JPH0417681B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying high-boiling polymerizable compounds. More specifically, the purification method uses a thin-film distillation apparatus to remove trace amounts of coloring components and high-boiling impurities that do not participate in polymerization, so that the high-boiling polymerizable compound to be purified has a relatively high purity. Regarding.

High-boiling point polymerizable compounds have been known for various fields of use, and one of the most important fields is their use as monomers for optical applications, particularly for plastic lenses. When a high boiling point polymerizable compound is used as a raw material for optical organic glass such as a plastic lens, it is required to have an extremely good hue and contain as few impurities that do not participate in polymerization as possible.

For example, one of the monomers for plastic cleansing has long been known under the trade name CR-39. The high boiling point polymerizable compound containing diethylene glycol bisallyl carbonate as the main component is
Even if the reaction conditions in the manufacturing process are strictly controlled, the highly pure target product obtained still contains a small amount of high-boiling polymerizable by-products with a boiling point higher than that of the target compound, as well as trace amounts of high-boiling polymerizable by-products. Contains coloring components and high-boiling impurities that do not participate in polymerization.

In this case, there is no problem even if a small amount of high-boiling point polymerizable by-products are mixed into the purified product, but even a very small amount of high-boiling point impurities that are not involved in polymerization and cause coloring components and turbidity and strength reduction are possible. It is necessary to remove as much as possible.

Among the high-boiling polymerizable compounds to be subjected to purification treatment, recrystallization is difficult, so when purifying by distillation, the material to be treated, which is a high-boiling polymerizable compound, is unstable at high temperatures. Therefore, polymerization in the rectification column causes polymer fixation and a decrease in yield, and column distillation is generally difficult.

Usually, in the chemical industry, when distilling and refining substances that are easily affected by heat or substances with high boiling points,
Thin film distillation is used to instantly distill compounds at high temperatures.

In this method, a condenser is built into the distillation apparatus under reduced pressure, and a cylindrical rotating body with a wiper etc. attached to the apparatus is operated to transfer the treated liquid charged in the form of a wet wall to the heating side of the column wall. A device that uses a device that spreads out a thin film to form a uniform treatment liquid film, evaporates low boiling point components within a short time, and simultaneously condenses them in a built-in condenser and takes them out as a rectified effluent, or a centrifugal method. This is a distillation method using a distillation device that forms a thin film using force.

However, even if such a thin film distillation method, which uses a wide evaporation surface and processes in a short time, is used,
In order to remove very small amounts of coloring components from the liquid to be treated and high-boiling point impurities that are not involved in polymerization, a relatively high-boiling point polymerizable compound of relatively high purity (for example, 95% or more) is distilled using a thin film distillation device. Although the target purified product evaporates instantaneously, since the purity of the liquid to be treated is high, the amount of high-boiling point impurities is small, and it is not flowed down onto the column wall as a liquid, so that a continuous thin film is not formed on the wall surface. As a result, the residence time under high temperature conditions becomes longer, and the remaining processing liquid becomes polymerized and sticks to the wall surface. This condition is extremely dangerous and if left untreated, the polymer will accumulate, eventually making it impossible for the wiper to rotate and leading to damage to the device. Furthermore, even if treatment operations are possible, the efficiency of removing contained impurities will be poor.

The inventors of the present invention have discovered the method of the present invention as a result of various studies aimed at solving these drawbacks.

That is, the present invention uses a thin film distillation apparatus to distill and purify a high-boiling point polymerizable compound containing a trace amount of impurities, and has a higher boiling point than the high-boiling point polymerizable compound to be subjected to the distillation purification. Moreover, this is a method for purifying a high-boiling point polymerizable compound, which is characterized by treating a high-boiling point inert compound with good compatibility by mixing and dissolving it in the high-boiling point polymerizable compound. This method enables continuous purification operations by allowing the liquid to be treated to flow down continuously without causing the treatment liquid to stick to the surface.

