JP7099113B2 - Manufacturing method of carbon fiber prepreg - Google Patents

Description

The present invention relates to a resin composition particularly suitable for heat resistant applications and a prepreg using the resin composition.

Epoxy resins are widely used as thermosetting resins due to their mechanical properties. In particular, epoxy resin is most often used as a matrix resin for fiber-reinforced composite materials using reinforced fibers such as carbon fiber and glass fiber.

However, if an epoxy resin is used, the heat resistance may be insufficient and the method of use is limited. It is known to use cyanate ester resin to improve heat resistance. Although the cyanate ester resin exhibits extremely high heat resistance, since the curing reaction starts from a high temperature of 200 ° C. or higher by itself, various catalysts are often added in order to lower the reaction starting temperature. The fiber-reinforced composite material is formed by laminating prepreg, which is an intermediate material, and attaching it to a mold, and then applying heat and pressure. However, the mold of a material having a heat resistance of 200 ° C or higher is very expensive. A method is often used in which the maximum heat resistance is exhibited by primary curing at a relatively low temperature of 150 ° C. or lower, demolding, and then applying a high temperature of 200 ° C. or higher. Therefore, it is required that the primary curing can be performed at 150 ° C. or lower to the extent that the mold can be removed.

Further, when preparing the prepreg, it is necessary to impregnate the inside of the reinforcing fiber sheet by lowering the viscosity of the matrix resin and applying pressure. As a method for lowering the viscosity, there are a lacquer method in which a matrix resin is dissolved in various solvents and a hot melt method in which a temperature (about 40 ° C. to 80 ° C.) at which a curing reaction does not start is applied. In the lacquer method, after impregnating with a matrix resin, the solvent is dried and removed by applying a temperature, but the solvent that cannot be completely removed may remain inside the molded product and cause voids. Therefore, a hot melt method that does not use a solvent is desirable, but it is a problem to achieve both reactivity that can be primary cured and thermal stability that can be hot melted.

As the curing reaction catalyst of the cyanate ester resin, a metal catalyst or an imidazole compound is generally used. Patent Document 1 discloses a cyanate ester-based resin composition using an imidazole compound as a catalyst. However, no consideration is given to low temperature curability at 150 ° C. or lower and thermal stability.

Japanese Unexamined Patent Publication No. 62-277466

INDUSTRIAL APPLICABILITY According to the present invention, a resin composition which is capable of primary curing at 150 ° C. or lower and has good thermal stability and is also excellent in heat resistance after curing, and a prepreg for a fiber-reinforced composite material which is excellent in heat resistance after molding. I will provide a.

As a result of diligent studies to solve the above problems, the present inventors have found that the above problems can be solved by specifically using an imidazole compound as a curing catalyst for a cyanate ester resin and further using a specific compound in combination. Has been completed. That is, the gist of the present invention lies in the following [1] to [6].
[1] A resin composition containing the following components (A), components (B) and components (C).
Component (A): Cyanate ester resin containing two or more cyanato groups in one molecule Component (B): Imidazole compound containing a substituent having a triazine ring Component (C): Epoxy resin and / or phosphorus System Curing Catalyst [2] The resin composition according to the above [1], wherein the component (A) is a mixture of a prepolymer and a monomer of a cyanate compound containing two or more cyanato groups in one molecule.
[3] The resin composition according to the above [1] or [2], wherein the component (A) is a bisphenol A type cyanate ester resin.
[4] The resin composition according to the above [1] or [2], wherein the component (A) is a novolak-type cyanate ester resin.
[5] The resin composition according to any one of the above [1] to [4], wherein the component (C) is an epoxy resin.
[6] A carbon fiber prepreg containing carbon fibers and the epoxy resin composition according to any one of the above [1] to [5] as a matrix resin.

The resin composition of the present invention can be primarily cured at 150 ° C. or lower, has excellent thermal stability, and has excellent heat resistance after curing.
The prepreg of the present invention has a primary curability that can be removed from the mold at 150 ° C. or lower, has excellent thermal stability, and the fiber-reinforced composite material after molding has excellent heat resistance.

