N-vinylacetamide-containing composition and method for producing the same

Abstract

The present invention addresses the problem of providing a composition which stably has high polymerizability, and from which an N-vinyl acetamide polymer is produced.　An N-vinyl acetamide-containing composition which is characterized in that if the peak area of N-vinyl acetamide as determined by a high-speed liquid chromatography measurement under specific conditions is taken as 1, the total of the peak areas at a retention time of from 31.5 minutes to 32.5 minutes, at a retention time of from 35.5 minutes to 36.5 minutes and at a retention time of from 39.5 minutes to 40.5 minutes is 1.1 × 10-4 or less.

Description

[Technical Field]

[0001] The present invention relates to an N-vinylacetamide-containing composition used in the production of N-vinylacetamide-based polymers that are used as binders, dispersants, flocculants, liquid absorbents, thickeners, etc., and a method for producing the same. [Background technology]

[0002] N-vinylacetamide-based polymers have been found to be useful in various fields, such as binders, dispersants, flocculants, liquid absorbents, and thickeners, and N-vinylacetamide, the monomer used to produce them, is industrially useful.

[0003] Many methods have been proposed for producing N-vinylacetamide. For example, one method is to produce the intermediate N-(1-alkoxyethyl)acetamide from acetamide, acetaldehyde, and an alcohol, and then synthesize it by thermal or catalytic decomposition. Another method is to synthesize ethylidenebisacetamide from acetamide and acetaldehyde, and then decompose it into N-vinylacetamide and acetamide.

[0004] However, N-vinylacetamide has been recognized as a vinyl monomer with low polymerizability, and there has been a demand for improvement in its polymerizability. The polymerizability of a monomer can vary greatly depending on the amount of polymerization inhibitors contained in the monomer as impurities. For this reason, the monomer may be purified by various methods to reduce the amount of polymerization inhibitors to an acceptable level or below.

[0005] From this perspective, attempts have been made to increase the purity of N-vinylacetamide synthesized by the above-mentioned thermal decomposition or catalytic decomposition by purification methods such as distillation, extraction, recrystallization, etc., to thereby enhance its polymerizability. Examples of purification methods disclosed include an extraction method using water and an aromatic hydrocarbon in Patent Document 1, a cooling crystallization method from a mixed organic solvent in Patent Document 2, an extraction method using an aqueous solution of an inorganic salt and an aromatic hydrocarbon in Patent Document 3, and an extractive distillation method using a polyhydric alcohol in Patent Document 4.

[0006] However, with any of the above methods, it was difficult to produce N-vinylacetamide, which has good polymerizability, as a monomer for stably obtaining high-molecular-weight polymers that can be used as flocculants, liquid absorbents, thickeners, etc.

[0007] Patent Document 5 reports that in order to synthesize a high-molecular-weight N-vinylcarboxylic acid amide polymer, it is important to reduce the content of N-1,3-butadienylcarboxylic acid amide in the N-vinylcarboxylic acid amide used. Furthermore, it clearly states that N-vinylcarboxylic acid amides having an N-1,3-butadienylcarboxylic acid amide content of 30 mass ppm or less are highly polymerizable. It also clearly describes a purification method for reducing this content.

[0008] Patent Document 6 discloses a method for producing N-vinylcarboxylic acid amide, which is characterized by having a step of controlling the content of a monomer in the N-vinylcarboxylic acid amide relative to a conventionally used polymerization monomer composition to 20 mass ppm or less.

[0009] However, even when N-vinylacetamide obtained by these methods is used as a raw material monomer, high polymerizability may not be stably obtained, especially after long-term storage after production, and there is room for further improvement. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 61-289069 [Patent Document 2] Japanese Patent Application Laid-Open No. 63-132868 [Patent Document 3] Japanese Patent Application Publication No. 2-188560 [Patent Document 4] U.S. Patent No. 4,401,516 [Patent Document 5] Japanese Patent Application Publication No. 8-81428 [Patent Document 6] International Publication No. 2017 / 145569 Summary of the Invention [Problem to be solved by the invention]

[0011] As described above, polymerization monomers for producing N-vinylacetamide-based polymers may not exhibit high polymerizability even when the content of N-1,3-butadienylacetamide or the content of unsaturated aldehydes is reduced, and it has been predicted that they contain some kind of polymerization inhibitor. An object of the present invention is to provide a composition for producing an N-vinylacetamide polymer, which has high and stable polymerizability. [Means for solving the problem]

[0012] The present invention relates to the following: [1] 1. A composition comprising N-vinylacetamide, In high performance liquid chromatography measurement under the following conditions, when the peak area of N-vinylacetamide is set to 1, the total peak area at retention times of 31.5 to 32.5 minutes, 35.5 to 36.5 minutes, and 39.5 to 40.5 minutes is 1.1 x 10 -4 An N-vinylacetamide-containing composition, characterized in that: (Measurement conditions) Column: Showa Denko Shodex (registered trademark) SB-802.5HQ x 2 Pump: Showa Denko Co., Ltd. Shodex (registered trademark) DS-4 Flow rate: 0.7ml / min Sample injection volume: 10 μL Column oven: Sugai U-620 Column oven temperature: 45°C UV / Vis detector: Shimadzu Corporation SPD-20A, measurement wavelength: 230 nm Eluent: acetonitrile / water = 1 / 9 (volume ratio) Sample: Dilute to 1% by mass with eluent

[0013] [2] In the high performance liquid chromatography measurement, when the peak area of N-vinylacetamide is taken as 1, the total of the peak areas at retention times of 31.5 minutes to 32.5 minutes, 35.5 minutes to 36.5 minutes, and 39.5 minutes to 40.5 minutes is 0.05 × 10 -5 The N-vinylacetamide-containing composition according to [1], characterized in that: [3] The N-vinylacetamide-containing composition according to [1] or [2], which is purified by crystallization.

