JP2006070115A - Resin composition for fiber-reinforced composite material, method for producing fiber-reinforced composite material using the composition, and fiber-reinforced composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a void-free, crack-resistant, high toughness, and short-cure-time fiber-reinforced composite material, to provide a resin composition suited for use in this method, and to provide a fiber-reinforced composite material using the resin composition. <P>SOLUTION: The resin composition comprises 100 pts. wt. (A) cyanate ester resin comprising 50 to 100 pts. wt. (A1) resin modified with 5 to 30 wt.% rubber and 0 to 50 pts. wt. (A2) resin not modified with a rubber and 0.01 to 0.5 pt. wt. (B) metal coordination type catalyst, has a viscosity in the range of 100 to 800 mPa s at 50 to 120°C, and keeps the above viscosity range for 1 hr or longer in the above temperature range. The fiber-reinforced composite material is obtained by subjecting the resin composition to the following steps (1) to (3) in the given order: (1) the step of arranging reinforcing fibers in a die, (2) the step of heating the resin composition at 50 to 120°C to impregnate the reinforcing fibers with the resin composition, and (3) the step of heating the entire to 120 to 200°C after the impregnation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fiber-reinforced composite material that can be suitably applied to aircraft structural materials, railway vehicle structural materials, golf shafts, fishing rods and other sports applications, and other general industrial applications, and a method for manufacturing the same. Moreover, this invention relates to the resin composition used in order to manufacture a fiber reinforced composite material.

  There is a need in the industry for a fiber reinforced composite material that is lighter, tougher and more resistant to heat, replacing the fiber reinforced composite material currently in use. For example, in the aerospace industry, considerable research has been done on the use of structural composites instead of metals. A structural composite material mainly composed of thermoplastic or thermosetting resin and glass or carbon fiber is excellent in mechanical strength such as specific strength and specific elastic modulus. Therefore, structural materials for sports such as golf shafts and fishing rods and aircraft structural materials. It has been used widely from the past to the present, and has obtained good results.

  As the resin constituting such a composite material, a thermosetting resin having excellent impregnation and heat resistance is often used, and the thermosetting resin has excellent adhesion to carbon fibers and excellent moldability. It is necessary to develop a high mechanical strength even in a high temperature and humid environment. In order to develop a high mechanical strength, not only the carbon fiber but also the elastic modulus of the resin is affected, and therefore, a resin having a high elastic modulus is desired. For this reason, phenolic resins, melamine resins, bismaleimide resins, unsaturated polyester resins, cyanate ester resins, epoxy resins, and the like are used as thermosetting resins depending on applications. In many applications typified by railway vehicle structures, there is a demand for materials having higher elastic modulus, heat resistance, and flame retardancy than those used so far. Cyanate ester resin is preferably used from such a demand.

  Also, as a molding method of the fiber reinforced composite material, a so-called injection molding method in which a matrix resin is injected into a mold and cured is the mainstream. As the injection molding method, a so-called resin transfer molding (RTM) molding method is frequently used in which a matrix resin is injected into a mold in which a reinforcing fiber base is set in advance.

  Non-patent document 1 (Polymer Composites, vol.19, No.2, pp.166-179) describes a method for obtaining a fiber-reinforced composite material using a cyanate ester resin as a matrix resin and an RTM molding method. After preparing a resin composition blended with acetylacetonate and nonylphenol, placing a reinforcing fiber preform on an aluminum mold, the resin was injected at 115 ° C to 135 ° C under a constant pressure, and the mold was 150 A method is described in which curing is performed at 200 ° C. for 20 minutes and then curing at 200 ° C. for 55 minutes. This method requires a high curing temperature to obtain a fiber-reinforced composite material as described above. In such a molding method, the higher the curing temperature, the higher the heat resistance of the fiber-reinforced composite material. However, when the curing temperature is high, a molding die having a size sufficient to cure the thermosetting resin in the molding of large composite structures such as aircraft wings and fuselage, submarine hulls, and railway vehicle structures is economical. Since it is not excellent in property, it is not preferable.

  As a method for molding at a relatively low temperature, Patent Document 1 (Patent No. 2743424) exemplifies a method using a fatty acid alkanolamide as a curing catalyst for a cyanate ester resin. In this case, flame retardant of the fatty acid alkanolamide used is used. This is not preferable as a matrix resin used when a high flame retardancy such as a railway vehicle structure is required because the flame retardancy of the resulting resin composition is lowered.

