JPH06166765A - Prepreg - Google Patents

Abstract

PURPOSE:To provide a prepreg excellent in handleability, moldability and mechanical strength. CONSTITUTION:The objective prepreg can be obtained by impregnating reinforcing fibers with a resin composition which is prepared by mixing, as curing agent, an urea derivative and/or dicyandiamide (DICY) and 1-6 pts.wt. of a polyvinyl acetal resin with (A) 100 pts.wt. of a preliminary reaction product obtained by reaction of (1) 5-10 pts.wt. of diaminodiphenylsulfone with (2) 100 pts.wt. of an epoxy resin <=500 in epoxy equivalent, having 1.8-2.5 epoxy groups in one molecule on an average.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in prepreg.

[0002]

2. Description of the Related Art Conventionally, a prepreg obtained by impregnating a unidirectionally aligned sheet such as carbon fiber, glass fiber and aromatic polyamide fiber or a woven fabric with a matrix resin has excellent mechanical properties after curing and molding. It is used in a wide range of applications, from aircraft to sporting goods such as fishing rods and golf shafts.

Such a prepreg is excellent not only in mechanical properties after curing but also in handleability [having appropriate tack (adhesiveness) and drapeability (flexibility)]. In addition, characteristics such as low resin flow during molding are required.

In response to such a request, Japanese Unexamined Patent Publication No. S58-872
No. 4 discloses a method for reducing surface tackiness by adding a polyvinyl formal resin to an epoxy resin,
Further, JP-A-60-155224 discloses a method of obtaining a resin for electronic parts having a low internal stress by blending an epoxy resin with a novolac type phenol resin and a polyvinyl acetal resin.

As described above, the polyvinyl acetal resin has good compatibility with the epoxy resin and is used for improving various epoxy resins, and various mixed fibers are impregnated with various reinforcing fibers to be used as a prepreg. It is also known.

[0006]

However, in the case of a chemical substance containing a functional group having a strong hydrogen-bonding property, the compatibility with the polyvinyl acetal resin is poor, and for example, dicyandiamide (DICY) is used as a curing agent, and the polyvinyl acetal resin is used. When the melted and homogenized epoxy resin is cured, a large amount of phase separation occurs during curing, and this phase separation causes a decrease in strength of the composite material after molding.

As a method for solving this problem, Japanese Patent Laid-Open No.
No. 3-37135 discloses a method of suppressing phase separation while using polyvinyl formal and DICY together by using a bisphenol type and phenol novolac type epoxy resin having a specific molecular weight. The bisphenol-type epoxy resin and the phenol novolac resin, which are limited to the above, are essential components.

The present invention solves the above conventional problems,
It is an object to provide a prepreg excellent in handleability, moldability, and mechanical strength.

[0009]

The present invention has the following constitution in order to achieve the above-mentioned conventional problems. That is, the present invention has an epoxy equivalent of 500 or less and an average of 1.8 in the molecule.
Diaminodiphenyl sulfone (DDS) 5 to 100 parts by weight of an epoxy resin having ˜2.5 epoxy groups
Preliminary reaction product [component A] 1 in which 10 to 10 parts by weight have been previously reacted
To 100 parts by weight of polyvinyl acetal resin [component B] 1
It is a prepreg characterized in that a reinforcing fiber is impregnated with a resin composition obtained by dissolving and mixing 6 to 6 parts by weight and mixing a urea derivative and / or dicyandiamide (DICY) [C component] as a curing agent.

The epoxy resin which is the component A in the present invention is not particularly limited as long as it has an average of 1.8 to 2.5 epoxy groups in the molecule and an epoxy equivalent of 500 or less. An epoxy resin having an epoxy equivalent of 300 or less is particularly preferable. When the epoxy equivalent exceeds 500, D
It is not preferable because the viscosity of the component A, which is a pre-reacted product with DS, becomes too high and the subsequent workability deteriorates.

In the present invention, a typical example of the epoxy resin preferably used is a bisphenol type epoxy resin, and among these, a bisphenol A type epoxy resin is particularly preferable from the viewpoints of handleability and economy.

Incidentally, in order to have various characteristics, it is possible to mix and use several kinds of epoxy resins, and modified products of the above epoxy resins can also be used.

Furthermore, the amount of DDS added to the pre-reacted component A must be 5 to 10 parts by weight with respect to the epoxy resin, and if it is less than 5 parts by weight, the effect of using this pre-reacted product is recognized. On the contrary, if it exceeds 10 parts by weight, gelation may occur in the preliminary reaction product, which is dangerous.

As the component A in the present invention, it is extremely important to use a preliminary reaction product obtained by previously reacting an epoxy resin with DDS, and the structure formed by this preliminary reaction serves to suppress excessive phase separation. A mixture obtained by simply mixing the epoxy resin and DDS cannot obtain such an effect. The preliminary reaction in this case is 120
It is desirable to carry out the treatment at a temperature of ˜160 ° C. for 1 to 20 hours depending on the desired molecular weight of the component A.

