Abstract: Polycarbonate resins containing repeating or recurring polymer chain units of the formula: ##STR1## wherein R represents alkyl are useful in high temperature applications, when thermoplastically molded into articles.

Abstract: A two step solvent-free process for the preparation of polycarbonates having a low degree of branching is disclosed. Accordingly, the process comprise(i) transesterifying in the melt, at temperatures of from 80.degree. to 250.degree. C. and under atmospheric pressure and for a time of up to five hours of diphenols and carbonic acid diaryl esters in the presence of a catalyst to form an oligocarbonate having a weight average molecular weight of from 8,000 to 18,000 and an OH-end group content of from 25 to 50%, and(ii) polycondensing of said oligocarbonate at temperatures of from 250.degree. C. to 295.degree. C. and pressures of from <500 mbar to 0. 01 mbar,said catalyst being present in an amount of 10.sup.-1 to 10.sup.-8 tool of a catalyst per tool of diphenol, said catalyst being at least one member selected from the group consisting of quaternary ammonium compounds and quaternary phosphonium compounds.

Abstract: A process for producing polycarbonates which comprises transesterifying by reacting (A) at least one compound selected from the group consisting of aromatic dihydroxy compounds, aliphatic dihydroxy compounds, bisesters of aromatic dihydroxy compounds, bisesters of aliphatic dihydroxy compounds, carbonates of aromatic dihydroxy compounds and carbonates of aliphatic dihydroxy compounds, with (B) at least one compound selected from the group of diaryl carbonates, dialkyl carbonates, and alkylaryl carbonates, at a transesterification temperature of 100.degree. C. to 330.degree. C. in the presence of an inert solvent in an amount of 1 to 60% by weight based on the total of the theoretical amount of polycarbonate produced from the said compounds (A) and (B) and the amount of the inert solvent. According to the present invention, a polycarbonate which is excellent in color tone (transparency), heat resistance, and water resistance can be efficiently and simply produced at a low cost.

Abstract: A process for preparing a halogenated polycarbonate wherein phenolic-terminated, halogenated carbonate oligomers are prepared in the presence of a coupling catalyst, and are then condensed by contact with a carbonate precursor.

Abstract: A process for preparation of a random copolycarbonate from an ortho-substituted dihydric phenol and a non-ortho-substituted dihydric phenol.

Abstract: Disclosed herein is a polycarbonate copolymer comprising repeating units respectively made of a bisphenol A and a tetrahalogenobisphenol A and having a trihalogenophenoxy group as an end group at the terminal, particularly both terminals thereof and a method for efficiently producing said polycarbonate copolymer. This polycarbonate copolymer is superior in impact resistance, flame retardance, molding thermostability and the like, is good in hydrolytic resistance, is much less liable to cause a mold rust and has high quality. Therefore, this polycarbonate copolymer will be extensively used in various industrial materials, for example as the flame retardant parts for household electric appliances, office automation apparatuses and the like.

Abstract: A method is provided for making polycarbonate by phosgenating a mixture of bisphenol and phenolic chain-stopper under interfacial reaction conditions in the presence of a phase transfer catalyst. A polycarbonate is obtained which is substantially free of diarylcarbonate.

Abstract: A method is provided for making flame retardant polycarbonates by phosgenating a mixture of bisphenols having up to about 50 mole % of tetrahalobisphenols, such as tetrabromobisphenols. There is employed a mixture of a phase transfer catalyst and a tertiary organic amine to provide high molecular weight copolymer without excessive phosgene usage.

Abstract: Diol-polycarbonates having the general formulaHO--(Ri--O--CO--O).sub.x ----(R.sub.2 --O--CO--O--).sub.y --R.sub.3 --OH (I)where R.sub.1, R.sub.2, R.sub.3, X and Y have the meaning specified in the text, are used in the synthesis of prepolymers which in turn can be used in reactive adhesive and/or sealing formulations of the hygro-, photo- or thermosetting type, and the procedure for their preparation. The sealing compositions deriving from these diolterminated-polycarbonates are mainly used in transport industry, in the textile and wood industry, for cellular products and in the bookbinding industry.

Abstract: A process for producing a branched polycarbonate comprising reacting a dihydric phenol, such as 2,2-bis(4-hydroxyphenyl) propane, a polyfunctional organic compound, such as 1,1,1-tris-(4-hydroxyphenyl)ethane, and phosgene to produce a polycarbonate oligomer, and then polycondensing with stirring the polycarbonate oligomer with a dihydric phenol, such as 2,2-bis(4-hydroxyphenyl) propane, and a monohydric phenol, such as p-tert butylphenol, whereby the interfacial area of the resultant emulsion is not less than 40 m.sup.2 /L.

