POLYCARBONATE HAVING IMPROVED CRITICAL THICKNESS

POLYCARBONATES AYANT UNE EPAISSEUR CRITIQUE AMELIOREE

English Abstract

??-????-?-???
PC-009-CIP
TITLE
POLYCARBONATE HAVING IMPROVED
CRITICAL THICKNESS
ABSTRACT OF THE DISCLOSURE
Polycarbonates are provided having improved critical
thickness values based on an aromatic diphenol preferably
bisphenol A and an aromatic diphenol thioether. By
incorporating 2 up to 20 mole percent of the aromatic
diphenol thioether based on the total diphenol content
into the polymer, the critical thickness of the article
molded from the polycarbonate is substantially improved.
PC-009-CIP

Claims

WHAT IS CLAIMED IS:
1. A copolycarbonate resin with a melt flow rate of 1-24
gram/10 min. at 300°C (ASTM 1238) consisting essentially of:
2 up to 20 mole percent of the sulfur containing
structural unit
(I) <IMG>
wherein R1 and R2 are hydrogen or lower alkyl groups having
1 to 4 carbon atoms and n equals 0 to 2, and from 80 to 98
mole percent of the structural unit
(II) <IMG>
wherein X is hydrogen, a C1 to C4 alkyl radical or a halogen
and n1 equals 1 or 2, and Z is a single bond, an alkylene or
alkylidene radical with 1 to 7 carbon atoms, a cycloalkylene
or cycloalkylidene radical with 5 to 12 carbon atoms, -O-,
-CO-, -SO- or -SO2-.
2. The copolycarbonate resin of Claim 1 wherein Z
is selected from the group consisting of methylene and iso-
propylidene.
PC-009-CIP
16

3. The copolycarbonate resin of Claim 1 wherein X
is selected from the group consisting of hydrogen, a C1-C4
alkyl radical, Br and Cl.
4. The copolycarbonate resin of Claim 3 wherein X
is selected from the group consisting of hydrogen and a C1-C4
alkyl radical.
5. The copolycarbonate resin of Claim 1 wherein
the sulfur containing structural unit is:
<IMG>
6. The copolycarbonate resin of Claim 2 wherein
X is hydrogen and Z is isopropylidene.
7. A process for preparing a copolycarbonate
comprising, reacting:
a. thiodiphenol; and
b. a compound of the structural formula
<IMG>
wherein X is hydrogen, a C1 to C4 alkyl group, or a halogen
and n1 equals 1 or 2 and Z is a single bond, an alkylene or
alkylidene radical with 1 to 7 carbon atoms, a cycloalkylene
or cycloalkylidene radical with 5 to 12 carbon atoms, -O-,
PC-009-CIP
17

-CO-, -SO-, or -SO2- with a carbonic acid derivative selected
from the group consisting of phosgene, carbonyl bromide, the
bischloroformic esters of (a) and/or (b) and diaryl carbonates,
under conditions selected to produce a copolycarbonate with a
melt flow rate of 1 to 24 gram/10 min. at 300°C (ASTM 1238)
wherein (a) is present in the reaction mixture from 2 up to
20 mole percent and (b) is present from 80 to 98 mole percent
based on the total moles of both (a) and (b).
8. The process of Claim 7 wherein the thiodiphenol
(a) is 4,4'-thiodiphenol.
9. The process of Claim 7 wherein Z is selected
from the group consisting of methylene and isopropylidene.
10. The process of Claim 7 wherein (b) is bisphenol
A.
11. The copolycarbonate resin of Claim 1 wherein
structural unit I is present in an amount from 2 to 19 mole
percent and structural unit II is present in an amount from
81 to 98 mole percent.
12. The copolycarbonate resin of Claim 1 wherein
structural unit I is present in an amount from 2 to 15 mole
percent and structural unit II is present in an amount from
85 to 98 mole percent.
13. The copolycarbonate resin of Claim 1 wherein
structural unit I is present in an amount from 2 to 10 mole
percent and structural unit II is present in an amount from
90 to 98 mole percent.
PC-009-CIP
18

Description

10947~ Mo-1607-P-CIP
POLYCARBONATE HAVING IMPROVED
CRITICAL THICKNESS
BACKGROUND OF THE INVENTION
Field of the Invention
S This invention relates to polycarbonate copolymers and
more particularly to polycarbonate copolymers having improved
critical thickness values.
Description of the Prior Art
Polycarbonates derived from reactions involving organic
dihydroxy compounds and carbonic acid derivatives have found
extensive commercial application because of their excellent
mechanical and physical properties. These thermoplastic
polymers are particularly suited for the manufacture of molded
articles where Lmpact strength, rigidity, toughness, thermal
and dimensional stability as well as excellent electrical
properties are required.
' However, one deficiency of polycarbonate when used in
molded articles is the low critical thickness values of the
polycarbonate polymer.
It is known that polycarbonate plastics exhibit high
notched IzOd (ASTM test D-256~ impact values. This value,
however, is dependent upon the thickness of the test specimen.
Typical notched Izod impact values for a 1/8" specimen are
about 16 ft.-lbs.per in. These high Izod values result
because specimens of 1/8" thickness are thinner than the
critical thickness of the polymer and therefore upon impact
a hinged or ductile break occurs.
PC-009-CIP

