Production method for (METH)acrylic acid

Abstract

The present invention provides: a production method that is for obtaining (meth)acrylic acid from a raw material containing 3-hydroxycarboxylic acid and / or a condensate thereof, and that suppresses polymerization of (meth)acrylic acid in a reaction vessel even in a reaction at a high temperature exceeding 100°C to enable production of (meth)acrylic acid at a high yield with high productivity; a production method that can be performed stably for a long period of time by suppressing an increase in viscosity of a reaction liquid with high productivity when producing (meth)acrylic acid from 3-hydroxycarboxylic acid. The present invention is a production method for (meth)acrylic acid, the method comprising a reaction step for obtaining (meth)acrylic acid from a raw material containing 3-hydroxycarboxylic acid and / or a condensate thereof. The method is characterized in that the reaction step is a step for performing: a reaction under a condition in which an iron-based compound exists in a reaction liquid containing (meth)acrylic acid, and 3-hydroxycarboxylic acid and / or a condensate thereof; and / or a reaction under a condition in which the neutralization rate of carboxylic acids in a reaction liquid containing 3-hydroxycarboxylic acid and / or a condensate thereof is set to 1-50 mol%.

Description

Method for producing (meth)acrylic acid

[0001] The present invention relates to a method for producing (meth)acrylic acid, and more particularly to a method for producing (meth)acrylic acid from a raw material containing a 3-hydroxycarboxylic acid and / or a condensate thereof.

[0002] (Meth)acrylic acid is widely used industrially as a raw material for acrylic resins and hydrophilic resins. A typical method for producing (meth)acrylic acid is a two-stage oxidation method in which fossil-derived raw materials, such as propylene or isobutylene, are subjected to catalytic gas-phase oxidation in the presence of an oxide catalyst using a fixed-bed multi-tubular continuous reactor to produce acrolein or methacrolein, which is then further catalytically oxidized (see Patent Documents 1 to 7). However, in light of growing awareness of environmental issues in recent years, there is a demand for producing (meth)acrylic acid from renewable resources rather than fossil resources, and attempts have been made to economically produce (meth)acrylic acid on a commercial scale using renewable resources such as biomass.

[0003] Examples of methods for producing (meth)acrylic acid from biomass include methods in which sugars are obtained from natural products such as agricultural crops or by decomposing cellulose, etc., and then the sugars are fermented to produce a 3-hydroxycarboxylic acid such as 3-hydroxypropionic acid (hereinafter also referred to as 3HP) or 3-hydroxyisobutyric acid, and acrylic acid is obtained from the 3-hydroxycarboxylic acid. Disclosed are a method for producing (meth)acrylic acid that includes a step of producing a composition containing a polymer of 3-hydroxycarboxylic acid and a step of carrying out a liquid-phase reaction to produce (meth)acrylic acid from the composition at a temperature exceeding 100°C (see Patent Document 8), and a method for producing acrylic acid from 3-hydroxypropionic acid using a first polymerization inhibitor having a boiling point of 30 to 200°C and a second polymerization inhibitor having a boiling point of 200°C or higher (see Patent Document 9). Furthermore, numerous other methods for producing (meth)acrylic acid by reacting a 3-hydroxycarboxylic acid have been disclosed (see Patent Documents 10 to 13). Also disclosed are production methods for acrylic acid by reacting a 3-hydroxycarboxylic acid in a liquid phase at 120 to 250°C, in which the ratio of a 3-hydroxycarboxylic acid oligomer to a 3-hydroxycarboxylic acid monomer is set within a specific range (see Patent Documents 14 and 15), and a method for producing acrylic acid by decomposing polypropiolactone using sodium acrylate, potassium carbonate, sodium carbonate, or the like as a catalyst (see Patent Documents 16 to 19).Also disclosed is a method for producing acrylic acid by contacting 3-hydroxypropionic acid or lactic acid with a liquid mixture containing a metal salt of 3-hydroxypropionic acid or lactic acid and water at a temperature higher than 150°C (see Patent Document 20).

[0004] International Publication No. WO 2005 / 095320 International Publication No. WO 2007 / 106100 Special Publication No. 2006-518766 Japanese Patent Publication No. 2000-159724 International Publication No. WO 2012 / 091114 Special Publication No. 2004-532855 International Publication No. WO 2011 / 002892 Japanese Patent No. 6078447 Korean Patent Publication No. 2023-0049853 U.S. Patent No. 7,166,743 Specification U.S. Patent No. 6,897,338 Specification International Publication No. 2011 / 100608 JP 2015-067567 A U.S. Patent No. 10,252,970 Specification U.S. Patent No. 9,809,526 Specification U.S. Patent No. 10,065,914 Specification U.S. Patent No. 10,703,707 Specification U.S. Patent No. 10,626,073 Specification U.S. Patent No. 1,099,989 Specification Japanese Patent No. 6,290,257

[0005] As described above, one known method for producing (meth)acrylic acid from biomass is to obtain 3-hydroxycarboxylic acid from natural products and then dehydrate it to produce (meth)acrylic acid. However, in both production methods, (meth)acrylic acid has high reactivity and can polymerize inside the reactor, which can cause gel formation in the reactor, causing problems and reducing the yield of (meth)acrylic acid. To suppress such polymerization of (meth)acrylic acid inside the reactor, a polymerization inhibitor is added to the reactor. However, typical polymerization inhibitors are not very effective at inhibiting polymerization at high temperatures above 100°C, where the reaction rate of the dehydration reaction of 3-hydroxycarboxylic acid is high. Therefore, it has been necessary to lower the reaction temperature at the expense of the productivity of (meth)acrylic acid.

[0006] Furthermore, the reaction rate from 3-hydroxycarboxylic acid to (meth)acrylic acid is slow, resulting in low productivity of (meth)acrylic acid. This makes the (meth)acrylic acid production process unnecessarily expensive, making it an undesirable production method from the perspective of industrial productivity. If the reaction is carried out under high-temperature conditions to increase productivity, the risk of (meth)acrylic acid polymerization, which can cause operational problems in the production equipment, increases. Furthermore, when producing (meth)acrylic acid from biomass, impurities specific to biomass can cause the reaction liquid to become highly viscous, making it difficult to continue operating the reactor. Thus, there are various challenges to stably producing (meth)acrylic acid from biomass with high productivity over long periods of time.

[0007] The present invention has been made in view of the above-mentioned current situation, and aims to provide a production method for obtaining (meth)acrylic acid from a raw material containing a 3-hydroxycarboxylic acid and / or a condensate thereof, which can produce (meth)acrylic acid with high productivity and high yield by suppressing polymerization of (meth)acrylic acid in a reactor even in a reaction at a high temperature exceeding 100°C, and a production method which can produce (meth)acrylic acid from 3-hydroxycarboxylic acid with high productivity and stably for a long period of time while suppressing an increase in viscosity of the reaction liquid.

[0008] The present inventors have investigated methods for inhibiting polymerization of (meth)acrylic acid in a reactor in a production process for obtaining (meth)acrylic acid from a raw material containing a 3-hydroxycarboxylic acid and / or a condensate thereof. They have found that iron-based compounds, which are not normally used as polymerization inhibitors and do not inhibit polymerization of (meth)acrylic acid in the presence of only (meth)acrylic acid, function as polymerization inhibitors for (meth)acrylic acid in the presence of 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid. Furthermore, the present inventors have found that iron-based compounds exhibit excellent polymerization inhibitory effects even in reactions at high temperatures exceeding 100°C, thereby enabling the production of (meth)acrylic acid with high productivity and high yield. Furthermore, they have also found suitable methods for producing hydrophilic resins and (meth)acrylic acid esters using the (meth)acrylic acid thus obtained.

[0009] Furthermore, the present inventors have investigated a production method for (meth)acrylic acid using 3-hydroxycarboxylic acid as a raw material with high productivity, which can be continued stably for a long period of time while preventing the reaction solution from becoming highly viscous. They have found that by carrying out the reaction by neutralizing the carboxylic acid in a reaction solution containing 3-hydroxypropionic acid and / or a condensate thereof to a predetermined neutralization ratio, (meth)acrylic acid can be produced with high productivity, and the reaction solution can be prevented from becoming highly viscous, allowing the production of (meth)acrylic acid to be continued stably for a long period of time, thereby completing the present invention.

[0010] That is, the present invention is as follows.

[0011] [1] A method for producing (meth)acrylic acid, comprising a reaction step of obtaining (meth)acrylic acid from a raw material containing a 3-hydroxycarboxylic acid and / or a condensate thereof, characterized in that the reaction step is a step of carrying out a reaction under conditions in which an iron-based compound is present in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, and / or a reaction under conditions in which a neutralization rate of carboxylic acid in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof is set to 1 to 50 mol %.

[0012] [2] The method for producing (meth)acrylic acid according to [1], wherein the reaction in the presence of an iron-based compound in the reaction liquid containing the 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid is carried out at a temperature of 100 to 300°C.

[0013] [3] The method for producing (meth)acrylic acid according to [1] or [2], wherein the concentration of the iron-based compound in the reaction solution containing the 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid in the reaction solution is 1 to 30,000 ppm in the presence of the iron-based compound.

[0014] [4] The method for producing (meth)acrylic acid according to any one of [1] to [3], wherein the reaction under conditions in which the neutralization rate of carboxylic acid in the reaction liquid containing the 3-hydroxycarboxylic acid and / or a condensate thereof is set to 1 to 50 mol % is carried out by adding an alkali metal compound.

[0015] [5] The method for producing (meth)acrylic acid according to any one of [1] to [4], wherein the average condensation degree of 3-hydroxycarboxylic acid in a reaction solution containing the 3-hydroxycarboxylic acid and / or a condensate thereof is 3 or less when the neutralization rate of carboxylic acid in the reaction solution is set to 1 to 50 mol %.

[0016] [6] The method for producing (meth)acrylic acid according to any one of [1] to [5], wherein the temperature of the reaction solution containing the 3-hydroxycarboxylic acid and / or its condensate is 130 to 250°C under the condition that the neutralization rate of the carboxylic acid in the reaction solution is 1 to 50 mol%.

[0017] [7] The method for producing (meth)acrylic acid according to any one of [1] to [6], wherein the pressure of the reaction solution containing the 3-hydroxycarboxylic acid and / or a condensate thereof is normal pressure or reduced pressure, under conditions where the neutralization rate of carboxylic acid in the reaction solution is 1 to 50 mol %.

[0018] [8] The method for producing (meth)acrylic acid according to any one of [1] to [7], characterized in that the reaction in the reaction step is carried out under conditions in which an iron-based compound is present in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, and the neutralization rate of carboxylic acid in the reaction liquid is set to 1 to 50 mol %.

[0019] [9] A method for producing a hydrophilic resin using a raw material containing a 3-hydroxycarboxylic acid and / or a condensate thereof, the method comprising: a reaction step of producing (meth)acrylic acid from a 3-hydroxycarboxylic acid and / or a condensate thereof in the presence of an iron-based compound in a reaction liquid containing the 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, and / or a reaction of producing (meth)acrylic acid in a reaction liquid containing the 3-hydroxycarboxylic acid and / or a condensate thereof at a neutralization rate of 1 to 50 mol % of carboxylic acid; and a polymerization step of polymerizing a monomer component containing (meth)acrylic acid obtained in the reaction step to produce a hydrophilic resin, wherein the main product among the products obtained in the reaction step is (meth)acrylic acid.

[0020]

[10] The method for producing a hydrophilic resin according to [9], wherein the hydrophilic resin is a water-absorbent resin.

[0021]

[11] The method for producing a hydrophilic resin according to [9], wherein the hydrophilic resin is a cosmetic additive.

[0022]

[12] A method for producing a (meth)acrylic ester using a raw material containing a 3-hydroxycarboxylic acid and / or a condensate thereof, the method comprising: a reaction step of producing (meth)acrylic acid from a 3-hydroxycarboxylic acid and / or a condensate thereof in the presence of an iron-based compound in a reaction liquid containing the 3-hydroxycarboxylic acid and / or the condensate thereof and (meth)acrylic acid, and / or a reaction of producing (meth)acrylic acid in a reaction liquid containing the 3-hydroxycarboxylic acid and / or the condensate thereof at a neutralization rate of 1 to 50 mol % of carboxylic acid; and an esterification step of reacting the component containing (meth)acrylic acid obtained in the reaction step with an alcohol or an epoxide to produce an ester, wherein the main product among the products obtained in the reaction step is (meth)acrylic acid.

[0023]

[13] The (meth)acrylic acid ester may be methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 1-octyl (meth)acrylate, 2-octyl (meth)acrylate, isononyl (meth)acrylate, isobornyl (meth)acrylate, isoamyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, or lauryl (meth)acrylate. The method for producing a (meth)acrylic acid ester according to

[12] , characterized in that the (meth)acrylic acid ester is any one of stearyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, or an ester of 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, glycerin, polyethylene glycol, and polypropylene glycol in which some or all of the alcohol groups are esterified with (meth)acrylic acid.

[0024] The method for producing (meth)acrylic acid of the present invention is a useful method that can effectively suppress the polymerization reaction of (meth)acrylic acid in a reactor even at high reaction temperatures exceeding 100°C, and / or effectively suppress the increase in viscosity of the reaction solution due to impurities specific to biomass-derived raw materials while increasing the reactivity of the reaction from biomass-derived 3-hydroxycarboxylic acid to (meth)acrylic acid, thereby producing (meth)acrylic acid from biomass raw materials with high productivity and high yield stably over a long period of time.

