Method for preventing polymerization in vinyl compound

Abstract

To provide a method for preventing polymerization of a vinyl compound having high polymerizability.SOLUTION: It has been discovered that effective prevention of polymerization in a vinyl compound is achievable by incorporating, as polymerization inhibitors, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone into the vinyl compound.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for inhibiting polymerization in vinyl compounds. [Background technology]

[0002] Vinyl compounds such as (meth)acrylic acid and (meth)acrylic acid esters tend to polymerize easily due to heat, etc. Therefore, various polymerization inhibitors are added to prevent the polymerization of vinyl compounds.

[0003] For example, Patent Document 1 describes the use of an N-oxyl compound such as bis-(2,2,6,6-tetramethyl-4-piperidinooxyl)-sebacate as a polymerization inhibitor for vinyl compounds, and Patent Document 2 describes that the N-oxyl compound in a vinyl compound can be stabilized by causing the vinyl compound to coexist with an N-hydroxy-2,2,6,6-tetramethylpiperidine compound and a 2,2,6,6-tetramethylpiperidine compound. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Tokuhei 4-14121 [Patent Document 2] Patent Publication No. 2001-181252 Summary of the Invention [Problem to be solved by the invention]

[0005] However, because vinyl compounds are highly polymerizable, it is difficult to prevent the polymerization of vinyl compounds even when using the above-mentioned method.Furthermore, if impurities such as acetic acid and sulfuric acid are present in the vinyl compounds, the polymerization of the vinyl compounds is accelerated, so it is difficult to prevent the polymerization even when using the above-mentioned method.

[0006] The present invention solves the above problems and provides a method for inhibiting polymerization in vinyl compounds. [Means for solving the problem]

[0007] The present inventors have found that the polymerization of vinyl compounds can be effectively prevented by including 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone as polymerization inhibitors in vinyl compounds.

[0008] That is, the present invention provides a method for preventing polymerization of a vinyl compound, wherein the vinyl compound contains a 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone.

[0009] The method according to claim 1, further characterized in that the vinyl compound contains 0.01 to 1000 ppm of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 0.01 to 1000 ppm of 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, 0.01 to 1000 ppm of hydroquinone, and 0.01 to 1000 ppm of benzoquinone.

[0010] The method according to claim 1 or 2, wherein the vinyl compound is at least one selected from the group consisting of (meth)acrylic acid, a (meth)acrylic acid ester compound, (meth)acrylonitrile, and vinyl acetate.

[0011] The method according to claim 1 or 2, characterized in that the weight ratio of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical to hydroquinone contained in the vinyl compound is 1:40 to 10:1.

[0012] The method according to claim 1 or 2, characterized in that the weight ratio of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical to 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine is 0.1:1 to 30:1.

[0013] The method according to claim 1 or 2, characterized in that the weight ratio of hydroquinone to benzoquinone is 1:2 to 60:1.

[0014] The method according to claim 1 or 2, wherein the vinyl compound contains 1 ppm or more of acetic acid and / or sulfuric acid. [Effects of the Invention]

[0015] The polymerization prevention method of the present invention is useful because it can effectively prevent the polymerization of highly polymerizable vinyl compounds. DETAILED DESCRIPTION OF THE INVENTION

[0016] The vinyl compound used in the present invention has a vinyl bond, and examples thereof include aromatic vinyl compounds, conjugated diene compounds, vinyl ester compounds, (meth)acrylic acid, (meth)acrylic ester compounds, (meth)acrylonitrile, and the like. Among these, (meth)acrylic acid, (meth)acrylic acid esters, (meth)acrylonitrile, and vinyl acetate are preferred. By using the polymerization inhibitor of the present invention, polymerization of the vinyl compound can be effectively prevented.

[0017] Specific examples of aromatic vinyl compounds include styrene, vinyltoluene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-t-butylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 2,4,6-trimethylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, vinylanthracene, N,N-diethyl-4-aminoethylstyrene, vinylpyridine, 4-methoxystyrene, monochlorostyrene, dichlorostyrene, styrenesulfonic acid, and divinylbenzene.

[0018] Specific examples of the conjugated diene compound include butadiene, isoprene, 2,3-dimethylbutadiene, 2-phenyl-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,3-octadiene, 1,3-cyclohexadiene, 2-methyl-1,3-octadiene, 1,3,7-octatriene, α-farnesene, β-farnesene, myrcene, and chloroprene.

