JP2017002178A - Method for producing oxymethylene copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method capable of stably, continuously producing an oxymethylene copolymer at a high yield and having a high molecular weight by a melt polymerization method.SOLUTION: A polymerization reaction raw material liquid obtained by mixing a mixed raw material liquid of trioxane and a co-monomer and a polymerization initiator at 135 to 300°C is circulated through the inside of a piping at a linear speed of 0.1 mm or more and is introduced into a static mixer type polymerization machine having no driving part provided with a stationary mixing element at the inside, and the time till the polymerization reaction raw material liquid is introduced into the polymerization machine after its contact and mixing with the liquid including the mixing raw material liquid and the polymerization initiator is controlled to 0.01 to 120 s.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an oxymethylene copolymer.

  Oxymethylene polymers have excellent mechanical and thermal performance, and in particular, oxymethylene copolymers have better thermal stability and moldability than oxymethylene homopolymers. Has been heavily used. There are a number of literatures on methods for producing oxymethylene copolymers. For example, Patent Document 1 discloses a tube type in which a static mixing element is provided inside as a reactor capable of producing a polyoxymethylene copolymer by a simple method, and the length and diameter are different in individual processing steps. A continuous reactor is disclosed.

  Patent Document 2 discloses that in a bulk polymerization method in which a produced oxymethylene copolymer is deposited at a temperature of 65 ° C. to 100 ° C., trioxane, 1,3-dioxolane, and a polymerization catalyst are contacted and mixed. It discloses a method for producing an oxymethylene copolymer that can be stably operated over a long period of time without causing poor supply to the polymerization machine due to blockage or narrowing of the piping through which the resulting polymerization reaction raw material flows. Specifically, when the polymerization catalyst is mixed with the mixed raw material liquid of trioxane and 1,3-dioxolane, and introduced into the polymerization machine to continuously produce the oxymethylene copolymer, the mixed raw material that circulates in the pipe Disclosed is a continuous production method of an oxymethylene copolymer in which the linear velocity of the liquid and the time from when the mixed raw material liquid and the polymerization catalyst are contacted and mixed to the time when the mixed raw material liquid is introduced into the polymerization machine are specified. . Further, Patent Document 2 discloses the connection position and the shape of the tip of the polymerization catalyst introduction pipe for introducing the polymerization catalyst into the mixed raw material liquid in which the above-described pipe is less likely to be blocked or narrowed.

  In addition, Patent Document 3 has a mixed region in which a raw material monomer and a polymerization catalyst are mixed, a polymerization region, and a deactivation region as a more excellent method for producing an oxymethylene copolymer. Disclosed is a method for producing an oxymethylene copolymer using a tubular reactor having a static mixing element, which is less than 90% of the diameter of the region and is composed of 1 to 5 inactive regions.

Japanese Patent No. 3285278 Japanese Patent No. 4092545 Japanese Patent No. 5502280

  A static mixer type polymerization machine with a stationary mixing element and no drive unit is a simpler device compared to a biaxial paddle type polymerization machine with a drive unit, but it has a low content viscosity. Further improvements in industrial use are desired, such as the need to change the diameter of the mixing region of the polymerization catalyst and the diameter of the polymerization / deactivation region where the content is highly viscous. In particular, in a melt polymerization method in which a polymerization reaction is performed at 135 ° C. to 300 ° C. and the generated oxymethylene copolymer is deactivated without precipitation, a high molecular weight oxymethylene copolymer is used by using a simple static mixer type polymerization machine. There has been little investigation on a method for stably and continuously producing a coalescence in a high yield.

  That is, an object of the present invention is to provide a production method capable of stably continuously producing an oxymethylene copolymer with a high molecular weight and a high yield in a melt polymerization method.

  As a result of diligent studies to solve the above-mentioned problems, the present inventors continuously used an oxymethylene copolymer by using a static mixer type polymerization machine having a driving unit equipped with a stationary mixing element inside. In the production of a polymerization reaction raw material liquid obtained by mixing a mixed raw material liquid of trioxane and a comonomer and a liquid containing a polymerization initiator at a temperature of 135 ° C. to 300 ° C., which is a temperature for performing a polymerization reaction, Circulating the inside of the pipe at a linear velocity and introducing it into the polymerization machine, and the time from when the polymerization reaction raw material liquid is brought into contact with and mixed with the mixed raw material liquid and the liquid containing the polymerization initiator to the polymerization machine By setting the specific range, it was found that an oxymethylene copolymer can be stably and continuously produced with a high molecular weight and a high yield, and the present invention has been completed.

That is, the present invention is as follows.
(1) A static mixer type polymerization machine (A) having a static mixing element inside and no drive unit, and a mixed raw material liquid containing trioxane and a comonomer are supplied to the polymerization machine (A). A method for producing an oxymethylene copolymer using a polymerization reaction apparatus, comprising a pipe (B) and a pipe (C) for supplying a liquid containing a polymerization initiator connected in the middle of the pipe (B). And the polymerization reaction raw material liquid obtained by mixing the said mixed raw material liquid and the liquid containing the said polymerization initiator in the connection part of the said piping (B) and the said piping (C) is 135 to 300 degreeC. The linear velocity obtained by mixing at a temperature and flowing through the pipe (B) after the connection portion of the polymerization reaction raw material liquid is 0.1 mm or more per second, and the polymerization reaction raw material liquid is Heavy weight from connection Time to reach the inlet of the machine (A) is 0.01 to seconds, the manufacturing method of the oxymethylene copolymer.
(2) The manufacturing method of the oxymethylene copolymer as described in (1) in which the front-end | tip of piping (C) is connected in the said connection part in the form which does not contact the inner wall of piping (B).
(3) The connection angle of the pipe (C) to the pipe (B) in the polymerization reaction apparatus is connected so as to be an angle of 90 degrees or less with respect to the upstream side of the pipe (B), (1) or ( The method for producing an oxymethylene copolymer according to 2).
(4) Any of (1) to (3), wherein the inner diameter of the polymerization machine (A) in the polymerization reaction apparatus is constant in a region of 90% or more of the region in the polymerization machine (A) where the polymerization reaction is performed. A method for producing the oxymethylene copolymer according to claim 1.
(5) The polymerization reaction apparatus further includes a polymerization terminator mixer (D) connected in series to the polymerization machine (A), and the maximum value of the inner diameter of the polymerization terminator mixer (D) is a polymerization machine. The manufacturing method of the oxymethylene copolymer as described in any one of (1)-(4) which is 90% or less of the maximum value of the internal diameter of (A).
(6) As the polymerization initiator, at least one selected from the group consisting of a protonic acid having a molecular weight per mole of 1000 or less, a protonic acid anhydride, and a protonic acid ester compound is used. ) The manufacturing method of the oxymethylene copolymer as described in any one of.
(7) Production of an oxymethylene copolymer according to any one of (1) to (6), wherein at least one salt of a protonic acid having a molecular weight per mole of 1000 or less is used together with the polymerization initiator. Method.
(8) The method for producing an oxymethylene copolymer according to (7), wherein a salt of a protonic acid having a molecular weight per mole of 1000 or less is supplied together with the polymerization initiator from the pipe (C).

  According to the present invention, in the melt polymerization method in which the polymerization initiator is deactivated without precipitating the oxymethylene copolymer produced by the polymerization reaction, the inside has a stationary mixing element, which is a simple polymerization reaction apparatus. In addition, it is possible to provide a production method capable of stably and continuously producing an oxymethylene copolymer with a high molecular weight and a high yield by using a static mixer type polymerization machine having no drive unit.

  In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. . Moreover, the numerical range shown using "to" shows the range which includes the numerical value described before and behind "to" as a minimum value and a maximum value, respectively. Further, the amount of each component in the composition means the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition.

  The method for producing an oxymethylene copolymer according to the present invention includes at least a static mixer type polymerization machine (A) having a stationary mixing element therein and no drive unit, and a mixed raw material liquid containing trioxane and a comonomer A polymerization reaction, which has a pipe (B) for supplying the polymerization machine (A) to the polymerization machine (A) and a pipe (C) for supplying a liquid containing a polymerization initiator connected in the middle of the pipe (B) Use the device. In that case, the polymerization reaction raw material liquid obtained by mixing the said mixed raw material liquid and the liquid containing the said polymerization initiator in the connection part of piping (B) and piping (C) is the temperature of 135 to 300 degreeC. Obtained by mixing, and the linear velocity flowing through the pipe (B) after the connection portion of the polymerization reaction raw material liquid is 0.1 mm or more per second, and the polymerization reaction raw material liquid is It is an essential requirement that the time from the connecting portion to the entrance of the polymerization machine (A) is 0.01 to 120 seconds.

  By doing so, there is no supply failure to the polymerization machine due to blockage or narrowing of the piping through which the polymerization reaction raw material liquid obtained by contacting and mixing trioxane, comonomer, and polymerization catalyst does not occur, so simple polymerization Using a static mixer type polymerization machine that has a static mixing element inside and a drive unit, which is a reaction device, oxymethylene copolymer is stably produced continuously with high molecular weight and high yield. Possible manufacturing methods can be provided.

  That is, according to the above method for producing an oxymethylene copolymer, a simple polymerization initiator can be used without using special production equipment necessary for polymerizing, pulverizing, mixing, melting, and transferring solids and powders. The mixing equipment and the static mixer type polymerizer enable stable and continuous production of high molecular weight oxymethylene copolymers with high yield, which is of great industrial significance. Hereinafter, the present invention will be described in detail.

