Flame retardant composition, fiber reinforced composite material

Abstract

The present invention relates to flame-retardant fiber-reinforced composites based on epoxy resin compositions containing at least one epoxy resin having an epoxy functionality of at least 2 and at least one organic phosphinic acid or its derivative (e.g., organic phosphinic acid-modified epoxy resin) reinforced with fibers having a thermal conductivity of 3 W / m·K or greater at room temperature, as well as prepregs for producing such flame-retardant fiber-reinforced composites. More specifically, composites are provided that contain a combination of a specific type of epoxy resin, a curing agent, and reinforcing fibers that provides sufficient flame retardancy to thin-layer laminates when cured at 163°C for 15 minutes. These cured composites are also suitable for a variety of applications requiring flame retardancy.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 62 / 923,177, filed October 18, 2019, and U.S. Provisional Application No. 63 / 082,272, filed September 23, 2020, the disclosures of each of which are incorporated herein by reference in their entirety for all purposes.

[0002] The present invention relates to flame retardant compositions, prepregs and fiber reinforced composites having a thermosetting epoxy resin matrix that have excellent flame retardancy and are suitable for fabrication using modern rapid cure heating systems. [Background technology]

[0003] Fiber-reinforced composite (FRC) materials (sometimes called fiber-reinforced composites), which contain reinforcing fibers and a matrix resin, are lighter than other conventional materials yet have excellent mechanical properties such as stiffness and strength. Therefore, they are used in a variety of applications, such as aircraft, spacecraft, automobiles, railroad vehicles, ships, sporting goods, and computers, and demand for them continues to increase over time. In industrial applications, improving flame retardancy while keeping raw material production costs and mechanical and thermal performance relatively low is becoming an increasingly common requirement.

[0004] Halogen flame retardants have traditionally been used to impart flame retardancy to various materials, including FRC. Examples of halogen flame retardants include halogenated epoxy resins containing halogens such as bromine and chlorine, such as tetrabrominated bisphenol A. However, halogen flame retardants are strongly avoided because they can release toxic gases, such as hydrogen halides and organic halides, during the combustion process. As a result, alternative flame retardant methods, including the addition of red phosphorus or phosphate ester compounds to the matrix resin, have become mainstream.

[0005] However, the method of adding red phosphorus or a phosphate ester compound to a matrix resin has the following problems: 1) a decrease in mechanical strength, 2) low storage stability, 3) the red phosphorus or phosphate ester compound gradually permeates into the environment over a long period of time, and 4) red phosphorus and phosphate ester compounds are easily hydrolyzed, making them difficult to use in printed circuit boards, electronic materials, and other applications that require insulation and water resistance.

[0006] A common additional halogen-free flame retardant method for resins is the addition of inorganic flame retardants such as metal hydroxides. However, adding a large amount of inorganic flame retardant causes a problem of reduced mechanical strength of the cured resin. This reduction in mechanical strength of the cured resin leads to a reduction in the mechanical strength of the fiber-reinforced composite material. It is difficult to achieve sufficient flame retardancy with an amount of inorganic flame retardant added that maintains the mechanical strength required for the fiber-reinforced composite material.

[0007] The present invention has been made in view of the above, and an object of the present invention is to provide a composite material that does not contain halogen-based flame retardants, red phosphorus, or phosphate esters, has excellent flame retardancy, and does not rely on the addition of inorganic flame retardants such as metal hydroxides. Summary of the Invention [Problem to be solved by the invention]

[0008] After extensive research, the present inventors have discovered that the use of a specific type of phosphorus-containing chemical in combination with a specific type of reinforcing fiber can impart excellent flame retardancy to a fiber-reinforced composite material. The flame retardant composition used to prepare such a fiber-reinforced composite material containing a phosphorus-containing chemical also maintains the mechanical and heat resistance properties of a similar epoxy resin-based flame retardant composition that does not contain such a phosphorus-containing chemical, provided that the formulation is adjusted to maintain the crosslink density of the cured epoxy resin composition. That is, the present invention includes the following embodiments. [Means for solving the problem]

[0009] (1) A flame retardant composition useful for producing a flame retardant fiber reinforced composite material, comprising (or consisting essentially of, or consisting of) i) an epoxy resin composition composed of component [A], component [B], and component [C], and ii) component [D]; the epoxy resin composition has a phosphorus content of at least 0.5 wt. %, based on the total weight of the epoxy resin composition; Component [A] is composed of at least one epoxy resin, Component [B] is composed of at least one organic phosphinic acid, Component [C] consists of at least one curing agent, and Component [D] is a flame retardant composition comprising at least one reinforcing fiber having a thermal conductivity of 3 W / m·K or greater at room temperature.

[0010] In one embodiment of the flame retardant composition, the at least one organophosphinic acid is represented by Formula (I):

[0011] [ka]

[0012] (In the formula, R 1 and R 2 are independently selected from alkyl groups having 1 to 10 carbon atoms and aryl groups having 6 to 10 carbon atoms. In one embodiment, the R of formula (I) 1 and R 2 are each ethyl groups.

[0013] In another embodiment, at least a portion of component [A] is pre-reacted with at least a portion of component [B].

[0014] (2) A flame retardant composition useful for producing a flame retardant fiber reinforced composite material, comprising: i) an epoxy resin composition containing component [C] and component [E]; and ii) component [D]; the epoxy resin composition has a phosphorus content of at least 0.5 wt. %, based on the total weight of the epoxy resin composition; Component [C] is composed of at least one curing agent, Component [D] is composed of at least one reinforcing fiber having a thermal conductivity of 3 W / m K or more at room temperature, and Component [E] is a flame retardant composition comprising at least one epoxy resin containing at least one residue of at least one organic phosphinic acid.

[0015] In one embodiment of the flame retardant composition, at least one residue of the at least one organophosphinic acid is represented by formula (II):

[0016] [ka]

[0017] (Wherein, R in formula (II) 1 and R 2 are independently selected from alkyl groups having 1 to 10 carbon atoms and aryl groups having 6 to 10 carbon atoms. Corresponds to.

[0018] In one embodiment, component [E] is a compound of formula (III):

[0019] [ka]

[0020] (Wherein, R in formula (III) 1 and R 2 are independently selected from an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms, and R in formula (III) 3 is a group in which at least one epoxy group has reacted to form a substituent -OP(=O)R 1 R 2is a residue of a multifunctional epoxy resin into which at least one epoxy resin corresponding to formula (III) has at least one unreacted epoxy group. In one embodiment, the epoxy resin comprises at least one epoxy resin corresponding to R in formula (III): 3 is the residue of at least one tetraglycidyldiaminodiphenylmethane.

[0021] In one aspect of the flame retardant composition, as disclosed hereinabove, the epoxy resin composition further comprises at least one accelerator. In one embodiment, the at least one accelerator comprises at least one aromatic urea. The at least one aromatic urea may be present in the epoxy resin composition in a total amount ranging from 0.5 to 7 PHR. In another embodiment, the at least one curing agent comprises at least one dicyandiamide. The at least one dicyandiamide may be present in the epoxy resin composition in a total amount ranging from 1 to 7 PHR.

[0022] In one embodiment of the flame retardant composition, component [A] of the epoxy resin composition comprises at least one tetraglycidyldiaminodiphenylmethane.

[0023] In another aspect of the flame retardant composition, the epoxy resin composition further comprises at least one thermoplastic resin. In one embodiment, the at least one thermoplastic resin comprises at least one polyvinyl formal.

[0024] In one embodiment, in the flame retardant composition, the at least one reinforcing fiber comprises at least one carbon fiber, which may be selected from the group consisting of pitch-based carbon fiber and PAN-based carbon fiber.

[0025] In one aspect, the at least one reinforcing fiber is a layer of the reinforcing fiber and the flame retardant composition of embodiment (1), embodiment (2), or both embodiment (1) and embodiment (2), in the form of a prepreg including a layer of the reinforcing fiber impregnated with an epoxy resin composition. In one embodiment, the layer of the reinforcing fiber is unidirectional. (Unidirectional, hereafter referred to as "UD")In another embodiment, the fiber reinforced composite material may be obtained by curing at least one prepreg at a temperature of 120°C to 180°C. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 shows the test setup for the neat resin flammability test inspired by the SFI 56.1 specification, as further described in the Examples. DETAILED DESCRIPTION OF THE INVENTION

[0027] As used herein, the phrase "epoxy resin composition" is used interchangeably with "epoxy composition," and the phrase "flame-retardant epoxy resin composition" refers to an epoxy resin composition that, upon curing, provides a cured resin having flammability properties such as a low burn time of less than 10 seconds and a low burn length of 0.7 inches or less, as determined by a flammability test modified from the SFI 56.1 Flammability Test Specification for application to neat resin specimens. As used herein, the phrase "flame-retardant composition" refers to a flame-retardant intermediate material for providing a flame-retardant fiber-reinforced composite, comprising at least one reinforcing fiber and an epoxy resin composition that, upon curing, provides a cured resin having flammability properties such as a low burn time of less than 10 seconds and a low burn length of 0.7 inches or less, as determined by a flammability test modified from the SFI 56.1 Flammability Test Specification for application to neat resin specimens. As used herein, the phrase "flame-retardant fiber-reinforced composite" refers to a flame-retardant material that is a composite of reinforcing fibers in a matrix of cured thermosetting resin (i.e., a thermosetting resin matrix). Thus, the phrase "compositions useful in the preparation of flame retardant fiber reinforced composite materials" refers to flame retardant compositions that can be cured to provide flame retardant fiber reinforced composite materials.