~094738
On the other hand, l/4" specimens exhibit a clean or
brittle break and give notched Izod impact values of only about
2.5 ft.-lbs. per in. The l/4" specimens are said to be above
the critical thickness of the polymer. "Critical thickness"
has been defined as the thickness at which a discontinuity in
Izod impact values occurs. In other words, it is the thic~ness
at which a transition from a brittle to a ductile break or
vice versa occurs. Thus a standard impact specimen of poly-
carbonate polymer thicker than the critical thickness exhibits
brittle breaks and those thinner than the critical thickness
exhibit hinged or ductile breaks. Further, a polycarbonate
based on bisphenol A with a melt flow of 3 to 6 grams/10
minutes at 300 C. (ASTM Dl238) has a critical thickness of
225 mils.
One approach to solving the critical thlckness problem has
been to incorporate polyolefin polymers into the polycarbonate
which has substantially improved critical thickness (See U.S.
Patent 3,437,631). But along with this improvement has come
detrimental effects such as colorant dispersion problems be-
cause of the diversity of chemical composition ~f the two
component system and also a lack of transparency since the
polyolefin and polycarbonate are i~compatible.
PC-009-CIP 2.

`` 10~4738
Thus in accordance with the invention a polycarbonate
is provided which has impro~ed critical thickness values and
is highly transparent.
BRIEF DESCRIPTION OF THE `INVENTION
A copolycarbonate having a melt flow of 1 to 24 gram/
10 min. at 300C (ASTM 1238) and having improved critical
thickness is provided which contains from up to 20 mole percent
; of the repeating structural unit
to-c-o /
~1
!~ wherein Rl and R2 are hydrogen or lower alkyl groups having
1 to 4 carbon atoms and n equals 0 to 2, and from 80 to 98
mole percent of the repeating structural unit
--I O-C-~- Z
wherein X is ~ydrogen, a Cl to C4 alkyl radical or a halogen,
prefera~ly Br or Cl,most preferably wherein X is hydrogen or
a Cl-C4 alkyl radical; and nl equals 1 or 2 and Z is a single
bond,an alkylene or alkylidene radical with 1 to 7 carbon atoms,
a cycloalkylene or cycloalkylidene radical with 5 to 12 carbon
atoms, -O-, -CO-, -SO- or -SO2-, preferably methylene or
isopropylidene.
DETAILED DESCRIPTION OF T~E INVE~ITION
When used herein ~copolycarbonate resin" means the
PC-009-CIP 3
.~

1094738
neat resin without additives; "polycarbonate" means the
copolycarbonate resin with additives therein.
The copolycarbonate resins of the invention may be
prepared by conventional methods for polycarbonate resins,
and may have a weight average molecular weight of 10,000
to Z00,000 and preferably a melt flow rate of 1 to 24
gram/10 min at 300C (ASTM 1238~.
Any suitable processes, reactants, catalysts,
solvents, and conditions and the like for the production of
the polycarbonate resins of this invention which are
customarily employed in polycarbonate resin syntheses may
be used such as disclosed in German Patent Nos. 1,046 r 311
and 962,274; U.S. Patents 3,028,365r 2,999,846, 3,248,414,
3,153,0Q8, 3,215,668, 3,187,065, 2,964,974~ 2,970,137,
2~991,273,and2,999~ 835. The preferred process is the
interfacial polycondensation process.
According to the interfacial polycondensation
process, copolycarbonate resins are obtained by reacting
the bisphenols represented by the structural formulae:
(x2nl (
HO ~ Z ~ ~
wherein X is hydrogen, a Cl to C4 al~yl radical, or a
halogenj prefexably Br or Cl~ most prefera~ly wherein X
is hydrogen or a Cl-C4 alkyl radical; and n1 equals 1 or
PC-009-CIP 4^
`~ `B

10~7~8
2 and wherein Z is a single bond, an alkylene or alkylidene
radical with 1 to 7 carbon atoms, a cycloalkylene or
cycloalkylidene radical with 5 to 12 carbon atoms, -0-,
-CO-, -SO- or -SO2-, preferably methylene or isopropylidene
and
(Rl)n (R21n
HO ~ S - ~ -OH
wherein Rl and R2 are hydrogen, lowex alkyl groups having
', 1 to 4 carbon atoms, with an alkaline earth metal oxide or
PC-009-CIP 5.

