JP2011184492A - Soluble terminally modified imide oligomer and varnish, and cured product thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a terminally modified imide oligomer having good solubility in an organic solvent and excellent storage stability and giving a cured product having excellent mechanical properties such as heat resistance, elastic modulus, and tension strength; and to provide a varnish. <P>SOLUTION: The terminally modified imide oligomer includes aromatic tetracarboxylic acids mainly containing 3,3', 4,4'-biphenyltetracarboxylic acids, aromatic diamine compounds mainly containing 2,4- and/or 2,6-tolylenediamine, and a terminal modifier having an unsaturated group such as 4-(2-phenylethynyl)phthalic anhydride. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to terminal-modified imide oligomers and varnishes and cured products thereof. In particular, a composite material obtained by thermosetting a fiber reinforced prepreg obtained by impregnating a fibrous reinforcing material with this terminal-modified imide oligomer is excellent in heat resistance, mechanical properties, etc., and suitable for applications such as aircraft and space industry equipment. It is.

  The terminal-modified imide oligomer is conventionally known as a matrix resin for molded products and fiber-reinforced composite materials because the cured product has excellent heat resistance. 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 discloses heat resistance of a cured product. And 3,3 ′, 4′-biphenyltetracarboxylic dianhydride and an aromatic diamine for the purpose of providing a terminal-modified imide oligomer having good properties and mechanical properties and high practicality and a cured product thereof A terminal-modified imide oligomer obtained by reacting a compound with 4- (2-phenylethynyl) phthalic anhydride and having a logarithmic viscosity of 0.05-1 and a cured product thereof are 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 in an organic solvent such as N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) at room temperature (herein, room temperature means 23 ° C. ± 2 ° C.). Only 20% by weight or less was dissolved, and it was difficult to obtain a highly concentrated solution composition (varnish). Moreover, when this varnish was stored, a phenomenon of gelation was often observed after several days, and there was a problem in storage stability.

  Patent Documents 2 and 3 disclose a terminal-modified imide oligomer having improved solubility in an organic solvent by using a diamine having a fluorene ring structure and a cured product thereof. It is described that the obtained terminal-modified imide oligomer has good solubility in NMP, and a varnish having a concentration of 40% by weight or more can be obtained. However, although the terminal-modified imide oligomer disclosed in Patent Document 2 has sufficient heat resistance of the cured product, when it is stored as a varnish, a gel often occurs in 1-2 months, and it is stored for a long time. It cannot be said that the stability is sufficient. In addition, the terminal-modified imide oligomer disclosed in Patent Document 3 does not generate a gel even when stored as a varnish for several months, but the cured product has a glass transition temperature (Tg) of 350 ° C. or less and is heat resistant. Is not good enough.

JP 2000-219741 A JP 2006-104440 A JP 2006-31699 A

  The present invention provides terminal-modified imide oligomers and varnishes having good solubility in organic solvents, excellent storage stability, and excellent heat resistance, elastic modulus, tensile strength, and other mechanical properties of cured products. With the goal.

但し、化学式（１）において、
Ｒ^ａは、その６０モル％以上が下記化学式（２）で示される４価のユニットであり、
Ｒ^ｂは、その６０モル％以上が下記化学式（３）で示される２価のユニットであり、
Ｘは、不飽和基を有する２価のユニットである。

The present invention is a terminal-modified imide oligomer represented by the following chemical formula (1) comprising a specific aromatic tetracarboxylic acid, an aromatic diamine compound or an aromatic diisocyanate compound, and a terminal modifier.

However, in chemical formula (1):
R ^a is a tetravalent unit of which 60 mol% or more is represented by the following chemical formula (2),
R ^b is a divalent unit of which 60 mol% or more is represented by the following chemical formula (3),
X is a divalent unit having an unsaturated group.

X in the chemical formula (1) is preferably a divalent unit selected from the group consisting of divalent units represented by the following chemical formula (4) and divalent units which are derivatives thereof.

