WO2006118319A1

WO2006118319A1 - Method for storing n-alkenyl carboxylic acid tertiary amide

Info

Publication number: WO2006118319A1
Application number: PCT/JP2006/309200
Authority: WO
Inventors: Toshiaki Kuriyama; Shukichi Ugamura; Shigeyuki Nozaki
Original assignee: Nippon Shokubai Co., Ltd.
Priority date: 2005-04-28
Filing date: 2006-04-27
Publication date: 2006-11-09

Abstract

An N-alkenyl carboxylic acid tertiary amide having excellent storage stability is provided, by wetting the inner wall surface contacting with the vapor phase part of a storage container. An N-alkenyl carboxylic acid tertiary amide is stored under such condition that relation between temperature (T1) at the inner wall surface contacting with a vapor phase part of an storage container of an N-alkenyl carboxylic acid tertiary amide, and liquid temperature (T2) of an N-alkenyl carboxylic acid tertiary amide, satisfies that (T1) - (T2) is not lower than -10 (oC).

Description

DESCRIPTION

METHOD FOR STORING N-ALKENYL CARBOXYLIC ACID TERTIARY AMIDE

Technical Field:

The present invention relates to a method for stable storing of an N-alkenyl carboxylic acid tertiary amide, for a long period.

Background Art:

N-vinyl-2-pyrrolidone, which is an N-alkenyl carboxylic acid tertiary amide, is useful as a reactive diluent, and a polymer thereof has conventionally been used widely in various fields such as pharmaceuticals, cosmetics, adhesives or pressure sensitive adhesive, paints, dispersing agents, ink, electronics parts, and photoresist material, due to having merits and advantages such as ecological compatibility, safety and hydrophilicity.

In this connection, N-vinyl-2-pyrrolidone is well-known to have nature that quality such as polymerization reactivity, pH, containing polymer concentration, and color valency changes over time in storage, or the like, and this change over time made handling of N-vinyl-2-pyrrolidone difficult such as requiring use thereof as soon as possible after synthesis. Therefore, stability in storage or the like of N-vinyl-2-pyrrolidone has been strongly desired.

A polymer of N-vinyl-2-pyrrolidone is industrially produced in general by a radical polymerization method using hydrogen peroxide or an organic peroxide or an azo-based organic compound as a polymerization initiator, in a polar solvent such as water or alcohol.

These radically polymerizable compounds are required to be handled by avoiding radical polymerization induced by radicals generating during storage, as is well-known in the case of acrylic acid or the like. Therefore, the addition of a compound having radical capturing ability represented by quinones as a stabilizer has beenwell-known. Furthermore, in the case of storage for a long period, storage in dark place is common.

On the other hand, generally, a basic substance is added for stabilization of pH, or the like. Therefore, a method for the addition of ammonia, N, N' -di-sec-butyl-p-phenylenediamine, sodium hydroxide, and the like has been proposed aiming at suppression of the quality change (JP-A-8-506580) .

In addition, the addition of an amine such as triethylamine is described in JP-A-7-252221. However, it aims at preventing polymerization in a purification step, and thus it is hard to say that a problem of storage stability, which is an object of the present invention, has already been solved. Presence of an alkali metal is effective to stabilize pH, and further, presence of N, N' -di-sec-butyl-p-phenylenediamine is considered to be effective to stabilize polymerization reactivity, pH, containing polymer concentration, color valency, and the like.

For storage of N-vinyl-2-pyrrolidone, a sealed tank, drum, and the like are generally used. However, even when the stabilizer is used, the quality such as polymerization reactivity, pH, containing polymer concentration, and color valency changed in some cases in long-term storage.

On the other hand, storage of an N-alkenyl carboxylic acid tertiary amide at dark and cool place maintained at about 25°C, that is temperature a certain degree lower than dangerous temperature (37°C) disclosed in literature or the like, or further lower temperature than that, in light shielded and sealed container, to suppress polymer generation, is described (JP-A-2003-291936) . However, there is no concept on controlling temperature (Tl) at the inner wall surface contacting with a vapor phase part of a container for storing an N-alkenyl carboxylic acid tertiary amide, and liquid temperature (T2) of an N-alkenyl carboxylic acid tertiary amide, in specified temperature range.

