JPH02199115A - Sealing agent - Google Patents

Abstract

PURPOSE:To obtain a sealing agent excellent not only in heat resistance and humidity resistance but also in mechanical properties and moldability by adding a curing agent for epoxy resin to an epoxy resin having a specified norbornene skeleton. CONSTITUTION:A sealing agent is obtained by adding a curing agent for epoxy resin (e.g. an amine, a polyamide or an acid anhydride) to an epoxy resin of formula I [wherein R<1> is a residue of an organic compound having l active hydrogen atoms; n<1>, n<2>...n<l> are each 0 or 1-100, and their sum is 1-100; l is 1-100; A is a group of formula II (wherein X is a group of formula III, IV or V, R<2> is H, an alkyl, a carboalkyl or a charbroil, and at least one group of formula III is contained in the resin component of formula I]. The sealing agent thus obtained has good humidity resistance, high heat resistance, excellent mechanical properties and excellent moldability, so that it has sufficient reliability when used in electronic and electric machine components.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a sealant using an alicyclic epoxy resin having excellent heat resistance, weather resistance, and water resistance.

[Prior Art] Conventionally, methods have been used to seal electronic components such as diodes, transistors, and integrated circuits using thermosetting resin compositions.

Stabbing using resin is economically advantageous compared to hermetic sealing methods using glass, metal, ceramic, etc., and is therefore widely put into practical use.

Among thermosetting resin compositions, epoxy resin compositions are most commonly used as sealing resin compositions in terms of reliability and cost.

The epoxy resins currently most widely used in industry are produced by the reaction of bisphenols and epichlorohydrin. This is a so-called Ebisu type epoxy resin.

This resin can be used in a wide range of products, from liquids to solids, and has the advantage that the epoxy group has high reactivity and can be cured at room temperature with polyamines.

However, although the cured product has excellent water resistance and is tough, it has drawbacks such as poor weather resistance, poor electrical quality such as tracking resistance, and low heat distortion temperature. . Especially recently, jtiiL
Epoxy resins made by reacting phenol or novolak resin with epichlorohydrin are used as sealing resins such as sI.

The resin contains several 1,100 pp of chlorine, which causes problems such as deteriorating the electrical characteristics of electrical parts. Alicyclic epoxy resins are examples of epoxy resins that do not contain chlorine and have excellent electrical properties and heat resistance.

These are produced by epoxidation reaction of compounds having a 5R ring and a 6-membered cycloalkenyl skeleton.

The epoxy groups of these resins are so-called internal epoxy groups and are usually cured by heating with acid anhydrides, but cannot be cured at room temperature with polyamines due to their low reactivity.

Therefore, the scope of use of alicyclic epoxy resins is extremely narrow.

Examples of alicyclic epoxy resins include (II) and (III
) is manufactured and used industrially.

[Problem to be solved by the invention] Not only when used in the sealant of the present invention, but also generally (I
I) is used as a heat-resistant epoxy diluent because of its very low viscosity, but it has the problem of being highly toxic and causing severe irritation to the skin of workers. Although (III) contains few impurities, has a low hue, and has a high heat deformation temperature of its cured product, it is susceptible to ester bonds and has poor water resistance.

Against this background, Japanese Patent Application Laid-Open No. 166675/1983 (
A novel epoxy resin having an oxycyclohexane skeleton was proposed in US Pat. No. 4,565,859).

This resin is solid at room temperature, and is advantageous in terms of workability when used as a sealant.

However, it is desired to improve heat resistance, moisture resistance, and the like.

Against this background, the present inventors have discovered that the above-mentioned problems can be alleviated by sealing with an epoxy resin into which a norbornene skeleton has been introduced.

We have arrived at the present invention.

[Configuration of the Invention] That is, the present invention relates to "(a) an epoxy resin represented by the general formula <I) [wherein R1 is an organic compound residue having one active hydrogen, nl
, R2...nj is 0 or an integer from 1 to 100, and the sum thereof is from 1 to 100. j represents an integer from 1 to 100] "A is represented by the following formula, and R2 is any one of H, an alkyl group, a carboalkyl group, and a carboaryl group.

(b) A sealing agent j characterized by containing as an essential component one or more curing agents for epoxy resins.

