U.S. patent number 3,644,170 [Application Number 04/883,947] was granted by the patent office on 1972-02-22 for fibrilating fibrous pulp stock in a gas stream.
Invention is credited to Teizo Mekata, Masaharu Shiraishi, Takashi Yoda.
United States Patent |
3,644,170 |
Mekata , et al. |
February 22, 1972 |
FIBRILATING FIBROUS PULP STOCK IN A GAS STREAM
Abstract
Pulp stock in the form of dehydrated pulp flakes having a
moisture content of between 20 and 50 percent is entrained in an
airstream and is fed into a fibrilator where it is subjected to a
three-dimensional turbulent flow resulting from the unidirectional
propulsive force of the airstream and centrifugal force caused by
rotating blades within the fibrilator. The flakes impinge upon one
another and when disintegrated are withdrawn from the fibrilator by
the unidirectional force of the airstream. The less fully
disintegrated flakes undergo mechanical impact with a toothed
surface in the fibrilator and are then withdrawn. The temperature
of the airstream may be controlled by a heat exchanger and the
moisture content thereof by valved water and steampipes connected
to the airstream carrying duct upstream of the fibrilator.
Inventors: |
Mekata; Teizo (Yoshiwara City,
Shizuoka-ken, JA), Yoda; Takashi (Yoshiwara City,
Shizuoka-ken, JA), Shiraishi; Masaharu (Yoshiwara
City, Shizuoka-ken, JA) |
Family
ID: |
12547013 |
Appl.
No.: |
04/883,947 |
Filed: |
December 10, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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598407 |
Dec 1, 1966 |
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Foreign Application Priority Data
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Jun 18, 1966 [JA] |
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41/39219 |
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Current U.S.
Class: |
162/21; 162/28;
241/5; 162/23; 162/261; 241/275 |
Current CPC
Class: |
D21B
1/12 (20130101) |
Current International
Class: |
D21B
1/00 (20060101); D21B 1/12 (20060101); D21d
001/38 () |
Field of
Search: |
;162/23,21,28,261,100
;241/275,260,299,188A,5,39,40 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bashore; S. Leon
Assistant Examiner: Tushin; R. H.
Parent Case Text
This is a continuation-in-part application of U.S. Pat. application
Ser. No. 598,407 filed Dec. 1, 1966 and now abandoned.
Claims
What is claimed is:
1. A process of fibrilating a pulp stock with high concentration,
which process comprises establishing a rapid unidirectional stream
in a gaseous phase exerting a propulsive force in a predetermined
direction, entraining a pulp stock in the form of dehydrated pulp
flake in said unidirectional stream to suspend the pulp flakes
therein, said pulp stock having a flake moisture concentration
between 20 and 50 percent, imparting to the suspension of said pulp
flakes a centrifugal force which is built up by a rotational force
having an axis of rotation substantially parallel to said
predetermined direction of said propulsive force for thereby
establishing a turbulent flow with combined propulsive and
centrifugal forces to cause said pulp flakes to impinge upon one
another and subject the pulp fibers therein to torsional and
frictional forces so as to be separated from one another as the
pulp flakes are disintegrated, withdrawing the disintegrated
portion of the pulp flakes from said turbulent flow under the
influence of said propulsive force, subjecting the remaining
portion of the pulp flakes to mechanical impact with a toothed
surface under the influence of said centrifugal force until said
remaining portion of the pulp flakes is reduced to small quantities
and withdrawing these small quantities from said toothed surface
under the influence of said propulsive force.
2. A process as set forth in claim 1, wherein said propulsive force
is about 0.4 to 1.5 kg./cm..sup.2.
3. A process as set forth in claim 2, wherein said centrifugal
force is built up with a rotational force resulting from a rotation
at about 3,000 to 6,000 r.p.m.
4. A process as set forth in claim 3, comprising adding moisture to
said unidirectional stream before the stream carries said pulp
flakes.
5. A fibrilator for fibrilating a pulp stock comprising a
cylindrical casing with closed ends, a rotatable shaft journaled to
said closed ends, a rotor on said shaft, a plurality of radial
blades on said rotor, a metallic lining attached to said casing on
the inner surface thereof, said lining having a toothed surface
extending halfway from the upstream end of said casing and merging
with an arcuately curved surface terminating at the downstream end
of said casing, an inlet duct connected to said casing at said
upstream end thereof to pass pulp flakes entrained in a rapid
unidirectional stream in a gaseous phase into said casing, an
outlet duct connected to said casing at the downstream end thereof
for discharging pulp flakes fibrilated in said casing, and a motor
driving said rotor via said shaft.
