U.S. patent application number 09/901727 was filed with the patent office on 2002-02-21 for process fo preparing polycarbonates.
This patent application is currently assigned to Korea Research Institute of Chemical Technology. Invention is credited to Choi, Il Seok, Choi, Kil-Yeong, Kim, Cheol-Hyun, Kim, Seung-Joo, Ko, Young Chan, Lee, Jae Heung, Lee, Kyong Soon, Yoon, Kwang Soo.
Application Number | 20020022711 09/901727 |
Document ID | / |
Family ID | 19678196 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020022711 |
Kind Code |
A1 |
Ko, Young Chan ; et
al. |
February 21, 2002 |
Process fo preparing polycarbonates
Abstract
The present invention relates to a process of preparing
polycarbonates and more particularly, to the process of preparing
polycarbonates through a melt polymerization reaction of
dihydroxyaryl compounds with diarylcarbonate, wherein said melt
polymerization is performed in the presence of a mixed catalyst
composed of an oxygen (O) or sulfur (S) containing compound having
lone-pair electrons and an alkali metal or alkaline earth metal
salt in an appropriate ratio at a reduced temperature by
accelerating a reaction rate to obtain high quality polycarbonates
with higher than 15,000 g/mole of a viscosity average molecular
weight and improved color.
Inventors: |
Ko, Young Chan; (Seoul,
KR) ; Choi, Il Seok; (Kyunggi-do, KR) ; Kim,
Cheol-Hyun; (Ulsan, KR) ; Yoon, Kwang Soo;
(Kyungsangnam-do, KR) ; Kim, Seung-Joo; (Ulsan,
KR) ; Choi, Kil-Yeong; (Daejeon, KR) ; Lee,
Jae Heung; (Daejeon, KR) ; Lee, Kyong Soon;
(Seoul, KR) |
Correspondence
Address: |
Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
1300 I Street, N.W.
Washington
DC
20005-3315
US
|
Assignee: |
Korea Research Institute of
Chemical Technology
|
Family ID: |
19678196 |
Appl. No.: |
09/901727 |
Filed: |
July 11, 2001 |
Current U.S.
Class: |
528/196 |
Current CPC
Class: |
C08G 64/307
20130101 |
Class at
Publication: |
528/196 |
International
Class: |
C08G 064/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 14, 2000 |
KR |
2000-40667 |
Claims
What is claimed is:
1. A process of preparing polycarbonates by melt polymerization of
an aromatic dihydroxy compound and a diarylcarbonate in the
presence of a catalyst, wherein said catalyst comprises a compound
having lone-pair electrons of oxygen (O) or sulfur (S) and alkali
metal or alkaline earth metal salt in the molar ratio of 20:1 to
1:20.
2. The process of preparing polycarbonates according to claim 1,
wherein said catalyst is used in the range of 10.sup.-7 to
10.sup.-2 mole to 1 mole of the aromatic dihydroxy compound.
3. The process of preparing polycarbonates according to claim 1,
wherein said compound having lone-pair electrons is an
oxygen-containing compound selected from the group consisting of
tetrahydrofuran, tetrahydropyran, 1,3-dioxane, 1,4-dioxane,
1,3-dioxepane, 1,3-dioxolan-2-one, tetronic acid, trimethylene
oxide, and 1,3,5-trioxane.
4. The process of preparing polycarbonates according to claim 1,
wherein said compound having lone-pair electrons is an
sulfur-containing compound selected from the group consisting of
tetrahydrothiophene, tetrahydrothiopyran-4-one, 1,4-thioxane,
1,3-dithiane, 1,3-dithiolane, ethylene trithiocarbonate,
tetrahydrothiophen-3-one, thianaphthene, trimethylene sulfide, and
1,3,5-trithiane.
5. The process of preparing polycarbonates according to claim 1,
wherein said alkali metal or alkaline earth metal salt is selected
from the group consisting of potassium acetate, sodium acetate,
rubidium acetate, cesium acetate, calcium acetate, magnesium
acetate, and zinc acetate.
