Fibrous white electrically conductive material and a white electrically conductive coating composition containing the same

Fibrous white electrically conductive material and a coating composition containing the same. The material is made from fiber of alkali titanate EQU aM.sub.2 O.TiO.sub.2.bH.sub.2 O wherein M is alkali metal including Li, Na and K EQU O<a.ltoreq.1/8.5 EQU O.ltoreq.b which is coated with tin oxide (2-500 parts by weight every 100 parts by weight of the fiber). The material is applied to paper, plastics or rubber and gives high electrical conductivity thereto.

This invention relates to a fibrous white electrically conductive material 
suitable for blending with paper, plastic or rubber in order to provide 
electrical conductivity. This invention particularly concerns a fibrous 
white electrically conductive tin oxide material having low specific 
volume resistivity and being superior in ability to provide electric 
conductivity per unit weight. Furthermore, the invention provides a white 
electrically conductive coating composition excellent in electrical 
conductivity, which contains the fibrous material mentioned above. 
Tin oxide powder is recently more familiar than electrical conductive 
powders of carbon black, silver, copper, aluminum and the like, in the 
field of antistatic plastics, coating composition and the like which 
requires white color tone, such as electrostatic copying paper. As is well 
known, an electrical conductivity-providing powdery agent is blended in a 
material such as paper, plastics rubber and the like. A large amount of 
the agent is needed so that adjacent powders at least are brought into 
contact each other, in order to obtain high electrical conductivity. When 
the powder is expensive, the use is limited. One of materials which is 
proposed to be able to form an electrically conductive circuit even in a 
small amount is tin oxide of acicular shape. Another material is an 
electrically conductive agent such as a fibrous material such as glass 
fiber or an organic high molecular material, which is coated with an 
electrically conductive material (Japanese Kokai 56-120519). 
However, a smaller amount of the acicular tin oxide than powders is enough 
so far as an amount to be employed is concerned, but electric conductivity 
brought about is not satisfactory yet. An amount of the electrically 
conductive material is able to save, too, when the fibrous material coated 
with an electrically conductive material is used, but desired electric 
conductivity is hardly obtained because the electrically conductive 
material is easily peeled off from the substrate fibrous material when the 
fibrous material is blended with a material to which electric conductivity 
is given, such as paper, plastics, rubber and the like. 
Another approach (Japanese Kokai 59-6235) is a white electrically 
conductive agent in which a tin oxide material is added to a fiber made 
from potassium titanate having the formula: 
EQU K.sub.2 O.nTiO.sub.2.mH.sub.2 O 
wherein n is a real number not greater than 8, m is zero or a real number 
not greater than 4. 
The agent is good in white color tone and is able to somewhat better 
electric conductivity than an agent in which an electrically conductive 
material is coated on a fibrous material such as glass fiber, but is not 
satisfactory yet. 
So far as a coating composition is concerned, fields of use are rapidly 
increasing in a vessel to reserve IC, various materials for electronics, 
construction materials such as a floor and a wall for a clean room and the 
like, which require to be in white or the other various colors and to have 
antistatic property. There are many proposals to this effect by using a 
coating composition which contains inorganic electrically conductive 
powders comprising mainly tin oxide, in place of carbon black, silver, 
copper and aluminum. However, these proposals are not economical, because 
a large amount of an electrically conductive material has to be 
incorporated in the coating composition in order to provide enough 
antistatic property. Furthermore, the coating composition gives a fatal 
difficulty, i.e., desired properties of resin component in the coating 
composition are lost. 
After having been studying to develope and obtain a white electrically 
conductive material which has low specific volume resistivity and is 
superior in electrical conductivity-providing ability per unit weight, the 
present inventors find that the desired object is achieved when a specific 
amount of a tin oxide material is applied on a fibrous alkali titanate 
having a specific formula. Furthermore, the present inventors succeed in 
obtaining a coating composition which is not expensive and able to provide 
a coating which is excellent in white color tone, electrical conductivity 
and antistatic property, when the composition contains a specific amount 
of the tin oxide material above. 