6. Apparatus for fibrilating a pulp stock in a gaseous phase, which
apparatus comprises means for conveying a supply of pulp stock in
the form of dehydrated pulp flakes, means for supplying a
unidirectional stream in a gaseous phase exerting a propulsive
force in a predetermined direction, means for feeding said pulp
flakes from said conveying means to said unidirectional stream at a
regulated rate, a fibrilator including a casing with an inner
toothed surface, a rotor mounted on a shaft and rotatable within
said casing about an axis of rotation substantially parallel to the
said predetermined direction of said propulsive force, means for
rotating said shaft, said rotor including a plurality of blades
radially mounted thereon for producing centrifugal force in said
casing, said fibrilator having an inlet for the introduction of the
unidirectional stream with the pulp flakes into the fibrilator, to
subject the flakes to a turbulent flow formed by the combination of
the propulsive and centrifugal forces in the fibrilator.
7. Apparatus as set forth in claim 6, wherein said means for
feeding said pulp flakes comprises a hopper to receive the pulp
flakes from said conveying means and a cylindrical casing with
closed ends communicating at its top with said hopper and at its
bottom with said means for supplying a unidirectional stream
through an outlet means.
8. Apparatus as set forth in claim 6, further comprising a valved
pipe for supplying air, a valve pipe for supplying water and a
valved pipe for supplying hot steam, said pipes all being
operatively connected with said means for supplying a
unidirectional stream for adjusting the moisture content and
temperature of said stream upstream of said means for feeding said
pulp flakes.
9. Apparatus as set forth in claim 8, further comprising means for
controlling the rate at which said pulp flakes are fed to said
unidirectional stream in accordance with the pressure of the
gaseous stream.
10. Apparatus as set forth in claim 8, further comprising means
operatively coupled with said valved pipe for supplying water to
control the amount of water introduced through said valved pipe in
accordance with the amount of water removed from the fibrilated
pulp stock downstream of said fibrilator.
11. Apparatus as set forth in claim 6, wherein said means for
supplying of unidirectional stream includes a heat exchanger for
adjusting the temperature in the said stream in a gaseous phase.
Description
The present invention is concerned, in general, with a papermaking
process and, in particular, with improvements in the method and
apparatus for the treatment of a pulp stock with high consistency
to suit the production of quality paper with sufficient
adaptability to printing.
It is the ordinary practice in the papermaking industry to have a
pulp stock subjected to a treatment known as beating after the pulp
stock has been passed through the cooking and bleaching processes.
The pulp stock thus subjected to the beating process is then
disintegrated into small quantities so that the fibers constituting
a major portion of the pulp stock are separated from one another,
shortened and bruised. In this beating process of a pulp stock, as
is well known, the concentration of the pulp stock is one of the
most important factors to increase the performance efficiency and
to reduce the production cost. Thus, having available an improved
method and apparatus adapted to treat a pulp stock with as high a
concentration as possible, say, of the order of 50 percent, has
doubtlessly been a matter of great consequence to the industry.
In the pulp refiners which have thus far seen wide service in the
treatment of a pulp stock, it is required to have the pulp stock
diluted in a liquid phase before the pulp stock is subjected to
beating. As a consequence, the concentration of the pulp stock is
usually limited to about 20 percent. This concentration of the pulp
stock could be increased to a certain extent, say, 10 percent or
so, provided suitable modifications are made to the method and
apparatus used. As long as, however, the necessity of having the
pulp stock diluted prior to the beating process is maintained, it
will be practically impossible to treat a pulp stock with a
concentration far higher than 20 percent without critically
impairing the pulp fibers contained in the pulp stock.
