The polymerization of cycloalkenamer is stopped by adding an alkyl vinyl derivative. Subsequently compound A is added, wherein compound A has at least one of the features i) or ii): i) at least one functional group or ii) at least one saturated or unsaturated aliphatic or aromatic heterocyclic ring having 3 to 14 ring atoms, wherein the ring atoms contain at least one carbon atom and at least one atom selected from oxygen, nitrogen and sulfur. A membrane filtration is subsequently carried out. This type of production produces polyalkenamers which are temperature-stable at 180° C.

A polyvinyl alcohol is produced in a method comprising: a polymerization step comprising polymerizing vinyl ester monomers by controlled radical polymerization in the presence of a radical initiator and an organic cobalt complex to obtain a polymer solution containing a polyvinyl ester; an extraction step comprising extracting a cobalt complex from the polymer solution by contacting an aqueous solution containing a water-soluble ligand with the polymer solution; and a saponification step comprising saponifying the polyvinyl ester after the extraction step to obtain a polyvinyl alcohol. A method for producing a polyvinyl alcohol is thus provided that has a narrow molecular weight distribution and a high number-average molecular weight with good hue and further good solubility in water.

A polyvinyl alcohol is produced in a method comprising: a polymerization step comprising polymerizing vinyl ester monomers by controlled radical polymerization in the presence of a radical initiator and an organic cobalt complex to obtain a polymer solution containing a polyvinyl ester; an extraction step comprising extracting a cobalt complex from the polymer solution by contacting an aqueous solution containing a water-soluble ligand with the polymer solution; and a saponification step comprising saponifying the polyvinyl ester after the extraction step to obtain a polyvinyl alcohol. A method for producing a polyvinyl alcohol is thus provided that has a narrow molecular weight distribution and a high number-average molecular weight with good hue and further good solubility in water.

A method for recovering a catalyst, wherein a solution containing a reaction mixture obtained by performing a hydrogenation reaction in a presence of a catalyst containing a platinum group metal is brought into contact with a fiber membrane having a group containing an amino group or a thiol group on a surface, thereby recovering the platinum group metal included in the solution is provided.

A method for recovering a catalyst, wherein a solution containing a reaction mixture obtained by performing a hydrogenation reaction in a presence of a catalyst containing a platinum group metal is brought into contact with a fiber membrane having a group containing an amino group or a thiol group on a surface, thereby recovering the platinum group metal included in the solution is provided.

The purpose of the present invention is to provide: a cross-copolymer in which a residual catalyst component remains in a reduced amount and which has improved transparency, applicability to medical materials and yellowish discoloration resistance; and a method for producing the cross-copolymer. According to the present invention, a cross-copolymer is provided, wherein the cross-copolymer is produced through a coordination polymerization step of carrying out copolymerization of an olefin monomer, an aromatic vinyl compound monomer and an aromatic polyene using a single-site coordination polymerization catalyst to synthesize an olefin-(aromatic vinyl compound)-(aromatic polyene) copolymer and a subsequent anionic polymerization step of carrying out polymerization in the co-presence of the olefin-(aromatic vinyl compound)-(aromatic polyene) copolymer and an aromatic vinyl compound monomer using an anionic polymerization initiator, the cross-copolymer being characterized in that the total mass of aluminum and lithium, which are residual catalyst components, contained in the cross-copolymer is 200 ppm or less.

The purpose of the present invention is to provide: a cross-copolymer in which a residual catalyst component remains in a reduced amount and which has improved transparency, applicability to medical materials and yellowish discoloration resistance; and a method for producing the cross-copolymer. According to the present invention, a cross-copolymer is provided, wherein the cross-copolymer is produced through a coordination polymerization step of carrying out copolymerization of an olefin monomer, an aromatic vinyl compound monomer and an aromatic polyene using a single-site coordination polymerization catalyst to synthesize an olefin-(aromatic vinyl compound)-(aromatic polyene) copolymer and a subsequent anionic polymerization step of carrying out polymerization in the co-presence of the olefin-(aromatic vinyl compound)-(aromatic polyene) copolymer and an aromatic vinyl compound monomer using an anionic polymerization initiator, the cross-copolymer being characterized in that the total mass of aluminum and lithium, which are residual catalyst components, contained in the cross-copolymer is 200 ppm or less.

A polyvinyl alcohol is produced in a method comprising: a polymerization step comprising polymerizing vinyl ester monomers by controlled radical polymerization in the presence of a radical initiator and an organic cobalt complex to obtain a polymer solution containing a polyvinyl ester; an extraction step comprising extracting a cobalt complex from the polymer solution by contacting an aqueous solution containing a water-soluble ligand with the polymer solution; and a saponification step comprising saponifying the polyvinyl ester after the extraction step to obtain a polyvinyl alcohol. A method for producing a polyvinyl alcohol is thus provided that has a narrow molecular weight distribution and a high number-average molecular weight with good hue and further good solubility in water.

A method for producing a polymer latex, includes: a stirring step of adding water to a polymer solution obtained by dissolution of a synthetic rubber in an organic solvent, to allow water to be stirred in the polymer solution, thereby providing a water-stirred polymer solution (A); an aqueous phase removal step of removing an aqueous phase from the water-stirred polymer solution (A), thereby providing an aqueous phase-removed polymer solution (B); an emulsification step of mixing the aqueous phase-removed polymer solution (B) with an aqueous solution including a surfactant, for emulsification in water, thereby obtaining an emulsified liquid (C); a solvent removal step of removing an organic solvent in the emulsified liquid (C); and a concentration step of concentrating the emulsified liquid from which the organic solvent is removed (D).

A method for recovering a catalyst, wherein a solution containing a reaction mixture obtained by performing a hydrogenation reaction in a presence of a catalyst containing a platinum group metal is brought into contact with a fiber membrane having a group containing an amino group or a thiol group on a surface, thereby recovering the platinum group metal included in the solution is provided.