JPS6259248A - Production of n-vinylformamide - Google Patents

Abstract

PURPOSE:To obtain the titled compound in high yield, by etherifying N-(alpha- hydroxyethyl)formamide with a polyhydric alcohol, heating the ether compound under reduced pressure in a liquid phase and carrying out thermal decomposition while distilling away N-vinylformamide. CONSTITUTION:N-(alpha-Hydroxyethyl)formamide is etherified with a polyhydric alcohol such as dihydric alcohol, etc., in the presence of a catalyst of a mineral acid such as sulfuric acid, etc., at 0-100 deg.C for 0.5-5hr, heated in a liquid phase at <=200Hg reduced pressure at 90-200 deg.C and thermal decomposition is carried out while distilling away formed N-vinylformamide, to give the aimed compound. EFFECT:A small amount of by-products such as resin component, etc., is formed, the temperature of the thermal decomposition is lower than a conventional gaseous-phase method so this process is advantageous with respect to heat energy. There is not such problem in operation as clogging of a reaction tube with resin like a gaseous-phase method and this process is an industrially improved method. USE:A polymerizable monomer to provide a water-soluble polymer as a flocculant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing N-vinylformamide.

[Conventional technology]

N-vinylformamide is useful as a polymerizable monomer that provides water-soluble polymers that are excellent as flocculants. ) A method is known in which formamide is etherified with alcohol, and then the etherified product is thermally decomposed at high temperature in the gas phase.

OH OH30HO+H! N0HO-→OH, -OH red HOHO R [Zhao point to be solved by the invention] In the above method, N-(α-hydroxyethyl)
Generally, a heptahydric aliphatic lower alcohol such as methanol is used as the alcohol for etherifying formamide, but in this case, the heat in the gas phase increases the decomposition rate of the etherified product. It is necessary to make the decomposition temperature as high as, for example, θθ°C or higher. Therefore,
In order to implement this method industrially, either the heat medium for heating is limited or a large amount of energy is required for heating. In addition, in this method, a large amount of Harz components are produced as by-products during pyrolysis, and as a result, not only does the yield of the target product decrease, but also the inside of the reaction tube of the shell-and-tube heat exchanger for gas phase pyrolysis is The components caused blockages, which caused operational problems.

[Means for solving problems]

In view of the above circumstances, the present inventors conducted various studies on a method for thermally decomposing an etherified product of M-(α-hydroxyethyl)formamide at low temperatures while suppressing the by-product of Harz components. -(α-Hydroxyethyl)formamide is reacted with a polyhydric alcohol to etherify it, and then the etherified product is heated in a liquid phase under reduced pressure, and while the N-vinylformamide formed is distilled off, the etherified product is heated. The present invention was completed by discovering that the object of the present invention can be achieved by performing decomposition.

The present invention will be explained in detail below.

In the present invention, N-(α-hydroxyethyl)formamide and polyhydric alcohol are reacted.
As α-hydroxyethyl)formamide, one obtained by one reaction with acetaldehyde is usually used. Although the reaction is carried out in the presence or absence of a solvent,
The melting point of the product is j2. ! ~j J, F 'C, but
When the process is carried out at lower temperatures, it is desirable to use a catalyst, such as hexane, hegetane, benzene, toluene, xylene, etc., which substantially dissolve the product. The mixture after the reaction is usually seeded or cooled and crystallized to precipitate crystals of the desired product, which can then be recovered by heating.

On the other hand, examples of polyhydric alcohols include triethylene glycol, ethylene glycol, diethylene glycol, propylene glycol, /, 3-1/, 4- or co, 3-butanediol, molecules *jθθ~/θθθ
Examples include polyethylene glycol or polypropylene glycol, natonolambda alcohols, or trihydric alcohols such as glycerin, but -hydric alcohols are usually preferred, and among them, N-vinylformamide after thermal decomposition is preferred. Triethylene glycol is preferred from the standpoint of separation from The amount of these polyhydric alcohols used is
001 for (α-hydroxyethyl)formamide
It is fine if the amount is more than 1 mole, but since polyhydric alcohol is usually used as a solvent without using @j solvent, for example, 0. j to 7 moles, preferably 1 to 7 moles.

