl) phthalic anhydride, having a logarithmic viscosity of 0.05 to 1, and a cured product thereof. It is disclosed. As an effect of the invention, a novel terminal-modified imide oligomer having high practicality can be obtained, and a novel terminal-modified polyimide having excellent mechanical properties such as heat resistance, elastic modulus, tensile strength and elongation can be obtained. It is described that a cured product can be obtained.

However, these terminal-modified imide oligomers are used in an organic solvent such as N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) at room temperature (in this specification, room temperature means 23 ° C. ± 2 ° C.). However, when this varnish is stored, it often gels after several days, and it is difficult to stably store a high concentration varnish for a long period of time. have. In addition, as one of the means for increasing the solubility, there is a method of introducing a structure having high flexibility, but in this case, the heat resistance of the cured product is generally lowered.
Japanese Patent No. 3551846 Special table 2003-526704 gazette PM Hergenrother and JG Smith Jr., Polymer, 35, 4857 (1994). R. Yokota, S. Yamamoto, S. Yano, T. Sawaguchi, M. Hasegawa, H. Yamaguchi, H. Ozawa and R. Sato, High Perform. Polym., 13, S61 (2001).

  The present invention is a novel terminal-modified imide that is excellent in moldability such as solubility in organic solvents, solution storage stability and low melt viscosity, and has high mechanical properties such as heat resistance and elastic modulus, tensile strength and elongation of cured products. An object is to provide oligomers and varnishes and cured products thereof.

（式中、Ｒ_１およびＲ_２は２価の芳香族ジアミン残基を、Ｒ_３は３，３’，４，４’−ビフェニルテトラカルボン酸類残基を表す。ｍおよびｎは、ｍ≧１、ｎ≧０、１≦ｍ＋ｎ≦２０および０．０５≦ｍ／（ｍ＋ｎ）≦１の関係を満たし、繰り返し単位の配列はブロック的、ランダム的のいずれであってもよい。）
上記１ヶ月以上の溶液保存安定性とは、有機溶媒Ｎ−メチル−２−ピロリドンに対して室温で溶解した状態で保存して、少なくとも１ヶ月経過までゲル化しないことをいう。 Terminal-modified imide oligomer of the present invention for solving the above-3,3 ', 4,4'-biphenyltetracarboxylic acid compounds 9,9-bis (4- (4-aminophenoxy) phenyl) aromatic containing fluorene Represented by the following general formula (1) obtained by reacting an aromatic diamine with 4- (2-phenylethynyl) phthalic anhydride, and a solid content concentration of 30 wt.% With respect to the organic solvent N-methyl-2-pyrrolidone at room temperature. It is a terminal-modified imide oligomer that can be dissolved in an amount of not less than 1% and has a solution storage stability of not less than 1 month.

(In the formula, R ₁ and R ₂ represent a divalent aromatic diamine residue, R ₃ represents a 3,3 ′, 4,4′-biphenyltetracarboxylic acid residue, and m and n are m ≧ 1. N ≧ 0, 1 ≦ m + n ≦ 20 and 0.05 ≦ m / (m + n) ≦ 1 are satisfied, and the arrangement of repeating units may be either block or random.)
The solution storage stability of 1 month or more means that the solution is stored in an organic solvent N-methyl-2-pyrrolidone in a dissolved state at room temperature and does not gel at least for one month.

Moreover, this invention provides the varnish containing the terminal modified imide oligomer represented by Formula (1).
Moreover, this invention provides the hardened | cured material obtained by heat-curing the terminal modified imide oligomer or its varnish represented by Formula (1).

  According to the present invention, a novel terminal-modified imide having excellent moldability such as solubility in organic solvents, solution storage stability and low melt viscosity, and high mechanical properties such as heat resistance and elastic modulus, tensile strength and elongation of the cured product Oligomers and varnishes and cured products thereof can be obtained. Since this imide oligomer varnish is greatly superior in hydrolysis resistance compared to an amic acid oligomer varnish, it can be stored stably for a long period of time without causing a decrease in viscosity.

