JPH07316130A - Stabilization of n-vinylpyrrolidone - Google Patents

Abstract

PURPOSE:To provide a method for stabilizing N-vinylpyrrolidone, highly effective in preventing its polymerization, having adequate effect against its polymerization and side reactions even at an elevated temperatures under a reduced pressures. CONSTITUTION:Stabilization of N-vinylpyrrolidone can be accomplished by adding at least one kind of compound selected from alkali and alkaline earth metal nitrites (pref. Na salts, K salts and Ca salts) and manganese-contg. salts (pref. manganese acetylacetonate) to N-vinylpyrrolidone. The amount of the stabilizer(s) to be used is pref. 80-1000ppm when used singly, or each 80-500ppm for combined use. These stabilizers can be applied for stabilizing N- vinylpyrrolidone not only during its storage or transport but also in distillating and purifying it (at 70-180 deg.C under a pressure of 10-200Torr).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for stabilizing N-vinylpyrrolidone, which is a raw material for polyvinylpyrrolidone used in petroleum recovery agents, cosmetics and the like.

[0002]

BACKGROUND OF THE INVENTION N-Vinylpyrrolidone (hereinafter abbreviated as NVP) is a raw material for polyvinylpyrrolidone useful as an industrial raw material. Easy to cause a reaction. Therefore, a stabilizing method in the NVP synthesis process as well as storage and transportation is necessary. In particular, in the distillation and purification steps after NVP synthesis, NVP is at a high temperature (70 ° C to 180 ° C).
C.) and reduced pressure (10 to 200 torr) conditions, side reactions such as polymerization are likely to occur and the yield of NVP is reduced.

Conventionally, amine compounds are said to be preferable as stabilizers for NVP (Chemical Industry, March issue, 52).
-56 (1974)). Aromatic amine compounds, phenolic compounds, phenothiazine, cuperone, etc. are generally known as stabilizers for basic vinyl monomers such as NVP. Group nitro compounds (JP-A-60-8120)
No. 1), sodium phosphates (JP-A-60-81202).
), An oxyquinoline compound (JP-A-60-812).
No. 03), quinone and quinone dioxime compounds (JP-A-60-81204).

However, according to the research conducted by the present inventor,
Under the high temperature and reduced pressure conditions such as those used for distillation and purification of NVP, conventional stabilizers did not provide a satisfactory effect for stabilizing NVP. That is, when an aromatic amine compound, a phenolic compound, a phenothiazine, a cuperone, an aromatic nitro compound, an oxyquinoline compound, a quinone or a quinone dioxime compound is used as a stabilizer, especially a mixed system of NVP and pyrrolidone after the synthesis. When trying to refine NVP by distillation,
In addition to the above polymerization, bis (2-pyrrolidone-1-yl) ethane was produced due to a side reaction of addition of pyrrolidone to NVP, and there was a problem that the yield of NVP was lowered.

[0005]

As described above, regarding the stabilization method of NVP, establishment of a stabilization technique in the NVP synthesis process as well as storage and transportation is an important issue. The present invention has been made in order to meet such a demand in the technical field of the related art, and its purpose is to have a large effect of preventing the polymerization of NVP, and to provide high temperature such as during distillation and purification of NVP,
It is an object of the present invention to provide a method capable of preventing NVP polymerization and side reactions between NVP and pyrrolidone even under reduced pressure and keeping NVP stable.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies to achieve the above object, and found that a nitrite of an alkali metal or an alkaline earth metal or a salt containing manganese is a stabilizer for NVP. It has been found that a remarkable effect is exhibited. The present invention has been achieved based on such knowledge.

That is, the present invention is characterized in that N-vinylpyrrolidone is allowed to contain at least one selected from (1) an alkali metal or alkaline earth metal nitrite and (2) a salt containing manganese. To a method for stabilizing N-vinylpyrrolidone.

The method of the present invention will be described in detail below. The substance used as a stabilizer in the present invention is a nitrite salt of an alkali metal or an alkaline earth metal, or a salt containing manganese, specifically, as a nitrite salt of an alkali metal or an alkaline earth metal, Examples thereof include sodium nitrite, potassium nitrite, calcium nitrite, barium nitrite, and the like, and manganese-containing salts include manganese acetylacetonate, manganese oxalate, manganese phosphate, manganese nitrate, and the like. Preferably, sodium nitrite, potassium nitrite,
Preference is given to using calcium nitrite or manganese acetylacetonate. These stabilizers may be used alone or in combination of two or more.

