JPH0820708A - Epoxy resin composition and prepreg prepared therefrom - Google Patents

Abstract

PURPOSE:To obtain the rein composition which can produce a prepreg that is excellent in storage atability at room temperature, is capable of being molded at relatively low temperatures, and causes no defects on the ground surface of its molded articles by incorporating a low-temperature-active potential curing agent and a specific whisker in an epoxy resin. CONSTITUTION:This epoxy resin composition for prepreg is prepared by mixing 100 pts.wt. of an epoxy resin (A), 3-60 pts.wt. of a low-temperature-active potential curing agent (B) (e.g. an amine-adduct potential curing agent and a microcapsule potential curing agent of a diaphragm-breaking type, which are activated at about 80 deg.C) and 0.05-30 pts.wt. of a whisker (C) with an aspect ratio of 3-500. The prepreg prepared from this resin composition has a proper workability and excellent composite characteristics, is excellent in storage stability at room temperature, is capable of being molded at a relatively low temperature around 80 deg.C, produces no wastes upon molding, and causes no defects on the ground and coating surface of its molded articles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is excellent in handling workability such as moderate tackiness (adhesiveness) and drapeability (flexibility) of prepreg and storage stability at room temperature, and can be used at a relatively low temperature around 80 ° C. Moldable, less resin flow at the time of molding, especially when molding tubular moldings made of fiber reinforced resin such as fishing rods and golf shafts, there is no furnace fall, and there are no defects such as scratches on the polished surface of these moldings. The present invention relates to an epoxy resin composition suitable for a fiber-reinforced composite material having excellent composite material properties.

[0002]

BACKGROUND OF THE INVENTION Fiber-reinforced composite materials such as carbon fibers are lightweight, have high strength and high elastic modulus, and are in the form of composites with resins, so-called prepregs, such as fishing rods, golf club shafts, and tennis. Sports / leisure fields such as rackets, industrial materials such as leaf springs and honeycomb structure materials, as well as automobile-related, aircraft materials, structural materials such as ships, electronic materials,
Widely used for various purposes such as civil engineering and building materials.

The properties required for such a prepreg for a fiber-reinforced composite material include not only excellent handling workability, storage stability at room temperature, and mechanical properties of a cured product, but also the properties of a ship or vehicle in recent years. For molding large-scale structural materials, and molding using wooden molds and resin molds, there is a demand for curing at a lower temperature and for a shorter time, which shortens the molding cycle,
There is an increasing demand to reduce energy costs.

By the way, as a matrix resin for such a prepreg for a fiber-reinforced composite material, an epoxy resin is used (Japanese Patent Laid-Open Nos. 62-127317 and 2-41314), and these matrix resins. A filler having a particle diameter of 10 times or less the diameter of the reinforcing single fiber, for example, graphite powder, carbon black, aluminum powder, silica powder, etc., is added to reduce the fluidity of the matrix resin during prepreg molding ( Kaisho 59
No. 227931) is used for manufacturing prepreg.

Further, as low-temperature curing prepregs, there are disclosed in Japanese Unexamined Patent Publications No. 5-9262 and No. 6-9802.
A prepreg using a latent curing agent that cures at a relatively low temperature of 100 ° C. or lower has been proposed. These matrix resins need to be impregnated into the reinforcing fibers at a lower temperature in order to prevent deterioration in storage stability during the production of the prepreg as compared with the conventional ones, and therefore the resin viscosity needs to be set to be low. .

In particular, for tubular fiber-reinforced composite materials such as fishing rods and golf shafts, a sheet-shaped prepreg in which carbon fibers or glass fibers are aligned in one direction or a prepreg obtained by impregnating a woven fabric of the above-mentioned reinforcing fibers with a matrix resin is released. Wrap the taped mandrel coated with the agent in the longitudinal direction in the direction according to the desired design, and then wind the heat-shrinkable tape in a spiral shape using a tape winder etc. while gradually overlapping it. Then, put it in a heating furnace, harden the matrix resin while applying tightening force with heat shrinkable tape, remove from the heating furnace and remove the tape after cooling, pull out the mandrel with a core removing machine etc. . However, the conventional prepreg has a drawback that the prepreg moves from the large diameter side of the mandrel toward the small diameter side during molding, that is, so-called furnace drop occurs. This is because heating causes the matrix resin to have low viscosity and to increase fluidity, so when the tightening force of the heat-shrinkable tape is applied in such a state, the mandrel has a taper, and the mandrel has a taper from the large diameter side to the small diameter side. A component force is generated and a so-called furnace drop occurs in which the prepreg moves in this direction. When this furnace drop occurs, the distribution of the matrix resin and the reinforcing fibers becomes uneven, and the desired physical properties of the composite material cannot be obtained, and it also causes defects in the molded product or warpage of the small diameter portion.

