JPH0414701B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in epoxy resin compositions containing an epoxy compound, a thiol curing agent, and an amine curing accelerator. In particular, the present invention relates to a curable epoxy resin composition with good workability and extended pot life without significantly reducing the curing speed or significantly increasing the resin viscosity. (Field of Industrial Application) The curable epoxy resin composition of the present invention has a low resin viscosity, a long pot life, and a fast curing speed, so it has excellent workability and can be used for various purposes, such as Applications include adhesives for general consumers such as household use and model assembly, as well as adhesives for manufacturing electrical equipment such as adhesives between micromotor ferrite magnets and cases, and optical communications. It can be used very advantageously in many applications, such as in the production of optoelectronic equipment, such as as an adhesive for assembling glass fiber connectors. Furthermore, it can be extremely advantageously used as a resin for encapsulating or sealing electronic parts, or as a molding material for electrically insulating materials. Furthermore, without using organic solvents,
Alternatively, it can be advantageously used as a paint. (Prior art) Conventionally, epoxy resin compositions containing a polyfunctional epoxy compound, a thiol curing agent, and an amine curing accelerator cure quickly at room temperature and at low temperatures below room temperature, and have excellent adhesive properties and heat resistance. It is widely used in various fields such as adhesives because it provides a cured product with high properties and chemical resistance. However, since this epoxy resin composition has a short pot life, it has the disadvantage that painting work and assembly work are time-limited. In order to improve the above-mentioned drawbacks of such epoxy resin compositions, the present inventors have previously proposed a method of significantly retarding the curing speed by adding an acidic compound such as carboxylic acid or carboxylic acid anhydride as a curing reaction retarder. proposed an invention relating to a composition that extended the pot life without causing any
Publication No.). And this invention is being implemented industrially. However, in this invention, when a polybasic acid or its anhydride is used as an acidic compound, it reacts with amines as a curing accelerator to form a salt and becomes a highly viscous liquid or solid, so the epoxy resin There is still the disadvantage that this results in an undesirable increase in the viscosity of the composition, thereby reducing the workability. This problem does not occur when a monobasic acid or its anhydride is added as an acidic compound, but since monobasic acid has one functional group, it causes a decrease in the crosslinking density in the cured resin product, resulting in a hardening process. It has a negative effect on the heat resistance and chemical resistance of objects. (Problems to be Solved by the Invention) The present invention provides a curable epoxy resin composition using a thiol compound as a curing agent and an amine as a curing accelerator. It is an object of the present invention to provide a curable epoxy resin composition which can be effectively extended without causing such troubles and has good workability and cured physical properties. (Means for Solving the Problems) As a result of various studies in order to solve the problems of the previous stage, the present inventors have discovered that a curable epoxy resin composition containing a thiol curing agent and an amine curing agent undergoes a curing reaction. It has been discovered that this objective can be achieved by incorporating a mercapto organic acid having one carboxyl group and at least one thiol group in one molecule as a retarder,
This completes the present invention. That is, the curable epoxy resin composition of the present invention includes an epoxy compound having an average of more than one epoxy group in one molecule, a thiol compound having an average of more than one thiol group in one molecule as a curing agent, And in epoxy resins containing amines as curing accelerators, one carboxyl group and at least one carboxyl group in one molecule as curing reaction retarders.
This composition is characterized by containing a mercapto organic acid having thiol groups. As the epoxy compound having an average of more than one epoxy group in one molecule in the present invention, any of various epoxy compounds used in ordinary epoxy resins can be used. To illustrate 2 to 3 of the epoxy compounds used, polyorthocresol formaldehyde poly(2.
Epoxy novolacs such as 3-epoxypropyl) ether, polyphenol formaldehyde poly(2,3-epoxypropyl) ether, epoxy compounds obtained by the reaction of bisphenol A or resorcinol with epichlorohydrin, epoxidized polyolefins, phthalic anhydride Examples include epoxy compounds obtained by the reaction of acid and epichlorohydrin. There are various thiol compounds having an average of more than one thiol group in one molecule, which are used as curing agents in the present invention. For example, 1.4-
Alkyl polythiols such as butanedithiol, 1,8-octanedithiol, 2,2'-bismercapto-diethyl ether, polyethers containing terminal thiol groups, polythioethers containing terminal thiol groups, trimethylolpropane trithioglycolate, pentaerythritol tetra Thiol compounds and epoxy compounds obtained by the esterification reaction of mercapto organic acids with polyols such as thioglycolate, dipentaerythritol hexathioglycolate, trimethylolpropane trithiopropionate, trimethylolpropane trithiobenzoate, etc. and hydrogen sulfide, thiol compounds with terminal thiol groups obtained by the reaction of polythiols such as 2,2'-bismercaptodiethyl ether, and epoxy compounds, and bis(dicycloethyl) formal. and thiol compounds obtained from sodium polysulfide. As the amines used as curing accelerators in the present invention, all amine curing agents for ordinary epoxy resins can be used. Examples of amines used include aliphatic amines, modified aliphatic amines,
