JPH02219821A - Production of polycarbonate diol - Google Patents

Abstract

PURPOSE:To facilitate the production of the title compound terminated entirely with hydroxyl groups and having a low ether bond content from a safe and easily handleable material by transesterifying an alkylene carbonate with a diol under pressure in the presence of CO2. CONSTITUTION:A polycarbonate diol is produced by transesterifying an alkylene carbonate (e.g. ethylene carbonate) with a diol (e.g. ethylene glycol or 1,5- pentanediol) under pressure in the presence of CO2 used may be gaseous, liquid or solid. According to the above process, a polycarbonate diol terminated entirely with hydroxyl groups and having a very low ether bond content can be produced in good efficiency. By reacting the obtained polycarbonate diol with a diisocyanate compound or the like, it can be used in the production of a polyurethane, a soft segment of a thermoplastic elastomer, a polymeric plasticizer or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to an improvement in a method for producing polycarbonate diols. More specifically, the present invention
The present invention relates to a method for efficiently producing polycarbonate diol, which is useful as a raw material for polyurethane, soft segments of thermoplastic elastomers, polymer plasticizers, etc., by transesterification of alkylene carbonate and diol.

Conventional technology Conventionally, polycarbonate diol has been a compound useful as a raw material for, for example, polyurethane, soft segment of thermoplastic elastomer, polymer plasticizer, etc., and it has generally been used by a method of reacting phosgene or a derivative thereof with a diol, or by a method of reacting with alkylene carbonate. It is manufactured by a method of reacting with diol. Examples of the former method include, for example, a method of reacting a diol with phosgene in the presence of a strong alkali compound (Japanese Unexamined Patent Application Publication No. 51-63894), a method of reacting a dialkyl carbonate with a diol (
JP-A No. 51-83693), method of reacting diaryl carbonate with diol (Japanese Patent Publication No. 46-42
384), and the latter method is
For example, by reacting ethylene carbonate and diol,
A method of removing the generated ethylene glycol azeotropically (Japanese Unexamined Patent Publication No. 144492/1982), a method of reacting a 5- to 7-membered alkylene carbonate with a diol having 4 to 40 carbon atoms in two stages (a method of Publication No. 63-12896), in the reaction between ethylene carbonate and diol, the ethylene carbonate concentration in the reaction system was set to 25% by weight.
A method of suppressing
Examples include.

However, the method of reacting phosgene or its derivatives with diols has limitations in that the phosgene used as a raw material is highly toxic and must be handled carefully for health management reasons, and the polycarbonate diol obtained by this method Since it is inevitable that groups other than hydroxyl groups such as alkoxy groups, phenoxy groups, and chloroformyl groups remain at the terminals, it has the disadvantage that polyurethane with a large molecular weight cannot be obtained when used as a raw material for polyurethane production, for example. .

In addition, although the method of reacting alkylene carbonate and diol does not have the above-mentioned drawbacks, the resulting polycarbonate diol contains ether bonds formed by ring opening of alkylene carbonate, so polyurethane produced using this as a raw material has the disadvantage that it is inferior in water resistance and heat resistance compared to those using polycarbonate diol that does not have an ether bond. In order to improve this drawback, a method has been proposed in which the content of ether bonds in the molecule is reduced (Japanese Patent Application Laid-Open No. 63-284222), but even with this, about 1% of the ether bonds in the molecule are reduced. cannot be avoided.

Problems to be Solved by the Invention Under these circumstances, the present invention has been developed by using safe and easy-to-handle alkylene carbonate and diol, all of which have hydroxyl groups at the ends, and which has an extremely low content of ether bonds. This was done for the purpose of providing a method for efficiently producing polycarbonate diol.

Means for Solving the Problems The present inventors have discovered that when producing polycarbonate diol by reaction with alkylene carbonate diol,
As a result of intensive research on a method for obtaining a target product with a low content of ether bonds, it was discovered that the target could be achieved by carrying out a transesterification reaction between an alkylene carbonate and a diol under pressure in the coexistence of carbon dioxide. The present invention was made based on this finding.

That is, the present invention provides a method for producing polycarbonate diol, which is characterized in that, in producing polycarbonate diol by transesterification with alkylene carbonate, the reaction is carried out under pressure in the presence of carbon dioxide. be.

The present invention will be explained in detail below.

Examples of the alkylene carbonate used as one of the raw materials in the method of the present invention include compounds represented by the general formula. R in this -IF formula (1) is preferably an alkylene group having 2 to 5 carbon atoms, and examples of such groups include ethylene group, 1,2-propylene group, trimethylene group, tetramethylene group, and pentamethylene group. ,
122-butylene group, 1.3-butylene group, 2,3-butylene group, 1.2-pentylene group, 1.3-bentylene group, 1,4-bentylene M, 2.3-bentylene L,
Examples include 2,4-benthylene group.

