JP2003171483A - Prepreg and fiber-reinforced composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent prepreg not occurring a peeling in a work of winding the prepreg on a mandrel in the production of a light weight composite material, especially a tubular material, also having less void in a formed material after curing and less fluctuation in its physical properties of the cured material, and a fiber-reinforced composite material. <P>SOLUTION: This prepreg obtained by impregnating a resin into a reinforcing fiber having 67-87 wt.% reinforcing fiber and on setting T mm as a total thickness of the prepreg is characterized by a fact that ΔVr, a resin content volume ratio at a part of 0.1T mm surface thickness at least on the surface side satisfied the following formula (1): 1.2≤ΔVr/Vr≤1.5 (wherein, ΔVr: the resin content volume ratio in the part of 0.1T mm thickness at the surface layer to the T mm total thickness of the prepreg; Vr: The resin content volume ratio in the total prepreg). Also, the fiber-reinforced composite material is obtained by heating for curing the prepreg. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excellent prepreg and a fiber-reinforced composite material which are excellent in winding workability, have few voids in a cured product, and have little variation in physical properties.

[0002]

2. Description of the Related Art A fiber-reinforced composite material composed of reinforcing fibers and a matrix resin is lightweight and has excellent mechanical properties.
Widely used for sports, aerospace, and general industrial applications. In particular, prepregs in which reinforcing fibers are aligned in one direction and impregnated with resin are used for golf shafts,
It is widely used for sports and leisure as an intermediate material for molded products such as fishing rods, badminton shafts and tennis racket frames. For application to tubular molded bodies such as fishing rods and golf shafts (hereinafter referred to as tubular bodies), the required amount of prepreg is wound around a metal core called mandrel with a predetermined length, diameter and taper. After that, a method of hardening and then pulling out the mandrel is widely used. The tubular body formed in this way is subjected to post-processing such as painting to be finished into a final product.

After winding the prepreg around the mandrel,
In the production of a tubular body to be cured, if the adhesiveness of the prepreg is insufficient or the flexibility of the prepreg is low, the prepreg may be peeled off during the work and the work efficiency will be reduced.

In recent years, fiber reinforced prepregs having a low resin content have been developed in order to further reduce the weight of molded products such as golf shafts and fishing rods. Generally, when the resin content is low, the adhesiveness of the prepreg is deteriorated, and the workability during the winding operation is deteriorated. If the winding workability is poor, the winding cannot be performed in a uniform state, and the physical properties of the cured product will vary.

[0005]

SUMMARY OF THE INVENTION In view of the background of the prior art, the present invention does not cause peeling during the operation of winding a prepreg around a mandrel in the production of a lightweight composite material, particularly a tubular body, and The object of the present invention is to provide an excellent prepreg and a fiber-reinforced composite material which have few voids in the molded product after curing and have little variation in physical properties of the cured product.

[0006]

The present invention employs the following means in order to solve the above problems. That is, the prepreg of the present invention is a prepreg obtained by impregnating reinforcing fibers with a resin, wherein the weight ratio of the reinforcing fibers is 67 to 87% by weight, and the total thickness of the prepreg is T [mm], The resin volume content ΔVr of at least the surface layer thickness 0.1T [mm] portion on the surface side of the prepreg satisfies the following formula (1).

1.2 ≦ ΔVr / Vr ≦ 1.5 (1) In the formula, ΔVr: resin volume content in the surface layer thickness 0.1T [mm] portion with respect to the total thickness T [mm] of the prepreg. Indicates.

Vr: Shows the resin volume content of the entire prepreg.

The fiber-reinforced composite material of the present invention is characterized in that the prepreg is heat-cured.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides the above-mentioned object, that is, in the production of a lightweight tubular body, peeling does not occur during the work of winding a prepreg around a mandrel, and the molded body after curing has few voids and is cured. An excellent prepreg with little variation in physical properties was eagerly studied, and the resin impregnation amount for the reinforcing fibers constituting the prepreg was set to a specific low content range in a specific part, and such a problem was solved at once. It is a thing that has been clarified.