According to the present invention, a fibrous white electrically conductive 
material is provided wherein 2-500 parts by weight of tin oxide is coated 
on 100 parts by weight of a fiber made from alkali titanate having the 
formula 
EQU aM.sub.2 O.TiO.sub.2.bH.sub.2 O 
wherein M is alkali metal selected from the group consisting of Li, Na and 
K, 
EQU 0&lt;a.ltoreq.1/8.5 and 0 .ltoreq.b. 
Furthermore, a white electrically conductive coating composition is 
provided, which comprises, every 100 parts by weight, 5-90 parts by weight 
of a fibrous white electrically conductive material defined above and 
95-10 parts by weight of resin. 
Alkali titanate from which a fiber is made has the formula 
EQU a.M.sub.2 O.TiO.sub.2 .bH.sub.2 O 
wherein M is alkali metal selected from the group consisting of Li, Na and 
K, preferably K, 
EQU 0&lt;a .ltoreq.1/8.5, preferably 1/13 .ltoreq.a .ltoreq.1/9, and 0.ltoreq.b, 
preferably 0.ltoreq.b.ltoreq.6. 
The fiber is 1.mu.-1000 .mu. long, preferably 10-100 .mu. long and has 
10-1000, preferably 20-500 of acicular ratio, under a microscope. If the 
symbols a and b are out of the scope defined above, electrical 
conductivity-providing ability per unit weight is lowered. If fiber is 
shorter than 1 .mu., it is very hard to form a uniform electrically 
conductive layer and to obtain desired electrical conductivity. If the 
fiber is longer than 1 mm, it is easily broken. If acicular ratio is less 
than 10, advantageous effect, i.e., an electrical circuit is able to form 
with a small amount of an electrically conductive material, disappears. If 
acicular ratio exceeds 1000, degradation is seen in disperability of the 
fibrous material in paper, plastics and rubber. 
2-500, preferably 20-200 parts by weight of tin oxide are applied on 100 
parts by weight of the fiber made from alkali titanate. If an amount of 
tin oxide is smaller than 2 parts by weight, it is very hard to keep good 
electrical conductivity. If an amount of tin oxide is larger than 500 
parts by weight, it is not economical because no better electrical 
conductivity is obtained corresponding to an amount of coating applied. 
Tin oxide may contain other compounds as long as they make no harm on an 
electrical conductivity-providing ability. The other compounds are, for 
example, Sb compounds. An amount of such compounds is 0.1-30, preferably 
1-20 % by weight in terms of Sb, on the basis of tin oxide. Sb serves to 
improve an electrical conductivity-providing ability of tin oxide. Sb is 
in the oxide form. If an amount of Sb is smaller than 0.1 % by weight, no 
improvement is expected in an electrical conductivity-providing ability. A 
greater amount of Sb than 30 % by weight gives undesirable influence, 
because an electrically conductive material is colored in blue. 
Any process is applied to coat a fiber made from an alkali titanate with a 
tin oxide material. One of processes is that the fiber is dispersed and 
suspended in a hot water (60.degree.-90 .degree. C.), solution in alcohol 
containing specific amounts of tin chloride with or without antimony 
chloride is added to the suspension, a tin oxide material with or without 
antimony oxide produced by hydrolysis is precipitated on the fiber, and 
then the fiber is filtered, dried and calcined. 
It is not certain why the present fibrous material in which a tin oxide 
material is coated on a fiber made from alkali titanate having the formula 
specified above is superior to a fiber made from the other metal oxide in 
respect to electrical conductivity-providing ability. Assumption is that 
alkali such as K contained in a fiber made from alkali titanate would be 
allowed to react with tin chloride, the initial form on precipitation, 
until strong bonding is produced. There is few peeling-off of a tin oxide 
material when the present fibrous material is blended as a filler. 
Furthermore, a fiber itself made from alkali titanate is so strong and 
highly elastic that there is few breakage of fiber. It is not certain, too 
why great difference is brought about in respect to electrical 
conductivity-providing ability, when the well known electrically 
conductive fibrous material is blended in resin, said material being made 
from alkali titanate having high mol ratio of M.sub.2 O against TiO.sub.2. 
Assumption is that alkali would be dissolved outfrom a fiber when 
heat-treatment is applied to, for example, in order to convert tin hydrate 
compound to tin oxide, until electrical conductivity of tin oxide would 
greatly be damaged. 
