JPH05295109A - Production of high-purity 2-pyrrolidone polymer - Google Patents

Abstract

PURPOSE:To easily obtain high-purity 2-pyrrolidone polymer having a high mol.wt. by washing 2-pyrrolidone polymer with an aqueous acid solution having a specific pH, separating the polymer from the solution, and drying it. CONSTITUTION:2-Pyrrolidone is polymerized in the presence of a basic polymerization catalyst (e.g. pottasium hydroxide) and carbon dioxide as a promotor. The obtained 2-pyrrolidone polymer is washed with an aqueous acid solution having a pH of 1-6. The polymer is then separated from the solution and dried. Thus, high-purity 2-pyrrolidone polymer can be easily obtained which has a high mol.wt. and from which the catalyst residue has been sufficiently removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-purity 2-pyrrolidone polymer, and more particularly to a method for producing a high-purity 2-pyrrolidone polymer having a low content of metal components and excellent thermal stability. ..

[0002]

2. Description of the Related Art A polymer of 2-pyrrolidone is known as nylon 4 and has attracted particular attention as a fiber material because it has properties similar to natural fibers such as cotton and silk. However, the 2-pyrrolidone polymer is extremely poor in thermal stability at high temperatures, and has a drawback that it is difficult to manufacture a fiber by a melt spinning method which is an economical manufacturing method of a fiber material. As a result of many studies aimed at improving this drawback, it was found that the higher the molecular weight of the 2-pyrrolidone polymer, the better the thermal stability, and a method relating to the production of a high-molecular weight polymer is disclosed in Japanese Examined Patent Publication No. 47-26678. Publication, US Patent 3
It is disclosed in Japanese Patent No. 174951. However, the thermal stability was not sufficient just by increasing the molecular weight.

Generally, a 2-pyrrolidone polymer is produced by polymerizing 2-pyrrolidone in the presence of a basic polymerization catalyst and carbon dioxide, which is a polymerization promoter, and the basic catalyst residue used at this time is 2- It is present as a large amount as an impurity in the pyrrolidone polymer. If this catalyst residue remains, the thermal stability of the 2-pyrrolidone polymer deteriorates, so the catalyst residue, especially the metal component that is a constituent component of the catalyst residue, must be sufficiently removed.

As a method for removing the basic catalyst residue in the 2-pyrrolidone polymer, a method of washing with a large amount of water is generally known. However, the catalyst residue is removed from the high molecular weight 2-pyrrolidone polymer. Is not easy, and the number of times of cleaning for complete removal is large, which is disadvantageous in the process. However, no proposal has been found regarding a method for efficiently removing the catalyst residue from the 2-pyrrolidone polymer.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to provide a method for producing a high-purity, high-molecular weight 2-pyrrolidone polymer which is sufficiently free from catalyst residues and has excellent thermal stability. ..

[0006]

As a result of various studies to obtain a method for producing a high-purity 2-pyrrolidone polymer which is an object of the present invention, a method for efficiently removing a catalyst residue was found. That is, the object of the present invention is to polymerize 2-pyrrolidone in the presence of a basic polymerization catalyst and carbon dioxide which is a polymerization co-catalyst, and to obtain a 2-pyrrolidone polymer having a pH of 1 to 1.
This can be achieved by washing in an aqueous solution of No. 6, separating the 2-pyrrolidone polymer from the aqueous solution, and drying.

The pH of the aqueous solution used for washing the 2-pyrrolidone polymer in the present invention is 1 to 6, preferably 3 to 5. p
When H is 1 or less, the polymer of 2-pyrrolidone may be hydrolyzed. When the pH is 6 or more, it takes a long time to remove the catalyst residue from the 2-pyrrolidone polymer,
The cleaning efficiency of the 2-pyrrolidone polymer becomes poor. The pH of the aqueous solution used for washing in the present invention is adjusted by a strong mineral acid such as hydrochloric acid, sulfuric acid, phosphoric acid, boric acid or the like or a mixture thereof, or acetic acid, trifluoroacetic acid, dichloroacetic acid,
It is carried out by adding a strong organic acid such as p-toluenesulfonic acid or the like and a mixture thereof to water.