[0014] [4] The N-vinylacetamide-containing composition according to any one of [1] to [3], which is produced using as a raw material a composition containing N-alkoxyethylacetamide purified by distillation. [5] An N-vinylacetamide polymer obtained by polymerizing the N-vinylacetamide-containing composition according to any one of [1] to [4]. [6] A method for producing the N-vinylacetamide-containing composition according to [1] or [2], A method for producing an N-vinylacetamide-containing composition, comprising a step C' of purifying a crude composition (3') containing N-vinylacetamide by crystallization.

[0015] [7] A step A' of adding an alkali to a crude composition (1') containing N-alkoxyethylacetamide and distilling the mixture to obtain a composition (2') containing N-alkoxyethylacetamide; and step B' of producing a crude composition (3') containing N-vinylacetamide from a composition (2') containing N-alkoxyethylacetamide through a dealcoholization reaction.

[0016] [8] A method for producing the N-vinylacetamide-containing composition according to [1] or [2], Step A: adding an alkali to a crude composition (1) containing N-alkoxyethylacetamide and distilling the mixture to obtain a purified composition (2) containing N-alkoxyethylacetamide; a step B of producing a crude composition (3) containing N-vinylacetamide from the purified composition (2) containing N-alkoxyethylacetamide through a dealcoholization reaction; and a step C of purifying the crude composition (3) containing N-vinylacetamide by crystallization.

[0017] [9] In high performance liquid chromatography measurement under the following conditions, when the peak area of N-vinylacetamide is set to 1, the total peak area at retention times of 31.5 to 32.5 minutes, 35.5 to 36.5 minutes, and 39.5 to 40.5 minutes is 1.1 x 10 -4 A method for selecting an N-vinylacetamide-containing composition, comprising determining whether or not the composition satisfies the following requirement, and selecting compositions that satisfy the requirement. (Measurement conditions) Column: Showa Denko Shodex (registered trademark) SB-802.5HQ x 2 Pump: Showa Denko Co., Ltd. Shodex (registered trademark) DS-4 Flow rate: 0.7ml / min Sample injection volume: 10 μL Column oven: Sugai U-620 Column oven temperature: 45°C UV / Vis detector: Shimadzu Corporation SPD-20A, measurement wavelength: 230 nm Eluent: acetonitrile / water = 1 / 9 (volume ratio) Sample: Dilute to 1% by mass with eluent [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a composition that contains N-vinylacetamide, can be used as a polymerization monomer for producing an N-vinylacetamide polymer, and has high and stable polymerizability, as well as a method for producing the composition. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 shows the results of high performance liquid chromatography measurement in Example 4. [Figure 2] FIG. 2 shows the results of high performance liquid chromatography measurement in Comparative Example 3. [Figure 3] FIG. 3 is a graph showing the relationship between the time to reach the standard temperature peak and the peak area in the polymerization test for the Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will now be described in further detail. The N-vinylacetamide-containing composition (hereinafter also simply referred to as the composition) according to the present invention is a composition that contains N-vinylacetamide and can be used as a polymerization monomer for producing an N-vinylacetamide-based polymer.

[0021] <Composition> The composition of the present invention is a composition containing N-vinylacetamide monomer as a main component (95% by mass or more), and in high performance liquid chromatography measurement under the following conditions, when the peak area of N-vinylacetamide (hereinafter also referred to as "S-NVA") is taken as 1, the sum (area ratio) of the peak area at retention times of 31.5 minutes to 32.5 minutes (hereinafter also referred to as "S32"), the peak area at retention times of 35.5 minutes to 36.5 minutes (hereinafter also referred to as "S36"), and the peak area at retention times of 39.5 minutes to 40.5 minutes (hereinafter also referred to as "S40") is 1.1 x 10 -4 Less than or equal to 1.0 × 10 -4 Less than or equal to 0.9 × 10 -4 A composition that satisfies this range is preferable as a monomer composition for polymerization because of its good polymerizability. The lower limit of the total peak area is not particularly limited, but is preferably 0.05 × 10 -5 or more, more preferably 0.1 × 10 -5 More preferably, 0.5 × 10 -5 That's all.

[0022] In this specification, for example, the peak area at a retention time of 31.5 minutes or more and 32.5 minutes or less means the area of a peak having a peak apex at 31.5 minutes or more and 32.5 minutes or less. When the baselines of peaks overlap, analysis can be performed by vertical splitting, baseline splitting, forced tailing processing, etc., with baseline splitting being preferred. Attempts to identify the structures of the compounds at the peaks S32, S36, and S40 were difficult.

