Note: Descriptions are shown in the official language in which they were submitted.
~761~;
The present invention relates to condwctive
fibers, particularly fibers obtained by forming a conduc-
tive layer on the surface of fibers with after-processing.
Conductive fibers wherein a conductive layer
containing carbon black or metal particles has been
formed on the surface of fibers (for example, film-like)
by after-processing, have been well-known. These con-
ductive fibers have been used for providing antis~atic
property to fibrous articles by mixing these fibers with
other fibers. These after-processed conductive fibers
are excellent in the antistatic property because of
presence of the conductive layer on the surface of fibers
and the conductivity of the fibers can be improved by
increasing the mixing ratio of the conductive particles,
and furthermore it is possible to obtain the conductive
fibers having excellent strength by selecting fibers
having high mechanical property for a base fiber ~support)
which is a component for retaining the strength.
In particular, the fibers using carbon black as the
conductive particles are stable in the properties and
easy in the production, so that the practicability is the
highest and these fi'bers are 'broadly used.
However, the conductive fibers in which the
conductive layer containing carbon 'black is present on
the surface of fibers, are colored black and when such
fibers are mi~ed in white or light color articles, the
appearance of the products is deteriorated, so that such
products almost cannot be practically used. Metal particles
in most case do not show such a deep coloration as in
carbon black b-ut in many cases the fibrous articles are
.' ~
colorecl gray o-r black and oxidation proceeds during use
and the color and the antistatic proper~y are deteriorated.
In general, metal partic]es are expensive and are poor in
the practicability.
The inventors have made diligent s~udies in
order to improve ~he prior drawbacks of conductive fibers
and found that conductive fibers having excellent
antistatic property, whiteness and stability can be
obtained by using conductive metal oxide particles and
accomplished the present invention.
The conductive fibers are obtained by forming
the conductive layer consisting mainly of conductive
metal oxide particles and a binding polymer on the s-urface
of fibers by after-processing.
The invention will now be described in detail
with reference to the accompanying drawings, wherein:
Figs. 1-4 are cross-sectional views of embodi-
ments of conductive layer coa-ted fibers according to the
present invention respectively; and
Fig. 5 shows the relation of the mixing ratio
of the conductive metal oxide particles to the binder
polymer~ to the specific resistance.
The conductive metal oxide particles in the
present invention are fine particles having conductivity
based on conductive metal oxides and are concretely
particles consisting mainly (not less than 50% by weight)
of a conductive metal oxide and particles coated with
a conductive metal oxide.
A major part of metal oxides are semi-condwctor
and do not show the enough conductivity to satisfy the
~8~6
object of the present invention. ~owever, the conductivity
is increased, for example, by adding a small amount (not
more than 50%, particularly not more than 25%) of a proper
secondary component (impurity) to the metal oxide, whereby
ones having the sufficient conductivity to satisfy ~he
object of the present invention can be obtained.
For example, a small amount of powdery oxide, hydroxide
or inorganic acid salt of aluminum, gallium, indium,
gelmanium, tin and the like is added to powdery zinc
oxide and the resulting mixture is fired under a reducing
atmosphere and the like to prepare conductive zinc oxide
powder. Similarly, conductive ti.n oxide powder can be
obtained by adding a small amount of antimony oxide to
tin oxide powder and firing the resulting mixture. It is
presumed that these added secondary components are
diffused and permeated by heating to form a solid solution
of a metal oxide (main component) and a foreign metal
oxide (secondary component), by which the conductivity is
developed. Furthermore, there is a case where metal
oxide is partially reduced and the formed metal element
has the function (improvement of conductivity) of the
secondary component. Even in the other secondary component
than the above described substances, if it can provide
conductive particles which can increase the conductivity
and do not considerably deteriorate whiteness and are
stable to water, heat, light and chemical agents generally
used for fibers, such a component can be used for the
object of the present invention.
As the conductive metal oxides, the above
3Q described zinc oxide or tin oxide is e~cellent in the
~g7~
conductivity, whiteness and stability and is rnost
preferable but even other metal oxides, if these oxides
have the satisfactory conductivity, whiteness and
stability, can be used for the object of the present
S invention.