[0028] As used herein, the terms "approximately," "about," and "substantially" refer to an amount close to the stated amount that still performs the desired function or achieves the desired result. For example, the terms "approximately," "about," and "substantially" can refer to an amount that is less than 10%, less than 5%, less than 1%, less than 0.1%, and less than 0.01% of the stated amount.

[0029] As used herein, the term "room temperature" has its ordinary meaning known to those of ordinary skill in the art and can include temperatures within the range of about 15°C to 43°C.

[0030] According to the present disclosure, a flame retardant composition includes (i) an epoxy resin composition and (ii) at least one reinforcing fiber. The epoxy resin composition includes component [A] including at least one epoxy resin, component [B] including at least one organic phosphinic acid, and component [C] including at least one curing agent. In one embodiment, the epoxy resin composition includes component [E], which is a reaction product of component [A] and component [B]. In one embodiment, the epoxy resin composition includes at least a portion of component [A] pre-reacted with at least a portion of component [B]. In another embodiment, the epoxy resin composition includes component [E] including at least one epoxy resin containing at least one residue of at least one organic phosphinic acid, and component [C] including at least one curing agent. In another embodiment, the epoxy resin composition includes component [A], component [C], and component [E]. In yet another embodiment, the epoxy resin composition includes component [B], component [C], and component [E]. The epoxy resin compositions of the present disclosure have a phosphorus content of at least 0.5 wt %, based on the total weight of the epoxy resin composition. In various embodiments, the epoxy resin compositions of the present disclosure maintain the mechanical and heat resistance properties of similar epoxy resin-based flame retardant compositions that do not contain such phosphorus-containing chemicals, but are formulated to maintain crosslink density in the cured epoxy resin composition.

[0031] In one embodiment, the flame retardant composition is completely free or substantially free of halogen substitution products, epoxy resins having a fluorene skeleton, and halogenated epoxy resins. In other embodiments, the flame retardant composition may include one or more of halogen substitution products, epoxy resins having a fluorene skeleton, and halogenated epoxy resins in an amount appropriate to further improve the flame retardancy of the composite.

[0032] Ingredients [B] In one embodiment of the flame retardant composition, component [B] consists of, consists essentially of, or consists of at least one organic phosphinic acid. The organic phosphinic acid utilized in the present invention is not particularly limited. Organic phosphinic acids are compounds containing at least one >P(=O)OH functional group, in which the phosphorus atom is further substituted with two organic groups (e.g., alkyl and / or aryl groups) that may be the same or different, with a carbon atom in each organic group directly bonded to the phosphorus atom. Organic phosphinic acids have the general formula R2PO2H, in which the two hydrogen atoms directly bonded to the phosphorus in the phosphinic acid (PO2H3) are replaced with the organic group R. The organic group R may be a hydrocarbon group, but in certain embodiments, it may contain one or more types of atoms in addition to carbon and hydrogen atoms, such as N, O, or halogens. For example, the organic group may be substituted with a hydroxyl or carboxylic acid group. However, in preferred embodiments, the organic phosphinic acid is halogen-free. Dialkylphosphinic acids, diarylphosphinic acids and alkylarylphosphinic acids, and combinations thereof, are all suitable for use in the present invention.

[0033] According to certain embodiments, the epoxy resin composition comprises a compound represented by formula (I):

[0034] [ka]

[0035] (In the formula, R 1and R 2 are independently selected from an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms). 1 and R 2 are identical to each other. 1 and R 2 are different from each other. The alkyl groups can be linear, branched, and / or alicyclic. Suitable alkyl groups having 1 to 10 carbon atoms include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, isooctyl, and cyclohexyl. Suitable aryl groups having 6 to 10 carbon atoms include, but are not limited to, phenyl, tolyl, and naphthyl.

[0036] Examples of suitable organic phosphinic acids include, but are not limited to, dimethylphosphinic acid, methylethylphosphinic acid, diethylphosphinic acid, dipropylphosphinic acid, ethylphenylphosphinic acid, di(isooctyl)phosphinic acid, diphenylphosphinic acid, methylbenzylphosphinic acid, naphthylmethylphosphinic acid, methylphenylphosphinic acid, and combinations thereof. Diethylphosphinic acid is particularly preferred for use in the present invention.

[0037] Flame-retardant epoxy resin compositions may contain an amount of organophosphinic acid in its unreacted form as shown in Formula (I) or its reacted form as shown in Formulas (II) and (III), or a mixture of the unreacted and reacted forms, such that the total phosphorus content is at least 0.5 wt.% of the total weight of the epoxy resin composition. When the amount of phosphorus is at least 0.5 wt.%, the epoxy resin composition, when cured, will pass most flame retardancy tests at the specified thickness. In other embodiments, the phosphorus content may exceed 1.5% to provide the cured epoxy resin composition with a level of flame retardancy sufficient to pass most test specifications, even with very thin test specimens. Typically, epoxy resin compositions need not contain more than 5 wt.% phosphorus to achieve satisfactory flame retardancy for most purposes and end uses. Additionally, increasing the phosphorus content without appropriate adjustments in crosslink density may reduce the mechanical performance of the cured epoxy resin composition. In certain embodiments, all or nearly all of the phosphorus content in the flame retardant epoxy resin composition is attributable to one or more of the organophosphinic acids and organophosphinic acid-modified epoxy resins described herein, although other types of phosphorus-containing compounds may also be present in addition to the organophosphinic acids and / or organophosphinic acid-modified epoxy resins. According to certain embodiments, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% or 100% of the phosphorus content of the flame retardant epoxy resin composition is provided by the organophosphinic acids and / or organophosphinic acid-modified epoxy resins.

[0038] Component [E] In certain embodiments of the present invention, the flame-retardant epoxy resin composition contains component [E], which comprises, consists essentially of, or consists of at least one epoxy resin containing at least one residue of at least one organic phosphinic acid (including any of the organic phosphinic acids described above). Such residue corresponds to the organic phosphinic acid reacted with the epoxy resin and thus becomes incorporated into the epoxy resin. Such epoxy resins further contain at least one epoxy group and can be considered organic phosphinic acid-modified epoxy resins or adducts of organic phosphinic acids with multifunctional epoxy resins. Epoxy resins useful as component [E] in the present invention can be obtained by reacting an organic phosphinic acid with a multifunctional epoxy resin (i.e., an epoxy resin containing two or more epoxy groups per molecule), with the stoichiometry controlled so that one or more epoxy groups of the multifunctional epoxy resin remain unreacted. During such a reaction, the acidic group of the organic phosphinic acid can ring-open the epoxy group of the starting multifunctional epoxy resin.

[0039] For example, at least one residue of the at least one organophosphinic acid may be represented by formula (II):

[0040] [ka]

[0041] (Wherein, R in formula (II) 1 and R 2 are independently selected from alkyl groups having 1 to 10 carbon atoms and aryl groups having 6 to 10 carbon atoms. It can correspond to.

[0042] In certain embodiments of the present invention, component [E] is a compound of formula (III):

[0043] [ka]

[0044] (Wherein, R in formula (III) 1 and R 2 are independently selected from an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms, and R in formula (III) 3 is a group in which at least one epoxy group has reacted to form a substituent -OP(=O)R 1 R 2 is a residue of a multifunctional epoxy resin into which at least one epoxy resin corresponding to formula (III) has at least one unreacted epoxy group. The epoxy resin may include at least one epoxy resin corresponding to:

[0045] Thus, in certain embodiments of the present invention, any one of the multifunctional epoxy resin structures present in the flame retardant epoxy resin composition contains at least one organophosphinic acid residue, one or more of the reactive sites (e.g., epoxy groups) of the multifunctional epoxy resin is occupied by the structure of formula (II), and at least one epoxy group of the starting multifunctional epoxy resin remains unreacted (and therefore available to react when the epoxy resin composition is cured).

[0046] As an illustrative and non-limiting example, a multifunctional epoxy resin that is a diglycidyl ether of bisphenol A can be reacted with one equivalent of diethylphosphinic acid to provide an organophosphinic acid-modified epoxy resin useful as or in component [E] of the present invention.

[0047] (CH3CH2)2P(=O)OH+GE-Ar-C(CH3)2-Ar-GE→(CH3CH2)2P(=O)OCH2CH(OH)CH2-Ar-C(CH3)2-Ar-GE (where Ar=arylene and GE=glycidyl ether). Any suitable arylene may be used, such as a benzene ring.

[0048] In certain embodiments, at least one epoxy resin containing at least one residue of at least one organic phosphinic acid may be preformed prior to formulating the flame-retardant epoxy resin composition by conducting an initial reaction between the one or more organic phosphinic acids and one or more multifunctional epoxy resins. Such pre-reaction may be carried out, for example, by combining these components to form a mixture and heating the mixture at a temperature and for a time effective to achieve the desired degree of reaction between the organic phosphinic acid and the multifunctional epoxy resin. Such heating may be carried out while stirring or otherwise agitating the mixture. Suitable reaction temperatures may include, for example, temperatures from 50°C to 150°C. Suitable reaction times may include, for example, reaction times from 0.1 to 5 hours. Depending on the stoichiometry selected, a portion of the multifunctional epoxy resin may remain unreacted, and the resulting reaction product, which is then used in the epoxy resin composition, is a mixture of an organic phosphinic acid-modified epoxy resin and a multifunctional epoxy resin that does not contain organic phosphinic acid residues.

