JP3013949B2 - Method for producing high-purity 2-pyrrolidone polymer - Google Patents

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 efficiently removing a catalyst residue and a higher fatty acid metal salt from a 2-pyrrolidone polymer obtained by a suspension polymerization method. And a method for producing a high-purity 2-pyrrolidone polymer having 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 has extremely poor thermal stability at high temperatures, and has a drawback that it is difficult to produce fibers by a melt spinning method, which is an economical method for producing fiber materials. As a result of many studies for the purpose of improving this defect, it was found that the higher the molecular weight of the 2-pyrrolidone polymer, the better the thermal stability, and the method for producing a high-molecular-weight polymer was disclosed in Japanese Patent Publication No. 47-26678. Gazette, US Patent 3
No. 174951 discloses this. However, 2-
The thermal stability of pyrrolidone polymers was not yet sufficient just to have a high molecular weight.

[0003] A method for obtaining a 2-pyrrolidone polymer by a suspension polymerization method is known. For example, Japanese Patent Publication No. 37-6746
In Japanese Patent Application Laid-Open Publication No. H11-157, 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 is disclosed. Compared to the bulk polymerization method,
In 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 the polymer has not been put to practical use.

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

According to Japanese Patent Publication No. 62-61054, the first stage of polymerization is a bulk polymerization in which the conversion of 2-pyrrolidone is reduced to 10%.
%, The resulting polymer is mixed with an insoluble hexane in the second step to carry out suspension polymerization to obtain a powdery 2-pyrrolidone polymer. In this method, the polymerization reaction is 2
This is disadvantageous in terms of the process, the residual basic catalyst remains, and the heat resistance is insufficient, so that it has not been put to practical use.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-purity, high-molecular-weight 2-pyrrolidone polymer which is sufficiently removed from a basic polymerization catalyst and a higher fatty acid metal salt residue and has excellent heat stability. It is to provide a manufacturing method.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a process for producing high purity, high molecular weight 2-pyrrolidone polymers. Generally, when a 2-pyrrolidone polymer is obtained by a suspension polymerization method, a dispersant such as a basic polymerization catalyst or a metal salt of a higher fatty acid is used. -It has been found that it remains in the pyrrolidone polymer and becomes an impurity to deteriorate the thermal stability of the 2-pyrrolidone polymer. Since no proposal has been found for effectively removing these from the 2-pyrrolidone polymer, various studies have been made and the present invention has been reached.

That is, an object of the present invention is to convert 2-pyrrolidone to a 2-pyrrolidone polymer obtained by the action of a basic polymerization catalyst and carbon dioxide gas as a polymerization co-catalyst.
After washing with an aqueous solution of the above, it can be achieved by further washing with an organic solvent. In the present invention, the pH of the aqueous solution used for washing the 2-pyrrolidone polymer is 1 to 6, preferably 3 to 5. If the pH is 1 or less, the 2-pyrrolidone polymer may be hydrolyzed, and if the pH is 6 or more, it takes a long time to remove the basic catalyst in the 2-pyrrolidone polymer and 2-
The efficiency of washing 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 or a mixture thereof, or acetic acid, trifluoroacetic acid, dichloroacetic acid, p-toluenesulfone. It is carried out by adding a strong organic acid such as an acid 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 is 1 to 30 times, preferably 5 to 10 times the volume of the 2-pyrrolidone polymer. If the volume is less than 1 volume, the cleaning effect is poor.
When the amount is more than the volume, there is no difference in the effect, but it takes time to separate the polymer, and the amount of the acid used is large, which is not economical. The temperature of the acidic aqueous solution for washing the 2-pyrrolidone polymer is 5 to 100C, preferably 20 to 80C. When it is lower than the lower limit, the washing 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 dispersing agent higher fatty acid metal salt in the 2-pyrrolidone polymer is separated into a higher fatty acid and a 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.

