Bleaching and brightness stabilization of lignocellulosic...

Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Treatment with particular chemical

Reexamination Certificate

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C162S072000, C162S076000, C162S078000, C162S082000, C162S160000

Reexamination Certificate

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10770474

ABSTRACT:
A method for the bleaching and brightness stabilization of lignocellulosic materials is described. The method involves the treatment of lignocellulosic materials, in particular, (a) wood pulps such as thermomechanical pulps (TMP) and chemithermomechanical pulps (CTMP), and (b) papers made from wood pulps, with a water-soluble phosphine or a phosphonium compound preferably containing at least one phosphorus hydroxyalkyl bond/linkage, for example a phosphorus hydroxymethyl bond/linkage (P—CH2OH). One example of such a water-soluble phosphine is the commercially available, tris(hydroxymethyl)phosphine (THP), P(CH2OH)3. One example of such a phosphonium compound is the commercially available, tetrakis(hydroxymethyl)phosphonium chloride (THPC), [P(CH2OH)4]Cl.

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Journal of Wood Chemistry and Technology, 11(4), 419-437 (1991), “A Study of the Photoyellowing of Paper Made from Bleached CTMP”, by R.S. Davidson et al.

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