Method for producing glycerol monomethacrylate

Abstract

To provide GMA- and CHPM-free glycerol monomethacrylate.SOLUTION: There is provided a method for producing glycerol monomethacrylate, comprising: an acid catalyst treatment step of reacting glycerin with methacrylic acid in the presence of an acid catalyst, mixing the resultant reaction liquid with a basic aqueous solution to neutralize the acid catalyst, thereby obtaining a primary treatment liquid; a by-product removing step of obtaining a secondary treatment liquid after bringing the primary treatment liquid into contact with a water-insoluble non-polar solvent; a target product extraction step of bringing the secondary treatment liquid into contact with a water-insoluble polar solvent and then obtaining a tertiary treatment liquid; an adsorption treatment step of obtaining a quaternary treatment liquid by bringing the tertiary treatment liquid into contact with the hydrotalcite supporting carbonate ions thereby separating both of them; and a solvent removing step of obtaining a purified glycerol monomethacrylate by removing solvent from the quaternary treatment liquid.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing glycerol monomethacrylate, and more particularly to a method for producing a glycerol monomethacrylate compound that is suitably used as a raw material for dental materials. [Background technology]

[0002] In dental treatment, the fabrication of dental restorations (or dental prostheses) such as inlays, onlays, crowns, bridges, and implant superstructures has become commonplace. Computer-aided design (CAD) and computer-aided manufacturing (CAM) systems, which utilize intraoral imaging to machine dental blanks to form dental restorations, are increasingly used. Here, a dental blank refers to a workpiece (also called a mill blank) that can be attached to a milling machine in a CAD / CAM system. Common examples include solid blocks shaped like rectangular parallelepipeds or cylinders, and solid disks shaped like plates or boards. Dental blanks often have a retaining pin attached to secure the workpiece to the milling machine. In such cases, the blank, integrated with the retaining pin, is sometimes referred to as a dental blank.

[0003] As the dental cutting material that constitutes the workpiece for dental cutting blanks, hybrid resin (also known as HR), which is made of a composite material in which inorganic fillers such as silica are dispersed in a resin matrix such as methacrylate resin, is often used because of its high workability (machinability), aesthetics, and strength.

[0004] These hybrid resin-based dental cutting materials are mainly used in the crown area, and when they are used as molar crowns or bridges, higher strength is required. As a dental cutting material that can meet these requirements, a "polyurethane composite material," which is a "composite material of polyurethane resin with a cross-linked structure and inorganic filler," has been proposed.

[0005] For example, Patent Document 1 describes a composition containing a polyurethane component (A) having a number average molecular weight of 1500 to 5000 and having a radical polymerizable group, which is obtained by polyaddition of a diol compound (a1) having one or more radical polymerizable groups with a diisocyanate compound (a2), a radical polymerizable monomer (B); a radical polymerization initiator (C); and a filler (D), and curing the composition by radically polymerizing the radical polymerizable groups of (A) with (B). The cured product obtained not only has a resin matrix portion made of a high-strength polyurethane resin but also has a crosslinked structure, and therefore corresponds to the above-mentioned "polyurethane composite material," and is excellent in strength and water resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2021 / 153446 Brochure [Patent Document 2] Special Publication No. 04-10465 [Patent Document 3] International Publication No. 2015 / 168771 Brochure Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, Patent Document 1 describes that it is preferable to use, as the radically polymerizable diol compound (a1), a compound having a radically polymerizable (meth)acrylate group and having 2 to 4 atoms constituting the main chain of a divalent organic residue interposed between two OH groups, and in the examples, glycerol monomethacrylate (hereinafter sometimes abbreviated as "GLM") is used.

[0008] Therefore, the present inventors produced the composite material using glycerol monomethacrylate, an industrially available radical-polymerizable diol compound. However, they found that trace amounts of substances harmful to the human body were detected in the composite material. Specifically, they found that glycidyl methacrylate (GMA), which has been identified as carcinogenic and mutagenic, and 3-chloro-2-hydroxypropyl methacrylate (CHPM), which has been identified as reproductively toxic and mutagenic, were extracted. Furthermore, to identify the route of contamination by these compounds, the present inventors analyzed glycerol monomethacrylate (GLM) and found that GMA and CHPM were present as impurities. One method for synthesizing GLM involves the ring-opening of epoxy groups via hydration (see Patent Document 2). Furthermore, GMA is generally synthesized using epichlorohydrin and methacrylic acid. Therefore, it is likely that CHPM, a by-product of GMA production, and unreacted GMA remained in the GLM produced by the above method.

[0009] There are problems with using materials that may contain even trace amounts of GMA or CHPM in dental applications that are used in the oral cavity. Therefore, an object of the present invention is to provide a method for producing glycerol monomethacrylate (GLM) that does not contain such compounds, and ultimately to provide a method for producing the polyurethane-based composite material that does not contain GMA or CHPM. [Means for solving the problem]

[0010] The present invention solves the above-mentioned problems, and a first aspect of the present invention is a method for producing glycerol monomethacrylate, comprising: a reaction step of reacting glycerol with methacrylic acid in the presence of an acid catalyst to obtain a reaction solution containing glycerol monomethacrylate (GLM) as a reaction target, reaction by-products including glycerol dimethacrylate, unreacted raw material compounds glycerol and methacrylic acid, and the acid catalyst; and an isolation step of isolating glycerol monomethacrylate from the reaction solution, The isolation step comprises: an acid catalyst treatment step of mixing the reaction solution with a basic aqueous solution to neutralize the acid catalyst and obtain a primary treatment solution consisting of a mixed aqueous solution of both solutions; a by-product removal step of removing the by-products from the first treated solution by selectively extracting them into the water-insoluble, non-polar organic solvent to obtain a second treated solution consisting of an aqueous solution from which the by-products have been removed; a target product extraction step in which glycerol monomethacrylate is selectively extracted from the secondary treatment solution into the water-insoluble polar organic solvent using the water-insoluble polar organic solvent to obtain a third treatment solution comprising an organic solvent solution containing glycerol monomethacrylate and glycerin, methacrylic acid, and the acid catalyst which are inevitably co-extracted, and in which the contents of glycerin and methacrylic acid per 100 parts by mass of glycerol monomethacrylate are 8 parts by mass or less and 7 parts by mass or less, respectively; an adsorption treatment step in which the tertiary treated liquid is contacted with hydrotalcite (hereinafter sometimes abbreviated as "CHT") supporting carbonate ions and then separated to adsorb and remove the acid catalyst and methacrylic acid from the tertiary treated liquid, thereby obtaining a fourth treated liquid consisting of an organic solvent solution from which these components have been removed; and a solvent removal step of removing the solvent from the fourth treated solution to obtain purified glycerol monomethacrylate; The method for producing glycerol monomethacrylate is characterized by comprising the steps of:

[0011] In the above-described method for producing glycerol monomethacrylate (hereinafter also referred to as the "GLM production method of the present invention"), the reaction in the reaction step is preferably carried out without a solvent and in the presence of a polymerization inhibitor. Furthermore, in the solvent removal step, it is preferable to obtain purified glycerol monomethacrylate having a purity of 90 (area%) or more, as defined by the ratio (area%) of the peak area of ​​glycerol monomethacrylate to the total area of ​​detected peaks obtained by high-efficiency liquid chromatography analysis, and in which the contents of the acid catalyst and methacrylic acid are 0.015 parts by mass or less and 6% by mass or less, respectively. Furthermore, it is preferable that the method be for producing glycerol monomethacrylate for use as a raw material for dental polyurethane resins.