In addition, for storage of N-vinyl-2-pyrrolidone, a sealed tank, drum, and the like are generally used, however, even when a stabilizer such as N, N' -di-sec-butyl-p-phenylenediamine is contained, the quality such- as polymerization reactivity, pH, containing polymer concentration, and color valency changed in some cases in long-term storage.

Disclosure of Invention Under these circumstances, it is an object of the present invention to provide a method for storing an N-alkenyl carboxylic acid tertiary amide, having excellent storage stability irrespective of the addition of a stabilizer or not, namely, small change in quality such as polymerization reactivity, pH, containing polymer concentration, and color valency even in long-term storage.

We have extensively studied to solve the problems and found that the problem could be solved by wetting the inner wall of a storage container, with an N-alkenyl carboxylic acid tertiary amide, in storing an N-alkenyl carboxylic acid tertiary amide.

According to the preaent invention, a method for storing an N-alkenyl carboxylic acid tertiary amide, characterized by wetting at least a part of the inner wall surface, which contacts with vapor phase part, of a storage container of an N-alkenyl carboxylic acid tertiary amide, with the amide, in storing an N-alkenyl carboxylic acid tertiary amide, can be provided.

According to this method, change in quality such as polymerization reactivity, pH, containing polymer concentration, and color valency is very small even in long-term storage.

On the other hand, it is an obj ect of the present invention to provide a method for storing an N-alkenyl carboxylic acid tertiary amide, having excellent storage stability, namely, small change in quality such as polymerization reactivity, pH, containing polymer concentration, and color valency, even in long-term storage.

We have extensively studied to solve the problems and clarified that stability was insufficient only by keeping a solution in storage at not higher than 25°C. Then we have also found that the problem can be solved and excellent stability can be attained by controlling temperature of the specified part of a container within a specified range, in storage of an N-alkenyl carboxylic acid tertiary amide. Furthermore, we have also found that the effect becomes higher by controlling temperature (Tl) at the inner wall surface contacting with the vapor phase part of the container for storing an N-alkenyl carboxylic acid tertiary amide, as a controlling method. It has also been found that control of temperature range, so that (Tl) - (T2), i.e. a value = (Tl) minus (T2) , is not lower than -10 (⁰C) , provided small change in quality such as polymerization reactivity, pH, containing polymer concentration, and color valency. In addition, according to the present invention, amethod for storing an N-alkenyl carboxylic acid tertiary amide, characterized by controlling relation between temperature (Tl) at the inner wall surface contacting with the vapor phase part of the container for storing an N-alkenyl carboxylic acid tertiary amide, and liquid temperature (T2) of the N-alkenyl carboxylic acid tertiary amide, so that (Tl) - (T2) is not lower than -10 (⁰C) , can be provided.

Use of the composition of the present invention can provide a method for storing an N-alkenyl carboxylic acid tertiary amide, having significantly excellent storage stability irrespective of the addition of a stabilizer or not, namely, small change in quality such as polymerization reactivity, pH, containing polymer concentration, and color valency, even in long-term storage.

Brief Description of Drawings

Fig. 1 shows evaluation equipment used in Examples.

Best Mode for Carrying Out the Invention

A first embodiment of the present invention is explained in detail below.

An N-alkenyl carboxylic acid tertiary amide used in the first embodiment of the present invention is not especially limited, but includes an N-alkenyl cyclic carboxylic acid tertiary amide, and particularly preferably N-vinyl-2-pyrrolidone (hereinafter may be abbreviated as "NVP") .

The explanation below is based onNVP, as a representative example of an N-alkenyl carboxylic acid tertiary amide.

A method for producing NVP used in the first embodiment is not especially limited, but includes, for example, a method for vapor phase dehydration reaction of N-hydroxyethyl-2-pyrrolidone, the Reppe reactionmethod, and the like.

