Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PULP REFINING ELEMENT
FIELD OF TI-IE INVENTION
The present invention rela-tes to pulp refining
elements. More particularly, the present invention relates
to a pair of elements for use in a refiner with a decreased
consumption of energy and for producing cellulosic pwlp
useful for making a high quality of paper.
BACKGROUND OF THE INVENTION
It is known that raw or mechanically, thermally
and/or chemically treated cellulosic fibrous material, for
example, wood chips, is conver-ted into pulp by means of a
beating or refining process. The beating or refining
process is an important process for producing pulp for
making paper.
The beating process is usually applied to a chemically
treated fibrous material suspended in a content of about
10% or less in water, by using a beater.
The refining process can be applied to any-of the
raw and mechanically, thermally and/or chemically treated
fibrous materials by using a refiner. This refining
process is very effectlve for defibering the fibrous
material into individual fibers and for the outer and
inter fibrillations and the cutting of the individual
fibers, so as to provide refined fibers having a proper
thickness, llength and surface area~ and to enhance the
swelling property and flexibility of the fibers. That is,
the pulp useful for maklng a high quality of paper can be
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obtained only by using the re~ining process.
The refining process can be conducted by using a
disc type refiner, conical type refiner or drum type
refiner.
The disc type refiner is provided with a pair of
refining elements (discs), each having a pulp refining
surface facing and parallel to the other, and closely
spaced from the other so as to form a very narrow gap
bet~een the pulp refining surfaces. At least one of the
elements is rotatable relative to the other. Each of -the
pulp refining surfaces has a feed end zone to which the
fibrous material to be refined is fed, and a discharge end
zone from which the resultant refined pulp is discharged.
Also, each of the pulp refining surfaces of the disc type
refiner is provided with a number of grooves extending
from the feed end zone to the discharge end zone of the
pulp refining surface, and a nlamber of ribs defining the
grooves therebetween.
In the dlsc type refiner, either one or both of the
elements are rotatable relative to the other. That is, in
the former case, one of the elements is fixed and the
other one is rotatable at a predetermined speed. In the
later case, both the elements are rotatable in an opposite
dlrection to each other. In the refining process, by
using the disc type refiner, the fibrous material is fed
to a portion of the gap between the pulp refining surfaces,
correspondinq to the feed end Eones of the surfaces,
travels through the gap while being refined, and then, is
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discharged through a portion of the gap corresponding to
the discharge end zones of the surfaces.
The conical type refiner is provided with a cone-
-shaped rotor element having a pulp refining outside
surface, the rotor element being contained in a shell
element having a cone-shaped pulp refining inside surface
surrounding the outside surface of the rotor. Usually,
the shell element is fixed unrotatably and the rotor
element is rotatable. Each of the conical outside surfaces
of the rotor element and the conical inside surfaces ~f
the shell element has a feed end zone located in a small
diameter portion of the conical surface, and a discharge
end zone located in a large diameter portion of the conical
surface. Also, each of the conical inside and outside
surfaces of the rotor element and shell element, is provided
with a number of grooves extencling in a straight line, or
in a spiral configuration, from the feed end zone to the
discharge end zone of each conical surface. In the refining
process by using the conical type refiner, the fibrous
material is fed into a feed end portion of the gap between
the conical inside and outside surfaces, travels through
the gap while being refined, and then, is discharged
through a discharge end portion of the gap.
The drum type refiner is provided with a drum-shaped
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rotor element having a drum-shaped outside peripheral
; surface, and an unrotatable shell element. The inside
~; peripheral surface of the shell element faces at least a
part of the outside peripheral surface of the rotor element
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in a parallel relationship. The outside peripheral surface
of the drum-shaped rotor element is provided with a number
of -the grooves extending in a straight line, or in a
spiral curve, from a feed end zone located on an end
portion of the drum-shaped surface to a discharge end zone
located on the opposite end portion of the drum~shaped
surface, and a number of ribs defining the grooves there-
between. The inside surface of the unrotatable sheel
element may be made of an abrassive stone, such as basalt
or lava. Otherwiser the inside surface of the shell may
have a number of grooves and ribs extendiny in the same
manner as that in the outside peripheral surface of the
drum-shaped rotor element. In the refining operations, by
using the drum type refiner, the fibrous material is
forced to travel through the gap between the outside
peripheral surface of the rotor element and the inside
surface of the shell element from a feed end portion to a
discharge end portion of the gap, by means of a pump,
while being refined.