The definitions of the following terms apply throughout the specification and claims.
"Cyanate ester resin" refers to a compound having a cyanate group in the molecule.

<Resin composition>
The resin composition of the present invention is characterized by containing the following components (A), components (B) and components (C).
Component (A): Cyanate compound containing two or more cyanato groups in one molecule Component (B): Imidazole compound containing a substituent having a triazine ring Component (C): Epoxy resin and / or phosphorus-based Curing catalyst

<Component (A)>
The component (A) is a cyanate ester resin containing two or more cyanato groups in one molecule.
Specific examples of the cyanate ester resin include bisphenol A dicyanate, 4,4'-methylenebis (2,6-dimethylphenylcyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, and bis (4). -Cyanate-3,5-dimethylphenyl) methane, 1,3-bis (4-cyanatephenyl-1- (methylethylidene)) benzene, bis (4-cyanatephenyl) thioether, bis (4-cyanatephenyl) ether, etc. Examples thereof include bifunctional cyanate resins, phenol novolac, cresol novolak, polyfunctional cyanate resins derived from dicyclopentadiene structure-containing phenol resins, and prepolymers in which these cyanate resins are partially triazine. Two or more kinds of cyanate ester resins may be used in combination.

Commercially available cyanate ester resins include bisphenol A type cyanate ester resin (manufactured by Mitsubishi Gas Chemicals Co., Ltd., TA), phenol novolac type polyfunctional cyanate ester resin (manufactured by Ronza Japan Co., Ltd., PT30), and bisphenol A disicianate. Prepolymer (manufactured by Mitsubishi Gas Chemicals Co., Ltd., TA-500), dicyclopentadiene structure-containing cyanate ester resin (manufactured by Ronza Japan Co., Ltd., DT-7000) and the like can be mentioned.

As the component (A), bisphenol A type cyanate ester resin or phenol novolac type polyfunctional cyanate ester resin is preferable, and bisphenol A type cyanate is preferable from the viewpoint of excellent heat resistance and mechanical properties when made into a cured product. Ester resins are particularly preferred. A prepolymer of bisphenol A type cyanate ester resin is preferable because it has a viscosity excellent in handleability when it is used as a prepreg. Further, it is preferable to use a mixture of the prepolymer of the bisphenol A type cyanate ester resin and the bisphenol A type cyanate ester resin because the desired viscosity can be adjusted.

<Component (B)>
The component (B) is an imidazole compound containing a substituent having a triazine ring.
The imidazole compound containing a substituent having a triazine ring has a substituent having a 1,3,5-triazine (also simply referred to as triazine or s-triazine) ring at the 1-position nitrogen of the imidazole ring. The triazine ring and the imidazole ring may be directly bonded, but are preferably bonded by an alkylene group having 1 to 4 carbon atoms, and particularly preferably bonded by an ethylene group. The substituent having a triazine ring preferably has an amino group at the 2nd and 4th positions in the triazine ring. The imidazole compound containing a substituent having a triazine ring may be an adduct with isocyanuric acid. By using the imidazole compound containing a triazine ring, the primary curability of the resin composition at 150 ° C. or lower can be enhanced.

Examples of imidazole compounds containing a substituent having a triazine ring include 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-S-triazine, 2,4-diamino-6-. [2'-Undecyl imidazolyl-(1')]-Ethyl-s-Triazine, 2,4-diamino--6-[2'-Ethyl-4'-Methylimidazolyl-(1')]-Ethyl-s- Examples thereof include triazine, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-S-triazine with isocyanuric acid addition salt and the like. These are commercially available under trade names (manufactured by Shikoku Chemicals Corporation) such as 2MZ-A, C11Z-A, 2E4MZ-A, and 2MA-OK. 2,4-Diamino-6- [2'-methylimidazolyl- (1')]-ethyl-S-triazine, 2,4-diamino-6- [2', which has an excellent balance between low-temperature curability and thermal stability. '-Methylimidazolyl- (1')]-ethyl-S-triazine isocyanuric acid addition salt is preferred.