On the other hand, Japanese Unexamined Patent Publication No. 57-22636 discloses that
Prior to winding the prepreg around the mandrel, a method has been proposed in which a thread or a thread impregnated with a thermosetting resin is spirally wound in the longitudinal direction of the mandrel and the friction thereof prevents the furnace from falling. However, in this method, not only the effect of preventing the furnace from falling is not sufficient, but also the yarn remains in the molded product, which is not preferable in terms of characteristics. Further, in Japanese Patent Laid-Open No. 59-159315, a temperature of 130 ° C. is applied to a matrix resin for prepreg before winding the prepreg around a mandrel.
There is proposed a method of preventing the furnace from falling by applying a thermosetting resin having a gel time of 80% or less of the above resin to the mandrel. However, this method requires a resin for undercoating whose gel time is adjusted by B-stage formation, and prior to molding, the step of applying this undercoating resin,
Air-drying is required, which significantly reduces productivity. Furthermore, these prepregs require a curing temperature of 100 ° C. or higher.

Regarding the handling property (tack and drape property) of the prepreg at the time of working, not only the productivity at the time of winding the shaft but also a defect (scratch etc.) on the surface of the molded product is required, so that appropriate characteristics are required. To be done. If the tackiness is too strong, air is likely to be entrained at the time of winding, and if it is too low, workability such as laminating the prepreg deteriorates. In addition, when the drape property is insufficient, the prepreg is wound at the end portion of the winding, and particularly carbon fibers having a high elastic modulus may be broken. However, these factors appear on the surface as defects such as scratches at the time of polishing and coating after molding the shaft, causing defective products and deteriorating the physical properties, resulting in a significant reduction in yield.

As described above, the prepreg using the conventional matrix resin composition has appropriate workability and excellent composite material properties, and has good storage stability at room temperature.
It was extremely difficult to provide a prepreg that is sufficiently cured by molding at 0 ° C. or lower, does not fall in the furnace during molding, and has no defects on the polished or coated surface of the molded product.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned drawbacks of the conventional method, prevent the furnace from falling during molding without performing a pretreatment step, and deteriorate the composite material properties. It is possible to carry out molding at a relatively low temperature of 100 ° C. or less without giving rise to a fiber-reinforced composite material molded product having desired properties. Further, the prepreg using the epoxy resin composition of the present invention has an appropriate winding workability at a normal winding temperature, and since the resin flow during molding can be freely controlled, it can be molded after polishing. The object of the present invention is to provide an excellent molded product having no defects (such as scratches) on the product surface.

[0011]

Means for Solving the Problems That is, the present invention relates to the following components (A), (B) and (C) (A) 100 parts by weight of an epoxy resin (B) 3 to 60 parts by weight of a low temperature active latent curing agent. Parts and (C) 0.05 to 30 parts by weight of whiskers having an aspect ratio of 3 or more and 500 or less as an essential component, and a prepreg using the same.

The present invention will be described in more detail below. The epoxy resin which is the component (A) used in the present invention is not particularly limited, and includes a bisphenol A type epoxy resin and other glycidyl ether type epoxy resins, for example,
Bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, glycidyl amine type epoxy resin, naphthalene type epoxy resin, brominated bisphenol A type epoxy resin, glycidyl ester type epoxy resin, Examples thereof include cycloaliphatic epoxy resins and heterocyclic epoxy resins. If desired, urethane-modified epoxy resin, rubber-modified epoxy resin, alkyd-modified epoxy resin, etc. may be used. Among these, bisphenol A type epoxy resin and novolac type epoxy resin are preferable from the viewpoint of balance of handling property, economical efficiency, and physical properties of composite material, but two or more kinds of these can be appropriately mixed and used according to required characteristics.

As the low temperature active latent curing agent as the component (B), those which are activated at 50 ° C. or higher are used, and preferably thermosetting latent curing agents which are activated at around 80 ° C. For example, an amine adduct-type latent curing agent that is activated by heat melting (Amicure: trademark of Ajinomoto Co., Inc.),
There are partition wall breaking type microcapsule type latent curing agents (Novacure: trademark of Asahi Chemical Industry Co., Ltd.) and the like. These latent curing agents have good storage stability at around 50 ° C and around 80 ° C. It activates more rapidly and cures the epoxy resin. The addition amount of these latent curing agents is 3 to 60 parts by weight with respect to 100 parts by weight of the epoxy resin which is the component (A). If it is less than 3 parts by weight, the curing will be slow and sufficient properties cannot be obtained, and if it exceeds 100 parts by weight, the storage stability at room temperature and the physical properties of the cured product will be significantly deteriorated, which is not preferable. Further, these latent curing agents have better curing reactivity at around 80 ° C. when used alone, but for the purpose of appropriate control of reactivity or storage stability,
Urea compounds, guanidine compounds, polyhydric carboxylic acid polyhydrazide compounds, amine imides, diaminomaleonitriles, guanamines, phenol resins, melamine resins, urea resins, etc. may be appropriately mixed and used as long as the characteristics are not deteriorated. it can.