[0049] Alternatively, the organic phosphinic acid and the multifunctional epoxy resin may undergo reaction in the presence of one or more additional components of the flame retardant epoxy resin composition after the flame retardant epoxy resin composition has been fully or partially formulated (e.g., either before or during curing of the flame retardant epoxy resin composition).

[0050] The above-described embodiment (at least one epoxy resin containing at least one residue of at least one organic phosphinic acid is present in the epoxy resin composition) allows for the preparation of specific types of flame-retardant epoxy resin compositions by controlling the reaction of different amounts of organic phosphinic acid with specific epoxy resins. As disclosed below, the selection of the type of epoxy resin allows for the tailoring of different formulations for toughness, glass transition temperature (Tg), and modulus. For example, a multifunctional epoxy resin having a functionality of 4 can be reacted with an organic phosphinic acid at an organic phosphinic acid to epoxy equivalent ratio of 1:4, 2:4, or 3:4.

[0051] In certain embodiments of the present invention, the flame-retardant epoxy resin composition includes component [E], which exists in a pre-reacted form or is formed during curing by the reaction of component [A] with component [B]. The multifunctional epoxy resin used to prepare the organic phosphinic acid-modified epoxy resin has a functionality of at least 3 or greater (i.e., three or more epoxy groups per molecule). When the multifunctional epoxy resin has a functionality of 3 or greater, it allows at least two of the epoxy groups to self-polymerize with each other or with at least one curing agent (after reaction with the organic phosphinic acid), enabling good crosslink density. In other embodiments of the present invention, the multifunctional epoxy resin has a functionality of 4 or greater, which can provide the advantage of increasing crosslink density and improving properties such as Tg. In yet another embodiment of the present invention, the multifunctional epoxy resin is a glycidylamine epoxy resin. In yet another embodiment of the present invention, the multifunctional epoxy resin is tetraglycidyldiaminodiphenylmethane. When the multifunctional epoxy resin is tetraglycidyldiaminodiphenylmethane, the epoxy resin composition can maintain a high Tg upon curing.

[0052] In some embodiments, when the flame retardant epoxy resin composition is cured, the glass transition temperature of the cured resin, as determined by the G' onset method (described in more detail in the Examples), is at least 100°C, in other embodiments at least 110°C, in still other embodiments at least 125°C, and in yet further embodiments at least 140°C. When the flame retardant epoxy resin has a Tg greater than 100°C, the cured fiber reinforced composite part can withstand deformation at higher temperatures and can have a higher use temperature to extend its applications.

[0053] In some embodiments, when the flame retardant epoxy resin composition is cured to provide a cured resin having a flexural modulus, the flexural modulus of the cured matrix at 25° C. is at least 3.0 GPa, in other embodiments at least 3.4 GPa, and in still other embodiments at least 3.8 GPa. When the flame retardant resin has a modulus greater than 3.0 GPa at 25° C., the fiber reinforced composite parts have high compressive strength, further expanding the material for more structural applications.

[0054] In the present invention, the type of epoxy resin is not particularly limited as long as it does not impair the effects of the present invention. Difunctional or higher functional epoxy resins and mixtures thereof can be used as the epoxy resin. The epoxy resin composition can also contain at least a certain amount of monofunctional epoxy resin in addition to one or more polyfunctional epoxy resins (i.e., epoxy resins containing two or more reactive epoxy groups in one molecule).

[0055] In embodiments in which the epoxy resin composition comprises component [E], i.e., at least one epoxy resin containing at least one residue of at least one organic phosphinic acid (organophosphinic acid-modified epoxy resin), such organic phosphinic acid-modified epoxy resin may be the only epoxy resin present in the epoxy resin composition. However, the epoxy resin composition may also comprise one or more additional epoxy resins that are not organic phosphinic acid-modified epoxy resins (i.e., epoxy resins that do not contain organic phosphinic acid residues).

[0056] Ingredient [A] Suitable epoxy resins include amines (e.g., diamines and compounds containing at least one amine group and at least one hydroxyl group, such as tetraglycidyldiaminodiphenylmethane, tetraglycidyldiaminodiphenyl ether, tetraglycidyldiaminodiphenyl sulfone, tetraglycidyldiaminodiphenylamide, triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, triglycidylaminocresol, and tetraglycidylxylylenediamine, as well as epoxy resins prepared using halogen-substituted products, alkynol-substituted products, hydrogenated products thereof, and the like. Resins), phenols (e.g., bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, bisphenol R-type epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, resorcinol epoxy resins, and triphenylmethane epoxy resins), naphthalene epoxy resins, dicyclopentadiene epoxy resins, epoxy resins having a biphenyl skeleton, isocyanate-modified epoxy resins, epoxy resins having a fluorene skeleton, and compounds having a carbon-carbon double bond (e.g., alicyclic epoxy resins). The epoxy resins are not limited to the above examples. Halogenated epoxy resins prepared by halogenating these epoxy resins can also be used. Furthermore, mixtures of two or more of these epoxy resins, and compounds having one epoxy group or monoepoxy compounds such as glycidyl aniline, glycidyl toluidine, or other glycidyl amines (particularly glycidyl aromatic amines), can be used to formulate the epoxy resin composition. However, when preparing a prepreg or a fiber-reinforced composite material using an epoxy resin composition, it is usually desirable to limit the amount of monofunctional epoxy resin to, for example, 20 PHR or less, 15 PHR or less, 10 PHR or less, or 5 PHR or less.

[0057] In one embodiment, the flame-retardant epoxy resin composition is completely free or substantially free of halogen substitution products, epoxy resins having a fluorene backbone, and halogenated epoxy resins. In another embodiment, the epoxy resin may contain one or more of the halogen substitution products, epoxy resins having a fluorene backbone, and halogenated epoxy resins in an amount suitable to improve the flame retardancy of the material.

[0058] Examples of commercially available tetraglycidyldiaminodiphenylmethane resins include "SUMI-EPOXY (registered trademark)" ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Nippon Steel Chemical Co., Ltd.), "jER (registered trademark)" 604 (manufactured by Mitsubishi Chemical Corporation), and "ARALDITE (registered trademark)" MY720, MY721, MY9655, and MY9655T (manufactured by Huntsman Advanced Materials).

[0059] An example of commercially available tetraglycidyldiaminodiphenyl sulfone is TG3DAS (Konishi Chemical Industry Co., Ltd.).

[0060] Examples of commercially available triglycidylaminophenol or triglycidylaminocresol resins include "SUMI-EPOXY (registered trademark)" ELM100 (manufactured by Sumitomo Chemical Co., Ltd.), "ARALDITE (registered trademark)" MY0500, MY0510, MY0600, and MY0610 (manufactured by Huntsman Advanced Materials), and "jER (registered trademark)" 630 (manufactured by Mitsubishi Chemical Corporation).

[0061] Examples of commercially available tetraglycidylxylylenediamine and its hydrogenated products include TETRAD-X and TETRAD-C (manufactured by Mitsubishi Gas Chemical Company, Inc.).

[0062] Commercially available bisphenol A epoxy resins include, for example, jER® 825, jER® 828, jER® 834, jER® 1001, jER® 1002, jER® 1003, jER® 1003F, jER® 1004, jER® 1004AF, jER® 1005F, jER® 1006FS, jER® 1007, jER® 1009, and jER® 1010 (manufactured by Mitsubishi Chemical Corporation). Commercially available brominated bisphenol A epoxy resins include jER (registered trademark) 505, jER (registered trademark) 5050, jER (registered trademark) 5051, jER (registered trademark) 5054, and jER (registered trademark) 5057 (manufactured by Mitsubishi Chemical Corporation). Commercially available hydrogenated bisphenol A epoxy resins include ST5080, ST4000D, ST4100D, and ST5100 (manufactured by Nippon Steel Chemical Co., Ltd.).

[0063] Examples of commercially available bisphenol F epoxy resins include jER (registered trademark) 806, jER (registered trademark) 807, jER (registered trademark) 4002P, jER (registered trademark) 4004P, jER (registered trademark) 4007P, jER (registered trademark) 4009P, and jER (registered trademark) 4010P (manufactured by Mitsubishi Chemical Corporation), as well as Epototo (registered trademark) YDF2001 and Epototo (registered trademark) YDF2004 (manufactured by Nippon Steel Chemical Co., Ltd.). Examples of commercially available tetramethylbisphenol F epoxy resins include YSLV-80XY (manufactured by Nippon Steel Chemical Co., Ltd.).

[0064] An example of a commercially available bisphenol S type epoxy resin is "EPICLON (registered trademark)" EXA-154 (manufactured by DIC Corporation).

[0065] Examples of commercially available phenol novolac epoxy resins include jER (registered trademark) 152 and jER (registered trademark) 154 (manufactured by Mitsubishi Chemical Corporation), Araldite (registered trademark) EPN1138 (manufactured by Huntsman Advanced Materials), and EPICLON (registered trademark) N-740, N-770, and N-775 (manufactured by DIC Corporation).

[0066] Commercially available cresol novolac epoxy resins include, for example, "EPICLON (registered trademark)" N-660, N-665, N-670, N-673, and N-695 (manufactured by DIC Corporation), and EOCN-1020, EOCN-102S, and EOCN-104S (manufactured by Nippon Kayaku Co., Ltd.).

[0067] An example of a commercially available resorcinol-type epoxy resin is "Denacol (registered trademark)" EX-201 (manufactured by Nagase ChemteX Corporation).