The prepreg of the present invention is a unidirectional prepreg obtained by aligning reinforced fibers in one direction and impregnating the reinforced fibers with a resin, and being sandwiched between a cover film and a release paper. . In the present invention, unless otherwise specified, this one-way prepreg is referred to as prepreg,
The cover film side of the prepreg is defined as the front side, and the release paper side is defined as the back side. The prepreg is manufactured by impregnating a reinforcing fiber aligned in one direction with a resin. Methods of resin impregnation include a hot melt method and a wet method, but in order to obtain the prepreg of the present invention, heating and pressurization can be independently applied by the hot melt method, and the timing can be shifted back and forth. preferable. That is, it is preferable to impregnate by first heating and then pressing with a non-heating roll. By not simultaneously applying pressure and applying temperature, but shifting the timing of applying pressure backward, it is possible to distribute the resin on the prepreg surface in a large amount without the resin impregnating the fiber too much. Become.

In the prepreg of the present invention, the ratio of the reinforcing fibers to the total weight of the reinforcing fibers and the resin needs to be 67 to 87% by weight, more preferably 80 to 87% by weight. If the ratio of the reinforcing fibers to the total weight of the reinforcing fibers and the resin is less than 67% by weight, the resin may flow out during molding of the cured product, disturbing the arrangement of the reinforcing fibers and leading to a decrease in strength. Further, when it exceeds 87% by weight,
The resin may not sufficiently spread between the reinforcing fibers to form voids, resulting in a decrease in strength of the cured product.

In the present invention, the total thickness of the prepreg is T
[Mm], the surface layer thickness of the prepreg is 0.1 T [m
It is necessary that the resin volume content ΔVr of the [m] portion satisfies the expression (1) with respect to the resin volume content Vr of the entire prepreg.

In a further preferred embodiment of the present invention, the following formula (1) is satisfied at 0.1T from both surfaces on both sides of the prepreg so that the adhesiveness of the prepreg on the back side and the front side is satisfied. Since the difference becomes small, the handling becomes easier, which is preferable.

1.2 ≦ ΔVr / Vr ≦ 1.5 (1) Here, the resin volume content is determined by the following method. Since the prepreg is unsuitable for measurement work, the prepreg is once cured and then measured.

The procedure is as follows. First, the prepreg is cut into a size of 5 cm square, the release paper is removed, and the fiber direction is aligned with the cover film attached to stack 5 to 10 layers, and 4 KP.
Press for 1 minute with a. Next, it is cured at 40 ° C. for 2 weeks and then at 130 ° C. for 2 hours. A cross section of the cured product in the direction of 90 ° with respect to the longitudinal direction of the fiber is ground, and the center of the polished surface is photographed at 100 times the thickness of the cured product. The area ratio of the fiber to the resin is calculated for the portion corresponding to the prepreg total thickness T and the portion corresponding to the surface layer 0.1T in the photographed image, and the fiber volume content is calculated.

If ΔVr / Vr is less than 1.2 in the equation (1), the amount of resin existing on the surface of the prepreg is small and peeling occurs at the time of winding the prepreg around the mandrel during the tubular body forming process, so that it frequently occurs. Correction work is required, which causes a problem in workability. Also, ΔV
When r / Vr is higher than 1.5, the voids inside the prepreg do not disappear even after the prepreg is cured to form a molded body, and voids remain. Therefore, it is necessary that the ratio of the resin volume content ΔVr of the surface layer 0.1T thickness portion to the resin volume content Vr of the entire prepreg is in the range of 1.2 or more and 1.5 or less.

When the prepreg is applied to a tubular body, the prepreg is cut into a required shape according to the design of the physical properties of the reinforcing fiber, the orientation of the reinforcing fiber, the number of windings, etc. (this cut prepreg is called a pattern), and a mandrel is formed. A tubular body is formed by winding a so-called metallic core material in a reinforcing fiber orientation according to the design, forming a tubular form, and then heat-curing.

