JPWO2009084320A1 - α-Hydroxymethyl acrylate compounds and process for producing the same - Google Patents

Abstract

The present invention provides an RHMA having a small amount of formaldehyde used as a raw material in a product and substantially not colored, and a practical production method thereof. A method of producing α-hydroxymethyl acrylate compounds by including a step of reacting an acrylate ester with formaldehyde in the presence of a catalyst, wherein the production method comprises subjecting a crude product obtained from the reaction step to reduced pressure. This is a method for producing α-hydroxymethyl acrylate compounds having a purification step of refluxing substantially all of the liquefied product as steam, and having a formaldehyde content of less than 200 ppm.

Description

The present invention relates to α-hydroxymethyl acrylate compounds and a method for producing the same. More specifically, the present invention relates to α-hydroxymethyl acrylate compounds having a low formaldehyde content, which are useful as raw materials for chemical products and pharmaceuticals, and a method for producing the same.

Hydroxyl group-containing vinyl compounds are rich in chemical reactivity such as addition reaction and polymerization reaction of the double bond site, and also have reactivity in hydroxyl group. Α-Hydroxymethyl acrylate compounds representing hydroxyl group-containing vinyl compounds are monomers for forming polymers; raw materials for producing various chemical products such as paints, adhesives, detergent builders and transparent resins; It is expected to be used in a wide range as an intermediate for pharmaceuticals such as virus agents, and industrial practical application is awaited.

Several methods for producing hydroxyl group-containing vinyl compounds typified by α-hydroxymethyl acrylate compounds have already been proposed. For example, α, β-unsaturated carboxylic acid esters and aldehydes can be easily produced by α-hydroxylalkylation in the presence of a tertiary amine catalyst. This reaction is widely known as the Morita-Baylis-Hillman reaction (see, for example, Non-Patent Document 1 or 2). Since a hydroxyl group-containing vinyl compound can be produced by a one-step reaction, it is currently the only industrial and practical one. It is a manufacturing method of a hydroxyl-containing vinyl compound (for example, refer patent document 1). However, when α-hydroxymethyl acrylate compounds are produced by Morita-Baylis-Hillman reaction, formaldehyde designated as a specific chemical substance is used as a reaction raw material, so formaldehyde is removed from α-hydroxymethyl acrylate compounds of products. This is essential from the environmental and product quality perspectives.

As a method for removing formaldehyde from a hydroxyl group-containing vinyl compound, it has been disclosed to remove formaldehyde by washing and purifying the hydroxyl group-containing vinyl compound with water (for example, see Patent Document 2). However, since the hydroxyl group-containing vinyl compound and formaldehyde are compatible with water, formaldehyde cannot be sufficiently removed even by washing with water, and usually remains at a ratio of about 500 to 1000 ppm, and further purified by distillation after washing with water. However, it cannot be reduced sufficiently. The formaldehyde content after purification shown in practice is 200 to 1000 ppm, and it can be said that the formaldehyde content can be reduced only to this extent in such a conventional technique.

As a method for removing impurities from 2- (1-hydroxymethyl) acrylic acid alkyl ester, the crude 2- (1-hydroxymethyl) acrylic acid alkyl ester obtained by the Morita-Baylis-Hilman reaction is dissolved in water, A purification method is disclosed in which impurities are extracted and removed using a specific solvent (see, for example, Patent Document 3). However, even in this method, since formaldehyde is readily soluble in water like the 2- (1-hydroxymethyl) acrylic acid alkyl ester, the removal of formaldehyde by the disclosed technique is insufficient.

After removing impurities from α-hydroxyalkyl acrylates using water, heat treatment is performed for the purpose of removing acetal compounds, which are impurities having a boiling point close to that of α-hydroxyalkyl acrylates, to change the compounds to high boiling point compounds. Thus, there is disclosed an impurity removal method that can be removed by subsequent distillation purification (see, for example, Patent Documents 4 and 5). However, since the formaldehyde does not change in this method, it cannot be sufficiently removed by distillation purification, and the removal of formaldehyde by the disclosed technique is still insufficient.

A method of removing formaldehyde by treating a hydroxyl group-containing vinyl compound with an aqueous solution of sodium hydrogen sulfite or an aqueous solution of hydrazine and then recovering and purifying the separated oil layer (for example, see Patent Document 2). . It is disclosed that formaldehyde can be reduced to 20 to 150 ppm by this treatment. The hydroxyl group-containing vinyl compound obtained by this method has room for contrivance to more sufficiently prevent the influence of impurities.

Furthermore, in producing a specific α-hydroxymethyl acrylate compound by reacting a specific acrylate compound with a specific aldehyde compound in the presence of a tertiary amine catalyst and water, the reaction is carried out by reacting the acrylate compound with a tertiary amine catalyst. A method for producing an α-hydroxymethyl acrylate compound in which the mole fraction of water of three components of an amine catalyst and water is carried out in the presence of a specific amount of water is disclosed (for example, see Patent Document 6). After completion of the reaction, the reaction solution is separated into an organic phase and an aqueous phase, and the target α-hydroxymethyl acrylate compound can be recovered by distillation of the organic phase. Prior to distillation of the organic phase, It has been shown that the organic phase is washed with an aqueous solution of an organic or inorganic acid. However, essentially like the prior art described above, such aqueous solution washing and distillation operations do not adequately remove formaldehyde.
Ciganek, E. “Organic Reaction (Org. React.)” (USA), 1997, 51, p201. Basavaiah, D., two others, “Chem. Rev.” (USA), 2003, 103, p811. Japanese Patent No. 2760954 (2nd page) JP-A-10-53547 (page 2, pages 6-8) Japanese Patent Laid-Open No. 5-70408 (pages 2 and 3) JP-A-9-67310 (Pages 2, 5) JP 2007-70607 A (page 2, 20) JP 2000-319228 A (2nd and 5th pages)

As described above, since it is very difficult to produce high-quality α-hydroxymethyl acrylate compounds (hereinafter also referred to as “RHMAs”) from which formaldehyde has been removed with high efficiency, the content of formaldehyde is small and the color is substantially colored. No RHMAs and their practical production methods have been desired.
The present invention has been made in view of the above-mentioned present situation, and provides RHMAs having a small amount of formaldehyde used as a raw material in a product and substantially free of coloring, and a practical production method thereof. It is the purpose.

The inventors have made various studies in order to obtain low formaldehyde-containing RHMAs, and as a result, high-efficiency production that effectively removes formaldehyde, which has been very difficult until then, without impairing the quality of the RHMAs. I found a way. That is, it has been found that RHMAs having an industrial and practical formaldehyde content of less than 200 ppm and having substantially no coloring problem can be obtained, and the RHMAs are provided at low cost. The present inventors have arrived at the present invention by conceiving that the problem can be solved brilliantly.