The "imidazole compound containing a substituent having a triazine ring" of the component (B) is preferably contained in the resin composition as a fine particle solid. Since it is contained in the resin composition as a fine-grained solid, it exists as a solid in the resin composition below a specific temperature, so that it is unlikely to act as a catalyst for a curing reaction. Since it dissolves in the inside and facilitates the curing reaction, it becomes easy to secure both thermal stability and low-temperature curing.

The particle size of the imidazole compound containing the substituent having a triazine ring of the component (B) is preferably 1 to 15 μm, more preferably 3 to 10 μm. By setting it to 1 μm or more, it becomes easy to secure thermal stability. When the thickness is 15 μm or less, low temperature curability is likely to be exhibited. The fine particle "imidazole compound containing a substituent having a triazine ring" can also be obtained as 2MZA-PW (manufactured by Shikoku Chemicals Corporation) or 2MAOK-PW (manufactured by Shikoku Chemicals Corporation).

The blending amount of the component (B) is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 2.0 parts by mass with respect to 100 parts by mass of the component (A). When the content is 0.1 part by mass or more, low temperature curability can be exhibited, and when the content is 5 parts by mass or less, deterioration of mechanical properties can be prevented.

<Component (C)>
The component (C) is an epoxy resin and / or a phosphorus-based curing catalyst.
By using the component (C) together with the "imidazole compound containing a substituent having a triazine ring" of the component (B), low temperature curability can be exhibited. The component (C) may contain either an epoxy resin or a phosphorus-based curing catalyst, and the epoxy resin and the phosphorus-based curing catalyst may be used in combination. Since the component (B) is powdery, it is preferable to mix it with a liquid epoxy resin from the viewpoint of handling. Therefore, the epoxy resin is preferable as the component (C).

The epoxy resin can be used without particular limitation, but a resin having two or more epoxy groups in the molecule is preferable from the viewpoint of enhancing the heat resistance of the cured product. Examples of the epoxy resin include bisphenol A type liquid epoxy resin such as jER828 (manufactured by Mitsubishi Chemical Co., Ltd.), bisphenol A type solid epoxy resin such as jER1001 (manufactured by Mitsubishi Chemical Co., Ltd.), jER630, and jER604 (all of which are Mitsubishi Chemical (Mitsubishi Chemical Co., Ltd.). MY05000, MY0600 (all manufactured by Huntsman Co., Ltd.) and other glycidylamine type liquid epoxy resins, jER807 (manufactured by Mitsubishi Chemical Co., Ltd.) and other bisphenol F type liquid epoxy resins, jER4004P (manufactured by Mitsubishi Chemical Co., Ltd.) ) Etc., bisphenol F type solid epoxy resin, jER152 (manufactured by Mitsubishi Chemical Co., Ltd.), etc. Examples thereof include phenol novolac type solid epoxy resin, other biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, bisphenol S type epoxy resin, phenol aralkyl type epoxy resin, naphthalene type epoxy resin, and alicyclic epoxy resin.

It is preferable to use a liquid epoxy resin because it is easy to handle. The epoxy resin may be used alone or in combination of two or more.
The epoxy resin is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass with respect to 100 parts by mass of the component (A). When the content is 0.1 part by mass or more, low temperature curability can be exhibited, and when the content is 5 parts by mass or less, deterioration of heat resistance of the cured product can be prevented.

Examples of the phosphorus-based curing catalyst include triphenylphosphine, triphenylphosphine triphenylborane, tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate and the like. These are commercially available under the trade names of TPP, TPP-S, TPP-K, and TPP-MK (manufactured by Hokuko Chemical Industry Co., Ltd.). Tetraphenylphosphonium tetra-p-tolylborate is preferable because it has an excellent curing accelerating effect.

The phosphorus-based curing catalyst is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass with respect to 100 parts by mass of the component (A). When the content is 0.1 part by mass or more, low temperature curability can be exhibited, and when the content is 5 parts by mass or less, deterioration of thermal stability can be prevented.

