Abstract: Disclosed are a water-insoluble copolymer having a constitutional unit (X) derived from a hydroxycarboxylic acid and a constitutional unit (Y) derived from an amino group-containing polyvalent carboxylic acid, wherein the molar ratio (X/Y) of constitutional units is 2/1?(X/Y)<8/1, and the amide bond proportion of the constitutional unit (Y) represented by the following formula (1) is defined by the following formulae (2-1) to (2-3); a production method thereof, and a resin composition containing the copolymer. Amide bond proportion (%)=A/Asp×100??(1) [A=number of moles of an amide bond in (Y), Asp=number of moles of (Y)] [when 2/1?(X/Y)<4/1] amide bond proportion (%)?25??(2-1) [when 4/1?(X/Y)?6.5/1] amide bond proportion (%)?30??(2-2) [when 6.

Abstract: The aqueous dispersion of the present invention is an aqueous dispersion in which a biodegradable resin composition (C) in the form of a fine solid is dispersed in an aqueous medium, and the biodegradable resin composition (C) comprises a copolymer (A) comprising a constituent unit (a-1) derived from a polyvalent carboxylic acid and a constituent unit (a-2) derived from a hydroxycarboxylic acid, and a biodegradable resin (B), and wherein the mass composition ratio [(A)/(B)] of the copolymer (A) to the biodegradable resin (B) is 1/99 to 100/0 provided that the total amount of the copolymer (A) and the biodegradable resin (B) is 100.

Abstract: It is an object of the present invention to provide a resin composition having improved heat resistance (high crystallinity) and transparency without impairing rigidity intrinsic to a polylactic acid based resin, a molded body formed from the resin composition, and a new polylactic acid based resin used in the resin composition. A polylactic acid based resin (A) according to the present invention is characterized by having a specific structural moiety and a weight average molecular weight (Mw) of 5,000 to 1,000,000. A polylactic acid based resin composition according to the present invention is characterized by containing the above-described polylactic acid based resin (A).

Abstract: It is an object of the present invention to provide a resin composition having improved heat resistance (high crystallinity) and transparency without impairing rigidity intrinsic to a polylactic acid based resin, a molded body formed from the resin composition, and a new polylactic acid based resin used in the resin composition. A polylactic acid based resin (A) according to the present invention is characterized by having a specific structural moiety and a weight average molecular weight (Mw) of 5,000 to 1,000,000. A polylactic acid based resin composition according to the present invention is characterized by containing the above-described polylactic acid based resin (A).

Abstract: A (meth)acrylic ester compound represented by the general formula (1) and a dental material containing the compound, wherein, in the formula, R11 represents a divalent aromatic group; R12 represents a hydrogen atom or a methyl group; R13 represents an aryl group; R14 represents a hydrogen atom or a methyl group; and X11, represents an oxygen atom or a sulfur atom. A polymerizable composition containing the (meth)acrylic ester compound and an optical part obtained by polymerizing the polymerizable composition are also provided. The cured composition can provide advantageous physical and optical properties.

Abstract: A (meth)acrylic ester compound represented by the general formula (1) and a dental material containing the compound, wherein, in the formula, R11 represents a divalent aromatic group; R12 represents a hydrogen atom or a methyl group; R13 represents an aryl group; R14 represents a hydrogen atom or a methyl group; and X11, represents an oxygen atom or a sulfur atom. A polymerizable composition containing the (meth)acrylic ester compound and an optical part obtained by polymerizing the polymerizable composition are also provided. The cured composition can provide advantageous physical and optical properties.

Abstract: A poly(thio)ester (co)polymer which comprises a repeating structural unit represented by the formula (1-A) as an essential structural unit: [wherein R11 is a divalent aliphatic hydrocarbon group which may contain at least one sulfur atom in a sulfide group; R12 is a mono- or poly-cyclic aliphatic or aromatic dicarboxylic acid residue; and X11 and X12 are each independently an oxygen atom or sulfur atom, and when X11 and X12 are the oxygen atoms, R11 is a divalent aliphatic hydrocarbon group containing at least one sulfur atom in the sulfide group]; and an optical component obtainable by molding the poly(thio)ester (co)polymer. The poly(thio)ester (co)polymer is excellent in transparency and optical characteristics (e.g., a higher refractive index, higher Abbe number, and lower birefringence), and has also good mechanical characteristics and thermal characteristics, and further is excellent in melt fluidity and injection moldability.

