JPH0241315A - Epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, good in elastic modulus, hardness and heat resistance. excellent in toughness and useful as civil engineering and building materials, etc., by mixing a bisphenol A-based epoxy resin with plural epoxy resin curing agents. CONSTITUTION:The objective composition obtained by blending (A) a bisphenol A-based epoxy resin having 450-700 number-average molecular weight and 1.3-3.0 ratio of weight-average molecular weight/number-average molecular weight and (B) an epoxy resin curing agent of a mixed system prepared by mixing (i) one or plural kinds of epoxy resin curing agents selected from amine-based curing agents, such as aliphatic and aromatic amines, phenolic curing agents, such as bisphenols and phenolic resins, and acid anhydrides, such as maleic and succinic anhydrides, with (ii) an epoxy curing agent expressed by formula I [X is -S-, -O-or formula II (R' and R'' are H, lower alkyl or phenyl); Y and Y'' are 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].

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. It is possible to obtain epoxy resin compositions such as civil engineering and construction materials, paints, lining materials, adhesives, electrical equipment molding materials, machine parts, jigs and tools, matrix resins for fiber reinforced composite materials (hereinafter abbreviated as FRP), etc. This invention relates to an excellent epoxy resin composition.

[Prior art]

Conventionally, epoxy resins have excellent heat resistance, high elastic modulus, hardness, and chemical resistance, and are particularly widely used in 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.

In particular, when used as a matrix resin for FRP, there is a problem with the mechanical strength of FRP, especially its toughness, which affects impact properties, fatigue properties, etc. For this reason, when using an epoxy resin as a matrix resin, it is necessary to impart flexibility to the matrix resin, that is, a cured epoxy resin, and to provide a cured epoxy resin with excellent mechanical strength, particularly 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. Seen.

Not only is it not possible to greatly 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 an epoxy resin composition is used as an epoxy resin composition for prepreg, 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 inventors of the present invention previously proposed that ``contains a bisphenol A-based epoxy resin and an epoxy resin curing agent, and 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 has been found that these materials do not exhibit stable properties over a wide temperature range, and that they have some problems in mechanical properties such as toughness and flexibility, as well as in rigidity and strength.

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, as well as physical properties such as rigidity and strength.

[Means to solve the problem]

According to the studies of the present inventors, 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 mixed epoxy resin curing agent. It was discovered.

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.
．． 3-3.0, and the epoxy resin curing agent is an amine-based curing agent such as aliphatic amine, aromatic amine, polyamide amine, dicyan polyamide; bisphenols, phenol Hffl, vinyl phenol polymers, etc. Phenolic curing agent; and one or more epoxy resins selected from acid anhydride curing agents such as maleic anhydride, succinic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, and methylhexahydrophthalic anhydride. Curing agent (A) and the following general formula: a group selected from a lower alkyl group and a phenyl group; ;Y and Y' are groups selected from H1 lower alkyl group and an electron-withdrawing group; A group selected from alkyl groups; m,
n is an integer of 1 to 4 and represents the number of substituents. ) The epoxy resin curing agent is a mixed type epoxy resin curing agent formed by mixing with the epoxy resin curing agent (B) shown in (B).

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.
Moreover, resin flowability increases during curing, and furthermore, physical properties, particularly toughness, of the cured product deteriorate, making it impossible to achieve the intended purpose of the present invention. In addition, when the number average molecular weight exceeds 700, good physical properties of the cured product including toughness can be obtained, but the tackiness and drape properties at room temperature decrease due to the lack of low molecular weight components, and at lower temperatures. The tackiness and drape properties deteriorate further, making it impossible to handle it as a prepreg.

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 fi
t/number average molecular weight) is 1.3 to 3.0, preferably 1,
It should be in the range of 5 to 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. Moreover, when 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 becomes too large.

If the number average molecular weight exceeds 700, the same results will occur, which is not preferable.

The bisphenol A-based epoxy resin used in the present invention is, 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 l or 2 represents the number of substituents. ) 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. Although a product was obtained, it was found that the network structure of the reacted epoxy resin became loose and there were some problems in terms of rigidity and strength.

