TWI911448B - Method for manufacturing polyacetal copolymers - Google Patents

Abstract

This invention relates to a method for manufacturing a polyacetal copolymer, wherein the polyacetal copolymer is in the form of tri- As the main monomer (a), a cyclic formaldehyde compound having at least one carbon-carbon bond is used as a comonomer (b). The method for manufacturing the polyacetal copolymer includes: step A, uniformly mixing a specific heteropolymeric acid as a polymerization catalyst (c) and the cyclic formaldehyde compound in a liquid phase; and mixing the mixture obtained in step A with tri... Step B, which involves uniform mixing in the liquid phase, will yield a mixture containing three... Step C involves feeding the mixture to a continuous polymerization apparatus for copolymerization, and Step D involves adding an alkaline deactivator (d) to the reaction product obtained in Step C for melt mixing to deactivate the polymerization catalyst (c).

Description

Method for manufacturing polyacetal copolymers

This invention relates to a method for manufacturing a polyacetal copolymer.

Polyacetal copolymers offer an excellent balance of mechanical properties, chemical resistance, and slip properties. Due to their ease of processing, they are widely used as typical engineering plastics, primarily for electrical and electronic components, automotive components, and various other mechanical parts. The industrial manufacturing method of polyacetal copolymers generally involves using three monomers as the main monomers… Cyclic ethers or cyclic formal, which have two or more adjacent carbon atoms as comonomers, boron trifluoride, or coordination compounds of boron trifluoride and ethers, which act as polymerization catalysts, are supplied to continuous reaction devices such as co-kneading single-shaft extruders, twin-screw extrusion mixers, and twin-paddle extrusion mixers to carry out continuous copolymerization reactions.

However, a relatively large amount (e.g., more than 3 × ^10⁻⁴ mol per 1 kg of monomer) of polymerization catalyst, such as commonly used boron trifluoride compounds, needs to be added. Therefore, the residual polymerization catalyst in the copolymer inevitably leads to copolymer decomposition, which limits the degree of polymerization of the resulting copolymer. In addition, there are problems such as a large number of unstable ends and the need for complicated stabilization steps.

To address this problem, it has been proposed to premix a heteropoly acid, acting as a polymerization catalyst, with part or all of a cyclic ether or cyclic formaldehyde having at least one carbon-carbon bond, which is a comonomer component, and then add this mixture to the three... A method for aggregation in (see Patent Document 1). Alternatively, a method for combining three... A method for copolymerization in which the copolymer monomer and the heteropolymeric acid or its acid salt, acting as a polymerization initiator (polymerization catalyst), are thoroughly mixed while remaining in a liquid phase (see Patent 2). Both methods attempt to reduce the concentration of the polymerization catalyst and improve the stability of the resulting copolymer. [Prior Art Documents] [Patent Documents]

[Patent Document 1] Japanese Patent No. 2958270 [Patent Document 2] Japanese Unexamined Patent Publication No. 11-302349

[The problem that the invention aims to solve]

The polymerization method described in Patent 1 or 2 has yielded some results in reducing the amount of polymerization catalyst and stabilizing the copolymer. However, there are still problems with the yield and formaldehyde production, and there is still room for improvement.

This invention addresses the aforementioned problems of conventional methods, aiming to provide a method for manufacturing polyacetal copolymers that ensures sufficient yield and minimizes formaldehyde production even with reduced polymerization catalyst dosage. [Means for Solving the Problems]

To solve the above problems, the inventors, after in-depth research, discovered that by first uniformly mixing cyclic formaldehyde (comonomer) and a specific heteropolymer acid (polymerization catalyst), and then... The (main monomers) are uniformly mixed in the resulting mixture, and then copolymerized. The polymerization catalyst is further deactivated by an alkaline deactivator, which can produce a polyacetal copolymer with a small amount of catalyst, ensure sufficient yield, and produce less formaldehyde, thus completing the present invention.

