JPH07118414A - Prepreg excellent in tack retentivity - Google Patents

Abstract

PURPOSE:To obtain a prepreg excellent in workability, heat resistance, extensibility and resin flow resistance by impregnating reinforcing fibers with, as matrix resin, a resin composition essentially comprising three kinds of resin, rubber powder and a curing agent. CONSTITUTION:The objective prepreg can be obtained by impregnating (I) as matrix resin, a resin composition essentially comprising (A) pref. 1-70 pts.wt. of a novolak-type epoxy resin, (B) pref. 1-70 pts.wt. of a bisphenol-type epoxy resin, (C) pref. 3-40 pts.wt., based on a total of 100 pts.wt. of the components A and B, of a phenoxy resin, (D) pref. 2-25 pts.wt., based on a total of 100 pts.wt. of the components A, B and C, of rubber powder and (E) pref. 1-10 pts.wt., based on a total of 100 pts.wt. of the components A and B, of a curing agent (pref. dicyandiamide) in (F) carbon fibers (pref. pitch-based carbon fibers) <=40tonf/mm<2> in tensile modulus.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention has a tensile elastic modulus of 40 tonf / m.
The present invention relates to a prepreg using a carbon fiber of m ² or more, more specifically to a prepreg having good workability, a good balance between heat resistance and elongation, and excellent resin flow resistance during molding and curing.

[0002]

2. Description of the Related Art Since carbon fiber is excellent in specific strength and specific elastic modulus, it is used as a composite material with a resin in the form of a so-called prepreg, for example, fishing rods, golf clubs and other sports / leisure products, leaf springs, rolls and the like. It has been widely used in the field of molding materials as an industrial material such as a honeycomb structure material, an automobile material, an aircraft material, a medical material material, and the like, and has recently been used for these applications. At present, carbon fibers are required to have higher specific strength and specific elastic modulus. Epoxy resins having excellent mechanical properties have been used for these prepregs, but as described above, as the carbon fibers with higher specific strength and specific elastic modulus are used, the epoxy resin used In particular, new characteristics are required.

However, the conventional epoxy resin composition still has some unsatisfactory points, and its use method and application are limited. Particularly, in the case of a prepreg using a carbon fiber having a tensile elastic modulus of 40 tonf / mm ² or more as a reinforcing fiber, the carbon fiber floats due to the elastic recovery of the carbon fiber (a part of the carbon fiber peels off from the release paper surface in the prepreg. ), And peeling of the bonding surface between the prepregs during the prepreg laminating work. That is, the prepreg is usually wound around a cylindrical paper tube at the time of manufacturing, but is unwound from this paper tube at the time of molding, cut into an appropriate size in a plane, and stored until the next step. In this storage, the tensile modulus is 4
In the case of a prepreg that uses carbon fiber of 0 tonf / mm ² or more as a reinforcing fiber, the prepreg cut into a flat surface has a restoring (elastic recovery) force that tries to return to the curved shape at the time of production, and the carbon A phenomenon called so-called floating occurs in which the fibers rise from above the prepreg.

Since the carbon fiber in the prepreg is a material having extremely strong anisotropy, it is generally laminated by changing the orientation angle of the carbon fiber according to the purpose. At the time of this lamination, the prepreg using the carbon fiber having a tensile elastic modulus of 40 tonf / mm ² or more had a problem that the prepregs, which were once bonded together, were peeled off with the passage of time.
There is a problem that work such as heating and pressurization is required again in order to return the prepreg to the original state in which the prepreg has once floated or peeled between the prepregs. A molded product using the resulting prepreg as it is causes defects in the molded product due to disordered orientation of carbon fibers and voids. This floating occurs when the tack (adhesion) force between the prepreg and the release paper decreases with time, that is, when the tack retention is low, and when the prepreg peels off and the prepreg tack retention is low. Occurs.

The tack retaining property is related to the shape and type of carbon fiber used in the prepreg and the characteristics of the resin. When the tensile modulus of the carbon fiber was less than 40 tonf / mm ² , the elastic recovery of the carbon fiber was low and it was not a problem.
At tonf / mm ^{2 and} above, problems such as floating and peeling between prepregs become significant. Although making the diameter of the carbon fibers thin is effective in improving the tack retention in terms of reducing elastic recovery, it is not preferable because of problems such as technical difficulty and reduction in production yield. Therefore, it is necessary to study with resin.In the conventional technology, workability such as initial tackiness and drapeability (suppleness) of the prepreg has been studied, but tackiness has been studied. Didn't.