When the pattern is wound around the mandrel, if the adhesiveness of the prepreg is low or the flexibility is low, it is difficult to attach the prepreg or it is difficult to follow the curved surface of the mandrel, resulting in poor workability. Further, at the time of winding, there are various methods such as pre-bonding patterns to each other, if necessary, and winding the bonded one around a mandrel to adjust the tubular shape. In most cases, winding is often done in several patterns.

In the case where a plurality of tubular bodies are produced in a lump, it may take time before starting the winding operation after pasting the patterns together, or after winding the first pattern and before winding the second pattern. Vacant At this time, if the adhesive strength of the prepreg is weak or the flexibility of the prepreg is low, the prepreg once wound causes peeling, and the fiber arrangement is disturbed at the peeled portion. In addition, it is necessary to correct the part where the peeling occurs, additional work is required, and the fiber arrangement may be disturbed due to the correction work.

The workability during the winding work is evaluated by the winding peeling index defined below. The roll peeling index is measured by the following procedure.

That is, the peeling index is 24 at room temperature.
The prepreg has a diameter of 18 at ℃ and 50% humidity.
This is to quantify the degree of peeling of the prepreg after being wound on a cylindrical mandrel having no taper of mm and left for 15 minutes.

The size of the prepreg to be wound is 100 mm
X 54 mm, 2 pieces are cut out for n = 1. The fiber direction is 45 degrees with respect to the cut-out longitudinal direction. next,
Wrap the prepreg around the cylindrical mandrel. For the first sheet, the back side of the prepreg is the mandrel side, and for the second sheet, the front side of the prepreg is the mandrel side. For the second sheet, the winding start position is a position shifted by 180 degrees from the winding start position of the first sheet. After the winding of the second prepreg is completed, the cylindrical mandrel around which the prepreg is wound is rotated back and forth by a weight 10 times to make the wound state even.
The weight is made by attaching a rubber mat to a flat plate having a size of about 150 mm × 250 mm and fixing a disc-shaped or flat plate-shaped weight and a handle on the opposite surface. The weight of the flat plate, the rubber mat and the weight is 60 to 65 N. . Using a weight, roll the cylindrical mandrel around which the prepreg is wound so that only the weight of the weight is applied, and then lean against the cylindrical mandrel and leave for 15 minutes so that no force is applied to the wound prepreg. To do. Then, the amount of peeling of the prepreg after 15 minutes is measured.

The position to be measured is within a range of 100 mm on the winding completion side of the second prepreg. The distance between the prepreg of the first sheet and the prepreg of the second sheet is measured for the part where the peeling occurs.

The measurement is performed from the winding completion position of the prepreg wound on the second sheet to the outer layer of the first prepreg on the line directed to the center of the cross section circle of the cylindrical mandrel. A portion in which the distance between the first prepreg and the second prepreg is 0 to 2 mm or less is S, a portion in which the distance is 2 to 4 mm or less is M, and a portion larger than 4 mm is L. Measure the lengths of the parts corresponding to S, M and L (mm)
Then, the peeling index is calculated by the following formula.

S: Maximum peeling height is less than 2 mm M: Maximum peeling height is 2 mm or more and less than 4 mm L: Maximum peeling height is 4 mm or more Rolling peeling index = S + 2M + 4L This rolling peeling index is 0 It is preferably in the range of -80, and prepregs exceeding this range need to be corrected because peeling occurs due to low adhesiveness during winding.

Regarding the voids of such a molded product, it is possible to judge the actual molded product. That is, when a prepreg is cured to form a composite material and a void is contained inside, the fracture easily progresses from this void, so that there is a problem that the physical properties are not sufficiently expressed. The presence or absence of voids is observed by magnifying the cross section of the molded product by 50 times or more with an optical microscope after mirror polishing the cross section of the molded product.

The reinforcing fiber used in the present invention preferably has a tensile elastic modulus in the range of 300 to 800 GPa,
More preferably, it is in the range of 300 to 600 GPa.