In the beating process of the pulp stock, the pulp stock is usually
disintegrated into small quantities as it is repeatedly thrown
against a serrated wall or passed between relatively moving
serrated walls under the influence of a unidirectional and/or
rotational force. The pulp stock is, in this manner, subjected to a
direct mechanical impact with the serrations so that the fibers in
the pulp stock more or less undergo a shearing action due to the
so-called "knife-edge" effect of the serrations. As the
consequence, a individual pulp fibers contained in the pulp stock
are sheared and torn apart finely so that the final product, or
paper, produced from such pulp stock lacks the viscosity required
to provide for adaptability to printing. It will be, in this
instance, self-explanatory that the shearing action exercised on
the individual pulp fibers may be reduced if the concentration of
the pulp stock forced to impinge upon the serrated wall is
decreased. This is why the pulp stock should be diluted before it
is subjected to beating. If, therefore, a pulp stock with a
concentration as high as 50 percent or so is fibrilated in the
method and apparatus of prior art type, the fibers in the pulp
stock would be almost pulverized and consequently the paper or
paper product produced from such pulp stock would be crucially void
of the viscosity required of quality printing.
The present invention, therefore, contemplates elimination of these
and other drawbacks that are inherent in the conventional method
and apparatus for fibrilating a pulp stock and it is an important
object of the invention to provide a new and improved method and
apparatus adapted for fibrilating a pulp stock for use in the
production of paper having adaptability in printing.
It is another important object of the invention to provide a new
and improved method and apparatus for fibrilating a pulp stock with
significantly increased performance efficiency and reduced
production cost.
It is still another object of the invention to provide a new and
improved method and apparatus for fibrilating a pulp stock with a
high concentration without impairing the quality of the pulp fibers
contained in the pulp stock.
It is still another important object of the invention to provide an
improved method and apparatus for fibrilating a pulp stock with a
concentration between 20 to 50 percent without imparting a direct
mechanical impact, or shearing action, to the pulp fibers in the
pulp stock while the pulp stock is being disintegrated into small
quantities.
It is still another important object of the invention to provide a
method and apparatus for fibrilating a pulp stock without need of
diluting the pulp stock in a liquid phase prior to the fibrilation
thereof.
In order to accomplish these objects of the invention, it is herein
proposed to use a pulp stock in the form of substantially
dehydrated flakes. The dry pulp flakes are suspended in an
atmosphere to which a combined unidirectional and rotational force
is imparted. A turbulent flow is thus induced in the suspension of
the pulp flakes with the result that the pulp fibers contained in
the pulp flakes are twisted and defibered without being subjected
to a direct mechanical shearing action or "knife-edge" effect. A
major portion of the pulp flakes is disintegrated, or fibrilated,
into small quantities in this manner and is then withdrawn from the
turbulent field. The remaining portion of the pulp flakes which is
not fully disintegrated is, because of its relatively great weight,
urged to approach a toothed surface under the influence of the
centrifugal action resulting from the rotational component of the
combined force applied thereto. The pulp flakes are then forced
against the toothed surface and, as soon as they are disintegrated,
the disintegrated portion is immediately withdrawn from the toothed
surface under the influence of the unidirectional propulsive
component of the force in the turbulent flow. The pulp flakes are
thus permitted to stay in the turbulent flow for only a limited
period of time and, as a consequence, the pulp fibers contained
therein are subjected to a minimum of shearing action by the
toothed surface. The result is that the viscosity of the final
paper is by no means impaired in the process of fibrilation of the
pulp stock and accordingly the paper produced in this manner is
specially suited for the purpose of quality printing.
The objects and advantages of the method and apparatus according to
the present invention will become more apparent from the following
description taken in conjunction of the accompanying drawings, in
which:
FIG. 1 is a schematic diagram showing the general construction
arrangements of a preferred embodiment of an apparatus adapted for
carrying out the method according to the invention;
FIG. 2 is a vertical sectional view of a pulp-feeding means used in
the apparatus shown in FIG. 1;
FIG. 3 is a longitudinal sectional view of a fibrilating means used
in the apparatus shown in FIG. 1; and
FIG. 4 is a section taken on line I--I of FIG. 3.
It is the usual practice in the art that the pulp stock at the
drying stage of the pulp-making process is dehydrated mechanically
normally up to 55 percent or even up to 60 percent at a maximum by
means of a press machine or centrifugal separator without sacrifice
to the quality of the fibers in the pulp stock. The moisture
remaining in the pulp stock thus dehydrated is deposited in the
open cells or interstices of the fibers so as to maintain a
swollen, flexible state of the pulp stock. The pulp stock in this
state can be most advantageously utilized in the treatment
according to the invention, because there is no need of dehydrating
the pulp stock for a second time to carry out the method of the
invention. The existence of the residual moisture deposit in the
fibers in the pulp stock, moreover, is advantageous for the mutual
impingement and torsion of the individual fibers placed under the
influence of a turbulent flow in the course of the fibrillation.