With respect to these problems, Patent Document 2 (Japanese Patent Laid-Open No. 2003-12819) does not require expensive molds, heating equipment, auxiliary materials, etc., and has excellent heat resistance, flame retardancy, and mechanical properties. A method of manufacturing a fiber reinforced composite material that provides a fiber reinforced composite material is disclosed. This publication exemplifies a method in which an active hydrogen-type catalyst is added to an isocyanate ester resin to perform primary curing at a temperature of 50 to 95 ° C., and then taken out from a mold and subjected to main curing at 130 to 250 ° C. Yes. Here, the primary molding at low temperature eliminates the need for expensive molds and heating equipment, but as shown in the examples, the primary curing takes a long time at 80 ° C. for 10 hours. Heating is required.
Japanese Patent No. 2743424 JP 2003-12819 A Polymer Composites, vol.19, No.2, pp.166-179

  In the RTM molding method, the viscosity at the time of pouring the resin composition into the fiber base material and the viscosity of the resin composition at the time of thermoforming are important, and it is generally said that about 10 to 800 mPa · s is optimum. ing.

  Specifically, in RTM molding, a low viscosity is essential for impregnating the resin composition into the reinforcing fiber, but if the viscosity of the resin composition is less than 10 mPa · s, the resin flows out from the reinforcing fiber. As a result, the wettability (retention property) is lowered, which causes voids. On the contrary, if the viscosity of the resin composition is too high, not only is it difficult to inject the resin composition, but also the wettability with the reinforcing fibers is reduced, which also causes voids. Also, if the injection temperature and the molding temperature of the resin composition are different (usually the molding temperature is higher than the injection temperature), the resin composition will decrease in viscosity when heated to the molding temperature. When the viscosity of the composition is less than 10 mPa · s, the wettability with the reinforcing fiber is similarly reduced, causing voids. When voids are generated in the material in this way, the mechanical strength may be greatly reduced. Further, since the moisture resistance is lowered, for example, the thermal cycle characteristics are deteriorated, and it is difficult to use the aircraft members in applications where the characteristics under high temperature and humid environment are required.

  In addition, it has been known that the addition of tougheners such as elastomers is effective for imparting toughness to fiber-reinforced composite materials, but it is only to add to the resin composition to promote the generation of voids. There is also. For example, in Non-Patent Document 1, a thermoplastic elastomer is used as a toughness improver. However, the viscosity increase of the resin composition due to the addition of the elastomer is large, and there is a problem in molding a large molded product. For example, according to FIG. 7 in the document, the viscosity at 135 ° C. is 300 mPa · s even at the lowest viscosity, and after about 30 minutes, it exceeds 800 mPa · s, which is the optimum range in RTM molding. As described above, since the viscosity is high, the resin cannot sufficiently wrap around the reinforcing fibers, and voids are formed. On the other hand, a material with poor toughness is susceptible to cracking upon impact.

  An object of the present invention is to provide a method for producing a fiber-reinforced composite material in which no void is formed, excellent toughness, and the curing time is short.

  Another object of the present invention is to provide a resin composition suitable for this production method, and further, mechanical strength such as toughness, flame retardancy, and molding using such a resin composition and production method. An object of the present invention is to provide a fiber-reinforced composite material having excellent properties.

  According to the study by the present inventors, when a fiber reinforced composite material is produced by the RTM molding method, it is extremely important to use a resin composition having a specific composition as a matrix resin and to regulate the viscosity at the time of molding the composition. It was found to be important.

  In particular, it is necessary to set the viscosity of the resin composition at an appropriate range when the resin composition is injected and when the resin composition is heated to the molding temperature after the resin composition is injected. In the present invention, by adjusting the blending of the resin composition and further using specific rubber fine particle components, viscosity adjustment and expression of physical properties of the fiber-reinforced composite material are achieved.

