Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
2000-06-01
2003-04-01
Wilson, James O. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S057000, C536S001110, C536S123100, C536S123120, C536S124000, C536S126000, C106S163010
Reexamination Certificate
active
06541627
ABSTRACT:
This application is a 371 of PCT/JP98/05462 Dec. 3, 1998.
This invention relates to a cellulose dispersion in which a cellulose is highly dispersed in a dispersing medium and which is high in transparency; to a spherical particulate or spherical composite particulate which is low in aggregable properties and large in hardness; and to a process for producing the same.
BACKGROUND ART
A cellulose which is a natural polymer or a particulate whose starting material is a cellulose and dispersions of them have been widely used as an additive agent for drug-molding; a food additive; a cosmetics additive; a binder for various molding purposes; a filter aid; a support for sustained release drug; and the like.
A dispersion in which a cellulose is the starting material and a cellulose particulate are, in all cases, used as a composite system in which it is mixed with and dispersed in other functional materials (drugs, oily agents, perfumes and the like). Therefore, they are required to have a function for highly dispersing the functional materials and allowing them to stably exist in the composite system (referred to hereinafter as the dispersion stability) is required.
However, the conventional cellulose dispersion has such a problem that the cellulose aggregates in an acidic area of pH≦3 and it does not function as an additive in acidic products. Moreover, a water-soluble polymer containing a water-soluble cellulose derivative (hydroxyethylcellulose, carboxymethyl cellulose or the like), though it is not a cellulose, has a high dispersion stability in a composite system and is utilized as a thickening agent for paints, cosmetics, cataplasms for drug or the like. These are usually used in the form of an aqueous solution of about 0.5 to 3% by weight; however, for example, it is difficult for a water-soluble cellulose derivative for a water-based paint to always keep the required good balance between viscosity and thixotropic properties (a phenomenon that the viscosity is high at a low shear rate and a viscosity reduction takes place at a high shear rate), and those having a such a viscosity that they are spreadable are low in thixotropic properties, and have problems such as run of liquid being caused and the like. In addition, the sticky feel and spinnability characteristic of a water-soluble polymer are often disliked in some use fields and problems have remained.
Moreover, it has long been desired to substitute for the water-soluble polymer a cellulose dispersion which is a natural material and has a thickening action and a dispersing action for the utilization as a coating agent such as a paint, a cosmetic or the like; however, the conventional cellulose dispersion lacks the smoothness and transparency of coating surface and the improvement of these properties has been required. That is to say, there has been desired a dispersion in which the conventional cellulose particulates are much more highly dispersed.
Furthermore, the water-soluble polymers are also employed in uses requiring the transparency of solution as in cosmetic emulsions and gel-like hair-dressing agent. The conventional cellulose dispersion is a uniformly white-turbid, opaque suspension and has been unable to be utilized at all in this field. In addition, even when a coloring material such as a dye, a pigment or the like is incorporated into the existing cellulose dispersion, there have been problems such as the color developability characteristic of the coloring material being unable to be secured and the like.
Accordingly, in order to impart to the cellulose dispersion a further function such as dispersibility, smoothness, transparency or the like to make it applicable to a wider industrial field, it has been desired to impart thereto so high a dispersion-stability as to be comparable to that of the water-soluble polymer in the complex system and further desired to finely divide the same and impart transparency thereto.
The conventional cellulose dispersions used as various additives is generally composed of a dispersing medium (usually water) and particulates obtained by a method for producing “microcrystalline cellulose (MCC)” and “microfibrilated cellulose (MFC)”.
As the prior art concerning the cellulose dispersions, JP-A-3-163,135 discloses a dispersion of a finely divided cellulose material. JP-A-3-163,135 discloses a technique of producing, by a depolymerization treatment and a subsequent wet grinding treatment, a suspension containing at least 2% by weight of an atomized cellulosic material in which the particle diameters whose integrated volume is 50% in the particle diameters distributions with relation to a volume are 0.3 to 6 &mgr;m and the integrated volume proportion of particles of not more than 3 &mgr;m in diameter is not less than 25%. There is a statement to the effect that as the starting cellulose material used for the production of the above dispersion, a regenerated cellulose material can also be used, but there are no working examples, and according to the above method, there are not obtained those that the fraction of cellulose II type crystal component is not more than 0.4 even when said starting material is used. Moreover, it is stated that a degree of polymerization of not more than 300 is preferred; however, substantially, it is considerably higher than the average degree of polymerization (DP) of the cellulose of the present invention. In addition, as shown in Comparative Example 2 of the present specification, no dispersion having transparency is obtained.
Furthermore, JP-A-3-163,135 states that by finely dividing the cellulose material in the cellulose dispersion, the development of thixotropic properties, water-retention characteristics, viscosity, dispersion stability and the like are improved, and simultaneously therewith, when it is used as, for example, a food additive, the rough feel, foreign matter feel and powdery feel of the food can be diminished and an improvement of sense of touch and an increase of the addition amount can be expected. The same publication points out simultaneously the limit of degree of finely dividing a group of cellulose type particulate additives, the deterioration of dispersion stability by too finely dividing them, the lower limit value (2% by weight) of the particulate concentration in the suspension at which the dispersion stabilization effect is exhibited, and the like.
JP-A-56-100,801 discloses a microfibrilated cellulose. This fibrilliform cellulose is ground in the form of fibers, and there are obtained those having a long diameter (L) of about 100 &mgr;m though and having a short diameter (D) of not more than 1 &mgr;m (L/D is large and the anisotropy is high). When a dispersion is intended to be prepared from such a microfibrilated cellulose, the dispersion of the present invention low in crystallinity, low in degree of polymerization and high in transparency which comprises a cellulose II type crystal as the main component is by no means obtained as pointed out in relation to JP-A-3-163,135.
JP-A-9-508,658 discloses a technique of preparing a liquid crystalline cellulose film from a colloidal dispersion composed of particles having a particle diameter of several to several hundreds nm by hydrolyzing natural cellulose particulates in concentrated sulfuric acid at a high temperature (60 to 70° C.). The cellulose crystallite obtained thereby has been substituted by a charge group to a derivative and aggregation and association are inhibited owing to this charge repulsion, and it has neither thickening effect nor dispersion-stabilizing effect of the cellulose additive as aimed at by the present invention and is different in industrial applicability. Specifically, there are stated application examples in which the optical characteristics of a film obtained from a liquid crystalline, colloidal dispersion are utilized. Since in the technique of the above-mentioned publication, sulfuric acid hydrolysis is effected under the conditions that the cellulose crystallite is not dissolved, no one that the fraction of the cellulose I type crystal componen
Matsui Toshihiko
Miyamoto Ikuya
Ono Hirofumi
Asahi Kasei Kabushiki Kaisha
McIntosh III Traviss C.
Pennie & Edmonds LLP
Wilson James O.
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