U.S. patent number 3,880,368 [Application Number 05/340,027] was granted by the patent office on 1975-04-29 for pulp refiner element.
This patent grant is currently assigned to Beloit Corporation. Invention is credited to John B. Matthew.
United States Patent |
3,880,368 |
Matthew |
April 29, 1975 |
Pulp refiner element
Abstract
A refining element for a pulp stock refiner having at least its
working edges composed of a relatively soft (e.g. nylon), less
stiff material, as compared to ferrous metals, whereby fibers of
pulp refined in a refiner having such elements are fibrillated and
made flexible and have less tendency to be cut into shorter
lengths, as compared to pulp fiber refined with ferrous metal
elements, as the stock is processed through the refiner.
Inventors: |
Matthew; John B. (West
Stockbridge, MA) |
Assignee: |
Beloit Corporation (Beloit,
WI)
|
Family
ID: |
23331562 |
Appl.
No.: |
05/340,027 |
Filed: |
March 12, 1973 |
Current U.S.
Class: |
241/296;
241/DIG.30; 241/102; 241/244 |
Current CPC
Class: |
D21D
1/30 (20130101); Y10S 241/30 (20130101) |
Current International
Class: |
D21D
1/00 (20060101); D21D 1/30 (20060101); B02c
007/12 () |
Field of
Search: |
;241/293-298,188A,DIG.5,DIG.30,244-245,102,291,300 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Custer, Jr.; Granville Y.
Assistant Examiner: Goldberg; Howard N.
Attorney, Agent or Firm: Veneman; Dirk J. Samlan; Bruce L.
Mathews; Gerald A.
Claims
What is claimed is:
1. An abrasion resistant, hydrolytically stable fiber refining
element for use in a pulp refiner having at least its fiber
contacting surfaces comprising a thermoplastic having a modulus of
elasticity between about 0.1 .times. 10.sup.6 psi to about 2.0
.times. 10.sup.6 psi and having a creep limit temperature above the
operating temperature within the refiner.
2. The refining element as set forth in claim 1, wherein:
the refining element comprises a disk for use in a disk type
refiner.
3. The fiber refining element as set forth in claim 1, wherein:
the refining element comprises a blade for use in a conical
refiner.
4. The fiber refining element as set forth in claim 1, wherein:
the refining element comprises a blade for use in a beater type
refiner.
5. The fiber refining element as set forth in claim 1, wherein:
the material comprises an acetal hompolymer.
6. The fiber refining element as set forth in claim 1, wherein:
the material comprises a polyarylsulfone.
7. The fiber refining element as set forth in claim 1, wherein:
the material comprises a polysulfone.
8. The fiber refining element as set forth in claim 1, wherein:
the material comprises a polyphenylene sulfide.
9. The fiber refining element as set forth in claim 1, wherein:
the material is a pure matrix thermoplastic.
10. The fiber refining element as set forth in claim 1,
wherein:
the modulus of elasticity is between about 0.2 .times. 10.sup.6 psi
to about 1.2 .times. 10.sup.6 psi.
11. The fiber refining element as set forth in claim 1,
wherein:
the material is Type 612 nylon.
12. The fiber refining element as set forth in claim 1,
wherein:
the material is Type 610 nylon.
13. The fiber refining element as set forth in claim 1,
wherein:
the material is treated with a flurocarbon compound to increase its
abrasion resistance.
14. The fiber refining element as set forth in claim 13,
wherein:
the material comprises a modified phenylene oxide.
15. An abrasion resistant, hydrolytically stable fiber refining
element for use in a pulp refiner having at least its fiber
contacting surfaces comprising a thermoplastic material, the pure
matrix form having a modulus of elasticity of between about 0.1
.times. 10.sup.6 psi to about 2.0 .times. 10.sup.6 psi and combined
with fiber reinforcement to increase its creep resistance, the
creep limit temperature of the composite material being above the
operating temperature within the refiner.
