JP2001335680A - Epoxy resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition having improved thermal resistance and/or toughness. SOLUTION: This epoxy resin composition comprises (A) an epoxy resin, (B) a curing agent, and (C) a nano-composite of a laminar silicates and an ethylene copolymer ionomer, where 1 to 50 pts.wt. of the nano-composite (C) is blended with 100 pts.wt. of the epoxy resin (A).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an epoxy resin composition having improved heat resistance and / or toughness.

[0002]

2. Description of the Related Art Epoxy resins are widely used as matrix resins for fiber-reinforced composite materials or as adhesives or sealing materials for integrated circuits because of their excellent heat resistance and chemical resistance. . In general, an epoxy resin having a higher crosslink density has higher heat resistance, but on the other hand, has a tendency to have lower toughness. Therefore, it is a major problem to improve toughness while maintaining heat resistance. In some applications, the heat resistance of the current product is not sufficient, and there is also a demand for one with further improved heat resistance.

[0003] In order to increase the toughness of epoxy resins, rubber modification methods in which a reactive elastomer is added have been studied for a long time. In this case, microphase separation in which rubber becomes fine particles occurs, and the rubber and the epoxy resin undergo plastic deformation, thereby improving toughness.However, there is a problem that an epoxy resin having excellent heat resistance and a high crosslinking density has a small effect of improving toughness. there were.

[0004] Incidentally, an ethylene copolymer ionomer is a polymer having an elasticity without blending a plasticizer, and is excellent in toughness, oil resistance, workability, etc., and has a carboxyl group in the molecular chain. It can be expected as an epoxy resin modifier. In fact, it has been studied as an interleaf material of a carbon / epoxy composite material, and it has been reported that good bonding with an epoxy resin and improvement in interlaminar fracture toughness of a CFRT composite material have been reported. However, the glass transition temperature of the ionomer varies depending on the type thereof, but is at most about 80 ° C., and is not so excellent in heat resistance. Therefore, when blended in an epoxy resin, a very large improvement effect cannot be expected.For example, in a formulation in which the toughness is improved, heat resistance is sacrificed, or in a formulation in which the heat resistance is improved, the degree is slight. Above, toughness was sometimes sacrificed.

[0005]

Therefore, the present inventors have studied a method for improving the toughness without substantially sacrificing the heat resistance of the epoxy resin. Further, although there was a decrease in toughness, a method for significantly improving heat resistance was also studied. As a result, they have found that desired improvement or improvement can be achieved by using a nanocomposite of an ionomer and a layered silicate instead of the ionomer.

Accordingly, an object of the present invention is to provide an epoxy resin composition having excellent heat resistance and toughness. Another object of the present invention is to provide an epoxy resin composition having significantly improved heat resistance.

[0007]

The present invention comprises an epoxy resin (A), a curing agent (B) and a nanocomposite (C) of a layered silicate and an ethylene copolymer ionomer. The present invention relates to an epoxy resin composition comprising 1 to 50 parts by weight of a nanocomposite (C) based on parts by weight.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The epoxy resin (A) used in the present invention has two or more epoxy groups and is cured by a curing agent such as a polyamine or an acid anhydride to form a resinous material. Things. For example, it is obtained by condensing epichlorohydrin with polyhydric phenols such as bisphenols or polyhydric alcohols. Bisphenol A type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol F type, bisphenol S type, bisphenol AF type, biphenyl type, naphthalene type, fluorene type,
Glycidyl ether type epoxy resins such as novolak type, phenol novolak type, orthocresol novolak type, tris (hydroxyphenyl) methane type and tetraphenylolethane type can be exemplified. Other glycidyl ester type epoxy resins obtained by condensation of epichlorohydrin with carboxylic acids such as phthalic acid derivatives and fatty acids, glycidylamine type epoxy resins obtained by reacting epichlorohydrin with amines, cyanuric acids, hydantoins, and various other Epoxy resins modified by the method can also be used.

