JPH05222161A - Latent curing agent and epoxy resin composition containing the same - Google Patents

Abstract

PURPOSE:To prepare a latent curing agent which is used for curing an epoxy resin, can be stored at normal temp., and enables the production of a uniform prepreg by compounding a Lewis acid with a specific epoxy compd. CONSTITUTION:A latent curing agent is prepd. by compounding 1-2 pts.wt. Lewis acid with 40-1,000 pts.wt. epoxy compd. having a secondary or tertiary amino group or a thioether group. An epoxy resin compsn. contg. the curing agent can be used for preparing a composite molding material. The material can be prepd. from the compsn. either by the method where a long fibrous reinforcement is placed in a mold and the mold is filled with a thermally melted resin (i.e. transfer molding) or by the method where the reinforcement is impregnated with a resin having a low gelling point. Thus is formed a stable prepreg, which can be molded and cured by heating to give a molded article.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an epoxy resin, and more particularly to a latent curing agent for an epoxy resin.

[0002]

BACKGROUND OF THE INVENTION Epoxy resins containing latent hardeners are already known. The latent curing agent is one that is inactive at room temperature and exhibits catalytic activity when heated to a predetermined temperature. Therefore, the epoxy resin molding method in which the curing process for forming a prepreg includes heating, that is, transfer molding, pull-through, filament winding,
The latent curing agent is effective for the compression molding method and the like. A mixture of BF ₃ and a nitrogen-containing compound can be given as an example of the latent curing agent used for the above-mentioned use.

In these conventional prepregs, there is a problem that the resin moves in the composite during storage and the distribution with respect to the reinforcing fiber becomes non-uniform. There is also a problem that storage in a cool and dark place is necessary in order to avoid hardening of the resin during storage. Furthermore, when a latent curing agent is mixed with an epoxy resin in the conventional transfer molding method, there is a problem that the physical properties of the cured product deteriorate due to the uneven distribution of the resin. Further, in the latent curing agent, an amine is usually used as the nitrogen-containing compound, but the unreacted residual amine moves to the surface layer of the resin and causes discoloration of the resin.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is a latent epoxy resin that can be stored at room temperature and can produce a uniform prepreg. To provide a hardening agent.

[0005]

The latent curing agent of the present invention which has been able to solve the above-mentioned problems is a Lewis acid: 1-2 parts by weight and (b) a secondary or tertiary amino group or thioether group. Epoxy compound having: gist of 40 to 1000 parts by weight. The latent curing agent of the present invention may be used alone or as a mixture with other epoxy compounds to form an epoxy resin compound.

[0006]

The present inventors can use it in various prepreg molding methods such as transfer molding, pull-through, filament winding, and compression molding, and it is stable at room temperature and rapidly crosslinks and cures when heated to a predetermined temperature. Various studies were conducted on liquid epoxy resin blends. As a result, they have found that a mixture of a Lewis acid and an epoxy compound as a latent curing agent is suitable. Furthermore, it has been found that it is effective to add a low-viscosity polyfunctional epoxy compound monomer to the compound of the present invention. Further, in order to control the viscosity and reactivity to obtain an appropriate gel time, it is also effective to further contain a low-viscosity monomer and / or a reactive prepolymer. Forming a prepreg involves two steps. That is,

(1) A step of impregnating a reinforcing resin into a liquid resin (preferably in an inert solvent) and preheating to form a partially cured product (hereinafter referred to as "B stage"). The prepreg molded in this process can be stored,
Moreover, it can be molded into an appropriate shape according to the application. (2) A step of heating and pressurizing to cure the prepreg and finally forming (hereinafter referred to as "final stage").

In molding the above prepreg, in order to control (a) the initial viscosity, (b) the gel time at low temperature and (c) the required curing time at the time of heating (for example, 100 ° C. or higher), an appropriate basicity is required. It is necessary to select an epoxy monomer having a functional group, a diluent and a polyfunctional epoxy monomer. The properties of the epoxy resin polymer and the composite containing it are determined by the composition of the compounded resin, the characteristics and amount of filler, the type of reinforcing fiber, and the thermal history.

The latent curing agent of the present invention or the epoxy resin compound containing the latent curing agent can be used for preparing a molding composite, and long-fiber reinforcing fibers are preliminarily placed in a mold to fill the hot-melt resin. Either a method (ie, transfer molding) or a method of impregnating a resin having a low gel temperature with a reinforcing fiber can be applied, and a stable prepreg is formed and a molded body is formed by heating in the subsequent curing process. You can

The components and reaction conditions of the compounded resin according to the present invention will be further described below. Composite of Lewis acid and epoxy compound The type of Lewis acid used in the present invention is not particularly limited,
For example, BF ₃ , BCl ₃ , BBr ₃ , AlCl ₃ , S
Those such as bF _{5 which} can be easily prepared are preferred, and especially B
F ₃ is preferred.

