Method for producing trioxymethylene or methylal

Abstract

The invention relates to a method for producing trioxymethylene or methylal. Provided is a method for producing trioxymethylene or methylal, which suppresses a decrease in the target reaction activity even when used for a long period of time and suppresses a change in the volume of a styrene resin. A method for producing trioxymethylene or methylal, said method comprising a step for producing trioxymethylene or methylal by reacting formaldehyde in the presence of a styrene-based resin having an electron-withdrawing group, the styrene resin has a peak 1 having a peak top in the range of 32 ppm to 57 ppm and a peak 2 having a peak top in the range of 120 ppm to 137 ppm in a solid 13C-NMR spectrum, and the area ratio (A1 / A2) of the area A1 of the peak 1 to the area A2 of the peak 2 is 1.00 to 1.40.

Description

Technical Field

[0001] The present invention relates to a method for producing trioxymethylene or methylal. Background Art

[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 is obtained by oxidizing methylal.

[0003] The production methods of trioxymethylene and methylal both use formaldehyde as a raw material and use an acid catalyst (such as sulfuric acid, benzenesulfonic acid, toluenesulfonic acid, silica-alumina, zeolite, cation exchange resin, etc.), and have common problems.

[0004] As an industrial method for producing trioxymethylene, a method using sulfuric acid is generally used, but there are problems such as corrosion of equipment, etc., and generation of a large amount of by-products and paraformaldehyde.

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

[0006] In addition, as a method with a good selectivity for trioxymethylene, Patent Document 2 discloses a method using a giant network cation exchange resin.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Publication No. 40-12794

[0010] Patent Document 2: Japanese Patent Publication No. 64-11025 Summary of the invention

[0011] Problems to be solved by the invention

[0012] When trioxane is produced using a cation exchange resin, it is preferred to bring a formaldehyde aqueous solution into contact with the cation exchange resin in order to produce trioxane efficiently.

[0013] However, when the formaldehyde aqueous solution is brought into contact with the cation exchange resin and the reaction is continued, there is a problem that the sulfonic acid groups are released from the cation exchange resin, the ion exchange capacity is reduced, and the synthesis activity of trioxymethylene is reduced.

[0014] Furthermore, when the reaction is continued for a long time, the cation exchange resin swells and increases in volume, so there is a problem of overfilling of the cation exchange resin depending on the filling amount of the cation exchange resin.

[0015] Therefore, an object of the present invention is to provide a method for producing trioxymethylene or methylal, in which a decrease in the target reaction activity is suppressed and a volume change of a styrene-based resin is suppressed even when used for a long period of time.

[0016] Means used to solve problems

[0017] The present inventors have conducted intensive studies and have found that the above-mentioned problems can be solved by adjusting the crosslinking degree of the styrene-based resin to a predetermined range, thereby completing the present invention.

[0018] That is, the present invention is as follows.

[0019] [1] A method for producing trioxymethylene or methylal, wherein:

[0020] The production method comprises the step of reacting formaldehyde in the presence of a styrene resin having an electron-withdrawing group to produce trioxymethylene or methylal.

[0021] The styrene resin is in solid 13 The C-NMR spectrum has a peak 1 having a peak top in the range of 32 ppm to 57 ppm and a peak 2 having a peak top in the range of 120 ppm to 137 ppm.

[0022] The area ratio (A1 / A2) of the area A1 of the peak 1 to the area A2 of the peak 2 is 1.00 to 1.40.

[0023] [2] The method for producing trioxymethylene or methylal according to [1], wherein the styrene-based resin is a cation exchange resin.

[0024] [3] The method for producing trioxymethylene or methylal according to [1] or [2], wherein the styrene-based resin contains a structural unit represented by the following formula (I) and a structural unit represented by the following formula (II).

[0025]

[0026] (In formula (I) and formula (II), R 1 , R 2 and R 3 are each independently a hydrogen atom, an alkyl group, an aryl group or a halogen atom;

[0027] X is an electron withdrawing group, and multiple Xs may be different from each other;

[0028] Y is an alkylene group, an arylene group or a single bond;

[0029] a is each independently an integer from 1 to 5;

[0030] b are each independently an integer of 1 to 4.)

[0031] [4] The method for producing trioxymethylene or methylal according to any one of [1] to [3], wherein

[0032] A catalyst filling tank filled with the styrene resin is provided,

[0033] The filling rate of the styrene-based resin in the catalyst filling tank is 20% to 90% of the volume of the filling portion in the catalyst filling tank.

[0034] [5] The method for producing trioxymethylene or methylal according to any one of [1] to [4], wherein the reaction of formaldehyde in the step is a continuous reaction.

[0035] [6] The method for producing trioxymethylene or methylal according to [4], wherein the residence time of formaldehyde in the catalyst-filled tank is 0.01 to 50 minutes.

