Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-05-11
2003-07-15
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S417000, C524S556000, C524S557000, C524S564000
Reexamination Certificate
active
06593408
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an organic polymer/inorganic fine particle-dispersed aqueous solution having excellent dispersion stability, a composite, production processes therefor and uses thereof.
BACKGROUND ART
In organic, inorganic and metallic base materials, materials having characteristics which can not be achieved by a single material can be produced by compounding thereof, and it is just an ordinary method in development of materials in these days. For example, a fiber-reinforced plastic material (FRP) obtained by compounding a glass fiber with a polymer has a strength which can not be achieved only by the polymer alone. On the other hand, observing this material from a glass fiber side, we can take a viewpoint that a glass fiber which is fragile and has poor processability in itself is turned into a material having moldability by compounding with a polymer. Thus, compounding makes it possible to allow functions and performances which can not be achieved by a single material to be revealed by making the best use of the characteristics of the respective base materials or making up the defects thereof. In conventional compounded materials, a size of a disparate material (dispersed phase) in a matrix (dispersion medium) is of an order of micrometer or larger, and effects expected from compounding in such a size have been brought.
It has come to be reported in many cases that microminiaturization of a dispersed phase of a compounded material into a nanometer order in combination with an advance in a technique to analyze a micro area represented by a scanning probe microscope (SPM) makes it possible to prepare materials having a high function and multifunctions or materials having a new function which have not been able to be achieved by conventional compounded materials, and attentions are paid thereto.
Known as examples of materials (hereinafter referred to as a nano-composite) obtained by compounding organic materials with inorganic materials in a nanometer order are nano-composites obtained by compounding stratified clay minerals such as clay and synthetic stratified silicates with polymers such as nylon and nano-composites of silica with polymers making use of a sol-gel method. In the former nano-composites, investigates are (1) a method of inserting an organic monomer between layers of a stratified compound to carry out polymerization, (2) an in-situ polymerization method of carrying out polymerization of a polymer and production and dispersion of a filler at the same time and (3) a method of carrying out mixing and dispersing a stratified compound and a polymer in the presence of an organic cation. These methods make use basically of a cleavage phenomenon of a filler following intercalation of an organic substance, so that an inorganic substance is restricted to a stratified clay mineral which can be dispersed as a structure of a nanometer order. In the latter nano-composites, nano-compounding an inorganic substance with an organic substance has become possible by synthesizing the inorganic substance at a low temperature by a sol-gel method. They have the merit that refined inorganic raw materials can be used but have the defects that the raw materials are expensive and the volume shrinks as the reaction goes on.
In a nano-composite of an organic polymer with an inorganic substance, worked out as well in addition to an intercalation method and a sol-gel method is a method in which an inorganic substance is mechanically pulverized into a nanometer order and then mixed with an organic polymer to obtain an organic-inorganic nano-composite. In general, however, it is recognized that it is difficult to mechanically pulverize an inorganic substance into a nanometer order, and even though can be pulverized, it is not easy to mix homogeneously with an organic polymer which is a disparate material in a nanometer order while inhibiting recoagulation.
The present inventors have paid attentions to that if used as a component for an organic-inorganic nano-composite are calcium phosphates such as hydroxyapatite (hereinafter abbreviated as HAp) and tricalcium phosphate (hereinafter abbreviated as TCP), which are not biologically toxic and have high affinity with an organic substance, there is a possibility they may be turned into very useful materials. HAp is an inorganic component constituting a hard tissue of a vertebrate, and researched is practical use thereof as a hard tissue-substituting material for an artificial bone, an artificial root of tooth and an artificial joint. An HAp sintered substance is a brittle material which is strong against compression but weak against tension if it is used alone, and it has the defect that the moldability is poor. Disclosed as a method for improving this defect in Japanese Patent Application Laid-Open No. Hei 10-229 is a technique for obtaining an organic-inorganic composite which is improved in stability in molding processing and well balanced in flexibility, strength, an elastic modulus, reproducibility and molding processability by mixing HAp with lactic acid base polyesters. This technique has been developed based on an idea to provide a material closer to an organism considering that HAp is present in an organism in the form of a compounded product with collagen which is a biopolymer. In this method, a composite is obtained by synthesizing a calcium phosphate compound such as HAp or TCP by a wet process, baking and pulverizing the resulting precipitate and then mixing it with a polymer by means of a mixer. Calcium phosphate particles used in this case have a size of 5 mm or less, and the organic polymer is restricted to a lactic acid base polyester. This material has achieved osteoconductivity and biocompatibility making the best use of the characteristics of the respective base materials, and it is not a material which is homogeneously dispersed in a nanometer order.
On the other hand, according to Japanese Patent Application Laid-Open No. Hei 7-101708, disclosed is a composite which comprises HAp powder having a crystal particle diameter of 0.5 &mgr;m (500 nm) or less and an organic substance such as collagen and which is close to a tooth and a bone of an organism. In this technique, obtained is a composite having a high Young's modulus by adding a mixed solution of collagen and phosphoric acid to a suspension of calcium hydroxide while vigorously stirring, filtering and drying the resulting precipitate to obtain a hydrate and applying a pressure of 200 MPa to the hydrate at 40° C. It is confirmed by Tanaka et al. [BIO INDUSATRY, Vol. 13 (No. 8), 28 (1996)] that this HAp-collagen composite is a nano-composite in which C axis of HAp nanocrystals (some nm) is orientated along collagen fibers (30 nm). However, included in producing materials close to a vital bone are the problems that a synthetic method in which strength close to that of a vital bone can freely be controlled has to be established and that a method of reducing antigenicity of collagen has to be established. Further, this material is not a material having a high transparency which is characteristic to a nano-composite since it has an oriented structure.
Inorganic substances such as calcium phosphate and calcium carbonate which can be synthesized by a liquid phase process are liable to be turned into a low crystalline substance or a fine crystal in many cases, and they are usually turned into a gelatinous precipitate. Usually, used is a material obtained by filtering, drying, baking and then pulverizing this precipitate, but it is difficult to pulverize them to a primary particle, and it is not easy as well to disperse and mix nano-order particles in a polymer. Thus, a practical method of producing a composite in which an inorganic substance including calcium phosphate synthesized by a liquid phase process is homogeneously dispersed in a nano order has not been available in conventional techniques.
The paper-making industry is an industry in which a large quantity of forest resources is consumed as raw materials and a great amount of e
Itoh Hiroshi
Oyanagi Toshiki
Takaki Toshihiko
Tanabe Masaru
Lipman Bernard
Mitsui Chemicals Inc.
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