Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
This invention relates to an antistatic thread, more
particularly the invention is concerned with a multi-component
thread.
Within the scope of the invention, the term thread
is to be understood to mean filaments, stable fibres, and
yarns or thread-bundles made of filaments and/or staple
fibres.
Multi-component antistatic threads are known in
which the thread configuration comprises filaments of at
least two synthetic polymer components, wherein one component
is an electrically non-conducting, filament-building or
forming, thermoplastic polymer and another component is formed
from a thermoplastic synthetic polymer with electrically-
conducting powders dispersed therein and which displays at
a test voltage of 1 kV a volume resistivity, according to
DIN 5~ 3~5, of less than 1013 ohms/cm.
Antistatic thread configurations of this type are
described in West German Offenlegungsschri-ft 23 37 103, Hull,
filed July 20, 197~, (Canadian Patent 1,019,127)
in which the conductive polymer forms the core o~ a core-shell
thread, the shell constituting at least 5~/O of the cross-
sectional area of the thread.
Although an adequate antistatic effect is obtained
in spite of the insuiating action of the core, this is achieved
largely by using large quantities of conducting carbon black.
As the carbon black content increases, the spinning properties
of the polymer/carbon black mixture fall sharply off, and
this leads to difficulties in the manufacture of bi-component
threads.
Stretching, especially when thread-building polymers
are used for the carbon black-containing core component, is
possible, without a considerable increase in electrical
- 1 - ~,
resistance, only at high stretching temperatures and with low-
melting point polymers. During processing into staple-fibre
yarns, the carbon-black cross-sections appearing at the cuts
are detrimental. The above-mentioned German Offenlegungsschrift
describes a method for measuring the thread-resistance which
differs from that in DIN 54 345, the results of which are valid
only for the relevant thread cross-section.
West German Offenlegungsschrift 26 23 672, Boe,
filed May 26, 1976 (U.S. Patent 3,969,559)
discloses another antistatic, synthetic bi-component thread,
one component of which contains electrically-conducting carbon
black. In this case, the other component only partly
envelops the carbon blac~-containing component, although not
less than 50~/O of the conductive component is enveloped, and
forms a curved interface. This means that only threads having
an asymmetrical cross-sectional arrangement can be spun.
West German Offenlegunggschrift 27 1~ 3~3, Paton et
al, filed April 25, 1977 (U.S. Patent 4,045,949)
describes an integral, electrically-conducting textile filament
consisting of 2 to 1000 electrically-conducting, longitudinally-
directed layers of filament-building polymer-material with
finely divided particles of electrically-conducting carbon black
in a concentration of about 3C% by weight, and, in conjunction
with each electrically-conducting layer, along at least one
main surface, a non-conducting layer of the filament-building
polymer material. From the point of view of colour, filaments
of this kind differ only slightly from those made only of a
mixture of conducting carbon black and filament-building mate-
rial.
Matrix-segment multi-component threads, and the pro-
duction and splitting thereof, are described in Canadian
Patent Applications S.~, 320~168, Kessler et al, filed January
24, 1979, and S.~. 322,710, Gerlach et al, filed March 2, 1979.
Also described therein are other known multi-component threads
with matrix-segment structures, but none of them is conductive
and has an antistatic effect.
The present invention provides antistatic threads
having a configuration such that a satis~actory antistatic
effect is obtained and the threads are as optically inconspicuous
as possible in te~tile products, such as woven fabrics,
tricots, fleeces, carpets, mats and the like.
According to the invention there is provided an
antistatic multi-component thread comprising at least two
synthetic polymer components including a first component
consisting of an electrically non-conducting, filament-~orming,
thermoplastic polymer, and a second component consisting of
a thermoplastic synthetic polymer with electrically-conducting
powder dispersed therein, which exhibits, at a test-voltage
of 1 kV, a volume resistivity, according to DI~, German
Industrial Standard, 54 345, of less than 10 ohms/cm.,
wherein one o~ said components ~orms a matrix-component and
the other forms at least two segment-components, said matrix
component separating said segment components and at least two
o said segment-components being disposed peripherally,
Matrix-segment thrèads are to be understood to mean
multi-component threads in which the individual segments and
the matrix are arranged continuously along the thread axis,
the thread cross-section being therefore substantially the
same over its length.
The matrix component is suitably the second component
containing the electrically-conducting powder, with the segment
components being ~ormed ~rom the electrically non-conducting
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first component, however, the matrix component may also be
formed from the electrically non-conducting first component
with the segment components being formed from the second
component.