[0036] [7] The method for producing trioxymethylene or methylal according to any one of [4] to [6], further comprising, before the step (P), passing a formaldehyde aqueous solution in an amount equal to or greater than the amount of the styrene-based resin filled through the catalyst filling tank.

[0037] Effects of the Invention

[0038] According to the present invention, even in long-term use, a decrease in the target reaction activity can be suppressed, and a volume change of the styrene-based resin can be suppressed to produce trioxymethylene or methylal. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The solid of the styrene resin of Preparation Example 5 13 C-NMR spectrum.

[0040] Figure 2 This is a flow chart schematically showing an example of a process for producing trioxymethylene according to the present embodiment.

[0041] Description of symbols

[0042] 1: Raw material supply pipeline

[0043] 2: Distillation Tower

[0044] 3: Catalyst filling tank

[0045] 4: Reboiler

[0046] 5: Distillation pipeline DETAILED DESCRIPTION

[0047] Hereinafter, a mode for implementing the present invention (hereinafter, simply referred to as “this embodiment”) will be described in detail. It should be noted that the present invention is not limited to the following description, and can be implemented with various modifications within the scope of the gist thereof.

[0048] In this embodiment, the process of producing trioxymethylene or methylal by reacting formaldehyde in the presence of a styrene resin having an electron withdrawing group, wherein the styrene resin is in a solid state. 13 The C-NMR spectrum has a peak 1 having a peak top in the range of 32 ppm to 57 ppm and a peak 2 having a peak top in the range of 120 ppm to 137 ppm, and the area ratio (A1 / A2) of the area A1 of the peak 1 to the area A2 of the peak 2 is 1.00 to 1.40. The area ratio (A1 / A2) of 1.00 to 1.40 is excellent in terms of reaction activity and suppression of volume change rate.

[0049] In a preferred embodiment, the styrene-based resin having an electron withdrawing group includes structural units represented by the following formula (I) and formula (II).

[0050]

[0051] In formula (I), R 1 , R 2 and R 3 are each independently a hydrogen atom, an alkyl group, an aryl group or a halogen atom;

[0052] X is an electron withdrawing group, and multiple Xs may be different from each other;

[0053] a is an integer of 1-5 for each independently.

[0054] In formula (II), R 1 , R 2 and R 3 are each independently a hydrogen atom, an alkyl group, an aryl group or a halogen atom;

[0055] X is an electron withdrawing group, and multiple Xs may be different from each other;

[0056] Y is an alkylene group, an arylene group or a single bond;

[0057] a is an integer of 1-5 for each independently.

[0058] b is an integer of 1-4 for each independently.

[0059] As R in formula (I) and formula (II) 1 , R 2 and R 3Examples of the alkyl group include linear, branched, and cyclic alkyl groups. Examples of the linear alkyl group include methyl, ethyl, propyl, and butyl groups. Examples of the branched alkyl group include isopropyl, isobutyl, and tert-butyl groups. Examples of the cyclic alkyl group include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups.

[0060] As R in formula (I) and formula (II) 1 , R 2 and R 3 Examples of the aryl group include phenyl, 1-naphthyl, 2-naphthyl, anthracenyl, and phenanthryl.

[0061] As R in formula (I) and formula (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.

[0062] R in formula (I) and formula (II) 1 , R 2 and R 3 The alkyl group and aryl group may or may not have a substituent. Examples of the substituent include: R 1 The alkyl group and halogen atom exemplified in

[0063] In a preferred embodiment, R 1 , R 2 and R 3 A hydrogen atom.

[0064] Examples of the electron withdrawing group X in formula (I) and formula (II) 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.

[0065] Examples of the alkylene group include linear, branched, and cyclic alkylene groups such as methylene and ethylene. The alkylene group may or may not have a substituent. Examples of the substituent group include: R 1 The alkyl group and halogen atom exemplified in

[0066] Examples of the arylene group of Y in formula (II) include phenylene and the like. The arylene group may or may not have a substituent. Examples of the substituent include: R 1 The alkyl group and halogen atom exemplified in

[0067] When Y in formula (II) is a single bond, the aromatic ring is directly bonded to the carbon of the main chain.

[0068] In a preferred embodiment, Y is a single bond.

[0069] The terminal of the compound including the structural unit represented by Formula (I) and Formula (II) is not particularly limited, and may have the above-mentioned substituent or a substituent derived from a polymerization initiator.

[0070] The styrene resin used in this embodiment is solid 13 The C-NMR spectrum has a peak 1 having a peak top in the range of 32ppm to 57ppm and a peak 2 having a peak top in the range of 120ppm to 137ppm, and the area ratio (A1 / A2) of the area A1 of peak 1 relative to the area A2 of peak 2 is 1.00 to 1.40. In a preferred embodiment, the area ratio (A1 / A2) is 1.39 or less, 1.35 or less, or 1.30 or less. In another preferred embodiment, the area ratio (A1 / A2) is 1.02 or more, 1.05 or more, 1.10 or more, or 1.12 or more. In one embodiment, the area ratio (A1 / A2) is 1.02 to 1.39.

