KR102780211B1 - Toe Frere - Google Patents

Abstract

The object is to provide a towpreg which does not cause flowing down from a paper tube when the bobbin is erected, and further has good shape stability of the bobbin because there is little winding during unwinding, so that handleability is excellent, and further has good tow expansion properties during filament winding molding, so that there are no voids and a high-quality molded product can be obtained. A towpreg comprising an epoxy resin composition comprising component [A] an epoxy resin, [B] an epoxy resin curing agent commonly used in [A], and further satisfying condition (I) and further satisfying either condition (X) or (Y), in which a reinforcing fiber bundle is impregnated.

Description

Toe Frere

The present invention relates to a toupreg that is particularly suitable for the manufacture of hollow containers or cylinders made of fiber-reinforced composite materials. More specifically, the present invention relates to a toupreg that is excellent in handleability and has a small void space, thereby enabling the production of a molded product of good quality.

Fiber-reinforced composite materials using reinforcing fibers such as carbon fiber and glass fiber are used in numerous fields such as aerospace, automobiles, railway vehicles, ships, civil engineering and construction, and sporting goods due to their excellent lightness. In particular, in applications requiring high performance, fiber-reinforced composite materials using continuous reinforcing fibers are used, and carbon fibers, which have excellent specific strength and elastic modulus, are often used as reinforcing fibers, and epoxy resins, which have excellent adhesion to carbon fibers, are often used as thermosetting resins.

In recent years, with the expansion of the use of carbon fibers, the molding method has also been spreading. Among these, filament winding is a method that is well suited to the manufacture of hollow containers such as pressure vessels and cylinders. Instead of the conventional wet method in which a bundle of reinforcing fibers unwound from a bobbin is immersed in a liquid thermoplastic resin and then wound on a frame, a method in which a thin intermediate substrate (hereinafter referred to as tow prepreg) in which a thermosetting resin is impregnated into a bundle of reinforcing fibers in advance is supplied and wound on a frame is attracting attention from the viewpoints of productivity and quality.

Towpregs are usually supplied in the form of bobbins wound on a paper tube for hundreds to thousands of meters, and are unwound at high speed in the molding process of fiber-reinforced composite materials. At this time, in addition to the fact that the bobbin does not flow down from the paper tube when it is erected and that the shape stability of the bobbin is good due to little winding during unwinding, the tow has good expandability during filament winding molding, and gaps are unlikely to form. In addition, in order to provide a towpreg with stable quality, it is also required that the epoxy resin before impregnation into the tow has little deterioration when stored for a long period of time.

Patent Document 1 discloses a towpreg formed by impregnating a bundle of reinforcing fibers with an epoxy resin composition in which dicyandiamide, a solid curing agent, is dispersed. However, in this towpreg, there is a problem in that, although no flow occurs from the core when the bobbin is erected, the tow has poor expansion properties during filament winding molding, and gaps are likely to form.

Patent Document 2 discloses a towpreg formed by impregnating a bundle of reinforcing fibers with an epoxy resin composition in which a halogenated boron amine complex is dissolved as a hardener. However, in this towpreg, the tow has good expansion properties during filament winding molding, and gaps are unlikely to form, but there is a problem that flow occurs from the core when the bobbin is raised.

Japanese Patent Publication No. 2016-190920 International Publication No. WO2013／183667

The present invention, taking this background into consideration, aims to provide a tow prepreg that satisfies all of the following requirements: no flow from the bobbin when the bobbin is erected; good shape stability of the bobbin due to less winding and fixation of the bobbin; and good tow expansion during filament winding forming, making it difficult for gaps to form.

In addition, the present invention aims to provide a tow prepreg which, even when using an epoxy resin that has been stored for a long period of time, prevents the occurrence of flowing out of the bobbin when the bobbin is erected, has good tow expansion properties during filament winding molding, and makes it difficult for gaps to form.

The present invention adopts the following means to solve such a problem. That is, the toe-preg of the present invention is a toe-preg formed by impregnating a reinforcing fiber bundle with an epoxy resin composition that includes the following components [A] and [B], and further satisfies condition (I) and further satisfies either condition (X) or (Y).

[A] Epoxy resin

[B] Epoxy resin hardener used in [A]

(Ⅰ) Immediately after preparing the epoxy resin composition comprising (i) components [A], [B] and the following component [C], or (ii) components [A], [B] and the following component [C1], the complex shear viscosity (η _0.1 ) measured at 25°C and a frequency of 0.1 Hz using a parallel plate vibration rheometer is 40 to 300 Pa s.

(X) (ⅰ) Contains components [A], [B] and the following component [C], and also satisfies conditions (Ⅱ) and (Ⅲ).

[C] Transition agent

(Ⅱ) Immediately after preparing the epoxy resin composition containing components [A], [B], and [C], the complex shear viscosity (η ₁₀ ) measured at 25°C and a frequency of 10 Hz using a parallel plate vibration rheometer is 50 Pa·s or less.

(Ⅲ) The ratio (η 0.1 / η 10 ) of the complex shear viscosity (η _0.1 ) measured at 25°C and a frequency of 0.1 Hz using a parallel plate oscillation rheometer to the complex shear viscosity (η ₁₀ ) measured at 25°C and a frequency of _{10 Hz} using a parallel plate oscillation rheometer is 1.5 or more.

(Y) (ⅱ) Contains components [A], [B] and the following component [C1], and also satisfies conditions (Ⅳ) and (Ⅴ).

[C1] Hydrophobic thixotropic agent

(Ⅳ) The thixotropy index (TI ₄ = η' _0.1 / η' ₁₀ ) of an epoxy resin composition prepared by mixing component [B] 4 days after preparing a main agent containing components [A] and [C1] is 1.5 or more. (Here, η' _0.1 is the complex shear viscosity measured at 25°C and a frequency of 0.1 Hz using a parallel plate oscillation rheometer, after mixing component [B] 4 days after preparing a main agent containing components [A] and [C1], and η' ₁₀ is the complex shear viscosity measured at 25°C and a frequency of 10 Hz using a parallel plate oscillation rheometer, after mixing component [B] 4 days after preparing a main agent containing components [A] and [C1].)

(Ⅴ) The content of component [C1] is 1.0 to 7.0 parts by mass per 100 parts by mass of component [A].

The towpreg of the present invention satisfies all of the following requirements: no flow from the bobbin when the bobbin is erected; little winding and tangling, thus providing good shape stability of the bobbin; good tow expansion during filament winding molding, thus making it difficult for gaps to form; and therefore, the towpreg of the present invention is excellent in handleability when manufacturing hollow containers such as pressure vessels or cylinders by the filament winding method, and further, a molded product of good quality can be obtained because there are few gaps.

In addition, the towpreg of the present invention can achieve both the following characteristics: no flow from the bobbin when the bobbin is erected even when an epoxy resin that has been stored for a long period of time is used; good tow expansion during filament winding molding, and the formation of gaps is difficult; therefore, the handleability is excellent during the manufacture of hollow containers such as pressure vessels or cylinders by the filament winding method, and a molded product having good quality and few gaps can be obtained.

Figure 1 is a schematic diagram showing the phenomenon of flowing out from the core of a towpreg bobbin.
Figure 2 is a schematic diagram showing the winding and fastening phenomenon of a towpreg bobbin.
Figure 3 is a drawing showing an example of the chemical structure of a hydrophobic surface treatment of a thixotropic agent.

The present invention has the following composition. That is, the toe-preg of the present invention is a toe-preg formed by impregnating a reinforcing fiber bundle with an epoxy resin composition that includes the following components [A] and [B], and further satisfies condition (Ⅰ), and further satisfies either condition (X) or (Y).

[A] Epoxy resin

[B] Epoxy resin hardener used in [A]

(Ⅰ) Immediately after preparing the epoxy resin composition comprising (i) components [A], [B] and the following component [C], or (ii) components [A], [B] and the following component [C1], the complex shear viscosity (η _0.1 ) measured at 25°C and a frequency of 0.1 Hz using a parallel plate vibration rheometer is 40 to 300 Pa s.

(X) (ⅰ) Contains components [A], [B] and the following component [C], and also satisfies conditions (Ⅱ) and (Ⅲ).

[C] Transition agent

(Ⅱ) Immediately after preparing the epoxy resin composition containing components [A], [B], and [C], the complex shear viscosity (η ₁₀ ) measured at 25°C and a frequency of 10 Hz using a parallel plate vibration rheometer is 50 Pa·s or less.

(Ⅲ) The ratio (η 0.1 / η 10 ) of the complex shear viscosity (η _0.1 ) measured at 25°C and a frequency of 0.1 Hz using a parallel plate oscillation rheometer to the complex shear viscosity (η ₁₀ ) measured at 25°C and a frequency of _{10 Hz} using a parallel plate oscillation rheometer is 1.5 or more.