[0012] The second aspect of the present invention is a diol compound (a1) having one or more radically polymerizable groups. a step of producing glycerol monomethacrylate represented by the formula (I) by the GLM process of the present invention to obtain purified glycerol monomethacrylate; The purified glycerol monomethacrylate obtained in the above step a first raw material composition preparation step of preparing a first raw material composition containing: a polymerizable monomer (B) having one or more radically polymerizable groups in the molecule and not undergoing a polyaddition reaction with either the diol compound (a1) or the diisocyanate compound; a radical polymerization initiator (C); and a filler (D); The first raw material composition and the diisocyanate compound (a2) are mixed to form the Purified glycerol monomethacrylate and the diisocyanate compound (a2) are subjected to a polyaddition reaction to form a polyurethane component (A) having a number average molecular weight of 1500 to 5000 and having a radical polymerizable group, and a polyurethane composition containing the polyurethane component (A), the polymerizable monomer (B); a radical polymerization initiator (C); and a filler (D), wherein the unreacted Purified glycerol monomethacrylate and / or a second raw material composition preparation step of preparing a second raw material composition which may contain unreacted diisocyanate compound (a2); and a curing step of radically polymerizing the radically polymerizable group in the polyurethane component (A) in the second raw material composition with the polymerizable monomer (B) to cure the second raw material composition, thereby obtaining a polyurethane composite material; ContainsThe method for producing the polyurethane composite material is characterized in that:

[0013] The method for producing the polyurethane composite material of the above form (hereinafter also referred to as the "composite material production method of the present invention") is preferably a method for producing a dental polyurethane composite material using glycerol monomethacrylate obtained by the GLM production method of the present invention for producing glycerol monomethacrylate for use as a raw material for dental polyurethane resin.

[0014] The third aspect of the present invention is a method for producing a material for dental cutting, which comprises the above-mentioned preferred embodiment of the GLM production method of the present invention. [Effects of the Invention]

[0015] According to the production method of the present invention, it is possible to efficiently produce highly pure glycerol monomethacrylate (GLM) that does not contain CHPM or GMA, which are of concern for their reproductive toxicity and mutagenicity. [Brief explanation of the drawings]

[0016] [Figure 1] This figure is a flowchart showing the flow of the GLM manufacturing method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] A known method for synthesizing glycerol monomethacrylate (GLM) without using glycidyl methacrylate (GMA) is the esterification reaction between glycerin and methacrylic acid (see, for example, Patent Document 3). The present inventors then attempted to produce GLM using this synthesis method. As a result, they found that (1) it is difficult to selectively esterify only one hydroxyl group in a glycerin molecule in the esterification reaction, and that significant amounts of by-products are produced, not only the desired monoester but also diesters, triesters, and even condensates of compounds containing hydroxyl groups; (2) these by-products can be relatively easily separated from GLM by extraction with a water-insoluble, nonpolar organic solvent such as toluene, taking advantage of their different hydrophilicity (or polarity) from GLM. However, trace amounts of unreacted glycerin, methacrylic acid, and acid catalyst, especially methacrylic acid and acid catalyst, remain in the aqueous layer, and (3) coloration occurs when a polyurethane composite material is produced using GLM containing methacrylic acid or an acid catalyst. It is thought that trace amounts of methacrylic acid and the acid catalyst remain because they have similar hydrophilic properties to GLM.

[0018] The present invention solves the above-mentioned new problem. Its key feature is that the aqueous layer is subjected to solvent extraction using a water-insoluble polar organic solvent, such as ethyl acetate, to selectively extract the target product, glycerol monomethacrylate (GLM), into the organic layer. The amount of coexisting methacrylic acid in the organic layer is reduced, and the amount of coexisting glycerin is reduced to a certain level relative to the target product, glycerol monomethacrylate, and then the acid catalyst and methacrylic acid are removed by anion adsorption treatment with CHT. This reduces the amount of methacrylic acid to be adsorbed and removes it, thereby reducing the amount of CHT used and preventing the adsorption inhibitory effect of glycerin, thereby improving the adsorption and removal efficiency. It is not known that glycerin inhibits the anion adsorption of the acid catalyst and methacrylic acid to CHT, and the mechanism is unclear. However, it is thought that glycerin swells CHT, facilitating the desorption of the adsorbed components.

[0019] The present invention will be described in detail below. In this specification, unless otherwise specified, the expression "x to y" using numerical values ​​x and y means "greater than or equal to x and less than or equal to y." In such an expression, when a unit is assigned only to the numerical value y, the unit also applies to the numerical value x.

[0020] 1. The GLM manufacturing method of the present invention The method for producing GLM of the present invention includes a reaction step in which specific raw materials are reacted with an acid catalyst to obtain a reaction solution containing a reaction target, reaction by-products, unreacted raw materials, and the acid catalyst, and a specific isolation step in which glycerol monomethacrylate is isolated from the reaction solution. These steps are described below.

[0021] (1) Reaction process In the reaction step, glycerin and methacrylic acid are subjected to an esterification reaction in the presence of an acid catalyst to obtain a reaction liquid containing glycerol monomethacrylate (GLM), which is the reaction target, reaction by-products including glycerol dimethacrylate, unreacted raw material compounds glycerin and methacrylic acid, and the acid catalyst.

[0022] It is preferable that the glycerin and methacrylic acid used as reaction raw materials are both highly pure, for example, 90% by mass or more.

[0023] The acid catalyst is not particularly limited as long as it is an acid that catalyzes an esterification reaction, specifically, a dehydration condensation reaction between glycerin and methacrylic acid, and for example, sulfuric acid, nitric acid, p-toluenesulfonic acid, etc. can be suitably used.

