U.S. patent application number 11/010392 was filed with the patent office on 2005-08-04 for papermaking press felt and papermaking press apparatus.
This patent application is currently assigned to ICHIKAWA CO., LTD.. Invention is credited to Kobayashi, Yasuhiko, Oda, Hiroyuki, Onikubo, Akira.
Application Number | 20050167069 11/010392 |
Document ID | / |
Family ID | 34525514 |
Filed Date | 2005-08-04 |
United States Patent
Application |
20050167069 |
Kind Code |
A1 |
Kobayashi, Yasuhiko ; et
al. |
August 4, 2005 |
Papermaking press felt and papermaking press apparatus
Abstract
A papermaking press felt includes a plurality of base materials
of an identical or a different type; and a fiber web layered on one
or both faces of at least one of the base materials and integrally
entwined therewith by needling. At least one of the base materials
is a woven fabric including a machine direction (MD) yarn and a
cross-machine direction (CD) yarn, such that one thereof is a twine
made from a filament having a fineness of 50 to 250 dtex, and the
other thereof is a single yarn having a fineness of 50 to 600
dtex.
Inventors: |
Kobayashi, Yasuhiko; (Tokyo,
JP) ; Oda, Hiroyuki; (Tokyo, JP) ; Onikubo,
Akira; (Tokyo, JP) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Assignee: |
ICHIKAWA CO., LTD.
|
Family ID: |
34525514 |
Appl. No.: |
11/010392 |
Filed: |
December 14, 2004 |
Current U.S.
Class: |
162/358.2 ;
139/383B; 162/900 |
Current CPC
Class: |
D21F 7/083 20130101;
D21F 3/045 20130101 |
Class at
Publication: |
162/358.2 ;
162/900; 139/383.00B |
International
Class: |
D21F 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 2003 |
JP |
P.2003-416156 |
Oct 29, 2004 |
JP |
P.2004-315124 |
Claims
What is claimed is:
1. A papermaking press felt, comprising: a plurality of base
materials of an identical or a different type; and a fiber web
layered on one or both faces of at least one of the base materials
and integrally entwined therewith by needling; wherein at least one
of the base materials is a woven fabric including a machine
direction (MD) yarn and a cross-machine direction (CD) yarn, such
that one thereof is a twine made from a filament having a fineness
of 50 to 250 dtex, and the other thereof is a single yarn having a
fineness of 50 to 600 dtex.
2. The papermaking press felt as claimed in claim 1, wherein the
woven fabric is woven with an end portion thereof closed, and the
woven fabric is wound a plurality of times to thus form a plurality
of fabric layers, such that the gap between the aligned twines is
filled by the flattening effect of the twine.
3. The papermaking press felt as claimed in claim 2, wherein the
woven fabric is a plain woven fabric.
4. The papermaking press felt as claimed in claim 1, of the first
press apparatus; wherein at least one of a pick-up felt and a
bottom felt of the first press apparatus and a top felt and a
bottom felt of the second press apparatus includes the one of
papermaking press felts. wherein the woven fabric is a multiwoven
fabric including a double-woven or a thicker structure, and the gap
between the aligned twines forming the multiwoven fabric is filled
by the flattening effect of the twine.
5. The papermaking press felt as claimed in claim 1, wherein the
twine is a loosely twisted twine given a final twist of 30 to 100
times per meter, with a ratio of a preliminary twist against the
final twist in a range of 1.2 to 1.4.
6. The papermaking press felt as claimed in claim 1, wherein either
of the machine direction (MD) yarn or a cross-machine direction
(CD) yarn constituting the woven fabric is a soluble filament.
7. A papermaking press apparatus, comprising: a pressing section
including a papermaking press felt; wherein the paper making press
felt includes: a plurality of base materials of an identical or a
different type, and a fiber web layered on one or both faces of at
least one of the base materials and integrally entwined therewith
by needling; and at least one of the base materials is a woven
fabric including a machine direction (MD) yarn and a cross-machine
direction (CD) yarn, such that one thereof is a twine made from a
filament having a fineness of 50 to 250 dtex, and the other thereof
is a single yarn having a fineness of 50 to 600 dtex.
8. A papermaking press apparatus; comprising: two pieces of
papermaking press felts that hold a wet paper web therebetween to
dewater from the wet paper web; wherein at least one of the
papermaking press felts includes: a plurality of base materials of
an identical or a different type, and a fiber web layered on one or
both faces of at least one of the base materials and integrally
entwined therewith by needling; and at least one of the base
materials is a woven fabric including a machine direction (MD) yarn
and a cross-machine direction (CD) yarn, such that one thereof is a
twine made from a filament having a fineness of 50 to 250 dtex, and
the other thereof is a single yarn having a fineness of 50 to 600
dtex.