The whiskers as the component (C) have an aspect ratio (fiber length / fiber diameter) of 3 or more, 50 or more.
Those of 0 or less, preferably 450 or less are used. If the aspect ratio is less than 3, the resin flow at the time of molding will not be sufficiently low, and if the aspect ratio exceeds 500, the impregnability into reinforcing fibers or the workability and moldability of prepreg will be adversely affected. These whiskers are not particularly limited, and examples thereof include aluminum borate, calcium carbonate, silicon carbonate, silicon nitride, potassium titanate, basic magnesium sulfate, zinc oxide, graphite, magnesia, calcium sulfate, magnesium borate, and diborate. One or more of titanium boride, α-alumina, chrysotile, etc. are appropriately used. Of these, aluminum borate, calcium carbonate, and silicon carbide whiskers are particularly excellent in properties and economical efficiency. The addition amount of these whiskers is 0.0 with respect to 100 parts by weight of the component (A).
5 to 30 parts by weight, preferably 0.5 to 15 parts by weight are used. If the amount is less than 0.05 parts by weight, the flow during molding will not be sufficiently reduced, and if it exceeds 30 parts by weight, the viscosity of the resin will increase and the impregnability into the fiber in the prepreg-forming step tends to deteriorate, such being undesirable.

In addition to the above components, if desired, a thermoplastic resin and an epoxide-reactive diluent are added to such an extent that the impregnability into the reinforcing fiber is not lowered or the reactivity, heat resistance, storage stability and the like are not lowered. May be. Examples of thermoplastic resin include phenoxy resin, polyvinyl butyral, polyvinyl formal, acetal resin such as polyvinyl phenyl acetal, polyether sulfone,
Examples thereof include polysulfone, polyetherimide, polyarylate and the like, and examples of the reactive diluent include phenyl glycidyl ether, butyl glycidyl ether, alkyl glycidyl ether, styrene oxide, octylene oxide and mixtures thereof. In addition, coupling agents such as silane and titanate compounds,
Additives such as releasing agents such as higher fatty acids and waxes, flame retardants such as halogens and phosphorus compounds, defoamers, colorants, low-temperature foaming agents and the like can be used if necessary.

The reinforcing fibers used in the production of these prepregs include carbon fibers, glass fibers, aramid fibers, polyester fibers, silicon carbide fibers, boron fibers,
Alumina fibers, polyethylene fibers, etc. may be mentioned, and one kind or two or more kinds of them may be appropriately used. Of these, carbon fiber is particularly preferable in terms of strength and conductivity of the obtained molded product after curing.

In order to manufacture the prepreg, a general prepreg manufacturing method can be applied, and the reinforcing base material is impregnated directly or by the film method, for example.
Either the direct impregnation method or the post-film-forming impregnation method may be used, but the solvent impregnation method requires a solvent distillation step and may reduce the stability of the resin composition, which is not preferable.

[0018]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples. The abbreviations of the compounds used in the examples and the test methods are as follows. <Raw material>"E828": Bisphenol A type epoxy resin (manufactured by Yuka Shell Co., Ltd.) "E1001": Bisphenol A type epoxy resin (manufactured by Yuka Shell Co., Ltd.) "PN-23", "MY-24": Amine adduct type Latent curing agent (manufactured by Ajinomoto Co.) "HX-3722": Microcapsule type latent curing agent (manufactured by Asahi Kasei Co., Ltd.) [E828 / curing agent = 2/3 parts by weight masterbatch] DICY: dicyandiamide (manufactured by Yuka Shell Co., Ltd.) ) DCMU: 3- (3,4-dichlorophenyl) -1,1
-N dimethyl urea (manufactured by Hodogaya Chemical Co., Ltd.) "Arborex YS2", "YS3": Aluminum borate whiskers (manufactured by Shikoku Chemicals Co., Ltd.) <Aspect ratio = 10 to 60>"Whiscals": calcium carbonate whiskers ( Shikoku Kasei Co., Ltd.) <Aspect ratio = 20 to 60>"R202": Fine silica, Aerosil R202 (manufactured by Nippon Aerosil Co., Ltd.)

<Measurement of resin flow> 10 prepregs
Cut to 0 x 100 mm and stack 4 plies,
After laminating the top and bottom perforated films and glass cloth on the outermost layer, press at 80 ° C and 3.5 kg / cm ² with a heating press,
Measure the resin flow.

<Evaluation of Winding and Furnace Falling> A prepreg was formed in an oblique layer (± 45 °) 3 ply and a straight layer (0 °) 3
It was cut to be ply. The cut prepreg was wound on a mandrel coated with a release agent by a rolling table. The heat shrink tape was then wrapped with a tape rubbing device. Suspend in a heating furnace with the large diameter side up, 80
Hardened at ℃ / 2 hours. After cooling to room temperature, measure the furnace falling.