[0024] The esterification reaction can be carried out by heating a mixture containing glycerin, methacrylic acid, and an acid catalyst according to a conventional method. The ratio of glycerin to methacrylic acid is preferably 1.1 to 10 moles, particularly 1.5 to 5.0 moles, of glycerin per mole of methacrylic acid, from the viewpoints of achieving a high conversion rate (reaction rate) based on methacrylic acid and suppressing the formation of by-products such as diesters, triesters, and condensations of compounds having hydroxyl groups. The amount of acid catalyst is typically 0.001 to 0.2 moles, preferably 0.005 to 0.1 moles, per 1.0 mole of methacrylic acid. The reaction is preferably carried out without a solvent, at a reaction temperature of 50 to 100°C for approximately 1.0 to 6.0 hours. The reaction can be carried out by adding a solvent capable of dissolving glycerin and methacrylic acid, but the reaction also proceeds without a solvent. However, when a solvent is added, the reaction system contains the solvent, which increases the volumes of the first treatment solution and the second treatment solution described below, thereby increasing the amounts of the water-insoluble nonpolar organic solvent and the water-insoluble polar organic solvent used. Therefore, from the viewpoint of the amount of organic solvent used in the isolation step, it is preferable to perform the isolation step without a solvent.

[0025] Furthermore, since the raw materials used and the resulting product contain methacrylic groups, it is preferable to carry out the reaction by adding a polymerization inhibitor to prevent polymerization during the reaction. Examples of polymerization inhibitors that are typically used include dibutylhydroxytoluene, hydroquinone, hydroquinone monomethyl ether, and phenothiazine. These polymerization inhibitors are typically added in an amount of 0.001 to 1.0 part by mass, preferably 0.01 to 0.5 part by mass, per 100 parts by mass of methacrylic acid.

[0026] When the reaction is carried out in this manner, the conversion rate (reaction rate) based on methacrylic acid is typically about 60 to 80%, and a reaction solution containing the reaction target, reaction by-products, unreacted raw material compounds glycerin and methacrylic acid, and an acid catalyst is obtained. As a result of investigating the reaction conditions, the inventors found that if the reaction proceeds beyond a conversion rate (reaction rate) of 80% based on methacrylic acid, condensation products between the target substance GLM and other compounds having hydroxyl groups are formed. Therefore, from the perspective of suppressing the formation of condensation products, it is preferable to set the conversion rate (reaction rate) based on methacrylic acid to 60 to 80%. Note that reaction by-products are still produced even when the formation of condensation products is suppressed. The main component is glycerol dimethacrylate, and its amount is typically about 0.1 to 20 parts by mass per 100 parts by mass of GLM. Glycerol trimethacrylate may also be contained, and the amount thereof is usually about 0.01 to 2 parts by mass per 100 parts by mass of GLM.

[0027] For example, when 2 moles of glycerin are reacted with 1 mole of methacrylic acid so that the conversion rate (reaction rate) based on methacrylic acid is about 70%, the reaction solution (hereinafter also referred to as "standard reaction solution") will contain about 100 parts by mass of glycerin, about 20 parts by mass of methacrylic acid, and about 2 parts by mass of by-products such as glycerol dimethacrylate, relative to 100 parts by mass of GLM.

[0028] (2) Analysis method for each component The amount of each component in the reaction solution and each treatment solution described below can be confirmed by the following analytical method.

[0029] That is, glycerin can be quantified by gas chromatography (GC) measurement under the following conditions, for example, using a calibration curve.

[0030] [GC measurement conditions] Detector: Flame ionization detector (FID) Column: Agilent J&W DB-5 (Agilent Technologies) Column temperature: 40 to 250°C.

[0031] Furthermore, methacrylic acid, glycerol monomethacrylate (GLM) and by-products can be quantified, for example, by high performance liquid chromatography (HPLC) measurement under the following conditions.

[0032] [HPLC measurement conditions] Detector: Photodiode array detector 210nm (PDA detector) Column: Inertsil ODS-2 (GL Sciences) Column temperature: 40℃ Developing solvent: acetonitrile / 1 wt% phosphoric acid aqueous solution = 50 / 50 Flow rate: 1ml / min. Furthermore, acid catalysts that can be measured by HPLC, such as p-toluenesulfonic acid, are measured by HPLC, while those that cannot be measured by HPLC but can be measured by ion chromatography, such as sulfuric acid and nitric acid, can be quantified based on ion chromatography under the following conditions, for example.

[0033] [Ion chromatograph measurement conditions] Detector: Electrical conductivity detector Separation column: Dionex IonPac AS18-fast (Thermo Fisher Scientific) Eluent: KOH aqueous solution Eluent flow rate: 1.0mL / min.

[0034] (3) Isolation process In the isolation step, glycerol monomethacrylate is isolated from the reaction mixture. The GLM production method of the present invention is characterized by the inclusion of five isolation steps: an acid catalyst treatment step, a by-product removal step, a target product extraction step, an adsorption treatment step, and a solvent removal step. Each step is described below.

[0035] (3-1) Acid catalyst treatment process In the acid catalyst treatment step, the reaction solution is mixed with a basic aqueous solution to neutralize and inactivate the acidic substances, the acid catalyst and methacrylic acid, as salts, and obtain a primary treatment solution consisting of a mixed aqueous solution of the two solutions. The basic aqueous solution is preferably added so that the pH of the resulting primary treatment solution is 6 to 9. Adding a basic aqueous solution with a pH higher than 9 will hydrolyze the GLM contained in the primary treatment solution, so a pH of 9 or less is preferred. Furthermore, by adjusting the pH to 6 or higher, sufficient amounts of the methacrylic acid and acid catalyst contained in the reaction solution can be neutralized. From the viewpoints of neutralizing the methacrylic acid and acid catalyst and preventing decomposition of GLM, a pH of 7 to 8 is more preferred. The pH can be measured using commonly used pH test paper. At this time, the acid catalyst and methacrylic acid are not completely neutralized to form salts, and residual acid catalyst and methacrylic acid remain in the primary treatment solution. The basic aqueous solution can be added in the appropriate amount, concentration, and volume described below. If a large amount of methacrylic acid is confirmed in the target product extraction process described below, additional washing can be performed to bring the amount of methacrylic acid within the range, and the acid catalyst can also be removed by adding additional CHT.

[0036] As the basic aqueous solution, any aqueous solution using a basic compound can be used without any particular limitation. Examples of suitable basic compounds include sodium hydroxide, potassium hydroxide, potassium carbonate, and sodium carbonate. The concentration of the basic aqueous solution is preferably 0.1 to 30% by mass, particularly 1.0 to 10% by mass, to avoid the generation of by-products during the neutralization treatment. The amount of basic aqueous solution used is preferably 1.0 to 5.0 times, particularly 2.5 to 3.5 times the volume (volume) of the reaction solution, from the viewpoints of workability and the residual rate of glycerin and methacrylic acid in the target product extraction step. The reaction solution and the basic aqueous solution are typically mixed by stirring at room temperature for approximately 0.1 to 1.0 hours. Since the primary treatment solution is an aqueous solution obtained by mixing the reaction solution and the basic aqueous solution, the components contained in the reaction solution remain intact in the primary treatment solution, except for the acid catalyst and methacrylic acid, which are neutralized and converted to salts, etc. Therefore, the primary treatment solution contains not only methacrylic acid but also methacrylate salts. However, since methacrylic acid is measured under conditions in which the developing solvent contains phosphoric acid in the (2) analysis method for each component, methacrylic acid is also converted into methacrylic acid in the HPLC measurement. Therefore, the primary treatment solution and the secondary treatment solution described below contain methacrylic acid and methacrylate salts. Therefore, the amount of each component relative to GLM in the primary treatment solution obtained when the standard reaction solution is used (hereinafter also referred to as the "standard primary treatment solution") does not change.

