JPH11152340A - Preparation of resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparation of a resin composition in which a prepreg can be used for a long time, and has appropriate draping property and tackiness after long storage, and which can give a molding of little void. SOLUTION: An epoxy resin, a dicyandiamide, and an urea compd. of the formula is mixed in the presence of no solvent, at a temperature of not higher than 90 deg.C and/or under a vacuum or a reduced pressure. In the formula, X1 , and X2 each show hydrogen group, chlorine group, nitro group, or methoxy group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing a resin composition, particularly to a fiber reinforced composite material (hereinafter abbreviated as FRP).
And a method for preparing a resin composition useful as a matrix resin.

[0002]

2. Description of the Related Art In recent years, fiber reinforced prepregs, especially carbon fiber reinforced prepregs, have been developed using carbon fiber reinforced composite materials (hereinafter, CFRs).
P) is widely used in the field of sports and leisure goods and aircraft, and its demand is increasing year by year. When handling this prepreg, the working time is limited, so that the working life is long, that is, a long storage life is required.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve this problem, to provide a long pot life, easy handling even after long-term storage, appropriate tackiness and drapability, and an FR.
An object of the present invention is to provide a method for preparing a resin composition which is excellent in physical properties when P or CFRP is used and can obtain a molded product without voids.

[0004]

Means for Solving the Problems In order to solve the above problems, the invention of claim 1 is a method for mixing an epoxy resin, dicyandiamide, and a urea compound represented by the following formula (1) in the absence of a solvent. And at a temperature of 90 ° C. or lower and / or under vacuum or reduced pressure.

[0005]

Embedded image

However, X ₁ and X ₂ in the formula (1) each represent any one of a hydrogen group, a chlorine group, a nitro group and a methoxy group.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The epoxy resin used in the present invention may be of any type, and is usually bisphenol A epoxy resin, bisphenol F epoxy resin, novolak epoxy resin,
Glycidylamine type epoxy resin, glycidyl ester type epoxy resin, glycidyl ether type epoxy resin,
An alicyclic epoxy resin and a mixture thereof can be used. Further, if necessary, a thermoplastic resin such as a phenoxy resin, a polyamide resin, a polysulfone resin, a polyether sulfone resin, a polyester resin, a polyvinyl formal resin, a nitrile rubber, a butadiene-acrylonitrile rubber, or the like may be added to these epoxy resins. Can also.

In the case of an epoxy resin mixture containing an epoxy resin or a thermoplastic resin which is solid at the mixing temperature, the mixture is heated to a temperature exceeding 90 ° C. once to melt the solid epoxy resin or the thermoplastic resin. After cooling to a temperature of 90 ° C. or lower, a curing agent and a curing accelerator can be added.

In the present invention, dicyandiamide is used as a curing agent, and a urea compound represented by the above formula (1) is used as a curing accelerator. Examples of the urea compound represented by the above formula (1) include 3- (3,4-dichlorophenyl) -1,1-dimethylurea and 3-phenyl-1,1
-Dimethylurea and the like. The amount of dicyandiamide is usually 1 to 10 parts by weight based on 100 parts by weight of the total amount of the resin mixture. The amount of the curing accelerator used is usually 1 to 1 based on 100 parts by weight of the total amount of the resin mixture.
0 parts by weight are used.

The upper limit of the mixing temperature of the curing agent and the curing accelerator and the epoxy resin composition is usually 90 ° C. or lower, and the lower limit is usually at room temperature or higher, preferably 70 to 90 ° C. If the temperature is higher than 90 ° C., the pot life of the prepreg becomes short, and if the temperature is too low, air bubbles are mixed into the epoxy resin composition or mixing becomes difficult, which is not preferable. The mixing of the resin composition is preferably performed so that air bubbles are not involved. By mixing under vacuum or reduced pressure, air bubbles generated by mixing can be removed.

Mixing under vacuum or reduced pressure is usually 100
It is preferably performed at Torr or less, preferably at 10 Torr or less.

[0012] If bubbles are present in the resin composition, voids (voids) are likely to remain in the molded article when the prepreg is molded, and the physical properties of FRP are inferior.

