U.S. patent application number 09/839310 was filed with the patent office on 2001-10-18 for ultraviolet absorbent.
This patent application is currently assigned to Merck Patent Gesellschaft mit Beschrankt. Invention is credited to Noguchi, Tamio, Watanabe, Yukitaka.
Application Number | 20010031272 09/839310 |
Document ID | / |
Family ID | 14939620 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010031272 |
Kind Code |
A1 |
Noguchi, Tamio ; et
al. |
October 18, 2001 |
Ultraviolet absorbent
Abstract
To provide an ultraviolet absorbent having high UV
shieldability, especially UV-A shieldability, high transparency and
good dispersibility. An ultraviolet absorbent, which comprises a
flaky substrate coated with ultra-fin zinc oxide particles having a
mean particle size of not larger than 100 nm, and which is
optionally treated with an organic silicone compound; and a method
for producing the ultraviolet absorbent, which comprises calcining
particles as coated with basic zinc carbonate in the presence of a
complex-forming agent.
Inventors: |
Noguchi, Tamio; (Iwaki-shi,
JP) ; Watanabe, Yukitaka; (Iwaki-shi, JP) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD.
SUITE 1400
ARLINGTON
VA
22201
US
|
Assignee: |
Merck Patent Gesellschaft mit
Beschrankt
Patents 64271 Darmstadt
Darmstadt
DE
64271
|
Family ID: |
14939620 |
Appl. No.: |
09/839310 |
Filed: |
April 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09839310 |
Apr 23, 2001 |
|
|
|
09296239 |
Apr 22, 1999 |
|
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Current U.S.
Class: |
424/401 ;
106/415; 106/418; 106/425; 424/59 |
Current CPC
Class: |
A61K 2800/413 20130101;
C09C 2220/103 20130101; A61K 8/11 20130101; A61K 2800/61 20130101;
C09C 2200/407 20130101; C01P 2004/64 20130101; C01P 2004/20
20130101; C09C 1/405 20130101; A61Q 17/04 20130101; C01G 9/02
20130101; C09C 1/0021 20130101; C09C 2200/505 20130101; B82Y 30/00
20130101; A61K 2800/651 20130101; B82Y 5/00 20130101; A61K 2800/412
20130101; C01P 2004/54 20130101; C01P 2006/12 20130101; C09C
2200/102 20130101; A61K 8/0262 20130101; A61K 8/27 20130101; A61K
2800/51 20130101; C09C 2210/20 20130101; A61K 2800/262
20130101 |
Class at
Publication: |
424/401 ; 424/59;
106/415; 106/418; 106/425 |
International
Class: |
A61K 006/00; A61K
007/42; A61K 007/00; C04B 002/00; C09C 001/04; C04B 014/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 22, 1998 |
JP |
98-126616 |
Claims
What is claimed is:
1. An ultraviolet absorbent comprising a flaky substrate with a
mean particle size of 0.5 to 10 .mu.m coated with ultra-fine zinc
oxide particles.
2. The ultraviolet absorbent of claim 1, wherein the flaky
substrate has a mean particle size of 2.0 to 4.0 .mu.m.
3. The ultraviolet absorbent of claim 1, wherein the zinc oxide
particles have a mean particle size not larger than 100 nm.
4. The ultraviolet absorbent of claim 1, wherein the zinc oxide
particles have a mean particle size not larger than 50 nm.
5. The ultraviolet absorbent of claim 1, wherein the flaky
substrate is mica, kaolin, sericite, talc, silica or alumina.
6. The ultraviolet absorbent of claim 1, comprising 30 to 250 parts
by weight of zinc oxide based on 100 parts by weight of the
substrate.
7. The ultraviolet absorbent of claim 1, comprising 50 to 150 parts
by weight of zinc oxide based on 100 parts by weight of the
substrate.
8. The ultraviolet absorbent of claim 1, prepared by calcining a
flaky substrate coated with leafy, basic zinc carbonate particles
having a mean major diameter of not larger than 350 nm and a ratio
of mean major diameter to mean thickness of not less than 10.
9. The ultraviolet absorbent of claim 1, prepared by calcining a
flaky substrate coated with basic zinc carbonate particles in the
presence of a complex-forming agent.
10. The ultraviolet absorbent of claim 1, wherein the ultra-fine
zinc oxide-coated particles are treated with an organic silicone
compound.
11. A method for producing an ultraviolet absorbent comprising (1)
adding to an aqueous suspension of a flaky substrate a
complex-forming agent , an aqueous solution of a zinc salt and an
alkali carbonate, while maintaining a predetermined pH of not lower
than 8.0, or (2) adding to an aqueous suspension of a flaky
substrate a complex-forming agent an aqueous solution of a zinc
salt, followed by an alkali carbonate followed by further adding an
alkaline solution to achieve a pH of not lower than 8, thereby
coating the flaky substrate with basic zinc carbonate particles,
and optionally filtering, washing and drying a thus-separated
solid, and calcining.
12. A cosmetic material, coating composition, plastic or ink,
comprising an ultraviolet absorbent of claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an ultraviolet absorbent
with high transparency and good dispersibility, as well as good
UV-A shieldability favorable for cosmetic materials. The absorbent
of the invention comprises a flaky substrate coated with ultra-fine
zinc oxide particles.
[0002] Energy of ultraviolet rays triggers off and causes skin
aging, deterioration of coating films, deterioration and
decomposition of plastics and fading of prints.
