JPH05329838A - Prepreg - Google Patents

Abstract

PURPOSE:To impart excellent tenacity to a prepreg for a fiber reinforced composite material consisting of a reinforcing fiber with the modulus of elasticity of 200GPa or more, a thermoplastic fiber having a core/sheath structure and a thermosetting matrix resin so that the thermoplastic fiber having a core/sheath structure is allowed to be locally present on the outer surface of the prepreg. CONSTITUTION:A prepreg for a fiber reinforced composite material is formed from a reinforcing fiber A with the modulus of elasticity of 200 GPa or more, a thermoplastic fiber B having a core/sheath structure and a thermosetting matrix resin C and the wt. ratio of A/C is set to 40/60-85/15 and the wt. ratio of B/C is set to 0.5/100-40/00. The thermoplastic fiber B is made locally present on the outer surface of the prepreg and the shear modulus of the core component of B is made larger than the modulus plasticity of the sheath component thereof and the volume ratio of core component/sheath component is set to 30/70-90/10. By this constitution, the prepreg having excellent tenacity without losing excellent handling properties, thermal properties and mechanical properties is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg for a fiber-reinforced composite material which can impart excellent toughness to a molded product obtained from the matrix resin without impairing the excellent thermal properties and mechanical properties of the matrix resin.

[0002]

2. Description of the Related Art Composite materials using high-strength and high-elasticity fibers such as carbon fibers as a reinforcing material have been widely used mainly for sports applications because of their excellent specific strength and specific elasticity. Thermosetting resins such as epoxy resins used as resins have various advantages, but have a drawback of poor toughness, so that their applications have been considerably limited. As a method of improving the defects of this thermosetting matrix resin, a method of adding a rubber component or a thermoplastic resin is generally used, but it is necessary to add a large amount in order to obtain a sufficient toughness improving effect. However, the solvent resistance and the like are deteriorated.

Further, for example, as disclosed in Japanese Patent Laid-Open No. 63-162732, it has been disclosed that by adding a thermoplastic resin in a powder form to a matrix resin, it is possible to achieve a high toughness of the thermosetting matrix resin. However, when the thermoplastic resin powder is uniformly dispersed in the matrix resin, or when the thermoplastic resin is dissolved in the matrix resin, the viscosity of the entire system increases, and impregnation becomes difficult only during prepreg production. In addition, problems such as a decrease in the tack level of the prepreg cannot be avoided.

Further, for example, in Japanese Patent Application Laid-Open No. 1-110537, spherical fine particles are provided near the surface of a prepreg (thickness of 30).
It is disclosed that the toughness of the composite material is effectively improved by localizing the prepreg tack within the range (% or less). However, even in this case, the reduction of the prepreg tack is unavoidable, and the process becomes complicated. New problems such as complicated quality control will occur.

Alternatively, a method of inserting a kind of adhesive layer called interleaf between the layers has been proposed, but it has not been widely put into practical use because the fiber content cannot be increased. (JP-A-60-231738, etc.)

[0006]

The object of the present invention is to impart excellent toughness to a molded product obtained from the thermosetting matrix resin without impairing the excellent thermal and mechanical properties of the thermosetting matrix resin, An object of the present invention is to provide a prepreg for a fiber-reinforced composite material, which has an appropriate tack level and drapeability and is excellent in handleability.

[0007]

The present invention comprises (A) a reinforcing fiber having an elastic modulus of 200 GPa or more, (B) a thermoplastic fiber having a core / sheath structure, and (C) a thermosetting matrix resin. A prepreg for fiber-reinforced composite material,
The ratio of each of the components (A), (B) and (C) is within the following range, and the thermoplastic fiber having the core / sheath structure of (B) is localized on the outer surface thereof. The main point is prepreg.