9. The papermaking press apparatus as claimed in claim 8, further
comprising: a first press apparatus which holds a wet paper web
with two pieces of felts for dewatering therefrom; and a second
press apparatus installed on a downstream side of the first press
apparatus; wherein at least one of a pick-up felt and a bottom felt
of the first press apparatus and a top felt and a bottom felt of
the second press apparatus includes the one of papermaking press
felts.
10. The papermaking press apparatus as claimed in claim 8, further
comprising: a first press apparatus which holds a wet paper web
with two pieces of felts for dewatering therefrom; and a second
press apparatus installed on a downstream side of the first press
apparatus; wherein each of a pick-up felt and a bottom felt of the
first press apparatus and a top felt and a bottom felt of the
second press apparatus includes the one of papermaking press
felts.
11. The papermaking press apparatus as claimed in claim 8, further
comprising: a first press apparatus which holds a wet paper web
with two pieces of felts for dewatering therefrom; wherein the one
of papermaking press felts is installed in the first press
apparatus.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a papermaking press felt
(hereinafter simply referred to as "felt" as the case may be) and a
papermaking press apparatus to be used in a papermaking machine.
More particularly, the present invention relates to a papermaking
press felt to be pressed in a pressing section of the papermaking
machine so as to squeeze water out of a wet paper web, and to a
papermaking press apparatus.
[0003] 2. Background Art
[0004] A papermaking machine is provided with a papermaking press
apparatus (hereinafter simply referred to as "press apparatus" as
the case may be), which dewaters a wet pulp (wet paper web) while
it presses in its pressing section formed in a paper layer forming
apparatus. Moisture in the wet paper web is squeezed out by
applying a pressure thereto with the press apparatus.
[0005] For example, FIG. 4 schematically shows a configuration of a
pressing section 700 of a conventional papermaking machine, wherein
a wet paper web (wet pulp) W transferred from a wire section 400 on
the side of the paper layer forming apparatus is introduced to the
pressing section side via a suction pick-up roll 701, and
transferred to a first press 1P by a pick-up felt.
[0006] Among the functions of the papermaking press felt, squeezing
water from a wet paper web is performed such that water is
transferred into the felt by a pressure while the wet paper web
passes between a pair of press rolls, and the water in the felt is
either discharged through a rear face of the felt, or aspired by a
suction box of the papermaking machine, to then be discharged out
of the felt system. Accordingly, water permeability and a function
to recover the original shape instead of remaining flattened
(durability against flattening) upon relief from the pressure are
essential factors required from the felt. Also, the dewatering
function based on such factors has to be maintained undegraded from
an initial stage of use.
[0007] Also, among the functions of the papermaking press felt,
when performing the feeding function of the wet paper web, the
pick-up felt 101 aspires the wet paper web (wet pulp) from the wire
section 400 via the suction pick-up roll 701 for transferring the
same to the pressing section side, therefore durability of the
water permeability is required, and also surface smoothness is
important to ensure that the wet paper web W sticks to the felt and
is kept from coming off.
[0008] Regarding the surface smoothing function (smoothness) of the
papermaking press felt for the wet paper, it is necessary to
upgrade the surface smoothness of the papermaking press felt in the
posterior steps 3P or 4P of the pressing section, so as to minimize
a difference between a contact area of the wet paper web W with the
roll and that with the felt.
[0009] Therefore, the felt is required to be in well balanced for
all these functions of dewatering, recovery against compaction and
surface smoothing, in each section.
[0010] Most of papermaking press felts generally used are either of
a batt-on-base type or batt-on-mesh type, constituted of a woven
fabric on which a staple fiber batt web is planted by a
needle-punch method.
[0011] Referring to FIG. 1, a structure of a popular felt will be
described. A papermaking press felt 10 is composed of a base
material 20 constituted of a woven fabric or the like and a staple
fiber layer 30 integrally entwined with the base material 20 by
needle-punching, and formed in an endless shape. The base material
20 is provided for securing a mechanical strength of the felt 10,
and a fabric woven with an MD yarn 22 and a CD yarn 21 is employed
in FIG. 1.
[0012] The felt 10 is utilized in a pressing section (FIG. 4) of
the papermaking machine as 101 to 104, as already stated. More
specifically, in the pressing section the felt is disposed over a
plurality of guide rolls with a tension applied thereto. And a high
pressure is applied to the felt and a wet paper web in the press
section constituted of a pair of press rolls or of a press roll and
a shoe, so as to squeeze water out of the wet paper web. Here, the
felt 10 runs in conformity with a 101. The first press 1P is
constituted as a double felt press through which the wet paper W
passes between a first press roll (grooved roll) 703 and a suction
press roll 702 via the pick-up felt 101 and a bottom felt 102, so
that water is squeezed out of the wet paper W through a nip of
these rolls 702 and 703 via the felts 101 and 102. Then, the wet
paper W is transferred to a second press 2P by the suction press
roll 702, to be dewatered by a nip of a second press roll (grooved
roll) 704 and of a center roll 705. The wet paper web W further
sticks to a surface of the center roll 705 to be thereby
transferred to a third press 3P, and is again dewatered while
passing between a nip portion of a third press roll (grooved roll)
706 and the center roll 705, together with a third press felt (P3
press felt) 103.