Thus, the present invention pays attention to the fact that the formaldehyde content of RHMAs is low and less than 200 ppm, making it useful industrially, and such low formaldehyde-containing RHMAs can be produced. It provides a new production method that can be said to be industrially practical.
For example, when producing RHMAs by removing formaldehyde, one method of removing formaldehyde includes a method of removing it by reflux. In one embodiment of the present invention, a so-called total reflux method is used instead of the usual distillation operation performed in the above-described prior art. Total reflux is a purification operation in which a crude product (also referred to herein as crude RHMAs) is vaporized under reduced pressure, and substantially all of the liquefied product is refluxed. Thereby, it becomes possible to make formaldehyde content of RHMA finally obtained by the manufacturing method of this invention into less than 200 ppm.

In order to remove formaldehyde contained in the above crude RHMAs, when a normal distillation operation as performed in the prior art is performed (when the reflux ratio is set as in a normal distillation operation), In order to perform fractional distillation of components using the difference in boiling point, a column is provided in the distillation column. However, in order to provide a column, it is necessary to install a shelf and use packing materials. Is not. When crude RHMAs containing a large amount of formaldehyde are distilled in this state, vaporized formaldehyde is precipitated as paraformaldehyde, and the inside of the distillation tower is contaminated. For this reason, the refinement | purification by the said reflux operation cannot be performed suitably, and formaldehyde cannot fully be removed from crude RHMAs. In addition, the above-described precipitation and contamination in the distillation tower cannot be completely suppressed only by washing with water prior to a normal distillation operation as in the prior art.
In the present invention, the formaldehyde content of the crude RHMAs can be sufficiently reduced in advance by the total reflux step described above before the purification step by distillation. By performing a purification step by distillation after this total reflux step, it is possible to sufficiently prevent formaldehyde from being deposited in the distillation column in the purification step by distillation, and the purification step by distillation can be suitably performed. .
Therefore, the total reflux step in the production method of the present invention can sufficiently remove formaldehyde from RHMAs, and can sufficiently prevent contamination in the distillation column. This makes it possible to suitably perform the subsequent purification step by distillation, and further to remove formaldehyde. By an industrially practical production method, the formaldehyde content of the obtained RHMAs can be finally reduced to less than 200 ppm, and industrially useful RHMAs can be obtained. This is the significant technical significance of the production method of the present invention.

The production method of the present invention can also be achieved by removing formaldehyde by adsorption using an adsorbent instead of or in addition to the above-described removal by reflux (a method using total reflux). be able to. Even when such a formaldehyde removal method other than total reflux is used, when the formaldehyde content of the crude RHMAs is sufficiently reduced and the distillation process is subsequently performed, vaporized formaldehyde is precipitated and the inside of the distillation column is removed. The distillation step can be suitably performed while sufficiently preventing contamination. As a result, the advantageous effects of the present invention can be exhibited as described above. As the adsorbent, porous solids and basic anion exchange resins are suitable.
In summary, the methods for suitably removing formaldehyde from crude RHMAs include (1) removal by reflux (total reflux method), (2) removal by formaldehyde adsorption using a porous solid, and (3) base. Removal by formaldehyde adsorption using a functional anion exchange resin.
And (4) Oxidation treatment using ozone can be used instead of these methods or together with these methods.
The present invention is a method for removing formaldehyde by applying at least one of the methods described above, and a method for producing RHMAs.

Further, if RHMAs do not substantially contain a formaldehyde-removing component, they can be substantially non-colored, and further, formaldehyde is less than 200 ppm, and the component is not substantially contained. Thus, it has been found that industrially useful RHMAs can be obtained.
As a method for removing formaldehyde contained in the crude RHMAs, in the prior art, as described above, after treatment with an aqueous solution of hydrazine or the like, the separated oil layer is recovered and purified. In such a case, in the RHMAs obtained by this method, sulfur-containing compounds and nitrogen-containing compounds remain as impurities. Coloring, which is considered to be the effect, will occur, and it will be improved by washing the oil layer part containing RHMAs, but since RHMAs are water-soluble, it will cause a reduction in the recovery rate by washing with water. Not. In addition, the recovery rate is lowered by the above processing itself, and in order to improve the recovery rate, complicated operations such as solvent extraction from the aqueous layer portion are required.
Since the RHMAs of the present invention contain substantially no formaldehyde-removing component, the resulting RHMAs can be substantially free of coloring. In addition, since such RHMAs do not need to be washed with water in order to eliminate coloration, it is possible to efficiently obtain a target product with a high recovery rate.
The RHMAs of the present invention are novel compositions, and exhibit the advantageous effects of the present invention described above. Therefore, the monomers provided to form the polymer, the raw materials for producing various chemical products and pharmaceuticals, It can be suitably used as an intermediate or the like.

That is, the present invention is a method for producing α-hydroxymethyl acrylate compounds by including a step of reacting an acrylate ester with formaldehyde in the presence of a catalyst, wherein the production method comprises a crude product obtained from the reaction step. This is a method for producing α-hydroxymethyl acrylate compounds having a purification step in which a product is vaporized under reduced pressure, and substantially all of the liquefied product is refluxed, and the formaldehyde content is less than 200 ppm.

The present invention is also a method of producing α-hydroxymethyl acrylate compounds by including a step of reacting an acrylate ester with formaldehyde in the presence of a catalyst, wherein the production method comprises a crude product obtained from the reaction step. It is also a method for producing α-hydroxymethyl acrylate compounds having a purification step of treating a product with an adsorbent and having a formaldehyde content of less than 200 ppm.
The present invention is also α-hydroxymethyl acrylate compounds obtained by the production method described above.
The present invention also provides the following general formula (1):

(In the formula, R represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 4 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Α-hydroxymethyl acrylate compounds comprising the compound represented by formula (1), wherein the α-hydroxymethyl acrylate compounds have a formaldehyde content of less than 200 ppm and are substantially free of formaldehyde removal components. It is also an α-hydroxymethyl acrylate compound which is not contained.
The present invention is described in detail below.

In the present invention, in order to reduce the formaldehyde content of RHMAs to less than 200 ppm, (1) reflux is performed, (2) adsorption is performed using a porous solid, and (3) basic anion exchange resin. At least one purification operation is performed from among the adsorption using the sucrose. Further, instead of these operations or together with these operations, (4) oxidation treatment using ozone may be performed. Among these, it is preferable to carry out reflux. In this case, in the present invention, purification by removing formaldehyde is performed by an operation by so-called total reflux. Below, each refinement | purification operation is explained in full detail.

(1) Removal by reflux As described above, when formaldehyde is to be removed only by distillation operation as in the prior art, it is necessary to provide a stage in the distillation column and perform fractional distillation. Formaldehyde is precipitated and contaminates the inside of the distillation tower, and the treatment becomes complicated, so it was not an efficient production method. As a result, the formaldehyde content cannot be reduced to less than 200 ppm, and when performing washing and distillation as in the prior art, or after treatment with an aqueous solution of a formaldehyde-removing component such as hydrazine, the separated oil layer part Even when recovering and purifying water, it is not an advantageous process because of the loss of RHMAs in water and the effect of coloring due to the formaldehyde removal component, and the quality is improved. RHMAs could not be obtained.
On the other hand, according to the so-called total reflux operation, there is no need to provide a stage for fractional distillation in the distillation column in the total reflux process, and when the distillation process is performed after the total reflux process, Can be sufficiently reduced to less than 200 ppm. It has been found that if the total reflux step is performed before the distillation step, the distillation operation can be performed in a state where the formaldehyde content is lowered, and thereby precipitation of paraformaldehyde can be sufficiently suppressed. is there. By applying such a process to the production of RHMAs, it is possible to obtain excellent RHMAs with improved quality.