[0023] (Measurement conditions) Column: Showa Denko Shodex (registered trademark) SB-802.5HQ x 2 Pump: Showa Denko Co., Ltd. Shodex (registered trademark) DS-4 Flow rate: 0.7ml / min Sample injection volume: 10 μL Column oven: Sugai U-620 Column oven temperature: 45°C UV / Vis detector: Shimadzu Corporation SPD-20A, measurement wavelength: 230 nm Eluent: acetonitrile / water = 1 / 9 (volume ratio) Sample: Dilute to 1% by mass with eluent

[0024] The composition of the present invention has a sufficiently low content of components corresponding to peaks at retention times of 31.5 to 32.5 minutes, 35.5 to 36.5 minutes, and 39.5 to 40.5 minutes in high performance liquid chromatography under the above measurement conditions. Because the content of impurity components corresponding to these peaks is sufficiently low, the composition of the present invention is not inhibited in polymerization, and it is believed that the composition can maintain sufficient polymerizability as a polymerization monomer even after long-term storage.

[0025] Although the composition of this embodiment is not particularly limited, it is preferable that the content of unsaturated aldehydes is low, usually 10 mass ppm or less, preferably 5 mass ppm or less, and more preferably below the detection limit in GC or HPLC. If the content of unsaturated aldehydes in the composition is within the above range, it is preferable because when used as a polymerizable monomer, it is less susceptible to polymerization inhibition by unsaturated aldehydes.

[0026] Examples of unsaturated aldehydes include crotonaldehyde, 2-ethyl-2-butenal, 2-methyl-2-pentenal, 2-hexenal, 2,4-hexadienal, 2,4-octadienal, 2,4,6-octatrienal, and 2-octenal.

[0027] Analysis of unsaturated aldehydes is carried out by either GC or HPLC. The content of the unsaturated aldehydes is the total content of each unsaturated aldehyde. For example, it is the total amount of crotonaldehyde, 2-ethyl-2-butenal, 2-methyl-2-pentenal, 2-hexenal, 2,4-hexadienal, 2,4-octadienal, 2,4,6-octatrienal, 2-octenal, etc. However, the detection limit of each unsaturated aldehyde must be 5 ppm by mass or less to be quantitatively determined. The measurement method used is gas chromatography (GC) or high performance liquid column chromatography (HPLC).

[0028] Furthermore, although the composition of this embodiment is not particularly limited, the content of N-1,3-butadienylacetamide is preferably 10 mass ppm or less, more preferably 5 mass ppm or less, even more preferably 1 mass ppm or less, and particularly preferably below the detection limit in high performance liquid column chromatography (HPLC). A low content of N-1,3-butadienylacetamide is preferred because of good polymerizability.

[0029] In this embodiment, N-1,3-butadienylacetamide can be identified by mass spectrometry (electron impact method), mass spectrometry (chemical ionization method), infrared absorption spectrometry, and ultraviolet absorption spectrometry. Mass spectrometry (electron impact method) 111, 69, 54, 43 Mass Spectrometry (Chemical Ionization) 112 Infrared absorption spectrum (cm -1 ) 3099, 1732, 1654, 1471 Ultraviolet absorption spectrum (nm) 237, 276 The quantitative determination of N-1,3-butadienylcarboxylic acid amide is preferably carried out by high performance liquid column chromatography, but is not limited to this method. For example, the measurement conditions for high performance liquid column chromatography described in the Examples are preferred.

[0030] The composition of the present invention may be obtained by any production method as long as it satisfies the above-mentioned requirements. That is, it may be obtained by a method of synthesizing N-vinylacetamide under conditions that minimize the by-production of components corresponding to the peaks with retention times of 31.5 to 32.5 minutes, 35.5 to 36.5 minutes, and 39.5 to 40.5 minutes, or it may be obtained by synthesizing N-vinylacetamide under conventionally known conditions and then removing the components corresponding to the peaks with retention times of 31.5 to 32.5 minutes, 35.5 to 36.5 minutes, and 39.5 to 40.5 minutes. Specific examples include a method in which a composition containing N-alkoxyethylacetamide used as a raw material for synthesizing N-vinylacetamide is purified in advance by a method such as distillation, a method in which a composition containing N-vinylacetamide is purified by a method such as crystallization, or a combination of these methods.

[0031] <Method for selecting compositions> The method for selecting a composition of the present invention is a method for determining whether a composition containing N-vinylacetamide satisfies the above-mentioned requirements and selecting a composition that satisfies the requirements. That is, when the peak area of N-vinylacetamide is defined as 1 in the above-mentioned high-performance liquid chromatography measurement, the composition containing N-vinylacetamide has a total area ratio (area ratio) of 1.1 × 10 for the peaks at retention times of 31.5 minutes to 32.5 minutes, 35.5 minutes to 36.5 minutes, and 39.5 minutes to 40.5 minutes. -4 Less than or equal to 1.0 × 10 -4 Less than or equal to 0.9 × 10 -4 In this method, the lower limit of the total peak area at the retention times of 31.5 minutes or more and 32.5 minutes or less, 35.5 minutes or more and 36.5 minutes or less, and 39.5 minutes or more and 40.5 minutes or less of the composition to be selected is not particularly limited, but from the viewpoint of purification costs, it is preferably 0.05×10 -5 or more, more preferably 0.1 × 10 -5 More preferably, 0.5 × 10-5 That's all.

