JPS61287938A - Production of prepreg sheet and lamination molding - Google Patents

Abstract

PURPOSE:To produce a prepreg sheet excellent in melt flow and heat resistance, by impregnating a fibrous reinforcement with a specified polyamic acid oligomer and imidating the oligomer. CONSTITUTION:A fibrous reinforcement is impregnated with an organic solvent solution, viscosity of 10-50,000cP, containing 2-60wt% polyamic acid oligomer of a weight-average MW of 500-10,000 of formula I (wherein R1 is a group of formula II or III, X is -CH2-, formula IV, -O-, -S-, -SO2-, a direct bond between aromatic rings, R2 is a group of formula V or VI, Y is -CH2-, formula IV, -O-, -S-, -SO2-, formula VII or VIII or a direct bond between aromatic rings, and n is an average of 0.5-10), and the oligomer is imidated either by dehydration by heating to 100-300 deg.C for 30-6hr or by adding a dehydrating/imidating agent to obtain a prepreg sheet containing a polyimide oilgomer of formula IX. Aplurality of said sheets are laminated and heated to a temperature higher than the glass transition temperature of the polyimide oligomer to obtain a lamination molding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a prepreg sheet useful as a heat-resistant composite material and a method for manufacturing a laminate molded article from the obtained prepreg sheet.

[Conventional technology]

In fields such as electronics, aerospace equipment, and transportation equipment, materials with superior high-temperature properties are required to improve the performance and reduce weight of various industrial materials.

Conventionally, epoxy resins, modified epoxy resins, phenolic resins, and other resins have been used as materials for prepregs for laminated molded bodies, but since these resins lack heat resistance, the obtained prepregs also have poor high-temperature properties. inferior. Furthermore, epoxy resins and the like have problems in storage stability and have the disadvantage of requiring storage at low temperatures.

Polyimide resins are known as materials that have improved these drawbacks. However, when a normal polyimide resin is completely cyclized into a polyimide state, its melt fluidity becomes extremely poor, making it difficult to use during molding. In this case, if the solvent or polyamic acid remains, the melt fluidity will improve, but due to the residual solvent or the vaporization of water generated by cyclization of the amic acid group during processing,
Voids occur in the molded product, reducing physical properties. For this purpose, D, J,
Progar et al. (U.S. Patent Nos. '4,065,345 and 4,094,862) 3.3', 4.
A polyimide resin is produced by reacting a tetracarboxylic dianhydride such as 4'-benzophenone tetracarboxylic dianhydride with a diamine such as 3,3'-diaminobenzophenone in an organic solvent to obtain a polyamic acid, which is then heated and imidized. developed. However, although the melt flowability of this polyimide resin has been improved, its performance is still not sufficiently satisfactory for use, for example, in impregnating prepreg sheets.

[Problem that the invention seeks to solve]

The present invention has been made based on the above-mentioned viewpoints, and an object of the present invention is a method for producing a prepreg sheet that has excellent melt flowability and is used for producing a heat-resistant laminate molded product. The object of the present invention is to provide a method for producing a heat-resistant laminate molded article using the same.

[Means for solving problems]

The present inventors have made extensive studies to achieve the above object, and as a result, have found that it is effective to use a polyamic acid oligomer having a specific structure, and have arrived at the present invention.

That is, the present invention provides general formula (I) (T) ○ -c-1-o-1-s-1-so2-1 or aromatic formula 0-1oM O
-1 or a direct bond between aromatic rings, and n is 0.5 to 10 on average. ] After impregnating a fibrous reinforcing material with an organic solvent solution of a polyamic acid oligomer represented by the formula, the polyamic acid oligomer is thermally imidized and/or chemically imidized to substantially form the formula ('n) [in the formula R1, R2 and n are RI + R in formula (I)
2 and n. ] This is a method for producing a prepreg sheet, characterized in that it is made from a polyimide oligomer represented by the following.

