JPH02105816A - Epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain an epoxy resin compsn. capable of providing a prepreg, with excellent toughness and flexibility and good workability and storage stability by incorporating a modifier having a straight-chain structure prepd. by modifying a sec. amine deriv. with an epoxy resin as an additive. CONSTITUTION:A modifier having a straight-chain structure prepd. by modifying a sec. amine deriv. of formula I (wherein R1 and R2 are each an alkyl, a cycloalkyl, an aryl or an aralkyl; A is a divalent group) (e.g., a compd. of formula II, III or IV) with an epoxy resin (conventional well-known epoxy resins can be used as they are) is incorporated in an epoxy resin as an additive to obtain an epoxy resin compsn. capable of providing a prepreg with excellent mechanical characteristics, specially toughness and flexibility, and good workability and storage stability.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an epoxy resin composition, and more specifically, to a prepreg having excellent mechanical properties, particularly toughness and flexibility, as well as good work stability and storage stability. The present invention relates to an epoxy resin composition that can be applied.

[Prior art]

Generally, epoxy resin compositions have heat resistance, elastic modulus, hardness,
Although it has excellent chemical resistance, it has the disadvantage of poor flexibility and toughness.

Recently, as a curing agent that increases the flexibility and toughness of epoxy resin compositions, the general formula (wherein R is an alkyl group having 1 to 3 H1 carbon atoms)
H is a group selected from an alkyl group having 1 to 3 carbon atoms and an electron-withdrawing group; n is an arbitrary number from 1 to 5). Epoxy resin curing agent (JP-A No. 61-40318) and the general formula R4, which is a further improved version of such epoxy resin curing agent, represent hydrogen, an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group, and ■ and Y' represent hydrogen. .

In the alkyl group or electron-withdrawing group, m and n indicate the number of substituents and represent an integer of 1 to 4. ) or a combination of such a curing agent and another specific curing agent (Patent Application No. 10885/1989 filed by the present applicant)
No. 9, Japanese Patent Application No. 108860/1983) has been proposed.

Epoxy resin prepregs using such curing agents have superior flexibility and toughness compared to conventional ones, but on the other hand, they do not have sufficient work stability and storage stability, which are important properties required for prepregs. For example, if left at room temperature for several hours, the properties of the prepreg such as tackiness and drapability will significantly deteriorate as the reaction progresses. Not only is it difficult to handle, but it also lacks long-term storage.

On the other hand, JP-A-61-223019, JP-A-61-23
No. 1021 etc., in order to improve the toughness of epoxy resin,
Blends of various thermoplastic resins have been proposed, but due to their high viscosity, these systems have poor workability when manufacturing prepregs, and furthermore, it is difficult to control the tackiness and drape properties of the resulting prepregs. Met.

〔the purpose〕

An object of the present invention is to provide a novel epoxy resin curing agent for prepregs that can provide epoxy resin prepregs with excellent mechanical properties, particularly flexibility and toughness, and good work stability and storage stability. .

〔composition〕

According to the present invention, it is characterized in that it is obtained by modifying a secondary amine derivative represented by the following general formula (1) with an epoxy resin and contains a modified product having a linear structure as an additive. An epoxy resin composition is provided.

R, NH-A-NHR.

(In the formula, R1 and R2 represent an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group, and A represents a divalent group.) As a result of intensive studies on additives that provide epoxy resin compositions with excellent work stability and storage stability, we found that additives that can be obtained by modifying the secondary amine derivative represented by the general formula (1) with an epoxy resin and directly It was discovered that a modified product having a chain structure is suitable for the above purpose. The present invention was made based on these findings.

To synthesize the additive used in the present invention, the general formula (1
) The secondary amine derivative represented by ) and the epoxy resin may be mixed directly or with the addition of a solvent and, if necessary, a reaction accelerator, to form a compound having a linear structure.

Solvents include alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, aromatic hydrocarbons such as benzene and toluene, and reaction accelerators include boron fluoride, triarylphosphine,
Imidazoles, tertiary amines, etc. can also be used.

The ratio of the secondary amine derivative to the epoxy resin varies depending on the types of raw materials used and reaction conditions, but the equivalent ratio is usually 1:20 to 1=1. Preferably 1:1G-1
:1 is better.

The reaction temperature is usually 20 to 180°C, preferably 30 to 15°C.
It is 0°C. When the reaction is carried out at a high temperature, it is preferable to carry out the reaction in as short a time as possible.