[0003] The quantity of UV rays falling within a wavelength range of
from 290 to 400 nm on the ground accounts for about 6 % of the
overall quantity of sunlight rays, of which those falling within a
short wavelength range of from 290 to 320 nm (hereinafter referred
to as UV-B) are about 0.5 % and those falling within a long
wavelength range of from 320 to 400 nm (hereinafter referred to as
UV-A) are about 5.5 %. Thus, the quantity of UV-A is large. As
having a longer wavelength, UV-A more easily passes through cloud
and windowpanes to cause more damage to the skin in daily life,
than UV-B. It is said that UV-B scatters on the surface of the skin
or is absorbed in the skin to cause sunburn and the like minor
inflammations of the surface of the skin, while UV-A penetrates
into the dermis below the epidermis of the skin to produce radicals
inside the skin tissue, and the radicals thus formed cause
photo-aging of the skin to produce wrinkles, to make the skin
flabby or to lower the elasticity of the skin, while additionally
having some negative influences on cell membranes and genes.
Accordingly, in order to protect the skin from ultraviolet rays, it
is important not only to shield the skin against the entire region
of ultraviolet rays but also to shield it against UV-A especially
in the field of cosmetics, and an increasing interest in UV-A
shielding is being taken (see the Journal of Cosmetic Technology,
31, No. 1, pp. 14.30, 1997).
[0004] Ultraviolet absorbents (UV-shielding agents) are grouped
into organic compounds and inorganic compounds. As the ultraviolet
absorbents of organic compounds, most typically mentioned are
benzotriazole compounds. Because of their UV absorbability, organic
ultraviolet absorbents are expected to exhibit quick-acting
Uv-shieldability, but their use is being reduced as they are
problematic in their persistence (activity endurance) and safety.
Accordingly, in these days, ultraviolet absorbents (UV-shielding
agents) of inorganic compounds free from such problems are being
widely noticed.
[0005] Most ultraviolet absorbents of inorganic compounds are to
exhibit two functions, one being the ultraviolet absorbability of
the inorganic compounds themselves and the other being the ability
to scatter UV rays (this is referred to as Mie scattering or
Rayleigh scattering) to be attained by controlling the particle
size of the compound particles. As typical examples of such
inorganic compounds, proposed were ultraviolet absorbents
comprising metal oxides, such as titanium oxide, zinc oxide, cerium
oxide and the like, of which the particle size was controlled (see,
for example, Japanese Patent Application Laid-Open (JP-A)
Sho-49-450, Hei-5-43682, and Japanese Patent Publication (JP-B)
Hei-7-23294).
[0006] However, the ultraviolet absorbents comprising such metal
oxides are problematic, as so mentioned hereinunder, and are not
satisfactory. For example, titanium oxide has an effective
absorption range around UV-B, and therefore its particle size must
be specifically controlled in order to make it have the
shieldability to scatter UV-A. It is said that fine-particle metal
oxides having a mean particle size of not larger than 0.1 .mu.m
have the most effective scatterability. However, such fine-particle
metal oxides easily aggregate, and therefore require dispersing
prior to use. For these reasons, the practical use of the oxides is
often difficult. On the other hand, zinc oxide has an effective
absorption range around UV-A, and is therefore especially favorable
for ultraviolet absorbents for cosmetic materials. However, the
compound is problematic in that its chemical stability is poor and
that its powder often aggregates. Cerium oxide is also has an
effective absorption range around UV-A and is favorable to UV-A
shielding. However, as being expensive, the use of the compound is
limited.
[0007] In order to prevent the particle aggregation, proposed was a
technique of applying ultra-fine particles of those metal oxides to
particulate substrates (bases), which are larger than the
ultra-fine particles, to thereby make the ultra-fine particles
adhered by the larger particulate substrates.
[0008] For example, JP-B Hei-5-87545 discloses titanium
oxide-coated particles; JP-B Hei-3-74641, Hei-9-188611 and JP-A
Hei-5-246823 disclose zinc flower-coated or zinc carbonate-coated
particles; and JP-A Hei-3-243666 discloses Zinc white-coated,
transparent flaky particles.
[0009] It is said that the metal oxide-coated materials in those
known techniques have transparency for visible rays and have UV-A
shieldability. However, the particle size of the flaky substrate to
be the base for those is not specifically defined, or, even if
defined, the particle size is too large so that the transparency of
the materials is poor and the specific surface area of the
materials is small. Therefore, in those materials, it is difficult
to enlarge the amount of the coating metal oxides which are
effective for absorbing and scattering ultraviolet rays.
Accordingly, the known materials could hardly exhibit their
ultraviolet shieldability. Moreover, nothing is written in the
published or laid-open specifications, relating to the particle
size and the morphology of the metal oxide particles carried by the
substrates on their surfaces; or the particle size of the metal
oxide particles defined in those specifications is too large. For
these reasons, the known UV absorbents could not satisfy the
requirements of good transparency in the range of visible rays and
good ultraviolet shieldability, especially that capable of
absorbing and scattering UV-A. Specifically, even those of the
known UV absorbents which are said to have UV-A shieldability and
transparency are still problematic in that their transparency is
not satisfactory since the particle size of the flaky substrates is
too large, and that their UV-absorbing and scattering ability is
not also satisfactory since the particle size of the fine-particle
metal oxides adhered on the surface of the substrates is not
satisfactorily controlled. Of the known UV absorbents, zinc oxide
has an absorption zone near UV-A by itself, and ultra-fine
particles of the oxide which are controlled to additionally have
UV-A scatterability are favorable to powdery UV-A shielding agents.