[0025] FIG. 1 is a diagram of a reaction apparatus used to prepare a reaction solution used in a test tube polymerization test in Preparation Example 1. It is also a diagram of an apparatus used to carry out the reaction of 3-hydroxypropionic acid in Examples 12 to 26 and Comparative Examples 6 to 9. It is also a diagram of a test apparatus used in tests to confirm the effects of various polymerization inhibitors in Example 1.

[0026] The present invention will be described in detail below. Note that a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

[0027] 1. Method for Producing (Meth)acrylic Acid <Reaction Step> The method for producing (meth)acrylic acid of the present invention is characterized by comprising a reaction step in which a reaction is carried out under conditions in which an iron-based compound is present in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, and / or a reaction is carried out under conditions in which a neutralization rate of carboxylic acid in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof is set to 1 to 50 mol %. The reaction in the reaction step in the method for producing (meth)acrylic acid of the present invention may be at least one of a reaction under conditions in which an iron-based compound is present in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, and a reaction under conditions in which a neutralization rate of carboxylic acid in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof is set to 1 to 50 mol %, but as described below, a reaction that satisfies both of these conditions is one preferred embodiment of the present invention. The reaction referred to here is a reaction including, as a reaction pathway, at least one of a dehydration reaction (intramolecular dehydration reaction and intermolecular dehydration reaction) of a 3-hydroxycarboxylic acid and / or a condensate thereof and a reaction of thermally decomposing a 3-hydroxycarboxylic acid condensate. In the following, the "reaction under conditions in which an iron-based compound is present in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid" will be explained first, followed by the "reaction under conditions in which the neutralization rate of carboxylic acid in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof is set to 1 to 50 mol %."

[0028] [Reaction in the Presence of an Iron-Based Compound in a Reaction Liquid Comprising a 3-Hydroxycarboxylic Acid and / or a Condensate Thereof and (Meth)acrylic Acid] As described above, the iron-based compound does not exhibit a polymerization inhibitory effect in the presence of (meth)acrylic acid alone, whereas it exhibits an inhibitory effect on the polymerization of (meth)acrylic acid in an environment in which a 3-hydroxycarboxylic acid and / or a condensate thereof coexists with (meth)acrylic acid.

[0029] In the method for producing (meth)acrylic acid of the present invention, when the reaction is carried out under conditions in which an iron-based compound is present in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, examples of the iron-based compound to be used include iron oxide, iron sulfate, iron acetate, and iron chloride, and one or more of these can be used. Among these, iron oxide, iron sulfate, and iron acetate are preferred. Iron oxide and iron acetate, which have excellent corrosion resistance, are more preferred.

[0030] In the method for producing (meth)acrylic acid of the present invention, when the reaction is carried out under conditions in which an iron-based compound is present in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, the amount of the iron-based compound used is not particularly limited as long as the polymerization reaction of (meth)acrylic acid is suppressed, but is preferably an amount that results in a concentration of the iron-based compound in the reaction liquid of 1 to 30,000 ppm, more preferably an amount that results in a concentration of 10 to 10,000 ppm, even more preferably an amount that results in a concentration of 50 to 5,000 ppm, particularly preferably a concentration of 100 to 5,000 ppm, and most preferably a concentration that results in a concentration of 150 to 5,000 ppm.

[0031] "Reaction under conditions in which the neutralization rate of carboxylic acid in the reaction liquid containing 3-hydroxycarboxylic acid and / or its condensate is 1 to 50 mol %" The reason why (meth)acrylic acid can be produced with high productivity and while preventing the reaction liquid from becoming highly viscous by setting the neutralization rate within this range is presumed to be as follows. In addition to 3-hydroxycarboxylic acid, condensates of 3-hydroxycarboxylic acid with various condensation degrees are present in the reaction raw materials. (Meth)acrylic acid is produced by decomposing dimers and trimers of these condensates into 3-hydroxycarboxylic acid and (meth)acrylic acid. Therefore, by increasing the proportion of condensates with a low condensation degree, such as dimers and trimers, in the reaction raw materials, a larger amount of (meth)acrylic acid can be produced. Neutralizing carboxylic acid in the reaction liquid can suppress the production of condensates with a high condensation degree and increase the proportion of condensates with a low condensation degree, such as dimers and trimers. However, adding too much base for neutralization inhibits the production of the condensate of 3-hydroxycarboxylic acid, which is a precursor of (meth)acrylic acid. In contrast, by adjusting the neutralization rate of carboxylic acid in a reaction solution containing a 3-hydroxycarboxylic acid and / or its condensate to 1 to 50 mol%, it is possible to increase the proportion of condensates with a low degree of condensation without inhibiting the production of the 3-hydroxycarboxylic acid condensate itself, thereby enabling efficient production of (meth)acrylic acid. Furthermore, the produced (meth)acrylic acid may react again with a 3-hydroxycarboxylic acid to produce a condensate, which is also one of the factors that reduces the productivity of (meth)acrylic acid. However, by partially neutralizing the carboxylic acid, it is possible to prevent the (meth)acrylic acid from reacting again with a 3-hydroxycarboxylic acid, thereby increasing the amount of (meth)acrylic acid produced and improving productivity. Furthermore, while the use of biomass-derived raw materials increases the viscosity of the reaction solution and hinders stable operation of the reactor, in the present invention, by adjusting the neutralization rate of carboxylic acid in the reaction solution to 1 to 50 mol%, it is also possible to effectively prevent the viscosity of the reaction solution from increasing. As a result, it is presumed that the method for producing (meth)acrylic acid of the present invention achieves stable operation of the reactor while increasing the productivity of (meth)acrylic acid.

[0032] In the method for producing (meth)acrylic acid of the present invention, when the reaction is carried out by setting the neutralization rate of carboxylic acid in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof to 1 to 50 mol %, the method may include a step of reacting the reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof under conditions where the neutralization rate of carboxylic acid in the reaction liquid does not satisfy 1 to 50 mol %, but the proportion of the time during which the neutralization rate is 1 to 50 mol % is preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, particularly preferably 90% or more, and most preferably 100% of the total time during which the reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof is carried out.

[0033] In the method for producing (meth)acrylic acid of the present invention, when the reaction is carried out with a carboxylic acid neutralization rate of 1 to 50 mol% in a reaction solution containing a 3-hydroxycarboxylic acid and / or a condensate thereof, the carboxylic acid neutralization rate in the reaction solution in the reaction step may be 1 to 50 mol%, but is preferably 3 to 47 mol%. It is more preferably 5 to 45 mol%, and even more preferably 7 to 40 mol%. The carboxylic acid neutralization rate in the reaction solution in the reaction step can be confirmed by the following calculation formula using the analytical values ​​obtained by the method described in the Examples below: (Neutralization rate of carboxylic acid) = 100 × (number of moles of cation of base used for neutralization × valence) / (number of moles of 3-hydroxycarboxylic acid unit). The method for maintaining the carboxylic acid neutralization rate in the reaction solution in the reaction step is not particularly limited, and examples include a method of extracting a carboxylic acid and / or a base described below from the reaction solution, and a method of adding a carboxylic acid and / or a base described below to the reaction solution.

[0034] In the reaction step of the method for producing (meth)acrylic acid of the present invention, when the reaction is carried out with a neutralization rate of carboxylic acid in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof being 1 to 50 mol %, the method for achieving a neutralization rate of carboxylic acid in the reaction liquid of 1 to 50 mol % is not particularly limited, but a method of adding a base is preferred. The base to be added is not particularly limited, but examples include metal compounds such as metal hydroxides and carbonates, and ammonia, and examples of metal compounds include metal compounds of metals in Groups 1 and 2 of the periodic table. Among these, the base to be added is preferably a metal compound of Group 1 of the periodic table, i.e., an alkali metal compound. More preferably, it is an alkali metal hydroxide or carbonate.

[0035] As described above, when a dimer or trimer of 3-hydroxycarboxylic acid is decomposed into 3-hydroxycarboxylic acid, (meth)acrylic acid is produced by the reaction of the 3-hydroxycarboxylic acid. Therefore, in order to increase the productivity of (meth)acrylic acid, it is preferable to increase the proportion of condensates with a low condensation degree, such as dimers or trimers, in the reaction raw materials, and the average condensation degree of the 3-hydroxycarboxylic acid condensates in the reaction solution is preferably 3 or less. The average condensation degree is more preferably less than 3.0, even more preferably 2.5 or less, and most preferably 2.0 or less. The average condensation degree of 3-hydroxycarboxylic acid in the reaction solution can be confirmed by the following calculation formula using analytical values ​​obtained by liquid chromatography: average condensation degree of 3-hydroxycarboxylic acid = (number of moles of 3-hydroxycarboxylic acid units / number of moles of 3-hydroxycarboxylic acids). Number of moles of 3-hydroxycarboxylic acid units = (number of moles of 3-hydroxycarboxylic acid + number of moles of dimer × 2 + number of moles of trimer × 3 + number of moles of tetramer × 4 + number of moles of pentamer × 5 + number of moles of hexamer × 6 + number of moles of heptamer × 7 + number of moles of octamers × 8 + number of moles of nonamers × 9 + number of moles of decamers × 10 + number of moles of 11amers × 11 + number of moles of 12amers × 12 + number of moles of 13amers × 13 + number of moles of 14amers × 14 + number of moles of 15amers × 15 + number of moles of 16amers × 16) Number of moles of 3-hydroxycarboxylic acids = (number of moles of 3-hydroxycarboxylic acid + number of moles of dimer + number of moles of trimer + number of moles of tetramer + number of moles of pentamer + number of moles of hexamer + number of moles of heptamer + number of moles of octamer + number of moles of nonamer + number of moles of decamer + number of moles of 10amer + number of moles of 11amer + number of moles of 12amer + number of moles of 13amer + number of moles of 14amer + number of moles of 15amer + number of moles of 16amer)

[0036] In the method for producing (meth)acrylic acid of the present invention, the temperature of the reaction step in which (meth)acrylic acid is obtained from raw materials containing a 3-hydroxycarboxylic acid and / or a condensate thereof is not particularly limited as long as the reaction proceeds, but is preferably 100 to 300°C. Since iron-based compounds sufficiently exhibit the effect of inhibiting the polymerization of (meth)acrylic acid even at such high reaction temperatures, such reaction temperatures can be employed in the reaction step. By carrying out the reaction at such temperatures, the reaction can be promoted, (meth)acrylic acid can be produced with higher productivity, and the production amount of (meth)acrylic acid can be increased. The temperature of the reaction step is more preferably 110 to 250°C, even more preferably 120 to 220°C. It is particularly preferably 120 to 200°C, and most preferably 130 to 180°C.

[0037] The pressure inside the reactor in which the reaction step is carried out is not particularly limited as long as the reaction proceeds, but is preferably 5 to 101 kPa. More preferably, it is 7 to 80 kPa, even more preferably, it is 10 to 60 kPa, and particularly preferably, it is 10 to 50 kPa. When the reaction step is carried out under reduced pressure conditions of 50 kPa or less, it becomes easy to gasify and recover the (meth)acrylic acid produced in the reaction.

[0038] The reaction time is not particularly limited, but when the raw material composition is not continuously supplied to the reactor, the reaction time is preferably 0.5 to 200 hours, more preferably 1 to 150 hours, and even more preferably 3 to 100 hours, in consideration of the production efficiency and yield of (meth)acrylic acid.

[0039] The time for the above reaction step is not particularly limited, but when the raw material composition is continuously supplied to the reactor and the reaction product is continuously withdrawn, the residence time is preferably 1 to 700 hours. It is more preferably 8 to 600 hours, and even more preferably 15 to 500 hours. The residence time can be confirmed by the following calculation formula: Residence time = (amount of liquid phase in reactor) / (amount of liquid phase withdrawn from reactor per unit time)

[0040] The reactor used in the reaction step only needs to be capable of heating, and no complicated equipment is required. Thus, the fact that the process can be carried out using a relatively simple device is one of the advantageous effects of the method for producing (meth)acrylic acid of the present invention. The reactor preferably has a structure that efficiently transfers heat to the raw material composition supplied in liquid form. Examples of such reactors include horizontal or vertical tube natural circulation heaters, forced circulation heaters, multi-tube heat exchangers, thin-film heat exchangers, and the like. Alternatively, a heating system using a jacket on the outside of the reactor or a coil installed inside the reactor may be used in combination.

[0041] The reaction step in the method for producing (meth)acrylic acid of the present invention is preferably carried out by retaining a certain amount of liquid phase in a heater, conducting a reaction to produce (meth)acrylic acid in the liquid phase while supplying the raw material composition thereto in liquid form, and then evaporating the produced (meth)acrylic acid and distilling it away from the reactor. By withdrawing the light-boiling component (meth)acrylic acid in gaseous form, insufficiently decomposed unreacted condensates remain in the reaction liquid, thereby improving the yield of (meth)acrylic acid. The residence time required for the production of (meth)acrylic acid can be controlled by the temperature, pressure, amount of heat, feed rate of the raw material composition, and the amount of liquid-phase liquid raw material present in the reactor. Furthermore, to suppress the distillation of 3-hydroxycarboxylic acid and / or its condensates or (meth)acrylic acid condensates, a distillation column may be installed in the reactor and refluxed. When distillation is performed, (meth)acrylic acid and water are recovered from the reaction liquid.

