JPH04239024A - Production of hydroxyl-terminated polycarbonate - Google Patents

Abstract

PURPOSE:To produce the title polycarbonate while improving the yield and reducing the amount of the recycled monomer by preparing a low-molecular weight polycarbonate from a carbonate monomer and a glycol monomer and reacting the polycarbonate with a carbonate monomer. CONSTITUTION:A carbonate monomer selected from an alkylene carbonate, a dialkyl carbonate and a diaryl carbonate is transesterified with a glycol monomer selected from (polyoxy)alkylene glycols at 80-250 deg.C while removing the alcohol by-product from the system to obtain a low-molecular weight polycarbonate having 2-10 units. The diaryl carbonate is further added to the reaction system of the low-molecular weight polycarbonate and reacted at 80-250 deg.C while removing the produced alcohol by-product from the system to form a high-molecular weight polycarbonate having 10 or more units, and the remaining carbonate monomer is removed from the reaction system.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polycarbonate having terminal hydroxyl groups for use in polyurethane, thermoplastic elastomer polymer plasticizers, paints, and the like.

0002

[Prior Art] A method for producing polycarbonate having terminal hydroxyl groups is disclosed in Japanese Patent Application Laid-open No. 55-56124.
Publication No. In this method, as is often done in the production of polyester, a carbonate monomer and a glycol monomer are transesterified to obtain a low molecular weight polymer, which is then self-condensed to obtain a high molecular weight polymer. In this method, a self-condensation reaction is carried out in the latter half of the process, so a large amount of glycol monomer is distilled out, resulting in a low yield of polycarbonate, and the harsh conditions of high temperature and high vacuum are applied for a long time. It is necessary. Furthermore, when recovering and reusing the glycol monomer distilled out during self-condensation,
Since the amount is large, the collection and recycling equipment and costs are large.

0003

[Problems to be Solved by the Invention] In view of this situation, the inventors of the present invention have solved the problem by reacting the low molecular weight polycarbonate with a carbonate monomer again at the stage where it is produced.
It has been found that high molecular weight polycarbonates can be easily obtained. Furthermore, the yield of polycarbonate is increased and the amount of glycol monomer recovered and recycled is reduced, making it an advantageous manufacturing process with low costs. The present inventors have completed the present invention based on these findings.

0004

[Means for solving the problems] That is, the present invention is (1)
When producing a polycarbonate having a terminal hydroxyl group, (i) one or more carbonate monomers selected from alkylene carbonate, dialkyl carbonate, and diaryl carbonate;
A first process in which one or more glycol monomers selected from alkylene glycol and polyoxyalkylene glycol are reacted while removing by-product alcohols from the system to produce a low molecular weight polycarbonate having 2 to 10 units. Step (ii) further adding the diaryl carbonate monomer to the reaction mixture of the first step and reacting while removing by-product alcohols from the system to link 2 to 10 units of low molecular weight polycarbonate and glycol monomer This is a method for producing a polycarbonate having a terminal hydroxyl group, which comprises a second step of producing a polymeric polycarbonate having 10 units or more, and (iii) a third step of removing the remaining carbonate monomer. Furthermore, the patent also includes a step of adding a glycol monomer to the produced high molecular weight polycarbonate to adjust the hydroxyl value.

[0005] The present invention will be explained in detail below. The carbonate monomer used in the present invention is selected from alkylene carbonate, dialkyl carbonate, and diaryl carbonate, and preferably ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, and diphenyl carbonate. These carbonate monomers may be used alone or in combination of two or more.

[0006] The glycol monomer used in the present invention is selected from alkylene glycols and polyoxyalkylene glycols, and particularly preferably alkylene glycols having 3 to 20 carbon atoms in the main chain, and also alkylene glycols having 3 to 20 carbon atoms in the main chain. is a polyoxyalkylene glycol having from 2 to 12. The alkylene mentioned here may include an alicyclic compound. These glycol monomers may be used alone or in combination of two or more.

Examples include ethylene glycol, 1,3
-Propanediol, 1,4-butanediol, 1,5
-Pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,7-heptanediol, 1,8-oftanediol, 1,9-nonanediol , 1,10-decanediol, 1,11-undecanediol, 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, 1,4-
Examples include dimethylolcyclohexane bishydroxytetrahydrofuran, di(2-hydroxyethyl)dimethylhydantoin, diethylene glycol, triethylene glycol, polypropylene glycol, polytetramethylene glycol, 6-hydroxyethylhexanol, 5-hydroxyethylpentanol, and the like.

