JP2000290599A - 2-cyanoacrylate-based adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve adhesive strength against peeling by blending a 2- cyanoacrylate whose acid content is below a specific value with a specific polyvalent compound. SOLUTION: The adhesive composition is prepared by blending a 2- cyanoacrylate having an acid content below 0.30×10-6 gram equivalent/g or a composition primarily comprising the 2-cyanoacrylate with a polyvalent compound and further with additive(s) such as a curing accelerator, anionic polymerization inhibitor, radical polymerization inhibitor, thickening agent, colorant, plasticizer, heat stabilizer, softening agent, filler, perfume and solvent. The polyvalent compound is one or more polyvalent compounds selected from a polyacidic carboxylic acid or a derivative thereof, an α-ketocarboxylic acid or a derivative thereof, and an aromatic compound or a derivative thereof, in which at least two phenolic hydroxyl groups are bonded to adjacent carbon atoms constituting the benzene ring or at least two phenolic hydroxyl groups and carboxyl groups are bonded to carbon atoms constituting the benzene ring. The polyvalent compound is blended in an amount of 10-10,000 wt.ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 2-cyanoacrylate adhesive composition having excellent adhesive strength, especially excellent peel adhesive strength.

[0002]

2. Description of the Related Art Due to its high anionic polymerizability, a 2-cyanoacrylate adhesive is polymerized and hardened in a short time by an anionic species such as moisture on the surface of an adherend or air, and is instantly bonded to bond various materials. Widely used as an agent.

However, the cured product of 2-cyanoacrylate is inflexible, hard and brittle, and when used as an adhesive, exhibits a high adhesive strength against a force in a shearing direction. There is a drawback that sufficient strength and impact resistance cannot be obtained.

[0004] In order to solve the above problem, there has been proposed a method of blending various additives with 2-cyanoacrylate in order to increase the impact strength and peel strength of the 2-cyanoacrylate adhesive. For example, Japanese Patent Application Laid-Open No. 52-77145
JP-A-52-78933 and the like, polyvalent carboxylic acids, JP-A-52-111936 and α-ketocarboxylic acid, and JP-A-55-104375 discloses a benzoate having two or more phenolic hydroxyl groups. JP-A-57-78469 proposes a 2-cyanoacrylate adhesive composition containing an acid or an ester thereof and pyrogallol.

On the other hand, it is known that by reducing the amount of impurities in a 2-cyanoacrylate adhesive composition, the adhesive strength is increased and the storage stability of the adhesive composition is improved. However, it is very difficult to obtain 2-cyanoacrylate having a purity higher than a certain level from the viewpoint of a production apparatus and production cost.
No. 1 only suggests that by reducing impurities in 2-cyanoacrylate, an excellent bonding speed and tensile shear strength are exhibited.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a 2-cyanoacrylate-based adhesive composition having excellent adhesive strength, in particular, peel adhesive strength.

[0007]

Means for Solving the Problems The present inventors have found that a polycarboxylic acid or a derivative thereof, an α-ketocarboxylic acid or a derivative thereof, that at least two phenolic hydroxyl groups are bonded to adjacent carbon atoms constituting a benzene ring. Or an aromatic compound in which at least two phenolic hydroxyl groups and a carboxyl group are bonded to a carbon atom constituting a benzene ring, or one or more selected from derivatives thereof (hereinafter referred to as “specific polyvalent In the 2-cyanoacrylate-based adhesive composition containing the compound (hereinafter referred to as “compound”), it was found that a slight amount of acidic impurities present in the composition had a great effect on the adhesive strength, particularly on the peel strength.
It has been found that by controlling the acid content to a certain value or less, a 2-cyanoacrylate-based adhesive composition having excellent adhesive strength, particularly excellent peel adhesive strength, can be obtained, and the present invention has been completed.

That is, the present invention relates to 2-cyanoacrylate or acid having an acid content of 0.30 × 10 ⁻⁶ gram equivalent / g or less.
-A 2-cyanoacrylate-based adhesive composition obtained by mixing a specific polyvalent compound with a composition containing cyanoacrylate as a main component.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. 2 used as a main component of the adhesive composition of the present invention
-Specific examples of cyanoacrylate include methyl-2-
Cyanoacrylate, ethyl-2-cyanoacrylate, propyl-2-cyanoacrylate, isopropyl-2-cyanoacrylate, butyl-2-cyanoacrylate, isobutyl-2-cyanoacrylate, amyl-2-cyanoacrylate, hexyl-2-cyano Acrylate, cyclohexyl-2-cyanoacrylate,
Octyl-2-cyanoacrylate, 2-ethylhexyl-2-cyanoacrylate, allyl-2-cyanoacrylate, benzyl-2-cyanoacrylate, methoxyethyl-2-cyanoacrylate, ethoxyethyl-
Examples thereof include 2-cyanoacrylate, methoxypropyl-2-cyanoacrylate, and tetrahydrofurfuryl-2-cyanoacrylate, and these 2-cyanoacrylates may be used alone or in combination of two or more.

