Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Waste paper or textile waste
Reexamination Certificate
2000-03-02
2002-05-21
Nguyen, Dean T. (Department: 1731)
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Waste paper or textile waste
C162S008000
Reexamination Certificate
active
06391150
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a process for the treatment of waste paper, sometimes referred to herein as with the exclusion of biocides and the total exclusion of chlorine compounds as well as with the virtual avoidance of hydrogen peroxide and/or peracetic acid, which also yields a recycled base tissue and optionally, to a tissue product that is suited for final consumption and that has a total germ count of less than 1000 CFU/g (colony-forming units per gram); the invention also relates to a device to carry out this process as well as to recycled base tissue paper and optionally, a tissue product that is suited for final consumption and that has a surface germ count of less than 20 CFU/dm
2
and a total germ count of less than 1000 CFU/g as a product. The above-mentioned germ counts are determined in a manner similar to DIN 54378 (surface germ count) and in a manner similar to DIN 54379 (total germ count).
The expression “with the exclusion of biocides,” which is used in conjunction with the process according to the invention, refers to biocide quantities that are present in small quantities, preferably in quantities of less than 0.01% by weight relative to the recycled base tissue or to the tissue product that is suited for final consumption.
Moreover, in this context, it should also be pointed out that the clear water that is used within the scope of the process according to the invention (for example, as a temperature-control medium in the papermaking machine, as shown in
FIG. 1
) is circulated and purified by means of a circulating-water treatment system (Sedifloat); right from the start, this water only has concentrations of biocide substances that lie below the detection limit of less than 0.1 ppm, since its HPLC analysis was negative. The DCM extract that was examined did not reveal any biocide either. As is known, in the above-mentioned circulating-water treatment system, the fine substances and fillers are separated almost quantitatively from the water and thus the treated water is used again for dilution purposes.
The article in the PTS Manuscript Volume 19/95, titled Microbiocides in Papermaking, Hygienic Aspects of the Use of Various Grades of Old Paper, by U. H{umlaut over (oo)}tmann, gives a general overview as to which starting materials, for example, a fiber raw material recovered from mixed household garbage, from mixed old paper, from industrial waste or mixed old paper or from raw material obtained from collections within the scope of Germany's Dual System can be used for waste paper processes. This general overview, however, does not provide any information that could anticipate the process according to the invention as claimed.
German Patent No. 26 07 703 relates to a process for the production of sanitized recycled paper made of waste containing paper, whereby a fraction—consisting essentially of paper fragments or a mixture of paper and plastic fragments which are retained by a screen having a mesh size of at least 20 mm—is separated from the waste in a generally known manner and is then subjected to a brief thermal treatment, whereby the fragments are heated to a temperature ranging from about 100° C. to 130° C. [212° F. to 266° F.], whereupon the fragments, optionally after separation of the plastic fraction, are compacted while a temperature of at least 100° C. [212° F.] is maintained, and the compacted fragments are kept at a temperature of about 100° C. to 110° C. [212° F. to 230° F.] for at least 24 hours at the appertaining temperature limit. The heat treatment is carried out by means of IR heat, that is to say, dry heat. This process is based on the objective of producing recycled paper that, in contrast to conventional processes, is no longer laden with a bacteria content in the order of magnitude of 10
9
heterotrophic colony-forming bacteria per gram of product and with an unknown amount of mold and mildew as well as with thermophilic organisms that not only pose a threat to the health of the operating personnel but that also lead to annoying odor and slime problems in the return water system of the papermaking machines. According to this process, the bacteria content is reduced to about 10
2
bacteria per gram of weighed-in material.
However, this state of the art does not suggest the subject matter of the present invention as claimed, that is to say, working in a medium containing water or in moist heat, nor does it give any indication that, by means of this process, the spores of the bacteria or fungi are to be activated before the germination.
European Preliminary Published Application No. 0,514,864 relates to a process for the treatment of secondary pulp comprising cellulose fibers and tacky contaminants that is made of old paper, whereby the pulp is brought into contact with a gas containing oxygen without added alkali under such conditions in terms of temperature and oxygen partial pressure and for such a period of time that the stickiness of the tacky contaminants is diminished, thus reducing problems involving operating conditions and relating to the product quality during the further processing of the cellulose fibers into the recycled paper product. This contacting procedure is preferably carried out at a temperature between 60° C. and 130° C. [140° F and 266° F.] at an oxygen partial pressure ranging from 34.5 to 3,100 kPa.
The outcome of this process is, on the one hand, a product with a low percentage of old paper that already has a suitable strength for special application purposes and, on the other hand, a product with a high proportion of recycled paper that can be used, for example, for newspapers, diapers, tissues, writing paper and printing paper. This state of the art is based on the objective of providing a treatment process of the type mentioned above for secondary pulps. This state of the art, however, makes no mention of the production of a recycled paper that is produced so as to be essentially free of biocides and that, as a result of this process, has a surface germ count of less than 20 CFU/dm
2
.
European Patent Specification No. 0,394,734 relates to a process for the sterilization of objects, preferably packaging material, using a gaseous sterilization means. However, this publication does snot give any indication of parallels to the treatment process according to the invention which functions without the use of biocides and which leads to a low bacterial load in the product of the process.
German Patent No. 3,001,862 relates to a process for the production of raw material for paper production using old paper, whereby old paper from trash is already treated with a disinfectant gaseous means when it is sorted out from the trash and only subsequently is the old paper treated, especially by means of dissolution and defiberization, for purposes of paper production. Ozone or chlorine are preferably used as the disinfectant or biocide. This neither anticipates nor suggests the process according to the invention, since this process of the state of the art—in contrast to the process according to the invention—is a dry process that makes use of disinfectants.
German Preliminary Published Application No. 2,214,786 relates to a process for the destruction of files and spent packaging tubes made of paper or paperboard, whereby the material to be disintegrated is first mechanically shredded and the shredded product is then compacted for purposes of volume reduction, whereby the shredded product is moistened before the compacting step. Preferably, ink-degrading as well as bactericidal substances and optionally binders are added to the water. Another subject matter of this state of the art is a suitable device to carry out the above-mentioned process. This state of the art is based on the objective of creating a process and a device of the above-mentioned type with which the shredded material can be compacted very tightly and also kept in this compacted form so that further treatment is facilitated. This does not suggest the process according to the invent
Berger Josef
Geishofer Friedrich
Burns Doane Swecker & Mathis L.L.P.
Nguyen Dean T.
SCA Hygiene Products GmbH
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