Trioxane or methylal production method

Abstract

To provide a trioxane or methylal production method which suppresses lowering of target reaction activity and corrosion of a device even when being used for a long time.SOLUTION: A trioxane or methylal production method includes a step of reacting formaldehyde, in the presence of a styrenic resin having an electron-attracting group, and producing trioxane or methylal, wherein the styrenic resin has a substituent containing at least one halogen atom, and has a retention rate of the halogen atom of 50% or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a process for the preparation of trioxane or methylal. [Background technology]

[0002] Trioxane is a cyclic trimer of formaldehyde and is mainly used as a raw material for the production of polyoxymethylene. Methylal is obtained by reacting formaldehyde with methanol, and high-concentration formaldehyde can be obtained by oxidizing methylal.

[0003] Both the methods for producing trioxane and methylal use formaldehyde as a raw material and an acid catalyst (e.g., sulfuric acid, benzenesulfonic acid, toluenesulfonic acid, silica alumina, zeolite, cation exchange resin, etc.), and have common problems.

[0004] The general industrial method for producing trioxane is to use sulfuric acid, but this method has problems such as corrosion of the equipment, generation of a large amount of by-products, and generation of paraformaldehyde.

[0005] As a method for solving these problems, a method using a styrene-based resin, particularly a cation exchange resin, has been proposed. As a method for producing trioxane from formaldehyde using a cation exchange resin, Patent Document 1 discloses a method using a cation exchange resin having an -SO3H group as an exchange group.

[0006] Furthermore, Patent Document 2 discloses a method of using a cation exchange resin having an electron-withdrawing group as a method for suppressing the elimination of sulfonic acid groups from a cation exchange resin. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 40-12794 [Patent Document 2] Japanese Patent Application Publication No. 4-273868 Summary of the Invention [Problem to be solved by the invention]

[0008] When producing trioxane using a cation exchange resin, it is preferable to bring an aqueous formaldehyde solution into contact with the cation exchange resin in order to produce trioxane efficiently.

[0009] However, when the reaction is continued while contacting the aqueous formaldehyde solution with the cation exchange resin, there is a problem that the sulfonic acid groups are eliminated from the cation exchange resin, decreasing the ion exchange capacity and the activity for synthesizing trioxane.

[0010] Furthermore, if the reaction is continued for a long period of time, the sulfonic acid group released will increase the sulfuric acid concentration in the process system, causing problems such as corrosion of equipment.

[0011] Therefore, an object of the present invention is to provide a method for producing trioxane or methylal, which is capable of suppressing a decrease in the target reaction activity and corrosion of the apparatus even when used for a long period of time. [Means for solving the problem]

[0012] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by ensuring that the halogen atoms in the styrene-based resin have a predetermined retention rate, and have thus completed the present invention.

[0013] That is, the present invention is as follows. [1] A process for producing trioxane or methylal, comprising the steps of: The method includes a step of reacting formaldehyde in the presence of a styrene-based resin having an electron-withdrawing group to produce trioxane or methylal, The method for producing trioxane or methylal, wherein the styrene-based resin has a substituent containing at least one halogen atom and has a halogen atom retention rate of 50% or more. [2] The method for producing trioxane or methylal according to [1], wherein the styrene-based resin is a cation exchange resin. [3] The method for producing trioxane or methylal according to [1] or [2], wherein the styrene-based resin contains structural units represented by the following formulas (I) and (II): [ka] In formulas (I) and (II), R 1 , R 2 and R 3 each independently represents a hydrogen atom, an alkyl group, an aryl group, or a halogen atom; X is an electron-withdrawing group, and a plurality of X's may be different from each other; Y is an alkylene group, an arylene group, or a single bond; Each a is independently an integer of 1 to 5; Each b is independently an integer of 1 to 4. [4] A distillation column and a catalyst packed tank are included. The catalyst-filled tank is filled with the styrene-based resin, The amount of the formaldehyde-containing raw material liquid fed to the bottom of the distillation column is represented as As, When the amount of bottom liquid withdrawn outside the process system is Ae, The method for producing trioxane or methylal according to any one of [1] to [3], wherein a ratio of Ae to As (Ae / As) is less than 0.10. [5] The method for producing trioxane or methylal according to [4], wherein the amount of bottoms liquid discharged outside the process system is the amount of bottoms liquid discharged from between the bottom of the distillation column and the catalyst-packed tank. [6] The method for producing trioxane or methylal according to any one of [1] to [5], wherein the reaction of formaldehyde in the step is a continuous reaction. [7] The method for producing trioxane or methylal according to any one of [4] to [6], wherein a residence time of formaldehyde in the catalyst-packed tank is 0.01 to 50 minutes. Effect of the Invention