A prepreg having a tensile elastic modulus of the reinforcing fiber of less than 300 GPa is not preferable because it requires a multi-layer winding in order to develop the desired physical properties and the physical properties vary greatly. The variation in physical properties is C.I. which is the percentage of the value obtained by dividing the standard deviation by the average value. V. It can be judged by the value, but under the same design, this C.I. V.
As the value increases, the variation in physical properties increases and the defective rate also increases, which is not preferable. If the elastic modulus of the reinforcing fiber exceeds 800 GPa, the prepreg becomes hard due to the high rigidity of the fiber, and even if the prepreg can be bonded and wound, it may come off by the time of the next step.

The basis weight of the reinforcing fiber used in the prepreg of the present invention is preferably 10 to 150 g / m ^{2, and} more preferably 50 to 150 g / m ² . If the basis weight of the reinforcing fibers is less than 10 g / m ² , the reinforcing fibers will be disturbed during the impregnation, and if it is attempted to avoid this, there is a high possibility that the impregnation cannot be performed sufficiently. In addition, the basis weight of the reinforcing fiber is 15
If it exceeds 0 g / m ² , the resin does not reach the central portion in the thickness direction during impregnation, resulting in a prepreg having an unimpregnated portion,
Voids may remain during curing, which may lead to deterioration of the physical properties of the molded product.

As the reinforcing fiber, carbon fiber, glass fiber, Kevlar fiber, etc. are generally used.
Particularly, carbon fiber is useful because it is light and has high strength.
Carbon fibers include twisted yarns, untwisted yarns, and untwisted yarns. Among them, untwisted yarns have no peculiarity because they are not twisted and have excellent properties such as spreadability.
It is preferable to use untwisted yarn.

It is preferable that the matrix resin contains an epoxy resin and a curing agent, and in particular, it contains a high molecular weight bifunctional epoxy resin having an epoxy equivalent of 450 or more. Is preferably 15 to 70% by weight, more preferably 15 to 55% by weight, based on 100% by weight of the total bifunctional epoxy resin. If it is less than 15% by weight, the tensile elongation of the resin may not be sufficient, so that the physical properties of the cylindrical composite may not be sufficiently exhibited. 70
If it exceeds 5% by weight, the flexural modulus may decrease, the bending properties of the cylinder may not be sufficiently exhibited, the heat resistance may decrease, and the viscosity of the epoxy resin composition may become too high.

Specific examples of the epoxy resin used in the present invention include a glycidyl ether obtained from a polyol, a glycidyl amine obtained from an amine having a plurality of active hydrogens, a glycidyl ester obtained from a polycarboxylic acid, and a plurality of glycidyl esters in a molecule. And a polyepoxide obtained by oxidizing the compound having a double bond. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin,
Bisphenol type epoxy resin such as tetrabromobisphenol A type epoxy resin, phenol novolac type epoxy resin, novolac type epoxy resin such as cresol novolac type epoxy resin, tetraglycidyl diaminodiphenylmethane, triglycidyl aminophenol, glycidyl such as tetraglycidyl xylene diamine An amine type epoxy resin or the like or a combination thereof is preferably used.

As the curing agent used in such an epoxy resin composition, any compound having an active group capable of reacting with an epoxy group can be used, but a compound having an amino group, an acid anhydride group or an azide group can be used. Are preferably used. Specifically, dicyandiamide, various isomers of diaminodiphenyl sulfone, and aminobenzoic acid esters are preferably used.

In addition to the above-mentioned epoxy resin and curing agent, other components such as polymer compounds, organic particles and inorganic particles can be appropriately added to the epoxy resin composition according to the purpose.

A thermoplastic resin is preferably used as the polymer compound. The blending of such a thermoplastic resin is preferable because it has the effect of optimizing the viscosity of the resin composition and the handleability of the prepreg, or enhancing the effect of improving the adhesiveness.

Such a thermoplastic resin has a main chain having carbon-carbon bonds, amide bonds, imide bonds, ester bonds, ether bonds, carbonate bonds, urethane bonds,
A thermoplastic resin having a bond selected from a urea bond, a thioether bond, a sulfone bond, an imidazole bond and a carbonyl bond is preferably used. Among these thermoplastic resins, a group of thermoplastic resins belonging to engineering plastics such as polyacrylate, polyamide, polyaramid, polyester, polycarbonate, polyphenylene sulfide, polybenzimidazole, polyimide, polyetherimide, polysulfone, and polyethersulfone are more preferable. Preferably used. Particularly preferably, polyimide, polyetherimide, polysulfone, polyethersulfone and the like are preferably used because they have excellent heat resistance.

