JP2008222702A - Polymerization inhibitor and polymerization inhibiting method for compound containing vinyl group - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymerization inhibitor which inhibits the polymerization of a (meth)acrylic acid ester during its production process and scarcely contaminating the (meth)acrylic acid ester product after the distillation and purification steps, etc., and to provide a polymerization inhibiting method. <P>SOLUTION: The polymerization inhibitor is a coordination compound of salicylic acid (SAL) and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4H-TEMPO) prepared by reacting SAL with 4H-TEMPO in an organic solvent at 50-100°C. The polymerization inhibiting method uses the compound as a polymerization inhibitor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polymerization inhibitor suitable for preventing polymerization of vinyl group-containing compounds such as acrylic acid esters and methacrylic acid esters (in the present invention, these are referred to as “(meth) acrylic acid esters”), and this polymerization prevention. The present invention relates to a polymerization prevention method using an agent.

  It is well known that N-oxyl compounds are effective as polymerization inhibitors for preventing polymerization during production and storage of vinyl group-containing compounds such as (meth) acrylic acid esters.

  For example, Japanese Patent Application Laid-Open No. 2000-103763 (Patent Document 1) describes a method for preventing polymerization of a vinyl group-containing compound by allowing a specific amount of water to coexist with a water-soluble N-oxyl compound. Japanese Patent Application Laid-Open No. 2003-267929 (Patent Document 2) discloses at least one selected from an N-oxyl compound, a manganese oxide, a copper salt compound, a 2,2,6,6-tetramethylpiperidine compound and a nitroso compound. A method for preventing polymerization of (meth) acrylic acid in combination with seeds is described. Japanese Patent No. 3825518 (Patent Document 3) describes a method for preventing polymerization of (meth) acrylic acid and its swell by using an N-oxyl compound and a cobalt compound in combination. Furthermore, in Japanese Patent Publication No. 4-14121 (Patent Document 4), polymerization of a vinyl group-containing compound using bis (2,2,6,6-tetramethyl-4-piperidinooxyl) sebacate compound or the like is performed. A method to prevent is described.

JP 2000-103763 A JP 2003-267929 A Japanese Patent No. 3825518 Japanese Patent Publication No. 4-14121

  In the production of (meth) acrylic acid esters and the like, distillation / purification is generally carried out at a temperature of about 40 to 200 ° C. under reduced pressure. Since the oxyl compound has a vapor pressure, it is inevitably accompanied by a distillate, but as a result, it is mixed in the product. However, in order to produce high-quality (meth) acrylic acid esters and the like, it is desirable to prevent such N-oxyl compound contamination.

  Therefore, the present invention relates to a vinyl group-containing compound such as (meth) acrylic acid ester, which is not mixed into the product during distillation and purification, and has a novel anti-polymerization effect that has a good anti-polymerization effect. It is intended to provide an agent and a method for preventing polymerization using the same.

  According to our studies, when an N-oxyl compound is reacted with an oxyacid, the resulting product has substantially no vapor pressure at a temperature in the range of 40-200 ° C. under reduced pressure (ie, Thus, it was found that the product was not mixed into the product during distillation and purification, and exhibited a good anti-polymerization effect. The present invention has been completed based on such findings.

  That is, the present invention is as follows.

    (1) A polymerization inhibitor for a vinyl group-containing compound comprising a coordination compound synthesized from at least one selected from oxyacids, polycarboxylic acids and polyhydric alcohols and an N-oxyl compound.

    (2) The polymerization inhibitor for a vinyl group-containing compound according to claim 1, wherein H of the carboxyl group and / or hydroxyl group which is a functional group of the oxyacid, polyvalent carboxylic acid and polyhydric alcohol remains.

    (3) Aliphatic or aromatic oxyacid and general formula (1)

Wherein Y is CH ₂ , CHOH, CHCH ₂ OH, CHCH ₂ CH ₂ OH, CHOCH ₂ OH, CHOCH ₂ CH ₂ OH, CHCOOH, CHCOCH ₃ or C═O. A vinyl group-containing compound polymerization inhibitor comprising a coordination compound obtained by reacting a compound with a compound in a solvent.

    (4) Aliphatic or aromatic oxyacids and general formula (2)

(Wherein Y is CHOH, CHCH ₂ OH, CHCH ₂ CH ₂ OH, CHOCH ₂ OH, or CHOCH ₂ CH ₂ OH), and obtained by reacting in a solvent. A polymerization inhibitor for a vinyl group-containing compound, comprising a coordination compound.
(Chemical structure)
In H-NMR analysis, the proton ratio is oxyacid: N-oxyl compound of general formula (2) = 1: 1, and the peak of H derived from the carboxyl group (—COOH) and hydroxyl group (—OH) of oxyacid, Moreover, the peak of H derived from the hydroxyl group (—OH) of the N-oxyl compound of the general formula (2) is observed.

    (5) In preventing the polymerization of the vinyl group-containing compound, as a polymerization inhibitor, an aliphatic or aromatic oxyacid, and the general formula (2)

(Wherein Y is CHOH, CHCH ₂ OH, CHCH ₂ CH ₂ OH, CHOCH ₂ OH, or CHOCH ₂ CH ₂ OH) and an N-oxyl compound represented by an organic solvent at 50 to 100 ° C. A method for preventing the polymerization of a vinyl group-containing compound, comprising using a coordination compound obtained by reacting at a temperature of 1.
(Chemical structure)
In H-NMR analysis, the proton ratio is oxyacid: N-oxyl compound of general formula (2) = 1: 1, and the peak of H derived from the carboxyl group (—COOH) and hydroxyl group (—OH) of oxyacid, Moreover, the peak of H derived from the hydroxyl group (—OH) of the N-oxyl compound of the general formula (2) is observed.

