Method for producing polyalkylene ether glycol di(METH)acrylate

Abstract

To produce polyalkylene ether glycol di(meth)acrylate that exhibits reduced coloration without undergoing a special purification step.SOLUTION: A method for producing polyalkylene ether glycol di(meth)acrylate comprises reacting polyalkylene ether glycol with a (meth)acrylic acid ester in the presence of a phenol compound, wherein the polyalkylene ether glycol is configured such that, when the polyalkylene ether glycol is heated at 135°C for 20 minutes in the presence of the phenol compound, the amount of phenoxy radicals generated is 1.0×1014 spins / g or less per gram of the polyalkylene ether glycol.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a polyalkylene ether glycol di(meth)acrylate. [Background technology]

[0002] (Meth)acrylic acid esters have a molecular structure based on a methacrylic group and exhibit various performances and characteristics. For example, methacrylic resins containing methacrylic acid esters as the main component have excellent properties such as weather resistance, transparency, surface gloss, mechanical strength, and moldability, and are used in many applications such as optical materials, signs, lighting covers, windows for machinery and equipment, aquarium tanks, and various display device components.

[0003] Many applications of (meth)acrylic esters require transparency, and the degree of coloration greatly affects their commercial value. Coloration resulting from (meth)acrylic esters can sometimes be a problem for methacrylic resins. Among (meth)acrylic acid esters, polyalkylene ether glycol di(meth)acrylates are used in optical materials, building materials, etc. because of their optical properties, flexibility, and hydrophilicity or hydrophobicity. However, (meth)acrylic acid esters can become discolored for various reasons during production or polymerization.

[0004] Since polyalkylene ether glycol di(meth)acrylate has a high boiling point and a low melting point, it is difficult to remove colored substances by distillation, crystallization, or the like. Conventionally, a method for reducing the coloring of polyalkylene ether glycol di(meth)acrylate has required a step of removing the coloring causative substances from the solution by adsorption treatment. For example, methods for adsorbing the coloring causative substances have been proposed, such as a method of washing the solution with an alkaline aqueous solution and treating it with activated carbon, activated clay, or a hydrotalcite compound (Patent Document 1), and a method of treating it with activated clay, hydrotalcite, or the like in the presence of moisture (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-80082 [Patent Document 2] JP 2002-338519 A Summary of the Invention [Problem to be solved by the invention]

[0006] A primary object of the present invention is to produce a polyalkylene ether glycol di(meth)acrylate having reduced coloration without undergoing a special purification step. [Means for solving the problem]

[0007] The present inventors have conducted intensive research in light of the problems in the prior art and have found that the above object can be achieved by using a specific polyalkylene ether glycol and reacting the polyalkylene ether glycol with a (meth)acrylic acid ester to produce a polyalkylene ether glycol di(meth)acrylate, thereby completing the present invention.

[0008] That is, the present invention includes the following configurations. [1] A method for producing a polyalkylene ether glycol di(meth)acrylate by reacting a polyalkylene ether glycol with a (meth)acrylic acid ester in the presence of a phenol compound, The polyalkylene ether glycol has a phenoxy radical content of 1.0×10 per gram of polyalkylene ether glycol when heated at 135° C. for 20 minutes in the presence of the phenol compound. 14 A method for producing polyalkylene ether glycol di(meth)acrylate, which is a polyalkylene ether glycol having a molecular weight of 1.0 or less spins / g. [2] The method according to [1], wherein the polyalkylene ether glycol is at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol. [3] The method according to [1] or [2], wherein the phenol compound is at least one selected from the group consisting of 2,6-di-tert-butyl-p-cresol, p-methoxyphenol, 2,6-di-tert-butylphenol, and 6-tert-butyl-2,4-xylenol. [4] The method according to any one of [1] to [3], wherein the reaction between the polyalkylene ether glycol and the (meth)acrylic acid ester is carried out in an environment further comprising a titanium tetraalkoxide or a zirconium tetraalkoxide. [5] The method according to [4], wherein the polyalkylene ether glycol and the (meth)acrylic acid ester are reacted at a temperature of 100 to 150°C. [6] The method according to [4] or [5], comprising reacting the polyalkylene ether glycol with the (meth)acrylic acid ester while passing an oxygen-containing gas through the reaction system. Effect of the Invention

[0009] According to the present invention, it is possible to provide a method for producing a polyalkylene ether glycol di(meth)acrylate in which coloring is suppressed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] As used in the specification and claims, the following terms have the following definitions: The "(meth)acrylate" is selected from "acrylate" and "methacrylate". The term "polyalkylene ether glycol di(meth)acrylate" refers to a diacrylic acid ester or dimethacrylic acid ester of a polyalkylene ether glycol. Specific examples include polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene ether glycol di(meth)acrylate, and the like.

