U.S. patent application number 14/920951 was filed with the patent office on 2016-02-11 for treated silicas and metal silicates for improved cleaning in dentifrice.
This patent application is currently assigned to JM Huber Corporation. The applicant listed for this patent is JM Huber Corporation. Invention is credited to Karl W. Gallis, William J. Hagar, Patrick McGill, Terry W. Nassivera.
Application Number | 20160038387 14/920951 |
Document ID | / |
Family ID | 50728136 |
Filed Date | 2016-02-11 |
United States Patent
Application |
20160038387 |
Kind Code |
A1 |
Gallis; Karl W. ; et
al. |
February 11, 2016 |
TREATED SILICAS AND METAL SILICATES FOR IMPROVED CLEANING IN
DENTIFRICE
Abstract
Treated silica materials are disclosed, together with methods of
making such materials and dentifrice compositions comprising the
treated silica materials.
Inventors: |
Gallis; Karl W.;
(Perryville, MD) ; Hagar; William J.; (Perryville,
MD) ; McGill; Patrick; (Darlington, MD) ;
Nassivera; Terry W.; (North East, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JM Huber Corporation |
Atlanta |
GA |
US |
|
|
Assignee: |
JM Huber Corporation
|
Family ID: |
50728136 |
Appl. No.: |
14/920951 |
Filed: |
October 23, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13835819 |
Mar 15, 2013 |
9186307 |
|
|
14920951 |
|
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|
|
61727831 |
Nov 19, 2012 |
|
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Current U.S.
Class: |
424/49 |
Current CPC
Class: |
A61K 8/0241 20130101;
A61K 2800/61 20130101; A61K 8/25 20130101; A61K 8/26 20130101; C01B
33/193 20130101; A61K 8/19 20130101; A61K 6/70 20200101; A01N 59/06
20130101; A61Q 11/00 20130101 |
International
Class: |
A61K 8/25 20060101
A61K008/25; A61K 8/19 20060101 A61K008/19; A61Q 11/00 20060101
A61Q011/00; A61K 8/26 20060101 A61K008/26 |
Claims
1-20. (canceled)
21. A dentifrice composition comprising: (i) a precipitated silica
material comprising from about 0.5 wt. % to about 10 wt. % of
aluminum, and wherein the precipitated silica material is
characterized by: a loss on ignition at 900.degree. C. of less than
about 3 wt. %; and a pellicle cleaning ratio (PCR) at 20% loading
of at least 90; and (ii) one or more dentifrice components selected
from an abrasive, a rheological aid, a whitener, a sweetener, a
flavoring additive, a surfactant, a colorant, or a combination
thereof.
22. The composition of claim 21, wherein the precipitated silica
material comprises from about 1 wt. % to about 4 wt. % of
aluminum.
23. The composition of claim 22, wherein the composition comprises
up to 35 wt. % of the precipitated silica material.
24. The composition of claim 21, wherein the composition comprises
up to 30 wt. % of the precipitated silica material.
25. The composition of claim 21, wherein the precipitated silica
material is further characterized by an Einlehner abrasion value in
a range from 18 to 34.8 mg lost/100,000 revolutions.
26. The composition of claim 21, wherein the precipitated silica
material is characterized by a pellicle cleaning ratio (PCR) at 20%
loading of from 90 to about 110.
27. The composition of claim 26, wherein the precipitated silica
material comprises from about 1 wt. % to about 4 wt. % of
aluminum.
28. The composition of claim 27, wherein the composition comprises
up to 35 wt. % of the precipitated silica material.
29. The composition of claim 26, wherein the composition comprises
up to 30 wt. % of the precipitated silica material.
30. The composition of claim 26, wherein the precipitated silica
material is further characterized by an Einlehner abrasion value in
a range from 18 to 34.8 mg lost/100,000 revolutions.
31. A dentifrice composition comprising: (i) a precipitated silica
material comprising from about 0.5 wt. % to about 10 wt. % of tin,
and wherein the precipitated silica material is characterized by: a
loss on ignition at 900.degree. C. of less than about 3 wt. %; and
a pellicle cleaning ratio (PCR) at 20% loading of at least 90; and
(ii) one or more dentifrice components selected from an abrasive, a
rheological aid, a whitener, a sweetener, a flavoring additive, a
surfactant, a colorant, or a combination thereof.
32. The composition of claim 31, wherein the precipitated silica
material comprises from about 1 wt. % to about 4 wt. % of tin.
33. The composition of claim 32, wherein the composition comprises
up to 35 wt. % of the precipitated silica material.
34. The composition of claim 31, wherein the composition comprises
up to 30 wt. % of the precipitated silica material.
35. The composition of claim 31, wherein the precipitated silica
material is further characterized by an Einlehner abrasion value in
a range from 18 to 34.8 mg lost/100,000 revolutions.
36. The composition of claim 31, wherein the precipitated silica
material is characterized by a pellicle cleaning ratio (PCR) at 20%
loading of from 90 to about 110.
37. The composition of claim 36, wherein the precipitated silica
material comprises from about 1 wt. % to about 4 wt. % of tin.
38. The composition of claim 37, wherein the composition comprises
up to 35 wt. % of the precipitated silica material.
39. The composition of claim 36, wherein the composition comprises
up to 30 wt. % of the precipitated silica material.
40. The composition of claim 36, wherein the precipitated silica
material is further characterized by an Einlehner abrasion value in
a range from 18 to 34.8 mg lost/100,000 revolutions.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of priority to
U.S. Provisional Patent Application Ser. No. 61/727,831, filed on
Nov. 19, 2012, which is hereby incorporated by reference in its
entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates to silica and silicate
materials, and specifically to treated silica and metal silicate
materials that can provide improved cleaning properties in a
dentifrice composition.
[0004] 2. Technical Background
[0005] Conventional dentifrice compositions comprise an abrasive
substance to assist in the removal of dental deposits. One such
dental deposit is pellicle, a protein film which adheres strongly
to tooth surfaces and often contains brown or yellow materials that
can result in tooth discoloration. A dentifrice should be
sufficiently abrasive to clean the tooth surface, but not so
abrasive as to damage the hard tissues of the tooth.
[0006] The performance of the dentifrice can thus be highly
sensitive to the aggressiveness of the abrasive substance.
Synthetic low-structure silica materials have been utilized as
abrasive substances due to their effectiveness as abrasives, as
well as their low toxicity characteristics and compatibility with
other dentifrice components, such as sodium fluoride.
[0007] To date, conventional abrasive materials have limitations
associated with maximizing cleaning and minimizing dentin abrasion,
as well as complexity in terms of manufacturing procedures.
Accordingly, there exists a general need to develop new dental
abrasives and dentifrices thereof that exhibit high pellicle film
cleaning properties and have acceptable dentin abrasion levels.
This need and other needs are satisfied by the compositions and
methods of the present disclosure.
SUMMARY
[0008] In accordance with the purpose(s) of the invention, as
embodied and broadly described herein, this disclosure, in one
aspect, relates to silica and silicate materials, and specifically
to treated silica and metal silicate materials that can provide
improved cleaning properties in a dentifrice.
[0009] In one aspect, the present disclosure provides a method for
preparing a silica material, the method comprising: heat treating a
silica material comprising a metal compound, wherein the metal has
a Mohs hardness value of at least about 5.5 in its oxide form, and
wherein heat treating comprises heating the silica material at a
temperature and for a period of time sufficient to dehydrate at
least a portion of the metal compound disposed on a surface of the
material.
[0010] In one aspect, the present disclosure provides a method for
preparing a dentifrice composition, the method comprising: heat
treating a silica material at a temperature of from about
400.degree. C. to about 900.degree. C. to form a heat treated
silica material, and then contacting the heat treated silica
material with one or more dentifrice components to form a
dentifrice composition.
[0011] In another aspect, the present disclosure provides a silica
material having one or more of the following: a metal ion disposed
on a surface thereof at a concentration of up to about 10 wt. %; a
loss on ignition at 900.degree. C. of less than about 3 wt. %; or
an increased degree of polymerization as compared to a conventional
silica material not exposed to a heat treatment step.