Next, the present invention will be explained in detail.

The general formula (
In the alicyclic epoxy resin represented by I), R1 is an organic residue having active hydrogen, and examples of the precursor organic substance having active hydrogen include alcohols, phenols, carboxylic acids, amines, Examples include thiols.

The alcohol may be a monohydric alcohol or a polyhydric alcohol.

For example, aliphatic alcohols such as methanol, ethanol, globanol, butanol, pentanol, hexanol, octatool, aromatic alcohols such as benzyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, 1
．． 3-butanediol, 1.4-butanediol, betanediol, 1.6-hexanediol, neopentyl glycol, oxypivalic acid neopentyl glycol ester, cyclohexane dimetatool, glycerin, diglycerin, polyglycerin, trimethylolpropane,
Examples include polyhydric alcohols such as trimethylolethane, pentaerythritol, and dipentaerythritol.

Examples of the phenols include phenol, cresol, catechol, pyrogallol, hydroquinone, hydroquinone monomethyl ether, bisphenol A, bisphenol F, 4,4°-ditoxybenzophenone, bisphenol S, phenol resin, and cresol novolak resin.

Carboxylic acids include formic acid, acetic acid, 10-pionic acid, butyric acid, fatty acids from animal and vegetable oils, fumaric acid, maleic acid, adipic acid, dodecanoic acid, trimellitic acid, pyromellitic acid,
Examples include polyacrylic acid, phthalic acid, isophthalic acid, and terephthalic acid. Also included are compounds having both a hydroxyl group and a carboxylic acid, such as lactic acid, citric acid, and oxycaproic acid.

Examples of amines include methylamine, ethylamine, 10-bylamine, butylamine, pentylamine, hexylamine, cyclohexylamine, octylamine, dodecylamine, 4,4°-diaminodiphenylmethane, isophorone diamine, toluenediamine, hexamethylene diamine, xylene diamine, Examples include diethylenetriamine, triethylenetetramine, and ethanolamine.

Examples of thiols include mercapto compounds such as methyl mercaptan, ethyl mercaptan, propyl mercaptan, and phenyl mercaptan, mercaptopropionic acid or polyhydric alcohol esters of mercaptopropionic acid, such as ethylene glycol dimercapto-10-pionic acid ester, and trimethylolpropane trimercaptopropionic acid. , pentaerythritol pentamercapto 10 pionic acid, and the like.

Furthermore, other compounds having active hydrogen include polyvinyl alcohol, polyvinyl acetate partial hydrolyzate, starch, cellulose, cellulose acetate, cellulose acetate butyrate, b-droxyethylcellulose,
Examples include acrylic polyol resin, styrene allyl alcohol copolymer resin, styrene-maleic acid copolymer resin, alkyd resin, polyester polyol resin, polyester carboxylic acid resin, polycaprolactone polyol resin, polypropylene polyol, polytetramethylene glycol, and the like.

Further, the compound having active hydrogen may have an unsaturated double bond in its skeleton, and specific examples include allyl alcohol, acrylic acid, methacrylic acid, 3-cyclohexenemethanol, tetra-dolphthalic acid, etc. There is.

In this case, the unsaturated double bond in the general formula (I) of the epoxy resin has a structure in which all or part of it is epoxidized.

n in general formula (I), n...nj
is 0 or an integer from 1 to 100.

The sum is from 1 to 100, but if it exceeds 100, the resin will have a high melting point and will be difficult to handle and cannot be used in practice.

o is an integer from 1 to 100.

Of the substituents X of A in formula (1), it is essential, but it is preferable that there are as many of them.

The smaller the number, the better.

That is, in the present invention, the substituent X is the main one.

The general formula (
The production of the alicyclic epoxy resin represented by I) is carried out in the following order.

First, 5-
vinylbicyclo[2,2,1]hept-2-ene-2-
Polyether compounds are produced by ring-opening polymerization of oxides.

This polyether compound is represented by a structural formula in which the side chain X of the portion A in the epoxy resin represented by the general formula (I) remains as a vinyl group. By epoxidizing the vinyl group portion of this polyether compound having a vinyl group side chain with an oxidizing agent such as a peracid, an alicyclic epoxy resin, which is the main component of the sealing agent of the present invention, can be produced. .

