JPH09255800A - Prepreg and fiber-reinforced resin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a prepreg which has no significant variation in resin content and possesses high flexural strength by impregnating a specified carbon fiber with a specified epoxy resin. SOLUTION: A carbon fiber having a tensile modulus of elasticity of not less than 200GPa and a tensile strength of not less than 3,900MPa is impregnated with an epoxy resin compsn. comprising an epoxy resin, a curing agent (e.g. dicyanamide), and a silica particle and having a thixotropy index of not less than 1.2 as defined by the formula TI=η0.1 /η10 [wherein η0.1 represents the viscosity (70 deg.C) at a frequency of 0.1Hz; and η10 represents the viscosity (70 deg.C) at a frequency of 10Hz]. Pref. epoxy resins usable herein include, e.g. one comprising, based on 100 pts.wt. epoxy resin, 10 to 25 pts.wt. liq. bisphenol A type epoxy resin, 40 to 60 pts.wt. solid bisphenol A type epoxy resin, and 30 to 40 pts.wt. phenol novolak type epoxy resin. The silica particle has a primary particle diameter of not more than 1μm and is added in an amt. of 1 to 10 pts.wt. based on 100 pts.wt. epoxy resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass cloth prepreg and a fiber reinforced resin molding, and more particularly to a prepreg and a fiber reinforced resin molding used for golf shafts, fishing rods, bicycle frames, tennis rackets and the like. is there.

[0002]

2. Description of the Related Art Fiber-reinforced resin moldings are used for fishing rods, golf shafts, bicycle frames, tennis rackets, etc. due to their excellent mechanical properties. In recent years, in order to pursue the ultimate performance of higher performance and lighter weight, the wall thickness is becoming thinner and thinner. Therefore, the resin flowing out of the system during molding, so-called resin flow, is optimized to contain the resin in the molded body. There is a strong demand for precise control of the rate.

Conventionally, in order to control the resin flow during molding, as disclosed in, for example, JP-A-1-318527 and JP-A-63-152644, a thermoplastic resin such as polyvinyl formal or nitrile is used. A method of compounding rubber or the like with an epoxy resin to increase the resin viscosity is used. However, in this case, the bending strength of the molded product is insufficient due to insufficient heat resistance of the compounded resin, and the impregnability of the prepreg is insufficient due to the low fluidity of the resin when impregnating the high-viscosity resin into the reinforcing fiber. There was a drawback that

Further, the surface of the molded product may be polished in order to improve the coating property of the resulting molded product and to remove the roughness of the surface layer of the molded product. Such surface polishing is carried out. At this time, when the above-mentioned thermoplastic resin, rubber, or the like is added, the disadvantage that heat generated during polishing causes shavings to melt and clogging the polishing agent is likely to occur.

[0005]

DISCLOSURE OF THE INVENTION The object of the present invention is to prevent the resin from flowing easily so that the variation in the resin content is small.
Another object of the present invention is to provide a prepreg excellent in impregnation property into reinforcing fibers, and further capable of enhancing bending strength in the obtained molded product, and a fiber-reinforced resin molded product.

[0006]

In order to solve the above problems, the present invention has the following constitution. That is, an epoxy resin composition composed of an epoxy resin, a curing agent and silica particles, and having a thixotropic index (TI) represented by the following formula of 1.2 or more has a tensile modulus of 200 GPa or more and a tensile strength of 3900 MPa or more. It is a prepreg characterized by being impregnated in carbon fiber.

TI = η _0.1 / η ₁₀ where η _0.1 is the viscosity of the epoxy resin composition at a frequency of 0.1 hertz measured at 70 ° C., and η ₁₀ is 70 ° C.
It is the viscosity of the epoxy resin composition measured at a frequency of 10 Hertz.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The prepreg and the fiber-reinforced resin molding of the present invention will be described in detail below.

In the prepreg of the present invention, an epoxy resin,
A highly viscous epoxy resin composition having a thixotropic index (TI) represented by the following formula of 1.2 or more, preferably 1.5 or more, which is obtained by mixing a curing agent and silica particles is used.

