Disclosed is a polycarbonate composition comprising (a) an aromatic dihydroxy compound/carbonic diester transesterification polycarbonate having terminal hydroxyl groups in a proportion of at least 20 mole %, based on the molar total of all terminal groups of the polycarbonate, and (b) a phenolic antioxidant in an amount satisfying the following formula (1): EQU 20.times.10.sup.5 M.ltoreq.X.ltoreq.20.times.10.sup.5 M+2,100(1) wherein X represents the amount of said phenolic antioxidant (ppm by weight), based on the weight of said polycarbonate, and M represents the amount of said terminal hydroxyl groups (mol/g-polycarbonate). The polycarbonate composition of the present invention has an advantage in that it is insusceptible to discoloration not only during production thereof and molding of the composition, but also when a molded article produced from the composition experiences high temperature atomosphere. The polycarbonate composition of the present invention can be advantageously used in the various fields where polycarbonates have conventionally been used.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a polycarbonate composition. More 
particularly, the present invention is concerned with a polycarbonate 
composition comprising: (a) an aromatic dihydroxy compound/carbonic 
diester transesterification polycarbonate having terminal hydroxyl groups 
in a proportion of at least 20 mole %, based on the molar total of all 
terminal groups of the polycarbonate, and (b) a phenolic antioxidant in an 
amount within a specific range as determined in accordance with the molar 
amount of the terminal hydroxyl groups. The transesterification 
polycarbonate composition of the present invention has an advantage in 
that it has high heat resistance or thermal stability during and after 
production thereof, that is, it is insusceptible to discoloration not only 
during production thereof and molding of the composition, but also when a 
molded article produced from the composition experiences high temperature 
atomosphere. 
2. Prior Art 
Polycarbonates have been widely used in various fields as engineering 
plastics which have excellent heat resistance, impact resistance and 
transparency. In recent years, many researches and developments have been 
made with respect to a process for the production of a polycarbonate by 
transesterification (which is hereinafter referred to as 
"transesterification process") as a substitute for a process for the 
production of a polycarbonate from an aromatic dihydroxy compound, and 
phosgene which is poisonous and is likely to pollute the environment 
(hereinafter referred to as the "phosgene process"). 
However, the transesterification process has a problem in that the 
polycarbonate produced by transesterification is susceptible to 
discoloration, as compared to the polycarbonate produced by the phosgene 
process. This is because the polymerization of a polycarbonate by 
transesterification needs to be conducted at high temperatures for a 
prolonged period of time. 
For producing a polycarbonatae by transesterification, wherein the 
polycarabonate is less likely to suffer discoloration during production 
thereof, various methods have heretofore been proposed. For example, 
Unexamined Japanese Patent Application Laid-Open Specification No. 
2-153923 discloses a method in which a specific reactor is used in order 
to accelerate the polymerization and suppress discoloration of a 
polycarbonate. Unexamined Japanese Patent Application Laid-Open 
Specification Nos. 5-125167, 5-125172, 5-140291 and 5-186582 disclose a 
method in which a reactor made of a specific material is used for solving 
the discoloration problem. Unexamined Japanese Patent Application 
Laid-Open Specification Nos. 5-310906, 6-287426 (corresponding to U.S. 
Pat. No. 5,455,324) and 5-46843 disclose a method in which a thermal 
stabilizer is added to a reaction mixture during the polymerization 
reaction. 
On the other hand, many proposals have also been made in which a thermal 
stabilizer and/or an antioxidant is added to a molten polycarbonate 
produced by a melt transesterification process in order to suppress 
discoloration of a polycarbonate during production thereof and impart an 
improved thermal stability to the produced polycarbonate. For example, 
Unexamined Japanese Patent Application Laid-Open Specification Nos. 
4-15221, 4-15222, 4-36346, 4-328124 and 5-112706 disclose methods in which 
various stabilizers, such as phosphorus-, epoxy-, phenolic- or sulfonic 
ester-stabilizers are added to molten polycarbonates. 
However, the above-mentioned prior art methods are not satisfactory to 
obtain polycarbonate compositions having high heat resistance or thermal 
stability during and after production thereof. Therefore, development of a 
discoloration-insusceptible polycarbonate composition has been earnestly 
desired. 
SUMMARY OF THE INVENTION 
In these situations, the present inventors have made extensive and 
intensive studies with a view toward developing a transesterification 
polycarbonate composition which is insusceptible to discoloration. As a 
result, it has surprisingly been found that, when the proportion of 
terminal hydroxyl groups in all terminal groups of a transesterification 
polycarbonate is at least 20 mol %, the polycarbonate is insusceptible to 
discoloration during production thereof and molding thereof. 
Conventionally, for the purpose of suppressing the discoloration of a 
transesterification polycarbonate composition, there have been no 
proposals in which attention is paid to the proportion of terminal 
hydroxyl groups in all terminal groups. This is considered to be due to 
the following well known fact that when the proportion of terminal 
hydroxyl groups in all terminal groups of a polycarbonate produced by the 
phosgene process is increased, not only cannot the discoloration be 
suppressed, but also the thermal stability and hydrolysis resistance of a 
molded article produced from the polycarbonate become poor. In fact, all 
the polycarbonate compositions on the market, which are produced by the 
phosgene process, have hydroxyl terminal groups in a proportion of not 
more than 15 mole %, based on the molar total of all terminal groups 
thereof. 
During the study, the present inventors noted that a molded article made of 
a transesterification polycarbonate having terminal hydroxyl groups in a 
large proportion, based on the molar total of all terminal groups, suffers 
serious discoloration when a molded article produced from the 
polycarbonate experiences high temperature atomosphere, although the 
polycarbonate itself is insusceptible to discoloration during production 
thereof and molding thereof. Therefore, the present inventors have made 
further intensive studies on the relation between the amount of the 
terminal hydroxyl groups and the effect of various thermal stabilizers and 
antioxidants, with a view toward improving the thermal stability of a 
transesterification polycarbonate having terminal hydroxyl groups in a 
large proportion, based on the molar total of all terminal groups. As a 
result, it has unexpectedly been found that, when a phenolic antioxidant 
is added to the above-mentioned transesterification polycarbonate in an 
amount within a specific range as determined in accordance with the molar 
amount of terminal hydroxyl groups of the polycarbonate, a polycarbonate 
composition can be obtained by transesterification which is insusceptible 
to discoloration even when a molded article produced from the composition 
experiences high temperature atomosphere. The present invention has been 
completed, based on the above findings. 
Therefore, it is a primary object of the present invention to provide a 
transesterification polycarbonate composition which has high heat 
resistance or thermal stability during and after production thereof, that 
is, it is insusceptible to discoloration not only during production 
thereof and molding of the composition, but also when a molded article 
produced from the composition experiences high temperature atomosphere. 
The foregoing and other objects, features and advantages of the present 
invention will be apparent from the following detailed description and 
appended claims taken in connection with accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
According to the present invention, there is provided a polycarbonate 
composition comprising: 
(a) an aromatic dihydroxy compound/carbonic diester transesterification 
polycarbonate having terminal hydroxyl groups in a proportion of at least 
20 mol %, based on the molar total of all terminal groups of the 
polycarbonate, and 
(b) a phenolic antioxidant in an amount satisfying the following formula 
(1): 
EQU 20.times.10.sup.5 M.ltoreq.X.ltoreq.20.times.10.sup.5 M+2,100(1) 
wherein X represents the amount of the phenolic antioxidant (ppm by 
weight), based on the weight of the polycarbonate, and M represents the 
amount of the terminal hydroxyl groups (mol/g-polycarbonate). 
For easy understanding of the present invention, the essential features and 
various embodiments of the present invention are enumerated below. 