However, as so mentioned hereinabove, the stability and the
dispersibility of the ultra-fine particles is not satisfactory, and
therefore the use of the particles is limited. Accordingly, the
application of the conventional powdery substances to cosmetic
materials, coating compositions, plastics and ink compositions is
limited with respect to the method of adding them and to their
amount to be added, since the transparency and the dispersibility
of the substances is not satisfactory, often resulting in that the
substances added or incorporated will have some negative influences
on the color tone of the resulting products and that the substances
are not easy to handle.
[0010] Given that situation, we, the present inventors already
proposed an ultraviolet-shielding pigment with good spreadability
and adherability especially favorable to cosmetic materials. The
pigment comprises a flaky powder coated with zinc oxide and barium
sulfate, and has UV-A shieldability, and this is so improved that
zinc oxide therein is prevented from aggregating (see JP-A
Hei-9-192021).
SUMMARY OF THE INVENTION
[0011] Having further studied to improve ultraviolet absorbents of
inorganic compounds, the inventors have succeeded in finding an
ultraviolet absorbent which has UV-A shieldability and improved
transparency and which aggregates little.
[0012] Specifically, the present invention provides a novel
ultraviolet absorbent, a method for producing it, and a cosmetic
material, coating composition, plastic or ink comprising the
ultraviolet absorbent, as in the following {circle over (1)} to
{circle over (6)}.
[0013] {circle over (1)} An ultraviolet absorbent with high
transparency and good dispersibility, which comprises a flaky
substrate coated with ultra-fine zinc oxide particles having a mean
particle size of not larger than 100 nm. "Mean particle size" is
used in the conventional sense, i.e., refers to the long axis of
the particle.
[0014] {circle over (2)} The ultraviolet absorbent of {circle over
(1)}, which is prepared by calcining a flaky substrate coated with
leafy, basic zinc carbonate particles having a mean major diameter
of not larger than 350 nm and a ratio, mean major diameter/mean
thickness, of not smaller than 10. In case of the basic zinc
carbonate, the particle shape is different from that of zinc oxide
particles. The particle shape of zinc oxide is relatively
spherical, but the crystal shape of the basic zinc carbonate is
like a leaf as described for the precursor in Examples 1-4. The
largest (major) length (diameter) in the plane of particle is used
to define the particle shape of the basic zinc carbonate.
[0015] {circle over (3)} The ultraviolet absorbent of {circle over
(1)} or {circle over (2)}, which is prepared by calcining a flaky
substrate coated with basic zinc carbonate particles in the
presence of a complex-forming agent.
[0016] {circle over (4)} The ultraviolet absorbent of any one of
{circle over (1)} to {circle over (3)}, wherein the ultra-fine zinc
oxide-coated particles are treated with an organic silicone
compound to be improved higher dispersibility.
[0017] {circle over (5)} A method for producing an ultraviolet
absorbent with high transparency and good dispersibility, which
comprises adding a complex-forming agent to an aqueous suspension
of a flaky substrate, then adding thereto an aqueous solution of a
zinc salt and an alkali carbonate both at the same time with the
resulting suspension being kept at a predetermined pH of not lower
than 8.0, or alternatively, adding thereto an aqueous solution of a
zinc salt first and then an alkali carbonate followed by further
adding thereto an alkaline solution to make the resulting
suspension have a pH of not lower than 8, thereby coating the flaky
substrate with basic zinc carbonate particles, then filtering it,
washing and drying the thus-separated solid, and thereafter
calcining it.
[0018] {circle over (6)} A cosmetic material, coating composition,
plastic or ink, which contains the ultraviolet absorbent of any one
of {circle over (1)} to {circle over (5)}.
[0019] The novel ultraviolet absorbent of the invention comprises a
flaky substrate coated with ultra-fine zinc oxide particles, in
which the coated particles are optionally treated with an organic
silicone compound. This is transparent in the region of visible
rays, while exhibiting ultraviolet shieldability, especially UV-A
shieldability, and is therefore favorably used as an additive to
cosmetic materials, coating compositions, plastics and ink
compositions because of its such excellent characteristics.
[0020] Any and every flaky substrate that is chemically and
thermally stable is usable in the ultraviolet absorbent of the
invention. For example, employed herein are mica, kaolin, sericite,
talc, flaky silica, flaky alumina and synthetic mica. Of those,
preferably selected are flaky substrates with high transparency for
use in the field requiring high transparency. In addition, it is
desirable to select flaky substrates of which the refractive index
is near to that of the materials and media to be combined
therewith.
[0021] Preferably, the flaky substrate has a mean particle size
falling between 0.5 and 10.0 .mu.m, more preferably between 2.0 and
4.0 .mu.m. Having a mean particle size falling within the defined
range, the flaky substrate gives ultraviolet-shielding powder with
high transparency. The fine-particle, flaky substrate having the
defined particle size for use in the invention may be obtained by
grinding a substrate material in a grinder, such as a Henschel
mixer, an atomizer, a ball mill, a planet mill, a jet mill or the
like, in any ordinary dry-grinding or wet-grinding method in which
the grinding step may be optionally combined with any
classification means of, for example, sieving, pneumatic
separation, centrifugation or sedimentation. Substrate particles
having a mean particle size of 0.5 .mu.m or smaller will easily
aggregate, and therefore require special devices in producing them,
resulting in lowering the production efficiency. Even if produced,
such fine particles are difficult to handle in transporting and
use. In fact, in addition, when used in cosmetic materials and
coating compositions, they are difficult to uniformly disperse, as
aggregating too much. Moreover, as they have a large specific
surface area, the viscosity in media particle size of from 2 to
.mu.m is used as the flaky substrate in this invention, the amount
of zinc oxide coated on the substrate is preferably from 70 to 130
parts by weight relative to 100 parts by weight of the substrate so
as to obtain the intended ultraviolet-shielding powder with high
transparency of the invention.