The polyvinyl acetal resin as the component B in the present invention plays a role of controlling the handling property (tack and drape property), and normally, if 5 parts or more is not added, such a controlling effect is not exhibited. Shows the controllability of the handleability with the addition amount of 1 to 6 parts by using the component A which is the above-mentioned preliminary reaction product, and it is better to add less than the addition amount of DDS in order to fully exert this control effect. Usually, a sufficient effect is obtained with 4 parts or less. In this case, if the addition amount of the polyvinyl acetal resin exceeds 6 parts, the viscosity of the resin increases and adjustment becomes difficult, and the mechanical properties after curing are also adversely affected, which is not preferable.

As the polyvinyl acetal resin of the component B, polyvinyl butyral or polyvinyl formal is preferably used, and it comprises a vinyl acetal part, a vinyl alcohol part, and a vinyl acetate part, and contains 70% or more of a vinyl acetal part, Average degree of polymerization is 10
It is preferably 00 or less.

There is no particular limitation on the method of adding the component B,
Since it does not affect the reaction between epoxy and DDS, DD
It may be dissolved in the epoxy before reacting with S, and may be dissolved while reacting the epoxy and DDS, or may be dissolved directly in the component A. In short, it is sufficient that the B component is dissolved in the A component before finally being cured by the C component which is the curing agent.

As the C component which is the curing agent in the present invention, a urea derivative and / or DICY is preferably used.

[0019]

EXAMPLES The present invention will be described in more detail with reference to the examples below. The abbreviations of the compounds in the examples and the respective test methods are as follows. All curing conditions were 130 ° C. × 1 hour.

EP828: Bisphenol A type epoxy resin (made by Yuka Shell Co., Ltd.) [Epoxy equivalent 184 to 194] EP834: Bisphenol A type epoxy resin (made by Yuka Shell Co., Ltd.) [Epoxy equivalent 230 to 270] EP1001: Bisphenol A type Epoxy resin (Okaka Shell Co., Ltd.) [Epoxy equivalent 450-500] DDS: Dimethyldiphenylsulfone PVF: Polyvinyl formal Vinilek K (Chisso) PVB: Polyvinyl butyral Denka butyral # 3
000-1 (manufactured by Denka) DCMU: 3,4-dichlorophenyl-N, N-dimethylurea DICY: dicyandiamide

[Bending test (3-point bending)] Device: Orientec Tensilon Sample shape: length 120 mm, width 10 mm, thickness 2 m
m Span length: 80 mm (L / D = 40) Indenter tip radius: 3.2 mm Crosshand speed: 1 mm / min Physical property values were calculated by the following formulas. Flexural strength (FS) = 3PL / 2wt ² [kg / mm ² ] Flexural modulus (FM) = P′L ³ / 4wt ³ a [kg / mm
² ]

However, P: maximum load [kg] L: span length [mm] w: sample width [mm] t: sample thickness [mm] a: initial deflection (crosshead displacement) [mm] p ': a Load [kg]

[Interlaminar Shear Strength (ILSS)] Device: Orientec Tensilon Sample shape: length 20 mm, width 10 mm, thickness 2 mm Span length: 80 mm (L / D = 4) Indenter tip radius: 1.6 mm Cross Hand speed: 1 mm / min Physical property values were calculated by the following formula. ILSS = 3P / 4wt [kg / mm ² ]

Example 1 EP828: 100 parts by weight of DDS was reacted with 100 parts by weight of DDS at 150 ° C. for 2 hours to 100 parts by weight of a preliminary reaction product (component A), and 4 parts by weight of PVF (component B) was added. In addition, dissolve and mix at 150 ° C for 3 hours,
4 parts by weight of DCMU and 4 parts of DICY (C component) were added to this mixture.
Parts by weight were added, and the mixture was uniformly mixed at 50 ° C. for 3 hours. The obtained resin composition and high-strength carbon fiber (TR manufactured by Mitsubishi Rayon Co., Ltd.
40, elastic modulus 24 t / mm ² ), and carbon fiber areal weight 20
A unidirectional prepreg with 0 g / m ² and a fiber volume content (Vf) of 60% was produced by the hot melt method.

When the obtained prepreg was subjected to a winding test in a room at 18 ° C. with a pipe having a diameter of 10 mm,
Both tack and drape were good. Further, when this prepreg was placed on an iron plate at 40 ° C. and a winding test was carried out in the same manner, the handling property was good.

Further, this prepreg is set to 500 mm × 50
When cut into 0 mm, laminated at 0 ° / 90 °, and pressed at 85 ° C. and 20 kg / mm ² for 3 minutes with a press, the initial length (707 mm) of the diagonal length including the resin that has flowed out
The amount of increase (defined as resin flow) is 5
The average point was 2.2 mm, which was very small.