The refining process applied to the fibrous material
is effective for enhancing the outer and inner fibrillations
of the refined fibers. This is also effective for enhancing
the swelling property and the flexibility of the fibers.
The above-mentioned refiners can be used for the
purpose of beating the fibrous materials. Accordingly,
the above-mentioned refining process and beating process
can be involved in term "refining process" in a wide
meaning.
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With respect to the reEining mechanism in the
reiiner, it is recognized that the fibrous material is
defibered when the fibrous material is brought into contact
with the edges of the ribs, and -the defibered fibers are
cut and/or compressed by the edges of the rotating ribs.
Also, it is recognized that, during the refining process
the defibered fibers travel from the feed end zone to the
discharge end zone through the grooves. That is, the
function of the grooves is merely recognized as a path ~or
the defibered fibers. For example, Goncharov, Bumazh
Pro. No. 5, 12-14(1971), discloses that, when an unbleached
sulfite pulp is refined with a disc type refiner, a very
strong force is applied onto a part of a rib from a tip
thereof to a level of 2.5 or 3 mm distant from the tip.
That is, when the refining operation is carried out under
ordinary conditions, the force applied to the tip part of
the rib is about 35 kg/cm2. This value of the force
corresponds to about 13 times an average value of the
force per unit area, cm2, applied to the entire outer area
of the rib.
That is, the refining effect is attained mainly by
the tip end portion of the rib, and the tip end portion is
worn away during the refining process.
However, van der Akker (Fundamentals of Papermaking
Fibres, Trans~ of the Symposium held at Cambridge, September,
1957, pages 435 through 446) states that about 99.9% of
the energy applied to a refiner is spend for wearing away
the ribs and converted to heat, and only about ~.1% of the
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applied energy is utilized to refine the fibrous material~
It is known that the specific power consurnption in
the operation of the refining process for refining chemical
pulp is about 200 to 800 kWh/T, the specific power consump-
tion for producing mechanical pulp from a refiner mechanicalpulp (RMP) is about 1400 to 1800 kWh/T and that from a
thermomechanical pulp (T~P) is about 2000 kWh/T or more.
That is, the power consumption necessary for refining -the
fibrous ma-terial by using a conventional refiner is very
large. Accordingly, it is strongly desirable to enhance
the efficiency of the refiner, so as to decrease the
consumption of enexgy necessary for refining the fibrous
material.
In the field of various types of refiners, it is
believed that the depth of the grooves in the pulp refining
surface should be at least 4 mm, because a depth of less
than 4 mm results in a poor flow of the ~ibrous material
between the pulp refining surfaces under an ordinary
pressure. For example, P. J. Leider and J. Rihs, Tappi,
Vol. 60, No. 9tl977), pages 98 through 102, state that the
decrease in the depth of the groove causes the throughput
of the fibrous material to decrease and that, when the
depth of the grooves is l/8 inch labout 3.2 mm), no flow
of the fibrous material occurs. In order to force the
fibrous matexial to flow through the groove having a depth
less than 4 mm, it is necessary to increase the pressure
applied to the fibrous mateial. The increase in the
pressure results in an increase in the consumption of
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energy for refining the fibrous material.
However, grooves having a depth of 4 mm or more,
cause a portion of the fibrous material fed into the
refiner to ~e accumulated in the grooves. The accumulated
fibrous material forms a thick ma-t which is fixed unmovably
in the groove. The mat acts as a force absor~er when the
fibrous material is exposed to the refining action of the
pulp refining surfaces. Therefore, the formation of the
mats in the grooves causes the efficiency of the refining
process to decrease.
