JPH1067729A - Production of 2-cyanoacrylate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject new compound useful as a main component for instantaneous adhesives in a high conversion by directly esterifying 2- cyanoacrylic acid with an alcohol in the presence of a cation exchange resin in mild conditions. SOLUTION: This new method for producing a 2-cyanoacrylate comprises reacting (A) 2-cyanoacrylic acid with (B) an alcohol (e.g. methanol or ethanol) as raw materials. The raw materials (A) and (B) are preferably used in an A/B molar ratio of 0.5-2, more preferably 0.9-1.2. An ion exchange resin used as the catalyst is preferably a cation exchange resin, and is used in an amount of 10-1000wt.%, preferably 200-600wt.%, based on the component A. A solvent such as C6 H6 is used in an amount of 200-300wt.%, preferably 500-1500 pts.wt., in order to remove water by-produced in the reaction. The reaction temperature is preferably 30-130 deg.C, more preferably 50-120 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing 2-cyanoacrylate widely used as a main component of an instant adhesive, and mainly to an adhesive production technique.

[0002]

2. Description of the Related Art 2-Cyanoacrylate generally comprises 2-cyanoacrylate.
It is synthesized and produced by reacting cyanoacetate with paraformaldehyde in the presence of a basic catalyst, performing dehydration condensation, and depolymerizing the obtained condensate.

However, 2-cyanoacrylates that can be industrially synthesized by a synthesis process including a dehydration condensation reaction and a depolymerization are limited to compounds having a lower alkyl as an ester residue. It is almost impossible to synthesize acrylates, high-boiling cyanoacrylates, and cyanoacrylates having heat-labile ester residues.

That is, a polyfunctional cyanoacrylate is
When this is synthesized by this process, a polyfunctional cyanoacetate corresponding to the polyfunctional cyanoacrylate is subjected to a condensation reaction with formaldehyde, but the condensate obtained by the reaction has a cross-linked structure, and its depolymerization Inevitably requires high heat, and depolymerization at high heat causes abnormal decomposition, and it is almost impossible to obtain the desired polyfunctional cyanoacrylate.

In the case of a high-boiling cyanoacrylate, a high vacuum and a high temperature are required to separate and purify the cyanoacrylate produced by the depolymerization, and thermal polymerization of the cyanoacrylate occurs during the separation and purification at a high temperature. In the case of a thermally unstable substrate, it is thermally decomposed during the reaction, and in any case, not only the yield of the target product is reduced, but also a purified product is often hardly obtained. is there.

As another method for synthesizing cyanoacrylate, anthracene or cyclopentadiene has been used so far.
A method utilizing the Diels-Alder reaction of cyanoacrylate (USP-4003942, JP-A-1-19746)
4, Japanese Unexamined Patent Publication No. 7-33726) are known, but they have the problems that the separation of the product is not easy and the synthesis process is complicated and unsuitable as an industrial method. For reacting cyanoacrylic acid with alcohol under a catalyst such as paratoluenesulfonic acid
However, this method is also difficult to separate the product from the catalyst, that is, removing the catalyst from the reaction product according to this method by washing with water has been carried out. -It is difficult to carry out because of polymerization of cyanoacrylate, and the method of separation by distillation is also difficult to employ because it causes thermal decomposition and hydrolysis of 2-cyanoacrylate.

[0007]

SUMMARY OF THE INVENTION The present inventors have made various
We studied a method for synthesizing 2-cyanoacrylate under mild conditions and at a high conversion rate. To develop a method for synthesizing 2-cyanoacrylate, which was difficult to produce with conventional methods, Synthesis that facilitates separation of materials
Research was conducted to find a manufacturing method.

[0008]

The present inventors have conducted various studies to solve the above-mentioned problems, and as a result, when alcohol is directly allowed to act on 2-cyanoacrylic acid in the presence of a cation exchange resin, mild conditions are obtained. The inventors have found that the esterification reaction proceeds at a high conversion rate to synthesize 2-cyanoacrylate, and thus completed the present invention.