The curing agent (B) which can be used in the present invention may be one widely used in epoxy resins, and may be diethylenetriamine, triethylenetetramine, metaxylylenediamine, isophoronediamine,
Amine curing agents such as 1,3-bisaminomethylcyclohexane, diaminodiphenylmethane, metaphenylenediamine, diaminodiphenylsulfone, dicyandiamide, organic acid dihydrazide, dodecenyl succinic anhydride,
Polyazelaic anhydride, hexahydrophthalic anhydride,
Tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, trimellitic anhydride,
Acid anhydride-based curing agents such as pyromellitic anhydride, benzophenonetetracarboxylic acid, tetrabromophthalic anhydride, and head anhydride; polyphenol-based curing agents such as novolak-type phenolic resins; polymercaptan-based curing agents such as polysulfide and thioester; and isocyanates Isocyanate-based curing agents such as prepolymers, tertiary amine-based curing agents such as benzyldimethylamine and 2,4,6-tris (dimethylaminomethyl) phenol, 2-methylimidazole, 2-ethyl-4-methylimidazole, Imidazole curing agents such as heptadecyl imidazole; Lewis acid curing agents such as BF ₃ monoethylamine and BF ₃ piperazine; and condensation curing agents such as phenol resins, urea resins, and melamine resins.

[0010] In the epoxy resin composition of the present invention,
A nanocomposite (C) composed of an ethylene copolymer ionomer and a layered silicate is used together with an epoxy resin (A) and a curing agent (B). Here is the nanocomposite (C)
The term “powder composition” refers to a powdery composition in which at least a part of an ionomer is inserted between layers of a layered silicate and finely dispersed in each other. Such a nanocomposite can be obtained by mixing an aqueous dispersion of an ionomer and an aqueous dispersion of a layered silicate with each other, and collecting a solid content by a method such as spray drying. One example of that method is
It is disclosed in JP-A-11-71109.

The ethylene copolymer ionomer used as a raw material of the nanocomposite is one in which at least a part of the carboxyl group of the ethylene / (meth) acrylic acid copolymer is neutralized. Here, the ethylene / (meth) acrylic acid copolymer is a random copolymer composed of ethylene and acrylic acid or methacrylic acid, and optionally other monomers. Such a copolymer can be obtained by radical copolymerization of each raw material at high temperature and high pressure. Examples of the other monomer include vinyl esters such as vinyl acetate, methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, and methyl methacrylate.

As the above copolymer, a nanocomposite can be easily produced, and the content of (meth) acrylic acid is 15 to 15 in order to effectively modify the epoxy resin.
35% by weight, especially 18-30% by weight, other monomer is 2%
0% by weight or less, preferably 10% by weight or less, having a melt flow rate at 190 ° C. and a load of 2160 g of 1 to 1000 g / 10 min, particularly 10 to 50 g
It is preferable to use one having 0 g / 10 minutes.

The ionomer in the nanocomposite is 10% or more, preferably 15 to 100%, of the carboxyl group of the ethylene / (meth) acrylic acid copolymer.
It is preferred to use those in which mol%, more preferably 20 to 100 mol%, has been neutralized with cations. Examples of the cationic species constituting the ionomer include one or more kinds of alkali metals such as lithium, sodium, and potassium; polyvalent metals such as calcium, magnesium, and zinc; and organic amines. Preferred are alkali metals and zinc, particularly preferred are alkali metals.

The layer silicate, which is the other component of the nanocomposite, usually has a layer thickness of about 7 to 15 °, and is mainly composed of magnesium silicate, aluminum silicate or the like. Specifically, smectite clay minerals such as montmorillonite, magnesia montmorillonite, tetum montmorillonite, beidellite, aluminian beidellite, nontronite, aluminonnontronite, saponite, hectorite, sauconite, and stevensite, vermiculite, halosite, There are mica, swellable fluorine mica, and the like, which may be natural or synthetic. Among them, the use of a smectite-based layered silicate is preferred. As these layered silicates, those having a particle size of about 1 to 30 μm are preferably used.