16. The fiber refining element as set forth in claim 15,
wherein:
the material is ultra high molecular weight polyethylene.
Description
BACKGROUND OF THE INVENTION
This invention relates to refiners which prepare paper pulp fibers
to the desired condition prior to their being delivered to the
papermaking machine. More particularly, this invention relates to
the fiber contacting blades or disks within the refiners which
actually modify the pulp stock fibers to the desired condition.
The structural network that makes up a paper sheet is comprised
essentially of cellulose fibers which are randomly distributed and
connected to one another by virtue of bonds between hydroxyl groups
which are formed when the water is removed from the sheet. The
strength characteristics of the resulting sheet are dependent on
the extent of the bonding and the strength of the fibers that make
up the sheet. Following a conventional pulping process, the pulp
stock consists essentially of individual fibers. These fibers are
relatively slender tube-like structural elements made up of a
number of concentric layers. Each of these layers (called lamellae)
consists of finer structural elements (called fibrils) which are
helically wound and bonded to one another to form the cylindrical
lamellae. The lamellae are in turn bonded to one another thus
forming a composite which in accordance with the laws of mechanics
has distinct bending and torsional rigidity. In addition, a
relatively hard outer sheath (called the primary wall) encases the
fiber. The primary wall is often partially removed during the
pulping process. The relative stiffness of the fiber, the relative
low surface area, and the presence of the primary wall all inhibit
bond formation and subsequently limit the strength of the paper
formed from these fibers.
It is generally accepted that it is the purpose of a pulp stock
refiner, which is essentially a milling device, to remove the
primary wall and break the bonds between the fibrils of the
outermost layers resulting in a "frayed" surface thus increasing
the surface area of the fiber multi-fold. The term "fibrillation"
is commonly used to describe this.
Fibrillation alone, however, is not sufficient to produce strong
paper. Fiber must also be made more flexible, so that during sheet
formation the fibers conform to and around one another producing
large areas of intimate contact. This increase in flexibility is
accomplished by a rapid and frequent flexure of the fiber until the
bonds between the concentric lamellae are broken down
(delaminated), the result being equivalent to the delamination of a
beam.
It is the purpose of the pulp stock refiner to modify the fibers in
accordance with the above requirements without significantly
reducing the length or individual strength of these fibers.
Various types of refiners are in use and these can be classified as
disk, conical, and beater types. Examples of these refiners and
their blade elements are shown and described in U.S. Pat. Nos.
3,118,622; 3,323,732, 3,326,480; 2,779,251; 3,305,183 and
2,934,278, which are incorporated herein by reference.
It is obviously not possible to carry out the required fiber
modification on each individual fiber in commercial practice. In
fact, it is a purely random statistical application of physical
forces within a pulp refiner that accomplishes the average overall
effect. As fibers pass through the refiner in a water slurry, they
are acted upon by the impinging edges of a rotating blade element
and a stationary or oppositely rotating blade element. A
characteristic of such prior refiners is the use of metal as the
blade element material. The most commonly used metal, steel, has a
modulus of elasticity of around 30 .times. 10.sup.6 psi. The
material which comprises the pulp fiber, however, has a modulus of
elasticity in the range of about 0.8 .times. 10.sup.6 psi to about
2.8 .times. 10.sup.6 psi. Thus, the relative delicacy of the paper
fibers is apparent.
Since the energy applied to the refiner is controlled by forcing
these blade elements into close proximity, and since steel elements
are extremely rigid as compared to the fiber, only an average
intensity of applied forces can be controlled, and a wide
distribution of force intensity is applied to the multitudes of
fibers. In refiners, intensity is a comparative term relating the
power required to operate the refiner, considering the speed and
pressure forcing the refiner blade elements together, with the
relative percent of fibers in a distribution curve which meet
certain standards, such as fiber length. The result is that while
some fibers might be treated with precisely the required intensity,
many are treated insufficiently, and many are treated at an
intensity level so high as to cut or otherwise damage the fibers.