In addition, NVP after production may be subjected to purification treatment or not. However, carrying out a purification step such as a distillation step, a crystallization step, or both steps, in particular, carrying out a crystallization step after a distillation step is preferable, in view of purity of NVP. A stabilizer may be added or may not be added to NVP usedin the first embodiment . The stabilizer is not especially limited, however, a metal hydroxide such as sodium hydroxide and potassium hydroxide,

N, N' -di-sec-butyl-p-phenylenediamine, and the like are preferable, -and N, N' -di-sec-butyl-p-phenylenediamine is further preferable. The addition amount of the stabilizer is not especially limited, and for example, 1 ppm to 5% is preferable, 3 to 3000 ppm is more preferable and 5 to 100 ppm is most preferable, based on total weight on NVP. The addition amount of the stabilizer less than 1 ppm may lower suppression effects of polymerization and increase in containing polymer concentration, while the amount over 5% may bring about coloring of NVP.

On the other hand, in the case of a metal hydroxide such as sodium hydroxide, 1 ppm to 5% is preferable, and 100 to 5000 ppm is further preferable, based on total weight on NVP. The addition amount of the stabilizer less than 1 ppm may lower suppression effects of polymerization and increase in containing polymer concentration, while the amount over 5% may bring about coloring of NVP.

Wetting degree of a storage container of NVP is not especially limited, as long as at least a part of the inner wall surface contacting with the vapor phase part of a storage container of NVP is in wetted state. Nearly whole inner wall surface contacting with the vapor phase part is preferably in wetted state. Specifically, in the case when a storage container is a fixed tank or the like, installment of a rotating-type nozzle or a sprinkler at the upper part of a storage container, and always feeding an NVP solution to the whole inner wall surface of the container contacting with the vapor phase part, including a top board, by means of showering is preferable. NVP solution temperature in showering to be the same temperature as solution temperature of NVP in the storage tank may sometimes be effective for storage stability. To carry out the showering by pumping the NVP present at the bottom of the container, so that the NVP in the container is counterchanged or sufficiently mixed is preferable. Because of small quantity of the addition amount of the stabilizer, stabilization of NVP in storage can be improved by uniformly dispersing the stabilizer in the container by such a method.

On the other hand, when the storage container is not a fixed one such as a drum, operation such as rotation or shaking of the container at regular time interval is effective . In this case, use of a drum tumbling machine, a drum shaker, and the like is suitable. By such continuous or intermittent rotation of a drum in up and down direction, or in vertical direction with a horizontal plane as an axis, NVP contained in the container can be mixed, and also the inner wall surface of the vapor phase part of the container can be made in wetted state, which enables to prevent polymerization of NVP.

Material of the NVP storage container used in the first embodiment is not especially limited, however, a polyolefin such as polyethylene and polypropylene, a fluorocarbon resin such as PFA (a copolymer resin of tetrafluoroethylene-perfluoroalkyl vinyl ether) and PTFE, stainless steel, aluminum are preferable, and in particular stainless steel is effective.

In addition, use of the inner surface of a storage containerby reducing surface roughness is suitable . Amethod therefore includes buff finish or electrolytic polishing in the case that material of the inner surface of the container is metal or stainless steel such as SUS304 and SUS316. A similar method is naturally applied to other material whose inner surface is coated or applied by lining with the above material .

Storage temperature of NVP is not especially limited as long as it is temperature enables to maintain NVP in liquid state, and preferably not higher than 80°C, further preferably not higher than 60 °C and most preferably not higher than 40°C. Among these, a temperature range not higher than 35°C and not lower that 15⁰C enables to bring about the maximum effect of the present invention. A temperature over 80°C may bring about increase in containing polymer concentration or coloring, even when a stabilizer is present.

Atmosphere of the vapor phase part of the storage container of an NVP solution used in the first embodiment is not especially limited, however, handling by avoiding contact with acidic gas such as carbon dioxide gas is preferable, specifically, inert gas such as nitrogen gas is preferable.

The term "storage" of the present inventionmeans usually storage in a container, or the like. "Preservation", or the like are also within the scope of the present invention. The present invention includes not only simple storage but also transfer or transportation. NVP used in the first embodiment is preferably stored as it is, or in the added state with the stabilizer only. In addition, it may be stored by mixing with water or other solvent. Furthermore, additives such as a pH adjuster, a buffer agent, a color protection agent, a deodorant and a colorant other than the above stabilizer may be added.

A second embodiment of the present invention is explained in detail below.

In the following example, NPV is used as a representative example of an N-alkenyl carboxylic acid tertiary amide.

