Note: Descriptions are shown in the official language in which they were submitted.
- i 162688
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POLYCARBONATE BLENDS HAVING IMPROVED FLOW AND
CRITICAL THICKNESS C~ARACTERISTICS
.. . . .. _ . _ _ . .. .
BACKGROUND OF THE INVENTION
. .
1. Field of the Invention
This invention relates to polycarbonate resin
blends and more particularly to polycarbonate resin blends
having improved critical thickness values and melt ~low
rates.
2. Description of_the Prior Art
Polycarbonate~ 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 requiring impact strength,
rigidity, toughness, thermal and dimensional stability
as well as excellent electrical properties. However,
one deficiency of polycarbonate when used in molded
articles is the low critical thickness values of the
polycarbonate polymer.
It is kno~n that polycarbonate plastics exhibit
high notched Izod (ASTM D-256) impact values. These
values, however, are dependent upon the thickness
of the test specimens. Typical notched Izod impact
values of a 1/8" specimen are about 16 ft.-lbs/inch.
These high Izod values result because a specimen of
a 1/8" thickness is thinner than the critical thickness
of the polymer and therefore upon impact a hinged
or ductile break occurs. On the other hand, a I/4"
specimen exhibits a clean or brittle break and gives
notched Izod impact values of only about 2.5 ft.-lbs/inch.
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The 1/4" 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
thickness at which a transition from a brittle to a
ductile break or vice versa occurs. Thus, a standard
impact specimen of polycarbonate polymer thicker than
the critical thickness exhibits brittle breaks and those
thinner than the critical thickness exhibit hinyed or
ductile breaks. Further, the critical thickness of a
polycarbonate based on bisphenol A with a melt flow of
3 to 6 grams/10 minutes at 300C (ASTM D-1238) has a
critical thickness of 225 mils.
One approach to solving the critical thickness
problem has been to incorporate polyolefin polymers
into the polycarbonate which has substantially improved
critical thickness (see U.S. Patent No. 3,437,631).
But along with this improvement has come detrimental
effects such as colorant dispersion problems, lack of
transparency, poor weld line strength, and worsened
flammability.
Another approach to solving the critical thickness
problem has been to prepare polycarbonate resins incor-
porating thiodiphenols which exhibit improved critical
thickness. Further, these polycarbonate resins based
upon thiodiphenol and particularly bisphenol A exhibit
high melt flows along with the improved critical
thickness. Such copolymers of thiodiphenol and bis-
phenol A are more fully disclosed in U.S. Patent No.
3,250,774. One disadvantage of such a system
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5 1626B8
is that the single copolymer must be prepared at the
desired level of thiodiphenol content for each particu-
lar use~
These aromatic diphenol-aromatic thiodiphenol
copolycarbonates have been shown to have superior toler-
ance for the presence of halogen. In particular, U.S.
Patent 4,174,359 discloses that these copolycarbonates
maintain high critical thickness values, e.g., more than
20~ mils in many cases, upon the incorporation of flame
retardin~ amounts o~ halogen. The halogen can be
carried by either monomeric compounds or polymers such
as the homopolycarbonate of 2,2-bis-(3,5-dibromo-4-
hydroxyphenyl) propane or copolycarbonates of this
monomer and 2,2-bis-(4-hydroxyphenyl~ propane, i.e.,
tetrabromo BPA~BPA copolymers.
In accordance with the invention a polycar-
bonate is provided which has improved critical thickness
~alues, is highly transparent, exhibits excellent weld
line strength, and exhibits acceptable flammability
ratings.
The composition of the polycarbonate of the
invention comprises an intimate mixture of an aromatic
polycarbonate resin which is the reaction product of an
aromatic diphenol and a carbonate precursor on the one
hand and an effective amount of an aromatic copolycar-
bonate which is the reaction product of an aromatic
diphenol, an aromatic thiodiphenol and a carbonate pre-
cursor, ~hich copolycarbonateischaracterized in that
it contains from about 2 to 50% of an aromatic thio-
diphenol, relative to the total moles of diphenol andaromatic thiodiphenol,
DET~I$ED DESCRTPTION OF THE INVENTION
~ hen used herein "polycarbonate resin" or
"resins" means the neat resin or resins without addi-
tives; "polycarbonate" means the polycarbonate resinor resins with additives therein
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The copolycarbonate resins of the invention may
be prepared by conventional methods for polycarbonate
resins, and may have an average molecular weight of
10,000 to 200,000, and preferably a melt flow rate of
1 to 24 grams/10 minutes at 300C (ASTM 1238).