Therefore, the inventors conducted further research and found that
Amine-based curing agents such as aliphatic amines, aromatic amines, polyamide amines, and dicyan polyamides used as epoxy resin curing agents; phenolic curing agents such as bisphenols, phenolic resins, and vinylphenol polymers; Maleic anhydride and succinic anhydride are combined with one or more epoxy resin curing agents (A) selected from acid anhydride curing agents such as methyltetrahydrophthalic anhydride, methylnadic anhydride, and methylhexahydrophthalic anhydride. A group selected from the following general formula lower alkyl group and phenyl group,
;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, ;m and n are integers of 1-4 and are substituted Represents the number of groups. ) If a mixed epoxy resin curing agent is used with the above bisphenol A epoxy resin, high toughness and sufficient heat resistance, rigidity and strength can be obtained. It has been found that it is possible to obtain a cured epoxy resin product.

When a mixed epoxy resin curing agent obtained by mixing a normal epoxy resin curing agent (A) with a specific curing agent (B) represented by the above general formula is used together with a bisphenol A-based epoxy resin, At the initial stage of the curing reaction of the cured epoxy resin, a chain polymer is formed by the curing agent represented by the above general formula, and at the later stage of the reaction, the hydroxyl group of the chain polymer and the glycidyl group on the epoxy resin side are formed. The reaction described above causes a cross-linking reaction one after another, and the other curing agent mixed at the same time causes a cross-linking reaction with the epoxy resin. It is understood that the two cross-linked structures are intricately intertwined with each other, and the morphology of the cured product is uniform, and that not only toughness but also sufficient rigidity and strength can be obtained.

In the present invention, the mixing ratio of the epoxy resin curing agent (A) and the epoxy resin curing agent (B) can be selected arbitrarily;
Preferably, the epoxy resin curing agent (A) has an active hydrogen content of 85 to 5%, and the epoxy resin curing agent (B) has an active hydrogen content of 15 to 95%.

Among the epoxy resin curing agents (A), particularly diaminodiphenylsulfone (OOS), diaminodiphenylmethane (DDM), and polyamide amine.

Dicyandiamide (DICY) and methylhexahydrophthalic anhydride are preferred.

In addition, in the epoxy resin curing agent (B), the amount of secondary aniline skeleton in which R is a lower alkyl group (for example, carbon number 1-6) is 60 mol% or more, preferably 80 mol%.
The above are alkyl groups, that is, the amount of the secondary aniline skeleton in which R is an alkyl group is 60 mol % or more, preferably 80 mol % or more of the total aniline skeleton.

In addition, in the epoxy resin curing agent (B), R has 1 carbon number.
~3 alkyl groups are preferred, where X is -CH,-(R'
, R// is H). Furthermore, in the epoxy resin curing agent (B), Y and Y' are one or more groups selected from H1 lower alkyl groups or electron-withdrawing groups. exists, and the electron-withdrawing groups are F, Cm, Br
is a halogen group, a nitro group, or a trifluoromethyl group, R/ and R/7 are preferably alkyl groups having 1 to 6 carbon atoms, particularly 1 to 3 carbon atoms, and m and n are preferably 1 or 2.

As mentioned above, when a mixed epoxy resin curing agent consisting of a mixture of the epoxy resin curing agent (A) and the epoxy resin curing agent (B) is used together with the bisphenol A-based epoxy resin.

In the initial stage of the curing reaction of the epoxy resin curing agent, a chain polymer is formed by the curing agent (B).6 In the latter stage of the reaction, the hydroxyl group in the chain polymer and the glycidyl group on the epoxy resin side are formed. A cross-linking reaction is caused one after another by the reaction, and at the same time, a cross-linking reaction with the epoxy resin is also performed by the mixed curing agent (A). Since these reactions proceed uniformly and continuously, the two bridging structures of the above-mentioned reactions exhibit a form in which they are intricately entangled with each other. The mixing ratio of the curing agents is preferably such that the epoxy resin curing agent (A) has an active hydrogen content of 85 to 5%, and the epoxy resin curing agent (B) has an active hydrogen content of 15 to 95%. (A) has an active hydrogen content ratio of 25 to 75%, and the epoxy resin curing agent (B) has an active hydrogen content ratio of 75 to 25%, allowing a very suitable crosslinking reaction to proceed, and the morphology of the cured product to be uniform. becomes. In particular, the cross-linking reaction caused by the curing agent (B) shows exceptionally excellent toughness;
It is believed that the cross-linking reaction caused by A) mainly contributes to improvements in elastic modulus, heat resistance, and further rigidity and strength.