If, in this instance, the pulp stock were to be dehydrated into a
sheet form with its moisture content of less than 20 percent, the
pulp fibers in the pulp stock, if treated in accordance with the
invention, would be finely torn apart or otherwise critically
damaged due to lack of flexibility in them.
The pulp stock thus dehydrated to a concentration range from 20 to
50 percent is then crushed into the form of flakes by the use of a
shredder or other suitable means.
According to the invention, the pulp flakes obtained in this manner
are then entrained in an atmosphere in which a three-dimensional
turbulent flow is established. This three-dimensional turbulent
flow is built up by a unidirectional propulsive force and a
separate rotational force superposed on the former force. The
unidirectional force may be obtained by a stream of compressed air
with a pressure ranging preferably from 0.4 to 1.5 kg./cm..sup.2,
while the rotational force may be obtained by a suitable rotary
member rotating preferably at the speed of 3,000 to 6,000 r.p.m.
The pulp flakes thus placed in such three-dimensional turbulent
flow are disintegrated as they impinge upon one another, during
which time the pulp fibers in the pulp flakes are subjected to
violent torsional stresses and are thereby separated from one
another. The disintegrated portion of the pulp flakes is
compulsorily withdrawn from the turbulent flow under the influence
of the unidirectional propulsive force applied thereto. This is
because of the fact that, as the pulp flakes are reduced to small
particles, they become less responsive to the centrifugal action
due to the reduced weight of the individual particles. The
remaining portion of the pulp flakes which are not fully
disintegrated into small particles is gradually carried outwardly
under the influence of the centrifugal action until the pulp flakes
strike against a toothed surface surrounding the pulp flakes. The
pulp flakes thus forced against the toothed surface are subjected
to mechanical impacts thereupon and are thereby comminuted into
small quantities. As the pulp flakes are comminuted, or fibrilated,
through impacts upon the toothed surface, they become less
responsive to the centrifugal action because of the reduced weights
of the small particles disintegrated from the pulp flakes and are
withdrawn from the toothed surface under the influence of the
unidirectional propulsive force. The pulp stock staying on the
toothed surface for only a limited period of time, the pulp fibers
in the pulp flakes undergo a minimum of shearing action by the
toothed surface.
If desired, the moisture content of the pulp flakes may be
increased or decreased by adjusting the moisture in the airstream
in which the pulp flakes are to be entrained, thereby enabling the
pulp flakes to impinge upon one another or upon the surrounding
toothed surface with regulated violence.
A preferred example of the apparatus adapted to carry out the above
described method according to the invention is illustrated in FIG.
1.
As shown, the dehydrated pulp stock in the form of flakes is
supplied through a conveyor 10 and feeding means 11. The feeding
means 11 is connected on the one hand with a source 12 of air
through a duct 13. This source 12 of air, which may actually be a
fan, blower, air compressor or any similar device, supplies a
continuous stream of air under a pressure ranging preferably from
0.4 to 1.5 kg./cm..sup.2. The feeding means 11, on the other hand,
is connected with a fibrilator 14 through a duct 15, the fibrilator
being constructed in a manner to be described later. The pulp
flakes fed from the feeding means 11 are entrained in the airstream
supplied from the source 12 through the duct 13 and are thereafter
introduced into the fibrilator 14 through the duct 15. The pulp
flakes fibrilated at and by this fibrilator 14 are then passed to a
cyclone or centrifugal separator 16 through a duct 17, where the
air entrapped in the fibrilated pulp stock is separated and removed
therefrom in usual manner. Designated at 18 is a dissolving vat
connected with the cyclone or centrifugal separator 16 and filled
with clear or white water supplied from a valved feeding pipe 19.
The feeding means 11 and fibrilator 14 are driven by motors 20 and
21 through couplings 20a and 21a, respectively.
If desired, the temperature and moisture content of the airstream
to be supplied to the fibrilator 14 through the ducts 13 and 15 may
be adjusted. For this purpose, valved air pipe 22, water pipe 23
and steampipe 24 communicating with the water pipe 23 all
communicate with the duct 13 through an ejector 25.
If further desired, the pressure of the airstream supplied from the
source 12 through the duct 13 and the power load on the motor 21
for the fibrilator 14 may be detected by a control means 26 to
regulate the speed of motor 20 for the feeding means 11.