TI = η _0.1 / η ₁₀ where η _0.1 is the viscosity of the epoxy resin composition at a frequency of 0.1 hertz measured at 70 ° C. and η ₁₀ is 70 ° C.
It is the viscosity of the epoxy resin composition measured at a frequency of 10 Hertz.

In order to reduce the resin flow during molding of the prepreg, it is effective to increase the viscosity of the epoxy resin composition. Known methods for increasing the viscosity of an epoxy resin composition include a method of using a high molecular weight epoxy resin and a method of adding a thermoplastic resin or an elastomer. On the other hand, prepregs are often manufactured by the hot-melt method.In the hot-melt method, a resin-supported sheet that is evenly coated with resin on release paper is sandwiched from one side or the top and bottom of the sheet-like reinforcing fiber and heated.・
Apply pressure. At this time, a large shearing force acts on the resin. Here, since the epoxy resin composition obtained by the method of adding a thermoplastic resin or an elastomer has a relatively small shear rate dependence, the shear stress rate with respect to the epoxy resin composition is large, and the resin-supporting sheet is produced or reinforced. Even when the resin is impregnated into the fibers, the resin has a high viscosity, which makes it difficult to manufacture a resin-carrying sheet having a particularly small coating thickness, and it becomes difficult to impregnate the reinforcing fibers with the resin. When a molded product such as a fishing rod or a golf shaft is produced using a prepreg made of an epoxy resin composition having a viscosity increased by adding a thermoplastic resin such as polyvinyl formal or an elastomer such as rubber, the molded product is obtained. In the step of performing the surface polishing, the problem that the shavings are fused due to the heat generated during polishing and the abrasive is clogged is also likely to occur.

Therefore, in the present invention, an epoxy resin composition having a large shear rate dependency, that is, a large thixotropic index (TI) is employed. The greater the TI, the greater the shear rate dependence of the resin. T of epoxy resin composition
When I is smaller than 1.2, the shear rate dependency of the resin becomes small, impregnating property of the prepreg becomes poor, and the resin flow at the time of molding becomes large, resulting in uneven resin content of the molded product. .

The epoxy resin composition according to the present invention has T
In order to set I in the above range, silica particles are contained as an essential component.

The viscosity of the epoxy resin composition containing silica particles has a large shear rate dependency, and the resin viscosity is large in a region where the shear rate is small, but the resin viscosity sharply decreases as the shear rate increases. Become. Therefore,
During the production of a resin-carrying sheet having a high shear stress rate for an epoxy resin composition or during the impregnation of a resin into a reinforcing fiber, the resin viscosity decreases, and the resin coating and the impregnation of the resin into the reinforcing fiber become easy. On the other hand, in the process of molding the fiber-reinforced resin molded product from the prepreg, since the shearing force acting on the resin is small in a general situation, the epoxy resin composition used in the present invention has a high resin viscosity in such a case The resin flow at that time can be reduced. Further, in the epoxy resin composition in which the silica fine particles are added to increase the viscosity, the problem that the molded article is clogged during polishing because of the high heat resistance of the silica particles can be solved.

The amount of silica particles added to the epoxy resin composition used in the present invention is preferably 1 to 15 parts by weight per 100 parts by weight of the epoxy resin. If the amount added is less than 1 part by weight, the effect of increasing the viscosity tends to be insufficient, and if the amount added exceeds 15 parts by weight, the mechanical properties of the fiber-reinforced resin molded product obtained may deteriorate.

The primary particle size of the silica particles used in the present invention is preferably 1 μm or less, and if the particle size is larger than 1 μm, the effect of increasing the viscosity may be insufficient. The primary particle diameter of silica particles is usually 0.005 μm.
That is all.

Specific examples of the silica particles usable in the present invention include "Aerosil" 20 manufactured by Nippon Aerosil Co., Ltd.
0, 380, R972, RX200, RY200, R2
02, R805, COK84 and the like.

By using the above epoxy resin composition in the prepreg, it is possible to increase the viscosity of the resin and reduce the amount of resin flow during molding, and thus reduce the variation in the resin content of the molded product. It is possible. Usually, as the viscosity of the resin increases, the impregnating property and tackiness of the prepreg tend to decrease. However, it is preferable to use at least the following three kinds of epoxy resins as the epoxy resin in order to make the TI more appropriate and the impregnating property and the tackiness of the prepreg more appropriate.