[0071] Figure 1 The solid of the styrene resin of Preparation Example 5 13 C-NMR spectrum. The horizontal axis represents the chemical shift value (ppm), and the vertical axis represents the relative intensity of the signal. The chemical shift value is the value obtained using glycine as an external standard.

[0072] like Figure 1 As shown in FIG. 1 , a peak having a peak top in the range of 32 ppm to 57 ppm is defined as “peak 1”, and a peak having a peak top in the range of 120 ppm to 137 ppm is defined as “peak 2”. Here, it is considered that peak 1 is attributed to aromatic carbon (sometimes including carbon of vinyl substituted on aromatic carbon), and peak 2 is attributed to aliphatic carbon.

[0073] A1 is the area of ​​the spectrum portion of Peak 1 surrounded by the line (baseline) connecting the flat spectrum portions without peaks on the left and right of Peak 1. Similarly, A2 is the area of ​​the spectrum portion of Peak 2 surrounded by the line (baseline) connecting the flat spectrum portions without peaks on the left and right of Peak 2. The area ratio (A1 / A2) can be calculated from the ratio of the peak area of ​​A1 to A2. For example, when the area of ​​Peak 1 A1=10.2 and the area of ​​Peak 2 A2=10.0, the area ratio (A1 / A2) is 10.2 / 10.0=1.02.

[0074] As a method for controlling the area ratio (A1 / A2), there can be mentioned a method of adjusting the crosslinking degree of the styrene resin. For example, there can be mentioned a method of adjusting the amount of the crosslinking agent added during polymerization; a method of adjusting the polymerization temperature in the polymerization process, especially adjusting the stirring speed, or a method of forcibly promoting the polymerization in the process where the polymerization speed slows down in the second half of the polymerization, etc. In addition, there can be mentioned a method of performing a specific treatment before actually using the styrene resin as a catalyst.

[0075] When adjusting the polymerization temperature of the styrene-based resin, the polymerization temperature is preferably adjusted to 78°C to 100°C, and more preferably adjusted to 86°C to 92°C, for example.

[0076] As means for promoting polymerization in the second half of polymerization, there are mentioned: raising the polymerization temperature in the second half of polymerization and adding an additional initiator. The polymerization temperature in the second half of polymerization is preferably adjusted to 88°C to 100°C, more preferably 92°C to 95°C.

[0077] The stirring speed is preferably adjusted to, for example, 20 rpm to 200 rpm, more preferably 50 rpm to 150 rpm.

[0078] As a method for performing a specific treatment before actually using the styrene resin as a catalyst, for example, a method of immersing the styrene resin in a formaldehyde solution can be cited. By removing the electron-withdrawing group that is detached during the period from the manufacture of the styrene resin to the filling of the styrene resin as a catalyst into the catalyst filling tank to the outside of the reaction system for obtaining trioxymethylene or methylal, it is easy to suppress the generation of by-products. Therefore, from the viewpoint of the reactivity change rate, for example, it is preferred that after the styrene resin is filled into the catalyst filling tank and before the step of reacting formaldehyde, a formaldehyde aqueous solution or a mixed solution of water, formaldehyde and methanol is passed through the catalyst filling tank.

[0079] When producing trioxymethylene, the formaldehyde solution passing through the catalyst filling tank is a formaldehyde aqueous solution. The concentration of formaldehyde in the formaldehyde aqueous solution is, for example, 30% to 80% by weight, preferably 60% to 75% by weight.

[0080] When producing methylal, the formaldehyde solution passed through the catalyst filling tank is a mixed solution of formaldehyde and methanol. The mixing ratio is, for example, formaldehyde:methanol in a molar ratio of 1:1 to 1:3, preferably 1:2.

[0081] In one embodiment, before the step of reacting formaldehyde in the presence of a styrene resin having an electron-withdrawing group to produce trioxymethylene or methylal, the process further includes a step (P) of passing a formaldehyde aqueous solution having an amount equal to or greater than but 10 times less than the amount of the styrene resin filled through a catalyst filling tank filled with the styrene resin.

[0082] In the process of making trioxymethylene or methylal by reacting formaldehyde in the presence of a styrene resin having an electron-withdrawing group, it is preferred to use a catalyst-filled tank filled with a styrene resin. The filling rate of the styrene resin in the catalyst-filled tank can be appropriately adjusted, for example, 20% to 95% of the volume of the filled portion in the catalyst-filled tank. In a preferred embodiment, from the viewpoint of the reactivity change rate, the filling rate is 95% or less, 92% or less, 90% or less, 85% or less, or 80% or less. In another preferred embodiment, the filling rate is more than 20%, more than 25%, more than 30%, more than 40%, or more than 50%. In one embodiment, the filling rate is 50% to 92%.

