JP2019210464A - Epoxy resin composition, prepreg, and fiber reinforced composite material - Google Patents

Abstract

To provide an epoxy resin composition excellent in quick curability and storage stability, and capable of suppressing alignment disorder of a fiber in pressing molding, a prepreg using the epoxy resin composition, and a fiber reinforced composite material by curing the prepreg.SOLUTION: There is provided an epoxy resin composition containing following components [A], [B], [C], [D], and [E], and satisfying following conditions (1) to (5). [A]: an epoxy resin. [B]: dicyandiamide. [C]: aromatic urea. [D]: boric acid ester. [E]: a particle. (1)0.005≤(content of the [D]/content of the [C])≤0.045. (2)0.9≤(active group molar number of the [A]/active hydrogen molar number of the [B])≤1.3. (3) 12≤(content of the [A]/content of the [C])≤26. (4) average particle diameter of the [E] is larger than 10 μm. (5) The [E] exists in insoluble state in the epoxy resin composition at 150°C.SELECTED DRAWING: None

Description

  The present invention relates to an epoxy resin composition preferably used as a matrix resin of a fiber reinforced composite material suitable for sports applications, aerospace applications and general industrial applications, and a prepreg and a fiber reinforced composite material using the epoxy resin composition as a matrix resin. is there.

  For the production of a fiber reinforced composite material, a sheet-like intermediate base material (prepreg) in which a reinforcing fiber is impregnated with a thermosetting resin is widely used. Molded products are obtained by laminating prepregs and curing them by heating, and they are applied to various fields such as aircraft and sports. As a thermosetting resin used as a matrix resin for a prepreg, an epoxy resin is widely used because of excellent heat resistance, adhesiveness, and mechanical properties.

  Here, the manufacturing method for obtaining a molded body using an autoclave, a heating furnace, etc. has a long molding cycle time. Therefore, in the manufacture of a fiber-reinforced composite material that emphasizes mass productivity, especially in automotive applications, a prepreg laminate is heated to a high temperature. A technique of molding at high pressure is often used. In general, there is a trade-off relationship between the cycle time for obtaining a molded body and the quality of the molded body, and the occurrence of fiber orientation disorder and deterioration of mechanical properties become a problem when pressurized at high temperature and pressure. Further, when the reactivity (fast curing property) of the epoxy resin is increased in order to shorten the cycle time, the storage stability of the prepreg is impaired, and the quality deterioration during storage becomes a problem. Therefore, it is desired to establish a technique for obtaining a fiber-reinforced composite material that achieves both storage stability and fast curability and can maintain high quality even under high pressure molding.

  Patent Document 1 discloses an epoxy resin composition having an excellent fast curability and a Tg not exceeding 140 ° C.

  Patent Document 2 discloses an epoxy resin composition having excellent storage stability, which contains dicyandiamide, an aromatic urea, and a boric acid ester.

  Patent Document 3 discloses a technology that uses an epoxy resin composition containing particles that swell at a specific temperature, thickens only at the temperature of heat curing, and suppresses fiber orientation disorder in the pressure molding. ing.

Japanese Translation of PCT International Publication No. 2006-500409 Japanese Patent Application Laid-Open No. 2006-148020 Japanese Patent No. 6131332

  The epoxy resin composition described in Patent Document 1 is excellent in rapid curability but has insufficient storage stability.

  The epoxy resin composition described in Patent Document 2 is excellent in storage stability but has insufficient fast curability.

  The thermosetting resin composition described in Patent Document 3 can suppress disorder in the orientation of fibers of the molded body by blending thickening particles. However, since the viscosity increases at the temperature of pressure molding, the flow of resin to the surface of the molded body is insufficient, and the surface quality cannot be said to be sufficient. Moreover, there was no mention regarding the storage stability of an epoxy resin composition.

  Therefore, in the present invention, an epoxy resin composition, a prepreg, which overcomes the drawbacks of the prior art, achieves both fast curability and storage stability, and can suppress fiber orientation disorder by pressure molding. And it aims at providing a fiber reinforced composite material.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found an epoxy resin composition having the following constitution, and have completed the present invention. That is, the epoxy resin composition of the present invention has the following configuration.

An epoxy resin composition comprising the following components [A], [B], [C], [D], and [E] and satisfying the following conditions (1) to (5).
[A]: epoxy resin [B]: dicyandiamide [C]: aromatic urea [D]: borate ester [E]: particles (1) 0.005 ≦ (content of component [D] / component [C] Content) ≦ 0.045
(2) 0.9 ≦ (number of moles of active group of component [A] / number of moles of active hydrogen of component [B]) ≦ 1.3
(3) 12 ≦ (content of component [A] / content of component [C]) ≦ 26
(4) The average particle diameter of component [E] is larger than 10 μm.
(5) Component [E] exists in an insoluble state in the epoxy resin composition at 150 ° C.

  Moreover, the prepreg of this invention consists of said epoxy resin composition and carbon fiber.

  Furthermore, the fiber reinforced composite material of the present invention is obtained by curing the above prepreg.

  By using the epoxy resin composition described in the present invention, there is provided a prepreg and a fiber-reinforced composite material that can achieve both fast curability and storage stability and can suppress fiber orientation disorder during pressure molding. Can be provided.

  The epoxy resin composition of the present invention contains [A] epoxy resin, [B] dicyandiamide, [C] aromatic urea, [D] boric acid ester, and [E] particles as essential components. First, components [A], [B], [C], and [D] will be described.

(Ingredient [A])
Component [A] in the present invention is an epoxy resin. [A] The epoxy resin is not particularly limited. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, novolac type epoxy resin, fluorene skeleton Epoxy resin, epoxy resin made from a copolymer of phenolic compound and dicyclopentadiene, diglycidyl resorcinol, glycidyl ether type epoxy resin such as tetrakis (glycidyloxyphenyl) ethane, tris (glycidyloxyphenyl) methane, tetra Glycidylamine type epoxy resins such as glycidyldiaminodiphenylmethane, triglycidylaminophenol, triglycidylaminocresol, tetraglycidylxylenediamine Etc., and the like. Epoxy resins may be used alone or in combination.

