Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
1999-04-09
2001-02-27
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C523S209000, C523S212000, C524S423000, C524S567000, C524S570000
Reexamination Certificate
active
06194070
ABSTRACT:
TECHNICAL FIELD
This invention relates to surface treated barium sulfate and, more particularly, to a surface treated barium sulfate product that provides desirable performance properties and improved processing in polymeric end use applications. The invention also relates to a method of preparing such a surface treated barium sulfate product.
BACKGROUND OF THE INVENTION
Natural barium sulfate (also commonly referred to as barite or barytes) is frequently used as an extender pigment and/or filler due to its chemical inertness (in both acid and alkali environments), high refractive index, low abrasiveness, low oil absorption, and resistance to corrosion. Barium sulfate is also known to promote flame retardancy and smoke suppression in polymeric end use applications. Given their high refractive index, barium sulfates of high brightness are desirable to use as a replacement for titanium dioxide (TiO
2
) in certain compositions such as pigmented polymeric compounds. Barite can be utilized to replace a portion of the more expensive TiO
2
pigment without having a deleterious impact on the compound's brightness and whiteness properties. Synthetic, precipitated barium sulfate pigments are used in a like fashion, but are typically available in finer particle size grades versus the mechanically ground, natural barites. Precipitated barium sulfate is commonly referred to as blanc fixe.
Despite barium sulfate's many end use advantages, it is not readily wetted or dispersed in organic based formulations such as polymeric compounds given its inert inorganic surface. Accordingly, lengthy processing times are typically required to obtain desired levels of dispersibility of the barite in such compounds. Further, fine and ultrafine particle barites in dry form tend to cake when stored and/or transported. Caking creates processing problems when the barite particles are added to end use formulations via automated dry feeders and the like.
SUMMARY OF THE INVENTION
The present invention is designed to overcome the deficiencies discussed above. It is an object of the invention to provide a surface treated barium sulfate product that is adapted to be readily dispersed in end use applications such as polymeric formulations. Good wet out and dispersion in polymers is important to the inventive product yielding improved processability during compounding and improved extension/spacing of TiO
2
.
It is a further object of the invention to provide such a treated barium sulfate product which when added to a polymeric compound does not have a deleterious impact on the physical properties of such compound.
It is another object of the invention to provide a method of treating a barium sulfate product with a hydrogen reactive polysiloxane that promotes improved manufacturing quality and consistency. Such hydrogen reactive polysiloxanes contain silicon-hydride groups as the reactive moiety.
In accordance with the illustrative embodiments and demonstrating features of the present invention, there is provided a surface treated barium sulfate product particularly suited for use in polymeric compositions such as those derived from a polyvinyl chloride or a polyolefin. The product comprises a plurality of barium sulfate particles and a silicon-hydride containing polysiloxane. This hydrogen reactive polysiloxane is deposited on the surface of the barium sulfate particles and bonds to this surface through means of a chemical reaction involving its reactive Si—H groups. The treatment level of the silicon-hydride containing polysiloxane can range from about 0.1% to about 2.0% by weight, but is preferably from about 0.5% to about 1.5% by weight on an active weight basis.
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patent: 3944705 (1976-03-01), Fujioka et al.
patent: 4263051 (1981-04-01), Crawford et al.
patent: 4505755 (1985-03-01), Shinozuka et al.
patent: 4551497 (1985-11-01), Shinozuka et al.
patent: 4818614 (1989-04-01), Fukui et al.
patent: 5393437 (1995-02-01), Bower
patent: 5401570 (1995-03-01), Heeks et al.
patent: 5-112430 (1993-05-01), None
patent: 08268840 (1996-10-01), None
patent: 09003211 (1997-01-01), None
patent: 10045523 (1998-02-01), None
Abstract JP 5-112430, May 1993.
Freeman Gary M.
Lynch Thomas J.
Outlaw Dwayne E.
Prowell Christina D.
J. M. Huber Corporation
Moore Margaret G.
Nieves Carlos
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