U.S. patent application number 10/870611 was filed with the patent office on 2005-12-22 for hydroentangling process.
Invention is credited to Neogi, Amar N., Westland, John A..
Application Number | 20050278912 10/870611 |
Document ID | / |
Family ID | 35479041 |
Filed Date | 2005-12-22 |
United States Patent
Application |
20050278912 |
Kind Code |
A1 |
Westland, John A. ; et
al. |
December 22, 2005 |
Hydroentangling process
Abstract
A hydroentangling process comprising providing fractionated
cellulosic fibers having a length weighted average length of at
least 2.4 mm and less than 2% on a weight basis of fines having a
length no greater than 0.2 mm, forming said fibers into a mat,
applying jets of fluid under pressure to the pulp fibers to
entangle said fractionated cellulosic fibers. The fibers may be
entangled with a nonwoven web.
Inventors: |
Westland, John A.; (Auburn,
WA) ; Neogi, Amar N.; (Kenmore, WA) |
Correspondence
Address: |
WEYERHAEUSER COMPANY
INTELLECTUAL PROPERTY DEPT., CH 1J27
P.O. BOX 9777
FEDERAL WAY
WA
98063
US
|
Family ID: |
35479041 |
Appl. No.: |
10/870611 |
Filed: |
June 16, 2004 |
Current U.S.
Class: |
28/104 |
Current CPC
Class: |
D04H 1/492 20130101;
D04H 1/498 20130101; D04H 1/425 20130101 |
Class at
Publication: |
028/104 |
International
Class: |
D04H 001/46 |
Claims
1. A hydroentangling process comprising providing fractionated
cellulosic fibers having a length weighted average length of at
least 2.4 mm, forming said fibers into a mat, applying jets of
fluid under pressure to the pulp fibers to entangle said
fractionated cellulosic fibers.
2. The hydroentangling process of claim 1 in which the fractionated
cellulosic fibers have less than 2% on a weight basis of fines
having a length no greater than 0.2 mm.
3. The hydroentangling process of claim 1 in which the fractionated
cellulosic fibers have a length weighted average length of at least
3.5 mm.
4. The hydroentangling process of claim 3 in which the fractionated
cellulosic fibers have less than 2% on a weight basis of fines
having a length no greater than 0.2 mm.
5. The hydroentangling process of claim 1 in which the fractionated
cellulosic fibers have a length weighted average length in the
range of 2.4 mm to 3.8 mm.
6. The hydroentangling process of claim 5 in which the fractionated
cellulosic fibers have less than 2% on a weight basis of fines
having a length no greater than 0.2 mm.
7. The hydroentangling process of claim 1 in which there is an
increase in pressure as the web passes through the fluid jets.
8. The hydroentangling process of claim 1 in which the pressure is
under 1000 psi.
9. A hydroentangling process comprising providing a non-woven web,
laying fractionated cellulosic fibers having a length weighted
average length of at least 2.4 mm on the web, applying jets of
fluid under pressure to the pulp fibers to entangle the
fractionated cellulosic fibers with the web.
10. The hydroentangling process of claim 9 in which the
fractionated cellulosic fibers have less than 2% on a weight basis
of fines having a length no greater than 0.2 mm.
11. The hydroentangling process of claim 9 in which the
fractionated cellulosic fibers have a length weighted average
length of at least 3.5 mm.
12. The hydroentangling process of claim 11 in which the
fractionated cellulosic fibers have less than 2% on a weight basis
of fines having a length no greater than 0.2 mm.
13. The hydroentangling process of claim 9 in which the
fractionated cellulosic fibers have a length weighted average
length in the range of 2.4 mm to 3.8 mm.
14. The hydroentangling process of claim 13 in which the
fractionated cellulosic fibers have less than 2% on a weight basis
of fines having a length no greater than 0.2 mm.
15. The hydroentangling process of claim 9 in which there is an
increase in pressure as the web passes through the fluid jets.
16. The hydroentangling process of claim 9 in which the pressure is
under 1000 psi.
17. The hydroentangling process of claim 9 in which said nonwoven
web is made of fibers selected from the group consisting of
polyester, polypropylene, rayon, lyocell, and aramid fibers and
mixtures thereof.
Description
BACKGROUND OF THE INVENTION
[0001] The oldest technique for consolidating a web is mechanical
bonding. The fibers are entangled to give strength to the web. One
method of entangling the fibers is spunlacing. Spunlacing is also
known as hydroentanglement, jet entanglement, water entangled,
hydraulically needled or hydraulically loomed. In spunlacing high
pressure jets of water strike a web so that the fibers in the web
become entangled and form a nonwoven web. The jets are usually
perpendicular to the web but may be angled in order to provide
different properties to the web.
