JPH0288624A - Epoxy curing agent - Google Patents

Abstract

PURPOSE:To obtain the subject composition, containing an acid anhydride, specific oxazoline compound and phenolic compound, etc., in a specific proportion and capable of providing heat resistance and toughness coexisting together at high levels. CONSTITUTION:The objective curing agent consisting of (A) 1mol acid anhydride (e.g. phthalic anhydride), (B) 0.05-0.4mol oxazoline compound expressed by formula I (X and D are bifunctional organic group; n is 0 or 1; the ring structure of formula II is 5-membered ring) [e.g. 2,2'-bis(2-oxazoline) or 2,2'-p-phenylenebis(2-oxazoline)] and (C) 0.01-0.4mol phenolic compound or 0.03-0.2mol mercaptan compound at the above-mentioned constituent ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an epoxy curing agent comprising an oxazoline-modified acid anhydride.

(Prior art) Acid anhydrides require stricter curing conditions than amine curing agents, but they have a long pot life and their cured products have poor electrical, chemical, and mechanical properties. It is widely used as a curing agent for epoxy resins because it is well-balanced, has low calorific value, makes it easy to make large molded products, and has low skin irritation.

However, since acid anhydride-cured epoxy resins are generally brittle, sufficient care must be taken to prevent cracks from forming in molded products with metal fittings embedded inside. In order to improve crack resistance, epoxy resins with large molecular weights are used, and long-chain aliphatic acid anhydrides and ductility imparting agents are blended. However, on the other hand, these methods have the drawback of lowering the physical heat resistance of the cured product.

The present inventors have already discovered that a cured product obtained from an oxazoline compound and an epoxy resin has properties that are equivalent to or better than conventional acid anhydride-cured epoxy resins in terms of physical heat resistance, crack resistance, and mechanical strength. However, based on the research results to date, the present inventors conducted intensive research with the aim of obtaining an even better epoxy curing agent. It has been discovered that acid anhydrides modified with oxazoline are excellent curing agents for epoxy resins. It has already been revealed in JP-A-55-151008 that oxazoline reacts with acid anhydrides to form a three-dimensional crosslinked structure under a specific catalyst, but in the case of the present invention, oxazoline and The purpose of this paper is to use acid anhydrides modified with phenolic compounds or mercaptan compounds as novel curing agents for epoxy resins.

(Problem to be Solved by the Invention) When a liquid epoxy resin with an average epoxy equivalent weight of 135 to 250 is cured at room temperature with a conventional acid anhydride, the glass transition temperature, tensile strength, or fracture of the cured product is There are limit areas as shown in FIGS. 1 and 2 between the toughness values, and it has been difficult to achieve both physical heat resistance and mechanical strength at a high level.

Furthermore, with epoxy resins using oxazoline compounds as curing agents, cured products with properties exceeding this limit can be obtained, but they have problems with chemical heat resistance and coloration due to oxidation during heat curing.

The present invention was made to solve the above-mentioned problems, and is superior to conventional acid anhydride-cured epoxy resins in terms of mechanical strength, physical heat resistance, and fracture resistance. It is an object of the present invention to provide an epoxy curing agent that has the following properties, has good workability, and provides a cured product that prevents coloring due to oxidation during curing.

[Structure of the invention]

(Means for Solving the Problem) In order to achieve the above object, the present invention includes (a)
Acid anhydride 1 mol (b) Oxazoline compound represented by the following general formula 0
．． 05 to 064 mol (C) The epoxy curing agent is formed with a composition ratio of 0.01 to 0.4 mol of a phenol compound or 0.03 to 0.2 mol of a mercaptan compound.

(Function) The acid anhydrides used in the present invention include phthalic anhydride,
Hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, nadic anhydride, methyl nadic anhydride, chlorendic anhydride, dodecynyl succinic anhydride, methyl succinic anhydride, anhydride Examples include pyromellitic acid, maleic anhydride, benzophenone tetracarboxylic anhydride, and the like. These may be used alone or as a mixture of two or more. From the viewpoint of workability, -valent acid anhydrides and liquid acid anhydrides are sufficient, but if heat resistance or mechanical properties are particularly important, polyvalent acid anhydrides alone or liquid acid anhydrides may be used. Preferably used in mixture with anhydride.

Examples of oxazoline compounds include primary compounds.

(I) Compounds when n=o 2.2'-bis(2-oxazoline), 2.2'-bis(4-methyl-2-oxazoline), 2゜2'-bis(
4,4-dimethyl-2-oxazoline), 2,2'-bis(4-ethyl-2-oxazoline), 2,2'-bis(4,4-diethyl-2-oxazoline), 2,2'-
Bis(4-propyl-2-oxazoline), 2,2'-
Bis(4-butyl-2-oxazoline), 2,2'-bis(4-phenyl-2-oxazoline), 2,2'-bis(4-cyclohexyl-2-oxazoline), 2,2'
Bisoxazoline compounds such as bis(4-benzyl-2-oxazoline).