The latent curing agent of the present invention can be easily prepared from a Lewis acid and an epoxy compound. For example, it is prepared by reacting a commercially available diethyl ether solution of BF ₃ with an epoxy compound and distilling off the ether under reduced pressure. still,
When another Lewis acid is used, it may be reacted directly. For example, BBr ₃ , BCl ₃ and SbCl ₅ are available as liquids. AlCl ₃ is available as a solid, and in this case, it is used by dissolving.

As the epoxy compound, one having a functionality of 1 to 4 may be used. Each epoxy group has the following formula [1] or [2]
As shown in the formula, it is bonded to the nitrogen atom of amine or the sulfur atom of thioether.

[0013]

[Chemical 1]

[0014]

[Chemical 2]

Further, each epoxy group may be bonded to a tertiary nitrogen atom as shown by the following formula [3].

[0016]

[Chemical 3]

Further, the epoxy compound may have one or more epoxy groups which are ether-bonded as shown in the following formula [4].

[0018]

[Chemical 4]

Preferred epoxy compounds include those represented by the following general formula [5].

[0020]

[Chemical 5]

In the formula, X represents --NH--, --S-- or a group represented by the following formula [6],

[0022]

[Chemical 6]

Al represents an aromatic, aliphatic, aromatic-aliphatic composite, carbocyclic or heterocyclic residue having at least one ring, and these residues further have two or more rings. In these cases, these rings are a single bond or a condensed ring via an intermediate group; L and L'each represent a single bond or an alkylene group having 1 to 4 carbon atoms; p is an integer of 1 to 4; Represents an integer from 0 to 4.

In the formula [5], p is preferably 1 or 2, g is preferably 0 or 1, and Al is preferably substituted by a benzene ring (alkyl having 1 to 4 carbons, haloalkyl having 1 to 4 carbons or halogen). Or a group represented by the following general formula [7].

[0025]

[Chemical 7]

In the formula, R represents a single bond or an alkylene group having 1 to 4 carbon atoms. Further, the epoxy compound may be a compound represented by the following general formula [8].

[0027]

[Chemical 8]

The mixing ratio of the above-mentioned Lewis acid and epoxy compound is preferably in the range of 1:20 to 1: 1000 by weight. This is because if the proportion of Lewis acid is too small, the effect as a curing agent is not sufficient, and if it is too large, appropriate curing characteristics cannot be obtained.

Epoxy Resin Blend The epoxy resin blend of the present invention (hereinafter sometimes referred to as "resin blend") comprises the compound described above as a latent curing agent (hereinafter sometimes referred to as "composite"). contains. The resin blend may contain only the composite as an epoxy component, or may contain other epoxy compounds in addition to the composite. The type of other epoxy compound is not particularly limited, but an epoxy prepolymer having at least one or more epoxy groups is exemplified, and preferably a glycidyl ether of a phenol compound having 1 to 2 or more hydroxyl groups (even a polyether is used). No problem), more preferably bisphenol A
Diglycidyl ether of.

The resin blends of the present invention include phenylglycidyl ether, butylglycidyl ether and / or at least one --O in the ring as a reactive diluent.
It is also effective to add an aliphatic cyclic compound having a -group. The aliphatic cyclic compound in that case is composed of a 5-, 6- or 7-membered ring having 1 or 2 -O- groups (further preferably, there is a -CO- group adjacent to the -O- group). It is preferably composed of butyrolactone, caprolactone, tetrahydrofuran, dioxane and the like. These reactive diluents are 0-500 wt% of the total formulation
It may be added in the ratio of.

It is also effective to add a rubber having a functional group or a thermoplastic resin having a functional group to the resin blend of the present invention. These rubbers or thermoplastics are
As functional groups, thiol, hydroxyl, carboxyl,
Having a functional group such as epoxy or anhydride,
Preferred examples include those having a functional group such as acrylic rubber particles, polybutadiene, butadiene-acrylonitrile copolymer, polyolefin, polyether sulfone, polyetherimide, polydimethylsiloxane, polyetherketone, and polycarbonate. When these rubbers or thermoplastic resins are added, they may be added in the range of 0 to 50 wt% based on the whole compounded body by a conventional method.

It is also effective that the resin blend of the present invention further contains a filler, for example, preferably a fibrous filler. By melting the resin blend of the present invention and impregnating it into the reinforcing fibers, it is possible to produce a prepreg that is gel-like, stable, and does not completely cure, and the obtained prepreg can be stored at room temperature. is there.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and all modifications and alterations within the scope of the gist of the preceding and the following are the present invention. It is included in the technical scope of.