(A) / (C) = 40/60 to 85/15 (weight ratio) (B) / (C) = 0.5 / 100 to 40/100 (weight ratio) of (B) in the present invention Thermoplastic fibers having a core / sheath structure are the most important components in the present invention. Because the fibrous material is used as the toughness-imparting material, the excellent handling property, thermal property, and mechanical property originally possessed by the base prepreg consisting of the reinforcing fiber and the thermosetting matrix resin are significantly impaired. This is because the object of the present invention, which is to provide a prepreg for a fiber-reinforced composite material, that can impart excellent toughness to a molded article can be achieved. That is, since the toughness imparting material is fibrous,
It can be effectively placed on the outer surface of the prepreg, which allows it to be effectively located between the layers of the fiber-reinforced composite material after molding, so a relatively small amount of toughness-imparting material can provide sufficient effect. Be done. Furthermore, since only a small part of the outer surface of the prepreg is covered with the thermoplastic fiber, the tackiness of the matrix resin as the base is not significantly impaired, so the problem of lowering the tack level, which was a problem with the conventional technology, does not occur. Not only that, the addition amount of the toughness-imparting material can be easily controlled and confirmed, and a great advantage can be obtained in quality control. In addition, as for the prepreg manufacturing, it is possible to use the conventional process as it is, and there is no process problem. These effects are effects that cannot be obtained by the conventional techniques, and are effects that are obtained only by using the fibrous toughness-imparting material.

It is also important that the fibrous toughness imparting material has a core / sheath structure. Generally, in order to improve the toughness, it is advantageous to use a thermoplastic resin having a low elastic modulus and a large energy absorption ability, but if a large amount of low elastic thermoplastic fiber is added, the decrease in the interlaminar shear strength becomes remarkable, which is preferable. Absent. On the contrary, when using a highly elastic thermoplastic fiber,
Although the problem of reduction in interlaminar shear strength does not occur, improvement in toughness is not always sufficient. As a result of intensive studies to develop a material satisfying both of the two contradictory properties of improving toughness and maintaining interlaminar shear strength, a high toughness thermoplastic resin was used as the sheath material and the core material had high elasticity. By using the thermoplastic resin of (1), the toughness can be improved as in the case of using the high toughness material alone, and the reduction of the shear strength can be suppressed. That is, the use of the core / sheath structure fibers makes it possible for the first time to effectively improve the toughness of the molded product without impairing the properties of the base prepreg, and thus it is possible to obtain the properties of the present invention which cannot be obtained by the prior art. It is the second effect.

The thermoplastic resin used for the sheath material of the fiber having the core / sheath structure of (B) in the present invention is preferably one having relatively low elasticity and high toughness, and specific examples thereof include polyethylene, polypropylene and polyamide. However, the present invention is not limited to these.

Further, since the thermoplastic resin of the sheath material of the fiber having the core / sheath structure of (B) of the present invention is in direct contact with the thermosetting matrix resin of (C), the adhesiveness with (C) is not sufficient. The better one is preferable, and therefore, one having a functional group capable of reacting with the thermosetting matrix resin (C) in the molecule is particularly preferable. For example, when (C) is an epoxy resin, the thermoplastic resin of the sheath material of the fiber having the core / sheath structure of (B) reacts with an epoxy resin such as an amino group, an amide group or a phenolic hydroxyl group. Those having a functional group capable of controlling are particularly preferable.

The core material of the fiber having the core / sheath structure of (B) is not particularly limited as long as it is a thermoplastic resin which maintains high elasticity to some extent at the temperature at which the composite material is usually used, but as described above. In order to prevent a large decrease in the interlaminar shear strength, it is preferable that the shear elastic modulus of the core component> the shear elastic modulus of the sheath component be satisfied. Further, those satisfying the following relationship are preferable in terms of the interlaminar shear strength at room temperature and high temperature. Particularly preferred.

Shear modulus of elasticity of the core component at room temperature ≧ 6.5
× 10 ⁹ dyn / cm ² Shear elastic modulus of core component at 100 ° C. ≧ 4.5 × 10
Specific examples of the ⁹ dyn / cm ² core component include amorphous polyamide, polyacetal, polycarbonate, polyarylate, polysulfone, polyetheretherketone, polyetherimide, polyimide, polyamideimide, polyphenylene oxide, polyphenylene sulfide, and polyphenylene sulfide. Examples thereof include so-called engineering plastics such as benzimidazole and polyallylsulfone, and super engineering plastics, but are not necessarily limited thereto.