[0006]

As described above, in the prepreg in which the carbon fiber having the tensile elastic modulus of 40 tonf / mm ² or more is used as the reinforcing fiber, the carbon fiber having the tensile elastic modulus of less than 40 tonf / mm ² is used as the reinforcing fiber. It is necessary to suppress the floating due to elastic recovery of the carbon fiber and the peeling due to the change with time of the pasted parts of the prepregs, that is, to use a resin composition having excellent tackiness retention property as compared with the above prepreg. However, if the elastic modulus of the epoxy resin used is increased just to prevent the floating, the floating of the carbon fiber can be prevented, but the initial tackiness of the prepreg is reduced, and the drapeability is reduced, resulting in poor workability. The problem of worsening will occur.

Here, as a patent document of a resin composition for prepreg with improved tackiness and drapeability, Japanese Patent Laid-Open No. 3-3
5106, JP-A-3-62821, and JP-A3-1190.
24, JP-A-63-152644, JP-A-54-991.
61, JP-A-63-308026, JP-A 1-2158
50, JP-A-62-1717, JP-A-3-220225.
Etc. However, these are only studies of workability due to initial tackiness and drapeability. In addition, there is also Japanese Unexamined Patent Publication No. 2-20546, which also relates to workability due to initial tackiness and drapeability, or shape retention of a prepreg pre-laid up during heat curing.

[0008]

The object of the present invention is to prevent floating even when carbon fiber having a tensile elastic modulus of 40 tonf / mm ² or more is used as a reinforcing fiber, and a gluing portion between prepregs is used. Another object of the present invention is to provide a prepreg that has good workability in that it does not peel off due to changes over time, has a good balance of heat resistance and elongation, and is excellent in resin flow resistance during molding and curing.

That is, in a prepreg using a carbon fiber having a tensile elastic modulus of 40 tonf / mm ² or more as a reinforcing fiber, the elasticity of the carbon fiber is higher than that of a prepreg using a carbon fiber having a tensile elastic modulus of less than 40 tonf / mm ² as a reinforcing fiber. Floating due to recovery,
It is necessary to use a resin composition that suppresses peeling of the pasted portions of the prepregs due to a change with time, that is, has excellent tack retention.

Therefore, the present invention has a tensile modulus of 40 to
Even when carbon fiber of nf / mm ² or more is used as a reinforcing fiber, the heat resistance and elongation, which have been conventionally required, are well balanced, and the resin flow resistance during molding and curing does not deteriorate, and it floats. An object of the present invention is to provide a prepreg obtained by impregnating a carbon fiber having a tensile elastic modulus of 40 tonf / mm ² or more with a resin composition that suppresses peeling due to aged deterioration of a bonded portion between prepregs and prepregs and provides good workability. It is

[0011]

Means for Solving the Problems The present inventors have previously combined a specific resin to obtain a resin composition for prepreg which has a good balance between heat resistance and elongation and is excellent in resin flow resistance during molding and curing. It was found that a product can be obtained (JP-A-1-201321).

Further, the inventors of the present invention conducted extensive studies to achieve the above-mentioned object, and as a result, the tensile elastic modulus was 40 tonf.
Even when using carbon fiber of / mm ² or more as a reinforcing fiber, the heat resistance and elongation are well balanced, and the float and prepreg-bonded parts are aged without impairing the resin flow resistance during molding and curing. The present invention is completed by suppressing peeling due to change and providing good workability. That is, the present invention provides the following A, B, C,
A prepreg characterized in that a resin composition comprising D and E components as essential components is used as a matrix resin and is impregnated with reinforcing fibers of F component: A novolac type epoxy resin B bisphenol A type epoxy resin C phenoxy Resin D Powder rubber E Curing agent F Carbon fiber with tensile modulus of 40 tonf / mm ² or more. Here, the respective proportions of the components A to D are: A novolac type epoxy resin 1 to 70 parts by weight B bisphenol A type epoxy resin 1 to 70 parts by weight C phenoxy resin 3 to 40 parts by weight D powder rubber 2 to 25 parts by weight ( It is preferable that the mixing ratio of the C component is 100 parts by weight of the total amount of the A and B components, and the mixing ratio of the D component is 100 parts by weight of the total amount of the A, B and C components).