Abstract: The present invention provides a process for producing a polycarbonate oligomer continuously, which comprises feeding (a) an aqueous alkali solution of a dihydric phenol and (b) phosgene into a tower type reactor from the bottom to react them in the reactor without using any organic solvent and discharging the reaction mixture from the top of the reactor. According to this process, an oligomer giving a polycarbonate of stable quality can be produced using a simple apparatus.

Abstract: A halogenated copolycarbonate, including a poly(ester/carbonate), which contains reduced levels of phenolic end groups and end groups which result from side reactions of process chemicals with the copolycarbonate chain, has improved resistance to the degradation-inducing effects of such end groups and has improved washability.

Abstract: This is a branched polycarbonate which comprises a branched structure derived from a branching agent such as 1,1,1-tris(4-hydroxyphenyl)ethane, a repeating unit (I) represented by the following general formula: ##STR1## a repeating unit (II) represented by the following general formula: ##STR2## and a tribromophenoxy group bonded to the terminal thereof, said branched polycarbonate having a viscosity average molecular weight of 10,000 to 50,000, a ratio of said branched structure of 0.1 to 2.0 mol % and a content of said repeating unit (II) of 10 mol % or less.This branched polycarbonate is excellent in flame retardancy, has sufficiently high mechanical properties and further is excellent in melt properties suitable for blow molding.

Abstract: Dihydroxydiphenyl cycloalkanes corresponding to the formula ##STR1## in which R.sup.1 and R.sup.2 independently of one another represent hydrogen, halogen, C.sub.1 -C.sub.8 alkyl, C.sub.5 -C.sub.6 cycloalkyl, C.sub.6 -C.sub.10 aryl and C.sub.7 -C.sub.12 aralkyl,m is an integer of from 4 to 7,R.sup.3 and R.sup.4, individually selectable for each X, independently of one another represent hydrogen or C.sub.1 -C.sub.6 alkylandX represents carbon with the proviso that, at at least one atom X, both R.sup.3 and R.sup.4 are alkyl,a process for their production, their use for the production of high molecular weight polycarbonates, the polycarbonates made from dihydroxydiphenyl cycloalkane of formula (I) and films made from these polycarbonates.

Abstract: A process for preparing a halogenated polycarbonate wherein phenolic-terminated, halogenated carbonate oligomers are prepared in the presence of a coupling catalyst, and are then condensed by contact with a carbonate precursor.

Abstract: A process for preparation of a random copolycarbonate from an ortho-substituted dihydric phenol and a non-ortho-substituted dihydric phenol.

Abstract: A process for preparing halogenated polycarbonate wherein the total amount of base, the end pH of the aqueous phase, and the amount of coupling catalyst employed in the reaction are controlled to selected levels.

Abstract: The invention relates to a method of preparing aromatic polycarbonates by catalytic interface polymerization of at least one bivalent phenol and a carbonyl halide in the presence of a polycondensation catalyst, which method is characterized in that the conversion is carried out in a two-phase system with continuous dosing of the carbonyl halide, which two-phase system is based on water and an organic solvent, in which the quantity of organic solvent at the beginning of the polycondensation lies between 10% and 75% of the quantity of organic solvent which is required at the polymerization temperature for dissolving the quantity of polycarbonate which may be formed from the quantity of bivalent phenol which is present at the beginning of the polycondensation, in that after dosing at least 20% of the carbonyl halide a remaining quantity of organic solvent is added which is at least sufficient to keep the formed polycarbonate in solution.

Abstract: A composition possessing a desirably high balance of resistance to thermal deformation and to chemical solvents, and reduced notch sensitivity, prepared from a polycarbonate having a glass transition temperature in excess of at least 165.degree. C., an aromatic polyester, a polyphenylene ether, and an elastomeric impact modifier.

Abstract: A thermoplastic polycarbonate molding composition resistant to gamma-radiation is disclosed. The composition incorporates about 0.05 to 5.0 percent by weight of and end-capped poly(alkyl oxide) conforming to ##STR1## where hal denotes bromine or chlorine, n is about 10 to 40 and x is 1 to 5.The composition was found to be resistant to the yellowing which characterized polycarbonate compositions upon exposure to gamma radiation. The composition of the invention not only has low initial color change upon exposure but also a small change in yellowness after long term storing.