The shear elastic modulus in the present invention is the shear elastic modulus measured under the following conditions.

[Shear Modulus Measurement Method] Device: RDS-7700 manufactured by Rheometrics
And equivalent test piece shape: 12 mm width x 2 mm thickness x 40 to 50
mm Length mode: Temperature Sweep Temperature rising rate: 5 ° C./step Holding time: 1 minute after the temperature stabilizes Strain rate: 10 RAD / SEC initial strain: 0.1% to 0.2% (B) in the present invention Regarding the combination of the core component and the sheath component of the thermoplastic fiber having the core / sheath structure, any combination is possible, for example, as long as the core / sheath structure can be formed by melt spinning. As described above, the shear modulus of the core component> the shear modulus of the sheath component is preferable, and a combination in which the core component and the sheath component have good adhesiveness is more preferable. If the adhesiveness between the core component and the sheath component is extremely poor, there is a possibility that breakage may occur at the interface between the core component and the sheath component of the thermoplastic fiber (B) having the core / sheath structure, which is not preferable.

An example of a preferable combination of the core component and the sheath component is an amorphous polymer having a glass transition temperature (Tg) higher than the maximum temperature (120 ° C. or lower in the case of an epoxy resin system) in which the base composite material is used. Can be cited as a core component, and a combination of crystalline polymers having a similar structure and having a lower shear modulus than the amorphous polymer of the core component in the temperature range from room temperature to the maximum temperature at which the composite material is used can be mentioned. ..

When the matrix resin is an epoxy resin type, the core component is an amorphous polyamide (eg TR-55).
(EMS-CHEMIE AG), Trogamid-
T (Dynamic Nobel), etc., with crystalline polyamide (eg, nylon 12, nylon 1) as a sheath component.
1, Nylon 612, etc.) can be exemplified as a preferable example, but the combination is not necessarily limited thereto.

The ratio of the core component to the sheath component of the thermoplastic fiber (B) having the core / sheath structure in the present invention is preferably in the range of core component / sheath component = 20/80 to 95/5, The range of 30/70 to 90/10 is particularly preferable.

The form of the fiber having the core / sheath structure of (B) is preferably a monofilament or a multifilament in which they are bundled, but is not necessarily limited thereto. The diameter of each filament is preferably 100 μm or less, and particularly preferably 50 μm or less.

When used as a multifilament, the total denier is preferably 1000 denier or less, and particularly preferably 500 denier or less.

The ratio of the fiber having the core / sheath structure of (B) is preferably 0.5 to 40 parts by weight based on 100 parts by weight of the thermosetting matrix resin of (C). If it is less than 0.5 parts by weight, a sufficient toughness improving effect cannot be obtained, and if it exceeds 40 parts by weight, not only the toughness improving effect reaches its peak but also the tack level of the prepreg is lowered, which is not preferable. It is more preferably 0.5 to 20 parts by weight.

It is important that the fiber having the core / sheath structure of (B) in the present invention is present near the outer surface of the prepreg. When it is completely buried in the center of the prepreg, sufficient toughness improving effect cannot be obtained. However, it is not preferable that the fibers having the core / sheath structure are completely raised from the surface of the prepreg, and most of the fibers are preferably embedded in the thermosetting matrix resin.
Further, it is more preferable that the fibers having the core / sheath structure are present in a state where they are evenly aligned in one direction, but the fibers are not necessarily limited thereto. Of course, it is also possible to align them in two or more directions at the same time and arrange them in a crossed manner, and a high effect can be obtained, but the process becomes complicated.
The alignment direction is not particularly limited and may be present at any angle to the reinforcing fiber, but aligning in the same direction as the reinforcing fiber is the easiest in the process.

Elastic modulus 200PG of (A) in the present invention
As the reinforcing fiber a or more, carbon fiber, graphite fiber, boron fiber, and other reinforcing fibers used in ordinary fiber-reinforced composite materials are used as they are, but the tensile strength is 3500 MPa.
The above carbon fibers and graphite fibers are preferably used. Among them, carbon fibers and graphite fibers having a high strength and a high elongation with a tensile strength of 4500 MPa or more and an elongation of 1.7% or more are most preferably used.