  Commercially available components [A] include “jER (registered trademark)” 828, 1001, 1007FS, 154, 4007P, 4010P (manufactured by Mitsubishi Chemical Corporation), “Epiclon (registered trademark)” 830, N- 740, HP7200, HP7200H, HP7200HH, HP7200HHH (manufactured by DIC Corporation), “Sumiepoxy (registered trademark)” ELM434, ELM100, ELM120 (manufactured by Sumitomo Chemical Co., Ltd.), “Araldite (registered trademark)” MY720 MY721, MY0500, MY0510, MY0600 (manufactured by Huntsman Advanced Materials), “Epototo (registered trademark)” YDF2001 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), and the like.

(Ingredient [B])
[B] in the present invention is dicyandiamide. Dicyandiamide is a compound represented by the chemical formula (H ₂ N) ₂ C═N—CN. Dicyandiamide is excellent in terms of imparting high mechanical properties and heat resistance to the cured resin, and is widely used as a curing agent for epoxy resins. Examples of such commercially available dicyandiamide include DICY7 and DICY15 (manufactured by Mitsubishi Chemical Corporation).

  It is preferable to mix component [B] as a powder in the epoxy resin composition from the viewpoint of storage stability at room temperature and viscosity stability during prepreg production. In addition, it is preferable to disperse component [B] in advance in a part of the epoxy resin of component [A] using a three-roll or the like in order to make the epoxy resin composition uniform and improve the physical properties of the cured product. .

  Component [B] can lower the curing temperature when used in combination with component [C] aromatic urea described below. In the present invention, in order to shorten the curing time, it is necessary to use the component [B] and the component [C] in combination.

(Ingredient [C])
Component [C] in the present invention is an aromatic urea compound. Component [C] acts as a curing accelerator and can shorten the curing time when used in combination with component [B].

  Examples of the component [C] include 3- (3,4-dichlorophenyl) -1,1-dimethylurea, 3- (4-chlorophenyl) -1,1-dimethylurea, 4,4′-methylenebisphenyldimethyl. Examples include urea, phenyldimethylurea, and toluenebisdimethylurea.

  Commercially available components [C] include DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.), “Omicure (registered trademark)” 24 (manufactured by PTI Japan), and “Dyhard (registered trademark)”. UR505 (made by CVC) etc. are mentioned.

(Ingredient [D])
Component [D] in the present invention is a borate ester. When component [D] is used in combination with component [C], the reaction between component [C] and component [A] at the storage temperature can be suppressed, so that the storage stability of the prepreg is significantly improved. Although the mechanism is not clear, since the component [D] has Lewis acidity, the amine compound liberated from the component [C] and the component [D] interact to reduce the reactivity of the amine compound. It is thought that there is not.

  Examples of the component [D] include trimethyl borate, triethyl borate, tributyl borate, tri-n-octyl borate, tri (triethylene glycol methyl ether) borate ester, alkyl borate ester such as tricyclohexyl borate, trimenthyl borate, tri Aromatic borate esters such as o-cresyl borate, tri-m-cresyl borate, tri-p-cresyl borate, triphenyl borate, tri (1,3-butanediol) biborate, tri (2-methyl-2, 4-pentanediol) biborate, trioctylene glycol diborate and the like.

  Further, as the borate ester, a cyclic borate ester having a cyclic structure in the molecule can also be used. Examples of the cyclic borate ester include tris-o-phenylene bisborate, bis-o-phenylene pyroborate, bis-2,3-dimethylethylenephenylene pyroborate, bis-2,2-dimethyltrimethylene pyroborate, and the like. .

  As a commercial item of component [D], "cure duct (registered trademark)" L-01B, L-07N, L-07E (above, Shikoku Kasei Kogyo Co., Ltd.) (a composition containing 5 parts by mass of a boric acid ester compound) Etc.).

Component [C] and component [D] contained in the epoxy resin composition of the present invention satisfy the following condition (1).
(1) 0.005 ≦ (content of component [D] / content of component [C]) ≦ 0.045.

  About condition (1), when the value shown by content of component [D] / content of component [C] of an epoxy resin composition exists in the range of 0.005-0.045, quick-cure property and preservation | save An epoxy resin composition having an excellent balance of stability is obtained. When the content of component [D] / content of component [C] is less than 0.005, the storage stability is insufficient. On the other hand, when the content of component [D] / content of component [C] exceeds 0.045, the curing time is insufficient. In addition, content of component [C] or content of component [D] is the compounding quantity of [C] boric acid ester or [D] boric acid ester with respect to 100 mass parts of epoxy resins of component [A]. is there.

  The storage stability of the epoxy resin composition of the present invention can be evaluated, for example, by tracking the change in glass transition temperature by differential scanning calorimetry (DSC). Specifically, the epoxy resin composition is stored in a constant temperature and humidity chamber for a predetermined period, and the glass transition temperature change before and after storage is measured by increasing the temperature from −20 ° C. to 150 ° C. at 5 ° C./min. Can be determined.

  The epoxy resin composition of the present invention preferably has a glass transition temperature change of 20 ° C. or less after being stored at 40 ° C. and 75% RH for 14 days. When the change in the glass transition temperature is 20 ° C. or less, the prepreg made of the epoxy resin composition exhibits further excellent storage stability.

  The curing time of the epoxy resin composition of the present invention can be evaluated by using, for example, a vulcanization / curing property tester Curlastometer V type (manufactured by JSR Trading Co., Ltd.). Specifically, the prepared epoxy resin composition is put into a die heated to 150 ° C., and a torque transmitted to the die by applying a torsional stress to increase the viscosity as the sample is cured is set to a maximum peak torque of 70. The time to reach% is evaluated as the time for demolding.

Component [A] and component [B] contained in the epoxy resin composition of the present invention satisfy the following condition (2).
(2) 0.9 ≦ (number of moles of active group of component [A] / number of moles of active hydrogen of component [B]) ≦ 1.3.