[0011] The method for producing a polyalkylene ether glycol di(meth)acrylate according to the embodiment is a method for producing a polyalkylene ether glycol di(meth)acrylate by reacting a polyalkylene ether glycol with a (meth)acrylic acid ester in the presence of a phenol compound, and uses the following polyalkylene ether glycol (A). (A) The amount of phenoxy radicals generated when polyalkylene ether glycol is heated at 135°C for 20 minutes in the presence of a phenol compound (hereinafter also referred to as the "amount of phenoxy radicals (P)") is 1.0 x 10 per gram of polyalkylene ether glycol. 14 Polyalkylene ether glycol having a spins / g or less.

[0012] [Polyalkylene ether glycol] The polyalkylene ether glycol is a dihydric alcohol having an ether bond, and specific examples thereof include polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol.

[0013] Polyethylene glycol is a compound represented by the following formula (1). HO-(CH2CH2O) m -H (1) In the formula (1), m is an average value, and is preferably a real number of 3 to 400. Since polyethylene glycol is produced by ring-opening polymerization of ethylene oxide and the number of additions varies, m in the formula (1) is the average value of the number of additions. Also, m is a value calculated from the measured value of the hydroxyl value.

[0014] Polypropylene glycol is a compound represented by the following formula (2). HO-(CH(CH2)CH2O) n -H (2) In the formula (2), n is an average value, and is preferably a real number of 3 to 400. Since polyethylene glycol is produced by ring-opening polymerization of propylene oxide and the number of additions varies, n in the formula (2) is the average value of the number of additions. Also, n is a value calculated from the measured value of the hydroxyl value.

[0015] Polytetramethylene ether glycol is a compound represented by the following formula (3). HO-(CH2CH2CH2CH2O) p -H (3) In the formula (3), p is an average value, and is preferably a real number of 3 to 40. Since polytetramethylene ether glycol is produced by ring-opening addition of tetrahydrofuran (THF), and the number of additions varies, p in the formula (3) is the average value of the number of additions. Also, p is a value calculated from the measured value of the hydroxyl value.

[0016] As the polyalkylene ether glycol (A), one type may be used alone, or two or more types may be used in combination. From the viewpoint of being relatively inexpensive and easily available, the polyalkylene ether glycol (A) is preferably at least one selected from polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol.

[0017] Polyalkylene ether glycol often contains an antioxidant to prevent oxidation deterioration during storage. A phenol compound is often used as the antioxidant. The present inventors have found that the amount of radicals generated when a polyalkylene ether glycol containing a phenol compound is heated correlates with the degree of coloration of a polyalkylene ether glycol di(meth)acrylate produced using the polyalkylene ether glycol as a raw material.

[0018] More specifically, when the polyalkylene ether glycol is heated, the peroxide contained in the polyalkylene ether glycol is cleaved to generate a radical. This radical is chemically unstable, but in the presence of a phenolic compound, it is presumed that the generated radical reacts with the phenolic compound to generate a relatively stable phenoxy radical. It is believed that this phenoxy radical is the cause of the coloration of the polyalkylene ether glycol di(meth)acrylate. In the present invention, the amount of phenoxy radicals (P) generated when the polyalkylene ether glycol is heated at 135° C. for 20 minutes is 1.0×10 14 By using the polyalkylene ether glycol (A) having a molecular weight of 0.01 to 0.01 spins / g or less, coloration of the resulting polyalkylene ether glycol di(meth)acrylate is suppressed, and therefore the polyalkylene ether glycol di(meth)acrylate can be produced without a special purification step for reducing coloration.