  According to the present invention, there are provided terminal-modified imide oligomers and varnishes having excellent solubility in organic solvents, excellent long-term storage stability, and excellent mechanical properties such as heat resistance, elastic modulus and tensile strength of cured products. Can do. A composite material obtained by thermosetting a fiber reinforced prepreg obtained by impregnating a fibrous reinforcing material with the terminal-modified imide oligomer of the present invention is excellent in heat resistance, mechanical properties, etc., and suitable for applications such as aircraft and space industry equipment. It is.

  The terminal-modified imide oligomer represented by the general formula (1) of the present invention includes aromatic tetracarboxylic acids mainly composed of 3,3 ′, 4,4′-biphenyltetracarboxylic acids, 2,4- and / or Or an aromatic diamine compound containing 2,6-tolylenediamine as a main component or an aromatic diisocyanate compound containing 2,4- and / or 2,6-tolylene diisocyanate as a main component, and 4- (2-phenylethynyl) ) A terminal modifier having an unsaturated group, such as phthalic anhydride (hereinafter sometimes abbreviated as PEPA), and the total equivalent of each acid group and the equivalent of each amino group or each isocyanate group, etc. The amount is preferably obtained by reacting in a solvent.

  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.

  The aromatic tetracarboxylic acids used in the present invention preferably contain the above 3,3 ′, 4,4′-biphenyltetracarboxylic acids, preferably 60 mol% or more, particularly 85 mol% or more. Only ', 4,4'-biphenyltetracarboxylic acids can also be used. Examples of other aromatic tetracarboxylic acids used in combination include 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride (a-BPDA), 3,3 ′, 4,4′-benzophenone tetra Carboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), 2,2-bis (3,4-dicarboxyphenyl) methane dianhydride, bis (3,4-carboxyphenyl) ether dianhydride Such as things.

  The aromatic diamine compound used in the present invention preferably contains 2,4- and / or 2,6-tolylenediamine, preferably 60 mol% or more, particularly preferably 85 mol% or more. Alternatively, only 2,6-tolylenediamine can be used. Moreover, 2,4- and / or 2,6-tolylene diisocyanate, which is a derivative obtained by modifying these amino groups into isocyanate groups, can be used instead. Examples of other aromatic diamine compounds used in combination include 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′-diamino Diphenyl ether (3,4'-ODA), 3,3'-diaminodiphenyl ether, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 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) fluorene, etc. It is.

  The terminal modifying agent having an unsaturated group used in the present invention is a dicarboxylic acid having an unsaturated group for oligomeric amine terminal modification (end cap) or a derivative thereof, specifically 4- (2-phenylethynyl). Phthalic anhydride, tetrahydrophthalic anhydride or derivatives thereof, such as methyl tetrahydrophthalic anhydride, nadic anhydride or derivatives thereof, such as methyl nadic anhydride, oxy anhydride, dimethoxy nadic anhydride, hexachloro nadic anhydride, etc. Maleic acid or derivatives thereof, such as dimethyl maleate anhydride, diisopropyl maleate anhydride, dichloromaleic anhydride and the like. Particularly, 4- (2-phenylethynyl) phthalic anhydride is preferable from the viewpoint of heat resistance and oxidation resistance. One type of terminal modifier may be used, or two or more types may be mixed and used.

  Solvents that can be used in preparing the terminal-modified imide oligomer of the present invention include N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAc), N, N-diethylacetamide, N- Examples include methyl caprolactam, γ-butyrolactone (GBL), and cyclohexanone. 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.

