JPH0832642B2 - Purification method of dicyclopentadiene - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing high-purity dicyclopentadiene [hereinafter abbreviated as DCP], more specifically, it can be carried out on an economical and industrial scale, The present invention relates to a method for producing high-purity DCP that can be used in injection molding.

(Prior Art) In recent years, a method of producing polydicyclopentadiene, which is a crosslinked thermosetting resin, by a reaction injection molding method using a metathesis catalyst composed of a tungsten compound or a molybdenum compound and an organoaluminum compound has attracted attention. However, when commercially available DCP (for example, purity 95% by weight) is used as this raw material, the polymerization activity is not sufficient, and therefore distillation has been repeated to increase the purity. However, in this method, the recovery rate of DCP was lowered, and even when it was highly pure, it was often inactive for polymerization in reaction injection molding.

Recently, a method (US Pat. No. 4,584,425) of distilling commercially available DCP and treating it with an adsorbent such as a molecular sieve or alumina or silica gel to remove polymerization inhibitors has been disclosed. However, since the distillation performance of this method is insufficient, it is necessary to leave a large amount of initial distillate and kettle residue, which has the drawback of low yield of high-purity DCP. However, there were industrial disadvantages such as increase of waste gas and treatment of waste adsorbent.

(Problems to be Solved by the Invention) Therefore, as a result of intensive studies to solve the above-mentioned drawbacks, the present inventors have found that when distillation is performed in the presence of a specific amount of an antioxidant, the reaction injection molding method has a high yield. The present inventors have completed the present invention by discovering that pure DCP can be produced by an industrially simple and economical process.

(Means for Solving the Problems) Thus, according to the present invention, when the crude dicyclopentadiene containing impurities is distilled to obtain high-purity dicyclopentadiene, a low-boiling point impurity removing step and a high-boiling point impurity removal step are performed. Provided is a method for purifying dicyclopentadiene, characterized in that each step is provided independently, and distillation in each step is carried out in the presence of an antioxidant of 200 ppm or more with respect to the amount of the crude dicyclopentadiene supplied. It

The crude DCP as a raw material used in the present invention is an endo isomer, an exo isomer or a mixture thereof, and its purity is usually 80% by weight or more, preferably 90% by weight or more. Components other than DCP include low boiling impurities and high boiling impurities. Specific examples of the former include hydrocarbons having 4 to 6 carbon atoms, cyclopentadiene, and chain conjugated diolefins such as butadiene, isoprene and piperylene. Examples include co-duplicates (vinyl norbornene, isopropenyl norbornene, propenyl norbornene, etc.). Among them, hydrocarbons having 4 to 6 carbon atoms must be sufficiently removed because they cause defective molding in reaction injection molding. As a concrete example of the latter,
For example, a trimer of cyclopentadiene, a co-dimerized product of cyclopentadiene and isoprene (methylbicyclononadiene), a compound in which oxygen is added to DCP (for example, 5 or 6).
-Hydroxy-3a, 4,7,7a tetrahydro-4,7-methano-
1H-indene, etc.).

Among them, the oxygenated product of DCP significantly interferes with the polymerization of reaction injection molding and therefore needs to be sufficiently removed, but this oxygen-containing compound is very small and its boiling point is close to that of DCP, so it is very difficult to separate by distillation. Moreover, it is a compound that is often easily produced in the distillation step.

In order to remove these impurities, in the present invention, a distillation step for removing low-boiling substances and a distillation step for removing high-boiling substances are independently provided. Any combination of these steps may be performed, but usually, a distillation step for removing low-boiling substances is preceded by a distillation step for removing high-boiling substances.

The distillation conditions for the distillation step for removing low-boiling substances are usually a reduced pressure of 5 to 200 torr, preferably 20 to 150 torr, and a bottom temperature of 50.
~ 130 ℃, preferably 80 ~ 120 ℃, under these conditions
C ₄ -C ₆ impurities ho Isuzu can be completely removed.

Distillation conditions for the distillation step for removing high-boiling substances are usually a reduced pressure of 5 to 150 torr, preferably 10 to 100 torr, and a bottom temperature of 60.
~ 130 ℃, preferably 70-120 ℃, thereby DC
P oxygenates can be removed almost completely.

In each distillation process, the thermal decomposition of DCP greatly affects the stabilization of operation and the purity, so it is necessary to be careful in controlling the distillation conditions. It is preferable that the pressure loss in the distillation column be as small as possible, and from this point of view, a spray column, a packed column or the like is used. Above all, a packed tower is preferably used for the purpose of improving the separation performance. As the packing material used in the packed tower, a low-pressure loss type packing material, for example, a regular packing material is preferred.
Distillation is carried out under strict control so as not to come into contact with oxygen.

