WO1993013156A1 - Terminal blocking agents for polyimide, polyimide varnish, and intermediate material for fiber-reinforced composite material prepared therefrom - Google Patents

Abstract

Compounds represented by general formula (1) (wherein R3 and R4 each independently represents a hydrogen atom or a C1-4 alkyl group) are useful as terminal blocking agents for polyimides. A PMR type polyimide varnish containing the compound of general formula (1), a tetracarboxylic acid dialkyl ester represented by general formula (2) (wherein R1 represents a direct bond, CH2, O, CO, SO2, S or C(CH3)2, and X represents a (C1-4) alkyl group) and a diamine represented by general formula (3) shows good storage stability and is particularly useful as a matrix resin to be compounded in fiber-reinforced composite materials.

Description

 Description Terminal sealant for polyimide, polyimide varnish, and intermediate material for fiber-reinforced composite material using the same

 The present invention relates to a PMR-type polyimide having excellent storage stability. More particularly, it relates to a PMR-type polyimide which is suitable as a matrix resin having good storage stability of a varnish and high mechanical properties of a fiber-reinforced composite material. . Background technology

Polycondensation-type polyimides become insoluble in organic solvents as the degree of polymerization increases, so when used as a matrix resin for composite materials, so-called amide acids before dehydration and ring closure In the state of prevolima, a method of dissolving in a high boiling point solvent such as n-methylvillidone (NMP) or dimethylformamide (DMF) and impregnating the reinforced textile has been adopted. However, in this method, it is difficult to remove condensed water and a high-boiling-point solvent generated by ring closure during molding, so that these volatile components remain in the molded article, voids are generated, and physical properties are reduced. There were problems such as a decrease. Therefore, an addition-curable polyimide was developed to solve the above problem. The addition-curable polyimide is an oligomer having a molecular weight of about 1500 and having an addition-reactive nadic acid at the end, and is converted into a polyimide polymer through an amido acid prepolymer. Thermosetting, which is crosslinked by ring-opening addition reaction of the terminal nadic acid Resin. However, addition-curable polyimides also have the problem of dissolving only in high-boiling solvents such as NMP and DMP. Therefore, as a result of research on improving the solubility, carboxylic anhydride-type monomers were obtained. Is esterified with alcohol and the alcohol is used as a solvent. PMR-type polyimid (in-situ Polymerization of Monomeric Reactants) swords are available at TRW Systems, Inc. [Journal of Applied Polymer Science (J.Appl.Polym.Sci.), 16, (1972), 905] In other words, PMR-type polyimid is based on conventional polyimid. It is characterized in that a varnish is prepared by dissolving a monomer in a low-boiling solvent, whereas a varnish is prepared by dissolving an amide acid prepolymer in a high-boiling solvent. PMR-, a typical resin in the imid 15 is a monomer such as 3,3 ', 4,4'-dimethylbenzoic acid benzoate (BTDE), monomethyl ester of nadic acid (NE) and 4,4'-diamino diphenyl methane (DDM) The varnish is prepared by dissolving the varnish directly in methanol, and the varnish is used to produce a prepreg by a wet process.However, NE is an aromatic test such as BTDE. Reactivity with diamins such as DDM is higher than that of dicarboxylic diesters, so that the reaction between NE and DDM proceeds preferentially during storage of varnish, producing low-molecular-weight bisnadiimide (BI). [AS Organic Coatings and Plastics Co., Ltd.] (ACS Organic Coatings and Plastics), 40, (1979), 935: J. Appl. Polym. Sci., 27, (1982), 4295 ]. As described above, the monomer composition in the prepared resin solution changes during storage, so that it was extremely difficult to produce a pre-preparer of stable quality. The resulting monomer forms a high molecular weight polyol, thereby changing the molecular weight distribution of the entire resin and deteriorating moldability such as a decrease in fluidity during molding. In addition, the composite material obtained in this manner reduced mechanical properties such as interlaminar shear strength and bending strength, and also had an adverse effect on heat resistance, such as a decrease in pyrolysis temperature. National SAMPE Symposium, 26, (1981), 89]. Disclosure of the invention

 An object of the present invention is to provide an R-type polyimide varnish excellent in storage stability without the above-mentioned disadvantages, a terminal sealant used for preparing such a varnish, and an impregnated with such a varnish. Textile material An object of the present invention is to provide an intermediate material for a reinforced composite material.