U.S. Patent 3,745,645 discloses a method for fabricat-
ing and operating a pair of relatively rotatable elemen-ts
having ribs and grooves formed between the ribs. The
height of the ribs (the depth of the grooves) is in a
range of from about 1.5 to about 5.0 times the width of
the ribs at the tips thereof. The grooves are partly
filled with a plastic filler material. When the tips of
the ribs wear down during the refining process, the height
of the filler material is reduced, so as to restore the
unfilled por-tion of the grooves substantially to the
original depth thereof. This U.S. patent discloses grooves
having a depth of 12 mm and partly filled with the filler
material having a height of 8 mm, so as to leave a 4 mm
free space at the top of the grooves. That is, in the
refiner of this U.S. patent, since the depth of the grooves
filled with the filler material is 4 mm, the grooves
cannot prevent the formation of the thick mat of the
fibrous material. In other words, the refiner of the U.S.
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patent cannot decrease -the comsumption of energ~ for the
refining process.
SUMMARY OF THE INVENl'ION
An object of the present invention is to provide a
pulp refining element for the use in a pulp refiner, which
element is effective for causing -the refiner to opera-te
with a high efficiency and wit:h a low consumption of
energy.
Another object of the present invention is to
provide a pulp refining element for the use in a pulp
refiner, which element is effective for producing a
enhanced quality of pulp.
The above-mentioned objects can be a-ttained by the
refining element of the present invention, which element
has a pulp refining surface having a feed end zone thereof
to which a fibrous material is fed and a discharge end
zone thereof from which the refined pulp is discharged,
the pulp refining surface being provided with a number
of grooves extending from the feed end zone to the
discharge end zone of the pulp refining surface and a
number of ribs defining the grooves therebetween, and
which element is characterized in that the bottom of at
least a portion of the grooves, the portion being located
in the discharge end zone of the pulp refining surface,
is covered with a layer of a synthetic polymer resin
in such a manner that the outer surface of the synthetic
polymer resin layer in a groove is O to 3 mm distant
: from the level of the tips of the ribs defining the groove
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therebetween toward -the bottom.
In the pulp refining element, it is important that
the bottoms of at least por-tions of the grooves located in
the discharge end zone of the pulp refining surEace be
5 covered with a layer of a synthetic polymer resin. Also,
it is important that the distance from the outer surface
of the synthetic polymer resin layer in a groove to the
level of the tips of the ribs defining the groo~e there-
between, that is, the depth of a free space above the
synthetic polymer resin layer in a groove, be in a range
of from 0 to 3 mm.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is fragmentary plan view of an embodiment of
the pulp refining surface of the element of the present
invention for use in a disc type refiner;
Fig. 2 is a fragmentary perspective view of an
embodiment of the pulp refinin~3 element of the present
invention for use in a disc type refiner;
Fig. 3 is a cross-sectional view of a pair of pulp
refining elements of the present invention for use in a
; conical type refiner;
Fig. 4 is a graph showing a relation between a
weight percent of a fraction of a refined pulp remaining
on a 24 mesh screen and an unscreened freeness of the
,~ 25 refined pulp;
Fig. 5 is a graph showing a relation between a
breakiny length of a refined pulp and a screened freeness
of the refined pulp;
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Fig. 6 is a yraph showing a relation between a tear
factor of a refined pulp and a screened freeness of the
refined pulp;
Fig. 7 is a graph showing a relation between a
breaking length of a refined pulp and a specific power
consumption in the production of the refined pulp;
Fig. 8 is a graph showing a relation between a
scattering coefficiert of a refined pulp and a specific
power consumption in the production of the xefined pulp;
Fig. 9 is a graph showing a relation between a -
specific power consumption in the production of a refined
pulp and an unscreened freeness of the refined pulp;
Fig. 1~ is a graph showing a breaking length of
another refined pulp and a specific power consump-tion in
the production of the refined pulp, and;
Fig. 11 is a graph showing a scattering coefficient
of another refined pulp and a specific power consumption
in the production of the refined pulp.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Fig. 1, a pulp refining element usable
for a disc type refiner has a pulp refinlng surface 1.