[I: Polymerization reactor]
The polymerization reaction apparatus that can be used for the production of the oxymethylene copolymer of the present invention includes at least a static mixer type polymerization apparatus (A) having a stationary mixing element therein and no drive unit, and trioxane. And a pipe (B) for supplying a mixed raw material liquid containing a comonomer such as 1,3-dioxolane to the polymerization machine (A), and a liquid containing a polymerization initiator connected in the middle of the pipe (B) If it has piping (C) for doing, the aspect will not be specifically limited. In addition to the above-described polymerization machine (A), pipe (B), and pipe (C), the polymerization reaction apparatus includes a preheater (hereinafter referred to as the present specification) for preparing and heating a mixed raw material liquid containing trioxane and a comonomer. Then, it may be referred to as “first preheater”), a polymerization terminator mixer (D), a termination reactor, and a reaction product (hereinafter referred to as “this product”) including an oxymethylene copolymer produced by the polymerization reaction. Pre-heating to remove unreacted monomers and decomposition products from a mixture of a polymerization terminator and a reaction product containing an oxymethylene copolymer produced by a polymerization reaction) A machine (hereinafter also referred to as “second preheater” in the present specification) may be further provided. The most preferred form is a continuous polymerization apparatus in which a first preheater, a polymerization machine (A), a polymerization terminator mixer (D), a stop reaction machine, and a second preheater are connected in series by a pipe. Hereinafter, each device will be described.

  The polymerization machine (A) is not particularly limited as long as it is a static mixer type that has a static mixing element inside and does not have a drive unit. Here, the static mixer is a continuous type that does not have a drive unit, mixes the fluid passing by a stationary mixing element installed inside, and can remove heat and heat from the outside by installing a jacket or the like. It is a tube type device. A static mixing element is an element that is fixed to the outer tube itself and has a shape suitable for mixing fluid that passes effectively by changing the flow of fluid passing through the inside. For example, a rectangular plate that is twisted 180 degrees and is composed of two types of elements, a right-handed twist and a left-handed twist, or a plate-like lattice that meshes with each other and is suitably used. Can be used. The shape and size of the polymerization machine (A) are appropriately determined according to the production form and production amount of the oxymethylene copolymer, and are not particularly limited. In the polymerization reaction using the above-described static mixer type polymerization machine (A), the internal region of the polymerization machine begins to produce an oxymethylene copolymer, but has a relatively low viscosity initial polymerization region, oxymethylene copolymer. Formation of coalescence proceeds and the polymerization is divided into late polymerization regions having a relatively high viscosity. At this time, for the purpose of improving the linear velocity of the polymerization reaction raw material liquid flowing through the inside of the polymerization machine and enhancing the stirring effect inside the polymerization machine, the diameter of each initial region is made smaller than the diameter of the late polymerization region. However, in order to obtain a simple apparatus, the inner diameter of the polymerization machine (A) should be constant in 90% or more of the areas in the polymerization machine (A) where the polymerization reaction is performed. It is preferable that the initial polymerization region and the late polymerization region have the same diameter.

  As described above, the polymerization reaction apparatus used in the present invention includes a pipe (B) for supplying a mixed raw material liquid containing trioxane and a comonomer to the polymerization machine (A). The pipe (B) is preferably a pipe that connects a first preheater and a polymerization machine (A) for preparing and heating a mixed raw material liquid containing trioxane and a comonomer. The inner diameter and length of the pipe (B) are appropriately determined according to the production amount of the oxymethylene copolymer, and are not particularly limited.

  As described above, the polymerization reaction apparatus used in the present invention includes a pipe (C) for supplying a liquid containing a polymerization initiator connected in the middle of the pipe (B). The connection mode of the pipe (B) and the pipe (C) is not particularly limited, but the tip of the pipe (C) is connected to the inner wall of the pipe (B) at the connection portion of the pipe (B) and the pipe (C). It is preferable to be connected in a form that does not contact. By connecting the pipe (C) so that the tip of the pipe (C) does not contact the inner wall of the pipe (B), blockage due to precipitation of oxymethylene copolymer generated by polymerization starting with contact and mixing of trioxane, comonomer, and polymerization catalyst is prevented. Hard to happen. Moreover, it is preferable that the connection angle of the pipe (C) with respect to the pipe (B) is connected so as to be an angle of 90 degrees or less with respect to the upstream side of the pipe (B). By setting the connection angle to 90 degrees or less, clogging due to precipitation of the oxymethylene copolymer is unlikely to occur. In particular, the tip of the pipe (C) is connected so as not to contact the inner wall surface of the pipe (B), and the connection angle of the pipe (C) to the pipe (B) is based on the upstream side of the pipe (B). It is particularly preferable that they are connected so as to have an angle of 90 degrees or less.

  As described above, the polymerization reaction apparatus used in the present invention may further include a first preheater for mixing and heating trioxane, a comonomer, a solvent added as necessary, and the like. . At this time, it is preferable that the 1st preheater is connected in series with the superposition | polymerization machine (A) via piping (B). The shape and size of the first preheater are appropriately determined according to the production form and production amount of the oxymethylene copolymer, and are not particularly limited. A static mixer type having a stationary mixing element and no drive is preferred.

  As described above, the polymerization reaction apparatus used in the present invention may further include a polymerization terminator mixer (D) for mixing the polymerization reaction product and the polymerization terminator. In the polymerization terminator mixer (D), the polymerization initiator contained in the polymerization reaction product reacts with the polymerization terminator to deactivate the polymerization initiator. In the present invention, the polymerization terminator mixer (D) is preferably connected in series to the polymerization machine (A). The shape and size of the polymerization terminator mixer (D) are appropriately determined according to the production form and production amount of the oxymethylene copolymer, and are not particularly limited. In order to effectively perform the reaction of the terminator, a static mixer type having a stationary mixing element inside and not having a driving unit is preferable. Static mixed elements are composed of two types of elements, a right-handed twist and a left-handed twist of a rectangular plate that is twisted 180 degrees, or a plate-like lattice that meshes with each other and intersects. Can be suitably used. A polymerization reaction product containing a large amount of oxymethylene copolymer has a high viscosity. Therefore, in order to complete the reaction between the polymerization initiator and the polymerization terminator, a polymerization reaction that circulates in the polymerization terminator mixer (D). It is preferable to increase the linear velocity of the mixture of the polymerization terminator and the polymerization terminator to increase the stirring inside the polymerization terminator mixer (D). The inner diameter of the polymerization terminator mixer (D) is not particularly limited, but in order to increase the linear velocity of the mixture of the polymerization reaction product and the polymerization terminator flowing through the polymerization terminator mixer (D), The maximum inner diameter of the polymerization terminator mixer (D) is preferably 90% or less of the maximum inner diameter of the polymerization machine (A).

  As described above, the polymerization reaction apparatus used in the present invention deactivates the polymerization initiator by further stirring the mixture of the polymerization reaction product and the polymerization terminator mixed in the polymerization terminator mixer (D). It may further have a stop reactor. At this time, it is preferable that the stop reactor is connected in series with the polymerization terminator mixer (D). The shape and size of the termination reactor is appropriately determined according to the production form and production amount of the oxymethylene copolymer, and is not particularly limited, but the reaction between the polymerization initiator and the polymerization terminator is performed. In order to perform effectively, the static mixer type which has a stationary mixing element inside and does not have a drive part is preferable.

  As described above, the polymerization reaction apparatus used in the present invention may further include a second preheater for removing unreacted monomers and decomposition products from the mixture of the polymerization reaction product and the polymerization terminator. At this time, the second preheater is preferably connected in series to the stop reactor. The shape and size of the second preheater are appropriately determined according to the production form and production amount of the oxymethylene copolymer, and are not particularly limited. A static mixer type having a stationary mixing element and no drive is preferred.

[II: Production method of oxymethylene copolymer (from raw material preparation to polymerization reaction step)]
In the method for producing an oxymethylene copolymer of the present invention, the polymerization reaction raw material liquid comprises a mixed raw material liquid containing trioxane and a comonomer and a liquid containing a polymerization initiator at a connection portion between the pipe (B) and the pipe (C). Get mixed. The temperature during mixing is usually 135 ° C to 300 ° C, preferably 140 ° C to 220 ° C, and most preferably 140 ° C to 190 ° C. When the temperature at the time of mixing is 135 ° C to 300 ° C, blockage of piping (B) or piping (C) due to precipitation of oxymethylene copolymer generated by polymerization starting with contact and mixing of trioxane, comonomer, and polymerization catalyst Is unlikely to occur.

  The linear velocity when the polymerization reaction raw material liquid obtained by mixing the mixed raw material liquid and the liquid containing the polymerization initiator flows in the pipe (B) is usually 0.1 mm or more per second, and 1.0 mm per second. The above is more preferable, and 10.0 mm or more per second is most preferable. If the linear velocity of the polymerization reaction raw material liquid is 0.1 mm or more per second, the mixing raw material liquid and the liquid containing the polymerization initiator are sufficiently mixed before the stirring efficiency is lowered due to the increase in viscosity caused by the progress of polymerization. As a result, a high molecular weight oxymethylene copolymer can be produced in high yield. The linear velocity is adjusted by the flow rate of the mixed raw material liquid and the inner diameter of the pipe (B). For the purpose of increasing the stirring efficiency, an orifice with a narrowed inner diameter of the pipe (B) near the tip of the pipe (C). You may adjust with.