[0032] <Method of producing the composition> The method for producing a composition of the present invention is a method for producing a composition containing N-vinylacetamide, which is used for producing an N-vinylacetamide-based polymer. N-vinylacetamide can be produced, for example, by the reaction steps represented by the following reaction scheme.

[0033] [ka] (In the formula, R1 represents an alkyl group having 1 to 5 carbon atoms, R2 represents a hydrogen atom, and R3 represents a methyl group.)

[0034] The lower part of the above formula shows a process for producing N-vinylacetamide from N-(1-alkoxyethyl)acetamide by dealcoholization reaction. The method for producing a composition containing N-vinylacetamide of the present invention may include this step, that is, a step of obtaining N-vinylacetamide from N-(1-alkoxyethyl)acetamide by dealcoholization reaction.

[0035] In the dealcoholization reaction step, N-(1-alkoxyethyl)acetamide is used as a raw material. In general, the N-(1-alkoxyethyl)acetamide obtained by the method described in the upper part of the above formula is an N-(1-alkoxyethyl)acetamide containing impurities, and this N-(1-alkoxyethyl)acetamide has conventionally been used as is in the dealcoholization reaction step.

[0036] The method for producing the first composition of the present invention includes the steps of: Step A: adding an alkali to a crude composition (1) containing N-alkoxyethylacetamide and distilling the mixture to obtain a purified composition (2) containing N-alkoxyethylacetamide; a step B of producing a crude composition (3) containing N-vinylacetamide from the purified composition (2) containing N-alkoxyethylacetamide through a dealcoholization reaction; and step C of purifying the crude composition (3) containing N-vinylacetamide by crystallization.

[0037] In step A, an alkali is added to a crude composition (1) containing N-alkoxyethylacetamide and a solvent to adjust the pH to preferably 8.0 to 8.5, and the resulting mixture is then distilled to purify the N-(1-alkoxyethyl)acetamide, thereby obtaining a purified composition (2) containing N-alkoxyethylacetamide. Examples of alkali that can be used include sodium hydroxide and potassium hydroxide. The purified composition (2) containing N-alkoxyethylacetamide preferably has an N-alkoxyethylacetamide content of 80% by mass or more, more preferably 85% by mass or more.

[0038] The step B is a step of producing a crude composition (3) containing N-vinylacetamide from the purified composition (2) containing N-alkoxyethylacetamide through a dealcoholization reaction. The conditions for the dealcoholization reaction are not particularly limited, but it is desirable to carry out thermal decomposition at a temperature of 300°C or higher, preferably about 350 to 450°C, under reduced pressure.

[0039] The crude composition (3) may be the composition itself after the dealcoholization reaction, but is preferably a composition from which at least a portion of the by-produced alcohol has been removed. That is, step B may include a step of removing at least a portion of the by-produced alcohol from the composition after the dealcoholization reaction. The by-produced alcohol can be removed, for example, by distillation to distill off the alcohol.

[0040] It is also preferable that the crude composition (3) is one from which at least a portion of the N-1,3-butadienylacetamide has been removed. That is, step B may include a step of removing at least a portion of the by-product N-1,3-butadienylacetamide from the composition after the dealcoholization reaction. N-1,3-butadienylacetamide can be removed, for example, by converting it into harmless N-butylacetamide or N-buteneacetamide by hydrogenation. N-1,3-butadienylacetamide can be removed by hydrogenation, for example, by contacting it with hydrogen gas using a column packed with a hydrogenation catalyst such as a Pd-Al2O3-based catalyst.

[0041] Step C is a step of purifying the N-vinylacetamide-containing crude composition (3) by crystallization. The N-vinylacetamide-containing crude composition (3) often contains impurities such as unreacted N-alkoxyethylacetamide in addition to N-vinylacetamide. In step C, crystallization can be performed to reduce the content of these impurities. In step C, crystallization may be performed once or may be repeated two or more times. In the present invention, it is preferable to perform crystallization two or three times in step C. Crystallization can be performed by a known method, for example, by dissolving the N-vinylacetamide in a solvent such as methylcyclohexane or ethyl acetate, cooling from about 35 to 45°C to about 5 to 10°C, precipitating N-vinylacetamide crystals, separating the crystals by filtration, or the like, and washing them as necessary.

[0042] The composition obtained by the method for producing a composition of the present invention has excellent polymerizability and maintains sufficient polymerizability even after long-term storage. This is thought to be because the method for producing a composition of the present invention provides a composition with a low content of components that inhibit polymerization.

