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EP 0 161 579 B1 |
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EUROPEAN PATENT SPECIFICATION |
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Mention of the grant of the patent: |
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07.02.1990 Bulletin 1990/06 |
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Date of filing: 30.04.1985 |
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International Patent Classification (IPC)5: D21F 1/00 |
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Dryer fabric having warp strands made of melt-extrudable polyphenylene sulphide
Trockengewebe mit Kettenfäden aus schmelzextrudierbaren Polyphenylensulfiden
Toile de séchage comprenant des fils de chaîne en polyphénylène sulphide extrudable
au fondu
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Designated Contracting States: |
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CH DE FR GB IT LI NL SE |
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Priority: |
01.05.1984 US 605825 26.04.1985 US 727665
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Date of publication of application: |
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21.11.1985 Bulletin 1985/47 |
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Proprietor: JWI Ltd. |
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Kanata, Ontario (CA) |
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Inventors: |
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- Baker, Samuel M.
Carleton Place, Ontario
K7C 1M1 (CA)
- Best, F. Brian
Ottawa, Ontario
K2A 3J6 (CA)
- Bhatt, Girish M.
Williston
Vermount 05495 (US)
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Representative: Dipl.-Phys.Dr. Manitz
Dipl.-Ing. Finsterwald
Dipl.-Ing. Grämkow
Dipl.Chem.Dr. Heyn
Dipl.Phys. Rotermund
Morgan, B.Sc.(Phys.) |
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Postfach 22 16 11 80506 München 80506 München (DE) |
(56) |
References cited: :
EP-A- 0 063 380 FR-A- 2 418 826 US-A- 4 290 209
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EP-A- 0 070 708 US-A- 4 267 227
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Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
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Background of Invention
(a) Field of the Invention
[0001] The present invention relates to fabrics made of synthetic materials and particularly,
but not exclusively, for use in dryer sections of papermaking machines involving high
temperature. Furthermore the present invention relates to monofilaments suitable for
use in such fabrics.
(b) Description of Prior Art
[0002] Increasingly dryer fabrics are being manufactured from monofilament strands because
such fabrics are easier to keep clean, thus retaining their drying efficiency, and
because they are essentially non- absorptive. These are normally of woven construction,
but in recent years an alternative non-woven construction is becoming popular - the
so-called "spiral fabrics" - which are assembled from a multiplicity of helical coils
connected together by inserted hinge pins. German patent DE 24 19 751 and U.S. 4,481,079
described this type of fabric. The predominant material used in such fabrics, whether
woven or spiral, is polyester, with polyamides used less frequently. Unfortunately
both of these classes of materials degrade at high temperature, a short-coming which
precludes their use in high temperature applications on paper machines. High temperature
applications are ones that result in operating temperatures of about 150°C or above.
[0003] Some manufacturers of woven fabrics have resorted to NOMEX
O or KEVLARO in order to cope with the extreme conditions prevalent in such high temperature
applications. Because neither polymer is mett- extrudable, monofilaments made from
them are not practicable and so these materials are employed in the form of composite
multifilaments, often resin coated. U.S. 4,159,618 teaches such a monofilament-like
composite strand for this purpose, but even these composites are deficient in that
they lose tensile strength when exposed to moist or dry heat (see Tables 1-3 in U.S.
4,159,618).
[0004] Considering now another property of dryer fabrics, it is highly desirable that such
fabrics be distortion resistant, that is, have inherent dimensional stability and
retain this property so as to resist skewing throughout their life on the paper machine.
Woven fabrics made with monofilament warp of round cross-section, and conventional
materials such as polyester while having the desirable advantages of running clean
and of non-absorptivity already mentioned, are generally deficient in distortion resistance
because of the minimal interlocking contact at the warp and weft cross-overs dictated
by the geometry of the respective strands. U.S. 4,290,209 discloses the use of rectangular
cross-section warp strands having a flattening ratio of about 2:1, whereby the resulting
fabric acquires superior properties of distortion resistance and surface smoothness,
along with more desirable permeability and elastic modulus. None of these improved
fabrics, however, are suitable for high temperature applications, again because of
the inherent tendency of the polymers normally used to degrade and lose strength.