[0012] In another aspect, the present disclosure provides a silica
material having an increased Einlehner abrasion value of at least
about 150%, as compared to a conventional non heat treated
precipitated silica and having an increase in RDA value still
within the acceptable RDA range after heat treatment, as compared
to a conventional non heat treated precipitated silica.
[0013] In yet another aspect, the present disclosure provides a
dentifrice composition comprising the silica material of any of the
preceding claims
[0014] Additional aspects of the invention will be set forth in
part in the description which follows, and in part will be obvious
from the description, or can be learned by practice of the
invention. The advantages of the invention will be realized and
attained by means of the elements and combinations particularly
pointed out in the appended claims. It is to be understood that
both the foregoing general description and the following detailed
description are exemplary and explanatory only and are not
restrictive of the invention, as claimed.
DESCRIPTION
[0015] The present invention can be understood more readily by
reference to the following detailed description of the invention
and the Examples included therein.
[0016] Before the present compounds, compositions, articles,
systems, devices, and/or methods are disclosed and described, it is
to be understood that they are not limited to specific synthetic
methods unless otherwise specified, or to particular reagents
unless otherwise specified, as such can, of course, vary. It is
also to be understood that the terminology used herein is for the
purpose of describing particular aspects only and is not intended
to be limiting. Although any methods and materials similar or
equivalent to those described herein can be used in the practice or
testing of the present invention, example methods and materials are
now described.
[0017] All publications mentioned herein are incorporated herein by
reference to disclose and describe the methods and/or materials in
connection with which the publications are cited.
[0018] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. Although
any methods and materials similar or equivalent to those described
herein can be used in the practice or testing of the present
invention, example methods and materials are now described.
[0019] As used herein, unless specifically stated to the contrary,
the singular forms "a," "an" and "the" include plural referents
unless the context clearly dictates otherwise. Thus, for example,
reference to "a filler" or "a solvent" includes mixtures of two or
more fillers, or solvents, respectively.
[0020] As used herein, the terms "optional" or "optionally" means
that the subsequently described event or circumstance can or can
not occur, and that the description includes instances where said
event or circumstance occurs and instances where it does not.
[0021] For purposes of this invention, a "dentifrice" has the
meaning defined in Oral Hygiene Products and Practice, Morton
Pader, Consumer Science and Technology Series, Vol. 6, Marcel
Dekker, N Y 1988, p. 200, which is incorporated herein by
reference. Namely, a "dentifrice" is " . . . a substance used with
a toothbrush to clean the accessible surfaces of the teeth.
Dentifrices are primarily composed of water, detergent, humectant,
binder, flavoring agents, and a finely powdered abrasive as the
principal ingredient . . . a dentifrice is considered to be an
abrasive-containing dosage form for delivering anti-caries agents
to the teeth." Dentifrice formulations contain ingredients which
must be dissolved prior to incorporation into the dentifrice
formulation (e.g. anti-caries agents such as sodium fluoride,
sodium phosphates, flavoring agents such as saccharin).
[0022] The Brass Einlehner (BE) Abrasion test used to measure the
hardness of the precipitated silicas/silica gels reported in this
application is described in detail in U.S. Pat. No. 6,616,916,
incorporated herein by reference, involves an Einlehner AT-1000
Abrader generally used as follows: (1) a Fourdrinier brass wire
screen is weighed and exposed to the action of a 10% aqueous silica
suspension for a fixed length of time; (2) the amount of abrasion
is then determined as milligrams brass lost from the Fourdrinier
wire screen per 100,000 revolutions. The result, measured in units
of mg loss, can be characterized as the 10% brass Einlehner (BE)
abrasion value.
[0023] The Radioactive Dentin Abrasion (RDA) values of dentifrices
containing the silica compositions used in this invention are
determined according to the method set forth by Hefferen, Journal
of Dental Res., July-August 1976, 55 (4), pp. 563-573, and
described in Wason U.S. Pat. Nos. 4,340,583, 4,420,312 and
4,421,527, which publications and patents are incorporated herein
by reference.
[0024] The cleaning property of dentifrice compositions is
typically expressed in terms of Pellicle Cleaning Ratio ("PCR")
value. The PCR test measures the ability of a dentifrice
composition to remove pellicle film from a tooth under fixed
brushing conditions. The PCR test is described in "In Vitro Removal
of Stain with Dentifrice" G. K. Stookey, et al., J. Dental Res.,
61, 1236-9, 1982. Both PCR and RDA results vary depending upon the
nature and concentration of the components of the dentifrice
composition. PCR and RDA values are unitless.
[0025] Disclosed are the components to be used to prepare the
compositions of the invention as well as the compositions
themselves to be used within the methods disclosed herein. These
and other materials are disclosed herein, and it is understood that
when combinations, subsets, interactions, groups, etc. of these
materials are disclosed that while specific reference of each
various individual and collective combinations and permutation of
these compounds can not be explicitly disclosed, each is
specifically contemplated and described herein. For example, if a
particular compound is disclosed and discussed and a number of
modifications that can be made to a number of molecules including
the compounds are discussed, specifically contemplated is each and
every combination and permutation of the compound and the
modifications that are possible unless specifically indicated to
the contrary. Thus, if a class of molecules A, B, and C are
disclosed as well as a class of molecules D, E, and F and an
example of a combination molecule, A-D is disclosed, then even if
each is not individually recited each is individually and
collectively contemplated meaning combinations, A-E, A-F, B-D, B-E,
B-F, C-D, C-E, and C-F are considered disclosed. Likewise, any
subset or combination of these is also disclosed. Thus, for
example, the sub-group of A-E, B-F, and C-E would be considered
disclosed. This concept applies to all aspects of this application
including, but not limited to, steps in methods of making and using
the compositions of the invention. Thus, if there are a variety of
additional steps that can be performed it is understood that each
of these additional steps can be performed with any specific
embodiment or combination of embodiments of the methods of the
invention.
[0026] Each of the materials disclosed herein are either
commercially available and/or the methods for the production
thereof are known to those of skill in the art.
[0027] It is understood that the compositions disclosed herein have
certain functions. Disclosed herein are certain structural
requirements for performing the disclosed functions, and it is
understood that there are a variety of structures that can perform
the same function that are related to the disclosed structures, and
that these structures will typically achieve the same result.
[0028] As briefly described above, the present disclosure provides
silica and silicate materials that can be used in dentifrice
compositions, methods for the preparation thereof, and dentifrice
compositions comprising the inventive silica and silicate
materials.
[0029] In the oral care industry, it would be desirable to have
dentifrice materials with improved cleaning properties. It would
also be advantageous for such dentifrice materials to exhibit
moderate dentin and enamel abrasion properties, so as to not damage
teeth during repeated use. Zinc and phosphate salts have been added
to dentifrice materials and can result in small improvements in
pellicle cleaning ratios (PCR), but further improvements are
needed. Manufacturers have traditionally used high hardness
abrasive materials, such as a-alumina (i.e., corundum), but these
materials can be expected to exhibit higher levels of enamel
abrasion (REA) and a lack of fluoride availability.
[0030] In one aspect, the silica materials of the present
disclosure can provide improved cleaning (e.g., PCR), while
maintaining desirable RDA and/or REA values. In a further aspect,
the silica materials can also provide desirable fluoride
availability. In various aspects, the silica materials of the
present disclosure comprise heat treated silica materials. In
another aspect, the silica materials of the present disclosure
comprise one or more metal ions present in their oxide form.
[0031] In one aspect, precipitated silica materials can be produced
by the destabilization and precipitation of amorphous silica from
soluble alkaline silicates by the addition of a mineral acid, acid
gas, or acidulating agent under conditions in which primary
particles initially formed tend to associate with each other, but
without agglomeration into a three-dimensional gel structure.
Silica
[0032] Silica materials suitable for use in dentifrice compositions
can comprise synthetically produced, precipitated silicas. In one
aspect, the silica material can be a low-structure silica material.
These silica materials can be produced using various procedures. In
one aspect, a silicate compound, such as, for example, sodium
silicate, can be contacted with a mineral acid to form a silicate
solution. The silicate solution can then be combined with sulfuric
acid and amorphous silica particles can be precipitated.