[0014] According to the present invention, it is possible to produce trioxane or methylal while suppressing a decrease in the target reaction activity and corrosion of the apparatus even after long-term use. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a flow diagram that illustrates an example of a process for producing trioxane according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention (hereinafter, simply referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the following description, and can be practiced in various modifications within the scope of the gist of the present invention.

[0017] In this embodiment, the method includes a step of producing trioxane or methylal by reacting formaldehyde in the presence of a styrene-based resin having an electron-withdrawing group, The styrene-based resin has at least one substituent containing a halogen atom, and the retention rate of the halogen atom is 50% or more.

[0018] In a preferred embodiment, the styrene-based resin having an electron-withdrawing group contains constitutional units represented by the following formulas (I) and (II). [ka] In formula (I), R 1 , R 2 and R 3 each independently represents a hydrogen atom, an alkyl group, an aryl group, or a halogen atom; X is an electron-withdrawing group, and a plurality of X's may be different from each other; Each a is independently an integer of 1 to 5. In formula (II), R 1 , R 2 and R 3 each independently represents a hydrogen atom, an alkyl group, an aryl group, or a halogen atom; X is an electron-withdrawing group, and a plurality of X's may be different from each other; Y is an alkylene group, an arylene group, or a single bond; Each a is independently an integer of 1 to 5. Each b is independently an integer of 1 to 4.

[0019] R in formula (I) and (I) 1 , R 2 and R 3 Examples of the alkyl group include linear, branched, and cyclic alkyl groups. Examples of linear alkyl groups include methyl, ethyl, propyl, and butyl groups. Examples of branched alkyl groups include isopropyl, isobutyl, and tert-butyl groups. Examples of cyclic alkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups.

[0020] R in formulas (I) and (II) 1 , R 2 and R 3 Examples of the aryl group include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, an anthryl group, and a phenanthryl group.

[0021] R in formulas (I) and (II) 1 , R 2 and R 3 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0022] R in formulas (I) and (II) 1 , R 2 and R3 The alkyl group and the aryl group may or may not have a substituent. Examples of the substituent include R 1 Examples of the alkyl group include the alkyl group and halogen atoms exemplified above.

[0023] In a preferred embodiment, R 1 , R 2 , and R 3 is a hydrogen atom.

[0024] Examples of the electron-withdrawing group X in the formulae (I) and () include a sulfonic acid group, a carboxylic acid group, a nitro group, a cyano group, a phosphoric acid group, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0025] Examples of the alkylene group include linear, branched, and cyclic alkylene groups such as methylene and ethylene groups. The alkylene group may or may not have a substituent. Examples of the substituent include R 1 Examples of the alkyl group include the alkyl group and halogen atoms exemplified above.

[0026] The arylene group of Y in formula (II) may be, for example, a phenylene group. The arylene group may or may not have a substituent. Examples of the substituent include R 1 Examples of the alkyl group include the alkyl group and halogen atoms exemplified above.

[0027] When Y in formula (II) is a single bond, the aromatic ring and the carbon of the main chain are directly bonded.

[0028] In a preferred embodiment, Y is a single bond.

[0029] The terminals of the compound containing the structural units represented by formulae (I) and (II) are not particularly limited, and may have the above-mentioned substituents or may have a substituent derived from the polymerization initiator.

[0030] The halogen atom retention rate of the styrene-based resin used in this embodiment is 50% or more from the viewpoint of the reactivity change rate. Specifically, the halogen atom retention rate is determined by the following procedure.

