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US 8,894,817 B1Granted
Wet end chemicals for dry end strength
AssigneeEcolab USA Inc.
InventorsWeiguo Cheng, Mei Liu
Life of this patent
Estimating the term…
Abstract
The invention provides methods and compositions for increasing the dry strength of paper. The invention utilizes a tailored strength agent whose size and shape is tailored to fit into the junction points between flocs of a paper sheet. The strength agents is in contact with the slurry for just enough time to collect at the junction points but not so much that it can migrate away from there.
Claims10
A method of increasing the dry strength of a paper substrate, the method comprising adding a flocculant and starch to a paper substrate and then adding a glyoxalated polyacrylamide (GPAM) copolymer to the paper substrate, wherein:
- said addition of GPAM occurs in the wet-end of a papermaking process after the substrate has passed through a screen but no more than 18 seconds before the substrate enters a headbox,
- the GPAM copolymer is constructed out of acrylamide-acrylic acid (AcAm-AA) copolymer intermediates having an average molecular weight of 5.7-9 kD, the GPAM copolymer has an average molecular weight of 0.6-3 MD.
Dependencies are inferred from the claim text.