[0019] The amount of phenoxy radicals (P) generated when polyalkylene ether glycol (A) is heated at 135°C for 20 minutes is 1.0 x 10 14 spins / g or less, preferably 6×10 13 spins / g or less, more preferably 4×10 13 When the amount of phenoxy radicals (P) is equal to or less than the upper limit, the amount of colored substances produced from the phenoxy radicals is reduced, and the coloring of the polyalkylene ether glycol di(meth)acrylate is reduced. The amount of phenoxy radicals (P) generated when polyalkylene ether glycol (A) is heated at 135°C for 20 minutes can be adjusted by the amount of peroxide contained in polyalkylene ether glycol (A). The peroxide contained in polyalkylene ether glycol (A) is generated by autoxidation of the ether bond with oxygen. The amount of this peroxide can be controlled by preventing the polyalkylene ether glycol (A) from coming into contact with oxygen during production and storage after production.

[0020] Phenoxy radicals can be observed using common measuring equipment. For example, they can be observed using an electron spin resonance (ESR) spectrometer. Furthermore, the amount of phenoxy radicals contained in a sample can be quantified based on the intensity observed by ESR. The radicals generated from polyalkylene ether glycol when heated in an environment in which a phenolic compound does not coexist are chemically unstable and have a short life span, and therefore cannot be observed by ESR.

[0021] [Phenol compounds] Examples of phenol compounds include o-cresol, m-cresol, p-cresol, 2-t-butyl-4-methylphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 2-t-butylphenol, 4-t-butylphenol, 2,4-di-t-butylphenol, 2-methyl-4-t-butylphenol, 4-t-butyl-2,6-dimethylphenol, 2,2'-methylene-bis(6-t-butyl-4-methylphenol), 2,2'-methylene-bis(6-t-butyl-4-methylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), and 3,5-di-t-butyl-4-hydroxytoluene. Among these, 2,6-di-tert-butyl-p-cresol, p-methoxyphenol, 2,6-di-tert-butylphenol, and 6-tert-butyl-2,4-xylenol are preferred.

[0022] These phenol compounds are often added as antioxidants to prevent deterioration of polyalkylene ether glycols due to autoxidation caused by oxygen during storage, and are also often added as polymerization inhibitors to prevent polymerization of the (meth)acrylic acid ester or polyalkylene ether glycol di(meth)acrylate when producing the polyalkylene ether glycol di(meth)acrylate by the reaction of the polyalkylene ether glycol with a (meth)acrylic acid ester. From the viewpoint of generating a chemically stable phenoxy radical by reacting with a peroxide, the phenol compound is preferably at least one selected from 2,6-di-tert-butyl-p-cresol, p-methoxyphenol, 2,6-di-tert-butylphenol, and 6-tert-butyl-2,4-xylenol.

[0023] The concentration of the phenol compound contained in the polyalkylene ether glycol is not particularly limited as long as it is an amount that can obtain the effect as an antioxidant for the polyalkylene ether glycol, and is preferably 10 to 1000 ppm by mass, more preferably 50 to 500 ppm by mass, and even more preferably 100 to 300 ppm by mass.

[0024] [(Meth)acrylic acid ester] Examples of the (meth)acrylic acid ester include methyl ester, ethyl ester, propyl ester, butyl ester, etc. of (meth)acrylic acid. Among these, methyl (meth)acrylate is preferred.

[0025] [Method for producing polyalkylene ether glycol di(meth)acrylate] The production method according to the embodiment is not particularly limited except that a polyalkylene ether glycol (A) is used in the transesterification reaction of a polyalkylene ether glycol with a (meth)acrylic acid ester in the presence of a phenol compound, and a known method or a method obtained by improving a known method can be used.

[0026] The transesterification reaction between the polyalkylene ether glycol (A) and (meth)acrylic acid is advantageous in terms of the yield, the absence of chlorine or sulfur-based compounds, the ready availability of raw materials, and the simplicity of the process. The transesterification reaction between the polyalkylene ether glycol (A) and the (meth)acrylic ester is carried out, for example, in the presence of a catalyst while removing the by-produced alcohol by azeotropy with the (meth)acrylic ester.

