Abstract: A curable composition and use thereof are provided. The composition can be useful in exhibiting excellent processability and workability, and providing a cured product which exhibits superior light extraction efficiency, crack resistance, hardness, thermal shock resistance, and adhesive properties, has superior reliability under severe conditions for a long period of time and prevents opacity and stickiness onto a surface thereof when cured. Also, the curable composition capable of preventing precipitation of an additive such as a fluorescent material or a photoconversion material and being formed into a cured product having excellent transparency even when the additive is added to the curable composition can be provided.

Abstract: Porous materials are fabricated using interpenetrating inorganic-organic composite gels. A mixture or precursor solution including an inorganic gel precursor, an organic polymer gel precursor, and a solvent is treated to form an inorganic wet gel including the organic polymer gel precursor and the solvent. The inorganic wet gel is then treated to form a composite wet gel including an organic polymer network in the body of the inorganic wet gel, producing an interpenetrating inorganic-organic composite gel. The composite wet gel is dried to form a composite material including the organic polymer network and an inorganic network component. The composite material can be treated further to form a porous composite material, a porous polymer or polymer composite, a porous metal oxide, and other porous materials.

Abstract: Improved mechanical properties of either clay or carbon nanotube (CNT)-reinforced polymer matrix nanocomposites are obtained by pre-treating nanoparticles and polymer pellets prior to a melt compounding process. The clay or CNTs are coated onto the surfaces of the polymer pellets by a milling process. The introduction of moisture into the mixture of the nanoparticles and the polymer pellets results in the nanoparticles more easily, firmly, and thoroughly coating onto the surfaces of the polymer pellets.

Abstract: Polyester-carbonate copolymers are prepared by copolymerizing lactide with a 1:4-3:6 dianhydrohexitol in the presence of a carbonate precursor and a polymerization catalyst. The copolymers have an elevated glass transition temperature, relative to polylactide resins.

Abstract: The present invention is directed toward a method for making a polymer that has nanostructures incorporated into the matrix of the polymer. The method of the present invention involves mixing a precursor solution for the polymer with a precursor for the nanostructures to form a mixture. Nanostructures are formed in the mixture from the precursor of the nanostructures, such that the nanostructures are surrounded by the precursor solution for the polymer. The polymer is formed from the precursor solution of the polymer, which results in the nanostructures being incorporated into the matrix of the polymer.

Abstract: The present invention is directed toward a method for making a polymer that has nanostructures incorporated into the matrix of the polymer. The method of the invention involves the following steps: mixing a precursor solution for the polymer with a precursor for the nanostructures to form a mixture; forming nanostructures in the mixture from the precursor of the nanostructures; and forming a polymer from the precursor solution of the polymer so that the nanostructures are incorporated into the polymer matrix.

Abstract: Provided are an optical material composition and an optical element that not only exhibit desirable anomalous dispersion properties but are also easy to process. The material composition for use in the optical element contains 5 weight % to 50 weight % of tin (IV) oxide fine particles (A), 49 weight % to 94 weight % of an organic compound (B) having one or more polymerizable functional groups in one molecule thereof, and 0.05 weight % to 5 weight % of a polymerization initiator (C).

Abstract: The present invention provides a coating composition for antireflection that includes a) a low refractive material having a refractive index of 1.2 to 1.45, b) a high refractive material having a refractive index of 1.55 to 2.2 and comprising high refractive fine particles and an organic substituent, in which the difference in the surface energy between two materials is 5 mN/m or more; an antireflection film manufactured using the coating composition for antireflection; and a method of manufacturing the antireflection film. According to the present invention, the antireflection film having excellent antireflection characteristic can be manufactured by one coating process, thereby reducing manufacturing cost.

Abstract: Provided is a thin film having self-supporting properties and having excellent strength, durability and flexibility and a method for manufacturing the thin film. A thin film having an interpenetrating net-work layer and having a film thickness of 500 nm or less, the interpenetrating net-work layer being constituted of at least a metal oxide and an organic polymer.

Abstract: Disclosed are processes for preparing polyareneazole polymers including contacting a molar excess of a free base in water with a terephthalic acid salt to form an aqueous mixture, adjusting the pH to precipitate a monomer complex, contacting the monomer complex with metal powder, and polymerizing the monomer complex. Polyareneazoles, filaments and yarns are also disclosed.

