Method for controlling elution rate of agent

A method for controlling an elution rate of a stainproofing agent being eluted from fibriform or corded materials immersed in seawater, which comprises treating said fibriform or corded materials, prior to said immersion, with a non-aqueous composition comprising:

• A:
• 4,5-dichloro-2-n-octylisothiazoline-3-one;
• B:
• a polymer selected from the group consisting of monopolymers of unsaturated monomers having the following formula (1), and hydrophilic copolymers of other unsaturated monomers copolymerizable with the above monopolymers, ##STR2## (wherein X is hydrogen or methyl group, n.sub.1 is an integer of 1-50, and R is an alkyl group or an acyl group having 1-18 carbon atoms);
• C:
• one or more compounds selected from the following components of C1-C.sub.4;
• C1:
• one or more members selected from dialkylpolysulfide derivatives having the following formula (2)
• R.sup.2 --(S)n2.sup.--R3 ( 2)
• (wherein R.sup.2, R.sup.3 are respectively alkyl groups having 1-20 carbon atoms, and n.sub.2 is an integer of 1-5),
• C2;
• a polybutene having a degree of polymerization 2-100,
• C3:
• a xylene/formaldehyde polycondensation products having an average molecular weight of 300-1000, and
• C4:
• a C.sub.9 aromatic hydrocarbon/formaldehyde polycondensation products having an average molecular weight of 350-700;
• D:
• organic solvent for A, B, and C.