The water used for washing in the present invention is distilled water, ion-exchanged water, etc., and the amount of water used for washing is 1 to 30 times by volume, preferably 5 to 10 times by volume that of the 2-pyrrolidone polymer. is there. If it is less than 1 volume times, the cleaning effect is poor, and if it is more than 30 volume times, there is no difference in effect, but it takes time to separate the polymer, and the amount of acid used is large, which is not economical. The temperature of the acidic aqueous solution for washing the 2-pyrrolidone polymer is 5 to 100 ° C., preferably 20 to
It is 80 ° C. If the temperature is lower than 5 ° C, the cleaning effect is poor and 1
If the temperature is higher than 00 ° C., the 2-pyrrolidone polymer is hydrolyzed to reduce the molecular weight, which is not preferable.

As the basic polymerization catalyst used in the present invention, compounds generally used in the anionic polymerization method of lactams can be used. Alkali metals such as sodium, potassium and lithium; alkali metal hydroxides, hydrides and alcoholates. Oxides and salts such as potassium hydroxide,
Sodium hydroxide, potassium methylate, sodium methylate, sodium pyrrolidone, potassium pyrrolidone; basic organometallic compounds such as lithium alkyl, potassium alkyl, sodium alkyl, aluminum alkyl aryls of alkali metal such as sodium phenyl, sodium naphthalene; Grignia Reagents such as butylmagnesium bromide and chemical formula (1)
And quaternary bases and the like.

[0010]

[Chemical 1] (Where R1, R2 and R3 are lower alkyl, R
4 is an alkyl group, an aryl group or an aralkyl group. )

Of these, potassium hydroxide, potassium methylate, sodium methylate, sodium pyrrolidone and potassium pyrrolidone are particularly preferable. When using potassium hydroxide, potassium methylate, sodium methylate, etc., mix excess 2-pyrrolidone with these compounds prior to polymerization, and remove water and alcohols by-produced by the reaction before use. Is preferred. The amount of the basic polymerization catalyst used in the present invention is 2-pyrrolidone 1 mol.
To 0.003 to 0.3 mol, preferably 0.0
It is 05 to 0.2 mol. If the amount used is less than the above lower limit or more than the above upper limit, the molecular weight of the polymer becomes low (relative viscosity is 5 or less), which is not preferable.

The carbon dioxide gas of the polymerization co-catalyst used in the present invention is preferably highly pure, but industrially available ones can be used as long as they do not particularly inhibit the polymerization. The amount of carbon dioxide used is 0.1 to 0.9 per 1 mol of the basic polymerization catalyst.
mol, preferably 0.2 to 0.6 mol. If the amount used is outside the above range, the molecular weight of the polymer becomes low, which is not preferable.

In the present invention, other known polymerization initiators can be used together with carbon dioxide gas. Other polymerization initiators that can be used together with carbon dioxide include acyl compounds of lactams such as acetylpyrrolidone and acetylcaprolactam, acyl compounds such as adipoylbiscaprolactam, acid anhydrides such as acetic anhydride and benzene anhydride, and toluene diisocyanate. Organic isocyanates, carbamide compounds such as 1,6-hexamethylenebiscarbamidocaprolactam, 1- (1-pyrrolin-2-yl) -2-pyrrolidone, 1- (1-azacyclohepter-1-en-2-yl) 2-pyrrolidone, 6-caprolactam-1- (1
-Azacyclopenter 1-en-2-yl) -1-aza-2-oxocyclopentane and quaternary ammonium salts such as tetramethylammonium chloride. These polymerization initiators are used in an amount smaller than the amount of carbon dioxide gas used.

The high molecular weight 2-pyrrolidone of the present invention is prepared by adding carbon dioxide gas to 2-pyrrolidone containing a predetermined amount of a basic polymerization catalyst to open the 2-pyrrolidone at a temperature of 100 ° C. or lower, preferably 15 to 70 ° C. It can be obtained by ring polymerization. A temperature of 100 ° C. or higher is not preferable because the polymerization rate becomes extremely slow. The carbon dioxide gas can be added by blowing carbon dioxide gas into 2-pyrrolidone containing a basic polymerization catalyst at a temperature of 150 ° C or lower, preferably 15 to 100 ° C.

Further, it may be copolymerized with γ-butyrolactone, α-piperidone, ε-caprolactam, laurolactam and the like within 20% by weight of the above-mentioned polymerization composition. As the polymerization operation, a batch method, a continuous method, an intermediate method thereof or the like can be applied, and as a polymerization reaction method, a bulk polymerization method or a solvent such as tetrahydrofuran, dioxane, hexane, toluene, xylene, dimethylformamide, N-methylpyrrolidone or the like is used. A suspension polymerization method, a solution polymerization method, an emulsion polymerization method, etc., using the above can also be used. The present invention will be specifically described below with reference to examples.