Abstract: An aliphatic polyester copolymer comprising an aliphatic carbonate unit (a) and an aliphatic polyester unit (b), and a molded body composed of said aliphatic polyester copolymer. The aliphatic polyester copolymer is excellent in heat resistance while having adequate mechanical properties and properties in the molten state.

Abstract: Provided are an optical material composition and an optical element that not only exhibit desirable anomalous dispersion properties but are also easy to process. The material composition for use in the optical element contains 5 weight % to 50 weight % of tin (IV) oxide fine particles (A), 49 weight % to 94 weight % of an organic compound (B) having one or more polymerizable functional groups in one molecule thereof, and 0.05 weight % to 5 weight % of a polymerization initiator (C).

Abstract: The object of the invention is to provide a curate liquid composition excelling in storage stability and curability and capable of forming a coat (film) which excels in antistatic properties, hardness, scratch resistance, and transparency on the surface of various substrates, a cured film of the composition, and an anti static laminate. This object is achieved by providing a curate liquid composition comprising the following components (A), (B), (C), and (D): (A) particles comprising an oxide of at least one element selected from the group consisting of indium, antimony, zinc, and tin as a major component, (B) a compound having two or more polymerizable unsaturated groups in the molecule, (C) a silicon-containing surfactant, and (D) a solvent.

Abstract: The present invention provides carboxy-terminated oligomeric polyester compositions useful in the preparation of “weatherable” polymeric materials, for example weatherable copolyestercarbonates. In one aspect the present invention provides an oligomeric polyester composition comprising structural units derived from at least one diacid, at least one diaryl carbonate and at least one diol. The structural units derived from the diacid are present in a molar excess of from about 10% to about 40% based on a ratio of moles of diacid-derived structural units to moles of diol-derived structural units present in the oligomeric polyester composition. The oligomeric polyester composition is further characterized by the presence of at least some phenoxy end groups.

Abstract: The present invention is a method for efficiently incorporating a nitrogen containing methine light absorber into a polyester resin. The method includes forming a reaction mixture comprising combining a diol component, a diacid component selected from the group consisting of dicarboxylic acids, dicarboxylic acid derivatives, and mixtures thereof, an antimony containing compound, a phosphorus containing compound, a metal containing compound, and a nitrogen containing methine light absorber. The reaction mixture is polymerized in a polycondensation reaction system. In another embodiment the light absorber is added while the reaction products of one reactor are being transferred to the next reactor in the polycondensation reaction system. The present invention is also directed articles made from the polyester resin.

Abstract: The invention relates to a composition suitable for catalysis in a process for the manufacture of polyester containing as Component I a carrier substance on which catalytically effective metal compounds are adsorbed and as Component II a phosphonic acid compound.

Abstract: The present invention is a method for efficiently incorporating a nitrogen containing methine light absorber into a polyester resin. The method includes forming a reaction mixture comprising combining a diol component, a diacid component selected from the group consisting of dicarboxylic acids, dicarboxylic acid derivatives, and mixtures thereof, an antimony containing compound, a phosphorus containing compound, a metal containing compound, and a nitrogen containing methine light absorber. The reaction mixture is polymerized in a polycondensation reaction system. In another embodiment the light absorber is added while the reaction products of one reactor are being transferred to the next reactor in the polycondensation reaction system. The present invention is also directed articles made from the polyester resin.

Abstract: Cyclic oligomers containing ester linkages are polymerized in the presence of a catalyst having at least one oxygen atom bonded to two metal atoms. At least one of the metal atoms is a tin atom, which is preferably tetravalent, i.e., bonded to three other groups in addition to the oxygen atom. The other metal atom may also be another tin atom, which is again preferably tetravalent, or a zinc, aluminum or titanium atom. The catalyst may contain multiple oxygen atoms that are bonded to two such metal atoms as described. These catalysts are active, efficient polymerization catalysts. They are often liquids at polymerization temperatures. The catalysts can be formed in situ in the polymerization process, which provides additional flexibility in the process and increased storage stability of starting materials.

Abstract: Disclosed are a resin dispersion and a cationic electrodeposition coating composition including the same, in which the dried coating film of the electrodeposition paint is lead-free and has an epoxy-acrylic double-layered structure for displaying excellent properties, and in which an organic solvent content can be minimized. A resin dispersion of a cationic electrodeposition includes an aqueous dispersion prepared by the following processes. The resin dispersion includes a cationic electrodeposition resin, deionized water, an acid for neutralization, a reaction product of manganese phosphate and an acid diluted in an deionized water to 10%, and a cationic surfactant.