The present white fibrous electrically conductive material is blended with 
a resin component in a coating composition in amounts of 5-90 parts by 
weight of the fibrous material, preferably 10-80 parts by weight of the 
fibrous material and 95-10 parts by weight of the resinous component, 
preferably 90-20 parts by weight of the resinous component, to make total 
of 100 parts by weight of the coating composition. 
Any coating composition, for example, paint, may be used. The composition 
usually consists of, for example, a solvent such as alcohol, ester, 
ketone, ether and water and a resinous component such as acrylic, vinyl, 
carbonate, polyester, urethane, epoxy and polypropylene. 
When an amount of the white fibrous electrically conductive material to be 
blended in the coating composition is smaller than that defined above, 
there is few electrical conductivity-providing ability. When an amount of 
the fibrous material is greater than that defined above, on the other 
hand, binding property of the resin component is lowered. 
If desired, an anionic surfactant such as sodium dialkylsulfosuccinate, 
sodium alkylnapthalenesulfonate, etc., a cationic surfactant such as 
stearyltrimethyl ammonium chloride or an ester surfactant such as sorbitan 
monostearate may be added when a fibrous electrically conductive material 
is blended with a coating composition, e.g., paint, in order to improve 
dispersability of the fibrous material. Alternatively, the fibrous 
material is treated with a surfactant before the material is blended with 
a coating composition. 
The present coating composition containing the white fibrous electrically 
conductive material above may be applied by any coating method, for 
example, spraying, a bar-coating method, a doctor blade method.

EXAMPLE 1 
Fibers (15 .mu. long on an average, 353 g) made from potassium titanate 
(0.08 K.sub.2 O.TiO.sub.2. 0.15 H.sub.2 O; acicular ratio=50) were added 
to water (20 l) and then the water was heated to 70 .degree. C. Solution 
of SnCl.sub.4 (620 g) in isobutanol (5 l) was added, with stirring, to the 
water over three hours, until a coating layer made from tin oxide 
precipitated was formed on the fibers. The fibers were filtered, washed 
with water and then treated in hot air (500 .degree. C.) for three hours 
in order to improve degree of crystallization of tin oxide. A white 
fibrous filler was obtained. Tin oxide content=45 % by weight. Electrical 
resistivity=4.times.10.sup.3 .mu. cm. 
The filler was blended with urethane resin in such an amount that the 
filler is 50 % by weight of the urethane resin and a sheet (30 .mu. thick) 
was prepared. Volume resistivity of the sheet=5.times.10.sup.6 .OMEGA. cm. 
The filler was blended with acrylic resin so that the filler is 50% by 
weight of the acrylic resin and the blended mixture was applied (30 
g/m.sup.2 in terms of solid) on a cloth made from polyester. Surface 
resistance of the cloth=3.times.10.sup.7 .OMEGA./.quadrature.. 
EXAMPLE 2 
Fibers (15 .mu. long on an average; 353 g) made from potassium titanate 
(0.08 K.sub.2 O.TiO.sub.2.0.15 H.sub.2 O; acicular ratio =50) were added 
to water (20 l) and then the water was heated on 70.degree. C. To the 
water was added, with stirring, solution of SnCl.sub.4 (520 g) and 
SbCl.sub.3 (118 g) in isobutanol (5 l) over three hours, until a coating 
layer made from tin oxide precipitated containing antimony compounds was 
formed on the fibers. The fibers were filtered, washed with water and 
treated in hot air (500 .degree. C.) for three hours in order to improve 
degree of crystallization of the tin oxide. A white fibrous filler was 
obtained. Amounts of antimony in terms of Sb and tin oxide =8% by weight 
and 41% by weight, respectively. Electrical resistivity =20 .OMEGA.cm. 
The filler was blended with urethane resin so that the filler is 30% by 
weight of the urethane resin and a sheet (30 .mu. thick) was prepared. 
Volume resistivity of the sheet =200 .OMEGA. cm. The filler was blended 
with acrylic resin in such an amount that the filler is 30% by weight of 
the acrylic resin and the blended mixture was applied (30 g/m.sup.2 in 
terms of solid) to a cloth made from polyester. Surface resistance of the 
cloth=3.times.10.sup.6 .OMEGA./.quadrature.. 