Any suitable process, reactant catalyst, solvent,
reaction condition and the like for the production of the
polycarbonate and copolycarbonate resins of this inven-
tion which are customarily employed in polycarbonate
resin syntheses may be used such as disclosed in
Mo-2~77.
PC-014.
~ 162688
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German Patent Nos. 962,274 and 1,046,311; and U.S.
Patent Nos. 2,964,794; 2,970,131; 2,991,273; 2,999,835;
2,999,846; 3,028,365; 3,153,008; 3,187,065; 3,215,668;
and 3,248,414. The preferred process is the interfacial
polycondensation process.
According to the inter~acial polycondensation
process, polycarbonate and copolycarbonate resins are
obtained by reacting the aromatic dihydroxy compounds
with an alkali metal hydroxide or alkaline earth metal
oxide or hydroxide to form the salt of the hydroxy
compounds. The salt mixture is present in an aqueous
solution or suspension and is reacted with pnosgene,
carbonyl bromide, or bischloroformic esters of the
aromatic dihydroxy compounds. An organicsolvent i5
provided in the reaction admixture which is a solvent
for the polymer but not for the aromatic dihydroxy salts.
Thus, chlorinated and non-chlorinated aliphatic hydro-
carbons or chlorinated and non-chlorinated aromatic
hydrocarbons are used as the organic solvent which
dissolves the condensation product. Suitable solvents
include cyclohexane, methylcyclohexane, benzene, toluene,
xylene, methylene chloride, chloroform, carbon tetra-
chloride and chlorobenzene.
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
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should be about -20 to ~150C, preferably about 0C
to 100~C.
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 N,N-dimethyl-
aniline; N,N-dimethyl-cyclohexylamine or preferably
pyridine and the like.
In still another process, diaryl carbonate can
be transesterified with the aromatic dihydroxy compounds
to form the polycarbonate resin.
It is to be understood that it is possible to
combine in a chemically meaningful way in the processes
described above 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 required
in order to obtain high molecular weight products. Other
methods of synthesis in forming the polycarbonate and
copolycarbonate resins of the invention such as dis-
closed in U.S. Patent No. 3,912,688, may also be used.
"Aromatic diphenol" as used herein means those
aromatic diphenols which do not include thiodiphenols.
The aromatic diphenols useful in the practice
of the present invention include the following compounds:
hydroquinone, resorcinol, dihydroxydiphenyls, bis-(hydroxy-
phenyl)-alkanes, bis-(hydroxyphenyl)-cycloalkanes, bis-
(hydroxyphenyl)-ethers, bis-(hydroxyphenyl)-ketones,
bis-(hydroxyphenyl)-sulphoxides, bis-(hydroxyphenyl)-
sulphones and a,~-bis-(hydroxyphenyl)-diisopropylbenzenes,
as well as their nuclear-alkylated and nuclear-halogenated
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compounds. These and ~urther suitable aromatic dihydroxy
compounds are described, for example, in U.S. Patent
Nos. 3,028,365; 2l999l835; 3,148,172; 3,271,368; 2,991,273;
3,271,367; 3,280,078; 3~014,891; and 2,9~9,846; in German
Offenlegun~sschriften (German Published Specifications)
1,570,703; 2,063,050; 2,063,052; 2,211,956; and 2,211,957;
in French Patent Specification 1,561,518; and in the
monograph "H. Schnell, Chemistry and Physics of Poly-
carbonates, Interscience Publishers, New York, 1964".