[0031] Halogen atom retention measurement Put the styrene resin into a graduated cylinder, add pure water until the styrene resin is completely submerged, and level the top surface of the styrene resin to the 125mL position. Remove the water from the styrene resin thoroughly and transfer it to a pressure-resistant container with a PTFE inner cylinder. Put 50mL of 67% by weight formaldehyde aqueous solution heated to 100°C into the container, stir with a spatula, and then remove the supernatant. After repeating this operation four times, add the formaldehyde aqueous solution up to the top surface of the styrene resin, seal the container, and place it in an oven preheated to 110°C. After 150 days (the time when it was placed in the oven is the starting time, and 24 hours is considered to be one day), remove the container from the oven and cool it to room temperature, then remove the styrene resin from the container and wash it with pure water. The halogen atom content of the styrene resin is measured by SEM-EDX using the following method, and the halogen atom retention rate before and after the long-term test is calculated. (SEM-EDX measurement) (Pretreatment) The sample is vacuum dried at 80℃ and 0.01MPa until the weight does not change, then ground into powder in an agate mortar, fixed to a sample stage, and treated with an osmium coating to make it conductive, to prepare an observation sample. The total of C, O, S, and halogen elements (F, Cl, Br, or I) detected within a 370μm x 250μm area is taken as 100% by weight, and the Cl or Br content (% by weight) is calculated. (SEM-EDX measurement conditions) Equipment: SU-70 (Hitachi High-Tech) Accelerating voltage: 10 kV Detector: SE, YAGBSE, EDX WD:15mm

[0032] Although the mechanism by which the effect of the present invention is exerted by using a styrene-based resin with a halogen atom retention rate of 50% or more is not clear, it is presumed that the halogen atom, which is an electron-withdrawing group, increases the temperature required for desulfonation and stabilizes it. In addition, by making the halogen atom retention rate 50% or more, the detachment of sulfonic acid groups from the styrene-based resin is reduced, the increase in sulfuric acid concentration in the process system is suppressed, and corrosion of equipment, etc. can be suppressed.

[0033] To prevent changes (often decreases) in reactivity, the retention rate of halogen atoms is preferably 60% or more or 70% or more. In one embodiment, the retention rate of halogen atoms is 100% or less, 80% or less, 75% or less, or 70% or less.

[0034] Methods for controlling the retention rate of halogen atoms in the styrene-based resin include, for example, (1) adjusting the amount of a precipitating agent added in polymerization, and (2) adjusting the amount of a crosslinking agent added. Methods (1) and (2) may be used alone or in combination.

[0035] The precipitant has the function of forming a porous structure of the styrene-based resin. Examples of the precipitant include 2-butanol, 2-methyl-2-butanol, and heptane. A preferred precipitant is 2-butanol. The amount of the precipitant added is, for example, 0% by weight or more, 40% by weight or more, 80% by weight or more, 120% by weight or more, or 160% by weight or more, and 200% by weight or less, 160% by weight or less, 120% by weight or less, 80% by weight or less, or 40% by weight or less, based on the total monomer weight in the polymerization.

[0036] The crosslinking agent has the function of forming a three-dimensional network structure of the styrene resin. Examples of the crosslinking agent include divinylbenzene, divinylbiphenyl, and trivinylbenzene. A preferred crosslinking agent is divinylbenzene. The amount of the crosslinking agent added is 5% by weight or more, 10% by weight or more, 15% by weight or more, 30% by weight or more, or 40% by weight or more, and 50% by weight or less, 40% by weight or less, 30% by weight or less, 15% by weight or less, or 10% by weight or less, based on the total monomer weight in the polymerization.

[0037] A preferred method for producing trioxane or methylal in this embodiment will be described. This embodiment includes a step of producing trioxane or methylal by reacting formaldehyde in the presence of a styrene-based resin having an electron-withdrawing group.

[0038] Method for producing trioxane Fig. 1 is a flow diagram showing a schematic example of a process for producing trioxane according to the present embodiment. In the example shown in Fig. 1, a raw material (aqueous formaldehyde solution) is supplied from a raw material supply line 1 to the bottom of a distillation column 2. Then, the liquid inside the distillation column 2 is circulated through a catalyst-packed tank 3 and a reboiler 4 at a predetermined temperature to synthesize trioxane. Then, trioxane, water, formaldehyde and by-products are distilled from a distillation line 5 at the top of the column. Next, the distillate containing trioxane is contacted with an organic solvent to extract trioxane into the organic solvent phase, and the extract is further purified to obtain high-purity trioxane.

