JPS621408B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a fiber-reinforced plastic (hereinafter abbreviated as FRP) having excellent composite physical properties.
The present invention relates to a low viscosity curable resin composition for producing. More specifically, it cures in a short time and has high heat resistance.
This invention relates to a curable resin composition with low viscosity and long pot life for producing FRP by filament winding method. The filament winding method is a molding method in which reinforcing material is impregnated with liquid resin and wound around a mandrel, and has traditionally been used to manufacture pipes and tanks. This molding method is limited by the continuous use of resin as a reinforcing material and the long pot life of the resin composition in order to manufacture large molded products.Currently, epoxy resins are mainly used as resins. However, unsaturated polyester resin is used. Epoxy resins have excellent physical properties and heat resistance for cured products, but because they generally have high viscosity, there are few resins that are suitable for filament winding, and the ones that can be used for filament winding are
There are only a limited number of types, such as those that contain a low-viscosity reactive diluent and those that use a low-viscosity acid anhydride as a hardening agent. Those with reactive diluents have lower heat resistance, and those with acid anhydride hardeners have lower heat resistance.
Moisture absorption of the curing agent during filament winding affects the curing characteristics and tends to cause performance deterioration. Furthermore, both have long curing times. On the other hand, unsaturated polyester resins have low viscosity, long pot lives, and cure in a short time, but have low heat resistance.
Furthermore, when unsaturated polyester resin uses carbon fiber as a reinforcing material, FRP with high interlaminar shear strength cannot be obtained due to poor adhesion to the carbon fiber and low elongation of the resin. Therefore, in order to overcome the drawbacks of epoxy resins and unsaturated polyester resins, curable unsaturated polyesters, that is, vinyl esters, were developed by adding α, β unsaturated carboxylic acids such as acrylic acid and methacrylic acid to epoxy resins. . This resin has both the excellent physical properties of a cured product of an epoxy resin and the curability of an unsaturated polyester resin, and has largely overcome the drawbacks of both of the above, but a resin with good heat resistance has not been obtained. As described above, epoxy resin, unsaturated polyester resin, and vinyl ester resin each have their own drawbacks, and they are suitable for use in FRP matrices for industrial materials such as drive shafts, which are expected to be mass-produced using the filament winding method in the near future. There is no resin that completely satisfies the characteristics required of a resin: good mechanical properties, high heat resistance, low viscosity, long pot life, and short curing time. Therefore, the present inventors conducted research to develop a matrix resin for filament winding that satisfies the above-mentioned requirements, and as a result, they arrived at the present invention. That is, in the present invention, unlike conventional vinyl ester resins, a crosslinking monomer such as styrene is added to a compound in which an epoxy resin and α,β unsaturated carboxylic acid such as acrylic acid or methacrylic acid are reacted in advance to form radicals. Rather than curing through polymerization, epoxy resin, unsaturated carboxylic acid, crosslinking monomer, and radical initiator are mixed and heated to cause a reaction between epoxy groups and carboxylic acid at the same time as radical polymerization, resulting in curing. It is characterized by this. Therefore, the curing time is as short as unsaturated polyester. However, since the present invention only mixes monomers that are difficult to react at room temperature, the product has a low viscosity and a very long pot life. Furthermore, since the present invention only needs to mix the monomers in the required proportions at the time of use, there is no need to worry about changes in the concentration composition over time or denaturation as with conventional unsaturated polyester resins and vinyl ester resins. Furthermore, since the present invention uses an epoxy resin, it has excellent adhesion to carbon fibers. In the present invention, as described above, since the reaction between epoxy groups and carboxylic acid must occur simultaneously with radical polymerization, the epoxy resin used is an epoxy resin that reacts quickly with carboxylic acid without a catalyst and only by heating. It must have a group. As described above, as epoxy resins, compounds having an epoxy group in the alicyclic carbon skeleton have excellent heat resistance and physical properties of cured products. However, since alicyclic epoxy compounds have high water absorption, they have poor water resistance, so it is necessary to improve the water absorption. However, in the present invention, heat resistance is improved by adding a novolak type epoxy resin. The aim is to reduce the water absorption rate without reducing it. In the present invention, the amount of novolac type epoxy resin added is determined by
30 to 180 parts by weight per 100 parts by weight, preferably 50 to 180 parts by weight
It is preferable to mix within the range of 150 parts by weight; if the amount exceeds this range, the heat resistance will decrease, while if the amount decreases, the reduction in water absorption will not be sufficient, which is not preferable. The novolak type epoxy compound may be used in the form of a monomer, or may be reacted with an unsaturated carboxylic acid in advance and used as a vinyl ester. When a novolak type epoxy compound is used as a monomer, an amine catalyst is required to carry out the epoxy-carboxylic acid reaction, but when it is used as a vinyl ester, a radical initiator is required as a catalyst. Just that is enough.
