Colloid systems and wetting agents; subcombinations thereof; pro – Continuous liquid or supercritical phase: colloid systems;... – Aqueous continuous liquid phase and discontinuous phase...
Reexamination Certificate
2000-03-27
2002-03-12
Metzmaier, Daniel S. (Department: 1712)
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous liquid or supercritical phase: colloid systems;...
Aqueous continuous liquid phase and discontinuous phase...
C516S088000, C516S033000, C106S286400, C428S412000, C423SDIG001
Reexamination Certificate
active
06355694
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sol of modified stannic oxide—zirconium oxide colloidal particles having a particle diameter of 4.5-60 nm which is formed by coating stannic oxide—zirconium oxide complex colloidal particles at their surfaces with colloidal particles of a tungsten oxide—stannic oxide—silicon dioxide complex having a particle diameter of 2-7 nm, and also to a preparation method thereof.
The sol according to the present invention is used as a component for a hard coating agent applied on a plastic lens surface and also for other various applications.
2. Description of the Related Art
A variety of metal oxide sols are already known.
There have been used sols of metal oxides having a high refractive index as a component of a hard coating agent applied on a plastic lens surface which is recently used much in order to improve the surface.
For example, a hard coating agent containing particles of metal oxides such as Al, Ti, Zr, Sn and Sb having a size of 1-300 nm is described in Japanese Patent Publication No. Sho 63-37142.
Although a stable sol of tungsten oxide alone is not known yet, Japanese Patent Application Laid-Open No. Sho 54-52686 proposes a sol obtained by addition of silicate in which a WO
3
:SiO
2
:M
2
O molar ratio (wherein, M represents alkali metal atom or ammonium group) is 4-15:2-5:1.
A silicate—stannate complex sol in which a molar ratio of Si:Sn is 2-1000:1 has been proposed in Japanese Patent Publication No. Sho 50-40119.
Further, Japanese Patent Application Laid-Open No. Hei 3-217230 proposes a stable sol comprising a modified metal oxide colloid having a particle diameter of 4.5-60 nm and which is formed by coating colloidal particulate surfaces of metal oxide having a particle diameter of 4-50 nm and a valence of 3, 4 or 5 as nuclei with colloidal particles of a tungsten oxide—stannic oxide complex having a WO
3
/SnO
2
weight ratio of 0.5-100 and a particle diameter of 2-7 nm, the stable sol containing 2-50% by weight of total metal oxides.
Further, Japanese Patent Application Laid-Open No. Hei 6-24746 proposes a stable sol of a modified SnO
2
-ZrO
2
complex which comprises particles formed by coating colloidal particle surfaces of metal oxide having a ZrO
2
/SnO
2
weight ratio of 0.02-1.0 and a particle diameter of 4-50 nm as nuclei with colloidal particles of a WO
3
-SnO
2
complex having a WO
3
/SnO
2
weight ratio of 0.5-100 and a particle diameter of 2-7 nm.
However, if these conventional metal oxide sols, particularly cationic metal oxide sols, are used as a component of a hard coating agent, the stability of the obtained hard coating agent is insufficient and also transparency, adhesion, weather resistance, etc. of a hardened coating coated with the hard coating agent are insufficient. Further, if an Sb
2
O
5
sol is used as a component of a hard coating agent, the Sb
2
O
5
sol can no longer improve a refractive index of the hardened coating sufficiently when a refractive index of a plastic substrate in a lens is 1.6 or more, since a refractive index of Sb
2
O
5
is about 1.65-1.70.
A sol of tungsten oxide described in the above-mentioned Japanese Patent Application Laid-Open No. Sho 54-52686 is obtained by adding a silicate to an aqueous tungstate solution which is obtained by decationizing an aqueous tungstate solution, but it is stable only at a strong acidic state and an effect for improving a refractive index of a coating is low in the case of use as a component of a hard coating agent.
A silicate—stannate complex sol described in the above-mentioned Japanese Patent Publication No. Sho 50-40119 is obtained by decationizing a mixed aqueous solution of an alkali silicate and an alkali stannate, but an effect for improving a refractive index of a coating is also low in the case of use as a component of a hard coating agent as described above.
