Chemistry: natural resins or derivatives; peptides or proteins; – Lignins or derivatives – Compound containing nitrogen attached directly or indirectly...
Reexamination Certificate
2000-10-12
2003-07-15
Acquah, Samuel A. (Department: 1711)
Chemistry: natural resins or derivatives; peptides or proteins;
Lignins or derivatives
Compound containing nitrogen attached directly or indirectly...
C530S506000, C530S507000, C527S400000, C527S603000, C524S076000
Reexamination Certificate
active
06593460
ABSTRACT:
The present invention relates to a method catalyzed through enzymes for the production of lignin graft polymer in solutions in which the polymerization product yield under the effect of organic peroxide combinations is high. The formation of undesirable, non-grafted side components is extensively suppressed. Furthermore the invention also covers lignin graft polymerization products produced according to the above-mentioned method with improved biological degradation as well as their utilization as building blocks in condensation resins, as binding and agglomeration media, as thickening media, as auxiliary products in petroleum drilling (drill rinsing fluid) and conveying, as a suspension and dispersion medium, as well as an auxiliary medium in textile and fiber upgrading.
Lignin is a high-molecular material which occurs in lignifying plants and is produced as a side product in the production of cellulose. Depending on the type of wood, the molecular structure of the lignin varies, i.e. the phenyl propane structure varies in the quantity of methoxy and hydroxy groups. Only a small portion of the lignin is water soluble, and the much greater, non-water-soluble portion can be extracted through solvents such as acetone or dioxane for example. The technical production utilizes mainly the alkaline or sulfite fusion process of wood, in which the water-soluble alkali or lignin sulfonates are produced as well as the organosolve process, in which the lignin is extracted from the wood by means of a mixture of solvent and water. The molecular weight of lignin lies in a range of 1000 to 150,000.
Since most of the lignin has always been burnt up in cellulose plants in order to obtain energy, many modification attempts were made in the past in order to provide a wider utilization for this occurring raw material. Processes in which a combination with synthetic polymerization products in form of graft polymers were realized were of particular interest.
Thus U.S. Pat. No. 4,687,828 describes high-molecular lignin graft polymers which are produced in polar, aprotic solvents with the utilization of the monomeric acrylamide and acrylamido-methylpropane sulfonic acid in a nitrogen atmosphere. As an initiator system a combination of calcium chloride, sulfuric acid, cer(IV) salt and auto-oxidation products of the dioxane (hydroperoxide) are used.
After a reaction period of 2 days at 30° C. the polymerization product is precipitated and separated in a non-solvent. Polymerization product with greater purity and improved solubility are obtained by renewed solving in water, dialysis during several days and freeze-drying. No information is given on the grafting degree, but from the examples it appears that only about 40% in weight of the lignin mass used is recovered, and the loss in monomer ranges within an extraction loss of approximately 80%. Other monomer types are not used in this method. Graft polymerizates are proposed for utilization as thickeners, flooding polymers and drill rinsing additives.
J. J. Meister et al report on the synthesis and characterization of radically polymerized lignin/acrylamide graft polymers [Journal of Polymer Science; Polymer Chemistry Edition, Vol. 22, 1963-1980 (1984)]. The graft polymerizates produced according to the method of U.S. Pat. No. 4,687,828 contained between 19 and 49% in weight of non-grafter homopolymer.
EP 442 508 A1 discloses a method for the production of graft polymerization products from lignin or lignin-containing wood pulp and non-saturated acrylate or methacrylate monomers which carries out the graft reaction in a solution excluding oxygen in the presence of halogen salt and a hydrogen peroxide initiator. Grafting is to produce fillers and reinforcers compatible with plastics. To separate side products the mixture of grafted and non-grafted components is dialyzed, the product yield varies considerably. No information is given concerning the degree of grafting or the grafting yield, since the substances are not separated. Non-lignin components remain in any case non-grafted.
WO 94/01488 teaches a method for enzymatic polymerization/modification of lignin or lignin-containing materials in water with peroxide and hydrogen peroxide at alkalic pH values, without using organic solvents. The lignin thus modified has a higher molecular weight and is used as binding material for wood particle boards. Polymerization in the presence of synthetic monomers is not described.
A method of lignin grafting which is a considerable improvement over the state of the art is described in DE 43 31 878 A1. Using radically oxidized enzymes, all organic combinations containing at least three carbon atoms and one oxygen, nitrogen or multiple binding function can then be grafted on lignin in water, organic solvents or water/solvent mixtures. As a result it becomes possible for the first time to make graft polymers from lignin, unsaturated monomers and other organic combinations. The reaction times are shorter than with other grafting methods and no inert gas atmosphere is needed. As a substrate, hydrogen peroxide is supplied for peroxidases and oxygen for phenoloxidases. The polymerization product yield is low and amounts to only 26% according to example 4. The grafting yield is also low with this enzymatic polymerization method.
No enzymatic lignin grafting method is known in the state of the art which combines the advantages of this method with increased polymerization product or grafting yield.
The task was therefore to find a method for the enzymatic grafting of lignin, lignin-containing substances and lignin sulfonates, making it possible to obtain higher grafting yields or at least higher polymerization product yields than in the state of the art, in particular than DE 43 31 878 A1 and through which it is possible to carry out the technical methods within acceptable reaction times. A further task of the invention was to prepare graft products from lignin, lignin-containing substances and lignin sulfonates with hydrophilically neutral, anionic, cationic unsaturated monomers and/or other organic combinations which make possible utilization in water or an aqueous fluid, and are amenable to biological decomposition.
The task is accomplished surprisingly in that the graft polymerization catalyzed through oxidizing enzymes is carried out on lignin in the presence of organic peroxides/hydroperoxides. In this method surprisingly neither the enzymes are damaged by the organic peroxides nor is the homopolymer portion increased, as may be expected when peroxidic initiators are added. By comparison with the utilization of hydrogen peroxide or oxygen, it is possible to note a clear increase in the polymerization yield and the portion of grafted monomer in the graft polymer increases. It is obviously and surprisingly possible to reduce the peroxide to a much lesser degree through the utilization of the combination of organic peroxides and oxidizing enzymes.
The yield in graft polymerization product according to the method of the invention is high and amounts preferably to more than 50% in weight, and more preferably over 60% in weight and most preferably over 75% in weight.
The graft polymerization products have an unexpected suitability for biological decomposition which is apparent through a decomposition of the molecular weight following the action of basidomycetes causing pocket rot. Following an incubation time of 48 days, the molecular weight is reduced by at least 50% through biological decomposition.
The utilization of organic peroxides with the enzymatic grafting has proven to be a decisive factor in increasing the grafting yield. Assuming its solubility in the solvent or solvent mixture used for grafting, the organic peroxides are used in quantities, as related to the monomers used, of 0.01 % in weight to 10% in weight, preferably of 0. 1% in weight to 5% in weight and most preferably of 0.25% in weight to 1.5% in weight. Organic aliphatic, cyclo-aliphatic and aromatic peroxides to be mentioned as examples are t-butylhydroperoxide, mono and dihydroxyperoxide of di
Hüttermann Aloys
Mai Carsten
Acquah Samuel A.
Proskauer Rose LLP
Stockhausen GmbH & Co KG
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