JPS60240740A - Prepreg sheet for laminating and manufacture of laminate - Google Patents

Abstract

PURPOSE:To obtain the titled prepreg sheet which can be stored at room temperatures for a long time and hot-pressed, by impregnating a fibrous reinforcement with a solution of a specified polyamic acid, followed by heating to polyimidize. CONSTITUTION:A fibrous reinforcement (e.g. glass fibers) is impregnated with a solution, having a viscosity of 10-2,000cp, of a polyamic acid of formula III, obtained by reacting a 3,3',4,4'-benzophenonetetracarboxylic anhydride of formula I (where n is an integer, representing the degree of polymerization) with a 3,3'-diaminobenzophenone of formula II in an organic solvent (e.g. N,N'-dimethylformamide) and is heated by raising the temperature at a rate of 2-7 deg.C/min to 150-250 deg.C to convert the polyamic acid to a polyimide of formula IV, giving the titled prepreg sheet containing 2-15wt% residual solvent. Then, a required number of plies of the sheets are laid up and heated to at least 280 deg.C and pressed under at least 10kg/cm<2> to obtain the laminate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel method for manufacturing a prepreg sheet for laminated molding to be used for molding a heat-resistant composite, and a method for manufacturing a laminated molded product from the obtained prepreg sheet. It is something.

[Conventional technology]

Conventionally, a combination of carbon fiber or glass fiber and epoxy resin has been commonly used as a material for composites, and woven fabrics, tapes, etc. of these fibers are impregnated with epoxy resin to form a prepreg sheet, and the prepreg sheet is made into a desired material. A method is adopted in which the epoxy resin is laminated in the shape of , and the epoxy resin is cured under heat and pressure to form a molded product.

By the way, prepreg sheets using epoxy resin have strict storage conditions, and are stored at -18° C. or lower.

In addition, when using a prepreg sheet using epoxy resin, it is necessary to raise the temperature from the storage temperature (-18°C or less) to the lamination work temperature at room temperature, and during this temperature rise, moisture is generated on the surface of the prepreg sheet. Condensation occurs, which causes deterioration in the performance of the resulting molded product, so extreme care is required when handling the prepreg sheet.

Furthermore, as mentioned above, the prepreg sheet using epoxy resin is heated from the storage temperature to the working temperature, the required quantity is collected, and the remaining prepreg sheet is stored at a low temperature again to perform a thermal cycle. The shelf life is 3 months or less even if stored at -18°C.

Even when forming a molded product by laminating the prepreg sheets, it is necessary to heat and press the laminated prepreg sheets in a vacuum state in an autoclave, resulting in expensive equipment and low productivity. This requires improvement.

As seen above, conventional prepreg sheets have various drawbacks.

[Problem that the invention seeks to solve]

The object of the present invention is to produce a prepreg that can be stored for more than one year in a normal room, is unaffected by the atmosphere, and can be heat-pressed, and a molded product made from the prepreg. The purpose is to provide a manufacturing method.

[Means to solve the problem]

The present inventors have finally arrived at the present invention as a result of intensive studies for the above purpose.

That is, the present invention impregnates a fibrous reinforcing material with a polyamic acid solution consisting of 3.3', 4.4'-benzophenone tetracarboxylic anhydride and 3,31-diaminobenzophenone, and then heats the impregnating material. The present invention provides a method for producing a prepreg sheet for laminated molding, characterized by polyimidizing the polyamic acid, and a method for producing a laminated molded article, characterized by laminating the obtained prepreg sheets and heating and pressurizing them.

The polyamic acid @) solution used in the present invention is 3°3'1
414'-benzophenonetetracarboxylic anhydride (I
) and 3.31-diaminobenzophenone (n) in an organic solvent, and the reaction follows the following formula.

(m) (Here, n is an integer and indicates the degree of polymerization.) By further heating, polyimide (■) can be obtained.
．． 2 to 1.2, preferably 0.4 to 0.8. In addition, [η] was measured using a solution dissolved in dimethylacetamide so that it was 0.5 g/d7.