[0033] The silicate compound can comprise any silicate compound
suitable for use in preparing a precipitated silica material. In
various aspects, any suitable alkali metal silicate can be used
with the methods described herein, including metal silicates,
disilicates, and the like. In one aspect a water soluble silicate,
such as, for example, a potassium silicate, a sodium silicate, or a
combination thereof, can be used. In other aspects, a silicate
compound having a desirable metal:silicate molar ratio (MR) can be
selected. For example, sodium silicates can generally have a
metal:silicate molar ratio of from about 1:1 to about 1:3.5. In one
aspect, the silicate compound can have a molar ratio of from about
1:1 to about 1:3.5, for example, about 1:1, 1:1.25, 1:1.5, 1:1.75,
1:2, 1:2.25; 1:2.5; 1:2.75; 1:3, 1:3.25, or 1:3.5; or from about
1:2.5 to about 1:3.5, for example, about 1:2.5; 1:2.75; 1:3,
1:3.25, or 1:3.5. In another aspect, the silicate compound can have
a molar ratio of about 1:3.32.
[0034] In one aspect, the silicate compound, such as, for example,
sodium silicate, can be contacted with a mineral acid to produce a
silicate solution. In general, any mineral acid capable of at least
partially dissolving the silicate compound and forming a silicate
solution can be used. In another aspect, the selection of a
particular mineral acid can vary, depending upon the specific
silicate compound being used. In various aspects, the mineral acid
can comprise nitric acid, hydrochloric acid, phosphoric acid, boric
acid, hydrofluoric acid, or a combination thereof. In other
aspects, other suitable acids can be utilized in addition to or in
lieu of any acid specifically recited herein. The silicate compound
and acid can be contacted in any suitable ratio so as to provide a
solution having a desirable silicate concentration. In one aspect,
the solution comprises from about 8 wt. % to about 35 wt. %
silicate, for example, about 8, 9, 11, 13, 15, 17, 19, 21, 23, 25,
27, 29, 31, 33, or 35 wt. % silicate. In another aspect, the
solution comprises from about 8 wt. % to about 20 wt. % silicate,
for example, about 8, 10, 12, 14, 16, 18, or 20 wt. % silicate. In
a specific aspect, the silicate solution can comprise about 19.5
wt. % silicate. In other aspects, the resulting silicate solution
can have a silicate concentration less than or greater than any
value specifically recited herein, and the present disclosure is
intended to cover such solutions. In still other aspects, silicate
solutions are commercially available and can be purchased and
utilized as-is (e.g., from Sigma-Alrich Corporation, St. Louis,
Mo., USA).
[0035] In another aspect, the silicate solution can have a silicate
concentration of from about 2 wt. % to about 10 wt. %, for example,
about 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9,
9.5, or 10 wt. %. In yet another aspect a silicate solution having
a higher concentration, for example, about 20 wt. %, can be diluted
in water to a lower concentration as described herein. For example,
a quantity of a 19.5 wt. % silicate solution can be diluted to a
concentration of about 5.5 wt. %.
[0036] The silicate solution can optionally be heated, for example,
to about 75.degree. C., about 80.degree. C., about 85.degree. C.,
about 87.degree. C., about 90.degree. C., or higher, and/or
stirred.
Dopant Metal
[0037] In one aspect, the resulting precipitated silica material
comprises one or more metal ions. In another aspect, the metal
ions, if present, have a Mohs hardness value of at least about 5.5
in their oxide form. In various aspects, the metal ions can
comprise aluminum, tin, or a combination thereof. In other aspects,
other metal ions not specifically recited herein can be used, and
the present disclosure is not intended to be limited to the metal
ions recited herein. In a specific aspect, the metal ion comprises
aluminum.
[0038] A metal ion, if present, can be introduced using a salt, for
example, a soluble salt of the metal. In one aspect, such a metal
salt can be at least partially solvated in an aqueous solution, a
sulfuric acid solution, or a silicate solution. In one aspect, the
metal salt can comprise a sulfate, a nitrate, a phosphate, a
carbonate, or a combination thereof. In another aspect, the metal
salt can comprise a sulfate, a nitrate, or a combination thereof.
In various exemplary aspects, the metal salt can comprise aluminum
sulfate, stannous nitrate, or a combination thereof.
[0039] The silicate solution, metal salt, and an acidulating agent,
such as, for example, sulfuric acid, can then be contacted. The
concentration and/or pH of the acidulating agent can be any
concentration and/or pH suitable for use in preparing a
precipitated silica material. In various aspects, the acidulating
agent can comprise from about 5 wt. % to about 35 wt. % sulfuric
acid, for example, about 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25,
27, 29, 31, 33, or 35 wt. %; or from about 12 wt. % to about 22 wt.
% sulfuric acid, for example, about 12, 13, 14, 15, 16, or 17 wt. %
sulfuric acid.
[0040] In one aspect, one or more metal salts can be dissolved in
the acidulating agent prior to contacting with the silicate. In
another aspect, the metal salt, if present, can be dissolved in
water or an acidic solution to be subsequently contacted with the
acidulating agent and/or silicate solution. The concentration of
the metal salt can vary, depending upon the reaction conditions and
concentration of other reactants, and the present invention is not
intended to be limited to any particular metal salt concentration.
In one aspect, the metal salt concentration can be from about 0.2 N
to about 0.4 N, for example, about 0.2, 0.22. 0.24, 0.26, 0.28,
0.29, 0.3, 0.32, 0.34, 0.36, 0.38, or 0.4 N. In another aspect, a
sulfuric acid solution comprising, for example, aluminum sulfate,
can have an aluminum concentration of from about 0.10 mol/L to
about 0.20 mol/L, for example, about 0.10, 0.11, 0.12, 0.13, 0.14,
0.15, 0.16, 0.17, 0.18, 0.19, or 0.20 mol/L. Similarly, a sulfuric
acid solution comprising, for example, stannous nitrate, can have a
tin concentration of from about 0.25 mol/L to about 0.35 mol/L, for
example, about 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32,
0.33, 0.34, or 0.35 mol/L
[0041] In a specific aspect, a quantity of diluted, for example,
about 5.5 wt. %, silicate solution can be disposed in a vessel, and
then additional silicate solution and a solution of sulfuric acid
containing a dissolved metal salt can simultaneously or
substantially simultaneously be added to the vessel. In such an
aspect, the solution in the vessel can optionally be heated and/or
stirred during reaction.
[0042] The silicate solution and acidulating agent, for example,
comprising the dissolved metal salt, can be added to the vessel
over a period of time. In one aspect, the silicate solution,
acidulating agent, metal salt, or any combination thereof, can be
added slowly so as to allow at least partial mixing in the reaction
vessel. In another aspect, the silicate solution and the
acidulating agent can be added simultaneously or substantially
simultaneously. In various aspects, the addition ratio of silicate
solution to acidulating agent, for example, comprising a metal
salt, if present, can be about from about 1:0.1 to about 1:0.6, for
example, about 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.33, 1:0.35,
1:0.4, 1:0.45, 1:0.5, 1:0.55, 1:0.6. In another aspect, the
addition ratio of silicate solution to acidulating agent can be
about 1:0.33, such that, for example, the silicate solution is
added at a rate of about 1.1 L/min and optionally a metal salt
containing sulfuric acid solution is simultaneously added at a rate
of about 0.33 L/min.
[0043] The silicate solution and acidulating agent can be added for
a fixed period of time or until exhausted. In one aspect, addition
of the silicate solution can be stopped after a period of time,
wherein addition of the acidulating agent continues for an
additional period of time. In one aspect, the addition of the
acidulating agent can be continued until a desired pH is reached in
the reaction vessel. In such an aspect, the acidulating agent can
be added until the pH in the reaction vessel is from about 4.5 to
about 6.5, for example, about 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2,
5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, or 6.5;
or from about 5.3 to about 5.7, for example, about 5.3, 5.4, 5.5,
5.6, or 5.7.
[0044] In another aspect, addition of the silicate solution and/or
acidulating agent can be stopped at any desired time and the pH of
the reaction vessel subsequently adjusted to a desired value.
[0045] In another aspect, the silicate solution can be neutralized
or at least partially neutralized by contacting with a metal salt
or a solution thereof, without the need for an acid.
