The invention relates to a process for producing a thermoplastic moulding compound comprising a thermoplastic copolymer A and a graft copolymer B (4), comprising: continuously drying the dewatered graft copolymer B (4) by supplying a drying gas (3) and the dewatered graft copolymer B (4), by moving the dewatered graft copolymer B (4) through the drying gas (3) and forming a fluidized bed (5), the drying gas (3) having a feed temperature TG,feed in the range from 50° C. to 160° C., and by removing dried graft copolymer B (4) and an offgas (7), wherein i. a starting temperature Tin of the fluidized bed (5) on feeding (9) of the dewatered graft copolymer B (4) is measured, ii. a finish temperature Tout of the fluidized bed (5) on removal (11) of the dried graft copolymer B (4) and/or of the offgas (7) is measured, iii. a difference ΔTact between the finish temperature Tout and the starting temperature Tin is formed and the difference ΔTact is compared with a target value ΔTtarget, and iv. the finish temperature Tout is adjusted by—increasing a mass flow rate of drying gas (3) supplied and/or the feed temperature TG,feed of the drying gas (3) when the difference ΔTact is smaller than the target value ΔTtarget or—reducing a mass flow rate of drying gas (3) supplied and/or the feed temperature TG,feed of the drying gas (3) when the difference ΔTact is greater than the target value ΔTtarget.