Examples include aromatic amines, modified aromatic amines, alicyclic amines, modified alicyclic amines, heterocyclic amines, modified heterocyclic amines, polyamide amines, modified polyamide amines, and tertiary amines. The curing reaction retarder used in the present invention is a mercapto organic acid having one carboxyl group and at least one thiol group in one molecule.
Examples include mercapto aliphatic monocarboxylic acids such as mercaptoacetic acid, mercaptopropionic acid, and mercaptobutyric acid, mercapto aliphatic monocarboxylic acids obtained by esterification reaction between hydroxy organic acids and mercapto organic acids, and mercaptobenzoic acid. Examples include mercapto aromatic monocarboxylic acids. The amount of mercapto organic acid used as a curing reaction retarder in the present invention varies depending on the type of mercapto organic acid and the desired degree of extension of pot life, etc., and cannot be generally specified. Relatively small amounts of up to 10% by weight relative to the compound are sufficient. Further, the mercapto organic acid may be added to the epoxy compound as it is and dissolved therein, or may be added to the thiol curing agent or the amine curing accelerator. Furthermore, the mercapto organic acid may be dissolved in a suitable solvent in advance and then added in the various manners described above. Various additives such as fillers, pigments, softeners, flow inhibitors, diluents, etc. can be added to the curable epoxy resin composition of the present invention, if necessary. Additionally, a silane coupling agent can be added to improve adhesion to metals and glass, especially water-resistant adhesion. These additives may be added in advance to either the epoxy compound or the thiol curing agent, or to both, or to the amine curing accelerator or the mercapto organic acid as a curing reaction retarder. It is also possible. Furthermore, it is also possible to mix the epoxy compound and the curing agent etc. at the time of mixing or after the mixing. (Effects, etc.) In the epoxy resin composition of the present invention, the mercapto organic acid as the curing reaction retarder reacts with the amines as the curing accelerator to form a salt, which can effectively retard the curing reaction. . Moreover, since the formed salt has a low viscosity, there is no risk of increasing the resin viscosity, and since the mercapto organic acid is a polyfunctional compound having carboxyl groups and thiol groups, the crosslink density in the cured resin increases. There is also no fear that the heat resistance and chemical resistance of the cured resin will be reduced due to a decrease in . Therefore, the curable epoxy resin composition of the present invention has a long pot life despite being fast curable, has a low resin viscosity, has excellent workability, and has good cured physical properties. . (Examples, etc.) Next, Examples and Comparative Examples will be further described in detail. "Parts" and "%" in these examples indicate "parts by weight" and "% by weight", respectively, unless otherwise specified. Examples 1 to 4 Katsupukiyure 3-800LC (trade name, Yuka Ciel Epoxy Co., Ltd., viscosity 115 Pa.s/25°C, mercaptan number
3.6 meq/g, specific gravity 1.15) in 100 parts, 2, 4, 6
-tris(dimethylaminomethyl)phenol
10 parts and various mercapto organic acids listed in Table 1 were mixed in the amounts listed in Table 1 to prepare a curing agent composition. The viscosity of this curing agent composition at 25°C is shown in Table 1.
It was as shown in. In addition, Kupkuure 3-800LC is a compound represented by the following general formula (in the formula, R represents an alkyl group, and n represents a number of 1 to 2). Next, a curable epoxy resin composition was prepared using 1 g of Epicote 828 (trade name, Bisphenol A-based epoxy resin, epoxy equivalent: 190, manufactured by Yuka Ciel Epoxy Co., Ltd.) and 1 g of the curing agent composition prepared as described above. The gelation time and setting time at 20°C were measured. The results were as shown in Table 1. Additionally, the same curable epoxy resin composition used in the above measurements, namely Epicote 828
A mixture of equal amounts of each curing agent composition was used as an adhesive, and the tensile shear adhesive strength at 20°C was measured. The results were as shown in Table 1. Comparative Example 1 A curable composition was prepared in the same manner as in Examples 1 to 4 except that no mercapto organic acid was used, and various tests were conducted in the same manner. The results were as shown in Table 1. In addition, each test (measurement) listed in Table 1 was conducted according to the following method. () Measuring method of viscosity JISK using an Emira rheometer and an electronic constant temperature water bath (SHARP MODEL TE-101C)
-Measure the viscosity at 25±0.2℃ according to 6833. () Method for measuring gelation time The epoxy compound and curing agent composition were
After curing for at least one night at a room temperature of 20℃,
Weigh out 1 g of each of the epoxy compound and the curing agent composition on a 30 x 100 x 0.3 mm tin plate in a room at 100°C, and mix with a glass rod. Stir regularly with a glass rod, and measure the time from the start of mixing until the viscosity suddenly increases, and use this as the gelation time. () Method for Measuring Set Time When measuring the gelation time described above, quickly take out a small portion of the uniformly mixed composition, use it as an adhesive, and attach two tin plates of the above dimensions to the center. Glue the glue in a cross pattern nearby, and measure the time from the start of mixing until the glue stops moving by hand, and use this as the set time. () Measuring method of tensile shear adhesive strength According to the method of JISK-6850. The adherend is a mild steel plate whose surface has been treated with #180 emery sandblasting. N is an abbreviation for Newton.