The composition containing 2-cyanoacrylate as a main component in the present invention means a curing accelerator, an anionic polymerization inhibitor, a radical, which is mixed with the above-mentioned 2-cyanoacrylate in a general 2-cyanoacrylate adhesive. It contains various additives such as a polymerization inhibitor, a thickener, a colorant, a plasticizer, a heat stabilizer, a softener, a filler, a fragrance, a dye, a pigment and a solvent.

Examples of the curing accelerator include additives such as polyethylene glycol or a derivative thereof, crown ether or a derivative thereof, and calixarene or a derivative thereof, which can be stably added to 2-cyanoacrylate and promote anionic polymerization.

The anionic polymerization inhibitor is added for the purpose of preventing anionic polymerization due to moisture or the like in the storage container, and specific examples thereof include sulfur dioxide, aromatic sulfonic acid, aliphatic sulfonic acid and sultone acid.

The radical polymerization inhibitor is added for the purpose of preventing radical polymerization due to light or the like during storage, and specific examples include hydroquinone and hydroquinone monomethyl ether.

According to the present invention, as the above-mentioned 2-cyanoacrylate or a composition containing 2-cyanoacrylate as a main component, an acid content of 0.30 × 10 ⁻⁶ gram-equivalent among various impurities present in these compounds. / G or less. The acidic impurities derived from the acid content are generated by hydrolysis of 2-cyanoacrylic acid produced by hydrolysis of 2-cyanoacrylate and cyanoacetate, which is one of the raw materials used for producing 2-cyanoacrylate, in the production stage. Although cyanoacetic acid is mentioned, other acidic impurities derived from an anionic polymerization inhibitor as an additive are also targets.

In the present invention, the acid content in 2-cyanoacrylate or a composition containing 2-cyanoacrylate as a main component is measured by the method proposed in Japanese Patent Application Laid-Open No. H10-140091. .

In this measurement method, in order to accurately measure a trace amount of acid content, analysis by gas chromatography which may decompose 2-cyanoacrylic acid or the like due to high temperature at the time of measurement is avoided, and a method by neutralization titration is used. In order to accurately grasp only the acid component that inhibits the properties of the adhesive, a specific discoloration range, that is, pH 4.5 to pH 4.5 is used.
It is determined by neutralization titration using an indicator having a discoloration range at 5.0, particularly preferably bromophenol blue. To increase the accuracy of the neutralization titration, water is added to the adhesive composition. 0.3 to 5 m of distilled water per 1 g of the composition
It is preferable to use 10 to 200 ml of an organic solvent such as acetone or methyl ethyl ketone in order to suppress polymerization of 2-cyanoacrylate by water. As an indicator of the neutralization titration, when the purpose is to measure the acid content in a composition containing 2-cyanoacrylate or 2-cyanoacrylate as a main component as in the present invention, pH 4.5 is used.
It is preferable to use an indicator having a color change range of from 5.0 to 5.0, specifically, bromophenol blue, 2,4-dinitrophenol, methyl yellow and the like, and it is particularly preferable to use bromophenol blue. As the alkali used for the neutralization titration, a strong base aqueous solution such as an NaOH or KOH aqueous solution is used, and the concentration is 1/10 to 1/10.
00 is preferred.

In the present invention, an adhesive composition is obtained by adding a specific polyvalent compound to 2-cyanoacrylate or the above-described 2-cyanoacrylate-based composition. The preferred number of carboxyl groups and phenolic hydroxyl groups in the specific polyvalent compound is 2 to 6, more preferably 3 to 4.

Among the specific polyvalent compounds, specific examples of polyvalent carboxylic acids or derivatives thereof include maleic acid, succinic acid,
Itaconic acid, glutaric acid, aconitic acid, propane-
1,2,3-tricarboxylic acid, 1-butene-2,3,4
-Tricarboxylic acid, 1-hexene-2,4,6-tricarboxylic acid, citric acid, butane-1,2,3-tricarboxylic acid, butane-1,2,3,4-tetracarboxylic acid, 1
-Pentene-2,4,5-tricarboxylic acid, cyclohexane-1,2,4-tricarboxylic acid, cyclohexane-
1,2,4,5-tetracarboxylic acid, tetrahydrofurantetracarboxylic acid, 3-methylcyclohexene-4,
5,6-tricarboxylic acid, ethane-1,1,2,2-tetracarboxylic acid, carboxymethyloxysuccinic acid, 2
-Oxo-1,1,3-propanetricarboxylic acid, nitrilotriacetic acid, 1-cyanopropane-1,2,3-tricarboxylic acid, 1-phenylpropane-1,2,3-tricarboxylic acid, 1,2-dibromo- 3-methylcyclohexane-4,5,6-tricarboxylic acid, phthalic acid, phthalic anhydride, ethylene glycol trimellitate, propylene glycol trimellitate, glycerin-1,3-ditrimellitate-2-acetate, hemi-mellitic acid, anhydride Hemimellitic acid, trimellitic acid, trimellitic anhydride, trimesic acid, melophanic acid, pyromellitic acid, pyromellitic anhydride, benzenepentacarboxylic acid, melitic acid, naphthalene-1,4,5-tricarboxylic acid, meconic acid, Benzophenonetetracarboxylic anhydride, biphenyltetracar Phosphate anhydride, 2,2-bis (3,4
Substituted or unsubstituted polycarboxylic acids such as -dicarboxyphenyl) hexafluoropropane dianhydride, ethylene glycol bisanhydrotrimellitate or glycerin-1,3-dianhydrotrimellitate-2-acetate or the like; Anhydrides or partial esters of