  In the present invention, the polymerization reaction raw material liquid is brought into contact with and mixed with the mixed raw material liquid and the liquid containing the polymerization initiator at the connection portion between the pipe (B) and the pipe (C), and then the inlet of the polymerization machine (A). The time to reach is usually 0.01 to 120 seconds, more preferably 0.1 to 60 seconds, and most preferably 0.1 to 30 seconds. Until the polymerization reaction raw material liquid reaches the inlet of the polymerization machine (A) after the mixed raw material liquid and the liquid containing the polymerization initiator are contacted and mixed at the connection portion between the pipe (B) and the pipe (C). If the time is 0.01 to 120 seconds, the mixed raw material liquid and the liquid containing the polymerization initiator are sufficiently mixed, so that a high molecular weight oxymethylene copolymer is produced in a high yield. it can. The polymerization reaction raw material liquid reaches the inlet of the polymerization machine (A) after the mixed raw material liquid and the liquid containing the polymerization initiator are contacted and mixed at the connection portion of the pipe (B) and the pipe (C). If the time until completion is in the range of 0.1 to 30 seconds, the polymerization initiator and the mixed raw material liquid are further sufficiently mixed, and the pressure loss due to the viscosity increase caused by the progress of the polymerization does not become excessive. Stable and continuous production is possible.

  In the present invention, the polymerization temperature is preferably a temperature at which the produced oxymethylene copolymer can maintain a liquid state from the time when the polymerization initiator is charged until the time when the polymerization terminator is charged. The polymerization temperature is usually 135 to 300 ° C. The polymerization temperature is preferably 140 to 220 ° C., and most preferably 140 to 190 ° C. when a ketone compound described later is not used in the liquid containing the polymerization initiator. When using a ketone compound together, 140-220 degreeC is preferable and 140-205 degreeC is the most preferable. If the polymerization temperature is 300 ° C. or less, the molecular weight and the polymerization yield of the produced oxymethylene copolymer are good, and if it is 135 ° C. or more, the produced oxymethylene copolymer is difficult to precipitate as a solid. Production by a simple polymerization reaction apparatus for handling as a liquid becomes possible.

  When polymerization is performed at a temperature at which the produced oxymethylene copolymer can maintain a liquid state from the time when the polymerization initiator is charged until the time when the polymerization terminator is charged, the polymerization reaction is a weak endothermic reaction, so If the amount of heat is not supplied from the outside, the temperature of the reaction product (polymerization reaction product) containing the oxymethylene copolymer generated with the progress of the polymerization reaction is lowered. On the other hand, when polymerization was performed at a temperature at which the generated oxymethylene copolymer could not maintain a liquid state from the time when the polymerization initiator was charged until the time when the polymerization terminator was charged, the generated oxymethylene copolymer crystals Since the heat generated by the conversion exceeds the endotherm generated by the polymerization reaction, the temperature of the polymerization reaction product increases with the progress of the polymerization reaction unless the heat generated by the difference or more is removed to the outside. Therefore, it can be judged that precipitation of the oxymethylene copolymer occurs in the reaction in which the internal temperature of the polymerization apparatus greatly increases.

  That is, in the present invention, it is preferable to carry out the polymerization reaction at a sufficiently high polymerization temperature such that the maximum temperature difference between the time when the polymerization initiator is charged and the time when the polymerization stopper is charged is less than 20 ° C. By performing the polymerization reaction at such a temperature, troubles due to precipitation of the oxymethylene copolymer during the polymerization reaction can be prevented even when manufacturing with a simple and inexpensive polymerization facility such as a static mixer type polymerization machine. Can do.

  The time (polymerization time) from the introduction of the polymerization initiator to the introduction of the polymerization terminator in the present invention is usually 0.1 to 20 minutes, preferably 0.4 to 5 minutes. If the polymerization time is 20 minutes or less, depolymerization hardly occurs, and if it is 0.1 minutes or more, the polymerization yield is improved. The polymerization terminator is charged at a polymerization yield of usually 30% or more, more preferably 60% or more.

  In the present invention, the polymerization reaction is usually carried out under a pressurized condition of 0.15 to 50 MPa, preferably 0.15 to 20 MPa, at least equal to or higher than the vapor pressure in the polymerization machine (A).

  As a form of the polymerization reaction in the present invention, solution polymerization carried out in the presence of an inert solvent is possible, but solvent-free polymerization carried out in the substantial absence of solvent, which does not require a solvent recovery cost, is preferred. When the solvent is used, the type of the solvent is not particularly limited, but aliphatic hydrocarbon solvents such as hexane, heptane, and cyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; 1,2-dimethoxyethane, diethylene glycol dimethyl ether , Ether solvents such as triethylene glycol dimethyl ether and 1,4-dioxane. Among them, although not essential in the present invention, a solvent having a boiling point at 1 atm of 115 ° C. or less is preferable. Such a solvent is easy to be separated from the produced oxymethylene copolymer and the recovered trioxane by distillation.

  In the present invention, the linear velocity of the reaction product (polymerization reaction product) containing the polymerization reaction raw material liquid and / or the produced oxymethylene copolymer flowing through the polymerization machine (A) is not particularly limited, but is usually 0.00 per second. 01-5000 mm, preferably 0.05-1000 mm per second, most preferably 0.1-500 mm per second. The Reynolds number at that time is not particularly limited because it is affected by the inner diameter of the polymerization machine (A) and the flow rate of the polymerization reaction raw material liquid and / or polymerization reaction product flowing through the polymerization machine (A). Is usually 27000 to 0.0000001, preferably 5000 to 0.0000005, and most preferably 3000 to 0.000001. If the Reynolds number is in the range of 27000 to 0.0000001, the polymerization reaction raw material liquid and / or the polymerization reaction product are sufficiently stirred during the polymerization reaction, so that the oxymethylene copolymer has a high molecular weight and a high yield. Can be continuously produced stably. Further, when the Reynolds number is 3000 to 0.000001, the polymerization reaction raw material liquid and / or the polymerization reaction product are further sufficiently stirred, and the pressure loss does not become excessive.

  The molecular weight of the oxymethylene copolymer obtained by the method for producing an oxymethylene copolymer of the present invention is usually 0.5 to 5 dl / g, expressed as an index of intrinsic viscosity. The intrinsic viscosity is preferably 0.7 to 3.5 dl / g, most preferably 0.9 to 2.5 dl / g.

[III: Mixed raw material liquid containing trioxane and comonomer]
In the method for producing an oxymethylene copolymer of the present invention, the mixed raw material liquid containing trioxane and a comonomer is a liquid containing at least trioxane and a comonomer and mixing them.

  The trioxane used in the present invention is a trimer of formaldehyde, and its production method is not particularly limited, and unreacted trioxane recovered in the production of the oxymethylene copolymer is also included. The trioxane may or may not contain a stabilizer. When the trioxane contains a stabilizer for improving stability during storage, for example, the amine compound is usually 0.00001 to 0.003 mmol per 1 mol of trioxane, preferably 0.001 mol per 1 mol of trioxane. It is preferable to contain 0.0001 to 0.0005 mmol, more preferably 0.00001 to 0.0003 mmol. If the content of the amine compound is 0.003 mmol or less, adverse effects such as deactivation of the polymerization initiator are hardly caused, and if it is 0.00001 mmol or more, generation of paraformaldehyde is suppressed during storage of trioxane.

  Examples of amine compounds that can be contained in the trioxane as a stabilizer include primary amines, secondary amines, tertiary amines, alkylated melamines, hindered amine compounds, and the like. These are used alone or as a mixture of two or more. As the primary amine, n-propylamine, isopropylamine, n-butylamine and the like are preferably used. As the secondary amine, diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine, piperidine, morpholine and the like are preferably used. As the tertiary amine, triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, triethanolamine and the like are preferably used. As the alkylated melamine, mono-, di-, tri-, tetra-, penta- or hexamethoxymethyl melamine which is a methoxymethyl substitution product of melamine or a mixture thereof is preferably used. Examples of hindered amine compounds include bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 1,2,3, 4-Butanetetracarboxylic acid tetrakis (2,2,6,6-tetramethyl-4-piperidinyl) ester, poly [[6- (1,1,3,3-tetramethylenebutyl) amino-1,3,5 -Triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidinyl) imino] hexamethylene [(2,2,6,6-tetramethyl-4-piperidinyl) imino], 1,2,2,6,6-pentamethylpiperidine, dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensation And N, N′-bis (3-aminopropyl) ethylenediamine · 2,4-bis [N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino] -1 , 3,5-triazine condensate is preferably used. Of these, triethanolamine is most preferably used.

  In addition, impurities other than metal components such as water, formic acid, methanol, formaldehyde, methylal, dioxymethylene dimethyl ether, and trioxymethylene dimethyl ether contained in trioxane are inevitably generated when trioxane is produced industrially. However, the total amount is preferably 100 mass ppm or less in trioxane, more preferably 70 mass ppm or less, and most preferably 50 mass ppm or less. Especially, it is preferable that water is 50 mass ppm or less, More preferably, it is 20 mass ppm or less, Most preferably, it is 10 mass ppm or less.