The reaction between N-(α-hydroxyethyl)formamide and a polyhydric alcohol is usually carried out in the presence of a mineral acid catalyst such as sulfuric acid, hydrochloric acid, nitric acid, or phosphoric acid. The amount of mineral acid catalyst used is usually 0.0% relative to N-(α-hydroxyethyl)formamide. /~This is Yu Komoru. One reaction time is usually 0-10
0"C1, preferably at 70 to 10°C, and the reaction time is usually carried out until 10 or more, preferably ?θ- or more of the raw material IJ-(α-hydroxyethyl)formamide is consumed, For example, for θ, !−r, N−(
This can be carried out by mixing the α-hydroxyethyl)formamide and stirring at a given time. In this reaction, N-(α-hydroxyethyl)formamide is hardly dissolved at the beginning of the reaction, but as the reaction progresses, it gradually dissolves, and by the end of the reaction, it is completely homogeneously mixed. A solution is obtained.

In addition, N-(α-hydroxyethyl) used as a raw material
Formamide may contain alkali components such as formamide, which is the raw material for its production, and potassium carbonate, which is a catalyst. In this case, the acid necessary to neutralize the alkali components is added and the It is desirable to carry out the reaction.

After completion of the reaction, the mixture is usually added with caustic alkali to neutralize the mineral acid catalyst, and at this time, a neutralized salt such as Glauber's salt is created. It is commonly understood that a part of this neutralized salt is added to the reaction system due to the action of water formed during the etherification reaction, but some of it precipitates as crystals, so if necessary, this can be removed by filtration. It is better.

In the present invention, the etherified product thus obtained is then
The essential requirement is to carry out thermal decomposition by heating in a liquid phase under reduced pressure and expelling the generated N-vinylformamide. That is, in the case of the present invention, since the etherified product is obtained by reaction with a specific polyhydric alcohol, only in this case can the thermal decomposition be carried out at a low temperature, and as a result, it is possible to perform the thermal decomposition even if it is not in the gas phase. , good thermal decomposition can be performed in the liquid phase.

Usually once pyrolysis? O--〇θ℃, preferably /CO~/J''0℃; if this temperature is too low, the decomposition of the ether compound will proceed well; on the other hand, if it is too high, , the amount of Harz component by-produced is large, and the desired N-vinylformamide cannot be obtained in high yield.In addition, the degree of vacuum is usually -0 mxHt or less, preferably 70 to 111 MHf; If the degree of pressure reduction is insufficient, N-vinylformamide cannot be obtained in high yield.

In the thermal decomposition in the present invention, the mixture obtained in the above-mentioned etherification reaction is usually subjected to subsequent thermal decomposition, but in this case, when the mixture is heated and heated under reduced pressure, generally water is distilled out first, and then water is distilled out. , After the polyhydric alcohol for the week is distilled off, N-vinylformamide produced by thermal decomposition and 1ff
Since alcohol is distilled out together with alcohol, this distillate is recovered. And, while the boiling point of N-vinylformamide is, for example, 2θ°C in 3-Yu Hp, the boiling point of polyhydric alcohol is much higher than this (in the case of triethylene glycol, it is about /J-0°C/3°C). Hp), so by further distilling this distillate under reduced pressure, N
-Vinylformamide and polyhydric alcohol can be easily separated. For example, when a polyhydric alcohol with a high boiling point such as polyethylene glycol is used, only N-vinylformamide is distilled out from the thermal decomposition VC, so there is no need to further separate the distillate.

The N-vinylborumamide recovered and sold here contains some other organic impurities, so if necessary,
Furthermore, high purity products can be obtained through fine trading. On the other hand, the similarly recovered polyhydric alcohol can be reused as a raw material for the etherification reaction.

