JP2875867B2 - Method for producing α-cyanoacrylates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improvement in a method for producing α-cyanoacrylates useful as an adhesive.

<Prior art> α-cyanoacrylates are generally produced by condensing cyanoacetate and formaldehyde in, for example, an organic solvent, and depolymerizing the obtained polymer under high temperature and reduced pressure. The crude α-cyanoacrylates obtained by the method are generally low in purity and inferior in adhesion performance, stability and the like. Therefore, the crude monomer is purified by distillation to obtain a high-purity α-cyanoacrylate.
-Obtained as cyanoacrylates.

Here, as a method for purification by distillation, phosphorus pentoxide, phosphoric acid, an acidic substance such as paratoluenesulfonic acid and a polymerization inhibitor such as hydroquinone, hydroquinone monomethyl ether, catechol, and pyrogallol are added, and SO ₂ is added.
For example, a method of performing heat distillation under reduced pressure under an acid gas stream such as described above is known.

<0006> However, in these conventional distillation purification methods in order to prevent gelation during distillation, is especially necessary to perform distillation by acid gas stream of such SO _2, Therefore, to obtain The α-cyanoacrylates contain a large amount of acidic gas, which must be further removed by degassing or the like.

In addition, since all of these acidic gases are released as waste gas, there is a need for a detoxification facility or the like, and there is a problem in industrial operation and environmental aspects.

Therefore, the industry does not require such a degassing step,
There has been a demand for the appearance of a distillation purification method that does not use harmful acidic gas.

<Means for Solving the Problems> In view of the above requirements, the present inventors have conducted intensive studies and studies on a distillation purification method using no acid gas, and finally found the method of the present invention.

That is, the method of the present invention is a method for producing α-cyanoacrylates, which comprises purifying the α-cyanoacrylate by distillation in the presence of a BF ₃ complex salt when purifying the α-cyanoacrylate.

A feature of the present invention is that stable distillation purification can be performed by adding a BF ₃ complex salt instead of an acid gas.

The BF ₃ complex used in the method of the present invention, specifically, BF ₃ and methyl ether, ethyl ether, n- propyl ether, isopropyl ether, n- butyl ether, BF ₃ etherate is complex with tetrahydrofuran, , BF ₃ and formic acid, acetic acid, complex salt is a BF ₃ carboxylic acid complex salt of the propionic acid or butyric acid, BF ₃ phenol, cresol, it may be mentioned BF ₃ phenol complex salt is a complex salt such as catechol or pigeon id hydroquinone .

As the α-cyanoacrylates according to the present invention, specifically, methyl-α-cyanoacrylate, ethyl-α
-Cyanoacrylate, propyl-α-cyanoacrylate, allyl-α-cyanoacrylate, butyl-α-
Cyanoacrylate, heptyl-α-cyanoacrylate, hexyl-α-cyanoacrylate, octyl-α
-Cyanoacrylate, decyl-α-cyanoacrylate, dodecyl-α-cyanoacrylate, (2-chloroethyl) -α-cyanoacrylate, (2-methoxyethyl) -α-cyanoacrylate, (2-ethoxyethyl) -α- Examples include cyanoacrylate, (2-butoxyethyl) -α-cyanoacrylate, benzyl-α-cyanoacrylate, phenyl-α-cyanoacrylate, and trifluoroisopropyl-α-cyanoacrylate.

In carrying out the method of the present invention, for example, cyanoacetic ester and formaldehyde are condensed in an organic solvent in the presence of a catalyst, for example, in the presence of a catalyst, and the resulting polymer is heated at a high temperature (about 150 ° C. or higher). Depolymerization is performed under reduced pressure to produce crude α-cyanoacrylates. This coarse α-
It is general to apply the distillation purification method of the present invention to cyanoacrylates.

That is, after the BF ₃ complex salt in crude α- cyanoacrylates produced by the above method was added a predetermined amount, a method generally performed, for example, under a reduced pressure of 1 to 10 mmHg, the temperature 30
It is carried out by distillation at 130C, preferably 35-100C.

In addition, for the purpose of further preventing coloration, improving the set time, etc., the distillation purification method of the present invention can be further applied to an α-cyanoacrylate monomer produced by distillation or the like, and in some cases, still more preferable. Give the result.

In the distillation purification process of the present invention, the amount of the BF ₃ complex is generally to the α- cyanoacrylates 100 parts
0.0001 to 1 part by weight, preferably 0.0005 to 1 part by weight.
It is in the range of parts by weight. If it is less than this range, the storage stability tends to decrease, and if it exceeds this range, the curing speed tends to be excessively low, so that it cannot function as an instant adhesive.

The BF ₃ complex salt to be added in the distillation purification method of the present invention itself can sufficiently exhibit the desired effect by itself, but if necessary, furthermore, conventionally known phosphorus pentoxide, phosphoric acid, para It can be used in combination with an acidic substance such as toluenesulfonic acid and a polymerization inhibitor such as hydroquinone, hydroquinone monomethyl ether, catechol, and pyrogallol, and in some cases, more preferable results can be obtained.

In carrying out the method of the present invention, it is more preferable to carry out the distillation under a stream of an inert gas such as nitrogen gas or helium gas. In this case, there is no need to perform a complicated operation such as removal of an acidic gas such as degassing after distillation, which is conventionally performed, which is convenient.

Usually, the effluent obtained as described above, further as a stabilizing agent, SO _2, SO _3, p-toluenesulfonic acid, propane sultone, methanesulfonic acid, BF ₃ etherate, HBF
_The final product can be finished by adding an anionic polymerization inhibitor such as ₄ in an optional amount.

