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Mo-3365 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 :
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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 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 ~ C-- (CH2)n - C - O- CH2-C-CH2-0 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.
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~ Q 3 ~ 9 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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~ (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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2 ~ .3 .'i ~ ~ .9 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.
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