[0022] The ultra-fine zinc oxide particles coated on the flaky
substrate may be prepared according to the method mentioned below.
specifically, a flaky substrate is suspended in water to give an
aqueous suspension, and then a complex-forming agent is added to
the suspension, which is thereafter heated at 60.degree. C. or
higher. Next, to the suspension containing the complex-forming
agent, dropwise added simultaneously are a solution of a zinc salt
and a solution of an alkali carbonate with the resulting suspension
being kept at a pH of not lower than 8.0, or alternatively, the
zinc salt solution is first added thereto and then a predetermined
amount of the carbonate solution is added thereto to make the
resulting suspension have a pH of not lower than 8. In any of these
methods, formed are leafy, ultra-fine, basic zinc carbonate
particles having a predetermined particle size on the surface of
the flaky substrate. The resulting precursor of the flaky substrate
coated with the ultra-fine, basic zinc carbonate particles having a
specific particle size and a specific particle morphology is
calcined to give the ultraviolet-shielding powder with high
transparency of the invention.
[0023] To form the basic zinc carbonate particles that constitute
the precursor, which is one important element in the method of
producing the ultraviolet absorbent of the invention, used is a
complex-forming agent. As the complex-forming agent, preferably
used is any of citric acid, oxalic acid,
ethylenediamine-tetraacetic acid, phthalic acid, maleic acid,
tartaric acid, and their alkali metal salts. Of those, especially
preferred is trisodium citrate, as it is easy to handle and is
economical. As so mentioned hereinabove, the complex-forming agent
is effective in controlling the particle size and morphology of the
coating, basic zinc carbonate particles. By the use of the
complex-forming agent, obtained are the intended basic zinc
carbonate particles having the specific particle size and
morphology. This is because, the complex-forming agent will act on
the basic zinc carbonate particles being precipitated and grown, by
which are formed precursor particles having a mean major diameter
of not larger than 350 nm and an aspect ratio of not smaller than
10. After having been calcined in the subsequent step, the
precursor particles will give ultra-fine zinc oxide particles. The
step of precipitating the ultra-fine, basic zinc carbonate
particles on the surface of the, flaky substrate is important for
obtaining the ultraviolet-shielding powder with high transparency
of the invention.
[0024] The amount of the complex-forming agent to e used in the
invention varies, depending on the type of the agent, but is
preferably not smaller than 0.005 mols per mol of the coating zinc
salt. If the amount is smaller than that, the particle size of the
ultra-fine, basic zinc carbonate particles to be formed may be
unfavorably too large. The uppermost limit of the amount is not
specifically defined. In general, however, the amount may be from
0.01 to 0.1 mols. A larger amount of the agent than 0.1 mols will
be meaningless to reduce the particle size of the ultra-fine, basic
zinc carbonate particles to be obtained.
[0025] The zinc salt to be used in this step may be any and every
water-soluble, inorganic or organic one, which includes, for
example, zinc chloride, zinc bromide, zinc iodide, zinc sulfate,
zinc nitrate, zinc phosphate, zinc acetate, and zinc oxalate. The
amount of the zinc salt to be used is preferably from 30 to 250
parts by weight, in terms of zinc oxide, relative to 100 parts by
weight of the flaky substrate. The amount may be suitably
determined, depending on the particle size of the flaky substrate.
Naturally, a flaky substrate having a small particle size shall
have a large specific surface area, and therefore can be coated
with a large amount of the zinc oxide. However, in the invention,
if the amount of the zinc oxide is smaller than 30 parts by weight,
the final product obtained could not exhibit good ultraviolet
shieldability, because of not enough amount of Zinc oxide particles
coated on the flaky substrate. On the contrary, if the amount is
larger than 250 parts by weight, the surface-coated particles will
aggregate through their contact and adhesion each other, resulting
in that the zinc oxide particles coated on the substrate may not
have the intended mean particle size of not larger than 100 nm,
most preferably not larger than 50 nm.
[0026] The alkali metal carbonate compound to be used in this step
may include, for example, potassium carbonate, sodium carbonate and
ammonium carbonate. However, ammonium carbonate is not preferred
herein in view of regulation of nitrogen dissolved water
discharge.
[0027] Where the carbonate is added to the substrate suspension
simultaneously with the zinc salt solution, the two are added to
the suspension while the pH of the resulting suspension is kept to
be a predetermined value. In this case, the pH of the suspension is
preferably not lower than 8, preferably not lower than 8.5, for the
precipitation of the intended basic zinc carbonate therein. Where
the zinc salt is first aded and then the carbonate is added, the
amount of the latter is preferably controlled that the final pH of
the resulting suspension is not lower than 8.0.
[0028] In the invention, any of those above methods is employable.
However, the former is preferred to the latter, in view of the
easiness in controlling the particle size of the particles to be
formed therein. According to any of those above methods, the
intended basic zinc carbonate is formed, and the surface of the
flaky substrate is coated with fine particles of the carbonate
precipitated thereon.