The present invention that solves the above problems is as follows: (1) A method for manufacturing a polyacetal copolymer, wherein the polyacetal copolymer is in the form of a tri- The method for manufacturing the polyacetal copolymer comprises, as a major monomer (a) comprising 90-99.9 mol% of the total monomers, and as a copolymer (b) a cyclic formaldehyde compound having at least one carbon-carbon bond, the method includes: step A, uniformly mixing an heteropolymeric acid represented by the following general formula (1) as a polymerization catalyst (c) and the aforementioned cyclic formaldehyde compound in a liquid phase; and mixing the mixture obtained in step A with the aforementioned three... Step B involves uniform mixing in the liquid phase; the mixture obtained in step B contains three... Step C: The mixture is fed to a continuous polymerization apparatus for copolymerization; and Step D: The alkaline deactivator (d) is added to the reaction product obtained in Step C for melt kneading treatment to deactivate the aforementioned polymerization catalyst (c); H _m [M ¹ _x ． M ² _y O _z ] ． nH ₂ O ． ． ． General Formula (1) [In General Formula (1), M ¹ represents a central element composed of one or two elements selected from P and Si. ^{M 2} represents one or more coordinating elements selected from W, Mo and V. x represents an integer of 1 to 10, y represents an integer of 6 to 40, z represents an integer of 10 to 100, m represents an integer of 1 or more, and n represents an integer of 0 to 50.]

(2) The method for manufacturing the polyacetal copolymer as described in (1) above, wherein the amount of the polymerization catalyst (c) used is 1.5 to 3.0 ppm by mass relative to the total amount of the main monomer (a) and the comonomer (b). [Invention Benefits]

According to the present invention, a method for manufacturing polyacetal copolymers can be provided that ensures sufficient yield and low formaldehyde production even with a reduced amount of polymerization catalyst.

[The form in which the invention is implemented]

<Method for Manufacturing Polyacetal Copolymers> The method for manufacturing polyacetal copolymers in this embodiment is a method using three... A method for manufacturing a polyacetal copolymer, comprising 90-99.9 mol% of the total monomers as the main monomer (a) and a cyclic formal compound having at least one carbon-carbon bond as the comonomer (b). The manufacturing method includes step A, which involves uniformly mixing an heteropolymeric acid represented by the following general formula (1) as a polymerization catalyst (c) and the cyclic formal compound in a liquid phase. Furthermore, the manufacturing method includes mixing the mixture obtained in step A with tri... Step B involves uniform mixing in the liquid phase. Further, the manufacturing method includes mixing the three components obtained in step B... The mixture is fed to a continuous polymerization apparatus for copolymerization in step C. The manufacturing method includes step D, in which an alkaline deactivator (d) is added to the reaction product obtained in step C for melt mixing treatment, thereby deactivating the polymerization catalyst (c). H _m [M ¹ _x ． M ² _y O _z ] ． nH ₂ O ． ． ． General formula (1) [In general formula (1), M ¹ represents a central element composed of one or two elements selected from P and Si. ^{M 2} represents one or more coordinating elements selected from W, Mo and V. x represents an integer of 1 to 10, y represents an integer of 6 to 40, z represents an integer of 10 to 100, m represents an integer of 1 or more, and n represents an integer of 0 to 50.]

In the manufacturing method of this embodiment, as shown in Figure 1, firstly, a specific heteropolymeric acid, serving as a polymerization catalyst (c), and a cyclic formaldehyde compound are uniformly mixed in the liquid phase using a liquid mixing device (first step) (step A). That is, in step A, the cyclic formaldehyde compound acts as a dispersion medium, enabling the uniform dispersion of the specific heteropolymeric acid, serving as the polymerization catalyst. Next, the mixture obtained in step A is mixed with triglycerides... The mixture is uniformly mixed in the liquid phase using a liquid mixing device (step B). That is, in step B, the three... The mixture is then combined with the heteropolymeric acid and cyclic formaldehyde compound that were uniformly mixed in step A, thereby affecting the three... The copolymer exhibits a higher degree of homogenization. Furthermore, because copolymerization is carried out under these highly homogenized conditions (step C), polyacetal copolymers can be obtained in high yields even with a reduced amount of polymerization catalyst. Moreover, due to the high yield, unreacted monomer residues after copolymerization do not require washing with water; an alkaline deactivator is directly added, and the polymerization catalyst is deactivated in the molten state (step D). This reduces the amount of unstable ends generated and improves stability, resulting in less formaldehyde production during molding. In this embodiment, since the amount of polymerization catalyst used is already small, the amount of residual polymerization catalyst is also small. Therefore, the adverse effects of residual polymerization catalyst during the molding process of the polyacetal copolymer and during the long-term use of the molded product can be suppressed.