The weight ratio of the ethylene copolymer ionomer to the layered silicate in the nanocomposite (C) is 10/90 to 95/5, preferably 30/70 to 90 /.
The range is 10. In this nanocomposite, at least a part of the ionomer is inserted between the layers of the layered silicate. Insertion of the ionomer between the layers of the layered silicate results in a state where the parallelism between the layers is lost or the layers are expanded.

The preparation of such a nanocomposite is carried out by thoroughly mixing an aqueous dispersion of an ionomer and an aqueous dispersion of a layered silicate and collecting a powdery solid. Specifically, the solid content concentration is 0.5 to 5% by weight,
Ionomer aqueous dispersion having a pH of 8 to 12 and an average dispersed particle diameter of 10 to 1000 nm, and a solid content of 0.1 to 3% by weight
By mixing at least a part of the ionomer between the layers of the layered silicate by mixing the layered silicate aqueous dispersion at a predetermined ratio under strong shearing conditions, the resulting mixture is spray-dried to obtain a particle size of 1%. A nanocomposite of about 30 μm can be recovered.

In the epoxy resin composition of the present invention, the curing agent (B) is used in a range of a stoichiometric equivalent (based on epoxy group) or less with respect to 100 parts by weight of the epoxy resin (A). (C) is 1 to 50 parts by weight, preferably 2 to 40 parts by weight, more preferably 2 to 40 parts by weight.
It is blended in the range of 30 parts by weight. Generally speaking, when the amount of the curing agent (B) used is close to the stoichiometric equivalent, the addition of the nanocomposite (C) can improve the fracture toughness without impairing the heat resistance. When the amount of the curing agent used is reduced from the stoichiometric equivalent, and when the ionomer component is a nanocomposite which is an alkali metal ionomer, the fracture toughness is lower than when using the stoichiometric equivalent of the curing agent. It is possible to remarkably improve heat resistance. However, even in this case, when the amount of the curing agent used is large, the fracture toughness value sharply decreases at a high temperature, for example, 200 ° C. or higher. Of the fracture toughness value of the resin composition is small, and may show a higher value than that of the composition containing multiple curing agents. On the other hand, when the amount of the curing agent used is subtracted from the stoichiometric equivalent, and when the ionomer component is a nanocomposite, which is a polyvalent metal ionomer, the heat resistance is considerably higher than when the stoichiometric equivalent of the curing agent is used. Because it drops
When the use amount of the curing agent is considerably reduced from the stoichiometric equivalent, for example, when it is half or less of the stoichiometric equivalent, the alkali metal ionomer-based nanocomposite is used rather than the polyvalent metal ionomer-based nanocomposite. It is preferable to use them.

The above-mentioned mixing results are considered as follows. That is, the epoxy resin and the curing agent react preferentially to form a crosslinked structure when the curing agent is in a sufficient amount, but simultaneously with the ionomer in the nanocomposite when the amount of the curing agent used is less than the theoretical amount. react. In this case, the alkali metal ionomer is rich in reactivity and forms a crosslinked product having a high crosslink density, but the polyvalent metal ionomer is assumed to be poor in reactivity and incompletely crosslinked.

Various additives can be added to the epoxy resin composition of the present invention, if necessary. Examples of such additives include antioxidants, stabilizers, ultraviolet absorbers, curing accelerators, release agents, adhesion promoters, flame retardants, flame retardant aids, pigments, inorganic fillers and the like. be able to.

[0020]

The present invention will be described in more detail with reference to the following examples.