<Handling workability: tackiness, drapeability> (Comprehensive judgment based on the laminated state of the oblique layer at 23 ° C., correctability, manual winding hardness, shaving after rolling table winding, etc.) ○: good, ×: bad

<Bending test (3-point bending)> ASTM D7
According to 90, device: UTM-made by Toyo Baldwin
Using 5T, sample shape: (length 100 mm, width 10
mm, thickness 2 mm), span length: 80 mm, crosshead speed: 2 mm / min.

<ILSS> According to ASTM D2344, sample shape: (length 12 mm,
Width 10 mm, thickness 2 mm), span length: 8 mm, crosshead speed: 2 mm / min.

(Example 1) 70 parts by weight of "E828",
30 parts by weight of E1001 was dissolved by stirring at 150 ° C. for 30 minutes and cooled to room temperature to obtain a base resin. This base resin is heated to 55 ° C and the "PN-23" is mixed with a stirrer to 2
A resin composition of the present invention was obtained by uniformly stirring and mixing 0 part by weight and 5 parts by weight of Arbolex YS2 for 30 minutes. A unidirectional prepreg was produced from the resin composition thus obtained and carbon fiber (manufactured by Toray Industries, Inc., "Torayca T300", elastic modulus 24 ton / mm ² ) by a hot melt method to obtain a prepreg of the present invention. The carbon fiber weight of this prepreg is 15
The resin amount was 0 g / m ² and the resin amount was 35%. This ply prepreg is laminated in one direction with 14 plies and autoclaved at 80 ° C.
A unidirectional laminate having a thickness of about 2 mm was molded by curing for 2 hours. Physical properties of the obtained composite material (Vf = 60% conversion value)
Is shown in Table-1.

This prepreg is easy to handle (tack,
Drapability) was good. In addition, the 10 shaft molded products obtained did not have any furnace falling. Further, the surface of this molded product was polished with a polishing machine and observed for surface defects (scratches, etc.), and good molded products without any defects were obtained.

(Examples 2, 3, 4, 5) Using the compositions shown in Table 1, resin compositions and prepregs of the present invention were obtained in the same manner as in Example 1. The workability of this prepreg was good, the molded product did not fall off the furnace, and no defects were observed on the polished surface.

(Comparative Example 1) According to the composition of Table-1, (C)
A prepreg was produced in the same manner as in Example 1 except that the components were not used. The basis weight of the prepreg is 150 g /
The resin amount was 35% in m ² . This prepreg had high tackiness, poor handleability, and large resin flow, and the furnace fell. Further, the occurrence of scratches after polishing the molded product was remarkable.

Comparative Example 2 A prepreg was produced in the same manner as in Example 1 except that "Aerosil R202" was used as the inorganic filler. The workability of this prepreg was relatively good, but the furnace fell, and the surface of the molded product was uneven.
Also, after polishing, several scratches occurred out of 10 scratches.

Comparative Example 3 According to the composition shown in Table 1, 4 parts by weight of DICY and 4 parts by weight of DCMU were used as the component (B),
A prepreg was produced by the same method as in Example 1 except that the component (C) was not used. The workability was poor, and the hardening was insufficient so that cutting was not possible.

[0030]

[Table 1]

[0031]

EFFECTS OF THE INVENTION The prepreg manufactured from the matrix resin containing the whiskers of the present invention can be appropriately adjusted in proper workability and resin flow at the time of molding, and can be molded by oven molding, internal pressure molding or the like. The law is flawless,
Also, since it can be cured at low temperature, it is also suitable for large-scale molding.
Various moldings having excellent composite material properties are obtained.
As described above, it is extremely useful for improving the reliability, productivity, and economic efficiency of the fiber-reinforced composite material.

Claims (6)

[Claims] 1. The following components (A), (B) and (C): (B) 3 to 60 parts by weight of a low temperature active latent curing agent and (C) an aspect ratio of 3 to 100 parts by weight of an epoxy resin (A). The epoxy resin composition for prepregs, characterized by containing 0.05 to 30 parts by weight of the whiskers of 500 or less. 2. The epoxy resin composition according to claim 1, wherein the low temperature active latent curing agent (B) is an amine adduct type latent curing agent. 3. The epoxy resin composition according to claim 1, wherein the low temperature active latent curing agent (B) is a microcapsule type latent curing agent. 4. The epoxy resin composition according to claim 1, wherein the whiskers (C) are aluminum borate. 5. The epoxy resin composition according to claim 1, wherein the whiskers (C) are calcium carbonate. 6. A prepreg obtained by impregnating a reinforcing fiber with the epoxy resin composition according to any one of claims 1 to 5.