(II) Compound 2.2'-p-phenylenebis(2-oxazoline) when n = 1,
2.2'-m-phenylenebis(2-oxazoline),
2*2'-o-phenylenebis(2-oxazoline),
2.2'-p-phenylenebis(4-methyl-2-oxazoline), 2.2'-p-phenylenebis(4,4-
dimethyl-2-oxazoline), 2.2'-m-phenylenebis(4-methyl-2-oxazoline), 2.2'
-m-phenylenebis(4,4-dimethyl-2-oxazoline), 2.2'-ethylenebis(2-oxazoline), 2゜2'-tetramethylenebis(2-oxazoline), 2.2'- xamethylenebis(2-oxazoline), 2,2'-octamethylenebis(2-oxazoline), 2,2'-decamethylenebis(2-oxazoline)
, 2,2'-ethylenebis(4-methyl-2-oxazoline), 2,2'-tetramethylenebis(4,4-dimethyl-2-oxazoline), 2,2'-cyclohexylenebis(2-oxazoline) ), 2,2′-diphenylenebis(2-oxazoline) and other bisoxazoline compounds.

These compounds may be used alone or as a mixture of two or more. Among these, 2°2'-m-phenylenebis(2-oxazoline) is preferred from the viewpoint of good compatibility with acid anhydrides and ease of handling.

Examples of the phenol compound include carbolic acid, hydroquinone, resorcinol, cresol, and bisphenol A, and from the viewpoint of ease of handling, carbolic acid or bisphenol A is preferable. These may be used in combination of two or more types.

In addition, as mercaptan compounds, phenylmercaptan, n-butylmercaptan, ethylene-bis-3-
Mercaptopropionate, trimethylpropane-tris-3-mercaptopropionate, pentaerythritol-tetra-3-mercaptopropionate, 4,
It contains 4'-oxy-bis-thiophenol, and from the viewpoint of ease of handling, phenylmercaptan or ethylene-
Bis-3-mercaptopropionate is preferred.

These may be used in combination of two or more types.

The blending amount of these compounds is as follows per 1 mole of acid anhydride:
Preferably, the range is 0.05 to 0.4 mol of an oxazoline compound, 0.01 to 0.4 mol of an oxycarboxylic acid, or a mercaptan compound. If the amount is less than this range, when used as an epoxy curing agent, there will be little effect on improving the heat resistance and toughness of the cured product, while if it is more than this range, precipitation or precipitation of components will occur, resulting in storage of modified acid anhydrides. Stability deteriorates. The reaction temperature is preferably 90°C to 160°C. If the temperature is below this range, the oxazoline, phenol compound, or mercaptan compound will not completely dissolve in the acid anhydride, so the reaction will not proceed uniformly. On the other hand, at temperatures above this range, a decarbonation reaction of the acid anhydride occurs, resulting in a decrease in performance as an epoxy curing agent.

The reaction time is preferably 0.1 to 4 hours. If the reaction time is shorter than this range, the reaction between oxazoline and phenol compound, oxazoline and mercaptan compound, or oxazoline and acid anhydride will be insufficient, and if the reaction time is longer than this range, the viscosity of the oxazoline-modified acid anhydride will increase. Workability is significantly impaired.

The oxazoline-modified acid anhydride having the composition and manufacturing method described above can be used without impairing the workability, which is an advantage of ordinary acid anhydrides, in improving the glass transition temperature and fracture of the cured epoxy resin cured with the oxazoline-modified anhydride. Toughness value and mechanical strength are improved.

Furthermore, coloration due to oxidation of the surface of the cured product during heat curing does not occur, which occurs when an epoxy resin is directly cured with an oxazoline compound.

(Example) Below, the present invention will be explained in further detail with reference to Examples and Comparative Examples.

Example 1 100 parts of methyltetrahydrophthalic anhydride (trade name: HN-2200, manufactured by Hitachi Chemical Co., Ltd.) as an acid anhydride, 2.2'-m-phenylenebis(2-oxazoline) (manufactured by Takeda Pharmaceutical Co., Ltd.) as an oxazoline compound company) 40
15 parts of carbolic acid (reagent grade) as a phenol compound were mixed therein and reacted at 140°C for 1 hour to obtain a homogeneous liquid composition.

Example 2 100 parts of tetrahydrophthalic anhydride (trade name: Rikacid TH5, manufactured by Shinnihon Rika Co., Ltd.) as an acid anhydride, and 2.2'-m-phenylenebis(2-
oxazoline) and 8 parts of bisphenol A (reagent grade) as a phenol compound were blended and reacted at 130°C for 1 hour to obtain a homogeneous liquid composition.