[0037] (3-2) By-product removal process In the by-product removal step, the primary treatment liquid is mixed with a water-insoluble, non-polar organic solvent, and the by-products are removed from the primary treatment liquid by selectively extracting them into the water-insoluble, non-polar organic solvent, thereby obtaining a secondary treatment liquid consisting of an aqueous solution from which the by-products have been removed.

[0038] The water-insoluble, nonpolar organic solvent is not particularly limited as long as it has a dielectric constant (measurement temperature) of 1.8 (25°C) to 2.4 (25°C) and is separable from the aqueous layer, and examples of such organic solvents include aromatic hydrocarbons such as benzene and toluene, and aliphatic hydrocarbons such as n-hexane, heptane, and cyclohexane. Aromatic hydrocarbons are preferred because they have high solubility in the by-products glycerol dimethacrylate and glycerol trimethacrylate, low solubility in the target product glycerol monomethacrylate, and are easily separable from the aqueous layer (which may be a saturated saline solution containing sodium chloride added).

[0039] The extraction procedure can be suitably carried out by stirring the primary treatment solution and the water-insoluble, nonpolar organic solvent at room temperature for approximately 0.01 to 1.0 hours, separating the solution, and recovering the aqueous layer. The amount of water-insoluble, nonpolar organic solvent used per run is preferably 10 times or less the volume (volume) of the primary treatment solution to increase the residual rate of GLM and efficiently remove by-products. This is because the solubility of the target product, GLM, and the by-product, glycerol dimethacrylate, is similar. If the amount of water-insoluble, nonpolar organic solvent used exceeds 10 times the volume (volume) of the primary treatment solution, not only glycerol dimethacrylate but also GLM will be removed at the same time. Therefore, it is preferable to use an amount of water-insoluble, nonpolar organic solvent 0.1 to 10 times, and particularly 0.1 to 5.0 times, the volume (volume) of the primary treatment solution. Although the extraction may be performed once, it is preferable to repeat the extraction procedure by adding additional water-insoluble, nonpolar organic solvent to the aqueous layer separated in the first extraction procedure to increase the rate of by-product removal. By repeating such extraction procedures, the removal rate of by-products improves, but the recovery rate of GLM gradually decreases. Therefore, it is preferable to limit the number of extractions to 15 times or less, and particularly 10 times or less.

[0040] For example, when the standard primary treatment solution is used and extracted approximately five times with a non-aqueous, non-polar organic solvent having a volume (capacity) 0.3 times that of the primary treatment solution, the residual rate of GLM (the ratio of the amount contained in the secondary treatment solution to the amount contained in the primary treatment solution) is approximately 90%, and the quantitative ratio of each component contained in the resulting secondary treatment solution (hereinafter also referred to as "standard secondary treatment solution") is approximately 100 parts by mass of glycerin, approximately 20 parts by mass of methacrylic acid, and approximately 0.1 parts by mass of by-products such as glycerol dimethacrylate, per 100 parts by mass of GLM.

[0041] (3-3) Target product extraction process In the target product extraction step, the secondary treatment liquid and a water-insoluble polar organic solvent are used to selectively extract glycerol monomethacrylate from the secondary treatment liquid into the water-insoluble polar organic solvent, thereby obtaining a tertiary treatment liquid consisting of an organic solvent solution containing glycerol monomethacrylate and glycerin, methacrylic acid, and the acid catalyst that are inevitably co-extracted, and in which the contents of glycerin and methacrylic acid per 100 parts by mass of glycerol monomethacrylate are 8 parts by mass or less for methacrylic acid and 7 parts by mass or less for glycerin, respectively.

[0042] The amounts of methacrylic acid and glycerin in the tertiary treatment solution must be 8 parts by mass or less and 7 parts by mass or less per 100 parts by mass of glycerol monomethacrylate (GLM). If the amounts exceed these upper limits, the adsorption effect of CHT is inhibited. If the amount of glycerin is 7 parts by mass or less, the effect of adsorption inhibition becomes negligible. However, from the viewpoint of improving the purity of glycerol monomethacrylate, the amount of glycerin contained in the tertiary treatment solution based on the above standard is preferably 4 parts by mass or less, particularly 3 parts by mass or less. On the other hand, although methacrylic acid is also removed in the subsequent adsorption treatment step, from the viewpoint of reducing the amount of CHT used, the amount of methacrylic acid is preferably 5 parts by mass or less, particularly 4 parts by mass or less, based on the above standard. The lower the lower limits of the content of these components, the better. However, the amount of glycerin is typically about 4 parts by mass and the amount of methacrylic acid is about 5 parts by mass based on the above standard. The amount of the acid catalyst contained in the obtained tertiary treatment liquid is preferably 0.4 parts by mass or less relative to 100 parts by mass of glycerol monomethacrylate.

[0043] The water-insoluble polar organic solvent used in the target product extraction step to obtain the tertiary treatment liquid is not particularly limited as long as it has a relative dielectric constant (measurement temperature) of 3.8 (25°C) to 9.5 (25°C) and is an organic solvent that separates from the aqueous layer, and examples of organic solvents that can be used include esters of ethyl acetate and butyl acetate, ethers such as diethyl ether, diisopropyl ether, dibutyl ether, and tetrahydrofuran, and halogenated hydrocarbons such as methylene chloride and chloroform. Esters are preferred because they have high solubility in the target product glycerol monomethacrylate and low solubility in glycerin and methacrylic acid, and are easily separable from the aqueous layer (saturated saline solution).

[0044] The extraction procedure can be carried out by stirring the secondary treatment solution and the water-insoluble polar organic solvent at room temperature for approximately 0.01 to 1.0 hours, followed by separation and recovery of the organic layer. The amount of water-insoluble polar organic solvent used in each extraction is not particularly limited. However, from the viewpoints of workability and the residual rate of glycerin and methacrylic acid in the target product extraction step, it is preferable to use an amount 0.1 to 5.0 times, and particularly 0.5 to 2.5 times, the volume (volume) of the secondary treatment solution. To increase the recovery rate of GLM, a new water-insoluble polar organic solvent may be added to the aqueous layer separated by extraction, followed by the extraction procedure, and the organic layer separated and recovered may be combined. However, because multiple extractions increase the amount of glycerin and methacrylic acid extracted, the number of extractions is usually no more than five, but no more than three, and particularly one, is preferred.