(Y) (ⅱ) Contains components [A], [B] and the following component [C1], and also satisfies conditions (Ⅳ) and (Ⅴ).

[C1] Hydrophobic thixotropic agent

(Ⅳ) The thixotropy index (TI ₄ = η' _0.1 / η' ₁₀ ) of an epoxy resin composition prepared by mixing component [B] 4 days after preparing a subject matter including components [A] and [C1] is 1.5 or more. (Here, η' _0.1 is the complex shear viscosity measured at 25°C and a frequency of 0.1 Hz using a parallel plate oscillation rheometer, after mixing component [B] 4 days after preparing a subject matter including components [A] and [C1], and η' ₁₀ is the complex shear viscosity measured at 25°C and a frequency of 10 Hz using a parallel plate oscillation rheometer, after mixing component [B] 4 days after preparing a subject matter including components [A] and [C1].)

(Ⅴ) The content of component [C1] is 1.0 to 7.0 parts by mass per 100 parts by mass of component [A].

(About ingredient [A])

Component [A] in the present invention is an epoxy resin. There is no particular limitation on such epoxy resin, and examples thereof include bisphenol type epoxy resins such as bisphenol A type, bisphenol F type, and bisphenol S type; glycidylamine type epoxy resins such as glycidylaniline type, diaminodiphenylmethane type, diaminodiphenylsulfone type, aminophenol type, metaxylenediamine type, and 1,3-bisaminomethylcyclohexane type; isocyanurate type, hydantoin type, phenol novolac type, orthocresol novolac type, dicyclopentadiene novolac type, biphenyl type, trishydroxyphenylmethane type, and tetraphenylolethane type epoxy resins. These epoxy resins may be used alone or may be used by appropriate mixing.

Among these epoxy resins, it is preferable to include a glycidylamine type epoxy resin because it has the effect of providing stability to the epoxy resin composition and preventing thickening of the epoxy resin composition during the preparation process of the epoxy resin composition, the manufacturing process of the toe prreg, and the preservation period of the toe prreg. By preventing thickening of the epoxy resin composition during these processes and periods, the impregnation state of the epoxy resin composition in the toe prreg can be improved, and the unwinding property during molding can be maintained well. Examples of the glycidylamine type epoxy resin include glycidylaniline type, diaminodiphenylmethane type, diaminodiphenylsulfone type, aminophenol type, metaxylenediamine type, and 1,3-bisaminomethylcyclohexane type. In addition, commercial products of such glycidylamine type epoxy resins include GAN (N,N-diglycidyl aniline, manufactured by Nihonga Yak Co., Ltd.), GOT (N,N-diglycidyl-o-toluidine, manufactured by Nihonga Yak Co., Ltd.), “Sumi Epoxy (registered trademark)” ELM-434 (tetraglycidyldiaminodiphenylmethane, manufactured by Sumitomo Chemical Co., Ltd.), “Araldite (registered trademark)” MY721 (tetraglycidyldiaminodiphenylmethane, manufactured by Huntman Japan Co., Ltd.), and “ARALDITE (registered trademark)” MY0510 (tetraglycidyl-p-aminophenol, manufactured by Huntman Japan Co., Ltd.).

The content of the glycidylamine type epoxy resin is preferably 10 parts by mass or more, more preferably 10 to 80 parts by mass, and particularly preferably 20 to 60 parts by mass, per 100 parts by mass of component [A]. By setting the content of the glycidylamine type epoxy resin to 10 parts by mass or more per 100 parts by mass of component [A], the effect of preventing thickening of the epoxy resin composition can be obtained. Furthermore, by setting the content of the glycidylamine type epoxy resin to 80 parts by mass or less per 100 parts by mass of component [A], an epoxy resin composition for toe-preg which provides a fiber-reinforced composite material having excellent balance of mechanical properties can be obtained.

(About ingredient [B])

In the present invention, component [B] is an epoxy resin curing agent that is compatible with component [A] included in the epoxy resin composition in the towpreg of the present invention. Here, being compatible with component [A] means that the epoxy resin composition to be impregnated into the towpreg does not substantially contain a solid epoxy resin curing agent, and compatibility can be confirmed when no particle component derived from the curing agent of the raw material is detected by a method such as observation using an optical microscope or particle size distribution measurement using a light scattering method. Therefore, component [B] needs to be a solid curing agent that can be dissolved in component [A] in a temperature range where a rapid reaction with component [A] does not begin and can maintain a compatible state at 25°C, or a liquid curing agent that can maintain a compatible state at 25°C, and from the viewpoint of not leaving a solid content, it is more preferable that it is liquid. By using component [B], it is possible to obtain a tow prefab which has good tow expansion properties during filament winding molding and which is unlikely to have gaps. Examples of such component [B] include aliphatic amines, aromatic amines, polyphenols, imidazoles, carboxylic acids, carboxylic anhydrides, carboxylic acid amides, mercaptans, and Lewis acids such as halogenated boron amine complexes. In addition, these epoxy resin curing agents may be used alone or as appropriate mixtures.

Among these epoxy resin curing agents, aromatic amines are particularly preferably used because they can obtain an epoxy resin composition for towpregs that provides a fiber-reinforced composite material with excellent balance of mechanical properties. Furthermore, from the viewpoint of not leaving behind a solid content, aromatic amines that are liquid at 25°C are more preferable. Here, aromatic amines are a general term for compounds having an amino group directly bonded to an aromatic ring. Examples of such aromatic amines that are liquid at 25°C include compounds having one aromatic ring, such as aminobenzylamine and diethyltoluenediamine, and compounds having two aromatic rings, such as 3,3'-diethyl-4,4'-diaminodiphenylmethane.

In addition, commercial products of these aromatic amines include ABAm (aminobenzylamine, Mitsui Chemical Fine Co., Ltd.), “jER Cure (registered trademark)” WA (diethyltoluenediamine, manufactured by Mitsubishi Chemical Corporation), “LONZACURE (registered trademark)” DETDA80 (diethyltoluenediamine, manufactured by Lonza Japan Co., Ltd.), and “KAYAHARD (registered trademark)” A-A (3,3'-diethyl-4,4'-diaminodiphenylmethane, manufactured by Nihon Kayaku Co., Ltd.).

The content of the liquid aromatic amine at 25°C is preferably an amount that provides 0.7 to 2.0 equivalents of active hydrogen for each epoxy resin component included in component [A], and is more preferably an amount that provides 0.7 to 1.8 equivalents. By setting the content of the liquid aromatic amine at 25°C to this range, an epoxy resin composition for towpreg that provides a fiber-reinforced composite material having excellent balance of mechanical properties can be obtained.

(About condition (Ⅰ))

The epoxy resin composition to be impregnated into the towpreg of the present invention must have a complex shear viscosity (η 0.1 ) of 40 to 300 Pa·s, as measured at 25°C and a frequency of 0.1 Hz using a parallel plate vibration rheometer immediately after preparing the epoxy resin composition containing (i) components [A], [B] and a component [ _C ] described later, or (ii) components [A], [B] and a component [C1] described later, more preferably 100 to 300 Pa·s. When η _0.1 is 40 Pa·s or more, flowing out of the bobbin when the bobbin is erected and winding and fastening during unwinding can be suppressed. In addition, when η _0.1 is 300 Pa·s or less, it is possible to prevent poor liquid feeding in the towpreg manufacturing process or poor formation of a resin film on a kiss roll.

In condition (I), immediately after preparing the epoxy resin composition means, in the case where the epoxy resin composition comprises (i) components [A], [B] and a component [C] described below, 1 hour after preparing the subject matter comprising components [A] and [C], 30 minutes after further mixing component [B] to complete the preparation of the epoxy resin composition; similarly, in the case where the epoxy resin composition comprises (ii) components [A], [B] and a component [C1] described below, 1 hour after preparing the subject matter comprising components [A] and [C1], 30 minutes after further mixing component [B] to complete the preparation of the epoxy resin composition.

(about condition (X))

In one embodiment of the present invention, it is necessary to satisfy condition (X). Condition (X) means that the epoxy resin composition includes (i) components [A], [B] and component [C] described below, and also satisfies conditions (II) and (III).

[C] Transition agent

(Ⅱ) Immediately after preparing the epoxy resin composition containing components [A], [B], and [C], the complex shear viscosity (η ₁₀ ) measured at 25°C and a frequency of 10 Hz using a parallel plate vibration rheometer is 50 Pa·s or less.

(Ⅲ) The ratio (η 0.1 / η 10 ) of the complex shear viscosity (η _0.1 ) measured at 25°C and a frequency of 0.1 Hz using a parallel plate oscillation rheometer to the complex shear viscosity (η ₁₀ ) measured at 25°C and a frequency of _{10 Hz} using a parallel plate oscillation rheometer is 1.5 or more.