Abstract: Disclosed is a novel polycarbonate which has(1) a repeating unit (I) represented by the general formula: ##STR1## and a repeating unit (II) represented by the formula: ##STR2## (All the symbols are as defined in the claims); (2) a trihalogenophenoxy group as the end group thereof; and (3) a viscosity average molecular weight of 10,000 to 50,000 and 1 to 10 mol % of the repeating unit (I) in the main chain.The polycarbonate is excellent in all of flame retardance, impact resistance, and a thermostability at molding. Accordingly, the polycarbonate of the present invention is extensively and effectively used as various industrial materials such as home electric appliances, office automation devices, construction materials and the like.

Abstract: Flame-resistant thermoplastic branched polycarbonates of high molecular weight are prepared from:(1) a carbonate precursor;(2) at least one dihydroxyaromatic compound of formula: ##STR1## where: R is a single bond, or a substituted or non-substituted linear or branched C.sub.1 -C.sub.5 alkylene radical, or a group chosen from O, S, SO.sub.2 and CO;X and Y, which may be the same or different, are H or CH.sub.3 ;m and n, which may be the same or different, are whole numbers from 1 to 4;(3) at least one halogenated pyrimidine compound of formula: ##STR2## where: R.sub.2, R.sub.3, R.sub.4, which may be the same or different, are chlorine or bromine or hydrogen, on condition that at least one is chlorine or bromine;R.sub.1 is chlorine or bromine, or a radical of formula: ##STR3## where Z is NH or S or O; (4) at least one polyfunctional organic compound as branching agent, characterized by possessing at least three equal or different groups chosen from the groups OH, COOH, COCl and SO.sub.2 Cl.

Abstract: New aromatic polycarbonates contain, in their bisphenol moiety, at least in part bisphenols of the type 1,1-bishydroxyphenylhexafluorodichlorocyclopentane, 1,1-bishydroxyphenylheptafluoromonochlorocyclopentane or 1,1-bishydroxyphenyloctafluorocyclopentane.

Abstract: A polycarbonate is produced by melt-polycondensing a dihydric hydroxy compound and a bisarylcarbonate in the presence of a catalyst system comprising an electron donative amine compound and a compound selected from among alkali metal compounds and alkaline earth metal compounds. The process of the invention eliminates the use of poisonous phosgene, prevents chloride ions from being incorporated into the product polycarbonate and remains in the reaction system longer to enable the preparation of high-molecular weight polycarbonates.

Abstract: Dihydroxydiphenyl cycloalkanes corresponding to the formula ##STR1## in which R.sup.1 and R.sup.2 independently of one another represent hydrogen, halogen, C.sub.1 -C.sub.8 alkyl, C.sub.5 -C.sub.6 cycloalkyl, C.sub.6 -C.sub.10 aryl and C.sub.7 -C.sub.12 aralkyl,m is an integer of from 4 to 7,R.sup.3 and R.sup.4, individually selectable for each X, independently of one another represent hydrogen or C.sub.1 -C.sub.6 alkyl andX represents carbon with the proviso that, at least one atom X, bothR.sup.3 and R.sup.4 are alkyl,a process for their production, their use for the production of high molecular weight polycarbonates, the polycarbonates made from dihydroxydiphenyl cycloalkane of formula (I) and films made from these polycarbonates.

Abstract: A branched polycarbonate having (1) an intrinsic viscosity of 0.3 to 2 dl/g, (2) a branching parameter of 0.05 to 0.9, (3) a degree of branching of 0.2.times.10.sup.-4 and optionally (4) a taking-off parameter of 2.5 to 20. The branched polycarbonate is useful as a raw material for blow-moldings.

Abstract: A process for the preparation of a phenol and solvent free polycarbonate resin is disclosed comprising(i) forming an oligomeric polycarbonate comprising structural units based on a diphenol corresponding to ##STR1## wherein R.sup.1 and R.sup.2 independently of one another denote a member selected from the group consisting of a hydrogen atom, a halogen atom, C.sub.1-8 alkyl, C.sub.5-6 cycloalkyl, C.sub.6-10 aryl and C.sub.7-12 aralkyl radicals,m is an integer of from 4 to 7,X represents carbon andR.sup.3 and R.sup.4 are individually selected for each X and independently of one another represent a hydrogen atom or a C.sub.1-6 alkyl radical, with the proviso that for at least one X atom, both R.sup.3 and R.sup.4 are alkyl radicals, and(ii) condensing said oligomeric polycarbonate at a temperature in the range of of 140 to 350.degree. C.