6. The process of preparing polycarbonates according to claim 1 or
claim 5, wherein said catalyst is a mixed catalyst of
tetrahydrofuran and potassium acetate.
7. The process of preparing polycarbonates according to claim 1 or
claim 5, wherein said catalyst is a mixed catalyst of
tetrahydrothiophene and potassium acetate.
8. The process of preparing polycarbonates according to claim 1 or
claim 5, wherein said catalyst is a mixed catalyst of
tetrahydrothiopyran-4-one and potassium acetate.
9. The process of preparing polycarbonates according to claim 1 or
claim 5, wherein said catalyst is a mixed catalyst of 1,4-dioxane
and potassium acetate.
10. The process of preparing polycarbonates according to claim 1 or
claim 5, wherein said catalyst is a mixed catalyst of
tetrahydropyran and potassium acetate.
11. The process of preparing polycarbonates according to claim 1 or
claim 5, wherein said catalyst is a mixed catalyst of 1,3-dithiane
and potassium acetate.
12. The process of preparing polycarbonates according to claim 1 or
claim 5, wherein said catalyst is a mixed catalyst of 1,4-thioxane
and potassium acetate.
13. The process of preparing polycarbonates according to claim 1 or
claim 5, wherein said aromatic dihydroxy compound is bisphenol
A.
14. The process of preparing polycarbonates according to claim 1 or
claim 5, wherein said diarylcarbonate is diphenylcarbonate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a process of preparing
polycarbonates and more particularly, to the process of preparing
polycarbonates through a melt polymerization reaction of a
dihydroxy compound with a diarylcarbonate, wherein said melt
polymerization is performed in the presence of a mixed catalyst
composed of an oxygen (O) or sulfur (S) containing compound having
one-pair electrons and an alkali metal or alkaline earth metal salt
in an appropriate ratio at a reduced temperature by accelerating a
reaction rate to obtain high quality polycarbonates with higher
than 15,000 g/mole of a viscosity average molecular weight and
improved color.
[0003] Polycarbonates are known to have excellent properties in
terms of transparency, impact resistance, mechanical strength and
heat resistance, and thus have been widely used in industry in
manufacturing transparent sheets, packaging materials, vehicle
bumpers, compact discs and the like.
[0004] A representative preparing method of polycarbonates is an
interfacial polymerization employing aqueous bisphenol A(BPA)
solution substituted with sodium and a phosgene-containing organic
solution. However, there are some disadvantages regarding to safety
and ecological problems in that the phosgene used as a starting
material and a chlorine-containing organic solvent used in the
polymerization are extremely toxic. Furthermore, it requires
excessive use of water to wash off the remaining
chlorine-containing salts and un-reacted reactants after the
polymerization.
[0005] A melt polymerization method, which produces polycarbonates
by direct polymerization of starting materials in melt state under
vacuum without using any solvents, has been introduced to solve the
above problems. This method has several advantages over the
above-mentioned interfacial polymerization in that it is possible
to lower manufacturing cost, pelletize produced polycarbonate
directly without any other treatment, and perform relatively simple
apparatus.
[0006] Generally, the melt polymerization is carried at a
temperature of 180-350.degree. C. If the reaction temperature is
lower than 180.degree. C., it is difficult to remove phenol
produced as a by-product during the polymerization thus resulting
in polycarbonates with low molecular weight. On the other hand, if
it is higher than 350.degree. C., a by-product, which changes the
product to a yellow color, can be generated or decomposition of the
product may occur. Although it is known that the melt
polymerization can be carried in the absence of a catalyst, it has
to be exposed for a prolonged time at an elevated temperature of
over 280.degree. C. to complete the reaction. So the use of an
effective polymerization catalyst is critical to attain high
quality polycarbonate.