[0019] Specific examples of the vinyl ester compound include vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, and vinyl cinnamate.

[0020] Specific examples of (meth)acrylic include acrylic acid and methacrylic acid. In the present invention, (meth)acrylic refers to acrylic acid and / or methacrylic acid.

[0021] Specific examples of the (meth)acrylic ester compound include ethyl (meth)acrylate, methyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, propyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, glycidyl (meth)acrylate, cyclohexyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and dimethylaminoethyl (meth)acrylate.

[0022] Specific examples of (meth)acrylonitrile include acrylonitrile and methacrylonitrile. In the present invention, (meth)acrylonitrile refers to acrylonitrile and / or methacrylonitrile.

[0023] The boiling point of the vinyl compound is not particularly limited, but for example, the boiling point is preferably 50° C. or higher, more preferably 60° C. or higher, and even more preferably 70 to 150° C. When the polymerization inhibitor of the present invention is contained in a vinyl compound having the above boiling point, the polymerization inhibitor can be sufficiently inhibited during distillation.

[0024] The polymerization inhibitor used in the present invention includes 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone, and by including these polymerization inhibitors in a vinyl compound, polymerization can be effectively inhibited. Note that the benzoquinone of the present invention includes the structural isomers 1,4-benzoquinone and 1,2-benzoquinone, and the hydroquinone of the present invention includes the structural isomers catechol and resorcinol.

[0025] The content of the polymerization inhibitor contained in the vinyl compound is not particularly limited as long as it can prevent polymerization of the vinyl compound, but it is preferable that the vinyl compound contains 0.01 to 1000 ppm of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 0.01 to 1000 ppm of 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, 0.01 to 1000 ppm of hydroquinone, and 0.01 to 1000 ppm of benzoquinone. More preferably, the composition contains 0.05 to 500 ppm of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 0.05 to 500 ppm of 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, 0.05 to 500 ppm of hydroquinone, and 0.05 to 500 ppm of benzoquinone. Even more preferably, the composition contains 0.1 to 400 ppm of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 0.1 to 400 ppm of 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, 0.1 to 400 ppm of hydroquinone, and 0.1 to 400 ppm of benzoquinone. With the contents within these ranges, polymerization of vinyl compounds can be effectively inhibited. The unit "ppm" refers to the content of the polymerization inhibitor relative to the mass of the vinyl compound.

[0026] The weight ratio of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical to hydroquinone contained in the vinyl compound is not particularly limited as long as it can prevent polymerization of the vinyl compound, but is preferably 1:40 to 10:1, more preferably 1:20 to 1:1, and particularly preferably 1:10 to 3:10.

[0027] The weight ratio of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical to 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine contained in the vinyl compound is not particularly limited as long as it can prevent polymerization of the vinyl compound, but is preferably 0.1:1 to 30:1, and more preferably 1:1 to 18:1.

[0028] The weight ratio of hydroquinone to benzoquinone contained in the vinyl compound is not particularly limited as long as it can prevent polymerization of the vinyl compound, but is preferably 1:2 to 60:1, more preferably 1:1 to 50:1, and particularly preferably 2:1 to 18:1.

[0029] The weight ratio of 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine to benzoquinone contained in the vinyl compound is not particularly limited as long as it can prevent polymerization of the vinyl compound, but is preferably 1:20 to 10:1, and more preferably 1:15 to 2:1.

[0030] The method of adding 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone is not particularly limited, and they may be added to the vinyl compound separately or simultaneously.

[0031] The vinyl compound used in the present invention may contain impurities such as by-products in the production process or impurities introduced from the starting materials for the vinyl compound. For example, the polymerization inhibitor effect is exhibited even when various impurities, including water, organic acids such as acetic acid, inorganic acids such as sulfuric acid, and aldehydes such as acrolein, are contained. In particular, when a vinyl compound contains impurities such as acetic acid or sulfuric acid, the vinyl compound is prone to polymerization. Therefore, by including the polymerization inhibitor of the present invention, polymerization can be effectively prevented.

[0032] The content of acetic acid and / or sulfuric acid contained in the vinyl compound is not particularly limited, but is preferably 0.1 ppm or more, more preferably 1 ppm or more, and particularly preferably 10 ppm or more, relative to the vinyl compound. Even when a vinyl compound contains a predetermined amount of acetic acid and / or sulfuric acid and is prone to polymerization, polymerization can be effectively prevented by adding the polymerization inhibitor of the present invention to the vinyl compound.

