Steam explosion treatment with addition of chemicals

Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Waste paper or textile waste

Reexamination Certificate

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

C162S068000, C162S078000, C162S090000

Reexamination Certificate

active

06506282

ABSTRACT:

BACKGROUND OF THE INVENTION
The use of steam or explosive decompression to disintegrate or fiberize wood fibers is well known in the art. However, due to the oxidation of wood and acid hydrolysis, steam explosion processes often result in a loss of brightness, strength and yield. Therefore, there is a need for improving the steam explosion process by minimizing one or more of these detrimental effects.
SUMMARY OF THE INVENTION
It has now been discovered that a steam explosion process can be improved by combining certain chemicals with the steam such that the high temperatures associated with the steam explosion process accelerate certain desired chemical reactions. In addition, the process of this invention is applied to individual fibers, rather than paper or wood particles, which substantially improves the effectiveness of the treatment. These individual fibers can be virgin pulp fibers or deinked fibers. The resulting modified fibers are able to form handsheets with higher bulk, less brightness reduction, less or no tensile reduction and a higher porosity.
More specifically, for example, the loss of brightness associated with conventional steam explosion processes can be improved by the addition, prior to steam explosion process, of: peroxide and caustic soda (NaOH); boric acid; free sugars and alditols such as glucitol, maltose, and maltitol; antioxidants such as ascorbic acid and 1-thioglycerol; and/or nitrogen-free complexing agents such as tartaric acid and gluconolactone.
Strength degradation can be reduced by adding monochloroacetic acid and caustic soda (NaOH) to the individual fibers prior to subjecting them to steam explosion. In addition, other chemicals can be used which contain a fiber reactive group and also contain one or more anionic groups to increase the negative charge density on the fiber surface. The fiber reactive groups which are responsible to form a covalent bond to hydroxyl groups on cellulose fiber, include groups such as monohaloalkyl, monohalotriazine, dihalotriazine, trihalopyrimidine, dihalopyridazinone, dihaloquinoxaline, dihalophtalazine, halobenzothiazole, acrylamide, vinylsulfone, beta-sulfatoethylsylfonamide, beta-chloroethylsulfone, and methylol. Suitable anionic groups include, without limitation, sulfonyl, carboxyl or salts thereof. In addition, the polymeric reactive compound (PRC), comprising a monomer with carboxylic acid groups on adjacent carbon atoms that can form cyclic anhydrides in the form of a five-membered ring could be added for strength improvement. A useful commercial compound is BELCLINE® DP 80 (FMC Corporation), which is a terpolymer of maleic acid, vinyl acetate and ethyl acetate.
In order to neutralize any acid generated in the steam explosion process of this invention, in addition to NaOH, other alkaline agents can also be applied to the fibers, such as NaHCO
3
, Na
2
CO
3
, Na
3
PO
4
and the like.
Hence, in one aspect the invention resides in a process for the treatment of cellulosic fibers comprising: (a) treating an aqueous slurry of individual cellulosic fibers containing brightness and/or strength enhancing chemicals with steam at super atmospheric temperature and pressure; and (b) explosively releasing the super atmospheric steam pressure to produce permanently curled fibers.
In another aspect, the invention resides in a paper sheet or an absorbent article comprising the curled fibers treated by the processes disclosed herein.
DETAILED DESCRIPTION OF THE INVENTION
A wide variety of cellulosic fibers can be employed in the process of the present invention. Illustrative sources of individual cellulosic fibers include, but are not limited to: wood fibers, such as wood pulp fibers; non-woody paper-making fibers from cotton fibers; fibers from straws and grasses, such as rice and esparto; fibers from canes and reeds, such as bagasse; fibers from bamboos; fibers from stalks with bast fibers, such as jute, flax, kenaf, cannabis, linen and ramie; and fibers from leaf fibers, such as abaca and sisal. It is also possible to use mixtures of one or more kinds of cellulosic fibers. Suitably, the individual cellulosic fibers used are from softwood sources such as pines, spruces, and firs, and hardwood sources such as oaks, eucalyptuses, poplars, beeches, and aspens.
As used herein, the term “fiber” or “fibrous” is meant to refer to a particulate material wherein the length to diameter ratio of such particulate material is 10 or greater.
It is generally desired that the cellulosic fibers used herein be wettable. As used herein, the term “wettable” is meant to refer to a fiber or material which exhibits a water-in-air contact angle of less than 90°. Suitably, the cellulosic fibers useful in the present invention exhibit a water-in-air contact angle from about 10° to about 50° and more suitably from about 20° to about 30°. Suitably, a wettable fiber refers to a fiber which exhibits a water-in-air contact angle of less than 90°, at a temperature between about 0° C. and about 100° C., and suitably at ambient conditions, such as about 23° C.
Suitable cellulosic fibers are those which are naturally wettable. However, naturally nonwettable fibers can also be used. It is possible to treat the fiber surfaces by an appropriate method to render them more or less wettable. When surface treated fibers are employed, the surface treatment is desirably nonfugitive; that is, the surface treatment desirably does not wash off the surface of the fiber with the first liquid insult or contact. For the purposes of this application, a surface treatment on a generally nonwettable fiber will be considered to be nonfugitive when a majority of the fibers demonstrate a water in air contact angle of less than 90° for three consecutive contact angle measurements, with drying between each measurement. That is, the same fiber is subjected to three separate contact angle determinations and, if all three of the contact angle determinations indicate a contact angle of water in air of less than 90°, the surface treatment on the fiber will be considered to be nonfugitive. If the surface treatment is fugitive, the surface treatment will tend to wash off of the fiber during the first contact angle measurement, thus exposing the nonwettable surface of the underlying fiber, and will demonstrate subsequent contact angle measurements greater than 90°. Suitable wettability agents include polyalkylene glycols, such as polyethylene glycols. The wettability agent is used in an amount less than about 5 weight percent, suitably less than about 3 weight percent, and more suitably less than about 2 weight percent, of the total weight of the fiber, material, or absorbent structure being treated.
It is desired that the cellulosic fibers be used in a form wherein the cellulosic fibers have already been refined into a pulp. As such, the cellulosic fibers will be substantially in the form of individual cellulosic fibers although such individual cellulosic fibers may be in an aggregate form such as a pulp sheet. The current process, then, is in contrast to known steam explosion processes that generally treat cellulosic fibers that are typically in the form of virgin wood chips or the like. Thus, the current process is a post-pulping, or post deinking, cellulosic fiber modifying process as compared to known steam explosion processes that are generally used for high-yield pulp manufacturing or waste-recycle processes.
The cellulosic fibers used in the steam explosion process of this invention are desirably low yield cellulosic fibers. As used herein, “low yield” cellulosic fibers are those cellulosic fibers produced by pulping processes providing a yield of 85 percent or less, suitably about 80 percent or less, and more suitably about 55 percent or less. In contrast, “high yield” cellulosic fibers are those cellulosic fibers produced by pulping processes providing a yield greater than 85 percent. Such pulping processes generally leave the resulting cellulosic fibers with high levels of lignin.
In general, the cellulosic fibers may be treated with chemicals in either a dry or a wet s

LandOfFree

Say what you really think

Search LandOfFree.com for the USA inventors and patents. Rate them and share your experience with other people.

Rating

Steam explosion treatment with addition of chemicals does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Steam explosion treatment with addition of chemicals, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Steam explosion treatment with addition of chemicals will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFUS-PAI-O-3000759

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.