<Effects of the Invention> According to the method of the present invention, distillation and purification can be performed stably without using an acid gas such as SO ₂ , and further, there is no necessity for a facility for removing an acid gas, and the like. This method has high practical value, for example, it can save the trouble of removing acidic gas, and can add an appropriate amount of an appropriate stabilizer as needed after distillation to obtain a final product. Further, the obtained α-cyanoacrylates may be free of any acidic gas which is conventionally inevitably contained, and therefore, the curing speed is generally shorter than that in the case of using the acidic gas. Thus, it also has the function and effect such as excellent storage stability.

<Examples> Hereinafter, the method of the present invention will be described in more detail with reference to Examples and Comparative Examples.

Synthesis Example 1 Synthesis of crude ethyl-α-cyanoacrylate A three-necked flask equipped with a stirrer, thermometer, water separator, and dropping funnel was charged with 60 parts of paraformaldehyde and 200 parts of toluene.
, 0.2 parts of piperidine, 226 parts of ethyl cyanoacetate was added to 60 parts with stirring and maintained at a temperature of 80 to 90 ° C.
Dropped over minutes. After the completion of the dropwise addition, the generated water was refluxed while being azeotropically separated, and reacted for about 6 hours until a theoretical amount of water was distilled off, thereby obtaining a toluene solution of the polymer. After desolvating the solution under normal pressure, 30 parts of tricresyl phosphate, 6 parts of phosphorus pentoxide, and 3 parts of hydroquinone were added and mixed well. After desolvation under reduced pressure, the mixture was heated to 170 to 200 ° C. under a reduced pressure of 3 mmHg to carry out depolymerization to obtain 212 parts of a crude ethyl-α-cyanoacrylate.

Synthesis Example 2 Synthesis of crude methyl-α-cyanoacrylate In Synthesis Example 1, 198 parts of cyanoacetic acid methyl ester was used in place of 226 parts of ethyl cyanoacetate, and 187 parts of crude methyl-α-cyanoacrylate was obtained in the same manner. Was.

Synthesis Example 3 Synthesis of crude propyl-α-cyanoacrylate In Synthesis Example 1, 254 parts of cyanoacetic acid propyl ester was used in place of 226 parts of cyanoacetic acid ethyl ester, and crude propyl-α-cyanoacrylate 237 was obtained in the same manner.
Got a part.

Synthesis Example 4 Synthesis of crude butyl-α-cyanoacrylate In Synthesis Example 1, 262 parts of cyanoacetic acid ethyl ester was used instead of 226 parts of cyanoacetic acid ethyl ester, and 262 parts of crude butyl-α-cyanoacrylate was obtained in the same manner as described below. Was.

Synthesis Example 5 Synthesis of crude (2-ethoxyethyl) -α-cyanoacrylate In Synthesis Example 1, 314 parts of cyanoacetic acid ethoxyethyl ester was used in place of 226 parts of cyanoacetic acid ethyl ester. 290 parts of (ethyl) -α-cyanoacrylate were obtained.

Examples 1 to 13 Hydroquinone (0.5 part) and phosphorus pentoxide (0.1 part) as polymerization inhibitors were used for the crude cyanoacrylates (100 parts) obtained by the methods described in the above Synthesis Examples 1 to 5.
Were added to obtain a BF ₃ complex salt according to the present invention in Table 1
Each of the various BF ₃ complex salts shown in Table 1 was added in the amount shown in Table 1, and 1
Distillation was carried out at a temperature of 35 ° C to 90 ° C under a reduced pressure of ~ 3 mmHg, and after a portion of the initial distillate was cut, high-purity purified monomers (90
Part). Table 1 shows the conditions of this distillation as Examples 1 to 13.
1 is shown.

For Comparative Examples 1 to 3 Comparative, Comparative Example 1 and 2 having been subjected to the said same vacuum distillation under conventional acid gas (SO ₂ gas) stream without using the present invention BF ₃ complexes, further acidic gases Table 1 shows the results obtained by performing the same distillation under reduced pressure in a nitrogen gas stream in the same manner as in Comparative Example 3.

Using the high-purity α-cyanoacrylate obtained by the above method, the results of a measurement of the curing rate of steel / steel and a test of storage stability by heating gelation days at 70 ° C. are shown in Table.
1 is shown.

Supplementary explanation in Table 1 (1) Distillation was performed under a nitrogen gas stream except for Example 3.

(2) Regarding the stabilizers, in all of Examples and Comparative Example 3, the stabilizers shown in Table 1 are shown in Table 1 with respect to 100 parts of high-purity ethyl cyanoacrylate obtained by distillation. The amount is added.

In Comparative Example 1, the state in which a large amount of SO ₂ gas was contained after distillation (as it was before degassing) was used as the final product, and in Comparative Example 2, the ethyl cyanoacrylate of Comparative Example 1 was degassed to obtain SO ₂ gas.
It was manufactured by adjusting ₂ to 0.003 parts.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C07C 253/34 C07C 255/23

Claims (3)

(57) [Claims] (1) A process for producing α-cyanoacrylates, which comprises purifying the α-cyanoacrylate by distillation in the presence of a BF ₃ complex salt. Wherein the addition amount of the BF ₃ complex is The method of claim (1) is in the range of 0.0001 parts by weight per 100 parts of α- cyanoacrylates. 3. The method according to claim 1, wherein the distillation temperature is from 30 ° C. to 130 ° C.