Particulate polymer matrix comprising a biocidal active substance, homogeneouslydistributed in the polymeric matrix, characterized in that: the polymer takesthe form of a thermoplastic polymer, where more than 90% of all particles havea particle size of less than 100 µm, preferably from 1 to 50 µm, and wherethe polymer matrix has an active substance content of from 2 to 80% by weight.