5-vinylbicyclo[2,2,11hept-2-ene-
2-oxide can be obtained by partially epoxidizing 5-vinylbicyclo[2,2,1]hebdo-2-ene obtained by the Diels-Alder reaction of butadiene and cyclopentadiene with peracetic acid or the like.

5-vinylbicyclo[2,2,1]hept-2-ene-
It is preferable to use a catalyst when synthesizing a polyether compound by polymerizing 2-oxide in the presence of active hydrogen.

Examples of catalysts include amines such as methylamine, ethylamine, propylamine, and piperazine; organic basic acids such as pyridines and imidazoles; tlA acids such as formic acid, acetic acid, and propionic acid; inorganic acids such as sulfuric acid and hydrochloric acid; Alcolades of alkali metals such as Lato, KOH,
Alkalies of NaOH-, BF3, Zncj2, Aj
Examples include Lewis acids such as Cj and SnCj4 or their complexes, and organometallic compounds such as triethylaluminum and diethylzinc.

These catalysts can be used in an amount of 0.01 to 10%, preferably 0.1 to 5%, based on the starting material.

The reaction temperature is -70 to 200°C, preferably -30°C to 1
It is 00℃.

The reaction can also be carried out using a solvent.

A solvent containing active hydrogen cannot be used.

i.e., ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, toluene,
Aromatic solvents such as xylene, ethers, aliphatic hydrocarbons, esters, etc. can be used.

The thus synthesized polyether compound having a vinyl group side chain is epoxidized with an epoxidizing agent, and the resultant compound has the general formula (I), which is used as the main component of the sealant of the present invention.
A cycloaliphatic epoxy resin represented by:

As the epoxidizing agent, peracids and hydroperoxides can be used.

As peracids, performic acid, peracetic acid, perbenzoic acid, trifluoroperacetic acid, etc. can be used.

Among these, peracetic acid is a particularly preferred epoxidizing agent because it is industrially available at low cost and has high stability.

As the hydroperoxides, hydrogen peroxide, tert-butyl hydroperoxide, cumene peroxide, etc. can be used.

A catalyst can be used during epoxidation if necessary.

For example, in the case of a peracid, an alkali such as soda carbonate or an acid such as sulfuric acid may be used as a catalyst.

In the case of hydroperoxide, the catalytic effect can be obtained by using a mixture of tungstic acid and caustic soda with hydrogen peroxide, a molar acid with hydrogen peroxide, or molybdenum hexacarbonyl with tert-butyl hydroperoxide. can.

The epoxidation reaction is carried out by adjusting the presence or absence of a solvent and the reaction temperature depending on the equipment and physical properties of the raw materials.

The usable reaction temperature range is determined by the reactivity of the epoxidizing agent used.

Regarding peracetic acid, which is a preferred epoxidizing agent, 0 to
70°C is preferred.

At temperatures below 0°C, the reaction is slow, and at 70°C, peracetic acid decomposes.

Also, for the tertiary butyl hydroperoxide/molybdenum dioxide diacetylacetonate system, which is an example of hydroperoxide, the temperature is 20°C to 150°C for the same reason.
is preferred.

The solvent can be used for purposes such as lowering the viscosity of the raw material and stabilizing the epoxidizing agent by diluting it.

In the case of peracetic acid, aromatic compounds, ether compounds,
Ester compounds, ketone compounds, etc. can be used as solvents.

The molar ratio of the epoxidizing agent to the unsaturated bonds can be changed depending on the purpose, such as how much unsaturated bonds are desired to remain.

When the objective is to obtain a compound with a large number of epoxy groups, it is preferable to add the epoxidizing agent in an amount equivalent to or more than the amount of the unsaturated group.

However, it is usually disadvantageous to exceed 2 times the molar amount due to economic efficiency and the problem of side reactions described below, and in the case of peracetic acid, 1 to
1.5 times the molar amount is preferable.

Depending on the conditions of the epoxidation reaction, the epoxy value of the olefin bond is accompanied by substituents in the raw materials, and as a result of the reaction with the epoxidation agent, modified substituents are generated and included in the target compound. .