A modified metal oxide sol described in the above-mentioned Japanese Patent Application Laid-Open No. Hei 3-217230 having a refractive index of 1.7 or more is stable, thus it can be used as a component of a hard coating agent for a plastic lens and it can satisfy almost all properties required for a hard coating such as damage resistance, transparency, adhesion, water resistance, weather resistance, etc.
A modified stannic oxide—zirconium oxide sol described in the above-mentioned Japanese Patent Application Laid-Open No. Hei 6-24746 having a refractive index of 1.7 or more is stable, thus it can be used as a component of a hard coating agent for a plastic lens, and it can satisfy almost all properties required for a hard coating such as damage resistance, transparency, adhesion, etc.
SUMMARY OF THE INVENTION
A modified metal oxide sol according to the present invention provides a stable sol of modified stannic oxide—zirconium oxide complex colloidal particles having good water resistance, moisture resistance, weather resistance and a high refractive index which overcomes yellowing due to ultraviolet radiation found when the conventional metal oxide sols are used and also overcomes such problems as water resistance and moisture resistance, and thus it provides a metal oxide sol which can be used by mixing with a hard coating paint as a component for improving properties of the hard coating applied on a plastic lens surface.
The present invention provides a stable sol which comprises modified colloidal particles of stannic oxide—zirconium oxide complex having a particle diameter of 4.5-60 nm, wherein the particles are formed by coating complex colloidal particles of a stannic oxide—zirconium oxide having a bonded structure of stannic oxide colloidal particles and zirconium oxide colloidal particles at a ZrO
2
/SnO
2
ratio of 0.02-1.0 based on weights of these oxides and having a particle diameter of 4-50 nm as nuclei, with colloidal particles of a tungsten oxide—stannic oxide—silicon dioxide complex having such a constitution that a WO
3
/SnO
2
weight ratio is 0.1-100, that a SiO
2
/SnO
2
weight ratio is 0.1-100 and having a particle diameter of 2-7 nm, and which contains 2-50% by weight of total metal oxides.
Further, a method for preparing a stable sol according to the present invention comprises the steps of:
a step (a) of mixing an aqueous stannic oxide sol which contains colloidal particles of stannic oxide having a particle diameter of 4-50 nm at a concentration of 0.5-50% by weight as its oxide, SnO
2
, with an aqueous oxyzirconium salt solution having a concentration of 0.5-50% by weight calculated as ZrO
2
, at a ZrO
2
/SnO
2
weight ratio of 0.02-1.0;
a step (b) of forming an aqueous stannic oxide—zirconium oxide complex sol having a particle diameter of 4-50 nm by heating the mixed solution obtained in the step (a) at 60-200° C. for 0.1-50 hours;
a step (c) of forming a sol of a tungsten oxide—stannic oxide—silicon dioxide complex by preparing an aqueous solution containing tungstate, stannate and silicate at a WO
3
/SnO
2
weight ratio of 0.1-100 and a SiO
2
/SnO
2
weight ratio of 0.1-100 and removing cations present in the solution;
a step (d) of mixing 100 parts by weight, calculated as the total of ZrO
2
and SnO
2
contained, of the aqueous stannic oxide—zirconium oxide complex sol obtained in the step (b) with 2-100 parts by weight, calculated as total of WO
3
, SnO
2
and SiO
2
contained, of the tungsten oxide—stannic oxide—silicon dioxide complex sol obtained in the step (c) having a particle diameter of 2-7 nm, a WO
3
/SnO
2
weight ratio of 0.1-100 and a SiO
2
/SnO
2
weight ratio of 0.1-100 at 0-100° C.; and
a step (e) of removing anions present in the aqueous modified stannic oxide—zirconium oxide complex sol obtained in the step (d) by bringing the sol into contact with an anion exchanger.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The sol of stannic oxide—zirconium oxide complex colloidal particles to be used as nuclear particles in the preparation of the sol according to the present invention can be prepared by the method comprising the above-mentioned steps (a) and (b). Stannic oxide colloidal partic
Iijima Motoko
Koyama Yoshinari
Suzuki Keitaro
Metzmaier Daniel S.
Nissan Chemical Industries Ltd.
Oliff & Berridg,e PLC
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