U.S. patent application number 15/218200 was filed with the patent office on 2016-11-17 for particulate zinc oxide with manganese ion dopant.
The applicant listed for this patent is Johnson & Johnson Consumer Inc.. Invention is credited to Susan Daly, Euen Thomas Graham Ekman Gunn, Prithwiraj Maitra, Eduardo Colla Ruvolo, JR., Yongyi Zhang.
Application Number | 20160331655 15/218200 |
Document ID | / |
Family ID | 53040443 |
Filed Date | 2016-11-17 |
United States Patent
Application |
20160331655 |
Kind Code |
A1 |
Daly; Susan ; et
al. |
November 17, 2016 |
PARTICULATE ZINC OXIDE WITH MANGANESE ION DOPANT
Abstract
A particulate metal oxide is provided that includes a cationic
portion containing a zinc portion, a first manganese dopant portion
and a second dopant portion selected from the group consisting of
iron and aluminum, wherein the zinc portion is about 99% by weight
or more of the cationic portion and the manganese dopant portion
and second dopant portion are present in a weight ratio of from
about 5:1 to 1:5.
Inventors: |
Daly; Susan; (Basking Ridge,
NJ) ; Gunn; Euen Thomas Graham Ekman; (Hopewell,
NJ) ; Maitra; Prithwiraj; (Hillsborough, NJ) ;
Ruvolo, JR.; Eduardo Colla; (Plainsboro, NJ) ; Zhang;
Yongyi; (Harrison, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Johnson & Johnson Consumer Inc. |
Skillman |
NJ |
US |
|
|
Family ID: |
53040443 |
Appl. No.: |
15/218200 |
Filed: |
July 25, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14862606 |
Sep 23, 2015 |
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|
15218200 |
|
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|
14269407 |
May 5, 2014 |
9144535 |
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14862606 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61K 8/27 20130101; A61Q
17/04 20130101; C01P 2002/52 20130101; C01G 9/02 20130101; A61K
2800/40 20130101; A61K 2800/61 20130101; C01P 2006/60 20130101;
A61K 8/26 20130101; A61K 8/19 20130101; A61K 2800/26 20130101 |
International
Class: |
A61K 8/27 20060101
A61K008/27; A61K 8/19 20060101 A61K008/19; A61Q 17/04 20060101
A61Q017/04; C01G 9/02 20060101 C01G009/02; A61K 8/26 20060101
A61K008/26 |
Claims
1. A particulate metal oxide comprising a cationic portion, wherein
the cationic portion comprises about 99% by weight or more of a
zinc portion, a first manganese dopant portion and a second dopant
portion selected from the group consisting of iron and aluminum,
wherein the first manganese dopant portion and the second dopant
portion are present in a weight ratio from about 1:5 to about
5:1.
2. The particulate metal oxide of claim 1 having a Long-Short
Absorbance Ratio that is greater than a Long-Short Absorbance Ratio
of a comparable particulate metal oxide.
3. The particulate metal oxide of claim 1, wherein the first
manganese dopant portion and the second dopant portion are present
in a weight ratio from 1:4 to about 4:1.
4. The particulate metal oxide of claim 1, wherein the first
manganese portion and the second dopant portion are present in a
weight ratio from 1:3 to about 3:1.
5. The particulate metal oxide of claim 1, wherein the first
manganese portion and the second dopant portion are present in a
weight ratio of 1:1.5.
6. The particulate metal oxide of claim 1 wherein the second dopant
portion is iron.
7. The particulate metal oxide of claim 1 wherein the second dopant
portion is aluminum.
8. The particulate metal oxide of claim 1 wherein the first
manganese dopant portion is divalent.
9. The particulate metal oxide of claim 1 wherein the first
manganese dopant portion is divalent and the iron dopant is
divalent.
10. The particulate metal oxide of claim 1 having a Long-Short
Absorbance Ratio of 1.75 or greater.
11. The particulate metal oxide of claim 1 having a Long-Short
Absorbance Ratio of 1.80 or greater.
12. The particulate metal oxide of claim 1, wherein the cationic
portion consists essentially of the zinc portion, the first
manganese dopant portion and the second dopant portion.
