Phosphoric acid metal compound-containing pearl pigment

A pearl pigment which is excellent in discoloration resistance and in affinity (dispersibility) with resins, a production method for the same, and a resin composition, paint and ink into which the above pearl pigment is incorporated. The pearl pigment comprises a flake substrate, titanium oxide coated on the surface thereof, and a phosphoric acid metal compound, or a phosphoric acid metal compound and a metal oxide coated on the surface of particles coated with titanium oxide.

BACKGROUND OF THE INVENTION 
The present invention relates to a novel pearl pigment using a flake 
substrate as a base material, more specifically to a novel pearl pigment 
which is excellent in resistance to discoloration caused by light and 
heat, as well as in affinity (dispersibility) with resins, a production 
method for the same, and a resin composition, paint and ink into which the 
above pearl pigment is incorporated. 
There are known and widely employed pearl (i.e., pearlescent or "nacreous") 
pigments in which a flake substrate is coated with metal oxides having 
high refractive indices, for example, titanium dioxide and zirconium 
oxide, to cause a pearlescent color to be revealed by an interference 
color generated by interference due to reflection of light. Also known are 
pearl pigments in which colored metal oxides, for example, iron oxide and 
chromium oxide, or colored pigments and dyes are impregnated into this 
coating layer to cause colored pearlescence to be developed. 
Among them, with respect to white-color (including an interference color) 
pearl pigments, well known is a pearl pigment which is composed of a 
coating layer using titanium oxide as a base material. Titanium oxide is 
well known as an optically active material (for example, see Susumu 
Okazaki, "Coloring Material," 606!, 333-341 (1987)), and it is reported 
that when this is mixed into paint and ink and kneaded into plastics, a 
resin component contacting this titanium oxide deteriorates (chalking; 
whiting) as time passes with light or heat energy as an initiator (see, 
for example, Okazaki, above, and Hiroshi Tsubomura, "Optical 
Electrochemical and Energy Conversion," Tokyo Kagaku Dohjin (1980), p. 
198). Further, it is said that when this titanium oxide is kneaded into a 
plastic comprising polyolefin, titanium oxide reacts with a phenol 
derivative (for example, BHT and the like) or aniline-derivatives light 
stabilizer to form a coordination complex or a coordination compound, 
which causes discoloration (see, for example, D. A. Holzen, "TI-PURE" 
Technical Report, Du Pont Japan, No. 84-003 (1)). These kind of problems 
are similarly found when using a pearl pigment in which titanium oxide is 
coated on the surface thereof. 
The present inventors have previously proposed a pearl pigment in which the 
defects described above are improved and which has a good dispersibility 
without discoloration and coagulation of the particles (see JP-A-6-16964). 
This pearl pigment is prepared by using, as a raw material, a white pearl 
pigment prepared by first coating titanium oxide on mica particles and 
coating respective metal oxides (or hydrates) of silicon, aluminum and 
zinc in order on these white titanium oxide-coated mica particles (that 
is, as an outer layer) by a wet method, wherein it has been intended to 
reduce the exposure of titanium oxide to light and heat energies coming 
from the outside with the above outer layer and enhance the dispersibility 
of the pigment itself. However, this production method requires the 
repetition of the processing operations of a hydrolytic reaction twice and 
dry processing (drying and calcination) and is therefore a disadvantageous 
production method. 
On the other hand, when a conventional pearl pigment in which metal oxides 
using titanium oxide as a base material are coated on a flake substrate is 
incorporated into a resin system, the pigment often moves to the surface 
of the resin composition, and this contaminates the surfaces of kneading 
rolls and calendar rolls in a molding machine to generate a phenomenon 
called plate out, which causes differences in the quality by product and 
lot. In order to solve this problem of plate out, a method has been 
proposed in which blended components for a resin composition are improved 
(see, for example, JP-A-63-317557), and in addition to this, in case of a 
pearl pigment, a pigment in which the surface is treated with a specific 
polymer, such as, for example, a pearl pigment coated directly with a 
polyester-polyurethane block copolymer having a tertiary amino group (see 
JP-A-63-46266). However, the use of these pearl pigments has been 
problematic in that the kind of resins able to be used is restricted. 
Further, there has been the problem that when a metal oxide (titanium 
oxide)-coated flake substrate pigment itself is used as is as a raw 
material for ink, raising the pigment content in order to emphasize 
pearlescence particularly in offset printing causes unevenness in printing 
as the number of printed sheets increases. This is because the affinity 
(dispersibility) of the pigment for an ink medium is low, and a phenomenon 
of so-called piling in which a pigment is separated from a medium and 
piles up on rolls, plate and blanket. 
SUMMARY OF THE INVENTION 
The present invention is intended to solve the problems that conventional 
techniques pose. That is, an object of the present invention is to provide 
a pearl pigment which is improved in discoloration resistance, reduced in 
plate-out in production, and in which the printing and dispersion 
characteristics of ink when the pearl pigment is used as mixed in with 
paint and ink or as incorporated into plastics, are improved. The 
invention also provides a convenient production method for the same, and 
resin, paint and ink compositions containing the pearl pigment obtained by 
the above production method. 
It has been found that the discoloration resistance of a pearl pigment, the 
affinity (dispersibility) thereof with a resin, and a printing aptitude in 
ink are notably improved by coating titanium oxide and a phosphoric acid 
metal compound, or titanium oxide, a phosphoric acid metal compound and 
other metal oxides on the surface of a flake substrate, while the intended 
pearlescence is maintained. 