(About component [C])

Component [C] in the present invention is a thixotropic agent included in the epoxy resin composition in the towpreg of the present invention. Here, thixotropy means a phenomenon in which the apparent viscosity decreases by adding shear stress, and returns to the original apparent viscosity over time when left to stand. In other words, it is a phenomenon in which the viscosity is high under low-frequency conditions and low under high-frequency conditions. By imparting thixotropy to the epoxy resin composition, a towpreg can be obtained that satisfies all of the following: no flow from the bobbin when the bobbin is erected; little winding and entanglement during the winding process, so that the shape stability of the bobbin is good; and good tow expansion during filament winding molding, so that gaps are unlikely to form.

Here, the flow-through from the bobbin when the bobbin is set up refers to a phenomenon in which, when a bobbin-shaped towpreg, in which a towpreg of several hundred to several thousand meters is wound on a bobbin and is set up so that the longitudinal direction of the bobbin is perpendicular to the surface of the work table, the towpreg slips and the bobbin shape collapses. A schematic diagram showing the flow-through phenomenon is shown in Fig. 1. Once the flow-through phenomenon occurs, a phenomenon in which the yarn is unraveled occurs at the end of the bobbin where the shape has collapsed, making it impossible to untie the tow. Since the flow-through phenomenon is a deformation that occurs over a relatively long period of time, its occurrence can be suppressed if the viscosity of the epoxy resin composition impregnated into the reinforcing fiber bundle is high under low-frequency conditions.

In addition, the winding fastening in the seam refers to a phenomenon in which, when a bobbin-shaped towpreg, which is a towpreg of several hundred to several thousand meters wound on a core, is mounted on a creel of a filament winding device and tension is applied to form, the bobbin is narrowed and deformed by the applied tension, resulting in unevenness on the surface of the bobbin or bulging of the end face of the bobbin. A schematic diagram showing the winding fastening phenomenon is shown in Fig. 2. When the winding fastening phenomenon occurs, a loosening phenomenon occurs in which the yarn is unwound at the bulged end of the bobbin, making it impossible to unwind the towpreg. Since the winding fastening phenomenon is a deformation that occurs over a relatively long period of time, its occurrence can be suppressed if the viscosity of the epoxy resin composition impregnated into the reinforcing fiber bundle is high under low-frequency conditions.

In addition, the tow widening during filament winding molding refers to the phenomenon in which the width of the tow prreg widens due to the pressure applied when wound on a liner of a pressure vessel or a mandrel used for molding a cylinder. If the tow prreg widening property is insufficient, a gap occurs near the mouth of the molded product, especially when manufacturing a pressure vessel, which causes a reduction in the burst strength. Since the widening property is a deformation that occurs over a relatively short period of time, if the viscosity of the epoxy resin composition impregnated into the reinforcing fiber bundle is low under high-frequency conditions, good widening property can be obtained.

In order to satisfy all of the following requirements: no flow from the bobbin when the bobbin is erected; good shape stability of the bobbin due to less winding of the bobbin; good tow expansion during filament winding molding, and less formation of gaps; the epoxy resin composition impregnated into the reinforcing fiber bundle needs to have high viscosity under low-frequency conditions and low viscosity under high-frequency conditions, and this can be achieved by the inclusion of a thixotropic agent.

Examples of such thixotropic agents include organic agents such as amide wax and hydrogenated castor oil, and inorganic agents such as silica, alumina, mixed oxides of aluminum and silicon, titanium oxide, light calcium carbonate, smectite clay minerals (montmorillonite, beidellite, bentonite, hectorite, saponite, etc.), sepiolite, and carbon black. Among these thixotropic agents, one having a large thixotropic effect is desired. From this viewpoint, it is preferable to include at least one selected from the group consisting of bentonite, particulate silica, and amide wax, and it is more preferable to include hydrophobic particulate silica. In addition, these thixotropic agents may be used alone or may be used in combination as appropriate.

An amide wax-based thixotropic agent is a thixotropic agent having an amide structure that is a condensation of a fatty acid and an amine. Commercially available products of such amide wax-based thixotropic agents include “Disparon (registered trademark)” 6500 (manufactured by Kusumoto Chemical Co., Ltd.) and “Taren (registered trademark)” VA-750B (manufactured by Kyoeisha Chemical Co., Ltd.).

A bentonite-based thixotropic agent is a thixotropic agent that uses a mineral having a layered structure as a raw material. In the present invention, an epoxy resin that has been modified with an organic compound so as to enhance the thixotropic effect is preferable. In addition, a mixture with a mineral having a structure other than a layered structure may also be used. Commercially available products of such bentonite-based thixotropic agents include “TIXOGEL (registered trademark)” MPZ (manufactured by Big Chemie Japan Co., Ltd.), “GARAMITE (registered trademark)” 7305 (manufactured by Big Chemie Japan Co., Ltd.), etc.

The particulate silica-based thixotropy-imparting agent is a particulate silica having a primary particle diameter of several nanometers to several tens of nanometers, and fumed silica obtained by a combustion heating decomposition method or the like is preferably used. Commercially available products of such particulate silica-based thixotropy-imparting agents include “AEROSIL (registered trademark)” 130 (manufactured by Nippon Aelosil Co., Ltd.), “AEROSIL (registered trademark)” 300 (manufactured by Nippon Aelosil Co., Ltd.), etc. Among the particulate silica-based thixotropy-imparting agents, a thixotropy-imparting agent using hydrophobic particulate silica that has been subjected to a hydrophobic surface treatment is more preferable because the thixotropy-imparting effect is large. The hydrophobic surface treatment is a treatment that bonds a hydrophobic substituent such as an alkylsilyl group such as a dimethylsilyl group or a trimethylsilyl group, or dimethylpolysiloxane, to the silanol groups on the surface of the particulate silica. Examples of commercially available thixotropic agents using such hydrophobic fine particle silica include “AEROSIL (registered trademark)” R972 (manufactured by Nippon Aerosil Co., Ltd.), “AEROSIL (registered trademark)” R812 (manufactured by Nippon Aerosil Co., Ltd.), “AEROSIL (registered trademark)” RY200S (manufactured by Nippon Aerosil Co., Ltd.), and “AEROSIL (registered trademark)” R805 (manufactured by Nippon Aerosil Co., Ltd.).

The content of the thixotropic agent is preferably 1.0 to 20 parts by mass, and more preferably 3.0 to 7 parts by mass, per 100 parts by mass of component [A]. By setting the content of the thixotropic agent in this range, a towpreg can be obtained that satisfies the following at a higher level: no flowing out of the core when the bobbin is erected; little winding and tangling during the bobbin is performed, so that the shape stability of the bobbin is good; and the tow expansion during filament winding is good, so that gaps are unlikely to form.

In addition, although "viscosity" is explained here as a general characteristic, in this application, this viscosity is evaluated using "complex shear viscosity" as an indicator.

(About condition (Ⅱ))

The epoxy resin composition to be impregnated into the towpreg of the present invention must have a complex shear viscosity (η 10 ) of 50 Pa·s or less, as measured at 25°C and a frequency of ₁₀ Hz using a parallel plate vibration rheometer immediately after preparing the epoxy resin composition containing components [A], [B] and [C], and is preferably 1.0 to 50 Pa·s, more preferably 4 to 50 Pa·s. When η ₁₀ is 50 Pa·s or less, the expandability of the tow during filament winding molding can be improved, and the lower η ₁₀ is, the better expandability is obtained. In addition, by setting η ₁₀ to 1.0 or more, it is possible to achieve both suppression of resin flying and good expandability of the tow.

In condition (II), immediately after preparing the epoxy resin composition means 1 hour after preparing the subject of the epoxy resin composition including components [A] and [C], and 30 minutes after further mixing component [B] to complete the preparation of the epoxy resin composition.

(About condition (Ⅲ))

The epoxy resin composition to be impregnated into the towpreg of the present invention must have a ratio (η 0.1 /η 10 ) of the complex shear viscosity (η _0.1 ) measured at 25°C and a frequency of 0.1 Hz using a parallel plate oscillation rheometer to the complex shear viscosity (η ₁₀ ) measured at 25°C and a frequency of 10 Hz using a parallel plate oscillation rheometer _{of 1.5} or more, and preferably 3.0 or more. If η _0.1 / η ₁₀ is 1.5 or more, a tow preg can be obtained that satisfies all of the following: no flow from the core when the bobbin is set up, little winding of the bobbin, thus providing good shape stability of the bobbin, and good tow expansion during filament winding molding, making it difficult for gaps to form. The larger η _0.1 / η ₁₀ , the better these balances can be maintained. Although there is no particular limitation on the upper limit, it is usually 300 or less.