The compounds of general formula terminal-modified imide oligomer represented by (1) is 3,3 ', 4,4'-biphenyltetracarboxylic acid compounds and 9,9-bis (4- (4-aminophenoxy) phenyl) Aromatic diamines containing fluorene and 4- (2-phenylethynyl) phthalic anhydride (hereinafter sometimes abbreviated as PEPA) are roughly equivalent to the total equivalent of each acid group and the equivalent of each amino group. An imide oligomer obtained by reacting in a solvent, preferably based on 4- (2-phenylethynyl) phthalic anhydride at the terminal (preferably both terminals) of the imide oligomer. It has an acetylene addition-polymerizable unsaturated end group and an imide bond in the main chain of the imide oligomer, and is preferably a solid at room temperature (23 ° C.) having a relatively low molecular weight satisfying the relationship of 1 ≦ m + n ≦ 20 ( A terminal-modified imide oligomer of the end shape). Furthermore, a terminal-modified imide oligomer that can be dissolved in an organic solvent such as NMP at a solid content of 30% by weight or more at room temperature is preferable. Furthermore, the terminal modified imide oligomer whose glass transition temperature (Tg) after hardening is 300 degreeC or more is preferable. Furthermore, the terminal modified imide oligomer whose tensile fracture elongation of the film after hardening is 10% or more is preferable.

  The 3,3 ′, 4,4′-biphenyltetracarboxylic acids are 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride Product (s-BPDA), or an acid derivative such as an ester or salt of 3,3 ′, 4,4′-biphenyltetracarboxylic acid, in particular, 3,3 ′, 4,4′-biphenyltetracarboxylic acid Anhydrides are optimal.

  Part of the 9,9-bis (4- (4-aminophenoxy) phenyl) fluorene (preferably not more than 50 mol%, particularly preferably not more than 25 mol%) is used as another aromatic diamine compound such as 1, 4-diaminobenzene, 1,3-diaminobenzene, 1,2-diaminobenzene, 2,6-diethyl-1,3-diaminobenzene, 4,6-diethyl-2-methyl-1,3-diaminobenzene, 3 , 5-diethyltoluene-2,6-diamine, 4,4′-diaminodiphenyl ether (4,4′-ODA), 3,4′-diaminodiphenyl ether (3,4′-ODA), 3,3′-diamino Diphenyl ether, 3,3′-diaminobenzophenone, 4,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 4,4′-diamino Phenylmethane, bis (2,6-diethyl-4-aminophenyl) methane, 4,4'-methylene-bis (2,6-diethylaniline), bis (2-ethyl-6-methyl-4-aminophenyl) Methane, 4,4′-methylene-bis (2-ethyl-6-methylaniline), 2,2-bis (3-aminophenyl) propane, 2,2-bis (4-aminophenyl) propane, 1,3 -Bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, benzidine 3,3′-dimethylbenzidine, 2,2-bis (4-aminophenoxy) propane, 2,2-bis (3-aminophenoxy) propane, 2,2-bis [4 ′ (4 '' - aminophenoxy) phenyl] hexafluoropropane, 9,9-bis (4-aminophenyl) can be replaced by and fluorene may be used in combination thereof alone, or two or more. In particular, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, or 1,3-bis (4-aminophenoxy) benzene is preferable as the aromatic diamine compound.

  In the present invention, 4- (2-phenylethynyl) phthalic anhydride is used as the unsaturated acid anhydride for terminal modification (end cap). The 4- (2-phenylethynyl) phthalic anhydride is preferably used in a proportion within the range of 5-200 mol%, particularly 5-150 mol%, based on the total amount of acids.

  Examples of the solvent include N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAc), N, N-diethylacetamide, N-methylcaprolactam, γ-butyrolactone (GBL), cyclohexanone, and the like. It is done. These solvents may be used alone or in combination of two or more. With respect to the selection of these solvents, known techniques for soluble polyimides can be applied.

  Since these imide oligomer varnishes have no fear of hydrolysis, they can be stably stored for a long period of time without causing a decrease in viscosity or the like as compared with an amic acid oligomer varnish. As a solvent for long-term storage, it is desirable to use an amide solvent such as N-methyl-2-pyrrolidone, which is a good solvent, in order to prevent gelation.