The present invention preferably provides a novel pearl pigment comprising 
a flaky (i.e., platelet-shaped) substrate, with titanium oxide coated on 
the surface thereof, and a phosphoric acid metal compound or a phosphoric 
acid metal compound and a metal oxide coated on the particles coated with 
titanium oxide. Metals include Zn, Al, Zr, Mg, Bi, Si, Ti, Ba, Sn and Ca. 
The present invention provides a novel pearl pigment in which after 
preferably coating titanium oxide on the surface of a flaky substrate, a 
substance is coated thereon: 
a) wherein the amount of the phosphoric acid component constituting the 
phosphoric acid metal compound to be coated is present in a proportion of, 
e.g. , 0.1 to 5 weight % in terms of P.sub.2 O.sub.5 based on titanium 
oxide (TiO.sub.2 basis); the metal element constituting the phosphoric 
acid metal compound and the metal oxide is preferably at least one 
selected from Zn, Al, Zr, Mg, and Bi; and the amount thereof is preferably 
present in a proportion of, e.g., 0.5 to 10 weight % in terms of metal 
oxide based on titanium oxide (TiO.sub.2 basis), or 
b) wherein the amount of the phosphoric acid component constituting the 
phosphoric acid metal compound to be coated is preferably in a proportion 
of, e.g., 0.1 to 5 weight % in terms of P.sub.2 O.sub.5 based on titanium 
oxide (TiO.sub.2 basis); the kinds of metals constituting the phosphoric 
acid metal compound and the metal oxide are preferably Zn, Al and Si, and 
the metal compounds thereof are coated in order; and the amounts thereof 
are preferably present in the proportions of, e.g., 0.5 to 10 weight % in 
terms of ZnO.sub.2 based on titanium oxide (TiO.sub.2 basis), 0.5 to 10 
weight % in terms of Al.sub.2 O.sub.3 based on titanium oxide (TiO.sub.2 
basis), and 0.5 to 5 weight % in terms of SiO.sub.2 based on titanium 
oxide (TiO.sub.2 basis), respectively. 
Further, the present invention provides: 
(1) a method for producing a pearl pigment, comprising: 
preparing an aqueous suspension of a flaky substrate, 
coating titanium oxide hydrate prepared by the hydrolysis of a titanium 
salt on the surface of the substrate, 
adding phosphoric acid or a phosphate compound and a salt of at least one 
metal selected from Zn, Al, Zr, Mg and Bi and then forming the hydrolysis 
product of the metal salt thereof and the phosphoric acid metal salt 
thereof with alkali to coat them on a coated particle surface thereof, and 
filtering and washing the coated particles, followed by drying and 
calcining them, or 
(2) a method for producing a pearl pigment, comprising: 
preparing an aqueous suspension of a flaky substrate, 
coating titanium oxide hydrate prepared by the hydrolysis of a titanium 
salt on the surface of the substrate, 
adding phosphoric acid or a phosphoric acid salt compound and a Zn salt to 
a coated particle surface to form the hydrolysis product of the Zn salt 
and the phosphoric acid metal salt thereof with alkali, then using an Al 
salt and alkali to form the neutralized hydrolysis product thereof, 
further adding a silicate compound to form a hydrolysis product thereof, 
and coating them in order, and 
filtering and washing the coated particles, followed by drying and 
calcining them. 
Further, the present invention provides a pearl pigment prepared by 
subjecting the pearl pigment thus obtained to a surface coating treatment 
with at least one modifying agent selected from a silane coupling agent, 
an organosiloxane compound, and/or an aliphatic carboxylic acid. In 
addition, the present invention provides paint, ink and resin compositions 
into which the pearl pigment of the present invention is blended. 
The novel pearl pigment according to the present invention is excellent in 
discoloration resistance, facility in kneading into resins, and 
printability when it is used for plastics, paint, and ink as a pearl 
pigment. 
Further, the production method according to the present invention is a very 
convenient and advantageous method in terms of production management and 
energy saving since after once preparing a suspension of a flaky 
substrate, intermediate processes such as drying and calcining in the 
middle of the process does not have to be carried out, and the reaction 
and treatment can be consistently carried out in succession in a 
suspension state (wet). 
The flaky substrate used in the present invention includes stratified clay 
minerals such as mica, kaolin, and talc, flaky oxides of metals selected 
from titanium, aluminum, silicon, and iron, and glass flakes. In 
particular, mica which is widely used as a flaky substrate for a pearl 
pigment is preferably used since it is readily available. The size thereof 
is preferably from about 2 to 200.mu. in terms of the average particle 
diameter and suitably selected within this range according to the 
applications thereof. For example, when it is used for ink, mica having an 
average particle diameter of as small as 10.mu. or less is preferably 
used. Mica having a thickness of 2.mu. or less, preferably 1.mu. or less 
is suitable for revealing pearlescence. 
The amount of titanium oxide coated in the present invention can be 
optionally in the range of from 15 to 200 weight % (based on the flaky 
substrate). Since the unit surface area is large when the diameter of a 
flaky substrate is small, the coated amount is increased, and reversely, 
since the unit surface area is small when the diameter of a flaky 
substrate is large, the coated amount is decreased. The optical thickness 
has to be fundamentally increased when an interference color is revealed, 
and the coated amount is increased by more than the coated amount in case 
of a silver color tone. Accordingly, the coated amount of titanium oxide 
is suitably determined according to an intended color tone, in accordance 
with conventional procedures known in the art. 
