Note: Descriptions are shown in the official language in which they were submitted.
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Mo-3365
PC-238
BLENDS OF POLYCARBONATES AND ALIPHATIC POLYESTERS
FIELD OF THE INVENTION
The invention relates to thermoplastic molding
compositions and more particularly to compositions containing a
5 homogeneous blend of a polycarbonate resin and an aliphatic
polyester resin.
SUMMARY OF THE INVENTION
The present invention concerns a thermoplastic
molding composition comprising a homogeneous blend of (~) a
o polycarbonate resins and ~ii) a polyester resin derived from
neopentyl glycol and an aliphatic diacid. The components of
the blend were found to be completely miscible and the blend to
exhibit a single ylass transition temperature. The compo-
sition of the invention is suitable for the preparation of
15 useful molded articles having improved optical properties.
BACKGROUND OF THE TNVENTION
There has long been an interest in developing polymer
blends as an alternative to developing new polymers.
Typically, a blend of two or more polymers has properties
20 similar to a copolymer of the two repeat units. Unfortunately,
significant deviations from the expected properties occur as a
result of the lack of compatibility between the polymeric
components of the blend. Polymer immiscibility, or lack of
compatibility between two polymers is due to a lack of
25 interaction between these two polymers and is believed to have
chemical or morphological reasons. Compatibility between two
or msre polymeric systems is rare in nature and compatible or
miscible blends are typically characterized by their single
glass transition temperature.
Several compatible blends entailing polycarbonate as
a component have been reported in the literature. Notable among
these are "Polyester-Polycarbonate Blends. V. Linear Aliphatic
polyesters" by C.A.Cruz at al, Journal of Applied Polymer
Science, Vol 24, pp. 2101-2112 (1979) which disclosed blends
35052AP0612
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having a single glass transition temperature containing any of
poly(ethylene succinate), poly(ethylene adipate) and
poly(1,4-butylene adipate3. Only partial miscibility was
reported for blends containing poly(hexamethylene sebacate).
In "Miscible Ternary Blends Containing Polycarbonate, SAN,
and Aliphatic Polyesters" By V.S.Shah et al , ibid Vol 32, pp.
3863-3879 (1986), single glass temperature blends were reported
for blends containing poly(1,4-butylene adipate),
poly(1,4-cyclohexanedimethylene succinate) or poly(~-capro-
o lactone).
Blends containing polycarbonate and aliphat;c
polyesters were disclosed in U.S. Patent 4,741,~64. Although a
large number of aliphatic polyesters were mentioned, there is
no indication of compatibility be$ween the components of the
blend. Also of possible relevance is the disclosure in U.S.
Patent 4,683,267 in regard to a adipate-carbonate copolyesters.
Essentially, the art recognized that miscible,
compatible blends of polycarbonate and linear polyesters are
possible and have defined a few suitable polyesters yet no
teaching is apparent as to the general means to predict which
aliphatic polyester is suitable for the preparation of
compatible blends with polycarbonates.
DETAILED DESCRIPTION OF THE INVENTION
The aliphatic polyester of the present invention is
characterized in that its weight average molecular weight is
about 500 to 10,000 and in that it is based on neopentyl glycol
and an aliphatic diacid. In contrast to the previously
reported aliphatic polyesters which were based on linear diols,
the polyester of the present invention is derived from a
branched diol conforming to
ICH3
HO-CH2- C- CH2 OH
CH3
Mo-3365
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While aliphatic diacids generally are suitable in the
present invention, adipict succinic, sebacic, malonic and
oxalic acids are particularly suitable. Adipic acid is most
preferred.
Structurally, the preferred aliphatic polyester of
the invention conforms to
O O CH3
~ C-- (CH2)n - C - O- CH2-C-CH2-0
CH3
wherein n is an integer of 4 to 6.
The preparation of the aliphatic polyester of the
invention may be carried out following conventional procedures,
such as have been described in U.S. Patent 4,857,561 which is
incorporated herein by reference. Polycarbonate resins
suitable in the practice of the invention are well kno~n and
are readily available in commerce. Among the suitable resins
mention may be made of Makrolon polycarbonate resins which are
the products of Mobay Corporation of Pittsburgh, Pa.