One is a liquid bisphenol A type liquid epoxy resin, and the epoxy equivalent of this epoxy resin is usually 150 or more and 230 or less, and the preferable amount thereof is 10 to 25 with respect to 100 parts by weight of the epoxy resin. Parts by weight. If the amount of the epoxy resin used is less than 10 parts by weight, the tackiness of the prepreg tends to be insufficient.
If the amount is more than the amount by weight, the resin viscosity tends to decrease and the resin flow during molding tends to increase. As the liquid bisphenol A type epoxy resin, specifically, Epicoat 828, Epicoat 827 (produced by Yuka Shell Epoxy Co., Ltd.), YD11
5, YD128 (Toto Kasei Co., Ltd.), EPC840, EP
C855 (manufactured by Dainippon Ink and Chemicals Inc.), GY250, GY
260 (manufactured by Ciba Geigy), DER317, DER3
24 (manufactured by Dow Chemical Co.) and the like.

The second is a solid bisphenol A type epoxy resin, and the epoxy equivalent of this epoxy resin is usually 400 to 3,000, and the preferable amount thereof is 40 to 60 per 100 parts by weight of the epoxy resin. Parts by weight. If the amount of the epoxy resin used is less than 40 parts by weight, the resin viscosity tends to be low and the resin flow during molding tends to be large, and if it is more than 60 parts, the adhesiveness of the prepreg and the heat resistance of the molded product will be insufficient. There is. As the solid bisphenol A type epoxy resin, specifically, Epicoat 1001, Epicoat 1004, Epicoat 100
7, Epicoat 1009 (produced by Yuka Shell Epoxy Co., Ltd.),
YD014, YD017 (Toto Kasei Co., Ltd.), EPC10
55, EPC2055, EPC7050 (manufactured by Dainippon Ink and Chemicals), DER661, DER667 (manufactured by Dow Chemical).

The third is a phenol novolac type epoxy resin, and the preferable amount thereof is the epoxy resin 10
It is 30 to 50 parts by weight with respect to 0 parts by weight. If the amount of the epoxy resin used is less than 30 parts by weight, the heat resistance of the molded body tends to be insufficient, and if it is more than 50 parts by weight, the adhesiveness of the prepreg may be insufficient. Specific examples of these phenol novolac type epoxy resins include Epicoat 152, Epicoat 154 (produced by Yuka Shell Epoxy Co., Ltd.), DEN431, DEN439 (produced by Dow Chemical Co., Ltd.), EPCN738, EPCN865 (produced by Dainippon Ink and Chemicals Inc.), EPN1139, EPN1299 (made by Ciba-Geigy) etc. are mentioned.

The epoxy resin is used in combination with a curing agent. The curing agent that is combined with the epoxy resin is
Any compound having an active group capable of reacting with an epoxy group can be used. A compound having an amino group, an acid anhydride group, a phenolic hydroxyl group, and an azido group, and a curing agent to which these compounds are encapsulated in a microcapsule to impart a latent property are suitable. Specific examples include guanidine compounds, urea compounds, imidazole compounds, various isomers of diaminodiphenyl sulfone, aminobenzoic acid esters, various acid anhydrides, phenol novolac resins, cresol novolac resins and various organic acid hydrazide compounds. In particular, various isomers of diaminodiphenyl sulfone are suitable for giving a cured product having good heat resistance. Further, an imidazole compound or a reaction product of an imidazole compound and an epoxy resin can be preferably used as a low temperature type curing agent.

A curing agent composed of a combination of a guanidine compound and a urea compound is most preferably used in the present invention for the purpose of realizing good storage stability of the prepreg and excellent heat resistance of the molded product. The guanidine compound generally includes the following compounds. Examples thereof include dicyandiamide, 2,6-xylenyl-piguanide, o-tolylpiguanide, diphenylguanidine, di-o-tolylguanidine, 1-o-tolylhyguanide, acetoguanamine, melamine and benzoguanamine.