Temperature (Tl) at the inner wall surface contacting with the vapor phase part of the storage container of the NVP solution used in the second embodiment is not especially limited, however, preferably not higher than 80°C, further preferably not higher than 60⁰C and most preferably not higher than 40 °C. Among these, a temperature range not higher than 35°C and not lower that 15°C enables to bring about the maximum effect of the present invention. Temperature in this range provides small change in quality such as polymerization reactivity, pH, containing polymer concentration, and color valency, exhibiting significantly excellent storage stability.

Relation between temperature (Tl) at the inner wall surface contacting with the vapor phase part of the storage container of the NVP solution used in the second embodiment, and liquid temperature (T2) of NVP satisfies " (Tl) - (T2) is not lower than -10 (⁰C)". The lower limit of (Tl) - (T2) is preferably -5°C, more preferably 0⁰C, and further preferably 1°C. While, the upper limit of (Tl) - (T2) is preferably 30⁰C, more preferably 20⁰C, and further preferably 10⁰C.

"Temperature (Tl) at the inner wall surface contacting with the vapor phase part of the storage container" here means temperature at the wall surface of the vapor phase part inside the storage container. As a thermometer to measure this temperature, a resistance thermometer bulb is used. Value shown 1minute after setting the thermometer at the wall surface of the vapor phase part is used as this temperature. Use of a thermocouple is also possible depending on the cases.

Further, solution temperature (T2) of NVP means temperature of the solution at the vicinity of the center part. As a thermometer to measure this temperature, a resistance thermometer bulb is used. Value shown 1 minute after setting the thermometer in a protective tube arranged at the vicinity of the center part of the container is used as this temperature. Use of a thermocouple is also possible depending on- the cases.

Temperatures "Tl" and "T2" in the second embodiment may^¬ be controlled simultaneously or may be controlled independently. Control of temperature (Tl) at the inner wall surface contacting with the vapor phase part of the storage container is preferable due to little impair of solution stability. Simultaneous control with solution temperature (T2) is further preferably in view of easy control.

The container of the second embodiment means a tank, drum, bottle, can or bulk container, and the like. The term "storage" of the present invention means usually storage in the above container, or the like. "Preservation" or the like are also within the scope of the present invention. The present invention includes not only simple storage but also transfer or transportation. Atmosphere of the vapor phase part of the storage container of the NVP solution used in the second embodiment is not especially limited, however, handling by avoiding contact with acidic gas such as carbon dioxide gas is preferable, specifically, inert gas such as nitrogen gas is preferable.

In the second embodiment, a control method for maintaining the relation between temperature (Tl) at the inner wall surface contactingwith the vaporphase part of the storage container of NVP, and liquid temperature (T2) of NVP, so that

"(Tl) - (T2)" is not lower than -10 (⁰C), is not especially limited, and includes specifically a method for keeping warm at the whole wall by installment of a jacket enabling to warm and cool the outer wall of the container, a method for partitioning a jacket in small parts, or the like. Use of such a method enables storage under the condition that temperature (Tl) of the wall contacting with the vapor phase part is higher than solution temperature (T2). Use of a coil or an electric heater enabling to warm and cool, in stead of the jacket or in combination with the jacket is also effective. In this case, the jacket, the coil, or the electric heater preferably covers up to a top board.

A stabilizer may be added or may not be added to the N-alkenyl carboxylic acid tertiary amide used in the second embodiment . A stabilizer when added is not especially limited, however, a metal hydroxide such as sodium hydroxide and potassiumhydroxide, N, N' -di-sec-butyl-p-phenylenediamine, and the like are preferable, and N, N' -di-sec-butyl-p-phenylenediamine is further preferable. The addition amount of the stabilizer is not especially limited, however, for example, 1 ppm to 5% is preferable, 3 to 3000 ppm is more preferable and 5 to 100 ppm is most preferable based on the N-alkenyl carboxylic acid tertiary amide, in the case of N, N' -di-sec-butyl-p-phenylenediamine. The addition amount of the stabilizer less than 1 ppm may lower suppression effects of .polymerization and increase in containing polymer concentration, while the amount over 5% may bring about coloring of NVP.