[0039] In one specific embodiment, a raw material liquid containing formaldehyde (hereinafter, sometimes simply referred to as "raw material liquid") is supplied to a catalyst-packed tank filled with a styrene-based resin. This styrene-based resin has a predetermined halogen atom retention rate. After the raw material liquid passes through the catalyst-packed tank, the target product trioxane or methylal is obtained. The reacted liquid containing trioxane or methylal is supplied to the bottom of a distillation tower, and trioxane or methylal is separated by distillation. The raw material liquid is supplied to the bottom liquid containing unreacted formaldehyde, and the bottom liquid is circulated between the bottom of the distillation tower and the catalyst-packed tank.

[0040] If the conventional method for producing trioxane or methylal is continued, sulfonic acid groups will be eliminated from the styrene-based resin, reducing the ion exchange capacity and decreasing the yield of the target product. In addition, sulfuric acid derived from the eliminated sulfonic acid groups will accumulate in the process system, increasing the sulfuric acid concentration, which may cause corrosion of equipment, etc.

[0041] Therefore, a part of the raw material to be supplied to the catalyst packed tank is withdrawn outside the process system to maintain the sulfuric acid concentration at a certain level or less. Such withdrawal of a part of the raw material outside the process system is preferably carried out from the bottom liquid of the distillation column.

[0042] When the amount of the raw material liquid containing formaldehyde fed to the bottom of the distillation column is As and the amount of the bottom liquid withdrawn from the process system is Ae, the ratio of Ae to As (Ae / As) may be appropriately adjusted, but from the viewpoint of the reactivity change rate, it is preferably less than 0.10, more preferably 0.08 or less, even more preferably 0.06 or less, and most preferably 0.04 or less. In addition, since the loss of the reaction liquid can be reduced, the ratio (Ae / As) is preferably less than 0.10 from the viewpoint of the productivity of the target product. The ratio (Ae / As) is, for example, 0 or more.

[0043] In one embodiment, the production method of the present embodiment includes a distillation column and a catalyst packed tank, The styrene-based resin is filled in a catalyst-filled tank, The amount of the formaldehyde-containing raw liquid fed to the bottom of the distillation column is As. When the amount of bottom liquid withdrawn outside the process system is Ae, The ratio of Ae to As (Ae / As) is less than 0.10.

[0044] In one embodiment, the amount of bottoms liquid withdrawn outside the process system is the amount of bottoms liquid withdrawn from between the bottom of the distillation column and the catalyst packed tank.

[0045] The ratio (Ae / As) refers to the ratio by weight (g) when the reaction type of the production method is batch or semi-batch. On the other hand, the ratio (Ae / As) refers to the ratio by weight per unit time (g / hr) when the reaction type of the production method is continuous.

[0046] In the preferred method for producing trioxane or methylal in this embodiment, the reaction type is not particularly limited, and examples thereof include a batch type, a semi-batch type, and a continuous type. As the reaction type, a continuous type is preferred.

[0047] The residence time of the raw material liquid in the catalyst-filled tank is not particularly limited and can be, for example, 0.01 to 60 minutes. In a preferred embodiment, the residence time is 50 minutes or less, 40 minutes or less, 30 minutes or less, 20 minutes or less, or 10 minutes or less. In another preferred embodiment, the residence time is 0.01 minutes or more, 0.1 minutes or more, or 1 minute or more.

[0048] In this embodiment, an aqueous formaldehyde solution may be used as a raw material. The concentration of formaldehyde in the aqueous formaldehyde solution is not particularly limited and is, for example, 30 to 80% by weight, and preferably 60 to 75% by weight.

