JPS58147417A - Amine-based curing agent for epoxy resin - Google Patents

Abstract

PURPOSE:The titled curing agent for epoxy resin, showing a solid state at room temperature, curable in a short time even at low temperature, obtained by reacting a bisphenol A-based epoxy resin with isophorone diamine. CONSTITUTION:(A) A bisphenol A-based epoxy resin (di- or polyglycidyl ether) shown by the formulaI(Y is bifunctional organic group containing 1-8atoms of C, O, S and N) having 1.7-2.2 epoxy groups per molecule on an average and 300-600 average molecular weight is reacted with (B) isophorone diamine shown by the formula II in a molar ratio of A:B of 1:(1.5-2.5), preferably 1:(1.7-2.3) for 30-200min at 80-150 deg.C, to give the desired curing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amine curing agent for epoxy resins that is solid at room temperature.

Hardeners that are solid at room temperature cannot be triblended like hardeners that are liquid or semi-solid at room temperature because they are finely pulverized and triblended with epoxy resin powder to create a powdered resin composition. It also has advantages in terms of workability and storage stability compared to curing agents that are difficult to triblend.

Conventionally, amine-based curing agents have been frequently used as typical hardening agents for epoxy resins, and among this type of curing agents, aromatic amines have generally been solid at room temperature. However, such aromatic amines have poorer reactivity with epoxy groups than aliphatic amines due to weak basicity and steric hindrance of the aromatic ring, and therefore are not suitable for epoxy resins with good properties. In order to obtain a cured product, they have the disadvantage that they must be heated at a higher temperature for a longer time than aliphatic amines.

In view of the above, the present invention aims to provide an amine-based curing agent for epoxy resins that is solid at room temperature and can be cured at low temperatures and in a short time. Bisphenol A-based epoxy resin having an average molecular weight of 300 to 600 and having an average of 1.7 to 2.2 epoxy groups, 1.5 to 2.5 per mole of this resin
An amine curing agent for epoxy resins consisting of a reactant with mol of inphorondiamine.

That is, the inventor focused on the fact that aliphatic curing agents have particularly high reactivity among amine curing agents, and developed specific compounds conventionally known as belonging to this aliphatic curing agent. In other words, inphorondiamine is used as a starting material, and this is reacted with a specific epoxy resin in a specific ratio,
When we obtained a reactant with an amino group left in the molecule,
This is solid at room temperature, has good compatibility with epoxy resins, and because of the excellent reactivity of inphorondiamine as a starting material, it can cure epoxy resins at low temperatures and in a short time. This is what I discovered.

The bisphenol A-based resin and boxy resin used in this invention have the following general formula; (wherein, Y is C, O, S
is a divalent organic group containing 1 to 8 atoms selected from N and N), and is obtained by reacting the corresponding bisphenols with epichlorohydrin by a known method. □ It is something that can be done.

Examples of bisphenols that can be used as raw materials include methylene bisphenol, isopropylidene bisphenol, octylidene bisphenol, bisphenol sulfide, bisphenol sulfone, bisphenol ether, and bisphenol amine. Among these, bisphenols in which Y in the above formula is an alkylene group or an alkylidene group having 1 to 8' carbon atoms, particularly 1 to 6 carbon atoms, are preferred, and a representative example thereof is isopropylidene bisphenol. be.

Such bisphenol A-based epoxy resin theoretically has two epoxy groups per molecule, but since it contains various by-products, it does not necessarily have the above value. There is no guarantee that it will be. The purpose of this invention is to:
It is sufficient that the average number of epoxy groups per molecule is within the range of 1.7 to 2.2.

In addition, the average molecular weight of the above resin is 11 about 300 to 6
It is necessary that the molecular weight is set within the range of 0.00, and if it is lower than the above, the reaction product with inphorondiamine tends to become liquid or semi-solid at room temperature of 4 degrees, and the average molecular weight is considerably higher than the above. In this case, the melting temperature or melt viscosity of the reactant becomes too high and it loses its function as a curing agent, both of which are inappropriate.

The inphorondiamine used in this invention has the following structural formula; % formula %, and one of the two amino groups contained in the molecule is the epoxy group of a bisphenol A-based epoxy resin. The other one remains in the reaction product and becomes an active site as an amine curing agent.

