Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1999-08-23
2001-12-25
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S198000
Reexamination Certificate
active
06333394
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the preparation of copolycarbonates, and more particularly to a method for their preparation which includes solid state polymerization.
Solid state polymerization is disclosed, for example, in U.S. Pat. Nos. 4,948,871, 5,204,377 and 5,717,056, the disclosures of which are incorporated herein. It typically involves a first step of forming a prepolymer, typically by melt polymerization (i.e., transesterification) of a dihydroxyaromatic compound such as 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) with a diaryl carbonate such as diphenyl carbonate; a second step of crystallizing the prepolymer; and a third step of building the molecular weight of the crystallized prepolymer by heating to a temperature between its glass transition temperature and its melting temperature. Use of this method is of increasing interest by reason of its effectiveness and environmental benefits.
The end uses for which the overall properties of polycarbonates make them particularly suitable potentially include many which require specific properties not possessed by aromatic polycarbonates as a genus, and in particular not possessed by bisphenol A polycarbonates. For example, polycarbonates are widely used for the fabrication of optical data-recording media, including optical disks as exemplified by compact audio disks and CD-ROM disks used in computers. By reason of the optical requirements of such disks, particularly those having read-write capability, it is essential or at least strongly preferred that they have low birefringence. Birefringence is the difference between indices of refraction for light polarized in perpendicular directions. Birefringence leads to phase retardation between different polarization components of the laser beam which reads the optical disk, thereby reducing readability. Polycarbonates prepared from bisphenol A have relatively high birefringence, which is typically lowered for optical purposes by incorporation of such monomers as 6,6′-dihdyroxy-3,3,3′,3′-tetramethyl-1,1′-spiro(bis)indane, hereinafter designated “SBI”, or 1,1,3-trimethyl-3-(4-hydroxyphenyl)-5-hydroxyindane (“CD-1”).
It is also frequently desirable to improve the processability of polycarbonates by the incorporation, for example, of “soft blocks” derived from aliphatic compounds such as alkanedioic acids or polyoxyalkylene glycols. This is particularly important in optical disk fabrication, since processability is generally degraded by the presence of such monomers as SBI and CD-1 as a result of such factors as increase in glass transition temperature.
Typical interfacial methods of polycarbonate preparation, by the reaction of one or more dihydroxyaromatic compounds under alkaline conditions with phosgene in a mixed aqueous-organic system, are frequently not adaptable to preparation of “soft block” polycarbonates since the alkaline environment can degrade the soft block monomer. Melt (transesterification) methods, by the reaction of the dihydroxyaromatic compounds with diaryl carbonate, are likewise of limited use because the high temperatures (on the order of 300° C.) required for building a high molecular weight polymer can cause thermal decomposition of the soft blocks.
The use of solid state polymerization (hereinafter sometimes “SSP”) conditions, which are usually milder and require lower polymerization temperatures than melt polymerization, could be of use for the preparation of copolycarbonates containing soft blocks and/or birefringence-decreasing units. However, many monomers, especially the soft block ones, may undergo degradation even under SSP conditions even though the structural units derived therefrom may be stable under the same conditions. An alternative method of incorporating the copolymeric units in a polymer ultimately produced by SSP is therefore necessary.
SUMMARY OF THE INVENTION
The present invention is based on the discovery that copolymeric units may be incorporated in a precursor copolycarbonate by various procedures, and said precursor copolycarbonate subsequently exposed to SSP conditions. The product is a high molecular weight copolycarbonate having the desired properties, which may include high processability and low birefringence.
The invention is a method for preparing a copolycarbonate which comprises:
(I) contacting (A) a precursor polycarbonate with (B) a monomeric or polymeric source of other structural units than those present in component A, which are to be incorporated in the copolycarbonate, said contact being under conditions promoting reaction of components A and B with incorporation of said structural units to form a precursor copolycarbonate;
(II) converting component A, component B or said precursor copolycarbonate to a polycarbonate of enhanced crystallinity, either prior to or following step I; and
(III) subjecting said copolycarbonate of enhanced crystallinity to solid state polymerization, following step II and either concurrently with or following step I.
DETAILED DESCRIPTION; PREFERRED EMBODIMENTS
The essential constituents employed in the method of this invention are sometimes designated “components” irrespective of whether they are or are not believed to undergo reaction during the practice of said method.
Component A, then, is a precursor polycarbonate. As used herein, “polycarbonate” includes copolycarbonates and polyestercarbonates. Suitable precursor polycarbonates may be prepared by the first step of a melt polycarbonate process or by bischloroformate oligomer preparation followed by hydrolysis and/or endcapping and isolation. Such oligomers most often have an intrinsic viscosity in the range of 0.06-0.30 dl/g, all intrinsic viscosity values herein being as determined in chloroform at 30° C.
The precursor polycarbonate may also be a high molecular weight homo- or copolycarbonate; i.e., one having an intrinsic viscosity above 0.30 dl/g. Numerous kinds of suitable high molecular weight homo- and copolycarbonates are suitable, including conventional linear polycarbonates in virgin form. They may be prepared from any of the known dihydroxy compounds useful as monomers, including dihydroxyaromatic compounds such as bisphenol A, SBI and others designated by name or structural formula (generic or specific) in U.S. Pat. No. 4,217,438, the disclosure of which is incorporated by reference herein.
Also included are branched polycarbonates, formed by the reaction of a linear polycarbonate or its precursor(s) with a branching agent such as 1,1,1-tris(4-hydroxyphenyl)ethane. It may also be a copolycarbonate, particularly a copolycarbonate oligomer or high molecular weight copolycarbonate containing units adapted to maximize solvent resistance. Such units will typically comprise about 25-50% of total carbonate units in the polymer.
Recycled polycarbonates, for example from compact disks, may also be employed. Such recycled material typically has a molecular weight which has been degraded from that of the originally polymerized material as shown by an intrinsic viscosity in the range of about 0.25-1.0 dl/g. It may be obtained from scrap polycarbonate by dissolution in a chlorinated organic solvent such as chloroform, methylene chloride or 1,2-dichloroethane followed by filtration of the insoluble material or by other art-recognized procedures for separation of non-polycarbonate constituents. Other types of polycarbonate, such as interfacially prepared polycarbonate and polycarbonate extruder wastes, may also be employed as precursors.
Component B is a source of other structural units than those present in component A, said other structural units intended to be incorporated in the product. The other units may be present in combination with units which are present in component A.
Thus, component B may be a monomeric compound. Suitable monomeric compounds include dihydroxy, preferably dihydroxyaromatic, compounds as illustrated by the dihydroxy compounds disclosed by name or formula (generic or specific) in U.S. Pat. No. 4,217,438, the disclosure of which is incorporated by reference herein.
Bailly Christian Maria Emile
Chatterjee Gautam
Chavan Nayaku Nivarati
Day James
Faber Rein Mollerus
Boykin Terressa M.
General Electric Company
Johnson Noreen C.
Stoner Douglas E.
LandOfFree
Copolycarbonate preparation by solid state polymerization does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Copolycarbonate preparation by solid state polymerization, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Copolycarbonate preparation by solid state polymerization will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2598364