Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carbohydrate or derivative as a reactant
Reexamination Certificate
1999-09-13
2001-06-26
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carbohydrate or derivative as a reactant
C528S271000, C528S300000, C528S301000, C527S300000, C527S604000, C428S035700, C428S221000, C428S357000, C430S031000
Reexamination Certificate
active
06252027
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermally formed article comprising a sugar polymer, a production process thereof, a toner cartridge, and a recording medium, and particularly to a thermally formed article which has biodegradability and recycling ability and is excellent in flexural strength and tensile strength, a production process thereof, a toner cartridge, and a recording medium.
2. Related Background Art
Environmental pollution of the earth is actualized, and not only industrial waste but also domestic refuse requires consideration for the environment. Under such circumstances, plastic resins, which are industrial materials, are also required to be treated so as to lighten a burden imposed on the environment. Alternatively, there is a demand for development of new materials which scarcely impose a burden on the environment and can be disposed.
The conventional methods for treating waste plastics are methods comprising degrading the waste plastics into low-molecular weight products by, for example, thermal cracking or chemical decomposition, and incinerating or burying the low-molecular weight products. However, the incineration is accompanied by exhaust of carbon dioxide and hence results in a cause of warming of the earth. When halogens, sulfur and/or nitrogen elements are contained in the resins, there is a possibility that the incineration may cause air pollution due to harmful gases. When the waste plastics are buried, almost all resins now practically used remain for a long period of time as they are. Additives and the like in the resins run out during this period to cause soil pollution.
In order to cope with such problems, the development of biodegradable polymers is actively conducted as polymers which do not adversely affect the global environment and the like upon the final disposal thereof (for example, Japanese Patent Application Laid- Open No. 5-287043). Biodegradable resins are roughly classified into three types: microbially produced products, natural products derived from plants and chemically synthesized products. An example of the microbially produced products is polyester copolymer of D-3-hydroxy-butyrate and 3-hydroxyvalerate by
Alcaligenes eutroplus
, which is marketed under the trade name of “Biopol”. These products are biodegraded by microorganisms.
Examples of the natural products include collagen, gelatin, starch, cellulose and chitosan. These products have biodegradability by themselves. Further, mixtures of starch and modified polyvinyl alcohol, cellulose esters obtained by chemically modifying cellulose, complexes of cellulose and chitosan, and the like are also known. In the chemically synthesized products, water-soluble polymers such as polyvinyl alcohol, polyethylene glycol, aliphatic polyesters such as polyethylene adipate and polycaprolactone, and the like exhibit biodegradability.
On the other hand, from the viewpoint of effective utilization of resources, it is known to reuse low-molecular weight products derived from waste plastics as raw materials for polymers. For example, polystyrene is recovered as a styrene monomer and a styrene dimer by catalytic cracking using a solid base catalyst to supply them as raw materials for repolymerization; and polyethylene terephthalate is degraded into dimethyl phthalate, ethylene glycol, terephthalic acid, etc. by a methanolysis process using methanol, a glycolysis process using ethylene glycol or a hydrolysis process using an acid or base, and these products are utilized as raw materials for polyethylene terephthalate, or other chemicals. However, in order to take out reusable components in these cases, it is necessary to fractionate and purify degradation products through many processes. As biodegradable polymers which can solve such a problem, the present applicant et al. disclosed sugar polymers, which can be biodegraded particularly by enzymolysis and permit effective reuse of the degradation products, in EP 814093A2.
Kurita et al. (Journal of Polymer Science: Polymer Chemistry Edition, 18, 365-370, 1980) describe copolymers of cellobiose with adipic acid or phthalic acid.
SUMMARY OF THE INVENTION
The development of these biodegradable plastics has been advanced to date from the viewpoint of biodegradability. The present inventors have evaluated the thermal formability of the copolymer of cellobiose and adipic acid disclosed by Kurita et al. with respect to the prediction that easiness in thermal forming and high strength of thermally formed articles will be required in order to spread such biodegradable plastics as substitutes for the conventional plastics. It has been then found that the copolymer has no softening point at any temperature lower than the decomposition point thereof and exhibits no thermoplasticity due to the little effect of adipic acid on internal plasticization. Similarly, with respect to the copolymer of cellobiose and phthalic acid, it has a decomposition point alone, and does not exhibit thermoplasticity due to strong interaction between polymeric main chains by the presence of an aromatic ring like phthalic acid.
The present inventors have thus carried out a further investigation. As a result, it has been found that substances which are easy to form thermally and provide thermally formed articles having excellent strength are included among the biodegradable sugar polymers described in EP 814093A2 filed by the present applicant et al.
The present invention has been completed on the basis of such findings, and an object thereof is to provide a biodegradable thermally formed article having excellent strength.
Another object of the present invention is to provide a process for producing a thermally formed article having excellent strength from a biodegradable polymer.
A further object of the present invention is to provide a toner cartridge and a recording medium which have excellent strength and can be disposed with a small burden on the global environment.
According to one aspect of the present invention, there is thus provided a thermally formed article comprising a sugar polymer represented by the following general formula:
wherein G is a residue of a monosaccharide, oligosaccharide or polysaccharide, R is a linear or branched alkylene group having at least 4 carbon atoms when G is the residue of the monosaccharide, or a linear or branched alkylene group having at least 6 carbon atoms when G is the residue of the oligosaccharide or polysaccharide, and n is an integer of 1 to 5,000.
The present inventors have carried out various investigations as to sugar-containing polymers. As a result, it has been found that the compounds represented by the general formula (I) have excellent thermoplasticity, thus leading to completion of the present invention. The sugar polymers represented by the general formula (I) each have a softening point at a temperature lower than the decomposition point thereof and hence permit producing excellent thermally formed articles.
In the general formula (I), G represents a residue of a monosaccharide, oligosaccharide or polysaccharide. When G is the residue of the monosaccharide, R is preferably a linear or branched alkylene group having at least 4 carbon atoms, preferably 4 to 14 carbon atoms, more preferably 4 to 10 carbon atoms. When G is the residue of the oligosaccharide or polysaccharide, R is preferably a linear or branched alkylene group having at least 6 carbon atoms, preferably 6 to 14.carbon atoms, more preferably 6 to 10 carbon atoms. These alkylene groups may be substituted by, for example, a methyl or ethyl group, or the like.
n is an integer of 1 to 5,000, preferably 50 to 2,000. G represents a sugar residue and may be trisubstituted or more highly substituted.
The sugar residue preferably forms an ester linkage when it is a residue of a sugar containing only hydroxyl groups, or an amide linkage and/or an ester linkage when it is a residue of an amino-group-containing sugar.
The sugar residue is preferably a residue of a monosaccharide, oligosaccharide or polysaccharide cont
Kikuchi Yoshihiko
Mihara Chieko
Minami Masato
Takeda Toshihiko
Acquah Samuel A.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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