  The comonomer in the present invention is not particularly limited as long as it is a comonomer that gives an oxyalkylene unit having 2 or more carbon atoms, but is preferably a comonomer that gives an oxyalkylene unit having 2 to 6 carbon atoms, and particularly preferably has 2 carbon atoms. A comonomer that provides oxyethylene units. The comonomer is not particularly limited as long as it is a comonomer copolymerizable with trioxane, such as cyclic ether, glycidyl ether compound, and cyclic formal. Specific examples of the comonomer include, for example, ethylene oxide, propylene oxide, butylene oxide, styrene oxide, methyl glycidyl ether, ethyl glycidyl ether, phenyl glycidyl ether, 1,3-dioxolane, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,3,5-trioxepane, 1,4-butanediol formal, 1,5-pentanediol formal, 1,6-hexanediol formal, and the like are used, and at least one selected from the group consisting of these is used. . The comonomer is preferably at least one selected from the group consisting of ethylene oxide, 1,3-dioxolane, diethylene glycol formal and 1,4-butanediol formal. Most preferably, 1,3-dioxolane is used from the viewpoint of copolymerization with trioxane.

  The total amount of impurities other than metal components such as water, formic acid, and formaldehyde contained in the comonomer is preferably 1000 ppm by mass or less, more preferably 200 ppm by mass or less, and even more preferably 100 ppm by mass or less. The mass ppm or less is most preferable.

  The amount of the comonomer used is 0.4 to 45% by mass with respect to trioxane, preferably 1.2 to 12% by mass, and most preferably 2.5 to 6% by mass. If the amount of the comonomer used is 45% by mass or less, the polymerization yield and the crystallization rate are hardly lowered, and if it is 0.4% by mass or more, unstable parts are reduced.

  In the present invention, the mixed raw material liquid is preferably composed of trioxane and a comonomer and is substantially solvent-free, but a solvent may be used in addition to trioxane and a comonomer. The type of solvent is not particularly limited, but aliphatic hydrocarbon solvents such as hexane, heptane, and cyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; 1,2-dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, Examples include ether solvents such as 1,4-dioxane. Among them, although not essential in the present invention, a solvent having a boiling point at 1 atm of 115 ° C. or less is preferable. Such a solvent is easy to be separated from the produced oxymethylene copolymer and the recovered trioxane by distillation.

[IV: Liquid containing polymerization initiator]
In the method for producing an oxymethylene copolymer of the present invention, the liquid containing a polymerization initiator contains at least a polymerization initiator. The polymerization initiator is a protonic acid which is a cationic polymerization initiator usually used for copolymerization of trioxane and a comonomer, and a protonic acid anhydride or a protonic acid ester compound is also used. As for these molecular weights, it is preferable that the molecular weight per mole is 1000 or less from the viewpoint that a high molecular weight oxymethylene copolymer can be produced in a high yield. That is, the polymerization initiator is preferably at least one selected from the group consisting of a protonic acid, a protonic acid anhydride, and a protonic acid ester compound having a molecular weight per mole of 1000 or less.

  The molecular weight per mole of the polymerization initiator is preferably 1000 or less, more preferably 800 or less, and most preferably 500 or less. The lower limit of the molecular weight per mole is not particularly limited, and the molecular weight per mole is, for example, 20 or more, preferably 36 or more.

  Examples of the protonic acid, protonic acid anhydride and protonic acid ester compound include perchloric acid, perchloric acid, and derivatives thereof such as perchloric acid, perchloric acid anhydride, trifluoromethanesulfonic acid, and trifluoromethanesulfonic acid anhydride. Fluorinated or chlorinated alkyl sulfonic acids and aryl sulfonic acids, acid anhydrides and ester compounds thereof; phosphinic acids or phosphonic acids such as bis (trifluoromethyl) phosphinic acid and trifluoromethylphosphonic acid and derivatives thereof Etc. These are used alone or as a mixture. Among them, at least one selected from the group consisting of perchloric acid, perfluoroalkylsulfonic acid, their acid anhydrides and their ester compounds is preferable. In view of production efficiency and economy, perchloric acid, perchloric acid Most preferred is at least one selected from the group consisting of anhydrides and perchlorate compounds.

  The amount of the polymerization initiator used (abundance in the reaction system) is usually in the range of 0.001 ppm by mass to 10% by mass, preferably 0.001 to 500 ppm by mass, with respect to the main monomer trioxane. It is a range, More preferably, it is the range of 0.01-200 mass ppm, Most preferably, it is the range of 0.01-100 mass ppm. If the amount of the polymerization initiator used is 10% by mass or less, the molecular weight of the oxymethylene copolymer is hardly lowered, and if it is 0.001 mass ppm or more, the polymerization yield is hardly lowered.

  The polymerization initiator is used as a single liquid or as a solution diluted with a solvent. That is, all or a part of the polymerization initiator may be diluted with a solvent. When diluting with a solvent, the solvent is not particularly limited, but an aliphatic hydrocarbon solvent such as hexane, heptane, and cyclohexane; an aromatic hydrocarbon solvent such as benzene, toluene, and xylene; 1,2-dimethoxyethane, diethylene glycol dimethyl ether, Examples include ether solvents such as triethylene glycol dimethyl ether and 1,4-dioxane. Among them, although not essential in the present invention, a solvent having a boiling point at 1 atm of 115 ° C. or less is preferable. Such a solvent is easy to be separated from the produced copolymer and the recovered trioxane by distillation. Further, a partial amount or a total amount of a comonomer such as 1,3-dioxolane may be used as a solvent.

[V: Other additives]
In the method for producing the oxymethylene copolymer of the present invention, the above-described polymerization initiator (at least one selected from the group consisting of a protonic acid, a protonic acid anhydride and a protonic acid ester having a molecular weight per mole of 1000 or less). Furthermore, it is preferable to use a salt of a protonic acid in combination. This increases the molecular weight per mole of the oxymethylene copolymer obtained and the polymerization yield. The reason is presumed that, for example, the combined use of the polymerization initiator and the salt of the proton acid suppresses the decomposition reaction of the copolymer during the polymerization and relatively predominates the growth reaction of the copolymer. Is done. That is, for example, at a polymerization temperature of 135 ° C. or higher, the salt of a protonic acid is present at a desired position in the vicinity of the active site of the copolymer, so that the active site of the copolymer is generally called back-biting. It is estimated that the decomposition reaction that attacks itself is suppressed.

  The salt of the protonic acid in the present invention is not particularly limited as long as it is a salt generated from an alkali component and a protonic acid. A salt of a proton acid is generated from a cation derived from an alkali component and an anion derived from a proton acid. From the viewpoint of production efficiency, the salt of the proton acid is preferably a salt formed from at least one alkali component selected from the group consisting of alkali metals, alkaline earth metals, ammonia and amine compounds and a proton acid. More preferably, the alkali component is at least one selected from the group consisting of alkali metals and alkaline earth metals.

  The protonic acid constituting the salt of the protonic acid is a compound that releases protons, and in order to produce a high molecular weight oxymethylene copolymer, it is preferably a protonic acid having a molecular weight per mole of 1000 or less. The molecular weight per mole of protonic acid is more preferably 800 or less, and most preferably 500 or less. The lower limit of the molecular weight per mole of the protonic acid is not particularly limited, and the molecular weight per mole is, for example, 20 or more, preferably 36 or more. Examples of such protic acids include inorganic acids such as sulfuric acid, hydrochloric acid, phosphoric acid, and perchloric acid; and organic acids such as fluorinated or chlorinated alkyl sulfonic acids or aryl sulfonic acids. Among these, at least one selected from the group consisting of perchloric acid and perfluoroalkylsulfonic acid is more preferable, and perchloric acid is most preferable in consideration of production efficiency and economy.

  The alkali component constituting the salt of the proton acid is preferably at least one selected from the group consisting of alkali metals, alkaline earth metals, ammonia and amine compounds, and is a group consisting of alkali metals and alkaline earth metals. More preferably, it is at least one selected from. Alkali metals include lithium, sodium, potassium, rubidium, cesium and the like. Alkaline earth metals are alkaline earth metals in a broad sense and include beryllium and magnesium in addition to calcium, strontium, barium and radium. Amine compounds include primary amines, secondary amines, tertiary amines, alkylated melamines, and hindered amine compounds. As the primary amine, n-propylamine, isopropylamine, n-butylamine and the like are preferably used. As the secondary amine, diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine, piperidine, morpholine and the like are preferably used. As the tertiary amine, triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine and the like are preferably used. As the alkylated melamine, mono-, di-, tri-, tetra-, penta- or hexamethoxymethyl melamine which is a methoxymethyl substitution product of melamine or a mixture thereof is preferably used. Examples of hindered amine compounds include bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 1,2,3, 4-Butanetetracarboxylic acid tetrakis (2,2,6,6-tetramethyl-4-piperidinyl) ester, poly [[6- (1,1,3,3-tetramethylenebutyl) amino-1,3,5 -Triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidinyl) imino] hexamethylene [(2,2,6,6-tetramethyl-4-piperidinyl) imino], 1,2,2,6,6-pentamethylpiperidine, dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensation N, N′-bis (3-aminopropyl) ethylenediamine-2,4-bis [N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino] -1, 3,5-triazine condensate and the like are preferably used.

