JP7192202B2 - Cyanate ester resin composition for fiber reinforced composite material, prepreg and fiber reinforced composite material - Google Patents

Description

The present invention relates to a cyanate ester resin composition for fiber-reinforced composite materials, prepregs and fiber-reinforced composite materials.

Epoxy resins have hitherto been the most popular matrix resin for carbon fiber- or glass fiber-reinforced composite materials applied to aircraft and the like, and are used in many airframe structures. For example, Patent Literature 1 discloses an epoxy resin composition containing an epoxy resin as a matrix, a thermoplastic resin for adjusting viscosity, a filler, and a curing agent, and the composition and reinforcing fibers. Composite resulting prepregs are disclosed.
However, the heat resistance of epoxy resin cured products is 200° C. or less, and imide-based high heat-resistant resins such as polyimide and bismaleimide resins have been used for portions requiring heat resistance exceeding 200° C.

Of these, polyimide resin has heat resistance up to 300°C, and can be said to be the most heat-resistant resin among the matrix resins for fiber-reinforced composite materials at present. For example, since it requires 1.4 MPa), it cannot be said that it is a material with high productivity.
On the other hand, bismaleimide resin has intermediate heat resistance (about 200 to 270°C) between epoxy resin and polyimide resin. 230 to 250° C. of aging (secondary curing), etc., and the above-mentioned heat resistance can be obtained by this, so it can be said that the productivity is higher than that of polyimide resin. However, the bismaleimide resin is inferior in long-term oxidation resistance, so it cannot be said that there are many examples of application to actual machines.

In recent years, attention has been focused on cyanate ester resins instead of these resins. Since the cyanate ester resin forms a triazine ring upon heating, it is possible to obtain heat resistance comparable to that of bismaleimide resin or polyimide resin.
However, while cyanate ester resin exhibits high heat resistance due to its high-density crosslinked structure, it has a rigid skeleton that is difficult to stretch. It has the drawback of poor elongation and toughness. Therefore, there is a demand for a cyanate ester resin composition with improved elongation and toughness.

JP 2011-99094 A

An object of the present invention is to provide a cyanate ester resin composition for fiber-reinforced composite materials which is excellent in elongation and toughness while maintaining the inherent high heat resistance of the cyanate ester resin.
Another object of the present invention is to provide a prepreg which is excellent in heat resistance, elongation and toughness, and which is excellent in workability at room temperature.
Another object of the present invention is to provide a fiber-reinforced composite material which is excellent in heat resistance, elongation and toughness and which can be applied to various uses.

As a result of extensive research, the present inventors have found that the above problems can be solved by blending a polyimide resin and a curing accelerator or a curing catalyst with a cyanate ester resin, and have completed the present invention.
That is, the present invention is as follows.

1. A cyanate ester resin composition for a fiber-reinforced composite material comprising (a) a cyanate ester resin, (b) a polyimide resin, and (c) a curing accelerator or a curing catalyst,
A cyanate ester resin composition for a fiber-reinforced composite material, wherein the proportion of the (a) cyanate ester resin is 50 to 85% by mass with respect to the composition excluding the (c) curing accelerator or curing catalyst. thing.
2. 2. The cyanate ester resin composition for a fiber-reinforced composite material as described in 1 above, wherein the (c) curing accelerator or curing catalyst is a phenolic resin.
3. The (b) polyimide resin is a bismaleimide resin, a linear polyimide resin or a crosslinked polyimide resin, and the blending ratio of the (b) polyimide resin is the composition excluding the (c) curing accelerator or curing catalyst The cyanate ester resin composition for fiber-reinforced composite materials according to claim 1 or 2, characterized in that it is 15 to 35% by mass based on the product.
4. The reaction initiation temperature (exothermic peak initiation temperature) determined by differential scanning calorimetry (DSC analysis) at a heating rate of 10°C/min is 100°C or higher and 150°C or lower, and the onset temperature is 150°C or higher and 190°C or lower. 4. The cyanate ester resin composition for fiber-reinforced composite materials according to any one of 1 to 3 above.
5. The cyanate ester resin composition for fiber-reinforced composite materials is kept at 150 to 190° C. for 1.5 hours or more, so that the curing reaction has progressed to a state where it can be removed from the mold. 5. The cyanate ester resin composition for fiber-reinforced composite materials according to any one of 1 to 4.
6. A prepreg obtained by impregnating glass fiber, quartz fiber or carbon fiber with the cyanate ester resin composition for fiber-reinforced composite material according to any one of the above 1 to 5 as a matrix.
7. 7. A fiber-reinforced composite material, which is a heat-cured body of the prepreg according to 6 above.