On the other hand, as diols, which are another raw material, aliphatic diols and alicyclic diols are used, specifically ethylene glycol, 1,3-propanedio-xxl, 4
-butanediol, 1,5-bentanediol, 3-methyl-1,5-bentanediol, 1,6-hexanediol, 1,7-hebutanediol, 1,8-octanediol 1.9-nonanediol, 1.10-decanediol, 1.11-tandecanediol, 1.12-dodecanediol, neopentyl glycol, 2-ethyl-1,6-hexanediol, 2-methyl-1 , 3-propanediol, 1.3-
Cyclohexanediol, 1,4-cyclohexanediol, 2,2'-bis(4-hydroxycyclohexyl)-propane, p-xylene diol, p-tetrachloroxylene diol, 1,4-dimethylolcyclohexane, bishydroxymethyltetrahydrofuran, Examples include di(2-hydroxyethyl)dimethylhydantoin, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, and tetramethylene glycol.

These diols may be used alone or
Two or more types may be used in combination (or, if desired, in combination with at least one selected from a small amount of polyhydric hydroxy compounds, such as trimethylolethane, trimethylolpropane, hexanetriol, pentaerythritol, etc.) It may also be used.

In the present invention, the ratio of the alkylene carbonate and diol used is usually a molar ratio of 1:1O to 10
:1. Preferably, the ratio is selected from 1:2 to 2:1. In addition, the reaction method is a batch method in which a predetermined molar ratio of alkylene carbonate and diol are charged all at once and reacted, or a method in which either the alkylene carbonate or the diol is charged in advance, and the remaining raw materials are added in portions or continuously. Either a semi-batch type or semi-continuous type in which the alkylene carbonate and the diol are fed and reacted, or a continuous type in which the alkylene carbonate and the diol are continuously fed and reacted can be used.

In the method of the present invention, it is necessary to carry out the reaction in the presence of carbon dioxide, but there are no particular restrictions on the form of this carbon dioxide, and any form of gas, liquid, or solid may be used. Can be done.

This carbon dioxide may be added to the reaction solution in advance, or may be bubbled through the reaction solution.

An ether bond is formed in the molecule by the reaction between alkylene carbonate and diol.During the reaction, alkylene carbonate decomposes to produce alkylene oxide and carbon dioxide, and this alkylene oxide reacts with diol to form hydroxyalkyl ether. Alternatively, it is thought that alkylene carbonate and diol undergo a decarboxylation reaction to produce hydroxyl alkyl ether. Therefore, if carbon dioxide is present in advance, the undesirable decomposition reaction and decarboxylation reaction described above will be suppressed, resulting in a decrease in the content of ether bonds.

However, even if such a mechanism is used to suppress side reactions, it is impossible to completely suppress them, and the production of several percent by-products is unavoidable. It was quite unexpected that the process resulted in polycarbonate diols containing almost no ether bonds.

Next, in the method of the present invention, the transesterification reaction between alkylene carbonate and diol is usually carried out without using a catalyst, but it may be carried out in the presence of a catalyst if desired in order to increase the reaction rate.

Examples of catalysts used in this case include Li and Na.

K, Pb, Ca, Mg, Sr, Zn, AQ
, Ti, V, Cr, Mn, Fe.

Go, Ni, Cu, Zr, Pd, Sn, S
b, metal chlorides, oxides, hydroxides such as Pb or fatty acid salts such as acetic acid, oxalic acid, lauric acid, sodium methylate, sodium ethylate, aluminum trisoypropoxide, isopropyl titanate, n-
Alcoholades and phenolates such as butyl titanate, or A12. Ti, Zn, Sn, Z
Any catalyst can be selected and used from among catalysts commonly used in transesterification reactions, such as other organometallic compounds containing metals such as r and Pb. The amount of these catalysts used is 1 x io-@~e weight% based on the total amount of alkylene carbonate and diol that are normally used.
, preferably in the range of I x 10-' to 0.1% by weight.

In the method of the present invention, it is necessary to carry out the reaction under pressure; however, if the pressure is too low, the dissolved concentration of carbon dioxide in the reaction solution will decrease, and the effect of the present invention will not be fully exhibited; If the pressure is too high, the equipment will become complicated and it will be economically disadvantageous, so the pressure is usually 1.01 to 100 atm, preferably 1.0 atm.
The pressure is selected within the range of 0.01 to 30 atm.

Further, the reaction temperature is usually selected within the range of 100 to 300°C, preferably 100 to 250°C. This temperature is 100
Below 300°C, the reaction rate is too slow to be practical;
If the temperature exceeds .degree. C., the produced polycarbonate diol may decompose, which is not preferable.