[0083] The reaction mode of the production method of the present embodiment is not particularly limited, and examples thereof include a batch mode, a semi-batch mode, and a continuous mode. As the reaction mode, a continuous mode is preferred.

[0084] The residence time of formaldehyde in the catalyst filling tank is not particularly limited, and can be set to, 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.

[0085] In the present embodiment, a formaldehyde aqueous solution may be used as a raw material. The concentration of formaldehyde in the formaldehyde aqueous solution is not particularly limited, and is, for example, 30% to 80% by weight, preferably 60% to 75% by weight.

[0086] An example of a mode for industrially implementing the present embodiment is as follows.

[0087] Method for producing trioxymethylene

[0088] Figure 2 1 is a flow chart schematically showing an example of a process for producing trioxymethylene according to the present embodiment. Figure 2 In the example of , a raw material (aqueous formaldehyde solution) is supplied from a raw material supply line 1 to the bottom (bottom) of a distillation tower 2. Next, the liquid inside the distillation tower 2 is circulated through a catalyst-filled tank 3 and a reboiler 4 at a predetermined temperature to synthesize trioxane. Then, trioxane, water, formaldehyde, and by-products are distilled out from a distillation line 5 at the top of the tower. Next, the distillate containing trioxane is brought into contact with an organic solvent, trioxane is extracted into the organic solvent phase, and then the extract is purified to obtain high-purity trioxane.

[0089] Method for producing methylal

[0090] In the production of methylal, formaldehyde aqueous solution and methanol are supplied as raw materials in the production of trioxymethylene. Figure 2 In the same process, methylal is synthesized and the produced methylal is distilled off from the top of the distillation tower 2.

[0091] Although the embodiment for implementing the present invention has been described above, the present invention is not limited to the above-described embodiment and various modifications can be made to the present invention without departing from the gist of the present invention.

[0092] Example

[0093] 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. It should be noted that the terms and the measuring methods of the characteristics in the examples and comparative examples are as follows.

[0094] (1) Peak area ratio (A1 / A2)

[0095] For the styrene-based resin used in this embodiment, a solid 13 The area ratio (A1 / A2) was measured by C-NMR under the following conditions.

[0096] Pre-treatment

[0097] A sample of a styrene-based resin to be measured was ground into powder, and vacuum dried at 25° C. and 0.01 MPa until the weight did not change. Next, the sample was placed in a sample tube for solid NMR made of zirconium oxide and measured.

[0098] solid 13 C-NMR measurement conditions

[0099] Device: Avance 500 manufactured by Bruker Japan

[0100] Observation core: 13 C

[0101] Observation frequency: 125.8MHz

[0102] Measurement method: CP / MAS method (pulse program cp)

[0103] 1 H pulse width: 90° pulse

[0104] Contact time: 2000 microseconds

[0105] Waiting time: 5 seconds

[0106] Cumulative times: 1024 times

[0107] Measurement temperature: room temperature (about 25°C)

[0108] Probe: 4mm probe

[0109] MAS speed: 8kHz

[0110] Chemical shift standard: glycine (external standard, 176.03ppm)

[0111] The measurement conditions of the gas chromatography method in the evaluation of the reactivity change rate described later are as follows.

[0112] (Gas chromatography measurement conditions)

[0113] Device: GC2014S manufactured by Shimadzu Corporation

[0114] Detector: Thermal conductivity detector (TCD)

[0115] Filler: Porapak T (50 / 80 mesh) manufactured by Waters Japan

[0116] Inlet temperature: 230°C

[0117] Column temperature: 125℃~180℃

[0118] Detection temperature: 230℃

[0119] (After holding for 8 minutes, increase the temperature to 180°C at 20°C / min and hold at 180°C for 15 minutes)

[0120] Carrier gas: Hydrogen

[0121] (2) Change rate of characteristics before and after long-term testing

[0122] (2-1) Long-term test (batch test)

[0123] The styrene resin obtained in the manufacturing example described later was placed in a measuring cylinder, and pure water was added until the styrene resin was completely immersed, and the upper surface of the styrene resin was leveled and aligned with the 125 mL position. The water of the styrene resin was fully removed, and the styrene resin was transferred to a pressure-resistant container with a polytetrafluoroethylene (PTFE) inner cylinder (PTFE inner cylinder sealed heating reactor, model: YHR-250N, capacity 250 mL).

