Branched halogenated polycarbonate having trihalo phenoxy end groups

This is a branched polycarbonate which comprises a branched structure derived from a branching agent such as 1,1,1-tris(4-hydroxyphenyl)ethane, a repeating unit (I) represented by the following general formula: ##STR1## a repeating unit (II) represented by the following general formula: ##STR2## and a tribromophenoxy group bonded to the terminal thereof, said branched polycarbonate having a viscosity average molecular weight of 10,000 to 50,000, a ratio of said branched structure of 0.1 to 2.0 mol % and a content of said repeating unit (II) of 10 mol % or less. This branched polycarbonate is excellent in flame retardancy, has sufficiently high mechanical properties and further is excellent in melt properties suitable for blow molding.

TECHNICAL FIELD 
The present invention relates to a novel branched polycarbonate and more 
specifically to a novel branched polycarbonate having excellent flame 
retardancy, mechanical strength and melt properties suitable for blow 
molding. 
BACKGROUND ART 
Conventionally, there have been known halogen-containing, flame retardant 
copolymerized polycarbonates disclosed in Japanese Patent Publication Nos. 
40715/1971 and 24660/1972 and Japanese Patent Application Laid-Open Nos. 
123294/1976, 136796/1976, 140597/1977, 50065/1979, 99226/1981 and the 
like. However, these polycarbonates have been found not to have 
satisfactory properties for an industrial use, with respect to flame 
retardancy, mechanical strength and melt properties suitable for blow 
molding. 
It has been known that branched polycarbonates with the improved flame 
retardancy are provided according to a method in which alkali metal salts 
of inorganic mineral acid, organic carboxylic aid or sulfonic acid are 
added thereto (as disclosed in Japanese Patent Publication No. 51497/1985) 
and a method in which flame retardant monomers, for example 
tetrabromobisphenol A, are copolymerized therewith (as disclosed in 
Japanese Patent Publication No. 12132/1980). However, the mechanical 
strength achieved by the former method has not been sufficiently high 
because of the contamination associated with the additives, while that of 
the latter method has been improved due to a branching agent contained 
therein but still not good enough for use in the industrial production. 
Thus, the present inventors have made extensive studies with a view to 
developing a novel polycarbonate which is excellent in flame retardancy, 
mechanical properties and melt properties suitable for blow molding. 
DISCLOSURE OF INVENTION 
As the result, it has been found that above problems can find a solution 
with a new polycarbonate in a branched shape, having a branched structure 
derived from a specific branching agent and further a trihalogenophenoxy 
group situated at the terminal thereof. The present invention has been 
completed based on this finding. Therefore, the present invention provides 
a branched polycarbonate which comprises a branched structure derived from 
a branching agent represented by the following general formula (A): 
##STR3## 
wherein R is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms 
and R.sup.1 to R.sup.6 each are a hydrogen atom, an alkyl group having 1 
to 5 carbon atoms or a halogen atom, a repeating unit (I) represented by 
the following general formula: 
##STR4## 
a repeating unit (II) represented by the following general formula: 
##STR5## 
wherein X.sup.1 to X.sup.4 each are a halogen atom and a 
trihalogenophenoxy group represented by the following general formula 
(III): 
##STR6## 
wherein X.sup.5 to X.sup.7 each are a halogen atom, as bonded to the 
terminal thereof, said branched polycarbonate having a viscosity average 
molecular weight of 10,000 to 50,000, a ratio of said branched structure 
of 0.1 to 2.0 mol % and a content of said repeating unit (II) of 10 mol % 
or less.