As a reactor that allows the reaction to proceed under such conditions,
A seed-type reactor may be used, or a back-type reactor may be used to carry out the pressurized flow reaction. The reaction mixture thus obtained is immediately subjected to a treatment for separating the produced polycarbonate diol. In this case, it is desirable to perform the separation in as short a time as possible to avoid the formation of by-products. The conditions for this are usually the degree of reduced pressure O0l~2Q
Toor.

The temperature is selected from the range of 150 to 250°C, and the residence time at this temperature is preferably within 3 hours, preferably within 1 hour.

Although a normal distillation column can be used as a separation device for separating the polycarbonate diol produced,
From the standpoint of efficiency, it is advantageous to use a tubular thin film evaporator or a tubular falling film evaporator.

Furthermore, in order to carry out the method of the present invention efficiently, a plurality of the above-mentioned reactors and separation devices may be appropriately combined and used.

The polycarbonate diol thus obtained preferably has an average molecular weight in the range of 500 to 10,000 in terms of use.

Effects of the Invention According to the present invention, by performing a dioltraester exchange reaction with an alkylene carbonate under pressure in the coexistence of carbon dioxide, a polycarbonate having all hydroxyl groups at the terminals and an extremely low content of ether bonds can be produced. Diol can be efficiently produced.

The polycarbonate I diol obtained by the method of the present invention can be used as a polyurethane, a soft segment of thermoplastic elastomer, a polymer plasticizer, etc. by reacting with a diisocyanate-1 compound.

Examples Next, the present invention will be explained in more detail with reference to examples.
The present invention is not limited to these examples in any way.

Note that the content of ether bonds was measured according to the method shown below.

That is, the obtained polycarbonate diol was hydrolyzed with a potassium hydroxide ethanol solution to form diol (HO
R, OH) and diols and alkylated/linked diols (H
OR, OR, 108) was analyzed by gas chromatography, the content of each was calculated, and the content of ether bonds (mol %) was determined according to the following formula. Content of ether bond (mol %) (l(ORIOR, OH): Number of moles of ether diol in the hydrolyzate (HOR, OH): Number of moles of diol in the hydrolyzate Example 1 Stirrer, HORIOR 1 in a 5Q autoclave equipped with a
Add 1.04 kg of 5-bentanediol, 1,6-hexanediol, 1.76 J29 of ethylene carbonate, and after purging with nitrogen several times, introduce carbon dioxide to reduce the overall pressure to L4. cya” and stirred at that vkiso°C for 4 hours. Then,
After cooling the OI crepe and removing the residual carbon dioxide inside, ethylene carbonate 1- (EC) 1.
37kg, ethylene glycol (EG) 0.2 to 9.
1.5-bentanediol (PDL) 0.764kg
, 1,6-hexanediol (HDL) 0.869 9, polycarbonate diol (pcDL) 0.77
A reaction solution consisting of 8 and 9 was obtained. Next, this liquid was fed to a thin film evaporator with a heat transfer area of 0.1 m'' at a rate of 0.F+bg/hr under conditions of 200°C and 1 OTorr, resulting in 0.296 kg of distillate and 3.0 kg of bottom liquid. 67b9 was obtained.

The composition of the distillate is 681% ethylene glycol, 14.4vt% ethylene carbonate, 1016 t% l,5-bentanediol, 7.2% 1,6-hexanediol.
It was wt%. The bottom liquid was then put back into the autoclave and the first reaction was repeated. After cooling, carbon dioxide was removed and its composition was analyzed.
o, 234#9, PDLo, 534bg, HDLo, 6
17bg, PCDLL, 3j29. 2 of this liquid
Distillate 2.2
'D19 (Composition: EG: lO, 3wt%, EC
44.1wt%, PDL23.6wt%, HDL22w
t%) and 1.415g of bottom liquid were obtained. This bottom liquid was mostly PCDL, but 8.4 wt % HDL remained. 220℃ in order to remove this snail.
Thin film evaporation was performed under the condition of 1 Torr and at a rate of lky/hr. The obtained bottom liquid is a viscous liquid with a hydroxyl value of 4.
9m9·KOH/9, and the amount of ether bond is 0.
It was 0.05 mol%. In addition, the PDL unit in the polymer and H
The molar ratio to the DL unit was 49:51.

Example 2 In a reactor similar to Example 1, PDLI, 04 to 9, HD
After adding Ll, 18JI9, and EC1,76&9 and purging with nitrogen several times, carbon dioxide was introduced up to 15 kg/cm'', and then the reaction temperature was raised to 200°C and stirred for 1 hour.

Next, after cooling, carbon dioxide was removed, and thin film evaporation was performed under the same conditions as in Example 1 to obtain EC, EG, PDL, HD.
Tometa liquid sail 3J29 consisting of L and 3.7jzg of bottom liquid were obtained.

This bottom liquid was reacted again in an autoclave for 2 hours, and then subjected to thin film evaporation twice under the same conditions as in Example 1 to obtain viscous liquid 1.32&9.