In the practice of the present invention, the amount of the above stabilizer used is, when used alone, 10 to 3000 ppm, preferably 80 to 1000 p, based on the mixed solution containing NVP.
It can be appropriately selected within the range of pm.

When an alkali metal or alkaline earth metal nitrite and a manganese-containing salt are used in combination, the nitrite content is 10 to 10 relative to the mixed solution containing NVP.
The salt containing 00 ppm and manganese is 10 to 1000 p
Each can be used within the range of pm. Preferably, the nitrite is appropriately selected within the range of 80 to 500 ppm and the manganese-containing salt within the range of 80 to 500 ppm.

The stabilizer used in the present invention can be used in combination with other known stabilizers. For example, N, N'-d
i-sec-butyl-p-phenylenediamine, N,
It can be used with phenylenediamines such as N'-di-phenyl-p-phenylenediamine.

The stabilizer used in the present invention has an NVP polymerization inhibitory effect at room temperature and at high temperature.
It can also be used at a temperature of 70 to 180 ° C. during distillation and purification after VP synthesis. Further, it can be used not only under normal pressure but also under reduced pressure conditions, and can also be used under conditions such as 10 to 200 torr used during NVP distillation.

Therefore, the stabilizer in the present invention is N
It can be applied not only to the stabilization when storing and transporting VP itself, but also to the stabilization when synthesizing NVP or during distillation and purification.

These stabilizers can be dissolved in NVP or partially suspended before use. In the case of synthesizing NVP, by charging a stabilizer together with a reaction raw material into a reaction tank, polymerization in the synthesis process can be prevented and it is inactive to the reaction itself.

When used for distillation after NVP synthesis, the object can be achieved by adding a dissolved or suspended stabilizer to the distillation pot or the column portion of the distillation column. At this time, nitrites of alkali metals or alkaline earth metals, salts containing manganese have a low vapor pressure and are not likely to be mixed in the product, and the thermal decomposition products thereof may also be mixed in the product. Absent.

When NVP is distilled and purified from a mixed solution of NVP and pyrrolidone produced by NVP synthesis, NVP is used.
In addition to the polymerization of (2), pyrrolidone is added to NVP to produce bis (2-pyrrolidone-1-yl) ethane,
By-production of pyrrolidone-1-yl) ethane can be prevented.

As described above, the NVP stabilization method according to the present invention is not only applied to the NVP itself, but also at a temperature of 70 ° C. or more and a reduced pressure of 200 torr or less, N
It exerts an effect sufficient to prevent polymerization and side reactions of VP. In particular, it has great significance as a method for stabilizing NVP under high temperature and reduced pressure.

[0018]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 A stirrer was placed in a 100 ml flask, and a thermometer and a reflux condenser were connected. 20g NVP in this flask
And pyrrolidone (hereinafter referred to as PyD) 20 g were added, and sodium nitrite was added as a stabilizer. Next, the inside of the flask was depressurized to 80 torr and heated in an oil bath so that the temperature of the mixed solution was set to 150 ° C. Then, after heating and stirring for 3 hours, N in the mixed solution
The weight of VP and PyD was analyzed. Also, this mixture is used as an acetone solution to measure turbidity (Fuji Digital Turbidimeter).
Was measured using. The results are shown in Table 1. In the table, BPE is bis (2-pyrrolidone-1-yl)
Abbreviation for ethane.

Table 1 Addition amount Heating time Liquid composition after heating (wt%) Turbidimeter (ppm) (h) NVP PyD BPE reading ─────────────────── ───────────── 500 0 50 50 50 2 500 500 3 50 50 0 4 300 3 3 50 50 0 4

Example 2 The procedure of Example 1 was repeated, except that 300 ppm of potassium nitrite or calcium nitrite was added as a stabilizer. The results are shown in Table 2. Table 2 Stabilizer Heating time Liquid composition after heating (wt%) Turbidimeter (No) Type (h) NVP PyD BPE reading ────────────────────── ─────────────── (1) Potassium nitrite 0 50 50 50 1 〃 3 3 50 50 0 4 (2) Calcium nitrite 0 0 50 50 0 3 3 〃 3 50 50 0 1

Example 3 The procedure of Example 1 was repeated except that manganese acetylacetonate was added as a stabilizer. The results are shown in Table 3. Table 3 Addition amount Heating time Liquid composition after heating (wt%) Turbidimeter (ppm) (h) NVP PyD BPE reading ─────────────────────── ───────── 100 0 50 50 0 1 100 3 50 50 50 0 4 300 3 50 50 50 3 3 500 3 50 50 0 1