[0042] The reaction step may be carried out under an air atmosphere or an inert gas atmosphere, but when a distillation column is installed in the reactor, it is preferably carried out under an air atmosphere. Oxygen can also be added to suppress polymerization in the distillation column. For example, it is particularly preferred to introduce an oxygen-containing gas mixture into the reaction product, the oxygen content of which in the gas phase is 18% by volume or less, preferably 5% by volume or less, which is below the explosion limit. Mixtures of inert gases and oxygen, such as nitrogen-oxygen, argon-oxygen, or carbon dioxide-oxygen, can also be used.

[0043] In the above reaction step, when the reaction is carried out under conditions in which the neutralization rate of carboxylic acid in the reaction solution containing a 3-hydroxycarboxylic acid and / or a condensate thereof is 1 to 50 mol %, it is preferable to add a polymerization inhibitor to prevent polymerization of the generated (meth)acrylic acid. Examples of polymerization inhibitors include methoquinone, manganese acetate, nitrosophenol, cupferron, N-oxyl compounds, copper dibutylthiocarbamate, phenothiazine, hydroquinone, and the above-mentioned iron-based compounds, and one or more of these can be used. Among these, iron-based compounds are preferred. When an iron-based compound is used, the reaction in the reaction step also corresponds to a reaction carried out under conditions in which an iron-based compound is present in the reaction solution containing a 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, and the effects of carrying out the reaction under conditions in which the above-mentioned iron-based compound is present can also be obtained. Thus, in a preferred embodiment of the method for producing (meth)acrylic acid of the present invention, the reaction in the reaction step corresponds to both "a reaction under conditions in which the neutralization rate of carboxylic acid in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof is 1 to 50 mol %" and "a reaction under conditions in which an iron-based compound is present in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid." The amount of the polymerization inhibitor used is preferably the same as the amount of the iron-based compound used.

[0044] The reaction step may be carried out by adding a base. The base to be added is not particularly limited, and examples thereof include metal compounds such as metal hydroxides and carbonates, and ammonia. Examples of metal compounds include metal compounds of Group 1 and Group 2 metals in the periodic table. Among these, the base to be added is preferably a metal compound of Group 1 metal in the periodic table, i.e., an alkali metal compound. More preferably, it is a hydroxide or carbonate of an alkali metal.

[0045] The reaction step may be carried out using a catalyst. Examples of the catalyst include acid catalysts and base catalysts as described below, with solid acid catalysts and solid base catalysts being particularly preferred. Crystalline metallosilicates such as zeolites; crystalline metallosilicates on which alkali metals, alkaline earth metals, transition metals, etc. are supported by methods such as ion exchange; natural or synthetic clay compounds such as kaolinite, bentonite, and montmorillonite; catalysts in which sulfuric acid, heteropolyacids, phosphoric acid or phosphates (alkali metal salts of phosphoric acid, alkaline earth metal salts, manganese phosphate, zirconium phosphate, etc.), alkali metals, or alkaline earth metals are supported on a carrier such as alumina or silica; Al ２ O ３ , SiO ２ , TiO ２ , ZrO ２ , SnO ２ , V ２ O ５ , SiO ２ -Al ２ O ３ , SiO ２ -TiO ２ , SiO ２ -ZrO ２ , TiO ２ -W.O. ３ , TiO ２ -ZrO ２ inorganic oxides or inorganic composite oxides such as; MgSO ４ , Al ２ (SO ４ ) ３ , K. ２ SO ４ , AlPO ４ , Zr(SO ４ ) ２ and solid acidic substances such as sulfates and phosphates of metals such as Al, etc.; and solid basic substances such as calcium oxide, magnesium oxide, and hydrotalcite. ２ O ３ , SiO ２ , SiO ２ -Al ２ O ３ , TiO ２, zeolite, zeolite supported with alkali metals or alkaline earth metals, catalysts in which phosphoric acid, phosphates, alkali metals or alkaline earth metals are supported on a carrier such as silica.

[0046] In the method for producing (meth)acrylic acid of the present invention, the method for supplying the iron-based compound and other polymerization inhibitors to the reactor in which the reaction step is carried out is not particularly limited, and the iron-based compound and other polymerization inhibitors may be supplied to the reactor before the 3-hydroxycarboxylic acid and / or its condensate, which are the raw materials for the reaction, are supplied to the reactor, or may be supplied simultaneously with the 3-hydroxycarboxylic acid and / or its condensate being supplied to the reactor, or may be supplied successively during the reaction. The iron-based compound and other polymerization inhibitors may be supplied directly to the reactor, or, when a distillation column is installed in the reactor, may be supplied from the distillation column.

[0047] <3-Hydroxycarboxylic Acid and Method for Producing the Same> Examples of the 3-hydroxycarboxylic acid used in the present invention include 3-hydroxypropionic acid, 3-hydroxyisobutyric acid, etc., and any of these may be used, but since acrylic acid obtained by reacting 3-hydroxypropionic acid is particularly highly reactive and easily polymerized, the technical significance of using the production method of the present invention is more fully realized when 3-hydroxypropionic acid is used as the 3-hydroxycarboxylic acid. Therefore, using 3-hydroxypropionic acid as the 3-hydroxycarboxylic acid is one of the preferred embodiments of the present invention.

[0048] The 3-hydroxycarboxylic acid used in the present invention can be obtained from various sources. However, from the viewpoint of suppressing global warming and protecting the environment, it is preferable to obtain it from a biological resource that can be recycled as a carbon source. Specifically, it is possible to use a product prepared by further fermenting sugars and sugar alcohols obtained by decomposing sugars and sugar alcohols obtained from agricultural crops, etc. In the present invention, it is preferable that at least a portion or all of the 3-hydroxycarboxylic acid contained in the raw material composition is a 3-hydroxycarboxylic acid obtained by fermentation. In other words, the method for producing (meth)acrylic acid of the present invention preferably includes a fermentation step, and the 3-hydroxycarboxylic acid used as the raw material is produced by the fermentation step. Furthermore, it is preferable that the raw material for the 3-hydroxycarboxylic acid is a biological resource such as biomass.

[0049] Known methods can be used to obtain 3-hydroxycarboxylic acids from biological resources. For example, a method described in WO 2008 / 027742 can be used, in which 3-hydroxycarboxylic acids are obtained by fermentation using glucose as a carbon source using Escherichia coli introduced with the beta-alanine aminotransferase gene derived from Streptomyces griseus ATCC21897. Alternatively, a method described in WO 2001 / 016346 can be used, in which 3-hydroxycarboxylic acids are obtained by fermentation using glycerol as a carbon source using Escherichia coli introduced with glycerol dehydratase derived from Klebsiella pneumoniae and aldehyde oxidase derived from Escherichia coli.

[0050] Although the above-mentioned known literature has been described as an example of a method for obtaining 3-hydroxycarboxylic acid, the microorganism or genetically modified microorganism used for fermentation is not particularly limited, and any 3-hydroxycarboxylic acid obtained by fermentation using an organism capable of producing 3-hydroxycarboxylic acid can be used in the production method of the present invention. Furthermore, 3-hydroxycarboxylic acid produced by contacting a raw material sugar with an organism other than fermentation can also be converted to (meth)acrylic acid by the production method of the present invention.

[0051] When a raw material composition containing a 3-hydroxycarboxylic acid and / or a condensate thereof obtained from a biological resource is used as a raw material for the production method of the present invention, the raw material composition is preferably obtained through a fermentation process and contains fewer impurities. Examples of impurities in the raw material composition obtained through a fermentation process include bacterial cells, proteins, amino acids, glucose, salts, etc. that are typically contained in a fermentation broth, as well as formic acid, acetic acid, propionic acid, butyric acid, succinic acid, fumaric acid, pyruvic acid, glycolic acid, lactic acid, ethanol, amino acids, 1,3-propanediol, glycerin, hydroxypropionaldehyde, alanine, etc., which may be by-produced together with the 3-hydroxycarboxylic acid during fermentation.

[0052] A method for obtaining a raw material composition containing a 3-hydroxycarboxylic acid and / or a condensate thereof with few impurities includes a method for preparing the raw material composition using a 3-hydroxycarboxylic acid that has been purified from a fermentation broth. Known methods can be used for the purification step from the fermentation broth. Specifically, methods include: precipitating a crude 3-hydroxycarboxylic acid obtained by fermentation using a calcium salt, recovering the calcium salt of the 3-hydroxycarboxylic acid, and then reacting it with an acid such as sulfuric acid to purify the 3-hydroxycarboxylic acid; or chemically converting the ammonium-form 3-hydroxycarboxylic acid obtained by fermentation into the 3-hydroxycarboxylic acid by electrodialysis or cation exchange, followed by purification. Furthermore, membrane separation procedures can also be used, such as removing impurities using a common filter cloth, a microfiltration membrane (MF membrane), or an ultrafiltration membrane (UF membrane), or concentrating the 3-hydroxycarboxylic acid using a reverse osmosis membrane (RO membrane). Alternatively, an amine solution of the 3-hydroxycarboxylic acid can be obtained by extraction by adding a water-immiscible amine solvent to an aqueous solution of the 3-hydroxycarboxylic acid or its ammonium salt obtained by fermentation and heating as necessary. Water can be added thereto and the mixture heated for back-extraction to obtain an aqueous solution of 3-hydroxycarboxylic acid. Purification can also be performed by evaporation or distillation, utilizing the vapor pressure of 3-hydroxycarboxylic acid. However, because the vapor pressure of 3-hydroxycarboxylic acid is low, operation under high reduced pressure is preferred. Furthermore, purified 3-hydroxycarboxylic acid can also be obtained by esterifying 3-hydroxycarboxylic acid with an alcohol, purifying and concentrating the resulting 3-hydroxycarboxylic acid ester by distillation, and then hydrolyzing the 3-hydroxycarboxylic acid ester. Water can also be removed from the aqueous solution of 3-hydroxycarboxylic acid by evaporation or distillation, followed by concentration. For example, a method using a multi-effect reactor is a suitable example.

[0053] A condensation product of 3-hydroxycarboxylic acid is a polymer in which 3-hydroxycarboxylic acids are linked together via intermolecular ester bonds, and a condensation product of 3-hydroxypropionic acid can be represented by the following formula (1).

[0054]

[0055] (In formula (1), n ​​represents a number of 1 or more.) In the above formula (1), n ​​is preferably 1 to 20. More preferably, it is 1 to 10.

[0056] In the present invention, the raw material for the reaction step may be a composition containing a 3-hydroxycarboxylic acid and / or a condensate thereof and a solvent. Examples of the solvent include water, alcohols, hydrocarbons, ethers, ketones, esters, amines, and amides, and these may be used singly or in combination. Among these, solvents having a boiling point lower than that of the 3-hydroxycarboxylic acid are preferred in terms of facilitating evaporation of the solvent, and water is preferred, for example.

[0057] When the raw material for the reaction step is a composition containing a 3-hydroxycarboxylic acid and / or a condensate thereof and a solvent, the concentration of the 3-hydroxycarboxylic acid and / or a condensate thereof in the composition is preferably 20 to 100% by mass, more preferably 30 to 99% by mass, and even more preferably 40 to 98% by mass, relative to 100% by mass of the composition.

[0058] In the present invention, the raw materials for the reaction step may contain components other than the 3-hydroxycarboxylic acid and / or its condensate and the solvent. Examples of other components include the above-mentioned by-products produced when synthesizing the 3-hydroxycarboxylic acid by fermentation or the like.

[0059] The content of components other than 3-hydroxycarboxylic acid and / or its condensate and the solvent contained in the raw materials for the reaction step used in the present invention is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, based on 100% by mass of the raw materials.

[0060] <Other Steps> The method for producing (meth)acrylic acid of the present invention may include other steps as long as it includes a reaction step of obtaining (meth)acrylic acid from a raw material containing a 3-hydroxycarboxylic acid and / or a condensate thereof. Examples of other steps include a step of recovering a reaction liquid containing the (meth)acrylic acid obtained in the reaction step, and a step of purifying the (meth)acrylic acid obtained in the reaction step. The purification step can be carried out by a method such as membrane separation, distillation, extraction, or crystallization.

[0061] The method for recovering the reaction solution containing (meth)acrylic acid obtained in the reaction step is not particularly limited, but recovery by distillation is preferred. The distillation recovery liquid contains (meth)acrylic acid, which is the main reaction product, and may also contain by-products, the solvent in the raw material composition, and impurities. When the solvent is water, the (meth)acrylic acid can be used as a raw material for polymer production in the form of an aqueous solution. Furthermore, by adding a purification step, high-purity (meth)acrylic acid can be obtained. The purification step can be carried out by known techniques such as membrane separation, distillation, extraction, crystallization, etc., or a combination of these techniques may be used. Among these, the purification step is preferably a step of purifying (meth)acrylic acid by distillation or crystallization.

[0062] 2. Method for Producing Hydrophilic Resin and Uses of Hydrophilic Resin (meth)acrylic acid can be produced by the above-described method. The (meth)acrylic acid thus produced can be used as a raw material for hydrophilic resins such as water-absorbent resins or water-soluble resins. In other words, the use of (meth)acrylic acid obtained by the production method of the present invention as a raw material for producing a hydrophilic resin is also one aspect of the present invention. The method for producing a hydrophilic resin of the present invention includes the above-described reaction step and a polymerization step in which a monomer component containing (meth)acrylic acid is polymerized to produce a hydrophilic resin, and is characterized in that the main product among the products obtained in the reaction step is (meth)acrylic acid. The (meth)acrylic acid obtained by the (meth)acrylic acid production method of the present invention has high quality with few impurities and is easy to control the polymerization reaction. Furthermore, using this (meth)acrylic acid as a raw material stabilizes the quality of the hydrophilic resin and improves various properties such as water absorption capacity and inorganic material dispersion ability. The method for carrying out the polymerization step to produce the hydrophilic resin is not particularly limited, and a method in which an initiator and other components are added to a monomer component containing (meth)acrylic acid and the polymerization reaction is allowed to proceed by heating or other methods can be used.

