JPS59182817A - Curable epoxy resin composition - Google Patents

Abstract

PURPOSE:The titled composition, obtained by incorporating a curing agent obtained by mixing a polythiol curing agent in a specific mixing proportion with an epoxy compound in the form of an adduct, and having a practical pot life without giving off a bad smell derived from thiol compounds. CONSTITUTION:A curable epoxy resin composition obtained by incorporating (A) a main agent consisting of an epoxy compound, preferably having <=1,500 molecular weight with (B) a polythiol compound curing agent consisting of a polythiol containing average two or more thiol groups, preferably 1,4-butanethiol in <=2 mixing ratio between the total number of the thiol groups in the component (B) and the number of total epoxy groups in the component (A) in the form of an epoxy-thiol adduct obtained by addition reaction of the components (A) and (B). EFFECT:The working atmosphere can be improved, and films having improved moisture and corrosion resistance are obtained by coating a metal therewith.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] This invention relates to improvements in curable epoxy resin compositions comprising an epoxy compound and a thiol compound.

[Background technology]

It is already known to use a thiol compound having a thiol group (-5ll, also referred to as a mercapto group) as a curing agent for epoxy resins. In this case, there are two ways to blend the thiol compound, one of which is
-17299 and Japanese Patent Application Laid-open No. 16800/1984, the thiol compound is blended in the form of a single substance, and other methods are described in Journal of Pain I...
Technology (Journal of Pa1nt T
technology), Volume 42, No. 540, 1
970, pages 37 to 41, in which a thiol compound is added to an epoxy compound and blended in the form of an epoxy-thiol adduct.

By the way, a blend of an epoxy resin and a thiol compound alone has a very slow curing speed and is therefore not practical. Therefore, tertiary amines are added as catalysts. In this way, the reaction between the epoxy group and the thiol group is greatly promoted, so that the pot life is shortened and curing occurs quickly even at low temperatures below room temperature.

On the other hand, depending on the application, the pot life is too short, which may result in time constraints and impede workability. In addition, there is the problem of bad odor specific to thiol compounds. Therefore, all of the above methods have been put into practical use only in special fields.

However, an epoxy cured product containing an epoxy resin as a main ingredient and containing a thiol compound as a curing agent and a tertiary amine as a curing accelerator has poor adhesiveness and chemical resistance. In particular, an epoxy cured product using a thiol compound in the form of an epoxy-thiol adduct has better adhesion and better mechanical properties. If the thiol compound is in the form of adak 1~, the toxicity derived from the thiol compound is also reduced. Therefore, in a curable epoxy composition capable of producing such a cured product, it is strongly desired to solve the problem of the pot life being too short and the problem of bad odor.

Regarding pot life, for example, JP-A-56-57820
In the technique described in the publication, an acidic compound is added to a composition consisting of an epoxy compound, a thiol compound, and an amine, and this is used as a curing reaction retarder to adjust the pot life. In this case, the acidic compounds include saturated aliphatic-basic acids and their acid anhydrides such as formic acid and acetic acid, unsaturated aliphatic-basic acids such as acrylic acid and meccrylic acid, halogenated fatty acids such as monochloroacetic acid, glyco- monobasic oxyacids such as oxalic acid, aldehydic acids and ketonic acids such as glyoxalic acid and amorphic acid, aliphatic polybasic acids such as oxalic acid and maleic acid, and their acid anhydrides, and aromatic acids such as benzoic acid. Basic acids, aromatic polybasic acids such as fucuric acid and their acid anhydrides, Lewis acids such as zinc chloride and ferric chloride, Lewis acid amine complex salts such as boron trifluoride monoethylamine complex salts, etc. are used. therefore,
In addition to the disadvantage of requiring these acidic compounds separately, there is concern that the addition of acidic compounds may have an adverse effect on physical properties and chemical properties. Needless to say, no measures have been taken to deal with the odor originating from the thiol compounds used.

[Purpose of the invention]

In view of the above circumstances, this invention addresses the conventional problems with curable compositions consisting of a combination of an epoxy resin, a thiol compound, and tertiary amines, that is, adjusts the short pot life to a practical pot life. At the same time, the objective is to eliminate the peculiar odor of thiol compounds and improve the working environment.