[0013] The wet paper W which has thus lost a considerable amount of
water is further transferred to a fourth press 4P by a paper roll
708 and a fourth press felt 104, to be dewatered between a nip
portion of a fourth press roll (grooved roll) 707 and a P4 top roll
709, and to finish the watering process in the pressing section.
Then, the wet paper web W is transferred from the 4P top roll 709
to a subsequent drying process where a drier cylinder 710 and so
forth are installed. Basic functions of the papermaking press felt
include squeezing water from a wet paper web (dewatering),
providing surface smoothness of the wet paper web (smoothness), and
feeding the wet paper web forward (wet paper web transference).
[0014] rotation of the press roll.
SUMMARY OF THE INVENTION
[0015] An environment where felt is used is becoming more and more
harsh in recent years, because of an increase in operating speed of
a papermaking machine associated with the progress in production
efficiency of the paper and an increase in pressure in a press
section. Accordingly, such an increase in the speed of a
papermaking machine and in pressure of a roll or a shoe in a
pressing section for improving productivity, which is the latest
trend with respect to papermaking machines, has incurred a drawback
that the papermaking press felt becomes flattened by the high
pressure and thereby loses its water permeability and capability of
recovery against compaction, thus significantly degrading its
dewatering performance.
[0016] Therefore, with respect to the water permeability and
durability in dewatering performance based on the recovering
capability against compaction, in particular among the functions
required from the felt, a still higher performance is being
required for use in a high-performance papermaking machine.
[0017] With an object to solve the above-mentioned problem, various
structures have been proposed. For example, it has been proposed to
increase a proportion of the base material in the felt, so as to
prevent flattening of the felt. As a method of increasing the
proportion of the base material, JP-A-2003-13385 and JP-A-6-280183
disclose a technique of stacking a plurality of layers of, for
example, a double-woven endless base fabric, or a plurality of
fabrics of a certain length joined together at the respective end
portions thereof to constitute an endless structure, layering a
staple fiber thereon, and integrally entwining the base fabric and
the staple fiber layer by needling.
[0018] Meanwhile, during an initial period of use in a papermaking
machine, the felt structure repeats compaction and recovery, to
thereby gradually reduce its thickness. Accordingly, it is well
known that the staple fiber of the felt structure is susceptible to
flattening. This is because the staple fiber, which is finer than
the base material, in felt structure becomes still finer due to the
repeated compaction. In an ordinary felt, a staple fiber of 1 to 50
dtex, and more preferably that of 3 to 30 dtex is employed. In the
case of employing a staple fiber having a thicker fineness than
such values or a felt having a thinner staple fiber layer,
flattening of the felt can be restrained, however surface smoothing
performance for a wet paper web, which is one of the major
functions of the felt, is degraded.
[0019] Here, a conventional technique for improving the surface
smoothing performance for a wet paper web is known, for example, in
JP-A-2003-13385. This literature discloses a felt structure
including a nonwoven fabric formed by arranging yarns only in a
transverse direction substantially in parallel, and interposed
between two or more fabric layers. The interposed nonwoven fabric
serves to alleviate an influence of a knuckle portion (ups and
downs of the yarn at an interlacing point of an MD yarn and a CD
yarn) of the woven fabric or the MD yarn, to the surface smoothing
effect for the wet paper web. However, since a felt structure
including such nonwoven cloth is heavier in basic weight, the
dewatering performance and ease of installment are degraded.
[0020] Also, utilization of a flat yarn has been proposed, for
improving the dewatering performance. An example is disclosed in
U.S. Pat. No. 5,651,394, wherein a twine made from a flat (having
an oval cross-section) monofilament yarn is employed for
constituting a woven fabric of a papermaking press felt, so as to
improve ease of installment in a papermaking machine due to having
less rigidity than a conventional woven fabric including a twine of
a circular monofilament yarn, and dewatering performance, because
of an increased volume of the woven fabric. This literature also
describes that since such felt can absorb vibration of the roll,
vibration of the papermaking machine can be reduced. However, the
twine made from such flat monofilament yarn has a bulky shape and
moreover a distortion, which degrades the surface smoothing
performance for the wet paper web.
[0021] It is an object of the present invention to provide a
papermaking press felt having an upgraded dewatering performance
which grants excellent surface smoothness to a wet paper web, and
particularly a papermaking press felt appropriate for high-speed
running, yet capable of providing a smooth surface to the wet paper
web, and a papermaking press apparatus provided with such felt.
