At Least One Transition Metal Atom Patents (Class 528/181)
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Patent number: 4647649Abstract: A method of producing aromatic polyesters by polycondensation of diols and carboxylic acids, comprising polycondensating said diols and said dicarboxylic acids in the presence of a sulfur compound of a general formula: ##STR1## wherein R.sub.1 represents a substituted or unsubstituted aryl, alkyl or aralkyl group, X represents a halogen atom.Type: GrantFiled: May 10, 1983Date of Patent: March 3, 1987Assignee: Tokyo University of Agriculture and TechnologyInventor: Fukuji Higashi
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Patent number: 4617368Abstract: The invention relates to a process for the production of colorless, heat-stable and hydrolysis-stable aromatic polyesters and polyester carbonates by conventional interfacial polycondensation of aromatic dicarboxylic acid dichlorides and diphenolates in which dicarboxylic acid dichlorides are used which have been obtained by chlorination from the dimethyl esters of the corresponding acids, and tertiary cycloaliphatic amines are used as catalysts.Type: GrantFiled: December 10, 1984Date of Patent: October 14, 1986Assignee: Bayer AktiengesellschaftInventors: Dieter Freitag, Ludwig Bottenbruch, Uwe Hucks
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Patent number: 4611049Abstract: A process for producing an aromatic polyester having an aromatic dicarboxylic acid as a main acid component and trimethylene glycol or tetramethylene glycol as a main glycol component from a starting material composed mainly of an aromatic dicarboxylic acid or its functional derivative and trimethylene glycol or tetramethylene glycol; wherein at least one organometallic catalyst selected from the group consisting of organotitanium compounds and organotin compounds and at least one promoter selected from the group consisting of organic sulfonic acids and aliphatic carboxylic acids and being capable of increasing the catalyst activity of the organometallic catalyst are added to the reaction system so that the promoter increases the catalytic activity of the organometallic catalyst, and an aromatic polyester having an increased degree of polymerization is formed at an increased rate of polymerization.Type: GrantFiled: April 25, 1985Date of Patent: September 9, 1986Assignee: Teijin LimitedInventors: Taketoshi Kuratsuji, Tetsuro Miki
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Patent number: 4593086Abstract: A process for producing aromatic ketone-sulfone copolymers which comprises polymerizing appropriate monomers by a Friedel-Crafts polymerization reaction using a Lewis acid catalyst. A controlling agent such as a Lewis base is added to the reaction medium. The reaction medium comprises, for example, aluminum trichloride as the Lewis acid, an organic Lewis base such as N,N-dimethylformamide or an inorganic Lewis base such as sodium or lithium chloride as the controlling agent, and a diluent such as methylene chloride or 1,2-dichloroethane. The amount of Lewis acid, the amount of Lewis base, the temperature of the reaction and the monomer to diluent molar ratio are varied depending on the monomer system to obtain melt-processable, high molecular weight, substantially linear polymers, for example prepared from copolymerization of p-phenoxybenzoyl chloride and p-phenoxybenzenesulfonyl chloride or of terephthaloyl chloride, 1,4-benzenedisulfonyl chloride and diphenyl ether, or of like monomers.Type: GrantFiled: October 11, 1984Date of Patent: June 3, 1986Assignee: Raychem CorporationInventors: Viktors Jansons, Heinrich C. Gors
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Patent number: 4590257Abstract: Boron- and nitrogen-containing compositions prepared by the reaction of a quaternary ammonium hydroxide with a trialkyl or triaryl borate are useful for the preparation of the active catalyst species in the transesterification of reaction for the production of polycarbonates or polyester-polycarbonates from diaryl carbonates (optionally in admixture with diaryl dicarboxylates) and dihydroxyaromatic compounds.Type: GrantFiled: July 5, 1983Date of Patent: May 20, 1986Assignee: General Electric CompanyInventor: Daniel J. Brunelle