[0124] Next, the formaldehyde aqueous solution is passed through a pressure-resistant container as a catalyst filling tank. That is, 50 mL of a 67 wt % formaldehyde aqueous solution heated to 100°C is placed in the pressure-resistant container, stirred and mixed with a spatula, and then the supernatant is removed. This operation is repeated 4 times. Next, the formaldehyde aqueous solution is added until the upper surface of the styrene resin is located, and the container is sealed. The container is placed in an oven (manufactured by ESPEC, model: LCV-233) preheated to 110°C. Taking the time when the container is placed in the oven as the starting reference, 24 hours later is regarded as 1 day, and after 150 days, the container is taken out of the oven and cooled to room temperature. Next, the styrene resin is taken out of the container and washed with pure water. In the case of synthesizing methylal, the formaldehyde aqueous solution is replaced with a mixed solution of formaldehyde and methanol (formaldehyde: methanol = 1: 2 (molar ratio)), and the preheating temperature of the oven is replaced with 70°C. Otherwise, the treatment is performed in the same manner.

[0125] (2-2) Volume change rate before and after long-term testing (%)

[0126] The styrene resin before and after the long-term test is placed in a measuring cylinder, pure water is added until the styrene resin is completely immersed, the upper surface of the styrene resin is leveled, the volume of the styrene resin is read from the scale of the measuring cylinder, and the volume change rate is calculated by the following formula. If the volume change rate is 150% or less, it is judged that the product can be manufactured without the problem of overfilling of the styrene resin.

[0127] Volume change rate (%) = "(volume of styrene resin after test, mL) / (volume of styrene resin before test, mL)" × 100

[0128] (2-3) Change rate of reactivity before and after long-term test (%)

[0129] 20 mL of styrene resin before and after the long-term test was measured and filled into a glass tube. A 67 wt % formaldehyde aqueous solution heated to 100°C was continuously supplied to a glass tube heated to 100°C at 200 g / hour. In the case of synthesizing methylal, a mixed solution of formaldehyde and methanol (formaldehyde: methanol = 1: 2 (molar ratio)) was continuously supplied to a glass tube heated to 70°C at 200 g / hour. 1 g of the reaction solution after the liquid was passed was sampled and 10 g of heated pure water was added to make a uniform solution. Using the solution before and after the long-term test, the concentration (wt %) of trioxymethylene or methylal as the target product was determined by gas chromatography. The reactivity change rate (%) before and after the long-term test was calculated by the following formula. If the reactivity change rate is 70% or more, it is judged that the target reaction activity can be suppressed even if it is used for a long time.

[0130] "Reactivity change rate (%) = target product concentration in the presence of styrene resin after the test (weight %) / target product concentration in the presence of styrene resin before the test (weight %) × 100"

[0131] (3) Characteristic change rate before and after long-term operation

[0132] (3-1) Long-term operation (continuous operation)

[0133] 150 mL of the styrene resin obtained in the production example described later was measured with a measuring cylinder and filled into a catalyst filling tank of 300 mL. Then, an aqueous formaldehyde solution in an amount equal to or greater than the filling amount was passed through the catalyst filling tank. Then, a 67 wt % aqueous formaldehyde solution heated to 100° C. was supplied to the bottom of an Oldershaw distillation tower (15 stages). Then, as Figure 2 As shown in FIG. 1 , a catalyst-filled tank is set on a circulation line. Next, a bottom liquid containing a formaldehyde aqueous solution and the synthesized trioxymethylene is circulated at a circulating liquid volume of 1500 g / hour. The bottom is heated by a heater and distillation is performed without reflux. Then, a distillate is taken out at a rate of 150 g / hour, thereby synthesizing trioxymethylene. The supply amount of the formaldehyde aqueous solution to the bottom is controlled so that the liquid level of the bottom liquid is constant.

[0134] (3-2) Volume change rate before and after long-term operation (continuous operation) (%)

[0135] The manufacturing equipment was operated for 150 days, and then the height from the bottom of the catalyst filling tank filled with styrene resin to the upper surface of the styrene resin was measured. This height was taken as the height of the styrene resin filling tank after long-term operation. Then, the volume change rate (%) was calculated by the following formula.

[0136] Volume change rate (%) = "(height of the styrene resin filling tank after long-term operation, cm) / (height of the styrene resin filling tank before long-term operation, cm)" × 100

[0137] (3-3) Change rate of reactivity before and after long-term operation (continuous operation) (%)

[0138] The manufacturing equipment was operated for 150 days, and then 1 g of the reaction solution after passing through the catalyst filling tank was sampled and 10 g of heated pure water was added to make a uniform solution. The concentration (weight %) of the generated trioxymethylene was measured by gas chromatography. The concentration was taken as the target product concentration in the presence of styrene resin after operation. Then, the reactivity change rate (%) before and after long-term operation was calculated by the following formula. If the reactivity change rate is 70% or more, it is judged that the target reaction activity can be suppressed from decreasing even in long-term use and the product is manufactured.

[0139] "Reactivity change rate (%) = target product concentration in the presence of styrene resin after long-term operation (weight %) / target product concentration in the presence of styrene resin before long-term operation (weight %) × 100"

[0140] (3-4) Determination of the retention rate of ion exchange capacity before and after long-term operation (continuous operation)

[0141] The production equipment was operated for 270 days, and then the styrene resin was taken out from the catalyst-filled tank and washed with pure water. The ion exchange capacity of the styrene resin was measured by the following method, and the retention rate of the ion exchange capacity before and after the long-term operation was calculated.