[0045] Because glycerin has a higher affinity for water than GLM, its amount in the extract can be reduced by extraction using a water-insoluble polar organic solvent. Furthermore, if the acid catalyst salt and methacrylic acid salt produced by neutralizing the acid catalyst and methacrylic acid are also highly water-soluble, most of them will remain in the aqueous layer and be removed. Typically, extraction under the above conditions can achieve the desired content of glycerin and methacrylic acid. For example, when extraction is performed approximately three times using the standard secondary treatment solution, the residual rate of GLM (the ratio of the amount contained in the tertiary treatment solution to the amount contained in the primary treatment solution) is approximately 80%, and the resulting tertiary treatment solution (hereinafter also referred to as the "standard tertiary treatment solution") contains approximately 5 parts by mass of glycerin, approximately 6 parts by mass of methacrylic acid, and approximately 0.1 parts by mass of by-products such as glycerol dimethacrylate per 100 parts by mass of GLM.

[0046] However, depending on the charging ratio of the reaction raw materials, the organic layer may contain glycerin and methacrylic acid in amounts exceeding the allowable upper limit, so it is preferable to carry out an analysis to confirm these amounts before proceeding to the next step. If the analysis results show that the contents of glycerin and methacrylic acid are not within the target range, a basic aqueous solution is added to the recovered organic solution to neutralize the methacrylic acid, which is extracted as a methacrylate salt into the aqueous layer together with glycerin, and the organic layer is separated and recovered, and this may be used as the tertiary treatment liquid.

[0047] (3-4) Adsorption treatment process In the adsorption treatment step, the tertiary treatment liquid is brought into contact with CHT and then separated, thereby adsorbing and removing the acid catalyst and methacrylic acid from the tertiary treatment liquid, thereby obtaining a fourth treatment liquid consisting of an organic solvent solution from which these components have been removed.

[0048] CHT means hydrotalcite carrying carbonate ions, and hydrotalcite capable of adsorbing anions between layers of an Mg / Al carbonate-type layered double hydroxide can be suitably used.

[0049] There are no particular restrictions on the amount of CHT used, but from the standpoint of adsorption efficiency and preventing excessive use, the amount can be determined based on the amounts of methacrylic acid and acid catalyst contained in the tertiary treatment liquid after confirming them, and the amount can be determined based on each of these amounts. A total of 1 to 50 parts by mass per 1.0 part by mass of methacrylic acid and 10 to 100 parts by mass per 1.0 part by mass of acid catalyst is preferred, and a total of 1 to 20 parts by mass per 1.0 part by mass of methacrylic acid and 10 to 50 parts by mass per 1.0 part by mass of acid catalyst is more preferred.

[0050] The method of adsorption treatment of the tertiary treatment liquid and CHT is not particularly limited, and the adsorption treatment can be carried out by adding CHT to the tertiary treatment liquid and stirring the mixture.

[0051] The amount of CHT used when filling a container with CHT and flowing the tertiary treatment liquid therein for adsorption treatment is not limited; it is possible to fill and use an excess amount of CHT relative to the methacrylic acid and acid catalyst contained in the tertiary treatment liquid. However, since there is a limit to the amount of methacrylic acid and acid adsorbent that can be removed, it is preferable to check the amount of methacrylic acid and acid catalyst contained in the tertiary treatment liquid, and when the amount of CHT reaches the removable mass parts per mass part of each, it is preferable to fill and use CHT again. The method for separating CHT is also not particularly limited, and separation can be performed by known methods such as filtration. Note that during adsorption treatment, it is preferable to add a dehydrating agent insoluble in a water-insoluble polar organic solvent, such as magnesium sulfate, for dehydration and separate and remove it together with CHT.

[0052] By performing the adsorption treatment under these conditions, the acid catalyst and methacrylic acid can be removed, and the amounts of methacrylic acid and acid catalyst contained in the resulting fourth-stage treatment solution can be set to 5 parts by mass or less of methacrylic acid and 0.010 parts by mass or less of acid catalyst, respectively, per 100 parts by mass of GLM, more preferably 4 parts by mass or less of methacrylic acid and 0.012 parts by mass or less of acid catalyst. For example, when the standard third-stage treatment solution is stirred once, the residual rate of GLM (the ratio of the amount contained in the fourth-stage treatment solution to the amount contained in the first-stage treatment solution) is approximately 80%, and the resulting fourth-stage treatment solution (hereinafter also referred to as the "standard fourth-stage treatment solution") contains approximately 4 parts by mass of glycerin, 4 parts by mass of methacrylic acid, 0.1 parts by mass of by-products such as glycerol dimethacrylate, and 0.010 parts by mass of acid catalyst per 100 parts by mass of GLM.

[0053] However, depending on the amount of acid catalyst remaining in the standard tertiary treatment solution, the amount of acid catalyst per 100 parts by mass of GLM may not be 0.015 parts by mass or less, so it is preferable to confirm the amount of acid catalyst by analysis before performing the solvent removal step. If the analysis shows that the amount of acid catalyst per 100 parts by mass of GLM is not 0.015 parts by mass or less, the acid catalyst can be removed by adding additional CHT and performing the adsorption treatment step again.

[0054] When a dental cutting material is produced using GLM containing methacrylic acid and an acid catalyst in amounts exceeding the above range as the raw material, diol compound (a1), in the method described in Patent Document 1, discoloration occurs. Although the detailed mechanism is unknown, it is speculated that discoloration occurs because the acidic substances, methacrylic acid and the acid catalyst, affect the polyaddition reaction that occurs when obtaining the polyurethane component.

[0055] (3-5) Solvent removal process In the solvent removal step, the solvent is distilled off from the fourth treatment liquid obtained in the adsorption treatment step. The solvent distillation is preferably carried out in the range of 20 to 100°C to prevent polymerization. The pressure may be 0.1 kPa to 50 kPa, depending on the temperature. Furthermore, when distilling off the solvent, it is preferable to add a polymerization inhibitor beforehand. The amount of the polymerization inhibitor added is preferably 0.001 to 1.0 part by mass, more preferably 0.01 to 0.5 part by mass, relative to 100 parts by mass of methacrylic acid used in the reaction step.

[0056] In this way, purified GLM can be obtained which has a purity of 90 (area %) or more, expressed as the ratio (area %) of the peak area derived from glycerol monomethacrylate to the total area of ​​the detected peaks obtained when analyzed by HPLC, and in which the contents of the acid catalyst and methacrylic acid are 0.015 parts by mass or less and 6 parts by mass or less, respectively. Furthermore, since GLM does not contain CHPM or GMA, it can be suitably used as the diol compound (a1) in the method shown in Patent Document 1.