Abstract: The present invention allows the production of a polymerizable hyperbranched polyester by introducing polymerizable unsaturated double bonds into the molecular terminals of a hyperbranched polyester polyol (A), which is obtained by condensation polymerization a polyhydroxy monocarboxylic acid in which there are at least two hydroxyl groups, the carbon atom adjacent to the carboxy group is saturated carbon atom, and the hydrogen atoms on said carbon atom are all substituted, by reacting the hyperbranched polyester polyol (A) and an alkyl ester of a carboxylic acid having a polymerizable unsaturated double bond (B) by a transesterification in the presence of at least one type of transesterification catalyst (C) selected from the group consisting of a dialkyl tin oxide and a stanoxane, without causing side reactions such as nucleophilic addition reactions of terminal hydroxyl groups to polymerizable unsaturated double bonds of the hyperbranched polyester polyol (A), or thermal polymerization of the polymerizable

Abstract: In polymerizing biodegradable polymer material, a compressed gas is used as a reaction solvent for a solution-polymerization, in order to prepare biodegradable polyester homopolymer and copolymer with a high molecular weight in a fine powder form with a particle size of 0.01˜1000 ?m.

Abstract: Polymers with biocidal action, process for their preparation and their use The invention relates to polymers consisting essentially of structural units of the formula (1) in which R1 is a C1-C4-alkylene group R2, R3 independently of one another, are a C8-C12-alkyl or alkenyl group R4 is methyl or ethyl R5 is hydrogen or methyl and whose molecular weight is between 1000 and 100 000 g/mol, to intermediates for their preparation, to a process for their preparation, and to their use as biocidal coating composition for surfaces and textiles.

Abstract: High consistency polymers have an inherent viscosity of from about 1.30 to about 1.55, wherein the inherent viscosity is characterized by a standard deviation of about 0.05 or less.

Abstract: The present invention provides processes for producing certain very low inherent viscosity polyesters. Also provided are the low inherent viscosity polyesters in discrete particulate form, and processes for producing the particulate polyesters. The discrete particulate materials are desirable for use in further processes.

Abstract: An improved process for the polymerization of polytrimethylene terephthalate by esterification of terephthalic acid or dimethylterephthalate with 1,3-propanediol (PDO), precondensation of the esterification product to produce a precondensation product, and polycondensation of the precondensation product to produce polytrimethylene terephthalate wherein excess PDO is removed from the esterification and/or polycondensation stages and PDO vapor is separated from the high boiling fraction (solid byproduct). The improvement comprises: (a) heating the solid byproduct in the presence of about 5 ppm to about 5000 ppm, based on metal, of a metal catalyst selected from the group consisting of one or more 3rd, 4th, or 5th row metal compounds from Groups 3-12 and Groups 14-15 of the Periodic Table (IUPAC 1989) at a temperature of from about 100° C. to about 240° C.

Abstract: A process is provided for manufacturing homo- and copolyesters of lactic acid by ring scission polymerization of its cyclic monomers in the presence of an initiator. Polymerization is carried out in the molten phase in the presence of an initiator system containing a compound of tin and at least one additional initiator chosen from the compounds of metal of the fourth subgroup.

Abstract: By the present invention, there are provided a catalyst for polyester preparation, which comprises a solid titanium compound containing titanium, oxygen, carbon and hydrogen and having a Ti—O bond and which has a maximum solubility in ethylene glycol, as measured when the catalyst is dissolved in ethylene glycol under heating at 150° C., of not less than 3,000 ppm in terms of a titanium atom, a catalyst for polyester preparation, which comprises a titanium-containing solution wherein a contact product of a hydrolyzate of a titanium halide or a hydrolyzate of a titanium alkoxide with a polyhydric alcohol is dissolved in ethylene glycol in an amount of 3,000 to 100,000 ppm in terms of a titanium atom, a process for preparing a polyester using the catalyst, and a polyester prepared by the process.

Abstract: A water slurry process is used to prepare a prepreg and to manufacture articles from macrocyclic polyester oligomers. In one embodiment, a process for preparing a water suspension of macrocyclic polyester oligomers includes the steps of contacting a macrocyclic polyester oligomer and a polymerization catalyst with water and a surfactant, and mixing the macrocyclic polyester oligomer and polymerization catalyst with water and the surfactant thereby forming a suspension. In another embodiment, a process for impregnating macrocyclic polyester oligomers for polymerization includes the steps of providing a suspension of a macrocyclic polyester oligomer and a polymerization catalyst in water, applying the suspension to a base material, drying to remove water from the suspension, and pressing the dried suspension to a desired form. In yet another embodiment, a composition of macrocyclic polyester oligomer includes a macrocyclic polyester oligomer, a polymerization catalyst, and water.