As the thermosetting matrix resin (C) in the present invention, any resin can be used as long as it is cured and at least partially forms a three-dimensional cured product.

Typical examples are epoxy resin, maleimide resin, polyimide resin, cyanate ester terminated resin, acetylene terminated resin, vinyl terminated resin, allyl terminated resin, and nadic acid terminated resin. Can be given.

An epoxy resin is used as the thermosetting matrix resin most suitable for the present invention. In particular, epoxy resins having amines and phenols as precursors are preferable. Specifically, tetraglycidyl diaminodiphenylmethane, triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, various isomers of triglycidyl aminocresol, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type Examples thereof include, but are not limited to, an epoxy resin, a phenol novolac type epoxy resin, and a cresol novolac type epoxy resin. Brominated epoxy resins obtained by brominating these epoxy resins are also used. These epoxy resins may be used alone, but may be used as a mixture of two or more kinds depending on the purpose.

The epoxy resin is usually used in combination with a curing agent, but the curing agent used in the present invention is not particularly limited, and a functional group capable of reacting with the epoxy resin such as an amino group or an acid anhydride group is appropriately used. However, aromatic amino compounds represented by various isomers of diaminodiphenyl sulfone, dicyandiamide, and aminobenzoic acid esters are suitable.

As the thermosetting matrix resin (C) in the present invention, a thermoplastic resin or an oligomer thereof may be added to the above thermosetting resin.
Especially polyimide, polyetherimide, polysulfone,
So-called engineering plastics such as polyether sulfone and polyether ether ketone are preferable from the viewpoint of heat resistance, and those having a functional group capable of reacting with a thermosetting resin at the molecular end or in the molecular chain are more preferable.

The amount of the thermoplastic resin component added to the thermosetting resin component is preferably 30% by weight or less, more preferably 15% by weight or less. If the amount of the thermoplastic resin component added is 30% by weight or more, the viscosity of the system becomes too high, which not only causes impregnation failure during prepreg formation, but also causes the prepreg tack property and drape property to significantly decrease. Become.

Further, a small amount of inorganic fine particles such as fine powder silica and an elastomer component such as butadiene / acrylonitrile copolymer are added to the thermosetting resin in a small amount within a range that does not sacrifice prepreg characteristics, processing characteristics, mechanical characteristics, thermal characteristics and the like. It is also possible to add.

The ratio of the reinforcing fiber (A) having a modulus of elasticity of 200 GPa or more to the thermosetting matrix resin (C) can be appropriately set according to the purpose, but the weight ratio is (A) / The range of (C) = 40/60 to 85/15 is suitable. A more preferable range is (A) / (C) = 60/40 to 75/25.

There is no particular limitation on the method for producing a prepreg from the reinforcing fiber (A) having a modulus of elasticity of 200 GPa or more, the thermosetting matrix resin (C) and the thermoplastic fiber (B) having a core-sheath structure. However, any method may be used as long as the desired prepreg can be obtained. For example, the following methods can be exemplified, but not limited to them.

[Method 1] A thermoplastic fiber having a core-sheath structure (B) is arranged on a base prepreg obtained from the reinforcing fiber (A) and the thermosetting matrix resin (C) and heated. Impregnation method.

[Method 2] Reinforcing fibers (A) and (B) are placed on a release paper coated with the thermosetting matrix resin (C).
And a thermoplastic fiber having a core-sheath structure are simultaneously supplied and impregnated.

[Method 3] After the thermoplastic fibers having a core-sheath structure of (B) are arrayed and fixed on the release paper coated with the thermosetting matrix resin of (C), the reinforcing fibers of (A) are overlaid. Method of combined impregnation.

[0036]

EXAMPLES The present invention will be described in detail with reference to the following examples, but the present invention is not necessarily limited to these.

In the examples, all parts by weight are parts by weight, and the epoxy resins used are as follows.