[0007] Theoretically, it is required to use the same molar amounts
of hydroxyl group in bisphenol A and ester group in
diphenylcarbonate to obtain high molecular weight of
polycarbonates. However, because diphenylcarbonate is more volatile
than bisphenol A, a little more diphenylcarbonate than bisphenol-A
is desirable to obtain polycarbonates with superior physical
properties. Generally, the molar ratio of
diphenylcarbonate/bisphenol A is within the range from 1.0 to
1.3.
[0008] There have been many prior arts disclosing the melt
polymerization to prepare polycarbonates by using a catalyst (U.S.
Pat. No. 5,221,761 (1993), EP Patent No. 584801 (1993), and JP
Patent Publication Nos. 7-003003 (1995) and 3-174443). Previously,
the melt polymerization was performed employing a catalyst used in
esterification or ester exchange reaction: (i) an alkali metal or
alkali earth metal oxide or hydroxide; (ii) an alkali metal or
alkali earth metal organic acid of inorganic acid; (iii) a sodium
or potassium salt of phenol or bisphenol A; and (iv) an organic
phosphorus and the like. Besides these catalysts, a nitrogen- or
phosphorus-containing basic compound has been to recently used as a
catalyst as shown in U.S. Pat. No. 5,142,018. However, the process
of preparing polycarbonates employing the catalyst mentioned above
has posed serious problems in that the reaction requires a high
reaction temperature and prolonged reaction time and the product
assumes a yellow color.
[0009] Consequently, development of novel catalysts is highly
required in order to produce high quality polycarbonates having
improved color at a reduced temperature within a short period of
time.
SUMMARY OF THE INVENTION
[0010] To solve aforementioned problems of the conventional melt
polymerization methods of preparing polycarbonates in the presence
of the catalyst, the present invention was completed by performing
the melt polymerization in the presence of a mixed catalyst
composed of a oxygen (O) or sulfur (S) containing compound having
lone-pair electrons and an alkali metal or alkaline earth metal
salt in an appropriate ratio.
[0011] Consequently, an object of this invention is to provide a
method of preparing polycarbonates by using the mixed catalyst,
which expedites the rate of the polymerization at a low temperature
to the production of polycarbonates with high quality and improved
color.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] In the process of preparing polycarbonates by melt
polymerization of aromatic dihydroxy compound and diarylcarbonate
in the presence of the catalyst, the present invention is
characterized by using the mixed catalyst mixed in molar ratio of
from 20:1 to 1:20 of an oxygen (O) or sulfur (S) containing
compound having lone-pair electrons and an alkali metal or alkaline
earth metal salt to produce high quality polycarbonates.
[0013] The present invention is described in detail as set forth
hereunder.
[0014] The present invention relates to a process of preparing high
quality polycarbonates with improved color tone by employing the
mixed catalyst, which can expedite the rate of the polymerization
at a low temperature.
[0015] The catalyst used in the present invention comprises a
compound having lone-pair electrons of oxygen (O) or Sulfur (S) and
an alkali metal or alkaline earth metal salt. The compound having
lone-pair electrons in the catalyst provides excellent activity in
the melt polymerization by incorporating with an alkali metal or
alkaline earth metal salt. But when the compound having lone-pair
electrons is used alone or when the alkali metal or alkaline earth
metal salt is used alone, there is no significant catalytic
activity increase in the polymerization and the polymerization rate
is similar to that of the reaction performed without any catalyst.
However, when the compound having lone-pair electrons is
incorporated with an alkali metal or alkaline earth metal salt, it
shows a synergy effect in the polymerization. In the preparation of
the catalyst, it is prefer to mix to be a molar ratio of the
compound having lone-pair electrons to alkali metal or alkaline
earth metal salt in the range of from 20:1 to 1:20. If the ratio is
below 20:1, the polymerization rate becomes slow. If it exceeds
1:20, it results in color deterioration of the resulting
product.