[0049] The content of halogen atoms in the styrene resin before the long-term test is not particularly limited, but the upper limit of the preferred range is 50% by weight, more preferably 40% by weight, and even more preferably 30% by weight. On the other hand, the lower limit of the preferred range is 2% by weight, more preferably 5% by weight, and even more preferably 10% by weight. By containing halogen atoms in the styrene resin, the elimination of sulfonic acid groups from the styrene resin is reduced, the increase in sulfuric acid concentration in the process system is suppressed, and corrosion of equipment, etc. can be suppressed.

[0050] Method for producing methylal In the production of methylal, an aqueous formaldehyde solution and methanol are supplied as raw materials in the production of trioxane, and methylal is synthesized by a process similar to that shown in FIG. 1, and the produced methylal is distilled from the top of the distillation column 2.

[0051] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. The present invention can be modified in various ways without departing from the gist of the present invention. EXAMPLES

[0052] The present invention will be described in detail below with reference to specific examples and comparative examples, but the present invention is not limited to the following examples. The terms and measurement methods for properties in the examples and comparative examples are as follows.

[0053] (1) Halogen atom retention rate (%) Elemental analysis was performed on the styrene-based resin before and after the long-term test using SEM-EDX under the following conditions. (Pretreatment) The styrene resin sample to be measured was vacuum dried at 80°C and 0.01 MPa until the weight did not change. The sample was then ground into powder in an agate mortar. The sample was fixed to a sample stage and subjected to an osmium coating to provide a conductive treatment, and used as an observation sample. The total of C, O, S, and halogen elements (F, Cl, Br, or I) detected within an area of ​​370 μm x 250 μm was taken as 100% by weight, and the Cl or Br content (% by weight) was calculated. (SEM-EDX measurement conditions) Equipment: SU-70 (Hitachi High-Tech) Accelerating voltage: 10 kV Detector: SE, YAGBSE, EDX WD:15mm The halogen atom retention rate (%) of the styrene-based resin was calculated from the following formula. Halogen atom retention rate (%) = "Halogen atom content after test (wt%) / halogen atom content before test (wt%)" x 100

[0054] (Gas chromatography measurement conditions) Equipment: Shimadzu GC2014S Detector: Thermal conductivity detector (TCD) Filler: Porapack T (50 / 80 mesh) manufactured by Japan Waters Inlet temperature: 230℃ Column temperature: 125-180℃ Detection temperature: 230℃ (After holding for 8 minutes, increase the temperature to 180°C at 20°C / min and hold at 180°C for 15 minutes) Carrier gas: Hydrogen

[0055] Long-term testing The styrene resin obtained in the manufacturing example described later was placed in a graduated cylinder, pure water was added until the styrene resin was completely immersed, and the top surface of the styrene resin was leveled to the 125 mL position. The water in the styrene resin was thoroughly removed, and the resin was transferred to a pressure-resistant container with a polytetrafluoroethylene (PTFE) inner cylinder (PTFE inner cylinder sealed heating reactor, model number: YHR-250N, capacity 250 mL). 50 mL of 67 wt% formaldehyde aqueous solution heated to 100°C was placed in the pressure-resistant container, stirred with a spatula, and the supernatant liquid was removed. This operation was repeated four times. Next, the formaldehyde aqueous solution was added up to the top surface of the styrene resin, and the container was sealed. The container was placed in an oven (manufactured by Espec, model number: LCV-233) that had been preheated to 110°C. The time when the container was placed in the oven was used as the starting time, and 24 hours later was considered to be one day, and after 150 days had passed, the container was removed from the oven and cooled to room temperature. Next, the styrene-based resin was taken out of the container and washed with pure water.

[0056] (2) Change in reactivity before and after long-term testing (%) 20 mL of styrene resin was measured and filled into a glass tube before and after the long-term test. A 67 wt% aqueous formaldehyde solution heated to 100°C was continuously fed at 200 g / hr into the glass tube heated to 100°C. 120 mL or more of the aqueous formaldehyde solution was passed through. 1 g of the reaction solution after passing through was sampled, and 10 g of heated pure water was added to make a homogeneous solution. Using the solutions before and after the long-term test, the concentration (wt%) of the target product, trioxane or methylal, was measured by gas chromatography. The reactivity change rate (%) before and after the long-term test was calculated using the following formula. If the reactivity change rate was 75% or more, it was determined that the target reaction activity could be suppressed from decreasing even after long-term use. Reactivity change rate (%) = "Concentration (wt%) of the target product in the presence of styrene-based resin after the test / Concentration (wt%) of the target product in the presence of styrene-based resin before the test" x 100

