阅读说明：本技术 纤维增强复合材料用环氧树脂组合物及纤维增强复合材料 (Epoxy resin composition for fiber-reinforced composite material and fiber-reinforced composite material ) 是由 本远和范 石川德多 平野公则 富冈伸之 于 2018-05-21 设计创作，主要内容包括：本发明提供B阶化容易并且以短时间表现固化性,可获得具有高耐热性的树脂固化物的环氧树脂组合物。进一步通过使用这样的环氧树脂组合物,从而提供抗弯强度优异的纤维增强复合材料。此外,以提供包含能够平稳且均匀地进行树脂固化的环氧树脂组合物,可获得表面品质良好并且抗弯强度优异的纤维增强复合材料的片状模塑料作为课题。纤维增强复合材料用环氧树脂组合物包含以下的(A)～(E)的成分。(A)环氧树脂,(B)双氰胺或其衍生物,(C)多异氰酸酯化合物,(D)式(1)所示的脲化合物(式中,R<Sup>1</Sup>和R<Sup>2</Sup>各自独立地表示H、CH<Sub>3</Sub>、OCH<Sub>3</Sub>、OC<Sub>2</Sub>H<Sub>5</Sub>、NO<Sub>2</Sub>、卤素、或NH-CO-NR<Sup>3</Sup>R<Sup>4</Sup>,R<Sup>3</Sup>和R<Sup>4</Sup>各自独立地表示烃基、烯丙基、烷氧基、烯基或芳烷基,或R<Sup>3</Sup>和R<Sup>4</Sup>一起形成同时包含R<Sup>3</Sup>和R<Sup>4</Sup>的脂肪族环,所述烃基、烯丙基、烷氧基、烯基、芳烷基、脂肪族环的碳原子数为1～8),(E)选自季铵盐、<Image he="59" wi="61" file="DDA0002278499670000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>盐、咪唑化合物、和膦化合物中的至少1种化合物。<Image he="268" wi="700" file="DDA0002278499670000012.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(The invention provides an epoxy resin composition which can be easily B-staged, can express curability in a short time and can obtain a resin cured product with high heat resistance. Further, by using such an epoxy resin composition, a fiber-reinforced composite material having excellent bending strength is provided. Further, by providing a fiber-reinforced composite material comprising an epoxy resin composition capable of smoothly and uniformly curing the resin, the fiber-reinforced composite material having good surface quality and excellent bending strength can be obtainedThe sheet molding compound of (3) is a subject. The epoxy resin composition for a fiber-reinforced composite material contains the following components (a) to (E). (A) Epoxy resin, (B) dicyandiamide or a derivative thereof, (C) polyisocyanate compound, and (D) urea compound represented by formula (1) (wherein R is 1 And R 2 Each independently representing H, CH 3 、OCH 3 、OC 2 H 5 、NO 2 Halogen, or NH-CO-NR 3 R 4 ，R 3 And R 4 Each independently represents a hydrocarbyl, allyl, alkoxy, alkenyl or aralkyl group, or R 3 And R 4 Together form and contain R 3 And R 4 The aliphatic ring of (1) is a C1-8 hydrocarbon group, allyl group, alkoxy group, alkenyl group, aralkyl group or aliphatic ring, and (E) is selected from quaternary ammonium salts, quaternary ammonium salts, At least 1 compound of a salt, an imidazole compound, and a phosphine compound.)

1. An epoxy resin composition for a fiber-reinforced composite material, which comprises the following components (A) to (E),

component (A): an epoxy resin, and a curing agent,

component (B): dicyandiamide or a derivative thereof, or a salt thereof,

component (C): a polyisocyanate compound which is capable of reacting with a polyisocyanate compound,

component (D): a urea compound represented by the formula (1),

R¹and R²Each independently representing H, CH₃、OCH₃、OC₂H₅、NO₂Halogen or NH-CO-NR³R⁴；R³And R⁴Each independently represents a hydrocarbyl, allyl, alkoxy, alkenyl or aralkyl group, or R³And R⁴Together form and contain R³And R⁴The aliphatic ring of (1) wherein the number of carbon atoms of the hydrocarbon group, allyl group, alkoxy group, alkenyl group, aralkyl group, and aliphatic ring is1 to 8,

component (E): selected from quaternary ammonium salts,At least 1 compound of a salt, an imidazole compound and a phosphine compound.

2. The epoxy resin composition for fiber-reinforced composites according to claim 1, wherein component (E) is at least 1 compound selected from quaternary ammonium salts and phosphine compounds.

3. The epoxy resin composition for fiber-reinforced composite materials according to claim 1 or 2, wherein the component (E) is contained in an amount of 1 part by mass or more and 15 parts by mass or less per 100 parts by mass of the component (A).

4. The epoxy resin composition for fiber-reinforced composite material according to any one of claims 1 to 3, wherein the component (D) is 2, 4-bis (3, 3-dimethylureido) toluene.

5. The epoxy resin composition for fiber-reinforced composite materials according to any one of claims 1 to 4, wherein the component (D) is contained in an amount of 1 to 15 parts by mass per 100 parts by mass of the component (A).

6. A sheet molding compound comprising the epoxy resin composition for fiber-reinforced composite material according to any one of claims 1 to 5, and a reinforcing fiber.

7. The sheet molding compound of claim 6, said reinforcing fibers being carbon fibers.

8. A sheet molding compound comprising a strand-like aggregate of discontinuous reinforcing fibers and an epoxy resin composition for a fiber-reinforced composite material,

in the plane of the bundle-like aggregate having the largest width in the direction perpendicular to the arrangement direction of the reinforcing fibers, if the acute angles formed by the sides formed by the arrangement of the end portions on both sides of the reinforcing fibers in the bundle-like aggregate with respect to the arrangement direction of the reinforcing fibers are defined as an angle a and an angle b, respectively, the angles a and b are 2 ° or more and 30 ° or less,

the epoxy resin composition comprises the following components (A) to (C), and the half-peak width Delta T in a heat flow curve with the vertical axis of the heat flow measured by differential scanning calorimetry and the horizontal axis of the temperature is 15-50 ℃,

component (A): an epoxy resin, and a curing agent,

component (B): dicyandiamide or a derivative thereof, or a salt thereof,

component (C): a polyisocyanate compound.