Hereinafter, an example of the manufacturing method will be described.
The terminal-modified imide oligomer of the present invention includes, for example, the aforementioned 3,3 ′, 4,4′-biphenyltetracarboxylic acid (particularly, this acid dianhydride) and 9,9-bis (4- (4-amino). Aromatic diamines containing phenoxy) phenyl) fluorene, and 4- (2-phenylethynyl) phthalic anhydride, the total amount of acid anhydride groups (or adjacent dicarboxylic acid groups) of all components and the total amount of amino groups Using each component in an approximately equal amount, each component is polymerized in the above-mentioned solvent at a reaction temperature of about 100 ° C. or lower, particularly 80 ° C. or lower to produce an “oligomer having an amide-acid bond”. Then, the amidic acid oligomer (also referred to as an amic acid oligomer) is added by a method of adding an imidizing agent at a low temperature of about 0 to 140 ° C. or by a method of heating to a high temperature of 140 to 275 ° C. By dehydration and cyclization, it is possible to obtain a terminal to 4- (2-phenylethynyl) imide oligomer having a phthalic anhydride residue.

As a particularly preferred production method of the terminal-modified imide oligomer of the present invention, for example, aromatic diamines containing 9,9-bis (4- (4-aminophenoxy) phenyl) fluorene are uniformly dissolved in the aforementioned solvent, and then 3 , 3 ′, 4,4′-biphenyltetracarboxylic dianhydride is added to the solution and uniformly dissolved, and then stirred at a reaction temperature of about 5 to 60 ° C. for about 1 to 180 minutes. (2-Phenylethynyl) phthalic anhydride is added and dissolved uniformly, and then reacted with stirring at a reaction temperature of about 5 to 60 ° C. for about 1 to 180 minutes to produce the terminal-modified amic acid oligomer. The solution is stirred at 140 to 275 ° C. for 5 minutes to 24 hours to imidize the amic acid oligomer to form a terminal-modified imide oligomer. If necessary, the reaction solution is cooled to near room temperature. It can be mentioned. In the above reaction, it is preferable that all or some of the reaction steps are performed in an atmosphere of an inert gas such as nitrogen gas or argon gas or in a vacuum.

  The terminal-modified imide oligomer produced as described above can be isolated by pouring the reaction solution into water or the like, if necessary, and isolated as a powdery product, or as a powdery product or when necessary. You may use it, melt | dissolving in a solvent, and you may use it as a solution composition (varnish) of a terminal-modified imide oligomer by making a reaction liquid as it is, or concentrating or diluting suitably. The terminal-modified oligomer of the present invention may be a mixture of different molecular weights. Moreover, you may mix the terminal modified imide oligomer of this invention with another soluble polyimide.

The cured product of the terminal-modified imide oligomer of the present invention can be obtained, for example, by coating the above-mentioned terminal-modified imide oligomer varnish on a support and heating and curing at 280 to 500 ° C. for 5 to 200 minutes. Further, the terminal-modified imide oligomer powder is filled in a mold such as a mold, and a preform is formed by compression molding at 1 to 1000 kg / cm ² at 10 to 280 ° C. for about 1 second to 100 minutes. The preform can be heated at 280 to 500 ° C. for about 10 minutes to 40 hours to obtain a cured product.

The following examples are given to illustrate the invention, but are not intended to limit the invention. The measurement conditions for each characteristic were as follows.
Test method (1) Infrared spectroscopic analysis (IR): Measured by KBr tablet method using FT / IR610 type manufactured by JASCO Corporation.
(2) Thermogravimetric analysis: A TGA-6300 type thermogravimetric analyzer (TGA) manufactured by Seiko Instruments Inc. was used at 10 ° C./min. It measured with the temperature increase rate of.
(3) Glass transition temperature: DSC-6200 type differential scanning calorimeter (DSC) manufactured by Seiko Instruments Inc. was used at 10 ° C./min. It measured with the temperature increase rate of.
(4) Rheology measurement: AR2000 type rheometer manufactured by TA Instruments, using a 25 mm parallel plate and 4 ° C./min. It measured with the temperature increase rate of.
(5) Tensile test: TENSILON / UTM-II-20 manufactured by Orientec Corporation was used at room temperature at a tensile rate of 5 mm / min. The shape of the test piece was a film having a length of 20 mm, a width of 3 mm, and a thickness of 100 to 120 μm.

