JPH0241314A - Epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, excellent in elastic modulus and hardness and useful as civil engineering and building materials, etc., by blending a bisphenol A-based epoxy resin having a specific number-average molecular weight with a specified epoxy resin curing agent. CONSTITUTION:The objective composition obtained by blending (A) a bisphenol A-based epoxy resin having 450-7000 number-average molecular weight and 1.3-3.0 radio of weight-average molecular weight/number-average molecular weight and (B) an epoxy resin curing agent expressed by formula I [X is -S-, -O- or formula II (R' and R'' are H, lower alkyl or phenyl), etc.; Y and Y' are H, lower alkyl or electron attracting group; R is H or lower alkyl; m and n are 1-4 and represent the number of substituent groups). Furthermore, e.g., a compound expressed by formula III, are preferably used as the component (B).

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention generally relates to an epoxy resin composition, and more specifically, an epoxy resin composition that has excellent elastic modulus, hardness, and heat resistance, and particularly has excellent toughness. Epoxy resin compositions, such as civil engineering and construction materials, paints.

Lining materials, adhesives, electrical equipment molding materials, mechanical parts,
The present invention relates to an excellent epoxy resin composition from which matrix resins for jigs and tools, fiber-reinforced composite materials (hereinafter abbreviated as FRP), etc. can be obtained.

[Prior Art] Conventionally, epoxy resins have excellent heat resistance, elastic modulus, hardness, and chemical resistance, and have been widely used especially for composite materials made of reinforcing fibers such as aramid fibers, glass fibers, and carbon fibers and matrix resins. . However, conventional epoxy resins have various problems depending on their purpose and method of use.

Especially the mechanical strength of FRP when used as a matrix resin for FRP.

Especially m1! There are problems with toughness, which affects properties, fatigue properties, etc. Therefore, when using an epoxy resin as a matrix resin, in order to impart flexibility to the matrix resin, that is, a cured epoxy resin product, and provide a cured epoxy resin product with excellent mechanical strength, especially toughness,
For example, various methods are being considered, such as selecting a hardening agent or adding a flexibility imparting agent.

Although such conventional methods can improve the flexibility of cured epoxy resin products to some extent, they also significantly reduce the physical properties such as elastic modulus, hardness, and heat resistance, which are the original characteristics of cured epoxy resin products. Not only is it not possible to significantly improve the toughness of FRP, but there is also the problem of lowering chemical resistance, weather resistance, water resistance, etc.

On the other hand, JP-A-62-127317 discloses an epoxy resin composition for prepregs comprising at least two polyepoxy compounds, a high molecular weight epoxy resin, dicyandiamide, and/or a curing accelerator in the molecule. There is.

[Problem to be solved by the invention]

However, when such epoxy resin compositions are used as prepreg epoxy resin compositions, there are problems with tackiness, drape properties, resin flow properties, workability, storage stability, etc., and improvements are desired. was.

In order to improve this point, the present inventors previously proposed that ``containing a bisphenol A-based epoxy resin and an epoxy resin curing agent, the bisphenol A-based epoxy resin has an epoxy equivalent of 190 or less and 40 parts by weight or less. "an epoxy resin composition characterized by having a total number average molecular weight of 600-1300" (Japanese patent application No. 63-773).
No. 25).

This epoxy resin composition has excellent tackiness, drapeability, workability, and storage stability when used as a prepreg resin, but according to subsequent studies by the present inventors, this epoxy resin has Due to its high number average molecular weight and high melt viscosity, it does not necessarily have good tack and drape properties at room temperature or lower temperatures, and furthermore, its tack and drape properties change depending on the environmental temperature. It was found that these materials did not exhibit stable properties over a wide temperature range, and that there were some problems with mechanical properties such as toughness and flexibility.

The present invention was made in view of the above circumstances, and its purpose is to exhibit excellent tack and drape properties not only at high temperatures but also at room temperature or lower temperatures, and which also exhibits excellent tack and drape properties over a wide temperature range. The object of the present invention is to provide an epoxy resin composition that remains stable over a long period of time and provides a molded article with excellent mechanical properties such as toughness and flexibility.

