JPH0621160B2 - Method for producing polycarbonate carbon dioxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a polycarbonate diol that exhibits excellent performance as a raw material for polyurethane widely used in various fields such as elastomers, adhesives and coatings. Is.

[Conventional technology]

Several methods are already known for the production of polycarbonate diols.

For example, a method of reacting a diol and phosgene in the presence of a strongly alkaline compound (JP-A-51-63894),
A method in which an aliphatic diol is reacted with ethylene carbonate and the produced ethylene glycol is azeotropically removed (JP-A-51-144492), and further, a 5- to 7-membered alkylene carbonate and a diol having 4 to 40 carbon atoms. 2
There is a method of obtaining a polycarbonate diol by dividing the reaction into stages (JP-A-55-56124).

[Problems to be solved by the invention]

In the production of such a polycarbonate diol, phosgene and an organic carbonate are used as a compound having a carbonate group as a raw material.

However, since phosgene is extremely toxic, it must be handled with care, and the production facilities for polycarbonate diol must also be carefully considered for safety.

When dimethyl carbonate, diethyl carbonate, diphenyl carbonate, etc. are used among the carbonic acid esters, when the carbonic acid ester is produced, a hydroxyl group-containing compound such as methanol, ethanol, phenol and phosgene are used as raw materials. Special consideration must be given to handling and equipment.

As described above, compared with the method for producing a polycarbonate diol using phosgene and its derivatives, the method for producing a polycarbonate diol using ethylene carbonate as a raw material is safe and does not require any special consideration for the polycarbonate diol production facility. But it is advantageous.

On the other hand, ethylene carbonate causes self-decomposition decarboxylation reaction at high temperature as shown by the following formula [I] to become ethylene oxide.

When the ethylene oxide produced here reacts with the diol which is a raw material for the production of the polycarbonate diol, the ring is opened as shown in the following formula [II] to form an ether bond.

Polyurethane obtained by reacting this ether bond-containing polycarbonate diol with diisocyanate is
Compared with polyurethane produced by using polycarbonate diol that does not contain ether bond, the physical properties such as water resistance and heat resistance are deteriorated, so that it cannot be used for the applications that could be used originally and it is economical. The loss is large.

[Means for solving problems]

In view of the present situation, the present invention provides a polycarbonate diol that suppresses the formation of ether bonds as much as possible and provides polyurethane with no deterioration in physical properties under industrial conditions under which the danger to raw materials and manufacturing equipment is significantly reduced. It can be obtained efficiently.

That is, the present invention controls the concentration of ethylene carbonate in the reaction liquid during the reaction period so as not to exceed 25% (% by weight; the same applies hereinafter) during the production of polycarbonate diol by transesterification of ethylene carbonate and diol. ㆝ Characterized by reacting.

In the present invention, one of the raw materials used is ethylene carbonate, which is a crystalline compound at a melting point of 36.4 ° C. at room temperature. Although the crystal can be supplied to the reactor, it is melted in advance and supplied. It is desirable to do.

As the other raw material diol, aliphatic diols and alicyclic diols having 4 to 20 carbon atoms can be mentioned, preferably 1,6-hexanediol, 3-methyl 1,5-pentanediol, There are cyclohexane 1,4-dimethanol and the like.

The final total supply ratio of such diol and ethylene carbonate is about 1/10 to 10/1 in terms of molar ratio, and considering economic efficiency, the molar ratio is 1 / 1.5 to 1.5 /. A range of 1 is preferred.

In order to carry out the reaction at such a molar ratio so that the concentration of ethylene carbonate in the reaction liquid does not exceed 25%, a method in which the diol is charged in advance in the reactor and ethylene carbonate is dividedly supplied to the reactor is used. To take
Alternatively, a method of continuously supplying and reacting can be adopted.

The ethylene carbonate supply during the reaction period
The control is carried out so that the concentration of ethylene carbonate in the reaction solution does not exceed 25%.

