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OwnerReijo Aksela, Outi Gronfors +7inventors
InventorsReijo Aksela, Outi Gronfors, Pasi Hagelberg, Perttu Heiska, Hanna-Mari Kangaslahti, Jori Kerala, Jarmo Reunanen, Esko Tirronen, Tarja Turkki
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The invention relates to a gypsum product which consists of essentially intact crystals having a size of between 0.1 and below 2.0 μm. The product is especially suitable as a coating pigment or filler in paper manufacture. The invention also relates to a process for the preparation of a gypsum product, wherein calcium sulphate hemihydrate and/or calcium sulphate anhydrite, water and a crystallization habit modifier are contacted so that the calcium sulphate hemihydrate and/or calcium sulphate anhydrite and the water are reacted with each other and form a crystalline gypsum product. The calcium sulphate hemihydrate and/or calcium sulphate anhydrite is/are used in such an amount that the reaction mixture formed from the calcium sulphate hemihydrate and/or calcium sulphate anhydrite, the water and the crystallization habit modifier has a dry matter content of between 50 and 84% by weight. Then, said gypsum product can be formed which consists of essentially intact crystals having a size of between 0.1 and below 2.0 μm.
1-19. (canceled)
A gypsum product consisting essentially of intact gypsum crystals obtained by crystallization and having a size from 0.1 to less than 2.0 μm.
A process for the preparation of a gypsum product wherein calcium sulfate hemihydrate and/or calcium sulfate anhydrite, water, and a crystallization habit modifier are contacted so that the calcium sulfate hemihydrate and/or calcium sulfate anhydrite and the water react with each other and form a crystalline gypsum product, wherein the calcium sulfate hemihydrate and/or calcium sulfate anhydrite is/are used in such an amount that the reaction mixture formed from the calcium sulfate hemihydrate and/or calcium sulfate anhydrite, the water, and the crystallization habit modifier has a dry matter content of between 50 and 84% by weight, and that the mixing is carried on until the gypsum product is formed which consists essentially of intact crystals having a size between 0.1 and 2.0 μm.
Dependencies are inferred from the claim text.