[Table] As is clear from the results in Table 1, the gelation time could be effectively extended by adding a small amount of the mercapto organic acid of the present invention. Moreover, in this case, the setting time was not significantly extended, and there was no decrease in adhesive strength. Furthermore, as is clear from the fact that there is no significant increase in the viscosity of the curing agent composition, the viscosity of the curable epoxy resin composition hardly increases due to the addition of the mercapto organic acid, and this curable epoxy resin The composition has excellent workability. Examples 5 to 7 A curing agent composition was prepared by adding 10 parts of 2,4,6-tris(dimethylaminomethyl)phenol as an accelerator and mercaptoacetic acid in various proportions to 100 parts of Katsupukyure 3-800LC. did. Using this curing agent composition, the viscosity of the curing agent composition, gelling time, setting time and tensile shear adhesive strength of the epoxy resin composition were measured in the same manner as in Examples 1 to 4. The results are shown in Table 2. It was as shown in.

[Table] As is clear from the results in Table 2, the gelation time can be effectively extended depending on the amount of mercapto organic acid added as a curing reaction retarder. Moreover, in this case, there was no significant prolongation of the setting time (the difference between the gelation time and the setting time was almost constant regardless of the amount of mercapto organic acid added). Also,
As is clear from the fact that the curing agent composition does not show a significant increase in viscosity due to the addition of the mercapto organic acid, the deterioration in workability due to the increase in the viscosity of the epoxy resin composition is almost negligible. Comparative Examples 3 to 7 100 parts of Katsupukyure 3-800LC, 10 parts of 2,4,6-tris(dimethylaminomethyl)phenol as an accelerator, and methyltetrahydrophthalic anhydride (known as a curing reaction retardant) as a curing reaction retarder. Curing agent compositions were prepared by adding mercaptosuccinic acid, mercaptosuccinic acid, or dimercaptosuccinic acid in various proportions. Example 1 using this curing agent composition and other conditions
The viscosity of the curing agent composition, the gelling time, the setting time, and the tensile shear adhesive strength of the epoxy resin composition were measured in the same manner as in Examples 4 to 4. The results were as shown in Table 3. As is clear from the results in Table 3, each of the curing reaction retarders (polycarboxylic anhydride or polycarboxylic acid having a thiol group) was able to effectively extend the gelation time depending on the amount added. However, on the other hand, it can be seen that the viscosity of the curing agent composition increases significantly depending on the amount added, and the epoxy resin composition using this curing agent composition is inferior in workability.

[Table] Examples 8 to 9 To 100 parts of Katsupukyure 3-800LC, 10 parts of 2,4,6-tris(dimethylaminomethyl)phenol as an accelerator and O-mercaptobenzoic acid were added.
A curing agent composition was prepared by adding 0.02 gram equivalent. Using this curing agent composition, the viscosity of the curing agent composition, gelling time, setting time, and tensile shear adhesive strength at room temperature and 60°C of the epoxy resin composition were measured in the same manner as in Examples 1 to 4. The results were as shown in Table 4. As is clear from the results in Table 4, the gelation time can be effectively extended by adding mercaptoacetic acid or O-mercaptobenzoic acid as a curing reaction retarder. Moreover, in this case, the setting time was not significantly extended. Further, as is clear from the fact that the curing agent composition does not exhibit a significant increase in viscosity due to the addition of the mercapto organic acid, the deterioration in workability due to the increase in the viscosity of the epoxy resin composition is almost negligible. Furthermore, regarding adhesive strength,
Compared to Comparative Example 1 in which no curing reaction retarder was added, the heat-resistant adhesive strength at both 20° C. and 60° C. was the same or higher, with no deterioration in performance. Comparative Examples 8 to 9 10 parts of 2,4,6-tris(dimethylaminomethyl)phenol as an accelerator and 0.02 gram equivalent of acetic acid and benzoic acid, which are known as curing reaction retarders, were added to 100 parts of Katsupukyure 3-800LC. and mixed uniformly to prepare a curing agent composition. Using this curing agent composition, the rest was Example 8.
The viscosity of the curing agent composition, the gelation time and setting time of the epoxy resin composition, and the tensile shear adhesive strength at room temperature and 60°C were measured in the same manner as in Items 9 to 9. The results were as shown in Table 4. As is clear from the results in Table 4, the addition of each curing reaction retarder can effectively extend the gelation time, and the increase in viscosity of the curing agent composition is negligible. The adhesive strength was the same or higher than that of the epoxy resin composition containing no curing reaction retardant (Comparative Example 1), and there was no decrease in adhesive performance.
It can be seen that the heat-resistant adhesive strength at 60°C decreases and is inferior to the constant-temperature adhesive strength.