9. The sheet molding compound according to claim 8, wherein the epoxy resin composition for a fiber-reinforced composite material comprises the following components (D) to (E),

component (D): a urea compound represented by the formula (1),

R¹and R²Each independently representing H, CH₃、OCH₃、OC₂H₅、NO₂Halogen or NH-CO-NR³R⁴；R³And R⁴Each independently represents a hydrocarbyl, allyl, alkoxy, alkenyl or aralkyl group, or R³And R⁴Together form and contain R³And R⁴The aliphatic ring of (1) wherein the number of carbon atoms of the hydrocarbon group, allyl group, alkoxy group, alkenyl group, aralkyl group, and aliphatic ring is1 to 8,

component (E): selected from quaternary ammonium salts,At least 1 compound of a salt, an imidazole compound and a phosphine compound.

10. The sheet molding compound as claimed in claim 9, wherein the component (E) is at least 1 compound selected from the group consisting of quaternary ammonium salts and phosphine compounds.

11. The sheet molding compound according to claim 9 or 10, wherein the component (E) is contained in an amount of 1 part by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the component (a).

12. The sheet molding compound as claimed in any of claims 9 to 11, wherein component (D) is 2, 4-bis (3, 3-dimethylureido) toluene.

13. The sheet molding compound according to any one of claims 9 to 12, wherein the component (D) is contained in an amount of 1 to 15 parts by mass based on 100 parts by mass of the component (A).

14. The sheet molding compound of any one of claims 8-13, said reinforcing fiber being carbon fiber.

15. A fiber-reinforced composite material obtained by curing the sheet molding compound according to any one of claims 6 to 14.

Technical Field

The present invention relates to an epoxy resin composition for fiber-reinforced composite materials suitable for fiber-reinforced composite materials for aircraft members, spacecraft members, automobile members, and the like, and a fiber-reinforced composite material using the epoxy resin composition.

Background

Fiber-reinforced composite materials composed of reinforcing fibers and a matrix resin can be designed to take advantage of the advantages of the reinforcing fibers and the matrix resin, and therefore, their applications are expanding from aerospace fields, sports fields, general industrial fields, and the like, and they are produced by various methods such as a prepreg method, a hand lay-up method, a fiber winding method, a pultrusion method, a Resin Transfer Molding (RTM) method, a Sheet molding compound (Sheet molding compound) molding method, and the like. Hereinafter, the sheet molding compound may be abbreviated as SMC.

Among these methods, the SMC molding method in which an intermediate base material composed of a matrix resin and discontinuous reinforcing fibers is molded by a heating press has recently attracted attention because of its excellent versatility and productivity.

A conventional prepreg method is a method in which an intermediate substrate called a prepreg, which is obtained by impregnating continuous reinforcing fibers (a form of being laid in one direction, a form of a woven fabric, or the like) with a matrix resin, is laminated in advance in a desired shape, and the matrix resin is cured by heating and pressurizing to obtain a fiber-reinforced composite material. However, this prepreg method is directed to the production of fiber-reinforced composite materials having high material strength required for structural materials for use in aircraft, automobiles, and the like, but it requires a large number of processes such as the production and lamination of prepregs, and therefore, it is only possible to produce them in small quantities, and is not suitable for mass production.

On the other hand, the SMC molding method is a method of obtaining a fiber-reinforced composite material in a desired shape by impregnating a resin composition serving as a matrix resin into a bundle-like aggregate of discontinuous reinforcing fibers (generally having a fiber length of about 5 to 100 mm) to form a sheet, B-staging (Bstage) the sheet to produce an intermediate substrate called SMC, and heating and pressurizing the SMC in a mold to shape the intermediate substrate and cure the matrix resin.

In the SMC molding method, the provision of a molding die makes it possible to mold a fiber-reinforced composite material in a short time without going through complicated steps of prepreg production and lamination, and in addition, has an advantage that even a fiber-reinforced composite material having a complicated shape can be easily molded.

As the reinforcing fiber, glass fiber, aramid fiber, carbon fiber, boron fiber, or the like can be used. As the matrix resin, both a thermosetting resin and a thermoplastic resin can be used, but a thermosetting resin which can be easily impregnated into the reinforcing fiber is often used. As the thermosetting resin, an epoxy resin, an unsaturated polyester resin, a vinyl ester resin, a phenol resin, a bismaleimide resin, a cyanate resin, or the like can be used. Among these, epoxy resins are widely used from the viewpoint of mechanical properties such as adhesiveness to reinforcing fibers, dimensional stability, and strength and rigidity of the resulting composite material.

The resin composition that becomes the matrix resin of the SMC needs to have a low viscosity in order to sufficiently impregnate the reinforcing fibers. On the other hand, the base resin after B-staging needs to be easily peeled off before molding from the films attached to both surfaces in the SMC production. In addition, the SMC must have flow characteristics such that a fiber-reinforced composite material having excellent mechanical strength can be obtained in which the reinforcing fibers are uniformly dispersed in the matrix resin during molding. Furthermore, in order to produce fiber-reinforced composite materials with high efficiency, it is essential to shorten the curing time of the matrix resin. Epoxy resins exhibit excellent heat resistance and good mechanical properties, and on the other hand, compared with vinyl ester resins and the like, it is difficult to perform B-staging to a level at which a fiber-reinforced composite material in which reinforcing fibers are uniformly dispersed in a matrix resin can be obtained, and curing time is long, and improvement thereof is required. On the other hand, in order to obtain a fiber composite reinforced material having good surface quality, which is regarded as important when applied to exterior parts of automobiles and the like, it is necessary to smoothly and uniformly cure a resin without excessively short curing time.