In order to insure that no fibers are extensively damaged, it would
be necessary to reduce the average intensity to a very low level
and "gently" refine the pulp repeatedly until, statistically
speaking, all of the fibers have received the appropriate
treatment. In practice, this could be accomplished by maintaining
low pressure levels between blades (many blades per disk or refiner
and relatively high speed) and passing the pulp stock through a
number of refiners in series, or many times through a single
refiner. This, if at all practical, is a costly process due to the
non-productive energy expended in the refiner as well as peripheral
equipment (pump, agitation tanks, etc.).
Even though steel refiner blades do have a long operating life
(anywhere from about 4 months to about 11 months, depending on type
of steel, in a disk refiner) and do refine the pulp fibers in a
manner satisfactory to produce a quality, saleable paper product,
these advantages are tempered by their inherent tendency to cut the
fibers into lengthwise segments shorter than actual fiber
length.
Attempts have been made to reduce the fiber cutting tendency of
refiners by using so called softer metal blade elements such as
bronze or aluminum. These materials have moduli of elasticity in
excess of 5 .times. 10.sup.6 psi and are also ineffective in
accomplishing the objective of not cutting the fibers lengthwise
into segments shorter than actual fiber length. In fact, blades
formed from these soft metallic materials exhibit a distinct
tendency to maintain very sharp edges as they wear and, as a
result, increase rather than reduce the degree of fiber
cutting.
Attempts have also been made to use very soft materials, such as
rubber or polyurethane elastomer. These materials have proven
ineffective since their moduli of elasticity are too low (1 .times.
10.sup.3 psi - 20 .times. 10.sup.3 psi) to efficienty produce the
required fiber surface modifications. Additionally, high hardness
polyurethane elastomers are prone to internal heat build-up, as are
hard rubbers, and subsequent failure when subjected to cyclic
deformation over an extended period.
SUMMARY OF THE INVENTION
The problems associated with cutting pulp fibers into lengthwise
segments have been mitigated by this invention. Instead of hard,
metal blade elements, it has been found that plastics, preferably
thermoplastics, made from certain synthetic resins fall into the
appropriate range of moduli of elasticity and at the same time
fulfill the requirements of strength, impact resistance, abrasion
resistance, and hydrolytic stability that would be expected in a
pulp refiner at normal operating temperatures. Elements made of
such materials fibrillate and delaminate the fibers without tending
to cut them lengthwise into segments. The use of a softer material
permits the element to conform somewhat to the impinging fiber
thereby producing a more uniform intensity of treatment on that
fiber as well as a more uniform distribution of intensity upon the
multitudes of fibers being acted upon at any instant by the many
blades in the refiner.
Surprisingly, these materials are relatively soft, having modulii
of elasticity of between about 0.1 .times. 10.sup.6 psi to about
2.0 .times. 10.sup.6 psi. They also must exhibit sufficient
resistance to abrasion and creep at their operating temperature
within the refiner.
Therefore, it is an object of the invention to provide a material
for use as a blade element in a pulp refiner having a modulus of
elasticity close to the modulus of elasticity of the pulp
fiber.
It is another object of this invention to use as the working
element of the blade, a material which is sufficiently soft so as
not to cut the fiber or otherwise damage it, but stiff enough to
produce the required surface modification.
It is another object of the invention to use as the working edge of
the blade, a material which has a modulus of elasticity which is
sufficiently high so that the required fiber surface modification
can be performed efficiently, that is to say with relatively low
energy expenditure.
Another object of the invention is to use, for at least the pulp
contacting edge of the blade element, a material which has a
modulus of elasticity between about 0.1 .times. 10.sup.6 psi to
about 2.0 .times. 10.sup.6 psi, which operates in a refiner below
its temperature at which creep occurs.