[0043] In the method for producing a composition of the present invention, preferably, the resulting monomer composition for polymerization has, when measured by high performance liquid chromatography under the above-mentioned conditions, a total of the peak areas at retention times of 31.5 minutes or more and 32.5 minutes or less, 35.5 minutes or more and 36.5 minutes or less, and 39.5 minutes or more and 40.5 minutes or less of 1.1 × 10 when the peak area of N-vinylacetamide is taken as 1. -4 or less, more preferably 1.0 × 10 -4 or less, more preferably 0.9 × 10 -4 A monomer composition for polymerization that satisfies this range is preferred because it has good polymerizability. The lower limit of the total peak area is not particularly limited, but is preferably 0.05 × 10 or less from the viewpoint of purification costs. -5 or more, more preferably 0.1 × 10 -5 More preferably, 0.5 × 10 -5 That's all.

[0044] The second method for producing a composition of the present invention is a method for producing a composition containing the N-vinylacetamide of the present invention described above. That is, in the method for producing a composition of the present invention, when the peak area of N-vinylacetamide is defined as 1, the sum of the peak areas at retention times of 31.5 to 32.5 minutes, 35.5 to 36.5 minutes, and 39.5 to 40.5 minutes is 1.1 × 10 -4 The following is a method for making the composition.

[0045] The second method for producing a composition of the present invention includes a step C' of purifying the crude composition (3') containing N-vinylacetamide by crystallization. The method for producing the second composition of the present invention preferably includes the steps of: A step A' of adding an alkali to a crude composition (1') containing N-alkoxyethylacetamide and distilling the mixture to obtain a composition (2') containing N-alkoxyethylacetamide; Step B' of producing a crude composition (3') containing the N-vinylacetamide through a dealcoholization reaction from a composition (2') containing N-alkoxyethylacetamide is included.

[0046] In the method for producing the second composition of the present invention, the specific operations of Step A', Step B', and Step C' are the same as Step A, Step B, and Step C described above in the method for producing the first composition of the present invention, respectively.

[0047] In such a method for producing the second composition of the present invention, the obtained composition contains N-vinylacetamide, has a low content of components that inhibit polymerization, is excellent in polymerizability, and has sufficient polymerizability even after long-term storage.

Example

[0048] Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

[0049] [Example 1] Preparation of N-vinylacetamide <Synthesis of N-(1-methoxyethyl)acetamide> 298 g of acetaldehyde (manufactured by Fujifilm Wako Pure Chemical Corporation), 651 g of methanol (manufactured by Junsei Chemical Co., Ltd.), and 100 g of acetamide (manufactured by Tokyo Chemical Industry Co., Ltd.) were reacted under a sulfuric acid (manufactured by Junsei Chemical Co., Ltd.) catalyst to obtain a crude composition (1) with a pH of 1.6 containing N-(1-methoxyethyl)acetamide.

[0050] <pH adjustment of the crude composition (1) containing N-(1-methoxyethyl)acetamide> A 48% by mass aqueous sodium hydroxide solution (manufactured by Junsei Chemical Co., Ltd.) was added to the obtained crude composition (1) containing N-(1-methoxyethyl)acetamide to adjust the pH to 8.0.

[0051] <Distillation purification of N-(1-methoxyethyl)acetamide> Next, the composition containing N-(1-methoxyethyl)acetamide with adjusted pH obtained above was distilled using a simple distillation apparatus under the conditions of a vacuum degree of 0.27 to 33 kPa (absolute pressure) and a bottom temperature of 90°C or higher and 100°C or lower. As a result, a composition (2) containing N-(1-methoxyethyl)acetamide with a purity of 92% by mass was obtained.

[0052] <Synthesis of N-vinylacetamide (Pyrolysis·Dealcoholation Reaction)> The composition (2) containing the purified N-(1-methoxyethyl)acetamide obtained above was fed at a rate of 1.5 g / min to a reactor (tubular reactor with an inner diameter of 20 mm and a length of 240 mm) maintained at 400°C and a pressure of 20 kPa (absolute pressure). A mixture of N-vinylacetamide and methanol produced by the pyrolysis reaction was condensed with a cooling pipe installed at the reactor outlet to recover crude N-vinylacetamide. The conversion rate of N-(1-methoxyethyl)acetamide was 90%.

[0053] <Purification of N-vinylacetamide> Next, a 0.3% by mass Pd-Al2O3 catalyst was filled in a column (the filling amount was set to an amount such that the catalyst amount was 1 ml with respect to 20 g of crude N-vinylacetamide). Then, crude N-vinylacetamide was circulated and flowed together with hydrogen gas under the conditions of a reaction temperature of 40°C, a hydrogen gas pressure of 0.03 MPa (gauge pressure), and a space velocity (SV value) in the catalyst-filled column of 100 / hr. A reaction to hydrogenate and reduce N-1,3-butadienylacetamide by-produced in the pyrolysis reaction was carried out for 4 hours. The crude N-vinylacetamide with reduced N-1,3-butadienylacetamide was distilled using a simple distillation apparatus under the conditions of a vacuum degree of 0.27 kPa (absolute pressure) or lower and a bottom temperature of 50°C or higher and 60°C or lower to remove methanol, and a crude composition (3) containing N-vinylacetamide was obtained.