The cyanate ester resin composition for fiber-reinforced composite materials of the present invention is obtained by blending a polyimide resin and a curing accelerator or curing catalyst with a cyanate ester resin, so that the high heat resistance inherent in the cyanate ester resin is maintained. Elongation and toughness can be improved. In addition, the cyanate ester resin composition for fiber-reinforced composite materials of the present invention can be removed from the mold at a relatively low temperature (for example, 170 ° C.) in a short time (for example, 2 hours), and productivity is improved by shortening the mold occupation time. can be improved.
Further, the prepreg of the present invention is obtained by impregnating glass fiber, quartz fiber or carbon fiber with the cyanate ester resin composition for fiber-reinforced composite material as a matrix, and is excellent in workability at room temperature.
Moreover, since the fiber-reinforced composite material of the present invention is a heat-cured body of the prepreg, it is excellent in heat resistance, elongation, and toughness, and can be applied to various uses.

It is a figure for demonstrating the measuring method of the onset temperature in DSC analysis.

The present invention will now be described in more detail.
The cyanate ester resin composition for fiber-reinforced composite materials of the present invention contains (a) a cyanate ester resin, (b) a polyimide resin and (c) a curing accelerator or a curing catalyst. Each component will be described below.

(a) Cyanate Ester Resin The (a) cyanate ester resin used in the present invention is not particularly limited. A cyanate ester resin can be represented, for example, by the following general formula.
Q-(O-C≡N)n
(Wherein, Q represents a divalent or higher organic group having an aromatic ring, and n represents an integer of 2 or more.)
More specifically, a cyanate ester resin represented by the following formula is suitable.

In the above formula, R1 to R7 each independently represent hydrogen or an alkyl group (eg, 1 to 4 carbon atoms), and k represents an integer of 1 or more.
X represents either of the following formulas.

In the above formula, each R independently represents hydrogen or an alkyl group (eg, having 1 to 4 carbon atoms).

Commercially available cyanate ester resins can be used, and examples thereof include Primaset PT-30 (formula (1) above) and Primaset PT-60 manufactured by Lonza Japan Co., Ltd.

(b) Polyimide resin The (b) polyimide resin in the present invention is not particularly limited, but is preferably a bismaleimide resin, a linear polyimide resin, or a crosslinked polyimide resin. As (b) polyimide resin in the present invention, for example, one represented by the following formula (3) can be used.

In the above formula, n is an integer of 1 or more and represents the number of repeating units, and X can have, for example, the following structure.

Also in the above formula, Y can have, for example, the following structure.

The (b) polyimide resin in the present invention contains a bismaleimide resin, and as the bismaleimide resin, for example, one represented by the following formula can be used.

In each of the above formulas, n is an integer of 1 or more and represents the number of repeating units.

Commercially available polyimide resins can be used, and examples thereof include BMI-2300 and BMI-4000 manufactured by Daiwa Kasei Kogyo Co., Ltd., and P84NT series manufactured by Evonik.

(c) Curing accelerator or curing catalyst The (c) curing accelerator or curing catalyst used in the present invention is not particularly limited as long as it can accelerate the thermal curing of the cyanate ester resin. Examples include cobalt and copper. metal complexes, alcohols, acids, amines, bases, and other known curing accelerators or curing catalysts. In the present invention, it is preferable to use a phenolic resin as component (c).
By using a phenolic resin as a curing accelerator or a curing catalyst, it is possible to lower the dielectric constant of the composition, so that it can be widely applied to heat-resistant composite materials such as radomes.
Specifically, a phenolic resin represented by the following formula is suitable.