The pulp refining surface 1 contains a feed end zone 2 to
which a fibrous material is fed, a discharge end zone 3
from which the resultant refined pulp is discharged, and a
middle zone 4 through which the fibrous material travels
from the feed end zone 2 to the discharge end zone 3. The
pulp refinin~ surface 1 is provided with a number of
grooves 5 extending from the feed end zone 2 to the discharge
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end zone 3 through the middle zone ~, and a number of ribs
6 deEining the grooves 5 therebetween.
Referring to Fig. 2, in a discharge end zone oE a
pulp refining surface 1 of an element for the use in a
disc type refiner, a number of grooves 5 defined by a
number of ribs 6, are filled with a synthetic polymer
resin. That is, the bottom of each groove 5 is covered
with a layer 7 of the synthetic polymer resin.
In a conical type refiner, as illustrated in Fig. 3,
a conical rotor 11 has a conical outside surface and a
shell 12 has a conical inside surface. Each of the conical
outside surface of the rotor 11 and the conical inside
surface of the shell 12 is provided with a number of
grooves 5, and a number of ribs 6 defining the grooves 5
therebetween. The bottom of each groove is covered with a
layer 7 of a synthetic polymer resin.
~iIn the pulp refining element of the present invention,
the bottoms o~ the grooves located in at least the discharge
end zone of the pulp refining surface/ are each covered
with a layer of a synthetic polymer resin. That is, the
bottoms of all grooves in the pulp refining surface may be
covered with the synthetic polymer resin layers. ~lso,
only the bottoms of the grooves located in the discharge
end zone may be covered with the synthetic polymer resin
layers. Furthermore, the bottoms of the grooves located
in the discharge end zone and at least a portion of the
~`~mlddle zone, and/or the feed end zone, may be covered with
the syn~thetlc polymer resin~layers.
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The synthetic polymer rPsin usable ~or the present
invention is not limited to a special type of polymer
resin. That is, the synthetic: polymer resin may be
selected from the group consisting of synthetic thermo-
plastic polymer resi.ns and synthetic thermosetting polymerresins.
The thermoplastic polymer may be selected from -the
group consisting of polyvinyl chloride, polyvinylidene
chloride, polystyrene, polyethylene, polypropylene, poly-
amides, polycarbonates, polyacetal, polyethersulfones,polyesters, polyphenyleneoxide, modified polyphenyleneoxide,
polyimides, polyamideimide acrylonitrile-butadiene-styrene
terpolymers, acrylic ester polymers, methacrylic ester
polymers, polymethylpentene, polysulfone, polyphenylene
sulfide, styrene-maleic anhydride-acrylic ester terpolymers
and polytetrafluoroethylene. ~!lore preferable theromplastic
polymers for the present invention are polyamides, for
example, nylon 11 and nylon 66, polyethylene, especially,
high density polyethylene, polypropylene, poly carbonate,
polymethylpentene, polysulfones, polyesters, polyphenylene
sulfide, polyphenyleneoxide, modified polyphenylene
oxides, for example, a blend of poiyphenylene oxides with
polystyrene.
The thermosettlng polymer may be selected from the
group consisting of phenol resins, diallylphthalate
resins, unsaturated polyester resins, alkid resins, epoxy
resins, silicone resins, polyurethane resins, melamine
resins and uFea resins. More preferable thermosetting
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polymers for the present invention are diallylph-thalate
resins and epoxy resins.
The synthetic polymer resin layer may contain a
large number of pores having a size of 200 microns or
less. The pores may be either connected to each other or
be independent from each other.