[0029] The mechanism of forming the fine-particle, basic zinc
carbonate is not always clarified. However, it is believed that, as
so mentioned hereinabove, the complex-forming agent and the alkali
carbonate existing in the system will control the nucleation speed
and the growth of the particles being formed therein, whereby the
intended, ultra-fine, basic zinc carbonate particles may be formed
on the surface of the substrate. The alkali metal carbonate is, in
addition to the complex-forming agent noted above, another
component for controlling the particle size and morphology of the
particles to be formed on the surface of the substrate. If only a
different basic substance such as an alkali hydroxide or ammonia is
used herein, in place of the carbonate, to form zinc hydroxide, and
if the substrate is coated with the thus-formed zinc hydroxide, the
intended, ultra-fine particles as defined may not be formed on the
substrate. Even if the substrate coated with such zinc hydroxide
particles is calcined, the resulting zinc oxide-coated powder has
poor transparency, though having ultraviolet shieldability in some
degree.
[0030] In the method of the invention, the suspension is, after the
zinc salt solution and the carbonate solution are added thereto,
stirred for about 30 minutes, and thereafter the solid is separated
from the suspension through filtration. The filtration is combined
with washing the solid with water. Alternatively, for the washing,
employable is also that, the solid residue obtained through the
filtration may be again dispersed in water, and the aqueous
dispersion may be again filtered, and these process are repeated.
After having been washed, the solid residue is dried at about 110
C. As a result of analysis through powdery X-ray diffractometry, it
was confirmed that, in the dried powder, the coating particles were
of basic zinc carbonate. (The basic zinc carbonate referred to
herein is meant to include "zinc compounded with CO.sub.3 and OH in
a composite state" and its hydrates.) SEM observation of the powder
verified that the coating particles had a mean major diameter of
not larger than 350 nm and were leafy to have an aspect ratio, mean
major diameter/mean thickness, of not smaller than 10. The flaky
substrate thus coated with such basic zinc carbonate particles is a
precursor, which is, after calcined, to be the intended, flaky
substrate coated with ultra-fine zinc oxide particles of the
invention.
[0031] The aspect ratio of the coating particles may be suitably
changed, by varying the complex-forming agent to be used and the
amount thereof relative to the zinc salt.
[0032] The dried powder is calcined at a temperature falling
between about 300 and 900.degree. C., preferably about 500 and
900.degree. C. Through SEM observation, the calcined powder was
found to be such that the coating particles therein have a mean
particle size of not larger than 100 nm. It is believed that, as a
result of calcining the dried powder, the carbonate moiety in the
coating, basic zinc carbonate particles is pyrolyzed to release
carbon dioxide therefrom so that the coating particles become
finer. If the powder is calcined at a temperature lower than
300.degree. C., the coating particles could not be oxidized
satisfactorily. However, if the powder is calcined at a temperature
higher than 900.degree. C., such high-temperature calcining will
induce solid-phase reaction of the coated, ultra-fine zinc oxide
particles formed, resulting in that the coated particles have a
large particle size. Through powdery X-ray diffractometry of the
calcined powder, the presence of zinc oxide in the powder was
confirmed. The thus-obtained powder can be used directly without
further treatment. However, in order to enhance its ability,
desirably, the powder is further pulverized and dispersed.
[0033] The thus-obtained powder may be treated with an organic
silicone compound, such as an alkylhydrogen-polysiloxane, to coat
the particles with the compound. This is to prevent the aggregation
of the coated substrate and to enhance the dispersibility of the
coated substrate, thereby facilitating the production of the
cosmetic material, the coating composition, the plastic and the ink
of the invention that comprises the coated substrate. To coat the
coated substrate with such an organic silicone compound, for
example, employable is any of a dry method of directly mixing the
silicone compound with the powder, or a wet method comprising
suspending the powder in water with silicone compound, and then
dewatering and drying it. In the dry process, the two may be
directly mixed, or alternatively, the two may be mixed along with
any other diluting solvent and the solvent used may be removed from
the mixture through vaporization. In the wet process, when an
alkylhydrogen-polysiloxane having high solubility in water is used,
special attention shall be paid in order to prevent the silicone
from flowing out without adhering onto the surfaces of the
particles. However, silicone compounds not completely dissolving in
water are unfavorable, since they could not naturally reach the
surfaces of the powder coated substrate and could not adhere
uniformly onto the surfaces of the coated substrate. In the wet
process, it is necessary that the alkylhydrogen-polysiloxane to be
used is suitably selected in consideration of the solubility of the
compound in the media, and the property relative to water of the
compound as to whether or not the compound is hydrophilic or
hydrophobic.
[0034] Alkylhydrogen-polysiloxanes usable herein include, for
example, methylhydrogen-polysiloxane, ethylhydrogen-polysiloxane,
propylethylhydrogen-polysiloxane, butylhydrogen-polysiloxane,
pentylhydrogen-polysiloxane, and hexylhydrogen-polysiloxane. Those
alkylhydrogen-polysiloxanes are to be suitably selected in
consideration of their polarity in cosmetic materials, coating
compositions, plastics and ink compositions and also of the related
legal controls on their use. For example, in cosmetic materials,
methylhydrogen-polysiloxane is favorably used in view of the legal
controls thereon. The product obtained in the wet process is
filtered to separate the solid residue from the suspension, and the
thus-separated solid residue is then dried. The powder thus
obtained in any of those wet and dry process is finally heated to
thereby bake the alkylhydrogen-polysiloxane onto the surfaces of
the powdery particles.