Abstract: Disclosed is a flame retardant polybutyleneterephthalate resin prepared be copolymerizing a phosphorus-based flame retardant represented by the following formula I and a butyleneterephthalate unit: wherein R1 and R2 are different or the same and are methyl or butyl including a hydroxyl group.

Abstract: A process for producing a wholly aromatic polyester which is excellent in heat resistance, mechanical properties and yet color and has a high degree of polymerization by melt polymerizing a dicarboxylic acid and a diol directly on an industrial scale at a low cost in a short period of time without esterifying the dicarboxylic acid or diol in advance. To produce the wholly aromatic polyester by reacting and molding an aromatic dicarboxylic acid such as terephthalic acid, an aromatic diol such as 2,2-bis(4-hydroxyphenyl)propane and a diaryl carbonate by heating, a combination of a specific pyridine compound and an alkali metal (bi)carbonate, a combination of a specific pyridine compound and an organic tin compound or a specific titanium compound is existent as a catalyst. Thereby, the wholly aromatic polyester having the above properties is obtained.

Abstract: Process that is capable of synthesizing a metal-containing resin having a good antifouling property in a short period of time without having such problems associated with the synthesis as gelation. The process for producing a metal-containing resin by conducting a copolymerization reaction of a monomer mixture (A) comprising 1 to 50% by weight of a carboxyl group-containing polymerizable unsaturated monomer (a) and 50 to 99% by weight of other polymerizable unsaturated monomer (b) in an organic solvent in the presence of water and an oxide or hydroxide of a metal having a valency of at least 2, wherein the amount of water is 1 to 30 parts by weight based on 100 parts by weight of the monomer mixture (A), and the formation of a metal carboxylate bond occurs together with the copolymerization of the monomer mixture (A); and an antifouling coating composition containing, as an active constituent, a metal-containing resin obtained by the production process.

Abstract: A resist composition for permanent protective coating of a printed wiring board, which resist composition is excellent in flame resistance and is obtained by incorporating as essential components a flame retardant containing 100 to 140 parts by weight of (a) aluminum hydroxide, 0.1 to 15 parts by weight of (b) a molybdenum compound and 0.1 to 10 parts by weight of (c) a zinc stannate type compound into 100 parts by weight of a resin.

Abstract: A rubber composition is obtained which exhibit improved strength, abrasion resistance and antistatic properties, as well as low rolling resistance. The rubber composition is characterized as being rendered conductive by incorporating into rubber a silica filler having a conductive surface layer as composed of carbon or conductive tin oxide.

Abstract: Block copolymers are prepared from polymerization of a macrocyclic oligoester and a dihydroxyl-functionalized polymer at an elevated temperature in the presence of a polymerization catalyst.

Abstract: A method of preparing a composition containing a fluorocarbon thermoplastic random copolymer comprising the steps of: (A) providing a mixture having: (i) a fluorocarbon thermoplastic random copolymer having subunits of: —(CH2CF2)x—, —(CF2CF(CF3)y—, and —(CF2 CF2)z—,  wherein x is from 1 to 50 or 60 to 80 mole percent, y is from 10 to 90 mole percent, z is from 10 to 90 mole percent, x+y+z equals 100 mole percent; (ii) a filler comprising zinc oxide; (iii) a curable amino functional polydimethyl siloxane copolymer comprising aminofunctional units selected from the group consisting of (aminoethylaminopropyl) methyl, (aminopropyl) methyl and (aminopropyl) dimethyl; and (iv) antimony-doped tin oxide particles; (v) a bisphenol residue curing agent; and (B) curing the mixture for 5 to 10 hours at a temperature in the range of 25° C. to 275° C.

Abstract: A dental material comprising a hardenable resin, a non-heavy metal oxide particle and a heavy metal oxide. The dental materials can be radiopaque, strong, translucent, or resistant to toothbrush abrasion, or combinations thereof.

