Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-12-19
2002-09-10
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S133000, C525S148000, C525S439000, C524S133000, C524S140000, C524S147000, C524S414000, C524S417000
Reexamination Certificate
active
06448334
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a thermoplastic composition comprising aromatic polycarbonate. In particular, the invention relates to a translucent polycarbonate composition having excellent physical properties.
Aromatic polycarbonates are engineering thermoplastics that combine desirable mechanical, optical, thermal, and electrical properties. When extruded in sheet form, aromatic polycarbonates have high transparency and excellent impact strength, making them ideal for a variety of glazing applications including roofs, greenhouses, sunrooms, and swimming pool enclosures. For structures in hot climates or for the southern exposure of structures in various climates, it is often desirable to use polycarbonate sheets having reduced light transmission in the form of opal whiteness and/or translucency.
It is known in the art that polycarbonate resins can be rendered translucent by the use of one or more inorganic additives such as titanium dioxide, zinc oxide, zinc sulfide, lead carbonate, and barium sulfate (see, for example, U.S. Pat. No. 4,252,916 to Mark, and Japanese Unexamined Patent Publication Nos. JP 06-306266 and JP 09-048911). It is also known to make polycarbonate translucent via addition of a partially fluorinated polyolefin (see, for example, U.S. Pat. No. 4,252,916 to Mark), a polyolefinic resin in combination with a plasticizer (see, for example, Japanese Unexamined Patent Publication JP 05-017599A), poly(dimethylsiloxane) gum in combination with finely divided silica (see, for example, U.S. Pat. No. 3,933,730 to Hoogeboom), poly(methyl silsesquioxane) (see, for example, European Patent No. 604,130 to Ohtsuka et al.), or spherical transparent thermoplastic particles (see, for example, International Publication No. WO 00/27927).
Of the above methods, the addition of light-scattering pigments, such as barium sulfate or calcium carbonate, is presently favored for commercial production of translucent polycarbonate compositions. However, the addition of such inorganic pigments adversely affects the physical properties of the sheet, especially its low temperature impact strength.
There remains a need for translucent polycarbonate formulations with improved low temperature impact strength.
BRIEF SUMMARY OF THE INVENTION
A translucent polycarbonate composition comprises:
about 60 to about 99.8 weight percent of an aromatic polycarbonate;
about 0.1 to about 30 weight percent of a cycloaliphatic polyester;
about 0.1 to about 8 weight percent of a polyolefin;
wherein the molded or extruded composition has a transmission of about 15% to about 65% at a thickness of 2.0 mm according ASTM D-1003; and wherein all weight percentages are based on the weight of the total composition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Translucency and high impact strength are provided by a thermoplastic composition comprising:
about 60 to about 99.8 weight percent of an aromatic polycarbonate;
about 0.1 to about 30 weight percent of a cycloaliphatic polyester;
about 0.1 to about 8 weight percent of a polyolefin;
wherein the molded or extruded composition has a transmission of about 15% to about 65% at a thickness of 2.0 mm according ASTM D-1003; and wherein all weight percentages are based on the weight of the total composition.
The inventors have discovered that polyolefins are especially suited for reducing the transparency of blends of aromatic polycarbonate and cycloaliphatic polyester while improving the low temperature impact strength of those blends compared to formulations relying on inorganic pigments for translucency. While polyolefins have sometimes been employed as impact modifiers in polycarbonate compositions, it should be noted that other types of impact modifiers, including methacrylate-butadiene-styrene (MBS) copolymers and styrene-(ethylene-butylene)-styrene block copolymers, have been found by the present inventors to be unsuitable for the present compositions because they do not provide the necessary reduction in transmittance at a similar concentration. It is therefore especially surprising that the desirable combination of properties is provided by the blends comprising polyolefins.
