Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2000-06-16
2002-09-24
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S404000, C428S405000, C428S407000, C523S212000, C524S265000, C524S267000, C524S269000
Reexamination Certificate
active
06455158
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the treatment of pigments and fillers using alkylsilanes and alkylsilane copolymers. The alkylsilane copolymers are prepared by the hydrolysis and condensation of monomeric or oligomeric silanes. The alkylsilanes and alkylsilane copolymers are particularly useful in the surface treatment of minerals for improving the dispersibility and processibility of the minerals in polymeric compositions. In particular, the alkylsilane copolymers of the present invention find particular utility in the surface treatment of titanium dioxide which is subsequently compounded with polyolefins, especially low density polyethylene. The alkylsilanes find particular utility in the silanization of clays, nanoclays, aluminum trihydroxides and magnesium hydroxides.
BACKGROUND OF THE INVENTION
Organo compounds have been extensively employed in the surface treatment of inorganic particulate materials such as inorganic oxide materials such as films, particulate fillers and pigments, and fibers (such as glass fibers, aluminum fibers and steel fibers) which act to reinforce resins or plastic materials into which it is incorporated.
The typical organosilicon treatment involves coating such surfaces with a hydrolyzate (and/or condensate of the hydrolyzate) of an organofunctional hydrolyzable silane.
In particular, organosilicon compounds have been used to modify pigments such as titanium dioxide in order to alter the dispersion characteristics of the pigment in a given matrix. Matrix materials commonly used include thermoplastic polymers such as low density polyethylene. Such treatment of titanium dioxide is well known in the art. For instance, U.S. Pat. No. 4,061,503 discloses the treatment of particulate titanium dioxide with a polyether substituted silicon compound for improving the dispersibility of titanium dioxide in pigmented and/or filled paints and plastics, and reinforced plastic composite compositions. The silane compound is described and claimed as having at least two hydrolyzable groups bonded to the silicon and an organic group which contains a polyalkylene oxide group, the silane being present on the surfaces of the titanium dioxide particles in an amount sufficient to improve the dispersibility of the particles in a resin or plastic medium.
U.S. Pat. No. 4,151,154 discloses a modified hydrophobic colored or magnetic pigment or filler comprising a hydrophobic pigment or filler containing from 0.05 to 10% by weight, based on the weight of the pigment or filler, or an organopolysiloxane.
Further, U.S. Pat. No. 4,810,305 discloses a modified hydrophobic pigment or filler containing 0.05 to 10 weight % of an organopolysiloxane with improved dispersibility in synthetic resins, and U.S. Pat. No. 5,607,994 and U.S. Pat. No. 5,631,310 disclose the use of alkylsilane for the treatment of TiO
2
to improve processibility in compounding with plastics and improve performance properties such as lacing resistance in a polymer matrix.
U.S. Pat. No. 4,950,779 describes a nonaqueous method of making silicone oligomers by using stoichiometric amounts of formic acid to effect the condensation of polyalkyoxysilanes or polyaminosilanes.
U.S. Pat. No. 5,932,757describes a mixture of oligomers of condensed alkylalkoxysilanes suitable for application in particular, to mineral surfaces, which substantially prevents wetting of the mineral surfaces by a hydrophilic liquid.
The present inventors have found that the hydrolysis and condensation of different silanes, as opposed to the self condensation of a single silane or silane oligomer, i.e. monomers, can produce alkylsilane copolymers and terpolymers which have a broader range of performance capabilities than a homopolymer. The alkylsilane copolymers and terpolymers of the present invention may be utilized for the surface treatment of fillers, pigments and so forth to improve the dispersibility of such compounds in a thermoplastic resins or polymers, including olefinic polymers such as low density polyethylene, even at extremely high loading levels. The treated filler or pigments of the present invention exhibit excellent compounding processibility, dispersion, and optical properties including whiteness and yellowness index, when blended with olefinic polymers in contrast to untreated fillers and pigments, or fillers and pigments treated with single silanes or silane oligomers or homopolymers. In particular, the present invention has found utility in the treatment of titanium dioxide pigment for improved dispersibility in low density polyethylene.
SUMMARY OF THE INVENTION
The present invention relates to the surface treatment of pigments and fillers with alkylsilanes and alkylsilane copolymers.
The alkylsilane copolymers of the present invention are prepared by hydrolysis and condensation of monomeric and/or oligomeric silanes. The alkylsilane copolymers have a plurality of hydrolyzable groups and comprise, in their backbone structures, at least two different monomers.
More specifically, the alkylsilane copolymer of the present invention has the following general structure:
R[SiR
1
R
2
O]
m
—[SiR
3
R
4
O]
n
R
5
where
R, R
1
, R
4
and R
5
are hydrolyzable groups such as alkoxy, halogen, acetoxy, hydroxy, and so forth, or mixture thereof;
R
2
is a nonhydrolyzable C
1
-C
20
, aliphatic, cycloaliphatic or aromatic hydrocarbon group directly or indirectly bonded to the silicon atom;
R
3
is selected from nonhydrolyzable and hydrolyzable groups different from R
2
;
and m and n are each independently 1 to 20.
The alkylsilanes may also be terpolymers of the following general formula:
R[SiR
1
R
2
O]
m
—[SiR
3
R
4
O]
n
—[SiR
6
R
7
O]
p
R
5
where R, R
1
, R
2
, R
3
, R
4
and R
5
are as described above;
R
6
may be a nonhydrolyzable group as defined for R
3
but different from R
2
and R
3
;
R
7
is a hydrolyzable group such as alkoxy, halogen, acetoxy, hydroxy, and so forth, or mixture thereof; and
m, n and p are each independently 1 to 20.
The alkylsilanes are alkyltrialkoxysilanes.
The alkylsilane copolymers and alkylsilanes of the present invention can be used to surface treat or silanize mineral type compounds such as pigments or fillers. In particular, the alkylsilanes are useful for the silanization of clays, nanoclays, aluminum trihydroxides and magnesium hydroxides.
This surface treatment or silanization improves the dispersibility and processibility of the pigments or minerals when compounded with polymeric materials. The materials require lower torque and pressure when melt compounded with polymeric materials in extruders.
The surface treated or silanized pigments or fillers of the present invention, in addition to the improvements noted above, also exhibit excellent optical properties including whiteness and yellowness index, hue, chroma and gloss.
DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
The compounds that can be treated or silanized using the alkylsilanes and alkylsilane copolymers and terpolymers of the present invention include pigments and fillers, inorganic particulate materials such as inorganic oxide materials such as films, and fibers (such as glass fibers, aluminum fibers and steel fibers) which act to reinforce resins or plastic materials into which it is incorporated. In particular, alkylsilanes and alkysilane copolymers and terpolymers can be used to treat white pigments and fillers.
Some specific materials for surface treatment or silanization include calcined clay, nanoclay, aluminum trihydroxide, magnesium hydroxide, and so forth. In particular, the alkylsilane copolymers of the present invention can be used to treat titanium dioxide which is often used as a pigment.
The TiO
2
pigments useful in the present invention generally are in the rutile or anatase crystalline form. They are commonly prepared by either a chloride process or a sulfate process. The optimum average particle size can range from about 0.005 to about 1 micron. The TiO
2
pigments may also contain ingredients added thereto to further improve dispersibility character
Alfonso Juan
Christie Robert E.
Mei Henry L.
Panzer Louis M.
Petty Herbert E.
Crompton Corporation
Dilworth Michael P.
Kiliman Leszek
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