[Disclosure of the invention]

The inventor decided to use the thiol compound in the form of an epoxy-thiol adduct because it yields an epoxy cured product that not only has excellent adhesiveness and chemical resistance but also has good mechanical properties. Then, we investigated what caused the above-mentioned drawbacks in this case, devised countermeasures, and conducted repeated experiments. As a result, the problem lies in the blending ratio when making the epoxy-thiol adduct, and by making this appropriate, the above-mentioned drawbacks can be eliminated at once, and surprisingly, the physical properties and chemical resistance are improved. They discovered that it was possible to obtain even better effects on the surface, and thus completed this invention. This point will be explained in more detail.

The problems with the curable epoxy compositions described in the Journal of Paint Technology stem from the following circumstances. That is, as is clear from Table 2 on page 38 of the same report, in this case, when producing an adduct of diglycidyl ether of bisphenol A and low molecular weight dimercaptan, the blending ratio is such that the amount of dimercaptan is higher than that of bisphenol. The amount of diglycidyl ether in A was extremely large, and in both cases, the equivalent ratio was about three times as much.

Therefore, unreacted dimercaptan produced epoxy
It will remain in the thiol adduct. That is, even though it was an epoxy-thiol adduct, in this case it was nothing more than a mixture of an epoxy-thiol adduct and a low molecular weight dimercaptan.

Conventionally, when adding a thiol compound to an epoxy compound, the well-known epoxy-amine adduct has the same formulation in principle, so in the same way as in this case,
The compounding ratio for the addition reaction is thiol group/epoxy group>
2 (In the case of an epoxy-amine adduct, the ratio is amino group/epoxy group>2.) That is, it was common general knowledge that the reaction had to be carried out in a state where the thiol group was in large excess compared to the epoxy group. The technology described in the above report probably also follows this kind of common technical knowledge. In contrast, the inventor considered that the above-mentioned problem may be caused by the unreacted thiol compound remaining in the epoxy-thiol adduct. Firstly, it is clear that this unreacted thiol compound is the cause of the malodor, and secondly,
It was speculated that this residual thiol compound was stimulated by tertiary amines and caused a shortened pot life. In this way, we decided to examine the epoxy-thiol blending ratio in detail. Unlike conventional methods, in order to prevent unreacted thiol compounds from remaining, in other words, when carrying out an addition reaction between all or a part of the epoxy compound serving as the main ingredient and the thiol compound, the total number of epoxy groups in the epoxy compound to be added is reduced by reducing the total number of epoxy groups in the epoxy compound to be added to the thiol compound. The total number of thiol groups was set to be greater than or equal to the total number of thiol groups, and the reaction was carried out in a state where the number of epoxy groups was in excess. In this way, unreacted thiol compounds, that is, low molecular weight mercaptan, can be completely eliminated, and at the same time, the low molecular weight mecabutane becomes a high molecular weight compound by addition of the epoxy compound, which eliminates the bad odor. It became possible to control the reaction with epoxy compounds, making it possible to extend the practical pot life.

This invention was completed through such studies, and it is a curable material that uses an epoxy compound as a main ingredient having an average of one or more epoxy groups in one molecule and a thiol compound as a curing agent that has a thiol group. In the epoxy resin composition, 1. The epoxy compound is a polythiol having an average of two or more thiol groups in one molecule, and at least a part of the epoxy compound as the main ingredient and the blending ratio (total number of thiol groups in the polythiol/epoxy The gist of the invention is a curable epoxy resin composition that is blended into the composition in the form of an epoxy-thiol adduct obtained by an addition reaction in advance under conditions such that the total number of epoxy groups in the compound is 2 or less. do. This will be explained in detail below.

As the epoxy compound having an average of one or more epoxy groups used in this invention, all epoxy compounds normally used in the production of epoxy resins can be used. For example, bisphenol diglycidyl ether obtained by the reaction of bisphenols such as bisphenol A or bisphenol F with epichlorohydrin, novolac type epoxy resin obtained by the reaction of epichlorohydrin with a novolac resin obtained from phenols such as phenol or cresol, and formalin, In addition to fatty diglycidyl ethers obtained by the reaction of aliphatic polyglycols and epichlorohydrin, hydrogenated bisphenol A, and alicyclic diglycidyl ethers obtained by the reaction of hydrogenated bisphenol FQ and epichlorohydrin, general reactivity n-butyl glycidyl ether as a diluent.