In addition, A- in the above structural formula represents a divalent group, specifically a divalent aliphatic hydrocarbon group which may have a substituent. is most effective when A is a divalent aliphatic hydrocarbon group, especially -CH,-, and then preferably A is an alkylene group having 1 to 3 carbon atoms, and as A (in the formula, R3 and R9 represents hydrogen, an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group; Y and Y' represent hydrogen, an alkyl group, or an electron-withdrawing group; m and n represent the number of substituents; According to the results of research experiments conducted by the present inventors, no matter which structure is selected, the toughness of the cured epoxy resin is In this case, it was found that the toughness was slightly inferior to the cases -〇〇 and -, but it was found to be advantageous in terms of heat resistance.

Further, as mentioned above, when A is a divalent aliphatic hydrocarbon group which may have a substituent, those having 1 to 6 carbon atoms, particularly those having 1 to 3 carbon atoms are particularly preferable. When the number of carbon atoms is 7 or more, the hardness of the cured epoxy resin increases.

The disadvantage is that heat resistance decreases.

In addition, Y and Y' in the above structural formula are 11 and have 1 to 6 carbon atoms.
Examples of the electron-withdrawing group include a halogen group such as F, CL Br, a nitro group, and a trifluoromethyl group. Among these, preferred are H or carbon number 1
-3 alkyl group, CQ, and if the number of carbon atoms is 7 or more, the hardness and heat resistance of the cured epoxy resin will be reduced.

Particularly preferable examples of the secondary amine derivatives represented by maximum (1) above are as follows.

CH3N)l (α2 soup mouth.

CH 1 volume * Tamejiru Inasai.

Panfu * Tamejiru Akebono Fake NHH side 2sho l□ Meiji (Torijiru Naishu H7) Between H6 CH3 CH3NH-CH-CH2-NHC,H.

9・ C) l, Nu-01-DI2-CH,C,H.

−・ CI, N)f-C-c)l, -NIICH.

C.I.

sound α, NH-C horse-C-CH, -NHOI.

Hm- H C) l, NH-DI-CH2-NHCH.

Br CH,N)I-C)l-CH2-NHC)l.

u13 (-x Its) As the epoxy resin used to modify the secondary amine derivative represented by the above general formula (1), conventionally known epoxy resins can be used as they are, and specific examples thereof include, for example, , (1) Glycidyl ether epoxy resin (bisphenol A.

F, S-based epoxy resin, novolac-based epoxy resin,
(brominated bisphenol A-based epoxy resin): (2) cycloaliphatic epoxy resin; (3) glycidyl ester-based epoxy resin; (4) glycidylamine-based epoxy resin;
5) Heterocyclic epoxy resin; Other various epoxy resins can be mentioned.

The hydroxyl group content, molecular weight, and viscosity of this epoxy resin-modified amine depend on the type of raw material epoxy resin used, the ratio of the secondary amine derivative represented by general formula (1) to the raw material epoxy resin, reaction temperature, and reaction time. The molecular weight is usually in the range of 2,000 to 40,000, preferably 4,000 to 30,000, although it varies depending on the reaction conditions.

If it is less than 2000, the effect of improving the toughness of the cured product is small;
Moreover, if it exceeds 40,000, the solubility in the epoxy resin decreases, which is not desirable.

The reason why the epoxy resin composition of the present invention containing the above-mentioned specific additives has excellent mechanical properties, particularly toughness and flexibility, as well as excellent work stability and storage stability, is not clear at present, but is as follows. This seems to be due to the following reasons.

(1) The epoxy resin composition of the present invention has a linear structure as an additive and contains a secondary amine modified with an epoxy resin having a hydroxyl group in its molecular chain. The higher-order structure of the cured product can be controlled into a continuous two-phase structure or a seabird structure, which makes it possible to
Toughness and flexibility are significantly increased compared to cured epoxy resins.

(2) The additive used in the present invention can reduce the reaction activity to room temperature or lower through preliminary reaction with the epoxy resin, so it is useful for epoxy resin prepregs containing this additive as an additive. Because the curing reaction proceeds very slowly at room temperature or lower, the physical properties of the composite do not change even if stored at 20°C for 3 months, and the tackiness and drapability of the composite do not change. It is thought that there will be no change in the characteristics of the prepreg.