The present invention will be examined in detail below. First, as the novolac type epoxy resin (component A) in the present invention, specifically, Espoxy SCN-701P, Espoxy SCN-702P, Espoxy SCN-703P, Espoxy SCN-704P (manufactured by Nippon Steel Chemical Co., Ltd.), Araldite ECN-. 1273, Araldite ECN-1280
(Manufactured by Japan Ciba Geigy) or ES manufactured by Sumitomo Chemical
CN-220 series, and their equivalents such as cresol novolac type epoxy resin and Espoxy SPN
-638 (manufactured by Nippon Steel Chemical Co., Ltd.), Epicoat 152, Epicoat 154 (manufactured by Yuka Shell Epoxy), EPPN-20
1 (manufactured by Nippon Kayaku Co., Ltd.), or a phenol novolac type epoxy resin which is an equivalent product thereof can be appropriately selected and used alone or in combination of two or more.

Since these epoxy resins (component A) have a small epoxy equivalent and a high crosslink density, the resulting cured molded article can be used as a molded article excellent in elastic modulus and heat resistance, but is used excessively. In either case, the elongation of the molded product is reduced, which causes embrittlement. Therefore, in consideration of such characteristics, 10 to 7 out of the total amount of the components A, B and C are considered.
0 parts by weight, preferably 20 to 50 parts by weight is added. If the amount of the component A resin is less than 10 parts by weight, it is impossible to impart a sufficient elastic modulus or heat resistance to the cured product.
On the other hand, if the amount is more than 70 parts by weight, the elongation of each cured product decreases and the material becomes brittle.

The bisphenol A type epoxy resin (component B) is specifically Espoxy SA-11.
5, Espoxy SA-115CA, Espoxy SA-1
27, Espoxy SA-128, Espoxy SA-13
4, Espoxy SA-011, Espoxy SA-01
4, Espoxy SA-01, Espoxy SA-01
9, Espoxy SA-7020 (manufactured by Nippon Steel Chemical Co., Ltd.), Epicoat 828, Epicoat 834, Epicoat 100
1, Epicoat 1004 (made by Yuka Shell Epoxy), Araldite GY-250, Araldite GY-260,
Araldite 6071 (manufactured by Nippon Ciba Geigy) or the like, and further, one of these equivalent products can be appropriately selected and one or more can be mixed and used.

The bisphenol A type epoxy resin as the B component is available in various grades from solid to liquid due to the difference in molecular weight. When blended with the matrix resin for prepreg, the viscosity is adjusted by appropriately mixing them. Further, the elongation of the molded product after curing is higher than that of the novolac type epoxy resin which is the A component. However, the heat resistance is poor. So the B component is A, B, and C
10 to 70 parts by weight, preferably 20 to 50 parts by weight of the total amount of the components are added. If the weight of component B is less than 10 parts by weight, sufficient elongation cannot be obtained, and if it exceeds 70 parts by weight, sufficient heat resistance cannot be imparted.

Next, the phenoxy resin (component C) used in the present invention is a linear polymer, has good compatibility with the epoxy resin, and has a high molecular weight so that the temperature dependence of viscosity is low. When added to the components, it has the property that the minimum viscosity of the resin at the time of molding and curing can be increased, so that it gives good properties as a matrix for prepreg. The phenoxy resin used here has an average molecular weight of about 10,000 to 100,000, and specific commercially available products include Espoxy SP.
-50 (Nippon Steel Chemical), Epicoat OL-53-B-
40, Epicoat OL-55-B40 (made by Yuka Shell Epoxy), DER684EK40 (made by Dow Chemical),
Phenothote YP50EX40 (Toto Kasei), PKH
H, PKHJ, PKHM-30 (made by UCC), etc.
In addition, select one of these equivalents as appropriate and use one or two.
A mixture of two or more species can be used.

Further, the amount of the component C added is required to be 3 to 40 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the total amount of the components A and B. If the compounding amount is less than 3 parts by weight, the minimum viscosity at the time of curing will be low and the resin flow resistance will be poor, and if it exceeds 40 parts by weight, the viscosity will be too high to be used as a matrix resin for prepreg.

