The invention relates to a novel type of sacrificial polymer or support material for 3D printing, comprising a block copolymer consisting of: at least one partially or totally hydrophilic elastomeric block, with a Tg of less than 30° C. and comprising at least one hydrophilic monomer, and at least one water-soluble thermoplastic block with a Tg of greater than 30° C. and comprising at least one monomer bearing a carboxyl group, said copolymer being extrudable and granulable, said copolymer being partially or totally soluble in water or in aqueous medium, and the mass proportion of the thermoplastic block being greater than 50% of the weight of said copolymer.