13. The particulate metal oxide of claim 1 wherein the first
manganese dopant portion is divalent and the second dopant portion
consists essentially of a divalent iron dopant and a trivalent
aluminum dopant, wherein the first manganese portion, the iron
dopant and the aluminum dopant are present in a weight ratio of
1:1:2.
14. A sunscreen composition comprising a cosmetically acceptable
carrier and the particulate metal oxide of claim 1.
Description
[0001] This application is a continuation of U.S. Ser. No.
14/862606 filed on Sep. 23, 2015, which is a continuation of U.S.
Ser. No. 14/269407 filed on May 5, 2014, the complete disclosures
of which are hereby incorporated herein by reference for all
purposes.
FIELD OF THE INVENTION
[0002] The invention relates to particulate zinc oxide. More
specifically, the invention relates to particulate zinc oxide that
is doped with manganese and a second dopant.
BACKGROUND OF THE INVENTION
[0003] Skin cancer is a significant public health concern which
represents 50% of diagnosed cases of cancer in the United States.
Ultraviolet radiation (UV) can cause molecular and cellular level
damage, and is considered the leading environmental factor
responsible for skin cancer. The prolonged exposure to UV
radiation, such as from the sun, can lead to the formation of light
dermatoses and erythemas, as well as increase the risk of skin
cancers, such as melanoma, and accelerate skin aging processes,
such as loss of skin elasticity and wrinkling.
[0004] The damaging effects of UV exposure can be suppressed by
topical application of sunscreens which contain compounds that
absorb, reflect or scatter UV, typically in the UVA (wavelengths
from about 320 to 400 nm) or UVB (wavelengths from around 290 to
320 nm) range of the spectrum. Numerous sunscreen compounds are
commercially available with varying ability to shield the body from
ultraviolet light.
[0005] Zinc oxide is a particulate material that is useful as a
sunscreen, since it absorbs and scatters ultraviolet radiation.
However, the inventors have recognized that a need exists for zinc
oxide having enhanced optical properties, particularly for use in
sunscreens and personal care products, more particularly for
enhanced UVA absorption.
SUMMARY OF THE INVENTION
[0006] According to one aspect of the invention, a particulate
metal oxide comprising a cationic portion is provided. The cationic
portion comprises about 99% by weight or more of a zinc portion, a
first manganese dopant portion and a second dopant portion selected
from the group consisting of iron and aluminum. The particulate
metal oxide has a Long-Short Absorbance Ratio that is greater than
a Long-Short Absorbance Ratio of a comparable particulate metal
oxide, as defined herein. The manganese dopant portion and the
second dopant portion may be present in a weight ratio from about
5:1 to about 1:5, or about 4:1 to about 1:4, or from about 1:3 to
about 3:1.
DETAILED DESCRIPTION OF THE INVENTION
[0007] The inventors have found that a particulate zinc oxide
having certain cationic dopants that are present in relatively low
levels and in particular ratios provides improved absorption in the
UVA portion of the electromagnetic spectrum over a comparable
particulate zinc oxide, as defined herein.
[0008] It is believed that one skilled in the art can, based upon
the description herein, utilize the present invention to its
fullest extent. The following specific embodiments are to be
construed as merely illustrative, and not limitative of the
remainder of the disclosure in any way whatsoever. 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 the invention belongs. Unless defined otherwise, all
references to percent are percent by weight.
Particulate Zinc Oxide Embodiments of the invention relate to
particulate metal oxides. By "particulate" it is meant a material
that is, under ambient conditions, a finely-divided, solid
material. As one skilled in the art will readily recognize, metal
oxides are ionic solids, generally comprising predominantly metal
cations and anions comprising predominantly oxygen anions arranged
in a crystalline lattice structure.
[0009] Accordingly, particulate metal oxides of the present
invention comprise a cationic portion. The cationic portion
comprises about 99% by weight or more of a zinc portion. According
to certain embodiments, the zinc portion is about 99% to about
99.75% of the cationic portion, such as from about 99% to about
99.5%, such as from about 99% to about 99.25%.