As described above, the method for removing formaldehyde in the production method of the present invention includes removal by total reflux. Because formaldehyde and RHMAs interact with each other, and paraformaldehyde is deposited in the distillation column as described above, the formaldehyde in the distillate should be reduced to less than 200 ppm by ordinary distillation purification operation alone. It is difficult. However, by maintaining the total reflux state of RHMAs under reduced pressure, formaldehyde, which is a non-condensable gas, is excluded to a vacuum system (hereinafter also referred to as a reduced pressure system or a reduced pressure line). The formaldehyde content can be sufficiently reduced, and the formaldehyde content of the RHMAs finally obtained by the production method of the present invention can be less than 200 ppm. In order to reduce the pressure during the total reflux, the gas phase portion of the distillation apparatus is sucked. At that time, the formaldehyde may be sucked and discharged from the distillation apparatus. Normally, formaldehyde is discharged from the decompression device by vacuum distillation.

An example of a total reflux apparatus used in a preferred embodiment of the present invention is shown in FIG.
In the said manufacturing method, the refinement | purification process which makes the crude product obtained from a reaction process a vapor | steam under reduced pressure, and recirculate | refluxs substantially all the liquefied things is included. For example, in a crude product vaporized under reduced pressure, vaporized components including formaldehyde are sucked under reduced pressure and removed from the distillation apparatus, while other components are liquefied, and the liquefied components are substantially reduced. All will be refluxed. For example, the crude product obtained from the reaction step is vaporized under reduced pressure, liquefied using a cooler (for example, a cooling pipe), and substantially all of the liquefied components are refluxed as they are (without fractionation operation). A preferred embodiment is a purification process in which the remaining components that are not liquefied (vaporized components including formaldehyde components) are sucked and removed under reduced pressure.
The total reflux step in the present invention is performed for the purpose of sucking vaporized components including formaldehyde and discharging them from the distillation apparatus, and therefore, a distillation column (in the present specification, containing substantially no filler). , Also referred to as an empty distillation tube), and such a form is preferable. Thereby, it can fully prevent that paraformaldehyde precipitates in the whole reflux process and contaminates the inside of the distillation column.
This total reflux treatment may be performed separately from the RHMAs distillation purification step described later, or may be performed simultaneously using the same apparatus as the distillation purification step. It is particularly preferable to carry out as a pre-process of the distillation purification process of RHMAs as will be described later.

In order to obtain RHMAs having a formaldehyde content of less than 200 ppm by the above method for removing formaldehyde by total reflux, a factor of “total reflux ratio” is very important.
The total reflux ratio represents the ratio of the total amount of steam at the time of reflux to the total charge of crude RHMAs before formaldehyde removal in carrying out total reflux. That is, the total reflux is calculated by the following formula:
Total reflux ratio = V / B
(Here, V represents the accumulated vapor amount [g] at the time of total reflux, and B represents the charged amount [g] of crude RHMAs).
V and B described in FIG. 1 represent the accumulated steam amount at the time of the total reflux and the charged amount of the crude RHMAs in the empty distillation tube 1, respectively.
In addition, the reflux ratio in normal distillation operation means ratio L / D of the liquid flow rate L (g / s) returned to the distillation column, and the liquid flow rate D (g / s) withdrawn.

In reducing the formaldehyde content to less than 200 ppm by the total reflux treatment, the total reflux ratio usually needs to be 0.5 or more.
That is, in the production method of the present invention, the total reflux ratio is obtained by V / B, where V is the cumulative vapor amount in the purification step and B is the amount of the crude product charged into the purification step. The purification step is preferably performed so that the ratio is 0.5 or more.
The total reflux ratio is more preferably 0.7 or more. More preferably, it is 0.8 or more, and particularly preferably 1.0 or more. Moreover, 100 or less is more preferable. More preferably, it is 50 or less, and particularly preferably 10 or less. For example, more preferably, it is 0.7-100, More preferably, it is 0.8-100, Especially preferably, it is 0.8-50, Most preferably, it is 1.0-10.

The pressure condition during the total reflux depends on the type of RHMA, but is preferably performed under a reduced pressure of 10 hPa to 150 hPa, more preferably 10 hPa to 120 hPa, and particularly preferably 10 hPa to 100 hPa. .
The treatment temperature during the total reflux is preferably limited to 160 ° C. or less from the viewpoint of preventing polymerization, although it depends on the type of RHMA. More preferably, it is performed at 80 ° C to 150 ° C, more preferably 100 ° C to 140 ° C.
The total reflux treatment time depends on the type of RHMA and the type of polymerization inhibitor (hereinafter also referred to as polymerization inhibitor), but is preferably within 24 hours from the viewpoint of polymerization prevention. is there. More preferably, it is 3 hours to 12 hours. More preferably, it is 4 hours to 10 hours.