(3) Since the reaction activity of the epoxy resin composition according to the present invention decreases to room temperature or lower, various shapes can be produced by appropriately selecting the temperature and time in the molding process and adjusting the curing reaction. It becomes easy to obtain a molded body.

Any conventionally known epoxy resin can be used as the epoxy resin used in the present invention, but examples of such epoxy resin include (1) glycidyl ether-based epoxy resin (
(bisphenol A, F, S-based epoxy resin, novolac-based epoxy resin, brominated bisphenol A-based epoxy resin); (2) cycloaliphatic epoxy resin; (3) glycidyl ester-based epoxy resin; (4) glycidylamine-based epoxy Resin: (5) Heterocyclic epoxy resin; Other various epoxy resins can be mentioned.

As a curing agent, examples of curing agents conventionally used in this type of field include (1) amine curing agents; aliphatic amines (diethylenetriamine, triethylenebutramine, tetraethylenepentamine, dipropylenetriamine, trimethyl); xamethylene diamine, polyether diamine, diethylaminopropylamine, menthene diamine, etc.), aromatic amines (metaphenylene diamine, diaminodiphenylmethane, diaminodiphenyl sulbuone, etc.), polyamide amine (condensation product of dimer acid and polyamine), dicyan Polyamide (dicyandiamide etc.), (
2) Phenol curing agent; bisphenols (bisphenol A, bisphenol F, bisphenol S, etc.),
Phenol resins (novolac phenol resin, novolac cresol resin), vinyl phenol polymers (poly P-vinyl phenol, etc.), (3) acid anhydride curing agent; maleic anhydride.

Succinic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, methylhexahydrophthalic anhydride, etc. are used. These curing agents may be used alone, or a plurality of curing agents may be used in combination as necessary.

The epoxy resin composition of the present invention is prepared, for example, by blending a curing agent as it is or by dissolving it into an epoxy resin at room temperature or under heating, and then mixing the above-mentioned additives. As a solvent, ketones (acetone,
Methyl ethyl ketone.

Preferred are methyl isobutyl ketone, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.), and amides (dimethylformamide, etc.).

In addition, when preparing the epoxy resin composition, reactive diluents such as olefin oxide, glycidyl methacrylate, styrene oxide, phenyl glycidyl ether; phenols, tertiary amines,
imidazoles, boron trifluoride complex salts, pyrazoles,
Curing accelerators such as aminotriazole; and fillers such as silica powder, aluminum powder, mica, and calcium carbonate may also be added.6 The amounts of these additives are usually used.

For the entire epoxy resin composition, the reactive diluent is 0.
~15% by weight, curing accelerator 0-5% by weight, filler 0
~70% by weight.

The epoxy resin composition prepared as described above gives a highly tough epoxy resin cured product by heating as it is, and furthermore, in the present invention, the epoxy resin composition can be added to carbon fiber, glass fiber, boron fiber, etc. An epoxy resin prepreg can also be obtained by impregnating reinforcing fibers such as organic fibers by a conventionally known method and then drying. in this case.

The form of the reinforcing fibers is not restricted and may be any of tapes, sheets, mats, textiles, etc.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

[Example of additive synthesis]

(Synthesis of additive A) Epoxy resin (trade name, Epicote 828, molecular weight 19
0, viscosity (50°C) 700 cps: manufactured by Yuka Shell Epoxy Co., Ltd.) 100 parts by weight and 50 parts by weight of a secondary amine derivative represented by the following formula (1) were heated at about 80°C for 48 hours using dioxane as a solvent. Additive A was obtained.

C)1. N) IQ-0 Odor 1° The molecular weight of this additive A was 3000, and it was found that it had a linear structure.

(Synthesis of Additive B) In the synthesis method of Additive A, the molecular weight of about 500
A compound having a linear structure of o was obtained.

This compound was designated as Additive B.

(Synthesis of Additive C) The second compound represented by general formula (1) used in the synthesis method of Additive A
A compound having a linear structure with a molecular weight of about 5000 was obtained in the same manner as the synthesis method for Additive A except that the R amine derivative was replaced with a compound represented by maximum (II) below. This compound was designated as Additive C.

CH, NH-+CH,←NHCH, (II) (Synthesis of additive) The molecular weight was about 1000 in the same manner as the synthesis method of additive A except that the reaction time was 2 hours. A compound having a linear structure was obtained. This compound was used as an additive 6 (Synthesis of Additive E) The molecular weight was about 5 ooo in the same manner as the synthesis method of Additive A except that one reaction time was 20 hours.
A compound having a linear structure of o was obtained.