[0035] In general, the powder is dewatered and heated at a
temperature not lower than 100.degree. C., preferably at about
130.degree. C., in consideration of the producibility of the powder
according to this invention. In the invention, the amount of the
alkylhydrogen-polysiloxane to be used may be not smaller than 0.5
parts by weight relative to 100 parts by weight of the powder to be
treated therewith. Though not specifically defining the uppermost
limit of the amount of the compound to be used the amount thereof
may be suitably determined in accordance with the economical aspect
and of the physical property of the compound. Normally 1 - 5 weight
parts are employable.
[0036] The powder thus obtained may be directly the ultraviolet
shielding powder with high transparency of the invention. If
desired, the powder may be pulverized using, for example, a ball
mill, an atomizer, a planet mill or the like and then it is
obtainable, to be an ultraviolet shielding powder having higher
dispersibility with no aggregation and having higher
transparency.
[0037] temperatures are set forth uncorrected in degrees Celsius;
and, unless otherwise indicated, all parts and percentages are by
weight.
[0038] The entire disclosure of all applications, patents and
publications, cited above and below, and of corresponding Japanese
application No. 98-126616, filed Apr. 22, 1998 is hereby
incorporated by reference.
EXAMPLES
Example 1
[0039] 50 g of mica having a mean particle size of 2.u .mu.m and a
specific surface area of 15.01 m.sup.2/g was added to 1 liter of
water to prepare an aqueous suspension. This suspension was heated
at 75.degree. C., to which was added 9.03 g (0.05 mols relative to
zinc) of a complex-forming agent of trisodium citrate dihydrate,
and stirred. Apart from this, 176.7 g of zinc sulfate 7-hydrate was
used to prepare an aqueous 20 wt. % solution of the salt. Also
prepared was an aqueous 30 wt. % solution of potassium carbonate.
The aqueous zinc sulfate solution was added to the suspension at a
rate of 3 ml/min, along with the aqueous potassium carbonate
solution with which the pH of the resulting suspension was kept to
be 8.5. After the addition, the suspension was stirred for about 10
minutes, then filtered and washed to obtain a solid residue. The
solid residue was dried at about 110.degree. C. for 8 hours, and
then calcined at 700.degree. C. The aggregates in the resulting
powder were pulverized, using a blender. In the final powder to be
obtained herein, the amount of zinc oxide was controlled to be 100
parts by weight relative to 100 parts by weight of mica. Through
its powdery X-ray diffractometry, the dried precursor powder was
found to have basic zinc carbonate therein. Through the SEM picture
of the powder, it was found that the coating particles existing in
the powder had a mean major diameter of 20 nm and were leafy to
have an aspect ration (mean major diameter/mean thickness) of 11.8.
In the calcined powder, the coating, ultra-fine zinc oxide
particles had a mean particle size of 40 nm. The powder obtained
herein had good dispersibility and high transparency.
Example 2
[0040] The same process as in Example 1 was repeated herein, except
that the complex-forming agent was not used. In the final powder
obtained herein, the amount of zinc oxide was 100 parts by weight
relative to 100 parts by weight of mica. Through the SEM picture of
the dried precursor powder, it was found that the coating particles
existing in the powder had a mean major diameter of 250 nm and were
leafy to have an aspect ratio (mean major diameter/mean thickness)
of 12.5. In the calcined powder, it was found that the, ultra-fine
zinc oxide coated substrate were partly aggregated. The ultra-fine
particles of Zinc oxide had a mean particle size of 50 nm except
for aggregated particles of Zinc oxide thereon.
Example 3
[0041] 150 g of mica havaing a mean particle size of 5.9 .mu.m and
a specific surface area of 7.7 m.sup.2/g was added to 1.5 liters of
water to prepare an aqueous suspension.
[0042] This suspension was heated at 75.degree. C., to which was
added 27.1 g (0.05 mols relative to zinc) of a complex-forming
agent of trisodium citrate dihydrate, and stirred. Apart from this,
530 g of zinc sulfate 7-hydrate was used to prepare an aqueous 30
wt. % solution of the salt. Also prepared was an aqueous 30 wt. %
solution of potassium carbonate. The aqueous zinc sulfate solution
was added to the suspension at a rate of 5 ml/min, along with the
aqueous potassium carbonate solution with which the pH of the
resulting suspension was kept to be 8.5. After the addition, the
suspension was stirred for about 30 minutes, then filtered and
washed to obtain a solid residue. The solid residue was dried at
about 110.degree. C. for 8 hours, and then calcined at 700.degree.
C. In the final powder to be obtained herein, the amount of zinc
oxide was controlled to be 100 parts by weight relative to 100
parts by weight of mica. Through its powdery X-ray diffractometry,
the dried precursor powder was found to have basic zinc carbonate
therein. Through the SEM picture of the powder, it was found that
the coated particles existing in the powder had a mean major
diameter of 330 nm and were leafy to have an aspect ratio (mean
major diameter/mean thickness) of 13.2. In the calcined powder, the
coated, ultra-fine zinc oxide particles had a mean particle size of
40 nm.
[0043] 100 g of mica having a mean particle size of 5.9 .mu.m and a
specific surface area of 7.7 m.sup.2/g was added to 2 liters of
water to prepare an aqueous suspension.