[0033] In the present invention, other known polymerization inhibitors for vinyl compounds may be used in combination, such as phenothiazine, methoquinone, copper dialkyldithiocarbamate, manganese acetate, p-phenylenediamine, etc. The content of the other polymerization inhibitor is not particularly limited as long as it is within a commonly used range, but it is usually preferably contained in the range of 0.01 to 10,000 ppm relative to the vinyl compound.

[0034] In the present invention, when handling vinyl compounds, specifically, for example, during purification of vinyl compounds, storage in tanks, transportation by tank trucks or the like, transfer via pipelines or the like, by including the polymerization inhibitor of the present invention in the vinyl compounds, polymerization is effectively prevented. During purification of vinyl compounds, this polymerization inhibitor effect can be obtained during purification and distillation of vinyl compounds. Regarding storage in tanks, this polymerization inhibitor effect can be obtained in all cases, such as product storage tanks and intermediate tanks between each step in a process. Regarding transportation via pipelines or the like, the effects of the present invention can be obtained in various situations, such as product transfer and transfer between each step in a process. [Example]

[0035] The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to these examples. In the examples and comparative examples, "ppm" is based on mass unless otherwise specified.

[0036] [Test reagents] Acrylonitrile (a reagent manufactured by Tokyo Chemical Industry Co., Ltd., distilled under reduced pressure to remove the stabilizer (methoxyhydroquinone) that was already included) Methacrylic acid (a reagent manufactured by Tokyo Chemical Industry Co., Ltd. is distilled under reduced pressure to remove the stabilizer (methoxyhydroquinone) that was already included) Vinyl acetate (a reagent manufactured by Tokyo Chemical Industry Co., Ltd., distilled under reduced pressure to remove the stabilizer (hydroquinone) that was already included) Lauroyl peroxide (reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) H-TEMPO (4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) H-TEMPOH (1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, reagent, manufactured by Alfa Chemistry) BQ (1,4-benzoquinone, reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) HQ (1,4-hydroquinone, reagent, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0037] [Acrylonitrile polymerization prevention test 1] Example 1 To 200 g of stabilizer-free acrylonitrile, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone were added as polymerization inhibitors in the amounts shown in Table 1. The mixture was then refluxed at 78°C under atmospheric pressure while introducing nitrogen gas at a rate of 50 mL / min. The time required for the polymer generated by polymerization to precipitate and turn the test solution cloudy was recorded as the induction period (unit: minutes). A longer induction period indicates a stronger polymerization inhibitory effect. The results are shown in Table 1.

[0038] Examples 2 to 7 A polymerization inhibition test was carried out in the same manner as in Example 1, except that the amounts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone added were changed to those shown in Table 1. The results are shown in Table 1.

[0039] (Comparative Examples 1 to 8) A polymerization inhibition test was carried out in the same manner as in Example 1, except that the amounts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone added were changed to those shown in Table 1. The results are shown in Table 1.

[0040] (Comparative Example 9) Except for not adding the polymerization inhibitor, a polymerization inhibition test was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0041] [Acrylonitrile polymerization prevention test 2] Example 8 To 200 g of stabilizer-free acrylonitrile, 10 ppm of acetic acid was added, followed by the addition of polymerization inhibitors 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone in the amounts shown in Table 1. The mixture was refluxed at 78°C under atmospheric pressure while introducing nitrogen gas at a rate of 50 mL / min. The time required for the polymer generated by polymerization to precipitate and turn the test solution cloudy was recorded as the induction period (unit: minutes). A longer induction period indicates a stronger polymerization inhibition effect. The results are shown in Table 2.

[0042] Examples 9 to 14 A polymerization inhibition test was carried out in the same manner as in Example 8, except that the amounts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone added were changed to those shown in Table 1. The results are shown in Table 2.

[0043] (Comparative Examples 10 to 17) A polymerization inhibition test was carried out in the same manner as in Example 8, except that the amounts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone added were changed to those shown in Table 2. The results are shown in Table 2.

[0044] (Comparative Example 18) A polymerization inhibition test was carried out in the same manner as in Example 8, except that no polymerization inhibitor was added. The results are shown in Table 2.