[0027] The amount of the polyalkylene ether glycol (A) and the (meth)acrylic acid ester used may be in excess of each other, but from the viewpoint of obtaining a polyalkylene ether glycol di(meth)acrylate with higher purity, it is preferable that the (meth)acrylic acid ester is in excess of the polyalkylene ether glycol (A). More specifically, it is preferable that the (meth)acrylic acid ester is 1.01 to 20 times by mole per mole of the polyalkylene ether glycol (A). The molar ratio of the (meth)acrylic acid ester is more preferably 1.1 times by mole or more from the viewpoint of further improving the reaction rate of the polyalkylene ether glycol (A). Also, from the viewpoint of further improving the productivity, it is more preferably 10 times by mole or less.

[0028] Examples of catalysts used in the ester exchange reaction include hydroxides, carbonates, and hydrogen carbonates of alkali metals such as lithium, sodium, and potassium; oxides, hydroxides, and carbonates of alkaline earth metals such as magnesium and calcium; alkali metal alkoxides such as lithium methoxide, sodium methoxide, sodium ethoxide, and potassium t-butoxide; alkali metal amides such as lithium amide, sodium amide, and potassium amide; titanium alkoxides such as tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, and tetra-n-butyl titanate; zirconium alkoxides such as zirconium n-propoxide and zirconium-n-butoxide; and tin compounds such as dibutyltin oxide and dioctyltin oxide.

[0029] Among these catalysts, preferred are alkali metal hydroxides, alkali metal carbonates, and alkali metal alkoxides, which can dissolve the catalyst in the aqueous phase by adding water, and titanium alkoxides and zirconium alkoxides, which can insolubilize the catalyst by adding water and can be easily removed by filtration. Furthermore, titanium alkoxides and zirconium alkoxides are more preferred because they produce less Michael adduct as by-products, titanium tetraalkoxides or zirconium tetraalkoxides are even more preferred, and titanium tetraalkoxides are particularly preferred. The catalyst may be used alone or in combination of two or more kinds.

[0030] The amount of the catalyst used is usually within a range of 0.000001 to 0.1 times by mole per mole of the polyalkylene ether glycol (A). From the viewpoint of improving the reaction rate, the amount of the catalyst used is preferably 0.000005 times by mole or more, and more preferably 0.00001 times by mole or more. Since post-treatment of the catalyst after the reaction is easy and the amount of waste can be reduced, the amount of the catalyst used is preferably 0.05 times by mole or less, and more preferably 0.01 times by mole or less.

[0031] When using a titanium-based catalyst, the catalyst is likely to lose its activity if there is a large amount of water in the reaction system, so it is preferable to dehydrate the liquid containing the polyalkylene ether glycol (A) and the (meth)acrylic acid ester before adding the catalyst. The dehydration method is not particularly limited, but examples thereof include azeotropic dehydration using a (meth)acrylic acid ester or a solvent, and adsorptive dehydration using molecular sieves.

[0032] From the viewpoints of productivity and the energy load required for solvent recovery, the transesterification reaction is preferably carried out without a solvent, but a solvent inert to the reaction can be used as necessary. Examples of the inert solvent include aliphatic hydrocarbons such as hexane, heptane, pentane, cyclohexane, etc., aromatic hydrocarbons such as toluene, xylene, etc., ethers such as diethyl ether, diisopropyl ether, etc., ketones such as diethyl ketone, diisopropyl ketone, etc. Among these, a solvent that easily forms an azeotrope with the by-produced alcohol is preferred. The amount of the solvent used is preferably 1 to 30 parts by mass per part by mass of the polyalkylene ether glycol (A).

[0033] The transesterification reaction is preferably carried out under normal pressure or reduced pressure. From the viewpoint of improving the reaction rate, the reaction temperature is preferably 20° C. or higher, more preferably 40° C. or higher, even more preferably 60° C. or higher, and particularly preferably 100° C. or higher. From the viewpoint of suppressing decomposition, coloration, polymerization, etc. of the (meth)acrylic acid ester and polyalkylene ether glycol di(meth)acrylate, the reaction temperature is preferably 150° C. or lower, more preferably 140° C. or lower, and even more preferably 130° C. or lower. The lower limit and upper limit of the reaction temperature can be arbitrarily combined, and for example, 100 to 150° C. are preferable.