[0068] Examples of commercially available naphthalene epoxy resins include "EPICLON (registered trademark)" HP-4032, HP-4032D, HP-4700, HP-4710, HP-4770, EXA-4701, EXA-4750, and EXA-7240 (manufactured by DIC Corporation).

[0069] Commercially available triphenylmethane epoxy resins include, for example, "jER (registered trademark)" 1032S50 (manufactured by Mitsubishi Chemical Corporation) and "Tactix (registered trademark)" 742 (manufactured by Huntsman Advanced Materials Co., Ltd.). s Examples of suitable EPPN-501H include EPPN-501H (manufactured by Nippon Kayaku Co., Ltd.).

[0070] Commercially available dicyclopentadiene-type epoxy resins include, for example, "EPICLON (registered trademark)" HP-7200, HP-7200L, HP-7200H, and HP-7200HH (manufactured by DIC Corporation), and "Tactix (registered trademark)" 558 (manufactured by Huntsman Advanced Materials). s Examples of suitable fluororesin include XD-1000-1L and XD-1000-2L (manufactured by Nippon Kayaku Co., Ltd.).

[0071] Commercially available epoxy resins having a biphenyl skeleton include, for example, "jER (registered trademark)" YX4000H, YX4000, and YL6616 (manufactured by Mitsubishi Chemical Corporation), and NC-3000 (manufactured by Nippon Kayaku Co., Ltd.).

[0072] Examples of commercially available isocyanate-modified epoxy resins include AER4152 (manufactured by Asahi Kasei Epoxy Corporation) and ACR1348 (manufactured by ADEKA Corporation), which have an oxazolidone ring.

[0073] Commercially available epoxy resins having a fluorene skeleton include, for example, OGSOL PG-100, CG-200, and EG-200 (manufactured by Osaka Gas Chemicals Co., Ltd.), and LME10169 (Huntsman Advanced Materials s (manufactured by)

[0074] An example of commercially available glycidyl aniline is GAN (manufactured by Nippon Kayaku Co., Ltd.).

[0075] An example of a commercially available product of glycidyl toluidine is GOT (manufactured by Nippon Kayaku Co., Ltd.).

[0076] When a cured epoxy resin composition having high heat resistance is desired, the epoxy resin may be selected from triglycidyl aminophenol, triglycidyl aminocresol, tetraglycidylamine, phenol novolac epoxy resin, cresol novolac epoxy resin, resorcinol epoxy resin, naphthalene epoxy resin, dicyclopentadiene epoxy resin, epoxy resin having a biphenyl skeleton, isocyanate-modified epoxy resin, alicyclic epoxy resin, triphenylmethane epoxy resin, and epoxy resin having a fluorene skeleton.

[0077] When a cured epoxy resin composition having high heat resistance and mechanical properties is desired, the epoxy resin may be selected from triglycidyl aminophenol, triglycidyl aminocresol, tetraglycidylamine, naphthalene epoxy resin, epoxy resin having a biphenyl skeleton, isocyanate-modified epoxy resin, alicyclic epoxy resin, triphenylmethane epoxy resin, and epoxy resin having a fluorene skeleton.

[0078] In certain embodiments of the present invention, when the flame-retardant epoxy resin composition cures, the burn time of the cured resin is less than 10 seconds, in other embodiments, 5 seconds or less, and in still other embodiments, 3 seconds or less, as determined by a flammability test modified from the SFI 56.1 flammability test specification for application to neat resin specimens. When the burn time is less than 10 seconds, good correlation with flammability test parameters for fiber-reinforced composites can be more easily seen (as described in more detail in the Examples section).

[0079] In certain embodiments of the present invention, when the flame retardant epoxy resin composition is cured, the burn length of the cured resin is 0.7 inches or less, in other embodiments 0.5 inches or less, and in still other embodiments 0.3 inches or less, as determined by a flammability test modified from the SFI 56.1 flammability test specification for application to neat resin specimens. When the burn time is less than 10 seconds, good correlation with flammability test parameters for fiber reinforced composites can be more easily seen (as described in more detail in the Examples section).

[0080] The epoxy resin may be selected from triglycidyl aminophenol, triglycidyl aminocresol and tetraglycidyl amine when it is desired to obtain a cured epoxy resin composition that has high heat resistance and mechanical properties and provides a fiber reinforced composite material of high surface quality composed of the cured epoxy resin composition and reinforcing fibers.

[0081] In one embodiment of the present invention, the first bisphenol epoxy resin may be contained in the epoxy resin composition without any particular limitation, as long as it is an epoxidized bisphenol material.

[0082] According to another embodiment, the flame-retardant epoxy resin composition has a viscosity of 1.0×10 at 40° C. 2 ~1.0×10 5 The viscosity at 40°C is preferably 1.0 x 10 poise. 2 By setting the viscosity at 40°C to 1.0 × 10 poise or more, a prepreg with appropriate cohesiveness can be obtained. 5 By keeping the viscosity at poise or less, it is possible to impart appropriate drapeability and tackiness when laminating prepregs. The viscosity at 40°C is 1.0 x 10 3 ~5.0×10 4 More preferably in the poise range, 5.0 x 10 3 ~2.0×10 4 It is particularly preferred to be in the poise range.

[0083] According to another embodiment, the minimum viscosity of the flame-retardant epoxy resin composition is preferably 0.1 to 200 poise, more preferably 0.5 to 100 poise, and particularly preferably 1 to 50 poise. If the minimum viscosity is too low, the fluidity of the matrix resin may become too high, which may result in the resin leaking out of the prepreg during prepreg curing. Furthermore, the desired resin fraction may not be achieved in the resulting fiber-reinforced composite material, the fluidity of the matrix resin in the prepreg may become insufficient, the prepreg consolidation process may end earlier than usual, and many voids may occur in the resulting fiber-reinforced composite material. If the minimum viscosity is too high, the fluidity of the matrix resin in the prepreg may decrease, the prepreg consolidation process may end earlier than usual, and many voids may occur in the resulting fiber-reinforced composite material.

[0084] Here, the viscosity at 40°C and the minimum viscosity are determined by the following method. Specifically, measurements are taken using a 40 mm diameter parallel plate rheometer (ARES, manufactured by TA Instruments) with a gap of 0.6 mm. A torsional displacement of 10 rad / s is applied. The temperature is increased from 40°C to 180°C at a rate of 2°C / min.

[0085] Ingredient [C] In a specific embodiment of the present invention, dicyandiamide is used as a curing agent. When dicyandiamide is used as a curing agent, the storage stability of the uncured epoxy resin composition is high and the heat resistance of the cured epoxy resin composition is high.

[0086] The amount of dicyandiamide may be in the range of 3 to 7 PHR per 100 PHR (i.e., 3 to 7 parts by weight of dicyandiamide per 100 parts by weight of the total amount of epoxy resin in the epoxy resin composition). When the amount of dicyandiamide is at least 3 PHR, the cured epoxy resin composition may have high heat resistance. When the amount of dicyandiamide is 7 PHR or less, the cured epoxy resin composition may have high elongation.

[0087] Commercially available dicyandiamide products include, for example, DICY-7 and DICY-15 (manufactured by Mitsubishi Chemical Corporation) and Dyhard (registered trademark) 100S (manufactured by AlzChem Trostberg).

[0088] In other embodiments of the present invention, a curing agent other than dicyandiamide may be added (either in place of dicyandiamide or in combination with dicyandiamide) as long as it does not impair the effects of the present invention. Examples of suitable curing agents include, but are not limited to, polyamides, amidoamines (e.g., aromatic amidoamines such as aminobenzamide, aminobenzanilide, and aminobenzenesulfonamide), aromatic diamines (e.g., diaminodiphenylmethane, diaminodiphenylsulfone [DDS]), aminobenzoates (e.g., trimethylene glycol di-p-aminobenzoate and neopentyl glycol di-p-aminobenzoate), aliphatic amines (e.g., triethylenetetramine, isophoronediamine), and fatty acids. Examples of the curing agent include cyclic amines (e.g., isophoronediamine), imidazole derivatives, guanidines such as tetramethylguanidine, carboxylic anhydrides (e.g., methylhexahydrophthalic anhydride), carboxylic hydrazides (e.g., adipic hydrazide), phenol novolac resins and cresol novolac resins, carboxylic amides, polyphenol compounds, polysulfides and mercaptans, and Lewis acids and Lewis bases (e.g., boron trifluoride ethylamine, tris-(diethylaminomethyl)phenol). Furthermore, such curing agents may be used in combination, including in combination with dicyandiamide.

[0089] accelerator In a specific embodiment of the present invention, at least one aromatic urea is used as an accelerator for the reaction between the epoxy resin and the curing agent and / or the self-polymerization of the epoxy resin. The use of at least one aromatic urea as an accelerator improves the storage stability of the epoxy resin composition and improves the heat resistance of the cured epoxy resin composition.

[0090] The amount of the at least one aromatic urea may be in the range of 0.5 to 7 PHR (i.e., 0.5 to 7 parts by weight of aromatic urea per 100 parts by weight of the total amount of epoxy resins in the epoxy resin composition). When the amount of the at least one aromatic urea is at least 0.5 PHR, the cured epoxy resin composition can have high heat resistance. When the amount of aromatic urea is 7 PHR or less, the epoxy resin composition has high storage stability.

[0091] Examples of suitable aromatic ureas include N,N-dimethyl-N'-(3,4-dichlorophenyl)urea, toluenebis(dimethylurea), 4,4'-methylenebis(phenyldimethylurea), and 3-phenyl-1,1-dimethylurea, and combinations thereof. Commercially available aromatic ureas include DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.), Omicure® U-24, U-24M, U-52, U-52M, and 94 (manufactured by Huntsman Advanced Materials). s Among these, aromatic urea having a plurality of urea groups may be used to promote rapid curing.