On the other hand, Figures 2 to 4 show the feeding states of each component to a continuous polymerization apparatus, etc., in conventional methods for manufacturing polyacetal copolymers. The state shown in Figure 2 is one in which the heteropolymeric acid (polymerization catalyst), cyclic formaldehyde compound (comonomer), and tri-... Instead of mixing, the mixture is sequentially fed to a continuous polymerization unit for copolymerization. Furthermore, the state shown in Figure 3 involves feeding a heteropolymeric acid (polymerization catalyst) and a cyclic formaldehyde compound (comonomer) into a liquid mixing unit to form a mixture, and then mixing this mixture with tri... The state sample is supplied to a continuous polymerization apparatus for copolymerization. Further, the state sample shown in Figure 4 is formed by copolymerizing a heteropolymeric acid (polymerization catalyst), a cyclic formaldehyde compound (comonomer), and tri-... The mixture is fed into a liquid mixing apparatus to form a mixture, and this mixture is then fed into a continuous polymerization apparatus for copolymerization. In any of the samples, although the components are mixed and copolymerized to a certain extent, the copolymerization is still insufficient. In the manufacturing method of this embodiment, since the components are mixed more uniformly than in the samples of Figures 2 and 3, a high efficiency can be achieved in terms of yield and suppression of formaldehyde production. The steps in the manufacturing method of this embodiment will be explained below.

[Step A] In Step A, the heteropolymeric acid represented by the aforementioned general formula (1), serving as a polymerization catalyst (c), and the cyclic formaldehyde compound, serving as a comonomer (b), are uniformly mixed in the liquid phase. Any mixing method can be used, as long as it enables uniform mixing in the liquid phase. Examples include methods such as continuous mixing via a confluence pipe, continuous mixing followed by further mixing using a static mixer, and supplying the mixed components to a container equipped with a stirrer.

Regarding the mixing time in the liquid phase, the shortest required mixing time is the time needed for the polymerization catalyst to be uniformly dispersed in the comonomer, which depends on the mixing method, the comonomer, the supply rate of the polymerization catalyst, etc. Furthermore, the longest mixing time must not exceed the time it takes for the reaction to proceed and for the polymer to begin settling; this is determined by the copolymerization reaction rate, which depends on the mixing temperature, comonomer concentration, and polymerization catalyst concentration. Therefore, the optimal mixing time depends on the mixing method, supply rate, mixing temperature, comonomer concentration, and polymerization catalyst concentration, and cannot be limited, but is generally chosen to be a mixing time of 0.01 to 60 seconds. This optimal mixing time can be easily determined experimentally through viscosity measurements, observations, etc. For example, when using a continuous liquid mixing device with high mixing efficiency, such as a static mixer widely used in industry, to produce polyacetal copolymers composed of general comonomers, a mixing time of 0.01 to 30 seconds is preferred, and 0.1 to 10 seconds is particularly preferred. The comonomer (b) and polymerization catalyst (c) used in step A will be described in detail below.

(Comonomer (b)) Cyclic formaldehyde having at least one carbon-carbon bond is used as copolymer (b). Typical examples of compounds used as copolymer (b) include, for example, 1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, and 1,3-dioxolane. Alkane (1,3-dioxane), etc. Among them, 1,3-dioxane is preferred from the perspective of polymerization stability. Furthermore, as long as it does not significantly reduce the performance of the obtained polyacetal resin composition, in addition to the main monomer (a) and comonomer (b), conventional modifying agent comonomers such as branching agents can be added as a third comonomer component.