    (6) A method for preventing polymerization of a vinyl group-containing compound, wherein the reaction mixture obtained when synthesizing the coordination compound according to (5) is added and used as a polymerization inhibitor.

    (7) The method for preventing polymerization of a vinyl group-containing compound according to any one of the above (1) to (6), wherein the vinyl group-containing compound is a (meth) acrylic acid ester.

  The polymerization inhibitor of the present invention exhibits almost the same effect as the N-oxyl compound for preventing the polymerization of vinyl group-containing compounds, and is distilled during distillation / purification at 40 to 200 ° C. under reduced pressure. Difficult to mix in things. For this reason, by using the polymerization inhibitor of the present invention, polymerization during distillation / purification at 40 to 200 ° C. is effectively prevented under reduced pressure, and the polymerization inhibitor is very little mixed. A high purity purified vinyl group-containing compound can be obtained (in other words, mixing of the polymerization inhibitor into the product is minimized).

  The polymerization inhibitor of the present invention is particularly preferably used for obtaining a high-purity (meth) acrylic acid ester.

  The polymerization inhibitor of the present invention is also suitably used for preventing polymerization during storage, transport or transfer of a vinyl group-containing compound.

  The polymerization inhibitor of the present invention comprises a coordination compound synthesized from an N-oxyl compound and at least one selected from oxyacids, polycarboxylic acids and polyhydric alcohols.

  Examples of the oxyacid include compounds in which the carbon chain is a saturated hydrocarbon such as glycolic acid, lactic acid, glyceric acid, malic acid, tartaric acid and citric acid, and carbon chains such as oxybenzoic acid and trioxybenzoic acid are aromatic. The compound which is a hydrocarbon is mentioned. Since these oxyacids have two or more functional groups in the molecule, isomers are also included.

  As the polyvalent carboxylic acid, carbon chains such as oxalic acid, malonic acid, succinic acid, adipic acid, butanetricarboxylic acid, hexanetricarboxylic acid, butanetetracarboxylic acid, pentanetetracarboxylic acid, dodecanetetracarboxylic acid are saturated hydrocarbons. Compounds such as maleic acid, fumaric acid, etc., carbon chain such as phthalic acid, trimellitic acid, pyromellitic acid, naphthalene dicarboxylic acid, naphthalene tricarboxylic acid, naphthalene tetracarboxylic acid, etc. The compound which is an aromatic hydrocarbon is mentioned. Since these polyvalent carboxylic acids have two or more functional groups in the molecule, isomers are also included. Among di-, tri- and tetra-carboxylic acids, carboxylic acid anhydrides are also included.

  Examples of the polyhydric alcohol include condensates such as ethylene glycol and propylene glycol (polyethylene glycol having 2 to 10 carbon atoms, polypropylene glycol, etc.), glycerin, trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol, diester. Compounds whose carbon chain is a saturated hydrocarbon such as pentaerythritol, 2,3,4,5-tetrahydroxyhexane, xylitol, mannitol, 2,6-dihydroxytoluene, catechol, tert-butylcatechol, pyrogallol, resorcin, 2, 4-bis (hydroxymethyl) phenol, 1,2,4-trihydroxybenzene, 1,3,5-trihydroxybenzene, 2,4,6-tris (hydroxyethyl) phenol, 1,2,4,5- Tetrahydro Carbon chain, such as Shibenzen the like compounds is an aromatic hydrocarbon.

  The N-oxyl compound, which is another raw material for the polymerization inhibitor of the present invention, is not particularly limited, and any N-oxyl compound can be used as long as it is generally used as a polymerization inhibitor for vinyl group-containing compounds. . Especially, the N-oxyl compound represented by the said General formula (1) or General formula (2) is used suitably. Representative examples of this N-oxyl compound include 2,2,6,6-tetramethylpiperidine-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-hydroxy Methyl-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-hydroxyethyl-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-hydroxymethoxy-2,2,6 6-tetramethylpiperidine-1-oxyl, 4-hydroxyethoxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-carboxy-2,2,6,6-tetramethylpiperidine-1-oxyl 4-acetoxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidine-1 Oxyl and the like. Of these, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl is preferably used.

  Among the polymerization inhibitors of the present invention, an aliphatic or aromatic oxyacid and a general formula (1)

Wherein Y is CH ₂ , CHOH, CHCH ₂ OH, CHCH ₂ CH ₂ OH, CHOCH ₂ OH, CHOCH ₂ CH ₂ OH, CHCOOH, CHCOCH ₃ or C═O. What consists of a compound which has the following physicochemical property obtained by making a compound react with the temperature of 50-100 degreeC in the absence of a catalyst in an organic solvent is suitable.
a. White crystals (25 ° C)
b. Slightly soluble in water (25 ° C) (colorless transparent liquid, white crystals precipitate)
c. Colored in acrylic acid (25 ° C.) (transparent orange), but colorless and transparent in ethylene glycol, ethanol and isobutanol.

  In addition, an aliphatic or aromatic oxyacid and the general formula (2)

(Wherein Y represents CHOH, CHCH ₂ OH, CHCH ₂ CH ₂ OH, CHOCH ₂ OH, or CHOCH ₂ CH ₂ OH) and the absence of a catalyst in an organic solvent. What consists of a compound which has the following chemical structure and physicochemical property obtained by making it react at the temperature of 50-100 degreeC below is suitable.
(Chemical structure)
In H-NMR analysis, the proton ratio is oxyacid: N-oxyl compound of general formula (2) = 1: 1, and the peak of H derived from the carboxyl group (—COOH) and hydroxyl group (—OH) of oxyacid, Moreover, the peak of H derived from the hydroxyl group (—OH) of the N-oxyl compound of the general formula (2) is observed.
a. White crystals (25 ° C)
b. Slightly soluble in water (25 ° C) (colorless transparent liquid, white crystals precipitate)
c. Colored in acrylic acid (25 ° C.) (transparent orange), but colorless and transparent in ethylene glycol, ethanol and isobutanol.