In view of such circumstances, a resin composition comprising an epoxy resin containing a hydroxyl group-containing sorbitol polyglycidyl ether and a polyisocyanate compound has been disclosed, and a method capable of B-staging the epoxy resin without impairing the excellent heat resistance inherent in the epoxy resin has been proposed (patent document 1).

Regarding the shortening of the curing time, the addition of a curing accelerator has been studied, and for example, a method of improving the curability by using a urea compound and an organotin compound in combination has been proposed (patent document 2).

In recent years, a method has been proposed in which a radical polymerizable unsaturated compound and a photopolymerization initiator are blended with an epoxy resin, and irradiation with ultraviolet light is performed to facilitate B-staging and improve curability (patent document 3).

Regarding the surface quality of the fiber-reinforced composite material, the shape of a bundle-like aggregate of discontinuous reinforcing fibers is studied, and a method of improving the homogeneity of the bundle-like aggregate and the resin by setting the angle between the end of the bundle-like aggregate and the arrangement direction of the reinforcing fibers to 12 °, for example, has been proposed (patent document 4).

Disclosure of Invention

Problems to be solved by the invention

In the method described in patent document 1, a high molecular weight material is produced by the reaction of sorbitol polyglycidyl ether and polyisocyanate, and thus sufficient B-staging is achieved, and high heat resistance is further exhibited, but curability is insufficient.

The method described in patent document 2 is not sufficient, although an effect of improving curability is observed, and is also insufficient in heat resistance.

In the method described in patent document 3, B-staging can be easily achieved by photopolymerization using a radical polymerizable unsaturated compound, and curability is further improved, but heat resistance is insufficient.

Further, in the method described in patent document 4, although a fiber-reinforced composite material having high homogeneity between the bundle aggregate and the resin and few voids can be obtained by press-molding an SMC composed of a vinyl ester resin and a bundle aggregate in which the angle between the end of the bundle aggregate of discontinuous reinforcing fibers and the alignment direction of the reinforcing fibers is 12 °, the vinyl ester resin may have a relatively large heat release amount immediately after the start of curing and may be cured rapidly, and therefore, a portion that progresses rapidly and a portion that progresses slowly may be generated in the process of completing the entire curing, and the surface quality may be adversely affected.

As described above, in the prior art, there are demands for a fiber-reinforced composite material which is difficult to be sufficiently B-staged and has both curability in a short time and high heat resistance, and for which more excellent surface quality and flexural strength are to be stably obtained.

Accordingly, a first object of the present invention is to improve the drawbacks of the prior art and to provide an epoxy resin composition which can be easily B-staged to exhibit curability in a short time and can give a cured resin product having high heat resistance. Further, by using such an epoxy resin composition, a fiber-reinforced composite material having excellent bending strength is provided. Further, a second object is to improve the drawbacks of these techniques and to provide an SMC which comprises an epoxy resin composition in which a matrix resin can be smoothly and uniformly resin-cured and which can obtain a fiber-reinforced composite material having good surface quality and excellent bending strength.

Means for solving the problems

In order to solve the above problems, an epoxy resin composition for a fiber-reinforced composite material according to a first aspect of the present invention has the following configuration. Namely, an epoxy resin composition for a fiber-reinforced composite material, which comprises the following components (A) to (E).

Component (A): epoxy resin

Component (B): dicyandiamide or derivatives thereof

Component (C): polyisocyanate compound

Component (D): a urea compound represented by the formula (1)

(R¹And R²Each independently representing H, CH₃、OCH₃、OC₂H₅、NO₂Halogen, or NH-CO-NR³R⁴。R³And R⁴Each independently represents a hydrocarbyl, allyl, alkoxy, alkenyl or aralkyl group, or R³And R⁴Together form and contain R³And R⁴The aliphatic ring of (1) is a hydrocarbon group, an allyl group, an alkoxy group, an alkenyl group, an aralkyl group, or an aliphatic ring, and the number of carbon atoms is1 to 8. )

Component (E): selected from quaternary ammonium salts,At least 1 compound of a salt, an imidazole compound, and a phosphine compound.

Further, in the first aspect of the present invention, there is also provided an SMC obtained by impregnating reinforcing fibers with the epoxy resin composition, and a fiber-reinforced composite material obtained by curing the SMC.

In order to solve the above problem, an SMC according to a second aspect of the present invention has the following configuration. That is, an SMC comprising a bundle-like aggregate of discontinuous reinforcing fibers and an epoxy resin composition for a fiber-reinforced composite material, wherein in a plane having a maximum width in a direction perpendicular to the arrangement direction of the reinforcing fibers, if the angles of acute angles formed by the arrangement of the ends on both sides of the bundle-like aggregate with respect to the arrangement direction of the reinforcing fibers are defined as an angle a and an angle b, respectively, the angles a and b are 2 ° or more and 30 ° or less, respectively, and the epoxy resin composition comprises the following components (a) to (C), and the half-peak width Δ T in a heat flow curve having a vertical axis of heat flow measured by differential scanning calorimetry and a horizontal axis of temperature is 15 ℃ or more and 50 ℃ or less.

Component (A): epoxy resin

Component (B): dicyandiamide or derivatives thereof

Component (C): a polyisocyanate compound.

Further, in the second aspect of the present invention, there is also provided a fiber-reinforced composite material obtained by curing the SMC of the second aspect.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the first aspect of the present invention, an epoxy resin composition for fiber-reinforced composite materials is provided which is easy to form a B-stage, has excellent curability and heat resistance, and can provide a fiber-reinforced composite material having high flexural strength.

Further, according to the second invention of the present invention, it is possible to provide an SMC which contains an epoxy resin composition in which a matrix resin can be smoothly and uniformly resin-cured and which can obtain a fiber-reinforced composite material having good surface quality and excellent bending strength.