Also, the amount of water to be supplied through the water pipe 23
to the airstream in the duct 13 may be regulated by a control means
27 through detection of the amount of water to be separated and
removed from the fibrilated pulp stock at the cyclone or
centrifugal separator 16. To control the temperature of the
airstream in the duct 13, the amount of air to be supplied through
the air pipe 22 and the amount of the steam supplied through the
steampipe 24 may be regulated by a control means 28 in accordance
with the temperature of water detected at the cyclone or
centrifugal separator 16.
The temperature of the airstream supplied from the airstream source
12 may also be changed with use of a suitable heat exchanger 29
combined with the source 12.
The detailed construction of the feeding means 11 is illustrated in
FIG. 2.
As shown, the feeding means 11 has a hopper 30 into which the
dehydrated pulp flakes are carried by the conveyor 10. The hopper
30 is supported by a generally cylindrical casing 31 with closed
ends. The cylindrical casing 31 has journaled in its end walls a
rotary shaft 32. The rotary shaft 32 is connected at one end to the
drive shaft of the coupling 20a of the motor 20 through one
sidewall of the casing and at the other end is supported rotatably
on the other sidewall of the casing through bearings (not shown).
The shaft 32 is provided radially with a plurality of blades 33.
The cylindrical casing communicates at its top with the hopper and
at its bottom with the duct 13 through an outlet 34.
In operation, the rotary shaft 32 is driven from the motor 20
through the coupling 20a so that the blades 33 rotate in the
cylindrical casing at a predetermined velocity. Thus, the pulp
flakes carried through the hopper 30 are fed into the duct 13
constantly through the outlet 34. The amount of the pulp flakes fed
into the duct 13 can be determined by the control means 26 in
accordance with the pressure of the airstream in the duct 13 and
the power load on the motor 21 for the fibrilator 14, as previously
discussed. The pulp flakes are thus entrained in the airstream
under pressure in the duct 13 and are then forced into the
fibrilator 14 through the duct 15.
The fibrilator 14 is constructed as illustrated in FIGS. 3 and 4.
As shown, the fibrilator 14 essentially comprises a generally
cylindrical casing 35 and a rotor 36 mounted therein. The casing 35
communicates through one end wall thereof with the duct 15 and
through the other end wall with the duct 17. The cylindrical casing
35 is provided on the internal peripheral wall thereof with a
metallic lining 37. The metallic lining 37 is finely toothed over
its surface 37a extending halfway from the upstream end wall and
merges with an arcuately curved wall surface 37b which terminates
at the upstream end of the duct 17, as clearly seen in FIG. 3. The
curved wall surface 37b may preferably curved approximately at
45.degree. to the internal surface of the cylindrical casing 35
thereby to avoid formation of a dead pocket.
The rotor 36 is supported on a rotary shaft 38 through end walls 39
and 40 and the rotary shaft 38, in turn, is supported rotatably on
the walls of the ducts 15 and 17 through bearings 41 and 41' and
packings 42 and 42', respectively.
The rotary shaft 38 is connected at one end with and driven by the
coupling 21a of the motor 21. The end wall 39 has formed centrally
therein a bore 43 to receive the leading end of the duct 15. On the
sidewalls 39 and 40 of the rotor 36 are radially supported a
plurality of blades 44, as clearly seen in FIG. 4.
In operation, the rotor 36 is rotated by the motor 21 through the
coupling 21a and revolution shaft 38. The revolution speed of the
rotor 36 may range from about 3,000 to about 6,000 r.p.m., which
may correspond to the circumferential speed of about 60 to 120
meters per second of the rotor 36. A field of constant centrifugal
force is thus created about the axis of the rotation of the rotor
36 through revolution thereabout of the blades 44 of the rotor
36.
The centrifugal force thus established in the casing 35 is acted
upon by a second, unidirectional force which is built up
substantially in the direction parallel to the axis of rotation of
the rotor 36, namely, perpendicular to the centrifugal force, by a
constant rapid stream of air supplied from the source 12 of the
airstream by way of the ducts 13 and 15. This unidirectional force
may be about 0.4 to 1.5 kg./cm..sup.2. The unidirectional force
being combined in superposed relationship with the centrifugal
force, a violent turbulent flow in a gaseous phase is established
in the casing 35.