The ratio of the substituents in the target compound and the modified substituents is determined by the type of epoxidizing agent, the molar ratio of the epoxy olefin bond, and the reaction conditions.

When the epoxidizing agent is peracetic acid, the modified substituents mainly have the structure shown below, and are generated from the produced epoxy group and the by-produced acetic acid. (Left below) The target compound can be extracted from the crude reaction solution by conventional chemical engineering means such as concentration.

In addition, the epoxy resin that is the main component of the sealant of the present invention is
It can be used in combination with other epoxy resins as long as the properties of the composition are not impaired.

Here, the other epoxy resin may be any commonly used epoxy resin, such as Ebibis type epoxy,
Included are epoxy diluents such as bisphenol F epoxy, novolac epoxy, cycloaliphatic epoxy and styrene oxide, butyl glycidyl ether.

Next, the curing agent used for curing the epoxy resin which is the main component of the sealant of the present invention will be described.

As the curing agent, curing agents used for known epoxy resins can be used, and include amines, polyamide resins, acid anhydrides, polymercaptan resins, novolak resins, dicyandiamide, amine complexes of boron trifluoride, etc. .

Here, the amines include the following.

Aliphatic polyamines such as diethylenetriamine, triethylenetetramine, menzendiamine, metaxylylenediamine, bis<4-amino-3-methylcyclohexyl)methane, adducts of the aliphatic polyamines and known epoxy compounds, and reaction with acrylonitrile. substances, reactants with ketones.

metaphenylenediamine, diaminodiphenylmethane,
Aromatic polyamines such as diaminodiphenylsulfone and diaminodiphenylsulfide, adducts of the aromatic polyamines and known epoxy compounds, secondary and tertiary amines such as tris(dimethylaminomethyl)phenol, piperidine, imidazole and derivatives thereof, and their derivatives. Salts, mixtures of the above amines, etc. are used.

Polyamide resins include fatty acids, reaction products of fatty acids such as dimer acid and trimer acid, and aliphatic polyamines.

Acid anhydrides include the following:

Phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic dianhydride, tetra-dolphthalic anhydride, hexahydrophthalic anhydride, methyltetra-dolphthalic anhydride, methylhex-dolphthalic anhydride, methyl anhydride Acid anhydrides such as nadic acid, succinic anhydride, dodecenylsuccinic anhydride, succinic anhydride, and mixtures of the above acid anhydrides.

Novolak resins include low molecular weight resinous products made by the condensation of phenol or a mixture of phenol and cresol, di-hydroxybenzene, and formaldehyde.

Amine complexes of boron trifluoride include monoethylamine, piperidine, aniline, butylamine, dibutylamine, cyclohexylamine, dicyclohexylamine,
Includes complexes of low molecular weight amine compounds such as tributylamine and triethanolamine and boron trifluoride.

Further, other curing agents include salts such as diazonium salts, iodonium salts, bromonium salts, and sulfinium salts of super strong acids such as boron tetrafluoride, phosphorus hexafluoride, and arsenic hexafluoride.

In addition, among these curing agents, aliphatic polyamines, aromatic polyamines, polyamide resins, and polymercaptan resins can be used in combination in any ratio, and can be used alone or in combination with a curing accelerator for the purpose of adjusting the curing speed. You can also.

The blending amount of the curing agent is 0.5 to 10% by weight, preferably 1 to Sjl% by weight, based on the resin composition.

If it is less than 0.5%, curing will be insufficient.

If it exceeds 10%, mechanical strength cannot be imparted to the molded product.

Here, the aforementioned secondary and tertiary amines can be used as the curing accelerator.

The acid anhydride can be used as it is, but a curing catalyst and a curing accelerator can also be used together for the purpose of adjusting the curing rate and improving the physical properties of the cured product.

Here, the curing catalysts are the aforementioned secondary and tertiary amines and tin octylate.

As curing accelerators, water, ethanol, propatool,
Isopropanol, cyclohexanol.

These include alcohols such as ethylene glycol, carboxylic acids such as acetic acid, propionic acid, succinic acid, and hexahydrophthalic acid, and amines having active hydrogen such as ethylenediamine and diethylenetriamine. The novolac resin can be used alone or in combination with a curing catalyst for the purpose of curing speed.