<Other ingredients>
Other components can be added to the resin composition of the present invention as long as the effects of the present invention are not impaired. Examples of other components include resins such as bismaleimide resin and thermoplastic resin, and additives such as fillers, solvents, pigments and antioxidants.
Bismaleimide resin is added for the purpose of improving heat resistance. Examples of the bismaleimide resin include 4,4'-diphenylmethane bismaleimide, bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide and the like.

The thermoplastic resin is added for the purpose of improving the toughness of the cured product of the resin composition. Examples of the thermoplastic resin include phenoxy resin, polyvinyl formal, polyether sulfone, and polyetherimide. The thermoplastic resin may be added as fine particles, and examples thereof include fine particles such as polyamide, polyimide, polyurethane, and polyether sulfone.

<Mixing method>
The method of mixing each component of the resin composition of the present invention can be carried out without particular limitation, but when mixing the fine particle substance, the fine particle substance and the liquid substance are mixed in an appropriate ratio. It is preferable to prepare a master batch sufficiently kneaded with three rolls or the like and add it to other constituents later, because the dispersed state of the fine particles can be made uniform.

The use of the resin composition of the present invention is not particularly limited, and can be applied as, for example, a matrix resin for a fiber-reinforced composite material, an adhesive for a structural material, or the like, and is used for a fiber-reinforced composite material. It can be particularly preferably used as a matrix resin.

<Reinforcing fiber>
The reinforcing fiber material for molding the fiber-reinforced composite material is not particularly limited, and for example, reinforcement of a general fiber-reinforced composite material such as carbon fiber, glass fiber, aramid fiber, alumina fiber, and silicon nitride fiber. Anything used as a fiber material can be used. In particular, it is preferable to use carbon fiber because it is excellent in specific strength and specific elastic modulus. Further, the form of the reinforcing fiber material is not particularly limited, and for example, a unidirectional material, a cloth, a mat, or a tow made of several thousand or more filaments can be used.

<Prepreg>
A prepreg can be obtained by impregnating a reinforcing fiber base material with the resin composition of the present invention and combining them. The prepreg for a fiber-reinforced composite material of the present invention can be produced by a known method using the resin composition of the present invention and the reinforcing fiber. As a method for producing a prepreg using the resin composition of the present invention, a hot melt method is preferable. When the resin composition is impregnated during the preparation of the prepreg by the hot melt method, it is preferably carried out at 80 ° C. or lower, more preferably 70 ° C. or lower in order to ensure the storage stability of the prepared prepreg. ..

The content of the resin composition in the prepreg is preferably 15 to 50% by mass, more preferably 20 to 45% by mass. When it is 15% by mass or more, the mechanical strength when it is made into a fiber-reinforced composite material can be exhibited, and when it is 50% by mass or less, the mechanical strength when it is made into a fiber-reinforced composite material can be increased. ..

(Prepreg fiber basis weight)
The fiber weight of the prepreg (content of reinforcing fiber per 1 m ² : FAW) may be appropriately set according to the use of the prepreg, and is usually 50 to 300 g / m ² .

(Thickness of prepreg)
The thickness of the prepreg may be appropriately set according to the intended use of the prepreg, and is usually 0.05 to 0.3 mm.
The thickness of the prepreg can be measured with a thickness gauge.

The resin raw materials used in the examples are shown below.
(Component (A))
TA: Bisphenol A dicyanate (manufactured by Mitsubishi Gas Chemical Company, Inc., trade name "TA")
TA-500: Prepolymer of bisphenol A dicyanate (manufactured by Mitsubishi Gas Chemical Company, Inc., trade name "TA-500")
XU-371: Phenolic novolak type cyanate ester resin (manufactured by Huntsman, trade name "Arocy XU-371")

(Component (B))
2MZA-PW: 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s-triazine (manufactured by Shikoku Chemicals Corporation, trade name "2MZA-PW")
2MAOK-PW: 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-S-triazine isocyanuric acid addition salt (manufactured by Shikoku Chemicals Corporation, trade name "Curesol 2MAOK-" PW ")

(Component (C))
jER828: Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name "jER828")
TPP-MK: Tetraphenylphosphonium tetra-p-tolylborate (manufactured by Hokuko Chemical Industry Co., Ltd., trade name "TPP-MK")