Another object of this invention is to provide a non-ferrous blade
element for a paper pulp refiner which fibrillates pulp fibers
without reducing the average fiber length as compared to fibers
refined with steel blade elements.
Still another object of the invention is to provide a thermoplastic
refiner blade element which is hydrolytically stable and abrasion
resistant.
Yet another object of the invention is to provide a refiner blade
element having such physical properties as to produce pulp fibers
to make paper having improved strength properties.
A feature of this invention is a refiner blade material which can
be molded into shape.
Another feature of the invention is that a refiner can be
constructed without any metallic blade elements for use in
industries where any metal in the refined pulp is extremely
undesirable.
These and other objects, features and advantages of the invention
will be apparent to one skilled in the art as the specification and
claims are read in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a face view of a disk for a disk refiner on which a
plurality of individual blade elements are formed.
FIGS. 2a and 2b are curves comparing the fiber length of a pulp
refined using nickel steel blade elements with the fiber length of
a pulp refined using nylon blade elements.
FIGS. 3a-3e, are curves comparing the properties of paper made from
a pulp refined using nickel steel with those of paper made from a
pulp refined using nylon blade elements.
FIG. 4 is a top view of a beater type refiner.
FIG. 5 is a side elevational view in section of the beater shown in
FIG. 4.
FIG. 6 is a side elevational view, partially in section, of a disk
type refiner.
FIG. 7 is a side elevational view, partially in section, of a
conical type refiner shell.
FIG. 8 is an end view of the conical shaped inner wall of the
refiner shown in FIG. 7 and showing the blade elements therein.
FIG. 9 is a perspective view of a conical refiner assembly.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 2a, 2b and 3a-3e, the merits of using a material
for refiner blade elements whose modulus of elasticity falls into
the previously specified range becomes apparent. In FIG. 2a, the
long fiber fraction of the pulp, as measured by the combined
percent retention on the 14 and 30 mesh screens of a Clark
Classifier, has not been significantly reduced when using nylon for
the blade refiner elements, even after refining to a Canadian
Standard Freeness as low as 250 ml. In the same figure, the fiber
length reduction when using the nickel steel (Ni-Hard) elements is
excessive at a C.S. Freeness level of 450 ml. Thus, for increased
intensity or refining time, a given quantity of pulp produces a
greater number of long, uncut fibers with plastic blade elements
than with steel blade elements. Conversely, at a specified
freeness, a greater number of longer fibers are produced with
plastic blade elements than with steel blade elements.
Statistically, this could be expressed on a distribution curve
(having the relative percent of fibers having a certain length to
the total number of fibers as one coordinate and the applied
intensity as the other coordinate) as a greater proportion of the
total number of fibers meeting a specified standard of refinement
for a given level of refiner intensity. All of these parameters and
tests are well known in the paper industry. Further, all tests run
to gather data for curves 2a, 2b and 3a-3e were conducted with
constant pulping consistency (4 percent) and stock through-put (83
gpm). Canadian Standard Freeness is a rough overall indicator of
pulp quality. A high number is desirable because it indicates the
pulp is "free," i.e. the water drains from it more rapidly. The
faster water drains from the pulp stock in the paper making
machine, the faster paper can be made. However, the higher
freeness, the less fibrillated and delaminated the stock is, so the
best pulp for a given paper machine speed is that having suitable
strength at the highest freeness. Conversely, at the same freeness
number, better quality pulp fibers will have higher tear factors,
breaking lengths and bulk values.
The effect of fiber length on the physical properties of paper made
from plups refined with the nickel steel and nylon elements (FIGS.
3b-3e) illustrates the considerable improvements in paper strength
which are possible when using a conformable material for the
refiner blade element. When using the nickel steel disks, the
maximum burst and tensile strengths are achieved at a C.S. Freeness
of about 500 ml. When using the nylon disks, the burst and tensile
strengths continue to increase until a maximum is reached at about
300 ml. These maximum values for the nylon disks are about 40
percent higher than those for the nickel steel. The fact that the
higher strength values were obtained at lower freeness readings is
indicative of the greater amount of fibrillation and longer fibers
refined with the nylon disks.
