Chemical composition and process

Process for the preparation of a slurry comprising adding a polymeric thickener and a buffer, or a combined thickener and buffer, to an aqueous slurry of thermally expandable microspheres comprising a thermoplastic polymer shell and a propellant entrapped therein, and adjusting the pH to a value exceeding about 2.5 and being within about ±1 pH-unit of a pKa of said buffer or combined thickener and buffer.

Process for the production of paper or nonwoven from fibres comprising the steps of adding a slurry comprising thermally expandable microspheres and a thickener to a stock comprising fibres or to a web of fibres, forming paper or nonwoven from the stock or the web, and applying heat to raise the temperature of the microspheres sufficiently for them to expand and thereby increase the bulk of the paper or the nonwoven, said slurry having a pH of at least about 2.5 and comprising a buffer having a PKa within about ±1 pH-unit of the actual pH.

Process for the production of paper comprising the steps of adding a slurry comprising thermally expandable microspheres to a stock containing cellulosic fibres, dewatering the stock on a wire to obtain paper, and drying the paper by applying heat and thereby also raising the temperature of the microspheres sufficiently for them to expand and increase the bulk of the paper, said slurry having a pH of at least about 2.5 and comprising a buffer having a pKa within about ±1 pH-unit of the actual pH.