[0142] (Ion exchange capacity determination)

[0143] Measure 20 mL of styrene resin and fill it into the chromatographic tube. Add pure water until it reaches the upper surface of the styrene resin. Set a receiver at the bottom of the chromatographic tube, inject 500 mL of 1 mol / L NaCl solution into the chromatographic tube, slowly open the stopcock of the chromatographic tube, and let the NaCl solution flow at a rate of 500 mL / hour. Close the stopcock after the liquid level of the chromatographic tube reaches the upper surface of the styrene resin. Use a 25 mL full-volume pipette to measure 25 mL of the liquid in the receiver and add 2 drops of phenolphthalein solution as an indicator. Titrate with 0.1 mol / L NaOH solution until it turns light pink and calculate the titration amount. The ion exchange capacity (eq / L) of styrene resin is calculated by the following formula.

[0144] Ion exchange capacity (eq / L) = "0.1 × (factor of 0.1 mol / L NaOH solution) × titration amount (mL)"

[0145] The retention rate (%) of the ion exchange capacity of the styrene-based resin was calculated by the following formula.

[0146] Ion exchange capacity retention rate (%) = "ion exchange capacity after long-term operation (eq / L) / ion exchange capacity before long-term operation (eq / L)" × 100

[0147] (3-5) Change rate of mechanical strength before and after long-term operation (%)

[0148] The production equipment was operated for 270 days, and then the styrene resin was taken out from the catalyst-filled tank and washed with pure water. The mechanical strength of the styrene resin before and after the long-term operation was measured using a load displacement meter under the following conditions.

[0149] (Load-displacement measurement conditions)

[0150] Load displacement measuring instrument: dynamometer (ZTA-5N)

[0151] Test speed: 0.5mm / min

[0152] The vacuum-dried particle-shaped sample is placed on a measuring table and the maximum load value (N) of crushing when compressed from above is measured. About 50 particles are measured and the average value is calculated.

[0153] The mechanical strength change rate (%) was calculated by the following formula: If the mechanical strength change rate was 70% or more, it was determined that the styrene-based resin was produced with reduced mechanical strength even after long-term use.

[0154] Mechanical strength change rate (%) = "(maximum load value after long-term operation) / (maximum load value before long-term operation)" × 100

[0155] Production Example 1: Production of Styrene Resin 1

[0156] A mixture 1 containing 360 g of styrene, 65 g of divinyl benzene and 3.8 g of benzoyl peroxide is prepared. Next, an aqueous solution in which 27 g of sodium chloride and 3 g of ammonium salt of a styrene-maleic anhydride copolymer are dissolved in 722 g of water is prepared. Next, mixture 1 is added to the aqueous solution to obtain mixture 2. When mixture 2 is stirred at 100 rpm, the organic phase is dispersed in the form of fine droplets. Mixture 2 is heated at 88°C for 6 hours to perform a polymerization reaction. Then, 0.5 g of benzoyl peroxide is added to mixture 2, and then heated at 94°C for 1 hour. Next, the generated beads are filtered, washed with water, and dried at 125°C for 5 hours. 421 g of a white opaque polymer is obtained in the form of spherical or elliptical particles. While stirring the obtained polymer 70 g and sulfuric acid 800 g, it is heated at 120°C for 7 hours. Next, the mixture containing the polymer is cooled to about 35°C and diluted with water. The solid product was filtered out, washed with water to remove water-soluble products, and then filtered to obtain 273 g of a styrene-based resin (cation exchange resin) as a sulfonated product.

[0157] Production Example 2: Production of Styrene Resin 2

[0158] A mixture 1 containing 360 g of styrene, 65 g of divinylbenzene, 3.8 g of benzoyl peroxide and 400 g of 2-butanol was prepared. Next, an aqueous solution in which 3 g of an ammonium salt of a styrene-maleic anhydride copolymer was dissolved in 722 g of water was prepared. Next, mixture 1 was added to the aqueous solution to obtain mixture 2. When mixture 2 was stirred at 100 rpm, the organic phase was dispersed in the form of fine droplets. Mixture 2 was heated at 88°C for 6 hours to perform a polymerization reaction. Then, 0.5 g of benzoyl peroxide was added to mixture 2, and then heated at 94°C for 1 hour. Next, steam was passed through the reaction mixture to remove the azeotropic mixture of 2-butanol and water. Next, the generated beads were filtered, washed with water, and dried at 125°C for 5 hours. 421 g of a white opaque polymer was obtained in the form of spherical or elliptical particles. By the same method as in Production Example 1, 270 g of a styrene-based resin (cation exchange resin) as a sulfonation product was obtained.