EXAMPLE 3 
Example 2 was repeated to obtain a white fibrous filler except that fibers 
(13 .mu. long on an average) made from potassium titanate (0.11 K.sub.2 
O.TiO.sub.2. 0.14 H.sub.2 O, acicular ratio=40) were used in place of the 
fibers described therein. Antimony in terms of Sb and tin oxide in the 
filler=8% and 41% by weight, respectively. Electrical resistivity=30 
.OMEGA.cm. 
The filler was blended with urethane resin in such an amount that the 
filler is 30 % by weight of the urethane resin and a sheet (30 .mu. thick) 
was prepared. Volume resistivity of the sheet=400 .OMEGA. cm. The filler 
was blended with acrylic resin so that the filler is 30% by weight of the 
acrylic resin and then the blended mixture was applied (5 g/m.sup.2 in 
terms of solid) to paper. Surface resistance of the paper=3.times.10.sup.7 
.OMEGA./.quadrature.. 
EXAMPLE 4 
"Perex NBL" (Tradename, manufactured by Kao Sekken Co., Ltd.) (15 parts by 
weight) was added as a dispersant to the fibrous filler (100 parts by 
weight) obtained in example 2, and the mixture was stirred in a ball mill 
(1 l) for one hour. No change in acicular ratio was observed under a 
transmission electron microscope after mixing. 
The filler (three parts by weight) was blended with a paint (urethane 7 
parts by weight and toluene 35 parts by weight) to obtain white 
electrically conductive paint. The paint was applied (4 .mu. thick) to a 
substrate by a doctor blade. Surface resistance and other properties are 
shown in Table 1. 
EXAMPLES 5-8 
Electrically conductive fibrous materials having properties shown in Table 
1 were prepared by the similar process to that in example 2. The fibrous 
materials were treated with dispersing agents shown in Table 1 to obtain 
paints. Properties are shown in Table 1. 
EXAMPLE 9 
Fibers (15 .mu. long on an average; 71 g) made from potassium titanate 
(0.08 K.sub.2 O.TiO.sub.2.0.15 H.sub.2 O; acicular ratio=50) were added to 
water (1 l) and then the water was heated to 70 .degree. C. To the water 
was added, with stirring, solution of SnCl.sub.4 (44 g) and SbCl.sub.3 (5 
g) in isopropanol (0.14 l) over three hours, until a coating layer made 
from tin oxide precipitated containing antimony compounds was formed on 
the fibers. The fibers were filtered, washed with water and treated in hot 
air (500 .degree. C.) for three hours in order to improve degree of 
crystallization of the tin oxide. A white fibrous filler was obtained. 
Amounts of antimony in terms of Sb and tin oxide=2.8 % by weight and 26 % 
by weight, respectively. Electrical resistivity =60.OMEGA.cm. 
The filler was blended with urethane resin so that the filler is 30 % by 
weight of the urethane resin and a sheet (30 .mu. thick) was prepared. 
Volume resistivity of the sheet=340 .OMEGA. cm. The filler was blended 
with acrylic resin in such an amount that the filler is 30 % by weight of 
the acrylic resin and the blended mixture was applied (30 g/m.sup.2 in 
terms of solid) to a cloth made from polyester. Surface resistance of the 
cloth=7.times.10.sup.6 .OMEGA./.quadrature.. 
COMATIVE EXAMPLE 1 
Example 1 was repeated except that fibers (15 .mu. long on an average) made 
from potassium titanate (0.16 K.sub.2 O.TiO.sub.2.0.5H.sub.2 O, acicular 
ratio =50) were used in place of the fibers therein, to obtain white 
fibrous filler. Tin oxide=48 % by weight. Electrical resistivity 
=7.times.10.sup.6 .OMEGA.cm. 
The filler was blended with urethane resin in such an amount that the 
filler is 50 % by weight of the urethane resin, and a sheet (30 .mu. 
thick) was prepared. Volume resistivity of the sheet =8.times.10.sup.9 
.OMEGA. cm. The filler was blended with acrylic resin in such an amount 
that the filler is 50 % by weight of the acrylic resin, and the blended 
mixture was applied (30 g/m.sup.2 in terms of solid) to a cloth made from 
polyester. Surface resistance of the cloth=5.times.10.sup.5 
.OMEGA./.quadrature.. 