[0092] In other embodiments of the present invention, any accelerator other than aromatic urea may be added (either instead of aromatic urea or in combination with aromatic urea) as long as it does not impair the effects of the present invention. Examples of suitable accelerators include, but are not limited to, sulfonic acid compounds, boron trifluoride piperidine, pt-butylcatechol, sulfonic acid compounds (e.g., ethyl p-toluenesulfonate or methyl p-toluenesulfonate), tertiary amines and their salts, imidazoles and their salts, phosphorus curing accelerators, metal carboxylic acids, and Lewis acids and Bronsted acids and their salts.

[0093] Examples of commercially available imidazole compounds or derivatives thereof include Curezol (registered trademark) 2MZ, 2PZ, and 2E4MZ (manufactured by Shikoku Chemical Industry Co., Ltd.) Examples of Lewis acid catalysts include boron trifluoride piperidine complex, boron trifluoride monoethylamine complex, boron trifluoride triethanolamine complex, boron trichloride octylamine complex, and complexes of boron trihalides with bases such as methyl p-toluenesulfonate, ethyl p-toluenesulfonate, and isopropyl p-toluenesulfonate.

[0094] Additives - Thermoplastic Resins thermoplastic resin In certain embodiments of the present invention, any thermoplastic resin may be included in the epoxy resin composition as long as it does not impair the effects of the present invention. Examples of suitable thermoplastic resins include thermoplastic resins that are soluble in epoxy resins and thermoplastic resins that are insoluble in epoxy resins and may be in the form of particles (i.e., thermoplastic particles). Other types of organic particles, such as rubber particles (including crosslinked rubber particles), may also be included in the epoxy resin composition.

[0095] As the thermoplastic resin soluble in epoxy resin, a thermoplastic resin having a hydrogen-bonding functional group, which is expected to have the effect of improving the adhesion between the cured epoxy resin composition and the reinforcing fiber, can be used. Examples of the thermoplastic resin having a hydrogen-bonding functional group soluble in epoxy resin include a thermoplastic resin having an alcoholic hydroxyl group, a thermoplastic resin having an amide bond, and a thermoplastic resin having a sulfonyl group.

[0096] Examples of thermoplastic resins having hydroxyl groups include polyvinyl acetal resins such as polyvinyl formal and polyvinyl butyral, polyvinyl alcohol, and phenoxy resin. Examples of thermoplastic resins having amide bonds include polyamides, polyimides, and polyvinylpyrrolidone. Examples of thermoplastic resins having sulfonyl groups include polysulfones. Polyamides, polyimides, and polysulfones may have functional groups such as ether bonds and carbonyl groups in their main chains. For example, the thermoplastic resin may be polyethersulfone. Polyamides may have a substituent on the nitrogen atom of the amide group.

[0097] Examples of commercially available thermoplastic resins that are soluble in epoxy resins and have hydrogen-bonding functional groups include polyvinyl acetal resins such as "Denkabutyral®" and "Denkaformal®" (manufactured by Denki Kagaku Kogyo Co., Ltd.) and "Vinylec®" (manufactured by JNC Corporation); phenoxy resins such as "UCAR®" PKHP (manufactured by Union Carbide Corporation); polyamide resins such as "Macromelt®" (manufactured by Henkel-Hakusui Corporation) and "Amilan®" CM4000 (manufactured by Toray Industries, Inc.); polyimides such as "Ultem®" (manufactured by SABIC Innovative Plastics) and "Matrimid®" 5218 (manufactured by Ciba Inc.); and polysulfones such as "SUMIKAEXCEL®" (manufactured by Sumitomo Chemical Co., Ltd.) and "UDEL®" (manufactured by Solvay Advanced Polymers Kabushiki Kaisha). and polyvinylpyrrolidone "Luviskol (registered trademark)" (manufactured by BASF Japan Ltd.).

[0098] Epoxy resin compositions useful in certain embodiments of the present invention may contain one or more acrylic resins. Acrylic resins are highly incompatible with epoxy resins, making them suitable for controlling viscoelasticity. Commercially available acrylic resins include the Dianale (registered trademark) BR series (manufactured by Mitsubishi Rayon Co., Ltd.), Matsumoto Microsphere (registered trademark) M, M100, and M500 (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), and Nanostrength (registered trademark) E40F, M22N, and M52N (manufactured by Arkema K.K.).

[0099] Rubber particles may be added. From the viewpoint of handleability, crosslinked rubber particles and core-shell rubber particles produced by graft polymerization of a different polymer onto the surface of the crosslinked rubber particles may be used as the rubber particles.

[0100] Examples of commercially available crosslinked rubber particles include FX501P (manufactured by Japan Synthetic Rubber Co., Ltd.), which is made of a crosslinked product of a carboxyl-modified butadiene-acrylonitrile copolymer, the CX-MN series (manufactured by Nippon Shokubai Co., Ltd.), which is made of acrylic rubber fine particles, and the YR-500 series (manufactured by Nippon Steel Chemical Co., Ltd.).

[0101] Examples of commercially available core-shell rubber particles include "PARALOID (registered trademark)" EXL-2655 (manufactured by Kureha Corporation) made of a butadiene-alkylstyrene methacrylate copolymer, "STAFILOID (registered trademark)" AC-3355 and TR-2122 (manufactured by Takeda Pharmaceutical Company Limited) made of an acrylic acid ester-methacrylic acid ester copolymer, "PARALOID (registered trademark)" EXL-2611 and EXL-3387 (manufactured by Rohm & Haas) made of a butyl acrylate-methyl methacrylate copolymer, and "KANE ACE (registered trademark)" MX series (manufactured by Kaneka Corporation).

[0102] Examples of thermoplastic resin particles that can be used include polyamide particles and polyimide particles. Due to their excellent toughness, polyamide particles are most preferred for significantly increasing the impact resistance of cured epoxy resin compositions. Among polyamides, nylon 12, nylon 11, nylon 6, nylon 6 / 12 copolymers, and nylons modified with epoxy compounds to have semi-IPN (interpenetrating polymer network) structures (semi-IPN nylons) as disclosed in Example 1 of JP-A-1-104624 impart particularly good adhesive strength when combined with epoxy resins. Examples of suitable commercially available polyamide particles include SP-500 (manufactured by Toray Industries, Inc.) and Orgasol (manufactured by Arkema Inc.), Grilamid® TR-55 (manufactured by EMS-Grivory), and Trogamid® CX (manufactured by Evonik Industries AG).

[0103] inorganic particles In certain embodiments of the present invention, any type of inorganic particles can be added as long as the effects of the present invention are not impaired. Examples of suitable inorganic particles include metal oxide particles, metal particles, and mineral particles. It is also possible to combine one or more types of inorganic particles. The inorganic particles may be used to improve or impart certain functions to the cured epoxy resin composition. Examples of such functions include surface hardness, anti-blocking properties, heat resistance, barrier properties, electrical conductivity, antistatic properties, electromagnetic wave absorption, UV shielding, toughness, impact resistance, and a low linear thermal expansion coefficient.

[0104] Examples of suitable metal oxides include silicon oxide, titanium oxide, zirconium oxide, zinc oxide, tin oxide, indium oxide, aluminum oxide, antimony oxide, cerium oxide, magnesium oxide, iron oxide, tin-doped indium oxide (ITO), antimony-doped tin oxide, and fluorine-doped tin oxide.

[0105] Examples of suitable metals include gold, silver, copper, aluminum, nickel, iron, zinc, and stainless steel. Examples of suitable minerals include montmorillonite, talc, mica, boehmite, kaolin, smectite, xonotlite, vermiculite, and sericite.

[0106] Examples of other suitable inorganic materials include carbon black, acetylene black, ketjen black, carbon nanotubes, graphene, aluminum hydroxide, magnesium hydroxide, glass beads, glass flakes, and glass balloons.

[0107] Inorganic particles of any suitable size can be used, for example, sizes ranging from 1 nm to 10 μm. Furthermore, the inorganic particles can have any suitable shape, for example, spherical, needle, plate, balloon, or hollow. The inorganic particles can be used simply as a powder or in a dispersion in a solvent such as a sol or colloid.

[0108] The surfaces of the inorganic particles may be treated with one or more coupling agents to improve dispersibility and interfacial affinity with the epoxy resin.

[0109] In various embodiments of the present invention, the epoxy resin composition may contain other materials in addition to or in place of the above-mentioned materials, as long as the effects of the present invention are not impaired. Examples of other materials that can be contained in the epoxy resin composition include a mold release agent, a surface treatment agent, a flame retardant (in addition to the organic phosphinic acid or the organic phosphinic acid-modified epoxy resin), an antibacterial agent, a leveling agent, an antifoaming agent, a thixotropic agent, a heat stabilizer, a light stabilizer, an ultraviolet absorber, a pigment, a coupling agent, and a metal alkoxide.

[0110] The components of the epoxy resin composition can be mixed using a kneader, planetary mixer, three-roll mill, twin-screw extruder, or the like. The epoxy resin(s) and any thermoplastic resins, excluding the curing agent(s) and accelerator(s), are added to the selected equipment. The mixture is then heated to a temperature in the range of 130 to 180°C while stirring to uniformly dissolve the epoxy resin. The mixture is then cooled to a temperature below 100°C while stirring, and the curing agent and any accelerator(s) are then added and kneaded to disperse the components. This method can be used to provide an epoxy resin composition with excellent storage stability.