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Patent number: 4560740Abstract: In the method for producing aromatic polyesters having excellent moldability, good thermal resistance and little dependence on molding temperature and providing molded products having little anisotropy, obtained from (A) one or more compounds selected from aromatic dicarboxylic acids and their derivatives and (B) one or more compounds selected from aromatic dihydroxy compounds and their derivatives, or (A), (B) and (C) one or more compounds selected from aromatic hydroxycarboxylic acids and their derivatives, a method characterized in that polymerization is carried out in a reaction system containing, together with (A), (B) and optionally (C), a quinone compound (D) and/or a complex obtained from (B) and (D) as well as an organic carboxylic acid anhydride, or a reaction product thereof.Type: GrantFiled: May 2, 1984Date of Patent: December 24, 1985Assignee: Sumitomo Chemical Company, LimitedInventors: Katsuji Ueno, Hiroaki Sugimoto, Kazuo Hayatsu
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Patent number: 4552947Abstract: An aromatic polyester having improved heat resistance, hydrolysis resistance and alkali resistance which comprises recurring units of the general formula: ##STR1## and recurring units of the general formula: ##STR2## wherein R.sup.1 and R.sup.2 are an alkyl or alkoxyl group having 1 to 4 carbon atoms, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are the same or different and each is an alkyl or alkoxyl group having 1 to 4 carbon atoms, Cl or Br, x and y are an integer of 1 to 4, z, x', y' and z' are 0 or an integer of 1 to 4, and X is an alkylidene or cycloalkylidene group having 1 to 8 carbon atoms, --O--, --S--, --SO.sub.2 -- or --CO--.Type: GrantFiled: April 14, 1983Date of Patent: November 12, 1985Assignee: Kanegafuchi Kagaku Kogyo Kabushiki KaishaInventors: Hiroshi Iwakiri, Masahiro Asada, Kazuya Yonezawa
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Patent number: 4533720Abstract: In a process for preparing aromatic polyesters (polyarylates) by heating a bisphenol (e.g., Bisphenol-A), at least one dicarboxylic acid (e.g., terephthalic acid and isophthalic acid) and acetic anhydride, a gamma-butyrolactone, such as gamma-butyrolactone, is employed a diluent, reducing sublimation of reactants, and resulting in higher molecular weight of the polymer.Type: GrantFiled: September 13, 1983Date of Patent: August 6, 1985Assignee: Phillips Petroleum CompanyInventor: Michael C. Yu
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Patent number: 4520168Abstract: Color improved polyarylates having a reduced viscosity of from about 0.1 to greater than 1.0 dl/gm produced by a process comprising the following steps:(a) reacting an acid anhydride derived from an acid containing from 2 to 8 carbon atoms with at least one dihydric phenol to form the corresponding diester; and(b) reacting said diester with at least one aromatic dicarboxylic acid at a temperature sufficient to form the polyarylate, wherein the improvement comprises carrying out said process in the presence of a particular solid adsorbent.Type: GrantFiled: March 27, 1984Date of Patent: May 28, 1985Assignee: Union Carbide CorporationInventors: James H. Kawakami, Benito See, Thomas R. Jones, Louis M. Maresca
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Patent number: 4482694Abstract: High molecular weight aromatic polyesters having a low content of end groups and a very slight inherent color can be obtained according to the phase interfacial process wherein particular amines and a slight alkali excess are used.Type: GrantFiled: April 25, 1983Date of Patent: November 13, 1984Assignee: Bayer AktiengesellschaftInventors: Dieter Freitag, Uwe Hucks, Hans-Jurgen Meissner
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Patent number: 4448909Abstract: A method for determining the concentration of additives in a compounding process by measuring the capacitance and dissipation factor (tan.delta.) of the mixture and converting such values to the concentrations of the additives. This method may also be utilized to determine the concentration of the polymers in the mixture. This method is preferably applied to a compounding process of blending polyphenylene oxide and polystyrene thermoplastic resins and is preferably applied to a continuous compounding process of these resins to determine therein the concentration of an aryl phosphate ester flame retardant.Type: GrantFiled: May 3, 1982Date of Patent: May 15, 1984Assignee: General Electric CompanyInventors: Joseph C. Golba, Jr., Prakash K. Shete