[0046] After contacting the silicate solution, the acidulating
agent, and the metal salt, the resulting solution can be allowed to
digest for a period of time. In one aspect, the solution can be
allowed to digest at a temperature of about 90.degree. C. for a
period of at least about 10 minutes. In other aspects, a digestion
step, if performed, can be performed for any suitable length of
time and at any suitable temperature, and one of skill in the art,
in possession of this disclosure, could readily determine
appropriate digestion conditions. After digestion, the resulting
precipitated silica material can be separated, for example, by
filtration, from the solution. The separated silica material can
optionally be washed to remove all or a portion of the acid and any
unreacted, dissolved silicate or metal salt. In one aspect, the
separated silica material can be washed, for example, with
deionized water, until a conductivity of about 1,500 .mu.S is
reached. In other aspects, the separated silica material can be
utilized as-is, or can be washed to a greater or lesser extent that
that specifically described herein. In another aspect, the
precipitated silica material can be dried, for example, by placing
in a 105.degree. C. oven overnight. In another aspect, the
precipitated silica material can be spray dried.
[0047] If desired, the precipitated silica material can optionally
be processed to achieve a desired average particle size or particle
size distribution. In various aspects, the precipitated silica can
be milled and/or ground to a desired average particle size, for
example, of about 10 .mu.m.
[0048] In one aspect, the reaction (e.g., contacting) of the
silicate solution, acidulating agent, and metal salt can be
conducted at an elevated temperature and/or while stirring so as to
avoid the formation of a gel or aggregation of silica particles. In
other aspects, it should be understood that the method of
contacting and/or mixing, concentration and addition rates of
reactants, temperature, and pH can each affect the properties of
the resulting precipitated silica.
[0049] In one aspect, the preparation of a precipitated silica can
be conducted as described in one or more of U.S. Pat. Nos.
2,739,073, 2,848,346, and 5,891,421, which are hereby incorporated
by reference in their entirety for the purpose of disclosing
methods for preparing precipitated silica materials. In other
aspects, one of skill in the art, in possession of this disclosure,
could readily determine appropriate reactants and reaction
conditions to prepare a desired precipitate silica. In another
aspect, the process to prepare a precipitated silica containing a
metal ion as described herein can be performed in a batch process,
a semi-continuous process, or a continuous process. In one aspect,
all or a portion of the steps are performed in a batch process. In
another aspect, the process can be at least partially continuous,
wherein a silicate solution and an acidulating agent comprising a
dissolved metal salt can be continuously fed into a loop reaction
zone, wherein at least a portion of the acidulating agent, metal
salt, and silicate react to form a precipitated silica.
Heat Treatment
[0050] In one aspect, the precipitated silica material prepared as
described above likely comprises one or more hydrated metal
species. As these species are typically soft, a heating step can be
used to dehydrate the metal centers on the silica surface and
produce, for example, metal oxides. In another aspect, the
precipitated silica material can be prepared without the use of a
metal salt having a desirable Mohs hardness. Any of a silica
material prepared with a metal salt having a desirable Mohs
hardness, a silica material prepared without such a metal salt, or
a combination thereof, can be subjected to a heat treatment step as
described herein.
[0051] The specific time and temperature at which a precipitated
silica can be heated can vary. In one aspect, the precipitated
silica can be heated for a time and at a temperature sufficient to
increase the degree of polymerization in the Si framework of the
material. In another aspect, the precipitated silica can be heated
for a time and at a temperature sufficient to dehydrate metals that
can be present on the surface of the silica material. In another
aspect, the precipitated silica can be heated for a time and at a
temperature sufficient to dehydrate at least a portion of metal
ions present on the silica surface. In yet another aspect, the
precipitated silica can be heated at a temperature less than that
needed to induce significant phase transitions or morphology
changes to the material. In still other aspects, the precipitated
silica can be heated such that meso and macro porosity of the
silica material are not significantly altered by the heat
treatment.
[0052] In one aspect, the precipitated silica can be heated at a
temperature of from about 400.degree. C. to about 900.degree. C.,
for example, about 400, 450, 500, 550, 600, 650, 700, 750, 800,
850, or 900.degree. C. In another aspect, the precipitated silica
can be heated at a temperature of from about 450.degree. C. to
about 650.degree. C., for example about 450, 500, 550, 600, or
650.degree. C. It should be appreciated that the time needed to
dehydrate all or a portion of the metal species, if present on a
silica surface, can vary depending on the temperature at which the
material is heated. In one aspect, a precipitated silica can be
heated at a temperature of about 550.degree. C. for a period of
greater than about 8 hours.
Heat Treated Silica Material
[0053] After heat treatment, the resulting silica material can
optionally have a metal concentration (i.e., of the metal from the
one or more metal salts) of up to about 10 wt. %, for example,
about 0.5, 1, 1.25, 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5,
3.75, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 wt. %.
In another aspect, the resulting silica material can have a metal
concentration of up to about 5 wt. %, for example, In yet other
aspects, the resulting silica material can have a metal
concentration of from about 1 wt. % to about 4 wt. %, for example,
about 1, 1.25, 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75,
or 4 wt. %.
[0054] In another aspect, the resulting silica material can have
aluminum oxide present on the surface thereof, for example, at a
concentration of from about 1 wt. % to about 4 wt. %. In yet
another aspect, the resulting silica material can be absent of or
substantially absent of a metal oxide, for example, when a metal
salt dopant is not utilized.
[0055] In another aspect, the resulting silica material can exhibit
a loss on ignition at 900.degree. C. of less than about 3 wt. %,
for example, about 1, 1.5, 2, 2.5, or 3 wt. %. In another aspect,
the resulting silica material can exhibit a log on ignition at
900.degree. C. of less than about 4 wt. %. In one aspect,
conventional precipitated silica materials typically have loss on
ignition values at 900.degree. C. of between 4 and 6, whereas
silica materials prepared as described herein, including heat
treatment, can have a loss on ignition at 900.degree. C. of about
2.5 or less.
[0056] In yet another aspect, the increased degree of
polymerization as compared to a conventional precipitated silica
can be detected via analytical techniques, such as, for example,
solid state .sup.29Si Nuclear Magnetic Resonance (NMR)
spectroscopy.
[0057] Solid State NMR can be a powerful technique for determining
the coordination environments of, for example, silicon atoms and
the degree of polymerization of, for example, a siliceous solid. In
solid state .sup.29Si NMR, silicon species can be identified as M,
D.sup.l, T.sup.m, and Q.sup.n (mono, di, tri and quaternary),
denoting the degree of oxygen substitution on the central silicon
atom, wherein the superscripts l, m and n refer to the number of
(--O--Si) linkages. Therefore, Q.sup.n=Si(OSi).sub.n(OR).sub.4-n
(n=1-4), T.sup.m=RSi(OSi).sub.m(OR).sub.3-m (m=1-3),
D.sup.l=R.sub.2Si(OSi).sub.l(OR).sub.2-l (l=1-2) and
M=R.sub.3Si(OSi), where R is some other group, such as, for
example, an organic group or hydrogen atom. As it pertains to
inorganic siliceous materials disclosed herein, the quaternary
species would be of greatest interest. Accordingly, a reduction in
the silanol containing Q.sup.2 and Q.sup.3 species with a
corresponding increase in the fully polymerized Q.sup.4 species can
be expected upon heat treatment as described herein.
[0058] In another aspect, enhanced resolution of the resulting
spectra can be obtained by employing "magic angle spinning" (MAS)
where the sample of interest is put into a rotor and spun at high
speeds, for example, >3000 rpm, while being tilted at the "magic
angle" of 54.74.degree. with respect to the applied magnetic field.
In such an aspect, this angle can be utilized because most of the
interactions that cause broadening (dipolar interactions, chemical
shift anisotropy (CSA) and differences in crystallite orientations)
have an angular dependence of 3 cos.sup.2 .theta.-1, wherein
.theta. is the angle between the applied magnetic field and the
principal axis. In such an aspect, if .theta.=57.74.degree., 3
cos.sup.2 .theta.-1=0 and the broadening effects are minimized. In
addition, spinning at high rpm effectively can allow for averaging
of the species since these solid materials are held in a fixed
orientation. Therefore, .sup.29Si MAS-NMR in essence can produce
relatively detailed information on the composition of siliceous
materials and any changes that can occur under various
conditions.