Abstract: A poly(thio)ester (co)polymer which comprises a repeating structural unit represented by the formula (1-A) as an essential structural unit: 1

Abstract: A biodegradable aliphatic polyester elastomer which has rubber-like elasticity, hardness of 80 or less in accordance with ASTM D 676-58T, and elastic modulus from 1.times.10.sup.5 Pa to 1.times.10.sup.8 Pa at 25.degree. C., and decomposes with ease in the natural environment, under composting conditions or under hydrolysis conditions. The biodegradable aliphatic elastomer can be obtained by crosslinking aliphatic polyester containing aliphatic unsaturated polybasic acid as a polymer constituting ingredient and having a weight average molecular weight of 15,000 or more.

Abstract: A degradable polymer and a process for preparing the degradable polymer which has a structure resulting from combination of a star-shaped polymer comprising a polyfunctional base compound of polycarboxylic acid having three or more carboxyl groups and/or anhydride of the same or aliphatic polyhydric alcohol having three or more hydroxyl groups and a unit of aliphatic hydroxycarboxylic acid, with aliphatic polyhydric alcohol having two or more hydroxyl groups or polycarboxylic acid having two or more carboxyl groups or anhydrides of the same. The degradable polymer leads to remarkably low coloration as compared with a polymer comprising polysaccharide as a polyfunctional base compound, has high melt tension as compared to common aliphatic polyester is excellent in processability on various molding methods, foam molding and blow molding in particular, and high transparency.

Abstract: A degradable copolymer obtained by heat-dehydration reaction of aromatic polycarbonate and aliphatic polyester in the presence of a catalyst, has degradability which cannot be exhibited by common aromatic polycarbonate, transparency equal to polycarbonate, thermal resistance which cannot be exhibited by common aliphatic polyester, melt flowability superior to common aromatic polycarbonate and other excellent characteristics, and thus can be widely used for processed articles which require severe properties.

Abstract: A preparation process of a degradable copolymer comprising carrying out dehydration polycondensation of polysaccharide (A) with one or more compounds (B) selected from the group consisting of:(b1) hydroxycarboxylic acid,(b2) polyhydroxycarboxylic acid,(b3) aliphatic polyhydric alcohol and aliphatic polybasic acid, and(b4) aliphatic polyester derived from aliphatic polyhydric alcohol and aliphatic polybasic acid.A copolymer having a high molecular weight, excellent toughness, transparency and heat resistance, and additionally having a high melt tension can be obtained with a reaction time less than a half of the conventional process. The copolymer obtained by the invention is a material suited for injection molding, extrusion, calendaring, blow forming, balloon forming, vacuum forming and foaming. Particularly, the copolymer obtained by the invention has a high melt tension and thus the molten copolymer is difficult to sag and flow and can be processed with ease into foams and blow bottles.

Abstract: A process for preparing a degradable copolymer of aliphatic polyester comprising the steps of reacting two or more kinds of aliphatic polyester homopolymer in the presence of a catalyst in a reaction mixture containing an organic solvent, and a degradable copolymer of aliphatic polyester obtained by said preparation process. The copolymers exhibits high transparency in addition to excellent strength and elongation, can be processed into various molded articles and formed items such as films and filaments, and can provide heat resistance by heat treatment of said molded articles and formed items. The copolymer can be suitably utilized for processed articles such as a film, breathable film, sheet, textile, monofilament, multifilament, yarn, non-woven fabric, flat yarn, staple, crimped fiber, ribbed tape, split yarn, conjugate fiber, laminate, blow-bottle, sheet, stretched sheet, foam and net.