Figure 1 is a side view of a laboratory-scale distillation apparatus used for normal thin film distillation, such as Smith distillation, and is also applicable to the method of the present invention.
Based on this, the method of the present invention will be explained.

Figure 1+1 shows a solution in which a high-boiling point inert compound is mixed and dissolved in a high-boiling point polymerizable compound, which is a liquid to be treated, and is kept in a heated state if necessary. The outer wall of the distillation column 2 is heated by a mantle heater 3, and a rod-shaped condenser 4 that can circulate cooling water is built in near the center of the column. It is communicated with a receiver 5 that receives a liquid for treating objects. Further, a rotating body 7 having a cylindrical frame is attached to the outside of the rod-shaped condenser so as to have a slight gap with the column wall, and is driven by a motor 6 during distillation. Further, a rod-shaped wiper 8 having several diagonally cut grooves is fitted into the frame of the rotating body via a spring.

When performing thin film distillation using this device, the solution 1 consisting of the high boiling point polymerizable compound of the liquid to be treated and the mixed and dissolved high boiling point inert compound is poured into a conduit by adjusting the dropping rate arbitrarily with a kettle. It is charged from 10. The charged liquid flowing down the tower wall is slid by the wiper 8 fitted in the rotating body and is evenly spread, forming a thin film that is instantaneously evaporated and mixed and dissolved. The vapor of the high-boiling point polymerizable compound having a lower boiling point than that of the inert compound is condensed by a condenser 4 installed in the center, collected in a receiver 5 as a rectified fraction treatment liquid, and taken out. In addition, high-boiling polymerizable by-products that have a boiling point higher than that of the target compound contained in the liquid to be treated, as well as coloring components and high-boiling impurities that do not participate in polymerization, are
Together with the mixed high-boiling inert compounds, it flows down the column wall and is collected in receiver 9.

The rectified fraction treated in this way and obtained from receiver 5 contains almost no impurities that cause coloring components or turbidity, and contains the desired high-boiling point polymerizable compound with high purity. It can be obtained with high recovery rate.

In the method of the present invention, the high boiling point inert compound dissolved in the liquid to be treated is 1 to 80% by weight based on the liquid to be treated.
Preferably it is used in an amount of 5 to 30% by weight. The amount of solvent used is 1
If the amount is less than 80% by weight, the effect is poor, and if it is more than 80% by weight, it is meaningless and economically unfavorable. Furthermore, the use of a solvent with poor compatibility with the liquid to be treated is not preferable, since the heated wall surface will repel the flowing liquid to be treated and cause the remaining treatment liquid to stick.

On the other hand, it is a more effective and desirable method to add a trace amount of a high-boiling polymerization inhibitor together with a high-boiling inert compound. Further, the high boiling point inert compound subjected to thin film distillation and recovered in the receiver 9 may be reused if necessary.

The purification method to which the present invention can be applied can be applied to any high-boiling point compound having an unsaturated group that can be purified using a normal thin film distillation apparatus, but it is particularly suitable for treating compounds with a purity of 95% or more. Alkylene glycol bisallyl carbonate compounds used in plastic lenses such as diethylene glycol bisallyl carbonate, triethylene glycol bisallyl carbonate, and tetraethylene glycol bisallyl carbonate;
Other diethylene glycol bisacrylate,
Suitable for removing trace impurities from compounds such as diethylene glycol bismethacrylate.

In addition, the high boiling point inert compound mixed and dissolved in these compounds to be treated is compatible with the compounds to be treated, has a high boiling point, and has a large difference in boiling point.
Any compound that can be easily separated from the target compound when subjected to thin film distillation can be used. For example, when treating alkylene glycol bisallyl carbonate, examples include polyethylene glycol, polypropylene glycol, etc. Particularly preferred compounds are those with an average molecular weight of 1000 ~2000 polyethylene glycol.

If either or both of the high-boiling polymerizable compound to be treated and the high-boiling inert compound to be mixed are solid, they are heated and melted, mixed, and charged into a thin film distillation apparatus while being kept warm. Examples are shown below.