[0059] In one aspect, the pellicle cleaning ratio of the inventive
silica material and/or a dentifrice comprising the inventive silica
material can be higher than a comparable precipitated silica not
subjected to a heat treatment step and/or not having a metal oxide
on the surface thereof. In another aspect, the pellicle cleaning
ratio can be improved by at least about 10%, for example, about 10,
12, 14, 16, 18, 20, 25%, or more using the preparation methods
described herein. In other aspects, the pellicle cleaning ration of
the resulting silica material can range from about 90 to about 110,
for example, about 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, or
110. In other aspects, the pellicle cleaning ratio of the resulting
silica material can be higher than 110, and the present invention
is not intended to be limited to any particular pellicle cleaning
ratio.
[0060] After heat treatment, the Einlehner abrasion values of the
resulting silica material are significantly increased. In various
aspects, the Einlehner abrasion values increase from about 90% to
about 450%, for example, about 90, 100, 110, 120, 130, 140, 150,
175, 200, 225, 250, 250, 275, 300, 325, 350, 375, 400, 425, or
250%; or from about 120% to about 200%, for example, about 120,
125, 130, 125, 140, 145, 150, 160, 170, 180, 190, or 200% after
heat treatment. In another aspect, the Einlehner abrasion value
increases about 150% after heat treatment. In conventional
precipitates silica materials, changes in the Einlehner abrasion
values typically correspond to changes in RDA and/or REA values.
Such a large increase in dentin abrasion would be unacceptable for
use in dentifrice materials as continued use would result in damage
to the tooth tissues. Surprisingly, the inventive precipitated
silica materials exhibit significant increases in Einlehner
abrasion values, as described above, without corresponding changes
in RDA and/or REA values. In one aspect, Einlehner abrasion can be
significantly increased while maintaining a desirable RDA and/or
REA value. In another aspect, the RDA value of the resulting silica
material can remain substantially the same or exhibit a small,
acceptable increase after heat treatment. In one aspect, the RDA
value after heat treatment remains within about 5% of the original
value (prior to heat treatment). In another aspect, the RDA value
can increase by up to about 25%, for example, about 5, 8, 12, 15,
18, 21, or 25% after heat treatment. In yet another aspect, the
increase in RDA can be about 10% of the corresponding increase in
Einlehner abrasion after heat treatment. For example, a heat
treated precipitated silica, prepared using aluminum sulfate, can
exhibit an increase in Einlehner abrasion after heat treatment of
about 215%, whereas the corresponding RDA value increases by only
about 22% after heat treatment. Thus, in one aspect, the methods of
the present disclosure allow for the decoupling of Einlehner
abrasion values and RDA/REA abrasion values. The techniques
described herein can provide a dentifrice abrasion compound capable
of providing improved pellicle cleaning ratio without damaging
tooth tissues.
Dentifrice Composition
[0061] The inventive precipitated silica materials can be
ready-to-use additives in the preparation of oral cleaning
compositions, such as dentifrices, toothpastes, and the like. In
one aspect, the heat treated precipitated silica material can be
combined with one or more dentifrice components, such as, for
example, abrasives, rheological aids, whiteners, sweeteners,
flavoring additives, surfactants, colorants, or other components to
form a dentifrice composition. If combined with other abrasives
(such as any of the products offered by J. M. Huber Corporation
under the trade name ZEODENT.RTM.), such an abrasive may be added
in any amount. In one aspect, the inventive silica material can be
used at a loading of about 20 wt. % in the dentifrice composition.
In other aspects, the inventive silica material can be used in
excess of 20% and up to about 25 wt. %, 30 wt. %, 35 wt. % or
more.
[0062] The inventive silica material can be utilized alone as the
cleaning agent component in a dentifrice compositions or in
combination with one or more other abrasive materials. Thus, a
combination of the inventive materials with other abrasives
physically blended therewith within a suitable dentifrice
formulation can be useful to accord targeted dental cleaning and
abrasion results at a desired protective level. Thus, any number of
other conventional types of abrasive additives may be present
within inventive dentifrices in accordance with this invention.
Other such abrasive particles include, for example, and without
limitation, precipitated calcium carbonate (PCC), ground calcium
carbonate (GCC), dicalcium phosphate or its dihydrate forms, silica
gel (and of any structure), amorphous precipitated silica (by
itself, and of any structure as well), perlite, titanium dioxide,
calcium pyrophosphate, hydrated alumina, calcined alumina,
insoluble sodium metaphosphate, insoluble potassium metaphosphate,
insoluble magnesium carbonate, zirconium silicate, aluminum
silicate, and so forth, can be introduced within the desired
abrasive compositions to tailor the polishing characteristics of
the target formulation (dentifrices, for example, etc.), if
desired, as well.
[0063] In addition, as noted above, the inventive silica material
can be used in conjunction with other abrasive materials, such as
precipitated silica, silica gel, dicalcium phosphate, dicalcium
phosphate dihydrate, calcium metasilicate, calcium pyrophosphate,
alumina, calcined alumina, aluminum silicate, precipitated and
ground calcium carbonate, chalk, bentonite, particulate
thermosetting resins and other suitable abrasive materials known to
a person of ordinary skill in the art.
[0064] In addition to the abrasive component, a dentifrice can
optionally comprise one or more organoleptic enhancing agents.
Organoleptic enhancing agents include humectants, sweeteners,
surfactants, flavorants, colorants and thickening agents, (also
sometimes known as binders, gums, or stabilizing agents).
Humectants serve to add body or "mouth texture" to a dentifrice as
well as prevent the dentifrice from drying out. Suitable humectants
can comprise polyethylene glycol (at a variety of different
molecular weights), propylene glycol, glycerin (glycerol),
erythritol, xylitol, sorbitol, mannitol, lactitol, and hydrogenated
starch hydrolyzates, as well as mixtures of these compounds.
Typical levels of humectants, if present, can range from about 20
wt % to about 30 wt % of a dentifrice composition.
[0065] Sweeteners can be added to a dentifrice composition to
impart a pleasing taste to the product. Suitable sweeteners include
saccharin (as sodium, potassium or calcium saccharin), cyclamate
(as a sodium, potassium or calcium salt), acesulfane-K, thaumatin,
neohisperidin dihydrochalcone, ammoniated glycyrrhizin, dextrose,
levulose, sucrose, mannose, and glucose.
[0066] In one aspect, surfactants can also be used in a dentifrice
composition to make the composition more cosmetically acceptable. A
surfactant, if used, can be a detersive material which imparts to
the composition detersive and foaming properties. Surfactants are
safe and effective amounts of anionic, cationic, nonionic,
zwitterionic, amphoteric and betaine surfactants such as sodium
lauryl sulfate, sodium dodecyl benzene sulfonate, alkali metal or
ammonium salts of lauroyl sarcosinate, myristoyl sarcosinate,
palmitoyl sarcosinate, stearoyl sarcosinate and oleoyl sarcosinate,
polyoxyethylene sorbitan monostearate, isostearate and laurate,
sodium lauryl sulfoacetate, N-lauroyl sarcosine, the sodium,
potassium, and ethanolamine salts of N-lauroyl, N-myristoyl, or
N-palmitoyl sarcosine, polyethylene oxide condensates of alkyl
phenols, cocoamidopropyl betaine, lauramidopropyl betaine, palmityl
betaine and the like can be used in a dentifrice together with the
inventive silica material. A surfactant, if present, is typically
used in an amount of about 0.1 to about 15% by weight, preferably
about 0.3% to about 5% by weight, such as from about 0.3% to about
2%, by weight.
[0067] Flavoring agents optionally can be added to dentifrice
compositions. Suitable flavoring agents include, but are not
limited to, oil of wintergreen, oil of peppermint, oil of
spearmint, oil of sassafras, and oil of clove, cinnamon, anethole,
menthol, thymol, eugenol, eucalyptol, lemon, orange and other such
flavor compounds to add fruit notes, spice notes, etc. These
flavoring agents can comprise mixtures of aldehydes, ketones,
esters, phenols, acids, and aliphatic, aromatic and other
alcohols.