Abstract: A blend of a macrocyclic polyester oligomer and a polymerization catalyst as a one component ready-to-use material with a long shelf life enables production of parts from macrocyclic polyester oligomers without the modification of existing equipment, thereby reducing time and cost of manufacture while expanding the application of macrocyclic polyester oligomers. In this blend material, the macrocyclic polyester oligomer remains intact in solid state at ambient conditions. Upon melting, the blend material initially forms low viscosity fluid, and then rapidly polymerizes to form high molecular weight polyesters which subsequently solidify to form crystalline polymers. In the case of certain macrocyclic polyester oligomers, for example, poly(1,4-butylene terephthalate), demolding can take place at the polymerization temperature, e.g., at about 180° C. to 200° C., because the resulting polyester polymer solidifies fairly rapidly at that temperature without cooling.

Abstract: Dental material based on polymerizable (for example ethylenically unsaturated) monomers, epoxides, ormocers, liquid crystal monomers, oxethanes, spiro-orthoesters or spiro-carbonates as binders, a catalyst for cold, hot and/or photo-polymerization, and fillers, and a process for its preparation. Porous glass ceramics, a process for their preparation and uses thereof are also described. Dental materials according to the invention are suitable as alternative materials to the use of amalgam fillings.

Abstract: The present invention provides a catalyst for polyester production capable of producing a polyester with high catalytic activity and a process for producing a polyester using the catalyst. The catalyst for polyester production comprises a solid titanium compound which is obtained by dehydro-drying a hydrolyzate obtained by hydrolysis of a titanium halide and which has a molar ratio (OH/Ti) of a hydroxyl group (OH) to titanium (Ti) exceeding 0.09 and less than 4. The present invention also provides a method to obtain a polyester having a small increase of the acetaldehyde content during the molding. This method comprises bringing a polyester, which is obtained by the use of a titanium compound catalyst and in which the reaction has been completed, into contact with a phosphoric ester aqueous solution or the like having a concentration of not less than 10 ppm in terms of phosphorus atom.

Abstract: For the production of polyesters and copolyesters, coprecipitates are used individually or in a mixture as polycondensation catalysts, the coprecipitates being prepared by simultaneous hydrolytic precipitation of a titanium compound and a metallic compound of a metal selected from the groups IA, IIA, VIIIA, IB, IIB, IIIB, and IVB, whereby the titanium compound and the metallic compound are, independently of one another, an alkylate, alcoholate, or carboxylate of titanium or the metal, respectively, and the molar ratio of the titanium compound to the metallic compound is ≧50:50 mol/mol. The coprecipitates exhibit a higher catalytic activity than Sb2O3 which results in a prefered amount of usage of only 10 to 100 ppm with respect to the esters or oligoesters to undergo polycondensation.

Abstract: The invention relates to transparent organic/inorganic composites with low hydroxyl group content, based on silicic acid heteropolycondensates having extremely low water uptakes. These composites are obtained for example by nonhydrolytic condensation of chlorosilanes with polymerizable groups and optionally fluorinated groups, with the help of a condensation agent (e.g., t-butanol) capable of non-hydrolytic condensation of this chlorosilane, and thermal and/or photochemical polymerization of the obtained condensation product, preferably in the presence of preferably fluorinated organic monomers.

Abstract: A composition and devices utilizing these compositions for providing protection against electrical overstress including a matrix formed of a mixture of an insulating binder, conductive particles having an average particle size of less than 10 microns, and semiconductive particles having an average particle size of less than 10 microns. The compositions exhibit improved clamping voltages in a range of about 30 volts to greater than 2,000 volts.

Abstract: The invention provides a process for producing high-molecular aliphatic polyesters capable of being substitutes for general-purpose resins that are required to have high toughness, in a simplified manner and at a high volume efficiency. Specifically, in the process, used as the starting material is an easily-available, low-molecular aliphatic polyester prepolymer to be prepared through polycondensation of inexpensive materials of an aliphatic hydroxycarboxylic acid such as lactic acid, glycolic acid or the like, an aliphatic polyalcohol such as butanediol or the like, and an aliphatic polycarboxylic acid such as succinic acid or the like, and the starting prepolymer is crystallized and thereafter polycondensed in a solid phase in the presence of a catalyst to give the intended, tough and high-molecular aliphatic polyester.