1. A polycarbonate composition comprising: 
(a) an aromatic dihydroxy compound/carbonic diester transesterification 
polycarbonate having terminal hydroxyl groups in a proportion of at least 
20 mole %, based on the molar total of all terminal groups of the 
polycarbonate, and 
(b) a phenolic antioxidant in an amount satisfying the following formula 
(1): 
EQU 20.times.10.sup.5 M.ltoreq.X.ltoreq.20.times.10.sup.5 M+2,100(1) 
wherein X represents the amount of the phenolic antioxidant (ppm by 
weight), based on the weight of the polycarbonate, and M represents the 
amount of the terminal hydroxyl groups (mol/g-polycarbonate). 
2. The polycarbonate composition according to item 1 above, wherein the 
polycarbonate (a) has terminal hydroxyl groups in a proportion of from 20 
to 80%, based on the molar total of all terminal groups of the 
polycarbonate. 
3. The polycarbonate composition according to item 1 or item 2 above, 
wherein the polycarbonate contains at least one metal selected from an 
alkali metal and an alkaline earth metal in an amount of not more than 800 
ppb by weight, based on the weight of the polycarbonate. 
4. The polycarbonate composition according to any of items 1 to 3 above, 
wherein the phenolic antioxidant is 
octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate. 
In the present invention, the polycarbonate (a) is produced from an 
aromatic dihydroxy compound and a carbonic diester by transesterification 
therebetween. 
In the present invention, the term "aromatic dihydroxy compound" means a 
compound represented by the following formula: 
EQU HO--Ar--OH 
wherein Ar represents a divalent aromatic group. 
Preferred examples of aromatic groups as Ar include divalent aromatic 
groups represented by the following formula: 
EQU --Ar.sup.1 --Y--Ar.sup.2 -- 
wherein each of Ar.sup.1 and Ar.sup.2 independently represents a divalent 
carbocyclic or heterocyclic aromatic group having from 5 to 70 carbon 
atoms, and Y represents a divalent alkane group having from 1 to 30 carbon 
atoms. 
In the divalent carbocyclic or heterocyclic aromatic groups as Ar.sup.1 and 
Ar.sup.2, at least one hydrogen atom may be substituted with a substituent 
which does not adversely affect the reaction, such as a halogen atom, an 
alkyl group having from 1 to 10 carbon atoms, an alkoxy group having from 
1 to 10 carbon atoms, a phenyl group, a phenoxy group, a vinyl group, a 
cyano group, an ester group, an amide group and/or a nitro group. 
Preferred Examples of heterocyclic aromatic groups as Ar.sup.1 and Ar.sup.2 
include aromatic groups having at least one hetero atom, such as a 
nitrogen atom, an oxygen atom or a sulfur atom. 
Illustrative examples of divalent carboxylic or heterocyclic aromatic 
groups as Ar.sup.1 and Ar.sup.2 include an unsubstituted or substituted 
phenylene group, an unsubstituted or substituted biphenylene group and an 
unsubstituted or substituted pyridylene group. Substituents for these 
groups are as described above. 
Examples of divalent alkane groups as Y include organic groups respectively 
represented by the following formulae: 
##STR1## 
wherein each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 independently 
represents a hydrogen atom, an alkyl group having from 1 to 10 carbon 
atoms, an alkoxy group having from 1 to 10 carbon atoms, a cycloalkyl 
group having from 5 to 10 ring-forming carbon atoms, a carbocyclic 
aromatic group having from 5 to 10 ring-forming carbon atoms and a 
carbocyclic aralkyl group having from 6 to 10 carbon atoms; k represents 
an integer of from 3 to 11; each X represents a carbon atom and has 
R.sup.5 and R.sup.6 bonded thereto; each R.sup.5 independently represents 
a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms, and 
each R.sup.6 independently represents a hydrogen atom or an alkyl group 
having from 1 to 6 carbon atoms, wherein R.sup.5 and R.sup.6 are the same 
or different; 
wherein at least one hydrogen atom of each of R.sup.1, R.sup.2, R.sup.3, 
R.sup.4, R.sup.5 and R.sup.6 may be substituted with a substituent which 
does not adversely affect the reaction, such as a halogen atom, an alkyl 
group having from 1 to 10 carbon atoms, an alkoxy group having from 1 to 
10 carbon atoms, a phenyl group, a phenoxy group, a vinyl group, a cyano 
group, an ester group, an amide group and/or a nitro group. 
Examples of divalent aromatic groups as Ar include groups respectively 
represented by the following formulae: 
##STR2## 
wherein each of R.sup.7 and R.sup.8 independently represents a hydrogen 
atom, a halogen atom, an alkyl group having from 1 to 10 carbon atoms, an 
alkoxy group having from 1 to 10 carbon atoms, a cycloalkyl group having 
from 5 to 10 ring-forming carbon atoms, or a phenyl group; each of m and n 
independently represents an integer of from 1 to 4, with the proviso that 
when m is an integer of from 2 to 4, R.sup.7 's are the same or different, 
and when n is an integer of from 2 to 4, R.sup.8 's are the same or 
different. 
Further, examples of divalent aromatic groups as Ar also include those 
which are represented by the following formula: 
EQU --Ar.sup.1 --Z--Ar.sup.2 -- 
wherein Ar.sup.1 and Ar.sup.2 are as defined above; and Z represents a 
single bond, or a divalent group, such as --O--, --CO--, --S--, 
--SO.sub.2, --SO--, --COO--, or --CON(R.sup.1)--, wherein R.sup.1 is as 
defined above. 
Examples of such divalent aromatic groups as Ar include groups respectively 
represented by the following formulae: 
##STR3## 
wherein R.sup.7, R.sup.8, m and n are as defined above. 
In the present invention, the aromatic dihydroxy compounds can be used 
individually or in combination. Representative examples of aromatic 
dihydroxy compounds include bisphenol A. It is preferred to use an 
aromatic dihydroxy compound in which the content of a chlorine atom, an 
alkali metal and an alkaline earth metal is low. It is more preferred to 
use an aromatic dihydroxy compound substantially free from a chlorine 
atom, an alkali metal and an alkaline earth metal. 
The carbonic diester used in the present invention is represented by the 
following formula: 
##STR4## 
wherein each of Ar.sup.3 and Ar.sup.4 independently represents a 
monovalent aromatic group. 
In each of Ar.sup.3 and Ar.sup.4, which independently represents a 
monovalent carbocyclic or heterocyclic aromatic group, at least one 
hydrogen atom may be substituted with a substituent which does not 
adversely affect the reaction, such as a halogen atom, an alkyl group 
having from 1 to 10 carbon atoms, an alkoxy group having from 1 to 10 
carbon atoms, a phenyl group, a phenoxy group, a vinyl group, a cyano 
group, an ester group, an amide group or a nitro group. Ar.sup.3 and 
Ar.sup.4 are the same or different. 
Representative examples of monovalent aromatic groups Ar.sup.3 and Ar.sup.4 
include a phenyl group, a naphthyl group, a biphenyl group and a pyridyl 
group. These groups may or may not be substituted with the above-mentioned 
substitutent or substituents. 
Preferred examples of monovalent aromatic groups as Ar.sup.3 and Ar.sup.4 
include those which are respectively represented by the following 
formulae: 
##STR5## 
Representative examples of carbonic diesters include di(unsubstituted or 
substituted)phenyl carbonate compounds represented by the following 
formula: 
##STR6## 
wherein each of R.sup.9 and R.sup.10 independently represents a hydrogen 
atom, an alkyl group having from 1 to 10 carbon atoms, an alkoxy group 
having from 1 to 10 carbon atoms, a cycloalkyl group having from 5 to 10 
ring-forming carbon atoms or a phenyl group; each of p and q independently 
represents an integer of from 1 to 5, with the proviso that when p is an 
integer of 2 or more, R.sup.9 's are the same or different, and when q is 
an integer of from 2 or more, R.sup.10 's are the same or different. 
