JPH1160558A - Production of n-vinylcaprolactam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To safely and efficiently produce the subject compound, capable of raising the reactivity even under a low acetylene partial pressure at a low temperature and useful as a raw material or the like for producing polyvinylcaprolactam by reacting acetylene with caprolactam in the presence of a specific solvent. SOLUTION: (A) Acetylene is reacted with (B) caprolactam in the presence of (C) a polyalkylene glycol dialkyl ether having preferably 150-300 deg.C boiling point (e.g. triethylene glycol dimethyl ether) at preferably 80-120 deg.C temperature under 0-4 kg/cm<2> .G acetylene partial pressure for 2-15 hr (in the case of batch operations) by using (D) an alkali metallic compound such as a potassium alcoholate as a catalyst to afford the objective compound. The molar ratio of the components D/B is preferably 0.02-0.20 and the concentration of the component D is preferably 0.2-1.0 mol/L. The component C is used in an amount of preferably 40-80 wt.% based on the total components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for producing N-vinylcaprolactam, wherein the reaction between caprolactam and acetylene is performed under low pressure and low temperature conditions. N-vinylcaprolactam is an important compound as a raw material for producing polyvinylcaprolactam by polymerization alone or as a raw material for copolymerization with another vinyl compound.

[0002]

2. Description of the Related Art Conventionally, a method proposed for a vinylation reaction of caprolactam with acetylene generally involves a high or high reaction condition. For example, in the method disclosed in Japanese Patent Publication No. 34-520, a pressure (about 70 to 352 kg / cm ² · G) and a temperature of 150 to 28 are sufficient to keep a mixture of lactam and acetylene in a liquid state.
A high pressure of 0 ° C. and a high temperature are used. This is a result of considering the efficiency of the vinylation reaction, but the higher the acetylene partial pressure, the higher the risk of acetylene decomposing and exploding.Therefore, using a high acetylene partial pressure for the reaction is However, it is disadvantageous in that it requires a special pressure-resistant reactor corresponding to the safety and the pressure. In the reaction using acetylene, a low temperature is more advantageous not only in terms of safety but also in terms of the material of the reaction equipment and energy balance.

[0003] On the other hand, caprolactam has a property of being easily ring-opening-polymerized in the presence of an alkaline compound as compared with other lactams such as pyrrolidone, etc. descend.

Therefore, in recent years, the reaction conditions have been set as low as possible,
Research into lowering pressure has continued. For example, JP-A-8-
In the method disclosed in Japanese Patent No. 245578, first, a lactam is reacted with an aqueous alkali metal hydroxide solution in a first step, and then in a second step, the temperature is 60 to 250 ° C. and the pressure is 1 to 1.
The reaction with acetylene is carried out at 100 bar. In the example showing a specific embodiment, the reaction temperature is relatively low at 90 ° C., but the pressure is 18 bar partial pressure of acetylene and the total pressure is 20 bar.
It uses a high pressure of bar.

Japanese Patent Application Laid-Open No. 4-501252 discloses a method in which a lactam and acetylene are reacted at a relatively low pressure and a low temperature using a specific catalyst. In this embodiment, the partial pressure of acetylene is 7 kg. / Cm ² · G and the reaction temperature is 150 to 160 ° C., which is still not sufficiently satisfactory.

As described above, in the reaction between acetylene and caprolactam, from the viewpoint of safety and loss due to polymerization of caprolactam, it is more preferable to use low temperature and low pressure. It was difficult to reduce both temperature and pressure because of the reduced rate and the difficulty in achieving high yields.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to increase the reactivity of acetylene with caprolactam under low-temperature and low-pressure conditions to obtain N-
An object of the present invention is to provide a method for producing vinyl caprolactam safely and efficiently.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in view of such circumstances, and as a result, it has been found that the presence of a specific solvent in the reaction system at the time of the reaction allows a high acetylene partial pressure and a high reaction temperature even at a low reaction temperature. It has been found that a high conversion of caprolactam (hereinafter sometimes simply referred to as conversion) and a high N-vinylcaprolactam yield can be obtained.