In the present invention, it is important to distill the crude DCP in the presence of an antioxidant in the above distillation step. As the antioxidant, phenol-based ones are preferable, for example, 4,4'-
Dioxydiphenyl, hydroquinone monobenzyl ether, 2.4-dimethyl-6-t-butylphenol, 2.6
-Di-t-butylphenol, 2.6-di-t-amylhydroquinone, 2.6-di-t-butyl-p-cresol,
4-Hydroxymethyl-2.6-di-t-butylphenol, 4,4'-methylene-bis- (6-t-butyl-o-
Cresol), butylated hydroxyanisole, phenol condensate, butylated phenol, dialkyl phenol sulfide, high molecular weight polyhydric phenol, bisphenol and the like. In addition, quino-based compounds such as t-butylcatechol, hydroquinone, resorcin, and pyrogallol can also be used. Among these 2.6-
Sublimable compounds such as t-butylphenol, 2.4-dimethyl-6-t-butylphenol and the like are preferred because of their effect on the gas layer in the distillation column.

The antioxidant may be supplied to the distillation column from any position such as the bottom, the top or the center of each step. However, it is preferable to supply the antioxidant into the raw material or the reflux liquid for the purpose of allowing the antioxidant to exist in the entire column. Further, when the antioxidant remains in the distillate from the first removal step, it is not always necessary to add the antioxidant in the next removal step.

The amount of the antioxidant used is 200 ppm or more, preferably 500 to 10,000 ppm, based on the crude DCP supplied to each step. If the amount is less than 200 ppm, an oxygen adduct of DCP is likely to be generated during the distillation operation, and it is unavoidable that it is mixed in the DCP to be purified by distillation. The upper limit is not particularly limited, but if it is excessively large, it is not economical.

In the present invention, the distillation temperature in each step is 130 ℃ or less, especially 1
The temperature is preferably 20 ° C or lower. If the distillation temperature is excessively high, the effect achieved by the coexistence of the antioxidant is reduced.

(Effect of the invention) Thus, according to the present invention, by the simple process of combining an antioxidant and distillation, as compared with the prior art,
High-purity DCP that can be used for reaction injection molding at low cost and on an industrial scale can be obtained.

(Example) Hereinafter, the present invention will be described more specifically with reference to Examples. Parts and% in Examples and Comparative Examples are based on weight unless otherwise specified.

Example 1 As crude DCP, endo isomers and exo isomers were combined (hereinafter referred to as DCP purity) 94.0%, cyclopentadiene 0.1%, vinylnorbornene 0.6%, and low-boiling point isopropenylnorbornene or propenylnorbornene. Codimer 3.9%, high-boiling codimer such as methylbicyclononadiene 1.3%, DCP oxygen-containing compound 0.1%
I used the one consisting of.

BHT (2.6-di-t-butylphenol) was added to this crude DCP.
Was added to 1.000 ppm and continuously supplied to the distillation column for removing low boiling point substances. Raschig ring for the distillation column (equivalent to 30 distillation stages)
Was operated under the conditions of a column bottom temperature of 110 ° C., a pressure of 120 torr and a reflux ratio of 20, and 8 parts were continuously extracted from the top of the column and 92 parts from the bottom of the column. The DCP purity in the bottom liquid at this time is 98.1%.
Met. The BHT content was 1100 ppm.

Next, the bottom liquid was continuously supplied to the high boiling point removal distillation column which is the next step. The high boiling point removal column is a packed column of regular packing (equivalent to 30 distillation stages), bottom temperature 105 ° C, pressure 90tor.
It was operated under the conditions of r and a reflux ratio of 10 and continuously withdrawn at a rate of 91 parts from the top of the tower and 9 parts from the bottom of the tower. In the top liquid at this time
The DCP purity was 99.3%. Oxygenated DCP was not detected, and co-dimer was recognized as other impurities.

When the polymerization activity of the high-purity DCP was evaluated using a catalyst of organic molybdate, diethylamine chloride, and propyl alcohol (hereinafter referred to as polymerization activity evaluation), the polymerization reaction proceeded easily.

Example 2 The same operation as in Example 1 was carried out except that 600 ppm of BHT was added to the reflux liquid of the distillation column for removing impurities having a low boiling point, instead of adding BHT to the crude DCP. The obtained DCP has a purity of 99.2.
%, And the result of evaluation of polymerization activity was that the polymerization reaction was easy.

Example 3 The same operation as in Example 1 was carried out except that 2.6-di-t-butyl-p-cresol was used instead of BHT. As a result, almost the same results as in Example 1 were obtained.

Comparative Example 1 When the same operation as in Example 1 was performed without adding BHT, the purity of the obtained DCP was 99.1%, but the polymerization reaction did not proceed in the result of evaluation of the polymerization activity.

Comparative Example 2 The same operation as in Example 1 was carried out except that the amount of BHT added was 100 ppm, and the purity of the obtained DCP was 99.1%.
However, the polymerization reaction did not proceed in the polymerization activity evaluation test.

Claims (1)

[Claims] 1. When distilling crude dicyclopentadiene containing impurities to obtain high-purity dicyclopentadiene, a low boiling point impurity removing step and a high boiling point impurity removing step are separately provided, and A method for purifying dicyclopentadiene, characterized in that the method is carried out by distillation in the presence of an antioxidant of 200 ppm or more based on the amount of crude dicyclopentadiene supplied.