In this embodiment, the amount of the cyclic formaldehyde compound used as the comonomer (b) is preferably 0.1 to 10 mol%, and more preferably 0.2 to 8 mol%, in the total amount of all monomers (the main monomer (a) and the comonomer (b)). When the amount of comonomer (b) is less than 0.1 mol%, the unstable ends of the crude formaldehyde copolymer produced by polymerization may increase and the stability may deteriorate. When the amount of comonomer (b) exceeds 10 mol%, the amount of polymerization catalyst (c) required for the copolymerization reaction increases, leading to a decrease in quality, and the resulting copolymer may soften, resulting in a decrease in melting point.

(Polymerization Catalyst (c)) In this embodiment, a heteropolymeric acid represented by the following general formula (1) is used as the polymerization catalyst (c). H _m [M ¹ _x ． M ² _y O _z ] ． nH ₂ O ． ． ． General formula (1)

In equation (1), ^M1 represents the central element composed of one or two elements selected from P and Si. ^M2 represents one or more coordination elements selected from W, Mo and V. x represents an integer between 1 and 10, y represents an integer between 6 and 40, z represents an integer between 10 and 100, m represents an integer greater than 1, and n represents an integer between 0 and 50.

Specific examples of the aforementioned heteropolymeric acids include phosphomolybdic acid, phosphotungstic acid, phosphomolybdic acid, phosphomolybdic vanadium, phosphomolybdic vanadium, phosphomolybdic vanadium, phosphomolybdic vanadium, silicotungstic acid, silicomolybdic acid, silicomolybdic vanadium, and silicomolybdic vanadium. Among these, considering the stability of polymerization and the inherent stability of the heteropolymeric acid, it is preferable that the heteropolymeric acid is any one or more of silicolybdic acid, silicotungstic acid, phosphomolybdic acid, or phosphomolybdic acid.

In the manufacturing method of this embodiment, as described above, copolymers can be obtained in high yield even with a reduced amount of polymerization catalyst (c). Specifically, the amount of polymerization catalyst (c) used relative to the total amount of the main monomer (a) and comonomer (b) can be 1.0 to 4.0 ppm by mass, preferably 1.5 to 3.0 ppm by mass. Even with such a small amount of polymerization catalyst, copolymerization can be carried out, thereby minimizing undesirable reactions such as decomposition and depolymerization of the polymer backbone by the polymerization catalyst, and has the effect of suppressing the formation of unstable formate end groups (-O-CH=O), hemiacetal end groups (-O- _CH2 -OH), etc., and is also economically advantageous.

In order to ensure a uniform reaction, it is preferable to dilute the polymerization catalyst (c) and mix it with the comonomer (b) using an inert solvent that does not adversely affect the polymerization. As inert solvents, esters obtained by condensing low molecular weight carboxylic acids with 1 to 10 carbon atoms, such as formic acid, acetic acid, propionic acid, and butyric acid, with low molecular weight alcohols with 1 to 10 carbon atoms, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol, 3-methyl-1-butanol, and 1-hexanol, are preferred, but not limited to these. Considering industrial applicability, methyl formate, ethyl formate, methyl acetate, ethyl acetate, butyl acetate, acetone, 2-butanone, and methyl isobutyl ketone are the most suitable. Although polymerization catalysts are suitable for dissolving in the above-mentioned inert solvents at concentrations of 1–30% by mass, they are not limited thereto.