[0045] As in Examples 1 to 7, when acrylonitrile was used and the polymerization inhibitors of the present invention, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone were contained, the induction period was 450 minutes or more and an excellent polymerization inhibitory effect was exhibited.On the other hand, as in Comparative Examples 1 to 9, when polymerization inhibitors having a configuration other than that of the present invention were used, the induction period was 450 minutes or less and the polymerization inhibitory effect was clearly inferior. Furthermore, when acrylonitrile contained acetic acid, polymerization was promoted as in Comparative Examples 10 to 18, and the induction period was 260 minutes or less. However, when the polymerization inhibitor of the present invention was contained as in Examples 8 to 14, the induction period was 390 minutes or more, and an excellent polymerization inhibitory effect was exhibited even in a situation where acetic acid was contained and polymerization was likely to occur.

[0046] [Table 1]

[0047] [Table 2]

[0048] [Methacrylic acid polymerization prevention test 1] Example 15 10 g of stabilizer-free methacrylic acid was placed in a test tube, and polymerization inhibitors (4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone) were added in the amounts shown in Table 3. The test tube was then immersed in a silicone oil bath set to 120°C under atmospheric conditions. The time it took for the test solution to solidify due to polymerization was defined as the induction period (unit: hours). A longer induction period indicates a higher polymerization inhibition effect. The results are shown in Table 3.

[0049] (Examples 16 to 24) A polymerization inhibition test was carried out in the same manner as in Example 15, except that the amounts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone added were changed to those shown in Table 3. The results are shown in Table 3.

[0050] (Comparative Examples 19 to 28) A polymerization inhibition test was carried out in the same manner as in Example 15, except that the amounts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone added were changed to those shown in Table 3. The results are shown in Table 3.

[0051] (Comparative Example 29) A polymerization inhibition test was carried out in the same manner as in Example 15, except that no polymerization inhibitor was added. The results are shown in Table 3.

[0052] [Methacrylic acid polymerization prevention test 2] Example 25 10 g of stabilizer-free methacrylic acid was placed in a test tube, and 10 ppm of sulfuric acid was added. Polymerization inhibitors, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone, were then added in the amounts shown in Table 3. The test tube was then immersed in a silicone oil bath set to 120°C under atmospheric conditions. The time it took for the test solution to solidify due to polymerization was defined as the induction period (unit: hours). A longer induction period indicates a stronger polymerization inhibition effect. The results are shown in Table 4.

[0053] (Examples 26 to 34) A polymerization inhibition test was carried out in the same manner as in Example 25, except that the amounts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone added were changed to those shown in Table 4. The results are shown in Table 4.

[0054] (Comparative Examples 30 to 39) A polymerization inhibition test was carried out in the same manner as in Example 25, except that the amounts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone added were changed to those shown in Table 4. The results are shown in Table 4.

[0055] (Comparative Example 40) A polymerization inhibition test was carried out in the same manner as in Example 25, except that no polymerization inhibitor was added. The results are shown in Table 4.

[0056] As in Examples 15 to 24, when methacrylic acid was used containing the polymerization inhibitor of the present invention, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone, the induction period was 23 hours or longer, and excellent polymerization inhibitory effects were exhibited.On the other hand, as in Comparative Examples 19 to 29, when the composition was other than the polymerization inhibitor of the present invention, the induction period was 22 hours or shorter, and the polymerization inhibitory effects were clearly inferior. Furthermore, when sulfuric acid was contained in methacrylic acid, polymerization was promoted and the induction period was 21 hours or less as in Comparative Examples 30 to 40. However, when the polymerization inhibitor of the present invention was contained as in Examples 25 to 34, the induction period was 22 hours or more in all cases, and an excellent polymerization inhibitory effect was exhibited even in conditions where sulfuric acid is contained and polymerization is likely to occur.

[0057] [Table 3]

[0058] [Table 4]

[0059] [Vinyl acetate polymerization prevention test 1] Example 35 10 g of stabilizer-free vinyl acetate was placed in a test tube, and 130 mg of lauroyl peroxide (polymerization catalyst) was added. The polymerization inhibitors, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone, were added in the amounts shown in Table 5. The test tube was then immersed in a water bath set at 65°C under atmospheric conditions. The time until bubbles appeared due to the polymerization reaction was measured. The same measurement was also performed on vinyl acetate without the polymerization inhibitor, and the time difference was recorded as the polymerization inhibition time (unit: seconds). A longer polymerization inhibition time indicates a higher polymerization inhibition effect. The results are shown in Table 5.