As the urea compound, a compound represented by the following formula is preferably used.

[0025]

Embedded image (In the formula, X and Y are hydrogen atom, chlorine atom, bromine atom,
Methyl group, methoxy group, ethoxy group, nitro group or -N
HCONR ₁ (R ₂ ), R ₁ and R ₂ are alkyl groups,
It represents an allyl group, an alkoxy group, an alkenyl group or an aralkyl group, and R ₁ and R ₂ may be taken together to form a heterocycle. ) Specific examples of such urea compounds include the following compounds. That is, N- (3-chloro-4-methoxyphenyl) -N, N'-dimethylurea, N- (4-
Chlorophenyl) -N, N'-dimethylurea, N- (3
-Chloro-4-ethylphenyl) -N, N'-dimethylurea, N- (4-chlorophenyl) -N, N'-dipropylurea, N- (3-chloro-4-methylphenyl)-
N, N'-dimethylurea, N- (3,4-dichlorophenyl) -N, N'-dimethylurea, N- (4-methyl-
3-nitrophenyl) -N, N'-dimethylurea, N-
(4-ethoxyphenyl) -N, N'-dimethylurea,
N- (4-chlorophenyl-carbamoyl) piperidine, N- (4-chlorophenyl-carbamoyl) morpholine and the like.

The preferred amount of the curing agent comprising a combination of guanidine compound and urea compound is epoxy resin 10
It is preferable that the guanidine compound and the urea compound are both 2 to 8 parts by weight with respect to 0 part by weight. When an aromatic diamine is used as a curing agent, an epoxy resin cured product having good heat resistance can be obtained.

The epoxy resin composition containing each of the above components can be prepared by kneading under heating using a kneader or the like.

Carbon fibers are used as reinforcing fibers in the prepreg of the present invention. The carbon fiber used in the present invention has a tensile modulus of elasticity of 200 GPa or more, preferably 280 GPa or more, and a tensile strength of 3900 MPa or more, preferably 4400 MPa, as measured by a strand tension test.
It has the above physical properties. When the tensile elastic modulus and the tensile strength are less than 200 GPa and less than 3900 MPa, respectively, the resulting fiber-reinforced resin molded article has a low bending strength, and it is necessary to make a thick composite material in order to exhibit desired properties. Is small. The upper limits of the tensile elastic modulus and the tensile strength of the carbon fiber are not particularly limited, but 800 and 800 are relatively easily available.
To 900 GPa or less and 8000 to 10000 MPa or less.

In the present invention, the reinforcing fiber used may be only carbon fiber, but it may be used in combination with other reinforcing fiber, and it is preferable to optimize it appropriately according to the use of the fiber-reinforced resin molded product.

After the above-mentioned carbon fiber is impregnated with a resin in the form of unidirectional, woven, yarn or mat to obtain a carbon fiber reinforced resin prepreg, the prepreg is subjected to a shaping process such as laminating and winding. A carbon fiber reinforced resin composite material is obtained by heat molding by a method such as pressing, autoclaving or lapping.

[0031]

The present invention will be described in more detail with reference to the following examples. In the present invention, the thixotropy index (TI) of the epoxy resin composition, and the strand tensile elastic modulus and strength of the carbon fiber were determined by the following methods.

(1) Thixotropic Index (TI) of Epoxy Resin Composition Using a viscoelastic device RDA-II manufactured by Rheometric Co., the epoxy resin composition is sandwiched between parallel plates having a radius of 20 mm and a frequency of 0.1 at 70 ° C. From the frequency-viscosity curve obtained by changing the frequency up to 100 Hz, the viscosity at frequency 0.1 Hz (η _0.1 ) and the viscosity at frequency 10 Hz (η ₁₀ ) were read and calculated according to the following formula.

TI = η _0.1 / η ₁₀ (2) Tensile Modulus and Strength of Carbon Fiber It was measured according to the resin impregnated strand test method of JIS R-7601. As resin prescription, "BAKELIT
E ″ ERL4221 / 3 boron fluoride monoethylamine / acetone = 100/3/4 parts were used by being mixed well.

