JPH05117368A - Curing agent for epoxy resin - Google Patents

Abstract

PURPOSE:To provide a curing agent for epoxy resins, containing a condensation product between a specified dimer acid component and an alkylenepolyamine as the active component, showing a remarkably low viscous liquid state and readily mixable with a liquid epoxy resin even in a solventless system. CONSTITUTION:A curing agent for epoxy resins, containing as the active component a condensation product between (A) a dimer acid component containing >=50wt.% chain dimer acid (ester) of the formula (R<1> and R<2> are H or lower alkyl; m, n, p and q are 0 or >=1 while satisfying m+n=13 and p+q=15) and (B) a 4-20C alkylenepolyamine.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel epoxy resin curing agent, and more specifically, a liquid substance having an extremely low viscosity,
The present invention relates to an epoxy resin curing agent composed of a condensation product of a dimer acid and a polyamidoamine, which can be easily blended with a liquid epoxy resin even in a solvent-free system and can give a flexible resin cured product.

[0002]

BACKGROUND OF THE INVENTION Dimer acid is a polyvalent carboxylic acid obtained by polymerization reaction of two or more molecules of unsaturated fatty acid, and is usually obtained as a mixture of two or more kinds, and various applications as a mixture. Have been offered to. This dimer acid is the highest molecular weight dibasic acid which is highly reactive and hydrophobic and which can be obtained industrially, and the polymer derived from it is amorphous and flexible and has good stability at low temperature. It is used in many fields because it shows sex. For example, a non-reactive dimer acid polyamide obtained from dimer acid as a raw material is tough, shows flexibility, and has good adhesive performance, and thus is used as a component of an adhesive, an ink, a surface coating agent, Reactive substances are compounded with epoxy resins as epoxy resin curing agents, and are used for surface coating of metals, plastics, ceramics, etc., or as two-component reactive adhesives.

Such dimer acid has hitherto been used as a catalyst using montmorillonite clay as a catalyst, and unsaturated resin acid as a dimer acid.
It is produced by a method of dimerizing at a high temperature of about 00 to 250 ° C. In this method, since the trans-double bond is generally conjugated to increase the thermal polymerization rate, tall oil fatty acid or soybean oil fatty acid having a high linoleic acid content is used as a raw material, and its industrial process is standardized. Has been done.

By the way, when dimer acid is produced by such a method, linoleic acid dimerizes,

[Chemical 2] In addition to the chain dimer acid represented by

[Chemical 3] as well as

[Chemical 4] A mixture containing the cyclic dimer acid represented by is obtained.

However, when the content of the cyclic dimer acid is high, the viscosity and the pour point become high. Therefore, when it is used as a curing agent for epoxy resin, for example, it is diluted with an organic solvent such as xylene or alcohol to lower the viscosity. It is necessary to use it, but using such a diluted product causes the impact resistance and high temperature stability in the cured epoxy resin to be impaired, and in recent years, it has been an organic solvent in terms of environmental pollution and work hygiene. Due to the tendency to limit the use of dimer acid, there is an increasing demand for a dimer acid type curing agent that can be used without requiring dilution. To respond to this request,
The content of the chain dimer acid in the dimer acid mixture may be increased, but the content of the chain dimer acid in the dimer acid mixture known so far is 40% by weight at most. Of american oil
Chemistry Society (J. Am. Oil Chemi
st's Soc. ) Volume 51, page 522 (1
974)], it was not possible to obtain a dimer acid mixture having a chain dimer acid content of 50% by weight or more.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a dimer acid type epoxy resin curing agent which has a low viscosity, a large fluidity at low temperature, and can be easily compounded in a liquid epoxy resin without being diluted with an organic solvent. It was made for the purpose of providing.

[0007]

Means for Solving the Problems The inventors of the present invention previously contained 50% by weight or more of a chain dimer acid or its ester or both by dimerizing a specific raw material under specific conditions. We succeeded in obtaining a dimer acid mixture with low viscosity and good low-temperature fluidity (Japanese Patent Application No. 2-1842).
94), and as a result of further studies, it was found that the purpose can be achieved by using a mixture of this dimer acid mixture with a specific alkylene polyamine as an epoxy resin curing agent, and based on that finding, The present invention has been completed.

That is, the present invention has the general formula

[Chemical 5] (In the formula, R ¹ and R ² are each a hydrogen atom or a lower alkyl group, and they may be the same or different, and m, n, p and q are each an integer of 0 or 1 or more. , M + n = 13, p + q = 15), and a dimer acid component containing at least 50% by weight of a dimer acid selected from the chain dimer acid and its ester, and an alkylene polyamine having 4 to 20 carbon atoms. The present invention provides an epoxy resin curing agent containing a condensation product as an active ingredient.

The dimer acid component used in the present invention is
Any of the dimer acid represented by the above general formula, its monoester, diester, and a mixture thereof may be used.
Further, during the production of this dimer acid, trimer acid or its ester may be produced as a by-product, but it may be used while containing such a substance, or as a raw material during the production of dimer acid. It is possible to use a substance containing a monovalent fatty acid or an ester thereof derived therefrom.

The dimer acid component has 1 carbon atom.
The unsaturated dimer of 8 unsaturated fatty acids such as oleic acid, linoleic acid and lower alkyl esters thereof such as methyl ester, ethyl ester, n-propyl ester, isopropyl ester, n-butyl ester and tert-butyl ester may be mentioned. it can. These may be a single component or a mixed component containing two or more kinds.