The blending amount of such a thermoplastic resin is preferably 1 to 20% by weight based on 100% by weight of the total epoxy resin in the epoxy resin composition, so that the epoxy resin composition can have a proper viscoelasticity. It has the effect of increasing the mechanical strength of the obtained carbon fiber reinforced plastic.

Further, rubber particles and thermoplastic resin particles are preferably used as the organic particles to be blended in the epoxy resin composition. These particles are preferable because they have the effects of improving the toughness of the resin and the impact resistance of the carbon fiber reinforced plastic member. Further, as the thermoplastic resin particles, polyamide or polyimide particles are preferably used.

Further, as such rubber particles, crosslinked rubber particles and core-shell rubber particles obtained by graft-polymerizing a different polymer on the surface of the crosslinked rubber particles are preferably used.

As the inorganic particles to be added to the epoxy resin composition, silica, alumina, smectite, synthetic mica, etc. can be added. These inorganic particles are compounded in the epoxy resin composition mainly for rheology control, that is, for imparting thickening and thixotropy.

The fiber-reinforced composite material molded by using the prepreg of the present invention can provide a material which has no void and has excellent mechanical properties.

Further, the molded product using the prepreg of the present invention can obtain a molded product which is free from deterioration in strength due to disorder of fiber arrangement and voids. In particular, the tubular product is preferably used for fishing rods and golf shafts. Things can be provided.

In the production of such a tubular body, after the winding of the prepreg around the mandrel is completed, a wrapping tape is wound on the wound pattern, the shape is maintained, and the prepreg is placed in a curing oven and heated and cured.

This wrapping tape is made of polypropylene, polyester, nylon or the like. The material, thickness and width of the tape are selected and used according to the application. After the curing is completed, the mandrel is removed, the wrapping tape is peeled off, and the tubular body is taken out.

When the cured tubular body is used for a golf shaft, the surface of the tubular body is subjected to polishing and post-coating processing, and a golf club head and a grip are attached to form a golf club shaft. In addition, when applying the cured tubular body to a fishing rod, as in the case of a golf club shaft, the tubular body surface is subjected to polishing and painting post-processing, and tubular bodies of slightly different diameters are joined together, Attach a threader and reel to make a fishing rod.

[0047]

EXAMPLES The present invention will be specifically described below with reference to examples. For the cylindrical bending test, a cylindrical composite material with an inner diameter of 10 mm was used, and it is described in "Certification Standards for Golf Club Shafts and Standard Confirmation Methods" (Edited by the Product Safety Association, 5 Industry No. 2087 approved by the Minister of International Trade and Industry, 1993). The bending fracture load was measured based on the three-point bending test method. Here, the distance between fulcrums was 300 mm and the test speed was 10 mm / min. C. V. Regarding the value, the value obtained by dividing the standard deviation of the measured value by the average value is shown as a percentage. Table 1 shows a list of examples and comparative examples.

(Example 1) "Epicoat" 1001
(Registered trademark, Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, bifunctional, epoxy equivalent 4
50-500) was applied to release paper using a reverse roll coater using 50 parts by weight of 100 parts of epoxy resin to form a resin film. Next, the carbon fiber "Torayca" (registered trademark, manufactured by Toray Industries, Inc., tensile elastic modulus 436 GPa, untwisted yarn) is aligned in one direction,
After uniformly opening the fibers, the above-mentioned resin films were placed on the upper and lower sides of the aligned carbon fibers, and a prepreg was produced by a hot melt method. At that time, a prepreg was produced by changing the timing of applying temperature and pressure. As a result, carbon fiber areal weight is 50 g / m ² , fiber content is 67% by weight, ΔVr / V
A prepreg with r = 1.5 was obtained. The roll peeling index of this prepreg was 0. A tubular body was produced using this prepreg, and the adhesive strength was high and the workability was good. In addition, a cross-section observation and a bending test were performed on this tubular body, but it was found that there was no void, the bending fracture load average value was 1050 N, and C.V. V. The value is 1.
It was 2%.