The unidirectional stream of air, as it is passed from the duct 13
to the duct 15 at the bottom of the feeding means 11, carries
thereon a regulated amount of dehydrated pulp flakes supplied
constantly through the opening 34 in the feeding means 11. The pulp
flakes thus carried in the airstream is forced to gush into the
casing 35 through the duct 15 and are then subjected to the violent
turbulent flow as they stay in the casing 35 of the fibrilator
14.
The individual pulp flakes so introduced into the casing 35 of the
fibrilator 14 are caused to rub and impinge upon one another and,
as a result, are disintegrated into small quantities. The pulp
fibers contained in the pulp flakes are, as the pulp flakes are
comminuted, subjected to torsional and frictional forces and are
thereby loosened from one another. The portion of the pulp flakes
rendered into small quantities with reduced weight in this manner
is less responsive to the centrifugal action because of the very
reduced weights thereof and is moved downstream under the influence
of the unidirectional propulsive force until they are discharged
out of the fibrilator 14 by way of the duct 17. The remaining
portion of the pulp flakes, which are not fully disintegrated at
this stage, are urged to approach the toothed surface 37a of the
lining 37 due to the centrifugal action exerted by the blades 44 of
the rotating rotor 36. The pulp flakes then are subjected to
mechanical impacts as they are forced against the toothed surface
37a. The pulp flakes staying on the toothed surface 37a are thus
subjected repeatedly to the disintegrating action as the bladed
rotor 36 rotates and are thereby reduced to small quantities. As
the pulp flakes are disintegrated in this manner, the pulp fibers
contained therein are also subjected to torsional and frictional
forces as the pulp flakes impinge upon one another and upon the
toothed surface 37. Since, at this moment, the individual particles
of the disintegrated pulp flakes are sufficiently lighter in weight
than the pulp flakes in the initial state, they are less subject to
the centrifugal action and consequently are forced out of the
casing 35 of the fibrilator 14 by the action of the unidirectional
propulsive force. Although, in this instance, a portion of the pulp
flakes is subjected to a direct mechanical impact with the toothed
surface, the pulp fibers in the pulp flakes are exposed to only a
minimum of shearing action by the teeth on the toothed surface
because the pulp flakes are withdrawn from the surface as soon as
they are disintegrated into small quantities with reduced
weights.
Thus, it will be understood that the pulp flakes can be fibrilated
without destroying the cellulosic system of the fibers contained
therein according to the invention. This has been ascertained by
microscopic examinations conducted by the inventors, the results of
which, however, are not herein presented.
If desired, the time period for which the pulp flakes are permitted
to stay in the fibrilator 14, which time period governs
significantly the quality of the disintegrated pulp flakes, may be
adjusted by regulating the velocity of the airstream supplied from
the blower or air compressor 12 and/or the rate of feed of the pulp
flakes supplied through the feeding means 11 by the adjustment of
the load on the motor 20, as desired.
It may be mentioned that the pulp flakes are proportionately more
responsive to the centrifugal action in the fibrilator 14 if they
contain more moisture. For this reason, it will be desirable to
adjust the moisture content of the air to be admixed to the pulp
flakes by regulating the amounts of air, water and hot steam
supplied through the valved pipes 22, 23, and 24, respectively.
It may also be mentioned that the pulp flakes supplied from the
conveyor 10 may be bypassed around the feeding means 11 and
introduced directly into the fibrilator 14 depending upon the
intended type of the finished paper or paper product. In such
instance, it will be advantageous to have the airstream source 12
located in the vicinity of the outlet of the duct. Where, moreover,
a blower or fan is used as the airstream source 12, the fan or
blower may be so arranged as to rotate concentrically with the
revolution shaft 38 of the fibrilator 14.
The advantages of the method, and the apparatus to be used therefor
as well, will be better understood from the following examples.
EXAMPLE 1
The flakes of unbleached pulp of 20 percent concentration were fed
to the feeding means 11 with its bladed shaft 32 rotating at the
speed of 300 r.p.m. These pulp flakes were then introduced into an
airstream supplied from the blower 12 with a propulsive force of
about 0.4 kg./cm..sup.2. The pulp flakes thus entrained on the
unidirectional propulsive stream of air were drawn into the
fibrilator 14 with its bladed shaft 38 rotating at a speed of about
3,000 to 6,000 r.p.m. The pulp flakes defibered in the fibrilator
14 were passed to the vat 18 filled with white water via the
cyclone 16 to obtain a pulp stock of 5 percent concentration. This
pulp stock was made into paper at a predetermined beating rate by a
process in compliance with the TAPPI Standards. Tests were
conducted on the resultant paper for strength at 20.degree. C.
temperature and 65 percent relative humidity and the results of the
tests were compared with those conducted on a paper produced from a
usual beat pulp prepared as a starting pulp material of 5 percent
concentration.