With respect to the method for coating titanium oxide hydrate on a flaky 
substrate according to the present invention, there can be employed known 
methods, for example, either a method by neutralized hydrolysis in which a 
titanium salt aqueous solution and an alkali solution are added at the 
same time while maintained (at about pH 2), or a method using heat 
hydrolysis in which a titanium salt compound is added in advance and heat 
is then applied. In this case, a rutilizing agent, for example, a tin salt 
can be used in order to convert titanium oxide crystal to a rutile type. 
Titanium tetrachloride, titanium trichloride, and titanyl sulfate are 
preferably used because of easier availability thereof. This reaction can 
run simultaneously with coating by the phosphoric acid metal compound. 
To coat with the phosphoric acid metal compound (wherein the titanium oxide 
is desired is a first layer, then after this hydrolytic reaction of 
coating by titanium oxide hydrate), phosphoric acid or a phosphate 
compound and a desired metal salt are added to a system of the suspension 
to form a phosphoric acid metal compound. In this case, phosphoric acid or 
the phosphate compound includes phosphoric acid, condensed phosphoric 
acid, and the alkaline metal salts thereof, e.g., phosphoric acid, 
disodium phosphate, monosodium phosphate, dipotassium phosphate, 
monopotassium phosphate, potassium pyrophosphate, sodium pyrophosphate, 
potassium tripolyphosphate, and sodium tripolyphosphate. Phosphoric acid, 
disodium phosphate, and dipotassium phosphate are preferably used from the 
viewpoint of easy availability and cost. The amount of this phosphoric 
acid or phosphate compound is used in a proportion of e.g., 0.1 to 5 
weight %, preferably 1 to 4 weight % in terms of P.sub.2 O.sub.5 based on 
the amount of titanium oxide in the finished product. An amount less than 
the above level provides lower effect, and even if the amount is increased 
more than this level, the degree of an increase in a discoloration 
resistance effect is small. In this case, if pH increases to more than 3 
after adding the phosphate compound, the reaction is preferably carried 
out after pH is once lowered to 3 or less with acid such as hydrochloric 
acid in a range in which the metal salt to be added subsequently is not 
hydrolyzed. 
In the method (1) described above, the salt of at least one metal selected 
from Zn, Al, Zr, Mg, and Bi is used as metal constituting the phosphoric 
acid metal compound and the metal oxide. The amount of this metal salt is, 
e.g., 0.5 to 10 weight % (based on TiO.sub.2), preferably 1 to 4 weight % 
in terms of metal oxide. Too small an amount thereof does not provide a 
sufficient effect, and too large amount causes the coagulation of 
particles themselves, which in turn causes a loss of pearlescence. The raw 
materials for these metal elements are suitably selected from chlorides, 
sulfates, nitrates, and oxychlorides thereof considering the availability 
thereof. 
In the method (2) described above, employed is a method in which in order 
to improve the discoloration resistance and prevent the particles from 
coagulating by sintering in the production and calcination, an Al salt and 
an Si salt are coated in order in the amounts of, e.g., from 0.5 to 10 
weight % in terms of Al.sub.2 O.sub.3 based on titanium oxide (as 
TiO.sub.2), and, e.g., from 0.5 to 5 weight % in terms of SiO.sub.2 based 
on titanium oxide (as TiO.sub.2), respectively. The use of this Al salt 
contributes particularly to a coagulation reduction effect of the product 
attributable to a sintering prevention action in calcination. The amount 
of 0.5 weight % or less in terms of the metal oxide (Al.sub.2 O.sub.3) 
greatly reduces the effect thereof, and the amount of 10 weight % or more 
not only does not increase the effect thereof but also causes a reduction 
in the pearl gloss of the pigment. The more preferred amount of it to be 
used, though this is influenced by the unit surface area of the flaky 
substrate, is usually from 1 to 4 weight %. The use of the Si salt 
improves the discoloration resistance effect, and the preferred amount 
thereof, though it is still influenced by the unit surface area of the 
flaky substrate, is from 1 to 3 weight % in terms of the metal oxide 
(SiO.sub.2). A decrease in this amount does not enhance the discoloration 
resistance effect, and an increase in the amount causes sintering in 
calcination which leads to coagulation and does not provide a pigment with 
satisfactory dispersibility, which leads to a reduction in the 
pearlescence. 
As described above, "the phosphoric acid metal compound" and "the 
phosphoric acid metal compounds and the metal oxide" described in the 
present invention describe a final product produced by a process in which 
the hydrolysis products of phosphoric acid or a phosphate compound and 
various metal salts are adhered on a flaky substrate, dried and calcined. 
Although not wishing to be restricted to a particular physical 
description, it is considered that these products exist in the state that 
they are composed of a phosphoric acid metal salt, the mixture of a 
phosphoric acid metal salt and a metal oxide, the mixture of P.sub.2 
O.sub.5 and other metal oxides, and the composite of P.sub.2 O.sub.5 and 
other metal oxides according to the ratio of the amounts of phosphoric 
acid (or a phosphate compound) to the metal salt used. During the 
calcination, some phosphoric acid metal salts decompose (for example, 
BiPO.sub.4, NaHPO.sub.4, BaHPO.sub.4) and some salts (for example Mg.sub.3 
(PO.sub.4).sub.2) fuse and are convened into the glass state. Phosphoric 
acid metal salts may be of the formula Zn.sub.3 (PO.sub.4).sub.2, 
AlPO.sub.4, Zr.sub.3 (PO.sub.4).sub.2, Mg.sub.3 (PO.sub.4).sub.2, 
BiPO.sub.4, Ti.sub.3 (PO.sub.4).sub.4, Zn.sub.2 P.sub.2 O.sub.7, Al.sub.4 
(P.sub.2 O.sub.7).sub.3, Ba.sub.2 P.sub.2 O.sub.7, Mg.sub.2 P.sub.2 
O.sub.7, TiP.sub.2 O.sub.7, SnP.sub.2 O.sub.7, and Ca.sub.2 P.sub.2 
O.sub.7. 