[0057] (3) Corrosion resistance 150 mL of the styrene resin obtained in the manufacturing example was measured with a graduated cylinder and filled in a catalyst-filled tank with a volume of 300 mL. A 67% by weight aqueous formaldehyde solution heated to 100°C was supplied to the bottom of an Oldershaw distillation tower (15 plates), a catalyst-filled tank was installed in the circulation line (bottom to catalyst-filled tank), and the bottom liquid was circulated at a circulation liquid rate of 1500 g / hr. The bottom was heated with a heater, distilled without reflux, and the distillate was extracted at 150 g / hr to synthesize trioxane. The amount of the aqueous formaldehyde solution supplied to the bottom was controlled so that the level of the bottom liquid was constant. The amount of the bottom liquid extracted was controlled so that the ratio of the amount of the aqueous formaldehyde solution supplied to the bottom was 0.01. A SUS304 test piece was installed in the circulation line of the bottom, and the corrosion state after continuous operation for 10 days was visually judged, and the corrosion resistance was evaluated according to the following criteria. Good: No corrosion observed Fair: Very little corrosion is observed Not acceptable: corrosion observed

[0058] Production Example 1: Production of styrene-based resin 1 Mixture 1 was prepared, consisting of 360 g of chlorostyrene, 65 g of divinylbenzene, 3.8 g of benzoyl peroxide, and 400 g of 2-butanol. Then, an aqueous solution was prepared by dissolving 27 g of sodium chloride and 3 g of ammonium salt of styrene-maleic anhydride copolymer in 722 g of water. Mixture 1 was then added to the aqueous solution to obtain Mixture 2. When Mixture 2 was stirred, the organic phase was dispersed in the form of fine droplets. Mixture 2 was heated to 86-92°C for 6 hours to carry out the polymerization reaction. Then, steam was passed through the reaction mixture to remove the azeotrope of 2-butanol and water. The resulting beads were then filtered, washed with water, and dried at 125°C for 5 hours. 540 g of white opaque polymer in the form of spherical or elliptical particles was obtained. 70 g of the resulting polymer and 800 g of sulfuric acid were heated to 118-122°C for 7 hours with stirring. Then, the mixture was cooled to about 35°C and diluted with water. The solid product was filtered, washed with water to remove water-soluble products, and filtered to obtain 273 g of a sulfonated product, a styrene-based resin (cation exchange resin).

[0059] Production Example 2: Production of styrene-based resin 2 The same treatment as in Production Example 1 was carried out except that chlorostyrene was changed to bromostyrene and 543 g of a polymer was obtained, thereby obtaining 270 g of a styrene-based resin as a sulfonation product.

[0060] Production Example 3: Production of styrene-based resin 3 The same treatment as in Production Example 1 was carried out except that the amount of divinylbenzene was changed to 29 g, thereby obtaining 271 g of a styrene-based resin (cation exchange resin) as a sulfonation product.

[0061] Production Example 4: Production of styrene-based resin 4 The same treatment as in Production Example 1 was carried out except that the amount of divinylbenzene was changed to 29 g and the amount of 2-butanol was changed to 500 g, thereby obtaining 275 g of a styrene-based resin (cation exchange resin) as a sulfonation product.

[0062] Production Example 5: Production of styrene-based resin 5 The same treatment as in Production Example 1 was carried out except that chlorostyrene was changed to styrene and 543 g of a polymer was obtained, thereby obtaining 270 g of a styrene-based resin (cation exchange resin) as a sulfonation product.

[0063] Production Example 6: Production of styrene-based resin 6 The same treatment as in Production Example 1 was carried out except that the amount of divinylbenzene was changed to 18 g and the amount of 2-butanol was changed to 600 g, thereby obtaining 271 g of a sulfonated product, a styrene-based resin (cation exchange resin).

