(19)

(11)

EP 4 816 611 A1

(12)

(43) Date of publication: 07.10.2026 Bulletin 2026/41 (21) Application number: 24801620.6 (22) Date of filing: 29.10.2024

(51) International Patent Classification (IPC):  D21C 1/02(2006.01) D21C 1/04(2006.01) (52) Cooperative Patent Classification (CPC): D21C 1/02; D21C 1/04 (86) International application number: PCT/FI2024/050580 (87) International publication number: WO 2025/114639 (05.06.2025 Gazette 2025/23)

(84) Designated Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC ME MK MT NL NO PL PT RO RS SE SI SK SM TR Designated Extension States: BA Designated Validation States: GE KH MA MD TN (30) Priority: 29.11.2023 GR 20230100987 (71) Applicant: UPM-Kymmene Corporation 00100 Helsinki (FI)	(72) Inventors: STÅHL, Marina 00100 Helsinki (FI) TAMPER, Juha 00100 Helsinki (FI) TURUNEN, Sami 00100 Helsinki (FI) NISSINEN, Vilho 00100 Helsinki (FI) ÖRSÅ, Folke 00100 Helsinki (FI) NITSOS, Christos 00100 Helsinki (FI) LAITILA, Mika 00100 Helsinki (FI) KAJANTO, Isko 00100 Helsinki (FI) (74) Representative: Papula Oy  P.O. Box 981 00101 Helsinki 00101 Helsinki (FI)