Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2002-02-13
2003-09-16
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C528S025000, C528S026000, C528S029000, C528S030000, C528S039000, C428S451000
Reexamination Certificate
active
06620516
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an organic domain/inorganic domain hybrid material. More particularly, the present invention is concerned with an organic domain/inorganic domain hybrid material comprising: an organic domain comprising at least one water-soluble or water-dispersible organic polymer having functional groups, and an inorganic domain, the organic domain and the inorganic domain being ionically bonded to each other though the functional groups of the organic polymer to form an ionically crosslinked structure, the inorganic domain comprising inorganic bridges, each of which independently comprises at least one silicon (Si) atom, at least two oxygen (O) atoms and at least two divalent metal atoms, wherein the silicon atom(s) and the oxygen atoms together form at least one —O—Si—O— linkage which is arranged longitudinally of the inorganic bridge, wherein each terminal of the inorganic bridge comprises the divalent metal atom, wherein the divalent metal atom is ionically bonded to the —O—Si—O— linkage of the inorganic bridge and to the functional group of the organic polymer, wherein the weight ratio of the organic domain to the inorganic domain is at least 1.0. The organic domain/inorganic domain hybrid material of the present invention is advantageous not only in that the material exhibits excellent water absorptivity, but also in that the material exhibits a characteristic wherein decomposition and regeneration of the material occur depending on pH (hereinafter, such a characteristic is frequently referred to as “pH-response property”), so that the material can be easily decomposed into the components thereof. Therefore, when the hybrid material of the present invention is used as a water absorptive material and the like, not only can the material after use be easily disposed by decomposing the material, but also the components obtained by decomposition of the material can be easily recycled, so that the hybrid material is advantageous from the viewpoint of prevention of environmental destruction and efficient utilization of resources.
2. Prior Art
Organic polymeric materials having excellent hydrophilicity have been widely used in the fields related to disposable diapers, sanitary products and the like, and the amount of use of such materials has been increasing. However, these hydrophilic polymeric materials generally become gels after use and, hence, currently, the materials (in the form of gels) after use are disposed by incineration. Therefore, from the viewpoint of the protection of environment and efficient utilization of resources, it has been expected to develop simple and economical methods for disposal and recycling of the materials.
Generally, with respect to the water absorptive materials composed only of organic polymers, the organic polymers are crosslinked through organic chemical bonds. Therefore, it has been difficult not only to decompose the materials into polymer chains, but also to regenerate the decomposed materials.
Recently, vigorous studies have been made on hybrid materials comprising a combination of at least two materials having different properties, because such hybrid materials exhibit excellent properties which cannot be obtained by a single material. Particularly, hybrid materials comprising a combination of an organic polymeric material and an inorganic material have been attracting much attention. Especially, the so-called “nano-composite material” comprising a hybrid of an organic polymeric material and an inorganic material, in which one of the organic polymeric material and the inorganic material is present in the form of nanometer-size domains, exhibits novel properties ascribed to its unique structure, and, hence, the development of applications of such nano-composite material is expected.
As examples of widely known nano-composite materials, there can be mentioned a hybrid material obtained by uniformly dispersing a lamellar silicate (e.g., clay) as an inorganic material in a polyamide resin as an organic polymeric material (see A. Usuki et al., J. Mater. Res., 8, [5], 1179 (1993)) and a material composed mainly of silica or composed mainly of an organic molecule, in which respective nano-size particles of silica and an organic molecule are mutually. finely dispersed, and which is produced by subjecting a silicon alkoxide as a raw material to sol-gel process in the presence of an organic molecule (oligomer or polymer) to form a silica (see Novak, M., Adv. Mater. 5,422 (1993) and Chujo, Y., and Encyclp. Poly. Sci. Tech., CRC Press, Boca Raton, 6, 4793 (1996)). In these documents, it is described to improve the mechanical properties of nano-composite materials or to produce an intermediate of a porous silica; however, these documents do not disclose a technique to produce a hybrid material exhibiting a high hydrophilicity.
Therefore, studies have been made to produce a hybrid material having a high hydrophilicity. For example, a hybrid material composed mainly of an inorganic material, in which a water-soluble polymer (such as polyacrylic acid or polymethacrylic acid) is intercalated between the layers of calcium silicate hydrate, has been developed (see H. Matsuyama et al., Chemistry of Materials, 11, [1], 16-19 (1999)). With respect to this hybrid material, the hybrid material which has absorbed water can be liquefied by adjusting the pH of the hybrid material to a high acidity side, so that decomposition of the material and recycling of the components obtained by decomposition of the material can be easily conducted. The material also has hydrophilicity. However, even when the hybrid material is produced using a large amount of water-soluble polymer, a part of the water-soluble polymer does not participate in the reaction for forming the hybrid material, so that the organic polymeric material/calcium silicate hydrate weight ratio of the hybrid material becomes less than 1 and, hence, the hybrid material does not exhibit satisfactory water absorptivity.
Further, with respect to a hybrid material exhibiting water absorptivity, Unexamined Japanese Patent Laid-Open Specification No. 12-051690 discloses, as a material for absorbing a salt-containing liquid, a hybrid material composed of a water-soluble polymer and clay or a synthetic calcium silicate. In the hybrid material obtained by the technique of the this patent document, the water-soluble polymer and the inorganic material (clay or a synthetic calcium silicate) are present in the form of a mixture of micro-size particles of the water-soluble polymer and the inorganic material; however, an extremely small amount of chemical linkages are formed between the polymer and the inorganic material. Specifically, the amount of the polymer chemically bonded to the inorganic material is less than 1 in terms of the weight ratio of the polymer (chemically bonded to the inorganic material) to the inorganic material. Further, in this hybrid material, the formation of the dispersion of the micro or nanosize inorganic material particles is not sufficient for the hybrid material to become transparent when the hybrid has absorbed water. Therefore, by the technique of this prior art document, it is impossible to obtain a hybrid material having excellent pH-response property (i.e., property to respond quickly to the change of pH) as well as high water absorptivity.
Further, for the purpose of developing an organic polymer type ameliorant for soil. Unexamined Japanese Patent Laid-Open Specification No. 10-330749 discloses a technique in which silicon is introduced into a water-soluble polymer by forming a covalent bond between the polymer and silicon, and the resultant silicon/polymer hybrid is crosslinked with calcium or the like. However, this technique only intends to obtain a material having excellent acid resistance and alkali resistance, and the material obtained by this technique does not exhibit a pH-response property.
SUMMARY OF INVENTION
In this situation, the present inventors have made extensive and intensive
Kurihara Masa-aki
Matsuyama Hiroyoshi
Asahi Kasei Kabushiki Kaisha
Dawson Robert
Zimmer Marc S
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