  Examples of the aliphatic oxyacid include oxyacids having a saturated hydrocarbon residue having 2 to 10 carbon atoms, such as glycolic acid, lactic acid, glyceric acid, malic acid, tartaric acid, and citric acid. Examples of the aromatic oxyacid include oxyacids having an aromatic hydrocarbon residue having 6 to 10 carbon atoms, such as oxybenzoic acids and trioxybenzoic acids. Since these oxyacids have two or more functional groups in the molecule, isomers are also included.

  Among the preferred polymerization inhibitors, salicylic acid is used as the aliphatic or aromatic oxyacid, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl is used as the N-oxyl compound. The compound obtained by use is particularly preferably used. Therefore, for the polymerization inhibitor of the present invention, salicylic acid (SAL) is used as an aliphatic or aromatic oxyacid, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1 is used as an N-oxyl compound. A case where oxyl (4H-TEMPO) is used will be described as an example.

When 4H-TEMPO and SAL are reacted in an organic solvent at a temperature of 50 to 100 ° C. in the absence of a catalyst, white crystals are obtained. When this white crystal was analyzed by H-NMR, the proton ratio was 4H-TEMPO: SAL = 1: 1, and the H peak derived from the carboxyl group (—COOH) of SAL and the hydroxyl group (—OH) of 4H-TEMPO were derived. A peak of H is recognized.
The crystal has the following physicochemical properties.
a. White crystals (25 ° C)
b. Insoluble in water at room temperature (25 ° C).
c. Dissolves in acrylic acid at room temperature (25 ° C.) to become an orange transparent liquid. However, it dissolves in ethylene glycol, ethanol and isobutanol, but becomes colorless and transparent. That is, it dissolves in any of ethylene glycol, ethanol and isobutanol, but becomes colorless and transparent.
d. Dissolves in acetone but does not color. Moreover, it becomes colorless and transparent.

  Therefore, it is estimated that the crystal is a coordination compound composed of 4H-TEMPO and SAL (see Example 1 described later).

More specifically, the following chemical structure obtained by reacting salicylic acid (SAL) and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4H-TEMPO) in a solvent A polymerization inhibitor for a vinyl group-containing compound, characterized in that it comprises a coordination compound having physicochemical properties, is a preferred embodiment.
(Chemical structure)
In H-NMR analysis, proton ratio is 4H-TEMPO: SAL = 1: 1, H peak derived from SAL carboxyl group (—COOH), and H peak derived from 4H-TEMPO hydroxyl group (—OH) Is recognized.
(Physical and chemical properties)
a. White crystals (25 ° C)
b. Slightly soluble in water (25 ° C) (colorless transparent liquid, white crystals precipitate)
c. Colored in acrylic acid (25 ° C.) (transparent orange), but colorless and transparent in ethylene glycol, ethanol and isobutanol.

  The above is an invention that more specifically specifies the reaction raw material. As a condition for the reaction, the above-mentioned polymerization inhibitor in which the above-mentioned solvent is an organic solvent is a preferred form. A polymerization inhibitor in which the solvent is a protic solvent is also a preferred form. A polymerization inhibitor in which the above reaction is performed in the absence of a catalyst is a preferred form. Specifically, it is a reaction for obtaining the polymerization inhibitor, but a reaction at a temperature of 50 to 100 ° C. in the absence of a catalyst in an organic solvent is a preferred form.

  In addition, as said organic solvent, although the organic solvent generally used can be used, methanol, ethanol, propanol, ethylene glycol, diethylene glycol, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, Protic solvents which are alcohols such as 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate are preferably used because of their high reactivity. Some solvents have high solubility with the product and are difficult to isolate. In that case, they may be added as a solution together with the solvent.

  Moreover, although it is the said reaction, reaction may be hard to advance in an aprotic solvent (for example, THF and DMSO) among water solvents or organic solvents. In that case, the reaction may be performed by applying a predetermined temperature. Alternatively, in order to improve the reaction timing, a method in which mixing efficiency is increased in a reactor equipped with a stirrer, such as increasing the speed of stirring, may be used so that the raw materials can be efficiently contacted. If necessary, the reaction is carried out at a temperature higher than room temperature.

  Although the reason why the above effect is obtained by using the polymerization inhibitor of the present invention has not yet been elucidated, the oxyacid is coordinated to the N—O group of the N-oxyl compound. It is believed that the polymer has substantially no vapor pressure while maintaining its own polymerization prevention performance.

  The polymerization inhibitor of the present invention is not limited to the one obtained from the above 4H-TEMPO and SAL, but the N-oxyl represented by the oxyacid and the general formula (1) or the general formula (2). A compound obtained by reacting a compound with an organic solvent in an organic solvent can also be used effectively.

  The amount of the oxyacid used is 0.3 to 10 mol, preferably 0.1 to 10 mol, more preferably 0.2 to 5 mol, still more preferably 0.5 to 5 mol, per mol of the N-oxyl compound. And more preferably 0.5 to 2 mol. If the amount of the N-oxyl compound is less than the amount of oxyacid used in the reaction, the salt compound is not easily produced efficiently. Therefore, if it is the range of the said molar ratio, since the production | generation of the said coordination compound concerning this invention becomes possible more efficiently, it is a preferable form in this invention.

  Further, as more preferable reaction conditions, the concentration of the N-oxyl compound in the solvent to be reacted is preferably in the range of 0.01 to 50% by weight. Furthermore, the range of 0.11 to 30% by weight is preferable. Most preferably, it is in the range of 0.5 to 10 wt%. When the concentration of the N-oxyl compound used for the reaction for obtaining the coordination compound is a low concentration of less than 0.01% by weight, the coordination reaction is difficult to proceed and it is difficult to obtain the target product efficiently. On the other hand, if the concentration of the N-oxyl compound is higher than 50% by weight, the N-oxyl compound may be precipitated and the reaction does not proceed easily. That is, it precipitates before participating in a coordination reaction, and the efficiency of reaction falls.

  Therefore, in order to efficiently and reliably produce the coordination compound for the purpose of the present invention and to separate it from the reaction system, it is preferable to use the raw materials in the above range.

  The reaction temperature is 130 ° C. or lower, preferably 120 ° C. or lower, and more preferably 100 ° C. or lower. Specifically, it is the range of 20-130 degreeC, More preferably, it is the range of 20-120 degreeC, More preferably, it is the range of 20-100 degreeC. More preferably, it is 50-100 degreeC, More preferably, it is the range of 80-100 degreeC. Even if the raw material is decomposed, the reaction temperature condition can be appropriately selected and employed as long as the target product of the present invention is produced in a predetermined amount. However, when considering the function as a polymerization inhibitor, the yield of the target product, the reaction rate, etc., it is preferable to adjust the temperature range.

Although it is a reason for adjusting the said reaction temperature, although it changes also with substituents, since the decomposition temperature of an N-oxyl compound is about 140 degreeC, when the reaction temperature is too high, it decomposes carelessly. (For example, 4H-TEMPO is 146 ° C.)
This is a reaction for producing the target compound that is the polymerization inhibitor of the present invention, but if the target compound that is the polymerization inhibitor is efficiently produced, the catalyst is not used even if the catalyst is used. May be. If the reaction is in the absence of a catalyst that does not use a catalyst, there is no need for a separation step from the catalyst residue, and the influence of the catalyst used or catalyst residue and the target product (production of by-products due to inadvertent reaction), etc. This is industrially advantageous.

  Therefore, in order to obtain the target compound of the present invention, it is a preferred form that the reaction in the solvent is carried out in the absence of a catalyst. Of course, if there is no problem in the production of the target compound even in the presence of a catalyst, it is possible to use the catalyst in the reaction.

  Moreover, in this invention, the manufacturing method of the polymerization inhibitor concerning the target compound in this invention using the said reaction turns into preferable embodiment. That is, this invention is also a manufacturing method of the coordination compound which can be used as a polymerization inhibitor synthesize | combined from at least 1 sort (s) chosen from an oxy acid, polyhydric carboxylic acid, and a polyhydric alcohol, and an N-oxyl compound.

  Further, the coordination compound according to the polymerization inhibitor of the present invention is preferably prepared by the method of producing the coordination compound after the above reaction, that is, in the presence of an organic solvent, as shown in the Examples. After reacting the compound with at least one selected from the group consisting of oxyacids, polycarboxylic acids, and polyhydric alcohols, the obtained crystals are separated or isolated from the reaction system, and the crystals are washed as necessary. It is a method of manufacturing through a process of purifying or purifying. The reason is that it is preferable in order to efficiently and surely perform the target coordination reaction. In the compound according to the present invention, by producing the target product through the steps as described above, an N-oxyl compound and at least one of an oxyacid, a polycarboxylic acid, and a polyhydric alcohol can be produced without causing an excessive side reaction. It has also been found that coordination can be carried out efficiently with either of them and crystals can be obtained with high purity.

  In addition, the N-oxyl compound and the oxyl compound after the above reaction, that is, in the presence of an organic solvent, for a reliable coordination reaction or for the reason that the purity of crystals obtained with few side reactions increases. After reacting with at least one of acid, polycarboxylic acid, and polyhydric alcohol, the obtained crystal was separated or isolated from the reaction system, and manufactured through a step of washing or purifying the crystal as necessary. It can be said that the compound of the present invention has an excellent polymerization preventing effect.

  The preferred purity of the compound according to the present invention is in the range of 80% to 100%. More preferably, the purity is in the range of 85% to 100%. Furthermore, it is in the range of 90% to 100%. Further preferred purity is in the range of 95% to 100%.

  In the present invention, a method for preventing polymerization of a vinyl group-containing compound using the coordination compound is also a preferred embodiment.

  Moreover, in this invention, provision as a polymerization inhibitor containing the said coordination compound also becomes a preferable form. The content of the coordination compound as a polymerization inhibitor composition in the present invention is preferably 50% if the polymerization inhibitor composition has a predetermined polymerization prevention function. The range is from wt% to 100 wt%. If the content of the coordination compound according to the present invention is large, its function (good polymerization prevention, low colorability, high boiling point component, so that it is difficult to distill on the distillation column distilling side, that is, the product side, etc.) is good. It is because it can be demonstrated to. More preferably, it is in the range of 60% to 100% by weight, further in the range of 70% to 100% by weight, and further in the range of 80% to 100% by weight.

  The polymerization inhibitor of the present invention can be used in the synthesis, recovery, storage, transportation, transfer, etc. in addition to the step of distilling and purifying the vinyl group-containing compound at a temperature in the range of 40 to 200 ° C. under reduced pressure. Effectively used to prevent polymerization.

  Representative examples of the vinyl group-containing compound of the present invention include (meth) acrylic acid esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate. , 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and the like. Higher boiling point styrene, vinyl styrene, divinyl benzene, various dialkyl acrylates, etc. have higher boiling point, avoid polymerization and coloring during purification (during distillation), and no excess polymerization inhibitor migrates to the product distilling side. The use of a vinyl group-containing compound for which the purification step is preferred for preventing polymerization is a preferred form.

  The polymerization inhibitor of the present invention includes a distillation / purification step at 40 to 200 ° C. under reduced pressure (for example, 1.3 to 500 hPa, preferably 2 to 100 hPa). Preferably used. Specifically, the reaction step of (meth) acrylic acid and alcohol in the presence of a catalyst, the separation step of (meth) acrylic acid ester, the separation step of the solvent, the separation step of the light boiling point material, the separation of the high boiling point material What is necessary is just to make the polymerization inhibitor of this invention coexist with (meth) acrylic acid ester in various processes, such as a process and an extraction process. The polymerization inhibitor of the present invention can prevent coloring of the vinyl group-containing compound during use, which has been a problem with conventional N-oxyl compounds. In addition, since it is difficult to shift to the distillation side during distillation, it does not cause an excessive polymerization preventing effect on the target vinyl group-containing compound as a product. In other words, it is possible to maintain good polymerizability as a vinyl group-containing compound as a product while exhibiting the necessary anti-polymerization performance during purification. Therefore, the form used at the time of the refinement | purification of the (meth) alkyl acrylate which has a hydroxyl group in said inside is preferable. Since the (meth) alkyl acrylate having a hydroxyl group is a vinyl group-containing compound that has high polymerizability, is difficult to be colored depending on the application, and requires high polymerizability as a product, the polymerization inhibitor of the present invention is used. Ideal for use.

  In addition, when the polymerization inhibitor according to the present invention is used in a distillation process or the like, it is effective in the gas phase part in order to more effectively prevent polymerization in the gas phase part due to a gas of a vinyl group-containing compound. A mode in which a polymerization inhibitor having a polymerization preventing function is used in combination is preferred.

  As an example of the method of using the polymerization inhibitor of the present invention, a vinyl compound having a high boiling point such as a range of 100 ° C. to 300 ° C. at normal pressure is distilled under reduced pressure. By distillation under this reduced pressure, the boiling point can be lowered and the temperature of the distillation column can be operated at a temperature in the range of 50 ° C to 150 ° C. In this case, the degree of vacuum in the distillation column is, for example, 4 to 100 hPa. It can be set as appropriate depending on the type of distillation column used for distillation. However, by adjusting the distillation conditions in this way, even if it is a highly polymerizable vinyl compound, the polymerization inhibitor moves to the distillate side without using a polymerization inhibitor up to an unnecessary amount. It is possible to purify in the distillation process under difficult conditions. The distillation column may be a plate-type distillation column having a distillation stage or a single distillation column.

  The polymerization inhibitor of the present invention can also be used when storing or transferring a vinyl group-containing compound such as (meth) acrylic acid ester.

  The polymerization inhibitor of the present invention can be used alone or in combination of two or more. Moreover, as long as the polymerization prevention function is not inhibited, it can also be used in combination with a conventionally known polymerization inhibitor of a vinyl group-containing compound.

  Generally, it can be used if it is industrially used. Specifically, for example, hydroquinone, methylhydroquinone, tert-butylhydroquinone, 2,6-di-tert-butylhydroquinone, 2,5-di-tert. -Phenol compounds such as butyl hydroquinone, 2,4-dimethyl-6-tert-butylphenol, hydroquinone monomethyl ether; N-isopropyl-N'-phenyl-para-phenylenediamine, N- (1,3-dimethylbutyl) -N '-Phenyl-para-phenylenediamine, N- (1-methylheptyl) -N'-phenyl-para-phenylenediamine, N, N'-diphenyl-para-phenylenediamine, N, N'-di-2-naphthyl -Paraphenylenediamines such as para-phenylenediamine Amine compounds such as thiodiphenylamine and phenothiazine; copper dibutyldithiocarbamate, copper diethyldithiocarbamate, dialkyldithiocarbamate such as copper dimethyldithiocarbamate; 2,2,4,4-tetramethylazetidine-1-oxyl, 2, 2-dimethyl-4,4-dipropylazetidine-1-oxyl, 2,2,5,5-tetramethylpyrrolidine-1-oxyl, 2,2,5,5-tetramethyl-3-oxopyrrolidine-1 -Oxyl, 2,2,6,6-tetramethylpiperidine-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 6-aza-7,7-dimethyl-spiro (4,5) decane-6-oxyl, 2,2,6,6-tetramethyl-4-acetoxypiperidine- -Oxyl, 2,2,6,6-tetramethyl-4-benzoyloxypiperidine-1-oxyl, 4,4 ', 4 "-tris- (2,2,6,6-tetramethylpiperidine-1- N-oxyl compounds such as oxyl) phosphite and 4,4′-bis- (2,2,6,6-tetramethylpiperidine-1-oxyl) sebacate; These polymerization inhibitors may be used alone or in combination of two or more. In addition, the amount of the polymerization inhibitor that is easy to color in combination may be adjusted depending on the purpose or may be avoided.

  The amount of the polymerization inhibitor of the present invention varies depending on the type of vinyl group-containing compound to be applied, application temperature conditions, etc., and thus cannot be generally specified, but is usually 0.0001 to 0.1% by mass of the vinyl group-containing compound. Yes, preferably 0.0001-0.01 mass%, more preferably 0.0001-0.001 mass%.

  There is no restriction | limiting in particular in the application method of the polymerization inhibitor of this invention, According to the method generally used for the polymerization prevention of a vinyl group containing compound, it can carry out suitably. For example, the polymerization inhibitor may be added as a powder, or may be dissolved in a product (meth) acrylic acid ester or other organic solvent and added as a solution. Moreover, you may add in the state of the reaction liquid before refine | purifying this polymerization inhibitor.

The invention is further illustrated by the following examples, which illustrate advantageous embodiments of the invention.
(Example 1)
Orange powder 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4H-TEMPO) 5 g (0.03 mol) and white powder salicylic acid (SAL) 15 g (0. 11 mol) and 80 g of ethanol as a solvent were charged in a glass round bottom flask equipped with a stirrer having a capacity of 200 ml, heated to 80 ° C. in an oil bath and reacted for 5 hours. The reaction solution was cooled to 30 ° C., and after a while, white crystals were precipitated. It was 2.5 mass% when the unreacted 4H-TEMPO density | concentration in the isolate | separated filtrate was measured by the liquid chromatography (4H-TEMPO reaction conversion rate 50%). The separated crystals were washed 5 times with 100 g of ultrapure water and dried under reduced pressure to obtain 4 g of white crystals.

The crystals were subjected to H-NMR analysis under the following conditions.
Device: AVANCE 300 (manufactured by BRUKER BIOSPIN)
Solvent: acetone-d6 (99.9%)
An NMR analysis chart is shown in FIG. For reference, the NMR analysis chart of the used SAL is shown in FIG. Specifically, FIG. 2 shows the H-NMR analysis chart of the compound obtained in Example 1 below, the H-NMR analysis chart of SAL at the top thereof, and compares the peaks of each other. .

  Moreover, since 4H-TEMPO is a paramagnetic compound having a radical, NMR measured by applying a magnetic field has an effect, and thus an NMR chart cannot be obtained. Instead, the NMR chart of piperidine is shown in FIG. FIG. 2 is an NMR analysis chart for confirming the —COOH group and —OH group of SAL, and FIG. 3 is an NMR analysis chart for confirming that the peak of the cyclohexyl ring of piperidine is sharp. Furthermore, the NMR chart of cyclohexanol is shown in FIG. FIG. 4 is an NMR analysis chart for confirming the —OH group of 4H-TEMPO. FIG. 5 is an NMR analysis chart for confirming the impurity peak of acetone-d6 used as a solvent.

  1 to 5, the crystal is a compound having a proton ratio of 4H-TEMPO: SAL = 1: 1, H derived from the carboxyl group (—COOH) of SAL and H derived from the hydroxyl group (—OH) of 4H-TEMPO. It can be seen that Since the SAL —COOH-derived H exists, the above crystals are not piperidium ions, and the 4H-TEMPO hydroxyl (—OH) -derived H and other functional groups H also exist. Thus, it is confirmed that the crystal does not have a covalent bond such as an ester bond. From the above, the crystal is presumed to be a coordination compound of SAL and 4H-TEMPO. Moreover, the reaction conversion rate of 4 g of the obtained crystals as 4H-TEMPO is 45%, which is consistent with the reaction conversion rate of 50% obtained from unreacted 4H-TEMPO in the filtrate separated by solid-liquid separation.

  In addition, regarding the NMR measurement conditions of the salt according to the present invention, first, NMR is measured under conditions where the structure of SAL in FIG. 2 can be confirmed. Under the conditions, the obtained salt is confirmed. It is preferable to perform the measurement according to the procedure.

  The NMR charts shown in FIGS. 3 to 5 were obtained from the site of SDBS (National Institute of Advanced Science and Technology) from October to November 2006. The address is http: // www. aist. go. jp / RIODB / SDBS.

The crystals had the following physicochemical properties: The concentration when the solution was dissolved and the color was observed was adjusted to 1% by weight (1 g of solute and 99 g of solvent). In addition, acrylic acid, ethylene glycol, ethanol, and isobutanol are solvents used for observing the solubility of crystals or the color that develops during dissolution, but acrylic acid is commercially available high-purity purified acrylic acid (Nippon Shokubai). A lot, 6G31HD) was used. Moreover, Nippon Shokubai Co., Ltd. lot: 6E22HA was used for hydroxyethyl methacrylate. In addition, all other organic solvents used in dissolution experiments and color development experiments are special grades made by Kanto Chemical Co., Inc., and the influence of impurities (for example, acid components) on the color (colored color) that develops during dissolution appears. I tried not to.
a) White crystals (25 ° C.)
b) It is hardly soluble in water at room temperature (25 ° C.) and becomes a colorless transparent liquid. White crystals are also precipitated.
c) Dissolves in acrylic acid at room temperature (25 ° C.) and becomes transparent orange. However, it dissolves in ethylene glycol, ethanol and isobutanol, but becomes colorless and transparent. That is, it dissolves in any of ethylene glycol, ethanol and isobutanol, but becomes colorless and transparent.
d) Dissolves in acetone but does not color. It becomes a colorless and transparent liquid. Moreover, when the said crystal | crystallization was melt | dissolved in acetone and the gas chromatography analysis (injection temperature: 200 degreeC, column temperature: 100 degreeC) was performed, only the peak derived from acetone was detected. When the vaporization chamber (insert glass) was confirmed, white crystals were attached. Therefore, from this analysis, the purity of the crystals obtained in the above examples is considered to be at least 99% or more.
(Example 2)
In Example 1, it carried out like Example 1 except having replaced with ethanol as a solvent and using 80 g of hydroxyethyl methacrylate. The reaction solution was cooled to 30 ° C., and after a while, white crystals were precipitated. When the concentration of unreacted 4H-TEMPO in the separated filtrate was measured by liquid chromatography, it was 0.2% by mass (reaction conversion rate of 4H-TMPO was 95%). Of white crystals were obtained. The reaction conversion rate of 4 g of the obtained crystals as 4H-TEMPO is 90%, which is consistent with the reaction conversion rate of 90% obtained from unreacted 4H-TEMPO in the filtrate separated by solid-liquid separation. Moreover, the analysis result in the obtained item d is the same as that of Example 1, and the crystal of Example 2 is considered to be 99% or more pure.
(Example 3)
In Example 1, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) which is an orange powder instead of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl The same procedure as in Example 1 was performed except that 80 g of hydroxyethyl methacrylate was used instead of ethanol as a solvent. The reaction solution was cooled to 30 ° C., and after a while, white crystals were precipitated. The concentration of unreacted TEMPO in the separated filtrate was measured by liquid chromatography and found to be 0.5% by mass (TEMPO reaction conversion 90%). The separated crystals were washed / dried to obtain 8 g of white crystals. It was. The reaction conversion rate of 8 g of the obtained crystals as TEMPO is 85%, which is consistent with the reaction conversion rate of 90% obtained from unreacted TEMPO in the solid-liquid separated filtrate.

  An NMR analysis chart of the crystal is shown in FIG. As in Example 1, from FIGS. 2, 3, 5 and 6, the crystal is a compound having a proton ratio of TEMPO: SAL = 1: 1, and H derived from the carboxyl group (—COOH) of SAL is present. From the fact that the crystal is not a piperidinium ion and is obtained from TEMPO having no functional group, the crystal is presumed to be a coordination compound of SAL and TEMPO.

The crystals were confirmed as in Example 1 for the following physicochemical properties.
a) White crystals (25 ° C.)
b) It is hardly soluble in water at room temperature (25 ° C.) and becomes a colorless transparent liquid. White crystals are also precipitated.
c) It becomes orange transparent dissolved in acrylic acid at room temperature (25 ° C.). However, it dissolves in each of ethylene glycol, ethanol and isobutanol but becomes colorless and transparent. That is, it dissolves in any of ethylene glycol, ethanol and isobutanol, but becomes colorless and transparent.
d) Dissolves in acetone but does not color. It becomes a colorless and transparent liquid. Moreover, when the said crystal | crystallization was melt | dissolved in acetone and the gas chromatography analysis (injection temperature: 200 degreeC, column temperature: 100 degreeC) was performed, only the peak derived from acetone was detected. When the vaporization chamber (insert glass) was confirmed, white crystals were adhered. Therefore, from this analysis, the purity of the crystals obtained in the above examples is considered to be 99% or more.
(Examples 4 to 9)
Example 1 except that N-oxyl compound, oxyacid, polyvalent carboxylic acid and polyhydric alcohol shown in Table 1 were used instead of 4H-TEMPO and SAL, and hydroxyethyl methacrylate was used instead of ethanol as a solvent. The same operation was performed. Since crystals did not precipitate even when the reaction liquid shown in Table 1 was cooled to 30 ° C., the unreacted N-oxyl compound concentration in the reaction liquid was measured by liquid chromatography to obtain the reaction conversion rate.

(Example 10)
0.1 g of white crystals obtained in Example 1, 0.1 g of methylhydroquinone and 1000 g of hydroxyethyl methacrylate were charged into a 1 L glass round bottom flask set in a vacuum distillation apparatus, the degree of vacuum was 4-6 hPa, the internal temperature Distillation was performed over 2 hours while bubbling air at 70 to 80 ° C. at 5 ml / min to obtain 950 g of purified hydroxyethyl methacrylate. In this distillation operation, no polymerization of hydroxyethyl methacrylate was observed.

Next, the purified hydroxyethyl methacrylate was immersed in an oil bath adjusted to 100 ° C., and the time until the temperature increase due to the heat of polymerization was observed was measured as the polymerization start time. Started.
(Comparative Example 1)
The hydroxyethyl methacrylate used as a raw material in Example 10 was immersed in an oil bath adjusted to 100 ° C. in the same manner as the purified hydroxyethyl methacrylate in Example 10, and the time until the temperature increase due to the heat of polymerization was observed was started. Measured as time. The polymerization start time was 8 hours.

Since the polymerization start times of Example 10 and Comparative Example 1 are the same, it can be seen that the white crystals used in Example 10 are not contained in the purified hydroxyethyl methacrylate, that is, are not distilled during distillation. . If it is distilled, the polymerization start time of the purified hydroxyethyl methacrylate should be extended compared to the polymerization start time of the raw material hydroxyethyl methacrylate. In addition, the above-described form, that is, a polymerization inhibitor that does not distill to the purified distillate side, can be said to be one of preferred embodiments of the present invention.
(Comparative Example 2)
In Example 10, the same operation as in Example 10 was performed except that 0.1 g of 4H-TEMPO was used instead of white crystals. Liquid chromatographic analysis of the purified hydroxyethyl methacrylate revealed that 20 ppm of 4H-TEMPO was contained. The polymerization start time was 25 hours. From these results, it can be seen that 4H-TEMPO is distilled during distillation and mixed into purified hydroxyethyl methacrylate.
(Example 11)
A glass container was charged with 100 g of hydroxyethyl methacrylate, and 0.002 g of white crystals obtained in Example 1 (0.001% by mass as 4H-TEMPO) was further added. When this container was immersed in an oil bath adjusted to 100 ° C. and the polymerization start time was measured, it was 14 hours.
(Comparative Example 3)
In Example 11, the polymerization initiation time was measured in the same manner as in Example 11 except that 0.001 g (0.001% by mass) of 4H-TEMPO was used instead of white crystals, and it was 14 hours.

From a comparison between Example 11 and Comparative Example 3, it can be seen that the white crystals have the same polymerization prevention effect as 4H-TEMPO.
(Comparative Example 4)
In Example 10, the same operation as in Example 10 was performed except that 0.02 g of 4H-TEMPO was used instead of white crystals. Liquid chromatographic analysis of the purified hydroxyethyl methacrylate revealed that 2 ppm of 4H-TEMPO was contained. The polymerization start time was 9 hours. In this comparative example, the conventional 4H-TEMPO compound is added to adjust the addition amount equivalent to the polymerization prevention effect in the subject matter of the present case to prevent polymerization, but the vinyl compound to be prevented from polymerization. When hydroxyethyl methacrylate is purified, 4H-TEMPO is mixed into the distillate. Therefore, even a conventional polymerization inhibitor having a relatively high boiling point, such as 4H-TEMPO, cannot avoid the shift to the distillate side in the purification step. Therefore, an excess polymerization inhibitor may migrate to the product side (vinyl compound), which may cause a problem.
(Comparative Example 5)
In Example 10, the same operation as in Example 10 was performed except that 4H-TEMPO 0.02 g and SAL 0.1 g were used instead of white crystals. Liquid chromatographic analysis of the purified hydroxyethyl methacrylate revealed that 2 ppm of 4H-TEMPO was contained. The polymerization start time was 9 hours. From this result, it can be seen that even in the presence of SAL, 4H-TEMPO equivalent to Comparative Example 4 is distilled during distillation and mixed into the purified hydroxyethyl methacrylate. The same phenomenon as in Comparative Example 4 from Comparative Example 5 (if the transition to the distillate side in the purification step is unavoidable in the polymerization prevention treatment by the usual method, or extra on the product side (vinyl compound) This may be a problem because some polymerization inhibitors may migrate.
(Example 12)
In Example 10, instead of white crystals, 0.4 g (0.02 g as 4H-TEMPO) of the reaction solution before cooling, which was heated to 80 ° C. in the oil bath in Example 2 and reacted for 5 hours, was used. The same operation as in Example 10 was carried out except that. Liquid chromatographic analysis of the purified hydroxyethyl methacrylate revealed that 4H-TEMPO was 1 ppm or less, and the polymerization start time was 8 hours. In this example, a distillate fraction was obtained when purifying hydroxyethyl methacrylate, which is a vinyl compound to be prevented from polymerization, by adding a reaction solution in which 95% of 4H-TEMPO was reacted without adding white crystals. This is equivalent to the effect of adding white crystals not mixed with 4H-TEMPO.

2 is a H-NMR analysis chart of the synthesized product obtained in Example 1. FIG. The H-NMR analysis chart of the compound obtained in Example 1 is shown below, and the H-NMR analysis chart of SAL is shown at the top. It is a H-NMR analysis chart of piperidine. It is a H-NMR analysis chart of cyclohexanol. 2 is a H-NMR analysis chart for confirming an impurity peak of acetone d6 used as a solvent in Example 1. FIG. 4 is a H-NMR analysis chart of the synthesized product obtained in Example 3.

Claims (7)

A polymerization inhibitor for a vinyl group-containing compound comprising a coordination compound synthesized from at least one selected from oxyacids, polycarboxylic acids and polyhydric alcohols and an N-oxyl compound. The polymerization inhibitor for a vinyl group-containing compound according to claim 1, wherein H of a carboxyl group and / or a hydroxyl group, which is a functional group of oxyacid, polycarboxylic acid and polyhydric alcohol, remains. Aliphatic or aromatic oxyacids and general formula (1)

Wherein Y is CH ₂ , CHOH, CHCH ₂ OH, CHCH ₂ CH ₂ OH, CHOCH ₂ OH, CHOCH ₂ CH ₂ OH, CHCOOH, CHCOCH ₃ or C═O. A vinyl group-containing compound polymerization inhibitor comprising a coordination compound obtained by reacting a compound with a compound in a solvent. Aliphatic or aromatic oxyacids and general formula (2)

(Wherein Y is CHOH, CHCH ₂ OH, CHCH ₂ CH ₂ OH, CHOCH ₂ OH, or CHOCH ₂ CH ₂ OH), and obtained by reacting in a solvent. A polymerization inhibitor for a vinyl group-containing compound, comprising a coordination compound.
(Chemical structure)
In H-NMR analysis, the proton ratio is oxyacid: N-oxyl compound of general formula (2) = 1: 1, and the peak of H derived from the carboxyl group (—COOH) and hydroxyl group (—OH) of oxyacid, Moreover, the peak of H derived from the hydroxyl group (—OH) of the N-oxyl compound of the general formula (2) is observed. In preventing the polymerization of the vinyl group-containing compound, as a polymerization inhibitor, an aliphatic or aromatic oxyacid and a general formula (3)

(Wherein Y is CHOH, CHCH ₂ OH, CHCH ₂ CH ₂ OH, CHOCH ₂ OH, or CHOCH ₂ CH ₂ OH) and an N-oxyl compound represented by an organic solvent at 50 to 100 ° C. A method for preventing the polymerization of a vinyl group-containing compound, comprising using a coordination compound obtained by reacting at a temperature of 1.
(Chemical structure)
In the H-NMR analysis, the proton ratio is oxyacid: N-oxyl compound of general formula (3) = 1: 1, and the peak of H derived from the carboxyl group (—COOH) and hydroxyl group (—OH) of the oxyacid, Moreover, the peak of H derived from the hydroxyl group (—OH) of the N-oxyl compound of the general formula (3) is observed. A method for preventing polymerization of a vinyl group-containing compound, wherein the reaction mixture obtained when synthesizing the coordination compound according to claim 5 is added and used as a polymerization inhibitor. The method for preventing polymerization of a vinyl group-containing compound according to any one of claims 1 to 6, wherein the vinyl group-containing compound is a (meth) acrylic acid ester.

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