Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G64/00—Macromolecular compounds obtained by reactions forming a carbonic ester link in the main chain of the macromolecule
  • C08G64/20—General preparatory processes
  • C08G64/30—General preparatory processes using carbonates
  • C08G64/307—General preparatory processes using carbonates and phenols
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G64/00—Macromolecular compounds obtained by reactions forming a carbonic ester link in the main chain of the macromolecule
  • C08G64/04—Aromatic polycarbonates
  • C08G64/06—Aromatic polycarbonates not containing aliphatic unsaturation
  • C08G64/14—Aromatic polycarbonates not containing aliphatic unsaturation containing a chain-terminating or -crosslinking agent

Definitions

• 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 US Patents 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.
• melt polymerization i.e., transesterification
• bisphenol A 2,2- bis(4-hydroxyphenyl)propane
• diphenyl carbonate such as diphenyl carbonate
• a third step of building the molecular weight of the crystallized prepolymer by heating to a temperature between
• 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.
• optical disks as exemplified by compact audio disks and CD-ROM disks used in computers.
• 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 ⁇ . ⁇ '-dihdyroxy-S S'.S'-tetra- methyl-1 ,1'-spiro(bis)indane, hereinafter designated "SBI", or 1,1,3-tri- methyl-3-(4-hydroxyphenyl)-5-hydroxyindane ("CD-1").
• 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.
• SSP solid state polymerization
• 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:
• step II subjecting said copolycarbonate of enhanced crystallinity to solid state polymerization, following step II and either concurrently with or following step I.
• Component A is a precursor polycarbonate.
• 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 25°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.
• a high molecular weight homo- or copolycarbonate i.e., one having an intrinsic viscosity above 0.30 dl/g.
• 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 US Patent 4,217,438, the disclosure of which is incorporated by reference herein.
• 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 he 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.
• a chlorinated organic solvent such as chloroform, methylene chloride or 1,2-dichloroethane
• 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.
• component B may be a monomeric compound. These include dihydroxy, preferably dihydroxyaromatic, compounds.
• polyoxyalkylene glycols which for the purpose of this invention are considered to be monomers even though they are polymeric in structure; e.g., polyethylene glycol or polypropylene glycol, typically having a number average molecular weight, Mn, in the range of about 150-50,000, or alkanedioic acids, the latter generally employed in the form of a diaryl ester for ease of inco ⁇ oration by the methods hereinafter discussed.
• Oligomeric or high molecular weight homo- and copolycarbonates similar to those used as component A, may also be employed, with the proviso that they contain units not present in component A.
• component B may be SBI, a polyoxyalkylene glycol or diphenyl dodecanedioate, or a polycarbonate or copolyestercarbonate of any molecular weight containing ⁇ units derived from one of these.
• step I of the method of this invention components A and B are brought into contact under conditions promoting reaction between them.
• Such conditions generally involve temperatures in the range of about 170-250°C, frequently including staged heating at progressively increasing temperatures.
• the conditions may be those known in the art to be applicable to melt polymerization to form oligomers, or to reactive extrusion or redistribution. They may include progressively decreased pressures, starting at atmospheric and terminating at about 100 torr or even lower, although decreasing pressure is not always necessary or even preferred.
• step I Since the reaction which occurs in step I is in essence an equilibration, the use of a dihydroxy compound alone as component B may result in an undesirable decrease in molecular weight. This may be an initial decrease followed by an increase or, on occasion, a permanent decrease. It is particularly noticeable if component B is a monomeric bisphenol such as SBI and the entire portion of both components is introduced initially. It may even be observed that the initial decrease is so great that an undesirable amount of time is needed to compensate for it.
• component B is a monomeric bisphenol such as SBI and the entire portion of both components is introduced initially. It may even be observed that the initial decrease is so great that an undesirable amount of time is needed to compensate for it.
• Two process variants may be employed, individually or in combination, to avoid such a decrease.
• An initial decrease may be avoided by introducing component B, especially when it is a monomeric bisphenol, incrementally during the reaction, with staged heating after each increment is added.
• a longer term decrease may be compensated for by the addition of diaryl carbonate, such as diphenyl carbonate, concurrently with the monomeric bisphenol, whereupon the two react to form additional carbonate structural units.
• Molar ratios of diaryl carbonate to monomeric bisphenol added at this stage are usually in the range of about 0.5-1.2:1, preferably 1:1.
• Suitable catalysts include those effective in such polycarbonate reactions as melt polymerization, redistribution, equilibration and solid state polymerization.