(Embodiment 2) "Epicoat" 1001
(Registered trademark, Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, bifunctional, epoxy equivalent 4
50 to 500) to 35 parts of epoxy resin
Part, "Epicoat" 1004 (registered trademark, Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, bifunctional, epoxy equivalent of 875 to 975) is used to reverse the epoxy resin composition using 20 parts per 100 parts of the epoxy resin. A roll coater was used to apply it on release paper to form a resin film. Next, carbon fiber "Torayca" (registered trademark, manufactured by Toray Industries, Inc., tensile elastic modulus 377GP
a, non-twisted yarn), carbon fiber areal weight is 150 g / m ² ,
A prepreg having a fiber content of 70% by weight was used in Example 1
Was prepared in the same manner as in. As a result, ΔVr / Vr = 1.
A prepreg of 4 was obtained. The roll peeling index of this prepreg was 4. A tubular body was produced using this prepreg, and the adhesive strength was high and the workability was good. Also,
A cross-section observation and a bending test were performed on this tubular body, but it was found that there was no void, the bending fracture load average value was 1280 N, and there was a variation in C.I. V. The value was 0.7%.

(Example 3) "Epicoat" 1001
(Registered trademark, Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, bifunctional, epoxy equivalent 4
50-500) was coated on a release paper using a reverse roll coater, using 46 parts of epoxy resin to 100 parts of epoxy resin to prepare a resin film. Next, the same carbon fiber as the carbon fiber “Torayca” (registered trademark, manufactured by Toray Industries, Inc., tensile elastic modulus 377 GPa, untwisted yarn) was used, and the carbon fiber areal weight was 75 g / m ² and the fiber content was 73% by weight. A prepreg of the above was prepared in the same manner as in Example 1. As a result, a prepreg with ΔVr / Vr = 1.3 was obtained. The winding peeling index of this prepreg was 0. A tubular body was produced using this prepreg, and it had high adhesive strength and good workability. In addition, a cross-section observation and a bending test were performed on this tubular body, but it was found that there was no void and the bending fracture load average value was 1490 N, which showed variation.
V. The value was 2.5%.

(Embodiment 4) "Epicoat" 1001
(Registered trademark, Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, bifunctional, epoxy equivalent 4
50 to 500) was applied to release paper using a reverse roll coater using 35 parts of 100 parts of epoxy resin to form a resin film. Next, using a carbon fiber "Torayca" (registered trademark, manufactured by Toray Industries, Inc., tensile elastic modulus 490 GPa, untwisted yarn), a prepreg having a carbon fiber basis weight of 100 g / m ² and a fiber content of 76% by weight was prepared. It was produced in the same manner as in Example 1. as a result,
A prepreg with ΔVr / Vr = 1.3 was obtained. The winding peeling index of this prepreg was 22. A tubular body was produced using this prepreg, and the workability was good.
In addition, a cross-section observation and a bending test were performed on this tubular body, and it was found that there was no void and the bending fracture load average value was 1060.
N.C., which shows variation. V. The value was 2.1%.

Example 5 The same epoxy resin composition as in Example 2 was applied onto release paper using a reverse roll coater to prepare a resin film. Next, using the same carbon fiber as in Example 2, the carbon fiber areal weight is 116 g / m ² ,
A prepreg having a fiber content of 80% by weight was used in Example 1
Was prepared in the same manner as in. As a result, ΔVr / Vr = 1.
A prepreg of 2 was obtained. The winding peeling index of this prepreg was 34. A tubular body was produced using this prepreg, and the drapeability was high and the workability was good. In addition, a cross-section observation and a bending test were performed on this tubular body, and it was found that the bending fracture load average value was 1280 N without voids.
And C. showing variations. V. The value was 1.3%.