Abstract: Flame-resistant thermoplastic branched polycarbonates of high molecular weight are prepared from:(1) a carbonate precursor;(2) at least one dihydroxyaromatic compound of formula: ##STR1## where: R is a single bond, or a substituted or non-substituted linear or branched C.sub.1 -C.sub.5 alkylene radical, or a group chosen from O, S, SO.sub.2 and CO;X and Y, which may be the same or different, are H or CH.sub.3 ;m and n, which may be the same or different, are whole numbers from 1 to 4;(3) at last one halogenated pyrimidine compound of formula: ##STR2## where: R.sub.2, R.sub.3, R.sub.4, which may be the same or different, are chlorine or bromine or hydrogen, on condition that at least one is chlorine or bromine;R.sub.1 is chlorine or bromine, or a radical of formula: ##STR3## where Z is NH or S or O; (4) at least one polyfunctional organic compound as branching agent, characterized by possessing at least three equal or different groups chosen from the groups OH, COOH, COCl and SO.sub.2 Cl.

Abstract: Thermoplastic, branched, high-molecular-weight polycarbonates endowed with flame-proof properties (self-extinguishing properties) are characterized in that they contain in their macromolecule carbonate units, units deriving from a di-hydroxy-aromatic compound having the formula: ##STR1## wherein: R is a single bond; orR is a linear or branched, either substituted or non-substitued, alkylene radical of from 1 to 5 carbon atoms; orR is selected from the group consisting of O, S, SO.sub.2, CO;X, Y which may be either equal to, or different from, each other, are either H or CH.sub.3 ;m, n which may be either equal to, or different from, each other, are integers comprised within the range of from 1 to 4;and units deriving from a halogenated macrocyclic compound having the formula ##STR2## wherein: R.sub.1 is H or OH or chlorine or bromine, andR.sub.2 is chlorine or bromine.

Abstract: The novel thermotropic polycarbonates having recurring structural units of the formulae ##STR1## have good mechanical properties and good processability. They can be used in conventional manner for manufacturing mouldings, filaments, fibres and films.

Abstract: A halogenated copolycarbonate, which contains reduced levels of phenolic end groups and end groups which result from side reactions of process chemicals with the copolycarbonate chain, has improved resistance to the degradation-inducing effects of such end groups and has improved washability.

Abstract: Flame-resistant thermoplastic branched polycarbonates of high molecular weight are prepared from:(1) a carbonate precursor;(2) at least one dihydroxyaromatic compound of formula: ##STR1## where: R is a single bond, or a substituted or non-substituted linear or branched C.sub.1 -C.sub.5 alkylene radical, or a group chosen from O, S, SO.sub.2 and CO;X and Y, which may be the same or different, are H or CH.sub.3 ;m and n, which may be the same or different, are whole numbers from 1 to 4;(3) at least one halogenated carbonyl compound of formula: ##STR2## where: Z is a group chosen from O, S, and NH;R.sub.1 and R.sub.2, which may be the same or different, are chlorine or bromine;R is hydrogen or chlorine or bromine or a C.sub.1 -C.sub.3 alkyl radical;p is zero or 1 or 2.

Abstract: Flame-resistant thermoplastic branched polycarbonates of high molecular weight are prepared from:(1) a carbonate precursor;(2) at least one dihydroxyaromatic compound of formula: ##STR1## where: R is a single bond, or a substituted or non-substituted linear or branched C.sub.1 -C.sub.5 alkylene radical, or a group chosen from O, S, SO.sub.2 and CO;X and Y, which may be the same or different, are H or CH.sub.3 ;m and n, which may be the same or different, are whole numbers from 1 to 4;(3) at least one halogenated triphenolbenzamido compound of formula: ##STR2## where: Z is a group chosen from CO and SO.sub.2 ;R.sub.1 is chlorine or brominep is 1 or 2.

Abstract: Thermoplastic branched polycarbonates of high molecular weight and which possess flame-resistant (self-extinguishing) properties are provided wherein said polycarbonates contain in addition to carbonate units, units derived from a dihydroxyaromatic compound, units derived from a halogenated triphenyl compound and units derived from a polyfunctional organic branching agent.

Abstract: This invention relates to thermoplastic, aromatic polycarbonates in which mesogenic compounds corresponding to the following formula ##STR1## are incorporated as chain terminating agents, to their preparation by the known processes for the preparation of polycarbonates, and to their use for the production of moulded articles for optical purposes.