Here, the complex shear viscosity (η _0.1 ) in condition (III) is the complex shear viscosity (η _0.1 ) obtained by condition (I), and η ₁₀ means the complex shear viscosity (η ₁₀ ) obtained by condition (II), and when the epoxy resin composition includes (i) components [A], [B], and the following component [C], it specifies the ratio of the complex shear viscosity (η _0.1 ) obtained by condition (I) to the complex shear viscosity (η ₁₀ ) obtained by condition (II).

(For condition (Y))

In another aspect of the present invention, it is necessary to satisfy condition (Y). Condition (Y) means that (ii) components [A], [B] and the following component [C1] are included, and conditions (IV) and (V) are also satisfied.

[C1] Hydrophobic thixotropic agent

(Ⅳ) The thixotropy index (TI ₄ = η' _0.1 / η' ₁₀ ) of an epoxy resin composition prepared by mixing component [B] 4 days after preparing a subject matter including components [A] and [C1] is 1.5 or more. (Here, η' _0.1 is the complex shear viscosity measured at 25°C and a frequency of 0.1 Hz using a parallel plate oscillation rheometer, after mixing component [B] 4 days after preparing a subject matter including components [A] and [C1], and η' ₁₀ is the complex shear viscosity measured at 25°C and a frequency of 10 Hz using a parallel plate oscillation rheometer, after mixing component [B] 4 days after mixing components [A] and [C1].)

(Ⅴ) The content of component [C1] is 1.0 to 7.0 parts by mass per 100 parts by mass of component [A].

(About component [C1])

In another aspect of the present invention, component [C1] is a hydrophobic thixotropic agent included in the epoxy resin composition in the toupreg of the present invention.

In another aspect of the present invention, the thixotropic agent is a hydrophobic thixotropic agent having a hydrophobic surface treatment applied to the surface of the thixotropic agent. By applying a hydrophobic surface treatment to the surface of the thixotropic agent, deterioration of the epoxy resin due to the gradual attenuation of thixotropy can be suppressed, and the quality of the epoxy resin composition can be maintained for a long period of time. Here, the hydrophobic surface treatment is a treatment for bonding a hydrophobic functional group to a reactive functional group on the surface of the thixotropic agent. The hydrophobic functional group is a functional group that is electrically neutral and is unlikely to undergo hydration by hydrogen bonding. Examples of the hydrophobic functional group include alkylsilyl groups such as a dimethylsilyl group, a trimethylsilyl group, a butylsilyl group, and an octylsilyl group, and dimethylpolysiloxane. Fig. 3 shows an example of a chemical structure when a hydrophobic surface treatment is applied to the surface of the thixotropic agent.

Among these hydrophobic functional groups, from the viewpoint of further suppressing the gradual attenuation of thixotropy, it is preferable to bind a hydrophobic functional group containing four or more carbon atoms to a reactive functional group on the surface of the thixotropy-imparting agent. Specific examples of the hydrophobic functional group to be bound include alkylsilyl groups such as a butylsilyl group and an octylsilyl group, dimethylpolysiloxane, and the like.

In hydrophobic surface treatment, since a functional group containing a hydrocarbon skeleton is generally used, the carbon content of the thixotropic agent can be used as an indicator of the hydrophobicity of the thixotropic agent. If the carbon content of the thixotropic agent is 0.6% or more, the thixotropic agent has hydrophobicity, so it can suppress the change in thixotropy with time in the epoxy resin composition. Here, if the carbon content is 2.0% or more, the effect of suppressing the change in thixotropy with time is large, so it is more preferable, and if the carbon content is 3.0% or more, it is even more preferable. In addition, the carbon content of a commercially available thixotropic agent is 10% or less, and it is preferable to use one in this range.

Examples of such hydrophobic thixotropic agents include silica and light calcium carbonate. Among these hydrophobic thixotropic agents, those with a large thixotropic effect are desired in order to suppress the flow-off immediately after the towpreg bobbin is manufactured. From this viewpoint, silica is preferable. In addition, fine particle silica is more preferable from the viewpoint that the thixotropic decay over time is particularly small and the thixotropic properties of the epoxy resin composition can be maintained for a long period of time. Examples of commercial products of such particulate silica include “AEROSIL (registered trademark)” R972 (dimethylsilyl-treated fumed silica, number of carbon atoms in hydrophobic functional group: 2, manufactured by Nippon Aelosil Co., Ltd.), “AEROSIL (registered trademark)” R812 (trimethylsilyl-treated fumed silica, number of carbon atoms in hydrophobic functional group: 3, manufactured by Nippon Aelosil Co., Ltd.), “AEROSIL (registered trademark)” RY200S (dimethylpolysiloxane-treated fumed silica, number of carbon atoms in hydrophobic functional group: 400 to 700, manufactured by Nippon Aelosil Co., Ltd.), “AEROSIL (registered trademark)” R805 (octylsilyl-treated fumed silica, number of carbon atoms in hydrophobic functional group: 8, manufactured by Nippon Aelosil Co., Ltd.). Among these fine particle silicas, “AEROSIL (registered trademark)” RY200S (hydrophobic functional group having 400 to 700 carbon atoms) and “AEROSIL (registered trademark)” R805 (hydrophobic functional group having 8 carbon atoms) are more preferable from the viewpoint of having high hydrophobicity on the surface of the thixotropic agent and thus being able to further suppress the gradual attenuation of thixotropy.

(About condition (Ⅳ))

The epoxy resin composition to be impregnated into the towpreg of the present invention is an epoxy resin composition prepared by mixing component [B] 4 days after preparing the subject matter including components [A] and [C1], and the thixotropy index (TI ₄ = η' _0.1 / η' ₁₀ ) of the composition must be 1.5 or more, and preferably 3.0 or more. There is no particular limitation on the upper limit, but it is usually 300 or less. (Here, η' _0.1 is the complex shear viscosity measured at 25°C and a frequency of 0.1 Hz using a parallel plate oscillation rheometer, after mixing component [B] 4 days after preparing a subject matter containing components [A] and [C1], and η' ₁₀ is the complex shear viscosity measured at 25°C and a frequency of 10 Hz using a parallel plate oscillation rheometer, after mixing component [B] 4 days after mixing components [A] and [C1].).

Here, η' _0.1 and η' ₁₀ , which are the bases for calculating the thixotropy index (TI), are respectively used as the values measured 30 minutes after the epoxy resin composition was prepared by mixing component [B] 4 days after the subject matter including components [A] and [C1] was prepared. This thixotropy index (TI) is an indicator of the degree of thixotropy of the epoxy resin composition. TI is obtained by dividing "the viscosity of the epoxy resin composition at 25°C and a frequency of 0.1 Hz" by "the viscosity of the epoxy resin composition at 25°C and a frequency of 10 Hz." By the inclusion of the thixotropy-imparting agent, the viscosity of the epoxy resin composition at a frequency of 0.1 Hz greatly increases. However, when the thixotropy decreases over time, the viscosity at a frequency of 0.1 Hz also decreases over time. As a result, TI decreases over time. The fact that TI maintains a value above a certain level means that the viscosity decay over time at a frequency of 0.1 Hz is small, and if the viscosity at a frequency of 0.1 Hz satisfies condition (Ⅰ), if TI ₄ is 1.5 or higher, the flow-through can be suppressed even in a towpreg manufactured using an epoxy resin that has been stored for 4 days.

(About condition (V))

The content of the hydrophobic thixotropic agent of component [C1] must be 1.0 to 7.0 parts by mass with respect to 100 parts by mass of component [A], and is preferably 2.5 to 7.0 parts by mass. By setting the content of the hydrophobic thixotropic agent to 1.0 part by mass or more, it is possible to suppress flowing down from the core when the bobbin is erected. In addition, when the blending amount is 7.0 parts by mass or less, it is possible to prevent poor liquid feeding in the towpreg manufacturing process and poor formation of a resin film on the kiss roll.

(About condition (Ⅵ))

The epoxy resin composition to be impregnated into the toupreg of the present invention preferably has a viscosity of 40 Pa·s or less at 40°C as measured using an E-type viscometer immediately after preparing the epoxy resin composition containing components [A], [B] and component [C1], and more preferably 0.5 to 40 Pa·s.

In condition (Ⅵ), immediately after preparing the epoxy resin composition means 1 hour after preparing the subject of the epoxy resin composition including components [A] and [C1], and 30 minutes after completing the preparation of the epoxy resin composition by further mixing component [B].

The production of toe-preg can be carried out by heating the epoxy resin composition to about 40°C, but when the viscosity of the epoxy resin composition at 40°C is high, it becomes necessary to lower the viscosity by heating at a relatively high temperature for liquid feeding. The higher the temperature, the faster the epoxy resin composition thickens, and the usable time until liquid feeding becomes impossible is short, which reduces the productivity of toe-preg. When the viscosity at 40°C is 40 Pa·s or less, the epoxy resin composition does not need to be heated to a high temperature, making it difficult to thicken, which improves the productivity of toe-preg, which is preferable.