Of these diphenyl carbonate compounds, preferred are those having a 
symmetrical configuration, such as di(unsubstituted)phenyl carbonate and a 
diphenyl carbonate wherein the phenyl group is substituted with a lower 
alkyl group, e.g., ditolyl carbonate and di-t-butylphenyl carbonate. 
Particularly preferred is diphenyl carbonate which has the simplest 
structure. 
These carbonic diesters may be used individually or in combination. It is 
preferred that these carbonic diesters have a low content of a chlorine 
atom, an alkali metal and an alkaline earth metal. It is most preferred 
that these carbonic diesters are substantially free from a chlorine atom, 
an alkali metal and alkaline earth metal. 
The ratio in which the aromatic dihydroxy compound and the carbonic diester 
are used (i.e., a charging ratio) may vary depending on the types of the 
aromatic dihydroxy compound and carbonic diester employed, the 
polymerization temperature and other polymerization conditions, and the 
desired molecular weight of a polycarbonate to be obtained and the desired 
proportions of the terminal groups in the polycarbonate. The carbonic 
diester is generally used in an amount of from 0.4 to 2.5 moles, 
preferably from 0.5 to 2.0 moles, more preferably from 0.5 to 1.5 moles, 
per mole of the aromatic dihydroxy compound. 
In the present invention, a polycarbonate having terminal hydroxyl groups 
in a proportion of at least 20 mol %, based on the molar total of all 
terminal groups of the polycarbonate, can be produced by controlling the 
above-mentioned charging ratio of the carbonic diester to the aromatic 
dihydroxy compound. 
Further, in the present invention, an aromatic polyhydric hydroxy compound 
or an aromatic monohydroxy compound can be used in combination with the 
above-mentioned aromatic dihydroxy compounds, as long as the effects of 
the present invention are not spoiled. The aromatic polyhydric hydroxy 
compound may be used for introducing a branch structure to the 
polycarbonate. The aromatic monohydroxy compound may be used for 
converting the terminal hydroxyl groups of the polycarbonate into 
different types of terminal groups, or for modifying the molecular weight 
of the polycarbonate. 
In the present invention, the molecular weight of polycarbonate (a) is not 
specifically limited. However, the weight average molecular weight of 
polycarbonate (a) is generally from 1,000 to 300,000, preferably from 
5,000 to 100,000, more preferably from 12,000 to 80,000. 
In the present invention, it is requisite that polycarbonate (a) have 
terminal hydroxyl groups in a proportion of at least 20 mol %, based on 
the molar total of all terminal groups of the polycarbonate. It is 
preferred that polycarbonate (a) have terminal hydroxyl groups in a 
proportion of from 20 to 80 mol %, more preferably from 30 to 70 mol %, 
based on the molar total of all terminal groups of the polycarbonate. When 
the proportion of terminal hydroxyl groups in polycarbonate (a) is smaller 
than the above-mentioned range, the polycarbonate composition suffers 
discoloration during production thereof. The proportion of terminal 
hydroxyl groups in polycarbonate (a) can be determined by nuclear magnetic 
resonance (.sup.1 H-NMR). 
In the polycarbonate composition of the present invention, from the 
viewpoint of achieving improved insusceptibility to discoloration, it is 
preferred that polycarbonate (a) be substantially free of a chlorine atom. 
In the present invention, the term "substantially free of a chlorine atom" 
means that both the following two requirements are satisfied: 
(1) the chlorine atom content must be 0.5 ppm or less, preferably 0.1 ppm 
or less in terms of chlorine ions as measured by potentiometric titration 
using an aqueous 1/500N silver nitrate solution or by ion chromatography 
(0.1 ppm is the detection limit of these measuring methods); and 
(2) the chlorine atom content must be 10 ppm or less as measured by the 
combustion method (10 ppm is the detection limit of this method). 
In the polycarbonate composition of the present invention, it is preferred 
that the amount of at least one metal selected from an alkali metal and an 
alkaline earth metal in the polycarbonate (a) be not more than 800 ppb 
(parts per billion) by weight, based on the weight of polycarbonate (a). 
Examples of alkali metals and alkaline earth metals include lithium, 
sodium, potassium, cesium, magnesium, calcium, strontium and barium. These 
metals which may be contained in the polycarbonate are, for example, 
catalyst residues, impurities originating from raw materials used for 
producing the polycarbonate, and other foreign matters which have entered 
the polycarbonate during the production thereof. When these metals are 
present in the polycarbonate, they are present in the form of, for 
example, ions, salts or complexes with an inorganic compound, salts or 
complexes with an organic compound. In the present invention, the form of 
alkali metals and alkaline earth metals which may be present in the 
polycarbonate is not specifically limited. The measurement of the amount 
of these metals in the polycarbonate composition can be conducted using a 
measuring method in which the polycarbonate is subjected to ashing 
treatment to obtain an ash, and the content of these metals in the 
obtained ash is measured by atomic absorption spectrometry. When the 
amount of the alkali metal and/or the alkaline earth metal is larger than 
the above-mentioned range, the heat resistance and discoloration 
insusceptibility of the polycarbonate composition tend to become low. It 
is more preferred that the amount of the alkali metal and/or alkaline 
earth metal be not more than 400 ppb by weight, more preferably not more 
than 200 ppb by weight. 
In polycarbonate (a) used in the polycarbonate composition of the present 
invention, it is also preferred that not only the amount of metallic 
impurities (e.g. iron) other than the alkali metal and/or alkaline earth 
metal, but also residual monomers, e.g., an aromatic dihydroxy compound, a 
carbonic diester and a residual aromatic monohydroxy compound be as small 
as possible. For example, it is preferred that the amount of the metallic 
impurities other than the alkali metal and/or alkaline earth metal be not 
more than 1 ppm by weight, based on the weight of polycarbonate (a). It is 
preferred that the amount of aromatic dihydroxy compound and carbonic 
diester be not more than 300 ppm by weight, based on the weight of 
polycarbonate (a). It is preferred that the amount of aromatic monohydroxy 
compound be not more than 200 ppm by weight, based on the weight of 
polycarbonate (a). The residual monohydroxy compounds include an aromatic 
monohydroxy compound by-produced in the polycondensation reaction for 
producing the polycarbonate, as well as an aromatic monohydroxy compound 
added to the reaction system as a molecular weight modifier or as an agent 
for forming a desired terminal group. The amount of metallic impurities 
other than the alkali metal and/or alkaline earth metal can be measured by 
the same method as used for measuring the amount of the alkali metal 
and/or alkaline earth metal. The respective amounts of aromatic dihydroxy 
compound, carbonic diester and aromatic monohydroxy compound can be 
measured by high performance liquid chromatography (HPLC) (SCL-6B, 
manufactured and sold by Shimadzu Corporation, Japan). 
Polycarbonate (a) of the polycarbonate composition of the present invention 
is produced from an aromatic dihydroxy compound and a carbonic diester by 
transesterification therebetween. The transesterification is conducted 
while heating in the presence or absence of a catalyst under reduced 
pressure or under an inert gas flow. The mode of the transesterification 
process, the polymerization equipment and the like are not specifically 
limited. 