Abstract: Novel polycarbonate resins, a process for production of said polycarbonate resins, and compositions containing said polycarbonate resins and glass fibers as major components are disclosed. The polycarbonate resins have: (1) a repeating unit (I) represented by the general formula (A): ##STR1## and a repeating unit (II) represented by the general formula ##STR2## (all the symbols are as defined in the appended claims); (2) a pentahalogenophenoxy group as the end group thereof; and (3) a viscosity average molecular weight of at least 5,000. The polycarbonate resins are excellent in all of flame retardance, fluidity, impact resistance and transparency. Thus the polycarbonate resins and compositions containing them are useful for production of, e.g., moldings for which all the above characteristics are required.

Abstract: Fire-retardant polycarbonates, polyester carbonates and polyesters based on dihydroxydiphenyl cycloalkanes ##STR1## in which R.sup.1 and R.sup.2 independently of one another represent hydrogen, halogen, preferably chlorine or bromine, C.sub.1 -C.sub.8 alkyl, C.sub.5 -C.sub.6 cycloalkyl, C.sub.6 -C.sub.10 aryl, preferably phenyl and C.sub.7 -C.sub.12 aralkyl, preferably phenyl-C.sub.1 -C.sub.4 -alkyl, more especially benzyl,m is an integer of 4 to 7, preferably 4 or 5, R.sup.3 and R.sup.4 may be individually selected for each X and, independently of one another, represent hydrogen or C.sub.1 -C.sub.6 alkyl andX is carbon,with the proviso that, at at least one atom X, R.sup.3 and R.sup.4 are both alkyl,the fire-retardant finish being provided by additives and/or comonomers.

Abstract: Thermoplastic aromatic polycarbonates having average molecular weights Mw of at least 10,000 which contain bifunctional carbonate structural units corresponding formula (I) ##STR1## in which R.sup.1, R.sup.2, R.sup.3, R.sup.4 independently of one another represent hydrogen, a C.sub.1-12 hydrocarbon, halogen,Y.sup.1, Y.sup.2, Y.sup.3 independently of one another represent hydrogen,C.sub.1-5 alkyl, a C.sub.6-12 hydrocarbon radical,at least two of the substituents Y.sup.1, Y.sup.2 and Y.sup.3 not being hydrogen and at least one of the substituents Y.sup.1, Y.sup.2 and Y.sup.3 being C.sub.1-5 alkyl,in quantities of from 100 to 1 mol-%, based on the total quantity of difunctional carbonate structural units in the polycarbonate.

Abstract: A polycarbonate resin comprising either a structural unit derived from a spiro ring-containing dihydric phenol, or such a structural unit and a structural unit derived from a dihydric phenol, and a process for producing the same. The polycarbonate resin has excellent flowability and moldability, and also improved optical properties (low refractive index, large Abbe number, etc.), and can be advantageously used in various fields, e.g., as a material for molded articles for optical use and other precision molded articles.

Abstract: A photoconductive imaging member comprised of a photogenerating layer, and a charge transport layer comprised of the N,N-bis(biarylyl)aniline charge transport polymers of the formula ##STR1## wherein A and B are independently selected from bifunctional linkages; Z is alkylenedioxy, arylenedioxy, or substituted derivatives thereof; R and R' are alkyl, aryl, alkoxy, aryloxy, or halogen; x and y are mole fractions wherein x is greater than 0 and the sum of x and y is equal to 1.0; a and b are the numbers 0, 1 or 2; and n represents the number of monomer units.

Abstract: An aromatic polyester carbonate comprising structural units represented by the following formulae (A), (B), (C), and (D) and satisfying the following relationship when the mole fractions of the structural units represented by the formulae (A), (B), (C), and (D) are defined as a, b, c, and d, respectively: ##EQU1## and having an inherent viscosity [.eta..sub.inh ] in a solution at a concentration of 0.5 g/dl in p-chlorophenol as a solvent at 50.degree. C. of 1.0 dl/g or higher, or being insoluble in the solvent, and having liquid crystal properties ##STR1## wherein R is the same or different and represent an alkyl, phenyl group or a halogen, and n represents an integer of 0 to 4; ##STR2## X.sup.1 represents a substituted or non-substituted phenyl group, an alkyl group having 3 to 6 carbon atoms or a halogen;X.sup.2 represents --O--, --S--, ##STR3## or --CH.sub.2 --; X.sup.3 may be the same or different and represents an alkyl group, phenyl group, or a halogen; and m represents an integer of 0 to 4.

