JP3354707B2 - Epoxy resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is very stable at room temperature and is cured at a relatively low temperature (80.degree. C.) in a short time. It relates to an epoxy resin composition that can be used.

[0002]

2. Description of the Related Art Epoxy resins have been used in a wide range of fields because of their excellent adhesiveness, corrosion resistance, mechanical properties, and electrical properties. For example, adhesives, sealants for electronic materials, paints / paving materials, and so on. Furthermore, in recent years, because of its excellent adhesiveness, mechanical properties, and heat resistance, it has been widely used from aircraft use to general-purpose use such as sports-related such as adhesion of building structures and matrix resins for fiber-reinforced composite materials.

The main characteristics required of such epoxy resins are not only excellent mechanical properties of the cured resin, but also long-term stability at room temperature, handling properties [appropriate flowability, tackiness, Excellent drapeability (flexibility) when formed into a sheet] and low-temperature curing or short-time curing.

[0004] In order to meet such demands, from room temperature to 80 to 9
There are already some resins that cure at a low temperature of 0 ° C. However, most of these are so-called two-part resin compositions in which the main agent and the curing agent are mixed immediately before curing, and the stability at room temperature after the two-part mixing is poor, and the pot life is long. It takes about several hours. Two-part curable resins generally have a low resin viscosity immediately after mixing, and are poor in handleability and working environment. On the other hand, as a one-part epoxy resin composition,
As disclosed in JP-A-43-616, a combination of an epoxy resin and a dibasic acid dihydrazide compound, a urea compound and an alcohol-based or phenol-based compound having a melting point of 50 ° C. or higher can be mentioned. Although the stability at 30 ° C. is more than 14 days,
Curing conditions at a relatively high temperature of 0 ° C. for 2 hours are required, and at a temperature of 90 ° C. or less, it cannot be practically used due to poor curing.

Japanese Patent Application Laid-Open No. 1-129084 discloses an adhesive comprising an epoxy resin, a reaction product of bisphenol A and monoglycidyl ether of bisphenol A, and an imidazole compound which is both a curing agent and a curing accelerator. ing. This resin composition also requires curing conditions of 96 ° C. for 2 hours. This resin composition has a large increase in viscosity when adjusting the resin, and it is difficult to form a film by hot melt.

Recently, amine adduct-type and microcapsule-type epoxy resin latent curing agents have been marketed. If these latent curing agents are used, they are excellent in stability at room temperature and at 80 ° C. It is possible to adjust the one-part type epoxy resin composition to be cured. On the other hand, good handling properties (tack and drapability) of the adhesive film and prepreg are also important factors. As a method of optimizing the handleability, a general method is to increase the viscosity of the resin by introducing a high-molecular-weight epoxy resin and introducing engineer plastic and rubber components.

However, when a high-molecular-weight epoxy resin is introduced into a material which cures at a relatively low temperature of about 80 ° C. to improve the handleability, the reactivity decreases due to a decrease in the mobility of the epoxy resin at the curing temperature. The curing reaction does not proceed sufficiently. This phenomenon is more remarkable when a catalyst which promotes ring-opening polymerization of epoxy is used as a curing agent. For example, a composition comprising a relatively low molecular weight epoxy resin of bisphenol A type, which is liquid at room temperature, and a commercially available latent curing agent, is sufficiently high to form a film even when sufficiently cured at 80 ° C. for 3 hours. The epoxy resin composition to which the molecular weight bisphenol A type had been added did not cure at 80 ° C. for 3 hours, and in severe cases, no longer cured at 80 ° C. Even in such a system, it is possible to cure at 80 ° C. for 3 hours by adding a large amount of a curing agent. However, using a large amount of an expensive latent curing agent is disadvantageous in terms of physical properties and cost of the cured resin. It is.