[0022] Specifically, it is an object of the present invention to
solve the above-mentioned problems by providing a papermaking press
felt that offers an upgraded dewatering performance (water
permeability), durability against flattening and surface smoothing
performance for a wet paper web, and a press apparatus.
[0023] Upon studying a felt structure that fits the above-mentioned
object, the present inventors have found that the object can be
achieved by employing a base material constituted of two (A and B)
or more layers, at least one base material B thereof is a woven
fabric formed of a twine and a single yarn having a specific
fineness, so that the twine turns to a flat cord when woven into
the fabric.
[0024] The present invention thus provides a papermaking press felt
comprising a plurality of base materials of an identical or a
different type; and a fiber web layered on one or both faces of the
base material and integrally entwined therewith by needling;
wherein at least one of the base materials is a woven fabric
constituted of a machine direction (MD) yarn or a cross-machine
direction (CD) yarn, such that one thereof is a twine made from a
filament having a fineness of 50 to 250 dtex, and the other thereof
is a single yarn having a fineness of 50 to 600 dtex.
[0025] Preferably, the above-mentioned papermaking press felt
includes a woven fabric having a closed end, more preferably a
plain woven fabric, which is wound a plurality of times to thus
form a plurality of fabric layers, such that the gap between the
aligned twines is filled by the flattening effect of the twine, to
thereby improve the surface smoothing performance for the wet paper
and resistance against flattening.
[0026] Preferably, a multiwoven fabric constituted of a
double-woven or a thicker structure, is employed as the base woven
fabric, so that the gap between the aligned twines constituting the
multiwoven fabric is filled by the flattening effect of the
twine.
[0027] Further, for facilitating the twine to turn to a flat cord,
it is effective to form a loosely twisted twine by giving a final
twist of 30 to 100 times per meter, with a ratio of a preliminary
twist against the final twist in a range of 1.2 to 1.4.
[0028] Also, to easily narrow the gap between the twines, it is
effective to employ a soluble filament yarn as either the MD yarn
or CD yarn, to implant thereon a staple fiber by needle-punching,
and then to dissolve the single yarn for removal which further
facilitates narrowing the gap between the twines.
[0029] The present invention also provides a papermaking press
apparatus, in which the above-mentioned papermaking press felt is
employed at least as one of the papermaking press felts for the
pressing section.
[0030] Especially with respect to a closed draw type papermaking
press apparatus designed to hold the wet paper between two pieces
of felts for dewatering, which imposes a harsh condition because of
a high-speed feeding and a high pressure, a superior resistance
against flattening and surface smoothing capability for the wet
paper web are required, however, since the papermaking press felt
according to the present invention can stand such harsh conditions
and maintain the superior dewatering capability to there by provide
a paper having an excellent surface smoothness, the present
invention is particularly suitable for a closed draw type
papermaking press apparatus.
[0031] The papermaking press felt according to the present
invention employs a twine thicker in fineness than a staple fiber
as either the MD yarn or the CD yarn, which can easily turn to a
flat cord when woven into a fabric, therefore a gap between the
twines in the woven fabric can be easily narrowed, and resultantly
a papermaking press apparatus provided with such felt offers a
superior surface smoothing capability for a wet paper web and
resistance against flattening.
[0032] In particular, when the felt is employed in a papermaking
press apparatus designed to hold the wet paper web between two
pieces of felts for dewatering, a prominent improvement in surface
smoothing capability for a wet paper web and resistance against
flattening can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The present invention may be more readily described with
reference to the accompanying drawings:
[0034] FIG. 1 is a schematic cross-sectional view showing a
conventional general-purpose papermaking press felt.
[0035] FIG. 2 is a schematic cross-sectional view showing a
papermaking press felt according to the examples 1 to 4 of the
present invention.
[0036] FIG. 3 is a schematic cross-sectional view showing a
papermaking press felt according to the comparative example 1.
[0037] FIG. 4 is a schematic drawing showing a press apparatus of a
papermaking machine.
[0038] FIG. 5 is a schematic drawing showing a press apparatus of a
papermaking machine in which the press felt according to the
present invention is installed.
[0039] FIG. 6 shows an apparatus for measuring compaction recovery
performance and resistance against flattening of a felt.
[0040] FIG. 7 shows an apparatus for measuring water permeability
coefficient of the felt.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] According to one embodiment of the invention, as a result of
weaving the fabric constituting the base material (B) with the
above-mentioned twine and single yarn, the twine obtains a flat
shape, and thereby a knuckle portion of the woven fabric becomes a
plane, and moreover the flat shape of the twine facilitates
narrowing a gap therebetween, by which the surface smoothing
performance can be upgraded despite having a reduced staple fiber
layer. Further, since the twine, which becomes flat, is thicker
than the staple fiber, the flattening of the felt as a whole can be
restrained.