Due to the range of modulii of elasticity which is required to
obtain the desired intensity (which influences the percent of
fibers treated to the desired degree of fibrillation and
delamination), the choice of refiner blade material is effectively
limited virtually to a plastic. While use of a plastic under such
extreme service conditions as would be expected in a high speed,
high power attrition mill, seems quite unreasonable, the specific
properties of certain plastics render them feasible, in fact,
advantageous, under normal refiner operating conditions.
The material to be used for refiner blade elements, in addition to
having the appropriate modulus of elasticity (stiffness), must
possess certain physical properties in order to economically
replace a metallic element in a commercial installation. The broad
requirements are (1) hydrolytic resistance, (2) abrasion
resistance, (3) creep resistance at operating temperature within
the refiner, and (4) heat resistance (related to creep resistance).
In general, the poor abrasion resistance of most thermosetting
plastics effectively precludes their use and limits the application
to a thermoplastic material.
The broad spectrum of requirements further limits the choice of
thermoplastic materials. Ultra high molecular weight polyethylene,
while exhibiting superb abrasion resistance and hydrolytic
stability, has proven unsatisfactory in pure matrix form due to a
lack of creep resistance, particularly at temperatures above about
70.degree. F. Creep resistance of ultra-high molecular weight
polyethylene is improved to a satisfactory level when it is
combined with a fiber material, such as type 610 or type 612 nylon.
In addition, due to its relatively low modulus of elasticity, 0.14
.times. 10.sup.6 psi, it is less efficient in refining than the
harder thermoplastics. Similarly, modified phenylene oxide sold
under the tradename Noryl (reg. TM), while exhibiting excellent
hydrolytic stability, creep resistance and heat resistance, has
proven unacceptable without being combined, or chemically
compounded, with other materials due to its lack of abrasion
resistance. Many thermoplastics, such as modified phenylene oxide,
can be made sufficiently abrasion resistant by treatment with a
flurocarbon compound.
On the other hand, nylon, although processing no outstanding
properties, generally exhibits sufficiently high properties in all
respects to provide acceptable performance for continuous use.
Nylon types 610 and 612 have been found to be especially suitable.
In order to provide sufficient hydrolytic stability, type 612 nylon
was used for the blade material of the elements used in the tests
from which the data of FIGS. 2a, 2b and 3a-3e was obtained. At
least one nylon, type 6--6, is hydrolytically unstable and,
therefore, unsuitable for this type of use. Fiberglas reinforcement
was added to the resin to provide improved creep resistance and
heat resistance. Long term tests have indicated that the useful
life of the nylon disks is approximately the same as the expected
life of a nickel steel disk, although somewhat less than that of a
milled stainless steel disk.
Other materials which exhibit suitable properties include the
acetal homopolymers, polyarylsulfones, polysulfones, and
polyphenylene sulfides. Reinforcing fibers, such as glass, may be
added to any of these to enhance creep resistance (this is
especially effective as temperatures increase), and they may be
compounded with flurocarbons (Telfon which is a registered
trademark for tetrafluoroethylene (TFE) fluorocarbon resin, for
example) to reduce friction and decrease the wear rate (increase
abrasion resistance).
For temperature applications of less than about 90.degree. F., a
thermoplastic polyester or a glass reinforced polypropylene might
also be used.
Plastics are particularly desirable because they are usually easily
molded, extruded and machined, thus lowering manufacturing costs,
For example, modified phenylene oxide sold under the tradename
Noryl (reg. TM) and the type of nylons sold under the tradename
Zytel (reg. TM) have been successfully molded into disk type blade
elements. Disk elements can be molded, cast or machined, while
blade elements (for conical or beater type refiners) can be
extruded and/or machined.