[0063] Furthermore, the (meth)acrylic acid obtained by the production method of the present invention can be suitably used for producing various (meth)acrylic acid derivatives, and the (meth)acrylic acid derivatives can be produced by carrying out a step for producing various (meth)acrylic acid derivatives (derivative production step) after the above-mentioned reaction step. A purification step may or may not be carried out between the reaction step and the derivative production step. The purity of the (meth)acrylic acid used in the derivative production step is not particularly limited.

[0064] Examples of the (meth)acrylic acid derivatives include (meth)acrylic acid esters and polymers thereof, (meth)acrylic acid salts and polymers thereof, etc. Specific examples of the (meth)acrylic acid esters include esters of (meth)acrylic acid such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, 2-ethylhexyl, 1-octyl, 2-octyl, isononyl, isobornyl, isoamyl, 2-methoxyethyl, 2-ethoxyethyl, tetrahydrofurfuryl, lauryl, stearyl, cyclohexyl, 2-hydroxyethyl, 2-hydroxypropyl, and 4-hydroxybutyl, as well as esters in which a portion or all of the alcohol groups of polyhydric alcohols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, glycerin, polyethylene glycol, and polypropylene glycol are esterified with (meth)acrylic acid. In addition, examples include esters in which various alcohols are modified with ethylene oxide and / or propylene oxide and then partially or completely esterified with (meth)acrylic acid, as well as esters such as 2-(vinyloxyethoxy)ethyl, α-(hydroxymethyl)methyl, α-(allyloxymethyl)methyl, etc. Specific examples of (meth)acrylate salts include sodium, potassium, calcium, magnesium, ammonium, and zinc salts.

[0065] The above-mentioned (meth)acrylic acid esters and (meth)acrylic acid salts can be (co)polymerized alone or in combination to produce various polymers. Examples of the polymers include poly(meth)acrylic acid esters, poly(sodium meth)acrylic acid, and crosslinked products thereof. Examples of the crosslinked products include water-absorbent resins and slightly crosslinked resins (commonly called carbomers). The (meth)acrylic acid obtained by the method for producing (meth)acrylic acid of the present invention is useful as a raw material for synthesizing (meth)acrylic acid derivatives such as (meth)acrylic acid esters; water-absorbent resins such as poly(meth)acrylic acid and sodium poly(meth)acrylate; etc.

[0066] The (meth)acrylic acid and hydrophilic resins produced by the present invention, as well as the various (meth)acrylic acid derivatives described above, are of high quality and can be suitably used in a variety of applications. For example, they can be used in a wide range of applications, including building materials, optical applications, automobiles, detergents, disposable diapers, sanitary materials, food applications, cosmetics, and pharmaceuticals. They can also be used as adhesives, pressure-sensitive adhesives, paints, coating agents, inks, superabsorbent resins, thickeners, water-retaining materials, vibration-damping materials, acrylic rubbers, acrylic fibers, acrylic resins, acrylic emulsions, molding resins, electronics materials, reactive diluents, and pharmaceutical raw materials. (Meth)acrylic acid derivatives, such as (meth)acrylic acid esters, are used in a wide range of applications, including building materials and optical applications. Other applications include printing ink solvents, printing ink compositions and ink cleaners for printing presses, plastic additives, antistatic agents, biodiesel, fuels and their additives, electrical insulating oils, lubricating oils, spilled oil recovery agents, industrial cleaners, paint solvents, urethane viscosity reducers, adhesive solvents, solvents for reactions, separation, purification, and extraction, and solvents for the textile industry.

[0067] The water-absorbent resin is a water-swellable, water-insoluble polymer gelling agent and is used in a variety of applications, including absorbent articles such as disposable diapers and sanitary napkins, soil water retention agents for agricultural and horticultural use, and industrial water-stopping agents. While many types of monomers and water-absorbent polymers are used as raw materials for the water-absorbent resin, poly(meth)acrylic acid (salt)-based water-absorbent resins using (meth)acrylic acid and / or its salts (hereinafter referred to as "(meth)acrylic acid (salt)") as monomers are most commonly used, due to the water-absorption performance and manufacturing costs of the water-absorbent resin. The uses of the water-absorbent resin are not particularly limited, but preferred examples include absorbent materials for absorbent articles such as disposable diapers (for infants and adults), sanitary napkins, and incontinence pads. In particular, the water-absorbent resin can be used as an absorbent material for high-concentration disposable diapers. The absorbent material can also contain an absorbent material such as pulp fibers in addition to the water-absorbent resin of the present invention. In this case, the amount of the water-absorbent resin in the absorbent body (hereinafter referred to as "core concentration") is preferably 30% by weight to 100% by weight, more preferably 40% by weight to 100% by weight, even more preferably 50% by weight to 100% by weight, still more preferably 60% by weight to 100% by weight, particularly preferably 70% by weight to 100% by weight, and most preferably 75% by weight to 95% by weight.

[0068] Examples of other absorbent articles include drip absorbers, freshness-preserving materials, portable toilets for disasters, pet sheets, cat litter, etc. Other uses of water-absorbent resins include soil water retention agents, seedling raising sheets, seed coating materials, anti-condensation sheets, disposable warmers, cooling bandanas, ice packs, medical waste liquid solidifying agents, surplus soil solidifying materials, water-damage preventing waste liquid gelling agents, water-absorbing sandbags, compresses, thickeners for cosmetics, water-stopping materials for communication cables of electric and electronic materials, gasket packing, sustained-release agents for fertilizers, various sustained-release agents (space disinfectants, air fresheners, etc.), wound protection dressings, anti-condensation building materials, oil moisture removers, paints, adhesives, anti-blocking agents, light diffusing agents, matting agents, additives for resins such as additives for decorative panels, additives for artificial marble, and additives for toner.

[0069] The method for producing (meth)acrylic acid of the present invention can naturally be incorporated into methods for producing (meth)acrylic acid derivatives and water-absorbent resins, and such methods for producing water-absorbent resins also constitute the present invention. Specifically, a method for producing a water-absorbent resin using a 3-hydroxycarboxylic acid as a raw material, the method comprising: a step of reacting a raw material containing a 3-hydroxycarboxylic acid and / or a condensate thereof to obtain (meth)acrylic acid; and a polymerization step of polymerizing a monomer component containing the (meth)acrylic acid to produce a water-absorbent resin; the method for producing a water-absorbent resin in which the main product obtained in the reaction step is (meth)acrylic acid, also constitutes the present invention. Here, "the main product obtained in the reaction step is (meth)acrylic acid" means that the proportion of the produced (meth)acrylic acid is 50% by mass or more relative to the total mass of the product obtained in the reaction step. The proportion of (meth)acrylic acid in the product obtained in the reaction step is more preferably 65% ​​by mass or more, and even more preferably 80% by mass or more.

[0070] The method for producing a water-absorbent resin of the present invention includes a step of polymerizing a monomer component containing (meth)acrylic acid obtained from a 3-hydroxycarboxylic acid and / or a condensate thereof, but if the production amount (supply amount) of non-petroleum-based acrylic acid alone does not match the required production amount of the water-absorbent resin due to the production amount (supply amount) or the amount of a trace component, petroleum-based (meth)acrylic acid may be used in combination as necessary. When non-petroleum-based (meth)acrylic acid and petroleum-based (meth)acrylic acid are used in combination, the ratio thereof is determined in the range of 0 / 100 to 100 / 0 by mass ratio, preferably 5 / 95 to 100 / 0, and more preferably 10 / 90 to 100 / 0.

[0071] Hydrophilic resins obtained by polymerizing (meth)acrylic acid obtained by the (meth)acrylic acid production method of the present invention can also be used as cosmetic additives. [Cosmetic Additives] The hydrophilic resins used as cosmetic additives may be crosslinked polymers obtained by crosslinking a monomer composition containing (meth)acrylic acid obtained by the (meth)acrylic acid production method of the present invention as a main component, as needed, and may contain a graft component. The hydrophilic resins used as cosmetic additives are obtained by polymerizing a monomer composition containing (meth)acrylic acid obtained by the (meth)acrylic acid production method of the present invention as a main component. The monomer composition may essentially consist of (meth)acrylic acid alone, or may contain other monomers copolymerizable with (meth)acrylic acid. Examples of other monomers include, but are not limited to, methacrylic acid, maleic acid, itaconic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamide, and salts thereof. These monomers may be used alone or in combination of two or more types. Among these, itaconic acid is preferred when used in combination with a monomer, since it can be obtained by fermentation and contributes to the use of biomaterials.

[0072] From the viewpoint of the performance of the cosmetic additive, the proportion of (meth)acrylic acid (salt) in the monomer composition is preferably 50 to 100 mol %, more preferably 70 to 100 mol %, and even more preferably 90 to 100 mol %, relative to the total amount of monomers (100 mass %). The proportion of the other monomers in the monomer composition is, for example, 0 to 50 mol %, and preferably 5 to 45 mol %.

[0073] When the crosslinking polymerization is carried out, a crosslinking agent is used. The crosslinking agent may be added before or after the polymerization of the monomer composition. Examples of the crosslinking agent include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and pentaerythritol di(meth)acrylate. Examples of the crosslinking agent include compounds having two or more ethylenically unsaturated groups in one molecule, such as tol triallyl ether neoallyl, N,N'-methylenebis(meth)acrylamide, triallyl isocyanurate, trimethylolpropane di(meth)allyl ether, triallylamine, tetraallyloxyethane, and glycerol propoxy triacrylate, and preferred are compounds having two ethylenically unsaturated groups in one molecule, such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate. Only one type of crosslinking agent may be used, or two or more types may be used.

[0074] The polymerization method for the monomer composition is not particularly limited, and any known or commonly used method can be used. Examples of the polymerization method include bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Among these, precipitation polymerization is preferred from the viewpoint of achieving superior thickening properties of the cosmetic additive and superior usability of the cosmetic.

[0075] A solvent may be used in the polymerization of the monomer composition. A hydrophobic organic solvent may be used as the solvent used in the polymerization of the monomer composition. Examples of the hydrophobic organic solvent include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, aliphatic alcohols, aliphatic ketones, and aliphatic esters.

[0076] Examples of aliphatic hydrocarbons include those having 5 or more carbon atoms, specifically n-pentane, n-hexane, n-heptane, etc. Examples of alicyclic hydrocarbons include those having 5 or more carbon atoms, specifically cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, etc. Examples of aromatic hydrocarbons include benzene, toluene, xylene, etc. Examples of aliphatic alcohols include those having 4 or more carbon atoms, preferably 4 to 6 carbon atoms, specifically n-butyl alcohol, n-amyl alcohol, etc. Examples of aliphatic ketones include those having 4 or more carbon atoms, preferably 4 to 6 carbon atoms, specifically methyl ethyl ketone, etc. Examples of aliphatic esters include those having 4 or more carbon atoms, preferably 4 to 6 carbon atoms, specifically ethyl acetate, etc.

[0077] The solvents such as hydrophobic organic solvents may be used alone or in combination of two or more. For example, the hydrophobic organic solvents listed above may be used alone or in combination of two or more.

[0078] As the solvent used in the polymerization of the monomer composition, in terms of controlling the precipitation of the polymer, it is preferable to use at least one selected from the group consisting of aliphatic hydrocarbons and alicyclic hydrocarbons in combination with at least one selected from the group consisting of aliphatic ketones and aliphatic esters, and it is more preferable to use an alicyclic hydrocarbon in combination with an aliphatic ester.

[0079] The mass ratio of the aliphatic hydrocarbons and alicyclic hydrocarbons to the aliphatic ketones and aliphatic esters used as a solvent for polymerization of the monomer composition (total mass of aliphatic hydrocarbons and alicyclic hydrocarbons / total mass of aliphatic ketones and aliphatic esters) is preferably 0 / 100 to 50 / 50, more preferably 10 / 90 to 30 / 70, and still more preferably 100 / 0 to 50 / 50, more preferably 90 / 10 to 70 / 30.

[0080] The mass ratio of the alicyclic hydrocarbon to the aliphatic ester (mass of the alicyclic hydrocarbon / mass of the aliphatic ester) used as the solvent for polymerizing the monomer composition is preferably 0 / 100 to 50 / 50, more preferably 10 / 90 to 30 / 70, and more preferably 100 / 0 to 50 / 50, more preferably 90 / 10 to 70 / 30.

[0081] A polymerization initiator can be used for polymerizing the monomer composition, and a radical polymerization initiator is preferably used as the polymerization initiator. The radical polymerization initiator is preferably a thermal polymerization initiator, and examples thereof include peroxide polymerization initiators and azo compound polymerization initiators. Examples of peroxide polymerization initiators include benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate, cumene hydroperoxide, cyclohexanone peroxide, t-butyl hydroperoxide, and diisopropylbenzene hydroperoxide. Examples of azo compound polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,3-dimethylbutyronitrile), 2,2'-azobis-(2-methylbutyronitrile), 2,2'-azobis(2,3,3-trimethylbutyronitrile), 2,2'-azobis(2-isopropylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-4-methoxy-2,4-dimethylvaleronitrile), 2-(carbamoylazo)isobutyronitrile, 4,4'-azobis(4-cyanovaleric acid), and dimethyl-2,2'-azobisisobutyrate. The polymerization initiators may be used alone or in combination of two or more.