The conductivity of the conductive metal oxide
particles is preferred to be not rnore than 104 n cm
(order), particularly not more than 102 Q cm, most
preferably not more than 101 Q-cm in the specific
resistance in the powdery state. In fact, the particles
having 102 Q cm-10~2 Q~cm are obtained and can be suitably
applied to the object of the present invention. (The
particles having the more excellent conductivity are more
preferable.) The specific resistance (volume resistivity~
is measured by charging 5 gr of a sample into a cylinder
of an insulator having a diameter of 1 cm and applying
200 kg of pressure to the cylinder from the ~Ipper portion
by means of a piston and applying a direct current voltage
(for example, 0.001-1,000 V, current of less than 1 ~).
The conductive metal oxide particles are
preferred to be ones having high whiteness, that is
having reflectivity in powder being not less than 40%,
preferably not less than 50%, more particularly not less
than 60%. T~le above describecl conductive zinc oxide can
provide the reflectivity of not less than 60%, particularly
not less than ~0%, and conductive tin oxide can provide
the reflectivity of not less than 50%, particularly not
less than 60%. Titanium oxide pa,rticles coated with
conductive zinc oxide or conductive tin oxide film can
provide reflectivity of 60-90%. While, the reflectivity
7!6~6
of carbon black particles is about 10% and the reflectivity
of metallic iron fine particles ~average grain siæe
0 05 ~m) is about 20%.
The reflectivity of the particles can be
measured by means of a reflection photometer by estimating
the reflectivity of magnesium oxide powder to be 100%.
The con~uctive metal o~ide particles must be
small in the grain size. It is not impossible to use the
particles having an average grain size of 1-2 ~m but in
general, the average grain size of less than 1 ~m,
particularly less than 0.5 ~m, more pre~erably less than
0.3 ~m is used. As the grain size is smaller, a higher
conductivit~ is shown in a lower mixing ratio, when
a binder polymer is mixed.
In the present invention, the conductive layer
is formed on the surface of ~ibers by after-processing.
The shape and arrangement of the conductive layer are
opti.onal but may be selected by taking the conductivity
and antistatic proper-ty, abrasion resistance and the like
into consideration. Figs. 1-4 are embodiments of the
cross section of the fibers of the present invention and
in these drawings, a numeral 1 shows the conductive layer
and a numeral 2 shows a support (base fiber). Fig. 1 is
an embodiment wherein the conductive layer forms a coating
film and surrounds completely the surface of the support
and Fig. 2 is an embodiment wherein the conduct:ive layer
covers a part of the surface of the support. The cross
section of the support may be circular or non-circular.
Fig. 3 shows an embodiment wherein a non-circular cross-
sectional support having recess po-rtions is used and the
-- 6 --
7~
conductive layers are formed at the recess portions and
this embodiment has the characteristic that the conductive
layers can be prevented from deterioration and separation
due to friction. Fig. 4 shows an embodiment wherein
a plurality of fibers (supports) are bonded by a conductive
layer. Other than the above described embodiments, there
are a large number of embodiments in the bonding and
arrangemen~ of the support and the conductive layer.
As the fibers applicable to the present inven-
tion, every fibers can be used. Among them, polyamides,
polyesters, polyolefins, polyvinyls and other synthetic
fibers are generally high in the strength and preferable
as the material for fibers of the present invention.
In general~ the fibers have been spun and then if necessary,
subjected to drawing and heat treatment, after which the
conductive layer is formed on the surface of fibers.
The conductive layer consists mainly of a con-
ductive metal oxide and a polymer or a starting material
for polymerizing the polymer, which is a binder and if
necessary, contai.ns a stabilizer, an antioxidant,
a dispersant for particles, a pigment and other additives.
rrhe formation of the conductive layer may be carried out
by the following means. That is, the above described
mixture of conductive layer-forming components is melted
and the melt i5 coated or applied on the base fibers and
then cooled and solidified (melting process). A soluti.on
of the mixt-ure of the conductive layer-forming components
in a proper solvent is coated or applied on the base
fibers and then the solvent is removed to soliclify the
conductive layer~forming components (solvent process).