That is, the present invention
[1] A resin composition for producing a fiber-reinforced composite material by impregnating and curing a reinforcing fiber, the resin composition including the following components (A) and (B), The resin composition characterized by having a viscosity at 50 to 120 ° C. of 300 to 800 mPa · s and maintaining a viscosity of 800 mPa · s or less in the above temperature range for 1 hour or more.
(A): 100 parts by weight of cyanate ester resin containing the following (A1) and (A2):
(A1): Cyanate ester resin modified with 5 to 30% by weight of rubber and 50 to 100 parts by weight of polytriazine derived from the resin (A2): Cyanate ester resin not modified with rubber and the resin 0 to 50 parts by weight of polytriazine derived from (B): 0.01 to 0.5 parts by weight of metal coordination catalyst

[2] The resin composition according to [1], wherein a viscosity of 10 mPa · s or more is maintained until the molding temperature is reached after heating at a temperature of 50 to 120 ° C. for 1 hour.

[3] The resin composition according to [1] or [2], wherein the rubber used for modifying the component (A1) is acrylic rubber particles or silicone rubber particles.

[4] The resin composition according to any one of [1] to [3], wherein the resin composition has a curing shrinkage rate of 1% or less when the composition alone is cured.

[5] The resin composition according to any one of [1] to [4], wherein the metal coordination catalyst of the component (B) is a cobalt (III) acetylacetonate complex.

[6] A method for producing a fiber-reinforced composite material, wherein the following steps (1) to (3) are performed in this order.
(1) A step of arranging reinforcing fibers using a mold,
(2) Heating the resin composition according to any one of [1] to [5] at a temperature of 50 to 120 ° C., and heating the resin composition to the reinforcing fiber disposed in the step (1). And (3) a step of heating the reinforcing fiber after impregnation with the resin composition at a temperature of 120 to 200 ° C. to obtain a fiber-reinforced composite material.

[7] In the method for producing a fiber-reinforced composite material according to [6], after the step (3), the obtained fiber-reinforced composite material is taken out from the mold and post-cured at a temperature of 200 to 250 ° C. The said manufacturing method to perform.

[8] A fiber-reinforced composite material obtained by impregnating a reinforcing fiber with the resin composition according to any one of [1] to [5] and curing.

[9] A fiber-reinforced composite material produced by the method according to [6] or [7].

[10] The fiber-reinforced composite material according to [8] or [9], wherein the reinforcing fiber is carbon fiber.

  According to the present invention, a fiber-reinforced composite material having excellent heat resistance, flame retardancy, and mechanical properties and particularly excellent toughness can be produced in a relatively short time without voids.

  The fiber-reinforced composite material of the present invention is a fixing material, a structural member, a reinforcing agent, a molding material, an insulating material, etc. in the fields of civil engineering / architecture, electricity / electronics, automobiles, railways, ships, aircraft, sports equipment, arts / crafts, etc. Are preferably used. Among these, it is suitable for aircraft structural members, satellite structural members and railway vehicle structural members that require weather resistance, flame resistance and high mechanical strength, sports fiber reinforced composite materials, that is, golf club shafts, fishing rods, etc. Can be used.

  As the cyanate ester resin of component (A) that can be used in the present invention, those disclosed in Patent Document 2 can be used and are represented by the following formula (I).

（式中、ｎは１以上の整数、Ａはｎ価の有機基である。）

(In the formula, n is an integer of 1 or more, and A is an n-valent organic group.)

  Specific examples of the cyanate ester resin represented by the above formula (I) include 1,3- or 1,4-dicyanate benzene, 4,4′-dicyanate biphenyl, and the following structural formula (II). Ortho-substituted dicyanate esters, such as

(In the above formula, R _{1 to} R ₄ groups represent a hydrogen atom or a methyl group, and may be the same or different from each other, X is a divalent group, and preferably an alkylene group having 1 to 4 carbon atoms. a phenylene group, -O -, - S -, - SO 2 -, - CO- and the like).
A polyphenylene oxide cyanate ester represented by the following structural formula (III):

(In the above formula, h is an integer satisfying h ≧ 0, i is an integer satisfying i ≧ 1, R _{5 to} R ₁₂ groups represent a hydrogen atom or a methyl group, and may be the same or different, and X is (It represents the same divalent group as X in the formula (II).)
A tricyanate ester represented by the following structural formula (IV):

(In the above formula, R _{13 to} R ₁₇ groups represent a hydrogen atom or a methyl group and may be the same or different from each other).
Furthermore, a polycyanate ester represented by the following structural formula (V),

(In the above formula, k is an integer of 1 or more, R _{18 to} R ₂₀ each represents a hydrogen atom or a methyl group, and may be the same or different, and X is the same as X in the formula (II)) Represents a divalent group).

