JPH0526808B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a resin composition for composite materials having excellent toughness. [Prior Art] Composite materials made of reinforcing materials such as carbon fibers, glass fibers, and aromatic polyamide fibers and epoxy resins are used for premium sports applications such as golf shafts and fishing rods due to their high specific strength and specific modulus. Widely used for structural materials such as aircraft. However, the epoxy resins used in these composite materials have insufficient performance for applications that require greater strength and toughness, and there is a strong desire for the emergence of epoxy resins with superior toughness. Many techniques have been proposed for improving the toughness of epoxy resins. One method is to oxidize a rubber such as acrylonitrile-butadiene copolymer into an epoxy resin, and then cure the epoxy resin to form a rubber phase as a dispersed phase to prevent cracks and improve adhesive strength. (For example, Japanese Patent Laid-Open No. 57-21450). Other methods include adding thermoplastic resins such as polysulfone and polyarylate to epoxy resins.
It can be mixed to suppress the propagation of cracks in cured resin,
There are ways to use this resin to improve the toughness of carbon fiber reinforced composite materials (for example, THE
BRITISH POLYMER JOURNAL, VOL.15,
MARCH, 1983, P.71, 28TH SAMPE
SYMPOSIUM, 1983, P.367, Japanese Patent Application Publication No. 1983-
134126). However, these methods are unsatisfactory in dramatically improving the toughness of composite materials, and furthermore, when these rubbers and thermoplastic resins are mixed, the viscosity of the epoxy resin becomes extremely high, making it difficult to manufacture or mold prepregs. There are problems such as poor impregnation with the reinforcing material, and homogeneous mixing of the epoxy resin and the modifier is often impossible unless a common solvent is used for both. Modification of epoxy resins with various polyamide resins has also been studied for a long time. Japanese Patent Publication No. 40-1874 discloses an adhesive composition consisting of an epoxy resin and methanol-soluble nylon, and Japanese Patent Publication No. 55-71771 discloses a structure consisting of an epoxy resin, an alkenylphenol polymer, and copolymerized nylon or nylon 12. JP-A-56-152832 discloses a powder epoxy resin composition for coating films comprising a solid epoxy resin, a solid resol type phenolic resin, and a linear polyamide resin. Also, U.S. Patent Nos. 2705223 and 2986539 and Japanese Patent Application Laid-open No. 1986-
Publication No. 53913 discloses a composition comprising a dimer acid polyamide and an epoxy resin, or a prepreg comprising this composition and reinforcing fibers. The dimer acid polyamides used in these patents have a substantially sufficient amount of end groups to be used as curing agents for epoxy resins. The compositions made of epoxy resin and polyamide resin exemplified above are unsatisfactory in terms of performance from the viewpoint of improving the toughness of composite materials.
Also, its structure is clearly different from the present invention. Furthermore, compositions made of dimer acid-based polyamides and epoxy resins that are reactive with epoxy resins have a large increase in viscosity due to the reaction, making it difficult to produce homogeneous products during the resin mixing process or pre-regulating process with reinforcing materials. It is inconvenient to obtain it. [Problems to be Solved by the Invention] One object of the present invention is to provide a composite material resin composition with excellent toughness. The object of the present invention is to provide a strong resin composition for composite materials that has an appropriate viscosity and provides a homogeneous product in prepreg manufacturing and molding processes. [Means for Solving the Problems] In order to solve the above problems, the present invention has the following configuration. That is, it is a resin composition for a composite material, which contains the following [A], [B], and [C] as essential components. [A] Polyepoxide [B] Aromatic amine curing agent [C] High molecular weight dimer acid polyamide having a terminal group concentration of 5 x 10 ^-4 molar equivalents or less per 1 g of polyamide The polyepoxide that can be used in the present invention is A compound having on average more than one epoxy group in the molecule, which epoxy group may be present as a terminal group or internal to the molecule. The polyepoxide may be a saturated or unsaturated aliphatic, cycloaliphatic, aromatic or heterocyclic compound, and may further contain halogen atoms, hydroxyl groups,
It may be a compound containing an ether group, for example, glycidyl compounds of bisphenols A, F and S, glycidyl compounds of cresolvolak or phenol novolak, glycidyl compounds of aromatic amines, and cycloaliphatic epoxy resins. be. Specific examples of such polyoxides include 1,4
-bis(2,3-epoxypropoxy)benzene and 4,4'-bis(2,3-epoxypropoxy) diphenyl ether. Another example of polyepoxide is a glycylidyl compound of polyhydric phenol. Examples of polyhydric phenols that can be used for this purpose include resorcinol, catechol, hydroquinone, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), and 2,2-bis(4-hydroxyphenyl)butane. , bis(4-hydroxyphenyl)