• A is unsubstituted p-phenylene
• Q is a monocationic carbon- and nitrogen-containing moiety containing 9-34 atoms
• Y is a bridging radical in which one or two carbon atoms separate the A values.
• Particularly suitable quaternary bisphenolates are those in which Y is isopropylidene and Q is a hexaalkylguanidinium cation, especially hexaethylguanidinium.
• Catalyst solution in this example is an aqueous solution of 28.54% (by weight) hexaethylguanidinium chloride and 10.09% sodium chloride.
• the purified product was shown by elemental analysis, atomic adsorption analysis and proton nuclear magnetic resonance spectroscopy to be the desired hexaethylguanidinium bisphenolate, having the stoichiometric proportions of three hydrogen atoms, one hexaethylguanidinium cation moiety and two bisphenol A dianion moieties.
• Typical combinations include an inorganic constituent such as an alkali metal hydroxide and an organic constituent such as a tetraalkylammonium hydroxide.
• Total catalyst concentration is most often about 1-1,000 ppm (by weight) based on component A.
• the product of step I is a precursor copolycarbonate comprising the structural units present in components A and B, formed by equilibration or the equivalent thereof.
• the proportion of structural units therein will, for the most part, be the same as the proportion in the combination of components A and B.
• the proportions of said components in the equilibration reaction mixture should correspond to the desired proportion of respective structural units in the product.
• This proportion is subject to wide variation, depending on the intended use of the product copolycarbonate, and is in no way critical for the purposes of the invention.
• the proportion of other structural units will be in the range of about 1-50 mole percent based on total units in the product.
• Step II is a step of enhancement of crystallinity. It may be and most often is performed on the precursor copolycarbonate produced in step I. However, it is also within the scope of the invention to enhance the crystallinity of either component A or component B, prior to performing step I. For example if component A is an SBI polycarbonate oligomer and component B is a bisphenol A polycarbonate oligomer, crystallinity enhancement may be performed on one of them after which they may undergo reaction to form a precursor copolycarbonate which itself inherently has enhanced crystallinity.
• Crystallinity enhancement may be achieved by known methods such as solvent treatment or heat treatment as disclosed in the aforementioned US Patent 4,948,871 and/or contact, typically at a temperature above about 110°C, with one or more catalysts as disclosed in the aforementioned US Patent 5,717,056.
• the catalysts used may include certain of those employed in step I, especially alkali metal hydroxides and alkoxides; quaternary bisphenolates; tetraalkylammonium hydroxides, alkoxides and carboxylates; and tetraalkylphosphonium hydroxides, alkoxides and carboxylates. It is sometimes found that the precursor copolycarbonate prepared in step I inherently has the necessary enhanced crystallinity. Thus, the invention embraces situations in which enhancement of crystallinity is inherent in and simultaneous with step I.
• Step III is the solid state polymerization step. It is effected at a temperature between the glass transition temperature and the melting temperature of the enhanced crystallinity polycarbonate precursor, most often about 10-50°C below its melting temperature. In general, temperatures in the range of about 150-270° and especially about 180-250°C are suitable.
• the solid state polymerization step may be achieved in the absence or presence of catalysts.
• catalysts may often be the same as those employed in step I and may function in both steps without further catalyst addition.
• Solid state polymerization may be conducted in a mixer capable of producing intimate gas-solid contact, such as a fixed bed, fluidized bed or paddle mixer, in contact with an inert gas such as nitrogen or argon which serves as the fluidizing gas if a fluidized bed is employed.
• Said inert gas may serve one or both of the purposes of fluidizing the mixture and volatilizing and removing by-products, including water, hydroxyaromatic compound (such as phenol) corresponding to the carbonate employed to produce the precursor copolycarbonate, and any volatile carbonate formed as a by-product.
• Programmed heating may be advantageously employed.
• the polymerization may be conducted at reduced pressure, typically less than about 100 torr, preferably with efficient mixing.
• Step III may be performed either concurrently with or following step I, provided it follows step II.
• step II may be employed on either component A or B to enhance its crystallinity, after which the SSP step may be conducted without a separate intervening step of oligomer formation. This is true, for example, when component B is a soft block monomer such as polyethylene glycol, which may be incorporated in the polymer during the SSP step.
• a 1-1 glass melt polymerization reactor was passivated by acid washing, rinsing with deionized water and overnight drying at 70°C. It was charged with 130.4 g (608.6 mmol) of diphenyl carbonate and 120 g (525.6 mmol) of bisphenol A.