[0010] The cationic portion further comprises a first manganese
dopant portion and a second dopant portion selected from the group
consisting of iron and aluminum. As used herein, "dopant", or
"dopant portion" means those cations, or portion of cations, that
are intimately incorporated into the crystalline lattice structure
of the metal oxide, as further described herein, thereby modifying
the electronic properties of the metal oxide. One skilled in the
art will recognize that the mere coating of a particulate metal
oxide with a material having metal cations is not sufficient in and
of itself to provide modified electronic properties of the metal
oxide, since mere coating will not provide intimate incorporation
of the metal cations into the crystalline lattice structure of the
metal oxide.
[0011] In addition to the zinc portion, the cationic portion
further comprises a first manganese dopant portion. The manganese
portion may be about 0.1% to about 0.75% by weight of the cationic
portion. According to certain embodiments, the manganese dopant
portion is about 0.15% to about 0.8% of the cationic portion, such
as from about 0.25% to about 0.75%. The manganese dopant portion
may exist in varying oxidation states.
[0012] According to one embodiment the manganese exists as either
Mn.sup.2+ or Mn.sup.3+. In another embodiment, the manganese exists
as Mn.sup.2+.
[0013] The cationic portion further comprises a second dopant
portion that is selected from the group consisting of iron and
aluminum. That is, in one embodiment the second cationic dopant
portion may consist of iron. In a second embodiment the second
cationic dopant portion may consist of aluminum. In a third
embodiment the second cationic dopant portion may comprise a
combination of iron and aluminum. The iron may exist in varying
oxidation states. According to one embodiment the iron exists as
either Fe.sup.2+ or Fe.sup.3+. In another embodiment, the iron
exists as Fe.sup.2+. Similarly, the aluminum may exist in varying
oxidation states. According to one embodiment the aluminum exists
as Al.sup.3+.
[0014] Similarly to the manganese dopant portion, the second dopant
portion may be about 0.1% to about 0.75% by weight of the cationic
portion. According to certain embodiments, the second dopant
portion is about 0.15% to about 0.8% of the cationic portion, such
as from about 0.25% to about 0.75%.
[0015] The sum of the manganese dopant portion and the second
dopant portion may be from about 0.25% to about 1% of the cationic
portion, such as from about 0.5% to about 1% of the cationic
portion, such as from about 0.75%, to about 1% of the cationic
portion, such as from about 0.85% to about 0.99% of the cationic
portion.
[0016] According to certain embodiments, the inventors have found
when the manganese portion and the third portion are present in a
particular weight ratio of manganese portion: third portion, that
is from about 1.5 to 5:1, or 1:3 to 3:1, (inclusive of endpoints),
particular benefits are achieved in UVA absorption. For example,
the weight ratio of manganese portion: third portion may be 1:3,
1:1, or 3:1, among other ratios within the above range. By way of
more specific examples, the cationic portion may be about 0.25% of
manganese portion and 0.75% third portion; or 0.5% manganese
portion and 0.5% third portion; or about 0.75% manganese portion
and 0.25% third portion.
[0017] As one skilled in the art will readily appreciate,
additional metal cations may be present in small concentrations in
the particulate metal oxide without compromising the properties
thereof. For example, in certain embodiments, small concentrations
of these additional cations may be collectively present in the
cationic portion in concentrations of, for example, less than about
0.5%, such as less than about 0.25%, such as less than about 0.1%.
According to certain embodiments, the additional cations may be
collectively present in the cationic portion in a concentration
from about 0.001% to about 0.25%, such as from about 0.001% to
about 0.1%. The additional cations may include cations of alkali
metals, alkaline earth metals; transition metals other than zinc,
manganese and iron; as well as cations of metals such as gallium,
germanium, gallium, indium, tin, antimony, thallium, lead, bismuth,
and polonium.
[0018] Particulate metal oxides of the present invention may be
made by various methods, such as methods reducing oxide ores using,
for example, carbon or other suitable reducing agents, and then
re-oxidizing. Other suitable methods include wet chemical methods.
One example of a wet chemical method includes mixing alkaline salt
solutions of the various cations and causing ZnO to precipitate by
reducing the pH using an acid such as oxalic or formic acid. A
particularly suitable wet chemical method is the so-called
"sol-gel" method, an example of which is described below.
[0019] According to one embodiment of the invention, the
particulate metal oxide formed by a method that includes combining
a solvent system comprising water with a zinc salt, a manganese
salt, and a third salt (e.g., an iron salt, an aluminum salt or
combinations thereof). According to certain embodiments, the ratio
of manganese cation to third salt cation is from 1:3 to about
3:1.