[0044] This suspension was heated at 75.degree. C., to which was
added 9.33 g (0.1 mols relative to zinc) of a complex-forming agent
of succinic acid, and stirred. Apart from this, 151.6 g of zinc
sulfate 7-hydrate was used to prepare an aqueous 20 wt. % solution
of the salt. Also prepared was an aqueous 30 wt. % solution of
potassium carbonate. The aqueous zinc sulfate solution was added to
the suspension at a rate of 3.5 ml/min, along with the aqueous
potassium carbonate solution with which the pH of the resulting
suspension was kept to be 8.5. After the addition, the suspension
was stirred for about 10 minutes, then filtered and washed to
obtain a solid residue. The solid residue was dried at about
110.degree. C. for 8 hours, and then calcined at 700.degree. C. In
the final powder to be obtained herein, the amount of zinc oxide
was controlled to be 43 parts by weight relative to 100 parts by
weight of mica. Through its powdery X-ray diffractometry, the dried
precursor powder was found to have basic zinc carbonate therein.
Through the SEM picture of the powder, it was found that the coated
particles existing in the powder had a mean major diameter of 330
nm and an aspect ratio (mean major diameter/mean thickness) of
13.2. In the calcined powder, the coated, ultra-fine zinc oxide
particles had a mean particle size of 40 nm.
Example 5
[0045] 1.5 kg of the powder obtained in the same manner as in
Example 1 was put into a 20-liter Henschel mixer, and stirred at
2800 rpm for 18 minutes. Next, 30 g of methylhydrogen-polysiloxane
was added thereto and further stirred at 350 rpm for 3minutes. The
resulting mixture was heated at 130.degree. C., while being further
stirred there in at 2800 rpm for 18minutes. Next, this was cooled
for about 6 minutes while being stirred at 2800 rpm, and then
further cooled to about 50.degree. C. at 350 rpm. Thus was obtained
the powder of the invention. The powder had better dispersibility
and higher transparency.
Example 6
[0046] 50 g of the powder obtained in the same manner as in Example
1 was suspended in 1 liter of water, and heated at 75.degree. C. To
this was added a 10 % solution of hydrochloric acid, with which the
pH of the suspension was controlled to be 7, and the resulting
suspension was stirred for about 10 minutes. Next, 1 g of
methylhydrogen-polysiloxane was added to the suspension with
stirring, and further stirred for about 30 minutes. Then, the
suspension was filtered and washed, and the solid residue obtained
was dried and heated at 130.degree. C. The aggregates existing in
the resulting powder were pulverized, using a blender, to obtain
the intended powder of the invention. The powder had better
dispersibility and higher transparency.
Comparative Example 1
[0047] 150 g of fine-powdery muscovite having a particle size of
from 1 to 15 .mu.m was suspended in 1.5 liters of water, and heated
at about 80.degree. C., to which was added 50.7 g of barium
hydroxide with stirring. Next, an aqueous solution of 10 wt. %
sulfuric acid was dropwise added to the resulting suspension at a
rate of 2 ml/min, with stirring, with which the pH of the
suspension was controlled to be finally 3. After the addition, the
suspension was stirred for about 10 minutes, to which was added
662.5 g of zinc sulfate, and further stirred for about 10 minutes.
Then, an aqueous 32 wt. % solution of sodium hydroxide was dropwise
added to this at a rate of 5 ml/min, with which the final pH of the
suspension was controlled to be 8.5. This suspension was filtered
to separate the solid residue therefrom, and the solid residue was
washed, then dried at about 105.degree. C. for 15 hours, and
thereafter calcined at 700.degree. C. In that manner, obtained was
an ultraviolet-shielding pigment in which 100 parts by weight of
powdery muscovite was coated with 25 parts by weight of barium
sulfate particles and 125 parts by weight of zinc oxide particles.
The SEM observation of the pigment verified that the barium sulfate
particles existing therein had a mean particle size of about 0.3
.mu.m and that the needle-like zinc oxide particles also existing
therein had a mean major diameter of 0.2 .mu.m.
Comparative Example 2
[0048] The same process as in Example 1 was repeated, except that
sodium hydroxide was used in place of potassium carbonate. In the
final powder obtained herein, the amount of zinc oxide was 100
parts by weight relative to 100 parts by weight of mica. Through
the SEM picture of the dried precursor powder, it was found that
the coated particles existing in the powder had a mean major
diameter of 170 nm and an aspect ratio (mean major diameter/mean
thickness) of 3.4. In the calcined powder, the coating, ultra-fine
zinc oxide particles had a mean particle size of 170 nm. [0038]
Evaluation of Ultraviolet Shieldability and Transparency of Powder
Samples
[0049] The powder samples obtained in Examples 1 to 6 and
Comparative Examples 1 and 2 were separately dispersed in a
PVC-type medium by hand (without using any mechanical means of
Hoover muller, three-roll mixer and the like) to prepare 20 wt. %
dispersions. Each dispersion was applied onto sheet glass, using an
applicator having a thickness of 120 .mu.m, to form thereon a film.
After having been dried, the film was subjected to
spectrophotometry, using Hitachi's 228 Model spectrophotometer, to
measure its transmittance within a wavelength range of from 200 and
900 nm. The transmittance at 300 nm indicates the data for UV-B;
that at 370 nm for UV-A; and that at 550 nm for visible rays. In
addition, the absorbance for UV-A and UV-B was also measured. FIG.