Further, another invention of the present invention is represented by the general formula (I) CI) -C-1-0-1-S-1-SO2-1 or aromatic O2, and Y is -CH2-1-C-1-0- 1-〇beko8
It is a direct bond between aromatic rings, and n is 0.5 to 10 on average. ] After impregnating a fibrous reinforcing material with an organic solvent solution of a polyamic acid oligomer represented by the formula, the polyamic acid oligomer is thermally imidized and/or chemically imidized to substantially form the formula (I1) (■) [in the formula R,, R2 and n are the same as R,, R2 and n in formula (1). ] This is a method for producing a laminate molded article, which comprises laminating prepreg sheets obtained as polyimide oligomers represented by the following formula and heating the prepreg sheets under pressure to a temperature equal to or higher than the glass transition temperature of the polyimide oligomer.

In the present invention, first, a polyamic acid oligomer is synthesized.

The polyamic acid oligomer is a tetracarboxylic dianhydride selected from the group consisting of formula (III) and formula (■) (III) (IV) [wherein X is the same as X in formula I and It], Formula (V) and formula (V1
) (v) (V1) [wherein Y is the same as Y in formula I, Il] and maleic anhydride are reacted in an organic solvent.

Examples of the tetracarboxylic dianhydride used in this method include pyromellitic anhydride, 3.3', 4°4'-
Benzophenone tetracarboxylic dianhydride, bis(3,
4-dicarboxyphenyl)ether dihydride, bis(3,4-dicarboxyphenyl)sulfonic anhydride, bis(3,4-dicarboxyphenyl)sulfonic anhydride, bis(3,4-dicarboxyphenyl)methani Examples include anhydrides, and particularly preferred tetracarboxylic dianhydrides include pyromellitic anhydride and 3.3; 4.4'
-benzophenone tetracarboxylic dianhydride.

These tetracarboxylic dianhydrides may be used alone or in combination with two
It is used by mixing more than one species.

Examples of diamine compounds used include 1,3-bis(3-aminophenoxy)benzene, 4,4'-bis(
3-aminophenoxy)biphenyl, 3゜3'-diaminobenzophenone, 3.4'-diaminobenzophenone, 3.3'-diaminodiphenylsulfone, 3.4'-
Diaminodiphenyl sulfone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane,
3.3'-diaminodiphenyl sulfide, 3.4'-
Examples include diaminodiphenyl sulfide, 3°3'-diaminodiphenyl ether, and 3,4'-diaminodiphenyl ether. A particularly preferred diamine compound is 1,3-bis(3-aminophenoxy)benzene.

These diamine compounds may be used alone or in combination of two or more.

Any combination of these tetracarboxylic dianhydrides and diamine compounds may be used, but pyromellitic dianhydride (hereinafter abbreviated as PMDA) and/or 3.3S 4 may be used as the tetracarboxylic dianhydride.
．． The combination of 4'-benzophenone tetracarboxylic dianhydride and 1,3-bis(3-aminophenoxy)benzene (hereinafter abbreviated as APB) as a diamine compound is particularly good, and the resulting polyamic acid The laminate molded article of the present invention using an oligomer has particularly good mechanical properties and heat resistance.

The molar ratio of each monomer in the production reaction of polyamic acid oligomer is 1.5 to 11 moles of diamine compound to 2 moles of maleic anhydride (hereinafter abbreviated as MAA);
0.5 to 10 mol of tetracarboxylic dianhydride is preferred.

The molecular weight of the obtained polyamic acid oligomer and polyimide oligomer was 500 in terms of weight average molecular weight (Mw).
~10,000, more preferably 800~2.500.

If the molecular weight is 10.000 or more, the fluidity is significantly reduced and it is unsuitable for use in impregnating prepreg sheets.

The reaction for producing polyamic acid oligomers is usually carried out in an organic solvent. Examples of organic solvents used in this reaction include N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylmethoxyacetamide, N-methyl-2-pyrrolidone, 1,3 -dimethyl-2-imidazolidinone, N
-Methylcaprolactam, 1.2-dimethoxyethane, bis(2-methoxyethyl)ether, l, 2-bis(2-methoxyethoxy)ethane, bis(2-(2-methoxyethoxy)ethyl)ether, tetrahydrofuran, 1 Examples include .3-dioxane, 1,4-dioxane, pyridine, picoline, dimethyl sulfoxide, dimethyl sulfone, tetramethylurea, hexamethylphosphoramide, and the like. Further, these organic solvents may be used alone or in combination of two or more.

The reaction temperature is usually below (a)°C, preferably below 50°C.