  An epoxy excellent in rapid curability when the value represented by the number of moles of active group of component [A] / the number of moles of active hydrogen of component [B] is in the range of 0.9 to 1.3 for condition (2) A resin composition is provided. When the number of moles of active group of component [A] / number of moles of active hydrogen of component [B] exceeds 1.3, the fast curability is insufficient. On the other hand, when the number of moles of active groups in component [A] / number of moles of active hydrogen in component [B] is less than 0.9, the cured product has insufficient mechanical properties.

In addition, the active group mole number of component [A] is the sum of the mole number of each epoxy resin active group, and is represented by the following formula.
Number of moles of active group of component [A] = (epoxy resin A mass / epoxy equivalent of epoxy resin A) + (epoxy resin B mass / epoxy equivalent of epoxy resin B) +... + (Epoxy resin W mass / epoxy Epoxy equivalent of resin W).

The number of active hydrogen moles of component [B] is determined by dividing the dicyandiamide mass by the active hydrogen equivalent of dicyandiamide, and is represented by the following formula.
Number of active hydrogen moles of component [B] = mass of dicyandiamide / active hydrogen equivalent of dicyandiamide.

Component [A] and component [C] contained in the epoxy resin composition of the present invention satisfy the following condition (3).
(3) 12 ≦ (content of component [A] / content of component [C]) ≦ 26.

  About the condition (3), when the value shown by content of component [A] / content of component [C] exists in the range of 12-26, the epoxy resin composition which is excellent in quick-curing property is given. When the content of component [A] / content of component [C] exceeds 26, the fast curability is insufficient. On the other hand, when the content of component [A] / content of component [C] is less than 12, the mechanical properties of the cured product become insufficient.

  In general, the rapid curability and the storage stability of the epoxy resin composition are in a trade-off relationship, and the fast curability and the storage stability cannot be compatible. Only when the epoxy resin composition of the present invention satisfies all of the above conditions (1) to (3), the trade-off between fast curability and storage stability is overcome, and a prepreg having both fast curability and storage stability is obtained. Can be obtained. Just satisfying any one or two of the conditions (1) to (3) cannot achieve both fast curability and storage stability.

  Subsequently, the component [E] will be described.

(Ingredient [E])
Component [E] included in the present invention is a particle. In the present invention, the volume average particle size of the component [E] needs to be larger than 10 μm (condition (4)). By making the volume average particle diameter larger than 10 μm, the particles are ubiquitous between the prepreg layers during the pressure forming of the prepreg laminate, and the friction force between the prepreg layers can be increased. The fiber orientation is not disturbed. That is, it is not certain that the particles are ubiquitous between the prepreg layers when the laminate is heated under pressure, but it is important that the particles are not buried between the carbon fibers constituting the prepreg. The upper limit of the range of the volume average particle diameter of the component [E] is preferably 1000 μm or less. Here, the volume average particle diameter is a value measured with a laser diffraction / scattering type particle size distribution measuring device in accordance with JIS Z8825-1 (2001).

  Furthermore, the component [E] is an epoxy resin composition formed by mixing the component [A], [B], [C], [D] and, if necessary, the component [F] thermoplastic resin described below. It is necessary to exist in an insoluble state at 150 ° C. within the object (condition (5)). The particles do not dissolve in other components, that is, exist in an insoluble state in the epoxy resin composition, so that the frictional force between the layers is expressed during pressing, and as a result, the fiber orientation is disturbed during pressing. Can be suppressed.

  Here, the solubility of the component [E] is the solubility of the epoxy resin composition in other components as described above, but the component [B] and the component [C] are cured of the epoxy resin composition. In this process, since it exists as a solid, it is practically difficult to determine the solubility of the component [E] from the resin composition containing the component [B] and the component [C]. Therefore, the solubility of component [E] is determined by the following method. That is, other components of the epoxy resin composition excluding component [B] and component [C], for example, a resin composition comprising component [A], component [D], and component [F], or an epoxy resin When the composition does not have the component [F], the resin composition composed of the component [A] and the component [D] is blended with the component [E] at room temperature and heated at 150 ° C. for 30 minutes. To prepare. The volume average particle diameter of the component [E] in the mixture is measured according to JIS Z8825-2 (2001), and the absolute value of the difference from the volume average particle diameter of the component [E] before and after heating and mixing is within 2%. If it exists, it can also be judged that it is insoluble in the epoxy resin composition used by this invention.

  The fiber orientation disorder at the time of pressure molding is, for example, the ratio (CA / PA) of the projected area (PA) of the prepreg laminate before pressure molding and the projected area (CA) of the molded body after pressure molding. Can be evaluated by comparing. Since the projected area (CA) of the molded body after pressure molding is not substantially smaller than the projected area (PA) of the prepreg laminate before pressure molding, CA / PA is 1.0. In this case, it is indicated that the orientation disorder of the fibers of the molded body does not occur. Further, it can be determined that the closer the CA / PA is to 1.0, the less the degree of disorder in the orientation of the fibers of the molded body.

  Component [E] contained in the epoxy resin composition is preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of component [A]. By satisfy | filling the said range, it is excellent in the balance of the orientation disorder | damage | failure of the fiber of a molded object, and mechanical property.

As a commercial item of component [E], for example, “Dymic beads (registered trademark)” UCN-5051D (crosslinked polyurethane, manufactured by Dainichi Seika Kogyo Co., Ltd.), “SUNBLACK (registered trademark)” SB900, SB320 (above, Asahi Carbon Co., Ltd.), Carbon ECP (Lion Co., Ltd.), “Mitsubishi (registered trademark)” Carbon Black RCF # 40 (Mitsubishi Chemical Co., Ltd.) and the like. The curing time is preferably 145 seconds or less. When the curing time is 145 seconds or less, it is possible to more effectively suppress the disorder of the orientation of the fibers of the molded body during pressure molding. This is because by increasing the curing speed in addition to the frictional force between the prepreg layers generated by the component [E] at the time of pressurization, the flow time of the resin accompanying the curing is shortened.