The epoxy resin composition according to the present invention generally has a viscosity of from 5,000 to 1,000,000 Poise at 25 ° C., preferably from 50,000 to 1,000,000 Poise.
e, having a viscosity of 500 to 30,000 Poise at 50 ° C., preferably 500 to 10,000 Poise. If the viscosity of the resin composition according to the present invention is higher than the above range, the prepreg is hardened and the tackiness is lost or the resin impregnating property to the reinforcing fiber is inferior.If the viscosity is low, the tackiness of the prepreg is too strong, and once the prepreg is laminated. The bonded prepregs do not peel off, making it impossible to correct the lamination of the prepregs, or increasing the resin flow from the prepregs during molding, which is not preferable.

In the present invention, if necessary, an inorganic filler or an organic filler such as talc, calcium carbonate, titanium dioxide, calcium sulfate, barium sulfate, carbon black, Teflon powder, polyethylene powder, polyamide powder, or the like may be added to the resin composition. EVA powder or the like can be added in an amount of 5 to 60 wt%. These fillers can be added before, during or after the addition of the curing agent or the curing accelerator.

The prepreg can be produced by a general method known to those skilled in the art. An epoxy resin composition serving as a matrix is prepared in the absence of a solvent and then separated using a reverse coaster or the like. A dry method is generally used in which a resin film is formed on a pattern paper, and a reinforcing resin or a fabric reinforcing fiber arranged in one direction is melt-impregnated with a resin in the form of a film.

The resin composition according to the present invention comprises a matrix resin of reinforcing fibers, specifically, a matrix resin such as carbon fiber, aramid fiber, glass fiber, boron fiber and the like.
Particularly useful as a matrix resin for carbon fibers such as pitch-based carbon fibers or polyacrylonitrile-based carbon fibers, rayon-based carbon fibers, and combined with these reinforcing fibers to form a prepreg, laminated, molded and cured to form an FRP molded article or CFRP molded article. It can be.

The prepreg obtained by the present invention has a tackiness of usually from 0.025 to 0.08 MPa, preferably from 0.03 to 0.06 MPa, and an excellent molded article without voids can be obtained.

The prepreg obtained by the present invention has a pot life of usually at least 1 month at 25 ° C., preferably at least 1 month.
Having a pot life of 5 months or more, easy handling of prepreg even after long-term storage, appropriate moderate tackiness and drapability, excellent physical properties when used as FRP or CFRP, no voids in molded products Can be obtained.

[0019]

EXAMPLES Examples will be shown below, but it goes without saying that the present invention is not limited to these examples.

The test of tackiness and drapability of the prepreg was performed by the following method. (Tackness) Tackness is obtained by crimping prepregs together.
Measure the peel force. As a measuring device, an Instron 4201 universal material testing machine (manufactured by Instron Japan) is used, the sample size is 25 × 25 mm, the loading speed is 1 mm / min, the adhesive load is 0.1 MPa, and the loading time is 45.
The measurement was performed under the conditions of a second and a peeling speed of 10 mm / min.

(Drapability) Drapability is an evaluation of the wrapping property of a prepreg around a mandrel. The prepreg was heated at a temperature of 23 ° C. and a humidity of 40% RH in a 5 mm diameter atmosphere.
The reinforced fiber was wound around a steel cylinder having a length of 100 cm so that the alignment direction of the reinforcing fibers was at an angle of 45 ° with respect to the longitudinal direction of the cylinder, and allowed to stand for 30 minutes. In the evaluation, those having no lift at the end point were regarded as acceptable.

(Example 1) YD128 (manufactured by Toto Kasei Co., Ltd.)
20 parts by weight and 80 parts by weight of YD011 (manufactured by Toto Kasei Co., Ltd.) are placed in a heating kneader and heated to 120 ° C. under reduced pressure of 10 Torr.
After dissolving the solid epoxy resin with stirring to reduce the temperature to 85 ° C., return to normal pressure, return 5 parts by weight of dicyandiamide and 3- (3,4-dichlorophenyl) -1,1-dimethylurea (hereinafter abbreviated as DCMU). 5 parts by weight), and sufficiently stirred and mixed at 85 ° C. under a reduced pressure of 10 Torr to obtain an epoxy resin composition for prepreg. Next, a commercially available high-strength carbon fiber (T700S manufactured by Toray Industries, Ltd., tensile strength 4.8 G)
Pa, tensile modulus 235 GPa) in one direction, and then heat-melt the epoxy resin composition for prepreg to obtain a matrix resin content of 33 wt% and MPT (moul).
ded ply thickness) A unidirectional prepreg of 0.125 mm was obtained. The tackiness of the obtained prepreg is 0.03.
The drapability was evaluated as acceptable in MPa. 1 at 25 ° C
After storage for a month, the prepreg was evaluated for tackiness, but showed no change and had good storage stability.