[0020] Any of a variety of salts may be used as sources of the
various cations. Examples include zinc acetate, zinc chloride,
manganese chloride, manganese sulfate, manganese acetate, ferric
chloride, ferric sulfate, and aluminum chloride, among other salts.
Additional components may be added to the mixture of the solvent
system and the salts. For example, a surfactant such as an
ethanolamine (e.g, triethanolamine) as well as homogenizing and or
pH adjusting agents such an alcohol and ammonia may be added as
well. Suitable alcohols include ethanol, 2-methoxyethanol, and the
like. Typically in a sol-gel process, a stable, colloidal solution
(sol) is formed after mixing the solvent system, the salts and the
optional surfactant, and homogenizing/pH adjusting agents. Over
time, a gel network comprising zinc cations, manganese cations and
cations of the third salt is then gradually formed, by
solidification and condensation of colloidal particles having
solvent system trapped therein. The gel network is then allowed to
dry, such as at ambient temperatures, to remove at least portions
of the solvent system. The dried gel network is then calcined,
heated at high temperatures in an oxygen-containing atmosphere, to
remove any remaining solvent system and/or residual organics and to
densify the gel network. Upon sufficient heating, the particulate
metal oxide is formed. According to certain embodiments, the
calcination is performed at a temperature of at least about
400.degree. C., such as from about 400.degree. C. to about
1200.degree. C., such as from about 600.degree. C. to about
1000.degree. C., such as about 700.degree. C.
[0021] According to certain embodiments, the particulate metal
oxides of the present invention are characterized by surprisingly
high Long-Short Absorbance Ratios (LSAR). "LSAR" is a measure of
the relative amount of absorbance in the long wavelength UVA-I and
visible region of the spectrum, which is the region of the spectrum
that is typically absorbed less by conventional sunscreens, yet is
still responsible for biological deleterious effects, as compared
with short wavelength absorbance. This ratio of absorbance across
long wavelengths to absorbance at shorter wavelengths thus provides
a basis for comparing the ability of the various doped particulate
metal oxides to absorb in this region of the spectrum. Long-Short
Absorbance Ratio may be determined by integrating (summing) the
absorbance from wavelengths ranging from 380 nm through 410 nm and
dividing this by the integration (sum) of absorbance from
wavelengths ranging from 340 nm through 350 nm.
[0022] According to certain embodiments of the invention, the LSAR
of particulate metal oxides of the present invention is greater
than the Long-Short Absorbance Ratio of a comparable particulate
metal oxide. As used herein, "comparable particulate metal oxide"
means a metal oxide the contains substantially the same weight
percentage of zinc cation portion as the inventive particulate
metal oxide, but which does not comprise both the manganese dopant
portion and second dopant portion selected from the group
consisting of iron and aluminum. For example, if the cationic
portion of the inventive particulate metal oxide includes iron
(such as about 0.1% by weight or more), then the comparable
particulate metal oxide will not include manganese or aluminum
dopant. If the cationic portion of the inventive particulate metal
oxide does not include iron (such as about 0.1% by weight of iron
or less), then the comparable particulate metal oxide has its
aluminum replaced with manganese. These particular comparable
compositions are selected as described above to provide high LSAR,
since, as described in the examples below, zinc-oxide doped with
only Fe generally has higher LSAR than zinc oxide doped with only
Mn, which has a higher LSAR than zinc oxide doped with only Al. The
following examples are illustrative of the principles and practice
of this invention, although not limited thereto. Numerous
additional embodiments within the scope and spirit of the invention
will become apparent to those skilled in the art once having the
benefit of this disclosure.
EXAMPLES
Example IA
Preparation of Inventive Examples
Inventive Example E1
[0023] Zinc oxide containing both iron and manganese dopant
portions was prepared by a sol-gel process utilizing zinc acetate
dehydrate and iron (II) chloride hexahydrate. In a 100-ml beaker,
20 ml distilled water and 30 ml triethanolamine were combined and 2
ml of ethanol was added drop-wise with continuous stirring until a
visibly homogeneous solution was obtained. In another beaker, 0.5M
iron (II) chloride hexahydrate was prepared (6.78 g iron chloride
in 50 mL water). In a third beaker, 0.5M zinc acetate dihydrate was
prepared. In another beaker, 0.5M of manganese (II) chloride was
prepared. The solutions were allowed to continue to stir for 2-3
hours. In a 500-ml beaker the TEA/water mixture as well as the zinc
acetate solution and iron (II) chloride solution were mixed.
