JP3142365B2 - Method for producing α-cyanoacrylate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for producing an .alpha.-cyanoacrylate monomer.

[0002]

2. Description of the Related Art A method for producing an α-cyanoacrylate monomer generally comprises obtaining an α-cyanoacrylate polymer obtained by reacting a cyanoacetate with formaldehyde in the presence of a condensation catalyst, and then depolymerizing the polymer. Then, a method of obtaining an α-cyanoacrylate monomer is performed.

Heretofore, it has been necessary to lower the viscosity of a polymer in order to smoothly carry out the subsequent depolymerization reaction, and a solvent or a plasticizer is used. A method using phosphates such as triphenyl phosphate and tricresyl phosphate and phthalates such as dioctyl phthalate as a solvent or a plasticizer conventionally used (Japanese Patent Publication No. 38-14567), diphenylphenyl Method using phosphonates such as phosphonates (US Patent
No. 3,444,233).

[0004]

However, when diphenylphenylphosphonate or triphenylphosphate is used, for example, they are solid at room temperature, and are dissolved by heating before addition of the polymer. It is difficult to use industrially compared to a liquid at room temperature, and phthalic acid esters, for example, when dioctyl phthalate is used, a monomer is required during the depolymerization reaction. Is likely to polymerize,
There are problems that the operation becomes complicated and the yield is low. On the other hand, when tricresyl phosphate is used, it does not have the above-mentioned disadvantages, but because of its high viscosity, it is difficult to dissolve the solvent before depolymerization, remove the solvent after depolymerization, etc. There is a problem that foaming easily occurs at the beginning of the reaction, and therefore the stock solution easily mixes into the distilling system at the time of removing the monomer, and the distillation operation becomes complicated.

[0005] In view of these circumstances, the present inventors have proposed the depolymerization of α-cyanoacrylate polymer.
As a result of intensive studies, they have found that the above problems can be solved at once by performing a depolymerization reaction of the α-cyanoacrylate polymer in the presence of cresyl diphenyl phosphate, and have completed the present invention.

[0006]

SUMMARY OF THE INVENTION The present invention is a method for producing an α-cyanoacrylate monomer, which comprises depolymerizing an α-cyanoacrylate polymer in the presence of cresyl diphenyl phosphate as a solvent.

Further, the present invention is to depolymerize an α-cyanoacrylate polymer obtained by reacting cyanoacetate with formaldehyde in the presence of a condensation catalyst in the presence of cresyl diphenyl phosphate as a solvent. A method for producing an α-cyanoacrylate monomer characterized by the following:

Furthermore, the present invention relates to a method for producing an α-cyanoacrylate monomer by depolymerizing an α-cyanoacrylate polymer obtained by reacting a cyanoacetate with formaldehyde in the presence of a condensation catalyst. A method for producing an α-cyanoacrylate monomer, wherein the condensation reaction and the depolymerization reaction are carried out using cresyl diphenyl phosphate as a common solvent.

The present invention is characterized in that cresyl diphenyl phosphate is used as a solvent for a depolymerization reaction or a condensation reaction and a depolymerization reaction. Cresyl diphenyl phosphate used in the present invention is industrially preferable because it is a low-viscosity liquid at room temperature and easy to use. In the method of the present invention, the amount of the solvent used is not particularly limited, but is usually 5 to 100 g, preferably 10 to 50 g, per 1 mol of formaldehyde used for the polymerization reaction.
It is.

As the cyanoacetate used in the present invention, known ones are used. Specifically, for example, cyanoacetic acid and methyl alcohol, ethyl alcohol, propyl alcohol, n-butyl alcohol, methoxyethyl alcohol and ethoxy Esters obtained by reaction with ethyl alcohol and the like.

As the formaldehyde used in the present invention, an aqueous formaldehyde solution or paraformaldehyde is used.