While there was observed no appreciable difference in the specific
bursting strength and breaking length, the paper produced by the
method according to the invention was considered to far excell the
conventionally beat paper especially in respect to the tearing
strength and elongation. This is shown in Table 1, wherein the
paper produced by the method according to the invention is referred
to as "A" and the paper produced from the conventional pulp stock
with low concentration as "B" (such denotation applies to all the
Tables that are to follow). ##SPC1##
EXAMPLE 2
The flakes of unbleached pulp of 30 percent concentration were
processed in the same manner as in Example 1. The resultant paper
was subjected to similar tests for comparison with the beat paper
produced in the known method. In this experiment, too, no
appreciable difference was observed as regards the specific
bursting strength and breaking length. The paper produced with use
of a pulp stock prepared in the method according to the invention,
however, showed nearly 100 percent greater specific tearing
strength and elongation. This is clearly seen in Table 2.
##SPC2##
EXAMPLE 3
Pulp flakes of 30 percent concentration were processed in a manner
similar to that used in Example 2 and were recycled from the
cyclone 16 back to the conveyor 10 for reprocessing in the feeding
means 11 and fibrilator 14. This recycling of the once fibrilated
pulp stock was intended to see if it would provide better results
than obtainable by the single cycling of the pulp stock. As is
observed in Table 3 below, however, the paper produced with use of
such reprocessed pulp stock is substantially no different in the
various aspects of the paper properties from the paper produced
from the pulp stock processed in a single cycling as in Example 2,
except only that the time period required for the beating was
reduced to a certain extent. Thus, it can be concluded that the
recycling of the pulp stock in the fibrilating line is superfluous,
only adding to the number of steps. ##SPC3##
EXAMPLE 4
The process adopted in Example 1 was followed, except that pulp
flakes of 40 concentration were used. The results of tests
conducted on the paper produced from the pulp stock thus fibrilated
are indicated in Table 4, from which it will be observed that,
while no appreciable improvement is achieved over the
conventionally produced paper especially in respect to the specific
bursting strength and breaking length, the paper obtained in this
example is recognized to have a remarkably greater specific tearing
strength and elongation, granting that the breaking length, in
particular, is rather lower than that of the paper prepared with
use of the pulp flakes of 30 concentration as in Example 2.
##SPC4##
EXAMPLE 5
The process of Example 1 was also followed, except that the
concentration of the pulp flakes as a starting material was
increased to 50 percent. The results of conducted tests on the
resulting paper, as indicated below, reveal that, while the
specific bursting strength and breaking length remain comparable to
those of the conventional paper, the paper prepared in this example
is superior to the conventional paper in respect to the elongation.
The specific tearing strength is, however, considered not
satisfactory. The tearing strength of the paper obtained in this
example may be improved to some extent if the degree of beating is
increased. ##SPC5##
EXAMPLE 6
The process of Example 1 was invariably followed, except that the
concentration of the pulp flakes was further increased to 60
percent. As seen from Table 6 below, the paper produced with use of
pulp stock with such a high concentration is considerably inferior
to the conventional paper at least with respect to the specific
tearing strength. As to the elongation property of the paper,
however, the paper produced from the pulp stock obtained in this
example is superior to that of the conventional paper. As regards
the specific bursting strength and breaking length, substantially
no difference is observed. It is thus considered from this example
that the concentration of the pulp stock should not exceed 60
percent from the view point of economical and operational
limitations in the moisture adjustment of the pulp required.
##SPC6##
For the purpose of better understanding of the major properties of
the paper produced from the pulp stock prepared by the method
according to the invention, the results of tests conducted on the
papers as stated in the above examples are tabulated in Table 7 by
the pulp stock and in percent ratios to the properties of
conventionally prepared paper. ##SPC7##
It should now be understood that the method and apparatus to carry
out the method according to the invention are given by way of
illustration only and that modifications thereof may be made which
are obvious to those skilled in the art without departing the
spirit and scope of the present invention as defined in the
appended claims.
* * * * *