(About ingredient [D])

The epoxy resin composition used in the towpreg of the present invention preferably contains core-shell rubber and/or liquid rubber as a toughening agent as component [D]. Here, the toughening agent refers to an additive generally used to increase the toughness of a cured resin product. By including component [D], the deformation ability of the cured resin product can be increased, and a pressure vessel with less performance degradation due to repeated use can be obtained. As such component [D], it is preferable to select from, for example, core-shell rubber particles having a core-shell structure in which rubber particles such as acrylic rubber particles, butadiene rubber particles, butadiene-styrene rubber particles, and silicone rubber particles are coated with a heterogeneous polymer, liquid rubber such as liquid NBR (nitrile-butadiene rubber), CTBN (terminal carboxyl group-modified NBR), ATBN (terminal amino group-modified NBR), and NBR with carboxyl groups modified in the main chain. Commercial products of such components [D] include “Kaneace (registered trademark)” MX-125 (liquid bisphenol A type epoxy resin master batch containing 25% styrene-butadiene rubber-type core shell rubber particles, manufactured by Kaneka Co., Ltd.), “Kaneace (registered trademark)” MX-150 (liquid bisphenol A type epoxy resin master batch containing 40% polybutadiene rubber-type core shell rubber particles, manufactured by Kaneka Co., Ltd.), “Kaneace (registered trademark)” MX-267 (liquid bisphenol F type epoxy resin master batch containing 37% polybutadiene rubber-type core shell rubber particles, manufactured by Kaneka Co., Ltd.), “Hypro (registered trademark)” 1300X13NA (terminal carboxyl group-modified butadiene nitrile rubber, manufactured by CVC Thermoset Specialties), etc. These hardeners can be used alone or in appropriate mixtures.

Among these components [D], it is more preferable to include core-shell rubber particles because it is possible to improve the deformation ability of the cured resin while maintaining the high thixotropy of the uncured resin composition. Core-shell rubber particles are particles in which a shell component polymer different from the core component is graft-polymerized onto the surface of a particulate core component mainly composed of a crosslinked rubber-like polymer or elastomer, thereby covering part or the entire surface of the particulate core component with the shell component.

In addition, the blending amount of this component [D] is preferably 3 to 30 parts by mass with respect to 100 parts by mass of component [A]. By setting the blending amount of component [D] within this range, an epoxy resin composition for toupreg that provides a fiber-reinforced composite material having an excellent balance of viscosity and mechanical properties of the epoxy resin composition can be obtained.

(Other additives, etc.)

The epoxy resin composition used in the toupreg of the present invention can contain various additives such as a thermoplastic resin, a rubber component, an antifoaming agent, a stabilizer, a flame retardant, a pigment, etc., within a range that does not lose the effects of the present invention. As the thermoplastic resin, a thermoplastic resin that is soluble in the epoxy resin is preferable. Examples of the thermoplastic resin that is soluble in the epoxy resin include polyvinyl acetal resins such as polyvinyl formal and polyvinyl butyral, polyvinyl alcohol, phenoxy resin, polyamide, polyimide, polyvinyl pyrrolidone, and polysulfone.

(About the method for preparing an epoxy resin composition)

Various known methods can be used for preparing the epoxy resin composition used in the toupreag of the present invention. For example, the composition may be mixed using a machine such as a kneader, a planetary mixer, a mechanical stirrer, a dissolver, or a three-roll machine, or may be mixed by hand using a beaker, a spatula, or the like. However, since the thixotropic agent (including the hydrophobic thixotropic agent (C1) which is the component [C] of the present invention) has an appropriate mixing method for expressing thixotropic properties depending on the product to be used, it is preferable to apply an appropriate and optimal method.

(About the manufacturing method of toupregue)

The toupreg of the present invention is obtained by impregnating a reinforcing fiber bundle with an epoxy resin composition used in the toupreg of the present invention. Here, as the reinforcing fiber bundle, a reinforcing fiber bundle composed of 1,000 to 70,000 filaments having a diameter of 3 to 100 ㎛ is usually used.

As the reinforcing fiber bundle used in the towpreg of the present invention, a fiber bundle composed of glass fiber, carbon fiber, aramid fiber, boron fiber, alumina fiber, silicon carbide fiber, etc. may be exemplified. Two or more of these fiber bundles may be mixed and used. Among these, a carbon fiber bundle is preferably used because a lightweight and high-strength fiber-reinforced composite material can be obtained. Specific examples of such carbon fiber bundles include carbon fiber bundles such as acrylic, pitch, and rayon, and in particular, an acrylic carbon fiber bundle having high tensile strength is preferably used.

In the towpreg of the present invention, the mass content (Rc) of the epoxy resin composition can be set without particular limitation depending on the purpose, but is preferably 20 to 40%, more preferably 20 to 30%, and most preferably 22 to 28%. When the mass ratio of the epoxy resin composition to the reinforcing fiber bundle is 20% or more, the occurrence of defects such as unimpregnated portions or voids inside the obtained fiber-reinforced composite material can be suppressed. In addition, when it is 40% or less, since the volume content of the reinforcing fiber bundle can be increased, the mechanical properties of the fiber-reinforced composite material can be effectively expressed, and this can contribute to weight reduction.

The toupreg of the present invention can be manufactured by various known methods. That is, the epoxy resin composition used in the toupreg of the present invention can be manufactured by a method in which the viscosity is lowered by heating without using an organic solvent, and a reinforcing fiber bundle is impregnated while being immersed, a method in which the epoxy resin composition that has been heated to lower the viscosity is applied as a film on a rotating roll or a release paper, and then transferred to one side or both sides of the reinforcing fiber bundle, and then pressurized and impregnated by passing it through a bending roll or a pressure roll, etc. Since a high-quality toupreg can be manufactured, the method for manufacturing the toupreg of the present invention preferably includes a step of bringing a rotating roll coated with the epoxy resin composition into contact with at least one side of the reinforcing fiber bundle. The toupreg is usually supplied in the shape of a bobbin wound on a core of several hundred to several thousand meters.

The toe-preg of the present invention can be used in numerous fields such as aerospace, automobiles, railway vehicles, ships, civil engineering and construction, and sporting goods, and in particular, can be suitably used in the manufacture of hollow containers such as pressure vessels and cylinders.

(Example)

Hereinafter, the present invention will be described in detail by examples. However, the scope of the present invention is not limited to these examples. In addition, the unit "part" of the composition ratio means a mass part unless otherwise specified. In addition, the measurement of various characteristics (physical properties) was performed under an environment of a temperature of 23°C and a relative humidity of 50%, with the number of measurements n = 1, unless otherwise specified.

<Materials used in examples and comparative examples>

(1) Reinforcing fiber bundle

·“Toreca (registered trademark)” T720SC-36K (tensile strength 5880 MPa, number of filaments 36000, total fineness 1650 tex, density 1.8 g/cm2, made by Toray Industries, Ltd.).

(2) Component [A]: Epoxy resin

·“jER (registered trademark)” 807 (liquid bisphenol F type epoxy resin, manufactured by Mitsubishi Chemical Corporation)

·GAN (N,N-diglycidyl aniline, manufactured by Nihonga Yak Co., Ltd.)

·“Sumiepoxy (registered trademark)” ELM-434 (Tetraglycidyldiaminodiphenylmethane).

(3) Component [B]: Epoxy resin hardener used in [A]

·“jER Cure (registered trademark)” WA (diethyltoluenediamine, manufactured by Mitsubishi Chemical Corporation)

·“DYHARD (registered trademark)” Fluid 111 (cyanamide, manufactured by AlzChem)

·“KAYAHARD (registered trademark)” MCD (methyl nadic anhydride, manufactured by Nihon Kayaku Co., Ltd.)

·Accelerator DY 9577 (boronic acid trichloride complex, manufactured by Huntmann Japan Co., Ltd.).

(4) Component [C]: thixotropic agent

·“AEROSIL (registered trademark)” RY200S (dimethylpolysiloxane-treated fumed silica (fine particle silica), carbon content: 3.5 to 5.0%, number of carbon atoms in hydrophobic functional groups: 400 to 700, primary particle size: 16 nanometers, manufactured by Nippon Aerosil Co., Ltd.)

·“AEROSIL (registered trademark)” 300 (hydrophilic fumed silica (fine particle silica), primary particle size 7 nanometers, manufactured by Nippon Aerosil Co., Ltd.)

·“Disparon (registered trademark)” 6500 (fatty acid amide wax, manufactured by Kusumoto Kasei Co., Ltd.)

·“GARAMITE (registered trademark)” 7305 (mixture of mineral and organic modified bentonite, manufactured by Big Chemie Japan Co., Ltd.).