Among these, when aconitic acid, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride and ethylene glycol bisanhydrotrimellitate are used, the resulting adhesive composition This is a preferred type because the peel adhesion strength of the object increases.

Among the specific polyvalent compounds, specific examples of α-ketocarboxylic acid or a derivative thereof include glyoxylic acid, pyruvic acid, α-ketosuccinic acid, α-ketoglutaric acid, and α-ketoglutaric acid.
Α-ketocarboxylic acids such as ketooctylic acid, α-ketovaleric acid, α-ketocaprylic acid, α-ketoundecanoic acid or α-ketophenylacetic acid or esters thereof. Of these, the use of pyruvic acid, α-ketosuccinic acid and α-ketoglutanic acid is a preferred type because the peel adhesive strength of the obtained adhesive composition increases.

In the specific polyvalent compound, at least two phenolic hydroxyl groups are bonded to adjacent carbon atoms forming a benzene ring, or at least two phenolic hydroxyl groups and a carboxyl group form a benzene ring. Specific examples of the aromatic compound or a derivative thereof bonded to a carbon atom include catechol, pyrogallol, di-
tert-butylcatechol, 1,2,4-benzenetriol, hexahydroxybenzene, tetrahydroxybenzene, 2,4-dihydroxybenzoic acid, 3,4-
Dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, methoxyethyl 2,4-dihydroxybenzoate, methoxyethyl 3,4-dihydroxybenzoate, 3, 4,5-trihydroxybenzoic acid, 3,4,5
-Methyl trihydroxybenzoate, ethyl 3,4,5-trihydroxybenzoate, n-propyl 3,4,5-trihydroxybenzoate, methoxyethyl 3,4,5-trihydroxybenzoate or 3,4, Ethoxyethyl 5-trihydroxybenzoate and the like.

Among these, pyrogallol, 3,4-
Dihydroxybenzoic acid, 3,4,5-trihydroxybenzoic acid, methyl 3,4,5-trihydroxybenzoate,
When n-propyl 3,4,5-trihydroxybenzoate and methoxyethyl 3,4,5-trihydroxybenzoate are used, the resulting adhesive composition is a preferred type because the peel strength of the resulting adhesive composition increases.

The preferred compounding amount of the specific polyvalent compound to be added to the 2-cyanoacrylate adhesive composition of the present invention is as follows:
It is in the range of 10 to 10000 wtppm of the whole adhesive composition. If it is less than 10 wtppm, the effect of the compounding is poor, and if it exceeds 10,000 wtppm, other properties such as instantaneous adhesiveness of the adhesive composition may be deteriorated.

The present invention relates to a 2-cyanoacrylate or a 2-cyanoacrylate having an acid content of 0.30 × 10 ⁻⁶ gram equivalent / g or less.
A 2-cyanoacrylate adhesive composition in which a specific polyvalent compound is blended with a composition containing cyanoacrylate as a main component, the acid content of which is 0.30 × 10 ⁻⁶ gram equivalent / g;
2-cyanoacrylate or a composition containing 2-cyanoacrylate as a main component, and a superior adhesive strength, particularly a peel adhesive strength, as compared with a 2-cyanoacrylate-based adhesive composition in which a specific polyvalent compound is added. It has the feature of showing. If the acid content of the original 2-cyanoacrylate or a composition containing 2-cyanoacrylate as a main component is 0.30 × 10 ⁻⁶ gram equivalent / g or less, as a result of blending the specific polyvalent compound, Acid content 0.30 × 10 ^-6
Even if the gram equivalent number / g is exceeded, the 2-cyanoacrylate-based adhesive composition shows excellent adhesive strength, particularly peel adhesive strength.