[0064] The styrene-based resins of Production Examples 1 to 6 are each represented by the formula (I) and the formula (II), 1 , R 2 and R 3 was a hydrogen atom, X was -SO3H, Y was a single bond, a was an integer of 1 to 5, and b was an integer of 1 to 4.

[0065] Examples 1 to 4 In Examples 1 to 4, the reactivity change rate and corrosion resistance were evaluated using styrene-based resins 1 to 4 obtained in Production Examples 1 to 4, respectively.

[0066] Example 5 150 mL of the styrene resin 1 synthesized in Production Example 1 was measured with a graduated cylinder and filled in a catalyst-filled tank with a capacity of 300 mL. A 67% by weight aqueous formaldehyde solution heated to 100°C was supplied to the bottom of an Oldershaw distillation tower (15 plates), a catalyst-filled tank was installed in the circulation line (bottom to catalyst-filled tank), and the bottom liquid was circulated at a circulation liquid rate of 1500 g / hr. The bottom was heated with a heater, distilled without reflux, and the distillate was extracted at 150 g / hr to synthesize trioxane. The amount of the aqueous formaldehyde solution supplied to the bottom was controlled so that the level of the bottom liquid was constant. The amount of the bottom liquid extracted was controlled so that the ratio of the amount of the bottom liquid extracted to the amount of the aqueous formaldehyde solution supplied was 0.01. After this state was continued for 1 hour, 1 g of the reaction liquid after passing through the catalyst-packed tank was sampled, and 10 g of heated pure water was added to prepare a homogeneous solution. The concentration (wt%) of the produced trioxane was measured using gas chromatography.

[0067] After the test was conducted for 150 consecutive days, 1 g of the reaction liquid after passing through the catalyst-filled tank was sampled, and 10 g of heated pure water was added to prepare a homogeneous solution. The concentration (wt%) of the produced trioxane was measured using gas chromatography.

[0068] Before the test started, a SUS304 test piece was placed in the bottom circulation line, and the corrosion state after 150 days of continuous testing was visually judged. After 150 days of continuous testing, the styrene resin was removed from the catalyst tank and washed with pure water. The halogen atom retention rate of the styrene resin was measured by SEM-EDX, and the halogen atom retention rate before and after the long-term test was calculated as described above.

[0069] Example 6 In the reactive distillation test of trioxane, the ratio of the amount of bottom liquid withdrawn to the amount of raw material fed was changed to 0.09, and the evaluations were carried out in the same manner as in Example 5.

[0070] Example 7 20 mL of the styrene resin 1 synthesized in Production Example 1 was measured with a graduated cylinder and transferred to a pressure-resistant container with a PTFE inner cylinder (PTFE inner cylinder sealed heating reactor, model number: YHR-250N, capacity 250 mL). 50 mL of a mixture of 30% by weight formaldehyde aqueous solution and methanol (molar ratio of formaldehyde simple substance to methanol is formaldehyde:methanol=1:2) heated to 70°C was placed in the above container, stirred with a spatula, and the supernatant liquid was removed. After repeating this operation four times, the mixture was added up to the position of the top surface of the styrene resin, the container was sealed, and placed in an oven (manufactured by Espec Corporation, model number: LCV-233) previously heated to 110°C. After 150 days (the time when it was placed in the oven is the starting time, and 24 hours later is considered as one day), the container was removed from the oven and cooled to room temperature, and the styrene resin was removed from the container and washed with pure water. The halogen atom content of the styrene resin was measured by SEM-EDX, and the halogen atom retention rate before and after the long-term test was calculated as described above. 20 mL of styrene resin before and after the long-term test was measured with a measuring cylinder and filled into a glass tube. A mixture of 30% by weight aqueous formaldehyde solution and methanol (molar ratio 1:2) heated to 70°C was continuously fed at 200 g / hr into the glass tube heated to 70°C. After passing 120 mL or more of the mixture, 1 g of the reaction liquid after passing was sampled, and 10 g of heated pure water was added to make a homogenous solution, and the concentration (weight %) of the generated methylal was measured using gas chromatography.