Exemplary production methods according to the present invention will be 
explained in more detail. 
The first production method (the production method (1) described above): 
The first step: coating titanium oxide hydrate 
A suspension prepared by dispersing a flaky substrate having a desired 
particle size in water is heated to 70.degree. C. or higher, and an 
aqueous solution of a titanium salt in which the concentration is adjusted 
is added to this suspension to adjust the pH to about 2. Further, the 
aqueous solution of the titanium salt is subsequently added under stirring 
together with an alkali solution while maintaining the pH at the above 
level. After adding the prescribed amount, the suspension is further 
stirred for about 10 minutes. 
The second step: adding phosphoric acid or a phosphate compound and a metal 
salt and coating the hydrolysis products thereof: 
Further added in order are phosphoric acid or a phosphate compound in an 
amount corresponding to from 0.1 to 5 weight % in terms of P.sub.2 O.sub.5 
based on the amount of titanium oxide calculated from the amount of the 
titanium compound added in the first step, and at least one metal salt of 
Zn, Al, Zr, Mg or Bi in an amount corresponding to from 0.5 to 10 weight % 
in terms of the metal oxide thereof based on the amount of the titanium 
oxide calculated above, wherein stirring is carried out for about 10 
minutes without specifically controlling the pH. In the case where the 
phosphate compound used in this step is, for example, disodium phosphate 
or sodium tripolyphosphate, the pH increases to some extent. When the pH 
increases to 3 or higher, it is once lowered to 3 or lower with mineral 
acids such as hydrochloric acid. Then, an alkali solution is gradually 
dropped to this suspension to raise the pH up to 7.0. 
Third step: after-treatment step 
The suspension obtained in the second step is filtered, and soluble free 
salts are removed by washing with water. After drying, the pigment thus 
obtained is calcined at from 700.degree. to 1200.degree. C. to thereby 
obtain the intended pearl pigment. 
Second production method (the production method (2) described above): 
The second step in the first production method is changed to the following 
operation. 
Added are phosphoric acid or a phosphate compound in an amount 
corresponding to from 0.1 to 5 weight % in terms of P.sub.2 O.sub.5 based 
on the amount of titanium oxide calculated from the amount of the titanium 
salt added in the first step, and a Zn salt in an amount corresponding to 
0.5 to 10 weight % in terms of the oxide thereof based on the amount of 
titanium oxide calculated above, wherein stirring is carried out for about 
10 minutes without specifically controlling the pH. In the case where the 
phosphate compound used in this step is, for example, disodium phosphate 
or sodium tripolyphosphate, the pH increases to some extent. When the pH 
increases to 3 or higher, it is once lowered to 3 or lower with mineral 
acids such as hydrochloric acid. Then, an alkali solution is gradually 
added dropwise to this suspension to raise the pH up to 5.5. An Al metal 
compound aqueous solution is added in an amount corresponding to from 0.5 
to 10 weight % in terms of Al.sub.2 O.sub.3 based on the amount of 
titanium oxide simultaneously with the alkali solution while maintaining 
the pH at 5.5. Then, an aqueous solution of a silicate compound is 
gradually added in an amount corresponding to from 0.5 to 5 weight % in 
terms of SiO.sub.2 based on the amount of titanium oxide without 
controlling the pH. After completing the addition, stirring is further 
carried out for 10 minutes. 
Thereafter, the treatment in the third step of the first production method 
described above is carried out to thereby obtain the intended pearl 
pigment. 
The present invention further includes pigments obtained by subjecting the 
pearl pigments obtained through the respective third steps described above 
to a surface treatment with surface treating agents such as a silane 
coupling agent, an organosiloxane compound and aliphatic carboxylic acid. 
These surface treatments increase both the affinity for resins and a 
discoloration resistance. In this case, alkyl trimethoxysilanes having an 
aliphatic chain with 8 or more carbon atoms are preferably used as the 
silane coupling agent. Also, methyl hydrogenpolysiloxane is preferably 
used as organosiloxane. Employed as the method for these surface 
treatments used in the present invention are a method in which the pearl 
pigment obtained through the third step in the first production method or 
the second production method is charged into a stirring mixer such as a 
Henshell mixer and a high-speed blender mixer manufactured by Worling Co., 
Ltd. and mixed with a surface treating agent added while stirring, or a 
method in which the components are charged in one lot and mixed, wherein 
employed is such a means that a heat treatment is provided through 
stirring according to necessity or a surface treating agent is mixed in 
advance into an organic solvent and added, followed by heating to remove 
the solvent. 
Without further elaboration, it is believed that one skilled in the art 
can, using the preceding description, utilize the present invention to its 
fullest extent. The following preferred specific embodiments are, 
therefore, to be construed as merely illustrative, and not limitative of 
the remainder of the disclosure in any way whatsoever. 
In the foregoing and in the following examples, all temperatures are set 
forth uncorrected in degrees Celsius and unless otherwise indicated, all 
pans and percentages are by weight. 
The entire disclosure of all applications, patents and publications, cited 
above and below, and of corresponding Japanese application 7-218303, filed 
Aug. 4, 1995, are hereby incorporated by reference.