In Figure 1, diaminodiphenylmethane (DDM) is used as the epoxy resin curing agent (A), and dimethyldiaminodiphenylmethane (DDM) is used as the epoxy resin curing agent (B).
The impact strength (IZOD) and glass transition temperature (Tg) of mixed epoxy resin curing agents when MeDDM) are mixed in various proportions are shown.

By referring to FIG. 1, the IZOD value of the mixed epoxy resin curing agent used in the present invention can be determined from the composite side line (
It will be appreciated that this will be considerably larger than that shown by the dotted line). In particular, it will be understood that when the epoxy resin (B) is mixed in an active hydrogen amount ratio of 15% or more, the IZOD value is dramatically improved. or.

The IZOD value shows the maximum value when the epoxy resin curing agent (B) is mixed with an active hydrogen amount ratio of 50%, but this is because the growth of chain polymers and the formation of a crosslinked structure are sufficient at this mixing ratio. This is because it is carried out in a well-balanced manner.

Furthermore, from the graph of the glass transition temperature Tg in FIG. 1, when a mixed epoxy resin curing agent is used as in the present invention, as the ratio of the epoxy resin curing agent (B) is increased, Tg
It is understood that g decreases gradually.

Particularly preferred examples of the epoxy resin curing agent (B) represented by the above formula are as follows.

As described above, the mixed epoxy resin curing agent used in the present invention usually has an active hydrogen equivalent of 0.6 to 1.4, preferably 0.0.
It is blended at a ratio of 8 to 1.2. If the active hydrogen equivalent ratio of the curing agent is less than 0.6 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.), and amides W4 (dimethylformamide, etc.) are preferred. Further, 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, 180°C
It was post-cured 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, Curing accelerators such as complex salts of boron trifluoride, pyrazoles, and aminotridesols; fillers such as silica powder, aluminum powder, mica, and calcium carbonate may also be added. Normally, the amounts of these additives used are: , the amount of monoreactive diluent is 0 to 15% by weight, the amount of curing accelerator is 0 to 5% by weight, and the amount of filler is 0 to 70% by weight, based on the curing agent and epoxy resin blend.

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 the epoxy resin 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 commonly available on the market 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.

Examples include glycidyl ester epoxy resins, glycidyl amine epoxy resins, and heterocyclic epoxy resins.

〔Example〕

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

Examples 1 to 7 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), 1007
(Epoxy equivalent: 1750-2200, number average molecular weight: 29
00), 1009 (epoxy equivalent weight 2400-3300
, number average molecular weight 3750) and 1010 (epoxy equivalent 3000-5000, number average molecular weight 5500) (manufactured by Yuka Shell ■, trade name), dimethyldiaminodiphenylmethane (MeDDM) or dimethyldiaminodiphenyl sulfone as the curing agent (B). (MeDDS) was prepared using diaminodiphenylmethane (DDM) or dicyandiamide (DICY) as the curing agent (A) in the proportions shown in Table 1 to prepare a matrix resin for prepreg.

In Example 7, Epikote 152 (epoxy equivalent: 172 to 179, average molecular weight: 37
0) (manufactured by Yuka Shell ■, trade name) was added in an amount of 20 parts by weight.

To explain further, in each Example, the epoxy resin components shown in Table 1 were heated and mixed at 150°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 exhibiting high toughness at room temperature.

Pour this into a mold made of two glass plates and a Teflon spacer, heat it at 100℃ for 2 hours, and then heat it to 200℃.
, heated in an oven for 2 hours to cure.