[0054] The obtained crude composition (3) containing N-vinylacetamide was cooled from 40°C to 10°C in a crystallizer to precipitate N-vinylacetamide crystals, which were then separated using a centrifugal filter. The separated crystals were washed with a solution of methylcyclohexane:ethyl acetate = 95:5 (mass ratio) to obtain 40 g of N-vinylacetamide. Furthermore, this N-vinylacetamide was added to 44 g of methylcyclohexane and 8 g of ethyl acetate in a crystallizer and heated to 40°C to completely dissolve, then cooled to 5°C and crystallized again to precipitate crystals, which were then separated using a centrifugal filter. The crystals were washed with a solution of methylcyclohexane:ethyl acetate = 95:5 (mass ratio) and dried at 25°C and 3 to 5 kPa (absolute pressure) to obtain 33.6 g of purified N-vinylacetamide.

[0055] This was analyzed by high performance liquid chromatography (HPLC) under the following measurement conditions. The area ratio was calculated from the peak area value (S32) at retention times of 31.5 to 32.5 minutes, the peak area value (S36) at retention times of 35.5 to 36.5 minutes, and the peak area value (S40) at retention times of 39.5 to 40.5 minutes, and the peak area value of N-vinylacetamide (S-NVA) using the following formula, and was found to be 0.34 × 10 -4 The peak of N-vinylacetamide appears in the retention time range of 43.5 minutes to 44.5 minutes. The contents of unsaturated aldehydes and N-1,3-butadienylcarboxylic acid amide were measured under the following conditions, but both were below the detection limit (ND).

[0056] (HPLC measurement conditions) a) Pump: Shodex (registered trademark) DS-4 manufactured by Showa Denko K.K. Flow rate: 0.7 ml / min b) Autosampler: Jasco AS-2055plus Sample injection volume: 10 μL c) Column oven: Sugai U-620 manufactured by Sugai Corporation Column oven temperature: 45°C d) UV / Vis detector: Shimadzu Corporation SPD-20A Measurement wavelength: 230 nm e) Column: Showa Denko Shodex (registered trademark) SB-802.5HQ x 2 f) Eluent: acetonitrile (Kanto Chemical Co., Ltd., for high performance liquid chromatography) / water (ion-exchanged water) = 1 / 9 (volume ratio) g) Sample: Dilute to 1% by mass with eluent. (Formula for calculating area ratio) Area ratio=(S32+S36+S40) / (S-NVA)

[0057] <Measurement of unsaturated aldehyde content> The total content of each unsaturated aldehyde is measured by gas chromatography (GC) and high performance liquid column chromatography (HPLC). The detection limit for each unsaturated aldehyde is 5 ppm by mass for both GC and HPLC. The GC method is performed under the following measurement conditions. Equipment: Shimadzu Corporation GC-2014 Column: HP-WAX φ0.25mm x 30m Flow rate: He 1cm 3 / min Spirit ratio: 40 Column temperature: 40°C (7 min) → temperature increase (25°C / min) → 130°C (15 min) → temperature increase (30°C / min) → 220°C (2 min) Injection temperature: 200℃ Detector: Flame ionization detector (FID) Detector temperature: 230℃

[0058] The HPLC method is performed under the following measurement conditions. Column: Showa Denko K.K.: Shodex (registered trademark) SIL-5B Flow rate: 1.0mL / min Column temperature: 40℃ Eluent: isopropyl alcohol (IPA) / n-hexane = 1 / 9 (mass ratio) Detector: UV detector, 254 nm

[0059] <Analysis of N-1,3-butadienylcarboxamide> The quantification of N-1,3-butadienylcarboxamide was confirmed, identified, and quantified by high-performance liquid column chromatography (HPLC) method with ultraviolet-visible light absorption spectrum. The measurement conditions are as follows. Column: Manufactured by Showa Denko K.K.: Shodex (registered trademark) SIL-5B Eluent: Isopropyl alcohol (IPA) / n-hexane = 1 / 9 (mass ratio) Column temperature: 40 °C Flow rate: 1.0 mL / min Detector: UV / Vis detector, 254 nm

[0060] Polymerization Test The polymerization test of the N-vinylacetamide-containing composition was carried out as follows. The standard temperature peak arrival time by the polymerization test of this example was 88 minutes. Here, the standard temperature peak arrival time is the time from the injection of the polymerization initiator until the temperature shows a maximum. Those with a standard temperature peak arrival time less than 130 minutes can be judged as good polymerization products.

[0061] [1] Prepare a 100 ml glass container equipped with a catalyst injection tube, a nitrogen gas injection tube, a nitrogen gas exhaust tube, and a thermometer. [2] Weigh 20 g of N-vinylacetamide and 58 g of ion-exchanged water into the glass container of [1]. [3] Heat to 30 °C in a water bath while bubbling with 50 ml / min of nitrogen gas. Nitrogen gas is ventilated until the polymerization is completed. [4] Add 48.4 g of ion-exchanged water to 1.6 g of VA-044 (2,2’-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, manufactured by Fuji Film Wako Pure Chemical Corporation) as a polymerization initiator and dissolve it. [5] Add 46.0 g of ion-exchanged water to 4.0 g of V-50 (2,2’-azobis(2-methylpropionamidine) dihydrochloride, manufactured by Fuji Film Wako Pure Chemical Corporation) as a polymerization initiator and dissolve it. [6] After one hour of nitrogen gas aeration, 1 g of the aqueous polymerization initiator solution from [4] and then 1 g of the aqueous polymerization initiator solution from [5] are added using syringes. [7] Remove the glass container from the water bath, remove the moisture on the surface of the glass with paper, then transfer it to an insulated container to continue polymerization. [8] The polymerization temperature was monitored, and the time from the addition of the polymerization initiator in [6] until the temperature of the N-vinylacetamide solution reached its maximum (standard temperature peak time) was used as an index of polymerization.