Thermoplastic aromatic polycarbonate resins suitable
in the context of the present invention have a weight avera~e
molecular weight of about 10,000 to 200,000 preferably 15,000
to 80,000. Polycarbonates of this type are based on dihydroxy
compounds of the formula
HO-Z-OH
wherein Z is a divalent aromatic radical having 6 to 20 carbon
atoms.
These include both mono nuclear and poly nuclear
dihydroxy compounds, which may contain heteroatoms and may be
substituted. The following are among the suitable compounds:
hydroquinone, resorcinol, dihydroxydiphenyls, bis-(hydroxy-
phenyl)-alkanes, bis-(hydroxyphenyl)-cycloalkanes, bis-
Mo-3365
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(hydroxyphenyl) sulphides, bis-(hydroxyphenyl) ethers,
bis-(hydroxyphenyl) ketones, bis-(hydroxyphenyl) sulphoxides,
bis-(hydroxyphenyl) sulphones, and ~,~'-bis-(hydroxyphenyl)-
diisopropyl-benzenes, and their nuclear-alkylated and
nuclear-halogenated compounds. These and other suitable
dihydroxy compounds are described in U.S. Patent Nos.
3,028,365; 2,999,835; 3,148,172; 3,271,368; 2,991,273;
3,271,367; 3,280,078; 3,014,B91; and 2,999,846, all of which
are incorporated herein by reference, in German Offenlegungs
o schriften Nos. 1,570,703; 2,063,050; 2,036,052; and 2,211,956;
French ~atent Specification No. 1,561,518 and in the monograph
H. Schnell, Chemistry and Physics of Polycarbonates,
Interscience Publishers, New York 1964.
Examples of preferred dihydroxy compounds are:
4,4'-dihydroxybiphenyl 2,2-bis-(4-hydroxyphenyl)-propane,
2,4-bis-(4-hydroxyphenyl)-2-methylbutane, 1,1-bis-
(4-hydroxyphenyl)cyclohexane, ~,~'-bis-(4-hydroxyphenyl)-
p-diisopropylbenzene, 2,2-bis-(3-methyl-4-hydroxyphenyl)-
propane, 2,2-bis-(3-chloro-4-hydroxyphenyl)-propane,
bis-(3,5-dimethyl-4-hydroxyphenyl)-methane, 2,2-bis-(3,5-
dimethyl-4-hydroxyphenyl)-propane bis-(3,5-dimethyl-
4-hydroxyphenyl3-2-methylbutane, 1,1-bis-(3,5-dimethyl-
4-hydroxyphenyl)-cyclohexane, ~,~'-bis(3,5-dimethyl-
4-hydroxyphenyl)-p-diisopropylbenzene, 2,2-bis-(3,5-dichloro-
4-hydroxyphenyl)-propane, and 2,2-bis-(3,5-dibromo-4-nydroxy
phenyl)-propane.
Examples of particularly preferred dihydroxy
compounds are: 2,2-bis-(4-hydroxyphenyl)-propane,
2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane,
2,2-bis(3,5-dichloro-4-hydroxyphenyl-propane, 2,2-bis-
(3,5-dibromo-4-hydroxyphenyl)-propane, and 1,1-bis-(4-hydroxy-
phenyl)-cyclohexane
Mixtures of the above mentioned dihydroxy compounds
may also be used.
Mo-3365
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Small amounts of branching agent, preferably between
about 0.05 and 2.0 mol (relative to diphenols employed) may be
added. These are compounds having a functionality of three or
more, in parti~ular those with three or more phenolic hydroxyl
groups, which are added for the purpose of improving the flow
properties. Examples of these compounds include phloroglucinol,
4-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-hep-2-ene, 4,6-dimethyl
-2,4,6-(4-hydroxyphenyl)-heptane, 1,3,5-tri-(4-hydroxyphenyl)
-benzene, 1,1,1-tri-(4-hydroxyphenyl)-ethane, tri-(4-hydroxy-
o phenyl)-phenylmethane, 2,2-bis-[4,4-bis-4-hydroxyphenyl-cyclo-=
hexyl]-propane, 2,4-bis-(4-hydroxyphenyl)-isopropyl-phenol,
2,6-bis-(2-hydroxy-5'-methylbenzyl-4-methylphenol,
2-(4-hydroxy-phenyl)-2-(2,4-dihydroxyphenyl)-propane,
hexa-[4-(4-hydroxy-phenylisopropyl)-phenyl] orthoterephthalic
acid ester, tetra-(4-hydroxyphenyl)-methane, tetra-
[4-(4-hydroxy-phenylisopropyl)-phenoxy-methane and
1,4-bis-[4',4"-dihydroxy-triphenyl)-methyl]-benzene. Other
suitable trifunctional compounds are 2,4-dihydroxybenzoic acid,
trimesic acid, cyanuric chloride and 3,3-bis-(3-methyl-4-
hydroxyphenyl)-2-oxo-2,3-hydroindole.