YH434L: Tetraglycidyldiamine type epoxy resin (manufactured by Tohto Kasei Co., Ltd.) ELM-100; Triglycidyldiamine type epoxy resin (manufactured by Sumitomo Chemical Co., Ltd.) Epicoat 807; Bisphenol F type epoxy resin (manufactured by Yuka Shell Co., Ltd.) Reference Example 1 Amorphous nylon, TR-55 (EMS-CHEMIE
AG: Tg = 155 ° C.) pellets at 120 ° C.
After vacuum drying for 2 hours, it was melted using the first extruder, while nylon 12 (Daicel Huls Company:
L2140: Tg = 41 ° C) pellets at 80 ° C for 12
After vacuum drying for a period of time, it is melted using a second extruder and each melt stream is guided to the spinning head, TR-55 becomes the core component, and the ratio of the core component / the sheath component is the volume ratio. At 70
After forming a composite flow so that it becomes / 30, the spinning temperature is 3
Melt spinning was performed at 05 ° C. and a spinning speed of 700 m / min to obtain a core / sheath structure fiber having a total denier of 90 d and 18 filaments.

Reference Example 2 A total was obtained in the same manner as in Reference Example 1 except that each discharge amount was adjusted so that the volume ratio of the core component (TR-55) / the sheath component (nylon 12) was 90/10. Denier 90
A d / 18 filament core / sheath structure fiber was obtained.

Reference Example 3 Amorphous nylon was converted from TR-55 to Trogamid-T.
(Daicel Huls Company: Tg = 148 ℃),
Core component (Trogamid-T) / Sheath component (nylon 1
A core / sheath structure fiber having a total denier of 90 d and 18 filaments was obtained in the same manner as in Reference Example 1 except that each discharge amount was adjusted so that the ratio of 2) was 50/50 in volume ratio.

Example 1 Epicoat 807,680 g, ELM-100,477
g, tetramethylbisphenol A, 426 g were charged into a reaction vessel and reacted at 120 ° C. for 8 hours to obtain these preliminary reaction products. 35 parts by weight of this preliminary reaction product were mixed with 25 parts by weight of Epicoat 807, 40 parts by weight of YH434L, and 50 parts by weight of diaminodiphenyl sulfone as a curing agent, and they were sufficiently mixed until the whole became uniform.

The resin composition obtained and Mitsubishi Rayon Co., Ltd.
A unidirectional prepreg was manufactured from a high strength medium elastic carbon fiber, MR60P manufactured by the hot melt method. C of prepreg
The F areal weight was 190 g / m ² , and the resin content was 34% by weight.

The prepreg of the present invention was produced by winding the core / sheath structure fibers produced in Reference Example 1 on both sides of this prepreg at 2 mm intervals.

A small piece having a predetermined size was cut out from this prepreg, laminated, and then a test piece for measuring post-impact compression strength was formed by autoclave molding. (Curing conditions: 180 ° C x 2
Time) Using this test piece, SACMA (Suppli
ers of Advanced Composite
R of Materials Association)
economed method SRM2-88
According to the above, the compressive strength after 270 lb-in impact was measured. The obtained compressive strength after impact was 357 MPa.

A width of 6.4 from a forming plate having the same laminated structure
A test piece having a length of 30 mm and a length of 30 mm was cut out and the interlaminar shear strength at 82 ° C. was measured under the conditions of L / D = 4 and crosshead speed = 1 mm / min. The interlaminar shear strength obtained is 56.
It was MPa.

Comparative Example 1 A unidirectional prepreg was produced in the same manner as in Example 1 except that a resin film having a resin content of prepreg of 36% by weight was used. Using this prepreg, the compressive strength after impact and the interlaminar shear strength were measured in the same manner as in Example 1 without attaching core / sheath structure fibers.

The resulting compressive strength after impact is 274MP.
a, the interlaminar shear strength at 82 ° C. was 62 MPa.

Example 2 Instead of the core / sheath structure fiber of Reference Example 1, the core / sheath structure of Reference Example 2 was used.
A prepreg was produced in the same manner as in Example 1 except that the sheath structure fiber was used, and the compressive strength after impact and the interlaminar shear strength were measured.

The resulting compressive strength after impact is 355 MP
a, the interlaminar shear strength at 82 ° C. was 58 MPa.