BEST MODE FOR CARRYING OUT THE INVENTION 
As stated above, a branched polycarbonate of the present invention 
comprises a branched structure derived from a branching agent represented 
by the following general formula (A): 
##STR7## 
In this general formula, R is a hydrogen atom or an alkyl group having 1 
to 5 carbon atoms, for example a methyl group, an ethyl group, a n-propyl 
group, a n-butyl group, a n-pentyl group and the like. R.sup.1 to R.sup.6 
each are a hydrogen atom, an alkyl group having 1 to 5 carbon atoms (for 
example, methyl group, ethyl group, n-propyl group, n-butyl group, 
n-pentyl group and the like) or a halogen atom (for example, chlorine 
atom, bromine atom, fluorine atom and the like). Specific examples of the 
branching agent represented by the general formula (A) include 
1,1,1-tris(4-hydroxyphenyl)methane; 1,1,1-tris(4-hydroxyphenyl)ethane; 
1,1,1-tris(4-hydroxyphenyl)propane; 
1,1,1-tris(2-methyl-4-hydroxyphenyl)methane; 
1,1,1-tris(2-methyl-4-hydroxyphenyl)ethane; 
1,1,1-tris(3-methyl-4-hydroxyphenyl)methane; 
1,1,1-tris(3-methyl-4-hydroxyphenyl)ethane; 
1,1,1-tris(3,5-dimethyl-4-hydroxyphenyl)methane; 
1,1,1-tris(3,5-dimethyl-4-hydroxyphenyl)ethane; 
1,1,1-tris(3-chloro-4-hydroxyphenyl)methane; 
1,1,1-tris(3-chloro-4-hydroxyphenyl)ethane; 
1,1,1-tris(3,5-dichloro-4-hydroxyphenyl)methane; 
1,1,1-tris(3,5-dichloro-4-hydroxyphenyl)ethane; 
1,1,1-tris(3-bromo-4-hydroxyphenyl)methane; 
1,1,1-tris(3-bromo-4-hydroxyphenyl)ethane; 
1,1,1-tris(3,5-dibromo-4-hydroxyphenyl)methane; 
1,1,1-tris(3,5-dibromo-4-hydroxyphenyl)ethane and the like. 
The branched polycarbonate of the present invention has the branched 
structure derived from said branching agents and specific examples thereof 
are those represented by the following general formula: 
##STR8## 
wherein m, n and o are integers, PC is a polycarbonate part and R and 
R.sup.1 to R.sup.6 are the same as described above. 
The ratio of the branched structure (the ratio of the branched nucleus) is 
0.1 to 2.0 mol %, preferably 0.2 to 1.0 mol % based on the whole 
polycarbonate. If the ratio is more than 2.0 mol %, the branched 
polycarbonate is liable to gelate and, if less than 0.1 mol %, it is poor 
in blow moldability. 
The branched polycarbonate of the present invention comprises a repeating 
unit represented by the general formula (I) and a repeating unit 
represented by the general formula (II). With respect to the general 
formula (II), X.sup.1 to X.sup.4 each are a halogen atom such as bromine, 
chlorine and fluorine. These X.sup.1 to X.sup.4 may be the same or 
different but ordinarily they often are the same. 
Furthermore, a trihalogenophenoxy group represented by the general formula 
(II) is bonded to the terminal, particularly to all terminals of the 
branched polycarbonate of the present invention. In the general formula 
(III), X.sup.5 to X.sup.7 each are a halogen atom such as bromine, 
chlorine and fluorine, as in the case of said X.sup.1 to X.sup.4. 
Meanwhile, X.sup.1 to X.sup.4 of said repeating unit represented by the 
general formula (II) and X.sup.5 to X.sup.7 of the general formula (III) 
may be the same or different. 
With respect to the molar fractions of the repeating units (I) and (II) in 
the branched polycarbonate of the present invention, it is important that 
said branched polycarbonate should have a content of the repeating unit 
(II) of 10 mol % or less, preferably 1 to 6 mol %. The branched 
polycarbonate is liable to have a low mechanical strength if it has the 
content of repeating unit (II) of more than 10 mol %. 
Furthermore, with respect to the polymerization degree of the branched 
polycarbonate of the present invention, it is appropriate that said 
polycarbonate should have a viscosity average molecular weight in a range 
of 10,000 to 50,000, preferably 15,000 to 40,000. The branched 
polycarbonate cannot have a sufficiently high mechanical strength such as 
impact resistance if it has a viscosity average molecular weight of less 
than 10,000 and is poor in moldability if more than 50,000. 
The branched polycarbonate of the present invention occurs as various forms 
of polymer such as random copolymer, block copolymer and alternating 
copolymer having a structure comprising said repeating units (I) and (II) 
and a trihalogenophenoxy group represented by the general formula (III) as 
bonded to terminal thereof. 