[0005] U.S. 4,359,501 discloses an industrial fabric, for use in applications involving
elevated temperatures, comprised of melt-extrudable polyaryletherketone monofilament
strands. This material, however, suffers the major disadvantage of being so costly
that the woven end product is not economically attractive to the specific paper mill
end-users already identified.
[0006] The present invention is directed towards solving these problems.
Summary of the Invention
[0007] Broadly, the present invention provides a dryer fabric for use in a dryer section
of a paper machine wherein at least the machine direction components of the fabric
are monofilaments made from polyphenylene sulphide or a blend of polyphenylene sulphide
with heat-stabilized polyamide 66 with the polyamide 66 being present in the range
of up to about 20% by night.
[0008] In a preferred embodiment of the invention the polyphenylene sulphide is blended
with about 6% by weight of heat-stabilized polyamide 66.
[0009] In another preferred embodiment the dryer fabric comprises a plurality of interwoven
warp and weft strands wherein at least the warps are monofilaments made from polyphenylene
sulphide or a blend of polyphenylene sulphide with heat-stabilized polyamide 66 the
warp strands having an essentially rectangular cross-section with the long axis of
the rectangle lying in the plane of the fabric.
[0010] In another preferred embodiment the dryer fabric comprises a multiplicity of helical
coils connected together by hinge pins wherein at least the helical coils are made
from polyphenylene sulphide or a blend of polyphenylene sulphide with heat-stabilized
polyamide 66.
[0011] In another preferred embodiment the dryer fabric comprises a multiplicity of helical
coils connected together by hinge pins wherein at least the helical coils are made
from polyphenylene sulphide or a blend of polyphenylene sulphide with heat-stabilized
polyamide 66 and wherein the helical coils have an essentially rectangular cross-section
when viewed in the machine direction with the long axis of the rectangle lying in
the plane of the fabric.
[0012] The present invention also comprises a monofilament as set forth in claim 12 and
a synthetic fabric made therefrom. Further advantageous embodiments of the invention
are defined in the subordinate class.
[0013] The present invention thus recognizes that monofilaments of the type described above
can also be used to advantage in other industrial applications where hydrolysis is
encountered. For the sake of completeness it should be pointed out that polyphenylene
sulphide fibres are known per se as can be seen from U.S. patent 3,919,177. However,
this disclosure does not recognize the property of polyphenylene sulphide monofilaments
which is of importance here, namely the resistance to hydrolytic degradation at elevated
temperatures. Another publication describing polyphenylene sulphide fibres is the
preliminary bulletin of Phillips Petroleum Company issued in Feb. 1983 describing
their "Ryton" (Registered Trademark) product. Although this publication demonstrates
the chemical inertness of polyphenylene sulphide, it was the present applicants who
first proved that a PPS monofilament was immune to hydrolytic attack.
Brief Description of Drawings
[0014]
Fig. 1 is a schematic view of a typical dryer section as used in a papermaking machine;
Fig. 2 is an enlarged sectional view of an all-monofilament plain weave dryer fabric
utilizing flattened warp strands;
Fig. 2A is a fragmented sectional view along section line A-A of Fig. 2;
Fig. 3 is an enlarged sectional view of an all-monofilament four-shaft eight-repeat
duplex-weave dryer fabric utilizing flattened warp strands;
Fig. 3A is a fragmented sectional view along cross-section line A-A of Fig. 3.
Fig. 4 is an enlarged cross-section view of the flattened warp strand;
Fig. 5 is a plan view of a part of a spiral dryer fabric with flattened spirals; and
Fig. 5A is an enlarged sectional view, along cross-section line A-A of Fig. 5, of
the spiral fabric viewed in the machine direction.