That is, the gist of the present invention is that acetylene and caprolactam are reacted with an alkali metal compound as a catalyst.
A method for producing vinyl caprolactam, wherein a temperature of 70 to 140 ° C. and a partial pressure of acetylene of 0 to 10 kg / cm ² · G in the presence of a polyalkylene glycol dialkyl ether;
In the method for producing N-vinylcaprolactam.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The catalyst used in the present invention is an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, or an alkali metal alcoholate such as sodium alcoholate or potassium alcoholate.

Among these, the alkali metal alcoholate can be prepared by a known method, for example, by reacting an alcohol with an alkali metal hydroxide at a molar ratio of 1 or less to the alcohol, and distilling off by-produced water. It can be prepared by removing. Alternatively, a solution obtained by further removing a part or all of the alcohol from the solution may be used. The alcohol used is not particularly limited, but a chain aliphatic alcohol or a cyclic aliphatic alcohol is used. The linear aliphatic alcohol is, for example, a linear or branched aliphatic alcohol having 1 to 10 carbon atoms, and may contain an unsaturated bond in the molecule. The cycloaliphatic alcohol is, for example, a cycloaliphatic alcohol having 5 to 8 carbon atoms.

The amount of the catalyst used in the reaction is generally 0.01 to 0.30, preferably 0.02 to 0.20, in a molar ratio based on caprolactam. If the molar ratio is less than 0.01, a sufficient effect cannot be obtained, and if the molar ratio exceeds 0.30, only a rise in cost will not be obtained, and no significant effect will be obtained. The concentration of the catalyst in the reaction system is generally 0.1 to
2.0 mol / l, preferably 0.2 to 1.0 mol / l
l. If the concentration is less than 0.1 mol / l, a large reactor is required, and if it is used at more than 2.0 mol / l, the loss in economical efficiency becomes large, which is not preferable.

[0013] The solvent used in the present invention includes:
Polyalkylene glycol dialkyl ether, which is a kind of polyether, is used, and polyalkylene glycol dialkyl ether having a boiling point in the range of 150 ° C. to 300 ° C. is particularly preferable. Specifically, for example, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetrapropylene glycol dimethyl ether, Examples thereof include dipropylene glycol diethyl ether and tripropylene glycol diethyl ether.
Also, a mixture of these polyalkylene glycol dialkyl ethers can be used as a solvent.

The use amount of these solvents is not particularly limited, but is preferably 30 to 90% by weight, more preferably 40 to 80% by weight, based on all components of the reaction system. If the amount is less than 30% by weight, the effect of the present invention is small, and if it exceeds 90% by weight, the degree of dilution of the reaction raw materials increases, which is disadvantageous in terms of the reaction rate.

In the method of the present invention, by diluting the reaction raw materials with the above-mentioned solvent, the conversion and yield of the reaction are remarkably improved even at a low temperature and a low pressure, but the production of a polymer or the like is also prevented.

The reaction temperature between caprolactam and acetylene is 70-140 ° C., preferably 80-120 ° C. If the temperature is lower than 70 ° C., a sufficient conversion cannot be obtained.
If the temperature exceeds 0 ° C., side reactions increase and selectivity decreases. The reaction time depends on other conditions such as the reaction temperature and the acetylene partial pressure. In the case of batch operation, it is usually 1 to 30 hours, preferably 2 to 15 hours.

In the present invention, the acetylene partial pressure is usually from 0 to
10Kg / cm ² · G, preferably a 0~4.0Kg / cm ² · G, more preferably 0~2.0Kg / cm ² · G. As described above, the higher the pressure is, the higher the reaction rate is. However, in order to prevent the decomposition and explosion of acetylene and to make the reaction safe, the pressure is preferably as low as possible. Therefore, the reaction pressure is set in consideration of these factors.