This compound was designated as Additive E.

Example 1 About 70 parts by weight of epoxy resin (trade name, Epicote 828: manufactured by Yuka Shell Epoxy Co., Ltd.), 50 parts by weight of additive A obtained in the synthesis example, 4 parts by weight of dicyandiamide, and 4 parts by weight of dichloromethylurea were added. The mixture was heated and mixed at ℃ to obtain an epoxy resin solution. This was poured into a mold consisting of two glass plates and a Teflon spacer, heated at 100°C for 2 hours, and further heated in an oven at 200°C for 2 hours.
hardened. Test pieces of the thus obtained cured epoxy resin were cut out from resin casting plates measuring 30 cffl x 30 cm x 3 mm, and tested for glass transition temperature (Tg) and Izod impact strength (IZOD).

The test results are shown in Table 1, and the cured product was SEM
When observed using a scanning electron microscope (a), it was found to have a continuous two-phase structure in which two phases each having a width of approximately l- were intricately arranged.

Next, carbon fibers (strength 350 kg/am'', elastic modulus 32 t/am'') were coated with this epoxy resin solution in one direction.
A prepreg was obtained by impregnating it with A storage stability test of this prepreg was conducted in the following manner. Table 1 shows the results.
Shown below.

[Storage stability test]

The ionic viscosity of the prepreg resin was measured at a constant temperature of 50° C. using a Niemetric System ■ (manufactured by Micromet Co., Ltd.).

Next, 12 layers of the prepreg obtained above were laminated.

A molded article was obtained by heating under curing conditions at 100°C for 2 hours and then at 200°C for 2 hours. The compressive strength after impact (CAI) of this molded body was measured. The results are shown in Table-1.

Examples 2.3, 4.5 In Example 1, Additive A was replaced with Additive B (Example 2),
An epoxy resin composition and an epoxy resin prepreg were obtained in the same manner as in Example 1, except that Additive C (Example 3), Additive D (Example 4), and Additive E (Example 5) were used. Their properties are shown in Table-1.

Comparative Example 1 In Example I, an epoxy resin composition and an epoxy resin prepreg were obtained in the same manner as in Example 1 except that additive A was not used. Their properties are shown in Table-1.

Comparative Example 2 An epoxy resin composition and a An epoxy resin prepreg was obtained. Their properties are shown in Table-1.

Table-1 (Note) (1) IZOD: Izod impact test value (2)
Tg Glass transition temperature (3) CAI: Compressive strength after impact (4) Storage stability test = ionic viscosity at 50°C
Time until the ionic viscosity exceeds 100 (measured with Niemetric System ■ manufactured by Micromet): Prepregs whose ionic viscosity exceeds 100 are virtually impossible to use.

〔Effect of the invention〕

Since the epoxy resin curing agent of the present invention has the above-described structure, it has the following remarkable effects.

(1) The epoxy resin composition of the present invention has a linear structure as an additive and contains a secondary amine modified with an epoxy resin having a hydroxyl group in its molecular chain. The higher-order structure of the product can be controlled to a continuous two-phase structure or a seabird structure, and as a result, toughness and flexibility are significantly increased compared to conventional homogeneous epoxy resin cured products.

(2) The additive used in the present invention can reduce the reaction activity to room temperature or lower through preliminary reaction with the epoxy resin, so it is useful for epoxy resin prepregs containing this additive as an additive. Because the curing reaction of the composite material progresses very slowly at room temperature or lower, the physical properties of the composite do not change even after being stored at 20°C for 3 months, and the tackiness and drapability of the composite material remains unchanged. It is thought that there will be no change in the characteristics of the prepreg.

(3) Since the reaction activity of the epoxy resin composition according to the present invention decreases to room temperature or lower, various shapes can be produced by appropriately selecting the temperature and time in the molding process and adjusting the curing reaction. It becomes easy to obtain a molded body.

Claims (1)

[Claims] (1) An epoxy resin composition obtained by modifying a secondary amine derivative represented by the following general formula with an epoxy resin, and containing a modified product having a linear structure as an additive. R_1NH-A-NHR_2 (In the formula, R_1 and R_2 represent an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group, and A represents a divalent group.)