[0111] Component [D] In the present invention, the fibers having a thermal conductivity of 3 W / m·K or greater are not particularly limited and may be any type of reinforcing fiber as long as they have a thermal conductivity of 3 W / m·K or greater at room temperature. In certain embodiments of the present invention, the thermal conductivity of the fibers is 5 W / m·K or greater at room temperature, in other embodiments 7 W / m·K or greater, and in still other embodiments 9 W / m·K or greater. The thermal conductivity of the fibers is determined from the thermal conductivity grade of the fibers provided by the supplier.

[0112] If supplier data is unavailable, the thermal conductivity of the reinforcing fiber can be calculated from the measured thermal diffusivity, density, and specific heat capacity as follows: The thermal diffusivity of the reinforcing fiber is determined using an AC thermal diffusivity measurement system, LaserPIT (manufactured by ADVANCE RIKO, Inc.), with a fiber bundle tightly pulled on a sheet-like sample holder. The density of the reinforcing fiber is measured by the gas exchange method using a dry automatic density meter (e.g., AccuPyc 1330-03 manufactured by Micromeritics Company) and an electronic analytical balance (e.g., AEL-200 manufactured by Shimadzu Corporation), and the specific heat capacity of the reinforcing fiber is measured by the DSC method using a differential scanning calorimeter (e.g., Discovery DSC 2500 manufactured by TA Instruments).

[0113] Surprisingly, when composites were tested for flammability, those reinforced with fibers having a thermal conductivity of 3 W / m·K or greater at room temperature (25°C) were found to have superior flammability resistance when compared to similar composites containing more insulating fibers.

[0114] Without being bound by theory, it is believed that higher thermal conductivity fibers, when combined with a flame-retardant epoxy resin composition and cured, result in shorter burn times and shorter burn lengths due to the greater amount of flame-retardant phosphorus-containing component (e.g., organic phosphinic acid or organic phosphinic acid-modified epoxy resin) reacting with the atmosphere at the same time. This is particularly evident at thinner specimen thicknesses, where the surface area of ​​the specimen exposed to the atmosphere is greater in proportion to the specimen volume.

[0115] Fibers with a thermal conductivity of 3 W / m K or greater at room temperature include, but are not limited to, metal fibers such as carbon fiber, graphite fiber, and silicon carbide fiber, tungsten carbide fiber, and natural / biofibers. The use of carbon fiber, in particular, can provide a cured FRC material that is both extremely strong and stiff, yet lightweight. Examples of suitable carbon fibers are those manufactured by Toray Industries, Inc., having a standard modulus of elasticity of about 200 to 280 GPa (TORAYCA® T300, T300J, T400H, T600S, T700S, T700G), an intermediate modulus of elasticity of about 280 to 340 GPa (TORAYCA® T800H, T800S, T1000G, T1100G, M30S, M30G), or a high modulus of elasticity of more than 340 GPa (TORAYCA® M40, M35J, M40J, M46J, M50J, M55J, M60J).

[0116] PAN-based and pitch-based carbon fibers are particularly suitable for use in the present invention. PAN-based carbon fibers are carbon fibers prepared from polyacrylonitrile fiber precursors, while pitch-based carbon fibers are carbon fibers prepared from pitch. Both types of carbon fibers are well known in the art.

[0117] The form and arrangement of the reinforcing fiber layers used to prepare the fiber-reinforced composite material of the present invention are not particularly limited. Any of the forms and spatial arrangements of reinforcing fibers known in the art can be used, such as long fibers in a certain direction, short fibers in random orientation, single tow, narrow tow, woven fabric, mat, knitted fabric, and braided fabric. As used herein, the term "long fiber" refers to a single fiber or a fiber bundle containing a single fiber that is substantially continuous over 10 mm or more. As used herein, the term "short fiber" refers to a fiber bundle containing fibers cut to a length of less than 10 mm. In particular, for end uses where high specific strength and high specific modulus are desired, a form in which the reinforcing fiber bundles are arranged in one direction is optimal. From the viewpoint of ease of handling, a cloth-like (woven) form is also suitable for the present invention.

[0118] The FRC material of the present invention can be manufactured using methods such as prepreg lamination, resin transfer molding, resin film infusion, hand layup, wet layup, sheet molding compound, filament winding, and pultrusion, although no particular limitations or restrictions apply in this regard.

[0119] Resin transfer molding is a method in which a liquid thermosetting resin composition is directly impregnated into a reinforcing fiber substrate and then cured. Because this method does not involve intermediate products such as prepregs, it has a high potential for reducing molding costs and is advantageously used in the production of structural materials for spacecraft, aircraft, railroad cars, automobiles, ships, etc.

[0120] The prepreg lamination molding method is a method in which a prepreg made by impregnating a reinforcing fiber substrate with a thermosetting resin composition is molded and / or laminated, and heat and pressure are applied to the molded and / or laminated prepreg to cure the resin, thereby obtaining an FRC material.

[0121] The filament winding method involves aligning one to several dozen reinforcing fiber rovings in one direction and winding them around a rotating metal core (mandrel) at a predetermined angle under tension while impregnating them with a thermosetting resin composition. After the roving wrap reaches a predetermined thickness, the roving is cured and then the metal core is removed.

[0122] The pultrusion method involves continuously passing reinforcing fibers through an impregnation tank filled with a liquid thermosetting resin composition, impregnating the fibers with the thermosetting resin composition, and then continuously stretching the impregnated reinforcing fibers using a tensioning machine to form them through a squeeze mold and a heating mold. This method offers the advantage of continuously molding FRC materials, and is therefore used to manufacture FRC materials for fishing rods, rods, pipes, sheets, antennas, architectural structures, and other applications. In particular, prepreg lamination molding may be used to impart excellent rigidity and strength to the resulting FRC material.

[0123] The prepreg may contain an epoxy resin composition and reinforcing fibers. Such a prepreg can be obtained by impregnating a reinforcing fiber substrate with the epoxy resin composition according to the present invention. Impregnation methods include a wet method and a hot melt method (dry method).

[0124] The wet method involves first immersing reinforcing fibers in a solution of an epoxy resin composition prepared by dissolving the reinforcing fibers in a solvent such as methyl ethyl ketone or methanol, removing the reinforcing fibers, and then evaporating the solvent using an oven or the like to impregnate the reinforcing fibers. The hot-melt method involves directly impregnating the reinforcing fibers with an epoxy resin composition that has been preheated and fluidized, or by coating the epoxy resin composition used as a resin film on release paper or the like, placing the film on one or both sides of a flat-shaped reinforcing fiber, and applying heat and pressure to impregnate the reinforcing fibers with the resin. The hot-melt method can produce a prepreg that is substantially free of residual solvent.

[0125] Prepreg: 40 to 700 g / m 2The carbon fiber weight may be between 40 g / m 2 If the carbon fiber weight is less than 700 g / m, the fiber content will be insufficient and the strength of the FRC material may decrease. 2 If the resin content exceeds 20%, the drapeability of the prepreg may be impaired. The prepreg may also have a resin content between 20 and 70% by weight. If the resin content is less than 20% by weight, impregnation may be insufficient, resulting in many voids. If the resin content exceeds 70% by weight, the mechanical properties of the FRC may be reduced.

[0126] Appropriate heat and pressure may be used in a prepreg lamination molding method, a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, or the like.

[0127] Autoclave molding is a process in which prepregs are layered on a tool plate of a predetermined shape, then covered with a bagging film and cured under heat and pressure while removing air from the laminate. This process allows for precise control of fiber orientation and, due to minimal void content, can produce high-quality molding materials with excellent mechanical properties. The pressure applied during the molding process can be 0.3 to 1.0 MPa, while the molding temperature can be in the range of 90 to 300°C (in one embodiment of the present invention, in the range of 180 to 220°C, e.g., 200 to 220°C).

[0128] The wrapping tape method involves wrapping prepreg around a mandrel or some other core rod to form a tubular FRC material. This method can be used to manufacture golf shafts, fishing rods, and other rod-shaped products. More specifically, this method involves wrapping prepreg around a mandrel and wrapping a wrapping tape made of a thermoplastic resin film over the prepreg under tension to secure the prepreg and apply pressure to the prepreg. After heating in an oven to cure the resin, the core rod is removed to obtain a tubular body. The tension used to wrap the wrapping tape can be 20 to 100 N. The curing temperature can be in the range of 90 to 300°C (in one embodiment of the present invention, in the range of 180 to 220°C, e.g., 200 to 220°C).

[0129] Internal pressure molding is a method in which a preform, formed by wrapping a prepreg around a thermoplastic resin tube or some other internal pressure applying device, is placed in a mold, and high-pressure gas is introduced into the internal pressure applying device to apply pressure while simultaneously heating the mold to mold the prepreg. This method can be used to form objects with complex shapes such as golf shafts, bats, and tennis or badminton rackets. The pressure applied during the molding process can be 0.1 to 2.0 MPa. The molding temperature can be between room temperature and 300°C, or in the range of 120 to 180°C (in one embodiment of the present invention, in the range of 180 to 220°C, e.g., 200 to 220°C).

[0130] FRC materials prepared from the compositions of the present invention containing specific epoxy resin compositions and reinforcing fibers are advantageously used in general industrial applications and aerospace applications. The FRC materials may also be used in other applications, such as sports applications (e.g., golf shafts, fishing rods, tennis or badminton rackets, hockey sticks, and ski poles) and vehicle structural materials (e.g., automobiles, bicycles, ships, and railroad cars), drive shafts, leaf springs, wind turbine blades, pressure vessels, flywheels, papermaking rollers, roofing materials, cables, and repair / reinforcement materials.