[Preparation of Nanocomposite] (1) Preparation of potassium ionomer-based nanocomposite (hereinafter abbreviated as NC (K)) A methacrylic acid content of 20% by weight and a melt flow rate of 60
g / 10 min ethylene / methacrylic acid copolymer and potassium hydroxide aqueous solution, solid content 3% by weight, neutralization degree 7
7% aqueous potassium ionomer dispersion and 3% by weight of montmorillonite (Kunimine F Co., Ltd.)
The aqueous dispersion was mixed with a homogenizer at a ratio of 3/1,
By spray drying, NC (K) having a potassium ionomer content of 75% by weight, a diameter of 3 to 20 μm, and a number average particle diameter of 5 μm was obtained.

(2) Preparation of zinc ionomer-based nanocomposite (hereinafter abbreviated as NC (Z)) Ethylene / methacrylic acid copolymer is replaced by ethylene having an acrylic acid content of 20% by weight and a melt flow rate of 300 g / 10 min.・ Acrylic acid copolymer is used, and instead of potassium hydroxide, an aqueous dispersion of ammonia and zinc oxide is used. Ammonia neutralization degree 90%, zinc neutralization degree 20%
Except that an aqueous dispersion of the ionomer was used.
NC having an ionomer content of 75% by weight, a diameter of 3 to 20 μm, and a number average particle diameter of 5 μm in the same manner as in the preparation of (K).
(Z) was prepared. Since ammonia is removed in the step of drying the nanocomposite, the finally obtained nanocomposite is a nanocomposite based on zinc ionomer.

Examples 1 to 11, Comparative Examples 1 to 4 80 ° C.
A predetermined amount of nanocomposite was added to a bisphenol A type epoxy resin [average molecular weight: 380, epoxy equivalent: 190, Epicoat 828 manufactured by Yuka Shell Epoxy Co., Ltd.] heated to a disperser (ULUTRA T manufactured by IKALABOTECHNIK).
URRAX T725basic) at 11000 rpm for 1 minute at 16000 rp
at 19000 rpm for 1 minute and at 80 ° C for 20 minutes.
After defoaming under reduced pressure for 4 hours,
4′-diaminodiphenylmethane (DDM) is added,
While maintaining the temperature at 60 to 80 ° C, the mixture was stirred with a propeller-type stirrer for 30 minutes so as not to foam. The mixture was poured into a container, kept at 120 ° C. for 2 hours, and post-cured at 180 ° C. for 6 hours to form a sheet having a predetermined shape.

For comparison, when the nanocomposite was not blended (Comparative Example 1), and when the DDM was not blended (Comparative Example 2), the methacrylic acid content of 20% by weight was finely divided by spray drying instead of the nanocomposite. Neutralization degree 7
Sheets were also prepared in the same manner when using a 7% potassium ionomer powder having an average particle diameter of 3 to 20 μm (hereinafter abbreviated as I (K)) (Comparative Examples 3 and 4).

Table 1 shows the formulations.

[0026]

[Table 1] Units in the table are parts by weight

The obtained sheet samples were evaluated for heat resistance and fracture toughness as follows.

[Dynamic Viscoelasticity Test] Rubbery flat elastic modulus (Gr) and glass transition point (Tg) determined by dynamic viscoelasticity test
Was used as a measure of heat resistance. That is, using a free damping vibration type viscoelasticity measuring device (RD-1100AD manufactured by Resca Co., Ltd.) using a torsional pendulum according to JIS-K7213, at a heating rate of 1.38 ° C./min and a test temperature of 0 to 300 ° C. A fixed torsion angle is given to the upper end of a rectangular test piece having a length of 85 mm, a width of 10 mm, and a thickness of 1 mm, and then the torsion angle and the vibration period are measured while freely attenuating. ', The loss elastic modulus G''and the loss tangent tan δ were calculated, and the values were illustrated. From these charts, the minimum value of the dynamic elastic modulus G ′ of the rubber-like flat portion is defined as the rubber-like flat elastic modulus (Gr), and the loss elastic modulus G ″
Was read as the glass transition temperature (Tg).