(Step (B)) In Step B, the mixture of the copolymer (b) obtained in Step A and the polymerization catalyst (c) is uniformly mixed with the molten main monomer (a) in the liquid phase. The mixing method in Step B is the same as in Step A, but the mixing time needs to be longer than the time required to achieve a fully mixed state, and shorter than the time required for the copolymer to precipitate during the induction period. Appropriate adjustments need to be made based on the type and concentration of the polymerization catalyst, the temperature of the liquid after mixing, etc. If the mixing in Step A is done properly, the mixing time in Step B can be shortened. Furthermore, using a continuous mixing device with high mixing efficiency in Step B can also shorten the mixing time. The mixing time is generally selected from 0.01 to 60 seconds, but considering the stability under actual conditions and the quality of the final polyacetal copolymer, 0.01 to 30 seconds is preferred, and 0.1 to 15 seconds is particularly preferred. The main monomer (a) used in step B will be described in detail below.

(Main unit (a)) Use three As the principal unit (a). Three It is a cyclic trimer of formaldehyde, generally obtained by reacting an aqueous solution of formaldehyde in the presence of an acidic catalyst, and then purified by methods such as distillation before use. The trimer used in the polymerization... To minimize impurities such as water and methanol Ideally. Additionally, the primary monomers used 90–99.9 mol% of the total monomers. Due to three It is a solid at room temperature, and is usually heated to a temperature higher than its melting point and used as a melt.

(Step (C)) In step C, the three items obtained in step B will be... The mixture is fed to a continuous polymerization apparatus for copolymerization. In this embodiment, in step B, the main monomer (a) (trimethylammonium di ... A mixture of copolymer (b) (a cyclic formaldehyde compound) and polymerization catalyst (c) (a predetermined heteropolymeric acid) is fed into a continuous polymerization apparatus for continuous copolymerization. Examples of continuous polymerization apparatus include co-kneading single-shaft extruders, twin-screw extrusion mixers, and twin-paddle extrusion mixers, among others. The three types proposed to date... Continuous polymerization apparatus, etc. It is also possible to use two or more types of polymerizers in combination. In the polymerization apparatus, the part in contact with the reactants needs to be adjusted to a suitable temperature for copolymerization (65-130°C).

The polymerization time depends on the concentration of catalyst, the concentration of comonomer, and the reaction temperature, and cannot be particularly limited. Generally, a polymerization time of 0.5 to 10 minutes is chosen.

In step C, furthermore, a suitable amount of a known chain transfer agent can be added as needed to appropriately adjust the degree of polymerization of the resulting copolymer to any value. Examples of such chain transfer agents include low molecular weight linear acetals such as methylal, methoxymethylal, dimethoxymethylal, trimethoxymethylal, and oxymethylene di-n-butyl ether. In step C, furthermore, components capable of forming known branched crosslinking structures can also be added as needed. These components are used to form branched crosslinking structures. Components with cross-linked structures include, for example, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, hexamethylene glycol diglycidyl ether, resorcinol diglycidyl ether, and bisphenol A diglycidyl ether.

The copolymer obtained above is a crude polyacetal copolymer that has not undergone deactivation of the polymerization catalyst and stabilization of the unstable ends. Therefore, the following step D is performed.

(Step D) In Step D, an alkaline deactivator (d) is added to the reaction product obtained in Step C (i.e., the crude polyacetal copolymer), and melt-blending is performed to deactivate the polymerization catalyst (c).

(Alkaline Deactivator (d)) The type and method of addition of the alkaline deactivator are not particularly limited, but it is preferable to use an alkaline deactivator that can deactivate the polymerization catalyst and stabilize the unstable ends of the crude polyacetal copolymer by directly adding the alkaline deactivator to the crude polyacetal copolymer for melt mixing without washing the copolymer. Specifically, the alkaline deactivator is preferably one of at least one selected from carbonates, bicarbonates, or carboxylates or their hydrates selected from alkaline metals or alkaline earth metals, and triazine ring compounds having an amino group or substituted amino group.

Furthermore, when using carbonates, bicarbonates, or carboxylates or their hydrates of alkaline metals or alkaline earth metals, the formaldehyde production in the final composition is particularly low, which is therefore preferable. Specifically, it is preferable to include at least one of sodium carbonate, sodium bicarbonate, sodium formate, sodium acetate, disodium succinate, sodium laurate, sodium palmitate, sodium stearate, and calcium stearate.

