Glass manufacturing – Processes – Sol-gel or liquid phase route utilized
Reexamination Certificate
1997-03-03
2003-07-15
Hoffmann, John (Department: 1731)
Glass manufacturing
Processes
Sol-gel or liquid phase route utilized
Reexamination Certificate
active
06591634
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
This Invention relates to a method for production of metal oxide glass films and micro-spherules ranging from a single component type to a multi-component type, these metal oxide film and micro-spherules being destined for use as a coating material for prevention of oxidation in metals, pressurized cooking utensils, various kinds of paper and films, and so forth.
b) Description of the Technical Background
As the technique for forming a coating film on the surface of metals and others, there has so far been known the glass-lining method or the ceramic coating method. The former is a technique of using the enamel-coating method, in which alkali-silicate type glass is baked on the metal surface in two stages, while the latter is a technique of using flame-coating method, in which a high temperature molten body of metal oxides, borides, carbides, etc. is spattered in the form of their micro-spherules so as to cause them to dash against the base body at a high speed, thereby forming the flame-coated film.
After these methods, there was developed a technique, different from the above-mentioned melting method, in which use was made of a liquid phase. This technique includes, for example, a liquid-immersion method using hexaflurosilisic acid (H
2
SiF
6
), a sol-gel method, and so forth. There are two ways for this sol-gel method: the one is to prepare sol (colloidal substance) from salt of a metal, which is then vitrified; and the other is to hydrolyze an organic metal compound such as metal alkoxide, and then vitrify the hydrolyzed product. The latter method, as one example, is first to mix ethyl silicate Si(OC
2
H
5
)
4
with ethyl alcohol and water, followed by hydrolyzing the mixture to obtain transparent gel, after which alcohol and water are evaporated for contraction and solidification. The thus obtained solid body is heat-treated at high temperature to obtain silica glass.
However, the above-mentioned conventional techniques require, without exception, the high temperature heat-treatment. Even in the sol-gel method, by which an organic metal compound is hydrolyzed, the heat-treatment at 1,100° C. or higher is inevitable for the ultimate complete dehydration, a volumetric contraction, at that time, of the hydrolyzed product is not negligible. Also, in such high temperature heat-treatment process, there takes place generation of gas from the interior of the glass body, which tends to produce micropores therewithin, these becoming a cause for inviting deterioration in the quality of the coating film, etc.. Further, in the conventional methods, there has not been known any example of producing multi-component type glass micro-spherules.
The present invention has been proposed in view of the above-described points of problem, and aims at providing a method for efficiently manufacturing transparent thin film and micro-spherules of a simple component type or an arbitrary multi-component type glass.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for producing a single component or a multi-component metal oxide glass film, which comprises: subjecting a hydrolyzable organic metal compound to hydrolysis in a reaction liquid consisting of water and an organic solvent, with halogen ions as a catalyst in the presence of boron ions, while adjusting pH value of the reaction liquid in a range of from 4.5 to 5.0, followed by dehydration and condensation; thereafter, applying a reaction product onto the surface of a base material; and vitrifying the surface coat at a temperature of 200° C. or below.
It is another object of the present invention to provide a method for producing a single component type or a multi-component type metal oxide glass micro-spherule which comprises: subjecting a hydrolyzable organic metal compound to hydrolyzation in a reaction liquid consisting of water and an organic solvent, with halogen ions as a catalyst in the presence of boron ions, while adjusting pH value of the reaction liquid in a range of from 8 to 10, followed by dehydration and condensation; thereafter, rinsing a sedimented reaction product with water for separation; and vitrifying said rinsed and separated product at temperature of 200° C. or below.
The foregoing objects, other objects as well as particular method of production according to the present invention will become more apparent and understandable from the following detailed description thereof, when read in conjunction with preferred examples.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
There is no particular limitation to the organic metal compound to be used as the material for the practice of the method according to the present invention. Any hydrolyzable organic metal compounds may serve for the purpose. Preferred organic metal compound is metal alkoxide, which is represented by a general formula ME
2
n
(OR
1
)
n−m
(where: M is a metal having oxidation number n; R
1
and R
2
represent the alkyl group; and m denotes an integer of 0 to (n−1)). R
1
and R
2
may be same or different. Preferred among these alkyl groups are the one where R
1
and R
2
contain four or less carbon atoms, i.e., methyl group CH
3
(hereinafter represented as Me), ethyl group C
2
H
5
(hereinafter represented as Et), propyl group C
3
H
7
(hereinafter represented as Pr), isopropyl group i-C
3
H
7
(hereinafter represented as i-Pr), butyl group; C
4
H
9
(hereinafter represented as Bu), isobutyl group i-C
4
H
9
(hereinafter represented as i-Bu), and other lower alkyl groups.
For metal alkoxide, there may be exemplified: lithium ethoxide LiOEt, niobium ethoxide Nb(OEt)
5
, magnesium isopropoxide Mg(OPr-i)
2
, aluminum isopropoxide Al(OPr-i)
3
, zinc propoxide Zn(OPr)
2
, tetraethoxysilane Si(OEt)
4
, titanium isopropoxide Ti(OPr-i)
4
, barium ethoxide Ba(OEt)
2
, barium isopropoxide Ba(OPr-i)
2
, triethoxyboran B(OEt)3, zirconium propoxide Zr(OPr)
4
, lanthanum propoxide La(OPr)
3
, yttrium propoxide Y(OPr)
3
, lead isopropoxide Pb(OPr-i)
2
, and so forth. These metal alkoxides are readily obtainable in the general market. They are also available in the general market in the form of low condensation product obtainable by partial hydrolysis, which can be used as the starting material.
According to the method of the present invention, the above-mentioned hydrolyzable organic metal compounds may be used as they are, for the reaction. It is however more desirable to use these compounds in dilution with a solvent for easy control of the reaction. The solvent for dilution may be any one which is able to dissolve the above-mentioned organic metal compound, and to be uniformly mixed with water. Generally, aliphatic lower alcohols are preferably used. Examples are: methanol, ethanol, propanol, isopropanol, butanol, isobutanol, ethyleneglycol, propyleneglycol, and their mixtures. Also usable are mixed solvents such as butanol+cellosolve+butyl cellosolve, xylol+cellosolve acetate+methyl isobutyl ketone+cylohexane, or others.
In case the metal contained in the above-mentioned organic metal compound is Ca, Mg, Al, and so forth, such metal reacts with water in the reaction liquid to produce a hydroxide, or, if carbonic acid ions CO
3
2−
are present, carbonate is produced to bring about sedimentation. To avoid such phenomena, it is desirable to add alcohol solution of triethanolamine as a masking agent.
Concentration of the organic metal compound, when it is mixed with a solvent for dissolution, should desirably be 70% (by weight) or below in an ordinary case, or more particularly in a range of from 5 to 70% (by weight).
The reaction solution to be used for practicing the method of the present invention consists generally of water and organic solvent. As the organic solvent for use in the reaction solution, any kind of organic solvents may serve for the purpose, provided that they can yield uniform solution with water, acid, and alkali, of which aliphatic lower alcohols to be usually used for dilution of the above-mentioned organic c
Armstrong Westerman & Hattori, LLP
Hoffmann John
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