Example 1 Liquid bisphenol A type epoxy resin having an epoxy equivalent of 188 (Epicoat 82)
8, manufactured by Yuka Shell Epoxy Co., Ltd.) 20 kg (20 parts),
Epoxy equivalent 470 solid bisphenol A type epoxy resin (Epicoat 1001, manufactured by Yuka Shell Epoxy Co., Ltd.) 50 kg (50 parts), phenol novolac epoxy resin (Epicoat 154, manufactured by Yuka Shell Epoxy Co., Ltd.) 30 kg (30 parts), Silica fine particles having a primary particle diameter of 0.012 μm (“Aerosil” 200, manufactured by Nippon Aerosil Co., Ltd.) 5 kg (5 parts), dicyandiamide (DICY-)
7, manufactured by Nippon Carbide Co., Ltd.) 5 kg (5 parts), 3- (3,
4-dichlorophenyl) -1,1-N-dimethylurea (DCMU-99, Hodogaya Chemical Co., Ltd.) 4 kg (4 parts)
Was stirred in a kneader to obtain a resin composition. The TI of the obtained resin composition was 1.5. A release paper was coated with this to obtain a resin-supported sheet.

First, a steel drum having a circumference of about 2.7 m is wound with the above-mentioned resin-carrying sheet in which a resin to be combined with carbon fibers is coated on a release paper, and then a tensile strength of 4900 MPa drawn from a creel on the resin-carrying sheet. , A tensile elastic modulus of 230 GPa and a number of single fibers of 12,000 filaments ("Torayca" T700SC, manufactured by Toray Industries, Inc.) are wound and arranged through a traverse, and the fibers are further arranged from above. After the resin-carrying sheet is covered again, the resin is impregnated into the fibers by rotationally pressing with a pressure roll to prepare a unidirectional prepreg having a width of 300 mm and a length of 2.7 m. At this time, the drum is heated to 60 to 70 ° C. to improve the resin impregnation between the fibers, and the fiber areal weight of the prepreg is adjusted to about 200 g / m 2 by adjusting the rotational speed of the drum and the traverse feeding speed. ² , resin amount 4
A prepreg of 0% by weight was produced.

The above two prepregs were superposed so that their fiber axes were orthogonal to each other, and pasted through a press roll heated to about 90 ° C., and the release paper on both sides was peeled off to obtain a two-layer prepreg sheet. Next, the above-mentioned two-layer prepreg sheet was wound three times around a mandrel having an outer diameter of 20 mm, the outer peripheral surface of which was coated with a silicone release agent, so that the fiber axis and the longitudinal axis of the mandrel were aligned. Furthermore, the polyester tape was spirally wound on the two-layer prepreg wound on the mandrel while applying a force of about 2.4 Kg and overlapping by 2 mm each, and then about 2 mm in a heating furnace at about 130 ° C. The epoxy resin was cured by heating for a time. After cooling, remove the mandrel, peel off the tape on the surface, and obtain the fiber-reinforced resin molded product with a length of 825 mm.
It cut | disconnected and it used for the 4-point bending test. The resin flow at this time was 1.6%.

The 4-point bending fracture test has a span distance of 750 m.
m, the distance between the indenters was 200 mm, and the indenter points were reinforced to prevent collapse and measured. The average bending strength of n = 10 was 912 MPa.

(Example 2) Carbon fiber was subjected to a tensile strength of 440.
0 MPa, tensile elastic modulus 377 GPa, single fiber number 12,
000 filament carbon fiber ("Torayca" M40
A molded product was produced in the same manner as in Example 1 except that the product was changed to JB, manufactured by Toray Industries, Inc.). The four-point bending strength of the obtained molded body was 834 MPa.

(Example 3) Silica particles having a primary particle size of 0.
A molded body was produced in the same manner as in Example 1 except that the silica fine particles of 014 (“Aerosil” R202, manufactured by Nippon Aerosil Co., Ltd.) were used. The TI of the resin and the flow at the time of molding were 2.3 and 0.9, respectively, and the four-point bending strength of the obtained molded body was 951 MPa.