[0042] Preferably, either of the MD yarn or the CD yarn is a twine
formed by twisting filaments of 50 to 250 dtex, more preferably 100
to 200 dtex in fineness. A thickness of the twine is not
specifically determined, however a twine of 500 to 3,000 dtex in
fineness is generally employed.
[0043] For further ensuring the effect of the embodiment that the
twine turns to a flat cord as a result of weaving the fabric with
the twine and single yarn having a specific fineness, it is
effective to form a loosely twisted twine by giving a final twist
of 30 to 100 times per meter, with a ratio of a preliminary twist
against the final twist in a range of 1.2 to 1.4. Employing such
loosely twisted twine facilitates narrowing a gap between the
twines constituting the woven fabric, since the twine easily turns
to a flat cord when woven into the fabric.
[0044] Here, in the case where the twine is twisted more than 100
times per meter either in the preliminary twist or final twist, the
twine becomes a tightly twisted twine, which is not appropriate for
achieving the advantage that the twine turns to a flat cord when
woven into the fabric. When the ratio of the preliminary twist
against the final twist is in a range of 1.2 to 1.4, the twine not
only easily turns to a flat cord when woven into the fabric, but
also attains a stable structure free from bumps or loosening. In
the case where the ratio of the preliminary twist against the final
twist deviates from the range of 1.2 to 1.4, the twine incurs
distortions and end downs in the woven fabric and is thereby
restrained from becoming flat.
[0045] Also, it is preferable that either of the MD yarn or the CD
yarn is a single yarn of 50 to 600 dtex, more preferably 100 to 400
dtex in fineness. Employing such single yarn as either of the
weaving yarns allows reducing an area occupied with a knuckle in
the woven fabric. This also leads to an improvement of the surface
smoothing performance for a wet paper web.
[0046] According to the embodiment of the invention, a felt is
provided wherein a gap between twines can be effectively narrowed
in a woven fabric, to thereby improve the surface smoothing
performance for a wet paper web and resistance against flattening.
Various methods may be employed for facilitating narrowing a gap
between the twines, one of which is employing a woven fabric having
a closed end, preferably a plain woven fabric, and winding such a
woven fabric a plurality of times to thus form a plurality of
fabric layers, such that the gap between the aligned twines is
filled by the flattening effect of the twine. Such a woven fabric
has an increased advantage that the twine in an upper fabric layer
can be so easily flattened that it fills a gap between the twines
in a lower fabric layer, and moreover the twine in the lower fabric
layer itself also easily becomes flat so as to narrow the gap
between the twines.
[0047] Also, in another embodiment intended for narrowing the gap
between the twines, a multiwoven fabric constituted of a
double-woven or a thicker structure, is employed as the base woven
fabric, so that the gap between the aligned twines constituting the
multiwoven fabric is filled by the flattening effect of the twine,
which further facilitates narrowing a gap between the twines of the
woven fabric, as in the case of the above-mentioned woven
fabric.
[0048] Also, for further facilitating the twine to turn to a flat
cord when woven into the fabric, and to fill the gap between the
aligned twines by the flattening effect, it is effective to reduce
the number of interlacing points of the MD yarn and the CD yarn in
the woven fabric. For such a purpose, the single yarn employed as
either the MD yarn or CD yarn may be a soluble filament, more
particularly a water-soluble filament yarn. Employing a woven
fabric constituted of such yarn, implanting thereon a staple fiber
by needle-punching, and then dissolving the single yarn for removal
further facilitates narrowing the gap between the twines.
[0049] Materials of the soluble filament yarn include a polyvinyl
alcohol, an acrylic, a polyester and so forth, among which the
water-soluble polyvinyl alcohol is preferable.
[0050] Except for the case of employing the soluble filament, a
nylon, a polyester and so forth are employed as materials of a
twine and the single yarn to weave the fabric, among which the
nylon is particularly preferable because of its superior strength
and durability.
[0051] Referring to FIG. 2, an embodiment of the present invention
will be described. To start with, a papermaking press felt 100
according to the present invention includes a base material 200 and
a staple fiber layer 300. The staple fiber layer 300 is formed by
integrally entwining the staple fiber with the base material 200 by
needle-punching. The base material 200 includes two base materials,
namely a base material A (210) and a base material B (220). One of
these 210 serves to secure a mechanical strength of the felt 100,
and various materials may be employed for constituting the same
without a specific limitation, as long as the material provides an
adequate strength. For example, a woven fabric constituted by
weaving the MD yarn 212 and the CD yarn 211 may be employed. While
two different types of the base materials 210 and 220 are layered
in FIG. 2, a similar material may be employed as long as the base
material B 220 satisfies the requirement of the present
invention.