Abstract: A preparation process of aliphatic polyester having a weight average molecular weight of 15,000 or more by conducting a direct polycondensation reaction of an aliphatic polyhydric alcohol or a mixed aliphatic polyhydric alcohol and an aliphatic polybasic acid or a mixed aliphatic polybasic acid, or additionally a hydroxycarboxylic acid or a mixed hydroxycarboxylic acid or an oligomer of the hydroxycarboxylic acid in a reaction mixture containing an organic solvent.The aliphatic polyester thus obtained contains an extremely small amount of impurities, has low color and can exhibit satisfactory strength in the form of films, filaments and other shaped articles.

Abstract: .alpha.-L-Aspartyl-L-phenylalanine methyl ester (.alpha.-APM) is prepared by catalytic hydrogenation of N-benzyloxycarbonyl-.alpha.-L-aspartyl-L-phenylalanine methyl ester (Z-.alpha.-APM). The catalytic hydrogenation is conducted in an aqueous suspension containing the Z-.alpha.-APM in the form of particles whose average particle size is not greater than 800 .mu.m. The starting Z-.alpha.-APM may contain up to 30 wt. % of its .beta.-isomer provided that the process additionally includes recrystallization of the .alpha.-APM, collection of the .alpha.-APM by filtration and recycling of the filtrate for use in the aqueous suspension of Z-.alpha.-APM.

Abstract: A preparation process of aliphatic polyester having a weight average molecular weight of 15,000 or more by conducting a direct polycondensation reaction of an aliphatic polyhydric alcohol or a mixed aliphatic polyhydric alcohol and an aliphatic polybasic acid or a mixed aliphatic polybasic acid, or additionally a hydroxycarboxylic acid or a mixed hydroxycarboxylic acid or an oligomer of the hydroxycarboxylic acid in a reaction mixture containing an organic solvent.The aliphatic polyester thus obtained contains an extremely small amount of impurities, has low color and can exhibit satisfactory strength in the form of films, filaments and other shaped articles.

Abstract: Disclosed is an improved process for the preparation of an N-protected .alpha.-L-aspartyl-L-phenylalanine methyl ester from an N-protected L-aspartic anhydride and L-phenylalanine methyl ester, the improvement which comprises employing the L-phenylalanine methyl ester in the form of a mineral acid salt thereof and conducting the reaction either (a) in an organic solvent and in the presence of a salt of an organic carboxylic acid, or (b) in an organic solvent comprising an organic carboxylic acid and in the presence of at least one member of the group consisting of an alkali metal or an alkaline earth metal inorganic base, an ammonium alkali metal or alkaline earth metal salt of an organic carboxylic acid and ammonium carbonate. The starting N-protected aspartic anhydride, e.g., N-benzyloxycarbonyl-L-aspartic anhydride, can be produced by the reaction of N-protected aspartic acid with phosgene.

Abstract: A method for separating .alpha.-L-aspartyl-L-phenylalanine methyl ester (.alpha.-APM) from a solution containing .alpha.-APM and impurities associated with the production thereof which comprises adding a mineral acid or an organic sulfonic acid to the solution in an organic carboxylic acid or in a solvent containing an organic carboxylic acid, and isolating the pure salt of .alpha.-APM which precipitates therefrom.

Abstract: A method for preparing .alpha.-L-aspartyl-L-phenylalanine methyl ester (.alpha.-APM), substantially free from acid ion contamination, is disclosed which comprises the steps of contacting a solution of a mineral acid salt or an organic sulfonic acid salt of .alpha.-APM in an aqueous solvent with an anion exchange resin in free base form, separating the resin from the thus-produced solution of .alpha.-APM; and isolating the .alpha.-APM therefrom, preferably with regeneration and recycling the resin.

Abstract: A cyclical process for producing and isolating a mineral acid salt of an amino acid methyl ester in high purity and yield from the reaction solution produced by esterifying an amino acid with methanol in methanol in the presence of a mineral acid, by cooling the resulting reaction solution to precipitate crystals of the mineral acid salt; filtering the crystals;drying the isolated wet crystals or washing with another organic solvent; and recycling the filtrate for reuse in the esterification reaction.