(Embodiment 6) "Epicoat" 1009
(Registered trademark, Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, bifunctional, epoxy equivalent 2
400-3300) to 2 parts for 100 parts of epoxy resin
The epoxy resin composition used in 2 parts was applied onto release paper using a reverse roll coater to prepare a resin film. Next, using the same carbon fiber as in Example 1, a prepreg having a carbon fiber areal weight of 125 g / m ² and a fiber content of 87% by weight was produced in the same manner as in Example 1. As a result, a prepreg with ΔVr / Vr = 1.4 was obtained. The winding peeling index of this prepreg was 60. A tubular body was produced using this prepreg, and the drapeability was high and the workability was good. Further, a cross-section observation and a bending test were carried out on this tubular body, but there were few voids, the bending fracture load average value was 1160 N, and C.V.
V. The value was 1.6%.

Comparative Example 1 The same epoxy resin composition as in Example 2 was applied onto release paper using a reverse roll coater to form a resin film. Next, carbon fiber "Torayca" (registered trademark, manufactured by Toray Industries, Inc., tensile elastic modulus 436G
(Pa, untwisted yarn) was aligned in one direction and uniformly opened, and then the above-mentioned resin film was placed above and below the aligned carbon fibers to prepare a prepreg by a hot melt method. As a result, the carbon fiber areal weight is 50 g / m ² and the fiber content is 6
A prepreg having a content of 7% by weight and ΔVr / Vr = 1.0 was obtained. The roll peeling index was 96. A tubular body was produced using this prepreg, but the drapeability was low and the workability was poor. In addition, a cross-section observation and a bending test were performed on this tubular body, and it was found that the number of voids was large, the bending fracture load average value was 1100 N, and C.V. V.
The value was 9.7%.

(Comparative Example 2) "Epicoat" 1001
(Registered trademark, Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, bifunctional, epoxy equivalent 4
50 to 500) to 50 parts of epoxy resin
Part, "Epicoat" 1009 (registered trademark, Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, bifunctional, epoxy equivalent 2400-3300) is used to reverse the epoxy resin composition using 30 parts per 100 parts of the epoxy resin. A roll coater was used to apply it on release paper to form a resin film. Next, carbon fiber "Torayca" (registered trademark, manufactured by Toray Industries, Inc., tensile elastic modulus 377GP
a, untwisted yarn), carbon fiber areal weight is 150 g / m ² ,
A prepreg having a fiber content of 70% by weight was used in Comparative Example 1
Was prepared in the same manner as in. As a result, ΔVr / Vr = 1.
A prepreg of 6 was obtained. The roll peeling index was 56. A tubular body was produced using this prepreg, and the adhesive strength was high and the workability was good. In addition, a cross-section observation and a bending test were performed on this tubular body, but it was found that the number of voids was large and the bending fracture load average value was 970 N. V. The value was 10.3%.

(Comparative Example 3) "Epicoat" 1009
(Registered trademark, Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, bifunctional, epoxy equivalent 2
400-3300) to 1 part for 100 parts of epoxy resin
The epoxy resin composition used in an amount of 4 parts was applied onto release paper using a reverse roll coater to form a resin film. Next, using the same carbon fiber as in Comparative Example 2, a prepreg having a carbon fiber areal weight of 75 g / m ² and a fiber content of 73 wt% was prepared in the same manner as in Comparative Example 1. As a result, a prepreg with ΔVr / Vr = 0.9 was obtained. The roll peeling index was 124. A tubular body was produced using this prepreg, but the adhesive strength was low and the workability was poor. In addition, a cross-section observation and a bending test were performed on this tubular body, but it was found that there were many voids and the bending fracture load average value was 11
C. 90 N, which shows variations. V. The value was 6.7%.

(Comparative Example 4) The same epoxy resin composition as in Example 4 was applied onto release paper using a reverse roll coater to prepare a resin film. Next, carbon fiber "Torayca" (registered trademark, manufactured by Toray Industries, Inc., tensile elastic modulus 490G
Pa, untwisted yarn) and carbon fiber areal weight of 100 g /
A prepreg having m ² and a fiber content of 76% by weight was produced in the same manner as in Comparative Example 1. As a result, ΔVr / Vr
A prepreg of 1.0 was obtained. Unwinding index is 35
It was 6. A tubular body was produced using this prepreg, but the adhesive strength was low and stable winding was not possible.