Meanwhile, it does not matter even if a small amount of other repeating 
units than (I) and (II) is mixed into the molecular chain of this branched 
polycarbonate. Such other repeating units are made from a third comonomer, 
for example bisphenolsulfone (BPS), thiobisphenol (TDP) and the like. The 
content (molar fraction) of these other repeating units is preferably 0 to 
20 mol %, more preferably 0 to 10 mol % based on the polycarbonate as the 
whole. If the content of these other repeating units is more than 20 mol 
%, the branched polycarbonate is liable to have a low mechanical strength 
undesirably. 
The branched polycarbonate of the present invention can be manufactured 
according to various methods. Preferred examples of the manufacturing 
method include the following two. 
In the first method of these two, the following materials are mixed and 
stirred in a predetermined amount and ratio: an alkaline aqueous solution 
of branching agent represented by the general formula (A); an alkaline 
aqueous solution (sodium hydroxide aqueous solution, potassium hydroxide 
aqueous solution, sodium carbonate aqueous solution and the like) of 
tetrahalogenobisphenol A (THA) (tetrabromobisphenol A, 
tetrachlorobisphenol A, tetrafluorobisphenol A and the like) which is the 
starting material of the repeating unit represented by the general formula 
(II); an alkaline aqueous solution of bisphenol A (BPA) which is the 
starting material of the repeating unit represented by the general formula 
(I) and an alkaline aqueous solution of trihalogenophenol (THP) 
(tribromophenol, trichlorophenol, trifluorophenol and the like) 
represented by the general formula (III); along with a solvent such as 
methylene chloride, chlorobenzene, pyridine, chloroform and carbon 
tetrachloride and a catalyst such as tertiary amine (triethylamine, 
trimethylamine and the like) or quaternary ammonium salt 
(trimethylbenzylammonium chloride and the like). Phosgene is then blown 
into the mixture to form a polycarbonate oligomer. The reaction 
temperature is not particularly limited but ordinarily in a range of 
0.degree. to 50.degree. C., preferably 5.degree. to 40.degree. C. The 
operating time is properly chosen in a range of 10 minutes to 3 hours. The 
reaction system is exothermic, preferably cooled with water or ice. 
Meanwhile, monohydric phenol such as p-tert-butylphenol or phenol can be 
used in combination herein by replacing a part (50 mol % or less) of 
trihalogenophenol. 
Next, BPA, said solvent, said alkaline aqueous solution and catalyst are 
added to the obtained polycarbonate oligomer solution, they are stirred 
and the reaction is continued to perform the interfacial polycondensation. 
A phase containing the reaction product is washed and subjected to the 
purifying treatment to obtain the desired branched polycarbonate. The 
reaction temperature is not particularly limited but ordinarily in a range 
of 0.degree. to 50.degree. C., preferably 5.degree. to 40.degree. C. The 
operating time is properly chosen in a range of 10 minutes to 6 hours. 
According to the second manufacturing method, BPA, said solvent and said 
alkaline aqueous solution are mixed and stirred and phosgene is blown into 
the mixture to form a polycarbonate oligomer. The reaction temperature is 
not particularly limited but ordinarily in a range of 0.degree. to 
50.degree. C., preferably 5.degree. to 40.degree. C. The operating time is 
in a range of 10 minutes to 3 hours. The reaction system is exothermic, 
preferably cooled with water or ice. 
Next, said branching agent, said THA and THP and said alkaline aqueous 
solution and catalyst are added to the so obtained polycarbonate oligomer 
solution, they are stirred and the reaction is continued to perform the 
interfacial polycondensation (pre-condensation) (the reaction temperature 
ordinarily is in a range of 0.degree. to 50.degree. C., preferably 
5.degree. to 40.degree. C. and the operating time is properly chosen in a 
range of 10 minutes to 3 hours). After the reaction, BPA, said alkaline 
aqueous solution and solvent are incorporated into the reaction system and 
they are reacted again. This step requires different reaction temperatures 
depending circumstances, but ordinarily the reaction temperature is in a 
range of 0.degree. to 50.degree. C., preferably 5.degree. to 40.degree. C. 
and the operating time is chosen in a range of 10 minutes to 6 hours. A 
phase containing the reaction product is washed and subjected to the 
purifying treatment to obtain the desired branched polycarbonate. 