The present invention provides, in one aspect, a terminal blocking agent for polyimide represented by the general formula [1]. [1]

In the formula, R ₃ and R ₄ are independently selected from the group consisting of hydrogen and an alkyl group having 1 to 4 carbon atoms. According to the present invention, in another aspect, a terminal blocking agent represented by the above formula [1], a tetraalkyl carboxylic acid dialkyl ester represented by the general formula [2], and a diamine represented by the general formula [3] The present invention provides a PMR-type polyimide varnish comprising:

 —In general formulas [2] and [3],

R, is a direct _{bond, CH z, 0, C0,} S0 z, S or C (CH _{3) Z,}

X is an alkyl group having 1 to 4 carbon atoms,

R z is a direct _{bond, CH 2, 0, C0,} S0 2, S or C (CH _{3) 2.} In still another aspect, the present invention provides an intermediate material for a fiber-reinforced composite material, in which the above-mentioned polyimid varnish is soaked in a reinforcing arrowhead. BEST MODE FOR CARRYING OUT THE INVENTION The compound of the present invention represented by the general formula [1] is used as a terminal blocking agent for polyimide. Polyimide is not limited to the PMR type, but is particularly useful for the PMR type polyimide as described below.

A study was conducted on the cause of the formation of BNI during storage by nadic acid monoalkyl ester (NE), a conventional nadic acid-type end capping agent, and the following conclusions were reached. In other words, BTDE, which is the main constituent of PMR-type polyimide, is excellent. There was a fundamental cause for the difference in chemical structure that NE is an alicyclic dicarboxylic acid monoalkyl ester, whereas an aromatic tetracarboxylic acid dialkyl ester. The reaction between the monoalkyl aromatic dicarboxylate and the aromatic amine starts at 100 cc or more, whereas the monoalkyl alicyclic dicarboxylate has high reactivity, so that the aromatic amine can be used even at room temperature. Reaction proceeds easily. Therefore, in order to solve this problem, it is necessary to lower the reactivity of the end capping agent and make it more reactive than other monomers constituting the main chain of the PMR-type polyimide. As shown in [1], a najimid-type end capping agent having an aromatic amine in the reaction part exhibits controlled reactivity and satisfies the above requirements. That is, by introducing an aromatic amine instead of using a highly reactive alicyclic dicarboxylic acid monoester as a reactive part of the end capping agent, the same effect as other monomers can be obtained. It became possible to provide reactivity.

 Specific examples of the compound represented by the general formula [1: · include 1-amino-4—nadimidobenzene, 111-amino-2—methyl-14nadiumimidbenzene and 1-aminodibenzene — Amino 2 and 6 — Dimethyl 4 — Nazimidbenzen.

The terminal blocking agent according to the present invention is a novel compound and can be synthesized by the following method. In the first method, nadic anhydride is reacted with ditroyurin or an alkyl-substituted product thereof in an acetamide solution, and nadimidonitrobenzene is used as an intermediate. Synthesized and then reduced using stannous chloride. The method shown in the following reaction formula (1)

第 2の方法は、 マ レイ ミ ドニ ト口ベンゼ'ン化合物を合成し、 次いで、 この化合物にシク ロペンタジェンを付加させ、 最後 にニ ト ロ基を還元する、 （ 2 ) の反応式に示す方法である。

The second method is to synthesize a maleimide nitrate benzene compound, then add cyclopentadiene to the compound, and finally reduce the nitro group, as shown in the reaction formula (2). It is.