[0052] The base material 210 may be a woven fabric constituted of a
MD yarn and a CD yarn having a narrower width than that of a felt
to be manufactured, which is spirally wound with adjacent edge
portions thereof joined to each other. Further, a woven fabric
constituted of a MD yarn and a CD yarn having substantially the
same width as that of a felt to be manufactured may be coaxially
wound, for constituting the base material. Also, apart from a base
material constituted of a woven fabric, a base material in which
the MD yarn is fixed with an adhesive, or in which the MD yarn and
the CD yarns are only layered without being woven may be
employed.
[0053] According to the present invention, another base material B
220 is layered on the base material A 210, so as to constitute an
entirety of the base material 200. The base material 220 is a woven
fabric constituted of a machine direction yarn (MD yarn) 222 and a
cross-machine direction yarn (CD yarn) 221, which are features of
the present invention. That is, either of the MD yarn or the CD
yarn is a twine made from a filament of 50 to 250 dtex in fineness,
and the other thereof is a single yarn of 50 to 600 dtex in
fineness, in the woven fabric.
[0054] The present invention also provides a papermaking press
apparatus in which the above-mentioned felt is installed. The felt
of the present invention may be applied to any type of papermaking
machine in addition to the one shown in FIG. 4, however, in the
case where the felt is employed in a closed draw type papermaking
press apparatus designed to hold the wet paper web W from both
sides with a top felt and a bottom felt and to transfer and press,
the advantage of the felt of the present invention can be more
effectively attained.
[0055] The closed draw type press apparatus is, as shown in FIG. 5,
constituted so as to hold the wet paper web W between the top felt
101 and the bottom felt 102 for transference and pressing, in order
to sustain the high-speed feeding performance for the wet paper. As
a result, the wet paper is assuredly retained stably (without
break) between the felts or on the felt at a high-speed, throughout
the entire travel in the pressing section.
[0056] The papermaking press apparatus 800 shown in FIG. 5
represents a configuration wherein two pressing apparatuses, namely
a first press apparatus 810 and a second press apparatus 820
provided on a downstream side thereof, are installed in series
along a feeding direction of the wet paper web W, and the first
press apparatus 810 is provided with a first roll 811 and a first
shoe press 812. The second press apparatus 820 is provided with a
second roll 821 and a second shoe press 822.
[0057] In the first press apparatus 810, usually the shoe press
apparatus is employed which applies a higher pressure than a
conventional papermaking machine, because of which the pick-up felt
101 and the bottom felt 102 are prone to be flattened to thereby
lose the dewatering capability, however, employing the felt of the
present invention here results in significant improvement in the
dewatering performance.
[0058] In the case of the second press apparatus 820 also, since
the wet paper web W is held between the top felt 105 and the bottom
felt 106 for transference and pressing, it is desirable to employ
the felt of the present invention for the top felt 105 and the
bottom felt 106, to further ensure durability of dewatering
performance and surface smoothness of the wet paper web W.
[0059] Further, while FIG. 6 shows a papermaking press apparatus
constituted of two shoe press apparatuses installed in series, one
of the shoe press apparatuses may be substituted with a roll press
apparatus, or may be omitted. However, in any of the cases,
employing the felt of the present invention allows achieving a
superior performance in dewatering, surface smoothing and so
forth.
EXAMPLES
[0060] Hereunder, the present invention will be described in
further detail based on several examples. In all the examples,
another base material B (220, 230, 240, 250) respectively
representing a feature of the present invention is layered on the
base material A (210) so as to constitute an entirety of the base
material 200.
[0061] The base material A 210 is constituted as follows, in all
the examples in common.
[0062] Structure of the Base Material 210:
[0063] (1) MD Yarn and CD Yarn
[0064] The twines specified below have been employed in common, as
both of the MD yarn and the CD yarn.
[0065] (2) Twisting condition: "2/2/220" (the values respectively
correspond to "the number of preliminarily twisted filaments for
final twisting/the number of single filaments for preliminary
twisting/fineness of the single filament=dtex")
[0066] (3) Preliminary twisting: S-twist, 250 times per meter
[0067] (4) Final twisting: Z-twist, 160 times per meter
[0068] Both the preliminary twisting and the final twisting are
more than 150 times per meter, by which the twines are defined as
tightly twisted twines.
[0069] (5) Twisting ratio (preliminary/final): 1.56
[0070] (6) Weaving:
[0071] MD yarn: 120 rows/5 cm, CD yarn: 40 rows/5 cm 3/1 1/3
endless double woven
EXAMPLE 1
[0072] As shown in FIG. 2, a felt has been fabricated by layering
the following woven fabric 220 as the base material B on the base
material A (210) to constitute the base material 200, and further
forming the staple fiber layer 300 (11 dtex, 600 g/m.sup.2)
[0073] Structure of the Woven Fabric 220:
[0074] (1) MD yarn: The twine specified below has been
employed.