[0008] These glycol monomers may be used in combination with a trifunctional or more functional hydroxy compound. Examples of these include trimethylolethane, trimethylolpropane, hexanetriol, pentaerythritol, and the like. Further, a mixture of polyols such as polyester polyols may be used.

The main reaction in the first step of the present invention is a transesterification reaction between a glycol monomer and a carbonate monomer, as shown in Chemical Formula 1 or Chemical Formula 2.

0010

[Chemical formula 1]

[0011]

[Case 2]

[0012] Since this reaction is an equilibrium reaction, it is necessary to remove by-product alcohols in order for the reaction to proceed efficiently. For selective removal, it is preferable to install a distillation column in the reactor. The reaction temperature is 80°C to 250°C. At a temperature of 250°C or higher, a decomposition reaction of polycarbonate tends to occur, and at a temperature of 80°C or lower, a transesterification reaction is slow. The pressure is gradually reduced to ensure the amount of distillate is between atmospheric and 5 mmHg. At the end of the first step, the molecular weight of the polycarbonate is between 2 and 10 units. The molecular weight can be adjusted by adjusting the charging ratio of carbonate monomer and glycol monomer. The molecular weight achieved can be adjusted by adjusting the amount of carbonate monomer removed from the reaction system. Usually this charging ratio is between 1/10 and 10/1.

When ethylene carbonate is used as the carbonate monomer, ethylene carbonate is decomposed in the reaction system and reacts with glycol to produce ether diol. When a large amount of ethylene carbonate is present in the system, the content of units having ether bonds in the polycarbonate increases. When it is desired to prevent contamination of ether bonds, the amount of ethylene carbonate in the reaction system should be suppressed to a level that is possible, taking into account the yield and production rate of the polymer. Incidentally, when dialkyl carbonate and sialyl carbonate are used as carbonate monomers, no ether bond is mixed.

The second step is a step in which diaryl carbonate is added to the reaction system and the low molecular weight polycarbonate and glycol monomer produced in the first step are linked with the diaryl carbonate. The main reaction is shown in chemical formula 3.

[0015]

[Chemical formula 3]

In the conventional technique described above, a high molecular weight polycarbonate was obtained by the reaction shown in the following formula 4, that is, a self-condensation reaction, whereas in the method of the present invention, a high molecular weight polycarbonate diol can be obtained by simply adding a carbonate monomer. The method of the present invention differs essentially from the prior art in that it is capable of:

[0017]

[C4]

Since the reaction of the present invention is an equilibrium reaction, it is necessary to remove by-product phenols in order for the reaction to proceed efficiently. For selective removal, it is preferable to install a distillation column in the reactor. Furthermore, it is most preferable to use diaryl carbonate because it has a large equilibrium constant. The reaction temperature is 80°C to 250°C. At temperatures above 250°C, decomposition reactions of polycarbonate tend to occur, and the polycarbonate may be colored by phenols produced as by-products. Furthermore, the reaction is slow at temperatures below 80°C. The pressure is gradually reduced to ensure the distillate is between atmospheric and 1 mmHg.

At the end of the second step, the molecular weight of the polycarbonate is greater than or equal to 10 units. The molecular weight can be controlled by the amount of carbonate monomer added. The molecular weight achieved can be adjusted by adjusting the amount of carbonate monomer removed from the reaction system. Usually, this amount is the first
1/ of the glycol monomer charged at the start of the process.
It is between 10 and 10/1.

The third step is a step of removing the remaining carbonate monomer. The temperature is 100-250°C and the pressure is 10-0.1 mmHg. Since this step does not increase the yield of polycarbonate, it is desirable to complete it in a short time in order to minimize the decomposition reaction of polycarbonate or carbonate monomer. It is efficient in the process to recover and reuse the carbonate monomer distilled out in this step.

The high molecular weight polycarbonate obtained by the present invention preferably has a number average molecular weight of 10,000 or less, more preferably 5,000 or less. In order to accurately control the molecular weight, it is desirable not to allow the reaction to proceed in the third step. A thin film evaporator may be used for this purpose. Using a thin film evaporator can shorten the residence time of the polymer, making it possible to remove residual monomer without allowing the polymerization reaction to proceed.

