JPS5951533B2 - Method for producing cyanonorbornene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides cyanonorbornene (5-cyanobicyclo[
2.2,1] Abbreviation for hepten-2.

), in detail, when synchropentadiene and acrylonitrile are subjected to a continuous heating reaction at a temperature of 160°C or higher and 200°C or lower, cyanonorbornene is added to the reaction raw material prior to the reaction, and then introduced into the reaction zone. The purpose of the present invention is to provide a method for obtaining cyanonorbornene stably and in a high yield by carrying out the reaction, thereby preventing the by-product of solid polymers that would be a hindrance to continuous operation.
Cyanonorbornene is a compound useful as a raw material for polymer production, and a method for producing it by the Diels-Alder reaction of cyclopentadiene and acrylonitrile has been known.

Cyclopentadiene, which is used as a raw material in this reaction, is highly reactive and easily dimerizes even at room temperature. Because it is an unstable substance, it is usually commercialized in the form of cyclopentadiene, which can be regenerated by thermal decomposition if necessary. used.
To produce cyclopentadiene from synchropentadiene, generally (-f) a vapor distillation method in which the mixture is fractionated while being thermally decomposed at a temperature of about 170°C; liquid phase decomposition method that decomposes and fractionates the
←→ Gas phase decomposition methods are known in which catalytic decomposition is performed in the gas phase at high temperatures of 260 to 350°C for a relatively short period of time, but these methods decompose 70 to 90% of pacyclopentadiene into monomers. However, a portion of the polymer becomes a higher-order polymer, which inevitably reduces the yield.Also, when the cyclopentadiene thus obtained is reacted with acrylonitrile, the formation of some by-products is inevitable. However, the overall yield is limited to about 65 to 85%. The present inventors have previously developed a method of using easily available synchropentadiene as a raw material and directly reacting it with acrylonitrile without going through the complicated and uneconomical steps described above, and have applied for a patent application (Patent Application No. 47). -91782) However, the method of the present invention prevents the undesirable adhesion of solids generated near the raw material introduction part of the reactor when the method is continuously carried out on an industrial scale, and enables long-term continuous operation. The aim is to make this possible.

In other words, when synchropentadiene and acrylonitrile are subjected to a batch heating reaction, as long as the temperature is sufficiently controlled by removing the reaction heat, there is almost no formation of solids that would inhibit the progress of the reaction. There is no problem, but since this reaction is carried out continuously in a flow system, solid matter precipitates near the raw material introduction part of the reactor and adheres to the tube wall, which gradually increases the flow resistance and reduces heat transfer. As the resistance increases, the pipe eventually becomes blocked, making continuous operation impossible.

According to the knowledge of the present inventors, this precipitated solid substance is mainly a cyclized polymer of the raw material acrylonitrile, and therefore, it is common sense that this is not a good means to prevent the formation of such hartz. It is considered effective to add a polymerization inhibitor such as hydroquinone or hyperquinone monomethyl ether. However, although these ordinary polymerization inhibitors can reduce the production amount of the above-mentioned ruts to some extent, it is difficult to say that they are sufficient for practical use. At high temperatures, the expected effect cannot be obtained and it cannot be an essential solution. As a result of various studies regarding this solution, the present inventors have found that by adding cyanonorbornene to the raw material in advance before introducing it into the reaction zone and then carrying out the reaction, the above-mentioned solution can be achieved.
- It has been found that the formation of roots can be effectively prevented.

To explain the method of the present invention in more detail, the amount of cyanonorbornene to be added to the raw material is usually 30 parts by weight or more, preferably 50 parts by weight, per 100 parts by weight of acrylonitrile.
It is preferable to use more than one part by weight, but in addition to the isolated and purified cyanonorbornene, 1 part of the reaction solution with a yield of cyanonorbornene of 85 to 90 qf) or more can be recycled and used as it is. , 1. The generation prevention effect of Ruth is actually better than the former 0 method, and the continuous operation operation point z:→Go2;←':. $:゜Since it is an unstable substance that easily polymerizes, great consideration must be given to controlling the reaction temperature, but by circulating a portion of the reaction solution and using it as a solvent, it is easier to control the reaction temperature. It also has the advantage of