[0016]

【Example】

-Specific method for polymerizing 2-pyrrolidone-Purified substantially anhydrous 2 in a flask equipped with a vacuum device
-Put 220 g (2.58 mol) of pyrrolidone,
After heating to ℃, 85% pure potassium hydroxide 15.5
2 g (0.235 mol in terms of potassium hydroxide) was added and the temperature was raised to 115 ° C. Then depressurize the inside of the flask (1
15 ° C., 5 mmHg or less), and 24 g of a mixture of water and 2-pyrrolidone produced as a by-product is distilled off to give 1 mol of 2-pyrrolidone
2 containing 0.1 mol of potassium pyrrolidone
Made a pyrrolidone solution. Dry nitrogen was introduced into this system to bring it to normal pressure, and after lowering the temperature of the liquid to 25 ° C., 3.3 g of carbon dioxide gas (0.075 mol, 0.32 mol per 1 mol of the basic polymerization catalyst potassium pyrrolidone) was added. After the introduction, polymerization was continued at 40 ° C. for 24 hours in a nitrogen gas atmosphere. The relative viscosity (ηγ), which is a measure of the molecular weight of the obtained 2-pyrrolidone polymer, the measurement of the amount of metal components contained in the 2-pyrrolidone polymer, and the heat reduction rate measurement of the 2-pyrrolidone polymer were measured. The procedure was as follows.

1. Measurement of ηγ (relative viscosity) 0.5 g of dried 2-pyrrolidone polymer was completely dissolved in 100 cc of m-cresol at room temperature, and then the flow-down time (unit: second) was measured at a temperature of 30 ° C. using an Ostwald viscometer. Then, the value calculated by the following formula.

2. Measurement of amount of contained metal component The amount of contained metal component in the 2-pyrrolidone polymer was obtained by decomposing the 2-pyrrolidone polymer with sulfuric acid and nitric acid and incinerated with ICP (manufactured by Nippon Jarrell Ash Co., Ltd., type ICAP-
575) It was determined by the quantitative method of measurement.

3. Heat reduction rate measurement The heat reduction rate of the 2-pyrrolidone polymer was measured by using TGA (Seiko Denshi Kogyo KK, SSC-560G) when heating the 2-pyrrolidone polymer at 10 ° C./min in a nitrogen atmosphere.
A value obtained by dividing the weight loss (g) of the 2-pyrrolidone polymer at the time of reaching each temperature by the weight (g) before weight loss is 100.
Multiplied by.

Examples 1 to 3 The polymer obtained by the 2-pyrrolidone polymerization method was pulverized, and 100 g of the pulverized product and 700 ml of water were 1500 m.
The polymer was washed with the acid, the washing water pH, the number of washings, and the washing time shown in Table 1 in a 1-liter stirring tank. Then, the 2-pyrrolidone polymer obtained by filtering and separating this mixed solution was further washed with 700 ml of water, and then dried under reduced pressure at 70 ° C. for 24 hours. The content of the metal component in the 2-pyrrolidone polymer is shown in Table-1, and the result of the heating reduction rate is shown in Table-2.

Examples 4 to 6 2 obtained by using sodium hydroxide in place of potassium hydroxide in obtaining a polymer by the 2-pyrrolidone polymerization method
The same procedure as in Example 1 was carried out except that the pyrrolidone polymer was used and washed under the conditions shown in Table 1. The results are shown in Table 1 and Table 2
It was shown to.

Comparative Examples 1 to 3 Example 1 under the conditions shown in Table 1 except that no acid was used.
I went the same way. The results are shown in Tables 1 and 2.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

The 2-pyrrolidone polymer obtained by polymerizing 2-pyrrolidone by the action of the basic polymerization catalyst and the polymerization promoter, carbon dioxide, is easily heat-stable by washing it with an aqueous solution of pH 1-6. High purity and high molecular weight 2
-Pyrrolidone polymers can be produced.

Claims (1)

[Claims] 1. 2-pyrrolidone is polymerized in the presence of a basic polymerization catalyst and carbon dioxide which is a polymerization cocatalyst, and the obtained 2-pyrrolidone polymer is washed with an aqueous solution having a pH of 1 to 6 from the aqueous solution. A method for producing a high-purity 2-pyrrolidone polymer, which comprises separating and drying a 2-pyrrolidone polymer.