Furthermore, in order to precisely adjust the hydroxyl value (molecular weight) of the polycarbonate, the following steps may be added. That is, in the third step, when most of the carbonate monomer in the reaction system has been distilled off, when the temperature is increased and the pressure is further lowered, the glycol monomer contained in the system begins to distill off. Distilling the glycol monomer reduces the hydroxyl value in the system and increases the number average molecular weight of the polycarbonate. When this step is added, in order to carry out the reaction efficiently, the reaction temperature is 150 to 250°C and the pressure is 10 to 0.1 mmHg. Furthermore, in order to efficiently remove the glycol monomer from the system, it is desirable to exhaust the gas directly without using a distillation column. For this purpose, it is also effective to use a thin film evaporator.

Another method for precisely adjusting the hydroxyl value is to measure the hydroxyl value at the stage when polycarbonate with an appropriate hydroxyl value is produced, and add a predetermined amount of glycol monomer based on this value. . The added glycol monomer depolymerizes the polycarbonate, increasing the hydroxyl value. The reaction temperature at this time is 150 to 250
It is ℃.

In the present invention, the reaction proceeds even without a catalyst, but a catalyst can also be used. A known transesterification catalyst is used as the catalyst. Examples include titanium alkoxides such as titanium tetrapropoxide and titanium tetrabutoxide, sodium, potassium,
Metals such as lithium, rubidium, cesium, magnesium, calcium, strontium, barium, aluminum, cobalt, germanium, cerium, manganese, lead, antimony, tin, zinc, their salts, their oxides, their complexes, their alkoxides, inorganic acids , organic acids, inorganic alkalis, organic alkalis, and the like.

When a catalyst is used, the reaction rate increases and the concentration of by-product alcohol in the system increases, which is advantageous in terms of productivity and operation of the process. When ethylene carbonate is used as the carbonate monomer, it is preferable to use titanium tetraalkoxide as a catalyst because the decomposition reaction of ethylene carbonate can be suppressed and the content of ether bonds in the polycarbonate can be reduced.

[0026]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but these do not limit the scope of the present invention.

[0027]

[Example 1]

[Step 1] 1037.95 g of 1,5-pentanediol (
12.58 mole) 1,6-hexanediol 147
4.74 g (12.50 mole) and 2201.9 g (25.02 mole) of ethylene carbonate were charged and reacted for 20 hours at a temperature of 150° C. and a pressure of 10 mmHg from atmospheric pressure. During this time, ethylene glycol and ethylene carbonate were distilled out from the top of the column in an azeotropic composition.

The main component of the reaction mixture remaining in the reactor had a terminal hydroxyl group and a hydroxyl value of 342 mgKOH/g (
It was a polycarbonate with a number average molecular weight of 328).

[0029]

[Step 2] 251.2 g of the reaction mixture from Step 1 and 173.34 g of diphenyl carbonate were charged into a 500 ml three-necked flask equipped with a distillation column and a stirrer. temperature is 1
The reaction was carried out for 10 hours at 50° C. and at a pressure ranging from atmospheric pressure to 14 mmHg (at the top of the column). During this time, phenol was distilled out from the top of the tower. The polycarbonate in the reactor has a hydroxyl value of 59.
It was 9 mgKOH/g (number average molecular weight 1870).

[0030]

[Step 3] Next, remove the distillation column from the reactor, allow direct exhaust, and reduce the temperature from 150℃ to 2℃ for 3 hours.
Diphenyl carbonate was distilled under conditions of 00°C and a pressure of 20 mmHg to 0.1 mmHg. The hydroxyl value is 3
9.9mgKOH/g (MN = number average molecular weight 2810
), and no diphenyl carbonate was observed in the polycarbonate. The yield was 98% based on the charged polycarbonate.

[0031]

[Example 2] 250 mL of the reaction mixture from Step 1 of Example 1 was placed in a 500 ml three-necked flask equipped with a distillation column and a stirrer.
1 g was taken, and 135.89 g of diphenyl carbonate was charged. Temperature is 150℃, pressure is 1mmH from atmospheric pressure
The reaction was carried out for 7 hours under the conditions of g. During this time, phenol was distilled out from the top of the tower. The hydroxyl value of the polycarbonate in the reactor was 62.2 mgKOH/g (MN = 1800).

