Patent ID: 7258868

Claim:
A substrate impregnated with a volatile material comprising pyrethrum to be dispensed from the substrate, the substrate comprising: a substrate formed from a medium having pores and passages, the substrate having a pore size of between 15 μm and 30 μm; and having a polymeric material coating interior surfaces of the pores and passages, the substrate having a pore size of between 15 μm and 30 μm; and volatile material disposed in the pores; wherein the volatile material is more volatile than the polymeric material and the polymeric material inhibits the volatile material from clogging the substrate if the substrate is heated; and wherein the polymeric material is selected from the group consisting of polyalkylsiloxanes and polyalkylarylsiloxanes where an alkyl group in the polysiloxane is a C 1 to C 10 alkyl group, phenolic materials, polyurethanes and fluorocarbon polymers; and wherein the polymeric material is selected from the group consisting of polyalkylsiloxanes and polyalkylarylsiloxanes where an alkyl group in the polysiloxane is a Cl to CiO alkyl group, phenolic materials, polyurethanes and fluorocarbon polymers.