[0057] 2. Composite manufacturing method of the present invention As described above, the purified GLM obtained by the GLM production method of the present invention can be suitably used as the diol compound (a1) in the method for producing a polyurethane composite material shown in Patent Document 1. Hereinafter, the composite material production method of the present invention, in which the purified GLM is used in the production of the polyurethane composite material, will be described.

[0058] The composite material manufacturing method of the present invention includes the following steps of preparing a first raw material composition, preparing a second raw material composition, and curing.

[0059] a step of obtaining purified glycerol monomethacrylate from glycerol monomethacrylate, which is the diol compound (a1) having one or more radical polymerizable groups, by the GLM production method of the present invention; First raw material composition preparation step: The purified glycerol monomethacrylate obtained in the above step a step of preparing a first raw material composition comprising: a polymerizable monomer (B) having one or more radically polymerizable groups in the molecule and not undergoing a polyaddition reaction with either the diol compound (a1) or the diisocyanate compound; a radical polymerization initiator (C); and a filler (D). Second raw material composition preparation step: The first raw material composition and a diisocyanate compound (a2) are mixed to prepare the second raw material composition. Purified glycerol monomethacrylate and the diisocyanate compound (a2) are subjected to a polyaddition reaction to form a polyurethane component (A) having a number average molecular weight of 1500 to 5000 and having a radical polymerizable group, and a polyurethane composition containing the polyurethane component (A), the polymerizable monomer (B); a radical polymerization initiator (C); and a filler (D), wherein the unreacted Purified glycerol monomethacrylate and / or a second raw material composition preparation step of preparing a second raw material composition which may contain unreacted diisocyanate compound (a2); Curing step: A step of radically polymerizing the radically polymerizable group in the polyurethane component (A) in the second raw material composition with the polymerizable monomer (B) to cure the second raw material composition, thereby obtaining a polyurethane composite material.

[0060] The present invention is characterized in that the purified GLM obtained by the GLM production method of the present invention is used as the diol compound (a1), thereby achieving the effect that the resulting polyurethane composite material does not contain CHPM and GMA, which are feared to be harmful.

[0061] Other than the above-mentioned features, the composite production method of the present invention is not particularly different from the production method for polyurethane composite materials shown in Patent Document 1, and the polymerizable monomer (B), diisocyanate compound (a2), radical polymerization initiator (C), and filler (D) that are specified as usable in Patent Document 1 can be used without any particular restrictions. For example, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, etc. can be suitably used as the polymerizable monomer (B), m-xylylene diisocyanate can be suitably used as the diisocyanate compound (a2), t-butyl peroxylaurate can be suitably used as the radical polymerization initiator (C), and silica-zirconia can be suitably used as the filler (D).

[0062] Furthermore, the conditions and procedures disclosed in Patent Document 1 can be used as they are for the first raw material composition preparation step, the second raw material composition preparation step, and the curing step. For example, with regard to the compounding ratio, it is preferable that the molar ratio of the diisocyanate compound (a2) to the radical polymerizable diol compound (a1):GLM (a2 / a1 molar ratio) is 1.0, the proportion of the mass of (B) to the total mass of (a1), (a2), and (B) is about 20 to 80 mass%, and the proportion of (D) in (a1), (a2), (B), (C), and (D) is about 60 to 85 mass%.

[0063] The polyurethane composite material produced by the composite material production method of the present invention can be suitably used as a dental polyurethane composite material for dental cutting processing materials. [Example]

[0064] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0065] 1. Manufacturing of GLM Example 1 (1) Reaction step: 22.1 g (0.24 mol) of glycerin, 10.3 g (0.12 mol) of methacrylic acid, 0.47 g (0.0048 mol) of p-toluenesulfonic acid monohydrate as an acid catalyst, and 0.13 g (0.00048 mol) of dibutylhydroxytoluene as a polymerization inhibitor were charged into a recovery flask equipped with a condenser, thermometer, and stirrer, and the mixture was heated in an oil bath to 90°C while stirring. The reaction was then carried out for 3 hours. After the reaction was completed, the recovery flask was removed from the oil bath and cooled to room temperature to obtain a reaction liquid.

[0066] (2) Acid Catalyst Treatment Step: 60 ml of a 5% by mass aqueous solution of potassium carbonate, a basic aqueous solution, was added to the reaction solution and neutralized by stirring at room temperature for 10 minutes to obtain a primary treatment solution. Analysis of the primary treatment solution confirmed that the conversion rate of the methacrylic acid base in the reaction was 70%. Furthermore, it was confirmed that the primary treatment solution (and the reaction solution) contained, in addition to the target product, glycerol monomethacrylate (GLM), 100 parts by mass of glycerin, 20 parts by mass of methacrylic acid, and 2 parts by mass of by-products (specifically, 1.5 parts by mass of glycerol dimethacrylate and 0.5 parts by mass of glycerol trimethacrylate) per 100 parts by mass of GLM. The analysis was performed using the analytical methods and conditions described in "(2) Analysis Method of Each Component" in "1. GLM Production Method of the Present Invention."

[0067] (3) By-product removal step: 30 ml of toluene, a water-insoluble, non-polar organic solvent, was added to the obtained primary treatment liquid and stirred. The toluene was then discarded and the aqueous layer was recovered. This operation was repeated five times to obtain a secondary treatment liquid. Analysis of the obtained secondary treatment liquid confirmed that, in addition to GLM, it contained 100 parts by mass of glycerin, 20 parts by mass of methacrylic acid, and 0.1 parts by mass of by-products per 100 parts by mass of GLM.

[0068] (4) Target product extraction step: 120 ml of ethyl acetate, a water-insoluble polar organic solvent, was added to the recovered second-stage treatment liquid and stirred. The ethyl acetate was then recovered. 120 ml of ethyl acetate was added to the remaining aqueous layer and stirred, and the same procedure was repeated three times to obtain a third-stage treatment liquid. Analysis of the obtained third-stage treatment liquid confirmed that it contained 5 parts by mass of methacrylic acid, 4 parts by mass of glycerin, and 0.1 parts by mass of by-products per 100 parts by mass of GLM.

[0069] (5) Adsorption Treatment Step: 0.01 g of dibutylhydroxytoluene, a polymerization inhibitor, was added to the obtained third-stage treated liquid, followed by 3.5 g of CHT, and the mixture was stirred at room temperature for 30 minutes. Subsequently, 7.0 g of magnesium sulfate was added as a dehydrating agent, and the mixture was stirred at room temperature for 10 minutes. The CHT and magnesium sulfate were then filtered to obtain a fourth-stage treated liquid. Analysis of the obtained fourth-stage treated liquid confirmed that it contained, per 100 parts by mass of GLM, 4 parts by mass of methacrylic acid, 4 parts by mass of glycerin, 0.1 parts by mass of by-products, and 0.010 parts by mass of acid catalyst. The CHT used was Kyoward 500 (manufactured by Kyowa Chemical Industry Co., Ltd.: MgO content 37.8% by mass, Al2O3 content 15.8% by mass, chemical composition: Mg6Al2(OH) 16 CO3) was used.