[0002] The web may be formed by airlaying the fibers onto a moving
belt to form a mat and passing the mat under a series of high
pressure jets that entangle the fibers. The fibers may be blended
or two or more webs may be airlaid before the spunlacing step.
[0003] There are variations on spunlacing. One variation is
airlacing. In airlacing, a mat of fibers is airlaid onto a nonwoven
web and the fibers in the air laid mat are hydroentangled with the
nonwoven mat. This process is disclosed in U.S. Patent Application
Publication US 2002/0168910, published Nov. 14, 2002, and in U.S.
Pat. No. 5,009,747, issued Apr. 23, 1991. The process includes
fiber preparation, carding, pre-entanglement, air-laying,
spunlacing, drying and winding.
[0004] Airlacing is generally a combination of carding and
air-laying but can also include airlaying blended fibers or two or
more airlaid webs. The web is bonded by spunlacing so that the
fibers of the various layers are entangled to produce the web.
[0005] In the airlace process, the non-woven web is carried on a
conveyor. The cellulosic pulp fibers are deposited as a mat on the
web by means of a stream of air. A second web may be placed on the
fiber mat, and the entire composite mat may be compacted if
desired.
[0006] In either spunlacing or airlacing, the main entanglement
takes place after final air-laid formation. The mat or composite
mat is bonded together by treatment with a series of water jets,
which entangles the pulp fibers into the non-woven web. The water
jets may act on one or both sides of the mat.
[0007] Cellulosic pulp fibers may be used in the formation of
spunlaced or airlaced mats A problem is that the fines or short
fibers normally found in cellulosic pulp reduce the efficiency of
the process. Some of the fines and short fibers are removed by the
water jets during the hydroentangling process. Water is reused in
the hydroentangling process and the fines and short fibers need to
be filtered out of the water stream before it is returned to the
water jets.
[0008] Another problem is that the fines and short fibers that
remain in the mat do not become attached to the non-woven web and
may dust from the formed product.
SUMMARY
[0009] In the present invention the fibers are separated into one
fraction in which the length weighted average fiber length is
longer than the length weighted average fiber length of the
starting pulp, and another fraction in which the length weighted
average fiber length is shorter than the length weighted average
fiber length of the starting pulp. These are referred to as the
long and short fiber fractions. The majority of the fines remain
with the short fiber fraction.
[0010] The long fiber fraction is used in a spunlaced process. The
long fiber fraction is made into a pulpboard or bale at the pulp
mill and transported to the plant where the spunlacing process take
place.
[0011] The fractionated cellulosic fibers are formed into a
hydroentangled mat. In one embodiment the fractionated cellulosic
fibers have a length weighted average fiber length of at least 2.4
mm. In another embodiment the fibers have a length weighted average
fiber length in the range of 2.4 mm to 3.5 mm. In another
embodiment the fibers have a length weighted average fiber length
of at least 3.5 mm. The mat of fibers may be entangled with a
nonwoven web or sandwiched between and entangled with nonwoven
webs.
[0012] This use of this long fiber fraction has a number of
benefits when compared to using the entire pulp material. The
energy needed to fiberize a pulp sheet or bale having only a long
fiber fraction is less than the energy required to fiberize a pulp
sheet or bale of the prefractionated pulp. There is less loss of
fiber in the hydroentangling process when only the long fiber
fraction is used giving a more efficient process. The process is
also more efficient because with the reduced amount of fines and
short fibers being recycled through the process there is less time
needed to clean and maintain filters. The airlaced product is
improved due to greater adhesion between the long fibers and the
non-woven web.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic view of apparatus for spunlacing a mat
of fibers.
[0014] FIG. 2 is a schematic view of apparatus for airlacing fibers
into a web.
DETAILED DISCUSSION
[0015] FIG. 1 shows an apparatus for spunlacing a mat of fibers.
The mat 10 is carried onto a conveyor 12 and passes under a series
of water jets 14, 16, 18 and 20. The water jets are usually at
increasing water pressure. There is a vacuum chamber 22 underneath
the conveyor 12. The water from the jets 14, 16, 18 and 20 pass
through the mat 10 entangling the fibers. The water is pulled from
the mat by the vacuum in chamber 22. The mat of entangled fibers
10' is transported into the dryer section 24 and dried. Dryer cans
26 are shown. The mat is then rolled up or boxed for shipment.