On the other hand, in the case of a metal hydroxide such as sodium hydroxide, 1 ppm to 5% is preferable, and 100 to 5000 ppm is further preferable, based on the N-alkenyl carboxylic acid tertiary amide. The addition amount of the stabilizer less than 1 ppm may lower suppression effects of polymerization and increase in containing polymer concentration, while the amount over 5% may bring about coloring.

Material of the NVP storage container used in the second embodiment is not especially limited, however, a polyolefin such as polyethylene and polypropylene, a fluorocarbon resin such as PFA (a copolymer resin of tetrafluoroethylene-perfluoroalkyl vinyl ether) and PTFE, stainless steel, aluminum are preferable, and in particular stainless steel is effective.

In addition, use of the storage container with the inner surface by reducing surface roughness is suitable. A method therefore includes buff finish or electrolytic polishing, and the like, in the case that material of the inner surface of the container is metal or stainless steel such as SUS304, SUS316, and the like. A similar method is naturally applied to other material whose inner surface is coated or applied by lining with the above material.

The N-alkenyl carboxylic acid tertiary amide used in the present invention is preferably stored as it is or in the added state with the stabilizer only, or it may be stored bymixing with water or other solvent . In addition, additives such as a pH adjuster, a buffer agent, a color protection agent, a deodorant and a colorant other than the above stabilizer may be added.. As for the contents other than the above, the first embodiment can be applied. Wetting of the inner surface contacting with the vapor phase of the storage container may be carried out or may not be carried out.

Examples

Examples relevant to the present invention are explained below, however, the present invention should not be limited by the Examples. (Production Example 1 of NVP)

N- (2-hydroxyethyl) -2-pyrrolidone derived from maleic anhydride as raw material was dehydrated in vapor phase to yield crude NVP.

This crude NVP was purified by distillation so that removal ratio of the initial distillates to be 20% by weight based on substance before distillation, and yield to be 60% by weight based on a stock solution before distillation to yield NVP (named as "NVP-Al") . On the resultant NVP, pH, polymer concentration and color valency were measured. Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 1. (Production Example 2 of NVP)

After the same operation as in Production Example 1, the resultant NVP was put in a 500 mL standard bottle, and then cooled in an incubator at 4°C for 24 hours. A part of the resultant solidified NVP was used as seed crystal and charged into 300 g of NVP obtained in Production Example 1, which had been maintained at 13°C in a 500 mL beaker, then subjected to stirring to yield a mixture solution with fine crystal of NVP. This solution was filtered using a suction filtering apparatus (Filter paper: No.2, produced from ADVANTEC Co., Ltd.) maintained at 13°C, then crystal on the filter paper was melted to yield NVP (named as "NVP-A2") .

On the resultant NVP, pH, polymer concentration and color valency were measured. Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 1.

(Production Example of NVP polymer)

Into a 500 mL flask equipped with a stirrer, a monomer feeding tank, a thermometer, a condenser and a nitrogen introducing tube, 320 g of water was charged, nitrogen gas was introduced and heated under stirring so that inner temperature became 70°C. Into this flask were added 80 g of NVP obtained in Production Example of NVP or an Example described later, and 0.08 g of 2, 2' -azobis (2-methylbutylonitrile) , and heated up to 95°C over 90 minutes. Polymerization was completed by heating at this temperature for two hours to yield an aqueous solution of an NVP polymer. K value of the resultant NVP polymer was measured. Analysis of NVP and the resultant polymer of NVP obtained using them was carried out by the following method. (Polymerization reactivity of NVP)

It was compared using K value of the resultant polymer from NVP. This K value was calculated by measurement of viscosity at 25°C, using a capillary viscometer, of a 1% by weight aqueous solution of the resultant NVP polymer from NVP using a method shown in Production Example, and using this measurement value and the following Fikentscher equation. Higher K value means high molecular weight.

(log ηrel)/C=[(75 K₀ ²) /(1+1.5 K₀C)] + K₀ K=IOOO K₀

wherein C represents weight (g) of apolymer in a 100 mL solution, and ηrel represents viscosity of a solution relative to a solvent.