(5) Component [C1]: Hydrophobic thixotropic agent

·“AEROSIL (registered trademark)” RY200S (dimethylpolysiloxane-treated fumed silica (fine particle silica), carbon content: 3.5 to 5.0%, number of carbon atoms in hydrophobic functional groups: 400 to 700, primary particle size: 16 nanometers, manufactured by Nippon Aerosil Co., Ltd.)

·“AEROSIL (registered trademark)” R805 (octylsilyl-treated fumed silica (fine particle silica), carbon content: 4.5 to 6.5%, number of carbon atoms in hydrophobic functional groups: 8, primary particle size: 12 nanometers, manufactured by Nippon Aerosil Co., Ltd.)

·“AEROSIL (registered trademark)” R812 (trimethylsilyl-treated fumed silica (fine particle silica), carbon content: 2.0 to 3.0%, number of carbon atoms in hydrophobic functional groups: 3, primary particle size: 7 nanometers, manufactured by Nippon Aerosil Co., Ltd.)

(6) Component [D]

·“Kaneace (registered trademark)” MX-150 (liquid bisphenol A type epoxy resin master batch containing 40% polybutadiene rubber core shell rubber particles, manufactured by Kaneka Co., Ltd.)

·“Kaneace (registered trademark)” MX-267 (liquid bisphenol F type epoxy resin master batch containing 37% polybutadiene rubber core shell rubber particles, manufactured by Kaneka Co., Ltd.)

·“Hypro (registered trademark)” 1300X13NA (terminal carboxyl group modified butadiene nitrile rubber (liquid rubber), manufactured by CVC Thermoset Specialties)

(7) Other ingredients

·“jER Cure (registered trademark)” DICY7 (epoxy resin hardener, dicyandiamide, manufactured by Mitsubishi Chemical Corporation)

·DCMU99 (Epoxy resin curing accelerator, 3-phenyl-1,1-dimethyl urea, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea, manufactured by Hodogaya Chemical Industry Co., Ltd.)

·“U-CAT” SA 102 (Epoxy resin curing accelerator, octylate of DBU, manufactured by San-Apro Co., Ltd.)

·“Vinylec” K (additive, polyvinyl formal resin, manufactured by JNC Corporation).

·“Srec” (registered trademark) KS (additive, polyvinyl acetal resin, manufactured by Sekisui Chemical Co., Ltd.)

·“BYK” (registered trademark) 1790 (non-silicon-based foaming agent, manufactured by Big Chemie Japan Co., Ltd.)

·“DOWSIL” (registered trademark) SH200Fluid (silicon-based defoaming agent, manufactured by Dow Toray Co., Ltd.)

<Method for preparing epoxy resin composition>

In a beaker, component [A] and, if necessary, other components were added, heated and stirred, and then component [C] was added and stirred to prepare the main agent. Next, component [B] was added, and stirred at 25°C to 65°C until component [B] (curing agent) was dissolved in the main agent, thereby obtaining an epoxy resin composition. It was confirmed by observation using an optical microscope that component [B] was dissolved in component [A] and that there was no solid component. In addition, the stirring temperature after addition of component [B] was performed in a temperature range at which a rapid reaction did not start, taking into account the reactivity of the epoxy resin and the epoxy resin curing agent. The component content ratios of examples and comparative examples are shown in Tables 1 to 7.

<Method for measuring viscosity of epoxy resin composition>

According to JIS K 7244-10 (2005), the frequency dependence of the viscosity of an epoxy resin composition was measured under the conditions shown below. The complex viscosity value at 0.1 Hz of the epoxy resin composition prepared by mixing component [B] after 1 hour by preparing a main agent containing component [A] and component [C] or [C1] obtained by this measurement was expressed as η _0.1 , and the complex viscosity value at 10 Hz was expressed as η _10. In addition, the complex shear viscosity at 25 °C and a frequency of 0.1 Hz of the epoxy resin composition prepared by mixing component [B] after preparing a main agent containing components [A] and [C1] and leaving it at 23 °C and 50% RH for 4 days was expressed as η' _0.1 , and the complex shear viscosity at 25 °C and a frequency of 10 Hz was expressed as η' ₁₀ . In addition, the measurement was performed 30 minutes after mixing the component [B] into the subject to make an epoxy resin composition.

Device: ARES-G2 (TA Instruments)

Plate composition: Aluminum φ40mm dispo plate

Aluminum φ42mm disposable cup

Gap: 1.0mm

Temperature: 25℃

Measurement frequency: 0.1 to 10 Hz

Variation: 10%.

<Method for calculating thixotropy index (TI)>

TI was calculated according to the following definition using η _0.1 , η ₁₀ , η' _0.1 , and η' ₁₀ measured according to the above <Method for Measuring Viscosity at 25°C of Epoxy Resin Composition>.

TI ₀ = η _0.1 / η ₁₀

TI ₄ = η' _0.1 ／η' ₁₀

Here, the TI when the subject was prepared and mixed with the hardener 1 hour later was expressed as TI ₀ , and the TI when the subject was prepared and then left to stand at 23°C and 50% RH for 4 days and the hardener was mixed was expressed as TI ₄ .

<Method for measuring viscosity at 40°C of epoxy resin composition>

In accordance with JIS Z 8803 (2011), the viscosity of an epoxy resin composition at 40°C was measured within 1 day of preparing a subject matter containing component [A] and component [C1] by mixing component [B] under the conditions shown below. In addition, the viscosity of the epoxy resin composition was adopted as the value 5 minutes after the start of measurement.

Device: E-type viscometer TVE-22H (manufactured by Tokisangyo Co., Ltd.)

Cone Rotor: Rotor No. 3°×R9.7

Rotor rotation speed: 50rpm

Shear rate: 100sec ^-1

Sample volume: 0.3mL

Temperature: 40℃.

<Method for evaluating the stability of epoxy resin composition>

As a method for evaluating the stability of the epoxy resin composition in the towpreg of the present invention, the viscosity of an epoxy resin composition prepared by mixing a main agent and a curing agent and leaving it at 25°C and 50%RH for 24 hours was divided by the viscosity immediately after preparation (30 minutes after preparation by mixing the main agent and the curing agent), and the thickening ratio was obtained as an index. In addition, as the viscosity of the epoxy resin composition, the complex shear viscosity (η ₁₀ ) measured at 25°C and a frequency of 10 Hz using a parallel plate vibration rheometer was used, and in the table showing the results, it was expressed as “thickening ratio after 25°C × 24 hours.”

<How to make toupreg>

Using a towpreg manufacturing device equipped with a creel, a kiss roll, a nip roll, and a winder, an epoxy resin composition adjusted to a temperature of 20 to 60°C was applied to one side of carbon fiber “Toreca (registered trademark)” T720SC-36K, and then passed through a nip roll to impregnate the inside of the reinforcing fiber bundle with the epoxy resin composition, thereby obtaining a towpreg. The bobbin of the towpreg was wound on a core of 2,300 m so as to have a cylindrical shape with a winding width of 230 to 260 mm at an initial tension of 600 to 1,000 gf and a wind ratio of 6 to 10.

<Method of measuring Rc of toe freige>

The Rc of the towpreg was obtained from the mass of the towpreg bobbin (W _A ), the mass of the core (W _B ), the mass per unit length of the carbon fiber (W _C ), and the length of the towpreg wound on the bobbin (W _D ) according to Equation (1). The Rc of the examples and comparative examples are shown in Tables 1, 2, 5, and 6.

[Number 1]

<Method for evaluating the flow-off phenomenon of toe-preg>

After adjusting the temperature of the bobbin of the towpreg wound at 2300 m to 25℃, it was installed so that the longitudinal direction of the pipe was perpendicular to the surface of the work table, and left to rest for 10 minutes, and the movement of the bottom of the cylindrical bobbin was measured. When the movement amount was 0 mm or more and less than 3 mm, it was assigned as A, when it was 3 mm or more and less than 10 mm, it was assigned as B, and when it was 10 mm or more, it was assigned as C, and the rankings were made. In terms of evaluation ranking, A is the best and C is the worst.

<Method of making a pressure vessel>

A 7.5 L polyethylene liner was installed in a filament winding molding device, and the towpreg of the present invention was wound over the entire liner. As a first layer, a hoop layer forming ±89° with respect to the axial direction of the liner was wound so that its thickness was 1.4 mm. Next, as a second layer, a helical layer forming ±20° with respect to the axial direction of the liner was wound so that its thickness was 2.2 mm. Furthermore, as a third layer, a hoop layer forming ±89° with respect to the axial direction of the liner was wound so that its thickness was 0.6 mm, thereby obtaining an intermediate body. In addition, the thickness of each layer was obtained by measuring the outer diameter with a caliper. The intermediate body was cured at 110°C for 6 hours while rotating in a curing furnace, thereby obtaining a pressure vessel.

