Condensation polymers of aldehydes or ketones with phenols only of aldehydes of formaldehyde, e.g. of formaldehyde formed in situ with phenols substituted by carboxylic or sulfonic acid groups
Condensation polymers of aldehydes or ketones with phenols only of aldehydes of formaldehyde, e.g. of formaldehyde formed in situ with phenols substituted by carboxylic or sulfonic acid groups