The invention provides a method for producing an oxymethylene copolymer including a polymerization step for cationically polymerizing trioxane and a comonomer at a polymerization temperature of from 135 to 300 C. in the presence of at least one salt of a protonic acid having a molecular weight of 1,000 or less, and at least one polymerization initiator selected from the group consisting of protonic acids having a molecular weight of 1,000 or less, protonic acid anhydrides having a molecular weight of 1,000 or less, and protonic acid ester compounds having a molecular weight of 1,000 or less; wherein the total concentration of metal components contained in the trioxane and comonomer used in the polymerization step is 300 ppb by mass or less.

The invention provides a method for producing an oxymethylene copolymer including a polymerization step for cationically polymerizing trioxane and a comonomer at a polymerization temperature of from 135 to 300 C. in the presence of at least one salt of a protonic acid having a molecular weight of 1,000 or less, and at least one polymerization initiator selected from the group consisting of protonic acids having a molecular weight of 1,000 or less, protonic acid anhydrides having a molecular weight of 1,000 or less, and protonic acid ester compounds having a molecular weight of 1,000 or less; wherein the total concentration of metal components contained in the trioxane and comonomer used in the polymerization step is 300 ppb by mass or less.

The present invention is directed to a method for producing an oxymethylene copolymer by subjecting trioxane and 1,3-dioxolane to copolymerization using boron trifluoride or a coordination compound thereof as a catalyst, wherein the copolymerization is conducted in the presence of a steric-hindrance phenol in an amount of 0.006 to 2.0% by weight, based on the weight of the trioxane, using 0.01 to 0.07 mmol of boron trifluoride or a coordination compound thereof as a catalyst, relative to 1 mol of the trioxane, and wherein, at a point in time when the polymerization yield becomes 92% or more, the formed oxymethylene copolymer and a polymerization terminator are contacted to terminate the polymerization.

The present invention is directed to a method for producing an oxymethylene copolymer by subjecting trioxane and 1,3-dioxolane to copolymerization using boron trifluoride or a coordination compound thereof as a catalyst, wherein the copolymerization is conducted in the presence of a steric-hindrance phenol in an amount of 0.006 to 2.0% by weight, based on the weight of the trioxane, using 0.01 to 0.07 mmol of boron trifluoride or a coordination compound thereof as a catalyst, relative to 1 mol of the trioxane, and wherein, at a point in time when the polymerization yield becomes 92% or more, the formed oxymethylene copolymer and a polymerization terminator are contacted to terminate the polymerization.

A high-quality polyacetal produced by a process including supplying a raw material comprising trioxane, a comonomer capable of copolymerizing with trioxane and a non-volatile protonic acid to a reactor of a continuous stirring/mixing machine type; carrying out a polymerization reaction of the raw material to produce a reaction mixture; vaporizing an unreacted monomer to separate the unreacted monomer from the reaction mixture and supplying the unreacted monomer to the raw material supplying; collecting a polyacetal copolymer from the reaction mixture into a collection unit which is arranged downstream from a discharge port and is adjusted to have a gauge pressure of 0.2 kPa or more; and adding a basic compound to the collected polyacetal and then subjecting the resultant mixture to a melt-kneading treatment to deactivate the non-volatile protonic acid.

A high-quality polyacetal produced by a process including supplying a raw material comprising trioxane, a comonomer capable of copolymerizing with trioxane and a non-volatile protonic acid to a reactor of a continuous stirring/mixing machine type; carrying out a polymerization reaction of the raw material to produce a reaction mixture; vaporizing an unreacted monomer to separate the unreacted monomer from the reaction mixture and supplying the unreacted monomer to the raw material supplying; collecting a polyacetal copolymer from the reaction mixture into a collection unit which is arranged downstream from a discharge port and is adjusted to have a gauge pressure of 0.2 kPa or more; and adding a basic compound to the collected polyacetal and then subjecting the resultant mixture to a melt-kneading treatment to deactivate the non-volatile protonic acid.

A process for producing a polyacetal copolymer, the process making catalyst deactivation easy and efficient. Trioxane as a major monomer is copolymerized with one or more comonomers that are a cyclic ether and/or cyclic formal having at least one carbon-carbon bond, using a nonvolatile protonic acid as a polymerization catalyst at 100 C. or lower until the conversion reaches 50% and thereafter at a polymerization environment temperature of 115 C. to 140 C. This process includes: a crushing step in which a dry-process crusher is used to obtain a crude polyacetal copolymer crushed to such a degree that when the crude copolymer is screened with a sieve having an opening size of 11.2 mm, 90 parts by weight or more thereof passes therethrough; and a deactivation step in which a basic compound (e) is added to the crude copolymer and the mixture is melt-kneaded to thereby deactivate the polymerization catalyst.

A process for producing a polyacetal copolymer, the process making catalyst deactivation easy and efficient. Trioxane as a major monomer is copolymerized with one or more comonomers that are a cyclic ether and/or cyclic formal having at least one carbon-carbon bond, using a nonvolatile protonic acid as a polymerization catalyst at 100 C. or lower until the conversion reaches 50% and thereafter at a polymerization environment temperature of 115 C. to 140 C. This process includes: a crushing step in which a dry-process crusher is used to obtain a crude polyacetal copolymer crushed to such a degree that when the crude copolymer is screened with a sieve having an opening size of 11.2 mm, 90 parts by weight or more thereof passes therethrough; and a deactivation step in which a basic compound (e) is added to the crude copolymer and the mixture is melt-kneaded to thereby deactivate the polymerization catalyst.

A production method for a polyacetal copolymer that makes deactivation of a catalyst simple and efficient and that achieves a high polymerization yield and high quality using equipment that does not require a cleaning step and a process that involves a simple operation technique. The production method for a polyacetal copolymer uses trioxane as a main monomer and a cyclic ether and/or a cyclic formal having at least one carbon-carbon bond as a comonomer. In the production method, a predetermined heteropoly acid is used as a polymerization catalyst to perform copolymerization, a predetermined salt is added to the reaction product, melt kneading processing is performed, and the polymerization catalyst is deactivated.

A production method for a polyacetal copolymer that makes deactivation of a catalyst simple and efficient and that achieves a high polymerization yield and high quality using equipment that does not require a cleaning step and a process that involves a simple operation technique. The production method for a polyacetal copolymer uses trioxane as a main monomer and a cyclic ether and/or a cyclic formal having at least one carbon-carbon bond as a comonomer. In the production method, a predetermined heteropoly acid is used as a polymerization catalyst to perform copolymerization, a predetermined salt is added to the reaction product, melt kneading processing is performed, and the polymerization catalyst is deactivated.