Detailed Description of the Invention
[0015] Referring to Fig. 1 there is schematically illustrated a sub-section of a typical
dryer section in a papermaking machine (not shown). The top tier dryer cylinders are
generally indicated at 10 and the bottom tier at 11. The paper web 13 passes in a
serpentine fashion over the top and bottom dryer cylinders as shown. An endless top
fabric 14 holds the paper web 13 tightly against the upper cylinders 10 as it passes
partially around the first upper cylinder, around a felt roll 15, partially around
the remaining top cylinders 10 and around the other intervening felt rolls 15, then
around return roll 16, passing over guide and tensioning rolls 24 and 23 respectively,
and then over other return rolls 16 before it passes again over the first dryer cylinder
to complete the cycle. Similarly, an endless bottom fabric 18 holds the paper web
13 tightly against the lower dryer cylinders 11 as it passes around these and the
intervening bottom felt rolls 19, return rolls 21, tensioning roll 25, guide roll
26, and other return rolls 21, substantially as shown.
[0016] Polyphenylene sulphide is a linear high molecular weight polymer having the repeating
unit
and is available commercially under the registered trademark RYTON from Phillips Chemical
Corporation. While priced at a fraction of the material of U.S. 4,359,501, pure polyphenylene
sulphide of the present invention is difficult to extrude. It is also lacking in "toughness"
required for industrial weaving.
[0017] We have found that monofilament polyphenylene sulphide has greatly superior resistance
to hydrolytic degradation than the polyester strands commonly used in dryer fabrics.
Table 1 shows the results of a test with the percent retained tensile strength of
a polyphenylene sulphide strand exposed to saturated steam at 130°C in a pressure
vessel (24 gauge psi) for a period of eight days, along with a polyester monofilament
strand of the same size.
Table 2 shows test results for the same materials when exposed to saturated steam
at 150°C.
[0018] It will be observed that in these accelerated tests the strength of the polyphenylene-sulphide
strand was not only retained but was, in fact, enhanced whereas the polyester strand
showed a rapid and catastrophic loss in strength. This extraordinary retention of
hydrolysis resistance, even after prolonged exposure, makes polyphenylene sulphide
an outstanding candidate material for use in paper machine dryer fabrics, particularly
in high-temperature applications.
[0019] Unfortunately, the material can only be extruded with difficulty in monofilament
form in the size range commonly used in dryer fabrics. Also during weaving the pure
material is subject to frequent warp breakages due to its lack of toughness and is
prone to scraping in the loom heddles and reed dents, all of which renders pure polyphenylene
sulphide difficult for heavy industrial weaving.
[0020] The addition of a heat-stabilized polyamide 66 to the polyphenylene sulphide before
extrusion has greatly alleviated these problems. Experiments in a range of blends
has confirmed the following important results:
1. the addition of polyamide 66 acts as a processing aid, which makes the commercial
extrusion of the blend a more viable process;
2. "toughness" is significantly enhanced. For example, the addition of 6% by weight
of heat-stabilized polyamide 66 increased the measured knot toughness by a factor
of seven times. This property is determined by subjecting a strand, which contains
a simple overhand knot, to tensile pull and producing a resulting load-elongation
diagram. The area under the curve is a measure of knot toughness;
3. full hydrolytic degradation resistance is retained;
4. there is no sacrifice in tensile strength when the polyamide is added to the pure
polyphenylene sulphide;
5. subsequent pilot plant and commercial weaving in a wide range of dryer fabric designs,
including those requiring high weaving tensions and high pick counts, confirms that
the use of the polyphenylene sulphide/6% polyamide blend in warp strands of dryer
fabrics reduced warp breakage and scraping to an acceptable level;
6. increasing the polyamide 66 from 6% to 20% increases the toughness of the monofilament,
however, the abrasion resistance decreases.