However, the greater the amount of reaction liquid returned to the raw material system, the lower the productivity and the larger the required reactor volume, which is economically disadvantageous. Furthermore, this is not preferable in terms of reaction operation since the reaction product and the partially unreacted raw material must be kept at a high temperature for a relatively long period of time, and therefore there is a limit to the amount of the reaction liquid that can be returned to the raw material system. It can be said that the appropriate feedback rate for effectively suppressing Hartz generation is within the range of about 10 to 80q6, preferably 30 to 60q1. There is no particular problem with the combined use of hydroquinone, hydroquinone monomethyl ether, or other polymerization inhibitors, and it is rather desirable to use them in combination as long as the above-mentioned effect of adding cyanonorbornene is ensured. However, if these are used in excess of necessary, they are not only ineffective, but also may have an adverse effect on the physical properties of the final cyanonorbornene polymer product, so the amount added should be between 10 and 1000 ppm.
Desirably, it should be kept at about 300 ppm. In addition, in the recently published Japanese Patent Application Laid-open No. 51-34139, in a method for producing cyanonorbornene etc. by the reaction of synchropentadiene and acrylonitrile etc., the entire reaction zone or After filling one portion with the final norbornene product or the assembled reaction product of the previous reaction and keeping it heated to a reaction temperature of 160 to 240° C., the starting materials are added separately or premixed to this reaction zone. However, in the method of the present invention, the starting materials are introduced into the reaction zone separately or in a premixed manner, and the starting materials are pretreated with cyanogen before being introduced into the reaction zone. The essential requirement is that norporene is added, so that the starting material introduced into the reaction zone at approximately room temperature is at an optimum reaction temperature of 160°C.
This is to prevent the formation of zero hartz mainly on the inner wall of the raw material supply pipe, etc. around the raw material introduction part which is the contact point that moves to the high temperature part whose heating is controlled to 200°C.

At this time, it is desirable that the starting raw material components, synchropentadiene and acrylonitrile, are mixed in advance and introduced into the reaction zone. However, if they are introduced separately, cyanonorbornene, which is added to prevent Harz formation, is at least mixed with acrylonitrile. It is necessary for them to coexist. In general, an excess of acrylonitrile will give better results in terms of starting material composition, but if it is too much, the yield will decrease,
Since there are harmful effects such as the formation of by-products, it is usually desirable to use 2 to 4 mol, preferably 2 to 3 mol, of acrylonitrile per 1 mol of synclopentadiene. The reaction temperature must be 160° C. or higher; if the temperature is lower than this, the reaction rate is slow (substantially sufficient yield cannot be obtained). On the other hand, if the temperature is too high, there are drawbacks such as a decrease in yield due to an increase in by-products, so heating above 200°C should be avoided. Hereinafter, the method of the present invention will be explained in more detail by showing typical examples.

Comparative Example Using a stainless steel autoclave with an internal volume of 140 g and equipped with a stirrer, 7 parts of a reaction raw material consisting of 53 parts by weight of acrylonitrile (parts by weight, same hereinafter) and 66 parts of synchropentadiene was added.
Continuously supplied at a rate of 0g/Hr, reaction temperature 180
When the reaction was carried out at ℃ (pressure 10k9/CwPG), cyanonorbornene was initially obtained with an average yield of 82-83%, but about 7 hours after the start of operation, near the reactor inlet (raw material supply pipe mouth) The pressure rose due to a blockage in the pipe, making it impossible to continue operation.

Next, in the same method as above, 20% each of hydroquinone and hydroquinone monomethyl ether were added as polymerization inhibitors.
A similar reaction was attempted using 0 ppm, but the continuous operation time was extended to 20 hours and 15 hours, respectively.
No substantive solution was reached.

Example 1 Reaction raw material composition containing 75% by weight of previously purified cyanonorbornene (11.13 parts of acrylonitrile,
When the reaction was carried out in the same manner as in the comparative example using 13.87 parts of synchropentadiene and 75 parts of cyanonorbornene, stable operation continued with no clogging of pipes such as the reactor inlet and outlet observed even after 50 hours. Ta.

The yield of cyanonorbornene in this reaction was 95
．． It was 0%. In addition, the raw material supply rate was set to 37"Hr,
The yields were 96.5%, 94.2% and 90.6% when lOOm''Hr and 195mVhr were set, respectively.Example 2 Two stainless steel autoclaves with an internal volume of 140Tnj and equipped with a stirrer were connected in series. The reaction was carried out in a flow system while maintaining the reaction temperature at 180°C.

However, at the beginning of the reaction, the reaction was carried out in batch mode for 2 hours, and when a steady conversion rate (approximately 96%) was reached, it was switched to flow mode and continuous operation was performed. Steady operating conditions in continuous flow-through operation include 53 parts of acrylonitrile, 66 parts of synchropentadiene, and 0.011 parts of hydroquinone.
The raw material consisting of 1.5 mVhr is supplied at a rate of 42 mVhr and introduced into the first reactor together with the circulating fluid 28 mVhr, and the distillate is subsequently introduced into the second reactor.The reaction distilled from the second reactor One part of 28 hours of product liquid of 70 mVhr is returned to the first reactor by a circulation pump and mixed with the raw material immediately before the raw material inlet. In this way, the reaction was carried out continuously, but
Even after 150 hours, no problems such as tube occlusion occurred.
The following good results were stably obtained.

Cyanonorbornene yield 96.0% Unreacted acrylonitrile 1.33% ″ Synchropentadiene 1.66% High boiling point byproduct 1.0q6

Claims (1)

[Claims] 1 Dicyclopentadiene and acrylonitrile at 160
1. A method for producing cyanonorbornene, which comprises adding cyanonorbornene to a reaction raw material in advance and then introducing it into a reaction zone to carry out the reaction during a continuous heating reaction at a temperature of ~200°C.