COMATIVE EXAMPLE 2 
Example 2 was repeated except that fibers (15 .mu. long on an average, BET 
specific surface area =10 m.sup.2 /g) made from titania (acicular ratio 
=40) in place of the fibers used therein, to obtain white fibrous filler. 
Antimony and tin oxide=8 % by weight in terms of Sb and 38 % by weight, 
respectively. Electrical resistivity=150 .OMEGA. cm. 
The filler was blended with urethane resin in such an amount that the 
filler is 30 % by weight of the urethane resin, and a sheet (30 .mu. 
thick) was prepared. Volume resistivity=1.times.10.sup.4 .OMEGA. cm. 
COMATIVE EXAMPLE 3 
Titania powder (BET specific surface area=5 m.sup.2 /g, 30 g) was added to 
water (0.8 l) and the water was heated to 90.degree. C. To the water was 
added, with stirring, solution of SnCl.sub.4 (75 g) and SbCl.sub.3 (17 g) 
in isobutanol (0.2 l) over three hours, until a coating of tin oxide 
precipitated containing Sb was formed on the powder. The powder was 
filtered, washed with water and treated in hot air (500.degree. C.) for 
three hours to produce white powdery filler. Specific resistivity =5 
.OMEGA. cm. 
The filler was blended with urethane resin so that the filler is 30% or 60% 
by weight of the urethane resin, and sheets (30 .mu. thick each) were 
prepared. Volume resistivities =1.times.10.sup.12 .OMEGA. cm for the 
former and 1.times.10.sup.6 .OMEGA. cm for the latter. 
COMATIVE EXAMPLE 4 
Example 2 was repeated except that no fiber made from potassium titanate 
mentioned therein was used, to obtain dark blue tin oxide power containing 
antimony. Electrical resistivity of the powder=1 .OMEGA. cm. 
The powder was blended with urethane resin so that the powder is 30 % by 
weight of the urethane resin, and a sheet (30 .mu. thick) was prepared. 
Volume resistivity of the sheet=1.times.10.sup.12 .OMEGA. cm. 
COMATIVE EXAMPLE 5 
"Tween 85" (trade name), a condensation product of sorbitan ester of 
trioleic acid with polyethylene oxide, was dissolved in water (5 l). The 
solution was separated into two solutions in equal volume. In one of the 
solutions was dissolved ammonium oxalate (23 g). In the other solution was 
dissolved SnCl.sub.2 (19 g). The two solutions were mixed at a time and 
the mixed solution was stirred slowly for five hours at room temperature. 
Tin oxalate in a needed shape precipitated was filtered, washed with water 
and then ethanol, dried in air (80 .degree. C.) for six hours and heated 
at 600 .degree. C. for one hour to obtain tin oxide in a needed shape. 
To the tin oxide (10 g) was added solution of antimony trichloride (0.1 g) 
in ethanol (10 g). The mixture was well mixed in a mortar and then ethanol 
was evaporated under heating. The mixture was heated at 600 .degree. C. 
for one hour to obtain blue fibrous tin oxide filler (20 .mu. long on an 
average; acicular ratio =20) containing antimony. Resistivity =10 .OMEGA. 
cm. 
The filler was blended with acrylic resin in such an amount that the filler 
is 30% by weight of the acrylic resin, and then the resin was applied (5 
g/m.sup.2 in terms of solid) to paper. Surface resistance of the 
paper=2.times.10.sup.8 .OMEGA./.quadrature.. 
COMATIVE EXAMPLE 6 
Example 2 was repeated except that commercial fiber made from potassium 
titanate (0.16 K.sub.2 O.TiO.sub.2.0.5 H.sub.2 O) was used in place of the 
fiber mentioned therein, to obtain fibrous filler. Antimony in terms of Sb 
and tin oxide=8% by weight and 42% by weight, respectively. Electrical 
resistivity=150 .OMEGA. cm. 
The filler was blended with urethane resin so that the filler is 30% by 
weight of the urethane resin and a sheet (30 .mu. thick) was prepared. 