Preferred bisphenols are those of the formula:
R R
HO ~ ~ - X ~ OH
R R
in which R is identical or different and denotes H,
Cl to C4 alkyl, Cl or Br; and in which X is Cl to C8
alkylene, C2 to C8 alkylidene, C5 to C15 cycloalkylene,
C5 to C15 cycloalkylidene, -SO2-, -SO-, -CO- or:
CH3 ~ CH3
CH3 3
Examples of these bisphenols are: 4,4'-dihydroxy-
diphenyl; 2,2-bis-(4-hydroxyphenyl)-propane (bisphenol
~); 2,4-bis-(4-hydro~yphenyl)-2-methylbutane; l,l-bis-
(4-hydroxyphenyl)-cyclohexane; ~,~-bis-(4-hydroxyphenyl)-
p-diisopropyl-benzene; 2,2-bis-(3-methyl-4-hydroxyphenyl)-
propane; 2,2-bis-(3-chloro-4-hydroxylphenyl)-propane
bis-(3,5-dimethyl-4-hydroxyphenyl)-methane; 2,2-bis-
(3,5-dimethyl-4-hydroxyphenyl)-propane; bis-(3,5-dimethyl-
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4-hydroxyphenyl)-sulphone; 2,4-bis-(3,5-dimethyl-4-
hydroxyphenyl)~2-methylbutane; 1,1-bis-(3,5-dimethyl-4-
hydroxyphenyl)-cyclohexane; ~,~-bis-(3,5~dimethyl-4-
hydroxyphenyl)-p-diisopropyl-benzene; 2,2-bis-(3,5-
dichloro-4-hydroxyphenyl)-propane; and 2,2-bis-(3,5-
dibromo-4-hydroxyphenyl)-propane (te~rabromobisphenol A)
propane.
Examples of particularly preferred bisphenols are:
2,2-bis-(4-hydroxyphenyl)-propane, 2l2-bis~(3,5-dimethyl-
4-hydroxyphenyl~-propane; 2,2-bis-(3l5-dichloro-4- -
hydroxyphenyl)-propane; 2,2-bis-(3~5-dibromo-4-hydroxy-
phenyl)-propane; and l,l-bis-(4-hydroxyphenyl)-cyclo~
hexane.
The most preferred bisphenol is 2,2-bis-(4-hydroxy-
phenyl)-propane (bisphenol A).
The aromatic thiodiphenols useful in the practice
of the invention are those representedby the structural
formula:
(Rl)n (R2)n
HO ~S ~OH
wherein Rl and R2, which may be the same or different,
are H, Cl to C4 alkyl, Cl or Br, preferably H or Cl to
C4 alkyl; and n is equal to 0, 1 or 2.
The aromatic copolycarbonates of the present inven-
tion preferably contain from about 6 to 50 mole percent,
preferably fro~ about 10 to 40 mole percent, of the
aromatic thiodiphenol, based on the total mole percent
of diphenols. Suitable aromatic copolycarbonates are
described in U.S. Patent No. 3,250,774.
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~ 18~688
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The aromatic polycarbonate and copolycarbonate
resins can be hranched due to the. incorporation of small
amounts, preferably o~ betwe.en about 0.05 and 2.0 mole
percent ~relative to diphenols employed~, of trifunc-
tional or more than trifunctional compounds, espe~iallycompQ.unds with three or more phenolic hydroxyl ~roups.
Polycarbonates of this type are described, for
example, in German Offenlegungsschriften (German Pub-
lished Speci~ications) 1,570,533; 1~595l762; 2,116,974;
and 2,113,347; British Patent Specification 1,079,821
and U.S. Paten-t Specification 3,544,514.