In addition, since the above RHMAs have high polymerizability, when refluxing the crude RHMAs, a polymerization inhibitor or molecular oxygen should be added to the treatment system in order to suppress the polymerization of the RHMAs. Is preferred.
Specific examples of the polymerization inhibitor include alkyl phosphates such as phosphoric acid, trimethyl phosphate, triethyl phosphate and tributyl phosphate, aryl phosphates such as diphenyl phosphate, trimethyl phosphite, Phosphites such as triethyl phosphate, triphenyl phosphite, phosphines such as trimethylphosphine, triethylphosphine, tributylphosphine, triphenylphosphine, tris (pentafluorophenyl) phosphine, trimethylphosphine oxide, triethylphosphine oxide, etc. Alkylphosphine oxide, trade name “ADK STAB 2112” (Asahi Denka), trade name “HCA” (Sanko), trade name “ADK STAB PEP-8” (Asahi Denka), trade name “ADK STAB 260” (Asahi Denka) ), Product name "Adekastab 010 ”(manufactured by Asahi Denka), trade name“ Adeka Stub HP-10 ”(manufactured by Asahi Denka), trade name“ Adeka Stub 329K ”(manufactured by Asahi Denka), trade name“ Adeka Stub PEP-24G ”(manufactured by Asahi Denka), trade name Phosphorus compounds such as “IRGAFOS168” (manufactured by Ciba); nonylphenol, mono-t-butyl-p-cresol, mono-t-butyl-m-cresol, 2,4-dimethyl-6-t-butyl-phenol, 2, 6-di-t-butyl-p-cresol (BHT), 2,6-di-t-butylphenol, 4-hydroxymethyl-2,6-di-t-butyl-phenol, methoquinone (MEQ), guaiacol, 3 -Methoxyphenol, 4-methoxyphenol, hydroquinone (HQ), methylhydroquinone, t-butylhydroquinone, catechol, 4-methyl Catechol, 4-t-butylcatechol (TBC), resorcinol, 2-methylresorcinol, 5-methylresorcinol, propyl gallate, trade name “Sumilyzer GM” (manufactured by Sumitomo Chemical), trade name “Sumilyzer GS” (manufactured by Sumitomo Chemical) , Phenolic compounds such as trade name “IRGANOX1222” (manufactured by Ciba); trade name “Sumilyzer TPL-R” (manufactured by Sumitomo Chemical), trade name “Sumilyzer TPS” (manufactured by Sumitomo Chemical), trade name “Sumilyzer TPD” ( Organic sulfur compounds such as Sumitomo Chemical Co., Ltd .; Lactone compounds (mixed products) such as trade name “IRGANOXHP2225FF” (Ciba), trade name “IRGANOXHP2341” (Ciba), trade name “IRGANOXHP2921FF” (Ciba); Dibutyldithiocarbamic acid Metal complexes such as zinc and copper dibutyldithiocarbamate; phenyl-α-naphthylamine, N, N′-diphenyl-p-phenylenediamine, 4,4-tetramethyldiaminodiphenylamine, piperidine, 2,6-dimethylpiperidine, 2, 2,6,6-tetramethylpiperidine (TEMP), piperidinooxy free radical, 2,6-dimethylpiperidino free radical, 2,2,6,6-tetramethylpiperidino free radical (TEMPO), trade name “ Amines or N-oxyl compounds such as CXA5415 (manufactured by Ciba), trade name “ZJ705” (manufactured by Ciba); nitroso compounds such as trade name “Q1300” (WAKO reagent), trade name “Q1301” (WAKO reagent), Examples include phenothiazine, but are not particularly limited Absent. Of these, phenol compounds, N-oxyl compounds, metal complexes, and phenothiazine are preferable. These polymerization inhibitors may be used alone or in a suitable mixture of two or more.
Although the addition amount of the said polymerization inhibitor is not specifically limited, Usually, what is necessary is just to make it the ratio with respect to crude RHMAs be in the range of 0.01 mass%-1 mass%.

As said molecular oxygen, oxygen-nitrogen mixed gas and air can be used, for example. In this case, an oxygen-containing gas may be blown into the reaction system (so-called bubbling). The polymerization inhibitor and molecular oxygen may be used in combination.

(2) A method for producing α-hydroxymethyl acrylates by reacting an acrylic ester removed by formaldehyde adsorption using a porous solid with formaldehyde in the presence of a catalyst, comprising at least α-hydroxymethyl acrylate compounds A method for producing α-hydroxymethyl acrylate compounds having a step of treating a composition containing aldehyde and formaldehyde with a porous solid is a preferred embodiment of the present invention.
The porous solid is not particularly limited, and examples thereof include various metal oxides represented by titania, metallosilicate, silica gel and the like, natural minerals such as clay, diatomaceous earth, and pumice, and carbon materials such as activated carbon. 1 type or 2 or more types can be used. Preferred are metal oxides, clays and activated carbons, and more preferred are metal oxides.

Examples of the metal oxide include single metal oxides such as silica, titania, zirconia, and magnesia, and composite oxides such as silica-alumina, titania-silica, silica-magnesia, and zeolite. Species or two or more can be used. Among these, silica, titania, silica-alumina, titania-silica, and zeolites are preferable, and titania and zeolites are more preferable.
The above zeolites are not particularly limited to those naturally occurring or obtained by synthesis, for example, zeolite A, zeolite X, zeolite Y, zeolite L, zeolite Ω, ZSM-5, β-zeolite Mordenite can be used, and zeolite A, zeolite X, zeolite Y, and ZSM-5 are preferred.
In the case of using the above-mentioned porous solid, the formaldehyde adsorption condition is limited to 160 ° C. or less from the viewpoint of preventing polymerization of RHMAs, but is not particularly limited, and preferably 0 ° C. to It is carried out in a temperature range of 150 ° C., more preferably 10 ° C. to 130 ° C., further preferably 20 ° C. to 130 ° C.
The time required for adsorption removal is not particularly limited, but is preferably 1 minute to 20 hours, more preferably 10 minutes to 5 hours.

The treatment at this time is preferably performed in the presence of a polymerization inhibitor, and specific examples, preferred forms, use modes, and the like of the polymerization inhibitor to be used are as described above. These polymerization inhibitors may be charged in a predetermined amount before the adsorption treatment, or may be added in portions during the adsorption treatment.
After the formaldehyde is adsorbed using the porous solid, the porous solid adsorbed with formaldehyde is removed by filtration to obtain RHMAs of products. At this time, if necessary, further purification may be performed by distillation or the like. In addition, the preferable form of distillation etc. are as mentioning later.
The filtration is preferably performed between room temperature and 120 ° C.
Such a preferable form is the same as the preferable form in the manufacturing method of this invention which has the refinement | purification process of said (1).

(3) A method for producing α-hydroxymethyl acrylate compounds by reacting a removed acrylic acid ester by formaldehyde adsorption using a basic anion exchange resin with formaldehyde in the presence of a catalyst, obtained from the reaction step A method for producing α-hydroxymethyl acrylate compounds having a step of treating the resulting crude product with a basic ion exchange resin is also a preferred embodiment of the present invention.
When adsorbing and removing formaldehyde using the above basic anion exchange resin, the basic anion exchange resin to be used is not particularly limited to an acrylic or styrene polymer skeleton.
The basic anion exchange resin includes a gel type and a macroporous type, but is not particularly limited to these types.

Specific examples of these basic anion exchange resins include Diaion SA, Diaion UBA120, Diaion PA300, Diaion PA400, Diaion HPA, Amberlite IRA400Cl, Amberlite IRA402BL, Amberlite IRA410Cl, Amberlite IRA411. , Dowex Monosphere 550A, Dowex Marathon MSA, Dowex Marathon A2 and other strongly basic anion exchange resins, Diaion WA10, Diaion WA20, Diaion WA21, Diaion WA30, Amberlite IRA67, Amberlite Weakly basic anion exchange resins such as Wright IRA96SB, Amberlite XT6050RF, Dowex 66, Dowex Marathon WBA There may be used one or two or more of these. Although not particularly limited, a weak basic anion exchange resin is preferable, and Diaion WA20 and Diaion WA21J are more preferable.

The conditions for removing formaldehyde by adsorption using the basic anion exchange resin described above depend on the basic anion exchange resin to be used, but it must be performed at a temperature lower than the heat resistant temperature of the basic anion exchange resin. There are no particular restrictions. The specific treatment temperature is preferably in the range of 0 to 150 ° C, and particularly preferably in the range of 0 to 100 ° C.

The treatment at this time is preferably performed in the presence of a polymerization inhibitor, and specific examples, preferred forms, use modes, and the like of the polymerization inhibitor to be used are as described above. These polymerization inhibitors may be charged in a predetermined amount before the adsorption treatment, or may be added in portions during the adsorption treatment.
Such a preferable form is the same as the preferable form in the purification step (1).