(Other ingredients)
2PHZ-PW: 2-Phenyl-4,5-dihydroxymethylimidazole (manufactured by Shikoku Chemicals Corporation, trade name "Curesol 2PHZ-PW")
2P4MHZ-PW: 2-Phenyl-4-methyl-5-hydroxymethylimidazole (manufactured by Shikoku Chemicals Corporation, trade name "Curesol 2P4MHZ-PW")
Zinc octylate: Zinc 2-ethylhexanoate (manufactured by Nihon Kagaku Sangyo Co., Ltd., trade name "Nikka Octix Zinc 18%")

(Evaluation of thermal stability)
The resin compositions prepared in each Example and Comparative Example were measured for isothermal viscosity as follows. The ratio of the viscosity after 6 hours to the viscosity at the start of measurement was determined.
Equipment: AR-G2 (manufactured by TA Instruments)
Plate used: Parallel plate with a diameter of 25 mm Plate gap: 0.5 mm
Measurement frequency: 10 rad / sec
Measurement temperature: 60 ° C
Measurement interval: 1 minute Stress: 300 Pa

(Making a resin plate)
The resin composition prepared in each Example and Comparative Example was injected into a gap sandwiched between two 4 mm-thick glass plates having a mold release treatment and a 2 mm-thick polytetrafluoroethylene (PTFE) spacer, and the temperature was 135 ° C. The mixture was heated for 120 minutes to obtain a primary cured resin plate. The primary cured resin plate was removed from the glass plate and heated at 250 ° C. for 2 hours in a free stand state to obtain a secondary cured resin plate.

(Measurement of glass transition point of cured product)
A test piece having a length of 55 mm, a width of 12.7 mm, and a thickness of 2 mm was cut out from the resin plate for each of the primary cured resin plate and the secondary cured resin plate. Bending mode using a dynamic viscoelasticity measuring device (DMA Q-800, manufactured by TA Instruments) under the conditions of frequency: 1 Hz, strain: 0.02%, and heating rate: 5 ° C / min. The storage elastic modulus E'was measured at. LogE'was plotted against temperature, and the temperature obtained from the intersection of the approximate straight line of the flat region before the transition of logE'and the approximate straight line of the region where logE' transitioned was defined as the glass transition point.

<Preparation of resin composition>
(Example 1)
jER828 and 2MZA-PW were mixed at a mass ratio of 1: 1 and uniformly dispersed using three rolls to obtain a paste-like masterbatch. TA and TA-500 were weighed in a flask so as to have the ratio shown in Table 1, and uniformly dissolved and mixed at 100 ° C. The temperature of the obtained solution was lowered to about 60 ° C., the above-mentioned masterbatch was added, and the mixture was stirred until uniform to obtain a resin composition 1.
The obtained resin composition 1 was evaluated. The evaluation results are shown in Table 1.

(Example 2)
TA and TA-500 were weighed in a flask so as to have the ratio shown in Table 1, and uniformly dissolved and mixed at 100 ° C. The temperature of the obtained solution was lowered to about 60 ° C., 2MZA-PW and TPP-MK were added, and the mixture was stirred until uniform to obtain a resin composition 2. The evaluation results of the obtained resin composition 2 are shown in Table 1.

(Example 3)
jER828 and 2MZA-PW were mixed at a mass ratio of 1: 1 and uniformly dispersed using three rolls to obtain a paste-like masterbatch. jER828 and TPP-MK were mixed at a mass ratio of 3: 2 and uniformly dispersed using three rolls to obtain a paste-like masterbatch. TA and TA-500 were weighed in a flask so as to have the ratio shown in Table 1, and uniformly dissolved and mixed at 100 ° C. The temperature of the obtained solution was lowered to about 60 ° C., the above-mentioned masterbatch was added, and the mixture was stirred until uniform to obtain a resin composition 3. The evaluation results of the obtained resin composition 3 are shown in Table 1.

(Example 4)
A resin composition was prepared and evaluated in the same manner as in Example 3 except that the ratio was changed as shown in Table 1.

(Examples 5 to 7)
A resin composition was prepared and evaluated in the same manner as in Example 2 except that the ratio was changed as shown in Table 1.