The amount of alkaline deactivator used in step C, relative to the crude polyacetal copolymer, is preferably 0.0002 to 0.01% by mass, and more preferably 0.0003 to 0.003% by mass.

In this embodiment, the aforementioned alkaline deactivating agent can be used as a single type or in combination of multiple types, and can be in the form of hydrates, mixtures, double salts, etc.

After such polymerization and deactivation, unreacted monomers can be further separated, recovered, or dried using conventional methods, as needed.

As needed, the polymer obtained as described above is further stabilized. Stabilization is achieved by hot-melt treatment or heating in an insoluble or soluble liquid medium to selectively decompose and remove unstable components. In particular, compared to conventional methods, the copolymerization in this embodiment has fewer unstable components at the polymerization end stage, thus greatly simplifying the stabilization process. It is achieved through melt extrusion and granulation in the presence of a predetermined stabilizer, resulting in a polymer with high stability even as the final product. Furthermore, as described above, the polyacetal copolymer obtained by the manufacturing method of this embodiment produces less formaldehyde when manufactured into molded articles. [Example]

The following examples further illustrate this embodiment, but this embodiment is not limited to the following examples.

[Examples 1-4] In each embodiment, as shown in Table 1, a predetermined heteropolymeric acid and a predetermined cyclic formaldehyde compound (comonomer) serving as polymerization catalyst are supplied to a first liquid mixing apparatus and uniformly mixed (step A). Here, a static mixer (5 mm inner diameter, 80 mm length) is used as both the first liquid mixing apparatus and the second liquid mixing apparatus shown below. Furthermore, the polymerization catalyst is used as a methyl formate solution. Next, the three... (relative to three) A mixture, including 1000 ppm methylal as a molecular weight regulator, is fed into a second liquid mixing unit and homogenized with a mixture discharged from a first liquid mixing unit (Step B). Next, the mixture discharged from the second liquid mixing unit is fed to one end of a continuous polymerization unit for copolymerization (Step C). The resulting crude methylal copolymer is then discharged from a discharge port located at the other end of the continuous polymerization unit. A continuous twin-screw polymer is used as the continuous polymerization unit. The continuous twin-screw polymerizer has a jacket on the outside for passing through the heating or cooling medium. Inside the jacket, along its major diameter, are two rotating shafts with multiple blades for stirring and propulsion. An 80°C heat medium is passed through the jacket of this continuous twin-screw polymerizer. While the two rotating shafts rotate at a constant speed, polymerization catalysts and monomers are supplied to one end for continuous polymerization. Furthermore, in Table 1, the amount of copolymer used is relative to three... The total amount (mass%) of the copolymer monomers and the amount of polymerization catalyst used are relative to three The total amount of copolymer monomers (in ppm by mass).

Next, to deactivate the polymerization catalyst, 0.002% by weight of sodium stearate was added to the crude polyacetal copolymer as an alkaline deactivating agent (step D). Further, 0.3% by weight of triethylene glycol-bis-[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate, 0.05% by weight of melamine, and 0.1% by weight of calcium stearate were added as stabilizers. The mixture was then melt-mixed and extruded using a twin-screw extruder with vent holes at a temperature of 220°C and a vacuum of 5 mmHg at the vent holes. Through these steps, the polyacetal copolymer was obtained. Furthermore, in the polymerization yield determination, the aforementioned crude polyacetal copolymer was separated from the polymerizer outlet, and samples taken per unit time were immersed in an ammonia solution to deactivate the catalyst and remove unreacted monomers. The dried mass was then measured, expressed as a percentage of mass relative to the supplied monomer. Table 1 shows the calculated polymerization yield.