Preferably, the cross-section of the thread comprises
at least three segmen-t components. The peripheral segment-
components are preferably completely separated by the matrix
component and there are preferably at least six and more
preferably at least twelve peripheral segment components.
The polymers employed in the first and second com-
; ponents may be the same or different and are suitably selected
from polyamides, copolyamides, polyesters and copolyesters.
In particular the first and second components may be formed
from polyamides with different contraction properties.
Electrically conducting powders which can be dispersed
in a thermoplastic polymer and produce a satisfactory anti-
static effect, include finely divided metallic powders, for
example, chromium powder and mixed metal oxide phases, or
example, mixtures of tin oxide and antimony oxide. Because
of their effectiveness and ease of procurement, pre~erence is
given to electrically-conducting carbon blacks which are
readily dispersed, in the form of an electrically conducting
powder, in thermoplastic polymers.
The invention is illustrated in particular and
preferred embodiments by reference to the accompanying drawings
in which Figures 1 to 11 illustrate thread cross-sections of
different configurations within the invention.
The -threads may be round with a circular cross-
section as shown in Figures 1 to 9, or they may be externally
profiled as shown in Figures 10 and 11. They may also be
of any desired external shape.
L9
With further reference to the drawings a signifies
the matrix component of the thread, and b signifies the segment
component of the thread.
If the threads of the invention are to be used in
the form of unsplit matrix-segment threads, it is advantageous
to disperse the electrically conducting powder in the matrix-
component. If, in particular, the threads are to be used
in the form of filaments, this is especially advantageous, and
in this case one or more substantially centrally disposed
segment-component may be arranged in the core of the thread,
the one or more central segment-components being completely
separated from the peripheral segment-component by a matrix-
component containing the electrically-conducting powder,
The substantially centrally disposed segment-com-
ponents may be in a regular or irregular arrangement in the
thread and are fully enclosed in the matrix component, such as
is illustrated in Figures 3, 4 and 5.
In an arrangement of this ~ind, only relatively small
amounts of conducting powder are required to achieve high
electrical conductivity.
It is advantageous to split the matrix-segment
multi-components from selected polymers having different
contraction characteristics, with the aid of contraction-
initiating agents, if the antistatic thread configurations
are to be processed, in admixture with other non-conducting
threads, into staple-fibre yarn. This splitting produces
split segment threads of very fine titre, for example, of
about 0,1 dtex, and, in the staple-fibre yarn, these are so
well covered by the other fibres forming the yarn, which are
of about 8 dtex, that they are inconspicuous, giving the
impression of a uniformly dyed or white yarn.
In the case of threads which are split into segment
and matrix components, the thread may suitably comprise seg-
ment- and matrix-fibres of infinite length in a random
arrangement and with different curvatures As a whole the
segment-fibres are more sharply curved than the matrix-
fibres.
Such threads may also have fixed areas of unsplit
multi-component fibres, in which the fixed areas are suit-
ably compacted and regularly disposed.
Thus an antistatic thread of the invention may be
unsplit, totally split or partially split into matrix- and
segment-components. In the case of partial splitting the
partly split multi-component fibres have mechanical adhesion
of the matrix- and segment-fibres. Slots may occur between
the matrix- and segment-fibres, or longitudinal grooves at the
edge of the multi-component fibre corresponding to the phase
boundaries. A particular thread which is partly split may be
characterized by the presence of both slots and grooves.
The threads o~ the invention may be produced by
known methods, for example, by the methods described in West
-~ ~ ` German Patent Application P 28 03 136.9
. .
~` employing the apparatus described therein. Aforementioned
-`` Canadian Patent Application S.N. 322,710 describes a m~thod
which is suitable for producing the threads if the multi-
component threads are to be split.
The aforementioned Canadian Patent Application S.~.
322,710 also contains teachings for the choice of polymers!
and for carrying out the splitting, which can be employed in
- the present invention.
The great effectiveness of the antistatic threads
of the invention appears to be attributable to the fact that
the conductive polymer parts extend as far as the surface of
the thread. If, for example, the matrix-component contains
carbon black, and if it is arranged, for example, as a three-
or four-pointed star with narrow rays in the interior of the
multi-component fibre, then contact between the conductive
matrix-component and the surface occurs over only a very
small portion of the periphery of the thread. This, however,
is enGugh to reinforce the effectiveness to an unexpectedly
high degree and, on the other~hand, the carbon black is scarcely
visible.
In this regard it is preferably that at least 2~/o
and more preferably about 5~/O of the periphery of each
peripheral segment not be enclosed by the matrix component.