[0034]

【Example】

Example 1 About 200 ml of 0.2 ml (0.23 g) of BF ₃ in diethyl ether and 34 g of tetraglycidyl paraxylylenediamine.
A latent curing agent was prepared by mixing the solution dissolved in acetone in 1) in a florentin flask. Diethyl ether and acetone were distilled off at 50 ° C and 10 mmHg using a rotary film evaporator to give a stable liquid curing agent.
An epoxy compound mixture or latent curing agent was obtained. The resulting mixture was used alone as a resin blend and poured into a glass mold and reacted at 180 ° C. for 10 minutes to obtain a cured product. The glass transition temperature of the highly crosslinked polymer thus obtained is 110 ° C.,
The modulus in the glassy region was about 3 GPa, and the modulus in the rubbery region was about 100 MPa.

Example 2 A liquid latent curing agent was obtained in the same manner as in Example 1 except that triglycidyl paraaminophenol was used instead of tetraglycidyl paraxylylenediamine. The obtained mixture was used alone as a resin blend and poured into a glass mold, followed by heating at 180 ° C. for 10 minutes to obtain a cured molded article. The glass transition temperature of the highly crosslinked polymer thus obtained is 110 ° C.,
The modulus in the glassy region was about 3 GPa, and the modulus in the rubbery region was about 100 MPa.

Example 3 A resin blend was prepared in the same manner as in Example 1 except that tetraglycidyl paraxylylenediamine was used in place of tetraglycidyl bisaminomethylcyclohexane to obtain a cured polymer. At 110 ° C., the modulus in the rubber-like region was about 3 GPa, and the modulus in the rubber-like region was about 100 MPa.

Example 4 Instead of tetraglycidyl paraxylylenediamine, triglycidyl aminophenol derivative "ELM-100"
A resin blend was prepared in the same manner as in Example 1 except that (Sumitomo Chemical Co., Ltd.) was used.

The resin blend thus obtained was poured into a glass mold provided with a glass fiber mat in advance. Partial reaction (B stage) was performed to obtain a rubbery prepreg.
This product could be stored at room temperature for several months. This prepreg was cured at 80 ° C for 1 hour to form a highly crosslinked and tough composite, and further cured at 200 ° C for 1 hour. The composite thus obtained contained 15% by weight of reinforced glass fibers, had a glass transition temperature of 250 ° C. or higher, and had a modulus of about 6 GPa in the glassy region near 250 ° C.

Example 5 A solution of BF ₃ in diethyl ether 0.8 ml (0.92 g) and "E"
A latent curing agent was prepared in the same manner as in Example 4 except that 17 g of LM-100 "in acetone was mixed. 1 part by weight of the obtained latent curing agent and 9 parts by weight of diglycidyl ether of bisphenol A (hereinafter referred to as "DGEBA") were mixed and precured at 80 ° C for 1.5 hours to obtain a rubber-like cured product. Further, final curing was carried out at 200 ° C. for 1 hour to obtain a highly crosslinked polymer. The glass transition temperature of this product is about 10 ° C, the modulus in the glassy region is about 3 GPa, and the modulus in the rubbery region is about 10
It was MPa.

Example 6 A latent curing agent was prepared in the same manner as in Example 5. 1 part by weight of the obtained latent curing agent and 4 parts by weight of DGEBA were mixed and preheated at 80 ° C. for 30 minutes to obtain a rubber-like solid. 20
Final heating at 0 ° C. for 1 hour gave a highly crosslinked polymer. The glass transition temperature of this product is about 70 ° C, the modulus in the glassy region is about 3 GPa, and the modulus in the rubbery region is about 100.
It was MPa.

Example 7 A latent curing agent was prepared in the same manner as in Example 5. 3 parts by weight of the obtained latent curing agent and 7 parts by weight of DGEBA were mixed and preheated at 80 ° C. for 10 minutes to obtain a rubber-like solid. Further, final heating was carried out at 200 ° C. for 1 hour to obtain a highly crosslinked polymer. The glass transition temperature of this product was about 100 ° C., the modulus in the glassy region was about 3 GPa, and the modulus in the rubbery region was about 150 MPa.

As is clear from the above examples, by using the latent curing agent of the present invention, it is possible to obtain an epoxy resin having excellent storage stability and good heat resistance and mechanical properties. Further, the latent curing agent of the present invention can be used alone or as a resin blend by mixing with another epoxy resin. It can be seen that the epoxy resin thus obtained has good heat resistance and mechanical properties.

[0043]

The present invention is configured as described above,
It has become possible to provide a latent curing agent that can be used alone as an epoxy resin compound or as a latent curing agent mixed with other epoxy compounds. Furthermore, the prepreg obtained using the resin blend of the present invention can be stored at room temperature and has excellent heat resistance and mechanical properties.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Anthony The Ryan Manchester Material Science Center U.M.Y.T.Gross Benault Street Manchester M17 Etch. HTS

Claims (3)

[Claims] 1. A Lewis acid: (1) to 2 parts by weight and (b) an epoxy compound having a secondary or tertiary amino group or a thioether group: 40 to 1000 parts by weight. Latent curing agent. 2. An epoxy resin blend containing the latent curing agent according to claim 1 alone or in a mixture with another epoxy compound. 3. A prepreg obtained by thermoforming the epoxy resin compound according to claim 2.