Abrasive tool making process – material – or composition – With inorganic material
Reexamination Certificate
2002-02-19
2004-03-16
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With inorganic material
C051S309000, C051S298000, C106S003000, C423S263000
Reexamination Certificate
active
06706082
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a crystalline ceric oxide sol that is approximately monodisperse, and a process for producing the sol.
2. Description of the Related Art
Japanese Patent Laid-open No. Hei 10-95614 discloses a process for producing ceric oxide particles in which the process comprises reacting a cerium (III) salt with an alkaline substance in (OH
−
)/(Ce
3+
) molar ratio ranging from 3 to 30 to form a suspension of cerium (III) hydroxide, and immediately blowing oxygen or a gas containing oxygen into the suspension under atmospheric pressure at a temperature of 10 to 95° C.
A sol comprising ceric oxide particles in a aqueous liquid prepared by the process disclosed in the Japanese patent publication has a specific surface area of 30 m
2
/g by gas adsorption method (BET method), and therefore the particle size thereof converted by BET method is 28 nm. The particle size of the sol measured by dynamic light scattering method is 306 nm. Accordingly, the ratio of the particle size measured by dynamic light scattering method to the particle size converted from a specific surface area by gas adsorption method is 11. Therefore, the sol is open to investigation on the sedimentation thereof, and there is a problem that the particles therein sediment and deposit on standing for a long time. Thus, in a case where the sol is used as an abrasive, it is necessary to re-disperse the sol by vigorously stirring it with a diaper and the like.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a process for producing a sol with high mono-dispersion properties. When the sol is used for polishing, it can prevent very small surface defects on the polished surface from occurring.
According to a first aspect of the present invention, there is provided a sol comprising crystalline ceric oxide particles, in which the particles have particle size I ranging from 10 nm to 200 nm and a ratio of particle size II to the particle size I ranging from 2 to 6, wherein the particle size I is a particle size converted from a specific surface area by gas adsorption method, and the particle size II is a particle size measured by dynamic light scattering method.
According to a second aspect of the present invention, there is provided a process for producing a sol comprising crystalline ceric oxide particles according to the first aspect, in which the process comprises the following steps A and B:
Step A of reacting a cerium (III) salt with an alkaline substance in (OH
−
)/(Ce
3+
) molar ratio ranging from 3 to 30 in an aqueous medium under an inert gas atmosphere to give a suspension of cerium (III) hydroxide, and immediately blowing oxygen or a gas containing oxygen into the suspension at a temperature of 10 to 95° C. under an atmospheric pressure to give a sol comprising crystalline ceric oxide particles, in which the particles have particle size I ranging from 10 nm to 200 nm and a ratio of particle size II to the particle size I ranging 10 or more, wherein the particle size I is a particle size converted from a specific surface area by gas adsorption method, and the particle size II is a particle size measured by dynamic light scattering method; and
Step B of wet-grinding the sol obtained in step A.
According to a third aspect of the present invention, in the process of the second aspect, the alkaline substance is a hydroxide of alkaline metal, an organic base or a mixture thereof.
According to a fourth aspect of the present invention, in the process of the second or third aspect, the gas containing oxygen is air or a mixed gas of oxygen and nitrogen.
According to a fifth aspect of the present invention, there is provided a process for producing a sol comprising crystalline ceric oxide particles according to the first aspect, wherein the process comprises the following steps a and b:
Step a of calcining cerium carbonate at a temperature of 300 to 1100° C. to give crystalline cerium oxide particles; and
Step b of wet-grinding the particles obtained in step a.
According to a sixth aspect of the present invention, in the process of the second to fifth aspect, the wet-grinding is carried out with a wet-ball mill, a sand grinder, an attritor, a perl mill an ultrasonic homogenizer, a pressure homogenizer or an ultimaizer.
According to a seventh aspect of the present invention, there is provided an aqueous slurry comprising organic-inorganic complex particles, in which the crystalline ceric oxide particles according to the first aspect are adsorbed on negatively charged polymer particles (polymer particles having negative charge).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The sol of the present invention comprises ceric oxide particles high in crystallinity. The ceric oxide particles have a specific surface area ranging from 4 to 83 m
2
/g by gas adsorption method (BET method), and the particle size thereof converted from the specific surface area value is 10 to 200 nm The particle size converted from specific surface area by the BET method (hereinafter referred to also as “particle size I”) shows the mean of the particle size of each particle.
Further, the particle size by dynamic light scattering method (hereinafter referred to also as particle size II) is measured with the aid of N4 (manufactured by Coulter Electronics, Inc.), DLS-6000 (manufactured by Otsuka Electronics Co, Ltd.), and the values range from 20 to 800 nm. The particle size determined by dynamic light scattering method shows that of particles in a sol. Therefore, when the particles are aggregated or held together, the particle size thereof is measured in such a state.
The crystalline ceric oxide particles in the sol of the present invention have particle size I ranging from 10 to 200 nm and a ratio of particle size II to a particle size I (that is, the ratio=(particle size by dynamic light scattering method)/(particle size converted from specific surface area by gas adsorption method)) ranging from 2 to 6. The low ratio means that the difference between the particle size converted from a specific surface area by gas adsorption method and the particle size measured by dynamic light scattering method is smaller than that of the prior sol comprising crystalline ceric oxide particles, and the particles in the sol of the present invention are relatively small state that they are aggregated and thus the sol is approximately monodisperse.
The sol of the present invention can be produced through the following steps A and B.
The step A for producing the sol of the present invention comprises reacting a cerium (III) salt with an alkaline substance in (OH
−
)/(Ce
3+
) molar ratio ranging from 3 to 30 in an aqueous medium under an inert gas atmosphere to give a suspension of cerium (III) hydroxide, and immediately blowing oxygen or a gas containing oxygen into the suspension at a temperature of 10 to 95° C. under an atmospheric pressure to give a sol comprising crystalline ceric oxide particles, in which the particles have particle size X ranging from 10 to 200 nm and a ratio of particle size II to the particle site I ranging 10 or more.
The cerium (III) salts include, for example cerium (III) nitrate, cerium (II) chloride, cerium (III) sulfate, cerium (III) carbonate, ammonium cerium (III) nitrate. The cerium (III) salts may be used alone or in a mixture thereof
The alkaline substances include, for example alkaline metal hydroxides, such as sodium hydroxide and potassium hydroxide; organic bases, such as ammonia, amines and quaternary ammonium hydroxide. In particular, ammonia, sodium hydroxide and potassium hydroxide are preferred. These may be used alone or in a mixture thereof.
The gases containing oxygen include, for example air, oxygen, a mixed gas of oxidizing gas, such as oxygen with an inert gas, such as nitrogen. Air is preferable from the view points of economical efficiency and handling.
The step B comprises wet-grinding the sol obtained in the step A.
In addition, the sol of the present invention can be prod
Nishimura Tohru
Ota Isao
Tanimoto Kenji
Marcheschi Michael
Nissan Chemical Industries Ltd.
LandOfFree
Crystalline ceric oxide sol and process for producing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Crystalline ceric oxide sol and process for producing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Crystalline ceric oxide sol and process for producing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3244532