Sufficient iron (II) chloride solution was added to provide 0.475%
by weight of iron cations relative to the total cationic portion
(zinc plus iron plus manganese). Similarly, sufficient manganese
(II) chloride solution was added to provide 0.475% of manganese
cations relative to the total cationic portion. Accordingly, the
total amount of added dopant was 0.95% percent by weight of
combined iron and manganese cations relative to the total cationic
portion.
[0024] Six milliliters of ammonium hydroxide (28% to 30% active)
was added with continuous heating at a temperature of about
45.degree. C. to 50.degree. C., with stirring for 20 minutes. About
10 ml of distilled water was added during this stirring step. This
solution was allowed to sit for thirty minutes and a white bulky
solution formed. This was washed 8-10 times with distilled water
and filtered on a filter paper. The residue obtained was put in an
oven for drying at about 60.degree. C. for 12 hours. The
yellow/white powder obtained was subjected to calcinations at 700
.degree. C. for 4 hours. After calcination, the material was ground
with a ceramic mortar and pestle. The resulting powder was mixed
with petrolatum to a concentration of 5% powder by mass.
Inventive Example E2-E3
[0025] Zinc oxide doped with both iron and manganese was prepared
by a sol-gel process utilizing zinc acetate dehydrate, iron (II)
chloride hexahydrate, and manganese (II) chloride similarly to
Inventive Example E1. For Inventive Example E2, sufficient iron
(II) chloride solution was added to provide 0.7125% by weight of
iron cations relative to the total cationic portion (zinc plus iron
plus manganese). Sufficient manganese (II) chloride solution was
added to provide 0.2375% of manganese cations relative to the total
cationic portion. Accordingly, the total amount of added dopant was
0.95% percent by weight of combined iron and manganese cations
relative to the total cationic portion, and the ratio of added iron
cations to manganese cations was 3:1. For Inventive Example E3,
sufficient iron (II) chloride solution was added to provide 0.2375%
by weight of iron cations relative to the total cationic portion
(zinc plus iron plus manganese). Sufficient manganese (II) chloride
solution was added to provide 0.7125% of manganese cations relative
to the total cationic portion. Accordingly, the total amount of
added dopant was 0.95% percent by weight of combined iron and
manganese cations relative to the total cationic portion, and the
ratio of added iron cations to manganese cations was 1:3.
Inventive Example E4-E6
[0026] Zinc oxide doped with both aluminum and manganese was
prepared by a sol-gel process utilizing zinc acetate dehydrate,
aluminum (III) chloride, and manganese (II) chloride. Aside from
substituting aluminum (III) chloride for iron (II) chloride, the
method was similar to Inventive Examples E1-E3. For Inventive
Example E4, sufficient aluminum (III) chloride solution was added
to provide 0.7125% by weight of aluminum cations relative to the
total cationic portion (zinc plus aluminum plus manganese).
Sufficient manganese (II) chloride solution was added to provide
0.235% of manganese cations relative to the total cationic portion.
Accordingly, the total amount of added dopant was 0.95% percent by
weight of combined aluminum and manganese cations relative to the
total cationic portion, and the ratio of added aluminum cations to
manganese cations was 3:1. For Inventive Example E5, sufficient
aluminum (III) chloride solution was added to provide 0.475% by
weight of aluminum cations relative to the total cationic portion
(zinc plus iron plus manganese). Sufficient manganese (II) chloride
solution was added to provide 0.475% of manganese cations relative
to the total cationic portion. Accordingly, the total amount of
added dopant was 0.95% percent by weight of combined aluminum and
manganese cations relative to the total cationic portion, and the
ratio of added aluminum cations to manganese cations was 1:1. For
Inventive Example E6, sufficient aluminum (III) chloride solution
was added to provide 0.2375% by weight of aluminum cations relative
to the total cationic portion (zinc plus aluminum plus manganese).