The synthetic polymer r~esin layer may contains one
or more additives, for example, pigments, anti-oxidants,
fillers and stabilizers. It is preferable that -the
synthetic polymer resin be selected from the resins
having high resistances to abrasion and deterioration
during the refining process, and capable of being easily
placed and solidified in the grooves, and readily cut in
the preparation of the resin layer~
Moreover, the synthetic polymer resin layer may
contain abrasive particles dispersed in at least the outer
surface portion of the the synthetic polymer resin layer.
The abrasive particles are effective for promoting the
defibering action of the pulp refining surface on the
fibrous material and for decreasing the specific power
consumption of the refining process.
For example~ when a fibrous material having a
; pulp consistency of 15% is refined by a refiner, it was
found that the pressure applied to the surfaces of the
grooves is in a range of from 1 to 4 kg/cm2. The surface
of the synthetic polymer resin layer containing the
abrasive particles can effectively defiber the fibrous -
material, even under the above-mentioned low pressure of
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from 1 to 4 kg/cm2.
The abrasive particles may be selected ~rom the
group consistin~ of fine particles of alumina, sil:icon
carbide, boron carbide, steel, chromium oxide, iron oxide,
garnet, emery siliceous sand, cement, glass and ceramics.
The abrasive particles preferably have an average size of
from 50 to 600 microns, and are preferably used in an
amount of from 30 to 90% by we:ight.
~ he layer of the synthetic polymer resin may be
formed in any conventional methods. For example, a powdered
or pelletized thermoplastic polymer resin is placed in the
grooves, and mel-ted at an elevated tempera-ture higher than
the melting point of the polymer resin, and then, cooled
to room temperature, so as to solidify the layers of the
polymer resin melt in situ in the grooves. Otherwise, a
melt of the thermoplastic polymer resin is poured into the
grooves and, then, solidified in situ. In the case where
a thermosetting resins is used, a liquid or powdered
thermosetting resin precursor is placed into the grooves
and heated to an elevated temperature, so as to thermoset
the resin precursor in the grooves.
In the case where the abrasive particles are used,
the abrasive particles may be uniforml~ mixed with the
entire amount of the synthetic polymer resin. Otherwise,
the resin layer containing the abrasive particles may be
formed in such a manner that a lower half portion of the
resin layer is made of a polymer resin containing no
abrasive particles and an upper half portion of the resin
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layer is formed by a mixture of the polymer resin and the
abrasive particles.
For example, a resin layer containing the abrasive
particles ~ay be prepared by placing a mixture of 7 parts
by weight of silicon carbide particles, having a grain
size of 60, and 3 parts by weight of a powdered poly-
carbonate, in the grooves, pressing the layers of the
mixture so as to make the layer of the mixture dense~ and
sintering the layer of the mi~ture at a temperature of
235C.
The bottom of the groove is covered with the synthetic
polymer resin layer in such a manner that the outer surface
of the synthetic polymer resin layer in each groove is 0
to 3 mm, preferably, 0 to 2.5 mm, more preferably, 0.5 to
2.5 mm, distant from the level of the tips of the ribs
defining the groove therebetwe~en toward the bottom. In
other words, the depth of a free space above the synthetic
polymer resin layer in each groove should be in a range of
from 0 to 3 mm, preferably, 0 to 2.5 mm, more preferably,
0.5 to 2.5 mm.
It the synthetic polymer resin layer projects
outward over the level of the tips of the ribs, this resin
layer will hinder the refining action of the ribs. Also,
if the distance between the outer surface of the resin
layer and the level of the tips of the ribs is more than
3 mm, the decrease in the specific power consump-tion in
the refining process will be poor.