[Table] Example 10 Epiquure QX-40 (trade name of pentaerythritol-tetramercaptopropionate manufactured by Yuka Ciel Epoxy Co., Ltd., mercaptan equivalent 7.69 eq/
Kg, viscosity 460mPa・s/25℃, specific gravity 1.2920℃/4
10 parts of N,N-dimethylbenzylamine to 90 parts of
A curing agent composition was prepared by adding 0.01 gram equivalent of 3-mercaptopropionic acid as a curing reaction retarder. The viscosity of this curing agent composition was as shown in Table 5. Next, Epomic R710 (trade name manufactured by Mitsui Petrochemical Epoxy Co., Ltd., an epoxy resin prepared by the condensation reaction of 4,4'-bishydroxyphenylethane and epihalohydrin, epoxy equivalent 173, viscosity
The gelation time at 20° C. of a curable epoxy resin composition using 5 g of the curing agent composition prepared as described above and 5 g of the curing agent composition (2900 mPa·s/25° C.) was measured. The measurement method is to cure the epoxy compound and the curing agent composition at room temperature of 20°C for at least one night, and then place the epoxy compound and the curing agent composition in a paper cup with a capacity of about 50ml in a room at 20±2°C. 5 each
A method was used in which the gelation time was determined by weighing out 1.5 g of each sample, mixing with a glass rod, repeating regular stirring with the glass rod, and measuring the time from the start of mixing until the viscosity suddenly increased. The results were as shown in Table 5. Furthermore, using this epoxy resin composition, Example 8
Set time at room temperature and 60°C in the same manner as in ~9.
The results of measuring the tensile shear adhesive strength are shown in Table 5. As is clear from the results in Table 5, the gelation time can be effectively extended by adding 3-mercaptopropionic acid as a curing reaction retarder. Moreover, in this case, the setting time was not significantly extended. Further, as is clear from the fact that the curing agent composition does not exhibit a significant increase in viscosity due to the addition of the mercapto organic acid, the deterioration in workability is almost negligible. Furthermore, we also provide comparative examples regarding adhesive strength.
Compared to the case in which no curing reaction retardant was added in No. 10, the adhesive strength at room temperature and the heat-resistant adhesive strength at 60°C were the same or higher, and no deterioration in performance was shown. Comparative Examples 10-12 90 parts of Epicure QX-40 and accelerator N, N-
10 parts of dimethylbenzylamine and a case without a curing reaction retardant, and a case in which propionic acid and dodecynylsuccinic anhydride, which are known as curing reaction retarders, were added.
A curing agent composition was prepared by adding 0.01 gram equivalent and mixing uniformly. Using this curing agent composition, the rest was Example 10.
The viscosity of the curing agent composition, the gelation time and setting time of the epoxy resin composition, and the tensile shear adhesive strength at room temperature and 60°C were measured in the same manner as in .
The results were as shown in Table 5. As is clear from the results in Table 5, when no curing reaction retarder is added, gelation time is extremely short and workability is poor. In addition, by adding propionic acid, which is known as a curing reaction retarder, the gelation time can be effectively extended.
The increase in viscosity of the curing agent composition was also negligible, and the adhesive strength at room temperature was also higher than that of an epoxy resin composition that did not contain a curing reaction retarder (Comparative Example 10).
Although there was no decrease in adhesive strength, on the other hand, the heat-resistant adhesive strength at 60°C decreased, indicating that the adhesive strength at high temperatures was inferior. Furthermore, by adding known dodecynylsuccinic anhydride, the gelation time can be effectively extended, and the adhesive strength at room temperature and 60°C is also lower than that of an epoxy resin composition containing no curing reaction retarder (Comparative Example 10).
It can be seen that although the adhesive strength was the same or higher than that of the curing agent composition, the viscosity of the curing agent composition was significantly higher, and the workability was significantly lower.

【table】

Claims (1)

[Claims] 1 Epoxy compounds having an average of more than one epoxy group in one molecule, thiol compounds having an average of more than one thiol group in one molecule as a curing agent, and epoxy resins containing amines as a curing accelerator , one carboxyl group and at least one carboxyl group in one molecule as a curing reaction retarder.
A curable epoxy resin composition comprising a mercapto organic acid having thiol groups.