[0062] [Example 2] In the same manner as in Example 1, 35.6 g of purified N-vinylacetamide was obtained. The area ratio was 0.86 × 10 -4 The contents of unsaturated aldehydes and N-1,3-butadienylcarboxylic acid amide were both below the detection limit. The standard temperature peak arrival time in the polymerization test was 108 minutes.

[0063] [Example 3] In the same manner as in Example 1, 36.4 g of purified N-vinylacetamide was obtained. The area ratio was 0.95 × 10 -4 The contents of unsaturated aldehydes and N-1,3-butadienylcarboxylic acid amide were both below the detection limit. The standard temperature peak time in the polymerization test was 115 minutes.

[0064] [Example 4] In the same manner as in Example 1, 34.8 g of purified N-vinylacetamide was obtained. The area ratio was 0.74 × 10 -4 The contents of unsaturated aldehydes and N-1,3-butadienylcarboxylic acid amide were both below the detection limit. The standard temperature peak time in the polymerization test was 105 minutes.

[0065] [Example 5] 36 g of purified N-vinylacetamide was obtained in the same manner as in Example 1. The area ratio was 0.88 × 10 -4The contents of unsaturated aldehydes and N-1,3-butadienylcarboxylic acid amide were both below the detection limit. The time to reach the standard temperature peak in the polymerization test was 113 minutes.

[0066] [Example 6] 30 g of N-vinylacetamide prepared in the same manner as in Example 1 (except that the amount charged was five times larger) was stored in a constant temperature bath at 20°C for one year, and then 33 g of methylcyclohexane and 6 g of ethyl acetate were added to a crystallizer and heated to 40°C until completely dissolved. After that, the mixture was cooled to 5°C and crystallized again to precipitate crystals, which were then separated using a centrifugal filter. The crystals were washed with a solution of methylcyclohexane:ethyl acetate = 95:5 (mass ratio) and dried at 25°C and 3 to 5 kPa (absolute pressure) to obtain 24.8 g of purified N-vinylacetamide. The area ratio was 0.45 x 10 -4 The contents of unsaturated aldehydes and N-1,3-butadienylcarboxylic acid amide were both below the detection limit. The standard temperature peak time in the polymerization test was 96 minutes.

[0067] [Example 7] The same procedure as in Example 6 was repeated, except that the storage period was changed from one year to three years, to obtain 22.2 g of purified N-vinylacetamide. The area ratio was 0.98 × 10 -4 The contents of unsaturated aldehydes and N-1,3-butadienylcarboxylic acid amide were both below the detection limit. The time to reach the standard temperature peak in the polymerization test was 113 minutes.

[0068] [Comparative Example 1] N-vinylacetamide prepared in the same manner as in Example 1 (except that the amount used was five times larger) was stored in a thermostatic chamber at 20°C for one year, and analyzed in the same manner as in Example 1. The area ratio was 4.39 × 10 -4 The contents of unsaturated aldehydes and N-1,3-butadienylcarboxylic acid amide were both below the detection limit. The standard temperature peak time in the polymerization test was 250 minutes.

[0069] Comparative Example 2 N-vinylacetamide prepared in the same manner as in Example 1 (except that the amount used was five times larger) was stored in a thermostatic chamber at 20°C for three years, and analyzed in the same manner as in Example 1. The area ratio was 16.02 × 10 -4 The contents of unsaturated aldehydes and N-1,3-butadienylcarboxylic acid amide were both below the detection limit. The standard temperature peak time in the polymerization test was 360 minutes.

[0070] Comparative Example 3 N-vinylacetamide prepared in the same manner as in Example 1 (except that the amount used was five times larger) was stored in a thermostatic chamber at 40°C for three months, and analyzed in the same manner as in Example 1. The area ratio was 58.30 × 10 -4 The contents of unsaturated aldehydes and N-1,3-butadienylcarboxylic acid amide were both below the detection limit. A polymerization test was carried out, but the standard temperature peak was not reached even after 24 hours.

[0071] [Comparative Examples 4 and 5] Two lots of N-vinylacetamide produced in the same manner as in Example 1 (except that the amount charged was five times larger) were stored in a refrigerated warehouse at 10°C for three years. When analyzed in the same manner as in Example 1, the area ratio was 1.26 × 10 -4 and 1.17 x 10 -4 The contents of unsaturated aldehydes and N-1,3-butadienylcarboxylic acid amide were both below the detection limit. The standard temperature peak arrival times in the polymerization test were 128 minutes and 124 minutes. The results of the above examples and comparative examples are shown in Table 1.

