Modified fibrous product and method of producing the same

Abstract

The present invention relates to a modified fibrous product and a method of producing the same. According to the method, transparent areas are generated in the fibrous product, such as in a paper or a cardboard sheet or in a paper or a cardboard web. According to the present invention, a carbohydrate derivative that includes a plasticizer is incorporated into the fibrous product, and the carbohydrate derivative, which is plasticized with the plasticizer, is brought, in a liquid state and under pressure, to migrate in between the fibres of the product in such a way that at least part of the plasticizer penetrates into the lumens of the fibres, in which case the fibrous product becomes transparent in the treated area. By using the solution, it is possible to simplify the method of further processing paper or cardboard for consumer packages. The present invention can be applied to, among other products, envelopes having a window through which the address is visible. Other applications are all kinds of foodstuff and consumer packages in which windows for product display are currently used.

Dependencies are inferred from the claim text.