[0060] Examples 36 to 44 A polymerization inhibition test was carried out in the same manner as in Example 35, except that the amounts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone added were changed to those shown in Table 5. The results are shown in Table 5.

[0061] (Comparative Examples 41 to 50) A polymerization inhibition test was carried out in the same manner as in Example 35, except that the amounts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone added were changed to those shown in Table 5. The results are shown in Table 5.

[0062] [Vinyl acetate polymerization prevention test 2] Example 45 10 g of stabilizer-free vinyl acetate was placed in a test tube, to which 10 ppm of acetic acid and 130 mg of the polymerization catalyst lauroyl peroxide were added. The polymerization inhibitors, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone, were added in the amounts shown in Table 6. The test tube was then immersed in a water bath set at 65°C under open-air conditions. The time until bubbles appeared due to the polymerization reaction was measured. The same measurement was also performed on vinyl acetate containing no polymerization inhibitor, and the time difference was recorded as the polymerization inhibition time (unit: seconds). A longer polymerization inhibition time indicates a higher polymerization inhibition effect. The results are shown in Table 6.

[0063] (Examples 46 to 54) A polymerization inhibition test was carried out in the same manner as in Example 45, except that the amounts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone added were changed to those shown in Table 6. The results are shown in Table 6.

[0064] (Comparative Examples 51 to 60) A polymerization inhibition test was carried out in the same manner as in Example 45, except that the amounts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone added were changed to those shown in Table 6. The results are shown in Table 6.

[0065] As in Examples 35 to 44, when vinyl acetate was used and the polymerization inhibitor of the present invention, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, hydroquinone, and benzoquinone were contained, the polymerization inhibition time was 315 seconds or longer, and excellent polymerization inhibition effect was exhibited.On the other hand, as in Comparative Examples 41 to 50, when the composition was other than the polymerization inhibitor of the present invention, the polymerization inhibition time was 310 seconds or shorter, and the polymerization inhibition effect was clearly inferior. Furthermore, when vinyl acetate contained acetic acid, polymerization was promoted and the polymerization inhibition time was 250 seconds or less as in Comparative Examples 51 to 60. However, when the polymerization inhibitor of the present invention was contained as in Examples 45 to 54, the polymerization inhibition time was 270 seconds or more in all cases, and an excellent polymerization inhibition effect was exhibited even in conditions where polymerization is likely to occur due to the presence of acetic acid.

[0066] [Table 5]

[0067] [Table 6] [Industrial Applicability]

[0068] By using the treatment method of the present invention as a method for preventing polymerization of vinyl compounds, polymerization can be effectively suppressed, the generation of fouling can be prevented during the production and purification of vinyl compounds, and efficient plant operation can be achieved.

Claims

1. A method for preventing polymerization of a vinyl compound, comprising the steps of: (a) preparing a vinyl compound containing a 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical; (b) preparing a vinyl compound containing a 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical; (c) preparing a vinyl compound containing a 4-hydroxy-2,2,6,6-tetramethylpiperidine; (d) preparing a vinyl compound containing a 4-hydroxy-2,2,6,6-tetramethylpiperidine free radical; (e) preparing a vinyl compound containing a 4-hydroxy-2,2,6,6-tetramethylpiperidine free radical; (f ...

2. The method according to claim 1, characterized in that the vinyl compound contains 0.01 to 1000 ppm of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical, 0.01 to 1000 ppm of 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, 0.01 to 1000 ppm of hydroquinone, and 0.01 to 1000 ppm of benzoquinone.

3. 3. The method according to claim 1, wherein the vinyl compound is at least one selected from the group consisting of (meth)acrylic acid, (meth)acrylic acid ester compounds, (meth)acrylonitrile, and vinyl acetate.

4. 3. The method according to claim 1, wherein the weight ratio of the 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical contained in the vinyl compound to hydroquinone is 1:40 to 10:

1.

5. 3. The method according to claim 1, wherein the weight ratio of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical to 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine is 0.1:1 to 30:

1.

6. 3. The method according to claim 1, wherein the weight ratio of hydroquinone to benzoquinone is 1:2 to 60:

1.

7. 3. The method according to claim 1, wherein the vinyl compound contains 1 ppm or more of acetic acid and / or sulfuric acid.

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