It suggests that it is common behaviour when writing a CSV file to wrap any strings which contain 'special characters' in quotes to avoid confusing other systems which may read them.
This probably doesn't help you and I would be happy to be proven wrong and that there is a solution here.
Is this causing you an issue for reading these files into other downstream systems or are you having trouble loading them back into Qlik (in which case maybe you could try 'qvd' instead of 'txt' as the format?).
The only less than ideal workaround I could suggest is using the replace function to either remove the apostrophe or replace it with something else e.g. `.