(pH of NVP)

NVP concentration was adjusted to 10% by weight using deionized water having a pH of 7.0 , and pH thereof was measured using a pH meter (F-12 model; electrode type #636β-10D, produced from Horiba, Ltd. )

(Polymer concentration of NVP)

NVP was analyzed using liquid chromatography (column: Shodex Asahipak GF-310 HG produced from Showa Denko K. K.) (solvent: water, temperature: 40⁰C, flow rate: 1.5 mL / min) , and concentration of NVP polymer was obtained by preparation of a calibration curve using commercial polyvinyl pyrrolidone (K-30: produced from Nippon Shokubai Co., Ltd.). (Color valency of NVP)

Color valency of NVP was measured by an APHA method using NVP as it is without dilution.

Example 1-1

Into a sealable container (an inner diameter of 3 cm, and a height of 20 cm) made of SUS304, were charged 100 g of NVP obtained in Production Example 2, and 0.001 g of N, N' -di-sec-butyl-p-phenylenediamine, and the inside of the container was purged with nitrogen, and sealed after oxygen concentration in the vapor phase part was adjusted to not higher than 1% by volume. Then, as is shown in Fig. 1, the container was attached on a rotation apparatus which rotates in height direction by a Three One Motor, and maintained in a thermostatic chamber at 40°C and 60°C for 45 days and 90 days under rotating the rotating apparatus in 1 rpm. The vapor phase part (B2) was present in the container, and by rotation of the container, an NVP solution (Bl) was moved, which could always maintain the inner wall surface of the vapor phase part (B2) of the container in wetted state with NVP solution (Bl) . Further, in Fig. 1, "A" is motor, "B" is Container, "C" is axis, and "D" is bearing.

The container was taken out after 45 days and 90 days, to measure pH, polymer concentration and color valency of the resultant NVP (NVP-Bl) . Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 1 below.

Example 1-2

By carrying out the same operation as in Example 1, except that NVP obtained in Production Example 1-1 was used, pH, polymer concentration and color valency of the resultant NVP (NVP-B2) were measured. Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 1 below.

Comparative Example 1-1

Into a sealable container (an inner diameter of 3 cm, and a height of 20 cm) made of SUS304, were charged 100 g of NVP obtained in Production Example 2, and 0.001 g of N, N' -di-sec-butyl-p-phenylenediamine, and the inside of the container was purged with nitrogen, and sealed after oxygen concentration in the vapor phase part was adjusted to not higher than 1% by volume.. Then the container was stood still in a thermostatic chamber at 40°C and 60°C for 45 days and 90 days.

The container was taken out after 45 days and 90 days, to measure pH, polymer concentration and color valency of the resultant NVP (NVP-Cl) . Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 1 below.

Comparative Example 1-2

By carrying out the same operation as in Comparative Example 1, except that NVP obtained in Production Example 1-1 was used, pH, polymer concentration and color valency of the resultant NVP (NVP-C2) were measured. Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 1 below.

Example 1-3 The same operation as in Example 1-2 was carried out, except that "0.001 g of

N, N' -di-sec-butyl-p-phenylenediamine" was not used.

The container was taken out after 45 days and 90 days, to measure pH, polymer concentration and color valency of the resultant NVP (NVP-B3) . Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 1 below.

Comparative Example 1-3

The same operation as in Example 1-3 was carried out, except that "The container was attached on a rotation apparatus which rotates in height direction by a Three One Motor, as shown in Fig.1. The container was maintained in a thermostatic chamber at 40⁰C and 60°C for 45 days and 90 days under rotating the rotating apparatus in 1 rpm. " was changed to "The container was maintained for 45 days and 90 days while standing still in a thermostatic chamber at 40°C and 60°C."

The container was taken out after 45 days and 90 days, to measure pH, polymer concentration and color valency of the resultant NVP (NVP-C3) . Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 1 below.

Example 1-4 The same operation as in Example 1-1 was carried out, except that "A sealable container made of PFA (a copolymer resin of tetrafluoroethylene-perfluoroalkyl vinyl ether) " was used instead of "A sealable container made of SUS304".

The container was taken out after 45 days and 90 days, to measure pH, polymer concentration and color valency of the resultant NVP (NVP-B4) . Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 1 below.