Sulfone (bisphenol S), bis(4-hydroxyphenyl)methane, tris((4-hydroxyphenyl)methane, 3,9-bis(3-methoxy,4-hydroxyphenyl)-2,4,8 ，
10-tetraoxaspiro[5,5]undecane,
Furthermore, 2,2-bis(4-hydroxytetrabromophenyl)propane and the like are included as the halogen-containing wenols. Another example of a polyepoxide is a glycidyl compound of a polyhydric alcohol. Examples of polyhydric alcohols that can be used for this purpose include glycerol, ethylene glycol, pentaerythritol, and 2,2-bis(4-hydroxycyclohexyl)propane. Examples of polyepoxides with internal epoxy groups include 4-(1,2-epoxyethyl)-1,2-
Examples include epoxycyclohexane, bis(2,3-epoxycyclopentyl)ether, 3,4-epoxycyclohexylmethyl-(3,4-epoxy)cyclohexanecarboxylate, and the like. Another example of a polyepoxide is a glycidyl compound of an aromatic amine. Aromatic amines that can be used for this purpose include diaminodiphenylmethane, metaxylylene diamine, m-aminophenol, p-aminophenol, and the like. Among these polyepoxides, diglycidyl ether of bisphenol A, cresol novolac or phenolvolak glycidyl compounds, diglycidyl compounds of diaminodiphenylmethane and glycidyl compounds of aminophenol are preferably used. Specific examples of the aromatic amine curing agent used in the present invention include metaphenylene diamine, diaminodiphenylmethane, diaminodiphenyl sulfone, and diaminophenyl sulfone is particularly preferably used. Furthermore, boron trifluoride/amine complexes, imidazole compounds, and the like can also be used as curing accelerators. The dimer acid polyamide used in the present invention is a polyamide produced from a dicarboxylic acid whose main component is a dimer acid obtained by dimerizing an unsaturated higher fatty acid, and a diamine such as ethylene diamine or hexamethylene diamine. The unsaturated higher fatty acids used are obtained by polymerization of drying oils, semi-drying oils, or raw materials rich in these free acids or simple aliphatic alcohol esters of these acids, especially linoleic acid. The term "dimer acid" as used herein includes not only individual dimer acids but also mixtures of dimer acids. Dimer acid mixtures are often predominantly dimers, but also include trimers, polymers, and monomers. Various dimer acids can be used, but those obtained by polymerizing substances rich in norylic acid or linolenic acid are readily available. As the dimer acid polyamide used in the present invention, for example, one obtained from a dimer of linolenic acid is called "macromelt".
(manufactured by Henkel Japan).
The high molecular weight polyamide used in the present invention is a solid polyamide having a softening temperature in the range of approximately 100 to 200°C, and has a terminal group concentration of 5 x 10 ^-4 molar equivalents or less per 1 g of polyamide. The terminal group concentration refers to the total amount of terminal amino groups and terminal carboxyl groups. It is particularly important that the polyamide used in the present invention has a sufficiently high molecular weight; if the polyamide has a low molecular weight, that is, the terminal group concentration exceeds 5 x 10 ^-4 molar equivalents per gram of polyamide, its reactivity with polyepoxide will be reduced. In addition, in the process of mixing polyepoxide and polyamide and the process of impregnating it with reinforcing material to produce prepreg, the two react and the viscosity increases, making it difficult to produce high-quality prepreg. . The amount of polyamide used is 5 to 100 parts by weight per 100 parts by weight of the total amount of polyepoxide and curing agent.
Parts by weight are preferably used, preferably 10 to 30 parts by weight. When the amount of polyamide used is less than 5 parts by weight, the effect of improving the toughness of the composite material is small, while when it is more than 100 parts by weight, homogeneous mixing becomes difficult and the heat resistance of the resin is greatly reduced. There is no particular restriction on the method of mixing each component of the present invention,
A suitable method can be selected depending on the properties of each component and the mixing state or dispersion state of the target compound. (A), (B) as an example of the mixing method
There is a method of forming a homogeneous solution at a relatively low temperature using a solvent in which each component (C) is dissolved, and another method is of mixing each component at a relatively high temperature without using a solvent. In the latter case, it is preferable to first melt the polyepoxide and polyamide at a high temperature, lower the temperature, and then mix the curing agent. [Function] In the present invention, by combining a polyepoxide, an aromatic amine curing agent, and a high molecular weight dimer acid polyamide, the brittleness of the epoxy resin is improved and a strong resin composition for composite materials is provided.
The aromatic amine curing agent improves the heat resistance of the cured product, and the high molecular weight dimer acid polyamide improves the heat resistance of the cured product.
The toughness of the epoxy resin can be improved without causing inhomogeneous or undesirable increases in viscosity in the step of blending each component and the step of impregnating it with a reinforcing agent to produce a prepreg. [Example] The present invention will be explained in more detail with the following example. The amount of each component in the examples represents parts by weight,