  The protonic acid salt may be a pure substance, that is, a compound isolated as a salt, or may be used without purifying a substance produced by an acid-alkali reaction. Alkali components in the case of using a substance generated by acid-alkali reaction without purification include alkali metal simple substance, alkaline earth metal simple substance, ammonia, amine compound, and alkali metal or alkaline earth metal hydroxide. , Alcoholates, organic acid salts, inorganic acid salts or oxides are preferably used.

  The amount of the protonic acid salt used (abundance in the reaction system) is usually 0.001 to 10% by mass, preferably 0.01 to 1% by mass, based on the main monomer trioxane. Most preferably, it is used in the range of 0.01 mass ppm to 100 mass ppm. If the amount of the protonic acid salt used is 10% by mass or less, it is difficult to cause a decrease in molecular weight or polymerization yield, and if it is 0.001 mass ppm or more, an effect of increasing the molecular weight is observed.

  The salt of the proton acid may be used by dissolving or suspending in the mixed raw material liquid containing trioxane and comonomer described above, or may be used by dissolving or suspending in the liquid containing the polymerization initiator described above. The polymer mixture (A) may be supplied from a pipe different from the mixed raw material liquid and the liquid containing the polymerization initiator. Among these, it is preferable to use by dissolving or suspending in a liquid containing the above-described polymerization initiator because a high molecular weight oxymethylene copolymer can be obtained in a high yield.

  The salt of the protonic acid is used alone or in the form of a solution or a suspension. That is, all or part of the protonic acid salt may be diluted with a solvent. Although it does not specifically limit as a solvent in the case of using it as a solution or suspension, Aromatic hydrocarbon solvents, such as hexane, heptane, a cyclohexane; Aromatic hydrocarbon solvents, such as benzene, toluene, xylene; 1, 2- dimethoxyethane , Ether solvents such as diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and 1,4-dioxane. Among them, although not essential in the present invention, a solvent having a boiling point at 1 atm of 115 ° C. or less is preferable. Such a solvent is easy to be separated from the produced copolymer and the recovered trioxane by distillation. Further, a partial amount or a total amount of a monomer or a comonomer such as trioxane or 1,3-dioxolane may be used as a solvent.

  The molar ratio of the polymerization initiator (preferably protonic acid) and the salt of protonic acid in the present invention is not particularly limited. The molar ratio of the polymerization initiator and the salt of the proton acid is preferably in the range of 1: 0.01 to 1: 2000, from the viewpoint of the molecular weight of the oxymethylene copolymer obtained and the polymerization yield, and is preferably 1: 0.05 to A range of 1:10 is more preferred, and a range of 1: 0.1 to 1: 5 is most preferred.

  In the method for producing an oxymethylene copolymer of the present invention, a polymerization initiator (at least one selected from the group consisting of a protonic acid having a molecular weight per mole of 1000 or less, a protonic acid anhydride, and a protonic acid ester) and 1 It is preferable to carry out the polymerization reaction by adding a ketone compound in addition to a salt of a protonic acid having a molecular weight per mole of 1000 or less. That is, the polymerization reaction is preferably carried out in the presence of a salt of a protonic acid having a molecular weight per mole of 1000 or less and a ketone compound.

  The ketone compound is not particularly limited as long as it is an aliphatic ketone or an aromatic ketone. The ketone compound is preferably acetone, methyl ethyl ketone, methyl-n-propyl ketone, diethyl ketone, 2-hexanone, 3-hexanone, methyl-t-butyl ketone, di-n-propyl ketone, diisopropyl ketone, diisobutyl ketone, di-n-amyl ketone. , Stearone, chloroacetone, s-dichloroacetone, diacetyl, acetylacetone, mesityl oxide, phorone, cyclohexanone, and benzophenone are used. These can be used individually by 1 type or in mixture of 2 or more types. Among them, acetone, methyl ethyl ketone, methyl-n-propyl ketone, diethyl ketone, 2-hexanone, 3-hexanone, methyl-t-butyl ketone, di-n-propyl ketone, diisopropyl ketone, diisobutyl ketone, di n-amyl ketone, diacetyl, acetylacetone, At least one selected from the group consisting of cyclohexanone and benzophenone is more preferable, and acetone is most preferable.

  The amount of the ketone compound used (abundance in the reaction system) is usually 0.001 to 30% by mass, preferably 0.01 to 1% by mass, based on trioxane as the main monomer. The most preferable range is 0.1 mass ppm to 0.5 mass%. If the amount of the ketone compound used is 30% by mass or less, the molecular weight of the oxymethylene copolymer and the decrease in the polymerization yield are unlikely to occur, and if it is 0.001 ppm by mass or more, the molecular weight of the oxymethylene copolymer An effect of increasing the polymerization yield is observed.

  In addition to the polymerization initiator (at least one selected from the group consisting of a protonic acid, a protonic acid anhydride and a protonic acid ester having a molecular weight of 1000 or less per mole) and a salt of a protonic acid, a ketone compound is used in combination. Thus, the effect of increasing the molecular weight and the polymerization yield of the oxymethylene copolymer can be more effectively achieved even at a higher polymerization temperature as compared with the case of using a polymerization initiator and a salt of a protonic acid. This is presumably due to, for example, the combined use of a ketone compound, which suppresses the decomposition reaction of the copolymer during the polymerization and relatively predominates the growth reaction of the copolymer.

  The ketone compound may be used by mixing with the above-described mixed raw material liquid containing trioxane and comonomer, or may be used by mixing with the liquid containing the above-described polymerization initiator. You may supply to a superposition | polymerization machine (A) from piping different from the liquid containing an agent. Among these, it is preferable to use a mixture with a mixed raw material liquid containing trioxane and a comonomer, or a liquid containing a polymerization initiator because a high molecular weight oxymethylene copolymer can be obtained in a high yield.

  The ketone compound is used as a single solution or a solution diluted with a solvent. That is, all or part of the ketone compound may be diluted with a solvent. Although it does not specifically limit as a solvent in the case of using as a solution, Aromatic hydrocarbon solvents, such as hexane, heptane, a cyclohexane; Aromatic hydrocarbon solvents, such as benzene, toluene, xylene; 1, 2- dimethoxyethane, diethylene glycol dimethyl ether, Examples include ether solvents such as triethylene glycol dimethyl ether and 1,4-dioxane. Among them, although not essential in the present invention, a solvent having a boiling point at 1 atm of 115 ° C. or less is preferable. Such a solvent is easy to be separated from the produced copolymer and the recovered trioxane by distillation. Further, a partial amount or a total amount of a comonomer such as 1,3-dioxolane may be used as a solvent.

  In the present invention, when a ketone compound is used for the polymerization reaction, the molar ratio of the polymerization initiator (preferably protonic acid) to the ketone compound is preferably in the range of 1: 0.1 to 1: 100,000, and 1: 5 to 1: A range of 10,000 is more preferred, and a range of 1:50 to 1: 5000 is most preferred.

  In the method for producing an oxymethylene copolymer of the present invention, the polymerization reaction may be performed in the presence of a molecular weight modifier. For example, for the purpose of adjusting the molecular weight of the oxymethylene copolymer, the molecular weight regulator can be used in an amount of 0.01 mass ppm to 10 mass% with respect to trioxane, and 0.1 mass ppm to 1 mass% is used. It is more preferable. Examples of the molecular weight regulator include carboxylic acid, carboxylic anhydride, ester, amide, imide, phenol compound, acetal compound and the like, and at least one selected from the group consisting of these is preferable. Among these, at least one selected from the group consisting of phenol, 2,6-dimethylphenol, methylal, and polyoxymethylene dimethoxide is more preferable, and methylal is particularly preferable.

  The molecular weight modifier is preferably mixed with the raw material trioxane or comonomer before contacting and mixing the liquid containing the polymerization initiator and the raw material trioxane or comonomer. By doing so, it is easy to obtain a high molecular weight oxymethylene copolymer in a high yield.

  The molecular weight regulator is used as a single solution or as a solution diluted with a solvent. That is, all or part of the molecular weight modifier may be diluted with a solvent. Although it does not specifically limit as a solvent in the case of using as a solution, Aromatic hydrocarbon solvents, such as hexane, heptane, a cyclohexane; Aromatic hydrocarbon solvents, such as benzene, toluene, xylene; 1, 2- dimethoxyethane, diethylene glycol dimethyl ether, Examples include ether solvents such as triethylene glycol dimethyl ether and 1,4-dioxane. Among them, although not essential in the present invention, a solvent having a boiling point at 1 atm of 115 ° C. or less is preferable. Such a solvent is easy to be separated from the produced copolymer and the recovered trioxane by distillation. Further, a partial amount or a total amount of a comonomer such as 1,3-dioxolane may be used as a solvent.

  In the method for producing an oxymethylene copolymer of the present invention, the polymerization reaction can be carried out in the presence of a sterically hindered phenol compound. When a sterically hindered phenol compound is allowed to coexist, the amount used is usually from 0.0001 to 2.0 mass%, preferably from 0.001 to 0.5 mass%, most preferably from 0.002 to 0, based on trioxane. .1% by mass. If the amount of the sterically hindered phenolic compound used is 2.0% by mass or less, it is difficult to cause a decrease in the molecular weight of the oxymethylene copolymer to be produced and a decrease in the polymerization yield. Since the formation of unstable moieties such as a formate end group structure in the methylene copolymer is further suppressed, adverse effects such as a decrease in heat or hydrolysis stability do not occur.