That is, the present invention relates to a method for producing 2-cyanoacrylate, which comprises subjecting 2-cyanoacrylic acid and an alcohol to an esterification reaction in the presence of a cation exchange resin.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for synthesizing 2-cyanoacrylate according to the present invention will be described below in detail. 2-cyanoacrylic acid used as a raw material in the present invention is disclosed in JP-A-8-505383.
Can be prepared by the method described in the above, but it is an easy, practical and preferable method by an ester exchange reaction between 2-cyanoacrylate and an organic acid found by the present inventors (Japanese Patent Application No. Hei 7-92969). That is, 2-cyanoacrylate is subjected to transesterification with an organic acid such as formic acid, acetic acid, propionic acid, and butyric acid at a reaction temperature of 10 ° C. to 130 ° C. in the presence of a transesterification catalyst such as a cation exchange resin. Cyanoacrylic acid can be obtained.

The alcohol used in the present invention includes:
Monoalcohols and polyols that are widely and generally used can be mentioned, and specific examples thereof include the following. In the present invention, various things can be used without being limited to these.

That is, monoalcohols include methanol, ethanol, n-propanol, i-propanol,
n-butanol, i-butanol, pentanol, hexanol, 2-ethylhexanol, n-octanol, n-nonanol, n-decyl alcohol, cyclohexanol, phenethyl alcohol, chloroethanol, 2,2,2-trifluoroethanol, Methoxyethanol, ethoxyethanol, etc., and diols include ethylene glycol, propylene glycol, butanediol, pentanediol, neopentyl glycol, hexanediol, octanediol, diethylene glycol, 1,4-cyclohexanedimethanol, polyalkylene glycol, and polycarbonate. Diol, bisphenol A, bisphenol A alkylene oxide adduct, hydrogenated bisphenol A, hydrogenated bisphenol A alkylene oxide adduct, polycaprolact Examples of polyols and polyols include trimethylolpropane, pentaerythritol, dipentaerythritol, glycerin and alkylene oxide adducts of these polyols, polyalkylene oxide polyols, polycarbonate polyols, polycaprolactone polyols and the like.

The molar ratio of the reaction between 2-cyanoacrylic acid and alcohol is not particularly limited. However, it is preferable to reduce the amount of unreacted raw materials after the reaction in order to purify the product. The molar ratio of cyanoacrylic acid / alcohol is preferably from 0.5 to 2, and more preferably from 0.9 to 1.2.

The ion-exchange resin used as a catalyst has a styrene, phenol, acrylic acid, methacrylic acid or the like as a base and a cation-exchange resin having a sulfonic acid group, a methylenesulfonic acid group, a carboxylic acid group or the like as an exchange group. Resins. Among them, a polystyrene sulfonic acid system which is strongly acidic and does not contain metal ions such as sodium is preferable because gelation and polymerization of the obtained 2-cyanoacrylate can be prevented. Depending on the type, there are a dry form and a water-saturated form, but the former is preferred. Further, it is preferable to remove water in the resin by washing with dilute hydrochloric acid as a pretreatment of the reaction, followed by washing with a reaction solvent or the like, and drying in order to allow the reaction to proceed efficiently.

The amount of the cation exchange resin used in the reaction is
The reaction solution is in a range where the stirring of the reaction solution can be performed and in a range where the reaction can efficiently proceed, and is generally 10 to 1000% by weight, preferably 200 to 1000% by weight based on 2-cyanoacrylic acid.
It is 600% by weight. When the amount of the cation exchange resin is small, the progress of the reaction is slightly slowed down, but there is no problem with the conversion.

In the esterification reaction of the present invention, in order to promptly remove water generated as the esterification proceeds, a solvent which can be azeotropic with water and which does not react with the cation exchange resin is used. It is preferable to use them in combination. Further, as a solvent to be used in combination, a solvent which can be refluxed at a temperature not so high for the reason described below, that is, benzene, toluene, xylene, trichloroethylene, methyl isobutyl ketone, etc. is preferable. The amount of the solvent to be used in combination is suitably from 200 to 3000% by weight, and preferably from 500 to 1500% by weight, based on 2-cyanoacrylic acid.

In the esterification reaction of the present invention, when 2-cyanoacrylate obtained by the esterification reaction is exposed to a high temperature, the polymerization reaction proceeds, which causes a large decrease in the yield of the target product. Also, the ion exchange resin may be degraded or decomposed at high temperatures, so that the
It is preferably carried out in a temperature range of 30 ° C, more preferably in a temperature range of 50 to 120 ° C. At this time, the reaction temperature can be controlled by adjusting the pressure in the reaction system.