 R

 The PMR-type polyimid varnish of the present invention comprises a terminal blocking agent represented by the general formula (1), a dialkyl tetracarbonate represented by the general formula (2), and an optional component represented by the general formula (3). It contains a diamine and an organic solvent as an optional ingredient.

—Specific examples of the dialkyl tetracarboxylate represented by the general formula [2] include 3, 3 ', 4, and 4' benzophenenot Dimethyl lacarboxylate and 3,3 ′, 4,4′-benzophenone tetracarboxylic acid getyl ester.

 Specific examples of the diamine represented by the general formula [3] include 44'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, and 4,4'dia Minodiphenyl methane, 3,3'-diaminodiphenylphenyl, 4,4'-diaminodiphenylsulfone and 3,3'-diaminodiphenylphenyl sulfone.

 The ratio of the above three components in the PMR-type polyimide varnish of the present invention is [1]: [2]: [3] = 2: (m ′ + 1): m (where m and m ′) Is a number from 0 to 10 and more preferably a number from 0.4 to 2; if m≥l, m 'no m = 0.6 to 1.4, and if m <l m-m ') =-0.4 to 10.4).

The PMR-type polyimide varnish comprises a terminal blocking agent represented by the general formula [1], a tetraalkyl dialkyl carbonate represented by the general formula [2], and a diamine represented by the general formula [3]. Can be prepared by dissolving the compound in an organic solvent. Examples of the organic solvent include alcohols represented by the general formula R'OH (where R 'is an alkyl group having 1 to 4 carbon atoms) (for example, methanol and ethanol) and dimethylforma. A mid or the like is used. The amount of solvent is from 0 to 20% by weight based on the amount of polyimide varnish. When the composition containing the three components [1], [2] and [3] is a liquid having an appropriate viscosity, the organic solvent is used. Agents need not be used.

 Polyimide oligo obtained from the above-mentioned PMR-type polyimid varnish is represented by the following formula, where n is the number of repeating units in the form of oligomers. Terminal blocking agent: tetraalkyl dicarboxylate: diamine By adjusting the molar ratio to 2: (n + 1): n, an arbitrary average molecular weight can be obtained. In the PMR-type polyimide varnish produced by Honki Akira, the chemical structure of diamine-type monomers and tetraalkyl carboxylic acid dialkylester-type monomers is calculated as the average molecular weight when they are converted into monomers. By doing so, resins with different heat resistance, physical properties, moldability, etc. can be obtained.

 As the average molecular weight of the resin obtained from the PMR type polyimid varnish increases as the molecular weight increases, the mechanical properties improve, but the heat resistance and moldability decrease. For this reason, the average number of repeating units n when it is oligomerized is preferably in the range of 0 to 10, and especially when n is in the range of 0, 4 to 2, a balance can be obtained in terms of heat resistance, moldability, and physical properties. It is suitable as a PMR type poly varnish.

The PMR-type polyimid varnish of the present invention may have its viscosity and viscosity adjusted as necessary, and may have the toughness, elastic modulus, elongation and other mechanical properties of a cured product obtained from this varnish. For the purpose of improvement, thermoplastic polymers such as polyethersulfone, polysulfone, thermoplastic polyimide, ebonashi resin, and diarylbisfuninol A and other reactive diluents are used. Appropriate amounts can be added. Usually, the amount of these additional components is Less than 40% by weight based on the total weight of polyamide varnish excluding organic solvent.

 The PMR-type polyimide varnish according to the present invention, when impregnated into reinforced textiles, has excellent tack and drape properties of the pre-bleder, has excellent moldability, and has a resin obtained by curing it. Excellent heat resistance and mechanical properties make it an excellent matrix resin for fiber-reinforced composite materials. In addition, it is also suitable as an adhesive or a molding material.

 When the PMR type polyimide varnish according to the present invention is used as a fiber-reinforced composite material, the reinforcing fibers include carbon fiber, graphite fiber, aramide fiber, silicon carbide fiber, alumina fiber, and borosilicate fiber. Fibers and glass fibers are used. Among these, high-strength carbon fibers are particularly preferred. It is also possible to mix and use different types of fibers. The form of textiles can be any form, such as long fibers, woven fabrics, knitted fabrics, mats, and cut fibers.