• a solid nickel stirrer was suspended in the mixture and the reactor was purged with nitrogen and heated to 180°C, whereupon the reaction mixture melted. Upon complete melting, it was allowed to equilibrate for 5-10 minutes, with stirring. There were then added, with stirring, 600 ⁇ l of a 0.221 M aqueous tetramethylammonium maleate solution and 500 ⁇ l of a 0.01 M aqueous sodium hydroxide solution. Heating at 180°C and stirring were continued for 5 minutes, after which the temperature was raised to 210°C and the pressure decreased to 180 torr, whereupon phenol began to distill. After 10 minutes, a bisphenol A polycarbonate oligomer had been produced.
• the oligomer was returned to atmospheric pressure and 11 g (27.6 mmol) of a polyethylene glycol having a Mn of 400 was added through a syringe. The temperature and pressure were brought to 210°C/100 torr for 60 minutes as phenol continued to distill. The temperature was then raised to 240°C for about 15 minutes, after which about 80% of the theoretical amount of phenol had been removed and the product was poured into an aluminum tray. The resulting precursor copolycarbonate oligomer had a weight average molecular weight, Mw, of 2,180.
• the precursor copolycarbonate was ground to a fine powder and suspended for 2 hours in a 70/30 (by volume) dimethyl carbonate-methanol mixture containing 100 ppm of tetramethylam- monium hydroxide. The suspension was filtered and the resulting copolycarbonate of enhanced crystallinity was dried for 12 hours in a vacuum oven at 110°C.
• a 9-g sample of a melt prepared bisphenol A polycarbonate having a Mw of about 32,000 was dissolved in 30 ml of methylene chloride and precipitated by addition of 50 ml of ethyl acetate, after which analysis showed the presence of sufficient crystallinity to undergo efficient SSP.
• Example 3 A 9-g sample of the polycarbonate employed in Example 3 was treated in the same manner to enhance crystallinity. SSP was conducted as in Example 3, except that three 1-g portions of SBI and three 2.16-mmol portions of diphenyl carbonate were introduced during the polymerization. The results are given in Table III.
• a 100-ml 3-necked flask was charged with 15.4 g (50 mmol) of SBI, 11.23 g (52.5 mmol) of diphenyl carbonate and 0.2268 mg (0.0012 mmol) of tetramethylammonium maleate.
• the mixture was heated under nitrogen for 60 minutes at 180°C, after which the pressure was reduced to 100 torr and then stepwise to 1 torr over 140 minutes.
• the temperature was increased to 200°C for 20 minutes, whereupon phenol began to distill.
• the temperature was further increased to 230°C (20 minutes), 250°C (20 minutes) and 270°C (30 minutes).
• the reaction was stopped when about 80% of theoretical phenol had been removed, whereupon an SBI polycarbonate oligomer having a Mw of 1,150 was isolated.
• the crystallinity of a 9-g portion of a bisphenol A polycarbonate oligomer prepared by melt polymerization and having a Mw of about 8,000 was enhanced by dissolving in dimethyl carbonate containing 100 ppm of tetramethylammonium maleate, stirring for 5 minutes, vacuum stripping and drying in a vacuum oven.
• a mixture of 9 parts of the enhanced crystallinity bisphenol A polycarbonate oligomer and 1 part of the SBI polycarbonate oligomer was subjected to SSP in a fluidized bed reactor under a nitrogen flow of 3 l/min, at 180°C for 1 hour, 210°C for 1 hour, 220°C for 2 hours and 230°C for 2 hours.
• the product copolycarbonate had a Mw of 39,600 and a Tg of 142°C.
• a mixture of 97.5 mmol of a bisphenol A polycarbonate having a Mw of 57,800 and 2.5 mmol of a polyethylene glycol having a Mn of 200 was extruded at 15.4-33.0 kg/hr and a screw speed of 250- 300 rpm, with the barrel set temperature at 240° C.
• the crystallinity of the resulting precursor copolycarbonate, formed by equilibration, was enhanced by dissolution in the dimethyl carbonate-methanol mixture of Example 1 with 100 ppm of the quaternary bisphenolate of Example 1, followed by drying.
• the enhanced crystallinity precursor polycarbonate was subjected to SSP in a fluidized bed reactor under a nitrogen flow of 8 l/min, at temperatures of 180°C for 2 hours, 190°C for 1 hour, 200°C for 1 hour, 210°C for 1 hour, 220°C for 2 hours and 230°C for 1 hour.
• the product copolycarbonate had a Mw of 43,700 and a Tg of 139°C.
• Example 6 The procedure of Example 6 was repeated, using a polyethylene glycol having a Mn of 400.
• the product copolycarbonate had a Mw of 47, 100 and a Tg of 139°C.

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• 1999
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