[0021] The means by which the additive improves toughness while preserving hydrolysis resistance
is not entirely known, but the successful monofilaments are characterized by having
the additive material present in small, discrete, elongated globules with the long
axis parallel to the axis of the monofilament. These discrete globules are not connected
to each other or to the outer boundaries of the monofilament, and are thus protected
from the harsh environment of the end use application of the filament. In order to
preserve the additive as discrete globules we have found that the melt viscosity of
the added material must be higher than the melt viscosity of polyphenylene sulphide
at the extrusion temperature and the amount of additive must be limited. Another factor
to consider in choosing the additive is that it must not degrade during extrusion
when it is temporarily exposed to the temperature required to melt the polyphenylene
sulphide, the range being 285°C to 315°C. Some additives which satisfy the above mentioned
requirements do not form globules because they are chemically incompatible with polyphenylene
sulphide and react in unsuitable ways.
[0022] In our experiments in blending to date, we have found that heat-stabilized polyamide
66 is the only additive to polyphenylene sulphide which successfully imparts the quality
of toughness to the resultant monofilament while preserving hydrolysis resistance.
Other materials may be found which can also impart the same quality to the blend.
Some factors which are important in choosing additives are: a higher viscosity at
extrusion temperature than polyphenylene sulphide, chemical compatability, resistance
to heat degradation during extrusion.
[0023] All types of dryer fabrics having monofilaments in the machine direction will benefit
in resistance to hydrolysis from this invention. Three preferred constructions utilizing
rectangular machine direction components are described below but the invention is
not limited to these constructions.
Figs. 2 and 2A depict a plain weave dryer fabric 30 representative of a single-layer
dryer fabric used in the papermaking industry. In Figs. 2 and 2A numeral 31 denotes
consecutive warp strands made from polyphenylene sulphide or a blend of polyphenylene
sulphide and polyamide 66 flattened to an essentially rectangular cross-section and
numeral 32 represents consecutive weft strands. In this structure each warp strand
31 passes over a first weft strand 32, under the second weft strand, over the third
and so on. Similarly, the adjacent warp strand passes under the first weft, over the
second, under the third and so on.
Figs. 3 and 3A depict a four-shaft eight-repeat duplex-weave dryer fabric 40, which
is a type commonly used in the papermaking industry. In Figs. 3 and 3A numerals 41,
42, 43 and 44 are consecutive warp strands, made from polyphenylene sulphide or a
blend of polyphenylene sulphide and polyamide 66, flattened to an essentially rectangular
cross-section. The weft is paired in two layers and numbered 48 to 57 as shown. In
this woven structure a warp strand 41 passes in sequence over a pair of weft strands
50-51, between the next pair 52-53, under the third pair 54-55, between the fourth
pair 56-57, and so on. The next consecutive warp strand 42 passes between the first
pair of weft strands 50-51, over the second pair, between the third pair and under
the fourth pair. Similarly, the third and fourth consecutive warp strands 43 and 44
are woven commencing under and between the first pair of weft strands respectively.
Fig. 4 depicts the essentially rectangular cross-section of the polyphenylene sulphide
or polyphenylene sulphide/polyamide blend warp strands. Such strands may be produced
by rolling round monofilament strands, or by slitting film, or, in the preferred embodiment
by melt-extruding through a specially shaped die. The flatness ratio a:b of the preferred
embodiment shown in Fig. 4 is 2:1 and is preferably between 1.5:1 and 2.5:1 for the
woven dryer fabric embodiments.
Figs. 5 and 5A depict a spiral construction dryer felt 60 comprising a plurality of
helical S-coils 61 joined together with adjacent Z-coils 62 by means of hinge pins
63. The designations 'S' and 'Z' indicate the direction of twist, following the convention
in the textile industry. The coils 61, 62 are wound using polyphenylene sulphide or
polyphenylene sulphide/polyamide blend strand material of essentially rectangular
cross-section with a flatness ratio a:b of 2:1 as shown in this preferred embodiment.
