Method of sulfonating an article and related apparatus

A method of sulfonating the surface of a resin-containing article, the method comprising:

• a) forming a first sulfonating gas composition, the sulfonating gas composition comprising a sulfur-containing gaseous compound provided from a gas source;
• b) contacting one or more first test samples with the first sulfonating gas composition;
• c) contacting the one or more first test samples with at least one neutralization composition;
• d) determining the amount of sulfur in the one or more first test samples by inductively coupled plasma analysis;
• e) measuring the amount of sulfur in the one or more first test samples by X-ray fluorescence;
• f) determining a calibration relationship between the amount of sulfur determined by inductively coupled plasma analysis and X-ray fluorescence wherein the amount of sulfur determined by inductively coupled plasma analysis is taken as an accurate value;
• g) forming a second sulfonating gas composition, the second sulfonating gas composition comprising a sulfur-containing gaseous compound provided from a gas source;
• h) contacting the article and one or more second test samples with the second sulfonating gas composition;
• i) contacting the article and the one or more second test samples with at least one neutralization composition;
• j) measuring the amount of sulfur in the first test sample by X-ray fluorescence using the calibration relationship determined in step f) to adjust the determined amount of sulfur;
• and
• k) adjusting concentration of sulfur-containing compound in the sulfonating gas composition or adjusting the time of sulfonation in subsequent sulfonation runs if the amount of sulfur determined in step j) is not equal to a predetermined value, wherein the first and second test sample each individually comprise a resin.

A method of sulfonating the surface of a resin-containing article, the method comprising:

• a) forming a sulfonating gas composition, the sulfonating gas composition comprising a sulfur-containing gaseous compound provided from a gas source;
• b) contacting the article with the sulfonating gas composition, the surface having an acid residue concentration formed thereon;
• c) contacting the article with a gaseous neutralization composition;
• and
• d) contacting the article with a liquid neutralization composition at a sufficient temperature to adjust the acid residue concentration.