Furthermore, when used as a vinyl ester,
The viscosity of the resin composition will be slightly higher, but if the alicyclic epoxy compound and carboxylic acid are reacted at room temperature or low temperature, the viscosity of the resin composition will be 10 ⁵ to 10 ⁸ poise at room temperature. Good prepreg and SMC can be manufactured. Next, as compounds having an epoxy group in the alicyclic carbon skeleton used in the present invention, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carbonate, 3,4-epoxy-6-methylcyclohexylmethyl -3,4-epoxy-6-
Methylcyclohexanecarboxylate, bis(3,4-epoxy-6-methylcyclohexylmethyl)adephate, bis(2,3-epoxycyclopentyl)ether, 2,2-bis(3,
4-epoxycyclohexyl)propane, cyclohexene vinyl monooxide, and the like. Examples of novolak type epoxy compounds include phenol novolak type epoxy compounds and O-cresol novolak type epoxy compounds. The carboxylic acid used in the present invention must be an unsaturated carboxylic acid capable of radical polymerization because it must react with an epoxy group and undergo radical polymerization. That is, the carboxylic acid used in the present invention is a dibasic acid such as maleic acid or fumaric acid, or a carboxylic acid having the general formula CH ₂ =
There are carboxylic acids represented by (CH ₂ ) _o COOH, such as acrylic acid, methacrylic acid, vinyl acetic acid, allyl acetic acid, and Δ-n-hexinoscinic acid. Further, part or all of the unsaturated carboxylic acid used in the present invention may be a carboxylic anhydride. Next, 1 equivalent of carboxylic acid may be used per 1 equivalent of epoxy group in the epoxy resin used in the present invention. However, this ratio may be changed for the purpose of adjusting the physical properties, pot life, viscosity, etc. of the cured product depending on the requirements, but in order to effectively carry out the present invention, it is necessary to On the other hand, carboxylic acids are preferably mixed in a proportion of 0.6 to 1.4 equivalents. Furthermore, the crosslinking monomer used in the present invention may be any monomer that undergoes radical polymerization such as styrene, diallyl phthalate, diallyl isophthalate, acrylic ester, and methacrylic ester, but from the viewpoint of heat resistance, styrene , diallyl phthalate, and diallyl isophthalate are preferred. The mixing ratio of the crosslinkable monomer in the resin composition is preferably 0.1 to 60% by weight, more preferably 10 to 40% by weight. The curing temperature for effectively implementing the present invention is 80~
A range of 160°C is preferred. For this reason, the radical initiators used in the present invention, such as benzoyl peroxide, t-butyl perbenzoate, dicumyl peroxide, and di-t-butyl peroxide, are suitable for radical initiators in the temperature range of 80 to 160°C. Any radical initiator that causes polymerization may be used, and is not particularly limited. To further improve mechanical properties and heat resistance,
Post-curing for 60 minutes is preferred. The heat distortion temperature of the cured resin of the present invention cured in this way is 150
℃ or more, and the interlaminar shear strength of FRP made of the resin composition of the present invention and carbon fiber is 10 to 12 Kg/mm ²
It has excellent composite physical properties. The present invention can use any reinforcing material that is normally used as a reinforcing material for FRP, such as glass fibers, organic fibers, and carbon fibers, and can also be applied to the case of using a mixture of carbon fibers, glass fibers, etc. Furthermore, the resin composition according to the present invention is not only suitable for filament winding, but also has a low viscosity and a long pot life. It is suitable not only as a composition, but also as a resin composition for SMC and prepreg. In carrying out the present invention, anhydrous silica,
Pigments, internal mold release agents, fillers, etc. may be added. Hereinafter, the content of the present invention will be explained in more detail with reference to Examples. Example 1 3,4-epoxycyclohexylmethyl-3,
4-Epoxycyclohexanecarboxylate 31
g and phenol novolac type epoxy resin Ep-
40g of vinyl ester obtained by reacting 152 (manufactured by Ciel Chemical Co., Ltd.) with acrylic acid and acrylic acid 17
g, 12 g of diallyl phthalate, and 1 g of t-butyl perbenzoate were added and mixed uniformly to prepare a resin liquid. In addition, vinyl ester is 27g of Ep-152.
It was synthesized by reacting 13g of acrylic acid with 13g of acrylic acid. The viscosity of this resin liquid measured with a B-type viscometer at 25°C was about 3 poise, and the pot life at 25°C was more than 24 hours. Next, in order to evaluate the performance of the resin composition, "Torayka" T-300 carbon fiber obtained by firing and surface-treating polyacrylonitrile fiber was impregnated with the resin liquid and was woven in one direction with a width of 20 cm. Prepreg was produced. The obtained prepreg was cut to a length of 30 cm, and 12 sheets were laminated, wrapped with Tetron taffeta, sandwiched between two Tetron films, and inserted between the hot plates of a hydraulic press to produce 7 kg/cm ^2. The film was cured at 140°C for 15 minutes under pressure. Furthermore, the obtained cured plate was post-cured at 165°C for 30 minutes. The carbon fiber content of the obtained cured board is 62% by volume
and ASTM-D-2344 and ASTM-D-
Interlaminar shear strength (ILSS) measured according to 790
) and bending properties are shown in the table, indicating that the composite had excellent physical properties. In addition, the strength retention rate at 150°C was 60% or more, and the strength retention rate after 20 hours of boiling was also 45% or more, indicating good water resistance.