[0034] Examples of reaction methods include a batch method in which all raw materials are charged into a single reactor and the reaction is completed, a continuous method in which raw materials are continuously supplied into a reactor and the reaction is carried out continuously, and a circulation method in which a reactor and a blending tank are provided and the raw materials are reacted in the reactor while being circulated between the reactor and the blending tank.

[0035] When the transesterification reaction is carried out while removing the by-produced alcohol from the system by azeotropy, it is preferable to use a multi-stage distillation column (rectification column). As the distillation column, for example, a packed column using packing such as Raschig rings, Lessing rings, Dixon packings, Paul rings, saddles, Sulzer packings, etc. made of stainless steel, glass, ceramics, etc., and a plate column such as a perforated plate column or a bubble cap column can be used.

[0036] The distillation tower and the reactor may be connected in any of the following ways: the distillation tower is connected to the top of the reactor, the distillation tower is connected to the top of another vessel connected to the reactor, or the reactor is connected to any position from the top to the bottom of the distillation tower. In any of the connection ways, the number of paths between the reactor and the distillation tower may be one or more, and a device such as a heat exchanger may be interposed in between.

[0037] After the transesterification reaction is completed, water is added to the reaction solution as necessary to dissolve or precipitate the catalyst, and the catalyst is removed by a method such as separation or filtration. Excess (meth)acrylic acid ester can be recovered before or after catalyst removal. The (meth)acrylic acid ester can be recovered by heating under normal or reduced pressure to evaporate and condense. Thereafter, the reaction solution is preferably dissolved in an organic solvent and washed with water or an aqueous solution containing a strongly basic compound.

[0038] Examples of the organic solvent include hydrocarbons, ethers, and ester-based solvents. The water used for washing is preferably distilled water or pure water deionized with an ion exchange resin or the like. The strongly basic compound is a Bronsted base, that is, a compound that can receive a proton and has a high ability to receive the proton. Specific examples of the strongly basic compound include hydroxides of alkali metals such as sodium and potassium, and oxides and hydroxides of alkaline earth metals such as magnesium and calcium. Among these, sodium hydroxide or potassium hydroxide is preferred from the viewpoint of solubility in water and ease of handling.

[0039] The amount of the strongly basic compound used is preferably an amount that makes the pH of the aqueous phase during washing equal to or higher than 11. There is no upper limit to the amount used, but from the viewpoint of the amount of wastewater, the amount is preferably 10 times or less, and more preferably 5 times or less, of the amount required for the aqueous phase during washing to reach a pH of 14. The concentration of the aqueous solution containing the strongly basic compound can be appropriately selected within the range of the solubility of the strongly basic compound, but is preferably 2% by mass or more, more preferably 3% by mass or more, from the viewpoint of the amount of wastewater.

[0040] The temperature for washing with the aqueous solution containing a strongly basic compound is preferably 0 to 80° C. From the viewpoint of operability, the washing temperature is more preferably 10° C. or higher, and even more preferably 20° C. or higher. From the viewpoint of suppressing decomposition, polymerization, etc. of the polyalkylene ether glycol di(meth)acrylate, the washing temperature is more preferably 70° C. or lower, and even more preferably 60° C. or lower.

[0041] The time for washing with the aqueous solution containing a strongly basic compound is preferably 10 minutes to 24 hours. When the time is 10 minutes or more, washing can be performed sufficiently, and coloring of the polyalkylene ether glycol di(meth)acrylate is sufficiently reduced. On the other hand, when the time is 24 hours or less, the treatment efficiency is greatly improved. Note that washing can also be performed multiple times using aqueous solutions containing different strongly basic compounds.

[0042] When washing with an aqueous solution containing a strongly basic compound, it is preferable to further wash with water in order to remove the strongly basic compound remaining in the organic layer. The water used for washing is preferably distilled water or pure water deionized with an ion exchange resin or the like. The number of washings is not particularly limited, but from the viewpoint of reducing the amount of wastewater, 1 to 3 times is preferable, since the effect of washing after the fourth time is small.