  Such a cyanate ester resin (A) may be composed of only a monomer, or may be used even if a few molecules are polymerized into an oligomer state. In the present invention, polytriazines formed by trimerization of these cyanate ester resins can also be used. For example, a trimeric polytriazine of a cyanate ester resin represented by the formula (I) has a structure represented by the following formula (VI).

  As cyanate ester resins that can be used in the present invention and polytriazines derived from these resins, the following are commercially available.

  Bisphenol A dicyanate (2,2'-bis (4-cyanatophenyl) isopropylidene) (for example, Lonza trade name "BADCy", Huntsman trade name "B-10"), prepolymerized product of BADCy (Mixture of cyanate ester resin and polytriazine) (for example, Lonza brand name `` BA200 '', Huntsman brand name `` B-30 '')

  Bisphenol AD dicyanate (1,1'-bis (4-cyanatophenyl) ethane) (for example, Lonza trade name "LECy", Huntsman trade name "L-10")

  Dicyanate of substituted bisphenol F (for example, trade name “METHYLCy” manufactured by Lonza, trade name “M-10” manufactured by Huntsman), prepolymerized product of METHYLCy (mixture of cyanate ester resin and polytriazine) (for example, M- 30)

  Cyanate ester of phenol dicyclopentadiene adduct (for example, trade name “XU-71787-02” manufactured by Huntsman)

  Phenol novolac type cyanate ester and prepolymerized product thereof (for example, trade names “PT-15”, “PT-30”, “PT-60” manufactured by Lonza)

  In the present invention, among 100 parts by weight of the cyanate ester resin (A), at least 50 parts by weight uses the cyanate ester resin (A1) modified with rubber. The rubber-modified cyanate ester resin (A1) may be a total amount of 100 parts by weight of the cyanate ester resin (A), and the remainder includes the cyanate ester resin (A2) that is not rubber-modified. May be. A1 and A2 may be used singly or in combination.

  The rubber-modified cyanate ester resin (A1) used in the present invention is produced, for example, by a method as disclosed in JP-A No. 64-70519. That is, at least one emulsion polymerizable monomer is emulsified in an aqueous colloidal dispersion of discontinuous resin-insoluble rubber particles maintained in a moderately stable state by a surfactant or an emulsifier, and an emulsion obtained is obtained. It is obtained by polymerizing to form a stable colloidal dispersion of resin-insoluble rubber particles, mixing the colloidal dispersion with a cyanate ester resin, and grafting the rubber particles.

  At this time, it is modified with 5 to 30% by weight of rubber. If the amount of rubber to be modified is less than 5% by weight, the effect of improving toughness is small. On the other hand, if the amount of rubber exceeds 30% by weight, the viscosity of the resin composition increases, making it difficult to adjust the viscosity range suitable for the present invention. give.

  Also, commercially available rubber-modified cyanate ester resins are available, for example:

  Bisphenol AD dicyanate (1,1′-bis (4-cyanatophenyl) ethane) (for example, trade name “LECy” manufactured by Lonza) added with 10% of core-shell type rubber fine particles or silicone rubber fine particles (for example, , Lonza brand name “LECy-10T” or “LECy-10TP”), 20% added (for example, Lonza brand name “LECy-20T”

  A bisphenol A dicyanate (2,2′-bis (4-cyanatophenyl) isopropylidene) (for example, trade name “BADCy” manufactured by Lonza) added with 10% rubber fine particles (for example, Lonza) (Product name “BA100-10T”)

  10% rubber fine particles added to cyanate ester of phenol dicyclopentadiene adduct (for example, trade name “XU-71787-02” manufactured by Huntsman) (for example, product name “XU-71787-07” manufactured by Huntsman)

  The cyanate ester resin may be liquid or solid at room temperature. In the present invention, the viscosity of the resin composition is adjusted by mixing a liquid and a solid. You can also.

Examples of the metal coordination catalyst of component (B) used in the present invention include copper acetylacetonate, cobalt (III) acetylacetonate (hereinafter referred to as Co (acac) ₃ ), zinc octylate, tin octylate, and naphthenic acid. Zinc, cobalt naphthenate, tin stearate, zinc stearate and iron, cobalt, zinc, copper, manganese, chelate compounds of titanium and bidentate ligands such as catechol, etc. can be used. From the viewpoint of moldability and pot life balance, Co (acac) ₃ can be preferably used.

