Abstract: A composition comprising particles which comprise a core material within a polymeric shell, wherein the core material comprises a hydrophobic substance, characterized in that the polymeric shell comprises a copolymer formed from a monomer blend which comprises, A) 30 to 90% by weight methacrylic acid B) 10 to 70% by weight alkyl ester of (meth)acrylic acid which is capable of forming a homopolymer of glass transition temperature in excess of 60° C. and C) 0 to 40% by weight other ethylenically unsaturated monomer. The core material can comprise an active ingredient selected from the group consisting of UV absorbers, UV reflectors, pigments, dyes, colorants, scale inhibitors, corrosion inhibitors, antioxidants, pour point depressants, wax deposition inhibitors, dispersants, flame retardants, biocides, active dye tracer materials and phase change materials. The composition has the advantage that the polymeric shell is highly impermeable to the core material even at elevated temperatures.

Abstract: A composition comprising particles which comprise a core material within a polymeric shell, wherein the core material comprises a hydrophobic substance, characterized in that the polymeric shell comprises a copolymer formed from a monomer blend which comprises, A) 30 to 90% by weight methacrylic acid B) 10 to 70% by weight alkyl ester of (meth)acrylic acid which is capable of forming a homopolymer of glass transition temperature in excess of 60 ° C. and C) 0 to 40% by weight other ethylenically unsaturated monomer. The core material can comprise an active ingredient selected from the group consisting of UV absorbers, UV reflectors, pigments, dyes, colorants, scale inhibitors, corrosion inhibitors, antioxidants, pour point depressants, wax deposition inhibitors, dispersants, flame retardants, biocides, active dye tracer materials and phase change materials. The composition has the advantage that the polymeric shell is highly impermeable to the core material even at elevated temperatures.