[0068] In addition, colorants can be added to improve the aesthetic
appearance of the dentifrice product. Suitable colorants are
selected from colorants approved by appropriate regulatory bodies
such as the FDA and those listed in the European Food and
Pharmaceutical Directives and include pigments, such as TiO.sub.2,
and colors such as FD&C and D&C dyes.
[0069] Thickening agents can, in various aspect, be useful in the
dentifrice compositions of the present invention to provide a
gelatinous structure that stabilizes the toothpaste against phase
separation. Suitable thickening agents include silica thickener;
starch; glycerite of starch; gums such as gum karaya (sterculia
gum), gum tragacanth, gum arabic, gum ghatti, gum acacia, xanthan
gum, guar gum and cellulose gum; magnesium aluminum silicate
(Veegum); carrageenan; sodium alginate; agar-agar; pectin; gelatin;
cellulose compounds such as cellulose, carboxymethyl cellulose,
hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxymethyl
cellulose, hydroxymethyl carboxypropyl cellulose, methyl cellulose,
ethyl cellulose, and sulfated cellulose; natural and synthetic
clays such as hectorite clays; as well as mixtures of these
compounds. Typical levels of thickening agents or binders can range
from about 0 wt % to about 15 wt % of a dentifrice composition.
[0070] Therapeutic agents are optionally used in the compositions
of the present invention to provide for the prevention and
treatment of dental caries, periodontal disease and temperature
sensitivity. Examples of therapeutic agents, without intending to
be limiting, are fluoride sources, such as sodium fluoride, sodium
monofluorophosphate, potassium monofluorophosphate, stannous
fluoride, potassium fluoride, sodium fluorosilicate, ammonium
fluorosilicate and the like; condensed phosphates such as
tetrasodium pyrophosphate, tetrapotassium pyrophosphate, disodium
dihydrogen pyrophosphate, trisodium monohydrogen pyrophosphate;
tripolyphosphates, hexametaphosphates, trimetaphosphates and
pyrophosphates, such as; antimicrobial agents such as triclosan,
bisguanides, such as alexidine, chlorhexidine and chlorhexidine
gluconate; enzymes such as papain, bromelain, glucoamylase,
amylase, dextranase, mutanase, lipases, pectinase, tannase, and
proteases; quaternary ammonium compounds, such as benzalkonium
chloride (BZK), benzethonium chloride (BZT), cetylpyridinium
chloride (CPC), and domiphen bromide; metal salts, such as zinc
citrate, zinc chloride, and stannous fluoride; sanguinaria extract
and sanguinarine; volatile oils, such as eucalyptol, menthol,
thymol, and methyl salicylate; amine fluorides; peroxides and the
like. Therapeutic agents can be used in dentifrice formulations
singly or in combination at a therapeutically safe and effective
level.
[0071] In another aspect, preservatives can also be optionally
added to the compositions of the present invention to prevent
bacterial growth. Suitable preservatives approved for use in oral
compositions such as methylparaben, propylparaben and sodium
benzoate, or combinations thereof, may be added in safe and
effective amounts.
[0072] The dentifrices disclosed herein can also a variety of
additional ingredients such as desensitizing agents, healing
agents, other caries preventative agents, chelating/sequestering
agents, vitamins, amino acids, proteins, other
anti-plaque/anti-calculus agents, opacifiers, antibiotics,
anti-enzymes, enzymes, pH control agents, oxidizing agents,
antioxidants, and the like. Water can be used in a dentifrice
composition to balance the composition, for example, from about 0
wt. % to about 60 wt. %, and provide desirable rheological
properties.
[0073] In yet another aspect, silica thickeners for use within a
dentifrice composition can include, as a non-limiting example, an
amorphous precipitated silica such as ZEODENT.RTM. 165 silica.
Other silica thickeners can comprise ZEODENT.RTM. 163 and/or 167
and ZEOFREE.RTM. 153, 177, and/or 265 silicas, all available from
J. M. Huber Corporation, Havre de Grace Md., U.S.A.
[0074] The present invention can be described by any of the
following exemplary and non-limiting aspects.
[0075] Aspect 1: A method for preparing a silica material, the
method comprising heat treating a silica material comprising a
metal compound, wherein the metal has a Mohs hardness value of at
least about 5.5 in its oxide form, and wherein heat treating
comprises heating the silica material at a temperature and for a
period of time sufficient to dehydrate at least a portion of the
metal compound disposed on a surface of the material.
[0076] Aspect 2: The method of Aspect 1, wherein heat treating
comprises heating the silica material at a temperature of at least
about 400.degree. C. for at least about 8 hours.
[0077] Aspect 3: The method of Aspect 1, wherein heat treating
comprises heating the silica material at a temperature of at least
about 550.degree. C. for at least about 8 hours.
[0078] Aspect 4: The method of Aspect 1, wherein, after heat
treating, the silica material has a metal concentration of up to
about 10 wt. %.
[0079] Aspect 5: The method of Aspect 1, wherein the silica
material is prepared by contacting a silicate solution, an
acidulating agent, and a soluble metal salt, wherein the soluble
metal salt comprises a metal ion having a Mohs hardness value of at
least 5.5 in its oxide form.
[0080] Aspect 6: The method of Aspect 5, wherein the metal ion
comprises one or more of aluminum, tin, or a combination
thereof
[0081] Aspect 7: The method of Aspect 5, wherein the metal ion
comprises aluminum.
[0082] Aspect 8: The method of Aspect 5, wherein the metal ion
comprises tin.
[0083] Aspect 9: A silica material prepared by the method of Aspect
1.
[0084] Aspect 10: A dentifrice composition comprising the silica
material of Aspect 9.
[0085] Aspect 11: A method for preparing a dentifrice material, the
method comprising heat treating a silica material at a temperature
of from about 400.degree. C. to about 900.degree. C. to form a heat
treated silica material, and then contacting the heat treated
silica material with one or more dentifrice components to form a
dentifrice material.
[0086] Aspect 12: The method of Aspect 11, wherein heat treating
comprises heating the silica material at a temperature of at least
about 400.degree. C. for at least about 8 hours.
[0087] Aspect 13: The method of Aspect 11, wherein heat treating
comprises heating the silica material at a temperature of at least
about 550.degree. C. for at least about 8 hours.
[0088] Aspect 14: A dentifrice material prepared by the method of
Aspect 11.
[0089] Aspect 15: A silica material having a loss on ignition at
900.degree. C. of less than about 3 wt. %.
[0090] Aspect 16: A silica material having one or more of the
following: a) a metal ion disposed on a surface thereof at a
concentration of up to about 10 wt. %; b) a loss on ignition at
900.degree. C. of less than about 3 wt. %; or c) an increased
degree of polymerization as compared to a conventional silica
material not exposed to a heat treatment step.
[0091] Aspect 17: The silica material of Aspect 16, having a metal
ion disposed on a surface thereof at a concentration of up to about
4 wt. %.
[0092] Aspect 18: The silica material of Aspect 16, having an
increased Einlehner abrasion value of at least about 150%, as
compared to a conventional non heat treated precipitated
silica.
[0093] Aspect 19: The silica material of Aspect 16, having an
increase in RDA value of up to about 25% after heat treatment, as
compared to a conventional non heat treated precipitated
silica.
[0094] Aspect 20: A dentifrice composition comprising the silica
material of any preceding Aspect.
[0095] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention
without departing from the scope or spirit of the invention. Other
embodiments of the invention will be apparent to those skilled in
the art from consideration of the specification and practice of the
invention disclosed herein. It is intended that the specification
and examples be considered as exemplary only, with a true scope and
spirit of the invention being indicated by the following
claims.
EXAMPLES
[0096] The following examples are put forth so as to provide those
of ordinary skill in the art with a complete disclosure and
description of how the compounds, compositions, articles, devices
and/or methods claimed herein are made and evaluated, and are
intended to be purely exemplary of the invention and are not
intended to limit the scope of what the inventors regard as their
invention. Efforts have been made to ensure accuracy with respect
to numbers (e.g., amounts, temperature, etc.), but some errors and
deviations should be accounted for. Unless indicated otherwise,
parts are parts by weight, temperature is in .degree. C. or is at
ambient temperature, and pressure is at or near atmospheric.