[0070] (6) Solvent Removal Step: Ethyl acetate was distilled off from the resulting fourth-treatment solution at 40°C under a reduced pressure of 6 kPa to obtain purified glycerol monomethacrylate. As a result of HPLC analysis, the purity of the purified glycerol monomethacrylate was 93%, and the content of methacrylic acid was 4 parts by mass and the content of acid catalyst was 0.010 parts by mass per 100 parts by mass of the resulting purified glycerol monomethacrylate. These analytical results are summarized in Table 1.

[0071] [Table 1]

[0072] Example 2 The same procedures as in Example 1 were carried out except that in the acid catalyst treatment step (2) of Example 1, the basic aqueous solution was changed to 30 ml of a 5 wt % aqueous potassium carbonate solution. The purities of methacrylic acid and glycerin in the third treatment solution, methacrylic acid and acid catalyst in the fourth treatment solution, and purified glycerol monomethacrylate, as well as the amounts of methacrylic acid and acid catalyst contained therein, are shown in Table 1.

[0073] Example 3 The same procedure as in Example 1 was carried out except that ethyl acetate was added and stirred only once in step (4) of extracting the target product in Example 1. The purities of methacrylic acid and glycerin in the third treatment solution, methacrylic acid and acid catalyst in the fourth treatment solution, and purified glycerol monomethacrylate, as well as the amounts of methacrylic acid and acid catalyst contained therein, are shown in Table 1.

[0074] Example 4 The same procedures as in Example 1 were carried out except that in the acid catalyst treatment step (2) of Example 1, the basic aqueous solution was changed to 90 ml of a 4 wt % aqueous potassium carbonate solution. The purities of methacrylic acid and glycerin in the third treatment solution, methacrylic acid and acid catalyst in the fourth treatment solution, and purified glycerol monomethacrylate, as well as the amounts of methacrylic acid and acid catalyst contained therein, are shown in Table 1.

[0075] Comparative Example 1 A reaction solution was obtained in the same manner as in (1) reaction step in Example 1, and the reaction solution was diluted with 60 ml of ethyl acetate, omitting (2) acid catalyst treatment step and (3) by-product removal step. 3.5 g of CHT was then added to the diluted solution, and the mixture was stirred at room temperature for 10 minutes. After stirring, the diluted solution was checked and found to be swollen, making it impossible to separate the CHT.

[0076] Comparative Example 2 The (1) reaction step and (2) acid catalyst treatment step were carried out in the same manner as in Example 1 to obtain a primary treatment solution. Subsequently, the (2) acid catalyst treatment step and the (3) by-product removal step were omitted, and 0.01 g of dibutylhydroxytoluene was added to the primary treatment solution, followed by 3.5 g of CHT, and the mixture was stirred at room temperature for 10 minutes. After stirring, the neutralized aqueous solution was checked to find that the CHT had swollen, making it impossible to separate the CHT.

[0077] Comparative Example 3 The (1) reaction step, (2) acid catalyst treatment step, (3) by-product removal step, and (4) target product extraction step were performed in the same manner as in Example 1 to obtain a tertiary treatment solution. Thereafter, the (5) adsorption treatment step was omitted, and the solvent was removed in the same manner as in the (6) solvent removal step. The purities of methacrylic acid, glycerin, and purified glycerol monomethacrylate in the tertiary treatment solution, as well as the amounts of methacrylic acid and acid catalyst contained therein, are shown in Table 1.

[0078] Comparative Example 4 The (1) reaction step, (2) acid catalyst treatment step, (3) by-product removal step, and (4) target product extraction step were performed in the same manner as in Example 2 to obtain a tertiary treatment solution. Thereafter, the (5) adsorption treatment step was omitted, and the solvent was removed in the same manner as in the (6) solvent removal step. The purities of methacrylic acid, glycerin, and purified glycerol monomethacrylate in the tertiary treatment solution, as well as the amounts of methacrylic acid and acid catalyst contained therein, are shown in Table 1.

[0079] Comparative Example 5 The (1) reaction step, (2) acid catalyst treatment step, (3) by-product removal step, and (4) target product extraction step were performed in the same manner as in Example 3 to obtain a tertiary treatment solution. Thereafter, the (5) adsorption treatment step was omitted, and the solvent was removed in the same manner as in the (6) solvent removal step. The purities of methacrylic acid, glycerin, and purified glycerol monomethacrylate in the tertiary treatment solution, as well as the amounts of methacrylic acid and acid catalyst contained therein, are shown in Table 1.

[0080] Comparative Example 6 The (1) reaction step, (2) acid catalyst treatment step, (3) by-product removal step, and (4) target product extraction step were performed in the same manner as in Example 4 to obtain a tertiary treatment solution. Thereafter, the (5) adsorption treatment step was omitted, and the solvent was removed in the same manner as in the (6) solvent removal step. The purities of methacrylic acid, glycerin, and purified glycerol monomethacrylate in the tertiary treatment solution, as well as the amounts of methacrylic acid and acid catalyst contained therein, are shown in Table 1.

[0081] Comparative Example 7 A 500 ml four-neck flask equipped with a thermometer, stirrer, reflux condenser, and dropping funnel was charged with 270 g (15 mol) of water, 0.1 g (0.001 mol) of sulfuric acid, and 0.014 g of hydroquinone. The reaction was continued for 5 hours at 70-80°C while 142.2 g (1 mol) of glycidyl methacrylate was added dropwise, followed by an additional hour. The temperature was then lowered to 30°C, and water was added, followed by 1.4 g of CHT. The mixture was then stirred for 30 minutes. The CHT was then removed by filtration, and 0.014 g of hydroquinone was added. The mixture was then dehydrated at 40°C under a reduced pressure of 0.4 kPa. The resulting reaction product weighed 153.8 g. The purity of glycerol monomethacrylate, its methacrylic acid content, and the amount of acid catalyst are shown in Table 1.

[0082] 2. Production and evaluation of polyurethane composite materials using GLM Examples 5 to 8 and Comparative Examples 8 to 12 The purified GLM obtained in Examples 1 to 4 and Comparative Examples 3 to 7 was used as the diol compound (a1), and polyurethane composite materials were produced by carrying out the first raw material composition preparation step, the second raw material composition preparation step, and the curing step as described below.

[0083] First, the various materials used and their amounts are shown below.