Comparative Example 1-4

The same operation as in Example 1-4 was carried out, except that "The container was attached on a rotation apparatus which rotates in height direction by a Three One Motor, as shown in Fig.1. The container was maintained in a thermostatic chamber at 40⁰C and 60⁰C for 45 days and 90 days under rotating the rotation apparatus in Lrpm. " was changed to "The container was maintained for 45 days and 90 days while standing still in a thermostatic chamber at 40°C and 60°C."

The container was taken out after 45 days and 90 days, to measure pH, polymer concentration and color valency of the resultant NVP (NVP-C4) . Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 1 below.

Example 1-5

The same operation as in Example 1-1 was carried out, except that "0.01 g of sodium hydroxide" was used instead of "0.001 g of N, N' -di-sec-butyl-p-phenylenediamine".

The container was taken out after 45 days and 90 days, to measure pH, polymer concentration and color valency of the resultant NVP (NVP-B5) . Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 1 below.

Comparative Example 1-5

The same operation as in Example 1-5 was carried out, except that "The container was attached on a rotation apparatus which rotates in height direction by a Three One Motor, as showninFig.1. The container was maintained in a thermostatic chamber at 40°C and 60⁰C for 45 days and 90 days under rotating the rotation apparatus in 1 rpm. " was changed to "The container was maintained for 45 days and 90 days while standing still in a thermostatic chamber at 40°C and 60⁰C." The container was taken out after 45 days and 90 days, to measure pH, polymer concentration and color valency of the resultant NVP (NVP-C5) .. Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 1 below.

TABLE 1

TABLE 1-continued

In Table 1: CM. : Container material

S. T.: Storage temperature

S. P.: Storage period

P. C: Polymer concentration CV. : Color valency.

Use of a storage method according to the present invention can provide an N-alkenyl carboxylic acid tertiary amide having small change in quality such as polymerization reactivity, pH, containing polymer concentration, and color valency, irrespective of the addition of a stabilizer or not, , even in long-term storage.

Example II-1

Into a container (an inner diameter of 6 cm, and a height of 20 cm) made of SUS304, were charged 283 mL of NVP obtained in Production Example 2, and 0.003 g of N, N' -di-sec-butyl-p-phenylenediamine, and the inside of the container was purged with nitrogen and oxygen concentration in the vapor phase part was adjusted to not higher than 1% by volume.

Then, solution temperatures was adjusted at 35⁰C, and wall temperature of the vapor phase part at 40 °C, by means of a first band heater at the bottom surface and lower side surface covering 10 cm area of the container, and by means of a second band heater at the top board and the upper side surface covering 10 cm area of the container, and then maintained for 45 days and 90 days. The container was taken out after 45 days and 90 days, to measure pH, polymer concentration and color valency of the resultant NVP (NVP-Dl) . Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 2 below.

Example II-2 The same operation was carried out as in Example II-l, except that solution temperature was set at 34 °C and wall temperature of the vapor phase part was set at 35⁰C.

Value of pH, polymer concentration and color valency of the resultant NVP (NVP-D2) were measured. Furthermore,

K value of a polymer polymerized according to (Production

Example of an NVP polymer) was measured. These results are shown in Table 2 below.

Example II-3

The same operation was carried out as in Example II-l, except that wall temperature of the vapor phase part was set at 30°C.

Value of pH, polymer concentration and color valency of the resultant NVP (NVP-D3) were measured. Furthermore,

K value of a polymer polymerized according to (Production

Comparative Example II-l

The same operation was carried out as in Example II-l, except that wall temperature of the vapor phase part was set at 20°C.

Value of pH, polymer concentration and color valency of the resultant NVP (NVP-El) were measured. Furthermore,

K value of a polymer polymerized according to (Production

Example II-4

The same operation was carried out as in Example II-l, except that a container made of PFA was used. Value of pH, polymer concentration and color valency of the resultant NVP (NVP-D4) were measured. Furthermore,

K value of a polymer polymerized according to (Production

Comparative Example II-2

The same operation was carried out as in Example II-4, except that wall temperature of the vapor phase part was set at 20°C.

Value of pH, polymer concentration and color valency of the resultant NVP (NVP-E2) were measured. Furthermore,

K value of a polymer polymerized according to (Production

Example II-5

The same operation as in Example II-l was carried out, except that "0.03 g of sodium hydroxide" was used instead of "0.003 g of N, N' -di-sec-butyl-p-phenylenediamine" .