Example 1 Slightly cloudy pale yellow crude diethylene glycol bisallyl carbonate (purity 97%, containing 2-3% high-boiling polymerizable by-products, trace amounts of other impurities,
APHA20-25) 120g and 12.0g (equivalent to 9%) of polyethylene glycol 1000 (average molecular weight 1000)
was added and mixed and dissolved.

This solution was dropped into a column with a wall temperature of about 200°C under a reduced pressure of 1 torr from the charging tube 10 using the apparatus shown in Figure 1 to perform thin film distillation. The processing time required 25 minutes, and 116 g of purified diethylene glycol bisallyl carbonate was obtained from the rectified fraction receiver 5. This product was almost colorless, had no turbidity, had a purity of 98%, contained 2% high-boiling polymerizable byproducts, and had an APHA of 5 to 10. In addition, the undistilled high-boiling cut obtained from receiver 9 was 16 g, and its composition was about 1% high-boiling polymerizable by-products and about 76 g of polyethylene glycol 1000.
%, approximately 10% of polymer polymerized during distillation, and impurities such as trace amounts of coloring components. In addition, the recovery rate of diethylene glycol bisallyl carbonate by thin film distillation is 97%, there is almost no deposit on the equipment wall after treatment, there is almost no change even after repeating the same distillation operation more than 10 times, and the wiper rotates well. It was hot.

Comparative Example 1 The operation was exactly the same as in Example 1 except that polyethylene glycol 1000 was not used, but the treatment liquid did not flow out as a liquid and the polymer stuck to the wall of the device, causing the wiper to malfunction and had to be discontinued. Nakatsuta. Moreover, the partially distilled low-boiling fraction was not decolorized by APHA20-25.

Example 2 150 g of triethylene glycol bisallyl carbonate (purity 99%, other high boiling point compounds 1%, APHP 15-20) with some turbidity and coloring
Polyethylene glycol 2000 (average molecular weight
2000) was added, mixed and dissolved, and then subjected to thin film distillation treatment at a vacuum of 1 torr and a lower wall temperature of approximately 220°C. Processing time required 30 minutes. 149 g of the distilled colorless low-boiling fraction was obtained from rectification receiver 5. (Triethylene glycol bisallyl carbonate, almost 100%,
APHA5-10) In addition, the high-boiling content that was not distilled was 16g (about 6g of triethylene glycol bisallyl carbonate).
%, other high-boiling compounds, polymers, and trace amounts of coloring components (approximately 94%). The recovery rate of triethylene glycol bisallyl carbonate by thin film distillation was 99%, and there was no deposit on the walls of the equipment after treatment.

[Brief explanation of drawings]

FIG. 1 is a side view of a thin film distillation apparatus that can be used when carrying out the method of the present invention. 1... Liquid to be treated, 2... Thin film distillation column, 3... Mantle heater, 4... Condenser, 5... Rectification receiver, 6... Motor, 7... Rotating body, 8... Wiper, 9...High boiling point receiver.

Claims (1)

[Claims] 1. In distilling and purifying a high-boiling point polymerizable compound containing a trace amount of impurities using a thin film distillation apparatus, a compound having a higher boiling point than the high-boiling point polymerizable compound to be subjected to the distillation purification. A method for purifying a high-boiling point polymerizable compound by thin film distillation, which is characterized in that a highly compatible high-boiling point inert compound is mixed and dissolved in the high-boiling point polymerizable compound. 2. The method according to claim 1, wherein the high boiling point polymerizable compound is a monomer for plastic lenses having a purity of 95% or more. 3. The method according to claim 2, wherein the monomer for the plastic lens is alkylene glycol bisallyl carbonate. 4. Claim 1, wherein the high-boiling inert compound mixed and dissolved in the high-boiling polymerizable compound is polyethylene glycol or polypropylene glycol.
The method described in section.