The reaction pressure is not particularly limited, and the reaction can be carried out at normal pressure.

The reaction time varies depending on the tetracarboxylic dianhydride used, the diamine compound, the type of solvent, and the reaction temperature.
The time is sufficient for the formation of polyamic acid oligomers, and is usually 4 to 24 hours.

Through such a reaction, a polyamic acid oligomer represented by the following formula (1) is obtained.

[In the formula, R1, R2 and n are as described above.

] The obtained polyamic acid oligomer solution usually has a concentration of 2 to 60%.
or the viscosity of the solution as measured by a Brookfield viscometer is 10
The range of centipoise to so, ooo is preferable in terms of ease of handling the solution and ease of impregnating the reinforcing material.

The average polymerization number n of the obtained polyamic acid oligomer is 0.5 to 10. Preferably it is 1 to 4. When the average polymerization number n is less than 0.5, the melt fluidity is good, but the physical properties of the resulting laminate are significantly impaired. Conversely, if n exceeds 10, good fluidity cannot be obtained.

The fibrous reinforcing material is then impregnated with the obtained polyamic acid oligomer solution.

Examples of the fibrous reinforcing material include carbon fibers, glass fibers, aromatic polyamide fibers, silicon carbide fibers, boron fibers, and woven and nonwoven fabrics thereof, and these fibers may be used alone or in combination.

Further, other reinforcing materials such as mica, calcium silicate, silica, alumina, etc. can also be used in combination with the fibers, if necessary.

The simplest impregnation method is to immerse the fibrous reinforcing material in a polyamic acid oligomer solution, but other methods may of course be used. The resin content to be impregnated is preferably 20 to 80% by weight of the entire prepreg sheet.

In the present invention, the impregnated polyamic acid oligomer is then dehydrated and imidized. The following two methods are generally used for dehydration imidization. The first method is a thermal imidization method in which imidization is performed by heating and dehydration, and the second method is a chemical imidization method in which imidization is performed by adding a dehydrating imidization agent.

For example, the first thermal imidization method is a method of heating and dehydrating the impregnated polyamic acid oligomer at 100 to 300° C. for 30 minutes to 6 hours to complete imidization.

The second chemical imidization method is the simplest method in which the impregnated polyamic acid oligomer is immersed in a dehydrated imidization agent. Examples of dehydration imidization agents include acetic anhydride,
One or a mixture of propionic anhydride, isobutyric anhydride, and butyric anhydride is used.

It is preferable to use the M water imidizing agent in an amount of 1 equivalent or more based on the carboxyl group present in the polyamic acid oligomer. Further, the dehydrating imidizing agent may be used after being diluted with an organic solvent. It is also possible to add an imidization catalyst at the same time, and examples of the catalyst include tertiary amines such as trimethylamine, triethylamine, tributylamine, pyridine, α-picoline, β-picoline, γ-picoline, and lutidine.

It is more preferable to use a solvent during this chemical imidization because the polyamic acid oligomer solvent in the prepreg can be extracted and removed. The prepreg sheet in which most of the imidization has been completed is further heated and dried to remove the solvent, unreacted imidizing agent, reactants of the imidizing agent, imidizing catalyst, and the like.

The volatile matter in the thermally imidized and/or chemically imidized prepreg sheet can cause blistering during the subsequent lamination operation, so it is preferable to remove it as much as possible. It is desirable that the 10 weight fi is 1% or less. Furthermore, there is no problem even if uncyclized amic acid groups remain in the polyimide oligomer to the extent that they do not significantly affect the physical properties.

The laminate molded product of the present invention is obtained by laminating the prepreg sheets obtained as described above by a conventional method and heating the stack under pressure to a temperature equal to or higher than the glass transition temperature of the polyimide oligomer contained in the prepreg sheet. The glass transition temperature of the polyimide oligomer contained in the prepreg sheet obtained by the method described above can be determined by, for example, the TMA method (
The numerical value obtained by the needle penetration method is usually in the range of 50 to 300°C, and the heating temperature is preferably 240 to 360°C.

The pressurizing pressure varies depending on the shape, but it is 1 to 5QQ kg /
aa 2 is desirable.

The prepreg sheet of the present invention can be stored indoors at room temperature. In addition, molding is easy, and a molded product of a desired shape can be obtained using a conventional molding machine such as a heat press or an autoclave.