Examples of reactors employable for performing the transesterification 
reaction include an agitation type reactor vessel, a wiped film type 
reactor, a centrifugal wiped film evaporation type reactor, a surface 
renewal type twin-screw kneading reactor, a twin-screw horizontal 
agitation type reactor, a wall-wetting fall reactor, a free-wall reactor 
having a perforated plate, and a wire-wetting fall reactor having a 
perforated plate and at least one wire. These various types of reactors 
can be used individually or in combination. 
In a wall-wetting fall polymerization using a wall-wetting fall reactor, at 
least one polymerizing material selected from the group consisting of: 
a molten monomer mixture of an aromatic dihydroxy compound and a carbonic 
diester, and 
a molten prepolymer obtained by reacting an aromatic dihydroxy compound 
with a carbonic diester, is fed in a molten state to an upper portion of a 
wall extending downwardly through a wall-wetting fall polymerization 
reaction zone, and allowed to fall along and in contact with the surface 
of the wall, thereby effecting the polymerization during the wall-wetting 
fall thereof. 
In a free-fall polymerization using a free-fall reactor, the same 
polymerizing material as mentioned above is fed in a molten state to a 
feeding zone having a perforated plate and allowed to pass downwardly 
through the perforated plate and fall freely through a free-fall 
polymerization reaction zone, thereby effecting the polymerization during 
the free-fall. 
In a wire-wetting fall polymerization using a wire-wetting fall reactor, 
the same polymerizing material as mentioned above is fed in a molten state 
to a feeding zone having a perforated plate and allowed to pass downwardly 
through the perforated plate and fall along and in contact with a wire 
through a wire-wetting fall polymerization reaction zone, thereby 
effecting polymerization of the polymerizing material during the 
wire-wetting fall thereof. 
The perforated plate to be used in a wire-wetting fall polymerization has 
at least one hole. The feeding zone in the wire-wetting fall reactor 
communicates, through the hole, with a polymerization zone comprising a 
wire-wetting fall polymerization reaction zone. The wire-wetting fall 
polymerization reaction zone has at least one wire in correspondence with 
the hole, and the wire is securely held at one end thereof in an upper end 
portion of the wire-wetting fall polymerization reaction zone and extends 
downwardly through the wire-wetting fall polymerization reaction zone. 
With respect to the positional relationship between the at least one wire 
and the perforated plate, and to the positional relationship between the 
at least one wire and the at least one hole of the perforated plate, there 
is no particular limitation as long as a polymerizing material fed to the 
feeding zone is enabled to pass downwardly through the perforated plate 
and fall along and in contact with the at least one wire toward the lower 
end of the at least one wire. The wire and perforated plate either may be 
or may not be in contact with each other. 
FIGS. 2 to 4 respectively show three examples of manners in which the wire 
is provided in correspondence with the hole of the perforated plate. 
In FIG. 2, the upper end of wire 104 is secured to support rod 123 provided 
above perforated plate 103, and wire 104 extends downwardly through hole 
121 of perforated plate 103. Wire 104 and support rod 123 are secured to 
each other at fixation point 122. It is possible that support rod 123 be 
omitted and the upper end of wire 104 be connected, for example, to the 
upper inner wall surface (not shown) of the wire-wetting fall reactor. 
In FIG. 3, the upper end of wire 104 is secured to the upper 
circumferential edge of hole 121 of perforated plate 103 at fixation point 
122, and wire 104 extends downwardly through hole 121 of perforated plate 
103. 
In FIG. 4, the upper end of wire 104 is secured to the lower surface of 
perforated plate 103 at fixation point 122, and wire 104 extends 
downwardly from the lower surface of perforated plate 103. 
Alternatively, the upper end of wire 104 may be positioned below hole 121 
of perforated plate 103. In such a case, a polymerizing material which has 
passed downwardly through perforated plate 103 may freely fall before 
falling along and in contact with wire 104 toward the lower end of wire 
104. This embodiment (in which a wire-wetting fall is immediately preceded 
by a free fall) is enabled, for example, by a method in which a wire is 
attached to a support rod as shown in FIG. 2, and support rod 123 having 
wire 104 attached thereto is provided not at a position above perforated 
plate 103 as shown in FIG. 2, but at a position below perforated plate 
103. 
Further, the wire-wetting fall polymerization may be followed by a 
free-fall polymerization wherein a wire-wetting fall polymerized product 
is consecutively allowed to fall freely through a free-fall polymerization 
reaction zone after leaving the lower end of the wire, wherein the 
free-fall polymerization reaction zone is provided downstream of and 
contiguously to the wire-wetting fall polymerization reaction zone. 
The transesterification reaction can be performed by either molten-state 
polymerization or solid-state polymerization. Further, for example, the 
transesterification reaction can also be performed by a method in which a 
molten-state transesterification is first conducted to obtain a 
prepolymer, and then the obtained prepolymer is subjected to solid-state 
polymerization under reduced pressure or under an inert gas flow, thereby 
elevating the polymerization degree. 
The temperature for conducting the transesterification is not specifically 
limited; however, the temperature is generally selected in the range of 
from 50.degree. C. to 350.degree. C., preferably from 100.degree. C. to 
300.degree. C. In general, when the transesterification reaction 
temperature is higher than the above-mentioned range, the final 
polycarbonate exhibits marked discoloration and poor thermal stability. In 
general, when the transesterification reaction temperature is lower than 
the above-mentioned range, the reaction rate becomes low, so that the 
reaction becomes impractical. A suitable reaction pressure is selected 
depending on the molecular weight of the polycarbonate in the reaction 
system. When the number average molecular weight of the polycarbonate in 
the reaction system is less than 1,000, a reaction pressure in the range 
of from 50 mmHg to atmospheric pressure is generally employed. When the 
number average molecular weight of the polycarbonate in the reaction 
system is in the range of from 1,000 to 2,000, a reaction pressure in the 
range of from 3 mmHg to 80 mmHg is generally employed. When the number 
average molecular weight of the polycarbonate in the reaction system is 
more than 2,000, a reaction pressure of 10 mmHg or less, preferably 5 mmHg 
or less is generally employed. 
For obtaining the discoloration-insusceptible polycarbonate composition of 
the present invention, it is preferred that the polymerization be 
conducted at a temperature of 280.degree. C. or lower, more preferably 
270.degree. C. or lower. When the polymerization temperature is higher 
than 280.degree. C., the amount of an aromatic monohydroxy compound tends 
to increase. Among the above-mentioned polymerization apparatuses and 
modes of the transesterification, a surface renewal type twin-screw 
kneading reactor, a twin-screw horizontal agitation type reactor, a 
free-fall reactor having a perforated plate, and a wire-wetting fall 
reactor having a perforated plate and at least one wire, and solid state 
polymerization method are preferred because the polymerization can be 
carried out efficiently at a polymerization temperature of 280.degree. C. 
or lower. Especially preferred are a free-fall reactor having a perforated 
plate, and a wire-wetting fall reactor having a perforated plate and at 
least one wire, and solid-state polymerization method. 