[0032] Next, the distillation column was removed from the reactor, and diphenyl carbonate was distilled out under conditions of a temperature of 150°C to 200°C and a pressure of 20mmHg to 0.5mmHg for 3 hours so that it could be directly evacuated. Ta. The hydroxyl value was 57.4 mgKOH/g (MN = 1950), and no diphenyl carbonate was observed in the polycarbonate. The yield was 97% based on the charged polycarbonate.

[0033]

[Example 3] 250 mL of the reaction mixture from Step 1 of Example 1 was placed in a 500 ml three-necked flask equipped with a distillation column and a stirrer.
3 g and 135.89 g of diphenyl carbonate were charged. The reaction was carried out for 6 hours at a temperature of 200° C. and a pressure ranging from atmospheric pressure to 1 mmHg. During this time, phenol was distilled out from the top of the tower. The polycarbonate in the reactor has a hydroxyl value of 5.
It was 8.7 mgKOH/g (MN = 1910).

[0034] Next, the distillation column was removed from the reactor, and diphenyl carbonate was distilled out under conditions of a temperature of 200°C and a pressure of 20 mmHg to 0.5 mmHg for 3 hours so that it could be directly evacuated. Hydroxyl value is approximately 56mgK
OH/g (MN = 2000), and no diphenyl carbonate was observed in the polycarbonate. The yield was 96% based on the charged polycarbonate.

[0035]

[Example 4] From the reaction mixture in Step 2 of Example 1, the temperature was changed from 200°C to 250°C, and the pressure was changed from 10 mmHg to 0.1
1,5-pentanediol and 1,6-
When hexanediol was distilled, the hydroxyl value was 37.1.
A polycarbonate of mgKOH/g (MN = 3017) was obtained.

[0036]

[Example 5] 27.333 kg of 1,5-pentanediol (2
63 mole), 1,6-hexanediol 26.34
6 kg (223 mole), 1,4-butanediol 1
．． 037 kg (12 mole), ethylene carbonate 42.651 kg (519 mole), diethylene glycol 1.048 kg (10 mole), 5-hydroxyethylpentanol 0.214 kg (1.6 mole)
), 6-hydroxyethylhexanol 0.164kg
(1.15 mole) was charged and reacted for 31.5 hours at a temperature of 130° C. and a pressure of 5 mmHg from atmospheric pressure. During this time, ethylene glycol and ethylene carbonate were distilled out from the top of the column in an azeotropic composition. The main component of the reaction mixture remaining in the reactor has a hydroxyl value of approximately 34 with terminal hydroxyl groups.
It was 0 mg KOH/g (MN = 330) polycarbonate.

[0037] Next, a 500 m
250.3 g of the above reaction mixture in a three-neck flask,
173.34 g of diphenyl carbonate and 0.064 g of titanium tetrabutoxide were charged. temperature is 130
℃ and the pressure was from atmospheric pressure to 1 mmHg for 10 hours. During this time, phenol was distilled out from the top of the tower. The hydroxyl value of polycarbonate in the reactor is 58.9mgKO
H/g (MN = 1900). Next, the distillation column was removed from the reactor so that it could be directly evacuated, and the temperature rose to 130°C and the pressure ranged from 20mmHg to 0.5mmHg for 3 hours.
Diphenyl carbonate was distilled off under mmHg conditions. The molecular weight is approximately 2560 (hydroxyl value 43.75mgKO
H/g), and no diphenyl carbonate was observed in the polycarbonate. The yield was 95% based on the charged polycarbonate.

[0038]

[Example 6] 78.0 g (0.0 g) of 1,5-pentanediol was placed in a 500 ml three-necked flask equipped with a distillation column and a stirrer.
75 mole), 1,6-hexanediol 88.6 g
(0.75 mole), 220 g of ethylene carbonate
(2.5 moles) and reacted for 15 hours at a temperature of 150° C. and a pressure of 10 mmHg from atmospheric pressure. During this time, ethylene glycol and ethylene carbonate were distilled out from the top of the column in an azeotropic composition. The main component of the reaction mixture remaining in the reactor has a terminal hydroxyl group and an average molecular weight of about 1500 (
It was a polycarbonate with a hydroxyl value of 74.7 mgKOH/g).