In this construction a range of flatness ratios between 1.1:1 and 2.5:1 can be used.
[0024] The woven dryer fabric of the present invention has a warp count preferably in the
range of 25 to 80 strands per inch (2.5 cm). Warp strands are made by polyphenylene
sulphide or a blend of polyphenylene sulphide and polyamide 66. The flattened warp
strands of the invention will have major axis measurements in the range of 0.0125"
to 0.050" (0.32 to 1.27 mm). With respect to weft it is not intended to limit the
material utilized to monofilaments. Since in the fabric of the invention the weft
strands are non-loadbearing, other materials resistant to high temperature and hydrolytic
degradation may be utilized, for example composite strands incorporating asbestos
or fibreglass.
[0025] The dryer fabric of spiral construction, which is another embodiment of the invention,
utilizes helical coils made from polyphenylene sulphide or a blend of polyphenylene
sulphide and heat-stabilized polyamide 66 up to 20% by weight of polyamide 66. Hinge
pins may be made from the same material or alternatively from other temperature resistant
materials such as the composite constructions already mentioned.
[0026] In the preferred embodiments above, rectangular shaped monofilaments have been used,
but round monofilaments and other cross-sectional shapes may also be used provided
they are made from the material of this invention. We have found that woven fabrics
made with rectangular warp strands of pure polyphenylene sulphide, and in a different
test with warp strands made from a 6% blend of polyamide 66 and polyphenylene sulphide
have superior resistance to distortion compared to equivalent fabrics made with monofilament
polyester warp material. Thus, the invention can be used to improve the distortion
resistance of fabrics made with round monofilaments which is normally troublesome.
1. A dryer fabric for use in a dryer section of a paper machine wherein at least the
machine direction components of the fabric are monofilaments made from polyphenylene
sulphide or a blend of polyphenylene sulphide with heat-stabilized polyamide 66, said
polyamide 66 being present in the range of up to about 20% by weight.
2. A dryer fabric as claimed in claim 1 wherein said polyphenylene sulphide is blended
with about 6% by weight of heat stabilized polyamide 66.
3. A dryer fabric as claimed in claim 1 wherein said machine direction components
are warp strands in a woven dryer fabric.
4. A dryer fabric as claimed in claim 3 wherein said warp strands are flattened warp
strands having an essentially rectangular cross-section with the long axis of the
rectangle lying in the plane of said fabric.
5. A dryer fabric as claimed in claim 4 wherein said woven dryer fabric has flattened
warp strands having an essentially rectangular cross-section with a flatness ratio
between 1.5:1 and 2.5:1.
6. A dryer fabric as claimed in claim 1 wherein said said machine direction components
comprise a plurality of helical coils connected together by hinge pins.
7. A dryer fabric as claimed in claim 6 wherein the monofilament of said helical coils
has an essentially rectangular cross-section when viewed in the machine direction
with the long axis of the rectangle lying in the plane of said fabric.
8. A dryer fabric as claimed in claim 7 wherein said rectangular cross-section has
a flatness ratio between 1.1:1 and 2.5:1.
9. A dryer fabric as claimed in claim 1 wherein said monofilaments are made from polyphenylene
sulphide and an additive which imparts toughness to the monofilament while preserving
the hydrolysis resistance inherent in polyphenylene sulphide, said additive having
characteristics of a higher melt viscosity than the polyphenylene sulphide at extrusion
temperatures, resistance to thermal degradation at extrusion temperatures, and chemical
compatibility with the polyphenylene sulphide, and wherein said additive is present
in small discrete elongated globules with the long axis of said globules parallel
to the axis of the monofilament.
10. A dryer fabric as claimed in claim 9 wherein said globules are not connected to
the outer boundaries of the monofilament.
11. A dryer fabric as claimed in claim 3 wherein said fabric has a warp count in the
range of 25 to 80 strands per 2.54 cm (per inch).