The contents of the polyepoxide are as follows. Epoxy A: Bisphenol A diglycidyl ether, Epicote 828 manufactured by Yuka Ciel Epoxy Co., Ltd. Epoxy B: Bisphenol A diglycidyl ether oligomer, Epicoat 1001 manufactured by Yuka Ciel Epoxy Co., Ltd. Epoxy C: diaminodiphenylmethane tetraglycidyl compound, ELM434 manufactured by Sumitomo Chemical Co., Ltd. Epoxy D: Tetrabromobisphenol A diglycidyl ether, Epiclon 152 manufactured by Dainippon Ink Co., Ltd. Example 1 100 parts of epoxy A and 33 parts of dimer acid polyamide "Macromelt" 6238 (softening temperature 138°C, terminal group amount 1.7 x 10 ^-4 molar equivalent/g) were placed in a flask and heated to 150°C in an oil bath with stirring. Heated. A clear viscous liquid was obtained after 3 hours. 32 parts of diaminodiphenyl sulfone was added to this solution and quickly and uniformly dissolved. After depressurizing the flask and defoaming,
The blended resin was poured into a mold and cured at 180°C for 2 hours to obtain a semitransparent cured plate with a thickness of 2 mm. The glass transition temperature of the cured product (measured using a differential calorimeter at a heating rate of 40°C/min) was 175°C, and the crosshead speed was 2.5 using a Shimadzu Autograph IS-5000.
The tensile elongation at break measured at mm/min was 6.7%. Similarly, a cured board was made from a mixture of epoxy A and diaminodiphenylsulfone without adding polyamide. The glass transition temperature of this material is
The temperature was 186°C, and the elongation at break was 6.0%. From this example, it was revealed that a cured product in which the dimer acid polyamide was homogeneously dispersed was obtained without a significant decrease in the glass transition temperature of the cured product. Example 2 Instead of “Macromelt” 6238 in Example 1,
“Macromelt” 6224 (softening temperature 126℃, terminal group amount
2.1×10 ^-4 molar equivalent/g) to obtain a transparent solution consisting of polyepoxide and polyamide. Diaminodiphenyl sulfone was added to this solution to obtain a uniformly dissolved resin composition. Example 3 A resin composition was prepared in the same manner as in Example 1 using 60 parts of epoxy A, 40 parts of epoxy B, 31 parts of "Macromelt" 6238, and 24 parts of diaminodiphenylsulfone. When this was cured at 180°C for 2 hours, a transparent cured plate was obtained. This indicates that the epoxy resin and polyamide are molecularly mixed. Example 4 60 parts of epoxy A, 40 parts of epoxy B, 24 parts of diaminodiphenylsulfone and "Macromelt"
A transparent solution was prepared by dissolving 34 parts of 6238 in 240 parts of a mixed solvent of trichlene/ethanol (1/1 ratio). Apply this solution to a plain weave cloth using "Torayca" T300 manufactured by Toray Industries, Inc. so that the resin content is 41%.
Impregnated. After air drying for one day, the solvent was removed by heat drying, and a homogeneous prepreg with tackiness and drapability was obtained. 24 sheets of this prepreg were laminated and cured in an autoclave at 180°C for 2 hours at a pressure of 6 kg/cm ² to a thickness of approximately 5 mm.
obtained a composite material. A falling weight energy of 680 kg cm/cm (sample thickness) was applied to this composite plate using a weight with a tip radius of 16 mm. The degree of damage caused by this impact test was measured using an ultrasonic deep damage imager model M400B manufactured by Canon Holosonic. The damaged area is shown in Table 1. Example 5 A composite material was prepared in the same manner as in Example 4, except that "Macromelt" 6900 was used instead of "Macromelt" 6238 in Example 4, and an impact test was conducted.
The results are shown in Table 1. Comparative Example 1 The polyepoxide and diaminodiphenylsulfone of Example 4 were dissolved in 190 parts of methyl ethyl ketone, and a composite material prepared in the same manner as in Example 4 was subjected to an impact test. The results are shown in Table 1. Example 6 35 parts of epoxy A, 35 parts of epoxy C, epoxy
A composite material was prepared in the same manner as in Example 4 using a resin composition consisting of 30 parts of D, 20 parts of "Macromelt" 6900, and 34 parts of diaminodiphenylsulfone, and an impact test was conducted. The results are shown in Table 1. Comparative Example 2 The polyepoxide and diaminodiphenylsulfone of Example 6 were dissolved in 190 parts of methyl ethyl ketone, a composite material was prepared in the same manner as in Example 4, and an impact test was conducted. The results are shown in Table 1.

【table】

〔Effect of the invention〕

(1) Impact damage to composite materials is reduced. (2) A homogeneous resin composition can be prepared by using or not using a solvent. (3) A resin composition with high heat resistance is provided. (4) Prepreg and composite materials with stable quality can be produced. (5) Can be molded using an autoclave without requiring special conditions. (6) A transparent resin composition or cured resin can be obtained by combining the constituent components.

Claims (1)

[Scope of Claims] 1. A resin composition for a composite material comprising the following [A], [B] and [C] as essential components. [A] Polyepoxide [B] Aromatic amine curing agent [C] High molecular weight dimer acid-based polyamide 2 having a terminal group concentration of 5 x 10 ^-4 molar equivalents or less per 1 g of polyamide 2 In claim 1, [B] ] A resin composition for a composite material, the component of which is diaminodiphenylsulfone.