[0016] Examples of the compound having lone-pair electrons include
oxygen-containing compound, sulfur-containing compound and a
mixture thereof. Particular examples of said oxygen-containing
compound are tetrahydrofuran, tetrahydropyran, 1,3-dioxane,
1,4-dioxane, 1,3-dioxepane, 1,3-dioxolan-2-one, tetronic acid,
trimethylene oxide, and 1,3,5-trioxane. Particular examples of said
sulfur-containing compound are tetrahydrothiophene,
tetrahydrothiopyran-4-one, 1,4-thioxane, 1,3-dithiane,
1,3-dithiolane, ethylene trithiocarbonate,
tetrahydrothiophen-3-one, thianaphthene, trimethylene sulfide, and
1,3,5-trithiane. Besides these oxygen-containing and
sulfur-containing compounds, other compounds having lone-pair
electrons can be also used. Particular examples of the alkali metal
or alkaline earth metal salt of the present invention include
potassium acetate, sodium acetate, rubidium acetate, cesium
acetate, calcium acetate, magnesium acetate, zinc acetate and the
like. The more-detailed description of the present method of
preparing polycarbonates by the melt polymerization of aromatic
dihydroxy compound and diarylcarbonate in the presence of the mixed
catalyst is given hereunder.
[0017] An aromatic dihydroxy compound, a diarylcarbonate and a
catalyst are placed into a reactor and heated to 170.degree. C. and
stayed for 1 hr to melt them. The reaction mixture is heated to
220-300.degree. C. and reacted for 2 hrs under atmospheric pressure
and is further reacted under pressure of 170 torr for 1 hr. The
pressure is decreased to below 2 torr and is then reacted for
additional 2 hrs to obtain the desired product.
[0018] The molar ratio of diarylcarbonate to aromatic dihydroxy
compound is preferred to be in the range of 1 to 1.3 and that of
catalyst used in the reaction is in the range of 10.sup.-7 to
10.sup.-2, more preferably 10.sup.-6 to 10.sup.-3 respectively.
[0019] The aromatic dihydroxy compound of the present invention is
expressed by the formula (1),
HO--Ar.sub.1--Z--Ar.sub.2--OH (1)
[0020] wherein Ar.sub.1 and Ar.sub.2 represent independently phenyl
group or its derivatives; and Z represents a single bond or --O--,
--CO--, --S--, --SO.sub.2--, --SO--, --CON(R.sub.1)-- or
--C(R.sub.2R.sub.3)-- linkage, where R.sub.1, R.sub.2 and R.sub.3
are independently a hydrogen atom or --(CH.sub.2).sub.nCH.sub.3
respectively, where n is an integer of 0 to 4.
[0021] The diarylcarbonate of the present invention is expressed by
the formula (2),
Ar.sub.3--O--C(.dbd.O)--O--Ar.sub.4 (2)
[0022] wherein Ar.sub.3 and Ar.sub.4 are independently phenyl or
its derivatives.
[0023] A viscosity average molecular weight (M.sub.v)of the
polycarbonate prepared by the above-mentioned polymerization were
estimated by using the following Equation 1, based on the intrinsic
viscosity ([.eta.]) measured at 25.degree. C. in chloroform.
[.eta.]=K.multidot.M.sub.v.sub..sup.a Equation 1
[0024] wherein K=0.012 cm/g and a=0.82.
[0025] And further, a color tone of the polycarbonate prepared by
the above-mentioned polymerization is measured with chromoscope and
a degree of the color was estimated by comparing b values.
[0026] The following examples are intended to be illustrative for
the present invention and should not be construed as limiting the
scope of this invention defined by the appended claims.