The prepreg was laminated in one direction to a thickness of 2 mm and molded in an autoclave under the conditions of a molding pressure of 1 atm, a molding temperature of 130 ° C. and a molding time of 1 hour. The obtained molded product was subjected to a bending test at 0 ° and 90 ° and an ILSS test, and the results are shown in Table 1.

(Example 2) A prepreg was produced under the same conditions as in Example 1 except that PVB was used instead of PVF as the B component. A winding test was conducted on the obtained prepreg in the same manner as in Example 1.
The tackiness and drapeability at 8 ° C. and 40 ° C. were good. The resin flow and mechanical properties were also measured in the same manner, and the results are also shown in Table 1.

(Example 3) EP834: 70 parts by weight and E
P100 1:30 30 parts by weight PVF 3 parts by weight 15 parts
Dissolve at 0 ° C x 3 hours, add 5 parts by weight of DDS to it,
The reaction was performed at 150 ° C. for 3 hours to obtain a resin in which the component B was dissolved in the component A, 4 parts by weight of DCMU was added to this resin, and the mixture was uniformly mixed at 50 ° C. for 30 minutes. A prepreg similar to that of Example 1 was formed using the obtained resin composition,
When a winding test was conducted in the same manner as in Example 1, it was found to be 18
The tack and drape properties were also good at ℃ and 40 ℃. The resin flow and mechanical properties were also measured, and the results are also shown in Table 1.

(Comparative Example 1: Example without using DDS) DD
A prepreg was formed in the same manner as in Example 1 using the resin composition produced in the same manner as in Example 3 except that S was not added. The obtained prepreg was subjected to a winding test, a resin flow test and a mechanical property measurement test in the same manner as in Example 1. The winding test showed a slightly tight tack at 40 ° C. The other results are shown in Table 1. As is clear from Table 1, the mechanical properties were not so good.

(Comparative Example 2: Example in which DDS and epoxy resin are not preliminarily reacted) EP834: 70 parts by weight and EP10
01:30 parts by weight of PVF 3 parts by weight 150 ° C ×
It was dissolved in 3 hours, 5 parts by weight of DDS and 4 parts by weight of DCMU were added thereto, and the mixture was uniformly mixed at 50 ° C. for 30 minutes. Using this resin composition, a prepreg was formed in the same manner as in Example 1. The obtained prepreg was subjected to a winding test, a resin flow test, and a mechanical property measurement test in the same manner as in Example 1. The winding test showed a slightly tight tack at 40 ° C. The other results are shown in Table 1. As is clear from Table 1, the mechanical properties were not so good.

(Comparative Example 3: Example not using component B) EP
828: 15 parts of DDS 10 parts by weight for 100 parts by weight
Preliminary reaction product (component A) 100 reacted at 0 ° C for 5 hours
4 parts by weight of DCMU and 4 parts by weight of DICY (component C) were added to the parts by weight, and they were uniformly mixed at 50 ° C. for 3 hours. A prepreg was formed in the same manner as in Example 1 using the obtained resin composition. When the obtained prepreg was subjected to a winding test, a resin flow test and a mechanical property measurement test in the same manner as in Example 1, the winding test showed that there was not much tack at 18 ° C. The other results are shown in Table 1. As is clear from Table 1, the resin flow was quite large.

[0033]

[Table 1]

[0034]

According to the present invention constructed as described above,
The following excellent effects are obtained. (1) Since it has appropriate tack and drape, it can be used along a complicated mold, and can be easily wound around a mandrel, etc., and its excellent handleability is insensitive to ambient temperature. In the range of 18 ° C to 40 ° C, it has the same handling property.

(2) Since the resin flow during molding is suppressed, the molding accuracy is excellent and the physical properties after molding are stable. (3) The mechanical properties after molding are very excellent.

Claims (3)

[Claims] 1. A diaminodiphenyl sulfone (D) based on 100 parts by weight of an epoxy resin having an epoxy equivalent of 500 or less and having an average of 1.8 to 2.5 epoxy groups in the molecule.
DS) 5 to 10 parts by weight of a preliminary reaction product [A
Ingredient] 100 parts by weight of polyvinyl acetal resin [B
Component] 1 to 6 parts by weight are dissolved and mixed, and a reinforcing fiber is impregnated with a resin composition in which a urea derivative and / or dicyandiamide (DICY) [C component] is mixed as a curing agent. 2. The polyvinyl acetal resin as the B component comprises a vinyl acetal portion, a vinyl alcohol portion, and a vinyl acetate portion, contains 70% or more of the vinyl acetal portion, and has an average degree of polymerization of 1,000 or less. The prepreg according to 1. 3. The prepreg according to claim 1, wherein the reinforcing fiber is carbon fiber, aramid fiber, glass fiber or boron fiber.