[Means to solve the problem]

According to the studies of the present inventors, it has been found that the above object can be achieved by using an epoxy resin having a number average molecular weight in a specific range and a specific molecular weight distribution, and by using a specific epoxy resin curing agent. Ta.

That is, the epoxy resin composition of the present invention contains a bisphenol A-based epoxy resin and an epoxy resin curing agent,
The bisphenol A-based epoxy resin has a number average molecular weight of 450 to 700, and a ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight/number average molecular weight) of 1.
．． 3 to 3.0, and the epoxy resin curing agent is a group selected from a lower alkyl group and a phenyl group of the following formula,
;Y and Y' are groups selected from H1 lower alkyl groups and electron-withdrawing groups, ;R is a group selected from H and lower alkyl groups, and n is an integer of 1 to 4; represents the number of ) is an epoxy resin curing agent.

The first bisphenol A-based epoxy resin used in the present invention
The feature is that its number average molecular weight is 450-700. Preferably it is in the range of 500 to 650. If the number average molecular weight is less than 450, the amount of low molecular weight components will be too large, resulting in poor tackiness and drape properties of the resulting prepreg.
Furthermore, resin flow properties increase during curing, and the physical properties, especially toughness, of the cured product decrease, making it impossible to achieve the intended purpose of the present invention. Also, if the number average molecular weight exceeds 700, good properties such as toughness may deteriorate. Although the physical properties of the cured product can be obtained, the tack and drape properties at room temperature deteriorate due to the small amount of low molecular weight components, and the tack and drape properties deteriorate further at lower temperatures, making it difficult to handle it as a prepreg. It becomes impossible.

The second feature of the epoxy resin used in the present invention is.

Ratio of weight average molecular weight to number average molecular weight (weight average molecular weight/
number average molecular weight) is 1.3 to 3.0. Preferably 1.5-
It is within the range of 2.7.

Ratio of weight average molecular weight to number average molecular weight (weight average molecular weight/
When the number average molecular weight is less than 1.3, the amount of low molecular weight components becomes too large, resulting in the same drawbacks as when the number average molecular weight is less than 450. Also, if the ratio of weight average molecular weight to number average molecular weight (weight average molecular weight/number average molecular weight) exceeds 3.0, the high molecular weight component will be too large, producing the same results as when the number average molecular weight exceeds 700. So I don't like it.

The bisphenol A-based epoxy resin used in the present invention is 5, for example, Epicoat 1001.1004 manufactured by Yuka Shell ■.
．． It can be prepared by appropriately mixing 1007.1009.1010 (trade name) and the like.

Furthermore, according to the studies of the present inventors, the general formula is a group selected from a lower alkyl group and a phenyl group;
is a group selected from H1 lower alkyl groups and electron-withdrawing groups; R is a group selected from H and lower alkyl groups; m and n are integers of 1 to 4, preferably 1
or represents the number of substituents which is 2. ) When an epoxy resin composition is prepared by using the epoxy resin curing agent shown in ) together with the bisphenol A-based epoxy resin described above, a chain polymer is easily formed, and the epoxy resin curing agent is particularly excellent in terms of toughness. It was found that a product could be obtained.

More surprisingly, when the crosslinking density is low, the elastic modulus and heat resistance are usually lowered, but when the aniline skeleton is It was found that when an epoxy resin composition was prepared from the individually linked epoxy resin curing agent and the bisphenol A-based epoxy resin, no decrease in elastic modulus or heat resistance was observed, and only the toughness was significantly improved. This is thought to be due to the fact that the curing agent is an aromatic amine and has a relatively rigid molecular skeleton.

Furthermore, it can be used as a group to connect two aniline skeletons, and has excellent heat resistance, flame resistance, chemical resistance, solvent resistance, elastic modulus, and compatibility with reinforcing fibers when used as a composite material. It has been found that this method can have excellent effects.

In the present invention, the epoxy resin curing agent having the above structural formula is used as the epoxy resin curing agent, and the amount of secondary aniline skeleton in which R is a lower alkyl group is 60 mol% or more, preferably 80 mol% or more. It is said to be more than Morbu. Such a curing agent is added in a stoichiometric amount to the bisphenol A-based epoxy resin.

