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
2001-09-05
2003-05-27
Short, Patricia A (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...
C525S448000, C525S466000, C524S128000, C524S537000
Reexamination Certificate
active
06569957
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to blends of polycarbonates and polyesters, and sheets and films formed therefrom that may be thermoformed without having to pre-dry the sheets and films.
BACKGROUND OF THE INVENTION
Polycarbonates are widely used in a variety of molding and extrusion applications. Films or sheets formed from the polycarbonates must be dried prior to thermoforming. If not pre-dried, thermoformed articles formed from the polycarbonates are characterized by the presence of blisters that are unacceptable from an appearance standpoint. Therefore, it would be desirable to provide a manner of forming thermoformed articles without the necessity of pre-drying the polycarbonate sheets or films.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide novel blends or compositions of polycarbonates and specific copolyesters.
It is a further object of this invention to provide novel films and sheets produced from the novel blends or compositions, which films and sheets are thermoformable without previous drying thereof, and wherein the presence of blisters is avoided.
These and other objects and advantages of the present invention will be apparent to those skilled in the art from the following detailed description and claims.
In accordance with the present invention, it has been found that the above and still further objects are achieved by combining at least one or more polycarbonates and at least one or more specified copolyesters, in specific proportions, to provide a new and novel blend or composition that is useful for many applications. In particular, novel sheets and films produced from the novel blends or compositions may be used for packaging food, clothing, pharmaceutical products, signs and skylights, and the like; and, unexpectedly it has been found that the sheets or films may be thermoformed without a necessity of pre-drying and produce articles free of undesirable blisters.
More particularly, in accordance with the present invention, a blend or composition is provided comprising from about 15 to about 40 weight percent (%) polycarbonate and from about 60 to about 85 weight % copolyester. Any polycarbonate may be used. The specific copolyesters used are based on an acid component comprising terephthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, or mixtures thereof containing from 15 to about 35 mol percent (%) isophthalic acid and a glycol component comprising from about 80 to 100 mol % 1,4-cyclohexanedimethanol.
In addition to the novel compositions, the present invention is also directed to films and sheets formed from the novel blends that are thermoformable without pre-drying, to provide articles and profiles free of blisters.
Additionally, the present invention is directed to articles of manufacture incorporating the novel compositions and films of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The novel blends or compositions of the present invention comprise at least one, or more, polycarbonates and at least one, or more specified copolyesters. The polycarbonate is present in an amount ranging from about 15 to about 40 weight %, based on the weight of the total blend or composition, and the copolyester is present in an amount ranging from about 60 to about 85 weight %, both based on the weight of the total blend or composition. The polycarbonate is preferably present in an amount of about 20 to 28 weight percent and the copolyester is preferably present in an amount of about 80 to 72 weight percent, based on the weight of the total blend composition.
The polycarbonate component of the blend or composition may be any polycarbonate. The polycarbonates suitable for use in the present invention are well known and are generally commercially available. The polycarbonates may be branched or linear. Suitable polycarbonates are exemplified, but not limited to, those described in U.S. Pat. Nos. 3,028,365; 3,334,154; 3,915,926; 4,897,453; 5,674,928; and 5,681,905, all of which are incorporated herein by reference. The polycarbonates may be prepared by a variety of conventional and well known processes which include transesterification, melt polymerization, interfacial polymerization, and the like. The polycarbonates are generally prepared by reacting a dihydric phenol with a carbonate precursor, such as phosgene. Suitable processes for preparing the polycarbonates of the present invention are described, for example, in U.S. Pat. Nos. 4,018,750; 4,123,436; and 3,153,008. Preferred polycarbonates for use in the present invention are aromatic polycarbonates, with aromatic polycarbonates based on bisphenol-A [2,2-bis(4-hydroxyphenyl) propane], such as are obtained by reacting bisphenol-A with phosgene, being more preferred. Diphenyl carbonate or dibutyl carbonate may be utilized in place of phosgene.
The copolyester component of the of the blend or composition of the present invention is at least one, or more of poly(1,4-cyclohexylenedimethylene terephthalate) (PCT), poly(1,4-cyclohexylenedimethylene naphthalenedicarboxylate) (PCN), poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) (PCC) copolyesters, or mixtures thereof, containing 15 to about 35 mol % isophthalic acid with a preferred amount being from 20 to about 30 mol % isophthalic acid. The copolyester comprises an acid component comprising from about 65 to about 85 mol percent of a dicarboxylic acid selected from terephthalic acid, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid or mixtures thereof; from about 15 to about 35 mol percent isophthalic acid; and from 0 to about 20 mol percent of other dicarboxylic acid units. The copolyester comprises a glycol component of about 80 to 100 mol percent 1,4-cyclohexanedimethanol (CHDM) and from 0 to about 20 mol percent other glycol units. The total dicarboxylic acid units is equal to 100 mol percent, the total glycol units is equal to 100 mol percent and the total polyester units is equal to 200 mol percent.
The CHDM and 1,4-cyclohexanedicarboxylic acid moieties used to prepare the copolyesters can be trans, cis or trans/cis mixtures of isomers. Any of the naphthalenedicarboxylic acid isomers or mixtures of isomers can be used with the 1,4-, 1,5-, 2,6-, and 2,7-isomers being preferred.
The other dicarboxylic acid(s) that can be used herein in amounts of from 0 to about 20 mol percent have from about 4 to about 40 carbon atoms. Exemplary of the other dicarboxylic acids suitable for use herein are sulfoisophthalic, sulfodibenzoic, succinic, glutaric, adipic, sebacic, suberic, dimer, dodecanedioic, and the like, or mixtures thereof.
The other glycol unit(s) that can be used herein in amounts of from 0 to about 20 mol percent contain from about 3 to about 12 carbon atoms. Exemplary of the other glycols suitable for use herein are propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, diethylene glycol, and the like, or mixtures thereof.
With respect to the composition of the copolyester, the glycol component preferably comprises 100 mol percent of 1,4-cyclohexanedimethanol. In another preferred embodiment, the acid component of the copolyester comprises 65 to 85 mol percent terephthalic acid. In a most preferred embodiment, the copolyester composition comprises 100 mol percent 1,4-cyclohexanedimethanol, about 26 mol percent isophthalic acid, and about 74 mol percent terephthalic acid.
The copolyester component of the blends of the present invention preferably have an inherent viscosity (I.V.) of from about 0.5 to about 1.5 dL/g, determined in accordance with ASTM Test Method D2857-70.
The copolyester component of the blends of the present invention may be prepared by processes well known in the art. For example, the copolyester components may be readily prepared by batch or continuous processes. These copolyesters are typically made in melt phase polycondensation reactions. However it is possible to use solid phase build up techniques well known in the art, if de
Conn Roy Lee
Thompson John Guthrie
Williams James Carl
Boshears B. J.
Eastman Chemical Company
Graves Bernie
Short Patricia A
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