  The blending amount of the metal coordination catalyst is 0.01 to 0.5 parts by weight with respect to 100 parts by weight of the component (A) from the viewpoint of achieving both curability and stability of the resin composition. If it is necessary, 0.03-0.3 weight part is more preferable. When the metal coordination catalyst exceeds 0.5 parts by weight, it gels in a short time, and the viscosity when heated to 50 to 120 ° C. increases rapidly, keeping the viscosity below 800 mPa · s for 1 hour or more. Since it may become impossible to remove, it is not preferable. On the other hand, if the amount is less than 0.01 parts by weight, it takes too much time for curing and is not practical. The viscosity of the resin composition of the present invention when heated to 50 to 120 ° C. is 300 to 800 mPa · s, more preferably 300 to 600 mPa · s.

  The internal stress can be estimated from the cure shrinkage of the resin itself, but cyanate ester resins are known to have less cure shrinkage than other thermosetting resins. It is an optimal resin for use in the invention. In particular, in a large-sized molded product, if the curing shrinkage is not 1% or less, cracks frequently occur at the time of curing, which causes a practical problem.

  In the resin composition of the present invention, in addition to the components (A) and (B), a resin component other than the cyanate ester resin (A) can be used as long as the effects of the present invention are not impaired. Such resin components include thermosetting resins such as epoxy resins, polyester resins, polyurethane resins, urea resins, phenol resins, melamine resins, benzoxazine resins, nylon resins, polyester resins, polyether ketone resins, polyphenylene sulfide resins. Further, thermoplastic resins such as polyethersulfone resin and thermoplastic polyimide can be used. The thermosetting resin here may partially contain a monomer or an oligomer.

  The cyanate ester resin (A) is a resin material that is excellent in flame retardancy as described above, but in order to impart higher flame retardancy, a known flame retardant is added within a range that does not impair the effects of the present invention. May be.

  Reinforcing fibers used in the present invention can cause the fiber-reinforced composite material to exhibit high moisture and heat resistance characteristics, specific strength, and specific modulus required for aircraft and railway vehicle applications.

  As the reinforcing fiber in the present invention, glass fiber, carbon fiber, aramid fiber, boron fiber, alumina fiber, nylon fiber, silicon carbide fiber or the like can be used. In order to obtain higher mechanical properties, glass fibers and carbon fibers are preferably used, and carbon fibers are more preferably used.

  When carbon fibers are used as the reinforcing fibers, those having a tensile elastic modulus of 200 GPa or more are preferable in order to achieve both impact resistance and rigidity of the obtained fiber-reinforced composite material. Among such carbon fibers, it is preferable to use a carbon fiber having a tensile elongation of 1.5% or more in a strand tensile test because a fiber-reinforced composite material having more excellent impact resistance can be obtained. Is more preferably 1.7% or more of carbon fiber.

  The tensile strength of the carbon fiber is preferably 3800 MPa or more, more preferably 4000 MPa or more, and further preferably 4500 MPa or more. If it is less than 3800 MPa, the resulting composite material has insufficient tensile strength, which may be difficult to apply to aircraft structural materials and structural materials for railway vehicles that require high mechanical strength. .

  The reinforcing fiber in the present invention can be used in combination of a plurality of reinforcing fibers.

  The form and arrangement of the reinforcing fibers are not particularly limited and can be appropriately selected from woven fabrics, non-woven fabrics, mats, knits, braids, unidirectional strands, rovings, choppeds, etc., but the fiber reinforcements are lighter and more durable. In order to obtain a composite material, the reinforcing fiber is preferably in the form of a continuous fiber such as a woven fabric, a unidirectional strand, or a roving. Here, a conventionally known woven fabric can be used as the woven fabric. The woven fabric is preferably a unidirectional fabric, a plain weave, a twill weave, an entangled weave or a satin weave using reinforcing fibers for the warp and glass fibers or organic fibers for preventing misalignment. In addition, since aesthetics, such as color luster, are given to a textile fabric, it is preferable to use the textile surface as the textile fabric which consists of carbon fibers.

