Method for making precipitated silica compositions and products thereof
A method of making abrasive compositions, and more particularly, it relates to a method of making precipitated silica abrasive compositions having excellent cleaning performance and lower abrasiveness with post-reactor sizing of the abrasive particles being performed directly via wet comminution and centrifugation, optionally followed by hydraulic chamber press filtering combined with vacuum dewatering and de-agglomeration is provided. By targeting a specific particle size range, it has been determined that higher pellicle film cleaning levels may be achieved without also increasing the dentin abrasion properties of the silica products themselves. As a result, dentifrices including such classified abrasive silica products, exhibiting particularly desirable cleaning benefits, can be provided for improved tooth polishing, whitening, and the like, without deleteriously affecting the hard tooth surfaces. Also encompassed within this invention also are products of this selective process scheme and dentifrices containing such particularly manufactured and classified silica products.
1. A method of providing a precipitated silica particulate composition, said method comprising the sequential steps of:
a) providing a plurality of precipitated silica particles that have not previously been dried prior to commencement of step “b”;
b) subjecting said plurality of particles to a comminuting step in a wet environment;
c) subjecting said wet-comminuted particles of step “b” to a particle size classification step wherein particles exhibiting a median particle size range of from about 0.1 to about 15 microns and a particle size span of less than or equal to 2 are collected;
d) subjecting said collected classified particles from step “c” to a dewatering step wherein said dewatered particles exhibit a moisture content of at most 60 wt %; and, optionally
e) subjecting said dewatered abrasive particles to a deagglomeration step.
2. The method of claim 1 wherein said collected classified particles from step “d” exhibit a median particle size of about 0.1 to about 10 microns and a particle size span of from about 0.5 to about 2.0.
3. The method of claim 2 wherein said collected classified particles from step “d” exhibit a median particle size of about 7 to about 9 microns, a particle size span of from about 1.25 to about 1.95.
4. The method of claim 1 wherein step “e” is present.
5. The method of claim 2 wherein step “e” is present.
6. The method of claim 3 wherein step “e” is present.
7. The method of claim 1 wherein said particles are amorphous precipitated silica particles and step “a” comprises the admixing of a sufficient amount of an alkali silicate and an acidulating agent to form precipitated silica particles.
8. The method of claim 2 wherein said particles are amorphous precipitated silica particles and step “a” comprises the admixing of a sufficient amount of an alkali silicate and an acidulating agent to form precipitated silica particles.
9. The method of claim 3 wherein said particles are amorphous precipitated silica particles and step “a” comprises the admixing of a sufficient amount of an alkali silicate and an acidulating agent to form precipitated silica particles.
10. The method of claim 4 wherein said particles are amorphous precipitated silica particles and step “a” comprises the admixing of a sufficient amount of an alkali silicate and an acidulating agent to form precipitated silica particles.
11. The classified and dewatered particulate composition produced by the method of claim 1 .
12. The classified and dewatered particulate composition produced by the method of claim 2 .
13. The classified and dewatered particulate composition produced by the method of claim 3 .
14. The classified and dewatered particulate composition produced by the method of claim 4 .