Here, the curing catalysts are the aforementioned secondary and tertiary amines.

Dicyandiamide can be used alone or in combination with a curing catalyst for the purpose of adjusting the curing rate.

Here, the curing catalysts are the aforementioned secondary and tertiary amines.

The amine complex of boron trifluoride can be used alone or in combination with a curing rate regulator for the purpose of adjusting the curing rate.

Here, any curing rate regulator may be used as long as it can be used in conventional epoxy resins, but specific examples include carboxylic acids, amines, acetylacetone complexes of metals, metals such as titanium, tin, etc. These include organometallic compounds, glycols, organoboron compounds, etc.

In addition to the curing agent and curing accelerator described above, a filler can also be used in the epoxy resin which is the main component of the sealant of the present invention, if necessary.

Any filler that can be used as a filler for resins may be used, but specific examples include silica sand, silica, alumina, diatomaceous earth, calcium carbonate, asbestos, glass, magnesium carbonate, and kaolin. ,
There is metal powder, etc. Various shapes can be used, such as fibrous, flake, etc.

The blending amount of the filler is preferably 25 to 90% based on the resin composition.

If it is less than 25%, mechanical properties cannot be improved, and if it exceeds 90%, moldability deteriorates and is not practical.

[Effects of the Invention] The sealant of the present invention thus obtained has good moisture resistance, high heat resistance, excellent mechanical properties, and excellent moldability, and is suitable for use in electronic and electrical parts. It exhibits sufficient reliability when used in applications such as

Next, the present invention will be explained with reference to Examples.

"Synthesis Example-1" [Synthesis of 5-vinylbicyclo[2,2,11hept-2-ene-2-oxide (vinylnorbornene oxide)] 5-vinylbicycloC2,2,11hept-2-ene (
1,697.4 g (14.15 mol) of vinylnorbornene) was charged into the reactor, and 1,075.8 g (14.15 mol) of peracetic acid was added to the reactor.
4,15 mol) as a t-ethyl acetate solution at a reaction temperature of 4.
The mixture was added dropwise over 5.5 hours while maintaining the temperature at 0°C.

After the completion of charging peracetic acid, the mixture was further aged at 40°C for 1 hour. The obtained reaction crude liquid was thoroughly washed with distilled water. A transparent liquid was obtained by rectifying the organic layer using a distillation column.

The boiling point of this liquid was 91° C. at 25 Torr.

According to infrared absorption spectrum analysis of the product, 810 cm,
The presence of an epoxy group absorption at 1270 cm, and the presence of vinyl group absorption at 1640 cm and 1820 cm, and NMR analysis revealed that this compound is represented by the following formula, 5-vinylbicyclo[2 ,2,1]hept-2-ene-2-oxide.

"Synthesis Example-2" Trimethylolpropane 9.8g (0,073 mol)
, 5-vinylbicyclo[2,2,1]hebdo-2-en-2-oxide (vinylnorbornene oxide) 150
g (1.1 mol) of B F 3 etherate 13.0
A solution of 5 g (0,092 mol) of ethyl acetate was mixed at 50° C. and reacted until the oxirane oxygen content was less than 1%.

The obtained reaction crude liquid was thoroughly washed with distilled water.

A viscous liquid was obtained by concentrating the organic layer.

Infrared absorption spectrum analysis of the product revealed that there was no absorption of epoxy groups at 810 cm and 1270 cm observed in the raw material, and 1080 cm - 11150 cm.
Absorption due to ether bond exists at m-', and absorption due to vinyl group remains at 1640 cm and 182 parts cm-'.

Furthermore, NMR analysis confirmed that this compound has a skeleton represented by the following formula.

CHO-[A]. 1-H CH3CH2CCH20-[A]. 2HCH20-[A
]. 3H [However, A represents the following structure.

nl, R2, n3 = average 5 80 g of this compound was dissolved in ethyl acetate and charged into a reactor, and 42" peracetic acid was added dropwise to this as an ethyl acetate solution over 2 hours while maintaining the reaction temperature at 50 ° C. .

After the completion of charging peracetic acid, ethyl acetate was added to the O-reaction crude solution that was further aged at 50° C. for 4 hours, washed with distilled water, and then the organic layer was concentrated to obtain a viscous liquid.