Abstract: The invention provides an optical article, such as optical disc substrates and optical fibers, made of a polycarbonate resin suitable for manufacturing articles for optical applications in respect of the high mechanical strength, e.g., high impact strength, and low birefringence by virtue of the unique molecular structure having molecular chain ends stoppered with 4-cumyl phenol as the chain-terminal stopping agent in the polycondensation reaction of a dihydric phenol compound, e.g., bisphenol A, and phospgene along with a narrowly specified viscosity-average molecular weight in the range from 10,000 to 17,000.

Abstract: Oligomeric carbonate dihydroxyaromatic-based chainstoppers are disclosed. One example of this type of chainstopper is a bisphenol A bischloroformate oligomer monocapped with phenol. These chainstoppers may be prepared by phosgenating a dihydroxyaromatic compound to terminate one or both of the terminal oxygen atoms with chlorocarbonyl groups, followed by reaction of the chlorocarbonyl-terminated material with a phenolic-type compound in the presence of an amine catalyst. The chainstoppers of the present invention are very useful in accurately controlling the molecular weight of polycarbonates formed by various processes, while also preventing the formation of undesirable by-products, such as diarylcarbonates.

Abstract: This invention relates to thermoplastic, aromatic polycarbonates prepared with the aid of chain terminating agents corresponding to formula (I) ##STR1## to a process for the preparation of these polycarbonates and to their use for the production of moulded articles for optical purposes.

Abstract: A process for producing polycarbonate is disclosed, comprising reacting a halogenated bisphenol-containing organic dihydroxy compound and a carbonate-forming derivative in a liquid medium in the presence of pentahalogenophenol as a molecular weight modifier. This polycarbonate is superior in flame retardance, impact resistance and fluidity, and further in transparency.

Abstract: Segmented block copolycarbonates from diphenols and tetrahalogenated diphenols are prepared by phosgenation, under interfacial reaction conditions, initially at a higher pH during which diphenol polycarbonate oligomers are formed, and thereafter at a lower pH during which tetrahalogenated diphenol bischloroformates are formed, followed by copolymerization utilizing an activated pyridine catalyst. Alternatively, diphenol polycarbonate oligomers and tetrahalogenated diphenol chloroformates may be coupled, utilizing an activated pyridine catalyst, to prepare segmented block copolycarbonates.

Abstract: Thermoplastic, branched, high-molecular weight polycarbonates endowed with properties of flame-resistance (self-extinguishing polycarbonates) are characterized by the presence in their polymeric chain of units deriving from a di-hydroxy-aromatic compound having the formula: ##STR1## wherein: R is a single bond; or is a substituted or non-substituted, linear or branched alkyl group containing from 1 to 5 carbon atoms; or is a group selected from O, S, SO.sub.2, CO;X and Y are equal to, or different from, each other and stay for H or CH.sub.3 ;m and n are integers, equal to or different from each other, ranging from 1 to 4;and of units deriving from a mono-halogenated tetraphenyl compound having the formula: ##STR2## wherein: R, R.sub.2, R.sub.4, R.sub.6 stay for OH;R.sub.1, R.sub.3, R.sub.5, R.sub.7, either equal to, or different, from one another, stay for OH, H, or a linear or branched alkyl group of from 1 to 5 carbon atoms.

Abstract: High molecular weight polycarbonates are prepared by reacting a sterically hindered, substituted aromatic bischloroformate with an alkali metal hydroxide in the presence of a substituted pyridine.

Abstract: The invention relates to a gas separation membrane comprsing a thin discriminating layer of bisphenol AF polycarbonate or polyestercarbonate.The invention further relates to a method of separating gases comprising(a) contacting with a feed gas mixture under pressure one side of a semi-permeable membrane comprising a thin discriminating layer of polycarbonate or polyestercarbonate, wherein the diphenolic residue in the polymer backbone is based on bisphenol AF;(b) maintaining a pressue differential across the membrane under conditions such that a component(s) of the feed gas selectively permeates through the membrane from the high pressure side to the low pressure side of the membrane;(c) removing the permeated gas which is enriched in the faster permeating component(s) from the low pressure side of the membrane;(d) removing the nonpermeated gas which is depleted in the faster permeating component(s) from the high pressure side of the membrane.

Abstract: Polycarbonate having a repeating unit (I) represented by the general formula: ##STR1## and a repeating unit (II) represented by the formula: ##STR2## a pentahalogenophenoxy group as bonded at the terminal thereof, and a halogen atom content of 3 to 20% by weight.