This supply of ethylene carbonate can be carried out for most of the time from the start of the reaction to the end of the reaction, but within 2/3 of the total reaction time, especially within 1/2 (both at the start To)) is preferable.

In the reaction, it is sufficient to use no catalyst, but an ester exchange catalyst such as dibutyltin dilaurate can be used if necessary.

However, it is desirable to use a catalyst that does not hinder the production of polyurethane using the obtained polycarbonate diol as a raw material or, if used, remove the catalyst after the reaction.

Since the above reaction is an equilibrium reaction, it is preferable to remove by-produced ethylene glycol out of the reaction system in order to proceed the reaction.

For this purpose, it is preferable to carry out the reaction at a temperature and pressure at which ethylene glycol can be removed.

In addition, since the boiling point and viscosity of the entire reaction solution increase as the reaction progresses, it is preferable to change the temperature and pressure accordingly to remove ethylene glycol and accelerate the reaction.

For this reason, it is preferable to control the reaction temperature at 100 to 200 ° C at the start of the reaction and at 180 to 250 ° C at the end of the reaction.

If the reaction temperature is lower than 100 ° C, the reaction rate will be slow and 250
If the temperature is higher than ° C, the raw materials ethylene carbonate, diol and the produced polycarbonate diol are decomposed, which is not preferable.

The reaction is preferably carried out under reduced pressure to efficiently separate and remove the produced ethylene glycol and to prevent decomposition of the raw material and the produced polycarbonate diol. Depending on the reaction temperature, the reaction may start at 30 to 300 Torr, then The degree of decompression gradually increases as the reaction progresses, and finally becomes 1
It is good to set it to about 30 Torr.

During the reaction, in order to efficiently separate and remove ethylene glycol, it is more efficient to use a reactor having a rectification function and return the distilled ethylene carbonate and diol to the reactor.

To control the ethylene carbonate concentration in the reaction solution,
The reaction solution collected from the reactor is analyzed and controlled.

The polycarbonate diol obtained by the method of the present invention changes from a normal temperature liquid to a solid depending on the type of diol used as a raw material.

Therefore, after completion of the reaction, the reaction solution may be filled into the desired container as it is, or in the case of a solid at room temperature, it may be filled into flakes with a flaker.

In addition, when using polycarbonate diol as a raw material for its main purpose, polyurethane, it is desirable to use as little water as possible. Therefore, to prevent it from absorbing moisture during filling and storage, a stopper, nitrogen, etc. It is desirable to fill with the inert gas.

[Work]

Generally, the chemical structure of a polycarbonate diol obtained from ethylene carbonate and a diol is as follows [III]
Can be expressed as

In the present invention, the portion of the ethylene oxide bond in the above formula, that is, the portion of Y, is set to 0 or as small as possible. Therefore, the ethylene carbonate concentration in the reaction solution is 25% throughout most of the reaction period. The reaction is controlled by controlling the amount so as not to exceed.

This is because the decomposition and decarboxylation reaction of ethylene carbonate is promoted by the increase in the concentration of ethylene carbonate in the reaction solution and the temperature rise, and in the reaction solution, the transesterification reaction between ethylene carbonate and diol and the above-mentioned decomposition and decarboxylation reaction are carried out. This is because, since it is a competitive reaction, the decomposition and decarboxylation reaction easily occurs when the ethylene carbonate concentration in the reaction solution is higher than 25%, as is clear in Examples and Comparative Examples described later.

Therefore, in the chemical formula of polycarbonate diol as described above, Y is set to 0 or as small as possible to keep the ethylene carbonate concentration in the reaction solution low, thereby promoting the transesterification reaction and decomposing decarboxylation reaction. Suppresses the ring-opening condensation reaction of the produced ethylene oxide.

As a result, the present invention has an excellent effect that a polycarbonate diol having a small number of ether bonds can be easily and effectively produced with good reproducibility.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 1.4 kg of 1,6-hexanediol was added to a glass flask No. 3 equipped with a stirrer, a thermometer, and a fractionating tube, heated at a temperature of 150 ° C. and a pressure of 50 Torr, and gradually depressurized. If the temperature was raised and the degree of vacuum was increased, ethylene carbonate was fed at 0.2 kg / h for 5 hours.

