Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2000-07-21
2002-12-17
Lovering, Richard D. (Department: 1712)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C423S338000, C424S070900, C502S405000, C502S407000
Reexamination Certificate
active
06495257
ABSTRACT:
The present invention relates to fine particulate silica gel, and fine particulate silica gel internally containing microparticles of a metal compound such as a metal oxide in the particles.
Fine particulate silica gel, such as fine spherical silica gel is employed in various uses, such as a separating material for liquid chromatography, a filler for cosmetics, a filler for resins, a carrier for catalysts and a spacer.
Further, fine particulate silica gel, such as fine spherical silica gel, internally containing microparticles of a metal compound in the particles (hereinafter referred to as “fine particulate silica gel internally containing microparticles of a metal compound”) is employed for e.g. an ultraviolet ray shielding agent, a photooxidation catalyst and an antibacterial agent.
Fine particles of silica gel are porous particles, wherein the pore structure measured by a nitrogen adsorption method has a pore volume of from 0.2 to 2 ml/g and a specific surface area of from 150 to 900 m
2
/g, and one having an oil absorption of at least 100 ml/100 g is preferably employed in various uses such as materials for cosmetics.
However, silica gel usually has a nature to highly absorb moisture in air, because of its porosity.
When silica gel having moisture highly absorbed is to be used as a blending material for a cosmetic, a phenomenon such that the oil absorption of e.g. a solvent decreases, occurs, which is problematic. On the other hand, if silica gel having moisture highly absorbed, is incorporated in a resin composition, followed by injection molding or extrusion molding, there will be a problem that the moisture adsorbed by silica gel particles will be desorbed, and the resin is likely to undergo foaming due to the generated steam.
Therefore, in a case where fine particles of silica gel are to be used for such a purpose, it is usually necessary to hermetically package them or accommodate them in a sealed container, so that they will not adsorb moisture in air during the storage. Further, when fine particles of silica gel are stored for a long period of time, adsorption of moisture to some extent is unavoidable, and at the time of use, it will be necessary o carry out burdensome treatment such as heating them at a temperature of at least 150° C. to desorb the moisture.
On the other hand, in a specific use such as use as a filler for cosmetics or a filler for resin films, it is often required that the mechanical strength of fine particles of silica gel be small. Namely, fine particles of silica gel are preferably readily disintegratable in order to reduce the porosity among particles in the final blend composition containing the fine particles of silica gel.
However, with respect to fine particles of silica gel, it has been very difficult to satisfy both demands for low hygroscopicity and low mechanical strength of the silica gel particles.
On the other hand, with respect to fine particulate silica gel internally containing microparticles of a metal compound, one having an oil absorption of at least 100 ml/100 g, is used as a filler for e.g. resin films or cosmetic materials. Here, basically the same problems as described above with respect to the particulate silica gel, exist.
Namely, also with respect to the fine particulate silica gel internally containing the metal compound, silica usually has a nature to highly absorb moisture in air, and when the particulate silica gel internally containing the metal compound, which has highly absorbed moisture, is used as a blending material for a cosmetic, phenomenon such that the oil absorption of e.g. a solvent will decrease, occurs, which is problematic.
Likewise, also in a case where the particulate silica gel internally containing the metal compound, which has highly absorbed moisture, is blended to a resin composition, followed by injection molding or extrusion molding, there will be a problem that the adsorbed moisture is likely to be desorbed, and the resin is likely to undergo foaming due to the generated steam.
Therefore, in a case where fine particles of such particulate silica gel internally containing a metal compound, are to be used for such a purpose, it will be necessary to hermetically package them or accommodate them in a sealed container to likewise shut out moisture in air. Further, in a case of storage for a long period of time, adsorption of moisture to some extent is unavoidable, and at the time of use, it will be necessary to carry out burdensome treatment such as heating them at a temperature of at least 150° C. to desorb the moisture.
Further, in a specific use such as use as a filler for cosmetics or a filler for resin films, it is often preferred that fine particles of silica gel are readily disintegratable, and the mechanical strength of particles is required to be small. Also with particulate silica gel internally containing microparticles of a metal compound, it has been also very difficult to satisfy both demands for low hygroscopicity and low mechanical strength.
It is an object of the present invention to provide fine particulate silica gel and fine particulate silica gel internally containing microparticles of a metal compound, having a low hygroscopicity, whereby the above-mentioned problems accompanied by adsorption of moisture in air, have been substantially solved, while maintaining an oil absorption of at least 100 ml/100 g which is a usual level of oil absorption.
A further object of the present invention is to provide fine particulate silica gel and fine particulate silica gel internally containing microparticles of a metal compound, which are readily disintegratable and have small mechanical strength, while maintaining the above properties.
The present invention has been made to solve the above problems.
Firstly, the present invention provides fine particulate silica gel having the following characteristics (1) to (3):
(1) average particle size: from 1 to 200 &mgr;m;
(2) oil absorption in accordance with JIS K5101: from 100 to 300 ml/100 g; and
(3) hygroscopicity represented by moisture adsorption under a relative humidity of 90% at 25° C. in accordance with JIS Z0701: not more than 20 wt %.
Namely, the fine particulate silica gel of the present invention has a feature that the hygroscopicity is low without lowering the oil absorption.
Secondly, the fine particulate silica gel has a particle shape which is preferably a fine spherical particle shape. Namely, a preferred particle shape is a fine spherical particle shape.
Thirdly, in the fine spherical particles of the second aspect, the average value of mechanical strengths of particles having particle sizes of from 2 to 10 &mgr;m, is from 0.1 to 1.0 kgf/mm
2
. Namely, the fine spherical particles having an average particle size of from 5 to 10 &mgr;m have a feature that their mechanical strength is lower than that of conventional particles.
Fourthly, the present invention provides fine particulate silica gel internally containing microparticles of a metal compound and having the following characteristics (1) to (4):
(1) average particle size: from 1 to 200 &mgr;m;
(2) proportion to SiO
2
of the microparticles of a metal compound in the particles: from 5 to 80 wt %;
(3) oil absorption in accordance with JIS K5101: from 100 to 300 ml/100 g; and
(4) hygroscopicity represented by moisture adsorption under a relative humidity of 90% at 25° C. in accordance with JIS Z0701: not more than 20 wt %.
Thus, the fine particulate silica gel internally containing microparticles of a metal compound according to the present invention, has a feature that the hygroscopicity is low without lowering the oil absorption.
Fifthly, in the fine particulate silica gel of the fourth aspect, the shape of particles internally containing the microparticles of a metal compound is a fine spherical particle shape. Namely, also in the case of the fine particulate silica gel internally containing microparticles of a metal compound, the preferred particle shape is a fine spherical particle shape.
Sixthly, in the fine particulate silica gel according to the fifth aspect, the ave
Inoue Masaki
Ono Eiichi
Terase Kunihiko
Asahi Glass Company Limited
Lovering Richard D.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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