Commercially available phenolic resins can be used, for example, HE100C-10 manufactured by Air Water Co., Ltd. (formula (4) above), DABPA manufactured by Daiwa Kasei Kogyo Co., Ltd. (formula (7) above), etc. are mentioned. In the above formula, both m and n are integers of 1 or more and represent the number of repeating units.

(d) Epoxy resin Further, in the present invention, (d) epoxy resin can be used for the purpose of further improving elongation and toughness as necessary. (d) Epoxy resin is preferably a difunctional or higher epoxy resin.
Examples of bifunctional epoxy resins include epoxy compounds having a bisphenyl group such as bisphenol A type, bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, bisphenol AF type, and biphenyl type. , a polyalkylene glycol type, an alkylene glycol type epoxy compound, an epoxy compound having a naphthalene ring, an epoxy compound having a fluorene group, and the like.
Examples of trifunctional or more functional epoxy resins include polyfunctional glycidyl ether type epoxy resins such as phenol novolak type, orthocresol novolak type, trishydroxyphenylmethane type, and tetraphenylolethane type epoxy resins.
More specifically, an epoxy resin represented by the following formula is suitable.

Commercially available epoxy resins can be used, for example YD-128 manufactured by Nippon Steel & Sumikin Chemical Co., Ltd. (formula (8) above), HP-4032SS manufactured by DIC Corporation (formula (9) above), DIC EXA7250 manufactured by Co., Ltd., VG3101L manufactured by Printec Co., Ltd. (Formula (11) above), and the like. In the above formula, n is an integer of 1 or more and represents the number of repeating units.

The (d) epoxy resin preferably has a structure that does not contain nitrogen atoms in its molecule. If nitrogen atoms are contained in the molecule, the effect of accelerating the reaction is excessively increased, and a sufficient working life of the resin composition may not be ensured.

(mixing ratio)
In the cyanate ester resin composition for fiber-reinforced composite materials of the present invention, the proportion of the (a) cyanate ester resin in the composition excluding the (c) curing accelerator or curing catalyst is 50 to 85% by mass. If the proportion of (a) cyanate ester resin is less than 50% by mass, the desired heat resistance cannot be imparted. Conversely, if it exceeds 85% by mass, the heat resistance deteriorates.
It is more preferable that the proportion of the (a) cyanate ester resin is 70 to 85% by mass with respect to the composition excluding the (c) curing accelerator or curing catalyst.
Further, the blending ratio of the (b) polyimide resin is preferably 15 to 35% by mass with respect to the composition excluding the (c) curing accelerator or curing catalyst from the viewpoint of heat resistance. More preferably, it is up to 25% by mass.

Further, when (d) an epoxy resin is blended, the epoxy resin (d) is preferably 10 to 20% by mass with respect to the cyanate ester resin composition for fiber-reinforced composite material of the present invention.

The cyanate ester resin composition for fiber-reinforced composite materials of the present invention can contain other additives as necessary. Additives include, for example, fillers, solvents, flame retardants, antioxidants, pigments (dyes), plasticizers, UV absorbers, surfactants (including leveling agents), dispersants, dehydrating agents, adhesion promoters. , antistatic agents, and the like.

The cyanate ester resin composition for a fiber-reinforced composite material of the present invention has a reaction initiation temperature (exothermic peak initiation temperature) determined by differential scanning calorimetry (DSC analysis) at a heating rate of 10°C/min at a temperature of 100°C or higher and 150°C or lower. and the onset temperature can range from 150°C to 190°C. Since the onset temperature indicates the temperature at which the curing reaction of the resin actively progresses, primary curing at 150 to 190° C. is possible when the onset temperature is in this range. In addition, since the reaction initiation temperature is within the above range, the reaction at room temperature does not easily proceed, and the working life can be extended.
The onset temperature in DSC analysis is obtained in the following manner. Turn on the temperature corresponding to the intersection of the baseline (L1) of the exothermic peak, which passes through the point (P1) where the exothermic peak rises on the DSC chart, and the tangent line (L2) at the point where the slope becomes maximum after the rise of the exothermic peak. Set temperature.