The polycarbonates according to the invention are
preferably prepared by the phase boundary process (as described
for instance in H. Schnell, Chemistry and Physics of
Polycarbonate, Polymer Reviews, Volume IX, page 33, et. seq.,
Interscience Publishers, (1964~), incorporated herein by
reference.
Regulatin~ the molecular weight of the polycarbonate
resin is attained by use of monohydric aromatic hydroxy
compounds. These are well known and include monophenols such
as isooctylphenol, cumylphenol, m- and p-methylphenol, m- and
p-ethylphenol, m- and p-propylphenol and m- and p-isopropyl-
phenol, p-bromophenol and m and p-butylphenol, and
para-t-butyl-phenol. The preferred embodiments entail a
polycarbonate resin having chain terminators conforming to
Mo-3365
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6-
~lo~
~ (I)
wherein R represents a branched alkyl radical consisting of 4
to 10 carbon atoms. Most preferred polycarbonate resins having
chain terminators of this type have been disclosed in U.S.
Patent 4,269,964 which is incorporated herein by reference.
The preferred polycarbonates represent an improvement in terms
of hydrolysis resistance, critical thickness and mechanical and
thermal properties.
The blends of the present invention are characterized
in that they have excellent clarity and color and they are
suitable for thermoplastic molding generally and in particular
for injection molding and extrusion
The blend comprise about 0.01 to 40 %, preferably
about 0.05 to 20% most preferably about 0.5 to 10 % polyester ,
said percents being relative to the weight of the blend.
The polycarbonate of the invention is characterized in
that its melt flow index is about 1 to 70 gm./10 minutes ,
preferably about 8 to 50 gm/10 min., most preferably the
polycarbonate has a weight average molecular weight of about
10,000 to 30,000.
Experimental
Compatible blends within the scope of the invention
have been prepared and their properties evaluated. The table
below summarizes the results of the evaluations as to the
compatibility and yellowness indices of several blends. In the
30 blends used in the comparisons, the polycarbonate resin was a
homopolycarbonate based on bisphenol A, characterized in that
its melt flow index as determined in accordance with ASTM
D-1238 is about 10 gram/10 minutes (g/10 min.). The aliphatic
polyester which was used in these experiments was derived from
35 neopentyl glycol and adipic acid and is characterized in that
its molecular weight was about 2000 gm/mole. The preparation
of the polyester was as follows:
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A ~ive liter flask was charged with 1673 parts of
neopentyl glycol (2% excess). 167 parts of propylene glycol
(10% of total neopentyl glycol) was added to help reflux the
neopentyl glycol that would otherwise be lost due to
sublimation. Nitrogen was bubbled through the flask and the
temperature of the flask raised to 160C. 2069 parts of adipic
acid were slowly added while stirring and the temperature was
raised to 220C at the completion of the addition. Water was
collected in the receiving flask. After the atmospheric cycle
, vacuum was slowly applied to the system and more water was
o distilled over (510 parts total water was collected~. The
excess neopentyl glycol and propylene glycol were distilled
over under vacuum. The polyester gave by titration an acid
number of less than 1 and an OH number of about 112. The
viscosity of the polyester at 25C as about 7000 mPa.s.
The preparation of the blends was carried out by
conventional means following conventional methods and equipment
for the manufacturing of thermoplastic molding compositions.
The glass transition temperature of the blends was
determined in accordance with ASTM 3418 and the yellowness
Index was determined in accordance with ASTM 1925.
Table 1
Composition Glass Transition Yellowness Index*
Temperature (C)
Polycarbonate resin
(control) 154 4.02
Polycarbonate + 1% polyester 146 3.68
Polycarbonate ~ 5% polyester 132 3.04
* determined from parts having a thickness of 100 mils which
30 were molded at 550F.
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The results which Point to that the blends have a
single glass transition temperature and that the glass
transition temperature decreases with respect to that of the
unblended polycarbonate resin indicate a compatible blend.
Mo-3365
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