<Method for evaluating the winding phenomenon of toe-preg>

After filament winding molding of the pressure vessel, whether or not a winding fastening occurred on the used bobbin was visually judged. If a winding fastening phenomenon occurred, it was evaluated as B, and if it did not occur, it was evaluated as A.

<Method for evaluating the expansion of toe-preg>

If the toe-preg expansion is insufficient, it easily becomes a starting point of destruction because a void is created around the pressure vessel's capillary, resulting in a decrease in the burst strength. Therefore, when the manufactured pressure vessel was cut and the cross-section of the fiber-reinforced composite material layer around the capillary was observed, the size of the largest void found was used as an index of the expansion. A void with a small void and good quality was rated as A, a void with a large void and poor quality was rated as C, and a void larger than that rated as A but smaller than that rated as C and at a practically acceptable level was rated as B.

(Example 1)

An epoxy resin composition was prepared according to the <Method for Preparing Epoxy Resin Composition> above, using 100 parts by mass of “jER (registered trademark)” 807 as component [A], 25.5 parts by mass of “jER Cure (registered trademark)” WA as component [B], and 2.5 parts by mass of “AEROSIL” RY200S as component [C] (also applicable to component [C1]). The mixing of component [C] was performed with 3 rolls after preliminary mixing was performed using a kneader. The complex shear viscosity (η _0.1 ) of this epoxy resin composition measured at 25°C and a frequency of 0.1 Hz was 43 Pa·s, the complex shear viscosity (η ₁₀ ) measured at 25°C and a frequency of 10 Hz was 2.4 Pa·s, and the thixotropy index (hereinafter abbreviated as TI: TI ₀ = η _0.1 / η ₁₀ ) immediately after mixing was 18. In addition, the viscosity at 40°C was 3.3 Pa·s, and the thickening ratio after standing at 25°C and 50% RH for 24 hours was 2.0.

Next, using this epoxy resin composition, a toupreg was obtained according to the above <Method for producing a toupreg>. When the flow phenomenon of this toupreg was evaluated, the amount of movement of the lower part of the cylindrical bobbin of the toupreg was 9 mm, which was evaluated as B.

Next, TI was calculated for the epoxy resin composition prepared by mixing component [B] 4 days after mixing components [A] and [C1], and a toepreg was prepared according to the above <Method for producing toepreg>. As a result, the TI (TI ₄ ) 4 days after mixing was 17, and the amount of movement of the lower end of the cylindrical bobbin of the toepreg was 9 mm. The degree of flowing out of the toepreg did not change before and after storage of the epoxy resin. By using a hydrophobic thixotropic agent, it was possible to suppress deterioration of the epoxy resin and suppress flowing out of the toepreg bobbin.

In addition, as a result of evaluating the forming of pressure vessels, the winding fastening phenomenon, and the expansion property using the obtained toe preg, the winding fastening and the expansion property were both evaluated as A.

(Examples 2 to 3)

An epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the content of “AEROSIL (registered trademark)” RY200S, which is component [C] (also corresponding to component [C1]), was changed, as shown in Tables 1 and 3. As a result of the evaluation, good results were obtained in all items.

(Examples 4 to 9)

An epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the composition was changed to include a glycidylamine type epoxy resin as component [A], as shown in Table 1 and Table 4. As a result of the evaluation, good results were obtained in all items, as shown in Table 1 and Table 4. In particular, the evaluation result of the thickening ratio after standing at 25°C and 50% RH for 24 hours was good, and it could be seen that these compositions including a glycidylamine type epoxy resin have excellent stability of the epoxy resin composition.

(Examples 10 to 11)

As shown in Table 2, as component [C], “Disparon (registered trademark)” 6500 was used, and the mixing of the above components was performed using a kneader at 90°C for 30 minutes, and other changes in the composition were made, and an epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1. As a result of the evaluation, good results were obtained in all items, as shown in Table 2.

(Example 12)

As shown in Table 2, an epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that “GARAMITE (registered trademark)” 7305 was used as component [C] and the other compositions were changed. As a result of the evaluation, good results were obtained in all items, as shown in Table 2.

(Example 13)

As shown in Table 2 and Table 4, an epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that “DYHARD (registered trademark)” Fluid 111 was used as component [B] and the other compositions were changed. As a result of the evaluation, good results were obtained in all items, as shown in Table 2 and Table 4.

(Example 14)

An epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that “DYHARD (registered trademark)” Fluid 111 was used as component [B] and “AEROSIL (registered trademark)” 300 was used as component [C], as shown in Table 2. As a result of the evaluation, good results were obtained in all items.

(Example 15)

As shown in Table 2 and Table 4, an epoxy resin composition, a toepreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that “KAYAHARD (registered trademark)” MCD was used as component [B], “U-CAT (registered trademark)” SA 102 was used as a curing accelerator, and other compositions were changed. As a result of the evaluation, good results were obtained in all items, as shown in Table 2 and Table 4.

(Example 16)

As shown in Table 2 and Table 4, an epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that Accelerator DY 9577 was used as component [B] and the other compositions were changed. As a result of the evaluation, good results were obtained in all items, as shown in Table 2 and Table 4.

(Example 17)

As shown in Table 3, an epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that “AEROSIL (registered trademark)” RY200S was changed to “AEROSIL (registered trademark)” R805 as the component [C1]. As a result, η _0.1 was 110 Pa s, and in the towpreg bobbin produced immediately after mixing components [A] to [C1], no bobbin flow-down phenomenon occurred. Next, an epoxy resin composition prepared by mixing component [B] 4 days after mixing components [A] and [C1] was evaluated, and TI ₄ was 38 (TI ₀ = 41), and the temporal attenuation of the thixotropy of the epoxy resin composition was suppressed. A towpreg was produced and evaluated using this resin, and no flow-down phenomenon occurred and the expandability was also good.

(Example 18)

As shown in Table 3, an epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that “AEROSIL (registered trademark)” RY200S was changed to “AEROSIL (registered trademark)” R812 as the component [C1]. As a result, η _0.1 was 145 Pa·s, and in the towpreg bobbin produced immediately after mixing components [A] to [C1], no flowing-down phenomenon occurred in the towpreg bobbin.

Next, when the epoxy resin composition prepared by mixing component [B] 4 days after mixing components [A] and [C1] was evaluated, TI ₄ was 32 (TI ₀ = 45), and the thixotropy of the epoxy resin composition was attenuated over time. When a towpreg was produced using this resin and evaluated, the evaluation of the flowing-down phenomenon changed from A to B. It can be seen that “AEROSIL (registered trademark)” R812 has a smaller carbon number of hydrophobic functional groups bonded to the surface of the thixotropy-imparting agent than “AEROSIL (registered trademark)” RY200S and “AEROSIL (registered trademark)” R805, and thus the effect of suppressing the thixotropy of the epoxy resin composition is small.

(Example 19)

As shown in Table 5, an epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the composition was changed to include a glycidylamine type epoxy resin as component [A]. As a result of the evaluation, good results were obtained in all items, as shown in Table 5.

(Examples 20 to 23)

As shown in Table 5, an epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the composition was changed to include core-shell rubber particles as component [D]. As shown in Table 5, the evaluation results were good in all items, and it could be seen that these compositions including component [D] had excellent flexural fracture elongation of the cured resin product.

(Examples 24 to 26)

An epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the composition was changed to include a terminal carboxyl group-modified butadiene nitrile rubber, which is a liquid rubber, as component [D], as shown in Table 5. The evaluation results are good in all items, as shown in Table 5, and it can be seen that the bending fracture elongation of the cured resin product is excellent in these compositions including component [D]. However, when liquid rubber was used, the thixotropy index tended to be smaller than when core-shell rubber particles were used.

(Example 27)

As shown in Table 7, an epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that “AEROSIL (registered trademark)” RY200S, which is component [C], was changed to “AEROSIL (registered trademark)” 300 and that its content was changed. As a result of the evaluation, good results were obtained in η _0.1 , η ₁₀ , TI ₀ , η ₄₀ , thickening ratio, and expandability. However, when an epoxy resin composition prepared by mixing component [B] 4 days after mixing components [A] and [C] was evaluated, TI ₄ was 1.0 (TI ₀ = 2.0), and the thixotropy of the epoxy resin composition decreased over time, so that the evaluation of the flowing phenomenon changed from B to C. Since “AEROSIL (registered trademark)” 300 is a hydrophilic thixotropic agent, it is understood that the epoxy resin composition cannot suppress the gradual decrease in thixotropy, resulting in the occurrence of a flowing phenomenon. This example satisfies condition (X) but does not satisfy condition (Y), and is treated as an example that does not exhibit a sufficient effect in explaining the effect of condition (Y).