Example 2 A commercially available high modulus carbon fiber (M46J manufactured by Toray Industries, tensile strength 4.22 GPa, tensile modulus 436 GPa) was aligned in one direction, and then the epoxy resin for prepreg obtained in Example 1 was obtained. The resin composition was heated and melted to obtain a matrix resin content of 33 wt% and MPT (moulded).
ply thickness) A unidirectional prepreg of 0.125 mm was obtained. The tackiness of the obtained prepreg is 0.03MP.
In a, the drapability was evaluated as acceptable. After storage at 25 ° C. for one month, the prepreg was evaluated for tackiness, but showed no change and had good storage stability.

(Example 3) The prepreg immediately after production in Example 2 is wound around a mandrel by two layers each as a bias layer of ± 45 ° orientation, and the prepreg immediately after production in Example 1 is formed into a straight layer and parallel to the mandrel. Orient 4
After layer winding, a polypropylene tape was wound at a tape tension of 3 kg / cm ² and cured in a heating furnace at 130 ° C. for 1 hour to obtain a shaft having an inner diameter of 10 mm. The cross section of the shaft was observed with an optical microscope at a magnification of 100 times, but no void was observed and the molding was good.

Example 4 The prepreg of Example 2 stored at 25 ° C. for one month was used as a bias layer, and the prepreg of Example 1 stored at 25 ° C. for one month was used as a straight layer, similarly to Example 3. By the method, a shaft having an inner diameter of 10 mm was obtained. The cross section of the shaft was observed with an optical microscope at a magnification of 100 times. As a result, no void was observed in both the bias layer and the straight layer, and the molding was good.

Comparative Example 1 An epoxy resin having the same amount of resin as in Example 1 was placed in a heating kneader and heated at 120 ° C. under normal pressure.
After stirring to mix to dissolve the solid epoxy resin, the mixture was cooled to 100 ° C, 5 parts by weight of dicyandiamide and 5 parts by weight of DCMU were added, and the mixture was sufficiently stirred and mixed at 100 ° C under normal pressure to obtain an epoxy resin composition for prepreg. . A prepreg was produced in the same manner as in Example 1 using T700S manufactured by Toray Co., Ltd. as carbon fibers using the resin composition. The tack of the prepreg immediately after production was 0.03 MPa, and the drapability was evaluated as acceptable. However, the prepreg after storage at 25 ° C. for one month had no tack and the drape was unacceptable.

Comparative Example 2 An epoxy resin having the same amount of resin as in Example 1 was placed in a heating kneader and heated at 120 ° C. under normal pressure.
After cooling to 85 ° C, 5 parts by weight of dicyandiamide and 5 parts by weight of DCMU were added, and the mixture was cooled to 85 ° C under normal pressure.
Was sufficiently stirred and mixed to obtain an epoxy resin composition for prepreg. A prepreg was produced in the same manner as in Example 1 using M46J manufactured by Toray Co., Ltd. as a carbon fiber using the resin composition, and the prepreg immediately after the production was used as a bias layer, and further, the prepreg immediately after production obtained in Comparative Example 1 Was formed in the same manner as in Example 3 as a straight layer, and the inner diameter was 10 mm.
I got a shaft. The cross section of the shaft is
Observation at a magnification of 00 revealed that many voids were observed in both the bias layer and the straight layer, and the molding state was inferior.

[0028]

According to the method for preparing the resin composition of the present invention, the pot life is long, easy to handle even after storage for a long time, has an appropriate tackiness and drapability, and is made of FRP or CF.
It is possible to obtain a molded article having excellent physical properties as RP and having no voids.

Claims (1)

[Claims] 1. Mixing an epoxy resin with dicyandiamide and a urea compound represented by the following formula (1) in the absence of a solvent, at a temperature of 90 ° C. or lower and / or under vacuum or reduced pressure: A method for preparing a resin composition, wherein the method is mixed. Embedded image Here, X ₁ and X ₂ in the formula (1) each represent any one of a hydrogen group, a chlorine group, a nitro group, and a methoxy group.