[0016] FIG. 2 shows airlacing. The apparatus would be the same as
the apparatus in FIG. 1. The difference between FIGS. 1 and 2 is
the web 30. The water jet 32, which is one of a series of water
jets, displaces the fibers in the mat 10" downwardly and entangles
the fibers with the web 30. The composite web is then dried as
shown in FIG. 1.
[0017] The pulp fibers that may be used are mechanical pulp fibers,
thermomechanical pulp fibers, chemithermomechanical pulp fibers,
and chemical pulp fibers made from either kraft or soda processes.
The pulp fibers can be bleached or unbleached. The pulp fibers can
be from hardwoods or softwood or combinations of hardwoods and
softwoods. The pulp fibers can be dried or never dried.
[0018] In these examples southern pine pulp was used, but any wood
pulp can be separated in the same fashion and used. The criteria
for pulp selection is based on being able to produce a long fiber
fraction in which the length weighted average fiber length is
greater than or equal to 2.4 mm. In one embodiment the long fiber
fraction has a length weighted average fiber length in the range of
2.5 to 3.8 mm. These fibers would be used in a spunlaced or
airlaced process.
[0019] The length weighted average fiber length (LWAFL) is
determined by the following formula:
LWAFL=.SIGMA.(l.sup.2.sub.x*n.sub.x)/.SIGMA.(l.sub.x*n.sub.x)
[0020] where l=bin median length, n=the bin fiber count and x=bin
#.
[0021] The pulp fibers may be blended with other fibers including
other pulp fibers, may be in layers including layers of other pulp
fibers or layers of other types of fibers. These fibers may be
spunlaced or placed on a nonwoven web or between nonwoven webs and
airlaced. The nonwoven webs may made of polyester, polypropylene,
rayon, lyocell or aramid fibers.
[0022] In one embodiment the pulp fibers in the mat would have a
length weighted average fiber length is greater than or equal to
2.4 mm. In another embodiment the pulp fibers in the mat would have
a length weighted average fiber length in the range of 2.4 to 3.8
mm. In another embodiment the pulp fibers have a length weighted
average fiber length greater than or equal to 3.5 mm. The pulp
fibers would have less than 2% by weight fines as defined
below.
[0023] In the following examples the fiber lengths and percent
fines was determined using a Fiber Quality Analyzer (Optest
Equipment Inc., Hawksbury, Ontario, Canada). Fines are determined
by the Fiber Quality Analyzer as fibers with a length less than 0.2
mm.
[0024] In the following examples the following terminology is used.
The starting pulp is an unfractionated commercial Southern pine
pulp fiber from the Weyerhaeuser Plymouth, North Carolina pulp
mill. It is designated PL416. It may be in a dried pulp sheet form
PS PL416, a never dried form ND PS416, or a slushed form S PL416.
The difference in these forms is the amount of water with the fiber
known as the consistency of the fiber. The fiber lengths and the
weight percentages of each fiber length will be the same within the
usual manufacturing tolerances.
[0025] This starting pulp will be fractionated into a long fiber
fraction (LF) and a short fiber fraction. The fractionation will be
either by a Bauer-McNett fractionator resulting in a Bauer-McNett
long fiber fraction BM LF or by a Bird Screen resulting in a Bird
Screen long fiber fraction BS LF.
[0026] PS PL416 was fractionated using a Bauer-McNett fractionator.
The Bauer-McNett fractionator was set up with screens of +12, +28,
+48, +100, +200 and -200. The material from the +12 and +28 screens
were combined for the long fiber fraction, while the remaining
fractions were combined for the short fiber fraction.
[0027] ND PL416 was fractionated using a Bird Screen. The Bird
Screen used was a Bird Model 100, with a 0.040" holes in the
basket. In the Bird Screen trials the fiber was separated into a
17% short fiber fraction and an 83% long fiber fraction. The ND
PL416 was diluted to 1.25% consistency and delivered to the screen
at about 40 psi. The accepts flow rate was 100 gpm. This resulted
in an accepts stream at 0.25% and a rejects stream at 1.5%.
[0028] The long fiber fraction and the PL416 pulp were made into
12".times.12" handsheets with a basis weight of 750 g/m.sup.2. The
fiberization energy was determined using a Kamas hammermill. The
long fiber pulp fraction has a lower fiberization energy than the
unfractionated fiber.
[0029] The results are shown in Table 1.
