Chemistry: natural resins or derivatives; peptides or proteins; – Lignins or derivatives
Reexamination Certificate
1999-06-04
2001-01-09
Nutter, Nathan M. (Department: 1711)
Chemistry: natural resins or derivatives; peptides or proteins;
Lignins or derivatives
C530S504000, C524S072000, C524S073000, C106S164010, C106S164400, C106S165010
Reexamination Certificate
active
06172204
ABSTRACT:
BACKGROUND OF THE INVENTION
This application relates to preparing compositions based upon lignin derivatives.
Lignin is a naturally occurring polymeric material found in the cell walls of vascular plant material such as wood. Processes such as chemical pulping to produce paper, bioethanol generation, and production of chemicals and pharmaceuticals from plant expression systems result in the formation of lignin derivatives as by-products. Lignin derivatives are materials resulting from a physico-chemical modification of the native biopolymer that facilitates their removal from the vascular plant cell walls. Because these derivatives have poor mechanical properties, they typically are either discarded or, in the case of paper-making operations, used as fuel for the pulp mill.
SUMMARY OF THE INVENTION
In general, the invention features a composition that includes the reaction product of a lignin derivative and a reactant selected from the group consisting of alkylating agents, acylating agents, and combinations thereof, in which the reaction product has a measurable cohesive strength. A “measurable cohesive strength” means that when a specimen is subjected to a tensile strength test performed in accordance with ASTM Standard Test Method D 638-97 (as modified according to the Examples, described infra), the specimen exhibits a value sufficiently high such that it can be detected and recorded. In contrast, materials such as free-flowing powders lack a measurable cohesive strength.
The composition further includes a plasticizer in an amount sufficient to cause the composition to exhibit plastic deformation in response to an applied tensile stress. Such compositions are prepared by blending the plasticizer with the reaction product. “Plastic deformation” refers to a phenomenon in which the deformation exhibited by the specimen is a function of the applied tensile stress and remains upon release of the stress.
The particular amount of plasticizer required for plastic deformation depends upon a number of factors, including the particular plasticizer and reaction product. In general, however, the amount of plasticizer is no greater than about 50% by weight, preferably no greater than about 40% by weight, and, more preferably, no greater than about 30% by weight, where all weight percentages are based upon the total weight of the composition.
Examples of suitable alkylating agents for reaction with the lignin derivative include diazomethane, dialkyl sulfates such as diethyl sulfate, and combinations thereof. Examples of suitable acylating agents for reaction with the lignin derivative include acid anhydrides, acyl halides, and combinations thereof. More than one reactant may be reacted with the lignin derivative. For example, a first alkylating agent may be reacted with the lignin derivative to form an alkylated lignin derivative, which is then reacted with a second alkylating agent, different from the first alkylating agent, to form the reaction product. Similarly, combinations of different acylating agents may be reacted, as well as combinations of acylating and alkylating agents, to form the reaction product. Where a combination of an acylating and an alkylating agent are employed, it is preferable to react the acylating agent first, followed by the alkylating agent.
Examples of suitable plasticizers include polyalkylene esters, polyalkylene glycols, and derivatives thereof. Examples of useful polyalkylene esters include poly(1,4-butylene adipate) and poly(trimethylene glutarate). Examples of useful polyalkylene glycols, and derivatives thereof, include polyethylene glycol, poly(ethylene glycol) methyl ether, and the reaction product of poly(ethylene glycol) and a Bisphenol A diglycidyl ether. In general, polyalkylene esters, polyethylene glycols, and derivatives thereof are particularly useful where the lignin derivative is reacted with an alkylating agent, whereas polyalkylene glycols and derivatives thereof are particularly useful when acylating agents are used.
Examples of suitable lignin derivatives include derivatives prepared according to a process that includes subjecting a lignin-containing biomass (e.g., plant material) to a lignin-removing process selected from the group consisting of the kraft, organosolv, steam explosion, soda, and autohydrolysis extraction processes. Lignin derivatives prepared according to the kraft pulping process and the organosolv pulping process are particularly useful. Preferably, the product of the lignin removal process is filtered, e.g., in alkaline solution, with an ultrafiltration membrane having a molecular weight cut-off of at least about 10,000 daltons.
The invention provides plasticized compositions based upon alkylated and acylated lignin derivatives having useful mechanical properties. Accordingly, the invention provides a useful application for the lignin-containing by-products of commercial processes.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims.
REFERENCES:
Li et al., “The First 85% Kraft Lignin-Based Thermoplastics*”,J. Poly. Sci.: Part B: Poly. Physics, 35:1899-1910 (1997).
Li et al., “Towards A New Generation Of Lignin-Based Plastics”,Proc. 8thInternat. Symp. Wood Pulp Chem. I, p. 705-12 (1995).
Li Yan
Sarkanen Simo
Fish & Richardson P.C. P.A.
Nutter Nathan M.
Regents of the University of Minnesota
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