[Evaluation of Formaldehyde Production (VOC)] Using the obtained polyacetal copolymer, flat test pieces (100mm × 40mm × 2mm) were formed under the following conditions. Two flat test pieces were sealed in a 10L PVC sampling bag and degassed. 4L of nitrogen gas was added, and the mixture was heated at 65°C for 2 hours. Then, 3L of nitrogen gas was extracted from the sampling bag at a rate of 0.5ml/min, and the generated formaldehyde was adsorbed onto a DNPH (2,4-dinitrophenylhydrazine) collection tube (Waters Sep-PakDNPH-Silica). Subsequently, the reaction product of DNPH and formaldehyde was extracted from the DNPH collection tube using acetonitrile solvent. The amount of formaldehyde produced was determined by high-performance liquid chromatography (HPLC) using a calibration curve method with standard substances of the DNPH and formaldehyde reaction product. The formaldehyde production per unit mass of test piece (μg/g) was calculated. The calculation results are shown in Table 1. (Molding Conditions) • Molding machine: FANUC ROBOSHOT α-S100ia (FANUC Ltd.) • Molding conditions: Cylinder temperature (°C) Nozzle - C1 - C2 - C3 190 190 180 160°C • Injection pressure: 60 (MPa) • Injection speed: 1.0 (m/min) • Mold temperature: 80 (°C)

[Comparative Examples 1-3] In Comparative Examples 1-3, the components were mixed and copolymerized in the manner shown in Figure 2. In each comparative example, as shown in Table 1, three components were sequentially supplied from one end of the continuous polymerization apparatus. (relative to three) The apparatus comprises 1000 ppm of formaldehyde (as a molecular weight regulator) and a cyclic formaldehyde compound (comonomer). A heteropolymeric acid (methyl formate solution) acting as a polymerization catalyst is supplied downstream for copolymerization. The crude formaldehyde copolymer is then discharged from an outlet located at the other end of the continuous polymerization apparatus. Subsequent processing is performed in the same manner as in Example 1 to obtain the polyacetal copolymer. The polymerization yield and formaldehyde production (VOC) are then measured as in Example 1. The results are shown in Table 1.

[Comparative Examples 4-7] In Comparative Examples 4-7, the components were mixed and copolymerized in the states shown in Figure 3. In each comparative example, as shown in Table 1, a heteropolymeric acid (methyl formate solution) and a cyclic formaldehyde compound (comonomer) acting as polymerization catalysts were supplied to a liquid mixing apparatus and mixed uniformly to obtain a mixture. Then, a mixture was prepared by feeding three... (relative to three) In a continuous polymerization unit containing 1000 ppm of formaldehyde as a molecular weight regulator, the mixture is fed to these three... Copolymerization is carried out downstream of the feed section. The crude polyacetal copolymer is then discharged from a discharge port located at the other end of the polymerizer. Subsequent processing is performed in the same manner as in Example 1 to obtain the polyacetal copolymer. Then, the polymerization yield and formaldehyde production (VOC) are measured as in Example 1. The measurement results are shown in Table 1.

[Comparative Examples 8-11] In Comparative Examples 8-11, the components were mixed and copolymerized as shown in Figure 4. In each comparative example, as shown in Table 1, the heteropolymeric acid (methyl formate solution), cyclic formaldehyde compound (comonomer), and tri-polymer were used as polymerization catalysts. (relative to three) A mixture (including 1000 ppm of formaldehyde as a molecular weight regulator) was supplied to a liquid mixing apparatus and homogenized. The mixture discharged from the liquid mixing apparatus was then fed to one end of a continuous polymerization apparatus for copolymerization. Subsequently, the crude polyacetal copolymer was discharged from an outlet located at the other end of the polymerizer. Subsequent processing was performed in the same manner as in Example 1 to obtain the polyacetal copolymer. Then, the polymerization yield and formaldehyde production (VOC) were measured as in Example 1. The results are shown in Table 1.