[0159] Production Example 3: Production of Styrene Resin 3

[0160] In Production Example 2, except that 72 g of divinylbenzene and 500 g of 2-butanol were used and 428 g of a polymer was obtained, the same treatment as in Production Example 2 was carried out to obtain 272 g of a styrene-based resin (cation exchange resin) as a sulfonated product.

[0161] Production Example 4: Production of Styrene Resin 4

[0162] In Production Example 1, except that 162 g of divinylbenzene was used and 517 g of a polymer was obtained, the same treatment as in Production Example 1 was carried out to obtain 271 g of a styrene-based resin (cation exchange resin) as a sulfonated product.

[0163] Production Example 5: Production of Styrene Resin 5

[0164] In Production Example 1, except that 29 g of divinylbenzene was used and 385 g of a polymer was obtained, the same treatment as in Production Example 1 was carried out to obtain 274 g of a styrene-based resin (cation exchange resin) as a sulfonated product.

[0165] Production Example 6: Production of Styrene Resin 6

[0166] In Production Example 1, except that 120 g of divinylbenzene was used and 475 g of a polymer was obtained, the same treatment as in Production Example 1 was carried out to obtain 274 g of a styrene-based resin (cation exchange resin) as a sulfonated product.

[0167] Production Example 7: Production of Styrene Resin 7

[0168] In Production Example 1, except that 29 g of divinylbenzene was used and the polymerization temperature after the addition of benzoyl peroxide was kept at 88° C. to obtain 385 g of a polymer, the same treatment as in Production Example 1 was carried out to obtain 274 g of a styrene-based resin (cation exchange resin) as a sulfonated product.

[0169] Production Example 8: Production of Styrene Resin 8

[0170] The same treatment as in Production Example 2 was carried out except that 500 g of sulfuric acid was used in the sulfonation of Production Example 2 to obtain 270 g of a styrene-based resin (cation exchange resin) as a sulfonation product.

[0171] Production Example 9: Production of Styrene Resin 9

[0172] The same treatment as in Production Example 2 was performed except that 500 g of 2-butanol was used as in Production Example 2 to obtain 421 g of a polymer. The same treatment as in Production Example 2 was performed except that 500 g of sulfuric acid was used as in sulfonation to obtain 268 g of a styrene-based resin (cation exchange resin) as a sulfonation product.

[0173] Production Example 10: Production of Styrene Resin 10

[0174] In Production Example 1, except that 180 g of divinylbenzene was used and 535 g of a polymer was obtained, the same treatment as in Production Example 1 was carried out to obtain 271 g of a styrene-based resin (cation exchange resin) as a sulfonated product.

[0175] Production Example 11: Production of Styrene Resin 11

[0176] In Production Example 1, except that 18 g of divinylbenzene was used and 374 g of a polymer was obtained, the same treatment as in Production Example 1 was carried out to obtain 273 g of a styrene-based resin (cation exchange resin) as a sulfonated product.

[0177] Production Example 12: Production of Styrene Resin 12

[0178] In Production Example 1, except that the polymerization temperature was changed to 78° C. and 383 g of a polymer was obtained, the same treatment as in Production Example 1 was carried out to obtain 135 g of a styrene-based resin (cation exchange resin) as a sulfonated product.

[0179] Production Example 13: Production of Styrene Resin 13

[0180] In Production Example 1, except that benzoyl peroxide was not added to the mixture 2 and 383 g of a polymer was obtained, the same treatment as in Production Example 1 was carried out to obtain 274 g of a styrene-based resin (cation exchange resin) as a sulfonated product.

[0181] Production Example 14: Production of Styrene Resin 14

[0182] In Production Example 1, except that 120 g of divinylbenzene was used, the stirring speed was changed to 20 rpm, and 432 g of a polymer was obtained, the same treatment as in Production Example 1 was carried out to obtain 274 g of a styrene-based resin (cation exchange resin) as a sulfonated product.

[0183] Production Example 15: Production of Styrene Resin 15

[0184] In Production Example 1, except that 120 g of divinylbenzene was used, the polymerization temperature was changed to 78° C., no benzoyl peroxide was added to the mixture 2, the stirring speed was changed to 20 rpm, and 384 g of a polymer was obtained, the same treatment as in Production Example 1 was carried out to obtain 274 g of a styrene-based resin (cation exchange resin) as a sulfonated product.

[0185] Regarding the styrene-based resins of Production Examples 1 to 15, in Formula (I) and Formula (II), R 1 , R 2 and R 3 is a hydrogen atom, X is -SO3H, Y is a single bond, a is an integer of 1 to 5, and b is an integer of 1 to 4. The styrene resin of Production Example 10 has a larger degree of crosslinking than the styrene resin of Production Example 1. The styrene resin of Production Example 11 has a smaller degree of crosslinking than the styrene resin of Production Example 1.