For the condensation reaction between the cyanoacetate and formaldehyde, a conventionally known method is applied. Specifically, for example, the reaction is performed using a lower alcohol, benzene, toluene, trichlene, or the like as a solvent, and triethylamine, diethylamine, piperidine, pyridine, or a compound that is a salt of these compounds as a catalyst. Further, acetic acid or the like may be present in the reaction system.

In the present invention, cresyl diphenyl phosphate can be used as a solvent for this condensation reaction. In this case, the subsequent depolymerization reaction can be carried out with the same solvent, which is extremely advantageous in industrial operation. is there. The temperature of the condensation reaction is usually 50 to 100 ° C.

A conventionally known method is applied to the depolymerization reaction of the present invention. Specifically, for example, the heating is performed at a heating temperature of 150 to 250 ° C. and under a reduced pressure of 1 to 100 mmHg.
Further, for the purification of the monomer, it can be purified by redistillation under reduced pressure.

The hydroxyl groups present at the molecular ends of the polymer obtained by the condensation reaction generate water in the depolymerization reaction. Therefore, during the depolymerization reaction, phosphorus pentoxide,
It is preferable to add a dehydrating agent such as acetic anhydride or propionic anhydride.

At this time, in order to prevent anionic polymerization of monomers in the gas phase, sulfurous acid gas, nitric oxide, hydrogen fluoride and the like can be used. Further, as a radical polymerization inhibitor, hydroquinone and pyrogallol are used. Can be used.

In order to stably store the monomer obtained by the depolymerization reaction, a nonvolatile acidic substance such as phosphoric acid, sulfuric acid, and oxalic acid; a volatile acidic substance such as sulfur dioxide, nitrogen oxide, and boron trifluoride; Hydroquinone, monomethyl ether of hydroquinone and the like can be added as a radical scavenger.

[0018]

The cresyl diphenyl phosphate used in the present invention is a low-viscosity liquid at ordinary temperature which is easy to handle, does not have the foaming problem seen in the conventional tricresyl phosphate, and can be used in a conventionally known solvent. The desired depolymerization reaction can be performed with a relatively small amount of use,
Furthermore, it is economically inexpensive, and its industrial use value is extremely large.

[0019]

EXAMPLES The present invention will be described below in more detail with reference to examples, but these examples do not limit the present invention.

Example 1 A 1-L glass four-necked flask equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser was charged with 200 ml of ethanol.
1, 0.5 g of piperidine and 6 of paraformaldehyde 6
Charge 1 g and raise the temperature while stirring. When the reflux of ethanol starts, 226 g of ethyl cyanoacetate is added dropwise in 60 minutes. After reacting for 5 hours after dropping, most of the ethanol is removed by distillation. Next, 300 ml of toluene is added to perform azeotropic dehydration. When the distilling of water stops, acetic acid 1
g, and 35.3 g of cresyl diphenyl phosphate (product name: CDP, manufactured by Daihachi Chemical Industry Co., Ltd.)
The toluene is removed by distillation. After distilling off toluene by distillation under reduced pressure, 2 g of phosphorus pentoxide and 1 g of hydroquinone were added, a distilling tube was attached, and a small amount of sulfur dioxide gas was passed.
Ethyl α-cyanoacrylate is distilled off while being thermally depolymerized at ℃.

The crude ethyl α-cyanoacrylate is blown at 53 to 56 ° C./2 to 3 mmH
g to obtain pure ethyl α-cyanoacrylate. 185 g.