Drawings

Fig. 1 is a schematic view of a plane having the largest width in a direction perpendicular to the arrangement direction of the reinforcing fibers of the bundle aggregate, and shows acute angles a and b formed by the sides formed by the arrangement of the end portions on both sides of the reinforcing fibers in the bundle aggregate with respect to the arrangement direction of the reinforcing fibers.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described.

First, an epoxy resin composition for a fiber-reinforced composite material according to a first aspect of the present invention will be described.

The epoxy resin composition for a fiber-reinforced composite material according to the first aspect of the present invention contains the following components (a) to (E).

Component (A): epoxy resin

Component (B): dicyandiamide or derivatives thereof

Component (C): polyisocyanate compound

Component (D): a urea compound represented by the formula (1)

(R¹And R²Each independently representing H, CH₃、OCH₃、OC₂H₅、NO₂Halogen, or NH-CO-NR³R⁴。R³And R⁴Each of which isIndependently represents a hydrocarbyl, allyl, alkoxy, alkenyl or aralkyl group, or R³And R⁴Together form and contain R³And R⁴The aliphatic ring of (1) is a hydrocarbon group, an allyl group, an alkoxy group, an alkenyl group, an aralkyl group, or an aliphatic ring, and the number of carbon atoms is1 to 8. )

Component (E): selected from quaternary ammonium salts,At least 1 compound of a salt, an imidazole compound, and a phosphine compound.

By blending the components (D) and (E) in the resin composition comprising the components (a), (B), and (C), it is possible to realize a viscosity at the time of B-staging at a level that cannot be realized only by blending the component (D) that has been conventionally known, and a short-time curability.

The component (a) of the first invention of the present invention is a component necessary for exhibiting heat resistance and mechanical properties. The epoxy resin of the component (a) is a compound containing 1 or more epoxy groups in the molecule.

The epoxy resin of the component (a) is not particularly limited as long as it is a compound containing 1 or more epoxy groups in the molecule. Examples of the 2-functional epoxy resin include a bisphenol a type epoxy resin, a bisphenol F type epoxy resin, a bisphenol S type epoxy resin, a biphenyl type epoxy resin, a dicyclopentadiene type epoxy resin, and an epoxy resin obtained by modifying these. Examples of the polyfunctional epoxy resin having 3 or more functions include, but are not limited to, a phenol novolac type epoxy resin, a novolac type epoxy resin such as a cresol novolac type epoxy resin, a tetraglycidyl diaminodiphenylmethane, a triglycidyl aminophenol type epoxy resin, a glycidyl amine type epoxy resin such as a tetraglycidyl amine type epoxy resin, a glycidyl ether type epoxy resin such as tetrakis (glycidyloxyphenyl) ethane or tris (glycidyloxymethane), an epoxy resin obtained by modifying the above epoxy resin, and a brominated epoxy resin obtained by brominating the above epoxy resin. Further, as the component (a), 2 or more of these epoxy resins may be used in combination. Among them, bisphenol a type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, and cresol novolac type epoxy resins can be particularly suitably used. The use of these epoxy resins has a further effect of improving the mechanical strength when the fiber-reinforced composite material is produced, compared with the case of using an epoxy resin having high rigidity, such as an epoxy resin having a naphthalene skeleton in the molecule. This is because, if an epoxy resin having high rigidity is cured in a short time, the crosslinking density increases, and therefore strain is likely to occur, whereas if the above epoxy resin is used, the possibility of such a problem occurring is low.

Examples of commercially available products of bisphenol a-type epoxy resins include "jER (registered trademark)" 825, "jER (registered trademark)" 826, "jER (registered trademark)" 827, "jER (registered trademark)" 828, "jER (registered trademark)" 834, "jER (registered trademark)" 1001, "jER (registered trademark)" 1002, "jER (registered trademark)" 1003, "jER (registered trademark)" 1004, "jER (registered trademark)" 1004AF, "jER (registered trademark)" 1007, "jER (registered trademark)" 1009 (manufactured by Mitsubishi chemical corporation, supra), "エ ピ ク ロ ン (registered trademark)" 850 (manufactured by DIC), "エ ポ ト ー ト (registered trademark)" YD-128 (manufactured by Nissan iron-on-gold chemical corporation), "DER (registered trademark)" 331, "DER (registered trademark)" 332 (manufactured by ダ ウ ケ ミ カ ル), and the like.

Examples of commercially available products of bisphenol F-type epoxy resins include "jER (registered trademark)" 806, "jER (registered trademark)" 807, "jER (registered trademark)" 1750, "jER (registered trademark)" 4004P, "jER (registered trademark)" 4007P, "jER (registered trademark)" 4009P (manufactured by mitsubishi chemical corporation, supra), "エ ピ ク ロ ン (registered trademark)" 830 (manufactured by DIC corporation), "エ ポ ト ー ト (registered trademark)" YDF-170, "エ ポ ト ー ト (registered trademark)" YDF2001, "エ ポ ト ー ト (registered trademark)" YDF2004 (manufactured by mitsui chemical corporation, supra), and the like. Further, a commercially available product of a tetramethylbisphenol F type epoxy resin as an alkyl substituent includes "エ ポ ト ー ト (registered trademark)" YSLV-80XY (Nippon Tekken chemical Co., Ltd.) and the like.

Examples of commercially available bisphenol S epoxy resins include "エ ピ ク ロ ン (registered trademark)" EXA-1515 (manufactured by DIC corporation).

Commercially available phenol novolac epoxy resins include "jER (registered trademark)" 152, "jER (registered trademark)" 154 (manufactured by mitsubishi chemical corporation, supra), "エ ピ ク ロ ン (registered trademark)" N-740, "エ ピ ク ロ ン (registered trademark)" N-770, "エ ピ ク ロ ン (registered trademark)" N-775 (manufactured by DIC corporation, supra).