[0082] By carrying out a step of drying the hydrophilic resin, the cosmetic additive can be obtained as a powder. Drying may be carried out under normal pressure or under reduced pressure. The drying temperature is, for example, 60 to 120°C, preferably 80 to 110°C. A drying temperature of 120°C or less makes it difficult for the hydrophilic resin to deteriorate, and can make it difficult for a decrease in viscosity and a deterioration in feel to occur. A drying temperature of 60°C or more improves the productivity of the drying step and allows for sufficient removal of the solvent.

[0083] From the viewpoint of productivity when precipitation polymerization is performed, the neutralization rate of the acid groups of the hydrophilic resin is preferably 50 mol% or less, more preferably 30 mol% or less, even more preferably 10 mol% or less, and particularly preferably 5 mol% or less. Neutralization may be performed on the monomer (monomer composition containing (meth)acrylic acid), on the hydrophilic resin after polymerization, or on both. Examples of neutralization salts include alkali metal salts of (poly)(meth)acrylic acid, such as sodium, potassium, and lithium, ammonium salts, and amine salts.

[0084] The hydrophilic resin (cosmetic additive) obtained by polymerizing (meth)acrylic acid obtained by the production method of the present invention may be subjected to a polymerization step or a drying step, and then to a classification step to make the particle size uniform.

[0085] (Transparency) It is preferable that the cosmetic additive does not cause turbidity. Transparent cosmetic products and products with various visual effects have been developed, and as long as the cosmetic additive does not cause turbidity, the visual effect can be freely selected.

[0086] (Feel of use of cosmetics) Cosmetic additives that have a fresh feel when used are preferred. The feel of the cosmetic when used and the texture when applied to the skin are important characteristics of cosmetics. There are a variety of options, such as a fresh and light feel or a moist and heavy feel. Among these, there are few cosmetic additives that can provide a fresh and light feel, and there is a high demand in the market. A sticky feel is an undesirable feel that many people find uncomfortable.

[0087] The cosmetic additive of the present invention can be used as a known or conventional cosmetic additive. Examples of the additive include thickeners, gelling agents, feel-improving agents, moisturizing agents, film-forming agents, UV absorbers, antibacterial agents, emulsifiers, surfactants, dispersants, etc. The additives may be used alone or in combination of two or more, and are preferably used as thickeners, gelling agents, feel-improving agents, moisturizing agents, or film-forming agents.

[0088] [Cosmetics] Cosmetics can be produced using the cosmetic additive of the present invention. The cosmetic contains at least the cosmetic additive of the present invention. The cosmetic may contain other ingredients in addition to the cosmetic additive of the present invention.

[0089] Examples of the other components include solvents (e.g., water, organic solvents, etc.), oils, lower alcohols, polyhydric alcohols, thickeners, moisturizers, surfactants (anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants), fatty acid alkanolamides, antioxidants, antioxidant aids, powder components (e.g., organic powders, pigments, dyes, etc.), natural water-soluble polymers, semi-synthetic water-soluble polymers, synthetic water-soluble polymers, chelating agents, sugars and derivatives thereof, amino acids and derivatives thereof, organic amines, polymer emulsions, pH adjusters (acids, alkalis, etc.), vitamins, preservatives / antibacterial agents, anti-inflammatory agents, various extracts, activators, blood circulation promoters, antiseborrheic agents, anti-inflammatory agents, fragrances, etc. One or more of the other components may be used.

[0090] The above-mentioned cosmetics include known or commonly used cosmetics, such as skin cosmetics, hair cosmetics, and bath cosmetics. Here, topical preparations are applied to the skin, nails, hair, etc. of the human body, and can be used to treat various diseases by incorporating active pharmaceutical ingredients, for example. Cosmetics are also applied to the skin, nails, hair, etc. of the human body, but are used for cosmetic purposes. Even when used as "topical preparations," they may actually be used in the same manner and dosage as cosmetics. Therefore, in this specification, the term "cosmetics" also includes such topical preparations. Examples of such topical preparations include antiperspirants, skin cleansers, topical skin preparations, hair cleansers, and topical hair preparations. Pharmaceutical uses of these topical preparations include hair growth agents, hair restorers, analgesics, disinfectants, anti-inflammatory agents, cooling agents, and skin anti-aging agents.

[0091] The skin cosmetics can be used on any part of the body, including the scalp, face (including lips, eyebrows, and cheeks), fingers, nails, and the entire body. Specific examples include skin cleansing products such as cleansing gel, cleansing cream, cleansing foam, facial cleanser, eye makeup remover, facial cleanser, liquid soap (body soap), hand soap, gel soap, shaving cream, nail polish remover, and anti-acne cosmetics; skin care products such as skin cream, scalp treatment, skin milk, milk lotion, emulsion, facial pack, body powder, essence, shaving lotion, and massage lotion; makeup products such as foundation, liquid foundation, oil-based foundation, makeup base, face powder, blusher, lip balm, rouge paste, lip gloss, eye cream, mascara, eyebrow pencil, and eyelash cosmetics; antiperspirants such as deodorants; UV protection products such as sunscreens and suntanning agents (sun tanning agents); and deodorant products.

[0092] Examples of the hair cosmetics include eyelash cosmetics, hair cleansers such as shampoos and rinse-in shampoos, hair styling products such as hair wax, hair curl retainers, setting agents, hair creams, hair sprays and hair liquids, hair coloring products such as hair dyes, hair color sprays, hair color rinses and hair color sticks, hair care products such as hair tonics, hair treatment essences and hair packs, and hair rinses or hair conditioning products such as oil rinses, cream rinses, treatment rinses, hair conditioners and hair treatments. Examples of the bath cosmetics include foam baths.

[0093] The form of the cosmetic preparation is not particularly limited, and may be any of a solution, emulsion, cream, solid, semi-solid, paste, gel, powder, multi-layered, mousse, water-in-oil type, or oil-in-water type emulsion composition (emulsion composition). The cosmetic preparation of the present invention can be formulated by known methods in the form of, for example, a solution, suspension, emulsion, cream, ointment, gel, liniment, lotion, aerosol, powder, spray, sheet preparation in which a sheet such as a nonwoven fabric is impregnated with the cosmetic preparation of the present invention, or stick preparation.

[0094] The content of the cosmetic additive of the present invention in the cosmetic is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, relative to the total amount (100% by mass) of the cosmetic, and is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 2.0% by mass or less.

[0095] 3. Production Method of (Meth)acrylic Acid Ester The production method of (meth)acrylic acid of the present invention can naturally be incorporated into production methods of (meth)acrylic acid esters, and such production methods of (meth)acrylic acid esters also constitute one aspect of the present invention. That is, a method for producing a (meth)acrylic acid ester using a raw material containing a 3-hydroxycarboxylic acid and / or a condensate thereof, the production method comprising: a reaction step of producing (meth)acrylic acid from the 3-hydroxycarboxylic acid and / or a condensate thereof in the presence of an iron-based compound in a reaction liquid containing the 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, and / or a reaction of producing (meth)acrylic acid in a reaction liquid containing the 3-hydroxycarboxylic acid and / or a condensate thereof at a neutralization rate of 1 to 50 mol %, and an esterification step of reacting the (meth)acrylic acid-containing component obtained in the reaction step with an alcohol or an epoxide to produce an ester, wherein the main product among the products obtained in the reaction step is (meth)acrylic acid, also constitutes one aspect of the present invention. Here, "the main product in the product obtained in the reaction step is (meth)acrylic acid" means that the proportion of (meth)acrylic acid produced is 50% by mass or more relative to the total mass of the product obtained in the reaction step. The proportion of (meth)acrylic acid in the product obtained in the reaction step is more preferably 65% ​​by mass or more, and even more preferably 80% by mass or more.

[0096] The conditions for the reaction step for producing the (meth)acrylic acid are as described above. The purity of the (meth)acrylic acid is not particularly limited, and a purification step may or may not be carried out after the reaction step.

[0097] The conditions for the esterification step are not particularly limited, and generally known methods can be used. Specifically, the esterification reaction may be carried out by heating in the presence of a catalyst. The catalyst may be selected from sulfuric acid, sulfonic acid, phosphoric acid, p-toluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid, dodecylsulfonic acid, etc., and an acidic ion exchange resin may also be used. A basic catalyst such as sodium hydroxide, potassium hydroxide, or a basic ion exchange resin may also be used.

[0098] The reaction temperature in the esterification step can be set as appropriate, but is preferably in the range of 40 to 120°C. The pressure can be set as desired, such as under atmospheric pressure, reduced pressure, or increased pressure. It is also preferable to carry out the esterification step in the presence of a polymerization inhibitor; specifically, it is preferable to use a quinone-based, phenol-based, phenothiazine-based, N-oxyl-based, or metal-based polymerization inhibitor. The reaction can also be carried out while blowing an oxygen-containing gas into the liquid phase and / or gas phase.

[0099] When the reaction in the esterification step is a reaction between (meth)acrylic acid and an alcohol, the charging ratio of (meth)acrylic acid to alcohol is not particularly limited, but it is preferable to carry out the reaction under conditions where either the (meth)acrylic acid or the alcohol is in excess in order to promote the reaction. Unreacted alcohol or (meth)acrylic acid can be recovered and recycled. The reaction can also be promoted by removing water produced during the esterification reaction. When the reaction in the esterification step is a reaction between (meth)acrylic acid and an epoxide, the charging ratio of (meth)acrylic acid to the epoxide, the reaction method, etc. are not particularly limited, and a general method can be used.

[0100] The (meth)acrylic acid ester produced in the esterification step is preferably further purified to increase its purity before use. The method for the purification step is not particularly limited, and common methods such as distillation, extraction, crystallization, and adsorption can be used.

[0101] The resulting (meth)acrylic acid ester can be used to produce a derivative by further carrying out an additional derivatization step, such as a transesterification reaction with various alcohols, a methylolation reaction using formaldehyde, or a reaction in which the methylolated derivative is further reacted with an alcohol for etherification.

[0102] The alcohol or epoxide used in the esterification step is not particularly limited, but examples of alcohols that can be used include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-ethylhexanol, 1-octanol, 2-octanol, isononyl alcohol, isobornyl alcohol, isoamyl alcohol, 2-methoxyethanol, 2-ethoxyethanol, tetrahydrofurfuryl alcohol, lauryl alcohol, stearyl alcohol, cyclohexanol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, glycerin, polyethylene glycol, polypropylene glycol, and alcohols obtained by modifying various alcohols with ethylene oxide and / or propylene oxide. Examples of epoxides that can be used include ethylene oxide, propylene oxide, butylene oxide, and glycidol. Of these alcohols or epoxides, it is preferable to use methanol, ethanol, n-butanol, 2-ethylhexanol, 2-octanol, isononyl alcohol, isobornyl alcohol, 2-methoxyethanol, ethylene oxide, and propylene oxide, and among these, it is preferable to use those derived from biomass.

[0103] The (meth)acrylic acid ester obtainable by the method for producing a (meth)acrylic acid ester of the present invention is not particularly limited, and specific examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 1-octyl (meth)acrylate, 2-octyl (meth)acrylate, isononyl (meth)acrylate, isobornyl (meth)acrylate, isoamyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, and methyl (meth)acrylate. Examples of the ester include tetrahydrofurfuryl acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, as well as esters in which a portion or all of the alcohol groups in polyhydric alcohols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, glycerin, polyethylene glycol, and polypropylene glycol are esterified with (meth)acrylic acid. Further examples include esters in which a portion or all of various alcohols modified with ethylene oxide and / or propylene oxide are esterified with (meth)acrylic acid. Of these, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-octyl (meth)acrylate, isononyl (meth)acrylate, isobornyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate are preferred, and among these, those derived from biomass are preferred.

[0104] Derivatives produced by subjecting the above-mentioned (meth)acrylic acid esters to an additional derivatization step include the above-mentioned various (meth)acrylic acid esters, 2-(vinyloxyethoxy)ethyl (VEEA), α-(hydroxymethyl)methyl (RHMA), α-(allyloxymethyl)methyl (AOMA), etc. When producing a derivative by a transesterification reaction, it is preferable to use an ester such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, or isobutyl (meth)acrylate as the raw material (meth)acrylic acid ester.

[0105] 4. Definition of Terms [1] Water-absorbent resin, water-absorbent resin powder, water-absorbent resin particles. In the present invention, the term "water-absorbent resin" refers to a water-swellable, water-insoluble polymer gelling agent. Furthermore, "water-swellable" refers to a CRC of 5 g / g or more as defined by ERT441.2-02, and "water-insoluble" refers to an Ext of 50 wt% or less as defined by ERT470.2-02. The "water-absorbent resin" is preferably a hydrophilic cross-linked polymer obtained by cross-linking an unsaturated monomer having a carboxyl group. However, the entire amount (100 wt%) does not need to be a cross-linked polymer, and additives and the like can be contained within a range that satisfies the above-mentioned performance (CRC, Ext). Furthermore, the term "water-absorbent resin" may refer to a "polymer cross-linked only internally (i.e., a polymer in which the cross-linking density of the interior and the surface is substantially the same)" or a "polymer cross-linked internally and on the surface (i.e., a polymer in which the cross-linking density of the surface is relatively high compared to the cross-linking density of the interior)." In this specification, for convenience, a polymer crosslinked only inside may be referred to as a "water-absorbent resin powder", and a polymer crosslinked inside and on the surface may be referred to as a "water-absorbent resin particle".