EXAMPLE 1
[0027] 1 kg of a mixture consisting of bisphenol A (BPA) and
diphenylcarbonate (DPC) mixed in the molar ratio of 1:1.06 was
placed in a 2 L resin kettle kept at room temperature equipped with
a stirrer, a nitrogen gas inlet, a reflux condenser, and a vacuum
pump. 2.5.times.10.sup.-4 mole of each tetrahydrofuran and
potassium acetate, relative to 1 mole of bisphenol A were added to
the reaction mixture. After eliminating moisture and oxygen by
alternatively applying vacuum and a nitrogen gas three times
respectively, the temperature of the reaction was gradually raised
with a rate of 1.5.degree. C./min with applying a nitrogen gas with
a rate of 0.2 L/min. When the temperature was reached to
170.degree. C., the reaction mixture was molten over 1 hr while
keeping the temperature. And then the temperature was gradually
raised to 240.degree. C. and allowed to react for additional 2 hr
while flowing a nitrogen gas with a rate of 0.2 L/min. After that,
the reactor pressure was reduced to 170 torr by using a vacuum pump
and the reaction continued for 1 hour. And further, the reactor
pressure was reduced again to 0.2 torr and reacted for 100 min.
Thus prepared polycarbonate was colorless and transparent and had
the viscosity average molecular weight of 18,300 g/mole and b value
of 5.
EXAMPLE 2
[0028] The reaction was performed in the same manner as Example 1
except that tetrahydrothiophene was used instead of
tetrahydrofuran. Thus prepared polycarbonate had the viscosity
average molecular weight of 18,200 g/mole.
COMPARATIVE EXAMPLE 1
[0029] The reaction was performed in the same manner as Example 1
except that no catalyst was added. Thus prepared polycarbonate was
colorless and transparent and had the viscosity average molecular
weight of 9,000 g/mole and b value of 4.
COMPARATIVE EXAMPLE 2
[0030] The reaction was performed in the same manner as Example 1
except that 2.5.times.10.sup.-4 mole of each tetramethylammonium
hydroxide, sodium bicarbonate and boric acid were used instead of
tetrahydrofuran and potassium acetate as catalyst. Thus prepared
polycarbonate was colorless and transparent and had the viscosity
average molecular weight of 16,500 g/mole and b value of 5.
[0031] The result of Examples 1-2 and Comparative Examples 1-2 are
summarized in Table 1
1 TABLE 1 Viscosity average Reaction molecular b Catalyst time
(min) weight value Example 1 Tetrahydrofuran/ 100 18,300 5
potassium acetate Example 2 Tetrahydrothiophene/ 100 18,200 5
potassium acetate Comparative -- 100 9,000 4 Example 1 Comparative
Tetramethylammonium 100 16,500 5 Example 2 hydroxide, sodium
bicarbonate and boric acid
[0032] As shown in Table 1, viscosity average molecular weights of
the polycarbonates prepared in Examples 1 and 2 are much higher
than that of the polycarbonate prepared without using a catalyst in
Comparative Example 1 and higher than that of the polycarbonte
prepared by using a catalyst disclosed in U.S. Pat. No. 5,142,018
in Comparative Example 2. And the polycarbonates prepared in
Examples 1 and 2 are more clear than those of prepared in
Comparative Examples 1 and 2.
EXAMPLE 3
[0033] The reaction was performed in the same manner as Example 1
except that tetrahydrothiopyran-4-one was used instead of
tetrahydrofuran. Thus prepared polycarbonate after reaction under
the vacuum for 120 min had the viscosity average molecular weight
of 17,300 g/mole and b value of 5.
COMPARATIVE EXAMPLE 3
[0034] The reaction was performed in the same manner as Example 1
except that only tetrahydrofuran was used as catalyst and potassium
acetate was not added. Thus prepared polycarbonate after reaction
under the vacuum for 120 min had the viscosity average molecular
weight of 4,400 g/mole and b value of 4.
COMPARATIVE EXAMPLE 4
[0035] The reaction was performed in the same manner as Example 4
except that only potassium acetate was used as catalyst and
tetrahydrofuran was not added. The reaction was performed with
potassium acetate itself according to Example 1. Thus prepared
polycarbonate after reaction under the vacuum for 120 min had the
viscosity average molecular weight of 11,900 g/mole and b value of
5.