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Patent number: 4448943Abstract: A method for determining the concentration of ingredients and other process variables in a polymerization process by measuring the capacitance and dissipation factor of the mixture and determining its dielectric constant at various stages of the process. By the use of an automatic capacitance bridge and a computer, the process variables can be determined and controlled in a matter of seconds.Type: GrantFiled: May 3, 1982Date of Patent: May 15, 1984Assignee: General Electric CompanyInventors: Joseph C. Golba, Jr., Marion G. Hansen
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Patent number: 4439586Abstract: An improved process for preparing a polyarylate having a reduced viscosity of from about 0.1 to greater than 1.0 dl/gm comprising the following steps:(a) reacting an acid anhydride derived from an acid containing from 2 to 8 carbon atoms with at least one dihydric phenol to form the corresponding diester; and(b) reacting said diester with at least one aromatic dicarboxylic acid at a temperature sufficient to form the polyarylate, wherein the improvement comprises carrying out said process in the presence of a particular solid adsorbent.Type: GrantFiled: June 30, 1982Date of Patent: March 27, 1984Assignee: Union Carbide CorporationInventors: James H. Kawakami, Benito See, Thomas R. Jones, Louis M. Maresca
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Patent number: 4429105Abstract: Provided is a method for preparing aromatic copolyesters of hydroxy naphthoic acid and hydroxy benzoic acid via an in situ esterification technique whereby there is no isolation of the esterified monomers. The process comprises reacting the aromatic hydroxy acid monomers with an agent such as acetic anhydride in order to esterify the hydroxy moieties and subsequently polymerizing the esterified hydroxy monomers without isolation thereof, all in the presence of from about 5 to 50 ppm iron. Advantageously, the process allows one to obtain a wholly aromatic polyester of high inherent viscosity and good melt stability while avoiding the time consuming step of having to isolate the esterified hydroxy monomers prior to polymerization.Type: GrantFiled: February 22, 1983Date of Patent: January 31, 1984Assignee: Celanese CorporationInventor: Larry F. Charbonneau
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Patent number: 4421908Abstract: Provided is a method for preparing melt-processable polyesters efficiently via the direct polymerization of a hydroxynaphthoic acid, an aromatic dicarboxylic acid and an aromatic diol. By the direct polymerization method, the hydroxy and acid moieties are reacted directly effectively and efficiently without the use of acetylated reactants in the presence of a catalyst comprising a metal selected from the group consisting of the Group IV and V metals.Type: GrantFiled: March 8, 1982Date of Patent: December 20, 1983Assignee: Celanese CorporationInventor: Anthony J. East
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Patent number: 4417044Abstract: A process for making polyetherimides involving reacting an aromatic bis(ether anhydride) with an organic diamine in an inert solvent to form a prepolymer solvent mixture, effecting solvent removal by thin-film evaporation, and heating the resulting prepolymer to a temperature above the glass transition temperature of the final polyetherimide product and less than 450.degree. C. to form the polyetherimide.Type: GrantFiled: May 25, 1982Date of Patent: November 22, 1983Assignee: General Electric CompanyInventor: Shashi L. Parekh
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Patent number: 4414380Abstract: Step-growth polymers can be prepared by reacting a mixture of diphenylether or di(phenoxyphenyl)sulfone with biphenylene and a phthaloyl halide in the presence of a Friedel-Crafts acylating catalyst. These polymers can be cured by heating in the range 300.degree.-340.degree. C., with cross-linking occurring by reaction of formed biphenylene diradicals.Type: GrantFiled: October 29, 1982Date of Patent: November 8, 1983Assignee: UOP Inc.Inventor: Raymond J. Swedo
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Patent number: 4398018Abstract: A thermotropic poly(ester carbonate) containing diacyl moieties such as terephthalate and carbonate moieties as well as dihydroxy-derived moieties is useful for forming fibers or films. The dihydroxy-derived moieties are at least 40% derived from t-butylhydroquinone, with hydroquinone and methylhydroquinone being exemplary second components. The polymers can be prepared by melt, solution or interfacial polymerization, are liquid crystalline in the melt and have glass transition temperatures above 100.degree. C.Type: GrantFiled: December 21, 1981Date of Patent: August 9, 1983Assignee: Allied CorporationInventors: Murali K. Akkapeddi, Bruce T. DeBona, Yu-Chin Lai, Dusan C. Prevorsek