  The epoxy resin composition of the present invention has the purpose of adjusting the viscoelasticity and improving the tack and drape characteristics of the prepreg and the mechanical properties and toughness of the resin composition within a range not losing the effects of the present invention. The thermoplastic resin [F] can be included.

  Examples of the thermoplastic resin [F] include polyvinyl acetal resins such as polyvinyl formal and polyvinyl butyral, polyvinyl alcohol, phenoxy resin, polyamide, polyimide, polyvinyl pyrrolidone, and polysulfone.

  In the epoxy resin composition of the present invention, the temperature showing the lowest viscosity when the temperature is raised from 40 ° C. to 250 ° C. at a rate of 5 ° C./min in dynamic viscoelasticity measurement is 110 ° C. or more and 140 ° C. or less. Preferably there is. When the temperature showing the minimum viscosity when the temperature is raised from 40 ° C. to 250 ° C. at a rate of 5 ° C./min in dynamic viscoelasticity measurement is in the range of 110 ° C. or more and 140 ° C. or less, the epoxy resin composition A fiber reinforced composite material obtained by heating and pressing a prepreg made of a material exhibits an excellent appearance. This is because the epoxy resin composition during pressure molding maintains appropriate fluidity during the curing process, so that the resin is sufficiently spread on the surface of the molded body or a resin film is formed on the surface.

  The temperature at which the epoxy resin composition of the present invention exhibits the minimum viscosity can be evaluated by tracking the change in viscosity by, for example, dynamic viscoelasticity measurement. Specifically, the epoxy resin composition prepared by the method described later is heated from 40 ° C. to 250 ° C. at a rate of 5 ° C./min using a rheometer (rotational dynamic viscoelasticity measuring device). The temperature can be evaluated at a temperature at which the epoxy resin composition exhibits a minimum viscosity.

  Next, the fiber reinforced composite material of the present invention will be described. Specifically, a fiber reinforced composite material containing the cured resin of the epoxy resin composition of the present invention as a matrix resin is obtained by laminating a prepreg composed of the epoxy resin composition of the present invention and then heating and curing. Can do. This will be specifically described below.

  For the preparation of the epoxy resin composition of the present invention, for example, a kneader, a planetary mixer, a three-roll extruder and a twin-screw extruder may be used for kneading. If uniform kneading is possible, a beaker and Use a spatula or the like and mix by hand.

  Examples of the method for producing a prepreg include a method obtained by impregnating a carbon fiber substrate with the epoxy resin composition of the present invention. Examples of the impregnation method include a hot melt method (dry method). In the hot melt method, carbon fiber is directly impregnated with an epoxy resin composition whose viscosity has been reduced by heating, or a film in which an epoxy resin composition is coated on a release paper is prepared, and then both sides of the carbon fiber are prepared. Alternatively, the film is impregnated with carbon fiber by overlapping the film from one side and heating under pressure. At this time, the fiber weight content of the prepreg can be adjusted by changing the amount of resin applied to the release paper.

  A method for producing a fiber-reinforced composite material includes a method of obtaining a molded body by heating and pressurizing the laminate of the prepreg. Specifically, a pressure molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, and the like can be appropriately used.

  The fiber reinforced composite material comprising the epoxy resin composition of the present invention is preferably used for general industrial applications. More specifically, it is preferably used for the production of structural materials such as automobiles, bicycles, ships and railway vehicles. Among them, it is possible to particularly preferably use for high cycle molding for an outer plate of an automobile or the like because both fast curing properties and storage stability are compatible and it is possible to suppress disorder of fiber orientation during pressure molding. . Moreover, since it is possible to suppress the deterioration of the mechanical properties of the fiber-reinforced composite material by suppressing the fiber orientation disorder, it can be widely used for structural members and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the description of these examples.

  The components used in this embodiment are as follows.

<Materials used>
Component [A]: Epoxy resin [A] -1 “jER (registered trademark)” 828 (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
[A] -2 “jER (registered trademark)” 1001 (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
[A] -3 “jER (registered trademark)” 1007FS (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
[A] -4 “Epotec (registered trademark)” YD136 (bisphenol A type epoxy resin, manufactured by KUKDO)
[A] -5 “jER (registered trademark)” 154 (phenol novolac type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
[A] -6 “Epototo (registered trademark)” YDPN638 (phenol novolac type epoxy resin, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.)
[A] -7 “Epiclon (registered trademark)” 830 (bisphenol F type epoxy resin, manufactured by DIC Corporation)
[A] -8 “Epototo (registered trademark)” YDF2001 (bisphenol F type epoxy resin, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.)
[A] -9 “jER (registered trademark)” 4010P (bisphenol F type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
[A] -10 “Sumiepoxy (registered trademark)” ELM434 (diaminodiphenylmethane type epoxy resin, manufactured by Sumitomo Chemical Co., Ltd.).

Component [B]: Dicyandiamide [B] -1 DICY7 (Dicyandiamide, manufactured by Mitsubishi Chemical Corporation).

Ingredient [C]: Aromatic urea [C] -1 “Omicure (registered trademark)” 24 (Toluenebisdimethylurea, manufactured by PTI Japan)
[C] -2 DCMU99 (3- (3,4-dichlorophenyl) -1,1-dimethylurea, manufactured by Hodogaya Chemical Co., Ltd.)
[C] -3 “Dyhard (registered trademark)” UR505 (4,4′-methylenebisphenyldimethylurea, manufactured by CVC).

Component [D]: Boric acid ester [D] -1 “Cureduct (registered trademark)” L-07E (a composition containing 5 parts by mass of a boric acid ester compound, manufactured by Shikoku Kasei Kogyo Co., Ltd.).

