JPH05295108A - Production of high-purity 2-pyrrolidone polymer - Google Patents

Abstract

PURPOSE:To easily obtain high-molecular 2-pyrrolidone polymer having excellent thermal stability and high purity by washing 2-pyrrolidone polymer obtained by suspension polymerization with an aqueous acid solution having a specific pH and then with an organic solvent. CONSTITUTION:2-pyrrolidone is suspension-polymerized in an aprotic solvent (e.g. tetrahydrofuran) in the presence of a basic polymerization catalyst (e.g. potassium hydroxide) and a promoter comprising a combination of carbon dioxide and a metal salt of a higher fatty acid (e.g. sodium laurate). The obtained 2-pyrrolidone polymer is washed with an aqueous acid solution having a pH of 1-6 and then with an organic solvent (e.g. ethanol). Thus, high-purity 2-pyrrolidone polymer can be easily obtained which has excellent thermal stability and a high mol.wt.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a high-purity 2-pyrrolidone polymer, more specifically, a catalyst residue and a higher fatty acid metal salt are efficiently removed from a 2-pyrrolidone polymer obtained by a suspension polymerization method. And a high-purity 2-pyrrolidone polymer excellent in 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. But 2-
The thermal stability of the pyrrolidone polymer was still insufficient only by increasing the molecular weight.

Further, a method of obtaining a 2-pyrrolidone polymer by a suspension polymerization method is known. For example, Japanese Patent Publication No. 37-6746
The publication discloses a method for obtaining a powdery 2-pyrrolidone polymer by using an alkali metal salt of a fatty acid such as sodium stearate as a dispersant in a saturated hydrocarbon that does not dissolve 2-pyrrolidone. Compared with the bulk polymerization method,
According to this method, impurities such as a basic catalyst residue and an alkali metal salt of a fatty acid remain in the produced 2-pyrrolidone polymer, and the heat resistance is insufficient and it has not been put to practical use.

In Japanese Patent Publication No. 48-42719, 2-
A method for obtaining a powdery 2-pyrrolidone polymer by using a nonionic surfactant such as a block polyether of ethylene oxide and propylene oxide as a dispersant in a saturated hydrocarbon that does not dissolve pyrrolidone is disclosed. Even with this method, the basic catalyst residue and the surfactant are not sufficiently removed, and the heat resistance is insufficient, which is not practical.

In Japanese Patent Publication No. 62-61054, the first stage of polymerization is bulk polymerization, in which the polymerization rate of 2-pyrrolidone is 10%.
In the second step, the resulting polymer and the insoluble hexane are mixed and then suspension polymerization is carried out to obtain a powdery 2-pyrrolidone polymer. This method has 2 polymerization reactions.
It becomes a step and is disadvantageous in the process, and the basic catalyst residue remains and the heat resistance is insufficient, and it has not been put to practical use.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to provide a high-purity, high-molecular weight 2-pyrrolidone polymer having a basic polymerization catalyst and a residue of a higher fatty acid metal salt sufficiently removed, and having excellent thermal stability. To provide a manufacturing method.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high purity, high molecular weight 2-pyrrolidone polymer preparation. Generally, when a 2-pyrrolidone polymer is obtained by a suspension polymerization method, a dispersant such as a basic polymerization catalyst or a higher fatty acid metal salt is used, but a metal component or a higher fatty acid metal salt separated from the basic polymerization catalyst is It was found that they remain in the pyrrolidone polymer and become impurities to deteriorate the thermal stability of the 2-pyrrolidone polymer. Since no proposal has been found to effectively remove these from the 2-pyrrolidone polymer, various studies have been made to reach the present invention.

That is, the object of the present invention is to provide a 2-pyrrolidone polymer having a basic polymerization catalyst of 2-pyrrolidone and a 2-pyrrolidone polymer obtained by the action of carbon dioxide gas as a polymerization co-catalyst at a pH of 1 to 6.
This can be achieved by washing with an aqueous solution of 1 and then with an organic solvent. 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. If the pH is 1 or less, the polymer of 2-pyrrolidone may be hydrolyzed, and if the pH is 6 or more, it takes a long time to remove the basic catalyst in the polymer of 2-pyrrolidone.
The cleaning efficiency of the 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, etc. or a mixture thereof, or acetic acid, trifluoroacetic acid, dichloroacetic acid, p-toluene sulfone. It is carried out by adding a strong organic acid such as an acid or a mixture thereof to water.