The polymerization by the transesterification process may be carried out in 
the absence of a catalyst. However, when it is desired to accelerate the 
polymerization, the polymerization can be effected in the presence of a 
catalyst. The polymerization catalysts which are customarily used in the 
art can be used without particular limitations. Examples of such catalysts 
include hydroxides of an alkali metal and of an alkaline earth metal, such 
as lithium hydroxide, sodium hydroxide, potassium hydroxide and calcium 
hydroxide; alkali metal salts, alkaline earth metal salts and quaternary 
ammonium salts of boron hydride and of aluminum hydride, such as lithium 
aluminum hydride, sodium boron hydride and tetramethyl ammonium boron 
hydride; hydrides of an alkali metal and of an alkaline earth metal, such 
as lithium hydride, sodium hydride and calcium hydride; alkoxides of an 
alkali metal and of an alkaline earth metal, such as lithium methoxide, 
sodium ethoxide and calcium methoxide; aryloxides of an alkali metal and 
of an alkaline earth metal, such as lithium phenoxide, sodium phenoxide, 
magnesium phenoxide, LiO--Ar--OLi wherein Ar represents an aryl group, and 
NaO--Ar--ONa wherein Ar is as defined above; organic acid salts of an 
alkali metal and of an alkaline earth metal, such as lithium acetate, 
calcium acetate and sodium benzoate; zinc compounds, such as zinc oxide, 
zinc acetate and zinc phenoxide; boron compounds, such as boron oxide, 
boric acid, sodium borate, trimethyl borate, tributyl borate, triphenyl 
borate, ammonium borates represented by the formula (R.sup.1 R.sup.2 
R.sup.3 R.sup.4)NB(R.sup.1 R.sup.2 R.sup.3 R.sup.4) wherein R.sup.1, 
R.sup.2, R.sup.3 and R.sup.4 are as defined above, and phosphonium borates 
represented by the formula (R.sup.1 R.sup.2 R.sup.3 R.sup.4)PB(R.sup.1 
R.sup.2 R.sup.3 R.sup.4) wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are 
as defined above; silicon compounds, such as silicon oxide, sodium 
silicate, tetraalkylsilicon, tetraarylsilicon and 
diphenyl-ethylethoxysilicon; germanium compounds, such as germanium oxide, 
germanium tetrachloride, germanium ethoxide and germanium phenoxide; tin 
compounds, such as tin oxide, dialkyltin oxide, dialkyltin carboxylate, 
tin acetate, tin compounds having an alkoxy group or aryloxy group bonded 
to tin, such as ethyltin tributoxide, and organotin compounds; lead 
compounds, such as lead oxide, lead acetate, lead carbonate, basic lead 
carbonate, and alkoxides and aryloxides of lead or organolead; onium 
compounds, such as a quaternary ammonium salt, a quaternary phosphonium 
salt and a quaternary arsonium salt; antimony compounds, such as antimony 
oxide and antimony acetate; manganese compounds, such as manganese 
acetate, manganese carbonate and manganese borate; titanium compounds, 
such as titanium oxide and titanium alkoxides and titanium aryloxides; and 
zirconium compounds, such as zirconium acetate, zirconium oxide, zirconium 
alkoxides, zirconium aryloxides and zirconium acetylacetone. 
These catalysts can be used individually or in combination. The amount of 
the catalyst is generally in the range of from 10.sup.-8 to 1% by weight, 
preferably from 10.sup.-7 to 10.sup.-1 % by weight, based on the weight of 
the aromatic dihydroxy compound used as a raw material. When a catalyst 
comprising an alkali and/or alkaline earth metal is employed and the 
catalyst residue is not removed after the polymerization, it is preferred 
that a catalyst comprising an alkali and/or alkaline earth metal be used 
in an amount such that the polycarbonate produced by the polymerization 
contains at least one metal selected from the alkali metal and alkaline 
earth metal in an amount of not more than 800 ppb by weight, based on the 
weight of the polycarbonate. 
The phenolic antioxidant (b) used as a component of the polycarbonate 
composition of the present invention is represented by the following 
formula (2): 
##STR7## 
wherein each of R.sup.11, R.sup.12 and R.sup.13 independently represents a 
hydrogen atom, a hydroxyl group, an alkoxyl group, or an unsubstituted or 
substituted hydrocarbon residue, with the proviso that at least one of 
R.sup.11, R.sup.12 and R.sup.13 represents an unsubstituted or substituted 
hydrocarbon residue. 
Specific examples of the above-mentioned phenolic antioxidants include 
2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-p-anisole, 
2,6-di-t-butyl-4-ethylphenol, 2,2'-methylene bis(6-t-butyl-p-cresol), 
2,2'-methylene bis(4-ethyl-6-t-butyl-p-phenol), 4,4'-methylene 
bis(6-t-butyl-p-cresol), 4,4'-butylidene bis(6-t-butyl-m-cresol), 
tetrakismethylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate!methane 
, 4,4'-thio bis(6-t-butyl-m-cresol), 
stearyl-.beta.-(3,5-di-t-buty-4-hydroxyphenyl)propionate, 
1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 
1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane and triethylene 
glycolbis3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate!. 
A preferable phenolic antioxidant is represented by the following formula 
(3): 
##STR8## 
wherein R.sup.14 represents a methyl group or a t-butyl group, R.sup.15 
represents a t-butyl group, A represents a C.sub.1 -C.sub.30 hydrocarbon 
residue or a C.sub.1 -C.sub.30 heterocyclic residue having a valence of b, 
a represents an integer of from 1 to 4 and b represent an integer of 1 or 
more. 
Specific examples of the above-mentioned phenolic antioxidants include 
tetrakismethylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate!methane 
, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate and triethylene 
glycol-bis3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate!. Of these, 
octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate is preferable. 
In the present invention, it is requisite that the polycarbonate 
composition comprise the phenolic antioxidant (b) in an amount satisfying 
the following formula (1): 
EQU 20.times.10.sup.5 M.ltoreq.X.ltoreq.20.times.10.sup.5 M+2,100(1) 
wherein X represents the amount of said phenolic antioxidant (ppm by 
weight), based on the weight of said polycarbonate, and M represents the 
amount of said terminal hydroxyl groups (mol/g-polycarbonate). 
The polycarbonate composition comprises the phenolic antioxidant (b) 
preferably in an amount satisfying the following formula (1'), more 
preferably in an amount satisfying the following formula (1"): 
EQU 30.times.10.sup.5 M.ltoreq.X.ltoreq.20.times.10.sup.5 M+1,600(1') 
EQU 35.times.10.sup.5 M.ltoreq.X.ltoreq.20.times.10.sup.5 M+1,200(1") 
wherein X and M are as defined above. 
When the amount of the phenolic antioxidant (b) is below the range defined 
by formula (1), a polycarbonate composition having satisfactory thermal 
stability cannot be obtained. On the other hand, when the amount of the 
phenolic antioxidant (b) is above the range defined by formula (1), it is 
likely that smoke is generated and a mold or roll is smudged during 
molding. 
The polycarbonate composition of the present invention can be produced by 
mixing the polycarbonate (a) with the phenolic antioxidant (b) in the same 
manner as in conventional methods for mixing a polycarbonate with an 
additive. Examples of methods for mixing the polycarbonate (a) with the 
phenolic antioxidant (b) include a method in which (a) and (b) are mixed 
uniformly using a Henschel mixer, a super mixer, a tumbling mixer, a 
ribbon blender or the like, and the resultant mixture is subjected to 
melt-kneading using a single-screw extruder, a twin-screw extruder, a 
Banbury mixer or the like; and a method in which (a) and (b) are mixed or 
kneaded in a molten state using a mixing tank, a static mixer, a 
single-screw, twin-screw or multi-screw extruder or the like. With respect 
to the temperature of the mixing or kneading in the above-mentioned 
method, there is no particular limitation, but the mixing or kneading is 
generally conducted at from 240.degree. to 350.degree. C. 
Thermal stabilizers and antioxidants other than the above-mentioned 
phenolic antioxidant may also be mixed in addition to the phenolic 
antioxidant. Further, the polycarbonate composition of the present 
invention may be mixed with additives other than thermal stabilizers and 
antioxidants, depending on the use of the final product of polycarbonate 
composition of the present invention. Examples of such additives include a 
weathering stabilizer, a mold release agent, a lubricant, an antistatic 
agent, a plasticizer, a polymer, such as a resin other than a 
polycarbonate or an elastomer, a pigment, a dye, a filler, a reinforcing 
agent, and a flame retardant. These additives can be used individually or 
in combination. It is preferred that a phosphorus stabilizer be mixed in 
addition to the phenolic antioxidant. 