Further, the present invention is a method for producing α-hydroxymethyl acrylate compounds by including a step of reacting an acrylate ester with formaldehyde in the presence of a catalyst, wherein the production method is a crude product obtained from the reaction step. It is also a method for producing α-hydroxymethyl acrylate compounds having a purification step of treating the product with an adsorbent and having a formaldehyde content of less than 200 ppm.
Examples of the purification step to be treated with the adsorbent include (2) those using a porous solid as the adsorbent and (3) those using a basic anion exchange resin as the adsorbent. That is, the adsorbent is preferably at least one selected from the group consisting of a porous solid and a basic anion exchange resin. More preferably, it is a basic anion exchange resin.

(4) Oxidation treatment using ozone The present invention further relates to a method for producing α-hydroxymethyl acrylate compounds by reacting an acrylate ester with formaldehyde in the presence of a catalyst, which is obtained from the reaction step. It is also a method for producing α-hydroxymethyl acrylate compounds having a step of treating the product with ozone.
As a method for removing formaldehyde, RHMA containing formaldehyde is oxidized with a predetermined amount of ozone and removed as formic acid.
Although the amount of ozone used depends on the amount of RHMA to be treated and the amount of formaldehyde contained, it is preferably 10 to 1000 ppm, particularly preferably 10 to 500 ppm, based on the RHMA to be treated.
The treatment temperature depends on the type of RHMA, but is limited to 160 ° C. or less from the viewpoint of preventing polymerization, but is preferably 30 ° C. to 150 ° C., more preferably 50 ° C. to 140 ° C.

The treatment at this time is preferably performed in the presence of a polymerization inhibitor, and specific examples, preferred forms, use modes, and the like of the polymerization inhibitor to be used are as described above. These polymerization inhibitors may be charged in a predetermined amount before the ozone treatment, or may be added separately during the ozone treatment.
Further, after the ozone treatment, low formaldehyde-containing RHMA substantially free of color may be obtained by distillation purification of RHMAs from which formaldehyde has been removed.
Such a preferable form is the same as the preferable form in the purification step (1).

Any one or more of these purification steps can be used to sufficiently remove formaldehyde. Furthermore, when performing the refinement | purification process by distillation after that, it can fully prevent that the vaporized formaldehyde precipitates as paraformaldehyde as mentioned above, and contaminates the inside of a distillation tower. Therefore, the purification process by distillation can be suitably performed, and thereby the formaldehyde content of RHMAs can be sufficiently reduced. Moreover, it can be made to contain substantially no formaldehyde-removing component, and industrially advantageous RHMAs that are substantially free of coloration can be obtained efficiently. In other words, the production method of the present invention preferably has a formaldehyde content of less than 200 ppm by further including a purification step by distillation after the purification steps (1) to (4).
In the above process, (2) and (3) are used for the regeneration and disposal of the treated porous solid (porous solid) and ion exchange resin, and in (4) the ozone generator and the ozone discharged outside the system. Although treatment is required, (1) is simple because it can be carried out by adjusting the operating conditions in the purification step by distillation, and the step (1) is a preferred embodiment in the production method of the present invention. Moreover, the said process may be implemented independently and may be implemented in combination of 2 or more. The above steps are preferably performed in combination with other purification steps such as distillation and washing of RHMAs. In this case, the order of the other purification steps and the steps of the present invention is not particularly limited, but will be described later. Thus, a form in which a purification step by distillation is performed after the above step is particularly preferable.

(Morita-Baylis-Hilman reaction)
The production method of RHMAs using the Morita-Baylis-Hilman reaction, which is the practical production method described above, will be described below. The production method (treatment method) of the present invention is obtained using acrylic acid ester and formaldehyde as raw materials. Any RHMA can be used without any particular limitation.
This production method is a reaction for obtaining RHMA by reacting various acrylic esters (hereinafter also referred to as acrylic esters) and formaldehyde (hereinafter also referred to as formaldehyde) in the presence of a catalyst.

As the catalyst, a tertiary amine used in the Morita-Baylis-Hilman reaction can be preferably used.
Specific examples of the tertiary amine include trialkylamines such as trimethylamine, triethylamine, tri-n-propylamine, and triisopropylamine; N, N-dimethylethylamine, N, N-dimethylpropylamine, N, N, N-dimethylalkylamine such as N-dimethylisopropylamine, N, N-dimethylbutylamine, N, N-dimethylisobutylamine, N, N-dimethyl-t-butylamine, N, N-dimethyl (trimethylsilyl) amine; N, N-diethylmethylamine, N, N-diethylpropylamine, N, N-diethylalkylamine such as N, N-diethylisopropylamine; and the like. These tertiary amines may be used alone or in combination of two or more. Of these tertiary amines, compounds having a relatively high solubility in water are preferred, and N-methylalkylamines (N-methylbenzene) having a boiling point of 100 ° C. or less at normal pressure and having at least one N-methyl group. Methyl compound) is more preferable, and N, N-dimethylalkylamine having a boiling point at normal pressure of 100 ° C. or less and having at least two N-methyl groups is more preferable. Particularly preferred is trimethylamine.

The catalyst can be used in various states such as liquid and gaseous, but is preferably used as a 5 to 80% by mass aqueous solution, and more preferably as a 20 to 60% by mass aqueous solution. By using the catalyst in the form of an aqueous solution, handling at the start of the reaction and at the time of the reaction is facilitated, and handling when the catalyst is recovered and reused after the completion of the reaction is facilitated.

The amount of the catalyst used is not particularly limited, but the catalyst / formaldehyde (molar ratio) is preferably 0.05 to 2, more preferably 0.05 to 1, and still more preferably. 0.07 to 0.9.

Specific examples of the acrylate esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, and acrylic acid. n-octyl, isooctyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate and other alkyl acrylates; cyclopentyl acrylate, cyclohexyl acrylate and other acrylates; phenyl acrylate, acrylic Examples include acrylic acid aryl esters such as acid o-methoxyphenyl, acrylic acid p-methoxyphenyl, acrylic acid p-nitrophenyl, acrylic acid p-methylphenyl, and acrylic acid p-t-butylphenyl. Of these acrylic acid esters, methyl acrylate, ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate are particularly suitable.
Preferred examples of the formaldehydes include 20-50% aqueous solutions of formaldehyde, paraformaldehyde, dioxane, trioxane and the like.

As for the usage-amount of the said acrylic ester (acrylate compound), it is preferable that acrylic ester / formaldehyde (molar ratio) is 0.5-10. More preferably, it is 0.8-8, More preferably, it is 1-8.
Although water is used in the above reaction, the amount of water is preferably 0.001% by mass to 60% by mass with respect to the total reaction liquid amount. More preferably, it is 0.005 mass% or more and 50 mass% or less, More preferably, it is 0.01 mass% or more and 40 mass% or less.
In the above reaction, an organic solvent can be used if necessary, but it is not particularly necessary to use it. The type of the solvent is not particularly limited as long as it is a compound that dissolves the substrate and catalyst used in the reaction and is inert to the reaction.