Comparative Example 2 A prepreg was produced in the same manner as in Example 1 except that a nylon 12 multifilament (total denier 90d, filament number 18 fil) was used in place of the core / sheath structure fiber of Reference Example 1, and after impact. The compressive strength and interlaminar shear strength were measured. The resulting compressive strength after impact is 353MP
a, the interlaminar shear strength at 82 ° C. was 39 MPa.

Example 3 Instead of the core / sheath structure fiber of Reference Example 1, the core / sheath structure of Reference Example 3 was used.
A prepreg was produced in the same manner as in Example 1 except that the sheath structure fiber was used, and the compressive strength after impact and the interlaminar shear strength were measured.

The resulting compressive strength after impact is 351 MP
a, the interlaminar shear strength at 82 ° C. was 52 MPa.

[0053]

INDUSTRIAL APPLICABILITY The prepreg of the present invention has not only handling properties equivalent to those of conventional prepregs having a thermosetting resin as a matrix, but also excellent moldings obtained without impairing thermal properties and mechanical properties. It can impart toughness and has a high resistance to delamination especially when it is subjected to an impact, so that it is suitably used as a structural material for aircraft and the like.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Murata 4-chome, Sunadabashi, Higashi-ku, Aichi Prefecture, Aichi Prefecture 60-61, Product Development Laboratory, Mitsubishi Rayon Co., Ltd. No. 60, Product Development Laboratory, Mitsubishi Rayon Co., Ltd. (72) Inventor Tetsuya Yamaoka, 2-1, 4-1, Ushikawa-dori, Toyohashi-shi, Aichi Sanryo Rayon Co., Ltd., Toyohashi Plant (72) Takashi Akita Ushikawa, Toyohashi-shi, Aichi 2 at Sanchome Rayon Co., Ltd., Toyohashi Works

Claims (10)

[Claims] 1. A reinforcing fiber having an elastic modulus of 200 GPa or more, (B) a thermoplastic fiber having a core / sheath structure, and (C).
A prepreg for a fiber-reinforced composite material comprising a thermosetting matrix resin, wherein the ratio of each of the components (A), (B), (C) is within the following range, and the core / sheath structure of (B) A prepreg characterized in that a thermoplastic fiber having a is localized on its outer surface. (A) / (C) = 40/60 to 85/15 (weight ratio) (B) / (C) = 0.5 / 100 to 40/100 (weight ratio) 2. The prepreg according to claim 1, wherein the ratio of each of the components (A), (B) and (C) is within the following range. (A) / (C) = 60/40 to 75/25 (weight ratio) (B) / (C) = 0.5 / 100 to 20/100 (weight ratio) 3. The prepreg according to claim 1, wherein (B) is a thermoplastic fiber having a core / sheath structure satisfying the following conditions. Shear modulus of core component> Shear modulus of sheath component 4. The prepreg according to claim 1, wherein (B) is a thermoplastic fiber having a core / sheath structure satisfying the following conditions. Shear modulus at room temperature of core component ≧ 6.5 × 10 ⁹ dyn /
cm ² Core component's shear modulus at 100 ° C ≧ 4.5 × 10 ⁹
dyn / cm ² 5. The prepreg according to claim 1, wherein (B) is a thermoplastic fiber having a core / sheath structure satisfying the following conditions. Core component: amorphous polymer Sheath component: crystalline polymer 6. The prepreg according to claim 1, wherein (B) is a thermoplastic fiber having a core / sheath structure satisfying the following conditions. Core component / sheath component = 30/70 to 90/10 (volume ratio) 7. The prepreg according to claim 1, wherein (A) is carbon fiber or graphite fiber having a tensile strength of 3500 MPa or more. 8. The prepreg according to claim 1, wherein (C) is a thermosetting resin containing an epoxy resin as a main component. 9. The (B) sheath component is an amino group, an amide group,
The prepreg according to claim 8, comprising a thermoplastic resin having a functional group capable of reacting with an epoxy resin such as a phenolic hydroxyl group. 10. The prepreg according to claim 4, wherein (B) is a thermoplastic fiber having a core / sheath structure satisfying the following conditions. Core component: Amorphous polyamide Sheath component: Crystalline polyamide