Furthermore, the epoxy resin curing agent will be explained in detail.0 According to the present invention, in the structural formula of the epoxy resin curing agent, R is H or a lower alkyl group (for example, having 1 to 6 carbon atoms), but one type It is not necessary, and two or more types may be mixed. However, in all R, 60 or more, preferably 8
0 mol% or more is an alkyl group, that is, the secondary aniline skeleton in which R is an alkyl group accounts for 6% of the total aniline skeleton.
The content is 0 mol % or more, preferably 80 mol % or more. That is, the curing agent used in the present invention is an aromatic diamine curing agent containing a secondary amine as a main component. It has been found that when the amount of secondary aniline skeleton in the total aniline skeleton is less than 60% by mole, the toughness of the cured epoxy resin product decreases. In other words, the reason why the curing agent used in the present invention provides a cured epoxy resin product having a high degree of toughness is that the curing agent of the present invention is an aromatic diamine-based curing agent whose main component is a secondary amine. It is thought that Also, among lower alkyl groups having 1 to 6 carbon atoms, those having 1 to 6 carbon atoms
-3 alkyl groups are preferred; if the number of carbon atoms is 7 or more, the hardness and heat resistance of the cured epoxy resin will decrease.

The cured epoxy resin produced from the epoxy resin composition according to the present invention has a lower crosslinking density due to its molecular structure than the cured epoxy resin produced using a conventional curing agent. This is considered to be because the epoxy resin curing agent used in the present invention has two aniline skeletons linked together and contains 2fi amine as a main component, which is advantageous for forming a linear molecular chain. Furthermore, analysis using gel permeation chromatography (GPC) revealed that such linear molecular chains are formed prior to the initial gelation of the curing reaction.

Cured epoxy resin products with low crosslinking density formed in this way usually tend to have a decrease in elastic modulus and heat resistance, but in the case of the present invention, this tendency is hardly observed, and only the toughness is significantly improved. do. This is thought to be due to the fact that the curing agent used in the present invention is an aromatic amine curing agent and has a relatively rigid molecular skeleton, as described above.

Furthermore, various structures are possible in the structural formula of the epoxy resin curing agent, and according to the results of research experiments by the present inventors, any structure selected increases the toughness of the cured epoxy resin. However, especially for high toughness,
The most effective is -CH,- (when R', R'' is H), and then it is preferable that R', R'' is an alkyl group having 1 to 3 carbon atoms, and when X and -P- When R' is selected, the toughness is slightly inferior to the case where R' is -CH2-, but it is advantageous in terms of heat resistance.

Further, R' and RIP are lower alkyl groups having 1 to 6 carbon atoms, but as mentioned above, those having 1 to 3 carbon atoms are particularly preferable, and when the number of carbon atoms is 7 or more, the epoxy resin cured product The disadvantage is that the hardness and heat resistance of the material decrease. In the structural formula, R' and RIP are not limited to one type, and two or more types may be mixed.

In addition, Y in the structural formula of the above epoxy resin curing agent, Y
' is selected from a lower alkyl group such as H1 having 1 to 6 carbon atoms or an electron-withdrawing group, and the electron-withdrawing group is F,
(4, halogen group such as Br, or nido.

Examples include a fluoro group and a trifluoromethyl group. Preferred among these are H, an alkyl group having 1 to 3 carbon atoms, and CQ; when the alkyl group has 7 or more carbon atoms, the hardness and heat resistance of the cured epoxy resin decrease. come. In the structural formula, Y and Y' are not limited to one type, and two or more types may be mixed.

Particularly preferred examples of the epoxy resin curing agent represented by the above-mentioned formula are as follows.

As described above, the epoxy resin curing agent used in the present invention usually has an active hydrogen equivalent of 0.6 to 1.4 per equivalent of the bisphenol A-based epoxy resin. Preferably 0°8-1.
It is blended at a ratio of 2 parts. The active hydrogen equivalent ratio of the curing agent is 0.
If it is less than 6 or greater than 1.4, the heat resistance and hardness of the epoxy resin curing agent will decrease, which is not preferable.