[0075] (a) Twisting condition: "2/2/220"
[0076] (b) Preliminary twisting: S-twist, 42 times per meter
[0077] (c) Final twisting: Z-twist, 30 times per meter
[0078] (d) Twisting ratio (preliminary/final): 1.40
[0079] (2) CD yarn: single yarn (fineness 330 dtex)
[0080] (3) Weaving:
[0081] MD yarn: 40 rows/5 cm, CD yarn: 34 rows/5 cm 3/1 plain
endless single woven
EXAMPLE 2
[0082] A felt of a similar structure to that of the example 1 has
been fabricated, except that the following woven fabric 230 has
been employed as the base material B instead of the woven fabric
220. In other words, 230 is layered instead of 220 in FIG. 2.
[0083] Structure of the Woven Fabric 230:
[0084] (1) MD yarn, CD yarn: The same as those of example 1.
[0085] (2) Weaving:
[0086] MD yarn: 40 rows/5 cm, CD yarn: 34 rows/5 cm
[0087] 3/1 plain single woven with an end closed, wound twice to
constitute the layered woven fabric 230.
EXAMPLE 3
[0088] A felt of a similar structure to that of the example 2 has
been fabricated, except that the woven fabric 240 in which the MD
yarn and the CD yarn are replaced with each other has been employed
as the base material B, instead of the woven fabric 230. In other
words, 240 is layered instead of 220 in FIG. 2.
EXAMPLE 4
[0089] The base material 200 has been constituted by layering the
woven fabric 250 serving as the base material B, in which a
water-soluble PVA single yarn is employed as the CD yarn, on the
base material 210 (250 is layered instead of 220 in FIG. 2). Then
the staple fiber has been integrally entwined with the base
material 200 by needle-punching so as to fabricate the papermaking
press felt 1000, after which the CD yarn has been dissolved by hot
water refining in a subsequent process, so that a layer 250 only
including the MD yarn remains on the base material 210.
[0090] Structure of the Woven Fabric 250:
[0091] (1) MD yarn: The same as the woven fabric 220 (example
1)
[0092] (2) CD yarn: Monofilament made of polyvinyl alcohol, 400
dtex
[0093] (3) Weaving: the same as example 2
COMPARATIVE EXAMPLE 1
[0094] As shown in FIG. 4, a woven cloth 260 constituted by
layering the same base material 210 on the base material 210 has
been employed, on which the staple fiber 300 has been layered as
the examples, so as to fabricate the felt.
[0095] Staple fiber has been implanted by needle-punching on the
woven fabrics prepared according to the above-mentioned examples 1
to 4 and the comparative example 1, and such needle-punched felts
have been refined in hot water and dried by hot air, to thereby
complete the papermaking press felt. Table 1 shows a structure of
the base material B in the respective examples.
1 TABLE 1 Staple fiber Structure of base material B layer Weaving
Basic weight Number MD yarn CD yarn structure (g/m.sup.2) Example 1
220 Twine of the Single yarn Plain endless 600 g/m.sup.2 present of
the single woven invention present fabric invention Example 2 230
Same Same Plain single Same woven fabric with an end closed, wound
twice Example 3 240 Single yarn of Twine of the Same Same the
present present invention invention Example 4 250 Twine of the
Water Same Same present soluble PVA invention single yarn according
to the present invention Comparative 210 Conventional Twine of the
Endless Same example twine present double woven invention
fabric
[0096] All these felts have been made with the same amount (basic
weight: g/m.sup.2) of staple fiber, and paper smoothness index,
compaction recovery and resistance against flattening of these
papermaking press felts have been evaluated through the following
steps.
[0097] (1) Paper Smoothness Index
[0098] An inverse of a value obtained based on distribution of a
distance between a peak and a trough of a surface unevenness of the
papermaking press felt, according to JIS B061-1982 (surface
roughness). The higher the index indicates, the smaller the
distance distribution is, and therefore the smoothness is
superior.
[0099] (2) Compaction Recovery, Resistance Against Flattening
[0100] The felts have been passed through an experimental apparatus
as shown in FIG. 6, and a thickness of the felts have been measured
by a sensor at an initial unpressed state, during compression by
press rolls and after release from the pressure, and the compaction
rate and recovery rate have been calculated by the following
formula, thus to evaluate the compaction recovery performance and
durability.
Compaction rate (%)=t.sub.1/t.sub.0.times.100
Recovery rate (%)=(t.sub.2-t.sub.1)/t.sub.1.times.100
[0101] (where t.sub.0: felt thickness at an initial state t.sub.1:
felt thickness when compressed t.sub.2: felt thickness immediately
after release from pressure)
[0102] The experimental apparatus is provided with a pair of press
rolls PR, PR, a plurality of guide rolls GR for supporting the felt
applying a certain tension thereto, a sensor (not shown) for
measuring a felt thickness when compressed by the press rolls, and
a second sensor (not shown) for measuring the felt thickness
immediately after being released from the pressure. The
experimental apparatus has been operated so as to generate a
pressure of 100 kg/cm and a felt driving speed of 1000 m/minute,
and the experiments have been continued for 120 hours.