Therefore, contrary to what might appear to be logically concluded,
some plastic materials, having particular physical properties, are
capable of performing quite well when used to make refiner disks or
blades. However, also contrary to what might appear to be logical,
the suitability of a material for use as refiner blade elements is
not a function solely of its hardness or stiffness (as measured by
its modulus of elasticity). It is a function of a combination of
these parameters which in turn may be affected by creep and heat
and abrasion resistance. More specifically, the creep limit of the
material is significant and this is defined as the maximum tensile
stress which can be applied to the material at a given temperature
without resulting in measurable creep. Therefore, the operating
temperature within the refiner becomes important. Depending on the
type of refiner (disk, conical or beater) and the applied load,
this operating temperature might range from about 50.degree. F. to
about 210.degree. F. If the temperature at which creep occurs is
within the range of refiner operating temperatures, a particular
material may not work in that type of refiner or at a particular
intensity, although it may be perfectly satisfactory in another
type of refiner having lower operating temperatures.
Shown below are Tables I through III which tabulate the test
results of disks made of Zytel (Reg. TM) and Ni-Hard (nickel alloy)
steel. The graphs in FIGS. 2a, 2b and 3a-3e were made from some of
the data in these tables.
The terms used in the following tables are all well known in the
paper industry, but for clarity, they will be identified as
follows: "BDT/D" means bone dry tons per day; "BHPD/BDT" means
brake horsepower per bone dry ton per day; "C.S. freeness" means
Canadian Standard freeness which is a measure of the rate with
which water drains from a stock suspension through a wire mesh
screen or a perforated plate; "bulk" means the apparent specific
volume of a sheet of paper when in a pile under a specified
pressure; "burst factor" is a numerical value obtained by dividing
the bursting strength in grams per square centimeter by the basis
weight of the sheet in grams per square meter; "tear factor" is the
tearing resistance in grams (per sheet) multiplied by 100 and
divided by the basis weight in grams per square meter; "breaking
length" is the length of a strip of paper, usually expressed in
meters, which would break of its own weight when suspended
vertically; "basis weight" is the weight in grams of a square meter
of paper.
TABLE I
__________________________________________________________________________
20" DD-3000 DISK REFINER SUPERIOR KRAFT (BLEACHED SOFTWOOD KRAFT)
1010 RPM MONO-FLO NI HARD DISKS 3,3,4 + 10.degree.
__________________________________________________________________________
OPERATING CONDITIONS Trial Raw Cir 1 2 3 4 5 Pass -- 1 1 1 1 1 1
__________________________________________________________________________
Consistency % -- 4.0 4.0 4.0 4.0 4.0 4.0 Through-Put -- 83 83 83 83
83 83 GPM Through-Put -- 20 20 20 20 20 20 BDT/D Applied Gross --
78 107 117 138 158 175 Energy BHP Net -- -- 29 39 60 80 97 Total
Gross -- -- 5.4 5.9 6.9 7.9 8.8 Energy Consumption Net -- -- 1.5
2.0 3.0 4.0 4.9 BHPD/BDT TAPPI PHYSICAL TEST RESULTS C.S.Freeness
ml. 655 625 600 580 550 505 455 Bulk cc/gm 1.83 1.78 1.76 1.73 1.68
1.63 1.63 Burst Factor 30.5 36.5 43.3 46.0 52.3 55.9 50.9 Tear
Factor 325 335 315 292 255 222 185 Bkg. Length M. 4280 4800 5610
5920 6780 7220 6970 Basis Weight g/M.sup.2 56.9 57.0 57.0 57.2 59.0
60.5 60.3 CLARK CLASSIFICATION RESULTS % FIBER RETAINED ON -- MESH
14 - Mesh % 45.3 51.7 51.6 53.8 53.5 45.7 31.2 30 - Mesh % 33.2
29.8 29.1 26.8 26.4 30.6 37.1 50 - Mesh % 8.7 8.1 8.3 8.1 8.6 10.6
13.8 100 - Mesh % 3.9 4.2 4.2 4.1 4.4 5.9 8.5 Thru 100 - Mesh % 8.9
6.2 6.8 7.2 5.1 7.2 9.4
__________________________________________________________________________
TABLE II
__________________________________________________________________________
20" DD-3000 DISK REFINER SUPERIOR KRAFT (BLEACHED SOFTWOOD KRAFT)