The organic solvent used in the present invention includes ethanol, methanol, isopropyl alcohol, acetone, chloroform, ethyl ether, benzene, petroleum ether, carbon disulfide, tetrahydrofuran, dioxane, toluene, xylene and the like. Preference is given to ethanol, isopropyl alcohol, ethyl ether and chloroform. The amount of the organic solvent used is 1 to 30 of the 2-pyrrolidone polymer treated in the acidic aqueous solution.
The volume is multiplied by volume, preferably 5 to 10 times. When the amount is less than the lower limit, no washing effect can be expected, and when the amount 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.

The aprotic solvent used as the solvent for the suspension polymerization of the present invention includes cyclic ethers such as tetrahydrofuran and dioxane, linear ethers such as ethyl ether and isopropyl ether, hexane, benzene, and the like.
Examples include toluene, xylene, dimethylformamide, hexamethylphosphoramide, dimethylacetamide, dimethylsulfoxide, dimethylsulfolane, and N-methylpyrrolidone. It is preferable to remove water by distillation or the like before use. The amount of the aprotic solvent used is 0.5 to 5 times the total amount of pyrrolidone used in the polymerization.
It is twice the volume, preferably 2 to 4 times the volume. 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 it takes time to separate the polymer.

As the basic polymerization catalyst used in the present invention, compounds generally used in anionic polymerization of lactamuls can be used, and 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 Aryls of alkali metals, such as sodium phenyl, sodium naphthalene; Grignard reagents;
Examples thereof include butylmagnesium bromide and the like, and a quaternary base represented by the chemical formula (1).

[0015]

Embedded image (Where R1, R2 and R3 are lower alkyl;
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 preferred. When using potassium hydroxide, potassium methylate, sodium methylate, etc., mix excess 2-pyrrolidone and these compounds prior to polymerization, and use after removing water and alcohols by-produced by the reaction. Is preferred. The amount of the basic polymerization catalyst used in the present invention is 1 mol of 2-pyrrolidone.
0.005 to 0.3 mol, preferably 0.0
3 to 0.2 mol. If the amount used is less than the lower limit or greater than the upper limit, the molecular weight of the polymer becomes low (5 or less in relative viscosity), which is not preferable.

The carbon dioxide of the polymerization co-catalyst used in the present invention is preferably high in purity, but industrially available carbon dioxide can be used as long as the polymerization is not hindered. The amount of carbon dioxide used is 0.1 to 0.9 with respect to 1 mol of the basic polymerization catalyst.
mol, preferably 0.2 to 0.6 mol. If the amount of carbon dioxide gas used is out of the above range, the polymerization rate is low, and the molecular weight of the obtained polymer is undesirably low.

In the present invention, other known polymerization initiators can be used together with carbon dioxide. Other polymerization initiators that can be used with carbon dioxide include acetylpyrrolidone, lactam acyl compounds such as acetylcaprolactam, acyl compounds such as adipoylbiscaprolactam, acetic anhydride, acid anhydrides such as benzene anhydride, and toluene diisocyanate. Organic isocyanates, carbamide compounds such as 1,6-hexamethylenebiscarbamidocaprolactam, 1- (1-pyrolin-2-yl) -2-pyrrolidone, 1- (1-azacyclohepta-1-en-2-yl) -2 -Pyrrolidone, 6-caprolactam-1- (1
-Azacyclopenta-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 used.

The higher fatty acid metal salt used as a dispersant in the present invention has a hydrocarbon group of higher fatty acid having 10 to 30 carbon atoms.
And 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, sodium behenate and the like. Is a metal salt of a higher fatty acid having a higher valency, and 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 of the present invention is 2
-0.1 to 5% by weight, preferably 1%, based on pyrrolidone
３3% by weight. If it is less than the lower limit, it is difficult to obtain a good powdery polymer, and if it is more than the upper limit, the molecular weight of the obtained 2-pyrrolidone polymer is low, and it takes time to remove the higher fatty acid metal salt from the polymer. Not preferred.