[0071] 150 mL of the styrene resin 1 synthesized in Production Example 1 was measured with a graduated cylinder and filled in a catalyst-filled tank with a volume of 300 mL. A mixture of 30% by weight aqueous formaldehyde solution and methanol (molar ratio 1:2) heated to 70°C was supplied to the bottom of an Oldershaw distillation tower (15 stages), a catalyst-filled tank was installed in the circulation line (bottom to catalyst-filled tank), and the bottom liquid was circulated at a circulation liquid rate of 1500 g / hr. The bottom was heated with a heater, distilled without reflux, and the distillate was extracted at 150 g / hr to synthesize methylal. The amount of the mixture supplied to the bottom was controlled so that the level of the bottom liquid was constant. The amount of the bottom liquid extracted was controlled so that the ratio of the amount of the bottom liquid extracted to the amount of the formaldehyde aqueous solution supplied was 0.01. A SUS304 test piece was installed in the bottom circulation line, and the corrosion state after continuous operation for 10 days was visually judged.

[0072] Comparative Example 1 Except for using styrene-based resin 5 instead of styrene-based resin 1, the same procedures as in Example 1 were carried out to carry out the various evaluations.

[0073] Comparative Example 2 Each evaluation was carried out in the same manner as in Example 1, except that the styrene-based resin 1 was replaced with the styrene-based resin 6.

[0074] The evaluation results are shown in Table 1. [Table 1] In the table, "T" in the target product represents trioxane, "M" represents methylal, and the halogen atom represents the type of halogen atom contained in the styrene-based resin (catalyst).

[0075] In Examples 1 to 7, the reactivity change rate and corrosion resistance of the styrene-based resin before and after the test were satisfactory.

[0076] On the other hand, in Comparative Example 1, the styrene resin did not contain halogen atoms, and therefore the reactivity change rate and corrosion resistance were unsatisfactory.

[0077] In Comparative Example 2, the retention rate of halogen atoms was outside the range of the present invention, and therefore the reactivity change rate and corrosion resistance were unsatisfactory. [Industrial Applicability]

[0078] INDUSTRIAL APPLICABILITY The present invention has industrial applicability as a method for producing trioxane or methylal, which suppresses a decrease in the target reaction activity and corrosion of the apparatus even after long-term use. [Explanation of symbols]

[0079] 1: Raw material supply line 2: Distillation tower 3:Catalyst filling tank 4: Reboiler 5: Distillation line

Claims

1. A method for producing trioxane or methylal, comprising the steps of: The method includes a step of reacting formaldehyde in the presence of a styrene-based resin having an electron-withdrawing group to produce trioxane or methylal, The method for producing trioxane or methylal, wherein the styrene-based resin has a substituent containing at least one halogen atom and has a halogen atom retention rate of 50% or more.

2. The method for producing trioxane or methylal according to claim 1, wherein the styrene-based resin is a cation exchange resin.

3. The method for producing trioxane or methylal according to claim 1, wherein the styrene-based resin contains structural units represented by the following formulas (I) and (II): 【Chemistry 1】 (In formulas (I) and (II), R １ , R ２ and R ３ each independently represents a hydrogen atom, an alkyl group, an aryl group, or a halogen atom; X is an electron-withdrawing group, and a plurality of X's may be different from each other; Y is an alkylene group, an arylene group, or a single bond; Each a is independently an integer from 1 to 5; Each b is independently an integer from 1 to 4.

4. A distillation column and a catalyst packed tank are included. The catalyst-filled tank is filled with the styrene-based resin, The amount of the formaldehyde-containing raw material liquid fed to the bottom of the distillation column is represented as As, When the amount of bottom liquid withdrawn outside the process system is Ae, 2. The method for producing trioxane or methylal according to claim 1, wherein the ratio of Ae to As (Ae / As) is less than 0.

10.

5. 5. The method for producing trioxane or methylal according to claim 4, wherein the amount of the bottoms liquid withdrawn outside the process system is the amount of the bottoms liquid withdrawn from between the bottom of the distillation column and the catalyst-packed tank.

6. 2. The method for producing trioxane or methylal according to claim 1, wherein the reaction of formaldehyde in the step is a continuous reaction.

7. 5. The method for producing trioxane or methylal according to claim 4, wherein the residence time of formaldehyde in the catalyst-packed tank is 0.01 to 50 minutes.

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