Some examples of compounds with three or more
than three phenolic hydroxyl groups which can be used
are phIoroglucinol; 4,6-dimethyl-2,4,6-tri-(4-hydroxy-
phenyl)-heptane-2,4,6-dimethyl-2r4,6-tri-(4-hydroxy-
phenyl)-heptane; 1,4,5-tri-(4-hydroxyphenyl)-benzene;
1,1,1-tri-(4-hydroxyphenyl)-ethane; tri-(4-hydroxy-
phenyl)-phenylmethane; 2,2-bis-[4,4-bis-(4-hydroxyphenyl)-
cyclohexyl]-propane; 2,4-bis-(4-hydroxyphenyl -isopropyl)-
20.phenol; 2,6-bis-(2-hydroxy-5'-methyl-benzyl)-4-methyl-
phenol; 2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-
propane; hexa-(4-(4-hydroxyphenylisopropyl)phenyl)
ortho-terephthalic acid ester; tetra-(4-hydroxyphenyl)-
methane; tetra-(4-(4-hydroxyphenylisopropyl)-phenoxy)-
methane; and 1,4-bis-((4l,4"-dihydroxytriphenyl)-methyl)-
benzene. Some of the other trifunctional compounds are
2,4-dihydroxybenzoic acid, trimes.ic acid, cyanuric
chlo~ide and 3,3-bis~(4-h.ydroxyphenyl)-2-oxo-2,3-dihydro-
indole.
3Q Th~e aromatic copqlycarbonates. of the present inven-
tion are intimately blended ~ith the aromatic polycar-
bonate resins in an ef~ective amount, ~ased on the
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1 1628~B
total weight of the blend~ to improve the critical thick-
ness properties o~ the aromatic polycarbonate resins.
Preferably, the aromatic c4polycarbonates are present
in from about 1 to 50 weight percent, most preferably
from about 10 to 50 weight percent, based on the total
weight of the blend.
Furthermore, the aromatic copolycarbonate-aromatic
polycarbonate blend of the present invention preferably
has an aromatic thiodiphenol content of about 5 to
10 20 weight percent, mQst preferably about 10 to 15 weight
percent, based ~n the total diphenol content.
The blends of the present invention may also contain
conventional resin additives such as glass fibers~ pigments,
dyes, UV stabilizers~ mold release agents and fillers.
The copolycarbonates and any additives, including
glass fibers~ may be intimatel~ blended with the aromatic
polycarbonate in known mixing devices such as kneaders,
single-screw extruders, twin-screw extruders, mills and
the like.
Although copolymers of bisphenols and thiodiphenols
are known, (see U.S. Patent No. 3,250,744)l the contem-
plated use of these polymers of the prior art was 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:
[ ~:
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1 1~2688
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to obtain good anchorage, but the prior art did not
recognize the improved critical thickness values obtained
if such copolymers are intimately blended with an aromatic
polycarbonate.
The invention will be further illustrated, but is
not intended to be limited by the fcllowing examples.
EXAMPLE 1
A copolycarbonate 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 discussed. The weight ratio
of bisphenol ~ to 4,4'-thiodiphenol was 9 to 1. The
copolycarbonate prepared was tested for physical,
mecha~ical and rheological proper~ies and the t~st resul~s
are reported on Table 1. The copolycarbonate was
found to be highly transparent.
EXAMPLE 2
Example 1 was repeated except that the ratio of
20 4,4'-thiodiphenol:bisphenol A was 30:70. Test results
of the copolycarbonate prepared in accordance with
Example 2 are shown on Table 1. The copolycarbonate of
Example 2 was found to be highly transparent.
EXAMPLE 3
The polycarbonate prepared according to Example 2
was intimately blended with a bisphenol A homopoly-
carbonate having a melt index of 3.3 grams/10 minutes
in the ratio of 1 part by weight copolycarbonate resin
to 2 parts by weight homopolycarbonate resin. The test
results of the polycarbonate of Example 3 are shown on
Table 1. The blend was found to be highly transparent.
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62688
EXAMPLE 4
Example 3 was repeated except that the ratio of
homopolycarbonate resin to copolycarbonate resin was
1:1. The test results of the blend are reported in
Table 1. The blend was highly transparent.
EXAMPLE 5
Example 3 was repeated except that the ratio of
copolycarbonate resin to homopolycarbonate resin was 1:5.
The test results of the blend are reported in Table 1.
The blend was found to be highly transparent.
EXANPLE 6
Example 1 was repeated except that the ratio of
thiodiphenol:bisphenol A was 40:60 on a weight basis.