  The terminal-modified imide oligomer of the present invention is, for example, an aromatic diamine containing the aforementioned 3,3 ′, 4,4′-biphenyltetracarboxylic acid (particularly, this acid dianhydride) and 2,4-tolylenediamine. The total amount of acid anhydride groups (or adjacent dicarboxylic acid groups) and the total amount of amino groups of the compound and 4- (2-phenylethynyl) phthalic anhydride, which is a terminal modifier, are approximately equal. Each component is polymerized in the aforementioned solvent at a reaction temperature of about 120 ° C. or less to produce an “oligomer having an amide-acid bond”, and then the amide-acid oligomer (amic Acid oligomer)) by dehydration and cyclization by adding an imidizing agent at a low temperature of about 0-140 ° C. or heating to a high temperature of 140-275 ° C. 4- 2-phenylethynyl) phthalic anhydride residues can be obtained imide oligomer having. When an aromatic diisocyanate compound is used in place of the aromatic diamine compound, an imide oligomer can be obtained by the same method.

  The amount of the dicarboxylic acid having an unsaturated group as a terminal modifier or a derivative thereof is adjusted so that the terminal-modified imide oligomer obtained has desired characteristics. In particular, the solubility of the obtained terminal-modified imide oligomer in an organic solvent such as NMP is 40 wt% or more at room temperature, the number average molecular weight is 3500 or less, and the glass transition temperature (Tg) of the cured product is 340 ° C. The above is preferable. Specifically, it is preferably used in a proportion that falls within the range of 10 to 200 mol%, particularly 25 to 100 mol%, based on the total amount of aromatic tetracarboxylic acids. In general, when the amount of the terminal modifier used is large, the monomers of the diamine and the terminal modifier increase and may precipitate in the solution. On the other hand, when the amount is small, the molecular weight of the oligomer increases, and there may be a problem that the solubility in an organic solvent is lowered or the moldability is lowered due to an increase in melt viscosity.

  Examples of the imidizing agent include 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, imidazoles such as benzimidazole, quinolines such as isoquinoline, pyridines such as pyridine, triethylamine, 1,8-diaza-bicyclo. Known amines such as (5,4,0) undecene-7 can be used.

  As a particularly preferable production method of the terminal-modified imide oligomer of the present invention, for example, an aromatic diamine compound containing 2,4-tolylenediamine is uniformly dissolved in the above-mentioned solvent, and then 3,3 ′, 4,4′-biphenyl. Tetracarboxylic dianhydride is added to the solution and dissolved uniformly, and stirred at a reaction temperature of about 5-80 ° C. for about 1-180 minutes. 4- (2-phenylethynyl) phthalic anhydride is added to this reaction solution. In addition, after uniformly dissolving, the mixture was reacted with stirring at a reaction temperature of about 5 to 80 ° C. for about 1 to 180 minutes to produce the terminal-modified amic acid oligomer, and then the reaction solution was stirred at 140 to 275 ° C. for 5 minutes. A method may be mentioned in which the amidic acid oligomer is imidized by stirring for 24 hours to form a terminal-modified imide oligomer, and if necessary, the reaction solution is cooled to around room temperature. 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 is obtained by thermally curing the terminal-modified imide oligomer alone or a composite material thereof and a fibrous reinforcing material in the presence or absence of a curing catalyst. For example, the terminal-modified imide oligomer varnish can be applied to a support and heat-cured at 280-500 ° C. for 5-200 minutes to form a film. 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 10 to 280 ° C. and 0.1 to 100 MPa for about 1 second to 100 minutes. The molded body can be heated at 280 to 500 ° C. for about 10 minutes to 40 hours to obtain a cured product.

  Further, a prepreg is formed by impregnating a varnish into a fibrous reinforcing material, for example, carbon fiber, heated at 140-275 ° C. for about 5-240 minutes, dried and imidized, and then at a temperature of 280-500 ° C. The fiber-reinforced composite material can be obtained by heating and curing at a pressure, preferably 0.1-100 MPa, for about 1 second-100 minutes. Moreover, a laminated board can be obtained by stacking a predetermined number of prepregs and curing them by heating and pressing using an autoclave, a hot press or the like.