Component [E]: Particle [E] -1 “Dymic Beads (registered trademark)” UCN-5150D (crosslinked polyurethane, manufactured by Dainichi Seika Kogyo Co., Ltd.)
[E] -2 “Mitsubishi (registered trademark)” carbon black RCF # 40 (carbon black, manufactured by Mitsubishi Chemical Corporation)
[E] -3 “Kane Ace (registered trademark)” MX-125 (core shell rubber particles, manufactured by Kaneka Corporation)
[E] -4 “Zefiac (registered trademark)” F320 (vinyl particles, manufactured by Aika Industry Co., Ltd.).

Component [F]: Thermoplastic resin [F] -1 “Vinylec (registered trademark)” K (polyvinyl formal, manufactured by JNC Corporation)
[F] -2 “Sumika Excel (registered trademark)” PES3600P (polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd.)
[F] -3 YP-50 (phenoxy resin, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.).

<Method for preparing epoxy resin composition>
In a stainless beaker, a predetermined amount of components other than [B] dicyandiamide, [C] aromatic urea, [D] boric acid ester, and [E] particles are added, heated to 150 ° C., and appropriately until each component is compatible. Kneaded. After the temperature was lowered to 120 ° C., [E] particles were blended and kneaded for 30 minutes. After the temperature was lowered to 60 ° C., the [D] borate ester component and [B] dicyandiamide were blended and kneaded for 30 minutes. Later, [C] aromatic urea was added and kneaded at 60 ° C. for 30 minutes to obtain an epoxy resin composition. The epoxy resin composition is as shown in Tables 1-4.

<Evaluation method of curing time of epoxy resin composition>
The curing time of the epoxy resin composition was measured using a curast meter V type (manufactured by JSR Trading Co., Ltd.), and the epoxy resin composition obtained by the above method was placed in a die heated to 150 ° C. The increase in viscosity accompanying the progress of curing of the sample was taken as the torque transmitted to the die, and the time when it reached 70% of the peak torque was taken as the curing time.

<Method for evaluating storage stability of epoxy resin composition>
The storage stability of the epoxy resin composition was measured by weighing 3 g of the initial epoxy resin composition obtained by the above method in an aluminum cup and leaving it in a constant temperature and humidity chamber for 14 days in an environment of 40 ° C. and 75% RH. When the glass transition temperature after T1 was T1 and the initial glass transition temperature T0, the amount of change in the glass transition temperature was defined as ΔTg = T1−T0, and the storage stability was determined by the value of ΔTg. The glass transition temperature was measured at 5 ° C./min from −20 ° C. to 150 ° C. using a differential scanning calorimeter (Q-2000: manufactured by TA Instruments) by weighing 3 mg of the epoxy resin after storage in a sample pan. The temperature was raised and measured. The midpoint of the inflection point of the obtained exothermic curve was obtained as the glass transition temperature.

<Evaluation method of flexural modulus of cured epoxy resin>
After the defoaming of the epoxy resin composition in a vacuum, the epoxy resin composition was cured for 90 minutes at a temperature of 150 ° C. in a mold set to a thickness of 2 mm with a 2 mm thick “Teflon (registered trademark)” spacer. A 2 mm plate-shaped resin cured product was obtained. A test piece having a width of 10 mm and a length of 60 mm was cut out from the cured resin, and a 3-point bend was performed using an Instron universal testing machine (Instron) at a span of 32 mm and a crosshead speed of 10 mm / min. The flexural modulus was measured. The average value of the values measured with the number of samples n = 5 was taken as the value of the flexural modulus.

<Method for measuring volume average particle diameter of component [E]>
Using a particle size distribution measuring apparatus LA-950 (manufactured by HORIBA), the volume average particle diameter of the particles dispersed in the air was measured three times according to JIS Z8825-1 (2001) with a dry unit. The average value was adopted.

<Method for confirming dissolved state of component [E]>
A predetermined amount of components other than [B] dicyandiamide, [C] aromatic urea, and [D] boric acid ester was placed in a stainless beaker at room temperature, and then heated to 150 ° C. and kneaded. After the temperature was lowered to 120 ° C., [E] particles were blended and kneaded for 30 minutes. After the temperature was lowered to 60 ° C., the [D] borate ester component was blended and kneaded for 30 minutes. An appropriate amount of the obtained resin composition was sandwiched between paste cell units, and a volume average particle size was calculated according to JIS Z8825-1 (2001) using a particle size distribution measuring apparatus LA-950 (manufactured by HORIBA). . The volume average particle size of the [E] particles was determined in the above <Method for measuring volume average particle size of component [E]>, and the one whose absolute value of the difference before and after kneading was within 2% was determined to be insoluble.

<Evaluation method of minimum viscosity observation temperature of epoxy resin composition>
3 g of the epoxy resin composition obtained according to the above <Preparation Method of Epoxy Resin Composition> is weighed and sandwiched between parallel plates having a diameter of 40 mm and a diameter of 50 mm, and a rotational dynamic viscoelasticity measuring apparatus (ARES W / FCO: The viscosity of the epoxy resin composition when the temperature was increased from 40 ° C. to 250 ° C. at a frequency of 3.14 rad / s and at a rate of 5 ° C./minute was measured using TA Instruments). At this time, the temperature at which the epoxy resin composition showed the lowest viscosity was taken as the value of the lowest viscosity observation temperature.

<Preparation method of prepreg>
The epoxy resin composition obtained according to the above <Preparation method of epoxy resin composition> was applied onto release paper using a knife coater to prepare two resin films. Next, the two resin films obtained were placed on carbon fiber “TORAYCA (registered trademark)” T700S-12K-60E (manufactured by Toray Industries Inc., basis weight 150 g / m ² ) arranged in one direction in a sheet shape. It piled up from both surfaces of the fiber, and was heated under pressure at a temperature of 85 ° C. and a pressure of 2 MPa to impregnate the thermosetting resin composition to obtain a prepreg. At this time, the amount of resin on the release paper was adjusted so that the fiber mass content (Wf) of the prepreg was 67%.

<Pressure forming method of prepreg laminate>
The prepreg produced according to the above <prepreg production method> was cut into a size of 240 mm square in the 0 ° and 45 ° directions, and 8 layers, pseudo, etc. in a laminated structure of [45/0 / −45 / 90] _s And a 240 mm square prepreg laminate was produced.

