Process for producing paper or board and a product thereof

A process for producing paper or board, comprising:

• slushing a stock of dried fibres in a slushing system comprising a pulper, and/or feeding a stock of never-dried fibres in a fibre line of an integrated paper mill;
• adding a polymeric strength additive comprising at least one polysaccharide to one or more of the stocks of dried fibres and never-dried fibres into the pulper or to the fibre line;
• deflaking and/or refining the stock in a deflaker and/or a refiner;
• directing a deflaked and/or refined stock from the deflaker and/or refiner into a mixing chest and from the mixing chest to a machine chest;
• obtaining a thin stock by diluting the deflaked and/or refined stock with white water from a white water silo;
• directing the the thin stock to a headbox;
• forming a web;
• and
• drying the web;
• wherein the polymeric strength additive has an intrinsic viscosity of at least 200 ml/g, and
• wherein consistency of the stock in the slushing system and/or in the fibre lines is 4-20 wt. % at the time and point of the addition of the polymeric strength additive.