As one of the methods for improving the handleability, Japanese Unexamined Patent Publication No.
Japanese Patent No. 262903 discloses that an epoxy resin composition for prepreg having excellent handleability can be obtained by using a curing agent curable at a low temperature and a reactive thickener. Hardens the epoxy resin and has poor physical properties, and is involved only in increasing the viscosity of the resin. Therefore, in order to cure at a low temperature, a large amount of a latent curing agent (0.5 to 3 equivalents of an epoxy equivalent) is required, and the curability at a low temperature described above has not been improved. No characteristics can be obtained.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, maintains its handleability at room temperature for 30 days or more, cures at 80 ° C. in a short time, and is practically satisfactory. It is an object of the present invention to provide a low-temperature curable epoxy resin composition having excellent curing characteristics, low production cost, and capable of producing a prepreg and an adhesive film by a hot melt method which is advantageous in working environment.

[0010]

The present invention adopts the following means to solve the above-mentioned problems. That is, the present invention
(A) Epoxy resin 1 having an average epoxy equivalent of 500 or less
(B) 0.2 to 2.5 times equivalent of (B) a heat-curable latent curing agent activated at 40 to 115 ° C or lower,
(C) 0.5 to 10 parts by weight of an aromatic amine , and (D)
An epoxy resin composition comprising an aromatic urea compound.

The feature of the present invention is that by using a latent curing agent, a curing accelerator or a curing aid, and an aromatic urea compound in combination with a curing agent, a film can be formed by a hot melt method, and the handling property is high. Even in the resin system where the epoxy resin is introduced with a molecular weight, the curing characteristics at low temperatures are good,
An object of the present invention is to provide a resin which does not change the stability and handleability of the epoxy resin at room temperature. In particular, the combined use of an aromatic urea compound is effective in lowering the activation temperature of the latent curing agent and improving the physical properties of the cured resin.

Specific examples of the epoxy resin of the component (A) of the present invention include bisphenol A, bisphenol F, bisphenol epoxy resin, novolak epoxy resin, brominated bisphenol A epoxy resin, and cycloaliphatic epoxy resin. Glycidyl ether-based epoxy resin, glycidyl ester-based epoxy resin, glycidylamine-based epoxy resin, and heterocyclic epoxy resin. These epoxy resins may be used alone or in combination of two or more. However, the average epoxy equivalent of the entire epoxy resin is preferably 500 or less and the average number of functional groups is preferably 2.7 or less. Epoxy resin equivalent is 500
If it exceeds, the molecular weight per epoxy group is too large,
The curability is reduced due to the reduced mobility.
It is more preferable that the epoxy equivalent is 400 or less.

As the heat-curable latent curing agent of the component (B) used in the present invention, commercially available products can be used. That is, PN-23 (amine adduct type) manufactured by Ajinomoto Co., H3615, H4070 (amine adduct type) manufactured by ACR, HX3721 and HX372 manufactured by Asahi Kasei Corporation.
2 (microcapsule type) and the like. In the present invention, these latent hardeners may be used alone, but other latent hardeners and hardeners may be used to the extent that there is no problem in stability at room temperature.
More than one kind may be combined.

As the curing accelerator and curing assistant of the component (C), aromatic diamine, polyamine and the like can be mentioned.
Specific examples of the aromatic diamine include, but are not limited to, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, and diaminodimethyldiphenylmethane. As specific examples of the polyamine, polyethylene diamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine are suitably used. In addition, as the polycarboxylic acid, in addition to polymerized fatty acids made from natural unsaturated fatty acids, short-chain dibasic acids or dibasic acids having an aromatic nucleus, epoxidized unsaturated fatty acids, alkenyl succinic acids, and the like can be used. But not limited to them.