In the esterification reaction of the present invention, hydroquinone and hydroquinone monomethyl ether may be added as radical polymerization inhibitors, and organic acids and inorganic acids may be added as anionic polymerization inhibitors.

[0019]

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

Example 1 25 parts by weight of purified ethyl 2-cyanoacrylate, 144 parts by weight of acetic acid and 200 parts by weight of a cation exchange resin (Amberlyst 15) were mixed with 2 parts by weight of a polymerization inhibitor paratoluenesulfonic acid and 2 parts of hydroquinone.
The reactor was charged together with parts by weight and reacted at 80 ° C. for 20 hours with stirring. As a result of proton NMR analysis of the reaction solution, 2-cyanoacrylic acid was found to be produced at a conversion of 25% based on the amount of ethyl acetate produced. 18 parts by weight of purified 2-cyanoacrylic acid, 17 parts by weight of dehydrated n-hexanol, 100 parts by weight of a cation exchange resin (Amberlyst 15), 0.9 part by weight of hydroquinone, and 200 parts by weight of benzene are placed in a reaction vessel and stirred. The mixture was dehydrated and refluxed at 80 ° C. for 4 hours. As a result of proton NMR analysis (solvent: deuterated chloroform) of the reaction solution, it was confirmed that hexylcyanoacrylate was produced at a conversion of 93% based on alcohol. After the reaction solution was filtered to remove the cation exchange resin, the solvent was distilled off, and the obtained crude product was distilled to obtain the desired product. FIG. 1 shows a proton NMR chart (270 MHz).

[Comparative Example 1] The 2-cyanoacrylate of Example 1 was subjected to an esterification reaction using p-toluenesulfonic acid or sulfuric acid as a catalyst, and was subjected to an ordinary method for producing an acrylic acid ester. An attempt was made to remove the catalyst by neutralization, but the resulting 2-cyanoacrylate was polymerized, and the objective could not be achieved.

Example 2 18 parts by weight of purified 2-cyanoacrylic acid, 10 parts by weight of dehydrated 1,6-hexanediol, 100 parts by weight of a cation exchange resin (Amberlyst 15), 0.9 part by weight of hydroquinone, 200 parts by weight of benzene were placed in a reaction vessel, and the mixture was dehydrated and refluxed at 80 ° C. for 2 hours while stirring. As a result of proton NMR analysis (solvent: heavy acetone) of the reaction solution, formation of hexamethylene biscyanoacrylate was confirmed at a conversion of 80% based on diol.
After the reaction solution was filtered to remove the cation exchange resin, the solvent was distilled off, and n-heptane was added to the obtained crude product to purify it by recrystallization. FIG. 2 shows a proton NMR chart (270 MHz) of the purified product.

COMPARATIVE EXAMPLE 2 The biscyanoacrylate of Example 2 was subjected to an esterification reaction using p-toluenesulfonic acid or sulfuric acid as a catalyst to obtain a product, and then separation from the catalyst by distillation was attempted. The desired product was not obtained at all, and a large amount of decomposition gas was generated due to high-temperature heating. Further, the reaction solvent was distilled off, and n-heptane was added to the obtained crude product for purification by recrystallization. However, the catalyst could not be removed.

[0024]

The 2-cyanoacrylate synthesis method of the present invention is a simple method of synthesizing 2-cyanoacrylic acid and an alcohol by heating and stirring in the presence of a cation exchange resin. 2-by filling
This makes it possible to continuously synthesize cyanoacrylate in large quantities. Further, it enables the synthesis of a polyfunctional cyanoacrylate, a high-boiling-point cyanoacrylate, and a cyanoacrylate having a heat-labile ester residue, which were difficult to produce by the conventional method. . Further, purification after the reaction can be performed more easily than when an acid catalyst such as paratoluenesulfonic acid is used, since the ion exchange resin can be removed by filtration.

[Brief description of the drawings]

FIG. 1 is a proton NMR chart (270 MHz) of hexylcyanoacrylate obtained in Example 1.

FIG. 2 is a proton NMR chart (270 MHz) of hexamethylene biscyanoacrylate obtained in Example 2.

Claims (1)

[Claims] 1. A method for producing 2-cyanoacrylate, comprising subjecting 2-cyanoacrylic acid and an alcohol to an esterification reaction in the presence of a cation exchange resin.