  Examples of the sterically hindered phenol compound include dibutylhydroxytoluene, triethylene glycol-bis-3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, pentaerythrityl-tetrakis-3- (3 , 5-Di-t-butyl-4-hydroxyphenyl) propionate, hexamethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2′-methylenebis (6- t-butyl-4-methylphenol), 3,9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl] propionyloxy) -1,1-dimethylethyl} -2 , 4,8,10-tetraoxaspiro [5,5] undecane, N, N′-hexane-1,6-diylbis [3- (3 5-di-t-butyl-4-hydroxyphenyl) propionamide], 3,5-bis (1,1-dimethylethyl) -4-hydroxybenzenepropionic acid 1,6-hexanediyl ester, and the like. At least one selected from the group consisting of Among them, triethylene glycol-bis-3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate, pentaerythrityl-tetrakis-3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate and 3,9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl] propionyloxy) -1,1-dimethylethyl} -2,4,8,10- At least one selected from the group consisting of tetraoxaspiro [5,5] undecane is more preferably used, and triethylene glycol-bis-3- (3-tert-butyl-4-hydroxy-5-methylphenyl). Propionate is most preferably used.

  The sterically hindered phenol compound may be used by mixing with the above-described mixed raw material liquid containing trioxane and a comonomer, or may be used by mixing with a liquid containing the above-described polymerization initiator. Alternatively, it may be supplied to the polymerization machine (A) from a pipe different from the liquid containing the polymerization initiator. Among these, it is preferable to use a mixture with a mixed raw material liquid containing trioxane and a comonomer, or a liquid containing a polymerization initiator because a high molecular weight oxymethylene copolymer can be obtained in a high yield.

  The sterically hindered phenol compound is added to trioxane alone or in the form of a solution. Although it does not specifically limit as a solvent in the case of using as a solution, Aromatic hydrocarbon solvents, such as hexane, heptane, a cyclohexane; Aromatic hydrocarbon solvents, such as benzene, toluene, xylene; 1, 2- dimethoxyethane, diethylene glycol dimethyl ether, Examples include ether solvents such as triethylene glycol dimethyl ether and 1,4-dioxane. Among them, although not essential in the present invention, a solvent having a boiling point at 1 atm of 115 ° C. or less is preferable. Such a solvent is easy to be separated from the produced copolymer and the recovered trioxane by distillation. Further, a partial amount or a total amount of a comonomer such as 1,3-dioxolane may be used as a solvent. In order to maintain the activity of the sterically hindered phenol compound during the polymerization reaction, it is desirable to add the sterically hindered phenol compound alone or a solution thereof at the inlet of the polymerization machine.

[VI: Method for producing oxymethylene copolymer (process after termination of polymerization reaction)]
In the present invention, the polymerization reaction can be stopped by adding and mixing a polymerization terminator to the polymerization reaction product. That is, it is preferable that the method for producing an oxymethylene copolymer of the present invention further includes a step of adding a polymerization terminator. The polymerization terminator is used in the form of a melt, a solution or a suspension. In the case of a batch system, the polymerization terminator is added to the polymerization machine (A) after the polymerization reaction, and is a continuous type. In this case, the polymerization reaction product and the polymerization terminator are continuously supplied to a mixing apparatus (polymerization terminator mixer (D), termination reactor). Among them, as described above, a method of continuous mixing using a static mixer type polymerization terminator mixer (D) or a stop reactor that does not have a drive unit equipped with a stationary mixing element is suitable.

  In the present invention, the linear velocity of the mixture of the polymerization stopper and the polymerization stopper flowing through the polymerization stopper mixer (D) and / or the stopper is usually 0.01 to 5000 mm per second, preferably 0.05 to 1000 mm per second. Most preferably, it is 0.1 to 500 mm per second. The Reynolds number at that time is not particularly limited because it is affected by the inner diameter of the polymerization terminator mixer (D) and / or the termination reactor and the flow rate of the mixture of the polymerization reaction product and the polymerization terminator flowing. However, it is usually 20 to 0.0000001, preferably 4.0 to 0.0000005, most preferably 2.0 to 0.000001. If the Reynolds number is in the range of 20 to 0.0000001, the reaction between the polymerization terminator and the polymerization initiator is sufficiently carried out, so that an oxymethylene copolymer can be stably and continuously produced with a high molecular weight and a high yield. . Moreover, if Reynolds number is 2.0-0.000001, reaction with a polymerization terminator and a polymerization initiator will be performed more fully, and pressure loss will not become excessive.

  Examples of the polymerization terminator include primary amines, secondary amines, tertiary amines, alkylated melamines, hindered amine compounds and other amine compounds; trivalent organic phosphorus compounds; alkali metal hydroxides, alkali metal alcoholates and the like. Alkali earth metal salts such as metal salts, alkaline earth metal hydroxides, alkaline earth metal alcoholates and the like can be mentioned, and at least one selected from the group consisting of these is preferred. That is, the polymerization terminator is at least one selected from the group consisting of amine compounds, alkali metal hydroxides, alkali metal alcoholates, alkaline earth metal hydroxides, and alkaline earth metal alcoholates. Is preferred. The polymerization terminators are used alone or as a mixture.

  As the primary amine, n-propylamine, isopropylamine, n-butylamine and the like are preferably used. As the secondary amine, diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine, piperidine, morpholine and the like are preferably used. As the tertiary amine, triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine and the like are preferably used. As the alkylated melamine, mono-, di-, tri-, tetra-, penta- or hexamethoxymethyl melamine which is a methoxymethyl substitution product of melamine or a mixture thereof is preferably used. Examples of hindered amine compounds include bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 1,2,3, 4-Butanetetracarboxylic acid tetrakis (2,2,6,6-tetramethyl-4-piperidinyl) ester, poly [[6- (1,1,3,3-tetramethylenebutyl) amino-1,3,5 -Triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidinyl) imino] hexamethylene [(2,2,6,6-tetramethyl-4-piperidinyl) imino], 1,2,2,6,6-pentamethylpiperidine, dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensation N, N′-bis (3-aminopropyl) ethylenediamine-2,4-bis [N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino] -1, 3,5-triazine condensate and the like are preferably used. Examples of alkali metal or alkaline earth metal hydroxides or alcoholates include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium methoxide, sodium methoxide, potassium methoxide, lithium ethoxide, sodium ethoxide, potassium ethoxy. , Magnesium hydroxide, calcium hydroxide, magnesium methoxide, calcium methoxide, magnesium ethoxide, calcium ethoxide and the like are preferably used.

  Among these, at least one selected from the group consisting of a hindered amine compound, an alkylated melamine, an alkali metal hydroxide, and an alkali metal alcoholate is preferable because it can be easily separated from the monomer when evaporating and separating the unreacted monomer. Is more preferable. Among the compounds described above, hindered amine compounds include bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, Dimethyl succinate, 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, N, N′-bis (3-aminopropyl) ethylenediamine, 2,4- Bis [N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino] -1,3,5-triazine condensate is more preferred. As the alkylated melamine, hexamethoxymethylmelamine is more preferable. As the alkali metal hydroxide or alcoholate, sodium hydroxide and sodium methoxide are more preferable. Of these, sodium methoxide is most preferred.

  In addition, as a polymerization terminator, the method of using an amine compound and an alkali metal or alkaline earth metal hydroxide or alcoholate in combination is colored by excess alkali metal or alkaline earth metal or the molecular weight of the oxymethylene copolymer is decreased. It is preferable to use an amine compound and sodium methoxide in combination.

  The aforementioned polymerization terminators are used alone or in the form of a solution or suspension. That is, all or part of the polymerization terminator may be diluted with a solvent. When the polymerization terminator is used in the form of a solution or suspension, the solvent used is not particularly limited. Solvents include water, alcohol solvents, acetone, methyl ethyl ketone, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,4-dioxane, hexane, cyclohexane, heptane, benzene, toluene, xylene, methylene. Various aliphatic and aromatic organic solvents such as dichloride and ethylene dichloride can be used. Among these, preferred are water and alcohol solvents, acetone, methyl ethyl ketone, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,4-dioxane, hexane, cyclohexane, heptane, benzene, toluene, xylene and the like. It is an aliphatic and aromatic organic solvent. Among them, although not essential in the present invention, a solvent having a boiling point at 1 atm of 115 ° C. or less is preferable. Such a solvent is easy to be separated from the produced copolymer and the recovered trioxane by distillation. As the polymerization terminator, a monomer or comonomer such as trioxane or 1,3-dioxolane may be used as a solvent. It is also preferable to dilute and add the polymerization terminator with a separately prepared polyacetal.

  The amount of the polymerization terminator used is usually 0.1 to 100 molar equivalents, preferably 1 to 10 molar equivalents, and most preferably in the range of 1 to 2 molar equivalents relative to the amount of polymerization initiator added. Used in. When the amount of the polymerization terminator used is 100 molar equivalents or less, it is difficult to cause a decrease in the molecular weight of the oxymethylene copolymer due to coloring or decomposition. Moreover, if it is 0.1 molar equivalent or more, the fall of the molecular weight of the oxymethylene copolymer by depolymerization, etc. hardly occur. In addition, the equivalent of a polymerization terminator means the number of moles required to deactivate 1 mol of a polymerization initiator.