Monoepoxy compounds such as phenyl glycidyl ether can also be used. It goes without saying that the number of glycidyl groups may be three or more.

In this invention, the thiol compound has an average of 2
A thiol compound having three or more thiol groups, ie, a polythiol, is used. Any thiol compound having an average of two or more thiol groups in one molecule can be used as the polythiol, but preferably one having 2 to 4 thiol groups in one molecule. It is.

Polythiols having five or more thiol groups in one molecule tend to gel during the synthesis of epoxy-thiol adducts, making the synthesis difficult. Preferred polythiols include alkyl polythiols.

Examples include ester compounds of polyol and thioglycolic acid. Specifically, 1.4-butanedithiol and 1.8-octanedithiol are examples.

As the polythiol, polyether dithiol represented by the following general formula, or an esterified product of a polyol represented by the following general formula % and thioglycolic acid may also be used. Examples of those represented by the latter formula include trimethylolpropane trithioglycolate, pentaerythritol 1-ltetraglycolate, and dipentaerythritol tetrathioglycolate.

Such a polythiol is preliminarily subjected to an addition reaction with all or part of the main ingredient, that is, an epoxy compound having an average of one or more epoxy groups in one molecule, and is blended in the form of an epoxy-thiol adduct.

In this case, the molecular weight of the epoxy compound is preferably 1500 or less. The molecular weight of the epoxy compound is 150
If it exceeds 0, the molecular weight of the synthesized epoxy-thiol adduct will become too large, and the subsequent reaction with the epoxy compound will be extremely slow, and the molecular chain between the thiol group that reacts with the epoxy group will become long. This is because if it is too long, the three-dimensional network bonds that characterize the epoxy cured product become loose, making it impossible to obtain practical properties of the cured product.

Epoxy-thiol adducts can be synthesized by conventional methods. In this case, tertiary amines are used as catalysts. Examples of tertiary amines include dicyandiamide, piperazine, N,N-dimethylaminobenzoic acid, imidazole-type ones such as piperazine acetate, imidazole acetate, 2-methylimidazole acetate, etc., as well as 2.4.6-1 Examples include phenol-type compounds such as -li(dimethylaminomethyl)phenol.

When making an adduct, the blending ratio of the epoxy compound and polythiol (total number of thiol groups in the polythiol/total number of epoxy groups in the epoxy compound) is 2 or less. Here, the total number of epoxy groups is the total number of epoxy groups (including the average) possessed by the epoxy compound reacted with polythiol (all or part of the main agent, and therefore the combination of different types when used together). ).

The same applies to the total number of thiol groups. In this way, since the blending ratio is 2 or less, all of the polythiol blended is necessarily added to the epoxy compound.

In this invention, 1. the thiol compound is used in the form of an epoxy-thiol adduct. Therefore, when this composition is used as a paint, that is, when it is applied to metal to form a film, it has been found to have superior moisture corrosion resistance compared to commonly commercially available polymercaptans and epoxy resins. This fact indicates that the same tendency is observed when a compound made from a precondensation product called amine adduct, which is a curing system of epoxy resin and amines, is used as a curing agent. ing.

In this invention, the equivalent ratio of the epoxy compound as the main ingredient and the epoxy-thiol adduct as the curing agent is preferably 8:1 to 1.2:1.

The curable epoxy resin composition of the present invention may contain various additives such as a reaction accelerator, a filler 2 coloring pigment, a flow inhibitor, a pigment dispersant, and a diluent, if necessary. As a reaction accelerator: 1. Known amines and phenols can be used as catalysts for the reaction between epoxy compounds and thiol compounds, depending on the conditions of use. Filler 2 As the coloring pigment, all those commonly used in the production of epoxy resins can be used. However, colored pigments, especially organic compound pigments, that react with epoxy groups or thiol groups are not preferred. As flow suppressants and pigment dispersants, commonly used silica-based and surfactants can be used, and as diluents, aromatic hydrocarbons can be used as long as they have the ability to dissolve epoxy compounds and thiol compounds. A wide range of solvents can be used, including esters, ketones, esters, ethers, and alcohols.