Sufficient manganese (II) chloride solution was added to provide
0.7125% of manganese cations relative to the total cationic
portion. Accordingly, the total amount of added dopant was 0.95%
percent by weight of combined aluminum and manganese cations
relative to the total cationic portion, and the ratio of added
aluminum cations to manganese cations was 1:3.
Inventive Example E7
[0027] Zinc oxide doped with iron, aluminum and manganese was
prepared by a sol-gel process utilizing zinc acetate dehydrate,
iron (II) chloride hexahydrate, aluminum (III) chloride, and
manganese (II) chloride. Aside from adding the additional source of
cations, the method was similar to Inventive Examples E1-E6.
Sufficient aluminum (III) chloride solution was added to provide
0.2375% by weight of aluminum cations relative to the total
cationic portion (zinc plus aluminum plus iron plus manganese).
Sufficient iron (II) chloride solution was added to provide 0.2375%
of iron cations relative to the total cationic portion. Sufficient
manganese (II) chloride solution was added to provide 0.475% of
manganese cations relative to the total cationic portion.
Accordingly, the total amount of added dopant was 0.95% percent by
weight of combined aluminum, iron, and manganese cations relative
to the total cationic portion. The ratio of added aluminum cations
to iron cations to manganese cations was 1:1:2 or, stated
differently, a Al plus Fe:Mn ratio of 1:1.
Comparative Example C1
[0028] Fe-doped zinc oxide was prepared by a sol-gel process
utilizing zinc acetate dehydrate and iron (II) chloride hexahydrate
in a manner similar to Inventive Examples E1-E3, except that
manganese (II) chloride was omitted, while maintaining the total
amount of added dopant at 0.95% by weight. Sufficient iron (II)
chloride solution was added to provide 0.95% by weight of iron
cations relative to the total cationic portion (iron plus zinc).
Accordingly, the total amount of added dopant was 0.95% percent by
weight of iron cations relative to the total cationic portion.
Comparative Example C2
[0029] Mn-doped zinc oxide was prepared by a sol-gel process in a
manner similar to that described above for Comparative Example C1,
except that manganese (II) chloride was used in place of iron (II)
chloride hexahydrate. Sufficient manganese (II) chloride solution
was added to provide 0.95% of manganese relative to the total
cationic portion (zinc plus manganese). Accordingly, the total
amount of added dopant was 0.95% percent by weight of manganese
cations relative to the total cationic portion.
Comparative Example C3
[0030] Al-doped zinc oxide was prepared by a sol-gel process in a
manner similar to that described above for Comparative Examples
C1-C2, except that aluminum (III) chloride was used. Sufficient
aluminum (III) chloride solution was added to provide 0.95% of
aluminum cations relative to the total cationic portion (zinc plus
aluminum). Accordingly, the total amount of added dopant was 0.95%
percent by weight of aluminum cations relative to the total
cationic portion.
Comparative Example C4
[0031] Undoped zinc oxide was prepared by a sol-gel process in a
manner similar to that described above, except that only zinc
acetate dehydrate was used, with no dopants (i.e., no aluminum,
iron, or manganese salts).
Example IB
Spectrophotometric Analysis of Zinc Oxide Samples.
[0032] Comparative Examples C1, C2, C3, and C4 and Inventive
Examples E1-E7 were separately dispersed to a concentration by
weight of 5% in petrolatum. Furthermore, a commercially available
zinc oxide, Z-Cote HP1, commercially available from BASF of
Ludwigshafen, Germany, was also dispersed in petrolatum (reported
as Comparative Example C5). Each of these test samples were
evaluated for UV-absorbance spectrum on Vitro-Skin (available from
Innovative Measurement Solutions of Milford, Conn.) using a
Labsphere 100 UV spectrophotometer (Labsphere, North Sutton, N.H.,
USA).
[0033] The test material was evenly applied over the Vitro-Skin at
2 mg/cm.sup.2 and compared with untreated Vitro-Skin. Absorbance
was measured using a calibrated Labsphere UV-1000S UV transmission
analyzer (Labsphere, North Sutton, N.H., USA). This was performed
in duplicate for each batch of synthesized sample.