[0043] In the above-mentioned ester exchange reaction and purification steps, a known polymerization inhibitor can be used. The polymerization inhibitor is preferably a polymerization inhibitor inactive against (meth)acrylic acid esters. For example, quinone-based polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether, and benzoquinone; alkylphenol-based polymerization inhibitors such as 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, 2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol, and 2,4,6-tri-tert-butylphenol; alkylated diphenylamine, N,N'-diphenyl-p-phenylenediamine, and phenol; Examples of the polymerization inhibitors include amine-based polymerization inhibitors such as thiazine, hindered amine-based polymerization inhibitors such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl, and 4-acetamino-2,2,6,6-tetramethylpiperidine-N-oxyl, and copper dithiocarbamate-based polymerization inhibitors such as metallic copper, copper sulfate, copper dimethyldithiocarbamate, copper diethyldithiocarbamate, and copper dibutyldithiocarbamate. These polymerization inhibitors may be used alone or in combination of two or more. The amount of the polymerization inhibitor to be added can be appropriately selected depending on the type and conditions, but is preferably in the range of 0.01 to 10,000 ppm by mass relative to the mass of the reaction liquid.

[0044] In the transesterification reaction and purification step, the polymerization-inhibiting effect may be improved by passing an oxygen-containing gas through the reaction liquid. EXAMPLES

[0045] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description.

[0046] [Abbreviation] BHT: 2,6-di-tert-butyl-p-cresol PTMG: Polytetramethylene ether glycol PTMGM: Polytetramethylene ether glycol dimethacrylate TEMPOL: 4-Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl

[0047] [ESR measurement] An electron spin resonance apparatus (product name: TE200, manufactured by JEOL Ltd.) was used to observe the radicals. Approximately 100 mg of PTMG containing 280 mass ppm of BHT per 1 g was added to a quartz tube with a diameter of 2 mm, which was then placed in the ESR tube and heated to 135°C. During the measurement, Mn was used as an internal standard sample. 2+ A 1000-mT MgO was inserted into the cavity. 20 minutes after the start of heating, ESR measurement was started. Measurements were performed over a range of ±7.5 mT from the center magnetic field over 8 minutes. Simulation analysis was performed using Excel on the obtained spectrum, and the amount of phenoxy radicals (P) was calculated. The following equation, which shows the absorption intensity I' (H) of a Gaussian ESR curve, was used for the simulation.

[0048]

number

[0049] The amount of phenoxy radicals (P) was calculated by integrating the simulated spectrum twice using the piecewise quadrature method in Excel. The signal area was normalized by the absolute area value given by the internal standard sample. Separately, for quantification, measurements were performed with an internal standard sample inserted using a TEMPOL aqueous solution or a TEMPOL / toluene solution with a known radical concentration. The amount of phenoxy radicals (P) was calculated by comparing the area value calculated above based on the TEMPOL concentration and area value.

[0050] [APHA measurement] 1.245 g of potassium chloroplatinate (PtCl4·2KCl) and 1.009 g of cobalt chloride crystal were dissolved in 100 mL of hydrochloric acid, and water was added to make the total volume 1000 mL. 10 mL, 20 mL, 30 mL, 50 mL, and 100 mL of this solution were each diluted to 500 mL to obtain standard solutions of color tone. These standard solutions corresponded to 10, 20, 30, 50, and 100 of APHA, respectively. These standard solutions were placed in a quartz cell with an optical path length of 50 mm, and using an ultraviolet-visible spectrophotometer UV-1700 (trade name, manufactured by Shimadzu Corporation), the absorption at a wavelength of 417 nm was determined, and a calibration curve was created from the APHA values and absorbances of each standard solution. The absorbance of the sample at a wavelength of 417 nm was measured in the same manner, and the color tone of the sample was calculated from the calibration curve. The smaller the APHA value, the more the coloring of the sample is suppressed.

[0051] [Water content] The water content was quantified by the Karl Fischer method using a trace moisture measuring device (product name: CA-200, manufactured by Nitto Seiko Analytic Co., Ltd.).