Furthermore, the branched polycarbonate of the present invention can be 
obtained according to the following methods, other than above-mentioned 
two processes. For example, there is a method wherein BPA, a branching 
agent and phosgene are reacted, followed by the reaction with THA and THP 
and then the reaction with BPA or a method wherein one oligomer is made of 
BPA and phosgene, another is made of THA and phosgene and then a branching 
agent and BPA are reacted with the so-obtained oligomers, and such like. 
The question when the catalyst should be added during the process for 
producing the branched polycarbonate is not subjected to any particular 
limitation, but it is preferable to add the catalyst when THA, THP and the 
branching agent are reacted. 
During above-mentioned interfacial polycondensation reaction, the repeating 
unit (II) is made from THA and the repeating unit (I) from BPA within the 
oligomer to be obtained. Therefore, the charge of THA and that of BPA are 
properly proportioned according to the molar fractions of the repeating 
units (I) and (II) of the forthcoming branched polycarbonate or according 
to the ratio of halogen atoms that branched polycarbonate has to contain. 
The inputs of THP and phosgene are the decisive factor in determining the 
polymerization degree respectively of repeating units (I) and (II) and 
further the polymerization degree and molecular weight of the branched 
polycarbonate as a whole. Thus, their inputs capable of achieving the 
object are chosen. Phosgene is blown into the reaction system by 
regulating the blow amount per hour properly in the way that the total of 
required phosgene is supplied by the time the reaction is brought to the 
end. 
With respect to above-mentioned reaction, phosgene can be replaced by 
various carbonic ester-forming derivatives, for example bromophosgene, 
bis(2,4,6-trichlorophenyl)carbonate, bis(2,4-dichlorophenyl)carbonate, 
bis(2-cyanophenyl)carbonate, trichloromethyl chloroformate and the like. 
The branched polycarbonate of the present invention can be obtained 
according to any of these manufacturing methods. 
As stated above, it is appropriate that the branched polycarbonate of the 
present invention should have the viscosity average molecular weight in a 
range of 10,000 to 50,000, preferably 15,000 to 40,000. The viscosity 
average molecular weight can be adjusted to this range chiefly by choosing 
a right amount of THP used as a molecular weight modifier. Ordinarily, THP 
is used preferably at a ratio of 0.01 to 0.1-fold mole based on dihydric 
phenols from which the polymer is made. 
Furthermore, BPA, the alkaline aqueous solutions and the catalyst such as 
triethylamine are added to the polycarbonate oligomer to conduct the 
interfacial polycondensation and form the polycarbonate. The catalyst is 
used preferably in an amount calculated by a rate of 
catalyst/chloroformate (or bromoformate and the like) group giving 0.0005 
to 0.03 (mole/mole). 
In the same case where BPA, the alkaline aqueous solutions and the catalyst 
such as triethylamine are added to the polycarbonate oligomer to conduct 
the interfacial polycondensation and form the polycarbonate, a caustic 
alkali required therefor is used preferably in an amount calculated by a 
rate of caustic alkali/hydroxyl group of phenols giving 0.5 to 5.0 
(mole/mole). 
Apart from the interfacial polycondensation, the branched polycarbonate of 
the present invention can also be obtained by the molten polycondensation 
and solid phase polymerization methods using carbonic ester-forming 
derivatives such as diphenyl carbonate, 
bis(2,4,6-trichlorophenyl)carbonate, dimethyl carbonate, diethyl carbonate 
and dibutyl carbonate. For the branched polycarbonate of the present 
invention, various additives can be used in response to needs, including 
halogen-containing flame retardants, other flame retrardants such as 
alkaline (earth) metal salt of organic sulfonic acid, mold release agents, 
lubricants, antioxidants, ultraviolet absorbers, pigments and the like. 
Likewise, other thermoplastic resins, glass fibers, inorganic fillers and 
the like can be mixed with this branched polycarbonate according to uses. 
Now, the present invention will be described in greater detail with 
reference to the examples and the comparative examples. 