Example 2 In a 500 ml glass four-necked flask equipped with a stirrer, thermometer, dropping funnel and reflux condenser, methanol 15 was added.
0 ml, 0.4 g of piperidine and 30 g of paraformaldehyde are charged, and the temperature is raised while stirring. When the reflux of methanol starts, 99 g of methyl cyanoacetate is added dropwise in 60 minutes. After dropping, 12 g of cresyl diphenyl phosphate (product name: CDP, manufactured by Daihachi Chemical Industry Co., Ltd.)
And heated and stirred at 70-75 ° C. for 50 minutes. The methanol is removed by distillation. If distilling stops, benzene 9
Add 0 ml and perform azeotropic dehydration. When no more water is distilled off, 2 g of orthophosphoric acid are added and the benzene is removed by distillation.
After distilling off benzene by distillation under reduced pressure,
4 g of phosphorus pentoxide and 2 g of hydroquinone are added, and a distilling tube is attached.
Then, the bath temperature is raised to 180 to 190 ° C. to distill α-methyl methyl cyanoacrylate. When the amount of distilling decreases, the temperature is gradually raised to 220 ° C. to complete the depolymerization reaction. The yield of α-methyl methyl acrylate is 88.8 g.

Example 3 Toluene 222 was placed in a 1-L glass four-necked flask equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser.
g, ethyl cyanoacetate 622 g and piperidine 0.5
g, and the temperature is increased while stirring. 165 g of paraformaldehyde are charged in small portions. When reflux begins, cool the flask and adjust the amount of paraformaldehyde added so as to gently reflux. Once paraformaldehyde has been added, continue refluxing for an additional hour. When the paraformaldehyde is completely dissolved, 2 g of p-toluenesulfonic acid is added, and toluene and water are removed by distillation at 100 ° C. or less under reduced pressure. Next, 3.6 g of phosphorus pentoxide, 3.6 g of hydroquinone and 100 g of cresyl diphenyl phosphate (product name: CDP, manufactured by Daihachi Chemical Industry Co., Ltd.) are added, and the temperature is raised under reduced pressure. The degree of pressure reduction is finally set at 5 mmHg, and while blowing a trace amount of sulfurous acid gas, the temperature is maintained at 180 to 195 ° C to distill out ethyl α-cyanoacrylate. The yield of ethyl α-cyanoacrylate is 585 g.

Example 4 The procedure of Example 3 was repeated, except that n-butyl cyanoacetate was used instead of ethyl cyanoacetate.
An n-butyl α-cyanoacrylate is obtained. The boiling point is
82-84 ° C / 2-3 mmHg.

Example 5 In Example 1, methoxyethyl cyanoacetate was used in place of ethyl cyanoacetate, and the procedure of Example 1 was followed to obtain methoxyethyl α-cyanoacrylate. Boiling point: 82-86 ° C / 2-3mmH
g.

Example 6 The procedure of Example 1 was repeated, except that ethoxyethyl cyanoacetate was used instead of ethyl cyanoacetate. The procedure of Example 1 was followed to obtain ethoxyethyl α-cyanoacrylate. Boiling point is 95-100 ° C / 2-3mm
Hg.

Continuation of the front page (56) References JP-A-51-32521 (JP, A) JP-B-44-25062 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 253 / 30 C07C 255/23 C07B 61/00 300

Claims (5)

(57) [Claims] 1. A method for producing an α-cyanoacrylate monomer comprising depolymerizing an α-cyanoacrylate polymer in the presence of cresyl diphenyl phosphate as a solvent. 2. The method for producing an α-cyanoacrylate monomer according to claim 1, wherein an α-cyanoacrylate polymer obtained by reacting a cyanoacetate with formaldehyde in the presence of a condensation catalyst is used. 3. The process for producing an α-cyanoacrylate monomer according to claim 2, wherein the amount of cresyl diphenyl phosphate used is 5 to 100 g per 1 mol of formaldehyde used in the condensation reaction. 4. A method for producing an α-cyanoacrylate monomer by depolymerizing an α-cyanoacrylate polymer obtained by reacting a cyanoacetate with formaldehyde in the presence of a condensation catalyst, comprising the steps of: A method for producing an α-cyanoacrylate monomer, wherein cresyl diphenyl phosphate is used as a solvent in the depolymerization reaction. 5. The process for producing an α-cyanoacrylate monomer according to claim 4, wherein the amount of cresyl diphenyl phosphate used is 5 to 100 g per 1 mol of formaldehyde used in the condensation reaction. [0001]