Next, 30 g of diphenyl carbonate was charged and reacted for 4 hours at a temperature of 150° C. and a pressure of 1 mmHg from atmospheric pressure. During this time, phenol was distilled from the top of the tower. The molecular weight of the polycarbonate in the reactor is 23
09 (hydroxyl value 48.5 mgKOH/g). Next, the distillation column was removed from the reactor so that it could be directly evacuated, and the temperature was increased to 150 °C and the pressure to 20 mm for 3 hours.
Diphenyl carbonate was distilled under conditions of Hg to 0.5 mmHg. The molecular weight is approximately 2594 (hydroxyl value 4)
3.2 mgKOH/g), and no diphenyl carbonate was observed in the polycarbonate. The yield was 96% based on the charged glycol.

[0040]

[Example 7] 8.26 kg (79.4 kg) of 1,5-pentanediol was placed in a 20 L reactor equipped with a distillation column and a stirrer.
mole), 1,6-hexanediol 8.26 kg (
70 mole), diphenyl carbonate 31.97k
g (149 mole) and reacted for 10 hours at a temperature of 150° C. and a pressure of 10 mmHg from atmospheric pressure. During this time, phenol was distilled from the top of the tower. The average molecular weight of the polycarbonate in the reactor is approximately 1200 (hydroxyl value 93.3
mgKOH/g).

Next, 2.9 kg of diphenyl carbonate was added, and the mixture was reacted for 4 hours at 150° C. and under pressure ranging from atmospheric pressure to 1 mmHg. During this time, phenol was distilled out from the top of the tower. The molecular weight of the polycarbonate in the reactor at this time is 1
800 (hydroxyl value 62.2 mgKOH/g). Next, the distillation column was removed and the system was directly evacuated while maintaining the temperature at 150° C., and diphenyl carbonate was distilled out under conditions such that the pressure was reduced from atmospheric pressure to 1 mmHg in 3 hours. The molecular weight is approximately 2050 (hydroxyl value 54.6mgKOH/g
), and no diphenyl carbonate was observed in the polycarbonate. The yield was 95% based on the charged glycol.

[0042]

[Example 8] 7.28 kg of 1,5-pentanediol (70 mo
le), 1,6-hexanediol 8.26 kg (70
mole) and the temperature is 100℃ under normal pressure.
I made it. Add 36% dimethyl carbonate to this mixture.
The mixture was added dropwise at a rate of 9 g/min to 7.5 g/min over time and stirred vigorously. During this time, the temperature was gradually raised to 200°C, and methanol was distilled from the top of the column. After the addition of dimethyl carbonate was completed, the reaction system was stirred for 12 hours while being maintained at 200°C, and then the pressure in the system was reduced from atmospheric pressure to 15 mmHg over 20 hours. During this time, methanol and dimethyl carbonate were azeotropically distilled from the top of the column. When these operations are completed, the number average molecular weight of the polycarbonate in the reactor is 1.1
It was 50.

Next, add 3.57k of diphenyl carbonate
g was added, and the reaction was carried out for 4 hours under conditions of 150° C. and atmospheric pressure to 1 mmHg. During this time, phenol was distilled from the top of the tower. The molecular weight of the polycarbonate at this time was 1600 (hydroxyl value 70 mgKOH/g). Next, the distillation column was removed, the system was directly evacuated while the temperature was maintained at 150° C., and diphenyl carbonate was distilled under conditions such that the pressure was reduced from atmospheric pressure to 1 mmHg in 3 hours. Molecular weight is approximately 17
24 (hydroxyl value 65.0 mgKOH/g), and no diphenyl carbonate was observed in the polycarbonate. Yield is 94% based on the charged glycol
Met.

[0044]

[Example 9] A 500ml separable flask equipped with a distillation column and a stirrer was charged with 88% of 1,6-hexanediol.
5g, 1,9-nonanediol 120.0g, 1,12
- Prepare 7.58 g of dodecanediol, 181.43 g of diethyl carbonate, and 0.35 g of metallic sodium,
The reaction is carried out at a temperature of 50°C to 150°C and a pressure of atmospheric pressure,
Ethanol was distilled off from the top of the column over a period of 7 hours. At this time, the molecular weight of the polycarbonate in the system is approximately 500 (hydroxyl value 2
24mgKOH/g).