In addition, the cyanate ester resin composition for fiber-reinforced composite materials of the present invention was held at 150 to 190° C. for 1.5 hours or more, for example, about 2 hours, so that the curing reaction progressed to a state where it could be removed from the mold. can be a state. That is, the cyanate ester resin composition for fiber-reinforced composite materials of the present invention can be removed from the mold at a relatively low temperature of 150 to 190 ° C. in a short time of about 2 hours, and the mold occupancy time is shortened. Productivity can be improved.

The prepreg of the present invention is obtained by impregnating glass fibers, quartz fibers or carbon fibers with the cyanate ester resin composition for fiber-reinforced composite materials of the present invention as a matrix. The form of these fibers is not particularly limited, and examples thereof include rovings, rovings aligned in one direction, woven fabrics, non-woven fabrics, knitted fabrics, and tulle.

The content of the fibers in the prepreg of the present invention is preferably 20 to 60% by mass from the viewpoint of the mechanical properties of the resulting fiber-reinforced composite material.

The prepreg of the present invention is not particularly limited in its manufacturing method. Examples thereof include a dipping method using a solvent and a hot-melt method which is a non-solvent method.

Also, the fiber-reinforced composite material of the present invention is obtained by heat-curing the prepreg.
The use of the fiber-reinforced composite material of the present invention is not particularly limited. Aircraft parts such as radomes, fairings, flaps, leading edges, floor panels, propellers, fuselage; motorcycle parts such as motorcycle frames, cowls, fenders; doors, bonnets, tailgates, side fenders, side panels, fenders, energy Automotive parts such as absorption members, trunk lids, hard tops, side mirror covers, spoilers, diffusers, ski carriers, engine cylinder covers, engine hoods, chassis, air spoilers, propeller shafts; leading vehicle noses, roofs, side panels, doors, bogies Exterior panels for vehicles such as covers and side skirts; Railway vehicle parts such as luggage racks and seats; Interiors, wing inner panels, outer panels, roofs, floors, etc. for wing trucks, aero parts such as side skirts for automobiles and motorcycles Parts: Housing applications for notebook computers, mobile phones, etc.; Medical applications such as X-ray cassettes and top plates; Acoustic product applications such as flat speaker panels and speaker cones; Golf heads, face plates, snowboards, surfboards, protectors, etc. Sports equipment applications; general industrial applications such as leaf springs, windmill blades, elevators (basket panels, doors).

Among the above materials, the fiber-reinforced composite material of the present invention is excellent in heat resistance, elongation, and toughness, and is also excellent in electrical properties such as low dielectric characteristics, and is particularly preferably used for radomes. Radomes, also called radar domes, are radio-transparent windows in the fields of aircraft technology and telecommunications. The radome has a single layer structure made of a fiber-reinforced composite material, a foam material, or a core layer formed in a honeycomb shape with glass fiber, aramid fiber, aluminum foil, etc., and a skin layer is provided on the outer surface. Multilayer structures of three or more layers are known, and the fiber-reinforced composite material of the present invention can be advantageously used as a skin layer.

The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

The following materials were used in the examples below.
(a) Cyanate ester resin Primaset PT-30 manufactured by Lonza Japan Co., Ltd.
(b) Polyimide resin BMI-2300 (polyphenylmethane type bismaleimide resin) manufactured by Daiwa Kasei Kogyo Co., Ltd.
Daiwa Kasei Kogyo Co., Ltd. BMI-4000 (bisphenol A diphenyl ether type bismaleimide resin)
Evonik P84NY1HG SF (linear polyimide resin)
(c) Phenolic resin DABPA manufactured by Daiwa Kasei Kogyo Co., Ltd.
HE100C-10 manufactured by Air Water Co., Ltd.
(d) Epoxy resin EXA7250 manufactured by DIC Corporation

Various resin compositions were prepared by kneading each material using a kneader according to the blending ratio (parts by mass) shown in Table 1 below.

For the various cyanate ester resin compositions obtained, the reaction initiation temperature (peak initial), onset temperature (peak onset), peak top temperature (peak top), and heat of fusion ΔH were measured at a temperature increase rate of 10 ° C./min. It was determined by scanning calorimetry (DSC analysis).
For DSC measurement, a differential scanning calorimeter 2920 manufactured by TA Instruments Co., Ltd. was used, and 5 to 10 mg of the resin composition was sampled in a sealed sample container and subjected to measurement.

