BAG PAPER AND METHOD FOR MAKING BAG PAPER Russian patent published in 2009 - IPC D21F11/00 D21H27/00 D21H27/10 D21H21/10 D21H17/29 D21H17/45 D21H17/68 

FIELD: textiles, paper.

SUBSTANCE: method refers to pulp-and-paper industry, specifically to method for making bag paper, as well as to bag paper with improved service properties. Method for making bag paper involves pulp beating stage at fibre concentration 28-40% and thereafter at fibre concentration 3-6%. It is followed by two-staged addition of reinforcing and at once flocculating agent to pulp. Then paper web is casted and dried. Further beating stage at fibre concentration 3-6% requires power consumption within 20-60 kWt/h per paper ton. The second stage of addition is followed with the third stage of addition implying flocculating agent preceding headbox. Herewith at the first stage, reinforcing and at once flocculating agent is cationic starch of fractional substitutionality 0.040-0.150 in amount 0.1-1.2% of absolutely dry fibre weight, or polyacrylamide in amount 0.1-0.5% of absolutely dry fibre weight. Specified agent is added to pulp, 5-120 minutes prior to paper web casting. At the second stage reinforcing and at once flocculating agent is added in amount 0.005-0.400% of absolutely dry fibre weight. Specified agent is added to pulp, 20-120 seconds prior to paper web casting. At the third stage flocculating agent is anionic montmorillonite microparticle dispersion. Specified agent is added to pulp in amount 0.05-0.50 % of absolutely dry fibre weight. Bag paper is made under the offered method.

EFFECT: lower consumption of reinforcing and flocculating polymers, improved pulp water yield on papermaking machine grid and enhanced consumer paper properties including paper air permeability.

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