The part of the segment periphery of the peripheral
segment-components enclosed in the matrix-component may have
a convex, substantially circular form or shape or an
irregular, for example, serrated ~orm. Tl~e perip~eral seg-
~20 ~ ment-components may be disposed symmetrically or non
- ~ ~ symmetrically in the thread cross-section.
Generally it is preerred that the area of the
second component, in the thread cross-section, be at least 5%
of the total area.
The carbon bIacks employed in the invention may be
selected from any of the electrically-conducting types
commercially available, providing they have sufficient
dispersivity for the thread configuration according to the
invention. In particular it is especially preferred to
employ carbon blacks having a maximal particle size of less
than 0.035 ~m.
Suitable carbon blacks are those having a DBP
absorption oE more than 120 ml/100 g of carbon black, for
example, acetylene black. ~he DBP number is the wetting
point with dibutyl phthalate which is determined in a special
kneading machine according to ASTM D 241~-25 T and which is
a criterion for carbon black structure.
Carbon blacks having a DBP absorption of 200 ml/100 g
or more are particularly suitable, because these are high-
conductivity carbon blacks. High-conductivity carbon blacks
produce good electrical conductivity in the threads.
The carbon black content is suitably from 12 to 45%,
by weight, based on the total weight of the carbon black
polymer mixture. Preferably the carbon black content is
from 20 to 35% by weight.
The carbon black may be mixed into the polymer-melt
in the manner used in pigmenting synthetic polymers. It may
also be desirable to add the carbon black before or during
- polymerization of the polymerizing additive. In both cases
satisfactory dispersion is achieved, and this translates in-to
satisfactory conductivity with relatively small quantities
of carbon black.
The antistatic threads of the invention may consist,
in whole or in part, of multi-component threads, one of the
components bein~ a polymer containing dispersed electrically-
conducting powder, for example, carbon black. In addition to
~`~ the multi-component threads, there may also be other threads
or types of fibres which are not conductive, for example,
conventional single-component threads and fibres made of
polyamide, polyester, and the like. For example, in the case
of a carpet yarn, `it is sufficient to mix with the conventional
~arn less than 3/O of the carbon black-containing multi-
component threads in order to provide the carpet with a high
3~9
degree of protection against electrostatic charging.
The invention is further illustrated in particular
and preferred emhodiments in the following examples.
Example 1
Antistatic fibres of the invention, having a con-
figuration as shown in Figures 8 and 9, were spun using a
spinning nozzle according to the aforementioned Canadian
Patent ApplicationS.N. 320,168 under otherwise conventional
spinning conditions, the matrix-component consisting of a
polyamide 6 containing 31%-of carbon black having a DBP
absorption of 125 ml/100 g of carbon black, the segment
component was also polyamide, pigmented with 7%, by weight,
of TiO2. The area-ratios of the matrix-component to the
segment-component each amounted to 1:10 and 1:5, Spinning
was carried out at a velocity of 1200 m/min, followed by
single-stage stretching with a ratio of 1:2.6.
The volume resistivity o~ the threads obtained was
determined according to DIN 54 345 over a fixed length of
5 cm, with a test voltage of 1 kV, at a temperature of 2LC
and 25% relative atmospheric humidlty. The results are shown
in Table I.
TAB _E I - .
Sample Cross-section Thread titre Area ratio Volume
of matrix resistivity
to segment ohm/cm
area
a Fig. 8 57 dtexf2 1 : 10 3,6 . 10
b Fig. 8 34 dtexf2 1 : 5 1,3 . 10
c Fig. 9 55 dtexf2 1 : 10 9,6 . 10
d Fig. 9 33 dtexfl 1 : 5 6,8 . 107
_ . . _ _ . _
g
In comparison with this, a non-conducting fibre made
of polyamide 6 exhibited, under the same conditions, an
electrical volume resistivity of 5 x 1013 ohms/cm.
Example 2
Thread samples c and d from Example 1 were each
processed into a carpet yarn with two 1260 dtex f 64 yarns.
The carpet yarns obtained were used to produce carpets which
were then subjected to a walking test during which the carpet
was walked upon at 20C and 25% relative atmospheric humidity
and the charge voltage was recorded. The voltage rose to a
maximal value which remained constant and provided the
measured results.
In the case of the sample from thread sample c, the
charge amounted to 1,4 kVj in the case of sample d, the
charge was 1,1 kV. The requirements for an antistatic carpet
were thus fully met.
`'
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