Commercially available cresol novolak type epoxy resins include "エ ピ ク ロ ン (registered trademark)" N-660, "エ ピ ク ロ ン (registered trademark)" N-665, "エ ピ ク ロ ン (registered trademark)" N-670, "エ ピ ク ロ ン (registered trademark)" N-673, "エ ピ ク ロ ン (registered trademark)" N-695 (manufactured by DIC Co., Ltd.), EOCN-1020, and EOCN-102S, EOCN-104S (manufactured by Nippon Chemicals Co., Ltd.).

The component (B) of the first invention in the present invention is dicyandiamide or a derivative thereof. Dicyandiamide is excellent in imparting high mechanical properties and heat resistance to a resin cured product, and is widely used as a curing agent for epoxy resins. Further, a resin composition using dicyandiamide as a curing agent is excellent in storage stability and therefore can be suitably used. The dicyandiamide derivative is a compound obtained by bonding dicyandiamide with various compounds, and is excellent in imparting high mechanical properties and heat resistance to a resin cured product, as with dicyandiamide, and also excellent in storage stability of a resin composition using the dicyandiamide derivative as a curing agent. Examples of the dicyandiamide derivatives include those obtained by bonding dicyandiamide to various compounds such as an epoxy resin, a vinyl compound, an acrylic compound, and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. These can be used alone in 1 kind, also can be combined with more than 2 kinds. Further, dicyandiamide may be used in combination. Examples of commercially available dicyandiamide products include DICY7 and DICY15 (manufactured by mitsubishi chemical corporation).

The component (B) in the fiber-reinforced resin composition of the present invention is preferably contained in an amount of 1 to 50 parts by mass based on 100 parts by mass of the component (a). When the component (B) is contained in an amount of 1 part by mass or more based on 100 parts by mass of the component (a), a good effect of improving curability is obtained, and therefore, it is preferable, and when the component (B) is contained in an amount of 50 parts by mass or less, high heat resistance is exhibited, and thus, it is preferable. From such a viewpoint, the amount is more preferably in the range of 1 to 20 parts by mass.

The component (C) in the first invention of the present invention is not particularly limited as long as it is a polyisocyanate compound having an average of 2 or more isocyanate groups in one molecule, and known aliphatic isocyanates and aromatic isocyanates can be used. Examples of the aliphatic isocyanate which can be used as the polyisocyanate compound of the component (C) include 1, 2-ethanediisocyanate, 1, 3-propanediisocyanate, 1, 12-dodecanediisocyanate, 1, 6-hexanediisocyanate, 1, 4-butanediisocyanate, 1, 5-pentanediisocyanate, propylene-1, 2-diisocyanate, 2, 3-dimethyl-1, 4-butanediisocyanate, butylene-1, 2-diisocyanate, butylene-1, 3-diisocyanate, 1, 4-diisocyanatohexane, cyclopentylene-1, 3-diisocyanate, isophorone diisocyanate, 1,2,3, 4-tetraisocyanatobutane, butane-1, 2, 3-triisocyanates, and the like. Examples of the aromatic isocyanate that can be used as the polyisocyanate compound of the component (C) include aromatic isocyanates such as p-phenylene diisocyanate, 1-methylphenylene-2, 4-diisocyanate, naphthalene-1, 4-diisocyanate, toluene diisocyanate, diphenyl-4, 4-diisocyanate, benzene-1, 2, 4-triisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate (MDI), diphenylpropane diisocyanate, tetramethylene xylene diisocyanate, polymethylene polyphenyl polyisocyanate, and those having a structure in which these aromatic isocyanates are linked with methylene or the like. Further, prepolymers obtained by prepolymerizing these polyisocyanate compounds with polyol compounds may also be used. These polyisocyanate compounds and the like may be used alone or in combination of 2 or more.

The component (C) in the fiber-reinforced resin composition of the first invention in the present invention is preferably contained in an amount of 1 to 50 parts by mass based on 100 parts by mass of the component (a). When the component (C) is contained in an amount of 1 part by mass or more based on 100 parts by mass of the component (a), B-staging is sufficiently advanced, and a fiber-reinforced composite material in which reinforcing fibers are uniformly dispersed in a matrix resin can be obtained, and high mechanical properties are exhibited, and therefore, when the component (C) is contained in an amount of 50 parts by mass or less, SMC is preferably sufficiently spread in a mold during hot press molding. From such a viewpoint, the content is more preferably in the range of 5 to 30 parts by mass.

The component (D) of the first invention of the present invention is a urea compound represented by the formula (1).

(in the formula, R¹And R²Each independently representing H, CH₃、OCH₃、OC₂H₅、NO₂Halogen, or NH-CO-NR³R⁴。R³And R⁴Each independently represents a hydrocarbyl, allyl, alkoxy, alkenyl or aralkyl group, or R³And R⁴Together form and contain R³And R⁴The aliphatic ring of (1) is a hydrocarbon group, an allyl group, an alkoxy group, an alkenyl group, an aralkyl group, or an aliphatic ring, and the number of carbon atoms is1 to 8. )

Here, R³And R⁴The hydrocarbon group in (1) is preferably an alkyl group. Further, R is contained in a hydrocarbon group, an allyl group, an alkoxy group, an alkenyl group, an aralkyl group, or both³And R⁴In the aliphatic ring (b), as long as the number of carbon atoms is1 to 8, a part of hydrogen atoms may be substituted by other atoms (for example, halogen atoms) or substituents than those listed above.

Examples of the urea compound represented by formula (1) as component (D) include 3-phenyl-1, 1-dimethylurea, 3- (3, 4-dichlorophenyl) -1, 1-dimethylurea, 3- (3-chloro-4-methylphenyl) -1, 1-dimethylurea, and 2, 4-bis (3, 3-dimethylureido) toluene, and 2 or more thereof may be used alone or in combination. Among these, 2, 4-bis (3, 3-dimethylureido) toluene is most preferable because it can drastically shorten the curing time.