Volume resistivity=1.times.10.sup.4 .OMEGA. cm. 
COMATIVE EXAMPLE 7 
Example 2 was repeated except that fiber (the same length as in Example 2) 
made of potassium titanate (0.13 K.sub.2 O.TiO.sub.2.6 H.sub.2 O; the same 
acicular ratio as in example 2) was used in place of the fiber mentioned 
therein, to obtain fibrous filler. Antimony in terms of Sb and tin oxide=8 
% by weight and 43 % by weight, respectively. Electrical 
resistivity=530.OMEGA. cm. 
The filler was blended with urethane resin in such an amount that the 
filler is 30% by weight of the urethane resin, and a sheet (30 + thick) 
was prepared. Volume resistivity=1.5.times.10.sup.3 .OMEGA. cm. 
As stated above, the present white fibrous tin oxide electrically 
conductive material has low volume resistivity. Filler made from the 
present fibrous material has remarkably greater electrical 
conductivity-providing ability per unit weight than electrically 
conductive filler which is commercially available made from flaky tin 
oxide and that in which such metal oxide powder as alumina, titania or 
silica is coated with a tin oxide electrically conductive material. 
Furthermore, so is the filler made from the present fibrous material when 
compared with filler prepared by coating glass fibers, alumina fibers, 
titania fibers, silica fibers or potassium titanate fibers in which ratio 
of potassium to TiO.sub.2 is greater than the present (symbol a) with tin 
oxide. A coating composition containing the present fibrous electrically 
conductive material has remarkably greater electrical conductivity than 
that containing any of the other fibrous electrically conductive 
materials. 
TABLE 1 
__________________________________________________________________________ 
fibrous electrically conductive material (A) 
pretreatment 
fiber base coating material 
Coating/ 
resist- digesting 
length 
acicular 
SnO.sub.2 
Sb base ivity period 
chemical composition 
(.mu.) 
ratio 
(%) (%) (%) (.OMEGA.cm) 
Surfactant 
(hr) 
__________________________________________________________________________ 
Example 4 
potassium titanate 
15 50 80.2 
15.7 
104 20 Perex NBL 
1 
(0.08K.sub.2 O.TiO.sub.2.0.15H.sub.2 O) 
Example 5 
potassium titanate 
15 50 80.2 
15.7 
104 20 -- -- 
(0.08K.sub.2 O.TiO.sub.2.0.15H.sub.2 O) 
Example 6 
potassium titanate 
15 50 80.2 
15.7 
104 20 Perex NBL 
1 
(0.08K.sub.2 O.TiO.sub.2.0.15H.sub.2 O) 
Example 7 
potassium titanate 
15 50 87.7 
9.7 42 95 Perex NBL 
1 
(0.08K.sub.2 O.TiO.sub.2.0.15H.sub.2 O) 
Example 8 
potassium titanate 
13 40 80.2 
15.7 
104 30 Perex NBL 
1 
(0.11K.sub.2 O.TiO.sub.2.0.14H.sub.2 O) 
Comparative 
titania powder 
0.5 1 80.2 
15.7 
104 5 Perex NBL 
1 
example 7 
__________________________________________________________________________ 
blending ratio (parts by weight) 
coated film 
electrically 
resin solvent surface 
brightness 
conductive amount amount 
thickness 
resistance 
by Hunter 
fiber variety 
(past) 
variety 
(past) 
(.mu.) 
(.OMEGA./.quadrature.) 
(%) 
__________________________________________________________________________ 
Example 4 
3 urethane 
7 toluene 
35 4 4 .times. 10.sup.5 
56 
Example 5 
3 urethane 
7 toluene 
35 4 5 .times. 10.sup.5 
55 
Example 6 
4 acrylic 
6 toluene 
15 4 1.5 .times. 10.sup.6 
58 
Example 7 
4 alkyd 6 toluene 
20 4 1.2 .times. 10.sup.7 
65 
Example 8 
3 urethane 
7 toluene 
35 4 1 .times. 10.sup.6 
56 
Comparative 
4 urethane 
6 toluene 
35 4 2.5 .times. 10.sup.9 
56 
example 7 
__________________________________________________________________________