Paper making and fiber liberation – Processes and products – Non-fiber additive
Patent
1998-10-06
2000-04-04
Silverman, Stanley S.
Paper making and fiber liberation
Processes and products
Non-fiber additive
1621811, 162158, 162183, 103486, 103416, 103DIG4, 501147, 501144, 501145, 501146, D21H 1769, D21H 1768, C04B 3302, C04B 3304
Patent
active
060456574
DESCRIPTION:
BRIEF SUMMARY
This invention relates primarily to paper making processes that utilise bentonite and to novel fluid bentonite concentrates suitable for use in these processes. The invention also relates to other processes in which such concentrates are useful.
There are many paper making processes which comprise providing a cellulosic suspension at a paper mill, mixing an activated bentonite dispersion into the cellulosic suspension and draining the suspension to form a wet sheet, which is then dried to provide paper (including paper board). In some instances the bentonite is added at the thick stock stage (for instance for stickies control) and the suspension is diluted to a thin stock before drainage, but in other processes the bentonite dispersion is added at the thin stock stage. It can be added before a polymeric retention aid, but there is particular interest in microparticulate processes, wherein the cellulosic suspension is subjected to shearing after adding the polymeric retention aid, and the bentonite is then added to the sheared suspension prior to drainage.
It is necessary that the bentonite should be in a highly swollen, activated, form and in practice this means that it should be in the form of a monovalent salt of bentonite such as sodium bentonite. Although there are some naturally occurring sources of sodium bentonite, most natural bentonites are alkaline earth bentonites, generally calcium or magnesium bentonites. The normal practice is to activate the alkaline earth bentonite by ion exchanging the calcium or magnesium for sodium or other alkali metal or ammonium ion. Generally this is done by exposing the bentonite to an aqueous solution of sodium carbonate, although some other activating materials are known, for instance as described in JP-A-64-45754.
Because of the high viscosifying effect of activated bentonite, it is not convenient to transport or handle a simple dispersion of activated bentonite in water which has a solids content of greater than around 5%. It is not convenient to supply such a dilute composition to the mill and so the normal way of supplying bentonite to a paper mill is in solid form. The mill mixes bentonite powder with water and optionally activating chemicals generally to form an activated dispersion having a solids content of around 3 to 5% and this is then generally diluted to around 0.05 to 1% prior to addition to the cellulosic suspension. This necessitates that the mill should be equipped with apparatus for handling and mixing the powder and the dilute dispersion.
It is known to make aqueous dispersions of bentonite having a higher solids content. The first disclosure of this in connection with the production of bentonite for paper making is in EP-A-485,124 wherein the bentonite is dispersed at high solids, for instance up to 27 to 30%, as a slurry in an aqueous solution of sodium chloride or other inorganic electrolyte. optionally some sodium polyacrylate can be used. The bentonite which is dispersed in this manner is preferably a commercial (typically calcium) bentonite containing sodium carbonate activator. Thus the activation of the bentonite is completed when the slurry is diluted with water to make a flowable dilute dispersion.
U.S. Pat. No. 5,266,538 is another disclosure of making concentrated bentonite slurries for paper making, again concentrating primarily on the use of sodium chloride or other inorganic electrolyte for depressing the viscosity of the slurry. In this publication, however, the bentonite is always introduced in sodium form. Various electrolytes are exemplified. Amongst these, there is an example of forming 25% bentonite gel with 2.5 or 5% sodium citrate in water. It is shown that these gels have viscosities respectively of 40,000 and 5,500 cps (Brookfield, 20 rpm) and that they gel on standing for 24 hours. The preferred material is said to be sodium chloride.
U.S. Pat. No. 5,391,228 repeats much of the disclosure of U.S. Pat. No. 5,266,538 but adds disclosure of a process in which calcium bentonite and sodium carbonate are slurried in aqueous s
REFERENCES:
patent: 4282059 (1981-08-01), Davidson
patent: 4305781 (1981-12-01), Langley et al.
patent: 4749444 (1988-06-01), Lorz et al.
patent: 4753710 (1988-06-01), Langley et al.
patent: 4913775 (1990-04-01), Langley et al.
patent: 4964954 (1990-10-01), Johansson
patent: 4969976 (1990-11-01), Reed
patent: 5006574 (1991-04-01), Sennett et al.
patent: 5223098 (1993-06-01), Cluyse et al.
patent: 5223463 (1993-06-01), Bilimoria et al.
patent: 5266538 (1993-11-01), Knudson et al.
patent: 5391228 (1995-02-01), Carroll
patent: 5512135 (1996-04-01), Carreet al.
patent: 5537934 (1996-07-01), Jensen et al.
Derwent Abstr. 94-242339 for EP 608986.
Derwent Abstr. 80-77455C for EP 17353.
Derwent Abstr. 89-287039 for EP 335575.
Allen Adrian Swinburn
Black Ian James
Stockwell John Oliver
Ciba Specialty Chemicals Water Treatments Limited
Crichton David R.
Fortuna Jos'e A.
Silverman Stanley S.
LandOfFree
Clay compositions and their use in paper making does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Clay compositions and their use in paper making, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Clay compositions and their use in paper making will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-361411