1 shows the transmittance of the samples of Example 1, Comparative
Examples 1 and 2; and Table 1 shows the data of the transmittance
and the absorbance of the samples tested herein for ultraviolet
rays (300 nm for UV-B and 370 nm for UV-A) and for visible rays
(550 nm).
1TABLE 1 Transmittance in ultraviolet and visible ray range, and
Absorbance in ultraviolet range Transmittance Absorbance UV-B UV-A
Visible Rays UV-B UV-A Sample 300 nm 370 nm 550 nm 300 nm 370 nm
Example 1 1.23 1.80 56.11 1.91 1.75 Example 2 1.47 1.48 52.31 1.84
1.83 Example 3 8.65 7.93 53.18 1.07 1.10 Example 4 7.69 10.14 71.92
1.12 1.00 Example 5 0.87 0.98 62.46 2.06 2.01 Example 6 1.30 1.90
67.03 1 .89 1.72 Comparative 6.97 5.08 26.30 1.16 1.29 Example 1
Comparative 1.92 0.99 35.17 1.72 2.01 Example 2
[0050] The samples of Examples 1 to 6 were found to have higher
transmittance in the visible ray range while having lower
transmittance in the ultraviolet range, than those of Comparative
Examples. Of those, the characteristics of the samples of Examples
5 and 6 that had been coated with a hydrogen-polysiloxane and had
been pulverized were much better to meet the object of the
invention.
Application Examples
[0051] using the ultraviolet-shielding powder samples obtained in
Examples 1 to 6, prepared were cosmetic materials (A: compact
powder, and B: foundation) each having the composition mentioned
below.
2 A: Formulation of Compact Powder: Composition: UV-shielding
pigment obtained in any of Examples 1 to 6 25 wt. pts. Coloring
pigment 5 wt. pts. Lanolin 3 wt. pts. Isopropyl myristate balance
Magnesium stearate 2 wt. pts. Talc 50 wt. pts.
[0052]
3 B: Formulation of Foundation: Composition: Talc (JA-46R,
manufactured by Asada Talc) 38 wt. pts. Mica (mean particle size:
about 8 .mu.m) 10 wt. pts. Magnesium stearate 3 wt. pts. Nylon
powder 12 8 wt. pts. Yellow iron oxide 1.9 wt. pts. Red iron oxide
0.8 wt. pts. Titanium oxide 1.0 wt. pts. Sample obtained in any of
Examples 1 to 6 30 wt. pts. Mineral oil (70) 3.9 wt. pts. (Caprylic
acid/capric acid) triglyceride 3.3 wt. pts. Butylparaben 0.1 wt.
pts.
[0053]
4 Composition A (acrylic melamine resin): Acrydic 47-712 70 wt.
pts. Superbeccamine G821-60 30 wt. pts. Composition B: UV-shielding
powder obtained in any of Examples 1 to 6 10 wt. pts. Pearly
pigment 10 wt. pts. Composition C (thinner for acrylic melamine
resin): Ethyl acetate 50 wt. pts. Toluene 30 wt. pts. N-butanol 10
wt. pts. Sorbesso #150 40 wt. pts.
2. Use in Coating Compositions
[0054] Using the ultraviolet-shielding powder samples obtained in
Examples 1 to 6, prepared were coating compositions in the manner
mentioned below.
[0055] Coating Composition (for automobiles)
[0056] 20 parts by weight of the composition B was mixed with 100
parts by weight of the composition A, which was then diluted with
the composition C to have a viscosity suitable for spray coating
(12 to 15 seconds as measured with Ford Cup #4). The resulting
mixture was sprayed over a substrate to form a base coat layer
thereon.
3. Use as Filler in Plastics
[0057] Using the ultraviolet-shielding powder samples obtained in
Examples 1 to 6, prepared were plastics in the manner mentioned
below.
5 Composition (plastic composition): High-density polyethylene
resin (pellets) 100 wt. pts. UV-shielding powder obtained in any of
Examples 1 to 6 1 wt. pt. Magnesium stearate 0.1 wt. pts. Zinc
stearate 0.1 wt. pts.
[0058] The pellets were dry-blended with the additives in the ratio
noted above, and molded through injection molding into plastic
moldings.
4. Use in Printing Ink
[0059]
6 Composition: CCST medium (nitrocellulose resin, manufactured by
Toyo 10 wt. pts. Ink Co.) UV-shielding powder obtained in any of
Examples 3 to 6 8 wt. pts.
[0060] A solvent, NC 102 (manufactured by Toyo Ink Co.) was added
to the ink composition noted above to prepare printing ink having a
viscosity of 20 seconds as measured with Zahn Cup No. 3.
[0061] As is obvious from Table 1, the ultraviolet absorbent of the
present invention has not only UV-shieldability but also high
transparency in the visible ray range. Therefore, when it is
incorporated into practicable cosmetic materials, coating
compositions, plastics and ink compositions, it has little
influence on the color change in those products. Accordingly, the
amount of the ultraviolet absorbent capable of being added to those
products may be increased, whereby the UV-shieldability of the
products can be increased.
BRIEF DESCRIPTION OF THE DRAWING
[0062] [FIG. 1] This shows the transmittance of the ultraviolet
absorbent samples obtained in Example 1 and Comparative Examples 1
and 2, in a wavelength range of from 200 nm to 900 nm.
[0063] The preceding examples can be repeated with similar success
by substituting the generically or specifically described reactants
and/or operating conditions of this invention for those used in the
preceding examples.
[0064] From the foregoing description, one skilled in the art can
easily ascertain the essential characteristics of this invention
and, without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
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