EXAMPLES 
Example 1 
(a-1) Muscovite (particle diameter: from about 10 to 60 .mu.m) in an amount 
of 80 g was suspended in demineralized water of 1 liter, and the 
suspension was heated to 75.degree. C. while stirring. A titanium 
tetrachloride aqueous solution in which titanium tetrachloride of 414 g 
per liter was dissolved was added to this suspension, and the pH was 
adjusted to 2.2, followed by maintaining it for 5 minutes. Then, the 
titanium tetrachloride aqueous solution described above was further added 
dropwise gradually while maintaining the pH at 2.2 with a 32% sodium 
hydroxide aqueous solution. The titanium tetrachloride aqueous solution of 
188 ml was added in total, whereby a suspension of titanium 
hydroxide-coated mica having a gloss of a silver color was obtained. 
(b-1) 85% phosphoric acid of 1.1 g and zinc chloride of 2.0 g were added to 
the suspension thus obtained and maintained for 10 minutes while stirring. 
Then, a 32% sodium hydroxide aqueous solution was slowly added dropwise to 
adjust the pH to 7.0. 
(c-1) Further, the coated pigment was filtered off from this suspension, 
and after washing with demineralized water and drying, the pigment was 
calcined at 900.degree. C., whereby a pearl pigment having a gloss of a 
silver color was obtained. 
Example 2 
A pearl pigment having a gloss of a silver color was obtained in the same 
manner as that described in Example 1, except that disodium 
hydrogenphosphate 12 hydrate in an amount of 3.5 g was substituted for 
phosphoric acid used in the step (b-1) of Example 1, wherein the pH 
increased to some extent but was maintained as it was for about 10 minutes 
while stirring, and the pH was then adjusted to 2.2 with a hydrochloric 
acid aqueous solution, followed by adding zinc chloride (ZnCl.sub.2 
powder) of 2.0 g. 
Example 3 
A pearl pigment was obtained in the same manner as that described in 
Example 1, except that 2.4 g of aluminum chloride 6 hydrate were 
substituted for zinc chloride used in the step (b-1) of Example 1. 
Example 4 
A pearl pigment was obtained in the same manner as that described in 
Example 1, except that magnesium chloride 6 hydrate in an amount of 3.0 g 
was substituted for zinc chloride used in the step (b-1) of Example 1. 
Example 5 
A pearl pigment was obtained in the same manner as that described in 
Example 1, except that the operation was carried out in which after 
dropwise adding an aqueous solution prepared by diluting a zirconium 
oxychloride aqueous solution (content 20% as ZrO.sub.2) with demineralized 
water to 60 g for about 20 minutes in place of zinc chloride used in the 
step (b-1) of Example 1, the suspension was maintained for 10 minutes 
while stirring, and a sodium hydroxide aqueous solution was then added 
slowly to adjust the pH value to 7. 
Example 6 
After the step (a-1) in Example 1, the final pH in the operation of the 
step (b-1) was adjusted to 5.5, and subsequently, a 6% aluminum chloride 6 
hydrate aqueous solution of 94.8 g was dropped for 30 minutes while 
maintaining the pH at 5.5 with a sodium hydroxide aqueous solution. Then, 
further added was the step in which a sodium silicate (SiO.sub.2 : 36%) 
solution of 1.67 g was diluted with water to 11.1 g, and this solution was 
added dropwise thereto for about 10 minutes. The operation of (c-1) in 
Example 1 was then carried out, whereby a pearl pigment having a gloss of 
a silver color was obtained. 
Example 7 
(a-2) Muscovite (particle diameter: from about 5 to 20 .mu.m) in an amount 
of 60 g was suspended in demineralized water of 1 liter, and the 
suspension was heated to 75.degree. C. while stirring. A titanium 
tetrachloride aqueous solution in which 414 g per liter of titanium 
tetrachloride were dissolved was added to this suspension, and the pH was 
adjusted to 2.2, followed by maintaining it for 5 minutes. Then, the 
titanium tetrachloride aqueous solution described above was further 
dropwise added gradually while maintaining the pH at 2.2 with a 32% sodium 
hydroxide aqueous solution. The titanium tetrachloride aqueous solution of 
211 ml was added in total, whereby a suspension of titanium 
hydroxide-coated mica having a gloss of a silver color was obtained. 
(b-2) 85% phosphoric acid in an amount of 1.3 g and zinc chloride of 2.3 g 
were added to the suspension thus obtained and maintained for 10 minutes 
while stirring. Then, a 32% sodium hydroxide aqueous solution was slowly 
added dropwise to adjust the pH to 5.5. Next, a 6% aluminum chloride 6 
hydrate aqueous solution of 124 g was added dropwise thereto for about 30 
minutes while maintaining the pH at 5.5. Then, an aqueous solution 
prepared by diluting a sodium silicate (SiO.sub.2 : 36%) of 2.2 g with 
water to 14.7 g was added dropwise for about 10 minutes and maintained for 
about 10 minutes. 
(c-2) Further, the pigment was filtered off from this suspension, and after 
washing with demineralized water and drying, the pigment was calcined at 
930.degree. C., whereby a pearl pigment having a gloss of a silver color 
was obtained. 
Example 8 
(a-3) Muscovite (particle diameter: from about 5 to 20 .mu.m) in an amount 
of 60 g was suspended in demineralized water of 1 liter, and the 
suspension was heated to 75.degree. C. while stirring. An aqueous solution 
of 22.6 ml in which tin tetrachloride 5 hydrate in an amount of 414 g per 
liter was dissolved as a rutilizing agent was prepared, and this aqueous 
solution was gradually added dropwise while maintaining the pH at 2.0 with 
a 32% sodium hydroxide aqueous solution. After maintaining for 15 minutes 
while stirring, a solution containing titanium tetrachloride in an amount 
of 414 g per liter was gradually added dropwise while maintaining the pH 
at 2.0 with a 32% sodium hydroxide aqueous solution. The titanium 
tetrachloride aqueous solution of 220 ml was added, whereby a suspension 
of titanium hydroxide-coated mica having a gloss of a silver color was 
obtained. 