12. A monofilament made from a blend of polyphenylene sulphide and an additive, said
additive imparting improved toughness to the resulting monofilament without substantially
reducing its hydrolysis resistance, said additive being added to the polyphenylene
sulphide in the range of 1% to 20% by weight and having the characteristics of
- higher viscosity at extrusion temperatures than polyphenylene sulphide;
- resistance to degradation during extrusion;
- chemical compatability with polyphenylene sulphide;
- being present in the monofilament in small discrete elongated globules with the
long axis of said globules parallel to the axis of the monofilament.
13. A monofilament as in claim 12 wherein the additive is heat-stabilized polyamide
66.
14. A monofilament as in claim 13 wherein the heat-stabilizing polyamide 66 comprises
about 6% by weight of the polyphenylene sulphide.
15. A monofilament as in claim 12 having a flattened essentially rectangular cross-section
with an axis ratio between 1.1 to 1 and 3 to 1.
16. A monofilament as in claim 15 with an axis ratio of about 2 to 1.
17. A monofilament as claimed in claim 15 having a major axis measurement in the range
from 0.32 to 1.27 mm (0.0125 to 0.050 inches).
18. A monofilament as in any one of the preceding claims 12 to 17 wherein said discrete
globules are not connected to the outer boundaries of the monofilament.
19. A synthetic industrial fabric comprising a fabric woven from monofilaments or
a fabric composed of a plurality of helically coiled monofilaments connected together
by hinge pins, wherein said monofilaments comprise monofilaments in accordance with
one of claims 12 or 13.
1. Trockengewebe zur Verwendung in einer Trockenpartie einer Papiermachine, bei der
mindestens die in Bearbeitungsrichtung verlaufenden Bestandteile des Gewebes Einzelfäden
aus Polyphenylensulphid oder einem Gemisch aus Polyphenylensulphid mit wärmestabilisiertem
Polyamid 66 sind, wobei das Polyamid 66 im Bereich bis zu 20 Gew.-% vorhanden ist.
2. Trockengewebe nach Anspruch 1, bei dem das Polyphenylensulphid mit etwa 6 Gew.-%
wärmestabsilisiertem Polyamid 66 gemischt ist.
3. Trockengewebe nach Anspruch 1, bei dem die in Bearbeitungsrichtung verlaufenden
Komponenten Kettfäden in einem gewebten Trockengewebe sind.
4. Trockengewebe nach Anspruch 3, bei dem die Kettfäden abgeflachte Kettfäden mit
einem im wesentlichen rechtwinkligen Querschnitt sind, wobei die längere Achse des
Rechtecks in der Ebene des Gewebes liegt.
5. Trockengewebe nach Anspruch 4, bei dem das gewebte Trockengewebe abgeflachte Kettfäden
mit einem wesentlichen rechtwinkligen Querschnitt mit einem Abflachungsverhältnis
zwischen 1,5:1 und 2,5:1 besitzt.
6. Trockengewebe nach Anspruch 1, bei dem die in Bearbeitungsrichtung verlaufenden
Komponenten eine Vielzahl von miteinander durch Gelenkstifte verbundene Wendelwicklungen
umfaßt.
7. Trockengewebe >nach Anspruch 6, bei dem der Einzelfaden der Wendelwicklungen in
Bearbeitungsrichtung gesehen einen im wesentlichen rechtwinkligen Querschnitt bestizt,
wobei die lange Achse des Rechtecks in der Gewebeebene liegt.
8. Trockengewebe nach Anspruch 7, bei dem das Abflachungsverhältnis des rechtwinkligen
Querschnitts zwischen 1,1:1 und 2,5:1 liegt.