Test results of the polycarbonate of Example 6 are reported
in Table 1. The polycarbonate was highly transparent.
EXAMPLES 7-9
The polycarbonate resin of Example 6 was blended at
various levels with bisphenol A homopolycarbonate resin
having a melt index of 3.3. The test results along with
the composition of the polycarbonates are reported in
Table 1. All of the polycarbonates were highly
transparent.
EXAMPLES 10-12
The polycarbonate resin of Example 6 was blended
at various levels with bisphenol A homopolycarbonate
resin having a melt index of 7.4 grams/10 minutes. The
test results along with the composition of the polycar-
bonates are reported in Table 1. All of the polycarbonates
were highly transparent.
EXAMPLE 13
Example 1 was repeated except that the ratio of
thiodiphenol:bisphenol A was 25:75 on a weight basis.
Test results of the polycarbonates of Example 13 are
reported in Table 1. The polycarbonate was highly
transparent.
Mo-2077
PC-014
i 162688
-12-
EXAMPLES 14-19
The polycarbonate resin of Example 13 was blended
at various levels with bisphenol A homopolycarbonate
resins having melt indices of 3.3 and 7.4. The test
results along with the compositions are reported in
Table 1. All of the polycarbonates were highly trans-
parent.
Mo-2077
PC-014
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Mo-2077
PC-014
~ 162688
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Mo-2077
PC-014
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Mo-2077
PC-014
~ 162688
--16--
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Mo-2077
PC-014
~ 162~88
-17-
As can be seen from Table 1, blending of a copoly-
carbonate resin having the aromatic thiodiphenol therein
with a homopolycarbonate resin improve~ the critical thickne~
over a polycarbonate fabricated solely from the homopoly-
carbonate.
Polycarbonates of 1/4" thickness (250 mils) are usefulin many applications, and therefore, it is desirable to
provide polycarbonates havin~ a critical thickness of 250 mils
or greater.
The results presented in Table 1 indicate that
critical thickness values equivalent to a BPA/TDP copoly-
carbonate with a 10 weight percent TDP level can be
achieved from a polyblend (in a 1:1 weight ratio) of a
BPA/TDP copolycarbonate having a 30 weight percent TDP
level and a melt index of 6.6 grams/10 minutes with a
BPA polycarbonate having a melt index of 3.3 grams/10
minutes. Thus, a 15 weight percent TDP le~el is required
in a polyblend to achieve impact and critical thickness
values equivalent to those of a BPA/TDP copolycarbonate
having a 10 weight percent TDP level.
- The exact compositions of the blend will also be a
function of the melt flow properties of the aromatic
diphenol-aromatic thiodiphenol copolycarbonate and the
aromatic diphenol polycarbonate. For example, a polyblend
of a BPA/TDP copolycarbonate (30 weight percent TDP
level and melt index of about 3-4) and a BPA polycarbonate
~melt index of about 3-4) in a weight ratio of 1:2 will
lower the TDP content of the polyblend to about 10 weight
percent required to achieve the critical thickness comparable
to the copolycarbonate cited in Example 1.
Mo-2077
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~ 162688
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The data from Table 1 demonstrates that there is a
correlation between melt index of the polycarbonate
resin blend and critical thickness values of 250 mils
or greater.
Table 2 demonstrates this correlation.
TABLE 2
Weight Percent TDP* Melt Index g/10 Critical Thickness
in Blend min. of Blend Value > 250 Mils
2.9 255
4.8 >250
18.75 7.1 >250
11.3 >255
*TDP is thiodiphenol.
Upon linear regression analysis, a critical thickness
15 of >250 mils will be achieved according to the following
equation:
y = 0.4239 (x) - 1.29
where y is the melt flow rate in grams/10 minutes and x
is the weight percent aromatic thiodiphenol in the blend.
Although the invention has been described in detail
in the foregoing for the purpose of illustration, it is
to be understood that such detail is solely for that purpose
and that variations can be made therein by those skilled
in the art without departing from the spirit and scope of
25 the invention except as it may be limited by the claims.
Mo-2-077
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