Further, whether or not the various cyanate ester resin compositions obtained were cured under primary curing conditions (170° C., 1.5 hours) was examined. Those cured to the point where they could be handled were evaluated as "○".

Moreover, the glass transition temperature was measured with respect to the obtained various cyanate-ester resin compositions. The glass transition temperature is the material after primary curing (170°C, 1.5 hours), the material after aging after primary curing (240°C, 3 hours), or after aging after primary curing (290°C, 3 hours). was determined by thermomechanical analysis (TMA analysis) at a heating rate of 10° C./min.
For the TMA analysis, a TMA4000S thermomechanical analyzer manufactured by Bruker AXS Co., Ltd. was used, and measurement was performed in expansion mode.

In addition, tensile strength, tensile modulus ( Tensile modulus), tensile strain) were investigated according to ASTM D638.

In addition, the various cyanate ester resin compositions thus obtained were allowed to stand at room temperature (23±5° C.) for 14 days, and changes in the degree of stickiness of the resin composition were confirmed by finger touch. A composition that maintained the degree of stickiness immediately after preparation was evaluated as "good". Others describe the degree of change.

The results are also shown in Table 1.

From the results in Table 1, the cyanate ester resin compositions for fiber-reinforced composite materials of the present invention of Examples contain (a) a cyanate ester resin, (b) a polyimide resin, and (c) a curing accelerator or a curing catalyst. Since the blending ratio of the (a) cyanate ester resin is 50 to 85% by mass with respect to the composition excluding the (c) curing accelerator or curing catalyst, the high heat resistance inherent in the cyanate ester resin is maintained. Excellent elongation and toughness while maintaining. In addition, the stickiness test showed good workability over a long period of time.
On the other hand, in Comparative Examples 1 and 2, the tensile strength and tensile strain were inferior to those of Examples because the (b) polyimide resin was not blended.
Since Comparative Example 3 is an example in which (b) the polyimide resin was not blended and (d) the epoxy resin was blended, the glass transition temperature of the material after aging decreased and the heat resistance deteriorated.
In Comparative Example 4, the blending ratio of (b) the polyimide resin was less than the lower limit specified in the present invention, so the glass transition temperature of the material after aging was lowered, resulting in deterioration in heat resistance.

Claims (5)

A cyanate ester resin composition for a fiber-reinforced composite material comprising (a) a cyanate ester resin, (b) a polyimide resin, and (c) a curing accelerator or a curing catalyst,
The mixing ratio of the (a) cyanate ester resin is 50 to 85% by mass with respect to the composition excluding the (c) curing accelerator or curing catalyst,
The (c) curing accelerator or curing catalyst is a phenolic resin,
The phenolic resin is selected from phenolic resins represented by the following (4) to (7) (in the following formula, m and n are both integers of 1 or more and represent the number of repeating units.)

characterized by
A cyanate ester resin composition for fiber-reinforced composite materials for radomes in aircraft . The (b) polyimide resin is a bismaleimide resin, a linear polyimide resin or a crosslinked polyimide resin, and the blending ratio of the (b) polyimide resin is the composition excluding the (c) curing accelerator or curing catalyst The cyanate ester resin composition for fiber-reinforced composite materials according to claim 1, characterized in that it is 15 to 35% by mass based on the product. The reaction initiation temperature (exothermic peak initiation temperature) determined by differential scanning calorimetry (DSC analysis) at a heating rate of 10°C/min is 100°C or higher and 150°C or lower, and the onset temperature is 150°C or higher and 190°C or lower. The cyanate ester resin composition for fiber-reinforced composite materials according to claim 1 or 2, characterized in that: A prepreg obtained by impregnating glass fiber, quartz fiber or carbon fiber with the cyanate ester resin composition for fiber-reinforced composite material according to any one of claims 1 to 3 as a matrix. A fiber-reinforced composite material, which is a heat-cured body of the prepreg according to claim 4.

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