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Abstract

A process for the preparation of coloured and expanded thermoplastic polyurethane (coloured ETPU) material which comprises the following steps:

a) providing thermoplastic polyurethane (TPU) material and at least one gaseous fluid wherein the melting temperature of the TPU material is above the supercritical temperature of the at least one gaseous fluidb) placing the TPU material in an autoclave together with a colorant and/or a fluorescent whitening agent (FWA), wherein the colorant is selected from at least one of a disperse dye, an acid dye and a pigment;c) increasing the pressure in the autoclave by introducing the at least one gaseous fluid at a temperature below the melting point of the TPU material and at least above the supercritical temperature of the at least one gaseous fluid at the applied pressure (saturation step); andd) allowing the non-expanded TPU material to saturate; ande) decreasing the pressure in the autoclave down to ambient pressure at a temperature between the melting temperature and the glass transition temperature (Tg) of the TPU material at such a rate that the TPU material expands (expansion step) to obtain coloured ETPU materialf) removing the coloured ETPU material from the autoclave.

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First Claim