Even more surprisingly, the use of an aromatic amine having an SO ₂ group in the molecule significantly improves the curing properties. This SO ₂ group affects the latent curing agent. The mechanism is not known in detail, but one possibility is considered as follows. For example, in the case of an amine adduct type latent curing agent, the reaction starts when the curing agent is dissolved in the epoxy resin. The polarity of the SO ₂ structure has the effect of increasing the solubility, and can increase the reactivity without affecting the stability at room temperature. Also, in the case of a microcapsule-type latent curing agent, it can be estimated that the SO ₂ structure affects the solubility of the shell and can similarly increase the reactivity without affecting the stability at room temperature. That is, SO ₂ has a function of lowering the activation temperature of the latent curing agent. This can be expected to improve the degree of curing of the low-temperature curable resin and improve the physical properties of the cured product and the adhesive strength. The addition amount of the aromatic amine is 0.5 to 10 with respect to 100 parts by weight of the epoxy resin.
Parts by weight are preferred. If the amount is less than 0.5 part by weight, the effect of accelerating the curing is not so obtained, and if it exceeds 10 parts by weight, the physical properties of the cured resin are deteriorated.

The component (D), which is the most important component of the present invention, is not particularly limited as long as it is an aromatic urea compound, but is preferably a compound represented by the following general formula.
Aromatic urea compounds can lower the apparent curing temperature of the latent curing agent without affecting the stability of the resin at room temperature, and can improve the mechanical properties of the cured resin. Can be The addition amount of the aromatic urea compound is preferably 1 to 20 parts with respect to 100 parts by weight of the epoxy resin. If it is less than 1 part, the effect of addition cannot be obtained, and if it exceeds 20 parts, the stability decreases. More preferably, it is 2 to 10 parts.

[0017]

Embedded image

(X ₁ and X ₂ represent —H or —Cl and may be the same or different.)

In order to improve the handleability, other additives such as thermosetting resins, engineering plastics, rubber components, inorganic fillers, etc. are used so as not to affect the curability, storage stability and physical properties of the cured product. May be dissolved or dispersed in an epoxy resin. For example, as a thermoplastic resin, PVF (polyvinyl formal), PES (polyether sulfone), PS (polysulfone), PA (polyarylate), PI (polyimide), polyamide, PE
EK (polyetheretherketone), PEI (polyetherimide), phenoxy resin, etc., high-molecular-weight epoxy resin as thermosetting resin, novolak and resole type phenol resin, maleimide resin, etc.
Rubber species such as TBN, NBR, Clayton, and acrylic, and thermosetting resins modified with them, and inorganic fillers include, but are not limited to, talc, mica, fillers, balloons such as silica, and the like.

By mixing these with an epoxy resin, the resulting resin composition has excellent drapability despite having a high viscosity, can be formed into a film by a hot melt method, and can handle the adhesive film. It is possible to impart a characteristic that the property is improved without depending on the room temperature. Particularly, addition of PVF, phenoxy resin, polyparabanic acid and various rubbers is preferable.

Since the epoxy resin composition of the present invention has excellent stability as described above, it is difficult to form a thin resin film on release paper by heating the resin, which has been difficult with conventional low-temperature curable resins. The film can be stably formed by the so-called hot melt film method. This makes it possible to produce a film of a low-temperature curable resin which does not rely on a lacquer method using a solvent, which has heretofore been used, which is very advantageous both economically and in terms of working environment.

The epoxy resin composition of the present invention can be used as an adhesive because it cures at a low temperature and has excellent peel strength. When used as an adhesive, the resin can be used alone, or can be used integrally with a nonwoven fabric or various fabrics as a support, but is not limited thereto.