(Comparative Examples 1 and 2)
A resin composition was prepared and evaluated in the same manner as in Example 3 except that the ratio was changed as shown in Table 1.

(Comparative Examples 3 to 5)
A resin composition was prepared and evaluated in the same manner as in Example 2 except that the ratio was changed as shown in Table 1.

(Example 8)
Using a comma coater, the resin composition 1 prepared in Example 1 was uniformly applied onto a release paper so as to have a resin basis weight of 35.2 g / m ² to form a resin film. Then, in a drum wind device, carbon fiber (manufactured by Mitsubishi Chemical Corporation, product name:) so that a sheet having a fiber grain of 125 g / m ² is formed on this resin film (the surface of the release paper on the resin film forming side). MR70) was wrapped around. Further, another resin film was bonded onto the carbon fiber sheet on the drum wind device. The carbon fiber sheet sandwiched between the two release papers and the resin film is heated and pressurized with a roller at 100 ° C. and a linear pressure of 0.2 MPa to impregnate the carbon fiber sheet with the epoxy resin composition, and the fiber texture is 125 g. A prepreg having a resin content of / m ² and a resin content of 36% by mass was prepared. Then, the prepreg was cut into a length of 300 mm × 300 mm, and 16 fibers were laminated in the same direction of the fiber orientation, placed in a bag, heated in an autoclave at 135 ° C. for 2 hours, and first cured to form the prepreg. A plate (fiber reinforced composite material) was produced. The fiber-reinforced composite material taken out of the bag was heated in an oven at 250 ° C. for 2 hours for secondary curing. The glass transition point was measured according to the method described in (Measurement of glass transition point of cured product) for each of the primary cured product and the secondary cured product. The evaluation results are shown in Table 2.

Examples 1 to 7 had low temperature curability and good thermal stability in the evaluation of primary curing at 135 ° C. for 2 hours, and also had good heat resistance after secondary curing. Comparative Examples 1 and 2 using imidazole having a triazine ring structure and containing no substituent did not have low temperature curability. Comparative Examples 3 to 4 containing no component (C) also did not have low temperature curability. Comparative Example 5 using a metal catalyst had low-temperature curability, but lacked thermal stability. As shown in Example 8, the prepreg of the resin composition of the present invention also had low temperature curability and good heat resistance of the cured product.

The resin composition of the present invention has excellent primary curability at a low temperature of 150 ° C. or lower, and also has excellent thermal stability, and also has excellent heat resistance by secondarily curing a cured product primary cured at a low temperature at a high temperature. It becomes a cured product having properties. Further, the prepreg of the present invention has excellent primary curability at a low temperature of 150 ° C. or lower, and also has excellent heat resistance and mechanical strength by secondarily curing a cured product primary cured at a low temperature at a high temperature. It becomes a fiber reinforced composite material. The resin composition and prepreg of the present invention are suitably used in fields where heat resistance is required, such as aircraft members, automobile members, bicycle members, railway vehicle members, and ship members.

Claims (5)

In a method for producing a carbon fiber prepreg, which comprises a carbon fiber and a resin composition containing the following components (A), components (B) and components (C) as a matrix resin, it is hot.
A carbon fiber prepreg in which the carbon fiber base material is impregnated with the resin composition by a melt method.
Production method.
Component (A): Cyanate ester resin containing two or more cyanato groups in one molecule Component (B): Imidazole compound containing a substituent having a triazine ring Component (C): Epoxy resin and / or phosphorus System curing catalyst The production of the carbon fiber prepreg according to claim 1, wherein the component (A) is a mixture of a prepolymer and a monomer of a cyanate compound containing two or more cyanate groups in one molecule.
Method . Claim 1 that the component (A) is a bisphenol A type cyanate ester resin.
Alternatively , the method for producing a carbon fiber prepreg according to 2. The method for producing a carbon fiber prepreg according to claim 1 or 2, wherein the component (A) is a novolak type cyanate ester resin. The method for producing a carbon fiber prepreg according to any one of claims 1 to 4, wherein the component (C) is an epoxy resin.