  The mold in the molding is a double-sided mold, the lower mold has a concave shape, the vertical and horizontal widths are both 250 mm, and it has a 25 mm cavity. The upper mold has a convex shape, the convex part fills the cavity part of the lower mold, and the material of the mold is SS400. In a state where the double-sided mold was heated and adjusted to 150 ° C. in advance, the laminate of the prepreg produced by the above method was placed in the center of the lower mold cavity, and then the mold was closed and pressurized at a surface pressure of 5 MPa for 6 minutes. . After 6 minutes, the prepreg laminate was removed from the double-sided mold to obtain a fiber-reinforced composite material.

<CA / PA evaluation method>
A prepreg produced according to the above <prepreg production method> was cut into a 300 mm square, and five layers were laminated in a configuration of [0 ° / 90 ° / 0 ° / 90 ° / 0 °] ₁ to 150 The sheet was sandwiched from above and below by two 500 mm square stainless steel plates heated to 0 ° C., and molded under the conditions of a pressing time of 10 minutes and a pressing force of 5 MPa to obtain a flat molded body. The molded body obtained by the above method was scanned and imaged at an equal magnification using a multifunction machine. With the image analysis software, the white portion and the black portion were binarized, the area of the black portion was calculated, and was used as the projected area (PA) of the molded body. The projected area (CA) of the laminate is 90000 mm ² because it is a 300 mm wide square. CA / PA was obtained from the values of PA and CA obtained by the above method.

<Surface quality evaluation method>
The surface of the molded body obtained according to the above <Pressure forming method of prepreg laminate> was observed. If it was good, the evaluation was A, and the case where slight resin withering occurred on the surface was evaluated as B. C evaluation was given when the resin withered and the meandering of the fiber had occurred.

<Evaluation method of 0 ° bending strength of unidirectional fiber reinforced composite material>
The prepreg produced in accordance with the above <prepreg production method> was cut into a 240 mm square size, the fiber directions were aligned, and 16 ply lamination was performed to produce a 240 mm square prepreg laminate.

  The mold in the molding is a double-sided mold, the lower mold has a concave shape, the vertical and horizontal widths are both 250 mm, and it has a 25 mm cavity. The upper mold has a convex shape, the convex part fills the cavity part of the lower mold, and the material of the mold is SS400. In a state where the double-sided mold is heated and adjusted to the molding temperature shown in the table in advance, the prepreg laminate prepared by the above method is placed in the center of the lower mold cavity, then the mold is closed, and the surface pressure is 5 MPa for 6 minutes. Pressurized. After 6 minutes, the fiber reinforced plastic obtained by removing the prepreg laminate from the double-sided mold was cut out to have a width of 15 mm and a length of 100 mm, and an Instron universal testing machine (manufactured by Instron) was used. Three-point bending was performed according to JIS K7017 (1988). The bending strength was measured by measuring at a crosshead speed of 5.0 mm / min, a span of 80 mm, a thickness of 10 mm, and a fulcrum diameter of 4 mm. The 0 ° bending strength was measured for six samples, and a conversion value with a fiber mass content of 60% by mass was calculated, and the average was obtained as 0 ° bending strength.

(Example 1)
[A] 30 parts by mass of “jER®” 828 as epoxy resin, 70 parts by mass of “jER®” 154, 12.5 parts by mass of DICY7 as [B] dicyandiamide, [C] aromatic 8.1 parts by mass of “Omicure (registered trademark)” 24 as a urea compound, 1.0 part by mass of “Cureduct (registered trademark)” L-07E as a mixture containing [D] borate ester, [E] particles As an example, an epoxy resin composition was prepared according to the above <Preparation Method of Epoxy Resin Composition> using 4 parts by mass of “Dymic Beads (registered trademark)” UCN-5150D. This epoxy resin composition (1) content of component [D] / content of component [C] is 0.006, (2) active group moles of component [A] / active hydrogen moles of component [B] Is 0.9, (3) content of component [A] / content of component [C] is 12.

  The volume average particle diameter of the component [E] particles contained in this epoxy resin composition was measured according to <Measurement method of volume average particle diameter of component [E]>, and was 15 μm. When the solubility of the particles was determined according to the confirmation method of the dissolution state>, the volume average particle diameter was 15 μm, and therefore, “insoluble” was determined.

  When this epoxy resin composition was measured according to <Evaluation Method of Curing Time of Epoxy Resin Composition>, it was 110 seconds and showed a good curing time.

  Further, ΔTg of this epoxy resin composition evaluated according to <Evaluation Method of Storage Stability of Epoxy Resin Composition> was 22 ° C. and showed good storage stability.

  Moreover, when the minimum viscosity observation temperature of this epoxy resin was measured in accordance with <Measurement Method of Minimum Viscosity Observation Temperature of Epoxy Resin Composition>, the minimum viscosity was shown at 108 ° C.

  Furthermore, when the bending elastic modulus of the epoxy resin composition was measured according to <Evaluation method of bending elastic modulus of epoxy resin composition>, it was 3.7 GPa.

  The prepreg was prepared according to the above <Prepreg Production Method>, and the CA / PA evaluated according to <CA / PA Evaluation Method> was 1.13.

  A fiber reinforced composite material (CFRP) was prepared by the method described in <Pressure forming method of prepreg laminate>, and the surface quality evaluated according to <Surface quality evaluation method> was B evaluation, which was good. It was.

  The 0 ° bending strength of the fiber reinforced composite material (CFRP) molded by the method described in the above <Method for evaluating 0 ° bending strength of unidirectional fiber reinforced composite material> showed a good value of 1640 MPa.