Example 4 The same procedure as in Example 1 was carried out except that sodium nitrite and manganese acetylacetonate [abbreviated as Mn (acac) ₂ ] were added as stabilizers. The results are shown in Table 4. Table 4 Addition amount (ppm) Heating time Liquid composition after heating (wt%) Turbidimeter NaNO ₂ Mn (acac) ₂ (h) NVP PyD BPE reading ─────────────── ───────────────────── 100 100 0 0 50 50 0 3 3 100 100 3 50 50 50 0 6 6 150 150 3 3 50 50 0 0 6 300 300 3 3 50 50 50 5

Comparative Example 1 The procedure of Example 1 was repeated except that no stabilizer was added or a conventional stabilizer was used. The results are shown in Table 5. Table 5 Stabilizer addition amount Liquid composition after heating (wt%) Turbidimeter (No) Type (ppm) NVP PyD BPE reading ───────────────────── ──────────────── (1) No additive 0 16 48 14 546 (2) Triethanolamine 1000 35 35 50 0 300 〃 500 32 32 50 0 365 〃 300 29 29 490 380 ( 3) Hexadecylamine 1000 33 33 50 0 350 〃 500 29 29 49 0 373 〃 300 26 26 48 0 385 (4) Cuperon 500 43 48 8 8 26 (5) p-nitrosodiphene 500 45 47 8 25 25 Luamine 300 41 41 45 10 (6) p-quinone dioxime 500 45 48 7 24 〃 300 44 46 9 38

Example 5 A 100 ml flask was equipped with a stir bar and a thermometer and a reflux condenser were connected. NVP100 in this flask
g, and then the stabilizer of the present invention was added. Then
The inside of the flask was depressurized to 80 torr and heated in an oil bath to set the temperature of the mixed solution to 150 ° C.
Then, after heating and stirring for 3 hours, the weight of NVP in the mixed solution was analyzed. Further, the turbidity of this mixed solution as an acetone solution was measured using a turbidimeter (Fuji Digital Turbidimeter).

Comparative Example 2 The procedure of Example 5 was repeated except that no stabilizer was added. The results of Example 5 and Comparative Example 2 described above are summarized in Table 6. In the table, PVP is an abbreviation for vinylpyrrolidone polymer.

Table 6 Stabilizer addition amount Liquid composition after heating (wt%) Turbidimeter (No) Type (ppm) NVP PVP reading ─────────────────── ───────────────── (1) Sodium nitrite 300 100 100 4 〃 100 100 0 4 (2) Potassium nitrite 300 300 100 0 4 〃 100 100 0 4 (3) Sub Calcium nitrate 300 100 0 4 〃 100 100 0 0 4 (4) Manganese acetyl 300 100 0 0 4 acetonate 100 100 0 5 (5) No additive (Comparative example 2) 0 27 73 635

[0028]

[Discussion] Examples 1 to 5 show a method for stabilizing N-vinylpyrrolidone according to the present invention. For example, Example 1 shows a case where sodium nitrite is added as a stabilizer to a mixed system of NVP and PyD. No change in NVP weight was observed between before heating (heating time 0) and after heating, and the numerical value of the turbidimeter was almost the same. That is, it can be seen that NVP is kept stable without polymerization of NVP or side reaction between NVP and PyD. It is also found that the NVP is kept stable even when the stabilizer is added to the NVP alone (Example 6). Further, the NVP was kept stable even when the heating temperature was 100 ° C. or 180 ° C. On the other hand, as shown in Comparative Example 1, when the conventional stabilizer was used, a decrease in the weight of NVP and the formation of BPE in which PyD was added to NVP were observed, and the turbidimeter showed a large value. It can be seen that polymerization of NVP and side reaction between NVP and PyD occur. As described above, the present invention can keep NVP stable even under high temperature and reduced pressure.

[0029]

According to the present invention, a temperature of 70 ° C. or higher, 20
Even under a reduced pressure of 0 torr or less, it was possible to provide a method capable of preventing the polymerization and side reactions of NVP and keeping NVP stable.

Claims (1)

[Claims] 1. N-vinylpyrrolidone with (1) an alkali metal or alkaline earth metal nitrite and (2)
A method for stabilizing N-vinylpyrrolidone, characterized in that at least one selected from manganese-containing salts is present.