-- 7
Alternatively, the surface of the base fibers is softened
by heating or a solvent and then the conductive particles
are contacted and stuck (or applied with electrostatic
force and the like) on -the surface of the base fibers,
after which the softened sur~ace is cooled or the solvent
is removed ~o solidify the conductive layer-forming
components. In addition to these processes, any processes
wherein the conductive layer consisting o~ the conductive
particles and a binder can be formed on the surface of
the fibers (possibly continuously in the longitudinal
direction of the fiber), may be applied to the production
of the fibers of the present invention.
The binders for forming the conductive layer
are polymers, and polyamides, polyesters, polyethers,
polyolefins, polyvinyl polymers, polyurethanes, polyureas,
polycarbonates, any other thermoplastic polymers, epoxy
series polymers, melamine series polymers, phenolformalin
series poly~ers, unsaturated polyester series polymers
and other thermosetting polymers, branched or cross-linked
polymers may be used. From these polymers, suitable
polymers may be easily selected depending upon the object
in view of film-forming ability, adhesion to the base
fibers, mixing ability to the conductive particles,
abrasion resistance, heat resistance, chemical resistance
and the like.
~he conductive layer must have the satisfactory
conductivity. In general, the conductive layer must have
a specific resistance of not more than about 106 n- cm,
preferably not more than 104 Q-cm, most preferably not
more than 102 Q-cm.
6~6~
Fig. 5 shows examples of the relation between
the specific resistance and the mixing ratio of the
conductive metal oxide particles ~o the polymer (binder).
The curve A is an embodiment of a mixture of conductive
particles having usual grain size (0.05-0.5 ~m) and
a crystalline polymer and shows the satisfactory conduc-
tivity at the mixing ratio of more than about 65%.
In Fig. 5~ ~he solid line shows the zone where the mixture
can be flowed by heating and the broken line shows the
zone where the -flowing is difficultly attained by heating.
That i9, in the mixing ratio of more than the point
P, a fluidity improving agen~, such as a solvent must be
used. The curve B is an embodiment of a mixture of
a polymer having a very low crystallinity and t~e conductive
particles and shows that in order to obtain the satisfactory
conductivity, the mixing ratio of the conductive particles
must be larger than that of the case using the crystalline
polymer (this is observed in many cases but is not always
the absolute rule). The curve C is an embodiment of the
mixture of the conductive particles having a very small
grain size (0.005-0.05 ~m) (easily form a chain structure)
and a crystalline polymer and shows the satisfactory
conductivity at the mixing ratio of not less than 30%.
Thus, the conductivity of the mixture of the conductive
particles and the binder polymer varies noticeably
depending upon the size and kind of the conductive
particles~ and the kind and crystallinity of the bi.nder
polymer, so that it is necessary to make adjustmen-t so
that the specific resistance is within the above described
range by se].ecting the proper mixing ratio.
_ g .
The fibers according to the present invention
have excellen~ conductivity and antistatic property and
the fibers having a high whiteness (for example, a reflec-
tivity of more than ~0%, particul.arly more than 60%) can
be easily produced and the fibers can be used for wide
scope of use and particularl~ may be satisfactorily used
for light colored fibrous articles. The fibers of the
present invention can provide the satisfactory antistatic
property to fibrous articles by mixing a small amount
(for example 0.1~10%) of natural or synthetic ibers in
continuous filament or cut staple fiber form. In a higher
mixing ratio (l0-100%), the articles having particularly
excellent antistatic property can be obtained. The mixing
with the other fibers may be carried out by blending,
doubling, double twisting, mix spinning, mix knitting,
mix weaving and any other well-known processes.
The following examples are given in illustration
of the invention and are not intended as limitations
thereof.
In the examples, all parts are by weight unless
otherwise stated.
Example 1
A mixture of 100 parts of zinc oxide powder and
2 parts of aluminum oxide powder was fired at an elevated
temperature in a nitrogen gas atmosphere containing
carbon monoxide to obtain conductive zinc oxide fine
particles Xl having an average grain size of 0.12 ~m,
a reflectivity of 78% and a specific resistance of 33 Q-cm.
On the other hand, a mixtwre of 100 parts of
tin oxide powder and 10 parts of antimony oxide was fired
- 10 -
~76~
at an elevated tempera~ure in a reducing atmoshere to
obtain condutive tin oxide fine particles X2 having
an average grain size of 0.10 ~m, a reflectivity of 70%
and a specific resistance of 12 Q-cm.