The following examples are given to illustrate the invention, but are not intended to limit the invention.
In the following examples, each abbreviation means the following compound.
s-BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride a-BPDA: 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride TDA: tolylenediamine TDI: tri Range isocyanate ODA: Oxydianiline PEPA: 4- (2-phenylethynyl) phthalic anhydride The measurement conditions for each characteristic were as follows.
Test Method (1) Differential Scanning Calorimetry: Using a DSC-50 manufactured by Shimadzu Corporation, measurement was performed at a heating rate of 10 ° C./min in a nitrogen atmosphere.
(2) Number average molecular weight (Mn): It was determined under the following conditions using a TOSOH HLC-8220 GPC gel permeation chromatograph analyzer. Using N-methyl-2-pyrrolidone (NMP) as a solvent and passing through a column (SuperAW2500 + SuperAW4000: TOSOH) at 40 ° C. and 0.3 ml / min, weight average molecular weight (Mw) 3.97 × 10 ⁵ , 1.89 × 10 ⁵ , 9.89 × 10 ⁴ , 3.72 × 10 ⁴ , 1.71 × 10 ⁴ , 9.49 × 10 ³ , 5.87 × 10 ³ , 2.5 × 10 ³ , 1.05 × 10 ^3. A calibration curve obtained from the elution time by RI detection of a polystyrene (PS) standard substance having a known molecular weight of ³ , 4.95 × 10 ² was prepared in advance, and Mw and Mn were calculated from the elution time.
(3) Thermogravimetric analysis: Measured using TGA-50 manufactured by Shimadzu Corporation. The temperature was raised from room temperature to 800 ° C. at a rate of 10 ° C./min in a nitrogen atmosphere. The temperature at which 5% weight loss (T _d5 ) was determined.
(4) Dynamic Viscoelasticity Measurement: Solid Instruments Viscoelasticity Analyzer RSAIII (tensile mode dynamic measurement, frequency 62.8 rad / sec (10 Hz)) manufactured by TA Instruments Co., Ltd., in an atmosphere nitrogen flow, 25 ° C. to 500 ° C. The temperature is measured at 3 ° C until 30 seconds after each temperature is reached, the temperature is raised to the next temperature, the measurement is repeated, and the maximum point of the loss elastic modulus (E ″) is obtained. It calculated | required as a point (Tg).
(5) Tensile test: The film was punched into an IEC540 standard dumbbell shape to obtain a test piece, and the elastic modulus, breaking strength, and elongation at break were measured at 30 mm between chucks and a pulling speed of 2 mm / min using TENILON manufactured by ORIENTEC. .

Example 1
In a four-necked 500 mL flask equipped with a nitrogen inlet tube, 2,1.7715 g (0.0740 mol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 11.3077 g of 2,4-tolylenediamine (0.0925 mol) and 9.1851 g (0.0370 mol) of 4- (2-phenylethynyl) phthalic anhydride were added, 122.9416 g of N-methyl-2-pyrrolidone was added, and then at 120 ° C. under a nitrogen stream. The reaction was continued, followed by stirring at 200 ° C. for 5 hours for imide bonding. After cooling, the reaction solution was poured into 1 L of ion exchange water, and the precipitated powder was separated by filtration. The powder obtained by washing with 100 mL of ion-exchanged water for 30 minutes and filtered off was dried under reduced pressure at 135 ° C. for 1 day to obtain a product.
The uncured product of the terminal-modified imide oligomer obtained above was soluble in NMP solvent by 40% or more at room temperature, and no gelation was observed for 3 months when stored at room temperature. A film-like cured product (thickness: 126 μm) obtained by heating this terminal-modified imide oligomer at 370 ° C. for 1 hour using a hot press has a Tg of 351 ° C. (solid viscoelasticity), 5% by TGA The decrease temperature was 524 ° C. In addition, the mechanical properties of the cured product in the form of a film were as follows: the elastic modulus was 3.3 GPa, the breaking strength was 100 MPa, and the breaking elongation was 3.5%.