Examples of phosphorus stabilizers include phos-phorus-containing acids, 
phosphorous esters, phosphinic esters, phosphoric esters and phosphonic 
esters. Representative examples of phosphorus-containing acids include 
phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric 
acid, polyphosphoric acid, phosphinic acids represented by the following 
formula (4): 
##STR9## 
and phosphonic acids represented by the following formula (5): 
##STR10## 
wherein each of R.sup.16 and R.sup.17 independently represents an alkyl 
group, such as an ethyl group, a butyl group, an octyl group, a cyclohexyl 
group, a 2-ethylhexyl group, a decyl group, a tridecyl group, a lauryl 
group, a pentaerythritol group and a stearyl group; an aryl group, such as 
a phenyl group and a naphthyl group; or an alkylaryl group, such as a 
tolyl group, a p-t-butylphenyl group, a 2,4-di-t-butylphenyl group, a 
2,6-di-t-butylphenyl group, a paranonylphenyl group and a dinonylphenyl 
group. 
More specific examples of phosphinic acids include phenylphosphonic acid. 
Examples of phosphorous esters include a phosphorous triester, a 
phosphorous diester and a phosphorous monoester which are, respectively, 
represented by the following formulae (6) to (9): 
##STR11## 
wherein each of R.sup.18, R.sup.19, R.sup.20, R.sup.21, R.sup.22, 
R.sup.24, R.sup.25, R.sup.26, R.sup.27, R.sup.28 and R.sup.29 
independently represents a hydrogen atom; an alkyl group, such as an ethyl 
group, a butyl group, an octyl group, a cyclohexyl group, a 2-ethylhexyl 
group, a decyl group, a tridecyl group, a lauryl group, a pentaerythritol 
group and a stearyl group; an aryl group, such as a phenyl group and a 
naphthyl group; or an alkylaryl group, such as a tolyl group, a 
p-t-butylphenyl group, a 2,4-di-t-butylphenyl group, a 
2,6-di-t-butylphenyl group, a paranonylphenyl group and a dinonylphenyl 
group; and each of R.sup.23 and R.sup.30 independently represents 
alkylene, allylene or arylalkylene. 
Specific examples of phosphorous triesters include 
tris(2,4-di-t-butylphenyl) phosphite, tris(nonylphenyl) phosphite, 
tris(dinonylphenyl) phosphite, triphenyl phosphite, tetraphenyldipropylene 
glycol phosphite, tetra(tridecyl)4,4'-isopropylidene diphenyl diphosphite, 
bis(tridecyl)pentaerythritol diphosphite, bis(nonylphenyl)pentaerythritol 
diphosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, 
bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, distearyl 
pentaerythritol diphosphite, a hydrogenated bisphenol A pentaerythritol 
phosphite polymer and tetraphenyltetra(tridecyl)pentaerythritol 
tetraphosphite. 
Specific examples of phosphorous diesters include diphenyl hydrogen 
phosphite, bis(nonylphenyl) hydrogen phosphite, bis(2,4-di-t-butylphenyl) 
hydrogen phosphite, dicresyl hydrogen phosphite, bis(p-t-butylphenyl) 
hydrogen phosphite and bis(p-hexylphenyl) hydrogen phosphite. 
Specific examples of phosphorous monoesters include phenyl dihydrogen 
phosphite, nonylphenyl dihydrogen phosphite and 2,4-di-t-butylphenyl 
dihydrogen phosphite. 
Examples of phosphinic esters include phosphinic monoesters and phosphinic 
diesters represented by the following formulae (10) and (11): 
##STR12## 
wherein R.sup.31 represents an alkyl group, such as an ethyl group, a 
butyl group., an octyl group, a cyclohexyl group, a 2-ethylhexyl group, a 
decyl group, a tridecyl group, a lauryl group, a pentaerythritol group and 
a stearyl group; an aryl group, such as a phenyl group and a naphthyl 
group; or an alkylaryl group, such as a tolyl group, a p-t-butylphenyl 
group, a 2,4-di-t-butylphenyl group, a 2,6-di-t-butylphenyl group, a 
paranonylphenyl group and a dinonylphenyl group; and each of R.sup.32, 
R.sup.33, R.sup.34, R.sup.35, R.sup.37 and R.sup.38 independently 
represents a hydrogen atom; an alkyl group, such as an ethyl group, a 
butyl group, an octyl group, a cyclohexyl group, a 2-ethylhexyl group, a 
decyl group, a tridecyl group, a lauryl group, a pentaerythritol group and 
a stearyl group; an aryl group, such as a phenyl group and a naphthyl 
group; or an alkylaryl group, such as a tolyl group, a p-t-butylphenyl 
group, a 2,4-di-tbutylphenyl group, a 2,6-di-t-butylphenyl group, a 
paranonylphenyl group and a dinonylphenyl group; and R.sup.36 represents 
alkylene, allylene or arylalkylene. 
A representative example of these compounds is 
tetrakis(2,4-di-t-butylphenyl) 4,4'-biphenylene diphosphinate. 
Examples of phosphoric esters include a phosphoric diester and a phosphoric 
monoester, which are represented by the following formulae (12) to (15): 
##STR13## 
wherein R.sup.19, R.sup.20, R.sup.22, R.sup.23, R.sup.24, R.sup.25, 
R.sup.27, R.sup.29 and R.sup.30 are as defined above. 
Specific examples of phosphoric diesters include diphenylhydrogen 
phosphate, bis(nonylphenyl) hydrogen phosphate, bis(2,4-di-t-butylphenyl) 
hydrogen phosphate, dicresyl hydrogen phosphate, bis(p-t-butylphenyl) 
hydrogen phosphate and bis(p-hexylphenyl) hydrogen phosphate. 
Specific examples of phosphoric monoesters include phenyl dihydrogen 
phosphate, nonylphenyl dihydrogen phosphate and 2,4-di-t-butylphenyl 
dihydrogen phosphate. 
Examples of phosphonic esters include phosphonic monoester represented by 
the following formulae (16) and (17): 
##STR14## 
wherein R.sup.31, R.sup.33, R.sup.35, R.sup.36, R.sup.37 and R.sup.38 are 
as defined above. 
Among these phosphorous stabilizers, phosphorous esters are especially 
preferred. The amount of stabilizer used is generally selected in the 
range of from 5 to 3000 ppm, relative to the amount of the polycarbonate. 
The polycarbonate composition of the present invention can be 
advantageously used in various fields where polycarbonates have 
conventionally been used. For example, the polycarbonate composition of 
the present invention can be advantageously used in the fields of glazing 
appliances, electric and electronic appliances, automobiles, appliances 
for food, miscellaneous goods and polymer alloys. 
BEST MODE FOR CARRYING OUT THE INVENTION 
Hereinbelow, the present invention will be described in more detail with 
reference to the following Examples and Comparative Examples, but they 
should not be construed as limiting the scope of the present invention. 
In the following Examples and Comparative Examples, various properties were 
measured as follows. 
(1) Measurement of the number average molecular weight and weight average 
molecular weight of a polycarbonate: 
The number average molecular weight and weight average molecular weight of 
a polycarbonate were measured by gel permeation chromatography (GPC) 
(column: polystyrene gel; and solvent: THF). 