[Table 1] Supply patterns of each component to continuous polymerization apparatus, etc. Cyclic formaldehyde (copolymer) Heterotropic polymeric acids (polymerization catalysts) Polymerization yield Formaldehyde production (VOC) Kind Usage (%) Kind Dosage (per ppm) % μg/g Implementation Examples 1 Figure 1 1,3-Dioxolane 3.1 Phosphoric acid 2.5 85 0.20 2 1,3-Dioxolane 3.1 Phosphoric acid 2.0 75 0.15 3 1,3-Dioxolane 3.1 Phosphoric acid 2.5 84 0.20 4 1,4-Butanediol formaldehyde 4.2 Phosphoric acid 2.5 83 0.21 Comparative example 1 Figure 2 1,3-Dioxolane 3.1 Phosphoric acid 5.5 78 1.00 2 1,3-Dioxolane 3.1 Phosphoric acid 5.0 68 0.90 3 1,3-Dioxolane 3.1 Phosphoric acid 5.5 76 1.00 4 Figure 3 1,3-Dioxolane 3.1 Phosphoric acid 4.0 80 0.70 5 1,3-Dioxolane 3.1 Phosphoric acid 3.5 70 0.60 6 1,3-Dioxolane 3.1 Phosphoric acid 4.0 79 0.65 7 1,4-Butanediol formaldehyde 4.2 Phosphoric acid 4.0 77 0.65 8 Figure 4 1,3-Dioxolane 3.1 Phosphoric acid 3.5 83 0.50 9 1,3-Dioxolane 3.1 Phosphoric acid 3.0 70 0.40 10 1,3-Dioxolane 3.1 Phosphoric acid 3.5 81 0.45 11 1,4-Butanediol formaldehyde 4.2 Phosphoric acid 3.5 80 0.45

As shown in Table 1, although the amount of polymerization catalyst used in Examples 1-4 was less than that in the comparative examples, the polymerization yield was higher and the amount of formaldehyde produced was lower. Therefore, it is shown that the method for manufacturing polyacetal copolymers of this embodiment can achieve sufficient yield and reduce formaldehyde production even with a reduced amount of polymerization catalyst.

without.

Figure 1 shows a conceptual diagram of the supply states of each component to the liquid mixing apparatus and the continuous polymerization apparatus in the manufacturing method of the polyacetal copolymer of this embodiment. Figure 2 shows a conceptual diagram of the supply states of each component to the continuous polymerization apparatus in a conventional method of manufacturing polyacetal copolymer. Figure 3 shows a conceptual diagram of the supply states of each component to the liquid mixing apparatus and the continuous polymerization apparatus in a conventional method of manufacturing polyacetal copolymer. Figure 4 shows a conceptual diagram of the supply states of each component to the liquid mixing apparatus and the continuous polymerization apparatus in a conventional method of manufacturing polyacetal copolymer.

Claims (2)

A method for manufacturing a polyacetal copolymer, wherein the polyacetal copolymer is in the form of tris... The method for manufacturing the polyacetal copolymer comprises, as a major monomer (a) comprising 90–99.9 mol% of the total monomers, and a copolymer (b) comprising 0.1–10 mol% of the total monomers, a cyclic formaldehyde compound having at least one carbon-carbon bond, comprising: step A, uniformly mixing an heteropolymeric acid represented by the following general formula (1) as a polymerization catalyst (c) and the cyclic formaldehyde compound in a liquid phase; and mixing the mixture obtained in step A with the three... Step B involves uniform mixing in the liquid phase; the mixture obtained in step B will contain three... Step C: The mixture is fed to a continuous polymerization apparatus for copolymerization; and Step D: The alkaline deactivator (d) is added to the reaction product obtained in Step C for melt mixing treatment to deactivate the polymerization catalyst (c); H _m [M ¹ _x ． M ² _y O _z ] ． nH ₂ O ． ． ． General Formula (1) [In General Formula (1), M ¹ represents a central element composed of one or two elements selected from P and Si; M ² represents one or more coordinating elements selected from W, Mo and V; x represents an integer of 1 to 10, y represents an integer of 6 to 40, z represents an integer of 10 to 100, m represents an integer of 1 or more, and n represents an integer of 0 to 50]. The method for manufacturing a polyacetal copolymer as described in claim 1, wherein the amount of polymerization catalyst (c) used is 1.5 to 3.0 ppm by mass relative to the total amount of the main monomer (a) and the comonomer (b).