[Fracture toughness test]
According to M-D5045-91a, using a screw-type universal testing machine (210B, manufactured by Intesco Corporation), a length of 60 m
The test was performed using a compact test piece having a m, a width of 62 mm and a thickness of 6 mm. A blade of a cutter was applied to a groove formed by machining on the test piece, and the blade was evenly hit with a hammer using a jig to form a sharp crack at the tip to form an initial crack having a length of 15 to 17 mm. From the load value and the initial crack length, a fracture toughness value (K _IC ) was calculated by the following equation.

[0030]

K _IC = (P / BW ^1/2 ) · f (a / W) where P is load (kN), B is specimen thickness (mm), W
Is the specimen width (mm), a is the initial crack length (mm), f
(A / W) is a shape factor and is derived by the following equation.

[0031]

(Equation 2) f (a / W) = (2 + a / W) (0.886 + 4.64a / W-13.32a ² / W ² +1)
4.72a ³ / W ³ -5.6a ⁴ / W ⁴ ) / (1-a / W) ^3/2

Table 2 shows the results. K _IC in the table
Are values measured at 23 ° C. and 200 ° C.

[0033]

[Table 2] *: Does not appear clearly

Comparative Example 1 is a two-component composition composed of an epoxy resin and a stoichiometric equivalent of DDM. Examples 5, 7, and 11 in which a nanocomposite was added to this composition.
, The rubber-like flat elastic modulus and the glass transition temperature are equivalent, but the fracture toughness value is considerably improved, and exceeds all the evaluation items as compared with Comparative Example 4 in which the ionomer is blended. I understand. Similarly, Example 3 and Comparative Example 3
It can also be seen from the comparison that the composition of the nanocomposite is superior to the composition of the ionomer in both heat resistance and fracture toughness.

When Examples 2 and 6 are compared with each other, and Examples 5 and 7 are compared with each other, it is found that the fracture toughness value is slightly improved by increasing the amount of the nanocomposite. Further, from the comparison between Examples 1 to 5 or the comparison between Examples 6 and 7, when the amount of DDM used was reduced from the stoichiometric equivalent, the fracture toughness value was reduced. And a remarkable improvement in heat resistance is observed (Example 2). When the fracture toughness values at 200 ° C. were compared, the values of Example 5 and Comparative Example 1 both sharply decreased and were lower than 0.1 MPa√mDDM, but those of Example 2 showed a small decrease and 0.25 MPa √m. In Example 1 in which the amount of DDM used was further reduced, the rubbery flat elastic modulus showed a high value, but the glass transition temperature was significantly lowered.

In Example 11 in which DDM and NC (Z) were blended in the stoichiometric equivalent, the fracture toughness value was higher than that in Example 5 in which NC (K) was blended.
This is probably due to the difference in the degree of neutralization of the ionomer used. In the case of the NC (Z) compound, the rubbery flat elastic modulus and the glass transition temperature decreased as the amount of DDM used was reduced (Examples 9 and 10), indicating a tendency different from that of the NC (K) compound. I have. This is because the epoxy resin and the ionomer do not react so much. It is considered that the reason is that the ionomer used has a low degree of neutralization and a different ionic species.

[0037]

According to the present invention, an epoxy resin composition having excellent heat resistance and toughness can be provided. According to the present invention, it is also possible to provide an epoxy resin composition having significantly improved heat resistance.

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Claims (3)

[Claims] 1. An epoxy resin (A), a curing agent (B), a layered silicate and a nanocomposite (C) of an ethylene copolymer ionomer, and the nanocomposite (C) is added to 100 parts by weight of the epoxy resin (A). 1) to 50 parts by weight of the epoxy resin composition. 2. The epoxy resin composition according to claim 1, wherein the curing agent is a polyamine or an acid anhydride. 3. The nanocomposite (C) has a ratio of a layered silicate and an ethylene copolymer ionomer of 10/90 to 3.
The epoxy resin composition according to claim 1, wherein the composition is in a range of 95/5 (weight ratio).