[0072] [Table 1]

[0073] From the above Examples and Comparative Examples, in the above-mentioned high performance liquid chromatography measurement, the sum of the peak areas at retention times of 31.5 minutes to 32.5 minutes, 35.5 minutes to 36.5 minutes, and 39.5 minutes to 40.5 minutes relative to the peak area of N-vinylacetamide (1) (hereinafter also referred to as "area ratio") was 1.1 × 10 -4 It was found that N-vinylacetamide-containing compositions that satisfied the following criteria and had sufficiently low amounts of impurities appearing at retention times of 31.5 to 32.5 minutes, 35.5 to 36.5 minutes, and 39.5 to 40.5 minutes exhibited excellent polymerization properties. -4 In the comparative N-vinylacetamide-containing compositions that did not satisfy the following conditions and had large amounts of impurities appearing at retention times of 31.5 minutes to 32.5 minutes, 35.5 minutes to 36.5 minutes, and 39.5 minutes to 40.5 minutes, the polymerizability was insufficient, even though the contents of unsaturated aldehydes and N-1,3-butadienylcarboxylic acid amide were both below the detection limit. [Industrial Applicability]

[0074] The composition according to the present invention can be suitably used as a polymerization monomer for producing an N-vinylacetamide polymer.

Claims

1. 1. A composition comprising N-vinylacetamide, In high performance liquid chromatography measurement under the following conditions, when the peak area of N-vinylacetamide is set to 1, the total peak area at retention times of 31.5 minutes to 32.5 minutes, 35.5 minutes to 36.5 minutes, and 39.5 minutes to 40.5 minutes is 0.45 × 10 -4 An N-vinylacetamide-containing composition characterized by: (Measurement conditions) Column: Showa Denko Co., Ltd. Shodex (registered trademark) SB-802.5HQ x 2 Flow rate: 0.7ml / min Sample injection volume: 10 μL Column oven: Sugai U-620 Column oven temperature: 45°C UV / Vis detector: Shimadzu Corporation SPD-20A, measurement wavelength: 230 nm Eluent: acetonitrile / water = 1 / 9 (volume ratio) Sample: Dilute to 1% by mass with eluent

2. In the high performance liquid chromatography measurement, when the peak area of N-vinylacetamide is taken as 1, the total of the peak areas at retention times of 31.5 minutes to 32.5 minutes, 35.5 minutes to 36.5 minutes, and 39.5 minutes to 40.5 minutes is 0.05 × 10 -5 The N-vinylacetamide-containing composition according to claim 1, characterized in that

3. 3. The N-vinylacetamide-containing composition according to claim 1, which is purified by crystallization.

4. The N-vinylacetamide-containing composition according to any one of claims 1 to 3, which is produced using as a raw material a composition containing N-alkoxyethylacetamide purified by distillation.

5. An N-vinylacetamide polymer obtained by polymerizing the N-vinylacetamide-containing composition according to any one of claims 1 to 4.

6. A method for producing the N-vinylacetamide-containing composition of claim 1 or 2, comprising: A method for producing an N-vinylacetamide-containing composition, comprising a step C' of purifying a crude composition (3') containing N-vinylacetamide by crystallization.

7. a step A' of adding an alkali to a crude composition (1') containing N-alkoxyethylacetamide and distilling the mixture to obtain a composition (2') containing N-alkoxyethylacetamide; and step B' of producing a crude composition (3') containing N-vinylacetamide from a composition (2') containing N-alkoxyethylacetamide through a dealcoholization reaction. The method for producing an N-vinylacetamide-containing composition according to claim 6,

8. A method for producing the N-vinylacetamide-containing composition of claim 1 or 2, comprising: A step A of adding an alkali to a crude composition (1) containing N-alkoxyethylacetamide and distilling the mixture to obtain a purified composition (2) containing N-alkoxyethylacetamide; a step B of producing a crude composition (3) containing N-vinylacetamide from the purified composition (2) containing N-alkoxyethylacetamide through a dealcoholization reaction; and a step C of purifying the crude composition (3) containing N-vinylacetamide by crystallization.

9. In high performance liquid chromatography measurement under the following conditions, when the peak area of N-vinylacetamide is set to 1, the total peak areas at retention times of 31.5 minutes to 32.5 minutes, 35.5 minutes to 36.5 minutes, and 39.5 minutes to 40.5 minutes is 1.1 x 10 -4 A method for selecting an N-vinylacetamide-containing composition, comprising determining whether or not the composition satisfies the following requirement, and selecting compositions that satisfy the requirement. (Measurement conditions) Column: Showa Denko Co., Ltd. Shodex (registered trademark) SB-802.5HQ x 2 Flow rate: 0.7ml / min Sample injection volume: 10 μL Column oven: Sugai U-620 Column oven temperature: 45°C UV / Vis detector: Shimadzu Corporation SPD-20A, measurement wavelength: 230 nm Eluent: acetonitrile / water = 1 / 9 (volume ratio) Sample: Dilute to 1% by mass with eluent

Images