1010 RPM MONO-FLO NYLON DISKS 3,3,4 + 10.degree.
__________________________________________________________________________
OPERATING CONDITIONS Trial Raw Cir 1 2 3 4 Pass -- 1 1 1 1 1
__________________________________________________________________________
Consistency % -- 4.0 4.0 4.0 4.0 4.0 Through-Put -- 83 83 83 83 83
GPM Through-Put -- 20 20 20 20 20 BDT/D Applied Gross -- 78 120 138
158 178 Energy BHP Net -- -- 42 60 80 100 Total Gross -- -- 6.0 6.9
7.9 8.9 Energy Consumption Net -- -- 2.1 3.0 4.0 5.0 BHPD/BDT TAPPI
PHYSICAL TEST RESULTS C.S.Freeness ml. 655 630 595 575 550 525 Bulk
cc/gm 1.83 1.82 1.78 1.72 1.71 1.68 Burst Factor 30.5 37.9 43.9
50.2 54.7 57.4 Tear Factor 325 330 305 283 250 239 Bkg. length M.
4280 4945 5685 6320 6890 7300 Basis Weight g/M.sup.2 56.9 60.2 57.7
60.2 59.6 58.6 CLARK CLASSIFICATION RESULTS % FIBER RETAINED ON -
MESH 14 - Mesh % 45.3 58.3 56.6 55.5 56.6 56.1 30 - Mesh % 33.2
26.3 26.4 24.1 22.9 23.0 50 - Mesh % 8.7 8.2 8.2 7.8 7.8 7.7 100 -
Mesh % 3.9 4.0 4.0 3.9 3.9 4.0 Thru 100 - Mesh % 8.9 3.2 4.8 8.7
8.8 9.2
__________________________________________________________________________
TABLE III
__________________________________________________________________________
20" DD-3000 DISK REFINER SUPERIOR KRAFT (BLEACHED SOFTWOOD KRAFT)
1010 RPM MONO-FLO NYLON DISKS 3,3,4 + 10.degree.
__________________________________________________________________________
OPERATING CONDITIONS Trial Cir 1 2 3 4 5 7 8 9 10 Pass 1 1 1 1 1 1
2** 2** 2** 2**
__________________________________________________________________________
Consistency % 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 Through-Put
83 83 83 83 83 83 83 83 83 83 GPM Through-Put 20 20 20 20 20 20 20
20 20 20 BDT/D Total Gross 85 105 125 147 165 187 293 312 334 355
Applied Energy Net -- 20 40 62 80 102 122 142 164 185 BHP Total
Gross -- 5.3 6.3 7.4 8.3 9.4 14.7 15.6 16.7 17.8 Energy Consumption
Net -- 1.0 2.0 3.1 4.0 5.1 6.1 7.1 8.2 9.3 BHPD/BDT TAPPI PHYSICAL
TEST RESULTS C.S.Freeness ml. 610 590 585 555 510 480 390 340 300
270 Bulk cc/gm 1.83 1.79 1.74 1.69 1.67 1.62 1.57 1.57 1.53 1.51
Burst Factor 38.0 39.1 47.2 53.9 62.2 63.5 74.0 79.1 81.0 79.0 Tear
Factor 330 345 300 250 240 250 205 190 185 180 Bkg. Length M. 4700
4955 5555 6580 7425 7965 8695 9525 10270 10200 Basis Weight g/M
61.9 60.1 61.9 59.5 61.1 61.2 59.9 58.9 60.8 61.5 CLARK
CLASSIFICATION RESULTS % FIBER RETAINED ON - MESH 14 - Mesh % 53.5
53.9 56.4 60.5 59.9 60.5 59.2 56.5 61.8 61.4 30 - Mesh % 29.7 26.8
24.3 22.9 21.1 21.2 21.2 19.8 20.7 20.7 50 - Mesh % 8.4 8.2 8.0 7.9
7.0 7.4 7.0 6.8 7.1 7.1 100 - Mesh % 4.2 3.7 3.7 3.9 3.6 3.7 3.9
3.2 4.4 1.9 Thru 100 - Mesh % 4.2 7.4 7.6 4.8 8.4 7.2 8.7 13.7 6.0
8.9
__________________________________________________________________________
From the tests conducted, knowledge of refiner operating conditions
and past experience, it has been discovered that plastics having a
modulus of elasticity between about 0.1 .times. 10.sup.6 psi and
about 2.0 .times. 10.sup.6 psi, preferably between about 0.2
.times. 10.sup.6 psi and about 1.2 .times. 10.sup.6 psi, with a
creep limit temperature (the maximum temperature at which creep
will not occur) above the refiner operating temperature will