〔Example〕

The present invention will be specifically explained with reference to Examples and Comparative Examples.

Example-1 (a) Production of polyamic acid oligomer In a 500++, F four-bottle flask, 150.5 g of N,N-dimethylacetamide and 58.4 g of AP8 were placed.
(0.20 mol) and stirred at 15°C under a stream of dry nitrogen.
25 mol) and MAA powder 14.7 g (0.15 mol)
were added alternately in equal amounts in 5 portions. The viscosity of the solution increases as it is added. After the addition was completed, the mixture was further stirred for 4 hours to complete the reaction. A part of the obtained polyamic acid oligomer solution was dropped into water, and the molecular weight (polystyrene molecular weight conversion value) of the precipitated polyamic acid oligomer powder was measured. As a result, the weight average molecular weight (MW) was 620, and the number average molecular weight (Mn) was 992. Also, the average polymerization number is 1
．． It was 7.

(b) Manufacture of prepreg sheet The polyamic acid oligomer solution obtained in (a) was heated with N.

After diluting the resin content with N-dimethylacetamide to 20% by weight, carbon fiber cloth (manufactured by Toho Veslon Co., Ltd., Vessite W-3121: 8-ply satin weave, 400 g/m2
) was immersed.

The obtained carbon fiber cloth was air-dried after soaking. This operation was repeated three times to obtain a prepreg sheet containing a polyamic acid oligomer. The obtained prepreg sheet was heated at 100°C for 1 hour.
Remove volatiles and imidize by heating and drying at 150°C for 1 hour, 180°C for 1 hour, and 220°C for 3 hours,
A prepreg sheet containing polyimide oligomer was obtained. The resin content in the prepreg sheet is 40% by weight, and the glass transition temperature of the resin is 116°C (TMAi needle penetration method).
Met.

(Four prepreg sheets obtained in C1 molding ('b) were laminated and molded using a compression molding machine at 300°C and 13 kg/cm2. The thickness of the obtained molded product was 1.51, and It was brown and strong.

The tensile strength of this molded body is 65 kg/mm” (2
3°C, fiber direction) (according to ASTM D-638. The same applies hereinafter.

), bending strength is 96 kg/mn2 (23°C, fiber direction) (according to ASTM D-790, the same applies hereinafter),
The glabella shear strength was 6.7 kg/mm2 (23°C, fiber direction) (according to ASTM D-2344; the same applies hereinafter).

Example 2 (a) Production of polyamic acid oligomer and preparation of prepreg sheet Polymerization was carried out under the same conditions as in Example 1 (a) to obtain a light brown transparent polyamic acid oligomer solution containing 40% by weight of the resin component. . 46 g of acetic anhydride and 7.5 g of l-ethylamine were added to the obtained polyamic acid oligomer solution.

An imidizing agent consisting of 40 g of N,N-dimethylacetamide was added and mixed. The obtained solution was applied to a carbon fiber cloth and pressed with a Teflon roll to impregnate it. The obtained prepreg sheet impregnated with polyamic acid oligomer and polyimide oligomer was heated at 100°C for 1 hour and at 150°C for 30 minutes.
The mixture was dried at 180° C. for 30 minutes and at 230° C. for 1 hour to obtain a polyimide oligomer-impregnated prepreg sheet. The glass transition temperature of the resin was 98° C., and the fiber content of the prepreg sheet was 58% by volume.

(b) Molding Four prepreg sheets obtained in (a) were laminated and molded at 300° C. and 13 kg/cs 2 using a compression molding machine.

The obtained molded product had a thickness of 1.5 mm, and was brown and strong.

The tensile strength of this molded body is 58 kg/mm2 (23℃
, fiber direction), bending strength is 83kg/mm” (
23℃, fiber direction), glabellar shear strength 6-2 kg/m
n+” (23°C, fiber direction).

