Stock material or miscellaneous articles – Composite – Of carbohydrate
Reexamination Certificate
1999-10-25
2001-08-28
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of carbohydrate
C527S400000, C527S403000, C435S101000, C524S073000, C524S074000
Reexamination Certificate
active
06280855
ABSTRACT:
This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/FI98/00021 which has an International filing date of Jan. 14, 1998, which designated the United States of America.
The present invention relates to an intermediate product for the preparation of polymerizates from lignin derivatives formed during pulping as well as to the use of said intermediate products in the production of wood materials.
In DE 37 992 C2, a process is described for the preparation of a binding agent for woodbased materials using phenolic substances, particularly lignin sulphonate, wherein enzymes are added to the phenolic substance for the purpose of activation, the enzymes polymerizing phenols oxidatively by a radical mechanism whereby the phenolic substance becomes an active binding agent. It is, indeed, previously known that this reaction takes place in the presence of oxygen, e.g. the oxygen in air, but such an activated binding agent has not been implemented previously for a longer period of time or by intensive aeration with oxygen.
It was unexpectedly found that lignin derivatives from the cellulose industry, such as kraft lignin or lignin sulphonate, when reacted intensively with oxygen, air, or other chemical oxidizing agent, or when the reaction is of long duration, form as an intermediate product a lignin product particularly capable of reacting. This intermediate product can be isolated and stored for longer periods, and it reacts with further, unactivated lignin derivatives to form a macromolecular polymerizate. The intermediate product can be characterized by reacting the material with laccase. After this reaction it has a typical ESR spectrum with a phenoxy radical signal in the region of about 3400 gauss, which signal, however, being a typical radical signal, does not remain unchanged in the long run. Unexpectedly, however, the higher reactivity of the intermediate product remains constant even after longer periods, such as months. Thus, this activated intermediate product is significantly more active when reacting with phenol-oxidizing enzymes than unpretreated lignin derivatives wherefore it forms the typical ESR spectrum with essentially greater intensity than lignin derivatives which have not been pretreated in this manner.
The intensity of the signal of the activated intermediate product is at least more than five times that of the signal of the lignin derivative serving as feedstock. The signal is measured, for instance, under the following conditions: 77° C.; 9.5 GHz, ESR attenuation 20 dB, mod. freq. 100 MHz; mod. amplitude 4.0 gauss.
The activated intermediate product can be obtained by treating technical lignin, such as lignin sulphonate, kraft lignin, organosolvlignin, acetosolvlignin or ASAM lignin, which are obtained from cellulose production, for a fairly long time in the presence of enzymes capable of oxidizing phenolic groups with air or oxygen. Already after a period of about three hours, particularly, however, after twenty hours, an increase in the phenoxy radical signal can be observed. When air or oxygen under pressure is introduced, the increased signal will appear after a considerably shorter period of time, for instance after 30 min.
The intermediate product can also be obtained by means of chemical oxidizing agents. For this purpose, agents common in lignin chemistry, such as potassium permanganate, bichromates or ozone may be used.
The enzymatic formation of the activated intermediate product is only possible in the presence of greater amounts of oxygen. Because only 9 mg/l of oxygen is dissolved in water in room temperature, the formation of the intermediate product is only enhanced by an increased supply of oxygen, either by aeration or by adding oxidizing agents.
Even when the oxygen balance is set for a longer period of time, a sufficient amount of oxygen may after a while have affected the lignin derivative.
In this connection it has emerged that such an amount of oxygen should be incorporated in the lignin-containing system that an essentially complete oxidation of the lignin is attained under the reaction conditions used. This need for oxygen, depending on the lignin used, was calculated as being 0.5 to 20 mg O
2
/g lignin, preferably 1 to 10 mg. In principle, however, it is of advantage to use excess oxygen.
The activated intermediate product will react in the presence of enzymes which oxidize phenolic groups for instance with unactivated lignin derivatives such as are obtained from, e.g. cellulose production, when polymeric lignin products are being formed, whereby the molar masses obtained are essentially higher than those obtained when enzymes capable of oxidizing phenols are allowed to affect lignin derivatives without the presence of activated lignin derivatives.
They are usually at least twice as high.
The lignin polymers obtained by polymerizing lignin derivatives in the presence of active intermediate products are suited for use when highly active binding agents for wood materials are produced.
REFERENCES:
patent: 4432921 (1984-02-01), Haars et al.
patent: 5846788 (1998-12-01), Pedersen et al.
patent: 6072015 (2000-06-01), Bolle et al.
patent: 6187136 (2000-02-01), Pedersen et al.
patent: WO 95/08588 A1 (1995-03-01), None
patent: WO 95/23232 A1 (1995-08-01), None
Hase Anneli
Niku-Paavola Marja-Leena
Qvintus-Leino Pia
Viikari Liisa
Acquah Samuel A.
Birch & Stewart Kolasch & Birch, LLP
Neste Chemicals Oy
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