These various additives can be added to either or both of the epoxy compound and the thiol compound in advance.

Next, examples will be described together with comparative examples.

In these examples, "part" and "%" indicate "1 part by weight" and "% by weight," respectively, unless otherwise specified.

[Example 1] 282 parts (1 mol, 2 thiol groups) of polypropylene glycol thioglycol shown by the following structural formula and 30 parts of xylene
Put 0 part in a reflux condenser and a colben equipped with a stirrer and add 80 to 90 parts.
The mixture was heated to 0.degree. C., 0.5 part of 2,4.6-tri(dimethylaminomethyl)phenol was added, and the mixture was stirred uniformly. Next, while stirring at 80 to 90°C, Epicote 828 (Shell Chemical Co., Ltd. diglycidyl ether of bisphenol A, epoxy equivalent weight 190, molecular weight 38
0) 190 parts (1 epoxy group) were added over 2 hours. After the addition was completed, the mixture was stirred at 90-95°C for 1 hour.

The epoxy-thiol adduct thus obtained (
The adduct (hereinafter referred to as "adduct") was a viscous liquid with the following structure and an active hydrogen equivalent of 1070. The blending ratio in this case (number of thiol groups in polythiol/number of epoxy groups in epoxy compound, hereinafter referred to as "blending ratio") was 2.

Next, the gelation time and odor at 20° C. of a composition using 190 parts of Epicote 828 and 1070 parts of the adduct prepared by the above method were examined. Furthermore, the glass transition temperature, tensile strength, and elongation of the cured product obtained from this composition were measured. Next, add this composition to 0°8 x 7Qx 150
Table 1 shows the results of coating the film on a polished soft steel plate with a thickness of 50 to 60 μm and evaluating the film performance.

[Example 2] 398 parts (1 part, 3 thiol groups) of trimethylolpropane trithioglycolate shown by the following structural formula and 2.4.6-
1.0 part of tri(dimethylaminomethyl)phenol was heated to 80 to 90°C and mixed uniformly in the same manner as in Example 1. Separately, 475 parts (1 epoxy group) of Epicor) 1001 (product of Shell Chemical Co., Ltd., diglycidyl ether of bisphenol A, epoxy equivalent weight 475, molecule 190Q) were dissolved in 79 parts of xylene and 79 parts of methyl isobutyl ketone in advance. , this 75%
Epicoat 1001i solution was added over 3 hours. Next, n-butyl glycidyl ether (epoxy equivalent: 14
0) 105 parts (0.75 epoxy groups) were added over 2 hours. After the addition was completed, the mixture was stirred at 90-95°C for 1 hour.

The adduct thus obtained is estimated to be a 1:1 mixture of two compounds with the following structures, and has an active hydrogen equivalent of 1040. It was a viscous liquid containing 86% active ingredient.

(Left below) OF( 01■ 1-I S (CH2) 2 Go -OCH2H5(
CJ(2)2CO1QC2 The blending ratio for this adduct synthesis was 1.71.

Next, 633 parts of the same 75% Epicor) 1001 solution as above and Epicor) 154 (Shell Chemical Co., Ltd. product, novolak type epoxy resin, epoxy equivalent 180) 2
The same evaluation as in Example 1 was performed on a composition using 4 parts of adduct and 1175 parts of the adduct prepared by the above method, and a cured product obtained from the composition. The results are shown in Table 1.

[Example 3] Pentaerythritol pencutioglycolate Ctl 20CO (Ctl 2 ) 2S I-148 represented by the following structural formula
8 parts (1 mol, 4 thiol groups) and 1.3 parts of 2.4.6-[dimethylaminomethylphenol] were heated to 80 to 90°C and mixed uniformly in the same manner as in Example 1. Then, to this, 75% Epicoat 100 similar to Example 2 was added.
633 parts of one solution (one epoxy group) was added over 4 hours. Furthermore, 150 parts of phenyl glycidyl ether (epoxy equivalent: 152) (1 epoxy group) was added to 2
Added over time. After the addition was completed, the mixture was stirred at 90-95°C for 1 hour.