Next, the temperature was increased stepwise to 15% over a period of 4 hours.
The temperature was gradually changed from 0°C to 200°C and the pressure was changed from atmospheric pressure to 20mmHg, and ethanol was further distilled from the top of the column. At this time, the molecular weight of the polycarbonate in the system is approximately 120
0 (hydroxyl value 93.3 mgKOH/g). Next, 40 g of diphenyl carbonate was added, and the mixture was reacted at 150° C. for 4 hours at a pressure ranging from atmospheric pressure to 1 mmHg. During this time, phenol was distilled out from the top of the tower. The molecular weight of the polycarbonate in the reactor at this time was 2100 (hydroxyl value 5
3.3 mgKOH/g).

Next, remove the distillation column, directly exhaust the system while maintaining the temperature at 150°C, and reduce the pressure from atmospheric pressure to 1 mmH.
3 hours. The molecular weight is approximately 2500 (hydroxyl value 44.8
mgKOH/g), and no diphenyl carbonate was observed in the polycarbonate. The yield was 95% based on the charged glycol.

[0047]

[Example 10] A 500 ml reactor equipped with a distillation column and a stirrer was charged with 178.8 g of 1,6-hexanediol, 141.3 g of ethylene carbonate, and 0.0640 g of titanium tetrabutoxide, and the temperature was 130°C and the pressure was high. The reaction was carried out at 5 mmHg from atmospheric pressure for 19 hours. During this time, an azeotrope of ethylene glycol and ethylene carbonate was distilled from the top of the column. The main component of the reaction mixture remaining in the reactor has a hydroxyl value of approximately 340 m with a terminal hydroxyl group.
gKOH/g of polycarbonate.

Next, 140 g of diphenyl carbonate was added, and the mixture was reacted for 6 hours at 130° C. under the conditions of atmospheric pressure to 0.5 mmHg. During this time, phenol was distilled out from the top of the tower. The molecular weight of the polycarbonate in the reactor at this time was 1900 (hydroxyl value 58.9 mgKOH/g). Next, the distillation column was removed, the system was directly evacuated while maintaining the temperature at 130°C, and the pressure was reduced from atmospheric pressure to 0.5 mmHg.
Diphenyl carbonate was distilled out under conditions such as time. Molecular weight is 2520 (hydroxyl value 44.4mgKO
H/g), and no diphenyl carbonate was observed in the polycarbonate. The yield was 96% based on the charged glycol.

When polycarbonate was hydrolyzed with an ethanol solution of potassium hydroxide and the solution was analyzed by gas chromatography, trace amounts of components other than 1,6-hexanediol were found.

[0050]

[Example 11] In a 500 ml separable flask equipped with a distillation column and a stirrer, 1,5-pentanediol 78
．． 0g, 88.5g of 1,6-hexanediol, and 132.0g of ethylene carbonate were charged, and the temperature was 150℃.
The reaction was carried out at a pressure ranging from atmospheric pressure to 10 mmHg for 15 hours. During this time, an azeotrope of ethylene glycol and ethylene carbonate was distilled from the top of the column. The main component of the reaction mixture remaining in the reactor was polycarbonate having an average molecular weight of about 350 with terminal hydroxyl groups.

Next, 134 g of diphenyl carbonate was charged at a temperature of 150°C and a pressure of 1 mmHg from atmospheric pressure.
The reaction was carried out for 4 hours under these conditions. During this time, phenol was distilled out from the top of the tower. The molecular weight of the polycarbonate in the reactor was approximately 1600 (hydroxyl value 70 mgKOH/g). Next, the distillation column was removed from the reactor so that it could be directly evacuated, and the temperature was increased to 150℃ and the pressure decreased from 20 to 0.0℃ over a period of 3 hours.
．． Diphenyl carbonate was distilled off under conditions of 5 mmHg.

Next, the temperature was raised to 200°C and 5mmHg
When the raw material glycol was distilled off at the following pressure, polycarbonate diol with a molecular weight of about 2000 (hydroxyl value 56 mgKOH/g) was obtained. The yield based on the charged glycol monomer was 96%.

[0053]

[Example 12] 1,5-pentanediol 78.
0g, 88.5g of 1,6-hexanediol, and 132.0g of ethylene carbonate were charged, and the temperature was 150°C.
The reaction was carried out at a pressure ranging from atmospheric pressure to 10 mmHg for 15 hours. During this time, an azeotrope of ethylene glycol and ethylene carbonate was distilled from the top of the column. The main component of the reaction mixture remaining in the reactor has an average molecular weight of about 3 with terminal hydroxyl groups.
50 polycarbonate.