SYNTHETIC EXAMPLE 
Synthesizing a Polycarbonate Oligomer 
2730 g of BPA, 10 liters of methylene chloride and 16.8 liters of a 2.0N 
sodium hydroxide aqueous solution were placed in a container having 
internal volume of 60 liters with a stirrer, stirred and cooled on a water 
bath, while phosgene is blown into them for 70 minutes. The so-obtained 
reaction solution was allowed to stand at room temperature and a methylene 
chloride solution of oligomer was isolated and formed in a lower phase. 
The oligomer was found to have a concentration of 320 g/liter, a number 
average molecular weight of 850 and a concentration of chloroformate 
groups of 0.7 mol/liter. 
EXAMPLE 1 
10 liters of the polycarbonate oligomer solution synthesized in said 
synthetic example, 196 g (0.36 mole) of tetrabromobisphenol A (TBA), 169 g 
(0.51 mole) of tribromophenol (TBP), 21.8 g (0.071 mole) of 
1,1,1-tris(4-hydroxyphenyl)ethane (THPE), 86.6 g (2.17 mole) of sodium 
hydroxide, 2.9 ml (0.021 mole) of triethylamine and 1.35 liters of water 
were placed in a container having internal volume of 50 liters with a 
stirrer and stirred for 60 minutes to react (pre-condensation) 
After the reaction was over, 457 g (2.00 mol) of BPA, 267 g (6.68 mole) of 
sodium hydroxide, 3.42 liters of water and 6.1 liters of methylene 
chloride were added to said reaction system and they were stirred to 
react. 
Sixty minutes later, the obtained reaction product was separated into a 
water phase and a methylene chloride phase containing a copolymer formed 
therein. 
The methylene chloride phase was washed with an alkali (0.01N sodium 
hydroxide aqueous solution), an acid (0.1N hydrochloric acid) and water in 
the named order. Methylene chloride was removed from the methylene 
chloride phase at 40.degree. C. under reduced pressure to obtain a white 
powdery copolymer. The copolymer was dried at 120.degree. C. and subjected 
to the pelletization. 
The so-obtained copolymer (the branched polycarbonate) was found to have a 
viscosity average molecular weight of 24,100 and a glass-transition 
temperature at 156.degree. C. The molecular weight distribution was 
determined by the gel permeation chromatography, resulting in a finding 
that a single peak was assigned to the distribution. 
This copolymer was subjected to NMR to determine the content of each 
comonomer, resulting in a finding of BPA: 93.6 mol %, TBA: 2.3 mol %, TBP: 
3.6 mol % and THPE: 0.5 mol %. 
The bromine content of the so-obtained pellet was determined, with the 
resulting finding of 6.1% by weight. The determination of the bromine 
content was conducted by decomposing a test sample with an alkali and 
analyzing the so-decomposed sample according to the Volhard method. The 
properties of the so obtained branched polycarbonate are shown in Tables 1 
and 2. FIG. 1 shows .sup.1 H--NMR spectrum and FIG. 2 shows IR spectrum. 
EXAMPLES 2 TO 6 AND COMATIVE EXAMPLES 1 TO 3 
These examples and comparative examples were carried out in accordance with 
substantially the same procedure as in Example 1, except that different 
monomers and different amounts of sodium hydroxide were used for the 
pre-condensation. The properties of the so obtained branched 
polycarbonates are shown in Tables 1 and 2. A p-t-butylphenol was used as 
PTBP in the Comparative Examples. 