Comparative Example-1 Production of ial polyamic acid oligomer 500 m 1 4th flask 165.5 g of N,N-dimethylacetamide SAP B 5B, 4 g (0
, 20 mol) and 27.25 g (0.125 mol) of PMDA powder and nadic acid anhydride (endo-bicyclo(2,2,
1) -5-Heptene-2,3-dicarboxylic anhydride) powder (24.6 g (0.15 mol)) was added in equal amounts alternately in five portions. The viscosity of the solution increases as it is added. After the addition was completed, the mixture was further stirred for 4 hours to complete the reaction. The obtained polyamic acid oligomer solution was light brown and transparent. A part of the obtained polyamic acid oligomer solution was dropped into water, and the molecular weight of the precipitated polyamic acid oligomer powder was measured. The result was the weight average molecular weight (Mw).
1,780, and the number average molecular weight (Mn) was 910. Moreover, the average polymerization number was 1.7.

(Manufacture of bl prepreg sheet A prepreg sheet impregnated with a polyimide oligomer was obtained using the polyamic acid oligomer 8 solution obtained in (a) in the same manner as in Example 1 (b). The resin content in the prepreg sheet was 42% by weight. %, and the glass transition temperature was 187°C.

(C) Molding Four prepreg sheets obtained in (b) were laminated and molded in the same manner as in Example-1 (C) to obtain a molded product with a thickness of 1.5+u.

The tensile strength of this molded body is 44 kg/mm2 (23℃
, fiber direction), bending strength is 56 kg/mm2 (23
°C, fiber direction), glabellar shear strength is 3.6 kg/mm
2 (23°C, fiber direction), which was inferior to Example-1 (C).

Examples 3 to 10 and Comparative Examples 2 to 5 Polymerization was carried out in the same manner as in Example 1(a) using various diamine compounds and tetracarboxylic dianhydride,
Furthermore, a polyimide oligomer-impregnated prepreg sheet was obtained in the same manner as in Example-1 (b). Using the obtained prepreg sheet, molding was carried out in the same manner as in Example 1(c), and the results shown in Tables 1 and 2 were obtained.

〔Effect of the invention〕

The polyimide oligomer impregnated prepreg sheet of the present invention has excellent melt flowability and is suitable as a material for a laminate molded product.

In addition, since the polyimide oligomer contained in the polyimide oligomer-impregnated prepreg sheet produced by the present invention has maleimide end groups, the maleimide end groups react with each other by boiling at 250 to 350°C to form a three-dimensional structure. and exhibits excellent heat resistance.

The present invention is constructed as described above, and an object of the present invention is to produce a novel prepreg sheet that exhibits particularly excellent strength even at high temperatures, and a laminate molded product with excellent heat resistance using this prepreg sheet. I can do it.

Claims (1)

[Claims] 1) General formula (I) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) [In the formula, R_1 is ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and ▲ Numerical formulas, chemical formulas, tables, etc. ▼Represents a group selected from the group consisting of ▼, where X is -CH_2-, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, -O-, -S-, -SO
_2-, or a direct bond between aromatic rings, R_2 represents a group selected from the group consisting of ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, and Y is - CH_2-, -C-, -O-, -S-,
-SO_2-, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, or it is a direct bond between aromatic rings, and n is an average value of 0.5 to 10. ] After impregnating a fibrous reinforcing material with an organic solvent solution of a polyamic acid oligomer represented by the formula, the polyamic acid oligomer is thermally imidized and/or chemically imidized to substantially form the formula (II) ▲Mathematical formula, chemical formula, table, etc. ▼ (II) [In the formula, R_1, R_2 and n are R_1 in the formula (I),
Same as R_2 and n. ] A method for producing a prepreg sheet, characterized in that it is made of a polyimide oligomer represented by: 2) General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) [In the formula, R_1 is from the group consisting of ▲There are mathematical formulas, chemical formulas, tables, etc.▼ and ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Represents a selected group;
_2-, or a direct bond between aromatic rings, R_2 represents a group selected from the group consisting of ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, and Y is - CH_2-, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, -O-, -S-, -SO_2-, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, or aroma It is a direct bond between rings, and n is 0.5 to 10 on average. ] After impregnating a fibrous reinforcing material with an organic solvent solution of a polyamic acid oligomer represented by the formula (I
I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (II) [In the formula, R_1, R_2 and n are R_1 in formula (I),
Same as R_2 and n. ] A method for producing a laminate molded article, which comprises laminating prepreg sheets obtained as a polyimide oligomer represented by the formula above and heating the prepreg sheets under pressure to a temperature higher than the glass transition temperature of the polyimide oligomer.