1TABLE 1 Length Weighted Average Fiber Percent fines, Fiberization
Sample length, mm % energy, kj/kg Bauer-McNett PL416 2.33 4.8 72
Long fiber fraction 3.73 1.1 23 Short fiber fraction 1.01 14.4 Bird
Screen PL416 2.29 5.0 123 Long fiber fraction 2.46 2.8 101 short
fiber fraction 1.38 13.8
[0030] Samples of the BS LF fibers, the ND PL416 fibers from the
Bird Screen trials and S PL416 fibers were made into 12".times.12"
handsheets with a basis weight of 750 g/m.sup.2. This approximates
the basis weight of commercial pulp board. The handsheets were
tested for Mullen burst and Burst index using TAPPI method T403
om-97, and tensile properties using TAPPI method T494 om-96. The
data is shown in Table 2. As can be seen in the Table, the long
fiber fraction had lower kamas fiberization energy, mullen, burst,
tensile index and tensile energy absorption (TEA). The ND PL416 was
nearly the same as the S PL416.
2 TABLE 2 Property S PL416 BS LF ND PL416 Kamas energy, kJ/g 75 65
79 Mullen burst, kPa 1587 1503 1545 Burst index, kN/g 1.87 1.84
1.88 Tensile index, Nm/g 10.62 9.65 10.35 TEA, J/m.sup.2 223 189
251
[0031] The BS LF fiber was converted to a pulp board on a Noble
& Wood pilot paper machine. This BS LF pulp board and PL 416
pulp board were then fiberized using a Fitz hammermill. The pulp
fibers were then compared for runnability or through-put on a
Dan-Web air laid machine. The pulps were hand feed into both sides
of the distribution head of the Dan Web machine. The load on the
distribution rotor in the head was monitored, and maintained at a
level that represented a feed rate that was about 90% of the
maximal feed rate for the system. The forming wire was run at a
constant speed. Under these conditions the through-put can be
measured by monitoring the basis weight of the web. The results of
the trials are given in Table 3. As can be seen, the basis weight
of the BS LF pulp was greater than PL416 pulp indicating a higher
through-put for the BS LF pulp.
3 TABLE 3 basis weight g/m.sup.2 energy hz density g/cm.sup.2
caliper mm PL416 140 0.618 0.0352 4.185 BS LF 187 0.606 0.0393
4.757
[0032] The BS LF board and PL416 pulp were used in a test of the
applicability of the long fiber fraction for improvements to the
airlaced process. The two pulps were airlaid into a web of 100
g/m.sup.2 using an M&J air laid line. This was layered onto a
30 g/m.sup.2 carded polyester web. This composite was then run
through spunlacing equipment at North Carolina University, Raleigh,
N.C. The hydroentagling was done by passing under three water jets
with increasing pressure at each jet. Three different pressure
regimes were conducted to determine the effect of pressure on the
pulp fibers. Generally lower water pressures are used to
hydroentangle wood pulp fibers because of the potential loss of
fiber. The web was oriented such that the water jets impinged on
the wood pulp side of the web.
[0033] The three pressure regimes used in the water jet heads
were:
[0034] (a) 200 pounds per square inch (psi) in the first head, 400
psi in the second head and 800 psi in the third head (200/400/800).
This is equivalent to approximately 14/27/54 bars.
[0035] (b) 200 pounds per square inch (psi) in the first head, 600
psi in the second head and 1000 psi in the third head
(200/600/1000). This is equivalent to approximately 14/41/68
bars.
[0036] (c) 200 pounds per square inch (psi) in the first head, 600
psi in the second head and 1200 psi in the third head
(200/600/1200). This is equivalent to approximately 14/41/82
bars.
[0037] The basis weight loss was determined for each of these
regimes for both BS LF fiber and PL416 fiber. The results are shown
in Table 4.
4 TABLE 4 100/400/800 200/600/1000 200/600/1200 PL416 20% 29% 36%
BS LF 8% 5% 15%
[0038] The long fiber may be used in hydroentangling as shown.
[0039] In a pulp mill unbleached pulp from brownstock system or
bleached pulp from the bleaching system or mechanical pulp may be
diluted and sent to a screening system. The type and size of screen
will depend on the kind or amount of fractionation. A typical
screen that may be used is the Kandant Black Clawson model 400 UVC
with 590 rpm motor. The size of motor may vary. An appropriate
sized pump would be used to carry the pulp from the dilution tank
to the screen.
[0040] In a pulp mill with an associated paper machine the short
fibers and fines could be used for paper furnish, replacing refined
fibers. The short fiber fraction should have a length weighted
average fiber length of 1.5 mm or less. The short fibers and fines
need not be refined in order to be used.
[0041] Those skilled in the art will recognize that the present
invention is capable of many modifications and variations without
departing from the scope thereof. Accordingly, the detailed
description set forth above is meant to be illustrative only and is
not intended to limit, in any manner, the scope of the invention as
set forth in the appended claims.
* * * * *