1094738
hydroxide or àlkali metal hydroxide to form the alkaline earth
metal or alkali metal salt of the bisphenols. The salt mixture
is present in an aqueous solution or suspension and is reacted
with phosgene, carbonyl bromide, or bischloroformic esters of
the diphenols.
An organic solvent is provided in the reaction admixture which
is a solvent for the polymer but not for the phenolic salts
hereinbefore described. Thus, chlorinated aliphatic
hydrocarbons or chlorinated aromatic hydrocarbons maybe used
as the organic sol~ent which dissolves the condensation product.
In order to limit the molecular weight one may use
monofunctional reactants such as monophenols, for example the
propyl-, isopropyl- and butyl-phenols, especially p-tert.
-butyl-phenol and phenol itself. In order to accelerate the
reaction, catalysts such as tertiary amines, quaternary
ammonium, phosphonium or arsonium salts and the like may be
used. The reaction temperature should be about -20~ to ~150C.,
preferably 0C to about 100C.
According to the polycondensation process in a homogeneous
phase, the dissolved reaction components are polycondensed in
an inert solvent in the presence of an equivalent amount of a
tertiary amine base required for absorption of the generated
HCl, such as e.g. N,N-dimethylaniline, N,N-dimethyl-cyclo-
hexylamine or preferably pyridine and the li~e. In still
another process, a diaryl carbonate can be transesterlied wi~h
the aromatic dihydroxy compounds to form the polycarbonate
r~sin.
PC-009-CIP 6.

10~ ~7~8
It is to be understood that it is possible to
combine in the processes described above in a chemically
meaningful way both the aromatic dihydroxy compounds, and
the monohydroxy compounds in the form of the alkali metal
salts and/or bis-haloformic acid esters, and the amount of
phosgene or carbonyl bromide then still re~uired in order to
obtain high-molecular products. Other methods of synthesis
in forming the polycarbonates of the invention such as
disclosed in U.S. Patent 3,912,688 may be used.
The two diphenols necessary for synthesizing the
repeat~ng structural units (I~ and (II) are thiodiphenol
and preferably 4,4'-thiodiphenol and a bisphenol preferably
having either methylene or isopropylidine linking the two
phenol rings. The most preferred bisphenol is bis-2-
(4-hydroxyphenyl)-propane; other bisphenols such as bis-
(4-hydroxyphenyl)-methane, bis-2-(-4-hydroxy-3l5-dimeth
phenyl) propane and the like may be utilized.
In addition to the 4,4'~thiodiphenol and the
bisphenols recited a~ove other di-(monohydroxyaryl)-alkanes
may be incorporated in the polymer at low levels (i,e. levels
whi~ch do not affect critical thickness values)~ Exemplary
dihydroxy compounds are taught by U.S~ Patent 3,028,365,
PC-009-CIP 7
s7~q~

1094738
As low as 2 mole percent of the 4,4'-thiodiphenol based on
the total diphenol shows improved critical thickness values
over a conventional bisphenol A while 10 mole percent of
4,4'~iodiphenol raises the critical thickness value of the
polycarbonate to levels equivalent to those blends of bisphenol
A polycarbonate with a polyolefin polymer. However, the
thiodiphenol based polycarbonate maintains transparency, good
colorant dispersability and other properties substantially
improved over the polycarbonate polyolefin blend.
Although copolymers of bisphenols and thiodiphenols are
known, (See U.S. Patent 3,250,744) the contemplated use of
these polymers of the prior art were as coatings and moldings
having good anchorage. The copolymers of the prior art have
from 20 to 100 mole percent of the repeating structural unit
tO-C-O-~)S~lL
to obtain good anchorage but the prior art did not recognize
the improved critical thickness values obtained with the above
structural unit from 2 to up to 20 mole percent in the
polymer.
The invention will be further described by illustration
in the following examples.
PC-009-CIP 8.

1094738
Example I
A copolycarbonate resin was prepared by reacting a mixture
of the disodium salts of bis-2-(4-hydroxyphenyl)-propane
(bisphenol A) and 4,4'-thiodiphenol with phosgene in accordance
with the interfacial polycondensation synthesis hereinbefore
5 discussed. The ratio of bisphenol A to 4,4'-thiodiphenol was
9 to 1. The copolycarbonate was tested for physical,
mechanical, and optical properties with the test results
reported on Table I. The copolycarbonate was found to be
highly transparent. Also Table II shows the effect of oven
aging at 105C on impact and critical thickness properties.
Example II
Example I was repeated except the mole ratio of 4,4'-
thiodiphenol : bisphenol A was 2:98. The copolycarbonate was
found to be highly transparent. Test results of Example II
lS and the following Examples are reported on Tables I and II.
Example III
Example II was repeated except the mole ratio of 4,4'-
thoidiphenol : bisphenol A was 20:80. The copolycarbonate
was found to be highly transparent.
Example IV
Example IV is a bisphenol A polycarbonate resin having
no 4,4'-thiodiphenol therein.
PC-009-CIP 9.