In the above reaction, both the acrylic ester as a reaction raw material and the RHMA as a product have a property of being easily polymerized. Therefore, in order to suppress polymerization during the reaction, a polymerization inhibitor or molecular oxygen is added to the reaction system. It is preferable to add.
Specific examples of the polymerization inhibitor are as described above. These polymerization inhibitors may be used alone or in a suitable mixture of two or more.

The addition amount of the polymerization inhibitor is not particularly limited, but usually, the ratio to the crude RHMAs may be in the range of 0.0001% by mass to 5% by mass, and the range is within this range. This is a preferred embodiment in the present invention.
As said molecular oxygen, oxygen-nitrogen mixed gas and air can be used, for example. In this case, an oxygen-containing gas may be blown into the reaction system (so-called bubbling). The polymerization inhibitor and molecular oxygen may be used in combination.
In the above reaction, the reaction temperature is not particularly limited as long as the reaction proceeds, but it is preferably performed at 40 to 160 ° C. in order to suppress the polymerization. When the reaction temperature is lower than 40 ° C., the reaction rate is small and the reaction time is too long, which is not preferable for industrial production of RHMAs. More preferably, it exists in the range of 60-100 degreeC.

Although the crude RHMA reaction liquid obtained by the above means depends on the physical properties of the catalyst, the catalyst is separated by a known method such as filtration, recrystallization, crystallization, distillation, extraction or washing treatment with water or an organic solvent. After that, the above-mentioned formaldehyde removal treatment is performed. If necessary, further purified RHMAs are obtained by a known purification method such as distillation. At this time, the purification of RHMAs may be performed before or after the removal of formaldehyde. At this time, the raw acrylates, catalyst and solvent may be recovered, and the whole or a part of the recovered amount may be used again as the reaction raw material, catalyst and solvent.
The treatment for recovering the acrylates may be a normal separation operation, and depending on the physical properties of the RHMAs, examples thereof include distillation and extraction with an organic solvent.

The crude RHMAs are obtained from a step of reacting an acrylate ester with formaldehyde in the presence of a catalyst. In the present invention, any composition containing at least α-hydroxymethyl acrylate compounds and formaldehyde has technical significance.
For example, the present invention can be summarized and summarized as follows. That is, the present invention relates to a method for producing an α-hydroxymethyl acrylate compound by reacting an acrylate ester with formaldehyde in the presence of a catalyst, the composition comprising the α-hydroxymethyl acrylate compound and formaldehyde. At least one of a step of refluxing the composition under reduced pressure, a step of treating the composition with a porous solid, a step of treating the composition with a basic ion exchange resin, and a step of treating the composition with ozone. This is a method for producing α-hydroxymethyl acrylate compounds having one step.

The purification method after the total reflux treatment depends on the physical properties of the corresponding RHMAs, but is not particularly limited as long as it is a normal purification treatment. For example, it is carried out by a treatment such as distillation, crystallization, crystallization. Of these, purification by distillation is particularly preferred.
That is, it is preferable that the production method of the present invention further includes a purification step by distillation after the above-described purification step.
In a purification process using ordinary distillation, when fractionation is performed for each component using a difference in boiling point, it is necessary to appropriately adjust the number of theoretical columns of the distillation column by putting a filler in the distillation column.
Here, as described above, since the formaldehyde content of the crude RHMAs is sufficiently lowered before the purification step by distillation, vaporized formaldehyde is precipitated as paraformaldehyde in the purification step by distillation, and the distillation. The inside of the tower can be sufficiently prevented from being contaminated, and the measures can be simplified. Therefore, it can be suitably purified by distillation using a distillation column containing a filler. From RHMAs, low-boiling components (such as raw materials such as formaldehyde), high-boiling components (such as dimers of the target product), etc. The impurities can be further sufficiently removed, and the effects of the present invention can be more fully exhibited.
The purification step by distillation is preferably a purification step by fractional distillation.

The treatment temperature during distillation (also referred to as bottom temperature or tower bottom temperature) is limited to 160 ° C. or less from the viewpoint of preventing polymerization, although it depends on the type of RHMAs and the treatment pressure, but preferably 80 ° C. to 150 degreeC, More preferably, it carries out at 90 to 140 degreeC.
The pressure condition during distillation depends on the type of RHMA and the distillation temperature, but is preferably performed under a reduced pressure of 10 hPa to 150 hPa, more preferably 10 hPa to 120 hPa, and particularly preferably 10 hPa to 100 hPa. It is.
The time for the distillation treatment depends on the kind of RHMAs and the kind of the polymerization inhibitor, but is preferably within 24 hours from the viewpoint of preventing polymerization, and preferably 3 hours to 12 hours.
In addition, since RHMAs have high polymerizability, when the crude RHMAs are subjected to distillation purification treatment, a polymerization inhibitor or molecular oxygen should be added to the treatment system in order to suppress the polymerization of RHMAs. Is preferred.

The distillation after the total reflux step is usually performed using a distillation column containing a filler. This is because the theoretical plate number of the distillation column is adjusted by adding a filler, and distillation is suitably performed. In addition, precipitation of paraformaldehyde can fully be prevented as described above.
As the above filler, irregular packing such as Raschig ring, Berle saddle, McMahon packing, cascade mini ring, cannon, pole ring, sulzer packing, mela pack, gem pack, techno pack, montz pack, glitch grid, flexi grid, snap grid, Regular packings such as perform grids can be used, and one or more of these can be used. Impurities can be removed more easily by adding a filler. Among them, those filled with sulzer packing (filler manufactured by Sumitomo Heavy Industries, Ltd.) are particularly preferable.

Specific examples, preferred forms, usage modes and the like of the polymerization inhibitor are as described above in the purification step (1).
As said molecular oxygen, oxygen-nitrogen mixed gas and air can be used, for example. In this case, an oxygen-containing gas may be blown into the reaction system (so-called bubbling). The polymerization inhibitor and molecular oxygen may be used in combination.

As described above, in the production method of the present invention, for example, an acrylic ester and formaldehyde are reacted in the presence of a catalyst, oil-water separation (amine removal), acrylic ester is removed, formaldehyde is removed, and purification is performed. It is preferable that it has the process performed by this. Here, according to the present invention, as removal of formaldehyde, any one of (1) removal by total reflux, (2) removal by formaldehyde adsorption using an adsorbent, (4) oxidation treatment using ozone, or Two or more can be performed.
This makes it possible to remove formaldehyde, which has been very difficult until now, effectively and without impairing the quality of the RHMAs. As a result, there is virtually no coloration problem, and industrial and practical formaldehyde RHMAs having a content of less than 200 ppm can be provided.
In the production method of the present invention, the formaldehyde content is preferably 180 ppm or less in the production method of the present invention. More preferably, it is 150 ppm or less. More preferably, it is 120 ppm or less. Particularly preferably, it is 100 ppm or less.