The epoxy resin cured product obtained in this way has a thickness of 3°cm.
A test piece was cut out from a resin casting plate measuring 30<em>x 3 m+a, and the impact strength (IZOD) was measured. The results are shown in Table-1. Moreover, this epoxy resin had tackiness, drapeability, resin flowability, handlingability, and storage stability suitable for use in prepregs, and was particularly excellent in toughness.

In addition, carbon fibers (strength 350 kg/m+a'', elastic modulus 3
2t/am") to obtain a prepreg. 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. It was.

Next, 12 layers of this prepreg were laminated and heated under the above-mentioned curing conditions to obtain a molded body. The results of measuring the post-impact compressive strength (C) of this molded body are shown in Table 1, Example 1
．． The composition of 2.3.4.5.6.7 had good workability during production and also had good properties as a prepreg.

Comparative Examples 1 to 11 Epoxy resin compositions, prepregs, and the like were prepared and tested in the same manner as described in Examples 1 to 7 using the composition ratios shown in Table 1. The results are shown in Table-1.

When compared to the present invention, it can be seen that tackiness, tack stability (temperature dependence of tackiness), storage stability, toughness, etc. are poor. It is also understood that the IZOD value and CAI value have decreased significantly.

The curing agent symbols in Table 1 indicate the following.

MeDDN Nidimethyldiaminodiphenylmethane Me
DDS Nidimethyldiaminodiphenylsulfone DI
CY: Dicyandiamide Note that data regarding the temperature dependence of the tackiness of prepregs using the epoxy resin composition according to Example 5, the epoxy resin composition of Comparative Example 8, and the epoxy resin composition of Comparative Example 9 as matrix resins is shown in the second table. As shown in the figure.

From Figure 1, even if the ratio of the weight average molecular weight to the number average molecular weight of the epoxy resin is 2.2 as in Comparative Example 8, the tack value of the epoxy resin with a number average molecular weight of 760 decreases as the temperature increases. It can be seen that the operability is poor because the temperature rises rapidly and the adhesiveness of the prepreg changes drastically. In addition, when the number average molecular weight of the epoxy resin exceeds 700 and the weight average molecular weight and number average molecular weight are outside the range of 1.3 to 3.0, as in Comparative Example 9, the prepreg becomes soft as the temperature rises. It is understood that too much prepreg becomes difficult to handle.

In contrast, the tack value of the prepreg using the epoxy resin matrix of the present invention (Example 5) 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.

In addition, the tack value is based on a sample coated with molten resin on paper for about 30 μs. Cut into strips of
This tack measuring device (Pikmatack manufactured by Toyo Seiki)
The sample was fixed to two upper and lower sample holders, and after being pressed for several seconds, it was peeled off at a constant speed (20+u+/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, as well as toughness and flexibility. Excellent flexibility, impact strength, breaking strength,
It has excellent crack resistance, adhesion, and adhesion against thermal shock. A prepreg containing this material exhibits excellent tack and drape properties not only at high temperatures but also at room temperature or lower temperatures.

Since the properties remain stable over a wide temperature range, workability and storage stability are dramatically increased.

[Brief explanation of the drawing]

Figure 1 shows the mixing ratio of the mixed epoxy resin curing agent of DDM and MeDDM, and the IZOD? i[r! ! ! It is a graph showing the relationship between the value and the glass transition temperature Tg value. Figure 2 shows 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.
This is a graph comparing . Figure 1 MeDDM/DDM 1ff164 Patent applicant Toa Fuel Industries Co., Ltd. too 85 70 50 25 Anbi Nishimi DM

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/
number average molecular weight) is 1.3 to 3.0, and the epoxy resin curing agent is an amine-based curing agent such as aliphatic amine, aromatic amine, polyamide amine, dicyan polyamide; bisphenols, phenolic resins, selected from phenolic curing agents such as polymers of vinylphenol; and acid anhydride curing agents such as maleic anhydride, succinic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, and methylhexahydrophthalic anhydride. One or more types of epoxy resin curing agent (A) and the following general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, X is ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ Numerical formulas, chemical formulas, tables, etc. There are ▼, ▲ 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 in that it is a mixed epoxy resin curing agent obtained by mixing an epoxy resin curing agent (B) shown in the following formula.