  Moreover, a preform can be applied as a form of the reinforcing fiber. Here, the preform usually means a laminate of woven fabrics made of long-fiber reinforcing fibers, or a fabric structure that is stitched and integrated with stitch yarns, or a fiber structure such as a three-dimensional fabric or braid. .

  The fiber reinforced composite material produced using the production method of the present invention preferably has a fiber volume fraction of 10 to 85%, more preferably 30 to 70%. If it is less than 10%, the weight of the resulting composite material becomes excessive, and the advantages of the fiber-reinforced composite material having excellent specific strength and specific elastic modulus may be impaired. If it exceeds 85%, poor resin impregnation will occur. The resulting composite material tends to have a lot of voids, and its mechanical strength may be greatly reduced.

The method for producing a fiber-reinforced composite material of the present invention is characterized in that the following steps (1) to (3) are performed in this order.
(1) A step of arranging reinforcing fibers using a mold,
(2) The step of heating the resin composition of the present invention at a temperature of 50 to 120 ° C. and impregnating the heated resin composition into the reinforcing fiber, and (3) 120 to 200 of the reinforcing fiber after impregnation with the resin composition. Heating at a temperature of ℃ to obtain a fiber reinforced composite material.

  In the step (1) in the present invention, the method of arranging the reinforcing fiber and the resin composition can be appropriately used depending on the production amount, size, shape, or the like of the target composite material. For example, the RTM method is preferably used when mass-producing a composite material having a relatively complicated shape in a short time. In the RTM method, materials other than the above-described preforms such as a metal plate, a foam core, and a honeycomb core can be set in the mold in advance, and thus can be used for various applications.

  The mold used in step (1) is preferably a hermetically sealed one, but so-called vacuum bagging can also be used. Further, it is usually preferable to use a metal such as aluminum, steel, or stainless steel as the material of the mold. Moreover, in order to heat a shaping | molding die, it is preferable to provide the heating function by a heat-medium circulation or a heater.

  In the step (2), the resin composition is heated at a temperature of 50 to 120 ° C., and the viscosity of the resin composition is adjusted to 300 to 800 mPa · s. More preferably, it is 300 to 600 mPa · s. In RTM molding, in order to impregnate the resin composition into the reinforcing fiber, it is essential that the viscosity is low. Conventionally, it was considered that a lower viscosity was preferable, but the viscosity of the resin composition was If the pressure is reduced to less than 10 mPa · s, the wettability with the reinforcing fiber is lowered, which tends to cause voids. If the viscosity at the time of heating at a temperature of 50 to 120 ° C. is 300 mPa · s or more, it is possible to maintain a viscosity of 10 mPa · s or more at the stage of heating to the molding (curing) temperature. On the other hand, if the viscosity of the resin composition is too high, not only is it difficult to inject the resin composition, but also the wettability with the reinforcing fibers is reduced.

  At this time, if the heating temperature for achieving an appropriate viscosity is less than 50 ° C., not only will it take time to raise the mold in step (3), but also the temperature difference between the resin injection temperature and the molding temperature. Therefore, when the resin is injected and heated to the molding temperature, the resin viscosity is reduced to less than 10 mPa · s, causing voids and the like. In the present invention, since the rubber-modified cyanate ester resin is contained as the component (A1), a decrease in the viscosity of the resin composition during heating from the resin injection temperature to the molding temperature is suppressed, and the flow of the resin composition It also has the role of maintaining the sex appropriately.

  On the other hand, when the heating temperature for obtaining an appropriate viscosity is higher than 120 ° C., the increase in the viscosity of the resin composition due to the reaction becomes excessive, gelation proceeds in a short time, and molding may be difficult.

  In the molding of a large molded product, it is necessary to provide sufficient time for the resin composition injection and the reinforcing fiber impregnation, and the composition can maintain the resin viscosity at 800 mPa · s or less for 1 hour or more in the heating temperature range. Is preferred. At this time, the increase in viscosity can be suppressed by making the addition amount of the metal coordination catalyst smaller than the amount specified in the present invention, but in this case, heating at a high temperature for a long time is required at the time of molding. From the viewpoint of economy and productivity, it is not preferable.

  In the step (3), the resin composition is cured by heating to 120 ° C. or more and 200 ° C. or less. Preferably they are 150 degreeC or more and 200 degrees C or less. The curing time is not particularly limited, but is usually cured in a short time of about 2 to 4 hours.