This compound had an oxirane oxygen content of 5.77%, and a patent absorption due to the epoxy group was observed at 1260011-' in the infrared absorption spectrum. Furthermore, absorption due to residual vinyl groups is observed at 1640 cm-', and 3450 ex
-' is an OH group, and 1730csa-1 shows absorption due to C-0- at 0. This compound has the structure of general formula (I) (R1 nitrimethylolpropane residue, n = average 5, epoxy group 1 = 3). , nl, containing a portion of the R23 group with acetic acid added thereto).

"Example-1" 100 parts by weight of the epoxy compound obtained in Synthesis Example-2, 50 parts of novolac type phenol resin (Gun-ei Chemical PSF4300, phenol equivalent 110), and 2-undecylimidazole (C, 1Z, Shikoku Kasei Kogyo) 1 part by weight and 400 parts by weight of fused silica powder were mixed at room temperature, kneaded at 90 to 95°C, cooled, and then pulverized.

A molding material was obtained.

The obtained molding material is made into tablets and preheated.

A molded product was obtained by injecting the mixture into a mold heated to 170° C. by transfer molding.

The properties of this molded product were measured and the results are shown in Table 1.
It was shown to.

"Comparative Example-1" 50 parts of novolac type phenol resin (Gun-ei Chemical PSF4300. Phenol equivalent: 110) in 100 parts of cresol novolac type phenol resin (epoxy equivalent: 201),
1 part by weight of 2-undecylimidazole (Ci 1Z, Shikoku Kasei Kogyo) and 400 parts by weight of fused silica powder were mixed at room temperature and transfer molded under the same conditions as in Example 1 to obtain a molded article. The mechanical properties of this molded article were measured and the results are also shown in Table 1.

"Example-2" 100 parts by weight of the epoxy compound obtained in Synthesis Example-2, 100 parts by weight of novolac type phenol resin (Gun-ei Chemical PSF4300, phenol equivalent weight 110), and 3 parts by weight of 2-undecylimidazole (C112, Shikoku Kasei Kogyo) and 400 parts by weight of fused silica powder were mixed at room temperature, kneaded at 90 to 95°C, cooled, and pulverized to obtain a molding material. The obtained molding material was made into a tablet, preheated, and injected into a mold heated to 170° C. by transfer molding to obtain a molded product.

The properties of this molded product were measured and the results are shown in Table 1.
It was shown to.

Table-1 (blank space below) Note: 1 Bending strength 1 Bending modulus is in kg/Itn
.

The upper row is the measured value at 20°C, and the lower row is the measured value at 120°C.

Note: 2 The thermal cycle test is a numerical value of (number of cracks/number of samples), and the number of cracks is a 25 x 25 x 3 inch copper plate embedded in the bottom of a 30 x 25 x 5 inch molded product.

Place it in a constant temperature bath at -40℃ and 200℃ for 30 minutes each.
Measurement of the number of cracks in the resin after 5 cycles.

Note=3 In the moisture resistance test, an electrical component having two aluminum wirings was transfer-molded at 170°C for 3 minutes using the sealing resin composition, and then cured at 180°C for 8 hours. 12 for 100 sealed electrical components obtained in this way.
5 due to aluminum corrosion when carried out in high pressure steam at 0°C.
Measurement of the time at which 0% wire disconnection (defect occurrence) occurs.

From the results in Table 1, it is clearly seen that the sealants using the sealant of the present invention are excellent in moisture resistance, heat resistance, and crack resistance.

Claims (1)

[Claims] (a) Epoxy resin represented by the general formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) [However, R^1 is an organic compound residue having l active hydrogens , n1, n2... nl is 0 or an integer from 1 to 100,
The sum is 1 to 100, l represents an integer from 1 to 100] "A is represented by the following formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ However, X is ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼、-C
H=CH2, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ R^2 is any one of H, an alkyl group, a carboalkyl group, a carboaryl group, ▲ There are mathematical formulas, chemical formulas, tables, etc. It is necessary that one or more ▼ be contained in the resin represented by the general formula (I).'' (b) A sealant characterized by containing a curing agent for epoxy resin as an essential component.