[0131] While embodiments have been described herein in a manner that enables a clear and concise specification to be written, it is intended and will be understood that the embodiments can be combined or separated in various ways without departing from the invention. For example, it will be understood that all preferred features described herein are applicable to all aspects of the invention described herein.

[0132] In some embodiments, the invention herein can be construed to exclude any element or process step that does not materially affect the basic and novel characteristics of the composition or process. Further, in some embodiments, the invention can be construed to exclude any element or process step not specified herein.

[0133] Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications in the details can be made without departing from the invention, within the scope and range of equivalents of the claims.

[0134] In certain embodiments of the present invention, the burn time of the flame retardant fiber reinforced composite material is less than 3 seconds, in other embodiments 2 seconds or less, and in still other embodiments 1 second or less, as determined by the SFI 56.1 flammability test standard. If the burn time is less than 3 seconds, as more plies are added to the fiber reinforced composite, the sample can pass multiple flammability test standards (as described in more detail in the Examples section).

[0135] In certain embodiments of the present invention, when the flame retardant epoxy resin composition is cured, the burn length of the flame retardant fiber reinforced composite, as determined by SFI 56.1 flammability test standard, is 2.0 inches or less, in other embodiments 1.8 inches or less, and in still other embodiments 1.6 inches or less. If the burn length is 2.0 inches or less, adding more plies to the fiber reinforced composite allows the sample to pass multiple flammability test standards (as described in more detail in the Examples section). [Example]

[0136] The present embodiment will be described in more detail below with reference to examples. Measurements of various properties were carried out using the methods described below. These properties were measured under environmental conditions of a temperature of 23°C and a relative humidity of 50%, unless otherwise specified. Prepregs were then produced from the resins of the examples using a hot-melt prepreg method. The components used in the examples and comparative examples are as follows:

[0137] Component [A]: <Epoxy resin> Epon™ 828 (Hexion, Inc.), a bisphenol A type epoxy resin with an EEW of 185-192 g / eq.

[0138] Epon™ 3002 (Hexion, Inc.), a bisphenol A type epoxy resin with an EEW of 520-590 g / eq.

[0139] Tetraglycidyldiaminodiphenylmethane, "Araldite®" MY9655T (Huntsman Advanced Materials) with an EEW of 117-134 g / eq s Made in Japan.

[0140] DOPO (dihydro-9-oxa-10-phospha-phenanthrene-10-oxide) modified multifunctional epoxy resin EXA-9726 (manufactured by Dainippon Ink and Chemicals, Inc.).

[0141] Ingredients [B] Diethylphosphinic acid Diphenylphosphinic acid Component [E]: <Adduct of organic phosphinic acid and multifunctional epoxy resin> Reaction product of diethylphosphinic acid and Araldite® MY9655T in an equivalent ratio of 1:4, respectively.

[0142] Component [C]: <Hardening agent> Dicyandiamide, "Dyhard®" 100S (AlzChem Trostberg GmbH) with an AEW of 12 g / eq.

[0143] 4,4-Diaminodiphenyl sulfone, "Aradur®" 9664-1 (Huntsman Advanced Materials s Made in <Accelerator> 2,4'-toluenebis(dimethylurea), "Omicure®" U-24M (Huntsman Advanced Materials s Made in Japan.

[0144] <Thermoplastic resin> Polyvinyl formal "Vinylec (registered trademark)" K (manufactured by JNC Corporation).

[0145] Component [D]: <Reinforcing fiber> Carbon fiber fabric T300-3k plain weave (Plain Weave fabric, hereinafter "plain weave fabric" may be referred to as "PW fabric"). ) Style #4163 (fiber manufactured by Toray Industries, Inc., fabric manufactured by Textile Products, Inc.).

[0146] Carbon fiber "TORAYCA (registered trademark)" T300B-3k-40B fiber (tensile strength: 3.5 GPa, tensile modulus: 230 GPa, elongation: 1.5%, manufactured by Toray Industries, Inc.).

[0147] Carbon fiber fabric T700S-12k plain weave CK6244C (fiber manufactured by Toray Industries, Inc., fabric manufactured by Textile Products, Inc.).

[0148] Carbon fiber "TORAYCA (registered trademark)" T700SC-12k-50C fiber (tensile strength: 4.9 GPa, tensile modulus: 230 GPa, elongation: 2.1%, manufactured by Toray Industries, Inc.).

[0149] Carbon fiber "TORAYCA (registered trademark)" T800SC-24k-10E fiber (tensile strength: 5.9 GPa, tensile modulus: 294 GPa, elongation: 2.0%, manufactured by Toray Industries, Inc.).

[0150] Carbon fiber "TORAYCA (registered trademark)" T1100GC-24k-71E fiber (tensile strength: 7.0 GPa, tensile modulus: 324 GPa, elongation: 2.0%, manufactured by Toray Industries, Inc.).

[0151] Carbon fiber "TORAYCA (registered trademark)" M40JB-12k-50B fiber (tensile strength: 4.4 GPa, tensile modulus: 377 GPa, elongation: 1.2%, manufactured by Toray Industries, Inc.).

[0152] Glass fiber S-2 glass (made by AGY).

[0153] Aramid fiber "Kevlar (registered trademark)" K-29 yarn (manufactured by DuPont de Nemours, Inc.).

[0154] (1) Resin mixture All ingredients except the curing agent and accelerator were dissolved in a mixer in the required amounts to prepare a mixture, and then the curing agent was mixed with the accelerator to obtain an epoxy resin composition. Table 1 summarizes the composition of various exemplary resin compositions, the curing conditions, and the properties of the resulting cured resins.

[0155] (2) Adduct formation The reaction product of diethylphosphinic acid and Araldite® MY9655T was prepared by constantly stirring epoxy resin and diethylphosphinic acid in a predetermined ratio at a temperature of 100° C. for 1 hour.

[0156] (3) Flammability of resin (burning time, burning length) The specimens detailed in the Examples and Comparative Examples were tested for flame retardancy according to a flammability test modified from the SFI 56.1 flammability test specification for application to neat resin specimens. The SFI 56.1 specification is specifically for CFRP testing. The test had to be modified because the example specimens were fiber-free at the time of testing.

[0157] Resin flammability testing involves high-shear mixing of degassed mixed resin under vacuum, pouring the resin between two plates using a 2 mm Teflon spacer, and curing at a specified temperature for a set time. In the example presented herein, the epoxy resin composition was cured at 163°C for 15 minutes and ramped to the temperature at a rate of 10°C / min. The cured resin plate was then demolded and machined into 2" x 3" test specimens. The resin plate was placed in the flammability test chamber as shown in Figure 1. The flame was at least 1550°F, the visible flame was approximately 22 mm high as measured from the burner base, and the faint outer blue cone of the flame was approximately 38 mm high from the burner base. The 3-inch side of the resin plate specimen was centered approximately 19 mm above the burner base. The flame was moved below the resin specimen and held in place for 15 seconds, at which point the flame was removed and the time required for the flame to extinguish was measured. Additionally, any drips of the flaming epoxy resin material were recorded, and the time that these drips remained ignited was recorded. The sighting of a drip was considered an automatic failure of the flammability test. The burn length of the specimen was also recorded. The burn time and burn length values ​​are used to characterize the flammability of the resin specimen. A lower burn time and a lower burn length are desirable qualities for a flame-retardant material.

[0158] (4) Resin glass transition temperature (Tg by DMA torsion) The cured epoxy resin composition was molded in the following manner. After degassing under vacuum and high-shear mixing, the epoxy resin composition prepared in (1) was poured into a mold set to a thickness of 2 mm using a 2 mm Teflon spacer. The epoxy resin composition was then cured at a set temperature for a set time. In the example presented herein, the resin was cured at a temperature of 163°C for 15 minutes and then ramped up to the above temperature at a rate of 10°C / min.

[0159] Next, using a dynamic viscoelasticity measuring device (ARES manufactured by TA Instruments), the test piece was heated from 50°C to 250°C at a rate of 5°C / min in accordance with SACMA SRM 18R-94, and subjected to Tg measurement in a 1.0 Hz torsion mode.

[0160] Tg was determined by finding the intersection of the tangent to the glass region and the tangent to the transition region from the glass region to the rubber region on the temperature storage modulus curve (also called G'Tg), and the temperature at this intersection was considered to be the glass transition temperature (also called G'Tg).

[0161] However, if the cured resin composition had one or more viscosity (G'') peaks, the Tg was determined in the following manner: The height of each peak was calculated by subtracting the peak height (MPa) by the corresponding valley preceding the peak. If the height of any one of these peaks exceeded 15 MPa, the corresponding transition on the G' curve was used to calculate the Tg.

[0162] (5) Resin flexural modulus The flexural properties were measured by the following procedure. As described in (4) above, a 10 mm x 50 mm test piece was cut from the cured epoxy resin composition obtained by the process under the glass transition temperature (Tg). The test piece was then subjected to a three-point bending test in accordance with ASTM D7264 using an Instron universal testing machine (manufactured by Instron Corporation). The test piece was tested at room temperature to obtain the RTD (Room Temperature Dry) flexural properties of the cured epoxy resin composition.