16 hours after starting the reaction, the temperature was 205 ° C and the pressure was 5 Torr.
The temperature was raised and the degree of vacuum was increased to obtain 1.7 kg of polycarbonate diol.

The amount of ethylene carbonate in the reaction solution was analyzed by gas chromatography at the start of the reaction and every 2 hours after the disclosure.

The results are shown in FIG.

The obtained polycarbonate diol has a hydroxyl value of 57 mg.
It was a milky white solid of -KOH / g at room temperature, and as a result of analysis, the ring-opening reaction product of ethylene oxide was 0.5 mol%.

The distillate obtained in the reaction solution was 0.6 kg,
It was a liquid containing ethylene glycol as a main component and unreacted ethylene carbonate and 1,6-hexanediol.

Comparative Example 1 Polycarbonate diol (1.6 kg) was obtained in the same manner as in Example 1 except that the whole amount of ethylene carbonate was supplied at the start of the reaction.

Regarding the amount of ethylene carbonate in the reaction liquid Example 1
The same was analyzed.

The results are shown in FIG.

The obtained polycarbonate diol has a hydroxyl value of 57 mg.
It was a milky white crystal of −KOH / g at room temperature. As a result of analysis, the ring-opening reaction product of ethylene oxide was 8 mol%.

The distillate obtained during the reaction was 0.7 kg, and was ethylene glycol. Unreacted ethylene carbonate. 1,6
It was a liquid containing hexanediol.

Example 2 0.2 kg of ethylene carbonate and 1.3 kg of cyclohexa-1,4-dimethanol were placed in a glass flask No. 3 equipped with a stirrer, a thermometer, and a fractionating tube, and the temperature of 160
The reaction was started at 80 ° C and a pressure of 80 Torr.

While increasing the reaction temperature and the degree of vacuum, ethylene carbonate was reduced to 0. kg was added 3 times to react.

20 hours after the start of the reaction, the temperature was raised to 210 ° C., the pressure was raised to 3 Torr, and the degree of vacuum was increased to obtain 1.4 kg of a polycarbonate diol having a hydroxyl value of 150 mg-KOH / g and a viscous liquid at room temperature.

As a result of analysis, the ring-opened reaction product of ethylene oxide was 1.2.
It was mol%.

The liquid distilled during the reaction was 0.6 kg.

〔The invention's effect〕

This invention, in the production of polycarbonate diol,
Throughout most of the transesterification period of ethylene carbonate and diol, the ethylene carbonate concentration in the reaction solution is controlled to an amount not exceeding 25% to carry out the reaction.

Therefore, by carrying out such control, the transesterification reaction can be promoted and the ring-opening condensation reaction of ethylene oxide produced by the decomposition decarboxylation reaction can be suppressed.

As a result, it has an excellent effect that a polycarbonate diol with a small amount of ether condensation can be easily and efficiently produced with good reproducibility.

In particular, ethylene carbonate used in this invention, unlike the extremely strong phosgene toxicity which is used in the manufacture of conventional polycarbonate diols, oral acute toxicity LD ₅₀ in mice originally have little toxicity and 10,400 mg / kg Since it is a compound, it requires no special handling.

Therefore, the present invention has great industrial value in that the above-mentioned excellent polycarbonate diol can be obtained by greatly mitigating the risk caused by the raw materials.

[Brief description of drawings]

FIG. 1 is a graph showing the amount of ethylene carbonate present in the reaction solutions in Example 1 and Comparative Example 1.

Claims (1)

[Claims] 1. When producing a polycarbonate diol by transesterification of ethylene carbonate and a diol, the concentration of ethylene carbonate in the reaction solution during the reaction period is controlled to an amount not exceeding 25% by weight to carry out the reaction. A method for producing a polycarbonate diol.