109473~
TABLE I
EXAMPLES I II III IV
Mole %
BPAl 90 98 80 100
(Control)
5 Monomers
TDP2 10 2 20
Izod3
(Notched)
Impact
(Ft. lbs/in)
1/8" 14.89 16.0 14.59 18.44
1/4" 14.96 7.98 14.75 3.20
Critical
Thickness
15 mils 255 247 >255 227
Relative
Viscosity4 1.340 1.318 1.377 1.355
Melt Index
g~10 min 2.9 3~6 2.5 3.1
Heat Distor-
tion5
Temp. C 135 - 133 134
%s found
(calc.) 1.12(1.32) 0.24(0.30) 2.42~2.63) -
Oxygen6
Index% 25.4 - 25.4 25.5
% Brightness 87.49 86.83 87.06 86.30
~ ~aze7 3.2 _ 1.5
Tensile
30 Strength psi 9000 - 8900 9800
Ultimate Ten-
sile Strength
psi 940~ - 9Q00 10,100
~ Elongation 8 - 10 8
~ Elongation
Failure 90 - 95 105
PC-009-CIP 10.

1094738
BPA is Bisphenol A
2TDP is 4,4'-thiodiphenol
ASTM D256
0.5g. resin/100 ml. methylene chloride at 25C
C under 264 psi load (ASTM-D-648)
ASTM D-2863
7ASTM D-1003
PC-OO9-CIP 11.

~09473B
TABLE II
AGING IN AIR AT 105C
EXAMPLES I III IV
Mole % BPA 90 80 100 (Control)
5Monomers TDP 10 20
1/8" Impact
(Ft. lbs/in)
Unaged 14.8914.59 16.68
24 hr. 14.0514.15 16.35
1048 hr. 14.8214.51 16.35
96 hr. 13.2214.15 16;84
148 hr. 14.3914.76 16.84
288 hr. 14.2013.59 16.30
Critical Thick-
ness Values
Unaged 255 >255 225
24 hr. 199 227 185
48 hr. 187 219 183
96 hr. 175 205 150
20148 hr. 170- 205 155
288 hr. 170 205 155
PC-005-CIP 12.

109`~738
As is shown in the data presented in Tables I and II
as low as 2 mole% of 4,4'-thiodiphenol based upon the
total diphenol content in the polycarbonate resin
improves the critical thickness of articles molded there-
from while maintaining substantially equivalent physical
and mechanical properties of the conventional bisphenol
A based on polycarbcnat~ resin.
While it has been known to synthesize polycarbonates
from sulfur containing diphenols such as 4,4'-sulfonyl
diphenol to incorporate the repeating structural unit
t ~~
into the polymer such structural units do not improve
the critical thickness values of polycarbonates based
partially on 4,4'-sulfonyl-diphenol. Table III shows
critical thickness values contrasting 4,4'-sulfonyl-
diphenol based polycarbonates with the 4,4'-thiodiphenol
based polycarbonates.
!
PC-OOg-CIP 13.

- 10~4738
TABL~ III
Mono~er Compositions Crltical Thickness Melt Flow
mole %) _mils(g/10 min.)
*BPAl SDP2
t90) (10) 215 6.2
BPA TDP3
(90) (10) 255 2.9
Random Copolymer
BPA
~100) Control 225 3.0
B~sphenol A
24,4'-Sulfonyldiphenol
34, 4'-Thlodiphenol
*The BP~(90)-SDP(10) copolycarbonate was found to have the
following additional properties:
~eat Distortion Temp at
264 psi, C 147
Imp~ct ft lbs/in (1/8") 14.80
Impact ft lbs/in (1/4") ~.65
Cri~ical Thickness 225
Tensile strength, psi 9300
Ultimate Tensile Strength, psi 9100
Elongation yiel~
Ultimate Elongation ~ 95
PC-009-CIP 14.

1094738
Thus copolycarbonates having a minimum of 2 mole per-
cent of 4,4'-thiodiphenol based upon the total diphenol
content in the polymer exhibit improved critical thickness
values over conventional polycarbonates and also copolycar-
bonates based on sulfonyl diphenols.
Although the invention has been described with refer-
ence to specific materials and testing procedures the inven-
tion is only to be limited in so far as is set forth in
the accompanying claims.
PC-OO9-CIP ~5