Furthermore, conductive fine particles X3
having an average grain size of 0.06 ~m, a reflectivity
of 86% and a specific resist~nce of 12 Q cm were obtained
by forming on surface of titanium oxide fine powder
a fired film of about 15% by weight per titanium oxide of
zinc oxide, mixing it with 2% by weight per zinc oxide of
aluminum oxide fine powder (grain size: 0.01 ~m) and the-n
firing them. Similarly, conductive fine particles X4
havi.ng an average grain size of 0.06 ~m, a reflectivity
of 86% ancl a specific resistance of 10 Q cm were obtained
by forming on surface of titanium oxide fine powder
a fired film of about 12% by weight of tin oxide, mixing
it with 8% by weight per tin oxide of an-timony oxide fine
powder (grain size: 0.01 ~m) and then firing them.
To a resin composition of 100 parts of bisphenol-
epichlorohydrin epoxy resin having an epoxy equivalent of
180-210 and 50 parts of polyamide resin having an amine
value of 290-310 was added 4 parts of methaphenylene
diamine and then methyl isobu-ty.l ketone was added thereto
so as to adjust a solid content to 30%. To 100 parts of
the resulting solution was added and mixed 75 parts of
the aforementioned conductive fine particles Xl, X2, X3
or X~ to obtain a respective paste solution Pll P2,
P3 or P4.
For comparison, 15 parts of conductive carbon
black fine powder was mixed with 100 parts of the 30%
- 11 -
solution of epo~y resin-polyamide resin in rnethyl isobuty~
ketone to obtain a paste solution P5.
In each of the aforementioned paste solutions
was i.mmersed a nylon monofilament o-f 15 deniers ~containing
1.7% of titanium oxide) at a yarn delivery rate of
1.5 m/min, which was then passed through a slit to adjust
a thickness of a coating film, drie~ by passing through
a hot-air dryer of ~0C and successivel~ passed through
an air bath of 150C for 10 minutes to continuously form
a condllctive coating film having an average thickness of
2.5 microns on the surface of the monofilament, whereby
there were obtained conductive monofilaments Al-A5 of
about 17 deniers having a sectional shape as shown in
Fig. 1, respectively.
The electric resistance (Q/cm) and reflectivity
(%) were measured wi,th respect to these conductive mono-
filaments Al-A5 to obtain results as shown in the following
Table l. As apparen-t from Table 1, the conductive mono-
filaments A1-A4 according to the present invention had
a good conductivity and were slightly greyish blue but
substantially white, while the monofilament A5 of the
comparative example was good in the conductivity but
black.
- 12 -
~7~i~;6
Table 1
fil~ment C~ ~ r ~ r~ ~
Al X 68 1.0 x lOl Present
. 1 lnvention
A2 X2 67 8.0 x lO9 "
A3 X3 74 5.0 x 109 "
A4 X4 75 3.0 x lO9 .,
A5carbon black 17 2.5 x 109 Comparative
example
. ....................... , __
Each of the conductive monofilaments A1-A5 was
doubled with nylon-6 yarn (2,600 d/140 f) and thereafter
subjected to a crimping treatment. Then, a tufted carpet
(loop pile~ F1, F2, F3~ F4 or F5 was produced by using
the conductive monofilament do~bled yarn (2617 d/141 f)
in one course in every six courses and the nylon-6 crimped
yarns (2600 d/140 f~ in other five courses. Similarly,
a tufted carpet ~loop pile) F6 was produced as a reference
example by using only nylon-6 crimped yarns (2600 d/140 f)
containing no cond-uct~ve monofilament.
The resulting carpet (F1-F6) was subjected
to a scouring, a dyeing (dyestuff: Nylon acid yellow
C-3CS made by I.C.I., concentration of dyestuff: 0.7% owf,
dyeing temperature: 100C) and a backing. Then, the
appearance of the carpet (particularly color shading) was
observed and also the charged voltage of human body when
a rnan put on leather shoes walked (25C, 20%RH) on the
carpet, was measurecl to obtain results as shown in the
following Table 2.
