Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Gas – vapor or mist contact
Patent
1996-11-07
2000-08-15
Alvo, Steve
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Gas, vapor or mist contact
162 72, 162 76, 162 83, 435278, D21C 9147, D21H 2502
Patent
active
061030597
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a novel process for modifying lignin-containing materials or similar substances by means of oxidation catalysts and highly effective mediators.
Industrially the most significant is the removal of lignin in the course of the production of pulp.
The sulfate and the sulfite process are to be mentioned as the processes currently chiefly used for pulp production. With both processes, pulp is produced by cooking and under pressure. The sulfate process operates with the addition of NaOH and Na.sub.2 S, while Ca(HSO.sub.3).sub.2 +SO.sub.2 is used in the sulfite process.
In addition, there exist some environmentally friendly cooking processes which operate with organic solvents.
All the processes have the main aim of removing the lignin from the plant material, wood or annual plants used.
The lignin which, with the cellulose and the hemicellulose, makes up the main constituent of the plant material (stem or trunk) must be removed, since otherwise it is not possible to produce papers which are non-yellowing and can be subjected to high mechanical stress.
Wood pulp production processes operate with stone grinders (mechanical wood pulp) or with refiners (TMP), which defibrillate the wood by grinding after appropriate pretreatment (chemical, thermal or chemical-thermal).
These wood pulps still comprise most of the lignin. They are used above all for the production of newspapers, illustrated journals and the like.
The possibilities of the use of enzymes for degradation of lignin have been researched for some years. The action mechanism of such lignolytic systems was clarified only some years ago, when it became possible to obtain adequate amounts of enzyme with the white rot fungus Phanerochaete chrysosporium under suitable growing conditions with additions of inductor. The previously unknown lignin peroxidases and manganese peroxidases were discovered by this research. Since Phanerochaete chrysosporium is a very effective degrader of lignin, attempts were made to isolate its enzymes and to use them in a suitable form for lignin degradation. However, this was not successful, since it was found that the enzymes lead above all to repolymerization of the lignin and not to degradation thereof.
Similar circumstances also apply to other lignolytic enzyme species, such as laccases, which degrade the lignin oxidatively with the aid of oxygen instead of hydrogen peroxide. It was found that similar processes occur in all cases. In fact, free radicals are formed which react with one another again and thus lead to polymerization.
There are thus currently only processes which operate with in vivo systems (fungus systems); the main focal points of optimization experiments are so-called biopulping and biobleaching.
Biopulping is understood as meaning treatment of chopped wood chips with live fungus systems.
There are 2 types of forms of application:
1. Pretreatment of chopped chips before refining or grinding in order to save energy during the production of wood pulps (for example TMP or mechanical wood pulp). Another advantage is the improvement which usually exists in the mechanical properties of the pulp, but a disadvantage is the poorer final whiteness. pulp (kraft process, sulfite process).
The aim here is a reduction in cooking chemicals, improvement in cooking capacity and "extended cooking".
Improved kappa reduction after cooking in comparison with cooking without pretreatment is also achieved as an advantage.
Disadvantages of these processes are clearly the long treatment times (several weeks), and above all the unsolved risk of contamination during treatment if sterilization of the chopped chips, which is uneconomical, is to be dispensed with.
Biobleaching likewise operates with in vivo systems. The cooked pulp (softwood/hardwood) is seeded with fungus before bleaching and is treated for days to weeks. Only after this long treatment time is a significant reduction in kappa number and increase in whiteness found, which renders the process uneconomical for implementation in the usual bleaching
REFERENCES:
patent: 3962033 (1976-06-01), Eriksson et al.
patent: 4002526 (1977-01-01), Brown et al.
patent: 4213821 (1980-07-01), Vanderhoek et al.
patent: 4294653 (1981-10-01), Lindahl et al.
patent: 4830708 (1989-05-01), Paice et al.
patent: 5203964 (1993-04-01), Call
Yang, "Bleaching of eucalyptus kraft pulp with the Enzone process", Yappi J. pp. 91-96, Jul. 1993.
Bio Engineering Apr. 1992, vol. 8, Dr. R.M. Fakoussa.
Alvo Steve
Lignozym GmbH
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