Next, 134 g of diphenyl carbonate was charged at a temperature of 150°C and a pressure of 1 mmHg from atmospheric pressure.
The reaction was carried out for 7 hours under these conditions. During this time, phenol was distilled out from the top of the tower. The molecular weight of the polycarbonate in the reactor was 2200 (hydroxyl value 50.9 mgKOH/g). Next, the distillation column was removed from the reactor, and diphenyl carbonate was distilled out under conditions of a temperature of 150° C. and a pressure of 20 to 0.5 mmHg for 3 hours so that it could be directly evacuated.

Next, the temperature was raised to 200°C and 5mmHg
When the raw material glycol was distilled off at the following pressure, polycarbonate diol with a molecular weight of about 2600 (hydroxyl value 43 mgKOH/g) was obtained. The yield based on the charged glycol monomer was 96%.

[0056]

[Example 13] In a 500 ml separable flask equipped with a distillation column and a stirrer, 1,5-pentanediol 78
．． 0g, 88.5g of 1,6-hexanediol, and 132.0g of ethylene carbonate were charged, and the temperature was 150℃.
The reaction was carried out at a pressure ranging from atmospheric pressure to 10 mmHg for 15 hours. During this time, an azeotrope of ethylene glycol and ethylene carbonate was distilled from the top of the column. The main component of the reaction mixture remaining in the reactor was polycarbonate having an average molecular weight of about 350 with terminal hydroxyl groups.

Next, 134 g of diphenyl carbonate was charged at a temperature of 150°C and a pressure of 1 mmHg from atmospheric pressure.
The reaction was carried out for 4 hours under these conditions. During this time, phenol was distilled out from the top of the tower. The molecular weight of the polycarbonate in the reactor was approximately 1600 (hydroxyl value 70 mgKOH/g). Next, the distillation column was removed from the reactor so that it could be directly evacuated, and the temperature was increased to 150℃ and the pressure decreased from 20 to 0 for 3 hours.
．． Diphenyl carbonate was distilled off under conditions of 5 mmHg.

Next, the temperature was raised to 200°C and 5mmHg
When the raw material glycol was distilled off at the following pressure, polycarbonate diol with a molecular weight of about 2000 (hydroxyl value 56 mgKOH/g) was obtained. The yield based on the charged glycol monomer was 96%. Next, the temperature was maintained at 150 to 200°C, and a predetermined amount of glycol monomer was added.
After reacting for 5 hours, a polycarbonate having a molecular weight of 1000 was obtained.

[0059]

[Comparative Example] 250.0 g of the reaction mixture from Step 1 of Example 1 was charged into a 500 ml three-necked flask equipped with a stirrer.
Temperature is 200℃, pressure is 10mmHg to 0.1mmH
The self-condensation reaction was carried out under the conditions of g for 10 hours. After the reaction is completed, polycarbonate diol with a molecular weight of 2020 and 150
I got g. The yield based on the charged polycarbonate was 68%.

[0060]

[Effects of the Invention] According to the method of the present invention, it is possible to obtain a polycarbonate diol having a terminal hydroxyl group in a high yield, and the yield of the glycol monomer base is high, and the molecular weight can be easily adjusted. be. Furthermore, when recovering monomers, the equipment is small and therefore the cost is low. For these reasons, the present invention is an extremely advantageous method for producing polycarbonate.

Claims (2)

[Claims] Claim 1: In producing a polycarbonate having a terminal hydroxyl group, (i) one or more carbonate monomers selected from alkylene carbonate, dialkyl carbonate, and diaryl carbonate, and alkylene glycol and polyoxyalkylene glycol; A first step of reacting one or more selected glycol monomers while removing by-product alcohols from the system to produce a low molecular weight polycarbonate of 2 to 10 units; (ii) a first step; The above-mentioned diaryl carbonate monomer is further added to the reaction mixture of the step, and the reaction is carried out while removing by-product alcohols from the system to connect the low molecular weight polycarbonate of 2 to 10 units and the glycol monomer to form a polymer of 10 or more units. A method for producing a polycarbonate having terminal hydroxyl groups, comprising a second step of producing polycarbonate, and (iii) a third step of removing remaining carbonate monomer. 2. The method for producing a polycarbonate having a terminal hydroxyl group according to claim 1, which comprises the step of adding a glycol monomer to the produced high molecular weight polycarbonate to adjust the hydroxyl value.