This liquid is PCD with a hydroxyl value of 5111g KOH/9.
L, and the content of ether bonds was 0.2 mol%.

This yield of PCDL corresponds to a conversion of 41% on a molar basis with respect to the starting EC.

Example 3 The reaction was carried out in the same manner as in Example 1 except that the pressure of carbon dioxide was changed to 1729/cya'', and the obtained PCD
An analysis of L was performed. The result is that the hydroxyl value of PCDL is 511.
It was I9.KOH/9 and contained 0.11 mol% of ether bonds. Also, PDL unit in PCDL and HD
The ratio with the L unit was 49.5-50.5 in molar ratio.

Example 4 A reaction was carried out under the same conditions as in Example 1, except that titanium tetrabutoxide 650!19 was added as a catalyst and the reaction time was 1 hour, to obtain a viscous liquid of 1.4729. This liquid is PCDL with a hydroxyl value of 40119 KOH/9.
, and no ether bond was detected.

Comparative Example 1 In a 512 glass reactor equipped with a stirrer, a thermometer and a fractionating tube, PDL1, 04 to 9, HDLI, 18
#9, put 9 in EC1,7, temperature 150℃, pressure 50
After heating and depressurizing with T6rr, EG and EC are extracted from the fractionating tube.
The pressure was reduced to 5 Torr over 10 hours while removing the gas, and the reaction was continued for an additional 5 Torr't' I 0 hours. After that, the reaction temperature was raised to 200°C and reacted for 5 hours,
2.37 kg of polycarbonate diol was obtained. The obtained polycarbonate diol was 95m9・KOH/9
As a result of analysis, the content of ether bonds is 2.8 mol%
Met.

The distillate obtained in the reaction solution weighed 1.61 kg and contained EC, PDL, and HDL, which were mainly composed of EC.

Comparative Example 2 PDLI, 04J1g, HD in the same reactor as Comparative Example 1
Put 9, EC1, 78kg into Ll, 18, temperature 150
After heating at a temperature of 5 Q Torr and reducing the pressure, the degree of vacuum was reduced to 5 Torr in 10 hours while removing the EC from the fractionating tube.
rr, and the reaction was continued for an additional 10 hours. This reaction solution was placed in a thin film evaporator with a heat transfer area of 0.1++1 at 200℃ for 5 minutes.
The bottom liquid obtained here was fed again at 220°C and 1 kg/hr under the conditions of 1 Torr to separate monomers and polymers, and PCDL2 .5 got a 9.

When the obtained PCDL was analyzed, the hydroxyl value was 801.
・KOH/9, and there are 2.4 ether bonds in it
It contained mol%. The distillate obtained was 1.48k
g, and contained EC, PDL, and HDL whose main component was EG.

Example 5.6 The reaction was carried out in the same manner as in Example 1, except that the amounts of 1,5-bentanediol (PDL) and 1,6-hexanediol (HDL) were changed as shown in the table below. Separation was performed. The results are shown in the table below.

(Note) EC charge amount: 2 1.76 kg Example 7 Into the same autoclave as in Example 1, 0.99 g of l,5-bentanediol and 1 g of 1,6-hexanediol were added.
12hg of neopentyl glycol O, 104J29, and 1.76g of ethylene carbonate were added, and reaction and separation were carried out under the same conditions as in Example 1 to form a viscous liquid. IJI
I got a 9.

This liquid contains neopentyl glycol units in the molecule according to NMR analysis, and the molar ratio of each unit and ether bond is 1, 5-bentanediol unit: 1.6-hexanediol unit: neobentyl glycol unit: Ether bond -46:46:8:o, oa. Moreover, the hydroxyl value of this liquid was 51u·KOH/9.

Example 8 Hydroxyl value 49m9·KOH/9 obtained in Example 1
, polycarbonate diol 5009 containing 0.05 mol% of ether bonds was placed in a 112 autoclave equipped with a thermometer and a stirrer, and after purging with nitrogen several times, carbon dioxide was sealed until the inside of the system reached lOkg/cm. After raising the reaction temperature to 200°C and stirring for 2 hours, the autoclave was rapidly cooled, the gas inside was removed, and the produced monomer was separated using a thin film evaporator.The conditions at this time were 220°C. , ITQr', and the feed amount is 0-21
2/hr. The obtained liquid was 490 g,
A liquid 10 consisting mostly of 1,5-bentanediol and 1,6-bentanediol as a distillate of a thin film evaporator
9 was obtained. The hydroxyl value of the obtained viscous liquid was 33.
It was 119.KOH/9.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] 1. A method for producing polycarbonate diol, which is characterized in that the reaction is carried out under pressure in the presence of carbon dioxide, in producing polycarbonate diol by transesterification reaction between alkylene carbonate and diol.