COMPARATIVE EXAMPLE 5
[0036] The reaction was performed in the same manner as Example 1
except that only 4-dimethylamino pyridine which was disclosed in
U.S. Pat. No. 5,548,041 was used as catalyst. Thus prepared
polycarbonate after reaction under the vacuum for 120 min had the
viscosity average molecular weight of 14,300 g/mole and b value of
6.
[0037] The result of Example 3 and Comparative Examples 3-5 are
summarized in Table 2.
2 TABLE 2 Viscosity average Reaction molecular b Catalyst time
(min) weight value Example 3 Tetrahydrothiopyran-4-one/ 120 17,300
5 potassium acetate Comparative Tetrahydrofuran 120 4,400 4 Example
3 Comparative Potassium acetate 120 11,900 5 Example 4 Comparative
4-dimethylamino pyridine 120 14,300 6 Example 5
[0038] As indicated in Table 2, when oxygen-containing or
sulfur-containing compound itself or alkali metal salt itself was
used in the polymerization, the increasing rates of the viscosity
average molecular weight were much slower or similar to that when
any catalyst was not used in the polymerization of Comparative
Example 1. Accordingly, the co-use of both oxygen-containing or
sulfur-containing compound and alkali metal salt is essential and
shows a synergy effect in the polymerization of the present
invention.
EXAMPLE 4
[0039] The reaction was performed in the same manner as Example 1
except that 1,4-dioxane was used instead of tetrahydrofuran. Thus
prepared polycarbonate after reaction under the vacuum for 40 min
and 70 min were colorless and transparent had the viscosity average
molecular weights of 18,000 and 21,500 g/mole respectively and b
values of both were 4.
EXAMPLE 5
[0040] The reaction was performed in the same manner as Example 1
except that tetrahydropyran was used instead of tetrahydrofuran.
Thus prepared polycarbonate after reaction under the vacuum for 100
min had the viscosity average molecular weight of 18,100 g/mole and
b value of 5.
EXAMPLE 6
[0041] The reaction was performed in the same manner as Example 1
except that 1,3-dithiane was used instead of tetrahydrofuran. Thus
prepared polycarbonate after reaction under the vacuum for 40 min
was colorless and transparent and had the viscosity average
molecular weight of 17,000 g/mole and b value of 5.
EXAMPLE 7
[0042] The reaction was performed in the same manner as Example 1
except that 1,4-thioxane was used instead of tetrahydrofuran. Thus
prepared polycarbonate after reaction under the vacuum for 40 min
was colorless and transparent had the viscosity average molecular
weight of 17,300 g/mole and b value of 5.
[0043] The result of Examples 4-7 is summarized in Table 3.
3 TABLE 3 Viscosity average Reaction molecular b Catalyst time
(min) weight value Example 4 1,4-dioxane/potassium 40 18,000 4
acetate 70 21,500 4 Example 5 Tetrahydropyran/ 100 18,100 5
potassium acetate Example 6 1,3-dithiane/potassium 40 17,000 5
acetate Example 7 1,4-thioxane/potassium 40 17,300 5 acetate
EXAMPLE 8
[0044] The reaction was performed in the same manner as Example 1
except that the reaction temperature was performed at a lower
temperature of 220.degree. C. instead of 240.degree. C. Thus
prepared polycarbonate after reaction under the vacuum for 100 min
had the viscosity average molecular weight of 17,000 g/mole and b
value of 5.
EXAMPLE 9
[0045] The reaction was performed in the same manner as Example 1
except that the amount of potassium acetate was reduced to
6.times.10.sup.-5 mole for each mole of BPA. Thus prepared
polycarbonate after reaction under the vacuum for 65 min had the
viscosity average molecular weight of 16,900 g/mole and b value of
3.
[0046] As described above, the melt polymerization of the present
invention is performed in the presence of the mixed catalyst in an
appropriate ratio of the compound having lone-pair electrons and
alkali metal or alkaline earth metal salt, which can expedite the
polymerization rate at a low temperature, to produce high quality
polycarbonates having high molecular weight and improved color
tone.
* * * * *