[0163] (6) Composite flammability test (burning length, burning time) For composite flammability testing, the specified fiber type was pre-impregnated with the specified resin type at the specified fiber basis weight (FAW) and resin content (RC). Single-ply test specimens were cut to a size of 12 inches by 12 inches and cured in an autoclave at 163°C for 15 minutes. The single-ply cured panels were machined into 3-inch by 12-inch test specimens with the 0° fiber direction parallel to the 12-inch long edge. These single-ply specimens were then tested according to the SFI 56.1 flammability test standard, and the burn length and burn time were recorded for each specimen.

[0164] (7) Thermal conductivity of fiber The thermal conductivities of the fibers listed in Tables 2, 3 and 4 come from reported values ​​provided by the fiber suppliers.

[0165] (8) Manufacturing of fiber-reinforced composite materials A prepreg was prepared by impregnating specific reinforcing fibers with a specific epoxy resin composition. The epoxy resin composition obtained by method (1) was applied to release paper using a knife coater to produce two resin films. Next, the two resin films prepared above were stacked in sheet form on both sides of a specific fiber structure, and the epoxy resin composition was impregnated using a roller and / or a vacuum bag to produce a prepreg with a specific carbon fiber basis weight and resin content.

[0166] (9) Fiber basis weight The resin weight per unit area (RAW) was determined before prepregging by taking a film of resin, cutting a 100 x 100 mm square sample, scraping off the resin on the square, and measuring the weight of the resin. The weight per unit area is calculated by dividing twice this weight by the area of ​​the square sample. The fiber weight per unit area (FAW) was measured in the same way after prepregging by cutting a 100 x 100 mm square sample, weighing the prepreg, and subtracting the RAW from this value.

[0167] (10)Resin content Resin content (RC) is the weight percent of resin in the prepreg.

[0168]

number

[0169] The properties of the cured epoxy resin compositions of the examples and comparative examples were evaluated using the following measurement methods.

[0170] (3) Flammability of resin (burning length, burning time, drip) (4) Glass transition temperature (Tg) of resin (5) Resin flexural modulus The properties of the fiber-reinforced composite material compositions of the examples and comparative examples were evaluated using the following measurement methods.

[0171] (6) Composite flammability test (7) Thermal conductivity of fiber (9) Fiber Weight (FAW) (10)Resin content Examples 1 to 11 and Comparative Examples 1 to 4 The various amounts of the epoxy resin composition for each example are summarized in Table 1, and the various amounts of the fiber-reinforced composite material for each example are listed in Tables 2, 3, and 4. The epoxy resin compositions shown in Table 1 were prepared according to the following method: All components except the curing agent and accelerator were dissolved in a mixer in predetermined amounts to prepare a mixture, and then the curing agent was mixed with a predetermined amount of accelerator to obtain the epoxy resin composition.

[0172] The prepared epoxy resin compositions were cured as described in the various test descriptions. The results of each test are listed in Table 1. The epoxy resin compositions were then combined with the listed fibers via a prepreg lamination process at the designated FAW and resin content. The results of the composite tests are listed in Tables 2, 3, and 4.

[0173] Examples 1 to 11 in Tables 2 and 3, which are embodiments of the present invention, provided good flammability results.

[0174] Examples 1 and 3 and Comparative Example 1 Comparative Example 1 utilized Example Resin 6 (which did not contain an organic phosphinic acid-containing compound), and Examples 1 and 3 utilized Example Resins 1 and 2 (which contained an organic phosphinic acid-modified epoxy resin), respectively. Comparative Example 1 had a burn time of 22 seconds and a burn length of 12 inches (full), while Examples 1 and 3 had a burn time of 0 seconds and burn lengths of 1.5 inches and 1.9 inches, respectively.

[0175] Example 2 and Comparative Examples 2 to 3 Example 2 and Comparative Examples 2-3 utilize different reinforcing fibers with different thermal conductivity values. All three examples have a burn time of 0 seconds (meaning the specimen self-extinguishes before the flame is removed from the specimen), but their burn lengths vary. The most thermally conductive fiber, T300 in Example 2, produced the shortest burn length (1.7 inches), while the more insulating fibers, S-2 glass in Comparative Example 2 and K-29 in Comparative Example 3, produced longer burn lengths (2.3 inches and 2.7 inches, respectively), with the highest burn length corresponding to the most insulating fiber.

[0176] Examples 1 and 4 and Comparative Example 4 In Examples 1 and 4 and Comparative Example 4, Comparative Example 4 used EXA-9726, which is a DOPO (dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) modified difunctional epoxy resin (i.e., an organic phosphoric acid modified epoxy resin), rather than an organic phosphinic acid modified difunctional epoxy resin as in Examples 1 and 4. Example 7 maintains a burn time of 0 seconds, but Comparative Example 4 has a longer burn time of 4 seconds.

[0177] [Table 1]

[0178] [Table 2]

[0179] [Table 3]

[0180]

Table 4

Claims

1. A flame retardant composition useful for producing a flame-retardant fiber-reinforced composite material, comprising: i) an epoxy resin composition composed of component [A], component [B], and component [C]; and ii) component [D]; the epoxy resin composition has a phosphorus content of at least 0.5 wt. %, based on the total weight of the epoxy resin composition; The component [A] is composed of at least one epoxy resin, The component [B] is composed of at least one organic phosphinic acid, The component [C] is composed of at least one curing agent, The component [D] is composed of at least one type of reinforcing fiber having a thermal conductivity of 3 W / m K or more at room temperature, and A flame retardant composition, wherein the component [A] comprises at least one tetraglycidyldiaminodiphenylmethane, and the tetraglycidyldiaminodiphenylmethane is pre-reacted with at least a portion of the component [B].

2. The at least one organophosphinic acid is represented by formula (I): 【Chemical 1】 (In the formula, R １ and R ２ are independently selected from alkyl groups having 1 to 10 carbon atoms and aryl groups having 6 to 10 carbon atoms.

2. The flame retardant composition of claim 1, comprising at least one organophosphinic acid corresponding to

3. 10. The flame retardant composition of claim 1, wherein the epoxy resin composition further comprises at least one thermoplastic resin.

4. 4. The flame retardant composition of claim 3, wherein the at least one thermoplastic resin comprises at least one polyvinyl formal.

5. R in the formula (I) １ and R ２ and each represent an ethyl group.

6. 10. The flame retardant composition of claim 1, wherein the at least one reinforcing fiber comprises at least one carbon fiber.

7. 7. The flame retardant composition of claim 6, wherein the at least one reinforcing fiber comprises at least one carbon fiber selected from the group consisting of pitch-based carbon fiber and PAN-based carbon fiber.

8. The flame retardant composition according to any one of claims 1 to 7, which is in the form of a prepreg, and the prepreg includes a layer in which the reinforcing fibers are impregnated with the epoxy resin composition.

9. 9. The flame retardant composition of claim 8, wherein the layer of the reinforcing fibers is unidirectional or woven.

10. A fiber reinforced composite material obtained by curing the flame retardant composition according to claim 8 at a temperature of 120°C to 180°C.

11. i) an epoxy resin composition comprising component [C] and component [E]; and ii) a flame retardant composition comprising component [D], the epoxy resin composition has a phosphorus content of at least 0.5 wt. %, based on the total weight of the epoxy resin composition; The component [C] is composed of at least one curing agent, The component [D] is composed of at least one type of reinforcing fiber having a thermal conductivity of 3 W / m K or more at room temperature, and The component [E] is composed of at least one epoxy resin containing at least one residue of at least one organic phosphinic acid, The component [E] is represented by formula (III): 【Chemistry 2】 (Wherein R in formula (III) １ and R ２ are independently selected from alkyl groups having 1 to 10 carbon atoms and aryl groups having 6 to 10 carbon atoms, and R ３ is a group in which at least one epoxy group has reacted to form a substituent -O-P(=O)R １ R ２ wherein at least one epoxy resin corresponding to formula (III) has at least one unreacted epoxy group. and wherein the at least one epoxy resin corresponds to R in formula (III) ３ is the residue of at least one tetraglycidyldiaminodiphenylmethane.

12. The at least one residue of the at least one organophosphinic acid has formula (II): 【Chemistry 3】 (Wherein, R in formula (II) １ and R ２ are independently selected from an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms.

12. The flame retardant composition of claim 11, which corresponds to:

13. The flame retardant composition according to claim 11, wherein the epoxy resin composition further comprises a component [A] composed of at least one epoxy resin.

14. 12. The flame retardant composition according to claim 11, wherein the epoxy resin composition further comprises a component [B] composed of at least one organic phosphinic acid.

15. 12. The flame retardant composition of claim 11, wherein the epoxy resin composition further comprises at least one thermoplastic resin.

16. 16. The flame retardant composition of claim 15, wherein the at least one thermoplastic resin comprises at least one polyvinyl formal.

17. R in formula (II) １ and R ２ and each are an ethyl group.

18. 12. The flame retardant composition of claim 11, wherein the at least one reinforcing fiber comprises at least one carbon fiber.

19. 12. The flame retardant composition of claim 11, wherein the at least one reinforcing fiber comprises at least one carbon fiber selected from the group consisting of pitch-based carbon fiber and PAN-based carbon fiber.

20. The flame retardant composition according to any one of claims 11 to 19, which is in the form of a prepreg, and the prepreg includes a layer in which the reinforcing fibers are impregnated with the epoxy resin composition.

21. 21. The flame retardant composition of claim 20, wherein the layer of the reinforcing fibers is unidirectional or woven.

22. A fiber reinforced composite material obtained by curing the flame retardant composition according to claim 20 at a temperature of 120°C to 180°C.

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