Abstract: The present invention is directed to a process of atom (or group) transfer radical polymerization for the synthesis of novel homopolymer or a block or graft copolymer, optionally containing at least one polar group, with well defined molecular architecture and narrow polydispersity index, in the presence of an initiating system comprising (i) an initiator having a radically transferrable atom or group, (ii) a transition metal compound, and (iii) a ligand; the present invention is also directed to the synthesis of a macromolecule having at least two halogen groups which can be used as a macroinitiator component (i) to subsequently form a block or graft copolymer by an atom or group transfer radical polymerization process; the present invention is also directed to a process of atom or group transfer radical polymerization for the synthesis of a branched or hyperbranched polymer; in addition, the present invention is directed to a process of atom or group transfer radical polymerization for the synthesis of a ma

Abstract: A process for preparing a biodegradable resin composition, comprising: providing a reaction mixture comprising at least one hydroxycarboxylic acid and, as a polymerization catalyst, a monoorganotin derivative; heating and stirring the reaction mixture, wherein the heating and stirring step is carried out under a reduced pressure to cause condensation polymerization or carried out in an organic solvent to cause azeotropic dehydrating polymerization. Also disclosed in a biodegradable resin composition prepared by the process.

Abstract: A method for producing polybutylene terephthalate comprising continuously esterifying a dicarboxylic acid component consisting essentially of terephthalic acid with a diol component consisting essentially of 1,4-butanediol followed by polycondensing the resulting oligomer, wherein the esterification is effected in a molar ratio, P, of the diol component to the dicarboxylic acid component to fall between 1.1 and 1.6, in the presence of a combination of an organic titanium compound and an organic tin compound that satisfies the following requirement:amount of organic titanium compound (mol %).ltoreq.0.08.times.P-0.07where P=molar ratio of diol component to dicarboxylic acid component, and is followed by the polycondensation.

Abstract: The invention provides non-antimony containing polymerization catalysts for the condensation of polyesters. The catalyst is in the form of a clear chlorine and/or bromine containing solution of a metal glycoxide and a metal glycolate having a pH in the range of from 0 to about 1, and containing chlorine and/or bromine atoms at a number ratio of chlorine and/or bromine to total metal cations in the catalyst ranging from about 0.5:1 to about 3:1. Polyesters produced with this catalyst have improved melt elasticity, and higher melt viscosity. The former property is desirable for the preparation of large and complex shaped polyester containers, and the latter property is desirable for melt spinning of industrial grade fibers and tire cords.

Abstract: A composition comprising (A) at least one mercapto-functional organosilicon compound having an average of a least two mercapto groups per molecule and (B) a cure initiator. The mercapto-functional organosilicon compound may include mercapto-functional organosilanes, mercapto-functional organosiloxanes, and mercapto-functional copolymers. The compositions of the present invention polymerize or cure to form compositions comprising reaction products of components (A) and (B). The cure initiator is a metal salt that produces a uniform cure throughout the composition, regardless of the amount of oxygen present. The cured products range in properties from soft gels to though elastomers to hard resins and are useful as molded articles, electrical encapsulants, and sealants.

Abstract: The present invention provides a one-liquid low temperature hardenable type colored enamel paint and a one-liquid low temperature hardenable type clear paint, which are used for coating of plastic materials and sufficiently harden even by baking at a low temperature and can form a hardened coating film that is excellent in contaminationproofing and acidproofing without damaging flexibility. The colored enamel paint comprises: resin components, which include a polyesterpolyol and an acrylic polyol; a crosslinking agent, which includes a blocked isocyanate as the essential component and may further include a melamine resin; a blocked isocyanate dissociation catalyst, which at least includes a dibutyltin dicarboxylate; and a pigment. The clear paint comprises: a resin component, which includes an acrylic polyol; the crosslinking agent; and the blocked isocyanate dissociation catalyst.

Abstract: The present invention provides a catalyst for polyester production capable of producing a polyester with high catalytic activity, a process for producing a polyester using the catalyst and a polyester produced thereby. The catalyst comprises a solid titanium compound obtained by dehydro-drying a hydrolyzate obtained by hydrolysis of a titanium halide and which has a molar ratio (OH/Ti) of a hydroxyl group (OH) to titanium (Ti) exceeding 0.09 and less than 4. In the process, the polyester is obtained by polycondensing an aromatic dicarboxylic acid, or an ester-forming derivative thereof, and an aliphatic diol, or ester-forming derivative thereof, in the presence of the catalyst. The resulting polyester has excellent transparency and tint, a titanium content of 1 to 100 ppm, a magnesium content of 1 to 200 ppm and a magnesium to titanium weight ratio of not less than 0.01.