JPH07309930A - Epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain an epoxy resin compsn. which cures in a short time at a low temp. and exhibits a high peeling strength. CONSTITUTION:The objective compsn. comprises 100 pts.wt. epoxy resin having an average epoxy equivalent of 500 or lower, a latent curative which can be activated by heating to 40-115 deg.C or lower in an amt. of 0.2-2.5 equivalents based on 1 equivalent of the resin, 0.5-10 pts.wt. cure accelerator or cure assistant (e.g. an arom. diamine), and an arom. urea compd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is extremely stable at room temperature and can be cured at a relatively low temperature (80 ° C.) in a short time, and can be used as a low-temperature-curable matrix resin for prepreg and a resin for adhesives. It relates to an epoxy resin composition that can be used.

[0002]

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

The main properties required of such epoxy resin are not only the mechanical properties of the cured resin, but also the long-term stability at room temperature and the handling property [moderate flowability, tackiness, It has an excellent drape property (flexibility) when formed into a sheet, and includes low temperature curing or short time curing.

In response to such demands, the temperature is from room temperature to 80 to 9
There are already some resins that cure at low temperatures of 0 ° C. However, most of these are so-called two-component resin compositions in which the main agent and the curing agent are mixed immediately before curing, and the stability at room temperature after mixing the two liquids is poor, and the pot life is long. It takes about several hours. The two-component curing type resin generally has a low resin viscosity immediately after mixing, resulting in poor handleability and working environment. On the other hand, as a one-component epoxy resin composition, JP
As disclosed in Japanese Patent Publication No. 1-43616, a combination of an epoxy resin, 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. Stability at 30 ℃ for 14 days or more, but 10
Curing conditions at a relatively high temperature of 0 ° C. for 2 hours are necessary, and at a temperature of 90 ° C. or lower, curing cannot be carried out practically and cannot be used practically.

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

Recently, amine adduct type and microcapsule type latent curing agents for epoxy resin 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 prepare a one-pack type epoxy resin composition that cures. On the other hand, it is also an important factor that the adhesive film and the prepreg have good handleability (tack and drape). As a method of optimizing the handling property, a method of increasing the viscosity of the resin by introducing a high molecular weight epoxy resin, an engineer plastic and a rubber component is a general method.

However, when a high molecular weight epoxy resin is introduced in a material which cures at a relatively low temperature around 80 ° C. in order to improve the handling property, the mobility of the epoxy resin at the curing temperature is lowered and the reactivity is lowered. The curing reaction does not proceed sufficiently. This phenomenon is more remarkable when a catalyst type which promotes ring-opening polymerization of epoxy is used as a curing agent. For example, a composition consisting of a relatively low molecular weight epoxy resin of bisphenol A type which is liquid at room temperature and a commercially available latent curing agent has a high enough degree 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 was added was not cured at 80 ° C. for 3 hours, and in severe cases, it was 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, but it is disadvantageous in terms of physical properties and cost of the cured resin to use a large amount of a latent expensive curing agent. Is.

As one of the methods for improving the handling property, Japanese Patent Laid-Open 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 low temperature and a reactive thickening agent. However, the reactive thickening agent is disclosed. Cures 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 low temperature, a large amount (0.5 to 3 times equivalent of epoxy equivalent) of a latent curing agent is required, the above-mentioned low temperature curability is not improved, and the mechanical properties of the resin are not improved. The characteristics cannot be obtained either.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, retains its handleability for 30 days or longer at room temperature, and cures at 80 ° C. in a short time, and is practically sufficient. An object of the present invention is to provide a low-temperature curable epoxy resin composition which has excellent curing characteristics, is inexpensive in production cost, and can be used to produce a prepreg and an adhesive film by a hot melt method which is advantageous in working environment.

[0010]

The present invention takes the following means in order to solve the above problems. That is, the present invention is
(A) Epoxy resin 1 having an average epoxy equivalent of 500 or less
0.2 to 2.5 times the equivalent of (B) a heat-curable latent curing agent that is activated at 40 to 115 ° C. or less, relative to 00 parts;
An epoxy resin composition comprising (C) 0.5 to 10 parts by weight of a curing accelerator or a curing aid, and (D) an aromatic urea compound.

A feature of the present invention is that a latent curing agent, a curing accelerator or a curing aid, and an aromatic urea compound are used in combination with a curing agent to form a film by the hot melt method, which is easy to handle. Even in a resin system in which an epoxy resin has a molecular weight introduced, the curing characteristics at low temperatures are good,
It is possible to provide a resin that does not change the stability and handleability of the epoxy resin at room temperature. In particular, it is characterized in that the effect of lowering the activation temperature of the latent curing agent and improving the physical properties of the cured resin can be obtained by using an aromatic urea compound in combination.

Specific examples of the epoxy resin as the component (A) of the present invention include bisphenol A, bisphenol F, bisphenol epoxy resin, novolac epoxy resin, brominated bisphenol A epoxy resin, and cycloaliphatic epoxy resin. Examples of the glycidyl ether-based epoxy resin, glycidyl ester-based epoxy resin, glycidyl amine-based epoxy resin, and heterocyclic epoxy resin. You may use these epoxy resins individually or in mixture of 2 or more types. However, it is preferable that the average epoxy equivalent of the whole epoxy resin is 500 or less and the average number of functional groups is 2.7 or less. Epoxy resin equivalent is 500
If it exceeds, the molecular weight per epoxy group is too large,
Due to the reduced mobility, the curability is reduced.
An epoxy equivalent of 400 or less is more preferable.

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, HX372 manufactured by Asahi Kasei.
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.
You can combine more than one type.