Next, the powder rubber (component D) used in the present invention is not particularly limited as long as it is a powder. The powdered rubber may have an average particle diameter of 1 mm or less. When the liquid rubber is used instead of the powdered rubber, it is impossible to achieve both suppression of floating of the prepreg and maintenance of good workability. That is, if the elastic modulus of the epoxy resin composition is increased in order to suppress the floating, the drape property of the prepreg and the initial tack property are deteriorated and workability is impaired. Further, if the elastic modulus of the epoxy resin is lowered with an emphasis on workability, the floating of the prepreg cannot be suppressed. Specifically, various powder rubbers such as diene rubber and nitrile rubber can be used. For example, it is a copolymer of butadiene and acrylonitrile and has an average molecular weight of 500.
It may be 0 or more, and further, this butadiene / acrylonitrile copolymer may be a carboxylic acid-modified one or a terpolymer. As a specific example, Nipol HF01,
Nipol HF21, Nipol 1411 (manufactured by Zeon Corporation)
Etc., considering the solubility with epoxy resin,
The bound acrylonitrile content is preferably 30% or more.

Further, the addition amount of the D component is required to be 2 to 25 parts by weight, preferably 5 to 20 parts by weight based on 100 parts by weight of the total amount of the A, B and C components. If the blending amount is less than 2 parts by weight, the prepreg cannot be sufficiently prevented from floating, and if it exceeds 25 parts by weight, the viscosity becomes high and it cannot be used as a matrix resin for prepreg.

In the present invention, the components A and B are mainly for adjusting the viscosity of the resin mixture and for balancing the heat resistance and elongation of the molded product, and the component C is mainly for molding and curing. To improve the resin flow resistance, the D component mainly suppresses the elastic recovery of the carbon fibers in the prepreg, and prevents the occurrence of floating and the peeling of the part where the prepregs are bonded together. To retain the property.

As the curing agent used as the E component,
Dicyandiamide is preferable, and a curing accelerator is particularly preferably used together. By using such a curing agent, 1
Curing is possible at a temperature of 40 ° C. or lower, and the shell life can be maintained at 20 ° C. for 2 months or longer. Further, as the curing accelerator, an imidazole derivative,
For example, Curesol 2P4MHZ manufactured by Shikoku Chemicals,
Alternatively, imidazole carboxylate or metal complex salt,
Alternatively, a urea compound, such as 3- (3,4-dichlorophenyl) -1-1-N dimethylurea, exhibits excellent effects.

In this case, the compounding amount of the E component curing agent is preferably 1 to 10 parts by weight per 100 parts by weight of the total amount of the A and B components, and if less than 1 part by weight, the curing becomes insufficient, If the amount is larger than the number of parts, the strength of the cured molded article will decrease. Moreover, the compounding amount of the curing accelerator is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the total amount of the components A and B, and 1
If it is less than 1 part by weight, a high curing temperature is required, and 1
If it is more than 0 parts by weight, the shelf life becomes short.

In the present invention, by using the components A to E, even if the tensile modulus of the carbon fiber (F component) is 40 tonf / mm ² or more, the floating can be suppressed and the beam between the prepregs can be prevented. It is possible to provide a prepreg that has good workability in that it does not peel off due to aging of the mating part, has a good balance of heat resistance and elongation, and is excellent in resin flow resistance during molding and curing. The carbon fiber may be polyacrylonitrile-based (PAN-based), pitch-based or the like as long as the tensile elastic modulus is 40 tonf / mm ² or more. Further, it may be a combination of a polyacrylonitrile system (PAN system) and a pitch system as disclosed in Japanese Patent Application No. 04-031888. However,
In pitch-based carbon fiber, the ability to improve such tack retention can increase its availability,
It is very useful in industry.

The prepreg of the present invention has the above-mentioned A,
B, C, D, E and F components are essential,
If necessary, anhydrous silica, a pigment and the like can be added.

[0027]

The present invention will be described in more detail with reference to the following examples. The test method in this case is as follows.

[Floating Test] A prepreg having a width of 1 m was produced, a paper tube having a diameter of about 30 cm was wound, left at room temperature for 1 day, cut into 1 m squares, and left standing on a flat desk for 2 hours. Then
After 2 hours, the floating of the prepreg is visually observed.

[Measurement of Resin Flow] Carbon fiber direction is 0
2mm thick by alternately laminating in the direction of ° and 45 °,
A wrapping tape was wrapped around a prepreg so that it was wound in a pipe shape with an inner diameter of 10 mm and a tension of 4 kgf was applied, and cured at 140 ° C. for 120 minutes, and the resin flow amount was calculated by the formula (1).