9. Trockengewebe nach Anspruch 1, bei dem Einzelfäden aus Polyphenylensulphid und
einem Zusatz hergestellt sind, der dem Einzelfaden Zähigkeit verleiht unter Aufrechterhaltung
des dem Polyphenylensulphid eigenen Hydrolyse-Festigkeit, wobei das Additiv Eigenschaften
einer höhren Schmelzviskosität als das Polyphenylensulphid bei Extrusionstemperaturen,
Widerstand gegen thermischen Abbau bei Extrusionstemperaturen und chemische Verträglichkeit
mit dem Polyphenylensulphid aufweist, und wobei der Zusatz als kleine diskrete längliche
Kügelchen vorhanden ist, mit der Längsachse der Kügelchen parallel zur Achse des Einzelfadens.
10. Trockengewebe nach Anspruch 9, bei dem Kügelchen nicht mit der Außenbegrenzung
des Einzelfadens in Verbindung sind.
11. Trockengewebe nach Anspruch 3, bei dem das Gewebe eine Kettzahl im Bereich von
25 bis 80 Kettfäden pro 2,54 cm (pro inch) besitzt.
12. Einzelfaden aus einem Gemisch aus Polyphenylensulphid und einem Zusatz, der dem
sich ergebenden Einzelfaden verbesserte Zähigkeit verleiht, ohne seine Hydrolyse-Festigkeit
wesentlich zu verringern, wobei der Zusatz zu dem Polyphenylensulphid im Bereich von
1 bis 20 Gew.-% hinzugefügt ist und die Eigenschaften besitzt.
- höhere Viskosität bei Extrusionstemperaturen als Polyphenylensulphid;
- Widerstand gegen Abbau während der Extrusion;
- chemische Verträglichkeit mit Polyphenylensulphid, und
- in dem Einzelfaden in kleinen diskreten länglichen Kügelchen vorhanden ist, wobei
die Längsachse der Kügelchen parallel zur Achse des Einzelfadens liegt.
13. Einzelfaden nach Anspruch 12, bei dem der Zusatz wärmestabilisiertes Polyamid
66 ist.
14. Einzelfaden nach Anspruch 13, wobei das wärmestabilisierte Polyamid 66 etwa 6
Gew.-% des Polyphenylensulphid umfaßt.
15. Einzelfaden nach Anspruch 12 mit einem abgeflachten im wesentlichen rechtwinkligen
Querschnitt mit einem Achsenverhältnis zwischen 1,1 zu 1 und 3 zu 1.
16. Einzelfaden nach Anspruch 15 mit einem Achsenverhältnis von etwa 2 zu 1.
17. Einzelfaden nach Anspruch 15 mit einer Abmessung der großen Achse im Bereich von
0,32 bis 1,27 mm (0,0125 bis 0,050 inch).
18. Einzelfaden nach einem der vorangehenden Ansprüche 12 bis 17, bei dem die diskreten
Kügelchen nicht mit der Außenbegrenung des Einzelfadens in Verbindung sind.
19. Synthetisches Industriegewebe mit einem aus Einzelfäden gewebten Gewebe oder einem
Gewebe, das aus einer Vielzahl von wendelförmig gewickelten Einzelfäden zusammengesetzt
ist, die durch Gelenkstifte miteinander verbunden sind, wobei die Einzelfäden Einzelfäden
nach einem der Ansprüche 12 oder 13 umfassen.
1. Toile de séchage pour l'utilisation dans une section de séchage d'une machine à
papier, dans laquelle au moins les composants de la toile suivant la direction de
la machine sont des monofilaments faits de poly(sulfure de phénylène) ou d'un mélange
de poly(sulfure de phénylène) avec un polyamide 66 stabilisé en température, ledit
polyamide 66 étant présent dans la plage de jusqu'à 20% en poids environ.
2. Toile de séchage selon la revendication 1, dans laquelle ledit poly(sulfure de
phénylène) est mélangé avec environ 6% en poids de polyamide 66 stabilisé en température.
3. Toile de séchage selon la revendication 1, dans laquelle lesdits composants suivant
la direction de la machine sont des brins de chaîne d'une toile de séchage tissée.