(2) Determination of the proportion of terminal hydroxyl groups in all 
terminal groups of a polycarbonate, and the amount of terminal hydroxyl 
groups in a polycarbonate: 
The proportion of terminal hydroxyl groups in all terminal groups (mol %) 
of a polycarbonate was determined by .sup.1 H-NMR. The amount of the 
terminal hydroxyl groups in the polycarbonate (mol/g-polycarbonate) was 
obtained from the proportion of terminal hydroxyl groups and the number 
average molecular weight of the polycarbonate by calculation. 
(3) Measurement of the content of an alkali metal and/or an alkaline earth 
metal in a polycarbonate: 
A polycarbonate was subjected to cold ashing treatment using PLASMA ASHER 
(LTA-102, manufactured and sold by YANAGIMOTO MFG. CO., LTD., Japan) and 
the content of an alkali metal and/or an alkaline earth metal in the 
treated polycarbonate was measured using Flameless Atomic Absorption 
Spectrophotometer (Z-9000, manufactured and sold by Hitachi Ltd., Japan). 
(4) Evaluation of the color of a polycarbonate composition: 
A polycarbonate composition was subjected to molding, by means of an 
injection molding machine (J100E, manufactured and sold by THE JAPAN STEEL 
WORKS. LTD., Japan), at a cylinder temperature of 290.degree. C. and a 
mold temperature of 90.degree. C. to obtain a test specimen having a 50 mm 
length, a 50 mm width and a 3.2 mm thickness. The color of the 
polycarbonate composition was evaluated, using the specimen, in accordance 
with the CIELAB method (Comission Internationale de 1'E-clairage 1976 
L*a*b* Diagram), and the yellowness of the specimen is expressed in terms 
of the b*-value. The larger the b*-value of the specimen, the higher the 
yellowness of the specimen. 
(5) Evaluation of the thermal stability of a polycarbonate composition: 
The yellowness (in terms of b*-value) of a specimen of a polycarbonate 
composition was determined. The specimen was manufactured in the same 
manner as in item (4) above. Then, the specimen was heated at 140.degree. 
C. in a Geer oven for 300 hours, and the yellowness of the heated specimen 
was determined. The difference in yellowness (which difference is 
expressed in terms of the .DELTA.b*-value) between the unheated specimen 
and the heated specimen was taken as an index of the thermal stability of 
the specimen. The smaller the .DELTA.b*-value of the specimen, the higher 
the thermal stability of the specimen. 
EXAMPLE 1 
A polycarbonate was produced by melt transesterification in accordance with 
the system as shown in FIG. 1. The system of FIG. 1 comprises a first 
stage and a second stage agitation polymerization, and a first stage and a 
second stage wire-wetting fall polymerization. 
In the first stage wire-wetting fall polymerization, first wire-wetting 
fall polymerizer 110A was used. In the second stage wire-wetting fall 
polymerization, second wire-wetting fall polymerizer 110B was used. Each 
of the first and second wire-wetting fall polymerizers is equipped with a 
perforated plate which has 50 holes having a diameter of 7.5 mm and 
arranged in a zigzag configuration. In each of the first and second 
wire-wetting fall polymerizers, 50 strands of 1 mm.phi. SUS 316 L wires 
are hung vertically from the respective holes of the perforated plate to a 
reservoir portion at the bottom of the wire-wetting fall polymerizer 110 
so that a polymerizing material will not fall freely (i.e., not free-fall) 
but fall along and in contact with the wires (i.e., wire-wetting fall). 
Illustratively stated, as shown in FIG. 2, each wire 104 is secured at the 
upper end thereof to support rod 123 provided above perforated plate 103, 
and extends downwardly through hole 121 of perforated plate 103. In each 
of the first and second wire-wetting fall polymerizers, the wire-wetting 
fall distance is 4 m. Only first wire-wetting fall polymerizer 110A has a 
recirculation line. 
The first stage agitation polymerization was batchwise conducted in first 
agitation type polymerizer vessels 3A and 3B, each having a capacity of 
100 liters, whereas the second stage agitation polymerization in second 
agitation type polymerizer vessel 3C, having a capacity of 50 liters, and 
the first stage and second stage wire-wetting fall polymerizations in 
first and second wire-wetting fall polymerizers 110A and 110B, were 
continuously conducted. 
The polymerization reaction conditions in both of first agitation type 
polymerizer vessels 3A and 3B were as follows: the reaction temperature 
was 180.degree. C., the reaction pressure was atmospheric pressure, and 
the flow rate of nitrogen gas was 1 liter/hr. 
In operation, polymerizing materials a monomer mixture of bisphenol A and 
diphenyl carbonate (each being substantially free of a chlorine atom) in a 
molar ratio of 1:1.05 and, as a catalyst, a disodium salt of bisphenol A 
(molar ratio of disodium salt of bisphenol A to bisphenol A in the monomer 
mixture was 2.8.times.10.sup.-8 :1)! were charged into each of first 
agitation type polymerizer vessels 3A and 3B. The monomer mixture in 
polymerizer 3A was polymerized in a molten state while agitating for 5 
hours to obtain prepolymer 4A. Outlet 5A was opened, and prepolymer 4A was 
fed to second agitation type polymerizer vessel 3C, having a capacity of 
50 liters, at a flow rate of 5 liters/hr. 
While feeding prepolymer 4A obtained in first agitation type polymerizer 
vessel 3A to second agitation type polymerizer vessel 3C, first agitation 
type polymerizer vessel 3B was operated to polymerize the monomer mixture 
of bisphenol A and diphenyl carbonate in the same manner as in the 
agitation polymerization in first agitation type polymerizer vessel 3A, to 
obtain prepolymer 4B. 
When first agitation type polymerizer vessel 3A became empty, outlet 5A of 
polymerizer 3A was closed and, instead, outlet 5B of polymerizer 3B was 
opened, so that prepolymer 4B was fed from first agitation type 
polymerizer vessel 3B to second agitation type polymerizer vessel 3C at a 
flow rate of 5 liters/hr. In this instance, the same polymerizing 
materials as mentioned above were charged in polymerizer 3A. While feeding 
prepolymer 4B obtained in first agitation type polymerizer vessel 3B to 
second agitation type polymerizer vessel 3C, polymerizer vessel 3A was 
operated, so that the monomer mixture charged therein was polymerized in 
the same manner as mentioned above. 
With respect to a batchwise polymerization in first agitation type 
polymerizer vessels 3A and 3B and to the alternate feedings of prepolymers 
4A and 4B from polymerizers 3A and 3B to second agitation type polymerizer 
vessel 3C, the same operation as mentioned above was repeated, so that the 
prepolymer (either prepolymer 4A or prepolymer 4B, alternately) was 
continuously fed to second agitation type polymerizer vessel 3C. 
In second agitation type polymerizer vessel 3C, a further agitation 
polymerization of prepolymers 4A and 4B, alternately fed from first 
agitation type polymerizer vessels 3A and 3B, was continuously carried out 
under polymerization reaction conditions wherein the reaction temperature 
was 245.degree. C., the reaction pressure was 70 mmHg and the flow rate of 
nitrogen gas was 2 liters/hr, thereby obtaining prepolymer 4C. 
When the volume of prepolymer 4C in second agitation type polymerizer 
vessel 3C reached 25 liters, part of prepolymer 4C was continuously fed to 
first wire-wetting fall polymerizer 110A so that the volume of prepolymer 
4C in second agitation type polymerizer vessel 3C was constantly 
maintained at 25 liters. The feeding of prepolymer 4C to first 
wire-wetting fall polymerizer 110A was conducted through inlet 101A 
provided in recirculation line 102A for polymerizer 110A. 
