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
1999-04-22
2001-08-28
Cain, Edward J. (Department: 1714)
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...
C423S069000, C423S111000, C423S335000, C423S610000, C423S625000, C524S493000, C524S497000
Reexamination Certificate
active
06281277
ABSTRACT:
TECHNICAL FIELD
The present invention relates to homogeneously surface-fluorinated metal oxide particulates and a process for manufacturing the metal oxide particulates. More specifically, the present invention relates to homogeneously surface-fluorinated metal oxide particulates in which the surface is hydrophobitized so that the particle is further improved in the stability, water repellency and dispersibility and prevented from deterioration for a long period of time, and also relates to a manufacturing process and a use thereof.
BACKGROUND ART
Metal oxide particulates are being widely used as a raw material for coating material, matting agent of chemical synthetic fiber, printing ink, cosmetic or milk-white glass, or as a modifier, colorant or pigment for rubber or resin. The surface of a metal oxide particulate is usually covered with a hydroxyl group and assumes to be hydrophilic. Therefore, in the blending of a metal oxide particulate into a resin, a coating material or a cosmetic material which are a hydrophobic material, the metal oxide is surface treated. For example, in the case of titanium oxide, a large number of surface treatments such as surface treatment with a higher fatty acid, surface treatment with an organic silicon compound, a silica-alumina treatment and a surface treatment with various coupling agents, are known and practiced so as to improve dispersibility of the titanium oxide. In the case of aluminum oxide and silicon oxide, attempts are being made to treat the particle surface with a silylating agent or the like.
These methods all are intended to control hydrophobicity or hydrophilicity of the surface or the surface activity by chemically substituting and thereby eliminating the hydroxyl group on the surface of the metal oxide particulate. However, in the case of adding a metal oxide particulate to a fluororesin or a fluorine-based coating material, the metal oxide particulate is preferably more intensified in the hydrophobicity and lipophobicity. For this purpose, the surface must be formed such that fluorine having a surface energy lower than water or oil covers the surface.
In order to solve these problems, for example, JP-A-59-184263 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a method of adding sodium fluoride to a titanium oxide suspended slurry and stirring the slurry. However, according to this method, when the titanium oxide is a superfine particulate, strong coagulation takes place in the drying step and good dispersibility cannot be obtained even if the coagulate is pulverized. Furthermore, according to this method, the fluorine atom is not bonded directly to the titanium atom, therefore, the titanium oxide surface is not fluorinated in any means.
JP-A-61-215216 discloses a method of using an organic fluorine compound as a hydrophobicity-imparting material in the production of a hydrophobic spherical titanium oxide particulate, however, also in this case, the titanium oxide surface is substantially not fluorinated.
JP-A-3-40919 discloses a method of contacting a fluorocarbon gas with superfine titanium oxide particulate and fluorinating the particle surface at a high temperature of from 200 to 400° C., however, due to the high reaction temperature of 200° C. or more, the thermal efficiency is not necessarily good.
JP-A-6-80901 discloses a pigment (titanium oxide) of which surface is modified with a fluorine gas. According to this method, the pigment can be surface treated at 150° C. or less and dispersibility of the pigment can be improved. However, this surface fluorination method fails in achieving a homogeneous fluorination ratio on the surface of the metal oxide particulate and the dispersibility fluctuates, therefore, in high-level uses, for example, in the case of use as an additive for a water super-repellent coating material or resin, the dispersibility is still in need of improvements.
The object of the present invention is to, by solving the above-described problems encountered in the techniques for producing metal oxide particulates having a substantially fluorinated surface, provide surface-fluorinated metal oxide particulates free of scattering in the physical properties (e.g., dispersibility, water repellency) depending on the particle or particle size at the surface treatment and favored with homogeneously fluorinated surface, and also provide an improved process for manufacturing the metal oxide particulates. More specifically, the object of the present invention is to provide surface-fluorinated metal oxide particulates having higher durability with respect to the physical properties such as water repellency, dispersibility and photostability, and an improved process for manufacturing the metal oxide particulates.
Another object of the present invention is to provide homogeneously surface-fluorinated metal oxide particulates, preferably a homogeneously surface-fluorinated titanium oxide particulate, and an improved thermoplastic resin composition containing the titanium oxide particulate pigment.
SUMMARY OF THE INVENTION
As a result of extensive investigations to solve these problems in conventional techniques, the present inventors have found a manufacturing process comprising reacting a metal oxide particulate with fluorine to fluorinate the surface of the metal oxide particulate, wherein the metal oxide particulate in the flowing state is surface treated. According to this process, the metal oxide particulate can be homogeneously fluorinated while allowing the fluorination reaction to proceed independently of the particle size and preventing the surface from being heterogeneously fluorinated, so that the physical properties of the particle, such as water repellency, dispersibility and photostability, can be more improved and freed from deterioration even in the long-term use. The present invention has been accomplished based on this finding.
Furthermore, it has been verified that among the homogeneously surface-fluorinated metal oxide particulates, titanium oxide particulate is more improved in the light fastness stability, water repellency and dispersibility than conventional titanium oxide particulates having a substantially fluorinated surface, has a high durability of the physical properties, can provide a film free of any partial defects due to contaminating of water adsorbed ascribable to the residual hydrophilic groups, and is suitable for the use particularly in a thermoplastic resin composition for a photographic resin coated paper such as a highly white thin film, which is obtained by incorporating the titanium oxide particulate as a white pigment into a thermoplastic resin.
Based on the above-described knowledge, the present invention provides homogeneously surface-fluorinated metal oxide particulates, a manufacturing process thereof, and a thermoplastic resin composition containing the titanium oxide particulate pigment.
(1) A process for manufacturing homogeneously surface-fluorinated metal oxide particulates, comprising surface reacting a fluorine gas with a metal oxide particulate while allowing the metal oxide particulate to flow.
(2) The process for manufacturing homogeneously surface-fluorinated metal oxide particulates as described in 1 above, wherein a fluorine-containing gas obtained by diluting fluorine is used.
(3) The process for manufacturing homogeneously surface-fluorinated metal oxide particulates as described in 2 above, wherein the diluting gas is a nitrogen or argon gas.
(4) The manufacturing process as described in any one of 1 to 3 above, wherein the reaction time and/or the concentration of the raw material fluorine gas and/or the reaction temperature are controlled to obtain a homogeneously surface-fluorinated metal oxide particulate having a controlled surface fluorination ratio.
(5) The process for manufacturing homogeneously surface-fluorinated metal oxide particulates as described in any one of 1 to 4 above, wherein the metal oxide is titanium oxide.
(6) The process for manufacturing homogeneously surface-fluorinated meta
Ishii Nobuaki
Sekiguchi Kazuo
Takahashi Hiroyuki
Wada Koichi
Cain Edward J.
Showa Denko Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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