  The heat resistance of the fiber-reinforced composite material thus obtained is usually 150 ° C. or higher, but after being taken out from the mold and post-cured at a temperature of 200 to 250 ° C., the heat resistance of a maximum of 250 ° C. or higher is obtained. Can be obtained. In applications where heat resistance is required, it is possible to cope by post-curing in this way. Further, the flame retardancy is also improved by increasing the heat resistance.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited only to these examples. In the examples, the physical property evaluation methods for the uncured resin, the cured resin, and the fiber reinforced composite material were performed under the following conditions.

1. Viscosity measurement of uncured resin
Using a Rheometrics viscoelastic spectrometer “RDA-II”, using a 25mmφ parallel plate, temperature / temperature sweep, measurement frequency 10Hz, temperature rise rate 2 ℃ / min. The temperature at which the complex viscosity (viscosity) was 600 mPa · s was measured. Next, constant temperature measurement was performed at that temperature, and the time until the viscosity exceeded 800 mPa · s was measured. If the viscosity did not exceed 800 mPa · s even after 120 minutes after the measurement, the measurement was stopped there. Further, after holding at a constant temperature for 1 hour, the viscosity at the molding temperature was measured.

2. Measurement of Curing Shrinkage of Resin Cured Product Based on ASTM D2566, the curing shrinkage of the resin when cured under the described conditions was measured. The curing shrinkage rate can also be obtained from the following formula from the specific gravity when uncured and after curing.
(Specific gravity after curing-Specific gravity when uncured) / (Specific gravity after curing)

3. Measurement of bending strength and toughness value of cured resin product According to JIS K7171, a bending test of a cured resin product (cured plate) and a bending fracture toughness test were performed according to ASTM D5045, respectively.

4). Measurement of tensile strength of fiber reinforced composite materials
In accordance with ASTM-D3039, tensile strength measurement was performed using an Instron 4208 type tester (Instron). The test piece dimensions were 25.4 mm wide and 229 mm long, and each piece was cut so as to be perpendicular or parallel to the reinforcing fiber. The ambient temperature was 23 ° C. and the crosshead speed was 1.27 mm / min.

5. Cross-sectional observation of fiber reinforced composite materials (voids, cracks)
After cutting the molded fiber reinforced composite material and polishing the cross section, the presence or absence of voids and cracks was observed with a microscope. Each evaluation of a void and a crack was evaluated as ◯ when it could not be confirmed and as x when it could be confirmed.

6). Manufacture of fiber reinforced composite material The molding die has a rectangular parallelepiped cavity of 300mm length, 300mm width and 1mm height, which consists of an upper mold and a lower mold, and a resin injection port at the center of the upper mold And having a resin spout at the four corners of the lower mold were used.

In addition, for the preform, carbon fiber cloth CO6343 (T300B-3K used, 198 g / m ² basis weight, manufactured by Toray Industries, Inc.) was cut so that each side was perpendicular to or parallel to the reinforcing fiber, and the side was 280 mm. A square layer with 5 layers was used.

Using these, the following steps (1) to (3) were performed in this order to obtain a fiber-reinforced composite material.
(1) The preform is set in a mold and clamped, and then the resin composition degassed for 5 minutes under vacuum is reduced in vacuum to the injection temperatures shown in Tables 2 and 3, respectively. For 5 minutes.
(2) Reinforcing fibers and the resin composition were heated for 1 hour at the primary molding temperatures shown in Tables 2 and 3, respectively, and further at 180 ° C. for 2 hours to cure the resin, thereby obtaining fiber reinforced composite materials.
(3) The fiber reinforced composite material was removed from the mold.

7). Used Materials The resin materials used in the examples and comparative examples are as follows.

Example 1
As rubber-modified cyanate ester resin (A1), A1-1 60 parts by weight and cyanate ester resin (A2) A2-2 40 parts by weight were mixed at 100 ° C., and then cooled to 50 ° C. as a metal coordination catalyst. Co (III) acetylacetonate (manufactured by Nippon Chemical Industry Co., Ltd.) 0.05 parts by weight was added, stirred for 10 minutes, extracted, and cooled to obtain a resin composition.
The temperature rising viscosity of this resin composition was measured, and a temperature of 65 ° C. at which the viscosity was 600 mPa · s was obtained. Further, the constant temperature viscosity at 65 ° C. was measured, and the viscosity did not exceed 800 mPa · s even when maintained for 2 hours. The viscosity at the time of raising the temperature after holding at 65 ° C. for 1 hour was measured, and the viscosity at 120 ° C., which is the primary molding temperature, was 80 mPa · s.
Using this resin composition, a fiber-reinforced composite material was produced in accordance with the above formulation 6. Table 2 shows the injection temperature, the molding temperature, and the results of the above evaluations 1 to 5.