The water used for washing in the present invention is distilled water, ion-exchanged water or the like, and the amount of water used is 1 to 30 times by volume, preferably 5 to 10 times by volume that of the 2-pyrrolidone polymer. If the volume is less than 1 time, the cleaning effect is poor and 30
If the amount is more than the capacity, 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 80 ° C. When it is lower than the lower limit, the cleaning effect is poor, and when it is higher than the upper limit, the 2-pyrrolidone polymer is hydrolyzed to lower the molecular weight, which is not preferable.

The dispersant higher fatty acid metal salt in the 2-pyrrolidone polymer is separated into the higher fatty acid and the metal component in an acidic aqueous solution, and most of the metal component is removed from the 2-pyrrolidone polymer by washing with water. Higher fatty acids cannot be sufficiently removed with water. This higher fatty acid could be removed by subsequently washing the 2-pyrrolidone polymer washed with an acidic aqueous solution with an organic solvent.

Examples of the organic solvent used in the present invention include ethanol, methanol, isopropyl alcohol, acetone, chloroform, ethyl ether, benzene, petroleum ether, carbon disulfide, tetrahydrofuran, dioxane, toluene and xylene. Ethanol, isopropyl alcohol, ethyl ether, chloroform are preferred. The amount of the organic solvent used is 1 to 30 of the 2-pyrrolidone polymer treated in the acidic aqueous solution.
The capacity is twice, preferably 5 to 10 times. If it is less than the lower limit, the cleaning effect cannot be expected, and if it is more than the upper limit, there is no difference in the effect, but it takes time to separate the polymer, which is not preferable from the viewpoint of productivity.

As the aprotic solvent used as the solvent for the suspension polymerization of the present invention, cyclic ethers such as tetrahydrofuran and dioxane, linear ethers such as ethyl ether and isopropyl ether, hexane and benzene,
There are toluene, xylene, dimethylformamide, hexamethylphosphoramide, dimethylacetamide, dimethylsulfoxide, dimethylsulfolane, N-methylpyrrolidone and the like. It is preferable to remove water from these by distillation or the like before use. The amount of aprotic solvent used is 0.5 to 5 of the total amount of pyrrolidone used for polymerization.
The capacity is double, preferably 2 to 4 times. When the amount is less than the lower limit, it is difficult to produce a good powder, and when the amount is more than the upper limit, there is no difference in effect, but it is not preferable from the viewpoint of productivity such that separation from the polymer takes time.

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; hydroxides and hydrides of alkali metals,
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. An aryl of an alkali metal such as sodium phenyl, sodium naphthalene; a Grignard reagent,
For example, butyl magnesium bromide and the like, and quaternary bases represented by the chemical formula (1) and the like.

[0015]

[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 0.005-0.3 mol, preferably 0.0
It is 3 to 0.2 mol. If the amount used is less than the lower limit or more than the upper limit, the molecular weight of the polymer becomes low (relative viscosity of 5 or less), which is not preferable.

The carbon dioxide gas of the polymerization promoter used in the present invention is preferably highly pure, but industrially available ones can be used as long as they do not 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. When the amount of carbon dioxide used is outside the above range, the polymerization rate is slow and the resulting polymer has a low molecular weight, 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-azacyclohepta-1-en-2-yl) -2 -Pyrrolidone, 6-caprolactam-1- (1
-Azacyclopent-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 higher fatty acid metal salt used as the dispersant in the present invention has 10 to 30 carbon atoms in the hydrocarbon group of the higher fatty acid.
And is a monovalent or divalent metal salt. Specific examples include sodium laurate, sodium myristate, potassium myristate, lithium myristate, sodium palmitate, potassium palmitate, sodium stearate, potassium stearate, sodium linoleate, lithium linoleate and sodium behenate. Higher fatty acid metal salt of valency, barium laurate, calcium myristate, zinc myristate, barium myristate, calcium palmitate, magnesium palmitate, zinc palmitate, calcium stearate, zinc stearate, calcium linoleate,
It is a divalent higher fatty acid metal salt such as calcium behenate.