[0084] Diol compound (a1): GLM 10.63 parts by mass Diisocyanate compound (a2): m-xylylene diisocyanate: 12.50 parts by mass Polymerizable monomer (B): ethylene glycol dimethacrylate: 5.79 parts by mass Radical polymerization initiator (C): tert-butyl peroxylaurate: 0.08 parts by mass Filler (D): silica-zirconia (average particle size: 0.4 μm, surface-treated with 3-(trimethoxysilyl)propyl methacrylate): 49.70 parts by mass and silica-titania (average particle size: 0.08 μm, surface-treated with 3-(trimethoxysilyl)propyl methacrylate): 21.30 parts by mass.

[0085] The production method is described below. First, the above (a1), (B), (C), and (D) were mixed in the aforementioned ratios to prepare a first raw material composition. Next, the above (a2) was added to the first raw material composition in the amount specified above, and the mixture was kneaded. The mixture was then left to stand in an incubator at 37°C for 168 hours to undergo a polyaddition reaction, yielding a second raw material composition. The resulting second raw material composition was then poured into a mold (12 mm long x 18 mm wide x 14 mm thick) and subjected to radical polymerization at 120°C for 15 hours under nitrogen pressure (0.35 MPa), yielding a polyurethane composite material.

[0086] During the process, THF was added to a sample of the second raw material composition, and the mixture was centrifuged. The supernatant was filtered and then subjected to GPC measurement to determine the polystyrene-equivalent number average molecular weight of the polyurethane component (A). In all examples, the number average molecular weight was 3,500.

[0087] The polyurethane composite material thus obtained was evaluated for extractability and coloration as follows. The results are shown in Table 2. In the table, "↑" means "same as above."

[0088] [Extract evaluation] 2.0 g of the obtained polyurethane composite material was pulverized, 50 ml of acetone was added, and the mixture was stirred at room temperature. The extract was then filtered to remove the polyurethane composite material, and the resulting extract was concentrated to 2.0 ml. The resulting extract was measured by GCMS under the measurement conditions shown below to confirm the presence of GMA and CHPM.

[0089] [GCMS measurement conditions] Measurement equipment: Agilent J&WGCMS (Agilent Technologies) Column: DB-WAX Injection temperature: 260℃ Column temperature: 40℃ to 250℃ at 10℃ / min Detection method: SIM mode. Molecular weight: GMA(69) CHPM(69).

[0090] [Coloring evaluation] The coloration of the polyurethane composite material was evaluated by visually observing the appearance of the polyurethane composite material and the cross section obtained by cutting the polyurethane composite material into approximately two equal parts. Whether the polyurethane composite material was colored or not was determined by observing the color change on the surface and cross section of the polyurethane composite material compared with the polyurethane composite material obtained in Comparative Example 12. If no color change was observed, it was marked as ◯, and if a color change was observed, it was marked as ×.

[0091] [Table 2]

Claims

1. A reaction step of reacting glycerin with methacrylic acid in the presence of an acid catalyst to obtain a reaction solution containing reaction by-products including glycerol monomethacrylate and glycerol dimethacrylate as the reaction target, unreacted raw material compounds glycerin and methacrylic acid, and the acid catalyst; and an isolation step of isolating glycerol monomethacrylate from the reaction solution; 1. A method for producing glycerol monomethacrylate, comprising: The isolation step comprises: an acid catalyst treatment step of mixing the reaction solution with a basic aqueous solution to neutralize the acid catalyst and obtain a primary treatment solution consisting of a mixed aqueous solution of both solutions; a by-product removal step of removing the by-products from the primary treated solution by selectively extracting them into the non-water-soluble, non-polar organic solvent to obtain a secondary treated solution consisting of an aqueous solution from which the by-products have been removed; a target product extraction step in which glycerol monomethacrylate is selectively extracted from the secondary treatment solution into the water-insoluble polar organic solvent using the water-insoluble polar organic solvent to obtain a third treatment solution comprising an organic solvent solution containing glycerol monomethacrylate and glycerin, methacrylic acid, and the acid catalyst which are inevitably co-extracted, and in which the contents of glycerin and methacrylic acid per 100 parts by mass of glycerol monomethacrylate are 8 parts by mass or less and 7 parts by mass or less, respectively; an adsorption treatment step of contacting the tertiary treated liquid with hydrotalcite supporting carbonate ions and then separating the two to adsorb and remove the acid catalyst and methacrylic acid from the tertiary treated liquid, thereby obtaining a fourth treated liquid consisting of an organic solvent solution from which these components have been removed; and a solvent removal step of removing the solvent from the fourth treated solution to obtain purified glycerol monomethacrylate; The method for producing glycerol monomethacrylate,

2. The method for producing glycerol monomethacrylate according to claim 1 , wherein the reaction in the reaction step is carried out without a solvent and in the presence of a polymerization inhibitor.

3. 3. The method for producing glycerol monomethacrylate according to claim 1 or 2, wherein the solvent removal step yields purified glycerol monomethacrylate having a purity of 90 (area %) or more, defined as the ratio (area %) of the peak area of ​​glycerol monomethacrylate to the total area of ​​detected peaks obtained by high-efficiency liquid chromatography analysis, and having contents of the acid catalyst and methacrylic acid of 0.015 parts by mass or less and 6 parts by mass or less, respectively.

4. The method for producing glycerol monomethacrylate according to any one of claims 1 to 3, which is used to produce glycerol monomethacrylate for use as a raw material for dental polyurethane resins.

5. a step of producing glycerol monomethacrylate, which is the diol compound (a1) having one or more radical polymerizable groups, by the method according to claim 1 to obtain purified glycerol monomethacrylate; a first raw material composition preparation step of preparing a first raw material composition comprising the purified glycerol monomethacrylate obtained in the above step; a polymerizable monomer (B) having one or more radically polymerizable groups in the molecule and not undergoing a polyaddition reaction with either the diol compound (a1) or the diisocyanate compound; a radical polymerization initiator (C); and a filler (D); a second raw material composition preparation step of mixing the first raw material composition with a diisocyanate compound (a2) to cause a polyaddition reaction between the purified glycerol monomethacrylate and the diisocyanate compound (a2) to form a polyurethane component (A) having a number average molecular weight of 1,500 to 5,000 and having a radically polymerizable group, thereby preparing a second raw material composition comprising the polyurethane component (A), the polymerizable monomer (B); a radical polymerization initiator (C); and a filler (D), and which may contain unreacted purified glycerol monomethacrylate and / or unreacted diisocyanate compound (a2); and a curing step of radically polymerizing the radically polymerizable group in the polyurethane component (A) in the second raw material composition with the polymerizable monomer (B) to cure the second raw material composition, thereby obtaining a polyurethane-based composite material; 2. A method for producing the polyurethane composite material, comprising:

6. 6. The method for producing a polyurethane composite material according to claim 5, wherein the purified glycerol monomethacrylate is a raw material for a dental polyurethane resin, and a dental polyurethane composite material is produced.

7. A method for producing a material for dental cutting, comprising the method for producing the dental polyurethane composite material according to claim 6.

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