[0023]

The present invention will be described more specifically with reference to the following examples. The abbreviations of compounds in the examples and comparative examples and the test methods are as follows. The curing conditions were 80 ° C. × 3 hours for both Examples and Comparative Examples. Ep828: Bisphenol A type epoxy resin (manufactured by Yuka Shell) Ep807: Bisphenol F type epoxy resin (manufactured by Yuka Shell) Ep1004: Bisphenol A type epoxy resin (manufactured by Yuka Shell) DDS: Diaminodiphenyl sulfone H3615: Amine Adduct type latent curing agent (A
CR Hardener) PN23: Amine adduct type latent curing agent (Ajinomoto Amicure) HX3722: Microcapsule type latent curing agent (Asahi Kasei Kogyo Co., Ltd. NOVACURE) DOLIS: 3 (3,4-dichlorophenyl)-
1,1-Dimethylurea (Hodogaya Chemical Industry Co., Ltd.) Amicure 24: (Ajinomoto Co.) Amicure 94: Aromatic urea compound (ACI)

[Measurement of Adhesive Strength] The tensile shear strength (adhesive strength) of this composition was evaluated in accordance with JIS-K-6848, 6850. First, a 12.5 mm wrap portion of a 25 × 100 × 1.5 mm aluminum plate (JIS 17S) is polished with sandpaper ( ^# 240) and degreased with acetone. The above-mentioned adhesive is uniformly applied on an aluminum plate, and is superposed on an aluminum plate which has been similarly treated.
Next, the sample was fixed at a pressure of 1 kg / cm ² , cured at 80 ° C. for 3 hours, and then gradually cooled to room temperature to obtain a sample. [Measurement of life] The adjusted resin is placed in a constant temperature dryer at 30 ° C. to add heat history. The viscosity at 30 ° C. of the resin after X days was measured by the above-mentioned viscosity measurement method, and the X day at which the viscosity became twice the viscosity of 0 day was defined as life. [Curing rate] The curing calorific value was measured by DSC to determine the curing rate. Apparatus: DuPont Measurement conditions: Rate 10 ° C / min

[Examples 1 to 12] Ep828, E as components (A) having the compositions shown in Table 1 (the numerical values are parts by weight).
p1004 was uniformly dissolved at 120 ° C. Then, as component (B), H3615, PN23, HX3722,
DDS as the component (C) and DCMU as the component (D) were uniformly mixed at 50 ° C. to obtain a resin composition of the present invention.

Next, using the obtained resin composition,
An adhesive film was manufactured by a hot melt film method. Using this adhesive film, the tensile shear strength at room temperature, and the life and cure rate of the adhesive film were measured. Table 3 shows the results.

[Comparative Examples 1 to 3] Ep828 and Ep1004 as components (A) having the compositions shown in Table 2 were uniformly dissolved at 120 ° C. Thereafter, the latent curing agent of the component (B) was mixed to obtain a comparative resin composition. An adhesive film was produced using this resin, and the life and the adhesive shear strength were measured under the same conditions as in Example 1. Table 3 shows the results.

Comparative Examples 4 to 6 Resins were prepared under the same conditions as in Comparative Examples 1 to 3 except that DDS was added as a curing agent, and then an adhesive film was produced. Table 3 shows the measurement results of the life and the adhesive shear strength.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

The epoxy resin composition of the present invention retains its handleability at room temperature for 30 days or more, cures at 80 ° C. in a short time, has practically sufficient curing characteristics,
The prepreg and the adhesive film can be produced by a hot melt method which is low in production cost and advantageous in working environment.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-322068 (JP, A) JP-A-5-310890 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 59/40-59/66 C08J 5/24 C09J 163/00-163/10

Claims (3)

(57) [Claims] (A) 0.2 to 2.5 times equivalent of a heat-curable latent curing agent activated at 40 to 115 ° C. per 100 parts of an epoxy resin having an average epoxy equivalent of 500 or less. An epoxy resin composition comprising (C) 0.5 to 10 parts by weight of an aromatic amine and (D) an aromatic urea compound. 2. The latent curing agent of the component (B) is a catalytic curing agent obtained by polymerizing an epoxy resin by ring-opening polymerization.
The epoxy resin composition according to the above. 3. The method according to claim 1, wherein (C) the aromatic amine contains SO in the molecule. ₂
3. The aromatic amine according to claim 1, which is an aromatic amine having a structure.
Epoxy resin composition.