 The ratio of the reinforcing fiber and the PMR type polyimide varnish in the fiber-reinforced composite material is preferably 30 to 80% by weight of the former and 70 to 20% by weight (excluding the organic solvent) of the latter. .

 The following examples illustrate the invention in more detail. Example 1

 1-Amino — 4 — Synthesis of N-Amidobenzene

a. 12 Tro 4 1 Naimidobenzene

1 138 g of trobenzene 138 g was dissolved in 500 ml of dimethyl acetate amide, and 164 g of nadiflic anhydride was added thereto. A solution dissolved in 500 m of dimethylacetamide was added dropwise with stirring at room temperature. After completion of the dropwise addition, the mixture was stirred at room temperature for 1 hour, 150 ml of triethylamine and 150 mi of benzene were added, and the mixture was reacted at 140 for 3 hours. After the completion of the reaction, the reaction mixture was left at room temperature for 24 hours. Poured into water, filtered the orange precipitate, washed with water and dried in vacuo.

 Yield 236 g (83%)

 Elemental analysis results (% by weight, values in Kazuko are total values)

 C; 63.98 (63.38) H; 4.11 (4.23) N; 10.02 (9.86) b, 1 —Amino 4 1nadiimidobenzene

 1 12-Tro 4-Nazimidobenzene 200 g was dissolved in acetonitrile, 850 g of stannic chloride dihydrate was added, and the mixture was reacted at 60 • c for 2 hours. After cooling to room temperature, the reaction solution was poured into water and neutralized with sodium carbon. The precipitate was filtered, dried in vacuo, and then subjected to soxhlet extraction with acetonitrile. Acetonitrile was distilled off under reduced pressure to obtain a white solid.

 Yield 130g (75¾)

 Elemental analysis results (% by weight, values in Kazuko are total values)

 C; 70.32 (70.87) H; 5.68C5.51); 10.87 (11.02)

Example 2

Ethanol was added to 3,3 ', 4,4'-benzophenonetetracarboxylic acid, and the mixture was completely dissolved by boiling at reflux for 3 hours to obtain a diesterified product (BTDE) solution. Next, the end capping agent 1-amino-4'-nadiimidobenzene (AΚ Β) and 4,4'-diaminodidiphenylmethane (DDM) were added to this solution. Was dissolved. At this time, it was added so that the molar ratio of ANB: BTDE: DDM was 2:32. Excess ethanol was depressurized and distilled from this solution to obtain a PMR-type polyimide varnish.

 When this varnish was preserved at 20 and subjected to high-performance liquid chromatography for one minute, the components did not change at all after 60 days, and the storage stability was good. there were.

 A prepreg was prepared by a hot melt method using a varnish stored at 20'c for 60 days and carbon fibers ("Tray power" T400 manufactured by Toray Industries, Inc.). The resin content of the obtained prepreg was 39.6%. The resulting pre-preda was cut to a length of 30 cm and a width of 20 cm, laminated, pressurized in an autoclave with 160 and 14 ciU, and then heated to 290 After holding for 2 hours and cooling to room temperature, the molded article was taken out of the autoclave. The obtained molded article was after-cured with 316 for 6 hours to obtain a molded article. The carbon fiber volume content in the obtained molded product was 60.2%, and the glass transition temperature measured by the DSC method was 332, indicating that it had good heat resistance.

Next, a test piece was cut out from the obtained molded article according to ASTM and D-790, and the bending characteristics were measured.The bending strength was 190 kg / « ² , and the bending elastic modulus was 13.8 t / h < ² . It had mechanical properties.