In the synthesis reaction using acetylene as a raw material, generally, an inert gas such as nitrogen, argon, or propane is introduced together with acetylene to carry out the reaction while diluting the acetylene. In the present invention, the reaction is carried out under a low pressure. Not necessarily.

The reaction system may be either a batch system or a continuous system. However, in the case of the continuous system, sufficient care must be taken since by-products generated in the reaction system, particularly polymers, are easily accumulated. Regardless of whether it is a batch type or a continuous type, 70 to 95% by weight is appropriate as a standard of the caprolactam conversion.

In order to make the reaction proceed favorably, it is particularly preferable to use a reactor capable of sufficiently performing gas-liquid countercurrent contact. The type of the reactor includes, for example, a packed tower, a bubble tower, a stirring tank, a spray tower, a tray tower, and the like, and a combination thereof may be used.

After the reaction, the target N-vinylcaprolactam can be recovered from the product by a conventional method. For example, first, N-vinylcaprolactam, a starting material caprolactam, a catalyst, a solvent, a mixed solution containing a solvent and by-products are simply recovered. By distillation, N
Separation into a distillate containing vinyl caprolactam, raw material caprolactam and most of the solvent, and a bottom consisting of a part of the solvent, catalyst and by-products mainly composed of polymer. afterwards,
The distillate is led to a rectification column, where it is separated by distillation into N-vinylcaprolactam, a solvent and raw material caprolactam. Naturally, the solvent and the starting caprolactam are recovered and reused.
The simple distillation and rectification are preferably carried out under reduced pressure so that caprolactam is not polymerized during the distillation to cause a raw material loss, or the desired N-vinylcaprolactam causes a side reaction to cause a reduction in yield. In that case, 0.01 ~
A pressure of 50 mmHg, preferably 0.10-20 mmHg is employed.

[0022]

EXAMPLES Examples of the present invention will be described below, but these are exemplifications for explanation, and the present invention is not limited by the following examples. The percentages (%) shown in the examples and comparative examples are on a weight basis.

Reference Example 1 (Preparation of Catalyst) In a 1-liter stainless steel reactor, 160 g of cyclohexanol and 14.0 g of potassium hydroxide (0.25 mol) were added.
l) was charged. This was heated to 150 ° C. with stirring, and water was evaporated together with cyclohexanol at normal pressure while introducing nitrogen into the liquid layer. 4.5g over 5 hours
(0.25 mol) was evaporated to prepare a potassium alcoholate of cyclohexanol (cyclohexanol solution).

Example 1 A 1 l stainless steel reactor containing 250 g (2.2 mol) of caprolactam and 150 g (about 0.25 mol of alcoholate) of potassium alcoholate of cyclohexanol (cyclohexanol solution) synthesized according to the above reference example. ) Was added, and 250 g of triethylene glycol dimethyl ether was further added as a solvent.
Subsequently, 100 ° C. under a reduced pressure of 10 mmHg with stirring.
In 96 hours, 96% of the unreacted cyclohexanol was distilled off. Thereafter, acetylene was introduced up to 0.28 kg / cm ² · G and reacted at 100 ° C. for 4 hours. During this time, acetylene was continuously supplied by the amount consumed.

When the obtained product was analyzed by gas chromatography, the conversion of caprolactam was 90%.
%, And the selectivity to N-vinylcaprolactam is 81%.
Met. Therefore, the yield of N-vinylcaprolactam in this example is equivalent to 73%.

Comparative Example 1 Without using a solvent, only caprolactam was used in an amount of 500 g corresponding to the total amount of caprolactam and the solvent in Example 1.
The reaction was carried out under the same conditions as in Example 1 except that (4.4 mol) was used. Caprolactam conversion is 45% and N-
The yield of vinylcaprolactam was only 7%. It can be seen that these values are significantly lower than in Example 1.