The adduct obtained in this way has the following structure,
Active hydrogen equivalent: 1172. It was a viscous liquid containing 87% active ingredient.

(Left below) lI C1-120CO (CH2) 2!51fCXs (C
, f(2) 2 CO0CH21-1s (CHz)
2CO0OCI-12 The blending ratio for this adduct synthesis was 2. Next, 633 parts of the same 75% Epicote 1001 solution as in Example 2, 633 parts of Epicote 1001 solution, 15424 parts of Epicote 15, and 1324 parts of Adduct prepared by the above method were used. The composition and the cured product obtained therefrom were evaluated in the same manner as in Example 1.

The results are shown in Table 1.

[Example 4] Polypropylene glycol thioglycol 4 of Example 1
23 parts (1.5 mol, 3 thiol groups); 2. /1
,6-! In the same manner as in Example 1, 0.3 parts of (dimethylaminomethyl)phenol and 141 parts of xylene were heated to 75 to 80°C and mixed uniformly. On the other hand, Epikote 154 (Novolak type epoxy resin manufactured by Shell Chemical Co., Ltd. Epoxy equivalent weight 1781 average 5.5 per molecule)
267 parts (epoxy group-containing material) 267 parts (epoxy group 1.5
Since 89 parts of xylene and 89 parts of methyl isobutyl ketone were dissolved in advance, this Epicoat 154i solution was added over a period of 4 hours. After the addition was completed, the mixture was stirred at 9° to 95° C. for 1 hour. The adduct thus obtained had the structure shown below in terms of model, and was a viscous liquid containing active hydrogen (II 502. active ingredient 68%) with a blending ratio of ↓ 2 for the adduct synthesis. Then,
A composition using 633 parts of the same 75% Epicoat 1001 melt as in Example 2 and 502 parts of the adduct obtained by the above method and a cured product obtained therefrom were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1] 99 parts of polypropylene glycol thioglycol used in Example 1 (0.35 mol, thiol group 0.
702 pieces) in a reflux condenser and a colchen equipped with a stirrer.
The mixture was heated to 00°C, 0.2 part of 2,4.6-1-li(dimethylaminomethyl)phenol was added, and the mixture was stirred uniformly. Then, while stirring at 100°C, Epikote 82
840.5 parts (epoxy group 0°213 (IliI>
was added over 2.5 hours. After finishing adding 130
The mixture was stirred at ℃ for 3 hours.

The adduct thus obtained has an active hydrogen equivalent of 483
It was a viscous liquid. The blending ratio used for this synthesis was 3.3
Met.

The compounding ratio and synthesis method are based on A in Table 2 on page 38 of the Journal of Paint Technology.

Epicor) 8 with 483 parts of adduct prepared by the above method
28 was cured, and the gelation time at 20°C, odor, and properties of the cured product were measured in the same manner as in Example 1. Further, the coating film performance was evaluated in the same manner as in Example 1.

The results are shown in Table 1.

[Comparative Example 2] 392 g of trimethylolpropane trithioglycolate used in Example 2 (1 mol, thiol group 3
In the same manner, 1.3 parts of 2.4.6- was added and reacted to synthesize an adduct.

The blending ratio used in this synthesis was 3.

The adduct blended by the above method has an active hydrogen equivalent of 3100
It was a viscous liquid.

Epico-1 with 310 parts of Adak l-1 prepared by the above method.
-828190 parts were cured, and the gelation time at 20°C, odor, and properties of the cured product were measured in the same manner as in Example 1.

The results are shown in Table 1.

(Margin below) Table 1 The test methods in Table 1 are as follows.

1) The following items are based on JIS K-5400.

Adhesion: Cut 1 mm wide goblets on the painted surface and perform a tape peeling test.The results are expressed as "number of gobs left on iron surface/number of gobs cut."

Hardness: Based on pencil scratch test.

Bending property: Bend 180° using a 3mmφ axis in a specified bending tester. The symbols indicating the results are ○: no cracks peeling, Δ: cracks occurring, and ×: peeling.

Tsuruto Spray: A cross hatch that reaches the iron surface is placed on the painted surface before the test, and the test is carried out using a spray test machine for 500 hours. After the test, perform a tape peeling test on the crosshatch area. The result is expressed as the distance from the cut part, with the cut part as the center.