  Further, when an amine compound and an alkali metal or alkaline earth metal hydroxide or alcoholate are used in combination as a polymerization terminator, the amine compound is usually 0.1 to 100 with respect to the added polymerization initiator amount. It is used in the range of molar equivalents, preferably 1-50 molar equivalents, most preferably 1-10 molar equivalents. On the other hand, the alkali metal or alkaline earth metal hydroxide or alcoholate is usually used in the range of 0.001 to 50 molar equivalents, preferably 0.01 to 5 molar equivalents, most preferably 0.1 to 2 molar equivalents. The By using an amine compound of 0.1 molar equivalent or more in combination with an alkali metal or alkaline earth metal hydroxide or alcoholate, the amount of alkali metal or alkaline earth metal hydroxide or alcoholate used is 50 molar equivalents or less. Even if it is reduced to a sufficient level, it has a sufficient polymerization termination effect, and at the same time, coloring with an excess alkali metal component or alkaline earth metal component found when using only an alkali metal or alkaline earth metal hydroxide or alcoholate, An adverse effect such as a decrease in molecular weight of the oxymethylene copolymer can be suppressed.

In the present invention, the polymerization reaction is usually stopped under a pressurized condition of 0.15 to 50 MPa, more preferably 0.15 to 20 MPa, at least equal to or higher than the internal vapor pressure. The termination of the polymerization reaction is usually carried out in a temperature range of 130 to 300 ° C, more preferably 135 to 250 ° C. The mixing time when adding a polymerization terminator to deactivate the polymerization initiator is usually 0.1 to 20 minutes, more preferably 1 to 10 minutes.

  The oxymethylene copolymer after stopping the polymerization reaction (hereinafter also referred to as “polymerization stop mixture”) usually contains 20 to 40% by mass of residual monomers and volatile components such as formaldehyde and tetraoxane which are decomposition products. . In addition, this oxymethylene copolymer usually contains 10% by mass or less of a thermally unstable portion caused by a hemiacetal terminal that generates formaldehyde by heating. In order to remove these, the method for producing an oxymethylene copolymer of the present invention is a step of subsequently removing at least a part of volatile components and thermally unstable portions as gas components by a degassing device (thermal stabilization step). It is preferable that it is further included.

  Examples of the degassing device include a flash pot, a vented extruder equipped with a uniaxial or biaxial screw, and a horizontal high-viscosity liquid degassing device equipped with a uniaxial or biaxial specially shaped stirring blade (for example, manufactured by Hitachi Plant Technologies, Ltd.). Spectacle blade polymerizer), thin film evaporator, spray dryer, strand deaerator and the like, and at least one selected from the group consisting of these is preferred. Among them, a single degassing device selected from the group consisting of a flash pot, an extruder with a vent equipped with a uniaxial or biaxial screw, a horizontal high-viscosity liquid degassing device equipped with a uniaxial or biaxial specially shaped stirring blade, etc. Or it is more suitable to use combining two or more sets. In order to promote the degassing of the volatile components, a substance having a boiling point of 200 ° C. or less at atmospheric pressure such as water is injected into these degassing apparatuses alone or together with a basic substance such as triethylamine, and then depressurized and removed. You can also care. Volatile components (gas components) separated by the degassing device may be liquefied by a pressurizing device or a condensing device, or absorbed by an absorbing device, and may be used as it is or purified by distillation or the like and recycled for a polymerization reaction. it can.

  In this invention, when the manufacturing method of an oxymethylene copolymer further includes the process of removing at least one part of a volatile component and a thermally unstable part as a gas component, the temperature of the said process is 130-300 degreeC, for example. Yes, preferably 160-250 ° C. Moreover, the pressure of the said process is 0.00001-50 MPa, for example, Preferably it is 0.0001-5 MPa.

  Therefore, in the method for producing an oxymethylene copolymer in the present invention, a polymerization reaction mixture or a polymerization reaction stop product is further subjected to flash pot, uniaxial or biaxial screw at a temperature of 130 to 300 ° C. under a pressure of 0.00001 to 50 MPa. In at least one degassing device selected from the group consisting of a vented extruder equipped with a horizontal high-viscosity liquid degassing device equipped with a uniaxial or biaxial stirring blade, It is preferable to further include a step of removing at least a part as a gas component. Furthermore, it is preferable to further include a step of liquefying the removed gas component and recycling part or all of it into the raw material trioxane. The method for liquefying the gas component is not particularly limited, and can be appropriately selected from commonly used methods. For example, it can be liquefied by pressurizing the gas component.

  By removing volatile components and thermally unstable parts as gas components by these methods, pelletization can be performed to obtain a moldable oxymethylene copolymer having good thermal stability.

  Further, in the process of removing the volatile components and the thermally unstable part, or in the subsequent process, an extruder equipped with a uniaxial or biaxial screw, a horizontal high viscosity equipped with a uniaxial or biaxial specially shaped stirring blade Stabilizers such as antioxidants and thermal stabilizers can be added and mixed by a melt mixing apparatus such as a liquid deaerator and a static mixer that are usually used industrially.

  Examples of the antioxidant include triethylene glycol-bis-3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate, pentaerythrityl-tetrakis-3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionate, 2,2′-methylenebis (6-tert-butyl-4-methylphenol), 3,9-bis {2- [3- (3-tert-butyl-4-hydroxy-) 5-methylphenyl] propionyloxy) -1,1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5,5] undecane, N, N′-hexane-1,6-diylbis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionamide], 3,5-bis (1,1-dimethylethyl) -4-hydroxybenzenepropionic acid 1 Include sterically hindered phenolic compounds such as 6-hexanediyl ester is at least one selected from the group consisting of are preferred.

  Examples of the heat stabilizer include melamine, methylol melamine, benzoguanamine, cyanoguanidine, triazine compounds such as N, N-diarylmelamine, organic compounds such as polyamide compounds, urea derivatives, urethane compounds; sodium, potassium, calcium, magnesium, barium And inorganic acid salts, hydroxides, organic acid salts, and the like. Among them, it is preferable to use at least one stabilizer selected from the group consisting of sterically hindered phenolic compounds and triazine compounds, and triethylene glycol-bis-3- (3-t-butyl-4-hydroxy The combination of -5-methylphenyl) propionate and melamine is most preferred.

  The method for producing an oxymethylene copolymer in the present invention preferably further includes a step of adding at least one stabilizer selected from the group consisting of a sterically hindered phenol compound and a triazine compound. When a stabilizer is added, the amount of stabilizer used is not particularly limited and can be appropriately selected according to the purpose. The usage-amount of a stabilizer is 0.0001-10 mass% with respect to an oxymethylene copolymer, for example, Preferably it is 0.001-5 mass%.

  The final product oxymethylene copolymer pellet obtained by the production method of the present invention has an unstable portion of 1.5 mass measured by a method such as weight loss when heated at 240 ° C. for 2 hours under a reduced pressure of 10 torr. %, Usually 1.4 to 0.1% by mass, and its proportion is small.

  As described above, the oxymethylene copolymer obtained by the production method of the present invention described in detail has the same excellent properties as the oxymethylene copolymer obtained by the conventional method and can be used for the same application. .

  In addition, the oxymethylene copolymer produced by the production method of the present invention includes a colorant, a nucleating agent, a plasticizer, a release agent, a fluorescent brightening agent or an antistatic agent such as polyethylene glycol and glycerin, and a benzophenone series. Additives such as light stabilizers such as compounds and hindered amine compounds can be added as desired.

  Examples and Comparative Examples of the present invention are shown below, but the present invention is not limited to these. The terms and measurement methods described in the examples and comparative examples are described below.

<Measurement of intrinsic viscosity>
The molecular weight of the oxymethylene copolymers obtained in the examples and comparative examples was evaluated using the intrinsic viscosity as a scale. The intrinsic viscosity is obtained by dissolving 0.1% by mass of an oxymethylene copolymer in p-chlorophenol to which 2% by mass of α-pinene and 0.1% by mass of tri-n-butylamine are added. Was measured at 60 ° C. If the intrinsic viscosity is 0.9 dl / g or more, it is good.

<Preparation of perchloric acid solution>
Perchloric acid (70% by mass aqueous solution, manufactured by Wako Pure Chemical Industries, Ltd.) was diluted with diethylene glycol dimethyl ether, and a perchloric acid-diethylene glycol dimethyl ether solution was prepared immediately before use in the polymerization reaction.

<Preparation of sodium perchlorate solution>
Sodium methoxide (28 mass% methanol solution, manufactured by Wako Pure Chemical Industries, Ltd.) and perchloric acid (70 mass% aqueous solution) are reacted in diethylene glycol dimethyl ether at 25 ° C so as to form a salt at a molar ratio of 1: 1. A NaClO ₄ -diethylene glycol dimethyl ether solution was prepared immediately before use in the polymerization reaction.