[0052] <Manufacture of PTMGM> [Example 1] A 300 mL four-necked flask equipped with a rectification column (inner diameter 26.4 mm, theoretical plate number 7), stirring blades, a thermometer, and an air blowing tube was prepared. 70.2 g of PTMG (trade name: PTG-650SN, average molecular weight 650, manufactured by Hodogaya Chemical Co., Ltd., p = 8.8 in the above formula (3)) containing 280 mass ppm of BHT per gram, 129.4 g of methyl methacrylate (MMA), 0.2147 g of sodium hypophosphite, and 0.0467 g of methoxyphenol were placed in the flask. The results of calculating the amount of phenoxy radicals (P) for the PTMG used by ESR measurement are shown in Table 1. The flask was heated in an oil bath while air bubbling and stirring the liquid in the flask. MMA and water were extracted by azeotropy at an internal temperature of 100 to 110°C. The water content of the liquid in the flask was analyzed, and after confirming that the water content was 4 mass ppm, 0.5834 g of tetra-n-butyl titanate was added. Thereafter, the reflux ratio was adjusted so that the internal temperature was 100 to 120°C and the column top temperature was in the range of 64 to 66°C, and the reaction was carried out while extracting MMA and methanol by azeotropy. The reaction liquid was analyzed using a nuclear magnetic resonance apparatus (trade name: JNM-EX270, manufactured by JEOL Ltd.), and after confirming that PTMG was not detected, the internal temperature was lowered to room temperature to terminate the reaction. Next, 6.18 g of pure water and 1.32 g of Celite 545 were added to the reaction solution, and the mixture was stirred at normal pressure and an internal temperature of 67 to 70°C for 1 hour. The mixture was filtered under reduced pressure using a Kiriyama funnel with a filter paper having a pore size of 1 μm. The filtrate was transferred to a flask, and the pressure was reduced at an internal temperature of 24 to 41°C to distill off the MMA. 127 mL of normal hexane and an aqueous solution of sodium hydroxide (concentration 10% by weight) were added to the obtained liquid and stirred, and then the liquid was separated to obtain an organic phase, which was washed three times with 25 g of pure water. The resulting liquid was concentrated using a rotary evaporator and low boiling point components were removed using a pump to obtain a purified PTMGM product.

[0053] [Example 2, Comparative Example 1] PTMGM was produced in the same manner as in Example 1, except that PTMG from a different production lot having a phenoxy radical amount (P) shown in Table 1 was used as PTMG.

[0054] The APHA values ​​measured for the PTMGM obtained in each example are shown in Table 1.

[0055] [Table 1]

[0056] As shown in Table 1, in Examples 1 and 2, which used PTMG with a phenoxy radical amount (P) below the specified value, the APHA of the resulting PTMGM was smaller and coloration was suppressed, compared to Comparative Example 1, which used PTMG with a phenoxy radical amount (P) exceeding the specified value. [Industrial Applicability]

[0057] INDUSTRIAL APPLICABILITY According to the present invention, polytetramethylene ether glycol di(meth)acrylate with little coloring can be produced, which is industrially useful.

Claims

1. A method for producing a polyalkylene ether glycol di(meth)acrylate by reacting a polyalkylene ether glycol with a (meth)acrylic acid ester in the presence of a phenol compound, comprising the steps of: The polyalkylene ether glycol has a phenoxy radical content of 1.0×10 per gram of polyalkylene ether glycol when the polyalkylene ether glycol is heated at 135° C. for 20 minutes in the presence of the phenol compound. １４ The present invention relates to a method for producing polyalkylene ether glycol di(meth)acrylate, which is a polyalkylene ether glycol having a viscosity of 1000 ppm or less.

2. The method according to claim 1 , wherein the polyalkylene ether glycol is at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol.

3. The method according to claim 1, wherein the phenol compound is at least one selected from the group consisting of 2,6-di-tert-butyl-p-cresol, p-methoxyphenol, 2,6-di-tert-butylphenol, and 6-tert-butyl-2,4-xylenol.

4. The method according to claim 1 , wherein the reaction between the polyalkylene ether glycol and the (meth)acrylic acid ester is carried out in an environment further comprising a titanium tetraalkoxide or a zirconium tetraalkoxide.

5. The method according to claim 4, wherein the polyalkylene ether glycol and the (meth)acrylic acid ester are reacted at a temperature of 100 to 150°C.

6. The method according to claim 4, wherein the polyalkylene ether glycol and the (meth)acrylic acid ester are reacted while passing an oxygen-containing gas through the reaction system.

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