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Patent number: 4393191Abstract: Provided is a method for preparing melt-processable polyesters efficiently via the direct polymerization of aromatic hydroxy acids. By the direct polymerization method, hydroxy and acid moieties are reacted directly without the use of acetylated reactants, thereby avoiding the disadvantages inherent in the case of acetylated reactants. The direct polymerization is conducted in the presence of a catalyst comprising a metal selected from the group consisting of the Group IV and V metals.Type: GrantFiled: March 8, 1982Date of Patent: July 12, 1983Assignee: Celanese CorporationInventor: Anthony J. East
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Patent number: 4387210Abstract: An aromatic polyester amide is produced by reacting hydroxyphenyl-aminophenyl-propane with aromatic dicarboxylic acid dihalide in the presence of an inert organic solvent, and bringing the organic solvent phase containing the mixture of the reaction products of the above reaction into contact with an aqueous phase containing an acid-acceptor, whereby completing polycondensation reaction. In order to control the dissolution of water into the organic solvent phase while maintaining an adequate level of miscibility between the organic solvent phase and the aqueous phase, a neutral salt of inorganic electrolyte, such as sodium chloride, is added to the aqueous phase containing the acid-acceptor.Type: GrantFiled: December 22, 1981Date of Patent: June 7, 1983Assignee: Mitsui Toatsu Chemical, Inc.Inventors: Nobukatsu Katoh, Yoshio Morimoto, Takashi Kataoka, Teruo Yuasa
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Patent number: 4387211Abstract: A new polyester resin is produced by condensation polymerization of (a) a diol component of the formula: ##STR1## wherein R.sup.1 is an alkylene group of 2 to 4 carbon atoms; and x and y are positive integers, the sum of them being 2 to 16 on an average, and (b) an acid component of polybasic (at least dibasic) carboxylic acid, anhydride thereof, and lower alkyl ester thereof, said acid component (b) containing 1 to 50 mol % of a dibasic carboxylic acid or anhydride thereof of the formula: ##STR2## where R.sup.2 and R.sup.3 are saturated or unsaturated hydrocarbon groups of 4 to 20 carbon atoms and 10 to 30 mol % of trimellitic acid or anhydride thereof. The polyester has improved toughness, abrasion resistance and flexibility.Type: GrantFiled: December 21, 1981Date of Patent: June 7, 1983Assignee: Kao Soap Co., Ltd.Inventors: Shinichiro Yasuda, Eiji Morimoto, Atsushi Sonobe
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Patent number: 4386196Abstract: An interfacial process for producing a poly(ester-carbonate) containing aromatic dihydroxy moieties derived from phenolphthalein. In the process, phenolphthalein polyester oligomers are formed first, and then the oligomers are reacted with phosgene and with additional aromatic or cycloaliphatic diacyl halide and with an aqueous solution of bisphenol-derived salt to form the poly(ester-carbonate).Type: GrantFiled: April 2, 1982Date of Patent: May 31, 1983Assignee: Allied CorporationInventors: Tse C. Wu, Leon Segal
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Patent number: 4383092Abstract: A process for the production of a substantially clear and colorless, or at most slightly tinted, polyarylcarbonates useful to form molded structural and engineering articles suitable to replace metal parts, or for use in electrical appliances to form lenses, safety shields, instrument windows and the like is disclosed.The tendency of color formation in polycarbonates and polyarylates prepared by transesterification and polycondensation is reduced or inhibited by carrying out the transesterification reaction while the reaction mixture contacts only metal surfaces of selective metals, or glass. The metal surfaces are provided by such metals as tantalum, nickel, or chromium or mixtures thereof. The reaction is carried out in reactors or systems which are substantially totally made of such metals, or reactors or systems clad or lined with a layer of such metals or glass.Type: GrantFiled: August 11, 1980Date of Patent: May 10, 1983Assignee: General Electric CompanyInventors: Allen W. Ko, John B. Starr, Jr.