One preferred embodiment of the production method of the present invention will be described below with reference to FIGS. Note that the present invention is not limited to these forms.
The crude product obtained from the step of reacting the acrylate ester with formaldehyde in the presence of a catalyst is fully refluxed using the total reflux device 4 shown in FIG. That is, in the empty distillation tube 1, the crude product is vaporized under reduced pressure, and a part of the vapor is liquefied in the cooler, and formaldehyde, which is unliquefied vapor, is removed to the decompression line. The liquefied product is substantially entirely put into the liquid storage 3 and returned to the empty distillation tube 1 to be refluxed. Thereby, the formaldehyde content of the crude product can be sufficiently reduced.

After the purification step for total reflux, a purification step by distillation is further performed using the fractional distillation apparatus 6 shown in FIG. Here, purification is performed by fractional distillation using the packed column type distillation column 5. Since the formaldehyde content is sufficiently reduced by the purification step in which the total reflux is performed, it is possible to sufficiently prevent the paraformaldehyde from being precipitated and aggregated in the packed column type distillation column 5. The steam is cooled by the cooler to become liquid and enters liquid 3 for liquid. Thereby, RHMAs can be suitably purified by separating RHMAs from impurities such as low-boiling components (raw materials, etc.) and high-boiling components (dimers of the target product, etc.).
As described above, the advantageous effects of the present invention can be sufficiently exhibited.
In addition, the manufacturing method of this invention can be made not to include substantially the process processed using the formaldehyde removal component mentioned later, and such a form is preferable. Thereby, as described later, the effects of the present invention can be more fully exhibited.

The present invention is also α-hydroxymethyl acrylate compounds obtained by at least one production method described above.
The preferable form of (alpha) -hydroxymethyl acrylate compounds of this invention will be obtained by the preferable form in the manufacturing method of this invention mentioned above.

The present invention further includes the following general formula (1);

(In the formula, R represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 4 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Α-hydroxymethyl acrylate compounds comprising the compound represented by formula (1), wherein the α-hydroxymethyl acrylate compounds have a formaldehyde content of less than 200 ppm and are substantially free of formaldehyde removal components. It is also an α-hydroxymethyl acrylate compound which is not contained.
Among these, R is preferably an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 4 to 8 carbon atoms, or an aryl group having 6 carbon atoms. More preferably, it is a C1-C4 alkyl group.

The formaldehyde removal component is washed with an aqueous solution of the formaldehyde removal component so that the formaldehyde contained in the RHMAs forms a salt with the component and is transferred into the aqueous layer to remove formaldehyde from the RHMAs. It is something that can be done. The formaldehyde-removing component is usually a compound (S-containing compound or nitrogen-containing compound) containing S and / or N elements that exhibits the above-described effects. Examples thereof include at least one compound selected from the group consisting of sulfites, amines, and salts thereof. Specific examples of these sulfites, amines and salts thereof are as disclosed in JP-A-10-53547. Among them, sodium bisulfite, hydroxylamine hydrochloride, and hydrazine can be mentioned. Such a formaldehyde-removing component has a strong coloring power as typified by hydrazine and the like, and has a great influence on a small amount.
Once washed with an aqueous solution of formaldehyde-removing component, even if the amount of formaldehyde-removing component is reduced by distillation, etc., the coloration based on the component is not substantially eliminated in an industrially simple process. I can't say that.

The present invention also relates to α-hydroxymethyl acrylate compounds represented by the above general formula (1), which are formaldehyde content of less than 200 ppm and are not colored α-hydroxymethyl acrylate compounds.
The non-colored α-hydroxymethyl acrylate compounds are α-hydroxymethyl acrylate compounds substantially free of coloring components, such as sulfur-containing compounds and / or nitrogen-containing compounds as described above. It does not contain a formaldehyde removal component. The preferable form of (alpha) -hydroxymethyl acrylate compounds of this invention will be obtained by the preferable form in the manufacturing method of this invention mentioned above.

The RHMA of the present invention is a monomer provided to form a polymer; a raw material for producing various chemical products such as paints, adhesives, detergent builders, transparent resins; and the like; manufacture of pharmaceuticals such as anticancer agents and antiviral agents It can be suitably used in applications such as raw materials (intermediates). Especially, it is preferable to use as a manufacturing raw material use of a pharmaceutical.

The present invention is also the use of RHMAs having a formaldehyde content of less than 200 ppm as a raw material for producing pharmaceuticals.
Thereby, it is possible to use a raw material for producing a pharmaceutical product produced by an industrially advantageous production method and having a sufficiently reduced formaldehyde content, and the pharmaceutical product can be suitably produced.
Preferred embodiments of the method of use of the present invention are the same as the preferred embodiments of the method for producing RHMAs and RHMAs of the present invention described above. For example, it is preferable that the RHMAs in the method of use of the present invention contain substantially no formaldehyde removal component.

According to the present invention, it is possible to effectively remove formaldehyde designated as a specific chemical substance without impairing the quality of RHMAs, and as a result, the content of formaldehyde has not been achieved in the past. It is possible to practically produce RHMAs that are reduced to less than 200 ppm and have high purity and substantially no coloring problems. Furthermore, the RHMAs having high purity and substantially no coloration obtained by the production method and having a formaldehyde content reduced to less than 200 ppm are monomers provided for forming a polymer; It can be suitably used in applications such as manufacturing raw materials for various chemical products such as agents, detergent builders, transparent resins, and the like, and pharmaceutical intermediates such as anticancer agents and antiviral agents.

FIG. 1 is a schematic view showing one preferred embodiment of a total reflux apparatus that can be used in the production method of the present invention. FIG. 2 is a schematic view showing one preferred form of a fractional distillation apparatus that can be used in the production method of the present invention.

Explanation of symbols

1: Empty column distillation tube 2: Cooler 3: Liquid 4: Total reflux device 5: Packed column type distillation column 6: Fractional distillation device

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited by the following examples, but may be implemented with appropriate modifications within a range that can meet the purpose described above and below. These are all included in the technical scope of the present invention. Unless otherwise specified, “part” means “part by weight” and “%” means “mass%”.

First, a method for measuring formaldehyde concentration will be described below.
Reagents include 0.2% MBTH (3-methyl-2-benzothiazolone hydrazine hydrochloride), 0.6% aqueous ferric sulfate ammonium solution, and formaldehyde standard solution (concentration measured according to JIS K1502). Using.

Method: Pipette 4 or more formaldehyde standard solutions stepwise into a 50 ml volumetric flask. After adding 5 ml of MBTH reagent, leave it for 30 minutes. Next, 10 ml of ferric ammonium sulfate reagent is added and left for 10 minutes. After dilution to 50 ml with pure water, the solution is further left for 30 minutes to complete color development. The absorbance of each solution is measured at a wavelength of 620 nm to prepare a calibration curve. The formaldehyde concentration of the unknown sample is measured by the same operation.

