Coating processes – Particles – flakes – or granules coated or encapsulated – Inorganic base
Patent
1994-02-15
1997-02-11
Beck, Shrive
Coating processes
Particles, flakes, or granules coated or encapsulated
Inorganic base
427212, 427215, 241 15, 241 38, 241 39, 241DIG4, B05D 700, B02C 100
Patent
active
056018754
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of effecting a physico-chemical reaction, in which method a crystalline or amorphous material A is crushed or ground.
In almost all materials, the surface is a very important part of the material. It may even be said that the rest of the material serves as a mere supporting structure for the surface. Typical examples are powders and fibres in which the strength/mass increases continuously as the surface area of the fibre increases, that is, its diameter decreases.
In ceramic and other materials, small grain size is of the greatest importance, that is, a high surface area/mass unit.
In solid substances, all chemical reactions and physical adhesions always occur on the surface.
Therefore various grinding techniques have been developed, which aim at increasingly small particle sizes, that is, greater surface areas/mass unit.
Surfaces have a great number of properties all of which are not necessarily positive or desired simultaneously in view of the intended use.
The most usual formation of coating occurring in material treatment takes place spontaneously, even in such a way that it is difficult to prevent. This usually takes place as molecules present in air, especially oxygen, settle on a newly formed surface in a layer of a few molecules. In a way, the surface is contaminated.
In this way the special properties of all surfaces change nearly automatically as they are modified by oxygen molecules, and the properties of all surfaces approach each other. This takes place especially in most grinding operations, which are carried out in the atmosphere according to a prevailing practice.
Contaminations caused by the molecules of air, "coatings", adhere so firmly to the surfaces that the removal of adsorbed air from a surface formed in grinding requires prolonged bombing with an electron beam even in a vacuum.
It is known that newly formed surfaces are more active for reactions typical of all surfaces than "old surfaces". This phenomenon can be explained in many ways, which can be fitted in two main categories. insulation", contamination.
Chemical terminology knows a concept in statu nascendi, which means "in the state of being born", whereby it is possible to effect a reaction, adsorption, etc. more rapidly and efficiently than without this situation. This is the same phenomenon as represented by the above two categories.
The present invention concerns especially grinding and treatment of material in connection with grinding for a subsequent process step.
On grinding crystalline, amorphous, e.g. glass-like material which is brittle and hard, that is, grindable, the grinding is only an intermediate step for an intended subsequent use of the material.
It has been known for a long time to grind inflammable powders in a protective gas due to the risk of explosion, for instance. The purpose of the protective gas is only to eliminate explosion, cf. U.S. Pat. No. 3,937,405.
The object of the invention is to provide a new method which prevents the formation of a disadvantageous transition zone between the material to be ground and the coating material or matrix material.
The method of the invention is characterized in that as soon as a new fractured surface is formed, it is brought into immediate contact with an environment V1 the physico-chemical property of which is so selected that a firm bond or compound is formed between the fractured surface and the molecules of the environment, at least one molecule of said bond or compound being adapted to its purpose for the further treatment of the crushed or ground material in another environment V2, whereby the physico-chemical property of the environment V1 is further so selected that components disadvantageous in view of the further treatment of the crushed or ground material are prevented from getting to the fractured surface.
The invention is also concerned with a product produced by the method of the invention. In one preferred embodiment the method of the present invention is characterized in that the bond or compound to be formed is com
REFERENCES:
patent: 3491953 (1970-01-01), Stephanoff
patent: 3675858 (1972-07-01), Stephanoff
patent: 3802909 (1974-04-01), Rockett et al.
patent: 3937405 (1976-02-01), Stephanoff
Derwent Abstract No. 88-188 727/27, Abstract of SU-1 357 383.
Derwent Abstract No. 88-41 164/06, Abstract of SU-1 318 570.
Derwent Abstract No. 87-127 407/18, Abstract of SU-1 255 605.
Beck Shrive
Maiorana David M.
Partek Concrete Ltd.
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