[0025]

2-cyanoacrylate in which a specific polyvalent compound is blended with 2-cyanoacrylate having an acid content of 0.30 × 10 ⁻⁶ gram equivalent number / g or less, or a composition mainly containing 2-cyanoacrylate. It is not clear why the system-based adhesive composition has a characteristic of exhibiting excellent adhesive strength, in particular, peel adhesive strength, but is presumed as follows. The specific polyvalent compound and the cured product of 2-cyanoacrylate exhibit adhesive strength due to interaction on the surface of the adherend.
However, the interaction is inhibited by the presence of a trace amount of acidic impurities. Therefore, by controlling the acidic impurities, excellent adhesive strength, particularly, peel adhesive strength can be obtained.

[0026]

The present invention will be described below in more detail with reference to examples. In addition, each measuring method is as follows.

(Method for Measuring Acid Content) A 3 g sample is precisely weighed in a 200 ml Erlenmeyer flask. This sample is diluted with 90 ml of special grade acetone. After shaking well, add 3 ml of distilled water. Add a few drops of bromophenol blue solution as an indicator. 1 / 100N NaOH using micro burette
The aqueous solution is added dropwise, and the point at which the color of the solution changes from yellow to blue is defined as the neutralization end point.

(Measurement of Aluminum T Peel Adhesive Strength) The peel adhesive strength using aluminum as an adherend was measured according to JIS K68.
The measurement was carried out according to the T-type peel adhesion strength test method of No. 54. However, aluminum test piece is 0.2mm thick JIS
A1050P pure aluminum described in H4000 was used, and the curing period was 3 days.

Examples 1 to 5 and Comparative Examples 1 to 4 As shown in Table 1, a specific polyvalent compound was purified from ethyl-2-cyanoacrylate, which was acidified to suppress acid content, and from an insufficiently purified acid content. A predetermined amount was added to each of a large amount of ethyl-2-cyanoacrylate to prepare a 2-cyanoacrylate-based adhesive composition, and various measurements were performed. The results are shown in Table 1.

[0030]

[Table 1] ^{* 1} : x10 ^-6 gram equivalent / g ^{* 2} : wtppm ^{* 3} : N / 25mm

As is clear from Table 1, when the specific polyvalent compound is added to 2-cyanoacrylate having an acid content of 0.30 × 10 ⁻⁶ gram equivalent / g or less, the same specific polyvalent compound is obtained. With an acid content of 0.30 × 10 ⁻⁶ gram equivalent /
It can be seen that the peel adhesion strength is clearly improved as compared with the case where the compound is added to a cyanoacrylate exceeding g.

Example 6 Various tests were conducted by adding 400 ppm of gallic acid to ethyl-2-cyanoacrylate having an acid content shown in Table 2. In addition, the thickness of the aluminum test piece used for the measurement of the aluminum T peel adhesion strength was 0.3 mm, the tensile speed was 100 mm / min, and the curing period was 7 days. Table 2 shows the results.

[0033]

[Table 2] ^{* 1} : × 10 ^-6 gram equivalent / g ^{* 3} : N / 25mm

As is apparent from Table 2, when the amount of acidic impurities is suppressed to a lower level than in the case where gallic acid is blended with the conventionally used ethyl-2-cyanoacrylate having a high acid content, the acid content is particularly low. Particularly high peel adhesion strength was obtained when using ethyl-2-cyanoacrylate of 0.3 × 10 ⁻⁶ gram equivalent / g or less.

Comparative Example 4 Acid content used in Example 6 0.15 × 10 ⁻⁶ gram equivalent /
The aluminum T peel adhesion strength was measured under the same conditions as in Example 6 without adding the specific polyvalent compound to g of ethyl-2-cyanoacrylate. The result was 7 N / 25 mm.

[0036]

Industrial Applicability The 2-cyanoacrylate adhesive composition of the present invention exhibits high adhesive strength, especially peel adhesive strength, so that it can be used as an instant adhesive for quasi-structures in industrial and household applications. It is widely available for many uses.

Continued on the front page F term (reference) 4J040 EE022 FA121 HA236 HB14 HB21 HB24 HB26 HB28 HB36 HB40 HB47 HD13 HD19 KA17 KA19 KA23 KA25 KA29 KA31 KA35 KA42 LA06

Claims (1)

[Claims] An acid content of 0.30 × 10 ⁻⁶ gram equivalent /
A 2-cyanoacrylate-based adhesive composition obtained by blending not more than g of a 2-cyanoacrylate or a composition containing 2-cyanoacrylate as a main component with one or more selected from the following groups. (1) polycarboxylic acid or a derivative thereof, (2) α-
Ketocarboxylic acid or a derivative thereof, (3) at least two phenolic hydroxyl groups are bonded to adjacent carbon atoms constituting a benzene ring, or
An aromatic compound in which a phenolic hydroxyl group and a carboxyl group are bonded to a carbon atom constituting a benzene ring, or a derivative thereof.