Example 1
To a three-necked 100 mL flask equipped with a thermometer, a stirrer, and a nitrogen inlet tube, 2.663 g (5 mmol) of 9,9-bis (4- (4-aminophenoxy) phenyl) fluorene and N-methyl-2- Add 8.8 mL of pyrrolidone and dissolve, and then add 1.177 g (4 mmol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride at room temperature for 2.5 hours at 60 ° C. under a nitrogen stream. The polymerization reaction was carried out for 1.5 hours and further at room temperature for 1 hour to produce an amic acid oligomer. To this reaction solution, 0.497 g (2 mmol) of 4- (2-phenylethynyl) phthalic anhydride was added and reacted at room temperature for 18 hours in a nitrogen stream, followed by terminal modification, followed by stirring at 175 ° C. for 5 hours for imide bonding. It was. In the terminal-modified imide oligomer obtained, R ₁ is represented by a fluorenylidene diphenyl ether group in the general formula (1), and m = 4 and n = 0 on average. After cooling, the reaction solution was poured into 200 mL of ion exchange water, and the precipitated powder was separated by filtration. The powder obtained by washing with 80 mL of methanol for 30 minutes and filtering was dried under reduced pressure at 60 ° C. for 1 day to obtain a product.
Yield: 4.120 g (99%).
IR (KBr, cm ⁻¹ ): 3482, 2211, 1775, 1720, 1685, 1615, 1597, 1560, 1542, 1498, 1446, 1420, 1374, 1290, 1239, 1170, 1112, 1085, 1014, 942, 915 , 876, 826, 779, 739, 691, 673
The uncured product of the terminal-modified imide oligomer obtained above was soluble in NMP solvent by 30% or more at room temperature, and no gelation was observed even after one month. The minimum melt viscosity before curing was 3260 poise (347 ° C.). A film-like cured product (thickness: 119 μm) obtained by heating this terminal-modified imide oligomer at 370 ° C. for 1 hour using a hot press has a Tg of 321 ° C. (DSC) and a 5% weight loss temperature by TGA is It was 551 degreeC. In addition, the mechanical properties of the cured product in the form of a film were as follows: the elastic modulus was 2.78 GPa, the breaking strength was 110 MPa, and the breaking elongation was 10.2%.

(Example 2 )
In a three-necked 100 mL flask equipped with a thermometer, a stirrer, and a nitrogen inlet tube, 2.131 g (4 mmol) of 9,9-bis (4- (4-aminophenoxy) phenyl) fluorene, 4,4′-diamino was added. Add 0.200 g (1 mmol) of diphenyl ether and 8.1 mL of N-methyl-2-pyrrolidone, dissolve, and then add 1.177 g (4 mmol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride; Under a nitrogen stream, polymerization reaction was carried out at room temperature for 2.5 hours, at 60 ° C. for 1.5 hours, and further at room temperature for 1 hour to produce an amic acid oligomer. To this reaction solution, 0.497 g (2 mmol) of 4- (2-phenylethynyl) phthalic anhydride was added and reacted at room temperature for 18 hours in a nitrogen stream, followed by terminal modification, followed by stirring at 175 ° C. for 5 hours for imide bonding. It was. The obtained terminal-modified imide oligomer has the above general formula (1), wherein R ₁ is a fluorenylidene diphenyl ether group, R ₂ is a diphenyl ether group, and R ₃ is 3,3 ′, 4,4′-biphenyltetracarboxylic acid. It is represented by an acid dianhydride residue , and m = 3 and n = 1 on average. After cooling, the reaction solution was poured into 200 mL of ion exchange water, and the precipitated powder was separated by filtration. The powder obtained by washing with 80 mL of methanol for 30 minutes and filtering was dried under reduced pressure at 60 ° C. for 1 day to obtain a product.
Yield: 3.910 g (98%).
IR (KBr, cm ⁻¹ ): 3481, 2111, 1775, 1720, 1615, 1597, 1542, 1498, 1447, 1420, 1374, 1290, 1239, 1171, 1112, 1086, 1014, 942, 915, 876, 828 , 740, 690, 674
The uncured product of the terminal-modified imide oligomer obtained above was soluble in NMP solvent by 30% or more at room temperature, and no gelation was observed even after one month. The minimum melt viscosity before curing was 2330 poise (343 ° C.). The film-like cured product (thickness 106 μm) obtained by heating this terminal-modified imide oligomer at 370 ° C. for 1 hour using a hot press has a Tg of 326 ° C. (DSC) and a 5% weight loss temperature by TGA is It was 553 ° C. Further, the mechanical properties of the cured product in the form of a film were as follows: the elastic modulus was 2.74 GPa, the breaking strength was 111 MPa, and the breaking elongation was 11.1%.