Comparative Example 2 Caprolactam and acetylene were reacted in the same manner as in Example 1 except that polyethylene glycol (average molecular weight: 200) was used instead of triethylene glycol dimethyl ether as a solvent. The whole reaction solution solidified, and almost no fluidity was observed. When a part of the coagulated product was collected and analyzed, the yield of N-vinylcaprolactam was only 5%.

Example 2 Caprolactam and acetylene were reacted in the same manner as in Example 1 except that the temperature for distillation of cyclohexanol and the reaction temperature were changed to 120 ° C. and the reaction time was set to 2 hours. Caprolactam conversion is 86%, N
-The yield of vinylcaprolactam was 69%.

Comparative Example 3 500 g of caprolactam alone (4.
The reaction was carried out under the same conditions as in Example 2 except that 4 mol) was used. The whole reaction solution solidified, and almost no fluidity was observed. When a part of this coagulate was collected and analyzed,
The yield of N-vinylcaprolactam was 10%.

Example 3 In Example 1, the amount of caprolactam used was changed to 300
g, caprolactam and acetylene were reacted in the same manner as in Example 1 except that the amount of triethylene glycol dimethyl ether used was changed to 200 g. The conversion of caprolactam was 78% and the yield of N-vinylcaprolactam was 6%.
It was 0%.

Example 4 Using tetraethylene glycol dimethyl ether as a solvent, the caprolactam and the solvent were used in amounts of 1 respectively.
The reaction between caprolactam and acetylene was carried out in the same manner as in Example 1 except that the reaction temperature was set to 00 g and 400 g, and the reaction temperature was set to 90 ° C. Caprolactam conversion is 85% and N-
The yield of vinyl caprolactam was 66%.

Examples 5 to 7 In these examples, potassium hydroxide was used instead of the potassium alcoholate of cyclohexanol used in Example 1 as a catalyst. Caprolactam 1 in reactor
00g and tetraethylene glycol dimethyl ether 4
00 g was charged. After heating to 70 ° C. in a nitrogen atmosphere to dissolve caprolactam, 14 g of potassium hydroxide
(0.25 mol) and distilled at 10 mmHg for 1 hour to produce 4.5 g of water (0.25 mol).
l) was removed. Then, 0.28 kg / cm of acetylene was added.
^It was introduced up to ² · G and reacted at the reaction temperature shown in Table 1. Table 1 shows the reaction conditions and the reaction results.

Example 8 Caprolactam and acetylene were reacted in the same manner as in Example 1 except that tripropylene glycol dimethyl ether was used as a solvent. Caprolactam conversion of 8
At 3%, the yield of N-vinylcaprolactam was 61%.

Table 1 shows the reaction conditions and reaction results of all Examples and Comparative Examples.

[0035]

[Table 1]

[0036]

According to the method of the present invention, the reactivity can be increased even at a low acetylene partial pressure and a low temperature, so that N-vinylcaprolactam can be produced safely and efficiently.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Satoshi Kakuda 3387-5 Goi, Ichihara-shi, Chiba (72) Inventor Hidenobu Oda 3387-5, Goi, Ichihara-shi, Chiba

Claims (5)

[Claims] 1. A process for producing N-vinylcaprolactam from acetylene and caprolactam in the presence of a polyalkylene glycol dialkyl ether at a temperature of 70 to 140 ° C. and a partial pressure of acetylene of 0 to 10 kg / cm. ^A method for producing N-vinylcaprolactam, characterized by reacting with ² · G. 2. The method according to claim 1, wherein the polyalkylene glycol dialkyl ether is selected from ethers having a boiling point of 150 to 300 ° C. 3. The amount of the polyalkylene glycol dialkyl ether used is 30 to 30% in all components in the reaction system.
3. The method according to claim 1, wherein the content is 90% by weight. 4. The method according to claim 1, wherein the catalyst comprising an alkali metal compound is an alkali metal alcoholate or an alkali metal hydroxide. 5. The production method according to claim 1, wherein the acetylene partial pressure is 0 to 4 kg / cm ² · G.