TABLE 1 
______________________________________ 
Used 
Weight of Starting Monomer (g) 
NaOH 
TBA BPS TDP THPE TBP PTBP (g) 
______________________________________ 
Example 1 
196 0 0 21.8 169 0 86.6 
Example 2 
341 0 0 21.8 169 0 118.6 
Example 3 
196 75 0 21.8 169 0 122.7 
Example 4 
196 0 162 21.8 169 0 185.0 
Example 5 
153 0 0 21.8 169 0 77.2 
Example 6 
196 0 0 32.7 169 0 93.1 
Comparative 
196 0 0 0 169 0 73.9 
Example 1 
Comparative 
196 0 0 21.8 0 76.6 86.6 
Example 2 
Comparative 
426 0 0 21.8 0 76.6 137.4 
Example 3 
______________________________________ 
TABLE 2 
______________________________________ 
Copolymerization Composition (mol %) 
BPA TBA BPS TDP THPE TBP PTBP 
______________________________________ 
Example 1 93.6 2.3 0 0 0.50 3.6 0 
Example 2 91.9 4.0 0 0 0.51 3.6 0 
Example 3 91.6 2.2 2.1 0 0.48 3.6 0 
Example 4 88.2 2.4 0 5.2 0.47 3.7 0 
Example 5 94.1 1.8 0 0 0.50 3.6 0 
Example 6 93.5 2.3 0 0 0.74 3.5 0 
Comparative 
94.2 2.3 0 0 0 3.5 0 
Example 1 
Comparative 
93.8 2.1 0 0 0.52 0 3.6 
Example 2 
Comparative 
90.7 5.2 0 0 0.50 0 3.6 
Example 3 
______________________________________ 
Izod 
Bromine Content Impact Strength*.sup.3 
(% by weight)*.sup.1 
Mv*.sup.2 
(kg .multidot. cm/cm) 
______________________________________ 
Example 1 6.1 23900 94 
Example 2 7.9 23700 82 
Example 3 6.0 24000 74 
Example 4 6.1 23700 77 
Example 5 5.5 24100 95 
Example 6 6.2 26500 90 
Comparative 
6.0 20800 92 
Example 1 
Comparative 
2.6 23900 90 
Example 2 
Comparative 
6.2 23700 25 
Example 3 
______________________________________ 
Flame Retardancy*.sup.4 
Non-Newtonian 
(1/16 inch) Parameter*.sup.5 
______________________________________ 
Example 1 V-0 61 
Example 2 V-0 58 
Example 3 V-0 55 
Example 4 V-0 58 
Example 5 V-0 62 
Example 6 V-0 69 
Comparative V-0 26 
Example 1 
Comparative V-2 55 
Example 2 
Comparative V-0 57 
Example 3 
______________________________________ 
*.sup.1 The copolymers decomposed with an alkali were analyzed according 
to the Volhard method. 
*.sup.2 The viscosity of methylene chloride was determined at 20.degree. 
C. by an Ubbelohde viscometer and then the viscosity average molecular 
weight was converted from the result thereof. 
*.sup.3 By using a test piece 1/8 inch thick and according to JISK-7110. 
*.sup.4 A vertical flame test was conducted by using a Flame Retardancy 
Test UL94 1/16 inch (thickness) according to Underwriter Laboratories 
Subject 94. 
*.sup.5 A nonNewtonian parameter was used to express blow moldability in 
terms of the value of physical properties. The nonNewtonian parameter 
means a ratio (D.sub.2 /D.sub.1) between the shearing rate at one shearin 
stress of 9 .times. 10.sup.5 dyn/cm.sup.2 (D.sub.1) and the shearing rate 
at another of 8 .times. 10.sup.6 dyn/cm.sup.2 (D.sub.2), under the 
condition of a temperature of 280.degree. C. and an orifice of L/D = 20/1 
The nonNewtonian parameter is preferably 30 to 90, more preferably 40 to 
80. When the parameter is less than 30, the branched polycarbonate is 
susceptible to greater drawdown and thus is poor in blow moldability. Whe 
it is more than 90, the branched polycarbonate has too high melt viscosit 
to be suitable for molding. 
INDUSTRIAL APPLICABILITY 
As stated above, the branched polycarbonate of the present invention 
possesses certain high valuable properties, particularly with respect to 
flame retardancy, impact resistance and further melt properties suitable 
for blow molding. Specifically, its flame retardancy was determined by 
using a UL-94 1/16 inch (thickness), resulting in a finding of V-0. 
Furthermore, it was found that impact resistance was 50 kg.cm/cm in terms 
of the Izod impact strength and that the melt properties suitable for blow 
molding were more than 30 in terms of the non-Newtonian parameter. 
Therefore, the branched polycarbonate of the present invention can find 
effective application in a wide variety of industrial materials, for 
example household appliances, business automation equipment, building 
materials, sheets and the like.