The thickness of the synthetic polymer resin layer
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ls no-t limited to a special range of value. However, the
thickness of the synthetic polymer resin layer is preferably
at least 1.0 mm, more preferably, in a ranye of from 1.5
to 4.0 mm. The outer surface of the synthetic polymer
resin layer is either smooth or slightly rough and either
flat or slightly concave or convex. In the case of a
rough, concave or convex outer surface of the resin layer,
the distance between a mean level of the outer surface and
the level of the tips of the ribs should be in a range of
from 0 to 3 mm. Also, the outer surface of the resin
layer may be entirely or partly sloped in such a manner
that the the closer to the discharge end of the pulp
refining surface, the smaller the distance between the
outer surface of the resin layer and the level of the tips
of the ribs. In this case, in the grooves located in at
least the discharge end zone, t:he largest distance between
the outer surface of the resin layer and the level of the
tips of the ribs should be in the range of Erom ~ to 3 mm.
The pulp refining element of the present invention
can be used in any of the disc type refiners, selected
from a single disc refiner, double disc refiner, floating
disc refiner, conical type refiner and drum type refiner.
The pulp refining element of -the present invention
can be utilized to refine a fibrous mateiral selected from
wood chips; mechanically, thermally and/or chemically
pretreated wood chips; mechanical pulp, such as ground
wood pulp, refiner mechanical pulp and thermomechanical
pulp; high yield pulps, such as chemiground pulp and
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semichemical pulp; bleached or unbleached chemical pulp,
such as ~raf-t pulp, sulfite pulp and soda pulp; oxyyen-pulped
and bleache~ pulp, and; secondary fiber pulp. The pulp
refining element of the presen-t invention can be utilized
for refining non-ligno-cellulosic fibrous material, such
as inorganic fiber material, synthetic fiber material and
synthetic pulp.
Usually, the fibrous material is fed in the form of
an aqueous suspension to the refiner. The pulp refining
element of the present invention is effec-tive for refining
the fibrous material in any content in the aqueous suspen-
sion. That is, the content of the fibrous material in the
aqueous suspension may be at a low level of less than 6%
by weihgt, a middle level of from 6 to 15% by weight, or a
high level of more than 15%, by weight.
The features and advanta,ges o~ the pulp refining
element of the present invention are explained in more
detail in the following examples.
Examples 1 through 3_and Com~arison-Example 1
In each of the Examples 1, 2 and 3 and Comparison
Example 1, a pulp refining plate, type 17804, which is a
trademark of a pulp refining element made by SPRAUT WALDRON
COMPANY, and which is used in a 12 inch single disc refiner,
was used. The pulp refining plate had a number of grooves
having a width of 3 mm in the middle zone and 4 mm in the
discharge end zone and a depth of 3.8 mm, and ribs each
having a width of 3.1 mm in the middle zone and 3.8 mm in
the discharge end zone. The grooves were filled with a
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powdered nylon 11, so that the dep-th of each free space
formed above the nylon 11 layer in each groove became zero
(Exarnple 1), 1 mm (Example 2), 2 mm (Example 3) or 3.8 mm
(Comparison Example 1).
The resultant pulp refining plate was placed in a
12 inch single disc refiner made by KUMAGAYA RIKI KOGYO
K. K., Japan.
An aqueous suspension of 6% or 15% by weight of a
refiner mechanical pulp was sub~ected to a refining process
by using the above-mentioned refiner.
The specific power consumption of the refining
process, the breaking length, tear factor and scattering
coefficient of the resultant pulp are shown in Figs. 4
through 8.
Fig. 4 shows relationships between the unscreened
freenesses and the weight percent of fractions remaining
on a 24 mesh screen, of the refined pulps of Examples 1
through 3 and Comparison Example 1, when the content of
the refiner mechanical pulp was 6% by weight. In view of
Fig. 4, it is clear that the weight percents of the fractions
on the 2~ mesh screen of the refined pulps obtained by
using the pulp refining elements of the present invention
are larger than that obtained by using another pulp refining
element which falls outside of the scope of the present
invention.
Fig. 5 shows the relationships between the screened
freenesses and the breaking lengths of the refined pulps
of Examples 1 through 3 and Comparison Example 1, when the
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concent o~ the refiner mechanical pulp was 6% by weight.
