4,172,720
1 2
those in its path, wherein the weight ratio of attritive
FLAKED METAL POWDERS! AND METHOD OF elements to finely divided metal is between 70:1 and
MAKING SAME 90:1, the weight ratio of finely divided metal to lubricant is between 100:1 to 20:1, and the weight ratio of
BACKGROUND OF THE INVENTION 5 mert liquid to finely divided metal is between 0.5:1 to
a. Field of the Invention 2.5:1.
This invention relates to the production of flaked The invention also relates to a method wherein said
metal powders, especially those having a narrow parti- finely divided metal is aluminum,
cle size distribution, whiter color, and a very high spar- The invention is also directed to a method wherein
kle effect. More particularly, the invention relates to 10 said finely divided metal is selected from the group
aluminum, nickel, stainless steel, brass, cupro nickel, consisting of copper, brass, bronze, stainless steel,
and bronze powders having the above characteristics. nickel, cupro nickel.
b. Description of Prior Art The invention is further directed to a method wherein In my U.S. Pat. No. 3,995,815, entitled "PRODUC- ^ attritive elements comprise metallic balls having
HON OF FLAKED METALLIC POWDERS" there 15 diameters between about 0.8 mm and 25.0 mm. is described a method of making these powders in
which the ratio of attritive elements to finely divided BRIEF DESCRIPTION OF DRAWINGS
metal is between 37:1 and 10:1 by weight. As a pre- ^ mvention is mustrated by means of the annexed
ferred condition, the ratio of mert liquid to finely di- drawing in which
vided metal« between 0.5:1 andA A by weight and the 20 ^ ^ ^ ^ ^ ... ... of de_ ratio of finely divided metal to lubricant is between 30:1 for continuous recirculation of msuffi. and 1:1 by weight. Although this process has been . „ . . .. , ... , .. ^ . , found to b£ quit^efficient, it is not possible to produce Pf10^ TMth a *°UoTM m. toP feed= A "flaked metal powders" with a narrow particle size . mG- 2 18 a ^matoc illustration of a device accorddistribution, an improved whiteness, and a very high 25 mgto another embodiment; . sparkle effect as required in today's applications, such as FIG. 3 is a schematic illustration of a device accordin decorative finishes, automotive and appliance appli- m8to vet another embodiment; cations, paints, inks, plastics, and the like. Recently, FIG. 4 fe a schematic illustration of a device accordthere has been disclosed in U.S. Pat. No. 3,776,473 and to a further embodiment; and its division U.S. Pat. No. 3,901,688, that it is possible to 30 FIG. 5 is a curve comparing the whiteness obtained produce aluminum flaked powders with high specular using the present invention and the teaching of the prior reflectivity by the wet ball milling process. The process art.
iscarried out using grinding balls to powder a volume npsrRTPTTnM Of Prppbrpkt^
ratio which varies between about 15:1 and 75:1 and DESCRI^ON OF PREFERRED
grinding balls to milling liquid volume ratio in the range 35 Umbuuimewis
of about 2:1 to about 1:1.25. This process is very uneco- The production of flaked metal powders in accor
nomical, time consuming and, although it produces dance with the present invention can be carried out in a
powders of high sparkle, it has been found that its suitable apparatus, such as the one disclosed in my U.S.
brightness is not sufficient in that when the pigment is pat. No. 3,995,815 dated Dec. 7, 1976. When utilizing
treated, the powder is not sufficiently white. Further- 40 sucn an apparatus, it will be realized that the agitator is
more, the size distribution is not narrow enough to fully made up of a plurality of rotating arms. It has been
satisfy modern requirements, such as in the automotive foun(j t0 be advantageous if the attritive elements are
paint industry. present in the enclosure in an amount to substantially
It has also been found that while the ratios of ingredi- cover the uppermost arm. The attritive elements which
ents mentioned m U.S. Pat. No. 3,776,473 may be useful 45 reused preferably consist of suitable grinding media
for tube mills, the products obtained with the equipment sucn ^ steej
described in my US. Pat. No. 3.W5.815 using the ratios Preferabiy( the weight ratio of attritive elements to
defined m U.S Pat. No. 3,776,473 are of very limited ^ ... meta] is afeout ?8:1 tQ 85;1 ^ wd fat
vahie because the fineness range makes them unaccept- ratio of fmely ... metaJ tQ lubricant b about 2*:1
and the weight ratio of inert liquid to finely divided
SUMMARY OF THE INVENTION metal is about 0.5:1 to about 1:1, and the volume ratio of
The applicant has found that it ispossible to obtain attritive elements t0kfert is abou<;8:?- , fc
flaked metal powders having a narrow particle size Best obtamed ^hen1*e a^tntlon ^T^'
distribution, an improved color and a very high sparkle 55 tween about 5 mmutes.««! <*>?ut 120 mmutes and when
effect using a combination of weight ratios for attritive ^ temr^rature is maintained at between about 38° C.
elements to finely divided metal, finely divided metal to about 50 c
lubricant and inert liquid to finely divided metal which accordance with a preferred embodiment, the
have not been disclosed in the prior art. volume ratio of attritive elements to inert liquid is pref
More particularly, the present invention relates to a 60 erably between 70:1 and 3:1.
method of making flaked metal powders with a narrow Preferably, the weight ratio of inert liquid to finely
particle size distribution, an improved color, and a very divided metal is 0.5:1 to 2.0:1.
high sparkle effect wherein a heterogenous liquid sys- In accordance with yet another preferred embodi
tem comprising an inert liquid and a lubricant and in- ment of the invention, the weight ratio of attritive ele
cluding at least one finely divided metal capable of 65 ments to finely divided metal is between 75:1 to 87:1,
being flaked, is subjected to attrition in an enclosure in the weight ratio of finely divided metal to lubricant is
which there are a plurality of attritive elements, an between 30:1 to 20:1, the weight ratio of inert liquid to
agitator being moved through the elements to displace finely divided metal is between 0.5:1 to 1.5:1 and the