<Examples and Comparative Examples>
Example 1
Production of an oxymethylene copolymer using a continuous polymerization apparatus in which a first preheater, a polymerization machine (A), a polymerization terminator mixer (D), a termination reaction machine, and a second preheater are connected in series by piping. Went. The first preheater, the polymerization machine (A), the polymerization terminator mixer (D), the stop reaction machine, and the second preheater used all have a static mixing element inside, and a heating jacket. It was a static mixer type having
In Example 1, continuous polymerization in which a pipe (C) for supplying a liquid containing a polymerization initiator was connected to a pipe (B) having an inner diameter of 3 mm connecting the first preheater and the polymerization machine (A). A device was used. At that time, the pipe (C) was connected such that the tip of the pipe (C) was not in contact with the inner wall of the pipe (B) and was inclined in the flow direction of the liquid flowing in the pipe (B). The connection angle of the pipe (C) to the pipe (B) was 20 degrees with respect to the river upper side of the pipe (B). Further, the inner diameter of the polymerization machine (A) was 9 mm, and the area where the inner diameter was 9 mm was 95% from the inlet to the outlet of the polymerization machine (A).
First, 2 kg / hr trioxane, 0.08 kg / hr comonomer 1,3-dioxolane, and methylal (molecular weight regulator) diethylene glycol dimethyl ether solution from the inlet of the first preheater, using a double plunger pump These raw materials were mixed in the first preheater. At that time, the amount of methylal used was an amount necessary for adjusting the intrinsic viscosity to 1.1 to 1.5 dl / g. The obtained mixed raw material liquid was heated in a 1st preheater to 150 degreeC which is polymerization temperature. In addition, the used trioxane contained 100 mass ppm of hexamethylene bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] which is a sterically hindered phenol compound as a stabilizer. Moreover, impurities, such as water, formic acid, and formaldehyde, were 20 mass ppm or less, respectively.
On the other hand, the liquid containing the polymerization initiator is perchloric acid (polymerization initiator) in an amount of 2.5 mass ppm with respect to trioxane and sodium perchlorate in an amount of 3.0 mass ppm with respect to trioxane. (NaClO ₄ ) was prepared by mixing immediately before use as a 3% by mass perchloric acid-diethylene glycol dimethyl ether solution and a 0.5% by mass NaClO ₄ -diethylene glycol dimethyl ether solution, respectively.
Next, a mixed raw material liquid containing trioxane, a comonomer, and a molecular weight regulator is supplied from the first preheater to the polymerization machine (A) through the pipe (B), and at the same time, the above-described polymerization is performed using a double plunger pump. The liquid containing the initiator was continuously supplied through the pipe (C). The liquid mixture (polymerization reaction raw material liquid) containing the mixed raw material liquid and the polymerization initiator thus obtained was supplied to the polymerization machine (A). At this time, the linear velocity of the polymerization reaction raw material liquid flowing through the pipe (B) having an inner diameter of 3 mm was 71 mm per second, and the residence time in the polymerization reaction raw material liquid was 4 seconds.
The polymerization reaction was carried out with the jacket temperature of the polymerization machine (A) being the same as the polymerization temperature described above. The polymerization machine (A) was operated under the condition that the linear velocity of the polymerization reaction raw material liquid was 8 mm per second. At this time, the average residence time of the polymerization reaction raw material liquid in the polymerization machine (A) was 2 minutes.
Thereafter, sodium methoxide equivalent to twice the amount of the polymerization initiator is used as a diethylene glycol dimethyl ether solution (solution concentration: 5 mmol / ml) in the middle of the pipe connecting the polymerization machine (A) and the polymerization terminator mixer (D). And continuously fed using a double plunger pump. In the polymerization terminator mixer (D), the polymerization reaction product and the polymerization terminator were mixed and then allowed to flow through the termination reactor.
The maximum value of the inner diameter of the used polymerization terminator mixer (D) was 40% of the maximum value of the inner diameter of the polymerization machine (A). The jacket temperature of the polymerization terminator mixer (D) and termination reactor was set to be the same as the polymerization temperature. The average residence time of the mixture of the polymerization reaction product and the polymerization terminator in the polymerization terminator mixer (D) and the termination reactor was 3 minutes in total.
Next, the mixture of the polymerization reaction product and the polymerization terminator is supplied to the second preheater, heated to a temperature of 235 ° C., and released in an atmospheric pressure flash pot to evaporate unreacted monomers and decomposition products, Furthermore, low boiling point substances were removed under reduced pressure to obtain an oxymethylene copolymer. At this time, a back pressure valve was installed at the outlet of the second preheater, and the pressure was adjusted so that the flow rate of the oxymethylene copolymer was stabilized. The polymerization yield of the obtained oxymethylene copolymer was 70%, and the intrinsic viscosity was 1.5 dl / g.

Comparative example 1
In Comparative Example 1, the pipe (C) for supplying the liquid containing the polymerization initiator is not in the middle of the pipe (B) having an inner diameter of 3 mm connecting the first preheater and the polymerization machine (A), but the polymerization machine ( An oxymethylene copolymer was produced using the same continuous polymerization apparatus as in Example 1 except that it was directly connected to the main body of A).
The oxymethylene copolymer is a polymerization in which a liquid containing a polymerization initiator is directly connected to the main body of the polymerization machine (A), not in the middle of the pipe (B) connecting the first preheater and the polymerization machine (A). It was obtained in the same manner as in Example 1 except that the polymerization vessel (A) was directly supplied from the pipe (C) for supplying the liquid containing the initiator. The amount of methylal used as the molecular weight modifier was the same as that of Example 1 as an absolute amount. The polymerization yield of the obtained oxymethylene copolymer was 53%, and the intrinsic viscosity was 0.8 dl / g.

<Description of Examples and Comparative Examples>
A static mixer type polymerization machine (A) having a stationary mixing element therein and no drive unit, and a pipe for supplying a mixed raw material liquid containing trioxane and a comonomer to the polymerization machine (A) (B ) And a polymerization reactor having a pipe (C) for supplying a liquid containing a polymerization initiator connected in the middle of the pipe (B), an oxymethylene copolymer is produced. The inside of the pipe (B) when the liquid containing the mixed raw material liquid and the polymerization initiator is mixed at a temperature of 150 ° C. at the connection portion of the pipe (B) and the pipe (C) to obtain a polymerization reaction raw material liquid. The linear velocity of the polymerization reaction raw material liquid to be circulated is 71 mm per second, and the time until the polymerization reaction raw material liquid reaches the inlet of the polymerization machine (A) from the connection part of the pipe (B) and the pipe (C) The oxime obtained in Example 1 for 4 seconds The polymerization yield of 70% of the alkylene copolymer, the intrinsic viscosity was 1.5 dl / g.
On the other hand, the pipe (C) for supplying the liquid containing the polymerization initiator is not in the middle of the pipe (B) having an inner diameter of 3 mm connecting the first preheater and the polymerization machine (A). Comparative Example 1 in which a liquid containing a polymerization initiator was directly supplied to a polymerization machine (A) from a pipe (C) directly connected to the polymerization machine (A) main body using a polymerization reaction apparatus directly connected to the main body of The polymerization yield of the oxymethylene copolymer obtained in 1) was 53% and the intrinsic viscosity was 0.8 dl / g, which was significantly inferior to the results of Example 1 in terms of polymerization yield and molecular weight.

Claims (8)

  A static mixer type polymerization machine (A) having a stationary mixing element therein and no drive unit, and a pipe for supplying a mixed raw material liquid containing trioxane and a comonomer to the polymerization machine (A) (B And a pipe (C) for supplying a liquid containing a polymerization initiator connected in the middle of the pipe (B), and a method for producing an oxymethylene copolymer using a polymerization reactor, A polymerization reaction raw material liquid obtained by mixing the mixed raw material liquid and the liquid containing the polymerization initiator at a connection portion between the pipe (B) and the pipe (C) is mixed at a temperature of 135 ° C to 300 ° C. And the linear velocity of the polymerization reaction raw material liquid flowing in the pipe (B) after the connection part is 0.1 mm or more per second, and the polymerization reaction raw material liquid is supplied from the connection part. Polymerizer ( Time to reach the inlet of) is 0.01 to seconds, the manufacturing method of the oxymethylene copolymer.   The manufacturing method of the oxymethylene copolymer of Claim 1 with which the front-end | tip of piping (C) is connected in the said connection part in the form which does not contact the inner wall of piping (B).   The connection angle of the pipe (C) to the pipe (B) in the polymerization reaction apparatus is connected so as to be an angle of 90 degrees or less with respect to the river upper side of the pipe (B). A method for producing an oxymethylene copolymer.   The inner diameter of the polymerization machine (A) in the polymerization reaction apparatus is constant in a region of 90% or more in a region in the polymerization machine (A) where a polymerization reaction is performed. A method for producing an oxymethylene copolymer.   The polymerization reaction apparatus further includes a polymerization terminator mixer (D) connected in series to the polymerization machine (A), and the maximum value of the inner diameter of the polymerization terminator mixer (D) is the polymerization machine (A). The manufacturing method of the oxymethylene copolymer as described in any one of Claims 1-4 which is 90% or less of the maximum value of the internal diameter of.   6. The polymerization initiator according to claim 1, wherein at least one selected from the group consisting of a protonic acid having a molecular weight per mole of 1000 or less, a protonic acid anhydride, and a protonic acid ester compound is used. The manufacturing method of the oxymethylene copolymer of description to term.   The method for producing an oxymethylene copolymer according to any one of claims 1 to 6, wherein at least one salt of a protonic acid having a molecular weight per mole of 1000 or less is used together with the polymerization initiator.   The method for producing an oxymethylene copolymer according to claim 7, wherein a salt of a protonic acid having a molecular weight per mole of 1000 or less is supplied together with the polymerization initiator from the pipe (C).