(Examples 2 to 12)
An epoxy resin composition, a prepreg, and CFRP were produced in the same manner as in Example 1 except that the resin composition was changed as shown in Tables 1 and 2, respectively. In these epoxy resin compositions, the content of (1) component [D] / component [C] is 0.006 to 0.045, and (2) the number of moles of active group of component [A] / component [B ] Was 0.9 to 1.2, and (3) content of component [A] / content of component [C] was in the range of 12 to 25. The volume average particle diameter of the particles used in these epoxy resin compositions was 15 to 24 μm, and the solubility of the component [E] particles in the epoxy resin was determined to be “insoluble”.

  The obtained epoxy resin composition had good curing time and storage stability as in Example 1. Moreover, the bending elastic modulus of the cured product was 3.6 to 3.9 GPa.

  The value of CA / PA was 1.09 to 1.35, and the surface quality of CFRP was as good as A or B evaluation. The fiber-reinforced composite material had a 0 ° bending strength as high as 1608 to 1699 MPa, and was excellent in mechanical properties.

(Comparative Example 1)
[E] An epoxy resin composition, prepreg, cured epoxy resin, and CFRP were prepared in the same manner as in Example 1 except that “Kane Ace (registered trademark)” MX-125 was added as particles. The resin composition and evaluation results are as shown in Table 3. (1) Component [D] content / component [C] content is 0.023, (2) Component [A] active group moles / component [B] active hydrogen moles is 1.0, (3) Content of component [A] / content of component [C] is 15. The volume average particle diameter of the particles was 0.1 μm, and the solubility of the particles was determined to be “insoluble”.

  The resulting epoxy resin composition had good curing time, storage stability, and flexural modulus, but the value of CA / PA was 1.90, and the fiber orientation disorder occurred. The 0 ° bending strength was as low as 1373 MPa. Further, since remarkable fiber orientation disorder occurred on the surface of the molded product, the surface quality of CFRP was set to C evaluation.

(Comparative Example 2)
[E] An epoxy resin composition, a prepreg, a cured epoxy resin, and CFRP were produced in the same manner as in Example 1 except that the particles were not added. The resin composition and evaluation results are as shown in Table 3. (1) Component [D] content / component [C] content is 0.033, (2) Component [A] active group moles / component [B] active hydrogen moles is 1.0, (3) Content of component [A] / content of component [C] is 22.

  The resulting epoxy resin composition had good curing time, storage stability, and flexural modulus, but the CA / PA value was 1.89, and the 0 ° bending strength of the fiber-reinforced composite material was as low as 1308 MPa. It was a thing. Since fiber meandering was scattered on the surface of CFRP, the surface quality of CFRP was set to C evaluation.

(Comparative Example 3)
[D] An epoxy resin composition, a prepreg, a cured epoxy resin, and CFRP were produced in the same manner as in Example 1 except that the boric acid ester was not added. The resin composition and evaluation results are as shown in Table 3. (1) Component [D] content / component [C] content is 0, (2) Component [A] active group moles / component [B] active hydrogen moles is 1.0, (3 ) Content of component [A] / content of component [C] is 23. The volume average particle diameter of the particles was determined to be 15 μm, and the solubility of the particles was determined to be “insoluble”.

  The resulting epoxy resin composition had good curing time and flexural modulus, but storage stability was insufficient. The value of CA / PA was 1.30, and the 0 ° bending strength of the fiber reinforced composite material was 1549 MPa, but remarkable resin wilt was observed on the surface of CFRP. Therefore, the surface quality of CFRP was evaluated as C. It was.

(Comparative Example 4)
[B] An epoxy resin composition, a prepreg, a cured epoxy resin, and CFRP were produced in the same manner as in Example 1 except that 13.7 parts of DICY7 was added as dicyandiamide. The resin composition and evaluation results are as shown in Table 3. (1) Component [D] content / component [C] content is 0.025, (2) Component [A] active group moles / component [B] active hydrogen moles is 0.8, (3) Content of component [A] / content of component [C] is 16. The volume average particle diameter of the particles was determined to be 15 μm, and the solubility of the particles was determined to be “insoluble”.

  The resulting epoxy resin composition had good curing time and storage stability, and the CA / PA value was 1.22, but a large amount of white solid precipitated on the surface of CFRP, so the surface quality of CFRP was C evaluation was made. Further, since the flexural modulus was remarkably as low as 3.0 GPa, the 0 ° bending strength of the fiber reinforced composite material was as low as 1442 MPa.

(Comparative Example 5)
[B] An epoxy resin composition, a prepreg, a cured epoxy resin, and CFRP were produced in the same manner as in Example 1 except that 6.9 parts of DICY7 was added as dicyandiamide. The resin composition and evaluation results are as shown in Table 3. (1) Component [D] content / component [C] content is 0.033, (2) Component [A] active group moles / component [B] active hydrogen moles is 1.7, (3) Content of component [A] / content of component [C] is 22. The volume average particle diameter of the particles was determined to be 15 μm, and the solubility of the particles was determined to be “insoluble”.

  The obtained epoxy resin composition had good storage stability and flexural modulus, but the curing time was insufficient. The value of CA / PA was 1.46, and the 0 ° bending strength of the fiber reinforced composite material was as low as 1489 MPa. The surface quality of CFRP was B rating.

(Comparative Example 6)
[C] An epoxy resin composition, a prepreg, a cured epoxy resin, and CFRP were produced in the same manner as in Example 1 except that 11 parts of “Omicure (registered trademark)” 24 was added as an aromatic urea. The resin composition and evaluation results are as shown in Table 3. (1) Component [D] content / component [C] content is 0.014, (2) Component [A] active group moles / component [B] active hydrogen moles is 1.0, (3) Content of component [A] / content of component [C] is 9. The volume average particle diameter of the particles was determined to be 15 μm, and the solubility of the particles was determined to be “insoluble”.

  The obtained epoxy resin composition had good curing time, but the storage stability and flexural modulus were remarkably low, and the 0 ° bending strength of the fiber reinforced composite material was as low as 1442 MPa. Although the value of CA / PA was 1.20, since resin withering was observed on the surface of CFRP, the surface quality of CFRP was set to C evaluation.