4. Toile de séchage selon la revendication 3, dans laquelle lesdits brins de chaîne
sont des brins de chaîne aplatis ayant une section transversale substantiellement
rectangulaire avec le grand axe du rectangle étendu dans le plan de ladite toile.
5. Toile de séchage selon la revendication 4, dans laquelle ladite toile de séchage
tissée possède des brins de chaîne aplatis ayant une section transversale substantiallement
rectangulaire avec un rapport d'aplatissement entre 1,5:1 et 2,5:1.
6. Toile de séchage selon la revendication 1, dans laquelle lesdits composants suivant
la direction de la machine comportent une pluralité d'enroulements hélicoïdaux liés
ensemble par des broches.
7. Toile de séchage selon la revendication 6, dans laquelle le monofilament desdits
enroulements hélicoïdaux possède une section transversale substantiellement rectangulaire
vu suivant la direction de la machine avec le grand axe du rectangle étendu dans le
plan de ladite toile.
8. Toile de séchage selon la revendication 7, dans laquelle ladite section transversale
a un rapport d'aplatissement entre 1,1:1 et 2,5:1.
9. Toile de séchage selon la revendication 1, dans laquelle lesdits monofilaments
sont faits de poly(sulfure de phénylène) et d'un additif qui confère de la dureté
au monofilament tout en conservant la résistance à l'hydrolyse propre au poly(sulfure
de phénylène), ledit additif possédant des caractéristiques de viscosité de fusion
supérieure à celle du poly(sulfure de phénylène) aux températures d'extrusion, de
résistance à la dégradation thermique aux températures d'extrusion, et de compatibilité
chimique avec le poly(sulfure de phénylène), et dans laquelle IequeI additif est présent
en globules discrets allongés avec le grand axe desdits globules parallèles à l'axe
du monofilament.
10. Toile de séchage selon la revendication 9, dans laquelle lesdits globules ne sont
pas liés aux frontières extérieures du monofilament.
11. Toile de séchage selon la revendication 3, dans laquelle ladite toile possède
un compte en chaîne dans la gamme de 25 à 80 brins par 2,54 cm (par inch).
12. Un monofilament fait d'un mélange de poly(sulfure de phénylène) et d'un additif,
ledit additif conférant une dureté augmentée au monofilament résultant sans réduire
sensiblement sa résistance à l'hydrolyse, ledit additif étant ajouté au poly(sulfure
de phénylène) dans la plage de 1 % à 20% en poids et possédant les caractéristiques
de
- viscosité supérieure à celle du poly(sulfure de phénylène) aux températures d'extrusion;
- résistance à la dégradation pendant l'extrusion;
- compatibilité chimique avec le poly(sulfure de phénylène);
- être présent dans le monofilament en petits globules allongés discrets, avec le
grand axe desdits globules parallèles à l'axe du monofilament.
13. Monofilament selon la revendication 12, dans lequel l'additif est un polyamide
66 stabilisé en température.
14. Monofilament selon la revendication 13, dans lequel le polyamide 66 stabilisé
en température représente environ 6% en poids du poly(sulfure de phénylène).
15. Monofilament selon la revendication 12, ayant une section transversale substantiellement
rectangulaire avec un rapport d'axe entre 1,1 à 1 et 3 à 1.
16. Monofilament selon la revendication 15, avec un rapport d'axe d'environ 2 à 1.
17. Monofilament selon la revendication 15, ayant une dimension de grand axe dans
la plage 0,32 à 1,27 mm (0,0125 à 0,050 inches).
18. Monofilament selon une quelconque des revendications précédentes 12 à 17, dans
ledit lesdits globules discrets ne sont pas liés aux frontières extérieures du monofilament.
19. Toile industrielle synthétique comprenant une toile tissée à partir de monofilaments,
ou une toile composée d'un pluralité de monofilaments enroulés en hélice et liés ensemble
par des broches, dans laquelle lesdits monofilaments comprennent des monofilaments
selon l'une des revendications 12 et 13.