The carpet F5 of the comparati~e example was
conspicuously obse-rved in ~he color shading (warp lines)
due to the black color of the conductive monofilament and
was considerably poor in the commercial value, while all
of the carpets Fl-F4 containing the conductive monofilament
accorcling to the present invention hardly showed color
shading and had an excellent antistatic property.
Moreover, the carpet F6 of the reference example
had no antistatic property and when a human walked on the
carpet and contacted with a metal, saisl human is applied
to a violent electric shock due to spark discharge.
Table 2
Conductive Presence of Charged
Carpet mono- co].or shading voltage of Remark
ilament (warp llnes) (V)
~ .
F A substantially 1 700 Present
1 1 absence _ ,invention
F2 A2 ~ -1,600 ,.
F3 A3 .. -2,000 "
F4 A4 ,. -1,600 ~,
conspicuous Compara-tive
F5 A5 presence -1,500 example
F6 none absence -7,500 example
Note) Charged voltage of human body is pre~ferred to be
not higher than 3,000 V (absolute value),
preferably not higher than 2,500 V.
Example 2
Fifteen parts of acrylonitrile-butacliene
copolymer (nitrile content: 32%~ and 10 parts of modified
- 14 -
l~B7666
phenol resin (trade ~ark: Durez 12687) were dissolved in
75 parts of methyl ethyl ketone, to which was added and
mixed 80 parts of the same conductive fine particles Xl,
X2, X3 or X4 as used in Example l, whereby a paste solution
Q1~ Q2~ Q3 or Q4 was prepared. For comparison, a paste
solution Q5 was prepared by mixing 15 parts of conductive
carbon black with lO0 parts of the above-described solution.
In a bath of each of these paste solutions was
immersed a polyethylene terephthalate ~hereinafter referred
to as polyester) monofilament of 12 deniers at a yarn
delivery rate of 3 m/min 3 which was then passed through
a slit to adjust a thickness of a coating film, dried by
passing through a hot-air dryer of 95C, and successively
passed ~hrough an air bath of 190C for 25 seconds to
contlnuously form a conductive coating film having
an average thickness of 2.7 microns on the surface of the
monofilament, whereby there were obtained conductive
monofilaments Bl-B5 of about 14 deniers having a sectional
shape as shown in Fig. 1, respectively.
The elec~ric resistance (Q/cm) and reflectivity
(%) were measured with respect to these conductive mono-
filaments Bl-B5 to obtain results as shown in the following
Table 3. All of the conductive monofilaments (B1-B4)
according to the present invention had an excellent con-
ductivity and were slightly greyish blue but substantially
white, while the conductive monofilament B5 of the
comparative example was black.
~ '
~1~7!E;6~;
Table 3
. _ . ._ _ __
EilamenL particle e ivity resiscance le. "k
Bl X 70 9.0 x 108 Present
1 invention
B2X2 70 5.8 x 108 "
B3X3 76 1.2 x 108 "
B4X4 75 2.5 x lo8 .,
B5carbon black 18 5.2 x 108 example
Each of these conductive monofilaments Bl-B5
was doubled with polyester crimped yarn 12600 d/200 f~ at
a tWistillg step. The resulting doubled yarn was scoured
in form of cheese, dyed (dyestuff: Dianics yellow AC-E
made by Mits-ubishi Kayaku K.K., con.centration of dyestuff:
0.5% owf, dyeing assistant: Bisnol P-55 made by Ipposha,
amount of dyeing assistant used: 2 g~Q, dyeing temperature:
130C), reduction cleared and dried. Then, a tufted
carpet (loop pile~ Gl, G2, G3J G4 or G5 was produced by
using the conductive monofilament doubled yarn (2614 d/201 f)
in one course in every six courses and the polyester
crimped yarns (2600 d/200 f) in other five courses.
After the resulting carpet was subjected to a backing,
the appearance (particularly color shading) was observed
and also the charged voltage of human body when a man put
on leather shoes walked (25~C~ 20%RH) on the carpet, was
measured to obtain results as shown in ~he following
Table 4.
As apparent from Table 4 ~ in the carpet G5 of
- 16 -
7~
the comparative example, the color shading as (warp
lines) was conspicuously observed due to the black color
of the conductive monofilament and was considerably poor
in the commercial value, while all of the c~rpets Gl-G4
containing the conductive monofilament according to the
present invention hardly showed color shading (warp
lines) and had an excellent antistatic property.