The component (D) in the fiber-reinforced resin composition of the first invention in the present invention is preferably contained in an amount of 1 to 15 parts by mass based on 100 parts by mass of the component (a). When the component (D) is contained by 1 part by mass or more based on 100 parts by mass of the component (a), good curing with improved curability can be obtained, and therefore, it is preferable, and it is more preferable if it is contained by 2 parts by mass or more, and it is further preferable if it is contained by 3.5 parts by mass or more. When 15 parts by mass or less of the component (D) is contained per 100 parts by mass of the component (a), the heat resistance is not lowered, and therefore, it is preferable, and when 10 parts by mass or less, the heat resistance is more preferable.

The component (E) of the first invention of the present invention is a quaternary ammonium salt,At least 1 compound of a salt, an imidazole compound, and a phosphine compound. Examples of the quaternary ammonium salt include tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetrabutylammonium bromide and the likeAs the salt, allyltriphenylphosphonium bromide is mentionedDiallyl diphenyl bromideEthyl triphenyl chlorideEthyl triphenyl iodideTetrabutylacetic acidTetrabutylphosphonium chlorideTetrabutyl bromideTetrabutyl iodideExamples of the imidazole compound include 2-phenylimidazole and 2-methylimidazole, and examples of the phosphine compound include triphenylphosphine. The component (E) is selected from the group consisting of quaternary ammonium salts,At least 1 compound selected from the salts, imidazole compounds, and phosphine compounds means that 1 selected from the above compounds can be used alone or in combination of 2 or more. Among them, the quaternary ammonium salt and/or the phosphine compound are preferable as the component (E) because the curing time can be greatly shortened.

The component (E) in the fiber-reinforced resin composition of the first invention in the present invention is preferably contained in an amount of 1 to 15 parts by mass based on 100 parts by mass of the component (a). When the component (E) is contained by 1 part by mass or more relative to 100 parts by mass of the component (a), B-staging sufficiently proceeds and curing with good improvement in curability can be obtained, and therefore, it is preferable, and it is more preferable if it is contained by 2 parts by mass or more, and it is further preferable if it is contained by 3.5 parts by mass or more. When 15 parts by mass or less of the component (E) is contained per 100 parts by mass of the component (a), the heat resistance is not lowered, and therefore, it is preferable, and when 10 parts by mass or less, the heat resistance is more preferable.

The viscosity at 70 ℃ of the epoxy resin composition of the first invention in the present invention is preferably 10 to 1000 mPas, more preferably 10 to 900 mPas, as measured with an E-type viscometer. The fiber-reinforced composite material having good surface quality can be obtained by making the impregnation of the reinforcing fiber with the epoxy resin composition having a viscosity of 1000 mPas or less at 70 ℃. Further, the viscosity of the epoxy resin composition having a viscosity of 10mPa · s or more at 70 ℃ is not so low at the time of resin impregnation, and therefore the resin does not flow out to the outside without being impregnated into the reinforcing fiber base material, and the reinforcing fiber base material is easily impregnated uniformly. The viscosity was measured for the epoxy resin composition obtained by mixing and stirring the respective components for 1 minute. Hereinafter, the mixing and stirring of the components for 1 minute in the preparation of the epoxy resin composition may be referred to as just after the preparation or just after the mixing.

The curability of the epoxy resin composition depends on the molding temperature, for example, the glass transition time at 140 ℃ of the resin composition after B-staging, and the shorter the glass transition time at 140 ℃ of the resin composition after B-staging, the higher the curability, and the shorter the curing time for forming the fiber-reinforced composite material. Therefore, in the SMC used particularly in the automotive field where productivity is important, an epoxy resin composition having a glass transition time at 140 ℃ of a resin composition after B-staging of less than 5 minutes is preferable, an epoxy resin composition having a glass transition time at 140 ℃ of less than 4 minutes is more preferable, and the shorter the time, the more preferable the shorter the time. Here, the vitrification time can be measured as follows. That is, the dynamic viscoelasticity of the epoxy resin composition at a predetermined temperature was measured using a thermal curing measuring apparatus such as ATD-1000 (made by Alpha Technologies, Inc.), and the complex viscosity was determined from the torque rise accompanying the curing reaction. At this time, the complex viscosity was adjusted to 1.0X 10⁷The time until Pa · s is set as vitrification time.

The heat resistance of the fiber-reinforced composite material obtained by using the epoxy resin composition for a fiber-reinforced composite material according to the first aspect of the present invention depends on the glass transition temperature of an epoxy resin cured product obtained by curing the epoxy resin composition. In order to obtain a fiber-reinforced composite material having high heat resistance, the glass transition temperature of an epoxy resin cured product obtained by heating at a temperature of 140 ℃ for 2 hours and completely curing is preferably 140 ℃ or higher and 250 ℃ or lower, and more preferably 150 ℃ or higher and 220 ℃ or lower. When the glass transition temperature is less than 140 ℃, the heat resistance of the cured epoxy resin may be insufficient. When the glass transition temperature exceeds 250 ℃, the crosslink density of the 3-dimensional crosslinked structure increases, and therefore the cured epoxy resin becomes brittle, and the tensile strength and impact resistance of the fiber-reinforced composite material may decrease. Here, the glass transition temperature of an epoxy resin cured product obtained by curing an epoxy resin composition was determined by measurement using a dynamic viscoelasticity measurement (DMA) apparatus. That is, DMA measurement was performed at an elevated temperature using a rectangular test piece cut out from a resin cured plate, and the temperature of the inflection point of the obtained storage elastic modulus G' was taken as Tg. The measurement conditions were as described in examples.