(Synthesis Example 1 (Synthesis of crude RHMAs))
Into a 3 L four-necked flask equipped with a thermometer, a gas blowing tube, a cooling tube, a stirrer and a water bath, 2066 g (24 mol) of methyl acrylate as an acrylate ester and 92% by mass of paraformaldehyde as a formaldehyde raw material 195. 8 g (6 mol in terms of formaldehyde), 237.8 g (1.2 mol) of 30% by mass trimethylamine aqueous solution as a catalyst, and 2.1 g of p-methoxyphenol as a polymerization inhibitor were charged. The ratio of p-methoxyphenol to methyl acrylate was 1000 ppm. Thereafter, the reaction solution was stirred and reacted at 70 ° C. for 8 hours while air was blown into the reaction solution.
After completion of the reaction, the reaction solution was transferred to a separating funnel and separated into an organic phase and an aqueous phase. Next, 100 g of water was added to the organic phase and washed with water. After separation into an organic phase and an aqueous phase, the organic phase was further washed with the same amount of water, and separated into an organic phase and a washing solution.
The obtained organic phase was transferred to a 2 L four-necked flask equipped with a thermometer, gas blowing tube, empty distillation tube, stirrer and oil bath, 5 g of phenothiazine was added as a stabilizer, and air was blown into it. While adjusting the internal temperature so as not to exceed 100 ° C., methyl acrylate was distilled off at a pressure of 400 to 133 hPa (300 to 100 mmHg). At this time, 616 g of crude RHMAs was obtained, and the formaldehyde concentration in the crude RHMAs was 15340 ppm.

Example 1
600 g of the crude RHMA obtained in Synthesis Example 1 was transferred to a 2 L four-necked flask equipped with a thermometer, gas blowing tube, empty distillation tube, stirring device, and oil bath, and the internal temperature was reduced while blowing air. Refluxing was performed at 110 to 120 ° C. and a pressure of 20 hPa (15 mmHg) for 10 hours. The liquid distilled at this time was cooled by a condenser at 10 ° C. and returned to the flask, and the gas components containing formaldehyde were removed to a vacuum system.
The integrated steam amount at this time was 801 g, the total reflux ratio was 1.3, and the formaldehyde concentration in the obtained crude RHMAs was 320 ppm.
407 g of RHMA-M having a formaldehyde concentration of 20 ppm was obtained by subjecting the crude RHMAs obtained by the above method to fractional distillation by the method described in Comparative Example 1 described later. The results are shown in Table 1.

(Examples 2 to 5)
In Example 1, the reflux time was changed to 8 hours (Example 2), 6 hours (Example 3), 5 hours (Example 4) or 4 hours (Example 5), and the polymerization inhibitor was dibutyldithiocarbamic acid. RHMA-M was obtained in the same manner as in Example 1 except that it was changed to copper (Example 2) and 2,2,6,6-tetramethylpiperidino free radical (TEMPO) (Example 3). The results of formaldehyde concentration in the total reflux ratio, crude RHMAs and purified RHMA-M are shown in Table 1.

(Example 6)
In Example 1, RHMA-M was obtained in the same manner as in Example 1 except that the pressure during reflux was changed to 40 hPa (30 mmHg) and the time was changed to 10 hours. The results of formaldehyde concentration in the total reflux ratio, crude RHMAs and purified RHMA-M are shown in Table 1.

(Comparative Example 1 (Purification of crude RHMAs))
The crude RHMAs obtained in Synthesis Example 1 were subjected to fractional distillation, and methyl 2-hydroxymethyl acrylate (hereinafter referred to as “RHMA-M”), which is a fraction having a tower top temperature of 86 to 87 ° C./13.3 hPa (10 mmHg). 418 g was obtained, and the formaldehyde concentration in this RHMA-M was 2260 ppm. The bottom temperature during rectification when this target product was obtained was 93.5 to 110 ° C.

From the examples and comparative examples described above, it was found that the critical significance of the numerical range of the present invention can be said as follows. That is, it was found that the formaldehyde content of α-hydroxymethyl acrylate can be less than 200 ppm by the production method of the present invention, and the advantageous effects of the present invention are exhibited, which is remarkable.

Regarding the technical significance of the upper limit of the numerical range, Example 5 is 180 ppm, which is lower than the upper limit. In Example 5, it is a level which can manufacture the product of (alpha) -hydroxymethyl acrylate compounds suitable as various chemicals and a pharmaceutical raw material. It goes without saying that such an effect, that is, the effect that it is possible to industrialize products of α-hydroxymethyl acrylate compounds that can be used as various chemicals and pharmaceutical raw materials is remarkable. Absent. In Examples 1 to 4 and Example 6, the formaldehyde content is set to a lower level. However, in these Examples, the effect of the present invention appears more remarkably.

In Examples and Comparative Examples described above, methyl 2-hydroxymethyl acrylate is prepared as RHMAs. However, as long as the RHMAs are prepared by reacting an acrylate ester with formaldehyde in the presence of a catalyst. It contains impurities such as formaldehyde and formaldehyde-removing components as long as it can be used as a monomer provided to form a polymer, an intermediate for various chemicals and pharmaceuticals, or a raw material for production. The mechanism for causing problems such as a decrease in polymerization and coloring is the same. Therefore, it can be said that all RHMAs have the same excellent effect under the purification conditions of the present invention. At least, in the RHMAs represented by the general formula (1), the advantageous effects of the present invention are sufficiently demonstrated by the above-described Examples and Comparative Examples, and the technical significance of the present invention is supported.

Claims (6)

A method for producing α-hydroxymethyl acrylate compounds by including a step of reacting an acrylate ester with formaldehyde in the presence of a catalyst,
The production method has a purification step in which the crude product obtained from the reaction step is vaporized under reduced pressure, and substantially all of the liquefied product is refluxed, and the formaldehyde content is less than 200 ppm. A method for producing α-hydroxymethyl acrylate compounds. In the production method, assuming that the cumulative vapor amount in the purification step is V and the amount of the crude product charged into the purification step is B, the total reflux ratio is obtained by V / B, and the total reflux ratio is 0.00. The method for producing an α-hydroxymethyl acrylate compound according to claim 1, wherein the purification step is performed so as to be 5 or more. A method for producing α-hydroxymethyl acrylate compounds by including a step of reacting an acrylate ester with formaldehyde in the presence of a catalyst,
This manufacturing method has the refinement | purification process which processes the crude product obtained from a reaction process with adsorption agent, Formaldehyde content shall be less than 200 ppm, The manufacturing method of alpha-hydroxymethyl acrylate compounds characterized by the above-mentioned. The α-hydroxymethyl acrylate according to any one of claims 1 to 3, wherein the production method further comprises a purification step by distillation after the purification step, so that the formaldehyde content is less than 200 ppm. Method for producing compounds. Α-Hydroxymethyl acrylate compounds obtained by the production method according to claim 1. The following general formula (1);

(In the formula, R represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 4 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Α-hydroxymethyl acrylate compounds comprising a compound represented by:
The α-hydroxymethyl acrylate compounds have a formaldehyde content of less than 200 ppm and substantially do not contain a formaldehyde removing component.

Images