[Evaluation of Tackiness and Drapability] When the prepreg was wound in a pipe shape to measure the resin flow, it was judged visually and visually.

[Measurement of glass transition temperature (Tg)] About 30 mg of the molded product after measuring the resin flow was cut out, and a differential scanning calorimeter (DSC) manufactured by Perkin Elmer Japan was cut out.
It measured using 7).

[Peeling Test (Tack Retention)] A prepreg was wound around a pipe having an outer diameter of 10 mm so that the carbon fiber directions were + 45 ° and −45 °, and the peeling distance of the bonding surface between the prepregs was elapsed with time. It was measured with.

Example 1 Epicoat 154 made of oiled shell epoxy as the novolac type epoxy resin of the component A, Araldite 6071 and Araldite GY250 manufactured by Ciba-Geigy as the component bisphenol A type epoxy resin of the component B, and Shin-Nihon as the phenoxy resin of the component C As a powder rubber of SP-50 and D component manufactured by Nippon Kagaku Co., Ltd., Nipol HF01 (acrylonitrile copolymerized butadiene rubber, molecular weight 2 to 100) manufactured by Nippon Zeon Co., Ltd.
10,000), dicyandiamide (hereinafter D
ICY) and 3- (3,4-dichlorophenyl) -1-1
-N dimethyl urea (Hodogaya Chemical Co., Ltd .: trade name DCMU9
9 or less DCMU), Eskinos NT-40 (Nippon Steel pitch-based carbon fiber, tensile strength 370 kgf / mm ² ; tensile modulus 40 tonf / m as carbon fiber of F component)
m ² ), a prepreg having a carbon fiber basis weight of 150 g / m ² and a resin content of 37 wt% was produced and evaluated.

Example 2 A prepreg was prepared and evaluated in the same manner as in Example 1 except that cresol novolac type epoxy (Araldite ECN1273 manufactured by Nippon Ciba Geigy) was used as the component A.

Example 3 A prepreg was manufactured and evaluated in the same manner as in Example 1 except that Nipol 1411 manufactured by Nippon Zeon was used as the D component.

Example 4 Eskyinos NT-80 (made by Nippon Steel) as the F component
A prepreg was manufactured and evaluated in the same manner as in Example 1 except that pitch-based carbon fiber having a tensile strength of 310 kgf / mm ² and a tensile elastic modulus of 80 tonf / mm ² ) was used.

Example 5 PKHM-30 (UCC) was used as a C component phenoxy resin.
Nipol 1411 as a D component powder rubber
A prepreg was manufactured and evaluated in the same manner as in Example 1 except that (manufactured by Zeon Corporation) was used.

Comparative Example 1 A prepreg was produced and evaluated in the same manner as in Example 1 except that the D component was omitted.

Comparative Example 2 A prepreg was manufactured and evaluated in the same manner as in Example 4 except that the C component was omitted.

Comparative Example 3 As the F component, Escainos NT-30 (manufactured by Nippon Steel Corporation)
A prepreg was manufactured and evaluated in the same manner as in Comparative Example 1 except that pitch-based carbon fiber having a tensile strength of 360 kgf / mm ² and a tensile elastic modulus of 30 tonf / mm ² ) was used.

Comparative Example 4 A prepreg was produced and evaluated in the same manner as in Example 1 except that the addition amount of SP-50 as the C component and the addition amount of Nipol HF01 as the D component were decreased as compared with those in Example 1, respectively. went.

Comparative Example 5 An attempt was made to produce a prepreg in the same manner as in Example 1 except that the addition amount of SP-50 as the C component and the addition amount of Nipol HF01 as the D component were increased as compared with those of the Example 1. However, it could not be manufactured due to its high viscosity.

Comparative Example 6 Except that the addition amount of SP-50 as the C component was 10 wt% and the addition amount of Nipol HF01 as the D component was 1 wt%.
A prepreg was manufactured and evaluated in the same manner as in Example 1.

Comparative Example 7 A prepreg was manufactured and evaluated in the same manner as in Example 1 except that the addition amount of SP-50 as the C component was 2 wt% and the addition amount of Nipol HF01 as the D component was 5 wt%. .