The high molecular weight 2-pyrrolidone of the present invention contains a predetermined amount of a basic polymerization catalyst in an aprotic solvent.
After uniformly dispersing the pyrrolidone and the dispersant, carbon dioxide is added, and the mixture is stirred at 100 ° C or lower, preferably 15 to 70 ° C.
It can be obtained by ring-opening polymerization of 2-pyrrolidone at a temperature of ° C. If the temperature is higher than 100 ° C., the polymerization rate becomes extremely slow, which is not preferable. Addition of carbon dioxide gas can be carried out by blowing carbon dioxide gas into a mixed solution of aprotic solvent, 2-pyrrolidone containing a basic polymerization catalyst, and a dispersant at a temperature of 150 ° C or less, preferably 15 to 100 ° C. .

Further, if it is within 20% by weight of the prepolymerized composition, it may be copolymerized with γ-butyrolactone, α-piperidone, ε-caprolactam, laurolactam and the like.
Hereinafter, the present invention will be described specifically with reference to Examples.

[0023]

【Example】

-Specific polymerization method of 2-pyrrolidone-220 g of substantially anhydrous 2-pyrrolidone (2.58 mo
l) was placed in a flask equipped with a stirrer and a decompression device, and 6
After heating to 5 ° C., potassium hydroxide 85% pure.
52 g (0.235 mol in terms of potassium hydroxide) was added, and the temperature was raised to 115 ° C. Thereafter, the pressure in the flask was reduced (115 ° C., 5 mmHg or less), and water produced as a by-product was
After distilling off 24 g of the pyrrolidone mixture, 2-pyrrolidone 1
A 2-pyrrolidone solution was prepared containing 0.1 mol of potassium pyrrolidone per mol. Dry nitrogen was introduced into the system to normal pressure, and the temperature of the solution was lowered to 25 ° C. After mixing this solution with 400 g of n-hexane, 4 g of sodium stearate was added as a higher fatty acid metal salt and mixed uniformly. Subsequently, at 25 ° C., 3.5 g of carbon dioxide gas with stirring.
(0.08 mol, basic catalyst potassium pyrrolidone 1 m
(0.34 mol based on the total weight of the flask), the flask was immersed in a water bath at 45 ° C., and polymerized with stirring under a nitrogen gas atmosphere for 24 hours. After the 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 the metal component contained in the 2-pyrrolidone polymer, and the decrease in heat of the 2-pyrrolidone polymer The rate measurement was performed by the following method.

1. Measurement of ηr (relative viscosity) After completely dissolving 0.5 g of the dried 2-pyrrolidone polymer in 100 cc of m-cresol at room temperature, the falling time (unit: second) was measured at a temperature of 30 ° C. using an Ostwald viscometer. And the value calculated by the following formula.

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

3. Heat decrease rate measurement The heat decrease rate of the 2-pyrrolidone polymer was measured by heating the 2-pyrrolidone polymer at 10 ° C./min under a nitrogen atmosphere using TGA (manufactured by Seiko Instruments Inc., SSC-560G).
The weight loss (g) of the 2-pyrrolidone polymer at each temperature was divided by the weight (g) before weight reduction to 100.
Multiplied.

Examples 1 to 6 Using higher fatty acid metal salts shown in Table 1 as dispersants,
Polymer 1 obtained by the polymerization method of 2-pyrrolidone
Put 00g and 700ml of water in a 1500ml stirring tank,
The pH of the washing water was adjusted using the acids shown in Table 1, and 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, the 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 dried under reduced pressure at 70 degreeC for 24 hours. Table 1 shows the content of the metal component in the 2-pyrrolidone polymer, and Table 2 shows the heating reduction rate.
It was shown to.

Comparative Examples 1 to 4 The same procedures as in Example 1 were performed 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 metal salt of a higher fatty acid in an aprotic solvent is converted into p-pyrrolidone
By washing with an aqueous solution of H1 to H6 and subsequently washing with an organic solvent, a high-purity and high-molecular-weight 2-pyrrolidone polymer can be easily produced.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-207824 (JP, A) JP-A-54-83094 (JP, A) JP-A-62-32121 (JP, A) 22215 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08G 69/00-69/50

Claims (1)

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