Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
1995-02-07
2001-05-08
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of silicon containing
C501S141000, C428S035600, C206S814000, C106S681000
Reexamination Certificate
active
06228501
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a porous body of polysaccharide or polysaccharide-clay composite as a material compatible with the global environment, and a process for its production.
2. Discussion of Background
Heretofore, plastic materials such as foamed styrols (polystyrenes) or styrene papers, have been widely used as shock-absorbing materials, heat insulation materials or sound-absorbing materials, since they are light in weight and inexpensive.
However, such conventional plastic materials are made of petroleum extracted by a man power from a deposit deep in the earth's crust, and they are typical materials which cause pollution to the global environment in such a way that at the time of incineration after their use, they produce a high temperature heat to damage incinerators and generate a large amount of CO
2
gas. Further, such plastic materials are likely to cause pollution to rivers or sea shores when left without being incinerated. To avoid such pollution to the global environment, a study is being conducted on readily degradable plastic materials such as biodegradable or photodegradable plastic materials.
However, up to now, there has been no material which is satisfactory for practical use, and it is still desired to develop a material which can be substituted for conventional plastic materials.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to overcome the drawbacks of conventional plastic materials such as foamed styrols or styrene papers and to provide a new material which is made solely of raw materials which are compatible with the global environment, which can easily be recovered and reused, which, when disposed, can readily be assimilated into natural soil and taken into the ecosystem, which is further effective for shock absorption, heat insulation or sound absorption and which can be substituted for plastic materials such as foamed styrols or styrene papers, as well as a process for producing such a new material.
The present invention provides a porous body of polysaccharide or polysaccharide-clay composite having fine pores, consisting essentially of a freeze-dried product of (a) an aqueous solution of at least one polysaccharide selected from the group consisting of starch, sodium alginate and carboxymethyl cellulose, or its derivative, or (b) a composite sol comprising such an aqueous sol and a clay sol.
Further, the present invention provides a process for producing a porous body of polysaccharide or polysaccharide-clay composite having fine pores, which comprises rapidly freezing (a) an aqueous solution of at least one polysaccharide selected from the group consisting of starch, sodium alginate and carboxymethyl cellulose, or its derivative, or (b) a mixed sol comprising such an aqueous solution and a clay sol, and vacuum drying the frozen product without melting ice.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As mentioned above, the present invention provides a porous body of a natural polysaccharide or its derivative, or a porous body of a composite of such a natural polysaccharide or its derivative with clay. Such a porous body is useful as a shock-absorbing material, a heat insulation material or a sound-absorbing material, as a substitute for conventional plastic materials.
This porous body is produced by freezing and vacuum drying as mentioned above. Preferably, the freezing is carried out rapidly at an average freezing rate of at least 1×10
−2
ml/sec. If the freezing rate is too low, it will be difficult to form a porous body with strength sufficient for practical use. Further, with the porous body of the present invention, it is possible to control the compression strength of the material by changing the ratio of the natural polysaccharide or its derivative to the clay.
The natural polysaccharide or its derivative to be used in the present invention is at least one member selected from the group consisting of starch, sodium alginate and carboxymethyl cellulose, and their derivatives including esters, ethers, hydrolyzates and oligomers which can be obtained by conventional modifications or conversions. As the clay, a natural clay such as montmorillonite, saponite, beidellite, kaolinite, allophane, or bentonite, or a synthetic clay prepared by chemically modifying or changing such a natural clay, may be employed. Depending upon the particular purpose, a natural fiber such as paper pulp, hemp or cotton, a coloring matter or a perfume may be added. With respect to mixing of the polysaccharide and the clay, an aqueous solution of the polysaccharide with a solid to liquid ratio of from 1:5 to 1:30 and a sol of the clay with a solid to liquid ratio of about 1:20 are preferably mixed in a weight ratio of from 20:80 to 70:30.
REFERENCES:
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patent: 4448914 (1984-05-01), Drinkuth et al.
patent: 4629713 (1986-12-01), Suzuki et al.
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patent: 5078793 (1992-01-01), Caton
patent: 5165915 (1992-11-01), Tokubo et al.
patent: 5208267 (1993-05-01), Neumann
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patent: 5288765 (1994-02-01), Bastioli
patent: P 38 05 852 A1 (1989-09-01), None
patent: 2 063 911 (1971-07-01), None
Clay Science 6, pp. 269 to 276 (1987), No month.
Derwent-Abstract 88-312169/44 of JP 63230581, No date.
Derwent-Abstract 85-239485/39 of JP 60155526, No date.
Derwent-Abstract 85-214256/35 of JP 60137813, No date.
German Office Action for German Patent Application No. 195 04 899. 7-44, dated Oct. 15, 1996 with English Translation.
Trans. Mat. Res. Soc. JPN., vol. 18A, pp. 157 to 160 (1994) (No month).
JICST-EPLUS-ABSTR. 940926684, 1994, (No month).
Nakazawa Hiromoto
Ohta Shun-ichi
Jones Deborah
National Institute for Research in Inorganic Materials
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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