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Patent number: 4350805Abstract: Process for preparation of poly(ester-carbonates) from aromatic diol bis(alkylcarbonates) and esters of dicarboxylic, and/or carboxylate-carbonate esters of hydroxy acids by suitably heating the reactants in the presence of a suitable polymerization catalyst.Type: GrantFiled: November 17, 1980Date of Patent: September 21, 1982Assignee: Eastman Kodak CompanyInventors: Winston J. Jackson, Jr., William R. Darnell
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Patent number: 4330668Abstract: In the production of an aromatic polyester by reacting at least one aromatic diester of the formula ##STR1## wherein R is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 8 carbon atoms; andAr.sub.2 is an arylene group,with at least one aromatic dicarboxylic acid of the formula ##STR2## wherein Ar.sub.2 is an arylene group,in the presence of a catalyst, the improvement which comprises employing a transition metal salt of naphthenic acid as the catalyst.Type: GrantFiled: May 16, 1980Date of Patent: May 18, 1982Assignee: Asahi Kasei Kogyo Kabushiki KaishaInventors: Sato Hideo, Takiguchi Teruo, Akimoto Norio, Ueno Ikuo
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Patent number: 4311823Abstract: In a process for producing aromatic polyesters by bulk condensation of polyester forming reactant the improvement which comprises using three reaction vessels, reacting a reactant compound with an acid anhydride to effect an alkanolylation reaction in the first reaction vessel to thereby prepare a monomer, removing the acids by-produced in said reaction, forming or not forming an oligomer from a part or whole of said monomer, then transferring the reaction product of the first vessel into the second reaction vessel, polycondensing said monomer and/or oligomer to produce a prepolymer in the second reaction vessel, transferring the reaction product of the second vessel into the third reaction vessel, and heating said prepolymer in said third reaction vessel, thereby obtaining an aromatic polyester of high polymerization degree.Type: GrantFiled: December 31, 1979Date of Patent: January 19, 1982Assignee: Sumitomo Chemical Company LimitedInventors: Shozaburo Imai, Haruo Suzuki, Kuniaki Asai, Katsuji Ueno
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Patent number: 4294953Abstract: A process for preparing a thermoplastic, randomly branched aromatic polycarbonate is disclosed which comprises reacting a carbonate precursor, a dihydric phenol, and a dianhydride branching agent and maintaining the resultant reaction medium at a pH of from about 9 to about 12 to thereby produce a thermoplastic randomly branched aromatic polycarbonate.Type: GrantFiled: May 31, 1979Date of Patent: October 13, 1981Assignee: General Electric CompanyInventors: Clayton B. Quinn, William Hilakos
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Patent number: 4293683Abstract: A method is provided for enhancing the rate of formation of polyetherimides under melt or solution polymerization conditions by using either an alkali metal carboxylic acid salt, or a zinc carboxylic acid salt as a catalyst. The aforementioned catalysts are employed in a polymerization mixture of aromatic bis(ether anhydride) and an organic diamine.Type: GrantFiled: July 11, 1980Date of Patent: October 6, 1981Assignee: General Electric CompanyInventors: Tohru Takekoshi, Howard J. Klopfer
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Patent number: 4293684Abstract: Polyetherimides having long chain aliphatic end groups have been found to exhibit significantly lower melt viscosities and higher notched izod impact values compared to comparable polyetherimides end capped with organic radicals derived from aromatic organic amines or aromatic organic anhydrides.Type: GrantFiled: March 26, 1980Date of Patent: October 6, 1981Assignee: General Electric CompanyInventor: Tohru Takekoshi
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Patent number: 4281099Abstract: Described herein is a process for preparing melt stable polyarylates having a reduced viscosity of from about 0.4 to greater than 1.0 dl/g which comprises reacting a diester derivative of a dihydric phenol with an aromatic dicarboxylic acid to produce a polyarylate having a reduced viscosity of from about 0.5 to greater than 1.0 dl/g, and then adding a stabilizing amount of an aromatic phenol to the polyarylate to form a polyarylate substantially free of anhydride linkages.Type: GrantFiled: October 29, 1979Date of Patent: July 28, 1981Assignee: Union Carbide CorporationInventor: Louis M. Maresca
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Patent number: 4267303Abstract: This disclosure is concerned with a single step process for the production of diphenol terminated polycarbonates by the transesterification of diphenols, bis-aryl carbonates and polymeric diols with aliphatically bound terminal hydroxyl groups. These diols are selected from polyesters, polyethers, polythioethers and polyacetals. The transesterification is carried out at elevated temperatures under vacuum optionally in the presence of a catalyst with the ratios of the reactants being such as to avoid the retention of any terminal aliphatic hydroxyl groups or aryl carbonate groups.Type: GrantFiled: August 27, 1979Date of Patent: May 12, 1981Assignee: Bayer AktiengesellschaftInventors: Klaus Konig, Manfred Schreckenberg, Christian Lindner, Carlhans Suling, Dieter Freitag