Examples 2-4, Comparative Examples 1-4
Tables 2 and 3 show the resin compositions of Examples and Comparative Examples, their injection temperatures, curing temperatures, and the results of the above evaluations 1 to 5.

As shown in Tables 2 and 3, by using the rubber-modified cyanate ester resin (A1) which is an essential component of the present invention, a fiber-reinforced composite material having excellent fracture toughness and free from voids and cracks can be obtained. . On the other hand, in Comparative Examples 1 and 3 in which the rubber-modified cyanate ester resin (A1) is not used, the fracture toughness value is low and cracks are also confirmed. In Comparative Example 1, since the 600 mPa · s temperature is 20 ° C., the resin viscosity is reduced to less than 10 mPa · s at the stage of heating to 120 ° C. which is the primary molding temperature, the wettability is deteriorated, and voids are generated. It has occurred. In Comparative Example 2, since the rubber-modified cyanate ester resin (A1) is used, the fracture toughness is excellent and cracks are not generated. However, the amount of Co (acac) ₃ of the curing catalyst is the specified amount of the present invention. Therefore, the reactivity becomes too high, the pot life cannot be maintained, and the impregnation of the resin is insufficient, so that voids are generated. In Comparative Example 4, a conventional epoxy type RTM resin was used, but the epoxy type had a large shrinkage in curing and low toughness, and cracks were generated.

Claims (10)

A resin composition for producing a fiber-reinforced composite material by impregnating and curing a reinforcing fiber, the resin composition comprising the following components (A) and (B): 50 of the resin composition A resin composition characterized by having a viscosity at ˜120 ° C. of 300 to 800 mPa · s and maintaining a viscosity of 800 mPa · s or less in the above temperature range for 1 hour or more.
(A): 100 parts by weight of cyanate ester resin containing the following (A1) and (A2):
(A1): Cyanate ester resin modified with 5 to 30% by weight of rubber and 50 to 100 parts by weight of polytriazine derived from the resin (A2): Cyanate ester resin not modified with rubber and the resin 0 to 50 parts by weight of polytriazine derived from (B): 0.01 to 0.5 parts by weight of metal coordination catalyst   The resin composition according to claim 1, wherein the resin composition retains a viscosity of 10 mPa · s or more until it reaches a molding temperature after being heated at a temperature of 50 to 120 ° C. for 1 hour.   The resin composition according to claim 1 or 2, wherein the rubber used for modifying the component (A1) is acrylic rubber particles or silicone rubber particles.   The resin composition according to any one of claims 1 to 3, wherein the resin composition has a curing shrinkage of 1% or less when cured by the composition alone.   The resin composition according to any one of claims 1 to 4, wherein the metal coordination catalyst of the component (B) is a cobalt (III) acetylacetonate complex. The manufacturing method of the fiber reinforced composite material characterized by performing the following processes (1)-(3) in this order.
(1) A step of arranging reinforcing fibers using a mold,
(2) The resin composition according to any one of claims 1 to 5 is heated at a temperature of 50 to 120 ° C., and the reinforced fiber disposed in the step (1) is impregnated with the heated resin composition. And (3) a step of heating the reinforcing fiber impregnated with the resin composition at a temperature of 120 to 200 ° C. to cure the resin to obtain a fiber-reinforced composite material.   The method for producing a fiber-reinforced composite material according to claim 6, wherein after the step (3), the obtained fiber-reinforced composite material is taken out from the mold and post-cured at a temperature of 200 to 250 ° C. .   A fiber-reinforced composite material obtained by impregnating a reinforcing fiber with the resin composition according to any one of claims 1 to 5 and curing the resin composition.   A fiber-reinforced composite material produced by the method according to claim 6 or 7.   The fiber-reinforced composite material according to claim 8 or 9, wherein the reinforcing fibers are carbon fibers.