According to the present invention, the curing agent may be mixed with the bisphenol A-based epoxy resin either as it is or dissolved in a solvent, heated to room temperature or, for example, 50°C. As a solvent,
Ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), cellosolve, etc.), amides (dimethylformamide, etc.) are preferred, and the curing conditions for the epoxy resin composition according to the present invention are usually 130°C for 2 hours, preferably After curing at 130°C for 2 hours, post-curing was performed at 180°C for 2 hours.

Furthermore, when preparing the epoxy resin composition of the present invention, reactive diluents such as olefin oxide, glycidyl methacrylate, styrene oxide, and phenyl glycidyl ether; phenols, tertiary amines, imidazoles, Hardening accelerators such as complex salts of boron trifluoride, pyrazoles, and aminotriazole; and silica powder.

Fillers such as aluminum powder, mica, calcium carbonate, etc. can also be added. Typically, the amounts of these additives used are 0-tS weight percent for reactive diluents, 0 to 5 weight percent for curing accelerators, and 0 to 70 weight percent for fillers based on the curing agent and epoxy resin formulation. It is said that

According to another aspect of the present invention, when it is desired to improve heat resistance etc. even at the cost of some toughness, another epoxy resin other than the bisphenol A-based epoxy resin may be added as an epoxy resin component to the whole epoxy resin. It can be contained in an amount of 50 parts by weight or less per 100 parts by weight of the resin. In this case, if the content of other epoxy resins exceeds 50 parts by weight, the toughness will be significantly reduced, which is not preferable.

As the other epoxy resin, one or more kinds of epoxy resins that are usually reprinted can be selected and used,
For example, glycidyl ether-based epoxy resins (bisphenol A, F, S-based epoxy resins, novolac-based epoxy resins, brominated bisphenol A-based epoxy resins), cycloaliphatic epoxy resins, glycidyl ester-based epoxy resins, glycidyl amine-based epoxy resins. , heterocyclic epoxy resins.

〔Example〕

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

Examples 1 to 5 In this example, as bisphenol A-based epoxy resins, Epicote 828 (epoxy equivalent weight 184 to 194, number average molecular weight 380), 1001 (epoxy equivalent weight 450 to
500, number average molecular weight 900), 1004 (epoxy equivalent weight 875-975, number average molecular weight 1600), 100
7 (epoxy equivalent 1750-2200, number average molecular weight 2900), 1009 (epoxy equivalent 2400-33
00, number average molecular weight 3750) and 1010 (epoxy equivalent weight 3000-5000, number average molecular weight 5500) (
A matrix resin for a prepreg was prepared by preparing Yuka Shell (trade name) (manufactured by Yuka Shell (trade name)) using the compounds shown in Table 1 as a curing agent and in the proportions shown in Table 1.

In Example 5, Epikote 152 (epoxy equivalent weight 172-179, number average molecular weight 3
70) (manufactured by Yuka Shell ■, trade name) was added in an amount of 20 parts by weight.

In each example, 1 epoxy resin component shown in Table 1 was added.
The mixture was heated and mixed at 50°C. This mixture was cooled to 80° C., and a stoichiometric amount of an epoxy resin curing agent prepared at the compounding ratio shown in Table 1 was added to prepare an epoxy resin composition having high toughness at room temperature.

This was poured into a mold consisting of two glass plates and a Tepron spacer, heated at 100°C for 2 hours, then further heated to 200°C.
It was heated in an oven for 2 hours to cure.

The epoxy resin cured product thus obtained is 30 cm
A test piece was cut out from a resin casting plate measuring 30cm x 3+s+m, and its impact strength (IZOD) was measured. The results are shown in Table-1. This epoxy resin had heat resistance and particularly excellent toughness.

In addition, carbon fibers (strength 350 kg/mm", elastic modulus 32t
/m112) to obtain a prepreg. It was found that this prepreg has excellent tackiness, and the tackiness does not change even in the temperature range of 15 to 30°C, indicating that there is no temperature dependence of tackiness. Laminated 12 layers of this.

A molded article was obtained by heating under the above-mentioned curing conditions. Table 1 shows the results of measuring the compressive strength after impact (CAI) of this molded body.