As used herein, the terms “polycarbonate” and “aromatic polycarbonate” include compositions having structural units of the formula
in which at least about 60 percent of the total number of R
1
groups are aromatic organic radicals and the balance thereof are aliphatic, alicyclic, or aromatic radicals. Preferably, R
1
is an aromatic organic radical and, more preferably, a radical of the formula
—A
1
—Y
1
—A
2
—
wherein each of A
1
and A
2
is a monocyclic divalent aryl radical having from 6 to 12 carbon atoms and Y
1
is a bridging radical having one or two bridging atoms that separate A
1
from A
2
. In an exemplary embodiment, one atom separates A
1
from A
2
. Illustrative, non-limiting examples of radicals of this type are —O—, —S—, —S(O)—, —S(O)
2
—, —C(O)—, methylene, cyclohexyl-methylene, 2[2,2,1]-bicycloheptylidene, ethylidene, isopropylidene, neopentylidene, cyclohexylidene, cyclopentadecylidene, cyclododecylidene, and adamantylidene. The bridging radical Y
1
can be a hydrocarbon group or a saturated hydrocarbon group such as methylene, cyclohexylidene or isopropylidene.
Preferred dihydroxy compounds include those in which only one atom separates A
1
and A
2
. As used herein, the term “dihydroxy compound” includes, for example, bisphenol compounds having the formula
wherein R
a
and R
b
each represent a halogen atom or a monovalent hydrocarbon group and may be the same or different; p and q are each independently integers from 0 to 4; and X
a
represents one of the groups of the formula
wherein R
c
and R
d
each independently represent a hydrogen atom or a monovalent linear or cyclic hydrocarbon group and R
e
is a divalent hydrocarbon group.
Some illustrative, non-limiting examples of suitable dihydroxy compounds include dihydric phenols and the dihydroxy-substituted aromatic hydrocarbons disclosed by name or formula (generic or specific) in U.S. Pat. No. 4,217,438 to Brunelle et al. A nonexclusive list of specific examples of the types of bisphenol compounds includes the following: 1,1-bis(4-hydroxyphenyl)methane; 1,1-bis(4-hydroxyphenyl)ethane; 2,2-bis(4-hydroxyphenyl)propane (hereinafter “bisphenol A” or “BPA”); 2,2-bis(4-hydroxyphenyl)butane; 2,2-bis(4-hydroxyphenyl) octane; 1,1-bis(4-hydroxyphenyl)propane; 1,1-bis(4-hydroxyphenyl)-n-butane; bis(4-hydroxyphenyl)phenylmethane; 2,2-bis(4-hydroxy-1-methylphenyl) propane; 1,1-bis(4-hydroxy-t-butylphenyl)propane; bis(hydroxyaryl)alkanes such as 2,2-bis(4-hydroxy-3-bromophenyl)propane; 1,1-bis(4-hydroxyphenyl)cyclopentane; and bis(hydroxyaryl)cycloalkanes such as 1,1-bis(4-hydroxyphenyl)cyclohexane; and the like, as well as combinations comprising at least one of the foregoing.
Aromatic polycarbonate resins typically are prepared by reacting the dihydroxy compound with a carbonate precursor, such as phosgene, a haloformate or a carbonate ester and generally in the presence of an acid acceptor and a molecular weight regulator. These aromatic polycarbonates can be manufactured by known processes, such as, for example, by reacting a dihydroxy compound with a carbonate precursor, in accordance with methods set forth in the literature including the interfacial polymerization and melt polymerization processes. Generally in the melt polymerization process, the dihydroxy compound is reacted with a diester carbonate such as diphenyl carbonate, whereas in the interfacial polymerization the dihydroxy compound is reacted with a carbonyl chloride such as phosgene.
It is also possible to employ aromatic polycarbonates resulting from the polymerization of two or more different dihydric phenols or a copolymer of a dihydric phenol with a glycol or with a hydroxy- or acid-terminated polyester or with a dibasic acid or with a hydroxy acid or with an aliphatic diacid in the event a carbonate copolymer rather than a homopolymer is desired for use. Generally, useful aliphatic diacids have from 2
Hendrix Bart Peter Gerard
Hoogland Gabrie
van Heeringen Mark
Verhoogt Hendrik
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