[0106] [2] Poly(meth)acrylic acid (salt)-based water-absorbent resin The water-absorbent resin obtained by the method for producing a water-absorbent resin of the present invention is a poly(meth)acrylic acid (salt)-based water-absorbent resin. In the present invention, the term "poly(meth)acrylic acid (salt)-based water-absorbent resin" refers to a water-absorbent resin made from (meth)acrylic acid and / or its salt (hereinafter referred to as "(meth)acrylic acid (salt)"). In other words, the poly(meth)acrylic acid (salt)-based water-absorbent resin is a water-absorbent resin having structural units derived from (meth)acrylic acid (salt) in the polymer and having a graft component as an optional component. Specifically, the poly(meth)acrylic acid (salt)-based water-absorbent resin is a water-absorbent resin that contains preferably 50 mol% to 100 mol%, more preferably 70 mol% to 100 mol%, even more preferably 90 mol% to 100 mol%, and particularly preferably substantially 100 mol% of (meth)acrylic acid (salt) relative to the total monomers involved in the polymerization reaction (excluding the internal crosslinking agent).

[0107] [3] EDANA and ERT "EDANA" is an abbreviation for European Disposables and Nonwovens Associations, and "ERT" is an abbreviation for EDANA Recommended Test Methods. ERT is a European standard (almost a global standard) for measuring the physical properties of water-absorbent resins. In the present invention, unless otherwise specified, the physical properties of the water-absorbent resin are measured in accordance with the original ERT (revised in 2002 / publicly known document).

[0108] [3-1] CRC (ERT441.2-02) "CRC" (centrifuge retention capacity) is an abbreviation for Centrifuge Retention Capacity, and means the water absorption capacity of a water-absorbent resin under no pressure. Specifically, 0.2 g of the water-absorbent resin is placed in a nonwoven bag, and then immersed in a large excess of a 0.9 wt% aqueous solution of sodium chloride for 30 minutes to allow the water-absorbent resin to freely swell, and then the water-absorbent resin is reacted using a centrifuge (250 G), and the water absorption capacity (unit: g / g) after the reaction.

[0109] [3-2] Absorption Capacity Under Pressure (AAP) (ERT442.2-02) "AAP" is an abbreviation for Absorption Against Pressure, and refers to the absorption capacity of a water-absorbent resin under pressure. Specifically, it is the absorption capacity (unit: g / g) after 0.9 g of a water-absorbent resin is swelled in a large excess of a 0.9 wt % aqueous sodium chloride solution for 1 hour under a load of 2.06 kPa (21 g / cm2, 0.3 psi). ERT442.2-02 uses the term "Asorption Under Pressure," but this is essentially the same. In the present invention, measurements are made by changing the load condition to 4.83 kPa (49 g / cm2, 0.7 psi). Although "AAP" is used in this specification, it is the absorption capacity measured under a load of 4.83 kPa.

[0110] [3-3] Soluble content (ERT470.2-02) The soluble content means the water-soluble content (amount of water-soluble components) of the water-absorbent resin. Specifically, it is the amount of dissolved polymer (unit: wt%) after 1.0 g of the water-absorbent resin is placed in 200 ml of a 0.9 wt % sodium chloride aqueous solution and stirred at 500 rpm for 16 hours. The amount of dissolved polymer is measured by pH titration.

[0111] [3-4] Residual Monomer (ERT430.2-02) The residual monomer means an unreacted monomer component remaining in a water absorbent resin. Specifically, the residual monomer is the amount of the residual monomer component extracted after adding 1.0 g of a water absorbent resin to 200 ml of a 0.9 wt % aqueous sodium chloride solution and stirring at 500 rpm for 1 hour, and is measured using high performance liquid chromatography.

[0112] [3-5] Vortex (JIS K7224 (1996)) Vortex is a method for evaluating the absorption rate of a water-absorbent resin. Specifically, 2.0 g of a water-absorbent resin is added to 50 g of a 0.9 mass % sodium chloride aqueous solution stirred at 600 rpm with a stirrer tip, and the time (unit: seconds) until the stirrer tip is covered with the liquid is measured.

[0113]

[0111] [3-6] Particle size distribution (ERT480.2-02) The particle size distribution means the particle size distribution of a water absorbent resin measured by sieve classification. Specifically, using a set of sieves with a diameter of 200 mm, sieve openings of 850 μm, 600 μm, 300 μm, 150 μm, and 45 μm, and a tray, 100.0 g of a water absorbent resin is classified for 10 minutes with a sieve shaker, and the amount of the water absorbent resin remaining on each sieve mesh and in the tray is measured, and the particle size distribution is calculated (unit: % by weight).

[0114] [4] Others In this specification, the range "X to Y" means "X or more and Y or less." Furthermore, the unit of weight "t (ton)" means "metric ton." Unless otherwise noted, "ppm" means "weight ppm," and "weight" and "mass," "weight %" and "mass %, "parts by weight" and "parts by mass" are treated as synonyms. Furthermore, "~ acid (salt)" means "~ acid and / or its salt," and "(meth)acrylic" means "acrylic and / or methacrylic."

[0115] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention should not be construed as being limited to these examples and comparative examples. Examples obtained by appropriately combining the technical means disclosed in each example are also included within the scope of the present invention. The electrical equipment used in the examples and comparative examples, as well as for measuring the physical properties of the water-absorbing agent, uses a 200V or 100V power supply unless otherwise noted. The physical properties of the water-absorbing agent were measured under conditions of room temperature (20°C to 25°C) and a relative humidity of 50±5% RH unless otherwise noted. For convenience, "liter" may be expressed as "l" or "L," and "weight %" as "wt%" or "%."

[0116] <Method for Analyzing the Amount of Polymer Produced> The polymer structure in the reaction solution contains an acrylic acid polymer main chain produced by addition polymerization at the double bond of acrylic acid, as well as side chains produced by condensation (ester bond) of 3HP at the carboxylic acid moiety of the acrylic acid polymer. In the present invention, the polymerization inhibition effect in the reaction solution was evaluated by comparing the amount of acrylic acid polymer main chain produced excluding the side chain, using the concentration-corrected RI intensity described below. As a specific analysis method, a 10-fold amount of 10 wt % NaOH aqueous solution was added to the reaction solution, and the solution was heated at 80°C for 1 hour to hydrolyze the 3HP condensate in the side chain, and analyzed using gel permeation chromatography (GPC) under the following conditions. Columns used: one each of TSKgel G3000PWxl and TSKgel G2500PWxl (manufactured by Tosoh Corporation); Eluent: water / disodium hydrogen phosphate / sodium dihydrogen phosphate = 98 / 1 / 1 (weight ratio); Detector: RI; Column temperature: 50°C; A calibration curve was prepared in advance using a known amount of acrylic acid polymer standard solution, and calculation was performed using the RI peak area at the retention time of a molecular weight of 800 or more. (Concentration-corrected RI intensity) = (RI peak area at the retention time of a molecular weight of 800 or more) / (dilution concentration in hydrolysis) / (GPC carrier dilution concentration).

[0117] <Analysis Method for Acrylic Acid, 3HP, and Its Condensate> The amounts of 3HP and its condensate, and acrylic acid in the aqueous 3HP solution, reaction solution, and reaction product were analyzed using high-performance liquid chromatography (HPLC) under the following conditions: Columns used: Two Inertsil ODS-4s (manufactured by GL Sciences Inc.) Eluent: acetonitrile / water / phosphoric acid / potassium dihydrogen phosphate = 35 / 64 / 0.7 / 0.3 (weight ratio) Detector: UV 205 nm and 220 nm Column temperature: 50°C Refractive index detector internal temperature: 35°C A calibration curve was prepared in advance using known amounts of standard solutions, and the weight % of the organic acid was calculated using the UV peak area.

[0118] <Acrylic Acid Yield> The yield of acrylic acid in the following examples was determined according to the following definition: Yield of acrylic acid (mol %) = 100 × (number of moles of acrylic acid produced) / (number of moles of 3HP units supplied) Number of moles of 3HP units = (number of moles of 3HP + number of moles of dimer × 2 + number of moles of trimer × 3 + number of moles of tetramer × 4 + number of moles of pentamer × 5 + number of moles of hexamer × 6 + number of moles of heptamer × 7 + number of moles of octamers × 8 + number of moles of nonamers × 9 + number of moles of decamers × 10 + number of moles of elevenmers × 11 + number of moles of dodecamers × 12 + number of moles of 1trimers × 13 + number of moles of 1tetramers × 14 + number of moles of 1pentamers × 15 + number of moles of 16amers × 16)

[0119] <Method for measuring viscosity of reaction liquid> The viscosity of the reaction liquid was measured using a rheometer under the following conditions: Measuring device manufacturer: Anton Paar Device name: Rheometer MCR102 Measuring jig: CP50 (diameter: 50 mm) Measuring temperature: 40°C Shear rate: 10 s －１ After the start of measurement, the analytical values ​​for 5 to 10 minutes were averaged and calculated.

[0120] <Method for measuring iron compound concentration and amount of base cation> The iron compound concentration and amount of base cation in the reaction solution are determined by inductively coupled plasma atomic emission spectrometry (ICP). The analysis was performed using an ICP analyzer (model name: Multi-type ICP atomic emission spectrometry analyzer ICPE-9000, manufactured by Shimadzu Corporation). A calibration curve was prepared in advance using a known amount of standard solution, and the concentration of each ion was calculated using the peak area. The iron compound concentration was determined by converting the iron ion analysis value into the molecular weight of the iron compound.

[0121] <Method for Measuring Neutralization Rate of Carboxylic Acid in Reaction Solution> The neutralization rate of carboxylic acid in the reaction solution was determined according to the following definition, using the amount of base cations determined by the ICP analysis and the number of moles of 3HP units determined by the analytical method for 3HP and its condensates: (Neutralization rate of carboxylic acid) = 100 × (number of moles of base cations used for neutralization × valence) / (number of moles of 3HP units).

[0122] <Method for Measuring Average Condensation Degree of 3HP in Reaction Solution> The average condensation degree of 3HP in the reaction solution can be confirmed by the following calculation formula using analytical values ​​of 3HP and its condensates. Average condensation degree of 3HP = (number of moles of 3HP units / number of moles of 3HPs). Number of moles of 3HP units = (number of moles of 3HP + number of moles of dimer × 2 + number of moles of trimer × 3 + number of moles of tetramer × 4 + number of moles of pentamer × 5 + number of moles of hexamer × 6 + number of moles of heptamer × 7 + number of moles of octamer × 8 + number of moles of nonamer × 9 + number of moles of decamer × 10 + number of moles of 11amer × 11 + number of moles of 12amer × 12 + number of moles of 13amer × 13 + number of moles of 14amer × 14 + number of moles of 15amer × 15 + number of moles of 16amer × 16). Number of moles of 3HPs = (number of moles of 3HP + number of moles of dimers + number of moles of trimers + number of moles of tetramers + number of moles of pentamers + number of moles of hexamers + number of moles of heptamers + number of moles of octamers + number of moles of nonamers + number of moles of 10amers + number of moles of 11amers + number of moles of 12amers + number of moles of 13amers + number of moles of 14amers + number of moles of 15amers + number of moles of 16amers)

[0123] <Physical Properties of Water-Absorbent Resin> Hereinafter, methods for measuring various physical properties of the water-absorbent resin according to the present invention will be described. (a) CRC The CRC (centrifuge retention capacity) of the water-absorbent resin according to the present invention was measured in accordance with the EDANA method (ERT441.2-02). (b) Absorption Capacity Under Load (AAP) The absorption capacity under load (AAP) of the water-absorbent resin according to the present invention was measured in accordance with the EDANA method (ERT442.2-02). In the present invention, the load conditions were changed to 4.83 kPa (49 g / cm2, 0.7 psi) for measurements. Although "AAP" is used in this specification, it is always the absorption capacity measured under a load of 4.83 kPa. (c) Extractable Content The extractable content of the water-absorbent resin according to the present invention was measured in accordance with the EDANA method (ERT470.2-02). (d) Residual Monomer The amount of residual monomer in the water-absorbent resin according to the present invention was measured in accordance with the EDANA method (ERT430.2-02). Specifically, 1.0 g of the water-absorbent resin was added to 200 ml of a 0.9% by mass aqueous sodium chloride solution, and the mixture was stirred at 500 rpm for 1 hour using a 35 mm long stirrer tip, followed by filtration. The amount of monomer eluted into the filtrate was measured by high-performance liquid chromatography. The amount of residual monomer is expressed as a mass ratio relative to the water-absorbent resin (unit: ppm). (e) Vortex The vortex of the water-absorbent resin according to the present invention was measured according to the following procedure. First, 0.02 parts by mass of edible blue No. 1 (brilliant blue), a food additive, was added to 1,000 parts by mass of a 0.9% by mass aqueous sodium chloride solution prepared in advance, and the liquid temperature was then adjusted to 30°C. Next, 50 ml of the 0.9% by mass sodium chloride aqueous solution was measured and placed in a 100 ml beaker, and 2.0 g of water-absorbent resin was added all at once while stirring at 600 rpm using a cylindrical stirrer tip 40 mm long and 8 mm in diameter at a cross section perpendicular to the length direction and a magnetic stirrer. The time until the water-absorbent resin absorbed the saline solution and covered the stirrer tip was measured as Vortex (unit: seconds). (f) Particle size distribution The particle size distribution of the water-absorbent resin according to the present invention was measured in accordance with the EDANA method (ERT480.2-02).Specifically, using a set of sieve meshes of 200 mm in diameter, 850 μm, 600 μm, 300 μm, 150 μm, and 45 μm, and a tray, 100.0 g of a water absorbent resin is classified for 10 minutes with a sieve shaker, and the amount of the water absorbent resin remaining on each sieve mesh and in the tray is measured, thereby calculating (unit: %) by weight.