The dimer acid component is obtained by polymerizing an unsaturated fatty acid or an ester thereof in the presence of a Lewis acid type or Bronsted acid type catalyst having high acid strength, and further hydrolyzing the ester when used as a raw material. As a raw material, oleic acid and its lower alkyl ester 70 can be obtained.
Those obtained by using an unsaturated fatty acid or a lower alkyl ester thereof containing at least wt% are preferable.

The dimer acid component thus obtained usually contains monomer components such as unreacted components and by-produced branched fatty acids, so these are removed by vacuum distillation, and then the distillation residue is separated into molecules. It may be purified by distillation and used, or may be used in a state in which the monomer component is contained.

Examples of the monovalent fatty acid and its ester that can coexist with the dimer acid component include, for example, caproic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid,
Behenic acid, myristoleic acid, palmitoleic acid, oleic acid, elaidic acid, linoleic acid and their methyl ester, ethyl ester, n-propyl ester, isopropyl ester, n-butyl ester, isobutyl ester, tert-butyl ester, etc. Be done. These may be used alone or in combination of two or more.

4 carbon atoms to undergo condensation reaction with the dimer acid
Examples of the alkylene polyamine of 20 to 20 include diethylene triamine, triethylene pentamine, tetraethylene pentamine, pentaethylene hexamine, and hexaethylene heptamine. These may be used alone or in combination of two or more.

Since the presence of a terminal amino group is required to act as a curing agent for an epoxy resin, the alkylene polyamine is a free or esterified carboxyl group in the dimer acid of the primary amino group therein. It is advantageous to use it in such a ratio that the equivalent ratio to the group is 0.8 or more and less than 2.0.

The condensation reaction is usually 120 to 250 under normal pressure.
C., preferably by heating at a temperature in the range 180 to 230.degree. Further, in order to prevent coloring of the product, it is advantageous to carry out under an atmosphere of an inert gas such as nitrogen gas. The reaction time depends on the reaction temperature and the type of raw material used and cannot be determined unconditionally, but usually about 2 to 5 hours is sufficient. Further, it is desirable that the reaction be aged under a reduced pressure for an appropriate time before the completion of the reaction. Although the viscosity of the reaction solution increases with the progress of the reaction, the reaction product does not solidify even after the completion of the reaction, and the transfer from the reaction container to the storage container is easy even at room temperature. Also,
If desired, at the end of the reaction, a solvent such as xylene or alcohol may be added as in the conventional products.

The epoxy resin curing agent containing the dimer acid polyamidoamine condensation product thus obtained as an active ingredient has a viscosity at 40 ° C. of 10,000 cp or less, which is extremely low compared to the conventional one.

[0018]

EFFECT OF THE INVENTION The epoxy resin curing agent of the present invention has an extremely low viscosity as compared with the conventional ones, can be easily compounded with a liquid epoxy resin without being diluted with an organic solvent, and has desirable physical properties. The epoxy resin can be cured without any damage.

[0019]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 As a raw material, a dimer acid composition containing 58% by weight of a linear dimer acid obtained by polymerizing oleic acid, 25% by weight of a cyclic dimer acid, and 17% by weight of trimer acid was used. Add diethylenetriamine so that the equivalent ratio of primary amino group / carboxyl group becomes 1.0, and under a nitrogen atmosphere, 2
The reaction was carried out at 00 ° C. for 2.5 hours and at 220 ° C. and 5 mmHg for 1 hour to obtain a dimer acid polyamidoamine condensation product.

Next, this dimer acid polyamidoamine condensation product was added and stirred at a ratio of 30 parts by weight to 100 parts by weight of an epoxy resin having an epoxy equivalent of 190 (Epicoat 819, manufactured by Yuka Shell Epoxy Co., Ltd.). Later,
When kept at room temperature for 48 hours, a transparent cured resin having a viscosity at 40 ° C. of 5500 cp was obtained.

Examples 2 to 9 and Comparative Examples 1 to 4 The procedure of Example 1 was repeated, except that the raw materials of the types and amounts shown in Table 1 were used. The results are shown in Table 1.

[Table 1] Note 1) Measured with B-type viscometer 2) Amount used per 100 parts by weight of epoxy resin 3) ○: transparent, ×: opaque

Example 10 A dimer acid polyamidoamine condensation product was prepared in exactly the same manner as in Example 5, except that the ethyl ester thereof was used in place of the dimer acid in Example 5. 5 parts of this was added to 100 parts by weight of the same epoxy resin as in Example 1.
When mixed at a ratio of 5 parts by weight and cured, a cured resin having a viscosity of 2000 cp at 40 ° C. and a transparent appearance was obtained.

Example 11 A dimer acid polyamidoamine condensation product was prepared in the same manner as in Example 6 except that isopropyl ester thereof was used instead of the dimer acid in Example 6. This was mixed with 55 parts by weight of 100 parts by weight of the same epoxy resin as in Example 1 and cured,
A cured resin having a viscosity of 2000 cp at 40 ° C. and a transparent appearance was obtained.

Claims (3)

[Claims] 1. A general formula: (In the formula, R ¹ and R ² are each a hydrogen atom or a lower alkyl group, and they may be the same or different, and m, n, p and q are each an integer of 0 or 1 or more. , M + n = 13, p + q = 15), and a dimer acid component containing at least 50% by weight of a dimer acid selected from the chain dimer acid and its ester, and an alkylene polyamine having 4 to 20 carbon atoms. An epoxy resin curing agent containing a condensation product as an active ingredient. 2. The condensation is carried out at a ratio such that the equivalent ratio of the primary amino group in the alkylene polyamine to the free or esterified carboxyl group in the chain dimer acid component is 0.8 or more and less than 2.0. The epoxy resin curing agent according to claim 1. 3. The epoxy resin curing agent according to claim 1, which has a viscosity at 40 ° C. of 10,000 cp or less.