(Comparative Example 7)
[C] An epoxy resin composition, a prepreg, a cured epoxy resin, and CFRP were produced in the same manner as in Example 1 except that 3 parts of “Omicure (registered trademark)” 24 was added as an aromatic urea. The resin composition and evaluation results are as shown in Table 4. (1) Component [D] content / component [C] content is 0.050, (2) Component [A] active group moles / component [B] active hydrogen moles is 1.0, (3) Content of component [A] / content of component [C] is 33. The volume average particle diameter of the particles was determined to be 15 μm, and the solubility of the particles was determined to be “insoluble”.

  The obtained epoxy resin composition had good storage stability and flexural modulus, but the curing time was insufficient. The value of CA / PA was 1.44, and the 0 ° bending strength of the fiber-reinforced composite material was as low as 1493 MPa. The surface quality of CFRP was B rating.

(Comparative Example 8)
[D] An epoxy resin composition, a prepreg, an epoxy resin cured product, and CFRP were added in the same manner as in Example 1 except that 7 parts of “Cureduct (registered trademark)” L-07E was added as a boric acid ester. Produced. The resin composition and evaluation results are as shown in Table 4. (1) Component [D] content / component [C] content is 0.048, (2) Component [A] active group moles / component [B] active hydrogen moles is 1.0, (3) Content of component [A] / content of component [C] is 14. The volume average particle diameter of the particles was determined to be 15 μm, and the solubility of the particles was determined to be “insoluble”.

  The obtained epoxy resin composition had good storage stability and flexural modulus, but the curing time was insufficient. The value of CA / PA was 1.44, and the 0 ° bending strength of the fiber-reinforced composite material was as low as 1498 MPa. The surface quality of CFRP was B rating.

(Comparative Example 9)
[B] Epoxy resin composition in the same manner as in Example 1, except that 5.3 parts of DICY7 as dicyandiamide, 3 parts of DCMU99 as [C] aromatic urea were added, and [E] particles were not added. A prepreg, an epoxy resin cured product, and CFRP were produced. The resin composition and evaluation results are as shown in Table 4. (1) Component [D] content / component [C] content is 0.050, (2) Component [A] active group moles / component [B] active hydrogen moles is 1.8, (3) Content of component [A] / content of component [C] is 33.

  Although the storage stability and bending elastic modulus of the obtained epoxy resin composition were good, the curing time was insufficient. The value of CA / PA was 2.50, and the 0 ° bending strength of the fiber reinforced composite material was as low as 1298 MPa. Since significant fiber meandering was observed on the surface of the CFRP, the surface quality of the CFRP was evaluated as C.

(Comparative Example 10)
[D] An epoxy resin composition, a prepreg, a cured epoxy resin, and CFRP were prepared in the same manner as in Example 1 except that the boric acid ester and [E] particles were not added. The resin composition and evaluation results are as shown in Table 4. (1) Component [D] content / component [C] content is 0, (2) Component [A] active group moles / component [B] active hydrogen moles is 1.0, (3 ) Content of component [A] / content of component [C] was 23.

  Although the curing time and bending elastic modulus of the obtained epoxy resin composition were good, the storage stability was remarkably low. The value of CA / PA was 1.90, and the 0 ° bending strength of the fiber reinforced composite material was as low as 1302 MPa. Since fiber meandering and resin withering were found on the surface of the CFRP, the surface quality of the CFRP was evaluated as C.

(Comparative Example 11)
[B] Example 1 except that 5 parts of DICY7 was added as dicyandiamide, [D] boric acid ester was not added, and “Zefiac®” F320 was added as [E] particles. An epoxy resin composition, a prepreg, an epoxy resin cured product, and CFRP were produced by the same method. The resin composition and evaluation results are as shown in Table 4. (1) Component [D] content / component [C] content is 0, (2) Component [A] active group moles / component [B] active hydrogen moles is 2.0, (3 ) Content of component [A] / content of component [C] is 20. The volume average particle diameter of the particles was 2 μm, and the solubility of the particles was determined as “dissolved”.

  Although the curing time and bending elastic modulus of the obtained epoxy resin composition were good, the storage stability was extremely low. The value of CA / PA was 1.80, and the 0 ° bending strength of the fiber reinforced composite material was as low as 1321 MPa. Since resin withering was found on the surface of CFRP, the surface quality of CFRP was evaluated as C.

  In addition, the unit of each component in a table | surface is a mass part.

  By using the epoxy resin composition described in the present invention, it is possible to provide a prepreg that is excellent in both fast curability and storage stability, and can suppress fiber orientation disorder in pressure molding, It is preferably used for industrial applications that require high cycle molding. Furthermore, since it is excellent also in surface quality, it is particularly preferably used for automobile outer plate applications.

Claims (5)

An epoxy resin composition comprising the following components [A], [B], [C], [D], and [E] and satisfying the following conditions (1) to (5).
[A]: epoxy resin [B]: dicyandiamide [C]: aromatic urea [D]: borate ester [E]: particles (1) 0.005 ≦ (content of component [D] / component [C] Content) ≦ 0.045
(2) 0.9 ≦ (number of moles of active group of component [A] / number of moles of active hydrogen of component [B]) ≦ 1.3
(3) 12 ≦ (content of component [A] / content of component [C]) ≦ 26
(4) The average particle diameter of component [E] is larger than 10 μm.
(5) Component [E] exists in an insoluble state in the epoxy resin composition at 150 ° C.   The epoxy resin composition according to claim 1, wherein a change in glass transition temperature after storage at 40 ° C. and 75% RH for 14 days is 20 ° C. or less.   The temperature at which the epoxy resin composition exhibits a minimum viscosity when the temperature is increased from 40 ° C to 250 ° C at a rate of 5 ° C / min in dynamic viscoelasticity measurement is 110 ° C or more and 140 ° C or less. 3. The epoxy resin composition according to 1 or 2.   A prepreg comprising the epoxy resin composition according to any one of claims 1 to 3 and carbon fiber.   A fiber-reinforced composite material obtained by curing the prepreg according to claim 4.