(Comparative Example 1)

An epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the composition was changed except that component [C] was not used, mixing by three rolls was not performed, and other changes were made, as shown in Table 6. As a result of the evaluation, as shown in Table 6, η _0.1 was low, and a flowing phenomenon and a winding phenomenon occurred.

(Comparative Example 2)

As shown in Table 6, an epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the content of “AEROSIL (registered trademark)” RY200S, which is the component [C], was changed. As a result of the evaluation, as shown in Table 6, η _0.1 was 25 Pa·s and η _0.1 / η ₁₀ was low at 1.2, resulting in a flowing phenomenon and a coiling phenomenon.

(Comparative Example 3)

As shown in Table 6, an epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the content of “AEROSIL (registered trademark)” RY200S, which is component [C], was changed and other compositions were changed. As a result of the evaluation, as shown in Table 6, while η _0.1 /η ₁₀ was 1.7, η _0.1 was low at 32 Pa·s, resulting in a flowing phenomenon and a coiling phenomenon.

(Comparative Example 4)

As shown in Table 6, an epoxy resin composition, a toe prreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the content of “AEROSIL (registered trademark)” RY200S, which is component [C], was changed and other compositions were changed. As a result of the evaluation, as shown in Table 6, since η _0.1 was as high as 500 Pa·s, the epoxy resin composition could not be sent from the toe prreg production device, and thus the toe prreg could not be produced.

(Comparative Example 5)

An epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the component [C] was not used, the additive “Vinylec (registered trademark)” K was used, mixing by three rolls was not performed, and other changes to the composition were made, as shown in Table 6. As a result of the evaluation, as shown in Table 6, although η _0.1 was high at 88 Pa s because component [C] was not included, a flowing phenomenon and a coiling phenomenon occurred.

(Comparative Example 6)

As shown in Table 6, an epoxy resin composition, a toepreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that “jER Cure (registered trademark)” DICY7 was used as an epoxy resin curing agent and DCMU99 was used as a curing accelerator. As a result of the evaluation, as shown in Table 6, although η _0.1 was 5.7 Pa s and η _0.1 / η ₁₀ was low at 1.0, no flowing-down phenomenon or winding phenomenon occurred. However, the expandability was evaluated as C, and it can be seen that when a solid epoxy resin curing agent, such as “jER Cure (registered trademark)” DICY7, which is not commonly used in component [A], was used, the expandability of the toepreg became insufficient.

(Comparative examples 7 to 8)

An epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the composition was changed except that the component [C1] was not used, mixing was not performed with three rolls, and other changes were made, as shown in Table 7. As a result of the evaluation, as shown in Table 7, η _0.1 was low, and a flowing phenomenon occurred.

(Comparative Example 9)

As shown in Table 7, an epoxy resin composition, a towpreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the content of “AEROSIL (registered trademark)” RY200S, which is a component [C1], and other compositions were changed. As a result of the evaluation, as shown in Table 7, η _0.1 was low at 24 Pa·s, and a flowing phenomenon occurred.

(Comparative Example 10)

As shown in Table 7, an epoxy resin composition, a toe prreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that the content of “AEROSIL (registered trademark)” RY200S, which is the component [C1], was changed. As a result of the evaluation, as shown in Table 7, η _0.1 increased to 776 Pa·s, resulting in poor liquid transfer of the epoxy resin composition in the toe prreg production device, and making it impossible to produce the toe prreg.

(Comparative Example 11)

As shown in Table 7, an epoxy resin composition was produced and evaluated in the same manner as in Example 1, except that the component [C1] was not used, mixing by three rolls was not performed, “Slex” (registered trademark) KS was used as an additive, and the other compositions were changed. As a result, the viscosity at 40°C was as high as 49 Pa·s, and liquid feeding at 40°C was not possible due to the manufacturing process of the toepreg. When heated to 60°C, liquid feeding was possible, but the viscosity of the epoxy resin composition was rapid, and the productivity of the toepreg decreased. In addition, when the flow phenomenon of the obtained toepreg was evaluated, a flow phenomenon occurred despite the fact that η _0.1 was as high as 236 Pa·s because it did not contain component [C1].

(Comparative Example 12)

As shown in Table 7, an epoxy resin composition, a toepreg, and a pressure vessel were produced and evaluated in the same manner as in Example 1, except that “jER Cure (registered trademark)” DICY7 was used as an epoxy resin curing agent, DCMU99 was used as a curing accelerator, and other compositions were changed. As a result, although η _0.1 was 24 Pa s and η _0.1 / η ₁₀ was low at 1.0, no flow phenomenon occurred. However, the expandability was evaluated as C, and it can be seen that the expandability of the toepreg became insufficient when a solid epoxy resin curing agent, such as “jER Cure (registered trademark)” DICY7, which is not commonly used in component [A], was used.

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[Table 7]

1: Toe Frere
2: Branch

Claims (10)

A towpreg comprising an epoxy resin composition comprising the following components [A] and [B], and further satisfying condition (Ⅰ) and further satisfying either condition (X) or (Y) by impregnating a bundle of reinforcing fibers.
[A] Epoxy resin
[B] Epoxy resin hardener used in [A]
(Ⅰ) Immediately after preparing the epoxy resin composition comprising (i) components [A], [B] and the following component [C], or (ii) components [A], [B] and the following component [C1], the complex shear viscosity (η _0.1 ) measured at 25°C and a frequency of 0.1 Hz using a parallel plate vibration rheometer is 40 to 300 Pa s.
(X) (ⅰ) Contains components [A], [B] and the following component [C], and also satisfies conditions (Ⅱ) and (Ⅲ).
[C] Transition agent
(Ⅱ) Immediately after preparing the epoxy resin composition containing components [A], [B], and [C], the complex shear viscosity (η ₁₀ ) measured at 25°C and a frequency of 10 Hz using a parallel plate vibration rheometer is 50 Pa·s or less.
(Ⅲ) The ratio (η 0.1 / η 10 ) of the complex shear viscosity (η _0.1 ) measured at 25°C and a frequency of 0.1 Hz using a parallel plate oscillation rheometer to the complex shear viscosity (η ₁₀ ) measured at 25°C and a frequency of _{10 Hz} using a parallel plate oscillation rheometer is 1.5 or more.
(Y) (ⅱ) Contains components [A], [B] and the following component [C1], and also satisfies conditions (Ⅳ) and (Ⅴ).
[C1] Hydrophobic thixotropic agent
(Ⅳ) The thixotropy index (TI ₄ = η' _0.1 / η' ₁₀ ) of an epoxy resin composition prepared by mixing component [B] 4 days after preparing a main agent containing components [A] and [C1] is 1.5 or more. (Here, η' _0.1 is the complex shear viscosity measured at 25°C and a frequency of 0.1 Hz using a parallel plate oscillation rheometer, after mixing component [B] 4 days after preparing a main agent containing components [A] and [C1], and η' ₁₀ is the complex shear viscosity measured at 25°C and a frequency of 10 Hz using a parallel plate oscillation rheometer, after mixing component [B] 4 days after preparing a main agent containing components [A] and [C1].)
(Ⅴ) The content of component [C1] is 1.0 to 7.0 parts by mass per 100 parts by mass of component [A]. In the first paragraph,
A towpreg, wherein the epoxy resin composition satisfies condition (X) and comprises, as component [C], at least one selected from the group consisting of bentonite, particulate silica, and amide wax. In the second paragraph,
A toupreme comprising hydrophobic particulate silica as component [C]. In any one of claims 1 to 3,
A toupreme, wherein the epoxy resin composition satisfies condition (X) and the content of component [C] is 1.0 to 20 parts by mass with respect to 100 parts by mass of the epoxy resin [A]. In the first paragraph,
A toupreme, wherein the epoxy resin composition satisfies condition (Y) and further, the epoxy resin composition satisfies condition (Ⅵ).
(Ⅵ) Immediately after preparing an epoxy resin composition containing components [A], [B], and [C1], the viscosity at 40°C measured using an E-type viscometer is 40 Pa·s or less. In paragraph 1 or paragraph 5,
A toupreme, wherein the above epoxy resin composition satisfies condition (Y), and the component [C1] is a hydrophobic thixotropic agent in which a hydrophobic functional group containing 4 or more carbon atoms is bonded to a reactive functional group on the surface of the thixotropic agent. In paragraph 1 or paragraph 5,
A toupreme wherein the above epoxy resin composition satisfies condition (Y) and the component [C1] is particulate silica. In any one of claims 1 to 3,
A toupreme comprising, as component [B], an aromatic amine in a liquid state at 25°C. In any one of claims 1 to 3,
A toupreme comprising a glycidylamine type epoxy resin as component [A]. In any one of claims 1 to 3,
A towpreg comprising at least one of core shell rubber and liquid rubber as component [D].