For comparison, the same as above except that monomeric monoester (NA) was used as the end capping agent and the molar ratio of NE: BTDE: DDM was 2: 2: 3. PMR type polyimide was prepared by the method. When this varnish was stored at 20 ° C and temporarily subjected to high-performance liquid π-matography one-fold analysis, 13% of bisnazymide was formed on the varnish after 60 days of basketing. The composition had changed. Using this varnish to create the pre-flop leg in the same manner as described above, molded flexural strength 162 was measured for the bending properties of the composite material Z ^«z, in flexural modulus 13. 6 t Bruno" ² Showed lower physical properties. Industrial applicability

 The terminal blocking agent represented by the general formula [1] of the present invention is useful as a polyimide terminal blocking agent to be incorporated into a PMR type polyimide varnish. This PMR type polyimide varnish has the property of having good storage stability, and is particularly useful as a matrix resin having high mechanical properties to be blended with the fiber reinforced composite material.

Claims

The scope of the claims 1. A terminal blocking agent for polyimide represented by the general formula [1]. (1)

Wherein R ₃ and R ₄ are independently selected from the group consisting of hydrogen and C _1-4 alkyl groups.  2. A PMR-type polymer containing a terminal blocking agent represented by the general formula [1], a dialkyl tetracarboxylate represented by the general formula [2], and a diamin represented by the general formula [3] Li Mi Dwanis. (1) (2)

H ₂ N-) hR ₂ -NH _Z [3] In the general formulas [1], [2] and [3],  R z and are independently selected from the group consisting of hydrogen and an alkyl group having 1 to 4 carbon atoms; R, is a direct bond, CH _2, 0, C0, S0 _2, S or C (CH _{3) 2,} X is an alkyl group having 1 to 4 carbon atoms, R z is a direct _{bond, CH 2, 0, C0,} S0 2, S or C (CH _{3) 2.} 3. The molar ratio of the components represented by the general formulas [1], [2] and [3] is [1]: [2]: [3] = 2: (m '+ 1): m (however, , M and m 'are numbers from 0 to 10; when m≥1, πι' Ζιη = 0.6 ~: I.4, when m <l (m- m ') = — 0.4 ~ The varnish according to claim 2, wherein the varnish is +0.4.  4. The varnish according to claim 3, wherein m and m 'are numbers from 0.4 to 2.  5. The varnish according to claim 2, wherein the varnish contains 20% by weight or less of an organic solvent based on the weight of the poly varnish.  6. PMR-type polymer comprising a terminal blocking agent represented by the general formula [1], a dialkyl tetracarboxylate represented by the general formula [2] and a diamine represented by the general formula [3] Intermediate material for fiber reinforced composites made by soaking mid varnish in reinforcing fabric. twenty one Two H0

0C C concealed 00H HzN Ι -Β ₂ H: C 3] —In general formulas [1], [2] and [3], R ₃ and R <are independently selected from the group consisting of hydrogen and an alkyl group having 1 to 4 carbon atoms; R, is a direct _{bond, CH 2, 0, CO,} S0 2, S or C (CH _{3) z,} X is an alkyl group having 1 to 4 carbon atoms, R z is a direct bond, a _{CH 2, 0, C0, S0} 2, S or C (CH _{3) Z.} 7. The proportion of the components represented by the general formulas [1], [2] and [3] in the PMR type polyimide varnish is [1] in molar ratio: [2]: [3] = 2: (m '+ 1): m (where m and m' are numbers from 0 to 10 and m 'no m = 0.6 to 1.4 when m≥l 7. The method according to claim 6, wherein when m <l, (m−m ′) = — 0.4 to +0.4.  5 Intermediate material for varnish composite materials. 8. The intermediate material for a composite material according to claim 7, wherein m and m 'are numbers from 0.4 to 2.  9. The intermediate tea material for a composite material according to claim 6, wherein the polyimide varnish contains 20% by weight or less of an organic solvent based on the weight thereof.  10. The intermediate material for a composite material according to claim 6, wherein the ratio of the reinforcing fiber to the PMR type polyimide varnish is 30 to 80% by weight of the former and 70 to 20% by weight of the latter.