Table 4
.. _ , . __ ..
No Conductive color shading humangbody Remark
. filament (warp lines) (V)
G B substantially +1 600 Present
1 1 absence , invention
lS G2 B2 ~ +1,500 I~
G3 B3 ,. ~1,300 .,
G4 B4 ll +19200 ll
G B conspicuous +1,500 Comparative
presence example
__
Note) The charged voltage of human body on a carpet
consisting of 100% polyester containing no
conductive monofilament was ~3,000 V.
Example 3
A mixtwre of 100 parts of tin oxide powder and
8 parts of antimony oxide was fired at an elevated
temperature in a reducing atmosphere to obtain conductive
ultrafine particles X5 having an average grain size of
0.012 ~m, a reflectivity of 66% and a specific resistance
of 15 Q~cm.
Twenty parts of the conductive ultrafine particles
- 17 -
7~
X5 was thoroughly mixed with 100 parts of a 25% solution
of acid dye-dyeable polyurethane (trade mark: Sunplene LQ
made by Sanyo Kasei K.K.) in dimethylformamide to prepare
a transparent and viscous mixed solution Rl. Similarlyg
a black paste mixed solution R2 was prepared as a compara-
tive example by using conductive carbon black instead of
the conductive ultrafine particle. In each of these
mixed~solutions was immersed nylon-66 yarn of 20 dj3 f
(containing 0.3/0 of ~itanium oxide~ at a yarn delivery
rate of 1.5 m/min, which was then passed through a slit
to adjust a thickness of a coating film. Thereafter, the
resulting coating ilm was solidified by passing through
a first bath of a 10% aqueous solution of dimethylformamide,
a second bath of water of 25C and a third bath of hot
water of 60C in this order and dried by passing through
a hot-air dryer of 120aC to continuously form a conductive ~:
coating film having an average thickness of 3.5 microns
on the surface of the yarn, whereby there were obtained
conductive yarns Cl and C2 of about 22 d/3 f having
a sectional shape as shown in Fig 4, respectively.
The electric resistance (Q/cm) and reflectivity
(%) were measured with respect to these two conductive
yarns C1 and C2 to obtain results as shown in the ollowing
Table S.
The conductive yarn C2 of the comparative
example was black, while the conductive yarn Cl according
to the present invention was colorless and showed a good
conductivity.
- 18 -
61~;6
Table 5
Yarn No. Conductive Reflectivity resistance Remark
partlcle ( /o) (n/cm)
__ ~ _
Cl X5 82.5 2.5 ~ 108 Present
C2 carbon black lg 3.0 x 108 example
Each of these conductive yarns Cl, C2 was
doubled with nylon-66 yarn 2600 d/140 f) and subjected to
a crimping treatment to obtain a crimped doubled yarn
having the conductive yarn ~2622 d/143 f). Then, a tufted
carpet (loop pile) Hl or H2 was produced by using the
conductive yarn doubled yarn in one course in e~ery six
lS courses and nylon-66 crimped yarn (2600 d/140 f) in other
five courses. The resulting carpet (Hl, H2) was subjected
to a scouring, a dyeing (dyestuff: Nylon acid yellow
C-3&S made by I.C.I., concentration of dyestuff: 0.7% owf,
dyeing temperature: 100C) and a backing. Thereafter,
the appearance (particularly color shading) was observed
and also the charged voltage of human body when a man put
on leather shoes walked (25C, 20%RH) on the carpet was
measured to obtain results as shown in the following
Table 6.
The carpet H2 of the comparative example was
conspicuously observed in the color shading (warp lines)
due to the black colo-r of -the conductive yarn and was
considerably poor in the commercial value, while the
carpet Hl according to the present invention showed no
color shading and had an excellent antistatic property.
- 19 -
3L~L6~7~
Table 6
Carpet Conduc- Presence of Charged voltage
tive color shading of human body Remark
No. yarn (warp lines) (V)
H1 C1absence -1,300 invention
H C2conspicuous -1,500 Co~parative
2 ~ __ presence _ example
- 20 -