In addition, in the present invention, in order to dilute the etherified raw material during thermal decomposition, a high boiling point solvent that is normally used as a heating medium may be added. This high boiling point solvent is of course inert and has a point higher than that of the raw materials and decomposition products by 48 points.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the scope of the invention.

Example/ N-(α
-Hydroxyethyl) formamide (hereinafter referred to as hydroxy form) crystal (M1 degree 73, formamide-containing II)
o, z%, K2O0, chi゛lid θ,! h) Prepare 309 and add triethylene glycol/￥rf/(Damol times the hydroxyl form) and sulfuric acid θ, 2 s g (
Add θ, j morti) to the neutralized electron hydroxyl form of K, 00°, and neutralize at once at λj - 410°C under stirring until the remaining amount of hydroxyl form in the reaction system reaches r%. The pH was adjusted to 2 by doing this.

After the completion of the reaction, the entire amount of the mixture (homogeneous solution) containing the etherified product was charged into a thermal decomposition reactor equipped with a vacuum distillation device, and the mixture was heated under the reduced pressure of JIIH7 at a liquid temperature of /gθ~/gθ℃ for 2 hours. Upon heating, a thermal decomposition reaction was carried out while distillate containing decomposition products was distilled off. Incidentally, the temperature at the top of the column at this time was 1°C to 30°C.

Distillate recovered by this thermal decomposition reaction/1311
The composition of the residue /, /g was analyzed and found to be as follows. From this, the yield of the target product N-vinylformamide to the hydroxyl form and the amount of Harz by-product in the residue were determined. The results shown in Table 1 were obtained.

(Composition of distillate) N-vinylformamide it, o titrid ethylene glycol r♂, qtlA and other organic components
0. ! Chi water 3. t%(
Composition of the residue) N-Vinylformia is d/hydroethylene glycol 6--Other organic components 2, halz/thi, inorganic salts, 3θ When simple distillation was carried out under these conditions, highly pure N-vinylformamide with a purity of 91% or more could be obtained.

The reaction was carried out in the same manner as in Example/, except that the alcohol shown in Table 1 was used and the thermal decomposition was performed under the conditions shown in Table 1. The results are shown in Table 1.

Comparative Example 3 In the method of Comparative Example/, thermal decomposition was carried out using a diameter of 10×1 length of 3
Using a reactor filled with glass beads with a diameter of 3% in a stainless steel tube of 0~, under a reduced pressure of /θθ11Ht, daj0
When gas-phase thermal decomposition of the ether compound was carried out continuously at 1°C and a residence time of 7 seconds, a systematic thermal decomposition reaction took place at first, but the reactor gradually became clogged, and after 3 hours all the ethers were completely decomposed. Due to blockage, the reaction was discontinued. In addition, when the amount of Harz in the reactor was subsequently analyzed, it was found to be less than that of the hydroxyl compound.

〔Effect of the invention〕

According to the present invention, N-(α-hydroxyethyl)formia is etherified using a polyhydric alcohol, and the etherified product is thermally decomposed in the liquid phase under reduced pressure, thereby converting the nitrous component and other components. There is little formation of hooked organisms called β, and the desired N-vinylformamide can be obtained in high yield. In addition, the method of the present invention is advantageous in terms of thermal energy because the number of times of thermal decomposition is lower than that of the conventional gas phase method. There are no operational problems. Therefore, the method of the present invention is industrially extremely excellent.

Sender: San-ai Kasei Kogyo Co., Ltd. Representative Patent Attorney Hase - 7 people

Claims (3)

[Claims] (1) N-(α-hydroxyethyl)formamide is reacted with a polyhydric alcohol to etherify it, and then the ether compound is heated in a liquid phase under reduced pressure to produce N
- A method for producing N-vinylformamide, which comprises carrying out thermal decomposition while distilling off vinylformamide. (2) The method according to claim 1, wherein the polyhydric alcohol is a dihydric alcohol. (3) Pyrolysis under reduced pressure of 20 mmHg or less, 90 to 20
The manufacturing method according to claim 1, characterized in that it is carried out once at 0°C.