The components used were as follows: [A component] Novolak type epoxy resin 1) Phenol novolak type Epicoat 154 Epoxy equivalent of Yuka Shell Epoxy
180g / eq 2) Cresol novolac type Araldite ECN1273 manufactured by Nippon Ciba Geigy Epoxy equivalent 220g / eq Softening point 73 ° C

[Component B] Bisphenol A type epoxy resin 1) Liquid SA-128 manufactured by Nippon Steel Chemical Epoxy equivalent 184-
194g / eq Viscosity 120-150 Poise Araldite GY250 Nippon Ciba Geigy epoxy equivalent 190g / eq 2) Solid SA-014 Nippon Steel Chemical epoxy equivalent 900
~ 1000g / eq softening point 91-102 ° C Araldite 6071 Nippon Ciba Geigy Epoxy equivalent 450-500g / eq softening point about 64 ° C

[Component C] Phenoxy resin 1) SP-50 made by Nippon Steel Chemical Epoxy equivalent of about tens of thousands to 100,000 g / eq Softening point about 200 ° C. 2) PKHM-30 UCC made of epoxy equivalent of about tens of thousands to 100,000 g / eq glass transition temperature about 35 ℃

[Component D] Powder rubber 1) Acrylonitrile copolymer butadiene rubber Nipol HF01 manufactured by Nippon Zeon, molecular weight 2
1 million average particle diameter about 0.5 mm Nipol 1411 manufactured by Nippon Zeon, molecular weight 2
1 million average particle size about 0.1 mm

[E component] Curing agent 1) Amine dicyandiamide 3- (3,4-dichlorophenyl) -1,1-N-dimethyl urea (curing accelerator) [F component] Carbon fiber 1) Escanoy NT-40 New Nittetsu made pitch system Tensile strength 370kgf / mm ² or more Tensile elastic modulus 40tonf / mm ² or more 2) Escanoy NT-80 Nippon Steel Pitch system Tensile strength 310kgf / mm ² or more Tensile elastic modulus 80tonf / mm ² or more 3) Escanoys NT-30 Nippon Steel pitch system Tensile strength 360kgf / mm ² or more Tensile modulus 30tonf / mm ² or more These results are shown in Table 1 below.

[0050]

[Table 1]

The following are clear from Table 1. That is, when the D component is absent or the amount thereof is small (Comparative Example 1, Comparative Example 3, and Comparative Example 6), floating occurs, peeling increases with the passage of time, and tack holding property decreases. C
If there is no component or the amount thereof is small (Comparative Example 2 and Comparative Example 7), the resin flow resistance is very poor, floating occurs, and the tack holding property is somewhat deteriorated. When the amounts of the C component and the D component were small (Comparative Example 4), the resin flow resistance was very poor, and the amount of floating was also large, the peeling became large with the passage of time and the tack holding property greatly decreased, and after 15 minutes. Became unmeasurable. In addition, when the amounts of the C component and the D component were too large (Comparative Example 5), the viscosity was high and the production was impossible.

On the other hand, in Examples 1 to 6, the resin flow resistance was excellent, the floating was hardly generated, the peeling was small even after 15 minutes, and the tack holding property was very good. is there.

[0053]

As is apparent from the above examples, according to the present invention, even when the carbon fiber having the tensile elastic modulus of 40 tonf / mm ² or more is used as the reinforcing fiber, the work conventionally required. It is possible to manufacture a prepreg that suppresses the occurrence of floating without impairing the resin flow resistance characteristics during molding and curing, and the balance of heat resistance, heat resistance and elongation, and contributing to the development of the industry. , There is an extremely large one.

Claims (3)

[Claims] 1. A resin composition having the following components A, B, C, D, and E as essential components is used as a matrix resin and is impregnated into reinforcing fibers of component F, which is excellent in tack retention. Prepreg: A novolac type epoxy resin B bisphenol A type epoxy resin C phenoxy resin D powder rubber E curing agent F carbon fiber having a tensile elastic modulus of 40 tonf / mm ² or more. 2. The prepreg excellent in tack retention according to claim 1, wherein the mixing ratio of the components A, B, C and D of the resin composition is as follows. A novolac type epoxy resin 1 to 70 parts by weight B bisphenol A type epoxy resin 1 to 70 parts by weight C phenoxy resin 3 to 40 parts by weight D powder rubber 2 to 25 parts by weight (compounding ratio of C component is the sum of A and B components) The amount based on 100 parts by weight and the mixing ratio of the D component are based on 100 parts by weight of the total amount of the A, B and C components). 3. The prepreg excellent in tack retention according to claim 1, wherein the F component is pitch-based carbon fiber.