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Patent number: 4195132Abstract: The present invention relates to novel, substantially insoluble and infusible plastics which are cross-linked by way of triazine rings and, optionally, by way of tri-substituted bis-oxymethylene urea groups or urethane groups.Type: GrantFiled: May 5, 1977Date of Patent: March 25, 1980Assignee: Bayer AktiengesellschaftInventors: Rudolf Sundermann, Gunther Rottloff, Ernst Grigat
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Patent number: 4181791Abstract: Aralkylene phenol resins, curable to thermoset polymers are made by reacting an aralkylene ester of formula R'(CH.sub.2 OYR,).sub.a, where R' is aromatic, Y is carbonyl or sulphonyl and R' is alkyl or aryl, a is 2 or 3 with a molar excess of a phenol or mixture thereof with a non-phenolic aromatic compound.Type: GrantFiled: October 6, 1975Date of Patent: January 1, 1980Assignee: Albright & Wilson LimitedInventors: Alfred G. Edwards, Glyn I. Harris
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Patent number: 4143031Abstract: There is described a family of copolyester compositions for producing heat nd flame resistant fibers, said compositions being prepared by polycondensating (A) an aromatic diacid, (B) a diol, (C) a tetrabrominated diol, (D) a derivative of a polyvalent metal, all said components being hereinbelow defined, the polycondensation process being carried out in several successive stages of copolycondensation of components (A), (B) and (C) until reaching a stable viscosity, then adding component (D), and stopping the reaction before the intrinsic viscosity of the composition decreases below a value proper for subsequent spinning.Type: GrantFiled: September 30, 1976Date of Patent: March 6, 1979Assignee: SNIA Viscosa Societa Nazionale Industria Applicazioni Viscosa S.p.A.Inventors: Aldemaro Ciaperoni, Giuseppe Quaglia, Gino Dall'Asta
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Patent number: 4124566Abstract: A process for preparing polyesters having superior thermal stability, transparency and chemical resistance, which comprises (1) a first step of esterifying (A) a difunctional carboxylic acid containing at least 60 mole% of an aromatic dicarboxylic acid, (B) 0 to 80 mole%, based on component (A), of an aliphatic diol and/or a dihydroxybenzene and (C) an aromatic monohydroxy compound in an amount of at least 210 mole% as a total of it and component (B) based on component (A), the esterification being performed until the degree of esterification reaches at least 80%, (2) subsequently, a second step of adding 0 to 80 mole%, based on component (A), of component (B) and a bisphenol (D) in an amount of 100 to 130 mole% as a total of it and component (B) based on component (A) to the reaction product obtained in the first step and reacting the mixture, the total amount of components (B) used in the first and second steps being 0 to 80 mole% based on component (C), and (3) performing at least the first of the above stType: GrantFiled: June 15, 1977Date of Patent: November 7, 1978Assignee: Teijin LimitedInventors: Noritsugu Saiki, Shizuka Kurisu, Shoji Kawase
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Patent number: 4115362Abstract: A process for preparing polyesters which comprises (1) a first step of esterifying (A) a difunctional carboxylic acid containing at least 60 mole% of an aromatic dicarboxylic acid, (B) 0 to 80 mole%, based on component (A), of an aliphatic diol and (C) an aromatic monohydroxy compound in an amount of at least 210 mole% as a total of it and component (B) based on component (A), the esterification being performed until the degree of esterification reaches 80 to 98%, and (2) a second step of adding 0 to 80 mole%, based on component (A), of component (B), and an aromatic dihydroxy compound (D) in an amount of 95 to 130 mole% as a total of it and component (B) based on component (A), to the reaction product obtained in the first step and reacting the mixture, the total amount of components (B) used in the first and second steps being 0 to 80 mole% based on component (A).Type: GrantFiled: April 4, 1977Date of Patent: September 19, 1978Assignee: Teijin LimitedInventors: Hiroo Inata, Shoji Kawase
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Patent number: 4101526Abstract: The reaction for the manufacture of linear polyesters by polycondensing dicarboxylic acids, hydroxycarboxylic acids or the esters and diols thereof is speeded up by the addition of 1 to 25% by weight of esters of phosphoric and/or phosphorous acid.Type: GrantFiled: January 26, 1977Date of Patent: July 18, 1978Assignee: Ciba-Geigy CorporationInventor: Lothar Buxbaum