(Example 4) After winding the prepreg obtained in Example 1 around a mandrel, one layer of glass fabric WEA-05E-105-F236N manufactured by Nitto Boseki Co. was wrapped around the outermost layer. Next, this laminate was set in a mold heated to 150 ° C. and molded at a pressure of 50 Kg / cm ² for 10 minutes. The resin flow during molding was 5.2%, and the four-point bending strength of the obtained molded body was 598 MPa.

(Example 5) The prepreg obtained in Example 1 was laminated on a smooth metal plate and sealed in vacuum with a nylon bag film, which was then autoclaved at 6 kg / cm.
^It was pressurized to ² and heat molded at 130 ° C. The resin flow during molding was 0.2%, and the three-point bending strength of the obtained molded body was 1.
It was 5 GPa.

(Comparative Example 1) Carbon fiber was used to obtain a tensile strength of 353.
0 MPa, tensile elastic modulus 230 GPa, single fiber number 12,
000 filament carbon fiber ("Torayca" T30
0B, manufactured by Toray Industries, Inc.), but a molded product was produced in the same manner as in Example 1. The obtained molded product had a four-point bending strength of 588 MPa, which was inferior to the examples.

(Comparative Example 2) A molded body was produced in the same manner as in Example 1 except that the addition amount of silica fine particles was changed to 2 parts. The TI of resin, the flow of molding is 1.1,
4.9, and the four-point bending strength of the obtained molded product is 608.
It was MPa, which was inferior to that of the example.

Comparative Example 3 A molded body was produced in the same manner as in Example 4 except that the prepreg obtained in Comparative Example 2 was used as the prepreg. The resin flow during molding was 9.6%, and the four-point bending strength of the obtained molded body was 500 MPa, which was inferior to that of Example 4.

Comparative Example 4 A molded body was produced in the same manner as in Example 5 except that the prepreg obtained in Comparative Example 2 was used as the prepreg. The resin flow during molding was 2.6%, and the three-point bending strength of the obtained molded body was 1180 GPa, which was inferior to that of Example 5.

[0046]

Industrial Applicability According to the present invention, a fiber reinforced resin having a small variation in resin content and a high bending strength, which is suitable for sports applications such as skis, snowboards, fishing rods, golf shafts, tennis rackets, and bicycle frames and aerospace applications. It is possible to provide a molded body and a prepreg suitable for molding the molded body.

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Claims (7)

[Claims] 1. A thixotropy index (TI) consisting of an epoxy resin, a curing agent and silica particles, and represented by the following formula:
A prepreg obtained by impregnating a carbon fiber having a tensile modulus of 200 GPa or more and a tensile strength of 3900 MPa or more with an epoxy resin composition having a ratio of 1.2 or more. TI = η _0.1 / η ₁₀ where η _0.1 is the viscosity of the epoxy resin composition at a frequency of 0.1 Hz measured at 70 ° C., and η ₁₀ is 70 ° C.
It is the viscosity of the epoxy resin composition measured at a frequency of 10 Hertz. 2. The prepreg according to claim 1, wherein the epoxy resin is a liquid bisphenol A type epoxy resin, a solid bisphenol A type epoxy resin, and a phenol novolac type epoxy resin. 3. 10 to 25 parts by weight of liquid bisphenol A type epoxy resin per 100 parts by weight of epoxy resin,
Solid bisphenol A type epoxy resin 40 to 60 parts by weight, and phenol novolac type epoxy resin 3
The prepreg according to claim 1 or 2, wherein the prepreg is contained in an amount of 0 to 40 parts by weight. 4. The prepreg according to any one of claims 1 to 3, wherein the silica particles are contained in an amount of 1 to 10 parts by weight based on 100 parts by weight of the epoxy resin. 5. The curing agent is dicyandiamide and 3-
(3,4-dichlorophenyl) -1,1-dimethylurea, The prepreg according to any one of claims 1 to 4, which is characterized in that. 6. The prepreg according to claim 1, wherein the silica particles have a primary particle size of 1 micron or less. 7. A fiber-reinforced resin molded product obtained from the prepreg according to any one of claims 1 to 6.