The SMC, which is the sheet molding compound of the first invention in the present invention, comprises the epoxy resin composition for fiber-reinforced composite materials of the first invention in the present invention and a reinforcing fiber. In the SMC of the first invention in the present invention, the type and length of the reinforcing fiber, the content ratio of the reinforcing fiber to the resin, and the like are not particularly limited, but usually, the reinforcing fiber is suitably used in which the fiber length is about 5 to 100mm, the average fiber diameter is 3 to 12 μm, and the basis weight of the reinforcing fiber is 0.1 to 5kg/m²And a reinforcing fiber having a carbon fiber content of 30 to 60% by weight. The method for producing the SMC according to the first aspect of the present invention is not particularly limited, and for example, the SMC according to the present invention is obtained by impregnating the epoxy resin composition according to the first aspect of the present invention with reinforcing fibers by a known method corresponding to the form of the reinforcing fibers, and then holding the composition at a temperature of about room temperature to 80 ℃ for several hours to several days to form a semi-cured state in which the viscosity of the resin composition is saturated. Here, a half-cured state in which the viscosity of the resin composition is increased and saturated is referred to as B-staging. The conditions for B-staging can be arbitrarily selected from the range of about room temperature to 80 ℃ and several hours to several days. In the evaluation of the present invention, B-staging conditions were employed under which the viscosity of the resin composition was saturated by holding the epoxy resin composition at 40 ℃ for 24 hours to form a semi-cured state. In the SMC of the first invention in the present invention, it is considered that the B-staging is mainly caused by the reaction of a polyisocyanate compound with a hydroxyl group in an epoxy resin, and as the viscosity of the epoxy resin composition after the B-staging, the viscosity at a molding temperature, for example, 140 ℃ as measured by DMA (ARES manufactured by TA イ ン ス ツ ル メ ン ツ) is preferably 100Pa · s or more and 10000Pa · s or less, and more preferably 500Pa · s or more and 10000Pa · s or less. If such an SMC is used, a desired fiber-reinforced composite material can be obtained.

The reinforcing fiber used in the SMC of the first invention of the present invention is not particularly limited, and examples thereof include glass fiber, carbon fiber, graphite fiber, aramid fiber, boron fiber, alumina fiber, silicon carbide fiber, and the like. These reinforcing fibers may be used in combination of 2 or more. Among these, carbon fibers and graphite fibers are preferably used in order to obtain a fiber-reinforced composite material that is lighter in weight and has higher durability. In particular, carbon fibers are suitably used for applications requiring lightweight and high strength, because they have excellent specific elastic modulus and specific strength.

As the carbon fiber, all kinds of carbon fibers can be used according to the application, but carbon fibers having a tensile elastic modulus of at most 400GPa are preferable from the viewpoint of impact resistance. Furthermore, from the viewpoint of strength, carbon fibers having a tensile strength of 4.4 to 6.5GPa are preferable, because a composite material having high rigidity and mechanical strength can be obtained. In addition, tensile elongation is also an important factor, and high-strength and high-elongation carbon fibers of 1.7 to 2.3% are preferable. Therefore, a carbon fiber having the properties of a tensile elastic modulus of at least 230GPa, a tensile strength of at least 4.4GPa, and a tensile elongation of at least 1.7% is most suitable.

Commercially available carbon fibers include "ト レ カ (registered trademark)" T800G-24K, "ト レ カ (registered trademark)" T800S-24K, "ト レ カ (registered trademark)" T700G-24K, "ト レ カ (registered trademark)" T300-3K, and "ト レ カ (registered trademark)" T700S-12K (manufactured by "imperial レ corporation)", and the like.

The fiber-reinforced composite material according to the first aspect of the present invention is obtained by curing the SMC according to the first aspect of the present invention. Fiber-reinforced composite materials obtained by curing SMC are required to have mechanical properties such as high heat resistance and bending strength, particularly when used in the automotive field. The fiber-reinforced composite material of the present invention can have a glass transition temperature of an epoxy resin cured product as a matrix resin of usually 140 ℃ or higher and 250 ℃ or lower, and therefore has excellent heat resistance, and high mechanical properties of the epoxy resin cured product are reflected, and therefore, it can exhibit a high flexural strength of 350MPa or higher, and more preferably 400MPa or higher.

Next, an SMC according to a second aspect of the present invention will be described.

An SMC according to a second aspect of the present invention is an SMC comprising a bundle-like aggregate of discontinuous reinforcing fibers and an epoxy resin composition for a fiber-reinforced composite material, wherein in a plane having a maximum width in a direction perpendicular to an arrangement direction of the reinforcing fibers, if angles of acute angles formed by edges formed by the arrangement of both sides of the reinforcing fibers in the bundle-like aggregate with respect to the arrangement direction of the reinforcing fibers are defined as an angle a and an angle b, respectively, the angle a and the angle b are 2 ° or more and 30 ° or less, the epoxy resin composition comprises the following components (a) to (C), and a half-peak width Δ T in a heat flow curve having a vertical axis of heat flow measured by differential scanning calorimetry and a horizontal axis of temperature is 15 ℃ or more and 50 ℃ or less.

Component (A): epoxy resin

Component (B): dicyandiamide or derivatives thereof

Component (C): polyisocyanate compound

Here, the angles a and b in the bundle-like aggregate of discontinuous reinforcing fibers constituting the SMC according to the second aspect of the invention are the angles shown in fig. 1.

By forming an SMC comprising a reinforcing fiber having an angle a and an angle b of 2 ° to 30 ° each and an epoxy resin composition comprising components (a) to (C) having a half-peak width Δ T of 15 ℃ to 50 ℃, the homogeneity of the reinforcing fiber and the resin can be improved to a level that could not be achieved by the prior art, and by highly suppressing surface irregularities caused by sink marks at the time of curing the resin, a fiber-reinforced composite material having good surface quality and high strength can be obtained.