In this invention, the reaction molar ratio of the two components is 1.5 to 2.5 mol, preferably 1.7 to 2.3 mol of isophoronediamine to mol of bisphenol A-based epoxy resin.
It is a mole. By setting the amount within this range, it is possible to obtain a reactant that is solid at room temperature and has performance suitable as a curing agent for epoxy resins.

In other words, when the molar ratio of inphorondiamine used is less than 1.5 mol to 1 mol of bisphenol A-based epoxy resin, the reactant may gel or become too high in molecular weight, becoming insoluble and infusible. The melting temperature or melt viscosity becomes too high, making it unsuitable as a curing agent for epoxy resins, and if the amount exceeds 2.5 moles, the reactant tends to become liquid or semi-solid at room temperature.

The reaction may be carried out using an appropriate organic solvent, but in general, in order to facilitate the removal of the reactant, bisphenol, which has been heated in the same manner as above, is added to inphorondiamine without using a solvent while stirring. A method of gradually adding and reacting Dole A type epoxy resin is preferable. The reaction temperature is usually 80 to 150°C, and the reaction time is about 30 to 200 minutes.

The reactant obtained in this way is solid at room temperature, and by pulverizing it and triblending it with a solid epoxy resin, it has good storage stability at room temperature. It is possible to obtain an epoxy resin composition that is cured by heating at a low temperature for a short period of time, such as 150° C. for 15 minutes. This composition is extremely useful for various uses such as paints and adhesives.

As detailed above, according to the present invention, it is possible to provide an amine curing agent for epoxy resins that is solid at room temperature and can be cured at low temperatures and in a short time, which has not been previously available.

Examples of this invention will be described below.

Example Inphorondiamine 30812m01) was added to a separable flask equipped with a heating stirrer and a reflux condenser,
It was heated to 150°C. At this time, in order to prevent the amine from being oxidized by oxygen in the air, the inside of the flask is replaced with nitrogen gas, and from then on, nitrogen gas is constantly fed into the flask until the reaction is completed, filling the flask with nitrogen gas. Oita.

While stirring inphorondiamine, the average molecular weight is approximately 38.
Bisphenol A type epoxy resin (Epicoat 1828 manufactured by Yuka Shell Co., Ltd.) 3805' (l mol) having an average of 2.0 epoxy groups per molecule at
The mixture was added over about 30 minutes from a dropping funnel heated to 0°C. After the addition was completed, stirring was continued for another 30 minutes to complete the reaction.

The reaction product thus obtained was solid at room temperature and could be easily ground into powder. When this reaction product was analyzed by infrared absorption spectroscopy, no absorption was observed at 10.95μ, which indicates the absorption of epoxy groups, indicating that the added epoxy resin had completely reacted.

Next, the above-mentioned pulverized reactant having an average particle diameter of 60 μm was used as a curing agent and tri-blended with a pre-prepared epoxy resin powder having an average particle diameter of 60 μm to obtain a powdered epoxy resin blend having the following composition. Ta. The results of room temperature storage and curing tests on this blend were as follows:
The results were as shown in the table below. Each test was measured and evaluated using the following method.

Composition of epoxy resin blend Reaction product (curing agent) 18 parts Storage stability The triblend was left in an atmosphere at 20°C for 3 weeks, and the gelation time on a hot plate at 150°C after standing was The ratio (T/TO) between gelation time (T) and gelation time (To) before standing was used as an index of storage stability.

Curing test> According to JIS-6850. The test piece material is JIS-G
- Cold rolled steel plate specified in 3141 is used, and the hardening is 1
The test piece was left in a dryer at 20°C for 15 minutes, and after taking out the test piece, the test was carried out in an atmosphere of 20°C.

Comparative Example A triblend product was obtained in the same manner as in the example except that 6 parts of diaminodiphenylmethane with an average particle size of 60 μm was used as a curing agent, and the same characteristics were evaluated as described above. It was as shown in the table.

As is clear from the results in the table above, the amine curing agent for epoxy resins of the present invention has excellent storage stability and is capable of curing epoxy resins at lower temperatures and in a shorter time than those of comparative examples. You can see that

Claims (1)

[Claims] (1) A bisphenol A-based epoxy resin having an average molecular weight of about 300 to 600 and having an average of 1.7 to 2.2 epoxy groups per molecule, and 1.5 to 2 epoxy groups per mole of this resin.
．． An amine curing agent for epoxy resins that is solid at room temperature and consists of a reaction product with 5 moles of inphorondiamine.