Example 1
Preparation of Silica Materials (Small Batch)
[0097] In a first example, metal doped silica materials were
prepared using aluminum sulfate and stannous nitrate. The inventive
silica materials were prepared on a two gallon scale, as described
below.
Aluminum Sulfate
[0098] 335 ml of sodium silicate solution (19.5%, 1.180 g/mL, 3.32
MR) and 835 ml of water were added to a 2 gallon reactor and heated
to 87.degree. C. while stirring at 300 RPM. Sodium silicate
solution (19.5%, 1.180 g/mL, 3.32 MR) and sulfuric acid (17.1%,
1.12 g/mL, containing aluminum sulfate at a concentration of 0.15
mol alum/L acid solution) were then simultaneously added at 64
ml/min and 19.5 ml/min, respectively, for 47 minutes. After 47
minutes, the flow of silicate was stopped and the pH was adjusted
to 5.5 with a continued flow of acid. Once pH 5.5 was reached, the
batch was allowed to digest for 10 minutes at 90.degree. C. After
digestion, the batch was filtered and washed to a conductivity of
about 1500 .mu.S and was dried overnight at a temperature of
105.degree. C. The batch was then mechanically milled, for example,
with a hammer mill, to an average particle size of approximately 10
.mu.m. The batch was then split into two parts. A first portion of
the batch was used without heat treatment. The second portion of
the batch was heated overnight at a temperature of 550.degree.
C.
Stannous Nitrate
[0099] 335 ml of silicate (19.5%, 1.180 g/mL, 3.32 MR) and 835 ml
of water were added to the 2 gallon reactor and heated to
87.degree. C. with stirring at 300 RPM. Silicate (19.5%, 1.180
g/mL, 3.32 MR) and sulfuric acid (17.1%, 1.12 g/mL, containing
stannous nitrate at a concentration of 0.29 mol stannous nitrate/L
acid solution) were then simultaneously added at 64 ml/min and 19.5
ml/min, respectively, for 47 minutes. After 47 minutes, the flow of
silicate was stopped and the pH was adjusted to 5.5 with continued
flow of acid. Once pH 5.5 was reached, the batch was allowed to
digest for 10 minutes at 90.degree. C. After digestion, the batch
was filtered and washed to a conductivity of about 1500 .mu.S and
was dried overnight at a temperature of 105.degree. C. The batch
was then hammer milled to an average particle size of approximately
10 .mu.m. The batch was then split into two parts. A first portion
of the batch was used without heat treatment. The second portion of
the batch was heated overnight at a temperature of 550.degree.
C.
[0100] The resulting samples were examined to determine a variety
of properties. Fluoride compatibility was determined by adding 7.0
g of silica abrasive (or 4.0 g of silica thickener) to a centrifuge
tube containing 30.0 g of a 1624 ppm solution of F. After mixing,
the solution was aged for 60 minutes on a rotating rack in an oven
at 60.degree. C. The samples were then centrifuged at 11,000 RPM
for 15 minutes or until there were no silica particles remaining
suspended in the solution. 10.0 ml of the centrifuged solution was
then added to 10 ml of TISAB II buffer solution and the fluoride
concentration was determined by fluoride ion selective
electrode.
[0101] Metal content was determined by ion coupled plasma/optical
emission spectroscopy (ICP/OES), wherein 2.0000 g of silica
material was wet with a few drops of deionized water in a platinum
crucible. 10 ml of perchloric acid (72%) and 10 ml of hydrofluoric
acid (48-50%) were added and the platinum dish was slowly heated on
a stir plate in a fume hood. As the platinum dish was heated, dense
white fumes were evolved. The sides of the crucible were then
carefully rinsed with boric acid (4%) and it was subsequently
heated to fumes. After cooling, the contents of the crucible were
transferred to a 250 ml volumetric flask and the crucible was
washed with deionized water to make sure all remaining contents
were quantitatively transferred. The dish was then rinsed with 5 ml
of hydrochloric acid (36%) and the washings were added to the
volumetric flask. Approximately 200 ml of deionized water were then
added to the volumetric flask, and if the resulting solution was
cloudy, it was heated on a low temperature hot plate until it
became clear. After cooling, 2.50 ml of a scandium internal
standard solution was added and the volumetric flask was filled to
the mark with deionized water. The concentrations of the metals in
the solution were then determined by ICP/OES.
TABLE-US-00001 TABLE 1 Summary of Physical Properties of Silica
Materials Prepared using Aluminum and Tin Aluminum Tin Not Heat Not
Heat Heated Treated Heated Treated Aluminum Sulfate Stannous
Nitrate Moisture (%) 3.6 1.6 4.7 0.8 BET (m.sup.2/g) 232 44 30 23
CTAB (m.sup.2/g) 44 40 84 45 Median particle size (.mu.m) 8.0 9.3
3.5 4.9 Sodium sulfate (%) <0.35 <0.35 <0.35 <0.35 Oil
absorption (cc/100 g) 54 50 46 48 5% Ph 8.2 8.4 9.0 8.1 Al (%) 1.28
1.39 0.07 0.06 Zn (%) -- -- -- -- Sn (%) -- -- 5.7 5.5 Ca (ppm) --
-- 518 405 Fe (ppm) 188 217 206 229 Mg (ppm) 48 49 32 44 Na.sub.2O
(%) 2.1 2.2 1.8 1.7 Fluoride compatibility (%) 34 52 77 97
Einlehner (mg lost/100k 7.4 18.0 18.0 34.8 rev)
[0102] The chemical and physical properties from analysis of each
of the precipitates silica materials are illustrated in Table 1.
The silicas produced were low structure, with oil absorption values
ranging from 50-61 cc/100 g. The oil absorption and the CTAB values
did not substantially change upon heating to 550.degree. C.,
indicating that the meso and macro porosity were not dramatically
impacted by the heating step. Although the BET surface area was
reduced in both cases, the reduction was likely due to a collapse
in volume in the micro porosity range. The Einlehner values for all
samples increased upon heating. While not wishing to be bound by
theory, this increase was likely due to further polymerization of
the Si-O-Si groups in the silica particles and the dehydration of
the metal adduct on the silica, resulting in the formation of a
less hydrated metal oxide species. Since the heat treatment of the
silica particles resulted in an increase in wall density and an
increase in the Mohs hardness of the metal oxide species (ex. 9.0
for alpha-alumina and -6.5 for stannous oxide), the resulting
Einlehner values were increased. Fluoride availability values for
the metal containing silica, with the exception of the aluminum
containing sample, were not negatively impacted with the
introduction of the metal species into the silica.
Example 2
Preparation of Silica Materials (Large Batch)
[0103] In a second example, silica materials were prepared in 30
gallon batches, as described below.
Silica (No Metal Adduct)
[0104] 5.6 L of silicate (19.5%, 1.180 g/mL, 3.32 MR) and 13.9 L of
water were added to the 30 gallon reactor and heated to 87.degree.
C. while stirring at 150 RPM. Silicate (19.5%, 1.180 g/mL, 3.32 MR)
and sulfuric acid (17.1%, 1.12 g/mL) were then simultaneously added
at 1.1 L/min and 0.33 L/min, respectively, for 47 minutes. After 47
minutes, the flow of silicate was stopped and the pH was adjusted
to 5.5 with continued flow of acid. Once pH 5.5 was reached, the
batch was allowed to digest for 10 minutes at 90.degree. C. After
digestion, the batch was filtered and washed to a conductivity of
about 1500 .mu.S and was spray dried. The batch was hammer milled
to an average particle size of approximately 10 .mu.m. The silica
was then split into two parts. One portion of the batch was
utilized without further heat treatment. The second portion of the
batch was heated overnight at a temperature of 550.degree. C.
Aluminum
[0105] 5.6 L of silicate (19.5%, 1.180 g/mL, 3.32 MR) and 13.9 L of
water were added to the 30 gallon reactor and heated to 87.degree.