[0124] Preparation Example 1 Using the apparatus shown in Figure 1, 171 g of a 95 wt% aqueous solution of 3-hydroxypropionic acid and 18 g of potassium hydroxide were added to the reactor. The pressure inside the system was reduced to 10 kPa, and the temperature was then increased. When the internal temperature reached 140°C, an 80 wt% aqueous solution of 3-hydroxypropionic acid was supplied to the reactor at a rate of 120 g / h. Air was also supplied to the gas phase of the reactor at a rate of 3 L / h. A mixed gas of the product and air was extracted from the reactor through a gas extraction tube and concentrated and collected in a condenser. After continuing this reaction for 5 hours, 284 g of the reaction liquid was extracted from the reactor, and this was used as the reaction liquid for the test tube polymerization test.

[0125] Examples 1-1 to 1-4, Comparative Examples 1-1 to 1-6 The reaction solution of Preparation Example 1 was placed in a test tube, and various polymerization inhibitors were added. The test tube was then capped with a perforated silicone stopper and placed in a heating device heated to 140°C for 3 hours. The test device is shown in Figure 2. After 3 hours, heating was stopped, and the amount of polymer produced (concentration-corrected RI intensity) and viscosity were evaluated by GPC analysis. The results are shown in Table 1.

[0126]

[0127] Example 2-1, Comparative Examples 2-1 and 2-2 In the test tube polymerization test of Example 1, the reaction was carried out in the same manner as in Example 1, except that the reaction temperature was changed to 100°C and the type and concentration of the polymerization inhibitor were changed as shown in Table 2. The results are shown in Table 2.

[0128]

[0129] Examples 3-1 to 3-3, Comparative Example 3-1 The reaction was carried out in the same manner as in Example 1, except that the concentration of iron (II) acetate was changed. The results are shown in Table 3.

[0130]

[0131] Reference Examples 4-1 to 4-3 Reactions were carried out in the same manner as in the test tube polymerization test of Example 2, except that the reaction solution was changed to 2-carboxyethyl acrylate and the type and concentration of the polymerization inhibitor were as shown in Table 4. The results are shown in Table 4. The 2-carboxyethyl acrylate contained 900-1100 ppm of methoquinone. The test in an atmospheric environment was carried out in an open system exposed to air.

[0132]

[0133] Example 5, Comparative Example 5 Reactions were carried out in the same manner as in Example 1, except that the temperature was 200°C, the pressure was 101 kPa, the raw material supply rate was 60 g / min, no catalyst was used, a polymerization inhibitor was added to the initial charge liquid, the operation time was 750 min, and the type and concentration of the polymerization inhibitor were as shown in Table 5. The results are shown in Table 5.

[0134]

[0135] Example 6: In a jacketed 3-L glass vessel equipped with a distillation column with three perforated trays without downcomers, 1240 g of a 95 wt % aqueous solution of 3-hydroxypropionic acid and 90 g of potassium hydroxide were added to the reactor, using 3-hydroxycarboxylic acid obtained from a sugar fermentation broth through a purification process. 2.3 g of iron (II) acetate was added to the reactor as a polymerization inhibitor. After reducing the pressure inside the system to 20 kPa, the temperature was raised to 150°C, and an 85 wt % aqueous solution of 3-hydroxypropionic acid was supplied at a rate of 600 g / h. The jacket was heated with heat transfer oil. Air was also supplied to the gas phase of the reactor at a rate of 3 L / h. The distilled vapor was condensed in its entirety in a cooling tube; 300 g / h was recycled to the distillation column as reflux, and 600 g / h was collected as product. The reaction was carried out for a total of 16 hours, yielding 8.7 kg of aqueous acrylic acid. The reaction solution in the reactor was withdrawn at a rate of 24 g / h, and the iron compound concentration, polymer production amount (concentration-corrected RI intensity), and viscosity of the withdrawn solution after 12 hours of operation were measured. The results are shown in Table 6.

[0136]

[0137] Preparation Example 2 The aqueous acrylic acid solution obtained by the method described in Example 6 was supplied to an azeotropic dehydrating column, and water and low-boiling impurities were distilled off using toluene as the azeotropic solvent to obtain crude acrylic acid. This crude acrylic acid was supplied to the bottom of a high-boiling impurity separation column having 27 perforated trays with weirs, and distilled at a reflux ratio of 1 to remove high-boiling impurities such as a dimer of acrylic acid (acrylic acid dimer), thereby obtaining crude acrylic acid. Hydrazine hydrate was added to the crude acrylic acid as an aldehyde treating agent, and the mixture was distilled in a simple distillation apparatus to obtain purified acrylic acid.

[0138] Example 7 Into a 2 L polypropylene container were charged 441.6 parts by weight of the purified acrylic acid obtained in Preparation Example 2, 182.0 parts by weight of a 48.5 wt % aqueous sodium hydroxide solution, 2.4 parts by weight of polyethylene glycol diacrylate (average number of polyethylene glycol units (average n number): 9), 1.35 parts by weight of a 2.0 wt % aqueous solution of diethylenetriaminepentaacetic acid trisodium, and 352.9 parts by weight of ion-exchanged water, and mixed to prepare an aqueous solution. The ion-exchanged water had been preheated to 40°C. Next, while stirring the aqueous solution, 187.0 parts by weight of a 48.5 wt % aqueous sodium hydroxide solution was charged to the aqueous solution over a period of about 30 seconds in an open-to-air state, and mixed to prepare an aqueous monomer solution. The temperature of the aqueous monomer solution rose to about 80°C due to the heat of neutralization and heat of dissolution generated during the mixing process. When the temperature of the aqueous monomer solution reached 78°C, 32.71 parts by weight of a 2.6 wt% aqueous solution of sodium persulfate was added as a polymerization initiator and stirred for approximately 5 seconds to obtain a reaction solution. The reaction solution was then poured into a stainless steel batt-shaped container in an open-to-air state. The batt-shaped container had a bottom dimension of 200 mm x 260 mm, a top dimension of 460 mm x 560 mm, and a height of 140 mm, a trapezoidal cross section at the center, and a silicone sheet attached to the inner surface. The batt-shaped container was preheated by placing it on a hot plate heated to 50°C before pouring the reaction solution into it. The polymerization reaction began within one minute after pouring the reaction solution into the batt-shaped container. The reaction solution expanded and foamed upward while generating steam, and then shrunk to a size slightly larger than the bottom of the batt-shaped container. The polymerization reaction (expansion and contraction) was completed within approximately one minute. This polymerization reaction yielded a hydrogel-like crosslinked polymer (hereinafter referred to as "hydrogel"). Next, the hydrogel was cut to an appropriate size, fed into a screw extruder, and pulverized to obtain a particulate hydrogel having a particle diameter of 0.1 to 2 mm. Next, the particulate hydrogel was spread on a wire mesh with an opening of 300 μm (50 mesh) and placed in a hot air dryer. The particulate hydrogel was then dried by passing hot air at 190° C. for 30 minutes, yielding a dried polymer.Subsequently, the dried polymer was put into a roll mill and pulverized, and then classified using two types of JIS standard sieves with mesh sizes of 710 μm and 150 μm, thereby obtaining an irregularly crushed water-absorbent resin powder (1). Next, 3.9 parts by weight of a surface-crosslinking agent solution (1) consisting of 0.4 parts by weight of ethylene carbonate, 0.7 parts by weight of propylene glycol, and 2.8 parts by weight of ion-exchanged water was added to 100 parts by weight of the water-absorbent resin powder (1) and mixed until uniform, thereby obtaining a humidified mixture (1). Subsequently, the humidified mixture (1) was heat-treated at 200 ° C. for 40 minutes, cooled to 60 ° C., and passed through a 710 μm mesh. Particles that did not pass through the 710 μm mesh were lightly crushed with a spatula on a mesh and passed through, and those that could not be completely crushed were removed. As a result, irregularly crushed surface-crosslinked water-absorbent resin particles (1) were obtained. Tables 7 and 8 show the physical properties of the water-absorbent resin powder (1) and the water-absorbent resin particles (1).

[0139]

[0140]

[0141] Example 8: A separable glass flask equipped with a thermometer, reflux condenser, and stirrer was charged with 33.0 g of the purified acrylic acid obtained in Preparation Example 2, 0.33 g of pentaerythritol triallyl ether neoallyl (trade name "Neoallyl P-30M", manufactured by Osaka Soda Co., Ltd.), 0.95 g of potassium carbonate, 43.4 g of ethyl acetate, and 173.6 g of cyclohexane, and the mixture was heated to 63°C with stirring. Nitrogen gas was passed through the reactor for 30 minutes with stirring, and then an initiator solution containing 0.355 g of 2,2'-azobis(2,4-dimethylvaleronitrile) as initiator, 10.0 g of ethyl acetate, and 40.0 g of cyclohexane was added dropwise from a dropping nozzle over 1 hour and 45 minutes to the polymerization reaction system maintained at a constant temperature of 63°C. After completion of all the dropwise addition, the reaction solution was heated to 70°C and aged for 4 hours and 15 minutes to complete the polymerization (precipitation polymerization). The reaction solution was then filtered to recover the polymer precipitate, which was then dried under reduced pressure at 105°C for 5 hours and 30 minutes to obtain cosmetic additive (1). The concentration of the obtained cosmetic additive (1) was adjusted to 0.5 wt%, and a measuring aqueous solution was also prepared with a 50 wt% aqueous sodium hydroxide solution to adjust the pH to 7.3 to 7.8. A B-type viscometer (TVB-10, rotor No. M4, manufactured by Toki Sangyo Co., Ltd.) was used to measure the viscosity, and the measurement was carried out under conditions of 25°C and a rotation speed of 4 rpm. The viscosity of the obtained cosmetic additive was 123.3 Pa s. The obtained cosmetic additive (1) was mixed with the various components shown in Table 9 to prepare a moisturizing gel whose pH was adjusted to 5.8 to 6.0. In addition to cosmetic additives, the moisturizing gel was prepared using 1,3-butylene glycol (manufactured by Daicel Corporation), glycerin (manufactured by Miyoshi Oil & Fats Co., Ltd.), EDTA-2Na (manufactured by Chubu Cherest Co., Ltd.), potassium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), sodium hyaluronate (manufactured by Kewpie Corporation), and phenoxyethanol (manufactured by Yokkaichi Chemical Co., Ltd.).

[0142]

[0143] The obtained moisturizing gel was filled into a UV quartz glass cell (optical path length 10 mm, optical path width 10 mm, fluorescent completely transparent, volume 3.5 ml) and visually evaluated for transparency, which was found to be clear and not cloudy. Furthermore, a sensory evaluation of the feel of the obtained moisturizing gel after use revealed a very refreshing feel. Furthermore, the moisturizing gel was applied to the upper arm, and a sensory evaluation of stickiness from the time it blended into the skin to immediately after blending was performed. No stickiness was felt at all.

[0144] The cosmetic additive obtained by the production method of the present invention can be used in various cosmetics other than the moisturizing gel. Table 10 shows formulation examples other than the moisturizing gel using the cosmetic additive (1) of Example 8 as reference cosmetics, but cosmetics using the cosmetic additive of the present invention are not limited to these. The pH of the reference cosmetics prepared according to the formulation in Table 10 using the cosmetic additive (1) of Example 8 was measured at 25°C using a glass electrode pH meter (model name: LAQUA F-72, manufactured by Horiba, Ltd.), and the viscosity was measured using a TVB-10 type viscometer (manufactured by Toki Sangyo Co., Ltd.) with a rotor No. 4 at a rotation speed of 12 rpm for 1 minute. The results are shown in Table 10. The components listed in Table 10 are as follows. 1,3-Butylene glycol: 1,3-butylene glycol (UK) (manufactured by Daicel Corporation), glycerin: concentrated glycerin for cosmetics (manufactured by Miyoshi Oil & Fats Co., Ltd.), xanthan gum: Ecogum T (manufactured by CP Kelco U.S., Inc.), (acrylates / alkyl acrylate (C10-30)) crosspolymer: Carbopol ETD2020 (manufactured by Lubrizol Corporation), sodium hydroxide: sodium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), phospholipids, others: LiNPOSOME-V-MC (manufactured by Lilac Pharma Co., Ltd.), phenoxyethanol: phenoxyethanol-S (manufactured by Yokkaichi Chemical Co., Ltd.)

[0145]

[0146] Example 9: An esterification reaction with n-butanol (petroleum-derived) was carried out using the purified acrylic acid obtained in Preparation Example 2. That is, 50 g of acrylic acid, 75 g of n-butanol (petroleum-derived), 1 g of p-toluenesulfonic acid, and 0.2 g of hydroquinone were charged into a 300 ml round-bottom flask, and the mixture was heated to 80°C for 5 hours to carry out the esterification step. After the reaction, the reaction solution was analyzed by gas chromatography, and it was confirmed that the amounts of acrylic acid and n-butanol had decreased and that n-butyl acrylate had been produced.

[0147] Example 10: An esterification reaction with n-butanol (biomass-derived) was carried out using the purified acrylic acid obtained in Preparation Example 2. That is, the esterification step was carried out in the same manner as in Example 9, except that n-butanol (biomass-derived) was used instead of n-butanol (petroleum-derived). After the reaction, the reaction solution was analyzed by gas chromatography, and it was confirmed that the amounts of acrylic acid and n-butanol had decreased and that n-butyl acrylate had been produced.