【table】

[Table] Comparative example 3,4-epoxycyclohexylmethyl-3,
4-Epoxycyclohexanecarboxylate 55
g, 32 g of acrylic acid, 13 g of diallyl phthalate, and 1 g of t-butyl perbenzoate were added and mixed uniformly to prepare a resin liquid. The viscosity of this resin liquid measured with a B-type viscometer at 25°C was less than 1 poise, and the pot life at 25°C was more than 24 hours. Next, in order to evaluate the performance of the resin composition, a cured plate was made in the same manner as in Example 1, and the physical properties were evaluated. The results are shown in the table, and the heat resistance before boiling was slightly better than in Example 1. However, after 20 hours of boiling, the physical properties deteriorated significantly and the water resistance was poor.

【table】

[Table] Example 2 A resin liquid was prepared in the same manner as in Example 1, except that 3 g of acrylic acid and 14 g of maleic anhydride were used instead of 17 g of acrylic acid in Example 1, and the same procedure as in Example 1 was carried out. A hardened plate was made and its bending properties were evaluated. As shown in the table, the results were good in both heat resistance and water resistance.

【table】

Claims (1)

[Claims] 1 Compound 100 having an epoxy group in the alicyclic skeleton
30 to 30 parts by weight of novolak type epoxy compound
A matrix resin for fiber-reinforced composite materials containing 180 parts by weight of an epoxy resin, an unsaturated carboxylic acid, a crosslinking monomer, and a catalyst. 2. The matrix resin for fiber-reinforced composite materials according to claim 1, which contains a novolak type epoxy compound as a vinyl ester obtained by reacting the compound with an unsaturated carboxylic acid.