Example 3 100 parts of methyl nadic anhydride (trade name: Kayahard MCD, manufactured by Nippon Kayaku Co., Ltd.) as an acid anhydride, 25 parts of 2.2'-m-phenylenebis(2-oxazoline) as an oxazoline compound, and 25 parts of 2.2'-m-phenylenebis(2-oxazoline) as a phenol compound. 10 parts of bisphenol A (reagent-grade) was blended and the temperature was 1.5 at 150°C.
A homogeneous liquid composition was obtained by reacting for a period of time.

Example 4 100 parts of methyltetrahydrophthalic anhydride (trade name: NH2200, manufactured by Hitachi Chemical Co., Ltd.) as an acid anhydride, 2.2'-m-phenylene bis(
2-oxazoline) (manufactured by Kurade Pharmaceutical Industry Co., Ltd.) and 5 parts of phenylmercaptan (reagent grade) as a mercaptan compound were blended and reacted at 130°C for 2 hours to obtain a homogeneous liquid composition.

Example 5 100 parts of tetrahydrophthalic anhydride (trade name: Rikacid TH1, manufactured by Shin Nippon Rika Co., Ltd.) as an acid anhydride, and 2.2'-m-phenylenebis(2-
oxazoline) and 10 parts of ethylene-bis-3-mercaptopropionate (reagent grade) as a mercaptan compound were blended and reacted at 130°C for 1 hour to obtain a homogeneous liquid composition.

Example 6 100 parts of methyl nadic anhydride (trade name: Kayahard MCD, manufactured by Nippon Kayaku Co., Ltd.) as an acid anhydride, 30 parts of 2.2'-m-phenylenebis(2-oxazoline) as an oxazoline compound, and 30 parts of 2.2'-m-phenylenebis(2-oxazoline) as a mercaptan compound Ethylene-bis-3-mercaptopropionate (reagent grade) 1
0 parts were blended and reacted at 140°C for 1=12 hours to obtain a homogeneous liquid composition.

Comparative Example 1 Methyltetrahydrophthalic anhydride (trade name: HN-2200, manufactured by Hitachi Chemical) was used as the acid anhydride.

Comparative Example 2 Tetrahydrophthalic anhydride (trade name: Rikacid TH1, manufactured by Shinnihon Rika Co., Ltd.) was used as an acid anhydride curing agent.

Comparative Example 3 Methyl nadic anhydride (trade name: Kayahard MCD1 manufactured by Nippon Kayaku Co., Ltd.) was used as the acid anhydride.

These acid anhydride curing agents are combined with bisphenol A diglycidyl ether type epoxy resin (trade name: G Y 26
0, manufactured by Ciba Geigy, epoxy equivalent: 190), it was blended so that (acid anhydride mole/epoxy equivalent) = 0.9, and tris-2,4,6 was added as a curing accelerator.
-Dimethylaminomethylphenol (Product name: DYO6
4. Ciba Geigy Co., Ltd.) was mixed with o, oos moles of silica powder (trade name: Crystallite A-1, Takimori Co., Ltd.) as a filler at 45% by volume at 100°C for 3 hours + 1
It was cured at 50° C. for 15 hours, and the properties of the cured product were investigated.

The results are shown in Tables 1 and 2. Furthermore, no coloration due to oxidation during curing was observed in any of the cured products.

(Left below) As is clear from these tables, the examples of the present invention have extremely superior mechanical properties and toughness compared to the comparative examples, and have heat resistance and mechanical properties (especially toughness) that were previously unachievable. can be achieved at a high level.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to provide a curing agent for epoxy resins that can achieve both heat resistance and mechanical properties (particularly toughness) at a high level, and its industrial value is extremely large.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the glass transition temperature and tensile strength of epoxy resin, and FIG. 2 is a diagram showing the relationship between the glass transition temperature and fracture toughness value of epoxy resin. Agent: Patent Attorney Nori Ken Yudo Daishimaru Ken Tensile Strength (~/77s)

Claims (1)

[Scope of Claims] (a) 1 mol of acid anhydride (b) 0 oxazoline compound represented by the following general formula
．． 05 to 0.4 mol ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼ [However, in the formula, X is a divalent organic group, D is a divalent organic group, n
is 0 or 1, and there are ▲mathematical formulas, chemical formulas, tables, etc.▼
The ring structure is a 5-membered ring. (c) An epoxy curing agent characterized by having a composition ratio of 0.01 to 0.4 mol of a phenol compound or 0.03 to 0.2 mol of a mercaptan compound.