To explain further, the epoxy resin compositions shown in Examples 1 and 2 had low viscosity and good workability during prepreg production. Further, the compositions of Examples 3 and 4 had good workability during production, and also had good properties as prepregs such as tackiness, drapeability, resin flowability, handlingability, and storage stability. The composition of Example 5 is suitable as an epoxy resin for machined parts.

Comparative Examples 1 to 7 Epoxy resin compositions, prepregs, etc. were prepared and tested in the same manner as described in Examples 1 to 5 above using the composition ratios shown in Table 1. The results are shown in Table-1.

When compared with the present invention, it can be seen that the tackiness, tack stability (temperature dependence of tack), storage stability, toughness, etc. are poor.

The curing agent symbols in Table 1 indicate the following.

MeDDM Nidimethyldiaminodiphenylmethane Me
DDS Nidimethyldiaminodiphenylsulfone DI
CY: Dicyandiamide In addition, data regarding the temperature dependence of tackiness of prepregs using the epoxy resin composition according to Example 2, the epoxy resin composition of Comparative Example 4, and the epoxy resin composition of Comparative Example 6 as matrix resins are shown in the drawings. show.

From the drawings, it can be seen that when the number average molecular weight of the epoxy resin and the ratio of the weight average molecular weight to the number average molecular weight are outside the range of the present invention, as in Comparative Example 4, the tack value decreases as the temperature rises, and the tackiness of the prepreg becomes extremely high. It can be seen that the operability is poor because the temperature changes to . Furthermore, when the number average molecular weight of the epoxy resin exceeds 700 as in Comparative Example 6, even if the weight average molecular weight and number average molecular weight are within the range of 1.3 to 3.0, the prepreg deteriorates as the temperature rises. It is understood that the prepreg becomes hard and becomes difficult to handle.

In contrast, the tack value of the prepreg using the epoxy resin matrix of the present invention (Example 2) remains within the appropriate level of 200 to 300 g even when the temperature changes, and its storage stability and workability are It can be seen that the results are good.

To measure the tack value, cut a sample of paper coated with molten resin to approximately 30 degrees and cut it into a 1 cm wide strip, and fix this in the upper and lower two sample holders of a tack measuring machine (Bikmatack manufactured by Toyo Seiki). After pressing for several seconds, it was peeled off at a constant speed (20 mm/min), and the stress at that time was taken as the tack value of the sample.

〔Effect of the invention〕

The epoxy resin composition according to the present invention configured as described above has a cured epoxy resin product obtained from the composition that has excellent heat resistance, elastic modulus, hardness, and chemical resistance, and particularly has excellent toughness. , flexible.

It has excellent impact strength, breaking strength, crack resistance against thermal shock, adhesion, and adhesion.

Prepreg containing this material exhibits excellent tack and drape properties not only at high temperatures but also at room temperature or lower temperatures, and these properties remain stable over a wide temperature range, resulting in excellent workability and excellent drape properties. Storage stability increases dramatically.

[Brief explanation of the drawing]

The drawing is a graph comparing the tack value and tack stability (temperature dependence of tack value) of prepregs using the epoxy resin composition according to the present invention and the epoxy resin composition according to a comparative example as matrix resins. Patent applicant Toa Fuel Industries Co., Ltd.

Claims (1)

[Claims] (1) Contains a bisphenol A-based epoxy resin and an epoxy resin curing agent, and the bisphenol A-based epoxy resin has a number average molecular weight of 450 to 700, and the ratio of the weight average molecular weight to the number average molecular weight (weight average Molecular weight/
The epoxy resin curing agent has a number average molecular weight of 1.3 to 3.0, and the epoxy resin curing agent has the following general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, X is ▲ Numerical formula, chemical formula, table, etc.) ▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼,▲There are mathematical formulas, chemical formulas, tables, etc.▼,▲There are mathematical formulas, chemical formulas, tables, etc.▼,▲
There are mathematical formulas, chemical formulas, tables, etc. ▼, -S-, -O-, ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼
R' and R'' are groups selected from H, lower alkyl groups and phenyl groups; Y and Y' are groups selected from H, lower alkyl groups and electron-withdrawing groups;
is a group selected from H and lower alkyl groups; m,
n is an integer of 1 to 4 and represents the number of substituents. ) An epoxy resin composition characterized by being an epoxy resin curing agent represented by: