JP2016199632A - Polymerization inhibitor for high temperature distillation, and method for inhibiting polymerization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymerization inhibitor for high temperature distillation capable of effectively inhibiting a polymerization reaction of a vinyl-type monomer in high temperature distillation of the vinyl-type monomer.SOLUTION: A polymerization inhibitor for high temperature distillation to be used in refining a vinyl-type monomer by high temperature distillation contains a compound represented by general formula (I), (where, R1 indicates an alkyl group or aryl group of 4-9 carbon atoms; and R2 indicates a hydrogen atom, or an alkyl group or aryl group of 4-9 carbon atoms.)SELECTED DRAWING: None

Description

  The present invention relates to a polymerization inhibitor for high-temperature distillation and a polymerization inhibition method. More specifically, the present invention relates to a polymerization inhibitor for high temperature distillation and a polymerization inhibition method that can be used for distillation purification of a vinyl monomer having a high distillation temperature during purification and that exhibits excellent polymerization inhibition performance even during high temperature distillation. .

  In recent years, for example, a photocurable resin using a vinyl monomer represented by acrylic acid or an acrylic acid derivative, or methacrylic acid or a methacrylic acid derivative as a raw material has transparency, weather resistance, chemical resistance, optical characteristics, and molding. Because of its excellent properties and electrical characteristics, it has applications as resists used in electronic materials, inks, adhesives, and electronics-related applications. Furthermore, the use is expanding recently.

  With the expansion of such applications, vinyl monomers having various chemical structures have been developed for the purpose of imparting various functions and properties.

  In the development of this vinyl monomer, the molecular weight of the vinyl monomer is increased (high molecular weight) or a substituent is introduced into the vinyl monomer. On the other hand, high molecular weight and introduction of substituents tend to increase the boiling point (high boiling point) of vinyl monomers.

  Here, in many cases, the vinyl monomer is purified by distillation for the purpose of achieving high purity after production.

  As described above, the vinyl monomer is usually purified. However, if the distillation purification treatment is performed as it is, a polymerization reaction is caused by heat during distillation, and efficient distillation purification becomes difficult. . Therefore, in order to prevent the polymerization reaction of the vinyl monomer at the time of distillation purification, distillation purification is performed by adding a polymerization inhibitor.

  In this distillation purification, if the boiling point of the vinyl monomer is high, it is necessary to increase the temperature during the distillation purification. Further, if the degree of vacuum during distillation purification is lowered, there is a problem that the polymerization inhibitor is distilled together with the vinyl monomer during distillation purification, and effective distillation purification cannot be performed.

  Further, many polymerization inhibitors used during distillation purification are colored. When the colored polymerization inhibitor is distilled together with the vinyl monomer during distillation purification of the vinyl monomer, the distilled and purified vinyl monomer is colored due to the colored polymerization inhibitor. This will lower the product value of vinyl monomers.

  As measures for preventing such product value from being lowered, for example, a polymerization inhibitor for (meth) acrylic acid esters containing a piperidine-1-oxyl derivative, and a polymerization prevention method for adding the same (for example, see Patent Document 1) )It has been known. Further, a polymerization inhibitor for vinyl monomers containing an N-oxyl compound as an active ingredient and a method for preventing polymerization of vinyl monomers (for example, see Patent Document 2) are known. Furthermore, in the method for producing a (meth) acrylic acid ester by transesterification, tetramethyl titanate is used as a catalyst, and N-oxyl compound and / or cyclohexane-1-spiro-2 ′-(4 ′) is used as a polymerization inhibitor. It is known to use -oxoimidazolidine-1'-oxyl) -5'-spiro-1 "-cyclohexane (for example, see Patent Document 3).

JP 2004-300031 A JP 2001-106708 A JP 2001-39925 A

  However, the polymerization inhibitors disclosed in Patent Documents 1 to 3 are generally derivatives of a compound called TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) (hereinafter sometimes referred to as “TEMPO derivative”). And relates to a derivative intended to increase the boiling point thereof. This TEMPO derivative exhibits high polymerization inhibition performance. However, the polymerization inhibition performance has serious drawbacks such as lack of durability. In addition, since the price is relatively high, it cannot be used in all situations and situations where the use of a polymerization inhibitor is necessary.

  In addition to the TEMPO derivatives, there are also known compounds in which R1 and R2 of the compound represented by the general formula (I) are both hydrogen atoms. A small amount may be distilled off with the monomer. Therefore, when distillation purification is performed at a high temperature, the polymerization inhibitor is mixed in the target vinyl monomer, and the value as a product is lowered.

  The present invention has been made in view of such problems of the prior art. The polymerization inhibitor for high-temperature distillation of the present invention comprises a compound having a specific substituent (R1 and R2) at a specific position (3- and 7-) of phenothiazine (a compound represented by the general formula (I)). contains. Phenothiazine (a compound in which R1 and R2 of the compound represented by the general formula (I) are both hydrogen atoms), which is a compound serving as a basis of this compound, is a general-purpose compound used for the purification of vinyl monomers by distillation. Polymerization inhibitor. However, the present inventor found that a conventional general-purpose polymerization inhibitor is highly purified during distillation purification of a vinyl monomer having a high boiling point (hereinafter sometimes referred to as “high-boiling vinyl monomer”). Attention was paid to the problem of distilling together with the boiling point vinyl monomer and mixing the polymerization inhibitor into the target vinyl monomer, thereby reducing the value of the product.

  As a result of extensive research, the compound represented by the general formula (I) among the innumerable compounds has excellent polymerization inhibition performance even during distillation purification of high-boiling vinyl monomers. In addition, it has been found that the polymerization inhibition performance has durability.

  That is, according to phenothiazine (compound represented by the general formula (I)) in which specific substituents (R1 and R2) are introduced at specific positions (3- and 7-) of phenothiazine, the above-mentioned problem is solved. It was found to be extremely effective. That is, the above compound does not impair the polymerization inhibition performance even during high-temperature distillation purification and has a high temperature at which vaporization starts. For this reason, it has been found that even when used for distillation purification of a high-boiling vinyl monomer, it is not distilled together with the high-boiling vinyl monomer, and the present invention has been completed.

  According to the present invention, the following high temperature distillation polymerization inhibitor and polymerization inhibition method are provided.

[1] A polymerization inhibitor for high-temperature distillation used for distillation purification of a vinyl monomer containing a compound represented by the following general formula (I) and having a high distillation temperature during distillation purification.

（一般式（Ｉ）中、Ｒ１は、炭素原子数４〜９のアルキル基、又はアリール基、Ｒ２は、水素原子、又は炭素原子数４〜９のアルキル基、若しくはアリール基である。）

(In general formula (I), R1 is an alkyl group having 4 to 9 carbon atoms or an aryl group, and R2 is a hydrogen atom, an alkyl group having 4 to 9 carbon atoms, or an aryl group.)

[2] The polymerization inhibitor for high-temperature distillation according to [1], wherein R1 and R2 in the general formula (I) are both octyl groups, or R1 and R2 are both cumyl groups.

[3] The polymerization inhibitor for high-temperature distillation according to [1] or [2] above is blended with a vinyl monomer-containing liquid before distillation purification containing a vinyl monomer having a high distillation temperature during distillation purification. A vinyl monomer that purifies the vinyl monomer from the obtained mixture and inhibits the polymerization reaction of the vinyl monomer by the polymerization inhibitor for high-temperature distillation. How to inhibit body polymerization.

[4] The polymerization inhibition method according to [3], wherein the vinyl monomer is acrylic acid, an acrylic acid derivative, methacrylic acid, or a methacrylic acid derivative.

[5] The method for inhibiting polymerization according to [3] or [4], wherein each of the acrylic acid derivative and the methacrylic acid derivative is a compound having a boiling point of 180 ° C. or higher at normal pressure.

[6] The method for inhibiting polymerization according to [3] to [5], wherein each of the acrylic acid derivative and the methacrylic acid derivative is a compound having a boiling point of 250 ° C. or higher at normal pressure.

  Since the polymerization inhibitor for high-temperature distillation of the present invention contains the compound represented by the general formula (I), the polymerization for high-temperature distillation is prohibited even when the vinyl monomer is purified by high-temperature distillation. The agent is difficult to distill with the vinyl monomer. Further, the purified vinyl monomer can be prevented from being colored. Furthermore, the polymerization of the vinyl monomer during distillation purification can be effectively inhibited.

  The polymerization inhibitor for high-temperature distillation of the present invention can reduce the cost of distillation purification of vinyl monomers because the compound represented by the general formula (I) is industrially easily available and inexpensive. it can.

  In the polymerization inhibition method of the present invention, even when the vinyl monomer is purified by distillation at high temperature, the polymerization inhibitor for high temperature distillation is difficult to distill together with the vinyl monomer, and the purified vinyl monomer is colored. Can be prevented, and polymerization of the vinyl monomer during distillation purification can be effectively inhibited.

  Further, the polymerization inhibiting method of the present invention can reduce the cost of distillation purification of vinyl monomers because the polymerization inhibitor for high temperature distillation used in the method of the present invention is industrially available and inexpensive. .

  Hereinafter, although the form for implementing this invention is demonstrated, this invention is not limited to the following embodiment. That is, it is understood that modifications and improvements as appropriate to the following embodiments are also within the scope of the present invention based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. Should be.

[1] Polymerization inhibitor for high temperature distillation:
The polymerization inhibitor for high-temperature distillation of the present invention contains a compound represented by the above general formula (I). Such a polymerization inhibitor for high-temperature distillation can effectively inhibit the polymerization reaction of a vinyl monomer having a high distillation temperature during distillation purification. And since the compound represented with general formula (I) contained in the polymerization inhibitor for high temperature distillation of this invention is a high boiling point, it is hard to distill with a vinyl-type monomer at the time of high temperature distillation refinement | purification. Therefore, when the polymerization inhibitor for high temperature distillation of the present invention is used, the polymerization reaction of the vinyl monomer is effectively inhibited, and the fractionation is favorably performed during the high temperature (about 180 ° C. or higher) distillation purification of the vinyl monomer. it can. And since this polymerization inhibitor for high-temperature distillation is difficult to be included in the vinyl monomer after distillation purification, even if the polymerization inhibitor for high-temperature distillation is colored, it is attributed to this polymerization inhibitor for high-temperature distillation. Thus, the vinyl monomer can be prevented from being colored.

  Further, polymerization inhibitors such as high molecular weight TEMPO derivatives are expensive and unrealistic for industrial use. However, the polymerization inhibitor for high-temperature distillation of the present invention is commercially available. Therefore, it can be sufficiently used for industrial distillation purification of vinyl monomers.

  On the other hand, phenothiazine, which is a conventional polymerization inhibitor, sometimes distills together with a vinyl monomer when a vinyl monomer having a high distillation temperature during distillation purification is purified by distillation. Therefore, the product value of the vinyl monomer obtained by distillation purification may be lowered. TEMPO derivatives show high polymerization inhibition performance in some fields, but are not general purpose. Moreover, the high molecular weight TEMPO derivative is expensive and unrealistic for industrial use.

  As described above, the polymerization inhibitor for high-temperature distillation of the present invention exhibits an excellent polymerization inhibition effect not found in conventional polymerization inhibitors when distillation-purifying vinyl monomers having a high distillation temperature during distillation purification. To do. This is particularly due to the compound represented by the general formula (I), and by using R1 and R2 in the compound represented by the general formula (I) as predetermined substituents, distillation during the distillation purification is performed. When the vinyl monomer having a high temperature is purified by distillation, the above excellent polymerization inhibition effect is exhibited.

[1-1] Compound represented by general formula (I):
In general formula (I), R1 is a group selected from an alkyl group having 4 to 9 carbon atoms or an aryl group. R2 is a group selected from a hydrogen atom, an alkyl group having 4 to 9 carbon atoms, or an aryl group. The alkyl group having 4 to 9 carbon atoms represented by R1 and R2 may be either saturated or unsaturated, and may be linear, branched, or cyclic.

  Furthermore, in the alkyl group having 4 to 9 carbon atoms or the aryl group, a part or all of the hydrogen atoms may be substituted with an organic group such as a halogen atom, an alkyl group, an alkoxy group, an alkenyl group, or an amino group. Good.

  Examples of the alkyl group having 4 to 9 carbon atoms represented by R1 and R2 include a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group. , Cyclooctyl group, cyclononyl group, 1-butenyl group, 2-butenyl group, 2-pentenyl group, chlorobutyl group, chloropentyl group, 2-ethylhexyl group, 2-methoxybutyl group, chlorocyclobutyl group, chlorocyclopentyl group, etc. Is mentioned.

  Examples of the aryl group having 4 to 9 carbon atoms represented by R1 and R2 include phenyl group, tolyl group, xylyl group, cumyl group, benzyl group, phenesyl group, sinamyl group, cycloaryl group, heteroaryl group, monochloro group, and the like. A benzyl group, a dichlorobenzyl group, a monomethylbenzyl group, etc. are mentioned.

  It is essential that the alkyl group or aryl group represented by R1 or R2 has 4 to 9 carbon atoms. On the other hand, when R1 and R2 are 3 or less carbon atoms, in high temperature distillation of a high boiling point vinyl monomer, it is distilled together with the vinyl monomer and is effective as a polymerization inhibitor during high temperature distillation purification. Difficult to get. Further, when R1 and R2 have 10 or more carbon atoms, polymerization inhibition properties are obtained, but this is not practical in production.

  Among these, it is preferable that R1 and R2 are both octyl groups, or R1 and R2 are both cumyl groups. As described above, since R1 and R2 are both octyl groups or R1 and R2 are both cumyl groups, the compounds have high boiling points. There is no distilling with the monomer. Therefore, it is possible to reliably and effectively inhibit the polymerization of the vinyl monomer and to isolate and purify the vinyl monomer almost completely by distillation purification (fractional distillation). In addition, since the polymerization inhibitor is not contained in the vinyl monomer after purification by distillation, the vinyl monomer after distillation purification (which has been purified by distillation) due to the mixing of the polymerization inhibitor. It is possible to prevent the vinyl monomer) from being colored.

  R1 and R2 may be the same or different.

  The substitution positions of R1 and R2 are the 3-position and the 7-position. Thus, by making the substitution position into the 3-position and the 7-position, the effect as a polymerization inhibitor at the time of high-temperature distillation purification of the vinyl monomer can be surely obtained.

  Specific examples of the compound represented by the general formula (I) include 3,7-dibutylphenothiazine, 3,7-dipentylphenothiazine, 3,7-dihexylphenothiazine, 3,7-diheptylphenothiazine, 3,7- Dioctylphenothiazine, 3,7-dinonylphenothiazine, 3,7-dicyclobutylphenothiazine, 3,7-dicyclopentylphenothiazine, 3,7-dicyclohexylphenothiazine, 3,7-dicycloheptylphenothiazine, 3,7-dicyclo Octylphenothiazine, 3,7-dicyclononylphenothiazine, di (2-ethylhexyl) phenothiazine, 3,7-diphenylphenothiazine, 3,7-ditolylphenothiazine, 3,7-dixylphenothiazine, 3,7-dicumylphenothiazine 3,7- Benzyl phenothiazine, 3,7-di-Fe farnesyl phenothiazine, 3,7-di-cinnamyl phenothiazine and the like.

  Among these, 3,7-dioctylphenothiazine and 3,7-dicumylphenothiazine are preferable, and these are effective as a component of a polymerization inhibitor used when high-boiling vinyl monomers are purified by distillation at high temperature. .

[1-2] Other components:
The polymerization inhibitor of the present invention may further contain other components in addition to the compound represented by the general formula (I). Examples of other components include 2,6-di (t-butyl) -4-methylphenol (BHT), t-butylcatechol, hydroquinone, 4-methoxyphenol, 2-methylhydroquinone, t-butylhydroquinone, 2 , 5-di-t-butylhydroquinone, 4-benzoquinone, 2,2'-methylenebis (6-t-butyl-4-methylphenol), 2,2'-methylenebis (6-t-butyl-4-ethylphenol) ), 2,2′-methylenebis [6- (1-methylcyclohexyl) -4-methylphenol], diphenylamine, N-nitrosodiphenylamine, N-nitroso-N-cyclohexylaniline, 4-aminodiphenylamine, 4-oxydiphenylamine, 4-phenylenediamine, N-isopropyl-N′-phenyl- Dialkylhydroxylamine represented by 4-phenylenediamine, N- (1,3-dimethylbutyl) -N′-phenyl-4-phenylenediamine, N, N′-diphenyl-4-phenylenediamine, phenothiazine, diethylhydroxylamine 2,2,6,6-tetramethylpiperidinyloxy compounds represented by 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy compounds, 2,4-dinitrophenol, 2,4 -Dinitrocresol, 2,4-dinitro-t-butylphenol, N-nitrosophenylhydroxylamine salt and the like.

  It is preferable that the content rate of another component is 0-90 mass%. That is, it is preferable that the content rate of the compound represented by general formula (I) is 10-100 mass%.

[2] Method for producing compound represented by general formula (I):
The compound represented by the general formula (I) is a method of producing phenothiazine by a known production method and then introducing an alkyl group having 4 to 9 carbon atoms or an aryl group into the produced phenothiazine, or sulfur and alkyl. Diphenylamine or arylated diphenylamine can be obtained by reacting in the presence of a catalyst.

[3] Polymerization inhibition method:
The polymerization inhibition method of the present invention is applied to a vinyl monomer-containing liquid before distillation purification containing a vinyl monomer (high boiling point vinyl monomer) having a high distillation purification temperature during distillation purification. A polymerization inhibitor for distillation is blended to obtain a mixture, and the vinyl monomer is purified by distillation from the resulting mixture, and the polymerization reaction of the vinyl monomer at that time is prohibited by the polymerization inhibitor for high temperature distillation. It is a method to do.

  According to such a polymerization inhibition method, the polymerization inhibitor for high temperature distillation is difficult to distill together with the vinyl monomer even when the vinyl monomer is purified by high temperature distillation. That is, a vinyl monomer having a high distillation temperature at the time of distillation purification can be favorably distilled and purified. In recent years, new high-boiling vinyl monomers have been used due to expansion of the use of polymers based on vinyl monomers, but these high-boiling vinyl monomers have been successfully improved. It can be purified by distillation.

  Furthermore, although the polymerization inhibitor for high temperature distillation may be colored, the distillation-purified vinyl monomer is colored due to the mixing of such a colored high temperature distillation polymerization inhibitor. Can be prevented.

  Further, the polymerization of the vinyl monomer during distillation purification can be surely prohibited. That is, the vinyl monomer can be fractionated favorably by distillation purification.

  A polymerization inhibitor such as a high molecular weight TEMPO derivative is expensive and therefore unrealistic for industrial use. However, the polymerization inhibitor for high-temperature distillation used in this method is industrial. Therefore, the above-mentioned problems are unlikely to occur.

  Here, in this specification, “inhibiting the polymerization reaction of vinyl monomers” means that vinyl monomers react with each other by heat or light to form a polymer unintentionally. It means to prevent it.

  In the polymerization prevention method of the present invention, a mixture is obtained by blending the above-mentioned polymerization inhibitor for high-temperature distillation into the vinyl monomer-containing liquid. This is because, for example, the above-mentioned polymerization inhibitor for high temperature distillation is previously contained in the raw material component of the vinyl monomer, and the vinyl monomer (vinyl monomer-containing liquid) is produced at the same time. Including the case where a mixture is obtained. Or the case where a polymerization inhibitor is added to this vinyl monomer containing liquid after a vinyl monomer (vinyl monomer containing liquid) is manufactured is included.

  Examples of vinyl monomers include acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, cyclohexyl acrylate, heptyl acrylate, octyl acrylate, and acrylic. 2-ethylhexyl acid, phenyl acrylate, benzyl acrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, stearyl acrylate, Glycidyl acrylate, 2-aminoethyl acrylate, trifluoromethyl methyl acrylate, 2-perfluoroethyl ethyl acrylate, isobornyl acrylate, adamantyl acrylate and its derivatives, bicyclohexyl acrylate and Acrylic acid derivatives such as derivatives thereof.

  Examples of the vinyl monomer include methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, heptyl methacrylate, octyl methacrylate. , 2-ethylhexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-methoxyethyl methacrylate, 3-methoxybutyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, methacrylic acid Stearyl, glycidyl methacrylate, 2-aminoethyl methacrylate, trifluoromethyl methyl methacrylate, 2-perfluoroethyl ethyl methacrylate, isobornyl methacrylate, methacrylic acid Manchiru and its derivatives, methacrylic acid derivatives such as methacrylic acid bicyclohexyl and derivatives thereof.

  Furthermore, examples of the vinyl monomer include aromatic vinyl monomers such as styrene, vinyl toluene, α-methyl styrene, chlorostyrene, styrene sulfonic acid, perfluoroethylene, perfluoropropylene, vinylidene fluoride, and the like. Fluorine-containing vinyl monomers, vinyl group-containing silanes such as vinyltrimethoxysilane and vinyltriethoxysilane, maleic anhydride, maleic acid, monoalkyl esters of maleic acid, dialkyl esters, fumaric acid, and fumaric acid mono Alkyl ester, dialkyl ester, maleimide, methyl maleimide, ethyl maleimide, propyl maleimide, butyl maleimide, hexyl maleimide, octyl maleimide, dodecyl maleimide, stearyl maleimide, phenyl maleimide, cyclohexyl maleimi , Acrylonitrile monomers such as acrylonitrile and methacrylonitrile, amide group-containing vinyl monomers such as acrylamide and methacrylamide; vinyl such as vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, vinyl cinnamate Examples include esters, conjugated dienes such as butadiene and isoprene, vinyl chloride, vinylidene chloride, allyl chloride, and allyl alcohol.

  According to the present invention, among the high-boiling vinyl monomers, it is possible to satisfactorily inhibit the polymerization reaction when the acrylic acid derivative or methacrylic acid derivative is purified by distillation at high temperature.

  Furthermore, among acrylic acid derivatives and methacrylic acid derivatives, those having a boiling point of 180 ° C. or higher at normal pressure (hereinafter sometimes referred to as “first high-boiling derivative”) are preferable, and boiling point of 250 at normal pressure is 250. Those having a temperature not lower than ° C. (hereinafter may be referred to as “second high-boiling point derivative”) are more preferable. According to the present invention, the polymerization reaction at the time of high-temperature distillation purification in such a compound can be effectively inhibited.

  Resins made from acrylic acid derivatives or methacrylic acid derivatives that satisfy the above conditions are excellent in transparency, weather resistance, chemical resistance, optical properties, moldability, electrical properties, etc., and should be used in various applications. Can do.

  Examples of the first high-boiling derivative include 2-ethylhexyl acrylate (213 ° C.), 2-ethylhexyl methacrylate (229 ° C.), glycidyl methacrylate (189 ° C.), hydroxyethyl methacrylate (205 ° C.) and the like. Can be mentioned.

  Examples of the second high-boiling derivative include isobornyl methacrylate (129 ° C./15 mmHg, 2-methyladamantyl methacrylate (80 ° C./0.17 mmHg), 2-ethyladamantyl methacrylate (89 ° C./0.04 mmHg), and methacrylic acid. Stearyl (235 ° C./10 mmHg) and the like can be mentioned.

  In the polymerization inhibition method of the present invention, the concentration of the polymerization inhibitor for high-temperature distillation in the mixture is preferably 10 to 5000 ppm, more preferably 10 to 300 ppm. The above range is sufficient for the high temperature distillation polymerization inhibitor to capture the radicals generated in the vinyl monomer. Therefore, the polymerization reaction of the vinyl monomer can be effectively inhibited. If the concentration of the polymerization inhibitor for high-temperature distillation is less than 10 ppm, the ratio of the polymerization inhibitor for high-temperature distillation to the vinyl monomer becomes small, so that a sufficient polymerization inhibition effect may not be obtained. On the other hand, if the concentration of the polymerization inhibitor for high-temperature distillation is more than 5000 ppm, the cost to be generated may become too large for the obtained effect. That is, since the polymerization inhibition effect is not sufficiently improved with respect to the amount used, the cost tends to increase.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

Example 1
<Polymerization prohibition performance>
Commercially available 2-ethylhexyl acrylate was extracted by washing with 30 ml of 10% NaOH aqueous solution three times. After washing, it was washed 3 times with ion exchange water, and it was confirmed that the pH became neutral. After confirmation, anhydrous magnesium sulfate was added and mixed uniformly, followed by filtration. 4-Methoxyphenol added as a polymerization inhibitor to a commercially available acrylic ester was removed to prepare an acrylic ester adjusting solution.

  As a polymerization inhibitor for high-temperature distillation, 3,7-dioctylphenothiazine (10 mg) was weighed and placed in a 10 ml volumetric flask and diluted with an adjustment solution. 0.1 ml of this solution was weighed with a micropipette, placed in a 10 ml volumetric flask and made up with a conditioning solution, and a 10 ppm test solution for a polymerization inhibitor for high temperature distillation was used. This test solution was put in a sample container for measuring a TG-DTA apparatus, kept at a predetermined temperature, and observed until the rise of the exothermic peak of DTA (thermal differential analysis), and this time was taken as an induction time. Table 1 below shows the time to rise of the exothermic peak for the polymerization inhibitor for high temperature distillation. The longer the induction time (the slower the time until the exothermic peak appears), the higher the effect as a polymerization inhibitor.

(Example 2)
The induction time was observed in the same manner as in Example 1 except that the same amount of 3,7-dicumylphenothiazine as in Example 1 was used as the polymerization inhibitor for high temperature distillation. The results are shown in Table 1 below.

(Comparative Example 1)
The induction time was observed in the same manner as in Example 1 except that no polymerization inhibitor was used. The results are shown in Table 1 below.

(Comparative Example 2)
The induction time was observed in the same manner as in Example 1 except that the same amount of phenothiazine as a conventional polymerization inhibitor was used as the polymerization inhibitor. The results are shown in Table 1 below.

  From Table 1, it can be seen that 3,7-dioctylphenothiazine and 3,7-dicumylphenothiazine have sufficient polymerization inhibition performance as a polymerization inhibitor during distillation purification, similarly to phenothiazine.

<Measurement of weight loss start temperature>
Example 3
As a polymerization inhibitor for high-temperature distillation, 3,7-dioctylphenothiazine was used, and weight loss with respect to temperature was measured using a TG-DTA apparatus (Rigaku TG 8120 (model number)). That is, the temperature at which weight loss began to be observed was examined. The results are shown in Table 2 below.

Example 4
As a polymerization inhibitor for high-temperature distillation, 3,7-dicumylphenothiazine was used, and a weight loss with respect to temperature was measured using a TG-DTA apparatus (Rigaku TG 8120 (model number)) in the same manner as in Example 3. That is, the temperature at which weight loss began to be observed was examined. The results are shown in Table 2 below.

(Comparative Example 3)
As a polymerization inhibitor, phenothiazine, which is a conventional polymerization inhibitor, was used, and a weight loss with respect to temperature was measured using a TG-DTA apparatus (Rigaku TG 8120 (model number)) in the same manner as in Example 3. That is, the temperature at which weight loss began to be observed was examined. The results are shown in Table 2 below.

  From Table 2, 3,7-dioctylphenothiazine and 3,7-dicumylphenothiazine exhibit good polymerization inhibition performance when used as a polymerization inhibitor for vinyl monomers having a high distillation temperature during purification. I understood. That is, in Examples 3 and 4, distillation purification could be performed without distilling to the fraction side even at a temperature higher than that of phenothiazine of Comparative Example 3 or even at a low degree of vacuum. .

  As is apparent from Tables 1 and 2, the “polymerization inhibitor for high-temperature distillation of vinyl monomers” of the present invention is a vinyl polymer (acrylate ester) as in the case of phenothiazine which is a conventional polymerization inhibitor. It was confirmed that the polymerization reaction of Further, it was confirmed that the “polymerization inhibitor for high-temperature distillation of vinyl monomers” of the present invention hardly precipitates even during distillation purification of vinyl polymers having a high distillation temperature during purification.

  The polymerization inhibitor of the present invention is suitable as a polymerization inhibitor during distillation purification of vinyl monomers having a high distillation temperature during distillation purification. The polymerization inhibition method of the present invention can be suitably employed as a method for inhibiting the polymerization reaction during distillation purification of vinyl monomers having a high distillation temperature during distillation purification.

Claims (6)

A polymerization inhibitor for high-temperature distillation, which is used for distillation-purifying a vinyl monomer containing a compound represented by the following general formula (I) and having a high distillation temperature during distillation purification.

(In general formula (I), R1 is an alkyl group having 4 to 9 carbon atoms or an aryl group, and R2 is a hydrogen atom, an alkyl group having 4 to 9 carbon atoms, or an aryl group.)   The polymerization inhibitor for high temperature distillation according to claim 1, wherein R1 and R2 in the general formula (I) are both octyl groups, or R1 and R2 are both cumyl groups.   The polymerization inhibitor for high temperature distillation according to claim 1 or 2 is blended with a vinyl monomer-containing liquid before distillation purification containing a vinyl monomer having a high distillation purification temperature during distillation purification to obtain a mixture. The vinyl monomer is purified by distillation from the obtained mixture, and the polymerization reaction of the vinyl monomer at that time is prohibited by the polymerization inhibitor for high temperature distillation. Method.   The polymerization inhibition method according to claim 3, wherein the vinyl monomer is acrylic acid, an acrylic acid derivative, methacrylic acid, or a methacrylic acid derivative.   The method for inhibiting polymerization according to claim 3 or 4, wherein each of the acrylic acid derivative and the methacrylic acid derivative is a compound having a boiling point of 180 ° C or higher at normal pressure.   The method for inhibiting polymerization according to any one of claims 3 to 5, wherein each of the acrylic acid derivative and the methacrylic acid derivative is a compound having a boiling point of 250 ° C or higher at normal pressure.