Colloid systems and wetting agents; subcombinations thereof; pro – Continuous liquid or supercritical phase: colloid systems;... – Aqueous continuous liquid phase and discontinuous phase...
Reexamination Certificate
1997-02-07
2001-02-06
Griffin, Steven P. (Department: 1754)
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous liquid or supercritical phase: colloid systems;...
Aqueous continuous liquid phase and discontinuous phase...
C423S277000, C423S305000, C423S328100
Reexamination Certificate
active
06184258
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to synthetic minerals. More particularly, the present invention relates a process for making synthetic microparticles and the use of such to improve the quality of the paper products produced therefrom. Even more specifically, the present invention relates to synthetic microparticles that are particularly suitable for use in papermaking processes where retention, drainage, and sheet formation are important.
1. Background of the Invention
Papermakers continue to look for ways to further improve the effectiveness of a retention system's ability to maximize filler and pulp fines retention in the final paper product. Over the last few years, inorganic microparticle retention aid systems have been developed in response to this need. Microparticle retention systems have several advantages. Some of these advantages include, higher retention levels, improved sheet formation, and better water drainage over the sheet forming section of the papermachine. These advantages allow the papermaker to produce a quality value-added product, to operate the papermaking process at higher levels of efficiency and to improve environmental conditions by operating a cleaner workplace. The cleaner work environment, the higher machine speeds, and the better quality sheet formation, result in tangible cost saving opportunities for the papermaker.
While there are several microparticle systems currently available to papermakers, two of these systems essentially enjoy most of the commercial success and are currently, most widely utilized. These include bentonite clay based systems and colloidal silica based systems. Bentonite is a naturally occurring clay which is found in deposits throughout the world. Bentonite clay consists mainly of aluminosilicate with lesser amounts of other elements such as, for example, calcium, magnesium, and iron. Bentonite based systems are particularly suitable for use in groundwood papermaking systems. Colloidal silica based systems are a specific form of microparticulate silica having very small i.e., 1 nm to 2 nm diameter particles, which are linked together in chains or networks to form three-dimensional structures known as microcels. The silica systems are particularly employed in wood-free mills and have not enjoyed widespread use in groundwood papermaking because they are expensive, when compared to other microparticles.
What has been found to be novel and unanticipated by the prior art is a process for the production of a synthetically produced bentonite-type inorganic microparticle and the subsequent use of such in papermaking processes where retention, water drainage, sheet formation and tangible cost saving opportunities are important.
It is therefore an object of the present invention to provide a microparticle retention aid system that is capable of use in papermaking processes to maximize filler and pulp fines retention, water drainage and sheet formation. Another object of the present invention is to provide a cost effective synthetically produced bentonite type inorganic microparticle when compared to silica based systems. A further object of the present invention to provide a method for improving the quality of the paper product.
These and other objects of the present invention will become apparent as further provided in the detailed specification which follows.
2. Related Art
International Publication No. WO 92/20862 discloses a process for improving the production of paper and paper products by adding a cationic polymer and an amorphous metal silicate separately to the papermaking furnish with sufficient mixing between additions. The order of addition of these components is not critical, however, the preferred order of addition is to add the polymer prior to the last high shear element. Subsequently the amorphous metal silicate is added before feeding the resultant mixture to the headbox of a paper making machine, without subjecting the mixture to any further substantial shear. Products produced according to the process of this invention are useful for increasing retention, drainage, formation in the production of paper from pulp slurries.
U.S. Pat. No. 3,784,442 discloses the reaction of sodium silicate and aluminum sulfate in an aqueous medium. The resulting precipitate is subsequently filtered, washed and dried. Products produced according to the process of this invention are useful as pigments, and moisture conditioners and are especially useful as rubber reinforcing materials and as a filler in papermaking.
U.S. Pat. No. 4,213,874 discloses a method for producing finely divided amorphous, precipitated alkali metal alumino silicates having increased ion exchange properties. The products of the invention have base or ion exchange capacities equal to known crystalline zeolitic base exchanges or absorbents and are useful as water softening and detergent additives.
SUMMARY OR THE INVENTION
What has been found to be novel and unanticipated by the prior art is a process for the production of a synthetically produced bentonite-type inorganic microparticles and the subsequent use of such in papermaking processes where retention, water drainage, sheet formation and tangible cost saving opportunities are important.
DETAILED DESCRIPTION OF THE INVENTION
Synthetic microparticles for use as retention aids in papermaking according to the instant invention are aluminosilicates, aluminophosphatosilicates, and aluminoboratosilicates.
The aluminosilicate microparticles are prepared by aqueous precipitation techniques using soluble salts of a meta-silicate and an aluminum (III). The aluminophosphatosilicates are prepared by aqueous precipitation techniques using soluble salts of a meta-silicate, an aluminum (III), and a phosphate. The aluminoboratosilicates are prepared by aqueous precipitation techniques using soluble salts of a meta-silicate, an aluminum (III), and a borate.
The preferred process for the preparation of the synthetic microparticles of the instant invention is an aqueous precipitation process using vigorous agitation, with the reactants being combined at ambient temperature. The reactants are typically from about 1 percent to about 10 percent by weight aqueous solutions. The preferred amounts of the specific reactants used in accordance with the instant invention are now described:
Aluminosilicate Microparticles
Aluminosilicate microparticles prepared according to the present invention have the general formula:
M
x
+n
[Al
x
Si
y
O
2x+y
]
−x
•zH
2
O
The values of x and y in the equation that are available in this method range from x/y=0.4 to x/y=0.7. The optimum value of x/y will vary according to the particular papermaking furnish being used.
Aluminophosphatosilicate Microparticles
Aluminophosphatosilicate microparticles prepared according to the instant invention can be described by the following general formula:
M
w
Al
x
Si
y
P
z
O
(½w+3/2x+2y+5/2z)
where M=H, Li, Na, K
The phosphate and meta-silicate solutions are first mixed together, then subsequently mixed with the aluminum sulfate solution to give the precipitation product. The aluminophosphatosilicate microparticles are preferred wherein the reactant molar ratio is about 0.70 Al/0.62 Si/0.36 P, the molar ratio may vary depending on the particular papermaking furnish being used.
Aluminoboratosilicate Microparticle
Aluminoboratosilicate microparticles prepared according to the instant invention can be described by the following general formula:
M
w
Al
x
Si
y
B
z
O
(½w+3/2x+2y+3/2z)
where M=H, Li, Na, K
The borate and meta-silicate solutions are first mixed together prior to mixing with the aluminum sulfate solution to give the precipitated product. The aluminoboratosilicate microparticles are preferred where in the reactant molar ratio is about 1.0 Al/1.0 Si/0.71 B, the molar ratio may vary some depending on the particular papermaking furnish being used.
The synthetic mineral microparticle product of the instant invention has a particle size
Griffin Steven P.
Hendrickson Stuart L.
Minerals Technologies Inc.
Morris Terry B.
Powell Marvin J.
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