C. while stirring at 150 RPM. Silicate (19.5%, 1.180 g/mL, 3.32 MR)
and sulfuric acid (17.1%, 1.12 g/mL, containing 0.25 mol alum/L of
acid solution) were then simultaneously added at 1.1 L/min and 0.33
L/min, respectively, for 47 minutes. After 47 minutes, the flow of
silicate was stopped and the pH was adjusted to 5.5 with continued
flow of acid. Once pH 5.5 was reached, the batch was allowed to
digest for 10 minutes at 90.degree. C. After digestion, the batch
was filtered and washed to a conductivity of .about.1500 .mu.S and
was spray dried. The batch was hammer milled to an average particle
size of approximately 10 .mu.m. The silica was then split into two
parts. One portion of the batch was utilized without further heat
treatment. The second portion of the batch was heated overnight at
a temperature of 550.degree. C.
Silica (No Metal Adduct)
[0106] 1.9 L of silicate (19.5%, 1.180 g/mL, 3.32 MR) and 4.8 L of
water were added to the 30 gallon reactor and heated to 87.degree.
C. while stirring at 150 RPM. Silicate (19.5%, 1.180 g/mL, 3.32 MR)
and sulfuric acid (17.1%, 1.12 g/mL) were then simultaneously added
at 1.1 L/min and 0.35 L/min, respectively, for 47 minutes. After 47
minutes, the flow of silicate was stopped and the pH was adjusted
to 5.5 with continued flow of acid. Once pH 5.5 was reached, the
batch was allowed to digest for 10 minutes at 90.degree. C. After
digestion, the batch was filtered and washed to a conductivity of
about 1500 .mu.S and was spray dried. The batch was hammer milled
to an average particle size of approximately 10 .mu.m. The silica
was then split into two parts. One portion of the batch was
utilized without further heat treatment. The second portion of the
batch was heated overnight at a temperature of 550.degree. C.
Aluminum
[0107] 1.9 L of silicate (19.5%, 1.180 g/mL, 3.32 MR) and 4.8 L of
water were added to the 30 gallon reactor and heated to 87.degree.
C. while stirring at 150 RPM. Silicate (19.5%, 1.180 g/mL, 3.32 MR)
and sulfuric acid (17.1%, 1.12 g/mL, containing 0.25 mol alum/L of
acid solution) were then simultaneously added at 1.1 L/min and 0.35
L/min, respectively, for 47 minutes. After 47 minutes, the flow of
silicate was stopped and the pH was adjusted to 5.5 with continued
flow of acid. Once pH 5.5 was reached, the batch was allowed to
digest for 10 minutes at 90.degree. C. After digestion, the batch
was filtered and washed to a conductivity of about 1500 .mu.S and
was spray dried. The batch was hammer milled to an average particle
size of approximately 10 p.m. The silica was then split into two
parts. One portion of the batch was utilized without further heat
treatment. The second portion of the batch was heated overnight at
a temperature of 550.degree. C.
Zeolex 7A
[0108] A control sample of Zeolex.RTM. 7A silica was split into
equal portions. One portion was utilized without further heat
treatment. The second portion was heated overnight at a temperature
of 550.degree. C.
[0109] The physical properties of the silicas prepared in the
30-gallon reactor are shown in Table 2. Silica samples and their
corresponding analogues containing .about.3% Al were prepared at
structure levels ranges of .about.60-80 and 45-60 cc/100 g. Heat
treatment overnight at 550.degree. C. resulted in a slight decrease
in oil absorption and water absorption values for all samples
tested. The BET surfaced area values dropped considerably after
heating, likely due to the collapse of microporosity in the
samples. The Einlehner values also increased for all samples
tested, both with and without aluminum present.
TABLE-US-00002 TABLE 2 Summary of physical properties from
30-gallon batches Silica Silica (no metal) Aluminum (no metal)
Aluminum Zeolex 7A Not Not Not Not Not Heated Heated Heated Heated
Heated Heated Heated Heated Heated Heated Moisture (%) 5.9 0.7 7.4
0.1 4.9 0.2 4.1 0.8 0.6 BET (m.sup.2/g) 118 40 311 98 63 29 282 69
119 CTAB (m.sup.2/g) 32 29 77 59 26 24 49 39 125 Median 9.3 9.5 8.3
8.0 10.0 10.9 7.5 8.0 9.5 particle size (.mu.m) Sodium 1.38 1.91
1.95 2.13 0.89 1.42 1.38 1.64 sulfate (%) Oil absorption 79 71 72
63 63 53 50 47 120 (cc/100 g) Water AbC 104 93 98 89 82 69 73 67
166 (cc/100 g) 5% pH 7.8 7.2 7.7 8.6 8.8 8.3 7.9 8.7 7.3 LOI (%)
5.4 1.9 7.5 2.8 6.1 1.8 9.4 2.1 Al (%) 0.07 0.07 2.80 3.36 0.12
0.14 2.85 3.39 5.0 Zn (%) -- -- -- -- -- -- -- -- -- Sn (%) -- --
-- -- -- -- -- -- -- Ca (ppm) 268 343 125 129 714 786 220 272 -- Fe
(ppm) 218 198 145 173 178 189 142 161 -- Mg (ppm) 82 96 72 87 343
366 122 145 -- Na.sub.2O (%) 0.92 1.04 2.40 2.88 1.01 1.17 2.32
2.69 -- Powder XRD Amorphous Fluoride 96 99 30 39 89 99 33 43
compatibility (%) Einlehner (mg 6.5 16.3 3.2 18.1 14.9 36.5 5.9
18.6 lost/100k rev)
[0110] Silica and Aluminum samples were formulated into toothpaste
compositions at 20% loading, as described in Table 3, below. PCR
and RDA testing were performed on the resulting toothpaste
compositions.
TABLE-US-00003 TABLE 3 Toothpaste formulation used for PCR/RDA
testing. Example # T1 T2 T3 T4 T5 T6 T7 Glycerin (99.7%) 11.00
11.00 11.00 11.00 11.00 11.00 11.00 Sorbitol (70%) 40.00 40.00
40.00 40.00 40.00 40.00 40.00 Deionized Water Q.S. Q.S. Q.S. Q.S.
Q.S. Q.S. Q.S. PEG-12 3.00 3.00 3.00 3.00 3.00 3.00 3.00 Cekol 2000
1.20 1.20 1.20 1.20 1.20 1.20 1.20 Tetrasodium 0.50 0.50 0.50 0.50
0.50 0.50 0.50 pyrophosphate Sodium saccharin 0.20 0.20 0.20 0.20
0.20 0.20 0.20 Sodium fluoride 0.24 0.24 0.24 0.24 0.24 0.24 0.24
Thickening Silica Zeodent 165 1.50 Abrasive Silica Silica (no
metal) - Not 20.00 -- -- -- -- -- -- Heat Treated Silica (no metal)
- Heat -- 20.00 -- -- -- -- -- Treated Aluminum - Not Heat -- --
20.00 -- -- -- -- Treated Aluminum - Heat Treated -- -- -- 20.00 --
-- -- Zeodent 103 -- -- -- -- 20.00 -- -- Zeolex 7A - Not Heat --
-- -- -- -- 20.00 -- Treated Zeolex 7A - Heat Treated -- -- -- --
-- -- 20.00 Titanium dioxide 0.50 0.50 0.50 0.50 0.50 0.50 0.50
Sodium lauryl sulfate 1.20 1.20 1.20 1.20 1.20 1.20 1.20 Flavor
0.65 0.65 0.65 0.65 0.65 0.65 0.65 Total 100 100 100 100 100 100
100
TABLE-US-00004 TABLE 4 Summary of PCR/RDA results. Example# T1 T2
T3 T4 T5 T6 T7 PCR #1 (IU, 20% 83 95 79 98 82 38 61 loading) PCR #2
(IU, 20% 101 109 94 104 103 56 79 loading) Average PCR 92 102 87
101 93 47 70 PCR Increase (%) 11 16 -- 49 RDA (IU, 20% loading) 190
207 177 217 184 28 54
[0111] PCR testing indicated that both silica (without a metal
adduct) and silica samples containing aluminum achieved higher
values after heat treatment. The average PCR increase for the
silica sample was 11% and the average increases for silica samples
containing aluminum increased by 16 and 49%. The RDA increased in
each case, but the RDA values were still in the normal range
typically observed for precipitated silica abrasives.
* * * * *