(Example 2)
To a four-necked 500 mL flask equipped with a nitrogen inlet tube, 15.0055 g (0.1228 mol) of 2,4-tolylenediamine and 172.0332 g of N-methyl-2-pyrrolidone were added, and after dissolution, 3,3 ′ , 4,4′-biphenyltetracarboxylic dianhydride 27.0952 g (0.0921 mol) was added, and polymerization reaction was carried out at 80 ° C. for 2 hours under a nitrogen stream to produce an amic acid oligomer. To this reaction solution, 15.2425 g (0.0614 mol) of 4- (2-phenylethynyl) phthalic anhydride was added, reacted at 80 ° C. for 2 hours under a nitrogen stream, and terminally modified, followed by stirring at 200 ° C. for 15 hours. Imido bond. After cooling, the reaction solution was poured into 1.5 L of ion exchange water, and the precipitated powder was separated by filtration. The powder obtained by washing 3 times with 100 mL of ion-exchanged water and filtered off was dried under reduced pressure at 135 ° C. for 1 day to obtain a product.
The uncured product of the terminal-modified imide oligomer obtained above was soluble in NMP solvent by 40% or more at room temperature, and no gelation was observed for 3 months when stored at room temperature. A film-like cured product (thickness 95 μm) obtained by heating the terminal-modified imide oligomer at 370 ° C. for 1 hour using a hot press has a Tg of 404 ° C. (solid viscoelasticity) and 5% by weight of TGA. The decreasing temperature was 496 ° C. In addition, the mechanical properties of the cured product in the form of a film were as follows: the elastic modulus was 3.1 GPa, the breaking strength was 95 MPa, and the breaking elongation was 3.3%.

(Example 3)
In a four-necked 500 mL flask equipped with a nitrogen inlet tube, 27.0369 g (0.0919 mol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 175.3630 g of N-methyl-2-pyrrolidone were added. 1,2-dimethylimidazole 0.0738 g (0.0008 mol) and water 0.8413 g (0.0467 mol) were added and heated to 130 ° C. under a nitrogen stream. After dissolution, 19.9984 g (0.1149 mol) of tolylene diisocyanate (Coronate T-80: 2,4-TDI / 2,6-TDI = 80/20) was added and polymerized at 130 ° C. for 2 hours to form an oligomer. did. To this reaction solution, 11.4018 g (0.0459 mol) of 4- (2-phenylethynyl) phthalic anhydride was added, reacted at 130 ° C. for 2 hours under a nitrogen stream, and terminally modified, followed by stirring at 200 ° C. for 10 hours. Imido bond. After cooling, the reaction solution was poured into 1.5 L of ion exchange water, and the precipitated powder was separated by filtration. The powder obtained by washing 3 times with 100 mL of ion-exchanged water and filtered off was dried under reduced pressure at 135 ° C. for 1 day to obtain a product.
The uncured product of the terminal-modified imide oligomer obtained above was soluble in an NMP solvent by 40% or more at room temperature, and no gelation was observed for 1 month when stored at room temperature. A film-like cured product (thickness: 105 μm) obtained by heating this terminal-modified imide oligomer at 370 ° C. for 1 hour using a hot press has a Tg of 369 ° C. (solid viscoelasticity), 5% by weight by TGA The decrease temperature was 544 ° C. In addition, the mechanical properties of the cured product in the form of a film were as follows: the elastic modulus was 2.5 GPa, the breaking strength was 95 MPa, and the breaking elongation was 4.0%.

(Comparative Example 1)
4,4′-oxydianiline 24.9786 g (0.1247 mol) and N-methyl-2-pyrrolidone 200.3501 g were added to a four-necked 500 mL flask equipped with a nitrogen inlet tube, and after dissolution, 3, 3 ', 4,4'-biphenyltetracarboxylic dianhydride 29.3844 g (0.0999 mol) was added, and polymerization reaction was performed at 120 ° C. for 2 hours under a nitrogen stream to produce an amic acid oligomer. To this reaction solution, 12.3837 g (0.0499 mol) of 4- (2-phenylethynyl) phthalic anhydride was added, reacted at 120 ° C. for 2 hours under a nitrogen stream, and terminally modified, and subsequently heated to 200 ° C. Crystals precipitated and did not dissolve even when the temperature was raised to 200 ° C. Film formation was attempted using the obtained crystal, but it did not show fluidity and a good film could not be obtained.