[0103] Based on the values of the compaction rate and the recovery
rate obtained through the above measurement, an overall evaluation
of the resistance against flattening has been carried out with
respect to the examples and the comparative example, and the
results are shown below in relative points. Here, the value of the
example 1 is defined as 3 points, which is used as a reference such
that a higher point in other examples is regarded as good and a
lower point as poor, and that the higher the point is, the better
performance is considered to be achieved.
[0104] (3) Evaluation of Durability of Water Permeability (Water
Permeability Coefficient)
[0105] An experimental apparatus as shown in FIG. 7 has been
employed to impose a load of 30 kg on the felt which has been
dipped in water for an hour, and a time taken for passing 30 liters
of water from a front face of the felt to a rear face thereof has
been measured. Such measurement has been executed with respect to
specimens not subjected to the above-mentioned evaluation of
compaction recovery and resistance against flattening and the
specimens that have gone through the 120 hour test, and a variation
of water permeability (water permeability coefficient) has been
worked out based on the respective measured values utilizing the
following formula, so as to evaluate the durability of water
permeability. The higher the coefficient is, the lower the
durability of water permeability.
Water permeability coefficient (%)=(water passing time of tested
specimens)/(water passing time of untested specimens).times.100
[0106] With respect to the felts fabricated according to the
examples and the comparative example, the measured physical
properties are shown in Table 2.
2 TABLE 2 Evaluation Resistance against flattening Total evaluation
Paper of smooth- Compac- resistance Water ness tion Recovery
against permeability index rate rate flattening coefficient Example
1 0.012 34% 28% 3 137% Example 2 0.015 37% 31% 5 121% Example 3
0.014 37% 31% 5 119% Example 4 0.020 35% 30% 4 123% Comparative
0.007 32% 26% 2 152% example
[0107] As is apparent in view of the results shown in Table 2, all
the papermaking press felts of the examples, provided with the
layered woven fabric constituted of the MD yarn and the CD yarn
such that either of the MD yarn or the CD yarn is a twine made from
a filament of 50 to 250 dtex in fineness, and the other thereof is
a single yarn of 50 to 600 dtex in fineness according to the
present invention, have achieved good points in both the paper
smoothness index and resistance against compaction, while the felt
according to the comparative example, provided with the base
material 210 in which the same twine is employed as the MD yarn and
the CD yarn has only shown a poor performance in both the paper
smoothness index and resistance against compaction. In addition,
regarding the felt of the example 4 in which the water-soluble
single yarn is employed as the CD yarn, since the CD yarn is
dissolved at an interlacing point of the MD yarn and the CD yarn
and no longer remains in the woven fabric, the felt achieves a
superior surface smoothness.
[0108] Based on such results, it is effective to employ the felt
according to the examples 2 and 3 as the pick-up felt of a
papermaking machine, because of the superior resistance against
flattening and durability in water permeability. By contrast, for
the posterior stages (3P, 4P), where surface smoothness is
particularly essential, it is effective to employ the felt
according to the example 4 which has achieved an excellent result
in paper smoothness index.
Industrial Applicability
[0109] The embodiment of the invention provides a felt having a
superior surface smoothing capability for a wet paper web and
resistance against flattening. In the case of employing such a felt
as a papermaking press felt, the surface smoothing capability for a
wet paper web can be maintained and flattening is restrained,
because of the superior compaction rate and recovery rate against a
pressure applied by a roll or a shoe during a papermaking process,
and resultantly the superior dewatering performance can be
maintained for a long period of time.
[0110] Also, employing a soluble filament yarn as either the
machine direction (MD) yarn or the cross-machine direction (CD)
yarn constituting the woven fabric results in producing a paper of
a superior surface smoothness.
[0111] The felt of the embodiment may be applied to various types
of papermaking machines, however, in the case where the felt is
employed in a closed draw type papermaking press apparatus, the
advantage in resistance against flattening and surface smoothing
performance for a wet paper can be duly attained despite the
high-speed operation.
[0112] Also, this type of press apparatus applies a higher pressure
than a conventional papermaking machine, because of which the felt
is prone to be flattened to thereby lose the dewatering capability,
however, employing the felt of the present invention having a
superior resistance against flattening allows maintaining a
high-level dewatering performance. In addition, degradation in
smoothness because of loss of direct contact between the wet paper
and the roll surface can also be overcome by employing the felt
according to the embodiment of the present invention. Thus, since
the felt of the present invention provides various advantages, the
felt can be appropriately employed as a high-performance felt,
under the current harsh operational conditions such as high speed
and high pressure.
* * * * *