In view o~ Fig. 5, it is clear that -the breaking lenyths
of the refined pulps o~ Example 1 through 3 are larger
than that of Comparison Example 1, when the unscreened
freenesses of the refined pulps are the same.
Fig. 6 shows a relationship between a screened
freeness and a tear factor of the refined pulp of each of
Example 1 through 3 and Comparison Example 1, when -the
content of the refiner mechanical pulp was 6% by weight.
It is clear from Fig. 6 that the tear fac-tors of the
refined pulps of Examples 1 through 3 are larger than that
of Comparison Example 1, when the screenecl freenesses of
the refined pulps are the same.
Fig. 7 shows a relationship between a specific
power consumption of a refining process and a breaking
length of a refined pulp of each! of Examples 1 through 3
and Comparison Example 1, when the content of the refiner
mechanical pulp was 15~ by weight. In view of Fig. 7, it
is evident that the breaking lengths oE the refined pulps
of Examples 1 through 3 are larger than that of Comparison
Example 1, when the specific power consumptions of the
refining processes of all the exampls and comparison
example are the same. Also, it is evident that the specifc
power consumptions o~ the refining processes of Examples 1
through 3 are smaller than that of Comparison Example 1,
when the breaking lengths of the resultant refined pulps
of all the examples and comparison example are the same.
Fig. 8 shows a relationship between a specific
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power consumption of the refining process and a scattering
coefficient of the refined pulp o:E each of Examples 1
through 3 and Comparison Example 1, when the content of
the refiner mechanical pulp in the aqueous suspension was
- 5 15~ by weigh-t. In view of Fi.g. 8, it is clear that the
scattering coefficients of the refined pulps of Examples 1
through 3 are larger than that of Comparison Example 1,
when all the specific power consumptions of the refining
processes of the examples and comparison example are the
same. Also, it is clear that the specific power consumpti.ons
of the refining proceses of Examples 1, 2 and 3 are smaller
than that of Comparison Example 1, when all the scattering
coefficients of the refined pulps of the examples and
comparison example are the same.
The same procedures as those mentioned above were
repeated, except that the nylon 11 was replaced with
polypropylene. The results were similar to those mentioned
above.
Examples 4 and_5
In Example 4, procedures identical to those described
in Example 2 were repeated, except that the nylon 11 was
: replaced with polycarbonate and the content of the refiner
; mechanical pulp in the aqueous suspension was 15~ by
weight. The polycarbonate layer was sintered at a temper-
25 ature of 235''C for 40 minutes.
In Example 5, procedures identical to those described
: in Example 4 were carried out, except that the polyca--bonate
was replaced with a mixture of 7 parts by weight of silicon
.
. ' ' . , : . .
- ' ~ ,' : ~
- 21 -
carbide particles having a grain size of 60 and 3 parts by
weiyht of polycarbonate.
Fig. 9 shows a relationship of the unscreened
freeness of the refined pulp and the specific power consump-
tion of the refining process of each of Examples ~ and 5.
In view of Fig. 9, it is clear that the specific power
consumption of a refining process for producing a refined
pulp having an unscreened freeness in Example 5, is about
2/3 times that for producing a refined pulp having the
same unscreened freeness as that in Example 5 and Example ~.
Fig. 10 shows a relationship between a specific
power consumption of a refining process and a breaking
length of a refined pulp of each of Examples 4 and 5. In
view of Fig. 10, it is clear that the abrasive particles
in the resin layer are effec-tive for decreasing the specific
power consumption of the refining process and for increasing
the breaking length of the resultant refined pulp.
Fig. 11 shows a relationship between a specific
power consumption o~ a refining process and a scattering
coefficient of a refined pulp of each of Examples 4 and S.
In view of Fig. 11, it is evident that the abrasive particles
in the resin layer are effective for increasing the scatter-
ing coefficient of the resultant refined pulp.
.. . . .
. . . . . .. . . .