The smaller the angles a and b between the edges formed by the arrangement of the ends of the reinforcing fibers in the bundle-like aggregate and the arrangement direction of the reinforcing fibers, the higher the homogeneity between the bundle-like aggregate and the resin, and therefore the greater the effect of improving the surface quality and strength in the fiber-reinforced composite material formed using the same. This effect is remarkable when the angles a and b are 30 ° or less. On the other hand, however, the smaller the angles a and b, the lower the operability of the bundle aggregate itself. Further, the smaller the angle between the arrangement direction of the reinforcing fibers and the knife for cutting, the lower the stability in the cutting step. Therefore, the angles a and b are preferably 2 ° or more. The angle a and the angle b are more preferably 3 ° or more and 25 ° or less. The angles a and b are more preferably 5 ° to 15 ° in view of balancing the effect of improving the surface quality and strength of the fiber-reinforced composite material with the manufacturability in the process of producing the bundle-like aggregate. Here, the angle is the angle shown in fig. 1 and is expressed by an absolute value as described above.

As a cutting device for a continuous reinforcing fiber bundle used for producing a bundle-like aggregate of discontinuous reinforcing fibers, there is a rotary cutter such as a cutter or a tow cutter, for example. The continuous reinforcing fiber bundle is inserted into the cutting device and cut while the longitudinal direction of the continuous reinforcing fiber bundle is inclined relative to the direction of a cutting blade provided in the cutting device.

The epoxy resin composition for a fiber-reinforced composite material used in the second aspect of the present invention contains the above-described components (a) to (C), and in a graph in which the abscissa represents temperature and the ordinate represents heat flow, the half-value width Δ T in a heat flow curve having the ordinate representing heat flow measured by differential scanning calorimetry and the abscissa representing temperature is 15 ℃ to 50 ℃. The definitions of the component (a), the component (B) and the component (C), and the preferable compounds, characteristics and content ratios of the component (a), the component (B) and the component (C) are the same as those of the epoxy resin composition for a fiber-reinforced composite material according to the first invention.

As a measurement apparatus used for Differential Scanning Calorimetry (DSC), for example, Pyris1 DSC (manufactured by Perkin Elmer) can be cited. Specifically, the epoxy resin composition is taken as aluminumAnd the sample plate is measured at the temperature range of 0-300 ℃ at the temperature rising speed of 10 ℃/min in the nitrogen atmosphere, so that a heat flow curve is obtained. In this graph, when the heat flow value at the apex of the convex exothermic peak formed by the resin curing reaction is taken as 100, the temperature difference Δ T between the temperatures at which the heat flow value becomes 50 is taken as the half-peak width, and when Δ T is 50 ℃ or less, uncured portions are not generated and the fiber-reinforced composite material is completely cured, so that when the SMC containing the epoxy resin composition is used, a high-strength fiber-reinforced composite material can be obtained. In addition, when Δ T is 15 ℃ or more, rapid curing accompanied by rapid heat release does not occur, and resin curing is smoothly and uniformly performed, so that a fiber-reinforced composite material having a uniform and good surface quality can be obtained when SMC including the epoxy resin composition is used. From the viewpoint of improving the surface quality of the fiber-reinforced composite material, Δ T is preferably 20 ℃ or more and 50 ℃ or less. In this case, the SMC is not particularly limited in the type and length of the reinforcing fiber, the content ratio of the reinforcing fiber to the resin, and the like, but it is generally preferred that the reinforcing fiber have a fiber length of about 5 to 100mm, an average fiber diameter of 3 to 12 μm, and a basis weight of 0.1 to 5kg/m²And a reinforcing fiber having a carbon fiber content of 30 to 60% by weight.

In addition, the epoxy resin composition for a fiber-reinforced composite material according to the second aspect of the present invention preferably further contains the above-mentioned component (D) and component (E). The definitions of the component (D) and the component (E), and the preferable compounds, characteristics and content ratios of the component (D) and the component (E) are the same as those of the epoxy resin composition for a fiber-reinforced composite material according to the first invention.

The method for producing SMC according to the second aspect of the present invention is not particularly limited, except that the cutting device satisfying the conditions of the angle a and the angle b is applied as a cutting device for a continuous reinforcing fiber bundle for producing a bundle-like aggregate of discontinuous reinforcing fibers. That is, the method for producing SMC using the epoxy resin composition for a fiber-reinforced composite material according to the first invention is the same as the method for producing SMC using the epoxy resin composition for a fiber-reinforced composite material according to the first invention, except that the process for blending the component (D) and the component (E) is not essential, and a cutting device for continuous reinforcing fiber bundles used for producing a bundle-like aggregate of discontinuous reinforcing fibers satisfies specific conditions.

The material of the reinforcing fiber used in the second aspect of the present invention is not particularly limited, and is the same as in the SMC according to the first aspect of the present invention.

The fiber-reinforced composite material according to the second aspect of the present invention is obtained by curing the SMC according to the second aspect of the present invention. Fiber-reinforced composite materials obtained by curing SMC are required to have mechanical properties such as high heat resistance, surface quality, and flexural strength, particularly when used in the automotive field. The fiber-reinforced composite material according to the second aspect of the present invention is excellent in heat resistance because the glass transition temperature of the cured epoxy resin as the matrix resin can be usually 140 ℃ or higher and 250 ℃ or lower. Further, the fiber-reinforced composite material according to the second aspect of the present invention is obtained by curing an epoxy resin composition capable of exhibiting high mechanical properties, in which the resin is cured smoothly and uniformly without rapid resin curing accompanied by rapid heat release, and SMC having a very high homogeneity in a bundle-like aggregate of discontinuous reinforcing fibers, and therefore, the surface unevenness caused by sink marks of the resin is small, and the fiber-reinforced composite material exhibits a good surface quality such that the arithmetic average roughness Ra of the surface is 0.4 μm or less, more preferably 0.3 μm or less, and further can exhibit a high flexural strength such as 350MPa or more, more preferably 400MPa or more.