Methods for producing final polymer A are provided that comprise the following steps: (A) providing a starting polymer V, the starting polymer V being obtainable by radical polymerization of the monomers (i), (ii), (iii), and (iv) as described herein in the amounts provided herein; and (B) hydrolyzing the provided starting polymer V under alkaline conditions to obtain the final polymer A, wherein the N—C(═O)R.sup.1 groups of formula (I) at least partially hydrolyze the monomers (i) polymerized into the starting polymer V to form primary amino groups.

Certain final polymers A obtained are useful for a method for producing paper or cardboard comprising adding certain final polymers A to a first aqueous pulp suspension, dewatering the obtained second aqueous pulp suspension containing certain final polymers A on a water-permeable substrate to a wet paper structure, and further dewatering of the wet paper structure into a paper or cardboard.

Methods for producing paper or cardboard are provided that comprise the steps (A) adding a final polymer A to a first aqueous fibrous material suspension, whereby a second aqueous fibrous material suspension containing final polymer A is created, wherein the final polymer A is obtainable by radical polymerisation of the monomers (i), (ii), (iii), (iv), and (v) as described herein in the amounts provided herein; and hydrolysing the starting polymer V in order to obtain the final polymer A, (B) dewatering the second aqueous fibrous material suspension containing final polymer A on a water-permeable substrate to form a wet paper structure, (C) dewatering the wet paper structure, whereby the paper or the cardboard is formed.

The present invention relates to a medical nonwoven fabric comprising gelable cellulose derivative short-cut fibers as prepared by the paper making process, a preparation method thereof, and an adhesion prevention barrier using the same. The present invention provides a single phase of medical nonwoven fabric comprising gelable cellulose derivative short-cut fibers, to induce capillary action of micropores formed between the fibers and thereby control the gelation time, and provides a composite nonwoven fabric formed by laminating a nonwoven fabric layer comprising a different kind of biodegradable polymer material not susceptible to gelation on the single-phase of medical nonwoven fabric comprising gelable cellulose derivative short-cut fibers, thereby improving dimensional stability and convenience of surgical procedure. The present invention further provides a dyed medical nonwoven fabric to improve visibility, allowing easiness of recognizing the placement or location of the medical nonwoven fabric.