(b-3) 85% phosphoric acid in an amount of 1.3 g and zinc chloride in an 
amount of 2.3 g were added to the suspension thus obtained and maintained 
for 10 minutes while stirring. Then, a 32% sodium hydroxide aqueous 
solution was slowly added dropwise to adjust the pH to 5.5. Next, 127 g of 
a 6% aluminum chloride 6 hydrate aqueous solution were added dropwise for 
about 30 minutes while maintaining the pH at 5.5. Then, an aqueous 
solution prepared by diluting 2.2 g of a sodium silicate (SiO.sub.2: 36 %) 
with water to 14.7 g was added dropwise for about 10 minutes and 
maintained for about 10 minutes. 
(c-3) Then, the same operation as that in the step (c-2) of Example 7 was 
carried out, whereby a pearl pigment was obtained. 
Comparative Example 1 
After carrying out the same operation as that in the step (a-1) of Example 
1, the operation of the step (c-1) in Example 1 was carried out to thereby 
obtain a titanium oxide-coated pigment. 
Comparative Example 2 
After carrying out the same operation as that in the step (a-2) of Example 
7, the operation of the step (c-2) in Example 7 was carried out to thereby 
obtain a titanium oxide-coated pigment. 
Comparative Example 3 
After carrying out the same operation as that in the step (a-3) of Example 
8, the operation of the step (c-2) in Example 7 was carried out to thereby 
obtain a rutile-type titanium oxide-coated pigment. 
Example 9 
(a-4) Muscovite (particle diameter: from about 2 to 8 .mu.m) in an amount 
of 140 g was suspended in demineralized water of 1.75 liter, and the 
suspension was heated to 75 .degree. C. while stirring. A titanium 
tetrachloride aqueous solution in which titanium tetrachloride in an 
amount of 414 g per liter was dissolved was added to this suspension, and 
the pH was adjusted to 2.2, followed by maintaining it for 5 minutes. 
Then, the titanium tetrachloride aqueous solution described above was 
further added dropwise gradually while maintaining the pH at 2.2 with a 
32% sodium hydroxide aqueous solution. The titanium tetrachloride aqueous 
solution in an amount of 810 ml was added in total, whereby a suspension 
of titanium hydroxide-coated mica having a gloss of a silver color was 
obtained. 
(b-4) 85% phosphoric acid in an amount of 5.2 g and zinc chloride in an 
amount of 9.2 g were added to the suspension thus obtained and maintained 
for 10 minutes while stirring. Then, a 32% sodium hydroxide aqueous 
solution was slowly added dropwise to adjust the pH to 5.5. 
(c-4) Further, the pigment was filtered off from this suspension, and after 
washing with demineralized water and drying, the pigment was calcined at 
880.degree. C., whereby a pearl pigment having a gloss of a silver color 
was obtained. 
Example 10 
A pearl pigment having a gloss of a silver color was obtained in the same 
manner as that described in Example 9, except that aluminum chloride was 
substituted for zinc chloride used in the step (b-4) of Example 9 and that 
8.2 g of 85% phosphoric acid and 17.2 g of aluminum chloride 6 hydrate 
were used. 
Example 11 
(a-5) Muscovite (particle diameter: from about 2 to 8 .mu.m) in an amount 
of 140 g was suspended in demineralized water of 1.75 liter, and the 
suspension was heated to 75.degree. C. while stirring. A titanium 
tetrachloride aqueous solution in which titanium tetrachloride in an 
amount of 414 g per liter was dissolved was added to this suspension, and 
the pH was adjusted to 2.2, followed by maintaining it for 5 minutes while 
stirring. Then, the titanium tetrachloride aqueous solution described 
above was further added dropwise gradually while maintaining the pH at 2.2 
with a 32% sodium hydroxide aqueous solution. The titanium tetrachloride 
aqueous solution in an amount of 810 ml was added in total, whereby a 
suspension of titanium hydroxide-coated mica having a gloss of a silver 
color was obtained. 
(b-5) A 3.8% bismuth nitrate 5 hydrate aqueous solution diluted with nitric 
acid in an amount of 241 g was added to the suspension thus obtained and 
maintained for 5 minutes while stirring. Then, a 8.5% phosphoric acid 
aqueous solution was slowly added dropwise to adjust the pH to 5.5. 
(c-5) Further, the pigment was filtered off from this suspension, and after 
washing with demineralized water and drying, 55 g of the pigment was 
measured and placed into a porcelain crucible (volume: 250 ml), and then 
calcined at 880.degree. C. for 20 minutes, whereby a pearl pigment having 
a gloss of a silver color was obtained. 
Comparative Example 4 
After carrying out the same operation as that in the step (a-4) of Example 
9, the operation of the step (c-4) in Example 9 was carried out to thereby 
obtain a titanium oxide-coated pigment. 
Comparative Example 5 
Only 85% phosphoric acid was used in the step (b-4) of Example 9, whereby a 
titanium oxide-coated pigment was obtained in the same manner as that 
described in Example 9. 