The organic solvent used in the present invention is N,N-dimethylformamide, N,N-dimethylacetamide, bis(2
-methoxyethyl) ether, N-methyl-2-pyrrolidone, tetrahydrofuran and the like are preferred.

The amount of solvent to be used is preferably such that the viscosity of the solution containing the polyamic acid is low, and the optimal amount is such that the viscosity is particularly in the range of 10 to 2000 centivoids. Further, the viscosity of the solution is a value measured at room temperature using a Brookfield viscometer.

Typical fibrous reinforcing materials include glass fiber, carbon fiber, aromatic polyamide fiber, and boron fiber.
These fibers may be used alone or in combination. Furthermore, other reinforcing materials such as silicon carbide fibers, mica, and calcium silicate may also be used in combination with the fibers, if necessary.

A simple method for impregnating the fibrous reinforcing material with a polyamic acid solution is to immerse the fibrous reinforcing material in a polyamic acid solution. In this case, the fibrous reinforcement material is immersed in a polyamic acid solution with a relatively low viscosity (about 10 to 50 centipoise), air-dried, and then air-dried with a relatively high viscosity (about 10 to 50 centipoise).
It is preferable to immerse the prepreg sheet in a polyamic acid solution (about 0 to 2,000 centivoids) because a uniform prepreg sheet with 1'.1 and a large impregnated amount can be obtained. Of course, other methods of impregnation may also be used.

In the present invention, the polyamic acid impregnated into the fiber reinforcing material is further heated and converted into polyimide to form a prepreg sheet. At this time, it is possible to remove the solvent used for impregnation, but it is also possible to remove the solvent at the same time as polyimidation. In addition, the solvent used for impregnation in the obtained prepreg was
If ~15% by weight, preferably 5~10% by weight remains, prepreg sheets can be laminated and pressure molded better, so a method of removing the solvent at the same time as polyimidation is desirable.

Note that since polyimidation proceeds by a dehydration reaction, bubbles may be generated if the polyimidation progresses rapidly, so it is desirable to sufficiently control the polyimidation temperature or the rate of temperature rise to that temperature.

The temperature for polyimidation is in the range of 150 to 250°C, preferably 180 to 220°C, and the rate of temperature increase varies depending on the solvent used, whether or not the solvent is removed, heating conditions (normal pressure or reduced pressure), etc. 2-b True.

Polyimide impregnated into prepreg becomes plastic when heated above 280°C, so by laminating the prepreg sheets obtained as above, reheating and pressing, each layer is bonded and formed into the desired shape. can be molded.

The heating temperature during lamination molding may be 280°C or higher, but preferably 300 to 350°C.

A temperature of 280° C. or lower is not preferable because almost no adhesion between the laminated sheets occurs.

In addition, the pressurizing pressure varies depending on the shape, but is usually 10 kg/cm.
It is sufficient if it is r& or more.

The prepreg sheet of the present invention can be stored indoors at room temperature for more than one year, and can be laminated indoors.

In addition, the above molding process is easy, and ordinary hot press molding can be used instead of an autoclave, which is required when using a prepreg sheet using epoxy resin, resulting in lower molding costs. You can also get

It has excellent adhesion with various metal materials such as aluminum alloys, and has the advantage that it can be bonded and integrated with structures made of the metals at the same time as molding during hot pressing.

〔Example〕

The present invention will be explained below with reference to Examples.

Example 1 3.3',4.4'-benzophenonetetracarboxylic acid anhydride and 3.31-diaminobenzophenone were dissolved in N,N-dimethylacetamide (DMAc) in an equimolar ratio and reacted, A solution containing 25% by weight of polyamic acid with [η] of 0.5 was obtained.

The polyamic acid solution was diluted with DMAc to give a 50 centipoise solution with a concentration of about 10% by weight.

Add carbon fiber woven cloth (Trading Card Cloth #6343) to this diluted solution.
, trademark) and then air-dried, and then immersed in a 25% by weight polyamic acid solution and air-dried.

Immersion in this 25 wt% polyamic acid solution - air drying for 40 min.
% by weight.