(Comparative Example 5) The same epoxy resin composition as in Example 2 was applied onto release paper using a reverse roll coater to prepare a resin film. Next, using the same carbon fiber as in Comparative Example 2, the carbon fiber areal weight is 116 g / m ² ,
A prepreg having a fiber content of 80% by weight was used in Comparative Example 1
Was prepared in the same manner as in. As a result, ΔVr / Vr = 1.
A prepreg of 1 was obtained. The roll peeling index was 288. A tubular body was produced using this prepreg,
The adhesive strength was low and the workability was poor. In addition, a cross-section observation and a bending test were performed on this tubular body, and it was found that the voids were large and the bending fracture load average value was 1210 N, which showed variation. V. The value was 8.8%.

(Comparative Example 6) The same epoxy resin composition as in Example 6 was applied onto release paper using a reverse roll coater to prepare a resin film. Next, using the same carbon fiber as in Comparative Example 1, the carbon fiber areal weight is 125 g / m ² ,
A prepreg having a fiber content of 87% by weight was used in Comparative Example 1
Was prepared in the same manner as in. As a result, ΔVr / Vr = 0.
A prepreg of 8 was obtained. The roll peeling index was 400. A tubular body was produced using this prepreg,
The adhesive strength was low, and winding molding was not possible.

[0060]

[Table 1]

As is clear from Table 1, in Examples 1 to 6 as compared with those in Comparative Examples 1 to 6, peeling did not occur during the winding operation in the production of the tubular body and after curing. It can be seen that the molded body of 1 has the characteristics of few voids and little variation in the physical properties of the cured product.

[0062]

According to the present invention, it is possible to provide a prepreg in which the work efficiency does not decrease during winding work of the prepreg, the cured product has few voids, and the physical properties are less varied.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F072 AA04 AA07 AA09 AB10 AC01                       AD28 AE01 AG03 AG12 AG22                       AH06 AH12 AH18 AH48 AJ03                       AK05 AL03 AL09                 4F205 AA39 AD02 AD16 AM32 HA06                       HA14 HA33 HA45 HB01 HC17                       HT02                 4J002 CD001 CD051 DA016 FA046                       FD147

Claims (9)

[Claims] 1. A prepreg obtained by impregnating reinforcing fibers with a resin, wherein the weight ratio of the reinforcing fibers is 67 to 87% by weight.
And the total thickness of the prepreg is T [mm], the surface layer thickness of at least the surface side of the prepreg is 0.
A prepreg characterized in that a resin volume content ΔVr of a 1 T [mm] portion satisfies the following formula (1). 1.2 ≤ ΔVr / Vr ≤ 1.5 (1) In the formula, ΔVr is the resin volume content in the surface layer thickness 0.1T [mm] portion with respect to the total thickness T [mm] of the prepreg. Vr: Shows the resin volume content of the entire prepreg. 2. The thickness T [mm] of the prepreg,
The prepreg according to claim 1, characterized in that the resin volume content ΔVr in the surface layer thickness 0.1T [mm] portion of each of the front and back surfaces satisfies the formula (1). 3. The prepreg according to claim 1, wherein the reinforcing fiber has a tensile elastic modulus in the range of 300 to 800 GPa. 4. The basis weight of the reinforcing fiber is 10 to 150 g / m.
The prepreg according to any one of claims 1 to 3, characterized in that it is ^2. 5. The prepreg according to claim 1, wherein the reinforcing fiber is a carbon fiber. 6. The prepreg according to claim 1, wherein the resin is an epoxy resin composition containing an epoxy resin and a curing agent. 7. The epoxy resin has an epoxy equivalent of 450.
The prepreg according to claim 6, wherein the high molecular weight bifunctional epoxy resin is contained in an amount of 15 to 70% by weight based on 100% by weight of the total epoxy resin. 8. A fiber-reinforced composite material obtained by heat-curing the prepreg according to claim 1. 9. The fiber-reinforced composite material according to claim 8, wherein the fiber-reinforced composite material is a tubular body.