Example 12 
The pearl pigment of 98 g obtained in Example 6 and SH1107 (manufactured by 
Toray Dow Corning Co., Ltd. ) of 2 g as the organosiloxane compound were 
put into a mixer (high speed blender mixer manufactured by Worling Co., 
Ltd.) having a volume of 1200 ml and mixed by stirring. Further, the 
suspension was subjected to a heat treatment at 130.degree. C., whereby a 
surface-treated pearl pigment having a good powder fluidity was obtained. 
Example 13 
The pearl pigment in an amount of 98 g obtained in Example 6 and stearic 
acid of 2 g were put into the mixer (high speed blender mixer manufactured 
by Worling Co., Ltd.) having a volume of 1200 ml and mixed by stirring 
while heating at 70.degree. C., whereby a surface-treated pearl pigment 
having a good powder fluidity was obtained. 
Discoloration resistance test: 
(1) Evaluation with n-propyl gallate 
n-Propyl gallate which is a kind of a phenol derivatives stabilizer 
discolored by contact with titanium oxide was used for evaluating 
discoloring property to compare and evaluate the pigments of the present 
invention described in the examples and the pigments described in the 
comparative examples. 
Preparation of test samples! 
A: The pigments in an amount of each 1 g obtained in the examples and the 
comparative examples and an ink medium (VS Medium manufactured by Dainichi 
Seika Co., Ltd.) in an amount of 9 g were put into a beaker and mixed 
sufficiently to homogeneity by stirring. 
B: The pigments in an amount of each 1 g obtained in the examples and the 
comparative examples and an ink medium (VS Medium manufactured by Dainichi 
Seika Co., Ltd.) in an amount of 9 g containing n-propyl gallate (Extra 
Pure manufactured by Kanto Chemical Co., Ltd.) in a proportion of 1% were 
put into a beaker and mixed sufficiently to homogeneity by stirring. 
Test method! 
The samples of A and B were coated on a black and white masking test paper 
with a bar coater No. 20. After drying, these two b values (yellow) were 
measured with a color meter (CR-200 manufactured by Minolta Camera Co., 
Ltd.). The difference .DELTA.b value (the b value of the sample B-the b 
value of the sample A) between these b values were then calculated. The 
results thereof are shown in Table 1. 
TABLE 1 
______________________________________ 
Sample .DELTA.b 
______________________________________ 
Example 1 +0.2 
Example 2 +0.8 
Example 3 +0.6 
Example 4 +0.6 
Example 5 +0.7 
Example 6 +0.3 
Example 7 +0.4 
Example 8 +0.3 
Comp. Example 1 
+5.9 
Comp. Example 2 
+6.7 
Comp. Example 3 
+4.8 
______________________________________ 
As shown in Table 1, it has been observed that all of the pigments 
according to the present invention have small .DELTA.b values and 
therefore excellent discoloration resistance. 
(2) Evaluation by black lamp 
The light resistance was evaluated with a black lamp having its main light 
source in the ultraviolet region. 
Preparation of test pieces! 
A sample pigment of 1 g and an anti-oxidation agent (BHT, Yoshinox 
manufactured by Yoshitomi Pharmaceutical Co., Ltd.) of 0.1 g were added to 
the substance prepared by blending HDPE (Hizex 2100J manufactured by 
Mitsui Petro-chemical Co., Ltd.) of 98.8 g with a wetting agent (liquid 
paraffin, Hi-White manufactured by Nippon Petroleum Co., Ltd.), and mixed 
well. This mixture was molded by injection to prepare a test piece with a 
height of 14.8 cm, a width of 7.5 cm and a thickness of 0.2 cm. 
Evaluating method! 
A light cabinet equipped with one black lamp (20 W, manufactured by Nippo 
Co., Ltd.) with emission in the ultraviolet region as a light source was 
prepared, and the test piece described above, which was separated by 20 cm 
from the light source, was left irradiated at room temperatures for 2 
weeks. The b values were measured with a color-difference meter before and 
after the irradiation, and the difference thereof was calculated in terms 
of the .DELTA.b value. The results thereof are shown in Table 2. 
TABLE 2 
______________________________________ 
Sample .DELTA.b 
______________________________________ 
Example 2 
+1.7 
Example 6 
+0.7 
Example 7 
+0.7 
Example 8 
+1.1 
Iriodin 100 
+5.1* 
Iriodin 120 
+5.4* 
______________________________________ 
*manufactured by Merck Japan Co., Ltd. 
As apparent from the results summarized in Table 2, it has been observed 
that the pearl pigments of the present invention have small .DELTA.b 
values and therefore excellent discoloration resistance as compared with 
Iriodin 100 (Pearl pigment composed of 29 wt. % titanium dioxide coated on 
mica with particle size of from 10 to 60.mu.) and Iriodin 120 (Pearl 
pigment composed of 38 wt. % titanium dioxide coated mica with particle 
size of from 5 to 20.mu.). 
(3) Evaluation by light irradiation and bedewing cycle 
Cycle test using by UV rays and bedewing (wetting) was carried out. 
Preparation of test pieces! 
Test pieces were prepared in the same manner as that described above, 
except that Hizex 6200B (manufactured by Mitsui Petrochemical Co., Ltd. ) 
was substituted for HDPE (Hizex 2100J). 
Evaluating method! 
A cycle test of irradiating and bedewing was carried out with a weather 
meter (dew panel light control weather meter manufactured by Suga Testing 
Machine Co., Ltd.) using a UV ray fluorescent lamp as a light source, 
wherein the test piece was set and exposed for 200 hours; and the b values 
before and after the exposure were measured with a color meter to 
calculate the .DELTA.b values. The results thereof are shown in Table 3. 