Examples of the hardening accelerator and hardening aid of the component (C) include aromatic diamines and polyamines.
Specific examples of the aromatic diamine include, but are not limited to, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, diaminodimethyldiphenylmethane and the like. As specific examples of polyamines, polyethylene polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine are preferably used. Further, as the polycarboxylic acid, in addition to polymerized fatty acids made from natural unsaturated fatty acids, short chain dibasic acids and dibasic acids having an aromatic nucleus, epoxidized unsaturated fatty acids, alkenyl succinic acid, etc. can be used. There are, but are not limited to, these.

Even more surprisingly, the use of aromatic amines having SO ₂ groups in the molecule significantly improves the curing characteristics. This SO ₂ group affects the latent hardener. 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 enhancing this solubility, and the reactivity can be enhanced without affecting the stability at room temperature. Also in the case of a microcapsule type latent curing agent, it can be presumed that the SO ₂ structure affects the solubility of the shell and similarly the reactivity can be enhanced 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 and adhesive strength of the cured product. The amount of aromatic amine added is 0.5 to 10 with respect to 100 parts by weight of the epoxy resin.
Weight parts are preferred. This is because if the amount is less than 0.5 parts by weight, the effect of promoting the curing is not obtained so much, and if it exceeds 10 parts by weight, the physical properties of the cured resin deteriorate.

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 compounds represented by the following general formula are preferred.
Aromatic urea compounds can apparently lower the activation temperature of the latent curing agent without affecting the stability of the resin at room temperature, and have the function of improving the mechanical properties of the cured resin. To be The amount of the aromatic urea compound added 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. It is more preferably 2 to 10 parts.

[0017]

[Chemical 1]

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

Further, in order to improve handleability, other additives such as thermosetting resins, engineering plastics, rubber components, inorganic fillers, etc. to the extent that they do not affect the curability, storage stability, physical properties of the cured product, etc. May be used after being 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 and the like, high molecular weight epoxy resin as thermosetting resin, novolac and resol type phenol resin, maleimide resin and the like, C as rubber component
Examples of rubber types such as TBN, NBR, Kraton, and acrylic, thermosetting resins modified with these, and inorganic fillers include talc, mica, fillers, balloons such as silica, and the like, but are not limited thereto.

By mixing these with an epoxy resin, the obtained resin composition has excellent viscosity even though it has a high viscosity, can be formed into a film by the hot melt method, and the adhesive film can be handled. It is possible to add a characteristic that the property becomes good regardless of the room temperature. In particular, 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 resin thin film on the release paper by heating the resin, which was difficult with the conventional low temperature curable resin. The so-called hot melt film method allows stable film formation. As a result, it becomes possible to produce a film that does not rely on the lacquer method using a solvent that has been commonly used for low-temperature curable resins, which is very economically and work environment-friendly.

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 may be used alone or in combination with a non-woven fabric as a support or various woven fabrics, but is not limited thereto.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the examples below. The abbreviations of the compounds in the examples and comparative examples and the test methods are as follows. The curing conditions were 80 ° C. × 3 hours in all of the examples and comparative examples. Ep828: Bisphenol A type epoxy resin (made by Yuka Shell Co., Ltd.) Ep807: Bisphenol F type epoxy resin (made by Yuka Shell Co., Ltd.) Ep1004: Bisphenol A type epoxy resin (made by Yuka Shell Co., Ltd.) DDS: Diaminodiphenylsulfone 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 Corp. Novacure) DOLIS: 3 (3,4-dichlorophenyl)-
1,1-Dimethylurea (Hodogaya Chemical Co., Ltd.) Amicure 24: (Ajinomoto Co.) Amicure 94: Aromatic urea compound (ACI Co.)

[Measurement of Adhesive Strength] The tensile shear strength (adhesive strength) of this composition was evaluated according to JIS-K-6848, 6850. First, a 12.5 mm lap portion of a 25 × 100 × 1.5 mm aluminum plate (JIS 17S) is polished with sandpaper ( ^# 240) and degreased with acetone. The above adhesive is evenly applied onto an aluminum plate and laminated on an aluminum plate treated in the same manner.
Next, the sample was fixed at a pressure of 1 kg / cm ² , held at 80 ° C. for 3 hours for curing, and then gradually cooled to room temperature to obtain a sample. [Life measurement] The adjusted resin is put in a thermostatic oven at 30 ° C to add a heat history. The viscosity of the resin at 30 ° C. after X days was measured by the above-mentioned viscosity measurement method, and the X days when the viscosity was twice the viscosity on day 0 was defined as the life. [Curing rate] The heating value for curing was measured by DSC to obtain the curing rate. Equipment: DuPont measurement conditions: Rate 10 ° C / min

[Examples 1 to 12] The compositions (numerical values are parts by weight) shown in Table 1 were used. First, as the component (A), Ep828 and Ep were used.
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 produced by the hot melt film method. Using this adhesive film, the tensile shear strength at room temperature and the life and curing rate of the adhesive film were measured. The results are shown in Table 3.

Comparative Examples 1 to 3 Ep828 and Ep1004 as components (A) having the compositions shown in Table 2 were uniformly dissolved at 120 ° C. Then, 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 adhesive shear strength were measured under the same conditions as in Example 1. The results are shown in Table 3.

[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 adhesive films were produced. The life and the adhesive shear strength measurement results are shown in Table 3.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

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

Claims (2)

[Claims] 1. A heat-curable latent curing agent that is activated at 40 to 115 ° C. (B) 0.2 to 2.5 times equivalents to 100 parts of epoxy resin (A) having an average epoxy equivalent of 500 or less. , (C) curing accelerator or curing aid 0.5 to 10
An epoxy resin composition comprising parts by weight and (D) an aromatic urea compound. 2. The latent curing agent of component (B) is a catalyst type curing agent obtained by polymerizing an epoxy resin by ring-opening polymerization.
The epoxy resin composition described.