The container was taken out after 45 days and 90 days, to measure pH, polymer concentration and color valency of the resultant NVP (NVP-D5) . Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 2 below.

Comparative Example II-3

The same operation was carried out as in Example II-5, except that wall temperature of the vapor phase part was set at 20°C.

Value of pH, polymer concentration and color valency of the resultant NVP (NVP-E3) were measured. Furthermore, K value of a polymer polymerized according to (Production Example of an NVP polymer) was measured. These results are shown in Table 2 below.

In Table 2:

Production Exp.1 (NVP-Al), Production Exp.2 (NVP-A2) , Exp. II-l (NVP-Dl), Exp. II-2 (NVP-D2), Exp. II-3 (NVP-D3) , Comp. Exp . II-l (NVP-El ) , Exp . II-4 (NVP-D4 ) , Comp . Exp . II-2 (NVP-E2 ) , Exp . II-5 (NVP-D5 ) , Comp . Exp . II-3 (NVP-E3 )

CM. : Containermaterial, Sta. : Stabilizer, W. T. : Wall temp.

(Tl: ⁰C) at vapor phase part, S. T.: Solution Temp. (T2: ⁰C), Dif.: (Tl) -(T2) (⁰C), S. P.: Storage period (Day), P. C:

Polymer concentration (ppm) , CV. : Color valency, and K: K value.

NN : N, N' -di-sec-butyl-p-phenylenediamine .

According to a storing method of the present invention, can be provided an N-alkenyl carboxylic acid tertiary amide having significantly excellent storage stability irrespective of the addition of a stabilizer or not, namely small change in quality such as polymerization reactivity, pH, containing polymer concentration, and color valency, even in long-term storage.

Claims

Claims :

1. Amethodfor storing anN-alkenyl carboxylic acid tertiary amide, comprising: wetting an inner wall surface contacting with a vapor phase part of a storage container of the N-alkenyl carboxylic acid tertiary amide, with the N-alkenyl carboxylic acid tertiary amide.

2. A method for storing of claim 1, wherein the N-alkenyl carboxylic acid tertiary amide is N-vinyl-2-pyrrolidone.

3. A method for storing of claim 1, wherein the N-alkenyl carboxylic acid tertiary amide contains a stabilizer in an amount of 1 ppm to 5% by weight, based on the weight of the N-alkenyl carboxylic acid tertiary amide.

4. A method for storing of claim 1, wherein material of the storage container is stainless steel, a polyolefin or a fluorocarbon resin.

5. A method for storing of claim 4, wherein material of the storage container is metal having reduced surface roughness by buff finish or electrolytic polishing.

6. A method for storing of claim 1, wherein a method for wetting at least a part of the inner wall with the N-alkenyl carboxylic acid tertiary amide is to carry out by showering.

7. A method for storing of claim 6, wherein the showering is carried out by laving the N-alkenyl carboxylic acid tertiary amide present at the bottom of the container, so that the N-alkenyl carboxylic acid tertiary amide in the container is counterchanged.

8. Amethod for storing anN-alkenyl carboxylic acidtertiary amide, comprising: controlling relation between temperature (Tl) at an inner wall surface contacting with a vapor phase part of a container for storing the N-alkenyl carboxylic acid tertiary amide, and liquid temperature (T2) of the N-alkenyl carboxylic acid tertiary amide, so that (Tl) - (T2) is not lower than -10 (⁰C).

9. Amethod for storing of claim 8, wherein the control of temperature (Tl) is carried out by warming or cooling the inner wall surface from the corresponding outer wall.

10. Amethod for storing of claim 8, wherein the N-alkenyl carboxylic acid tertiary amide is N-vinyl-2-pyrrolidone.

11. A method for storing of claim 8, wherein the N-alkenyl carboxylic acid tertiary amide contains a stabilizer in an amount of 1 ppm to 5% by weight, based on the weight of the N-alkenyl carboxylic acid tertiary amide.

12. A method for storing of claim 8, wherein material of the storage container is stainless steel, a polyolefin or a fluorocarbon resin.

13. A method for storing of claim 12, wherein material of the storage container is material having reduced surface roughness by buff finish or electrolytic polishing.