(Comparative Example 2)
To a three-necked 100 mL flask equipped with a thermometer, a stirrer, and a nitrogen inlet tube, 2.002 g (10 mmol) of 4,4′-oxydianiline and 12 mL of N-methyl-2-pyrrolidone were added and dissolved. , 3,3 ′, 4′-biphenyltetracarboxylic dianhydride (2.354 g, 8 mmol) was added and a polymerization reaction was carried out at room temperature for 2 hours under a nitrogen stream 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. 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.
The uncured product of the terminal-modified imide oligomer obtained above was soluble in NMP solvent by about 20% at room temperature, but gelation was observed after 1 day when stored at room temperature. A film-like cured product (thickness 86 μm) obtained by heating this terminal-modified imide oligomer at 370 ° C. for 1 hour using a hot press has a Tg of 337 ° C. (DSC) and a 5% weight loss temperature by TGA is It was 574 ° C. In addition, the mechanical properties of the cured product in the form of a film were as follows: the elastic modulus was 2.6 GPa, the breaking strength was 118 MPa, and the breaking elongation was 15.5%.

(Reference example)
To a four-necked 500 mL flask equipped with a nitrogen inlet tube, 15.0152 g (0.1229 mol) of 2,4-tolylenediamine and 161.65 g of N-methyl-2-pyrrolidone were added, and after dissolution, 3,3 ′ , 4,4′-biphenyltetracarboxylic dianhydride 32.136 g (0.1091 mol) was added and a polymerization reaction was carried out at 80 ° C. for 2 hours under a nitrogen stream to produce an amic acid oligomer. To this reaction solution, 6.7680 g (0.0273 mol) of 4- (2-phenylethynyl) phthalic anhydride was added, reacted at 80 ° C. for 2 hours under a nitrogen stream, and terminally modified, followed by stirring at 200 ° C. for 10 hours. Imido bond. After cooling, the reaction solution was poured into 1.5 L of ion exchange water, and the precipitated powder was separated by filtration. The powder obtained by washing 3 times with 100 mL of ion-exchanged water and filtered off was dried under reduced pressure at 135 ° C. for 1 day to obtain a product.
The uncured product of the terminal-modified imide oligomer obtained above was soluble in NMP solvent at room temperature by 25%. This terminal-modified imide oligomer was heated at 370 ° C. for 1 hour using a hot press, but a good film was not obtained. The Tg of the cured product was 377 ° C. (solid viscoelasticity), and the 5% weight loss temperature by TGA was 546 ° C.

  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 (8)

A terminal-modified imide oligomer represented by the following chemical formula (1).

However, in chemical formula (1):
R ^a is a tetravalent unit of which 60 mol% or more is represented by the following chemical formula (2),
R ^b is a divalent unit of which 60 mol% or more is represented by the following chemical formula (3),
X is a divalent unit having an unsaturated group.

The terminal-modified imide oligomer according to claim 1, wherein X is a divalent unit selected from the group consisting of a divalent unit represented by the following chemical formula (4) and a divalent unit that is a derivative thereof. .

  The terminal-modified imide oligomer according to claim 1 or 2, wherein the number average molecular weight is 3500 or less.   A varnish obtained by dissolving the terminal-modified imide oligomer according to any one of claims 1 to 3 in an organic solvent.   The varnish according to claim 4, wherein the concentration of the terminal-modified imide oligomer is 30% by mass or more.   Hardened | cured material obtained by heat-curing the terminal modified imide oligomer in any one of Claims 1-3.   A prepreg for a fiber-reinforced composite material comprising an organic solvent solution of the terminal-modified imide oligomer according to any one of claims 1 to 3 and a fibrous reinforcing material.   A fiber-reinforced composite material obtained by heat-curing the prepreg of claim 7.