[0148] Example 11 An esterification reaction with 2-ethylhexanol was carried out using the purified acrylic acid obtained in Preparation Example 2. That is, the esterification step was carried out in the same manner as in Example 9, except that 120 g of 2-ethylhexanol (petroleum-derived) was used instead of 75 g of n-butanol (petroleum-derived). After the reaction, the reaction solution was analyzed by gas chromatography, and it was found that the amounts of acrylic acid and 2-ethylhexanol had decreased, and the production of 2-ethylhexyl acrylate was confirmed.

[0149] Examples 12 to 26 and Comparative Examples 6 to 10: The apparatus shown in FIG. 1 was assembled, and the predetermined amount of 95 wt % 3-hydroxypropionic acid (3HP) aqueous solution and the predetermined amount of base shown in Table 11 were added to the reactor. The amount of base was (100 × moles of potassium or sodium added to the reactor / moles of 3HP units added to the reactor). The pressure inside the system was reduced to the predetermined pressure shown in Table 11, and the temperature was raised. At the predetermined reaction temperature shown in Table 11, an aqueous 3HP solution with a predetermined water concentration was fed at a predetermined rate. Air was also fed into the gas phase of the reactor at a rate of 3 L per hour. A mixed gas of the product and air was extracted from the reactor through a gas extraction tube, and the gas was condensed and collected using a condenser. The reaction was continued until a certain amount of liquid remained in the reactor and the balance between the raw materials and the product stabilized. The collected liquid obtained at the stable state was analyzed by liquid chromatography to confirm the amount of acrylic acid produced. In addition, a portion of the reaction liquid in the reactor was withdrawn when stable, and the average condensation degree of 3HP in the reaction liquid and the neutralization rate of carboxylic acid in the reaction liquid were confirmed. In Table 11, the space-time yield is the value obtained by dividing the amount of acrylic acid withdrawn as a gas per hour by the liquid volume of the reactor, and the neutralization rate is the neutralization rate of carboxylic acid in the reaction liquid when stable. The average condensation degree of 3HP is the average condensation degree of 3HP in the reaction liquid when stable. For the reaction continuity, "◯" was given to cases where continuous operation was possible, and "-" was given to cases where gel-like acrylic acid polymer was produced, the reaction liquid solidified, and operation could not be continued.

[0150]

[0151] Examples 27 to 30, Comparative Example 10 Reactions were carried out in the same manner as in Example 12, except that the amount of base, etc. were changed as shown in Table 12. The viscosity of the reaction solution was also measured. The results are shown in Table 12.

[0152]

[0153] From the results in Table 11, by using the production method of the present invention, it is possible to achieve a reaction temperature of 100 kg / h m even at a relatively low temperature of 130 to 150°C. ３It was confirmed that the above space-time yield could be achieved. From the results in Table 12, it was confirmed that by adjusting the amount of base added, it was possible to significantly reduce the viscosity of the reaction solution while minimizing the decrease in space-time yield. From these results, it was confirmed that the production method of the present invention allows the production of (meth)acrylic acid to be carried out stably for a long period of time with high productivity and while suppressing the increase in viscosity of the reaction solution.

[0154] Example 31: A 3-L jacketed glass vessel equipped with a distillation column with three perforated trays without downcomers was charged with 1,240 g of a 95 wt % aqueous solution of 3-hydroxypropionic acid and 90 g of potassium hydroxide, using 3-hydroxycarboxylic acid obtained from a sugar fermentation broth through a purification process. 2 g of iron acetate was added to the reactor as a polymerization inhibitor. After reducing the pressure inside the system to 20 kPa, the temperature was raised to 150°C, and an 85 wt % aqueous solution of 3-hydroxypropionic acid was supplied at a rate of 600 g / h. The jacket was heated with heat transfer oil. Air was also supplied to the gas phase of the reactor at a rate of 3 L / h. The distilled vapor was condensed in its entirety in a cooling tube; 300 g / h was recycled to the distillation column as reflux, and 600 g / h was collected as product. The reaction was carried out for a total of 16 hours, yielding 8.7 kg of aqueous acrylic acid. The collected liquid was analyzed by liquid chromatography to confirm the amount of acrylic acid produced and the space-time yield. The reaction solution in the reactor was extracted at a rate of 24 g / h to check the neutralization rate of the carboxylic acid. The viscosity of the reaction solution was also measured. The results are shown in Table 13.

[0155]

[0156] Preparation Example 3 The aqueous acrylic acid solution obtained in Example 31 was supplied to an azeotropic dehydrating column, and water and low-boiling impurities were distilled off using toluene as an azeotropic solvent to obtain crude acrylic acid. This crude acrylic acid was supplied to the bottom of a high-boiling impurity separation column having 27 perforated trays with weirs, and distilled at a reflux ratio of 1 to remove high-boiling impurities such as a dimer of acrylic acid (acrylic acid dimer), thereby obtaining crude acrylic acid. Hydrazine hydrate was added to the crude acrylic acid as an aldehyde treating agent, and the mixture was distilled in a simple distillation apparatus to obtain purified acrylic acid.

[0157] Example 32 An aqueous solution was prepared by adding 439.4 parts by weight of the purified acrylic acid obtained in Preparation Example 3, 181.1 parts by weight of a 48.5 wt % aqueous sodium hydroxide solution, 1.9 parts by weight of polyethylene glycol diacrylate (average number of polyethylene glycol units (average n number): 9), 1.35 parts by weight of a 2.0 wt % aqueous solution of diethylenetriaminepentaacetic acid trisodium, and 351.7 parts by weight of ion-exchanged water to a 2 L polypropylene container and mixing them. The ion-exchanged water had been preheated to 40°C. Next, while stirring the aqueous solution, 196.1 parts by weight of a 48.5 wt % aqueous sodium hydroxide solution was added to the aqueous solution over a period of about 30 seconds in an open-to-air state, and mixed to prepare an aqueous monomer solution. The temperature of the aqueous monomer solution rose to about 80°C due to the heat of neutralization and heat of dissolution generated during the mixing process. When the temperature of the aqueous monomer solution reached 78°C, 28.45 parts by weight of a 3.0 wt% aqueous solution of sodium persulfate was added as a polymerization initiator and stirred for approximately 5 seconds to obtain a reaction solution. The reaction solution was then poured into a stainless steel batt-shaped container in an open-to-air state. The batt-shaped container had a bottom dimension of 200 mm x 260 mm, a top dimension of 460 mm x 560 mm, and a height of 140 mm, a trapezoidal cross section at the center, and a silicone sheet attached to the inner surface. The batt-shaped container was preheated by placing it on a hot plate heated to 50°C before pouring the reaction solution into it. The polymerization reaction began within one minute after pouring the reaction solution into the batt-shaped container. During the polymerization reaction, the reaction solution expanded and foamed upward in all directions while generating water vapor, and then shrunk to a size slightly larger than the bottom of the batt-shaped container. The polymerization reaction (expansion and contraction) was completed within approximately one minute. This polymerization reaction yielded a hydrogel-like crosslinked polymer (hereinafter referred to as "hydrogel"). Next, the hydrogel was cut to an appropriate size, fed into a screw extruder, and pulverized to obtain a particulate hydrogel having a particle diameter of 0.1 to 2 mm. Next, the particulate hydrogel was spread on a wire mesh with an opening of 300 μm (50 mesh) and placed in a hot air dryer. The particulate hydrogel was then dried by passing hot air at 190° C. for 30 minutes, yielding a dried polymer.Subsequently, the dried polymer was put into a roll mill and pulverized, and then classified using two types of JIS standard sieves with mesh sizes of 850 μm and 150 μm, thereby obtaining an irregularly crushed water-absorbent resin powder (2). Next, 3.5 parts by weight of a surface-crosslinking agent solution (2) consisting of 0.4 parts by weight of ethylene carbonate, 0.6 parts by weight of propylene glycol, and 2.5 parts by weight of ion-exchanged water was added to 100 parts by weight of the water-absorbent resin powder (2) and mixed until uniform, thereby obtaining a humidified mixture (2). Subsequently, the humidified mixture (2) was heat-treated at 200 ° C. for 40 minutes, cooled to 60 ° C., and passed through a mesh size of 850 μm. Particles that did not pass through the mesh size of 850 μm were lightly crushed with a spatula on a mesh and passed through, and those that could not be completely crushed were removed. As a result, irregularly crushed surface-crosslinked water-absorbent resin particles (2) were obtained. Tables 14 and 15 show the physical properties of the water-absorbent resin powder (2) and the water-absorbent resin particles (2).

[0158]

[0159]

Claims

1. A method for producing (meth)acrylic acid, comprising a reaction step of obtaining (meth)acrylic acid from a raw material containing a 3-hydroxycarboxylic acid and / or a condensate thereof, characterized in that the reaction step is carried out under conditions in which an iron-based compound is present in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, and / or under conditions in which the neutralization rate of carboxylic acid in the reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof is set to 1 to 50 mol %.

2. The method for producing (meth)acrylic acid according to claim 1, wherein the reaction in the presence of an iron-based compound in the reaction liquid containing the 3-hydroxycarboxylic acid and / or its condensate and (meth)acrylic acid is carried out at a temperature of 100 to 300°C.

3. The method for producing (meth)acrylic acid according to claim 1 or 2, characterized in that the concentration of the iron-based compound in the reaction solution containing the 3-hydroxycarboxylic acid and / or its condensate and (meth)acrylic acid, in the presence of an iron-based compound, is 1 to 30,000 ppm.

4. A method for producing (meth)acrylic acid according to any one of claims 1 to 3, characterized in that the reaction under conditions in which the neutralization rate of carboxylic acid in the reaction liquid containing the 3-hydroxycarboxylic acid and / or its condensate is 1 to 50 mol % is carried out by adding an alkali metal compound.

5. A method for producing (meth)acrylic acid according to any one of claims 1 to 4, characterized in that the average condensation degree of 3-hydroxycarboxylic acid in the reaction solution containing the 3-hydroxycarboxylic acid and / or its condensate is 3 or less when the neutralization rate of carboxylic acid in the reaction solution is set to 1 to 50 mol %.

6. A method for producing (meth)acrylic acid according to any one of claims 1 to 5, characterized in that the temperature of the reaction solution containing the 3-hydroxycarboxylic acid and / or its condensate is 130 to 250°C under conditions where the neutralization rate of carboxylic acid in the reaction solution is 1 to 50 mol%.

7. A method for producing (meth)acrylic acid according to any one of claims 1 to 6, characterized in that the pressure of the reaction solution containing the 3-hydroxycarboxylic acid and / or its condensate is normal pressure or reduced pressure during the reaction under conditions where the neutralization rate of carboxylic acid in the reaction solution is 1 to 50 mol %.

8. A method for producing (meth)acrylic acid according to any one of claims 1 to 7, characterized in that the reaction in the reaction step is carried out under conditions in which an iron-based compound is present in a reaction liquid containing a 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, and the neutralization rate of the carboxylic acid in the reaction liquid is 1 to 50 mol %.

9. A method for producing a hydrophilic resin using a raw material containing 3-hydroxycarboxylic acid and / or a condensate thereof, the method comprising: a reaction step of producing (meth)acrylic acid from 3-hydroxycarboxylic acid and / or a condensate thereof in the presence of an iron-based compound in a reaction solution containing 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, and / or a reaction of producing (meth)acrylic acid by adjusting the neutralization rate of carboxylic acid in the reaction solution containing 3-hydroxycarboxylic acid and / or a condensate thereof to 1 to 50 mol %, and a polymerization step of polymerizing the monomer component containing (meth)acrylic acid obtained in the reaction step to produce a hydrophilic resin, wherein the main product among the products obtained in the reaction step is (meth)acrylic acid.

10. The method for producing a hydrophilic resin according to claim 9, wherein the hydrophilic resin is a water-absorbent resin.

11. The method for producing a hydrophilic resin according to claim 9, wherein the hydrophilic resin is a cosmetic additive.

12. A method for producing a (meth)acrylic ester using a raw material containing a 3-hydroxycarboxylic acid and / or a condensate thereof, the method comprising: a reaction step of producing (meth)acrylic acid from a 3-hydroxycarboxylic acid and / or a condensate thereof in the presence of an iron-based compound in a reaction liquid containing the 3-hydroxycarboxylic acid and / or a condensate thereof and (meth)acrylic acid, and / or a reaction of producing (meth)acrylic acid in a reaction liquid containing the 3-hydroxycarboxylic acid and / or a condensate thereof with a neutralization rate of 1 to 50 mol % of carboxylic acid; and an esterification step of reacting the (meth)acrylic acid-containing component obtained in the reaction step with an alcohol or an epoxide to produce an ester, wherein the main product among the products obtained in the reaction step is (meth)acrylic acid.

13. The (meth)acrylic acid ester is selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 1-octyl (meth)acrylate, 2-octyl (meth)acrylate, isononyl (meth)acrylate, isobornyl (meth)acrylate, isoamyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, lauryl (meth)acrylate, and (meth)acrylate. p) The method for producing a (meth)acrylic acid ester according to claim 12, wherein the (meth)acrylic acid ester is any one of stearyl acrylate, cyclohexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, or an ester of 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, glycerin, polyethylene glycol, and polypropylene glycol in which a part or all of a plurality of alcohol groups is esterified with (meth)acrylic acid.

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