(Comparative Example 1)
To a three-necked 100 mL flask equipped with a thermometer, a stirrer, and a nitrogen introduction tube, 2.002 g (10 mmol) of 4,4′-diaminodiphenyl ether and 16 mL of N-methyl-2-pyrrolidone were added and dissolved, 2.354 g (8 mmol) of 3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added and polymerization reaction was performed under a nitrogen stream for 2.5 hours at room temperature, 1.5 hours at 60 ° C., and 1 hour at room temperature. To produce an amic acid oligomer. To this reaction solution, 0.993 g (4 mmol) of 4- (2-phenylethynyl) phthalic anhydride was added and reacted at room temperature for 18 hours under a nitrogen stream, followed by terminal modification, followed by stirring at 175 ° C. for 5 hours for imide bonding. It was. Precipitation of imide oligomers was observed during the imidization reaction. After cooling, the reaction solution was poured into 120 mL of ion exchange water, and the precipitated powder was separated by filtration. The powder obtained by washing with 60 mL of methanol for 30 minutes and filtered off was dried under reduced pressure at 60 ° C. for 1 day to obtain a product.
Yield: 4.834 g (97%)
IR (KBr, cm ⁻¹ ): 3482, 2212, 1774, 1719, 1616, 1559, 1542, 1500, 1458, 1420, 1376, 1290, 1241, 1171, 1116, 1087, 1015, 943, 880, 832, 762 , 740, 690, 673
The uncured product of the terminal-modified imide oligomer obtained above was insoluble in the NMP solvent. Since this terminal-modified imide oligomer did not show melt fluidity even at 300 ° C. or higher, a good molded product (film-like cured product) could not be obtained.

  The present invention is excellent in moldability such as solubility in organic solvents, solution storage stability and low melt viscosity, can be easily formed into a film, and has mechanical properties such as heat resistance and elastic modulus, tensile strength and elongation of the cured product. These are highly terminally modified imide oligomers and varnishes, and cured products thereof, which can be used in a wide range of fields that require easy moldability and high heat resistance, including aircraft and space industry equipment.

Claims (6)

Aromatic diamines including 3,3 ′, 4,4′-biphenyltetracarboxylic acids and 9,9-bis (4- (4-aminophenoxy) phenyl) fluorene and 4- (2-phenylethynyl) phthalic anhydride It is represented by the following general formula (1) obtained by reacting with the above, and can be dissolved in an organic solvent N-methyl-2-pyrrolidone at a solid content concentration of 30 wt% or more at room temperature, and can be stored stably for 1 month or more. Terminal-modified imide oligomer having properties.

(In the formula, R ₁ and R ₂ represent a divalent aromatic diamine residue, R ₃ represents a 3,3 ′, 4,4′-biphenyltetracarboxylic acid residue, and m and n are m ≧ 1. N ≧ 0, 1 ≦ m + n ≦ 20 and 0.05 ≦ m / (m + n) ≦ 1 are satisfied, and the arrangement of repeating units may be either block or random.)   A varnish obtained by dissolving the terminal-modified imide oligomer according to claim 1 in an organic solvent.   Hardened | cured material obtained by heat-curing the terminal modified imide oligomer of Claim 1.   Hardened | cured material obtained by heat-curing the varnish of Claim 2.   The hardened | cured material of Claim 3 or 4 whose glass transition temperature (Tg) is 300 degreeC or more.   The cured product according to claim 3 or 4, wherein the elongation at break in a film shape is 10% or more.