[0034] From the absorbance measurements, the relative amount of
absorbance in the long wavelength UVA-I and visible region of the
spectrum (the region of the spectrum that is typically absorbed
less by conventional sunscreens, yet is still responsible for
biological deleterious effects) as compared with short wavelength
UVA I absorbance was determined. This ratio of absorbance across
long wavelengths to absorbance at shorter wavelengths thus provides
a basis for comparing the ability of the various doped particulate
zinc oxides to absorb in this region of the spectrum. Specifically,
a "Long-Short Absorbance Ratio" (LSAR) was determined for each
sample by integrating (summing) the absorbance from wavelengths
ranging from 380 nm through 410 nm and dividing this by the
integration (sum) of absorbance from wavelengths ranging from 340
nm through 350 nm. The mean Long-Short Absorbance Ratio is
reported, and where doped zinc oxide synthesis was conducted in
triplicate, standard deviation is also reported as a non-zero
value.
[0035] As a standard of comparison, an "Expected Value" for
Long-Short Absorbance Ratio (LSAR.sub.expected) is also reported in
Table I. The Expected Value is calculated assuming a (linear)
weighted average of the absorbance of each of the component
dopants. For example, the Expected Value for Inventive Example E2,
since it is Fe:Mn, 3:1 would be
LSAR.sub.expected=[(3/4).times.LSAR.sub.measured,
Fe]+[(1/4).times.LSAR.sub.measured,
Mn]=[(3/4).times.1.67]+[(1/4).times.1.53]=1.63
[0036] The results for doped zinc oxide samples are shown in Table
1. Similarly, the results for undoped zinc oxide samples and
commercially available Z-Cote HP1 are shown in Table 2.
TABLE-US-00001 TABLE 1 LSAR.sub.expected Percent LSAR.sub.measured
Expected Differ- Mean/ Value ence Cation Std Dev. (Calcu- (Calcu-
Example Cations Ratio (Measured) lated) lated) Comparative Fe --
1.67/0.049 -- -- Example C1 Comparative Mn -- 1.53/0.064 -- --
Example C2 Inventive Fe:Mn 3:1 1.84 1.63 12.9% Example E2 Inventive
Fe:Mn 1:1 1.82/0.050 1.60 13.8% Example E1 Inventive Fe:Mn 1:3 1.80
1.56 15.3% Example E3 Comparative Al -- 1.42 -- -- Example C3
Comparative Mn -- 1.53/0.064 -- -- Example C2 Inventive Al:Mn 3:1
1.67 1.45 15.1% Example E4 Inventive Al:Mn 1:1 1.77/0.035 1.47
20.4% Example E5 Inventive Al:Mn 1:3 1.63 1.50 8.67% Example E6
Inventive Al:Fe:Mn 1:1:2 1.84 1.53 20.2% Example E7
TABLE-US-00002 TABLE 2 Long-Short Absorbance Ratios of Undoped Zinc
Oxide and Z-COTE HP-1 LSAR.sub.measured Mean/ Std Dev. Example
Cations (Measured) Comparative Zinc only 1.46 Example C4
Comparative Zinc 0.87 Example C5 (Z-COTE HP-1)
[0037] As shown in Tables 1 and 2 above, the inventive examples are
metal oxides having a cationic portion that is more than 99% zinc
and further including magnesium ion dopant and a second dopant
selected from iron and/or aluminum. As shown, the manganese dopant
portion and the second dopant portion are present in a ratio from
1:3 to 3:1.
[0038] It is particularly surprising that in each case, when two
dopants were used, the Long-Short Absorbance Ratio was higher than
a comparable metal oxide having either of the two components
dopants alone. For example, Fe-doped, Comparative Example C1 has a
higher Long-Short Absorbance Ratio than Mn-doped, Comparative
Example C2. Rather than having a Long-Short Absorbance Ratio that
is a "blend" between the two, such as given by the (expected)
weighted average, Inventive Examples E1-E3 have a Long-Short
Absorbance Ratio that is considerably (12.9% to 15.3%) higher than
the expected value. Even more surprising, Inventive Examples E1-E3
have a Long-Short Absorbance Ratio that is actually higher than the
larger of Comparative Examples C1 and C2.
[0039] Similarly, when three dopants were used, e.g. manganese,
iron and aluminum, the Long-Short Absorbance Ratio was higher than
when using any of the three component dopants alone.
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