In first wire-wetting fall polymerizer 110A, a wire-wetting fall 
polymerization of prepolymer 4C was continuously carried out under 
polymerization reaction conditions wherein the reaction temperature was 
250.degree. C., and the reaction pressure was 1.5 mmHg and the flow rate 
of nitrogen gas was 1 liter/hr, thereby obtaining prepolymer 111A, while 
recirculating a part of obtained prepolymer 111A to the feeding zone 
(having perforated plate 103A) of first wire-wetting fall polymerizer 110A 
through recirculation line 102A at a recirculation rate of 200 liters/hr. 
When the volume of prepolymer 111A at the bottom of first wire-wetting fall 
polymerizer 110A reached 10 liters, part of prepolymer 111A was 
continuously fed to second wire-wetting fall polymerizer 110B so that the 
volume of prepolymer 111A in first wire-wetting fall polymerizer 110A was 
constantly maintained at 10 liters. 
In second wire-wetting fall polymerizer 110B, a wire-wetting fall 
polymerization reaction was continuously carried out under polymerization 
reaction conditions wherein the reaction temperature was 250.degree. C., 
and the reaction pressure was 0.6 mmHg and the flow rate of nitrogen gas 
was 1 liter/hr, thereby obtaining polycarbonate composition 111B. 
When the volume of polycarbonate composition 111B at the bottom of second 
wire-wetting fall polymerizer 110B reached 10 liters, polycarbonate 
composition 111B was continuously withdrawn from second wire-wetting fall 
polymerizer 110B through outlet 109B by means of discharge pump 108B so 
that the volume of polycarbonate composition 111B in second wire-wetting 
fall polymerizer 110B was constantly maintained at 10 liters. 
The above-mentioned series of polymerization reactions was continuously 
carried out for 700 hours. 
The polycarbonate was substantially free of a chlorine atom, and had 
terminal hydroxyl groups in a proportion of 48 mol %, based on the molar 
total of all terminal groups of the polycarbonate, and a weight average 
molecular weight of 25,100. The amount of terminal hydroxyl groups 
contained in the polycarbonate was 9.6.times.10.sup.-5 
(mol/g-polycarbonate). Further, in the polycarbonate, the content of 
sodium (alkali metal) was 5 ppb by weight. 
The above-obtained polycarbonate was blended with 1,000 ppm of 
octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate as a phenolic 
antioxidant to thereby obtain a polycarbonate composition. 
With respect to the obtained polycarbonate composition, the color and 
thermal stability were evaluated by the above-mentioned methods. Results 
are shown in Table 1. 
EXAMPLES 2 AND 3, AND COMATIVE EXAMPLES 1 TO 3 
The production of a polycarbonate composition and the evaluation of the 
obtained polycarbonate compositions were conducted in substantially the 
same manner as in Example 1, except that the amount of the phenolic 
antioxidant was 0 ppm (Comparative Example 1), 150 ppm (Comparative 
Example 2), 500 ppm (Example 2), 1,200 ppm (Example 3) or 3,000 ppm 
(Comparative Example 3). Results are shown in Table 1. Further, in 
Comparative Example 3, vigorous occurrence of mold smudge was observed. 
EXAMPLE 4 
The polymerization reaction was conducted in substantially the same manner 
as in Example 1, except that the diphenyl carbonate was used in an amount 
such that the molar ratio of bisphenol A to diphenyl carbonate became 
1:1.10. The obtained polycarbonate had terminal hydroxyl groups in a 
proportion of 23 mol %, based on the molar total of all terminal groups of 
the polycarbonate, and a weight average molecular weight of 24800. The 
amount of terminal hydroxyl groups contained in the polycarbonate was 
4.6.times.10.sup.-5 (mol/g-polycarbonate). The obtained polycarbonate was 
blended with 150 ppm of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) 
propionate as a phenolic antioxidant to thereby obtain a polycarbonate 
composition. With respect to the obtained polycarbonate composition, the 
color and thermal stability were evaluated by the above-mentioned methods. 
Results are shown in Table 1. 
EXAMPLE 5 
The polymerization reaction was conducted in substantially the same manner 
as in Example 1, except that the diphenyl carbonate was used in an amount 
such that the molar ratio of bisphenol A to diphenyl carbonate became 
1:0.90. The obtained polycarbonate had terminal hydroxyl Groups in a 
proportion of 72 mol %, based on the molar total of all terminal Groups of 
the polycarbonate, and a weight average molecular weight of 25300. The 
amount of terminal hydroxyl Groups contained in the polycarbonate was 
14.3.times.10.sup.-5 (mol/g-polycarbonate). The obtained polycarbonate was 
blended with 1000 ppm of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) 
propionate as a phenolic antioxidant to thereby obtain a polycarbonate 
composition. With respect to the obtained polycarbonate composition, the 
color and thermal stability were evaluated by the above-mentioned methods. 
Results are shown in Table 1. 
COMATIVE EXAMPLE 4 
35 kg of polymerizing materials monomer mixture of bisphenol A and 
diphenyl carbonate in a molar ratio of 1:1.20 and, as a catalyst, a 
disodium salt of bisphenol A (molar ratio of disodium salt of bisphenol A 
to bisphenol A in the monomer mixture was 2.8.times.10.sup.-8 :1)! were 
charged into an agitation type polymerizer vessel and were molten at 
180.degree. C. under atmospheric pressure. After the agitation at 
180.degree. C. for 2 hours under atmospheric pressure, the temperature of 
the polymerizer vessel was gradually elevated and the pressure in the 
vessel was gradually reduced as follows, to thereby advance the 
polymerization. The reaction mixture was held while agitating, first, at 
240.degree. C. under 15 mmHg for 1 hour, second, at 260.degree. C. under 5 
mmHg for 3 hours, and finally, at 280.degree. C. under 0.1 mmHg for 5 
hours. 
The obtained polycarbonate had terminal hydroxyl groups in a proportion of 
4 mol %, based on the molar total of all terminal groups of the 
polycarbonate, and a weight average molecular weight of 24,800. The amount 
of terminal hydroxyl groups contained in the polycarbonate was 
0.8.times.10.sup.-5 (mol/g-polycarbonate). 
The above-obtained polycarbonate was blended with 500 ppm of 
octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate as a phenolic 
antioxidant to thereby obtain a polycarbonate composition. 
With respect to the obtained polycarbonate composition, the color and 
thermal stability were evaluated by the above-mentioned methods. Results 
are shown in Table 1. 
COMATIVE EXAMPLE 5 
The production of a polycarbonate composition and the evaluation of the 
properties thereof were conducted in the same manner as in Example 1, 
except that 1000 ppm of tris(nonylphenyl) phosphite, which is widely used 
as a thermal stabilizer for a polycarbonate, was blended with the 
polycarbonate in place of the phenolic antioxidant. Results are shown in 
Table 1. 
TABLE 1 
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Color 
Thermal stability 
(b*) (.DELTA.b*) 
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Example 1 3.3 2.8 
Example 2 3.5 3.3 
Example 3 3.3 2.6 
Comparative 3.3 16.9 
Example 1 
Comparative 3.3 13.1 
Example 2 
Comparative 3.6 2.5 
Example 3 
Example 4 3.8 3.6 
Example 5 3.4 3.1 
Comparative 5.2 4.0 
Example 4 
Comparative 3.5 16.8 
Example 5 
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INDUSTRIAL APPLICABILITY 
The polycarbonate composition of the present invention has an advantage in 
that it is insusceptible to discoloration not only during production 
thereof and molding of the composition, but also when a molded article 
produced from the composition experiences high temperature atomosphere. 
Accordingly, the polycarbonate composition of the present invention can be 
advantageously used in various fields where polycarbonates have 
conventionally been used as materials for appliances, for example, as a 
material for glazing appliances, electric and electronic appliances, 
automobile appliances, appliances for food, miscellaneous goods and 
polymer alloys.