The carbon fiber woven fabric to which polyamic acid was attached was heated to 200°C at a heating rate of 7°C/min in a nitrogen atmosphere, and heated at that temperature for 2 hours to obtain a prebrig sheet in which polyamic acid was converted into polyimide. .

The amount of residual solvent in this prepreg sheet was 0.5% by weight.

Stack 10 sheets for each storage temperature and store at 340°C.
A flat plate of 10cm square and 3ilIm thick was formed by hot pressing. The bending strength of each of these flat plates is 60
kg/mm, 58kti/mm, 61 to 9/'myn'
, and almost no difference was observed.

As will be seen, the prepreg/-t of the present invention can be stored at room temperature.

Example 2 Using the polyamic acid solution obtained in Example 1, a carbon fiber woven fabric was first impregnated with a 10% by weight polyamic acid solution, and after removing the excess solution with a rubber roll, a 25% by weight polyamic acid solution was applied. .

Next, this woven fabric was gradually heated at a heating rate of 5° C./min, and heating was continued at that temperature to prepare sample sheets having different amounts of residual solvent as shown in Table 1.

After storing these replica sheets at 100°C for 30 days, 10 sheets each were taken out and stacked to form a 60 mm diameter sheet.
It was molded at 340°C using a bowl-shaped mold with a depth of 10 mm and a pressure of 50 mm and 91 cr.

The appearance of the obtained molded product and the occurrence of cracks on the surface due to the impact caused by the falling hard ball were observed.

The results are shown in Table-1.

Table 1 As shown in Table 1, if the amount of residual solvent is too small, problems may occur in the appearance of the molded product, and if it is too large, the processability is good, but cracks may occur after a single impact. Since this tends to occur, it is found that it is desirable to keep the amount of residual solvent in the range of 2 to 15% by weight.

Example 3 In Example 1, the solvent was bis(2-methoxyethyl)
Instead of ether, a polyamic acid solution (concentration 20% by weight) with [η] of 0.6 was prepared.

This solution was applied to a glass fiber woven fabric (Nittobo WF'-230) and impregnated by pressing it with a rubber roll, then the temperature was raised to 200°C at a heating rate of 5°C/min, and the temperature was maintained for 3 hours. A sample sheet was prepared by heating.

Five of the obtained sample rig sheets were stacked one on top of the other, sandwiched between two iron plates whose surfaces had been sandblasted, and hot pressed at 340°C.

When the adhesive strength of the iron plate was measured, it was 200 to 9/crl.
It can be evaluated.

Example 4 Using 10 pieces of each of the samples 2 obtained in Example 2, the same molded products as in Example 2 were molded at the molding temperature and pressure shown in Table 2, and the residual void ratio (%) in the molded products was ) and the occurrence of cracks due to falling rigid balls. The results are shown in Table 2.

Table 2 As shown in Table 2, it was found that if the molding temperature was too low, the adhesion between the prebrig sheets was poor, and it was determined that the optimal molding temperature was 300 to 350°C.

〔Effect of the invention〕

The sample rig sheet of the present invention is advantageous in that it can be stored at room temperature and can be molded into a molded product by hot pressing, and has a wide range of industrial applications.

patent applicant Mitsui Toatsu Chemical Co., Ltd.

Claims (3)

[Claims] (1) Polyamic acid obtained by impregnating a fibrous reinforcing material with a polyamic acid solution consisting of 3.3', 4.4'-benzophenone tetracarboxylic anhydride and 3,31-diaminobenzophenone, and then heating the material to impregnate it. A method for producing a prepreg sheet for laminated molding, characterized by converting acid into polyimide. (2) The method for producing a prepreg sheet for laminated molding according to claim 1, wherein the amount of residual solvent in the prepreg sheet after polyimidation is 2 to 15% by weight. (3) A fibrous reinforcing material was impregnated with a polyamic acid solution consisting of 3.3', 4.4'-benzophenone tetracarboxylic anhydride and 3,3'-diaminobenzophenone, and then heated to impregnate it. A method for producing a laminate molded article, which comprises polyimidizing polyamic acid, laminating a prepreg sheet and tx L + the prepreg sheet, and pressurizing while heating at 280° C. or higher.