TABLE 3 
______________________________________ 
Sample .DELTA.b 
______________________________________ 
Example 6 
+2.3 
Example 7 
+2.6 
Example 8 
+1.0 
Iriodin 100 
+5.3 
Iriodin 120 
+6.7 
______________________________________ 
It is observed from the results summarized in Table 3 that all of the 
pigments according to the present invention have low levels of 
discoloration. 
(4) Exposure evaluation in an ammonia gas atmosphere 
The test pieces were irradiated with a fluorescent lamp in an ammonia gas 
atmosphere in order to evaluate them. 
Preparation of test pieces! 
HDPE (Hizex 2100J manufactured by Mitsui Petrochemical Co., Ltd.) in an 
amount of 980 g and the pigment of 20 g were charged into a Henshell mixer 
and mixed thoroughly. This mixture was molded by injection to prepare test 
pieces in the same manner as described above. 
Evaluating method! 
The test pieces were set and tightly closed in a desiccator (diameter of 
the middle plate: 210 mm) into which 500 ml of 28% aqueous ammonia were 
placed. A lamp was adjusted so that the illuminance on the surface of the 
test pieces became 2000 lux, and the test pieces were irradiated with a 
fluorescent lamp at room temperature for 100 hours. The b values before 
and after the irradiation were measured with a color meter to calculate 
the .DELTA.b values. The results thereof are shown in Table 4. 
TABLE 4 
______________________________________ 
Sample .DELTA.b 
______________________________________ 
Example 7 
+1.0 
Example 8 
+1.0 
Iriodin 100 
+5.4 
Iriodin 120 
+7.8 
______________________________________ 
It has been observed from the results summarized in Table 4 that all of the 
pigments according to the present invention have low levels of 
discoloration. 
Offset printing test: 
An offset priming aptitude was evaluated according to the following method. 
Preparation of ink! 
A pearl pigment of 36 g was added to an ink medium (TK Mark 5, new 
ultra-glossy medium M; manufactured by Toyo Ink Co., Ltd.) of 64 g, and 
this mixture was kneaded with three rolls (NS-400B) manufactured by 
Kodaira Seisakusho Co., Ltd. to homogeneity, whereby ink for evaluation 
was prepared. 
Evaluation of pigment transferability! 
An ink in an amount of 0.4 ml for evaluation was put on the three points of 
a rubber roll of an RI tester (RI-2) manufactured by Akira Seisakusho Co., 
Ltd., and then the ink was kneaded for 3 minutes. A blanket on which an 
art paper for transferring a pigment was fixes was rotated by one 
revolution at a speed of 100 revolutions per minute to transfer the 
pigment put on the rubber roll thereon. The surface of the art paper was 
photographed with a metallurgical microscope, and the area occupied by the 
pigment in a unit area was measured from the photograph. The 
pigment-transferred amount is defined by this occupying area, and it is 
judged that the larger this value is, the more excellent the pigment 
transferability is. Further, observed were the metal of the RI tester 
after transferring the pigment thereon and the presence of piling on the 
rubber roll. The pigment in which piling is not found is judged to have a 
high affinity (dispersibility) for the ink medium. The results thereof are 
shown in Table 5. 
TABLE 5 
______________________________________ 
Pigment transfer 
Sample amount (cm.sup.2) 
Piling 
______________________________________ 
Example 9 114 None 
Example 10 108 None 
Example 11 102 None 
Comp. Example 4 
88 Present 
Comp. Example 5 
90 None 
______________________________________ 
It is observed from the results summarized in Table 5 that the pigments 
according to the present invention have large pigment-transfer amounts and 
no piling and is excellent in an offset printing aptitude as compared with 
the pigments of the comparative examples. 
The pigments obtained in Example 9 and Example 10 were evaluated in terms 
of the offset printing aptitude with a commercial offset printing machine 
(Ryobi: 3302M) manufactured by Ryobi Co., Ltd. As a result thereof, it has 
been confirmed that piling has not occurred. 
Evaluation test for a plate out resistance: 
The plate-out of a pigment which is problematic when it is incorporated 
into plastics and processing was evaluated according to the following 
method. 
Preparation of test samples! 
A compound prepared by blending a pigment of 5 parts with a soft polyvinyl 
chloride compound (containing DOP of 80 parts per 100 parts of PVC) in an 
amount of 100 parts was kneaded for 3 minutes with two rolls heated to 
150.degree. C. A sheet wound round the roll was removed, and the soft 
polyvinyl chloride compound was further kneaded at the same temperature 
for 3 minutes. The pigment (plate out pigment) adhered on the surface of 
the roll was removed and processed into a sheet with a thickness of about 
1.5 mm. This sheet was separated from a roll face and processed again into 
a sheet with a thickness of 0.5 mm in the press conditions of 170.degree. 
C. and 20 kg/cm.sup.2, whereby a sample for evaluation was prepared. 
Evaluation of plate-out property! 
The number of pigments distributed at optional 12 points in the sample 
prepared for evaluation was counted under a metallurgical microscope at a 
magnification of 100, and a plate-out amount was defined by an average of 
the number. The smaller this value is, the more excellent the plate out 
resistance is. The results thereof are shown in Table 6. 
TABLE 6 
______________________________________ 
Sample Plate out amount 
______________________________________ 
Example 6 122 
Example 12 39 
Example 13 102 
Comp. Example 1 
338 
______________________________________ 
It has been observed from the results summarized in Table 6 that all of the 
pigments according to the present invention have small plate out amounts 
and are therefore excellent in plate-out resistance. 
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. 
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.