2) Evaluation by appearance observation after immersion in water at 20°C for 20 days is based on ΔSTM D-714.

3) Gelation time: Prepare 100g of sample and heat at 20°C.
Adjust the sample temperature and leave it for a while. The result is the time it takes for the sample to solidify.

4) Tensile Crab According to JIS K-6911, 5, 18, 3.

5) Elongation: Measure the total length at the time of tensile strength measurement, and calculate the elongation rate with respect to the initial value.

6) Smell 220 people were asked to smell the odor, and if 90% or more of the odor was judged to be able to withstand the work, it is marked as ○, and the others are marked as △ or ×.

7) Cured product Tg: TMA (Thermal M
1 by mechanical 8n-analysis)
The sample temperature is increased at a rate of °C/1 minute, and the inflection point of needle penetration is taken as Tg.

〔Effect of the invention〕

As described above, the curable epoxy resin composition according to the present invention uses a polythiol having an average of two or more thiol groups in one molecule as the thiol compound as the curing agent, and uses this polythiol as the thiol compound as the curing agent. part, and the blending ratio (total number of thiol groups in polythiol/total number of epoxy groups in epoxy compound) is 2 or less. ,
Unreacted thiol compounds remain in the adduct, so there is no bad odor characteristic of thiol compounds, and the pot life is appropriately adjusted, making it very practical.

The pot life is adjusted only by the blending ratio of the epoxy resin and thiol compound during adduct formation, and no acidic compounds are used, so it is excellent in terms of cost, physical properties, and chemical resistance. As shown in Table 1, adhesion, glass transition temperature, and hardness are maintained at the same level as conventional products, and in addition, tensile strength, elongation, bendability, and chemical properties (as measured by tsuruto spray and water immersion tests) are maintained. ) is superior to conventional methods.

Agent: Patent Attorney Takehiko Matsumoto Procedural Amendment (Spontaneous) April 1983, 8゛ 2, Title of Invention: Curable Epoxy Resin Composition 3, Relationship with the Case of Person Making the Amendment Address of Patent Applicant 2-1-2 Oyodokita, Oyodo-ku, Osaka City
Name: Nippon Paint Co., Ltd. Representative: Masao Suzuki 4, No agent 6, Scope of Claims and Detailed Description of the Invention in the specification to be amended 7
, Contents of the amendment (the entire text of the scope of claims column of the 11th specification is corrected as shown in the attached sheet).

(2) On page 9, lines 2 and 3 of the specification, the words "epoxy compound" are corrected to read "thiol compound."

2. Claims (1) A curable epoxy resin composition containing an epoxy compound having an average of one or more epoxy groups in one molecule as a main ingredient and a thiol compound having a thiol group as a curing agent, wherein the above ±, -t-water compound has an average of 2 (
[A polythiol having a thiol group of 1i1 or more is subjected to a caustic addition reaction with at least a part of the epoxy compound as the main ingredient under conditions such that the blending ratio (total number of thiol groups in the polythiol/total number of epoxy groups in the epoxy compound) is 2 or less A curable epoxy resin composition, characterized in that the curable epoxy resin composition is blended into the composition in the form of an epoxy-thiol adduct obtained by

(2) The equivalent ratio of the main agent and curing agent is 0.8:1 to 1.2:1
The curable epoxy resin composition according to claim 1, which is blended so as to have the following properties.

Claims (2)

[Claims] (1) A curable epoxy resin composition containing an epoxy compound having an average of one or more epoxy groups in one molecule as a main ingredient and a thiol compound having a thiol group as a curing agent, wherein the epoxy compound is contained in one molecule. A polythiol having an average of two or more thiol groups is subjected to an addition reaction in advance with at least a part of the epoxy compound as the main ingredient under conditions such that the blending ratio (total number of thiol groups in the polythiol/total number of epoxy groups in the epoxy compound) is 2 or less. A curable epoxy resin composition, characterized in that the epoxy resin composition is blended into the composition in the form of an epoxothiol adduct obtained by (2) The equivalent ratio of the main agent and curing agent is 0.871 to 1.2:1
The curable epoxy resin composition according to claim 1, which is blended so as to have the following properties.