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US 4,070,283 AGranted
Controlled surface porosity particles and a method for their production
AssigneeE. I. Du Pont de Nemours and Company
InventorJoseph Jack Kirkland
Life of this patent
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Abstract
Superficially porous macroparticles of improved characteristics are formed from an impervious core having a diameter in the range of about 5 to about 500 microns, at least two monolayers of like microparticles adhered to the core, each microparticle having an average diameter in the range of about 0.005 to about 1.0 micron, and at least two monolayers of like ultramicroparticles adhered to the surface of the microparticles, each ultramicroparticle having a diameter in the range of about 1.0 to about 15 millimicrons.
Claims13
As an article of manufacture, a powder of superficially porous macroparticles comprising:
- a. an impervious core having an average diameter in the range of about 5 to about 500 microns;
- b. at least two monolayers of like microparticles adhered to said core, each microparticle having an average diameter in the range of about 0.005 to about 1 micron;
- and
- c. at least two monolayers of like ultramicroparticles adhered to the surface of said microparticles, each of said ultramicroparticles having an average diameter in the range of about 1.0 to about 15 millimicrons, the diameter of said ultramicroparticles being no more than one quarter of the average diameter of the pores between the microparticles, and the combined microparticle and ultramicroparticle layers constituting from about 0.002 to about 25% of the total volume of the macroparticles.
1 more element
A process for producing a powder of superficially porous macroparticles comprising the steps of:
- a. providing a powder of macroparticles each comprising an impervious core having an average diameter in the range of about 5 to about 500 microns and at least two monolayers of microparticles adhered to said core, each microparticle having an average diameter in the range of about 0.005 to about 1 micron;
- and
- b. coating said microparticles with at least two monolayers of ultramicroparticles, each ultramicroparticle having an average diameter in the range of about 1.0 to about 15 millimicrons, the diameter of said ultramicroparticles being no more than one quarter the average diameter of the pores between the microparticles adhered to said core.
A process for producing a powder of superficially porous macroparticles comprising the steps of:
- a. effecting contact between the surface of a substrate and a first dispersion of microparticles which are irreversibly adsorbable onto the surface of said substrate, said substrate comprising a plurality of inorganic particles having an average diameter in the range of about 5 to about 500 microns, said first dispersion being a dispersion of inorganic microparticles having an average diameter in the range of about 0.005 to about 1 micron and containing sufficient microparticles to at least cover the total surface area of said substrate;
- b. rinsing off any excess first dispersion so that the surface of said substrate is coated with a single layer of inorganic microparticles;
- c. effecting contact between the coated substrate and a second dispersion of organic colloidal particles which are irreversibly adsorbable onto the coated surface of said substrate, the number of particles in the second dispersion being at least sufficient to cover the coated surface of said substrate;
- d. rinsing off any excess second dispersion so that the previously coated surface of said substrate is further coated with a single layer of colloidal organic particles;
- e. effecting contact between the surface of the previously coated substrate and a third dispersion of microparticles which are irreversibly adsorbable onto the surface of the previously coated substrate, said third dispersion being a dispersion of inorganic microparticles having an average diameter in the range of about 0.5 to about 50 microns and contacting sufficient microparticles to at least cover the total surface area of the previously coated substrate;
- f. rinsing off any excess third dispersion so that the previously coated surface of said substrate is coated with a second single layer of inorganic microparticles;
- g. removing the organic material whereby a powder of macroparticles is formed;
- h. contacting the powder so formed with a sol of ultramicroparticles having an average diameter in the range of about 1.0 to about 15 millimicrons, the diameter of said ultramicroparticles being no more than one quarter of the average diameter of the pores between the microparticles adhered to said substrate, the number of ultramicroparticles in the sol being at least sufficient to cover the surface of the microparticles attached to said substrate, whereby the microparticles are coated with a single layer of ultramicroparticles;
- i. rinsing off any excess sol;
- j. contacting the ultramicroparticles with a monolayer of organic material;
- k. repeating steps (g) and (i) at least once so that the microparticles adhered to said substrate are coated with at least two monolayers of like ultramicroparticles;
- and
- l. removing the organic material.
10 more elements
Dependencies are inferred from the claim text.