The amount of the higher fatty acid metal salt used in the present invention is 2
-0.1-5% by weight with respect to pyrrolidone, preferably 1
~ 3% by weight. When it is less than the lower limit, it is difficult to obtain a good powdery polymer, and when it is more than the upper limit, the molecular weight of the obtained 2-pyrrolidone polymer becomes low, and it takes time to remove the higher fatty acid metal salt from the polymer. Not preferable.

The high molecular weight 2-pyrrolidone of the present invention contains a predetermined amount of basic polymerization catalyst in an aprotic solvent.
After uniformly dispersing the pyrrolidone and the dispersant, carbon dioxide gas is added, and the mixture is stirred at 100 ° C. or lower, preferably 15 to 70.
It can be obtained by ring-opening polymerization of 2-pyrrolidone at a temperature of ° C. A temperature of 100 ° C. or higher is not preferable because the polymerization rate becomes extremely slow. Carbon dioxide can be added by blowing carbon dioxide into a mixed solution of an aprotic solvent, a 2-pyrrolidone containing a basic polymerization catalyst, and a dispersant 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 prepolymerized composition.
The present invention will be specifically described below with reference to examples.

[0023]

【Example】

-Specific polymerization method of 2-pyrrolidone- 220 g (2.58 mo) of substantially anhydrous 2-pyrrolidone
l) was placed in a flask equipped with a stirrer and a vacuum device,
After heating to 5 ° C., potassium hydroxide with a purity of 85% 15.
52 g (0.235 mol in terms of potassium hydroxide) was added, and the temperature was raised to 115 ° C. After that, the inside of the flask was decompressed (115 ° C., 5 mmHg or less), and the by-product water and 2-
24 g of a mixture of pyrrolidone was distilled off to give 2-pyrrolidone 1
A 2-pyrrolidone solution containing 0.1 mol of potassium pyrrolidone per mol was prepared. Dry nitrogen was introduced into this system to bring it to normal pressure, and the temperature of the liquid was lowered to 25 ° C. After mixing 400 g of this liquid and n-hexane, 4 g of sodium stearate as a higher fatty acid metal salt was added and uniformly mixed. Then, at 25 ° C, 3.5 g of carbon dioxide under stirring
(0.08 mol, basic catalyst potassium pyrrolidone 1 m
(0.34 mol relative to ol), the flask was immersed in a water bath at 45 ° C., and polymerization was carried out under a nitrogen gas atmosphere with stirring for 24 hours. After completion of the polymerization, the polymer and n-hexane were separated by filtration.

The relative viscosity (ηr), which is a measure of the molecular weight of the obtained 2-pyrrolidone polymer, the amount of metal components contained in the 2-pyrrolidone polymer, and the decrease in heating of the 2-pyrrolidone polymer were measured. The rate was measured by the following method.

1. Measurement of ηr (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 6 The higher fatty acid metal salts shown in Table 1 were used as the dispersant,
Polymer 1 obtained by the polymerization method of 2-pyrrolidone
Pour 00g and 700ml of water into a 1500ml stirring tank,
Using the acids shown in Table-1, adjust the pH of the wash water to 1
After stirring and washing for an hour, the polymer and water are separated, and
The polymer was washed with 00 ml and filtered. Then, this polymer and 700 ml of ethanol were mixed in a 1500 ml stirring tank, and after stirring for 1 hour, the polymer and ethanol were separated, and the polymer was washed with 500 ml of ethanol,
It was 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 heating reduction rate is shown in Table-2.
It was shown to.

Comparative Examples 1 to 4 The same procedure as in Example 1 was carried out under the conditions shown in Table 1. The results are shown in Tables 1 and 2.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

The 2-pyrrolidone polymer obtained by suspension polymerization of 2-pyrrolidone in the presence of a basic polymerization catalyst, a polymerization initiator and a higher fatty acid metal salt in an aprotic solvent is used as a polymer.
A 2-pyrrolidone polymer of high purity and high molecular weight can be easily produced by washing with an aqueous solution of H1 to H6 and then washing with an organic solvent.

Claims (1)

[Claims] 1. A suspension polymerization of 2-pyrrolidone in aprotic solvent in the presence of carbon dioxide gas which is a basic polymerization catalyst and a polymerization promoter and a higher fatty acid metal salt is obtained.
A method for producing a high-purity 2-pyrrolidone polymer, which comprises washing a polymer of pyrrolidone with an aqueous solution having a pH of 1 to 6 and then washing with an organic solvent.