Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Process of treating scrap or waste product containing solid...
Reexamination Certificate
2000-02-16
2001-02-20
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Process of treating scrap or waste product containing solid...
C424S234100, C528S491000, C528S492000
Reexamination Certificate
active
06191176
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to polymeric materials and more particularly to polyesters, as well as methods for making and degrading polyesters. The invention also relates to a mixed culture of microorganisms that is able to degrade polymers containing a hydrolyzable backbone polyester and a method for making this mixed culture of microorganisms.
The majority of plastic materials available today are made from petroleum. Such petroleum-based plastics are difficult to degrade, biologically or otherwise. Because of the extensive use of petroleum-based plastics by both consumers and industry, a considerable amount of waste is created. This causes ecological problems because the waste is stored in landfills and other waste disposal systems and accumulates without degradation. Furthermore, petroleum is an expensive component of plastic.
Biodegradable polymers have been synthesized to provide alternatives to petroleum-based plastics. They are often synthesized from starch, sugar, natural fibers or other organic biodegradable components in varying compositions. However, such biodegradable polymers often lack desirable physical characteristics, and this limits their use to specific situations. Many biodegradable polymers are blended polymers or composite polymers and thus do not have uniform mechanical properties. Still further, most known biodegradable polymers are aliphatic polyesters that have low softening points (T
m
), which prevents their use as a material in a variety of fields.
In order to overcome the deficiencies found with conventional plastics and biodegradable polymers, a degradable polymer having enhanced strength and flexibility and a method for making such a degradable polymer are needed for a variety of applications. Still further, a polymer that is made from organic substances rather than petroleum-based compounds and a method for making this polymer are needed. In addition, certain formulations of this polymer should be biodegradable. A mixed culture of microorganisms that can be used to degrade the polymers of the present invention and other polymers and a method for making this mixed culture are also needed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide degradable polymers having uniform mechanical properties and high softening points allowing them to replace petroleum-based plastics for various applications and a method for making such polymers in order to avoid the use of petroleum-based plastics and the waste generated by using such compounds.
It is a further object of the present invention to provide a mixed culture of microorganisms that can completely degrade different polyesters into respiratory gases and biomass and a method for making this mixed culture so that waste can be removed from the environment.
Another object of the present invention is to provide non-toxic degradable polymers and a method for making these polymers so that they can be used in the human body as drug-loaded matrices, surgical thread and surgical implants.
Still another object of the present invention is to provide biodegradable polymers having physical strength so that they can be used as a packaging material that can be disposed of by degradation.
According to the present invention, the foregoing and other objects are achieved by a thermoplastic main chain aliphatic polyester, a thermoset heterochain polyester, or a thermoset heterochain aromatic polyester. Each of these polymers are embodiments of the present invention that are made by reacting various organic compounds with blocked glutamic acid. The thermoplastic main chain aliphatic polyester is made by reacting diol with blocked glutamic acid. The thermoset heterochain and thermoset heterochain aromatic polyesters are formed by reacting an epoxy compound with blocked glutamic acid. All of these polyesters can be hydrolyzed into monomers when treated with certain biological catalysts such as the enzyme lipase. Furthermore, the thermoplastic main chain aliphatic polyester and the thermoset heterochain polyester can be completely degraded into respiratory gases and biomass using certain mixed cultures of microorganisms. One such mixed culture of microorganisms, which is an embodiment of the present invention, is comprised of the mixture of
Rhizopus chinesis, Rhizopus delemar, Penecillium pinophilum, Aspergillus niger
and
Pseudomonas aeruginosa
. The polyesters of the present invention may be used in medical applications, agricultural applications, packaging applications, packing applications, and any other applications where plastics are used.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
REFERENCES:
patent: 4446257 (1984-05-01), Kooifmans et al.
patent: 4536525 (1985-08-01), Freese et al.
patent: 5521011 (1996-05-01), Ishidoya et al.
patent: 5606009 (1997-02-01), Sakashita et al.
patent: 5614585 (1997-03-01), Matsukawa et al.
patent: 5686540 (1997-11-01), Kakizawa
patent: 5756650 (1998-05-01), Kawamonzen et al.
patent: 5844066 (1998-12-01), Kakizawa
Tadros Raef M.
Timm Delmar C.
Acquah Samuel A.
Board of Regents of University of Nebraska
Shook Hardy & Bacon LLP
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