[0186] (Example 1 to Example 10)

[0187] In Examples 1 to 5, 6, 8 and 10, styrene resins 1 to 5, 8, 6 and 7 were used to synthesize trioxymethylene, respectively, and the evaluations described in (2) Property change rate before and after long-term test were performed. In Example 7, the filling amount of the styrene resin in the long-term test was changed to 230 mL, and the evaluations were performed in the same manner as in Example 1. In Example 9, the evaluations were performed in the same manner as in Example 8, except that the operation of removing the supernatant liquid four times in (2-1) the long-term test was not performed. The evaluation results are shown in Table 1.

[0188] (Comparative Example 1 to Comparative Example 7)

[0189] In Comparative Examples 1 to 3, 4, and 5 to 7, styrene resins 10 to 12, styrene resin 7, and styrene resins 13 to 15 were used instead of styrene resin 1, respectively, and in the (2-1) long-term test, the four operations of removing the supernatant were not performed. Each evaluation was performed in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0190] (Example 11)

[0191] The evaluations were performed in the same manner as in Example 1 except that a mixed liquid of formaldehyde and methanol was used as a raw material to synthesize methylal. The evaluation results are shown in Table 1.

[0192] (Comparative Examples 8 to 9)

[0193] In Comparative Examples 8 and 9, each evaluation was performed in the same manner as in Example 11 except that styrene-based resin 10 and styrene-based resin 11 were used, respectively, instead of styrene-based resin 1. The evaluation results are shown in Table 2.

[0194] [Table 1]

[0195]

[0196] In the table, "T" of the target product represents trioxymethylene, and "M" represents methylal.

[0197] [Table 2]

[0198]

[0199] In the table, "T" of the target product represents trioxymethylene, and "M" represents methylal.

[0200] (Example 12 to Example 15)

[0201] In Examples 12, 13, 14, and 15, styrene resin 1, 2, 8, and 9 were used to synthesize trioxane, and the evaluation described in (3) Property change rate before and after long-term operation was performed. The evaluation results are shown in Table 3.

[0202] [Table 3]

[0203]

[0204] In the table, "T" of the target product represents trioxymethylene, and "M" represents methylal.

[0205] In Examples 1 to 15, the decrease in the reactivity change rate of the styrene-based resin before and after the test was suppressed. In addition, in Examples 1 to 15, the volume change rate of the styrene-based resin before and after the test was a satisfactory result.

[0206] On the other hand, since the area ratio (A1 / A2) of Comparative Examples 1 and 3 to 8 exceeded the upper limit of the present invention, the decrease in reaction activity could not be suppressed. In addition, since the area ratio (A1 / A2) of Comparative Examples 2 and 9 was less than the lower limit of the present invention, the volume change of the styrene resin could not be suppressed.

[0207] Industrial Applicability

[0208] The present invention can provide a method for producing trioxymethylene or methylal, in which a decrease in the target reaction activity is suppressed even when used for a long period of time, and a volume change of a styrene-based resin is suppressed.

Claims

1. A method for producing trioxymethylene or methylal, wherein: The production method comprises the step of reacting formaldehyde in the presence of a styrene resin having an electron-withdrawing group to produce trioxymethylene or methylal. The styrene resin is in solid 13 The C-NMR spectrum has a peak 1 having a peak top in the range of 32 ppm to 57 ppm and a peak 2 having a peak top in the range of 120 ppm to 137 ppm. The area ratio (A1 / A2) of the area A1 of the peak 1 to the area A2 of the peak 2 is 1.00 to 1.

40.

2. The method for producing trioxymethylene or methylal according to claim 1, wherein: The styrene resin is a cation exchange resin.

3. The method for producing trioxymethylene or methylal according to claim 1, wherein: The styrene-based resin comprises a structural unit represented by the following formula (I) and a structural unit represented by the following formula (II), In formula (I) and formula (II), R 1 , R 2 and R 3 are each independently a hydrogen atom, an alkyl group, an aryl group or a halogen atom; X is an electron withdrawing group, and multiple Xs may be different from each other; Y is an alkylene group, an arylene group or a single bond; a is each independently an integer from 1 to 5; b is an integer of 1-4 for each independently.

4. The method for producing trioxymethylene or methylal according to claim 1, wherein: A catalyst filling tank filled with the styrene resin is provided, The filling rate of the styrene-based resin in the catalyst filling tank is 20% to 90% of the volume of the filling portion in the catalyst filling tank.

5. The method for producing trioxymethylene or methylal according to claim 1, wherein: The reaction of formaldehyde in the above process is a continuous reaction.

6. The method for producing trioxymethylene or methylal according to claim 4, wherein: The residence time of formaldehyde in the catalyst-filled tank is 0.01 to 50 minutes.

7. The method for producing trioxymethylene or methylal according to claim 4, wherein: The method further includes, before the above step, a step (P) of passing a formaldehyde aqueous solution in an amount equal to or greater than the amount of the styrene-based resin filled through the catalyst filling tank.

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