CS269567B1 - A method for determining sulfur bound in the form of sulfo groups in a sulfonated polyphenylene oxide - Google Patents

Abstract

The solution relates to the method of determining sulfur in the form of sulfo groups in sulfonated polyphenylene oxide by measuring the transmission línira-ϊ ■ spectra. The essence of the solution is me-| ' ration of spectra from KBr tablets containing: · from 3 to 5 percent by weight of the sample in ob- , ' ! ranges from 4000 to 400 cm", while evaluating the integrated absorbance of the analytical absorption bands with maxima at 561 and 663 cm,1 and the band of the internal Standard at 1610 cm" using the mass relationship S Ai 561 * Ai 663 A CS 26 95 67 B l Ai 1610 where A| A^ and A^ are integrated absorbances at wavelengths of 561, 663, and 1610 cm"1, and the empirical constants A and 8 are determined in advance by calibrating spectral measurements and an analytical method for sulfur determination. By determining sulfur according to the present invention, it is possible to speed up the analytical method used so far, on the basis of which the technological process of preparing sulionized spinning solutions can be precisely controlled polyphenylene oxide as well as to control the quality of the chemically bonded sulfur.

Description

The invention relates to a method for determining sulfur in sulfonated polyphenylene oxide in the range from 0 to 3 percent sulfur by weight.

Unsulphonated polyphenylene oxide / poly/2,6-dimethyl-1,4 phenylene oxide// is a polymer with excellent electrical, mechanical, thermal and chemical properties, which are listed, for example, in the encyclopedia /Mark, H. F.: Encyclopedia of Polymer Science and Technology), Vol. 10, New York 1969/. In addition to its main use in electrical engineering and mechanical engineering, it is advantageously used for the production of porous membranes for separation processes. For the preparation of flat membranes and hollow fibers, polyphenylene oxide modified with sulfur groups is preferably used, which has higher hydrophilicity and better separation properties.

Sulfonated polyphenylene oxide has the following chemical structure:

The ratio between native and sulfonated cores varies depending on the sulfur content. It is assumed that at a sulfur content of about 1.2 percent by weight, every twentieth core of the polymer is sulfonated.

In order to control the sulfur content in sulfonated polyphenylene oxide before preparing the spinning solutions, it is necessary to have a suitable analytical method available. Currently, the method of determining sulfur by mineralization of the solution in an oxygen atmosphere on a platinum contact is used. The combustion products are quantitatively captured in diluted hydrogen peroxide according to the procedure developed at the VÚOS. The determination of sulfur by this method is very time-consuming due to the slow mineralization.

The essence of the determination of sulfur in the form of sulfonated groups in sulfonated polyphenylene oxide according to the present invention consists in preparing a KBr tablet from the powdered polymer with a concentration of 3 to 5 percent by weight of the sample and measuring the transmission infrared spectrum in the range from 4000 cm ^- * to 400 cm ^-1 . The integrated absorbances of the analytical absorption bands of sulfur at 561 and 663 cm ^-1 and the absorption band of the internal standard of polyphenylene oxide at 1610 cm ^-1 are evaluated in the spectrum. The relationship is used to determine the sulfur content

Γ “1 ^{1 A} i 1610 in which AA and A. , ,, _n are the integrated absorbances of the bands at wavenumbers 561, 1 /oli 1 ooP 1 lolu

663 and 1610 cm , and the empirical constants A and B are determined in advance by calibrating the spectral measurements and the analytical method for determining sulfur.

The advantage of the sulfur determination according to this invention is a significant acceleration of the method used so far, since the time of one analysis does not exceed 1 hour. This allows the quality of the input raw materials of sulfonated polyphenylene oxides to be controlled just before the preparation of the spinning solutions. Another advantage is the possibility of registering other chemical bonds of sulfur

CSZ69 567 01 on polyphenylene oxide except for sulfo groups, which is manifested by the appearance of new absorption bands in the spectra.

Example 1

For spectral determination of sulfur content, a sample of sulfonated polyphenylene oxide was used, in which 0.67 wt. sulfur was determined by the mineralization analytical method. A tablet with a concentration of 4 wt. of powdered polymer in KBr was prepared from this sample in the usual manner. An infrared spectrum was recorded from the prepared KBr tablet, in which the integrated absorbances of the analytical absorption bands of sulfur ^{at wavelengths} 561, 663 cm”^· and the absorption band of the internal standard at 1610 cm”^ were evaluated. ·

The calculated values of the integrated absorbances were substituted into the mass ratio % S ^A i 561 * ^A i 663 ^A i 1610 where the empirical constants A and B for the IPS B8 infrared spectrometer have the values • — 9

A = -3.625 .10 , 8 = 0.14383. The spectrally determined sulfur content in this sample was 0.61 wt.%.

Example 2

For the determination of the sulfur content using infrared spectra, a sample of sulfonated polyphenylene oxide was used, in which 3.14 wt.% sulfur was determined by the analytical mineralization procedure. A KBr tablet with a concentration of 4 wt.% of the sample in KBr was prepared from the powdered polymer using the usual procedure. The integrated absorbances of the analytical sulfur absorption bands at 561 and 663 cm~^ as well as the absorption band of the internal Standard at 1610 cm ^- ^ were evaluated in the recorded infrared spectrum. The calculated values of the integrated absorbances were inserted into the relationship as in Example 1. Thus, the sulfur content in this sample was determined to be 2.21 wt.%. Furthermore, new absorption bands were observed in the spectrum in the region from 1200 to 400 cm ^-1 , indicating that in addition to sulfur chemically bound via sulfo groups, the sample also contains sulfur bound in other ways. This may negatively affect the preparation process of a suitable spinning solution, and therefore such samples must be sorted out.

Claims (1)

SUBJECT OF THE INVENTION Method for determining sulfur bound in the form of sulfo groups in sulfonated polyphenylene oxide, characterized in that a transmission infrared spectrum in the range from 4000 to 400 cm ^-1 is recorded from KBr tablets containing from 3 to 5 percent by weight of the sample, while evaluating the integrated absorbance of the analytical absorption bands with maxima at 561 cm~^ and 663 cm~l and the absorption band of the internal standard at 1610 cm~^ using the mass ratio S ^A i 561 * ^A i 663 ^A i 1610 where A. cg., A. ,ζ-t 3 A. . ,. _n are the integrated absorbances at wavenumbers 561, 663 and 1610 cm~ and the empirical constants A and B are determined in advance by calibrating the spectral measurements and the analytical method for determining sulfur.