provide an excellent percentage of properly modified individual
pulp fibers per unit of refined pulp when used as the material
comprising the blade elements in a refiner. Ceramic materials,
including glass, tile, concrete and brick, and wood which have
modulii of elasticity falling within a 1.0 .times. 10.sup.6 psi -
10 .times. 10.sup.6 psi range, which slightly overlaps the above
range for acceptable plastic materials, either do not work nearly
as well or not at all; no rubber compounds or rubber-soft
materials, such as polyurethane elastomers, work satisfactorily as
blade elements in modern refiners for a commercially competitive
period of time, and none of these materials is intended to be
included within the category of claimed materials. Of course, steel
and other materials having modulii of elasticity above the level of
about 10 .times. 10.sup.6 psi do perform successfully in that the
pulp stock is refined sufficiently to be saleable but, as the tests
have shown, stock refined using disks having physical properties
set forth above will be of superior quality. The steel disks also
have the disadvantages of higher manufacturing costs and
maintenance as aforementioned.
In the above discussion, some relative terms are used, such as
"relatively low energy expenditure," "fibers treated
insufficiently," "economically replace," "sufficiently abrasion
resistant," and "acceptable performance." These are used where a
numerical value would be either inadequate, impossible, misleading
or non-informative, or all of these. Basically, the terms refer to
the degree of quality of the fibers refined utilizing refiner
elements composed of these materials to the quality of pulp fibers
refined with steel blade elements. The same applies to comparisons
between physical characteristics and operating economies wherein
these terms are used to relate the materials of the invention with
steel blade elements. Thus, if the pulp fibers refined by blade
elements composed of the materials of this invention, and the costs
of installing and utilizing them in refiners, are commercially
competitive in the paper industry, then it can be said the
particular combination of physical properties allows the refiner to
be "economically" operated with "sufficiently" abrasion resistant
elements to provide "acceptable" performance. Thus, for example,
there is no numerical value to identify what is "sufficient" in the
measurement of abrasion resistance.
In summary, the materials which will provide the desired pulp fiber
quality and meet the objectives set forth have a modulus of
elasticity of between about 0.1 .times. 10.sup.6 psi to about 2.0
.times. 10.sup.6 psi, preferably between about 0.2 .times. 10.sup.6
psi to about 1.2 .times. 10.sup.6 psi. They do not include rubbers,
polyurethane elastomers, ceramic materials including glass, tile,
concrete and brick, and wood. They must be hydrolytically stable,
abrasion resistant, or capable of being made sufficiently abrasion
resistant, and able to operate without deforming at the
temperatures encountered in the particular type of refiner they are
used in. They must be either creep resistance in pure matrix form
or capable of being treated to be creep resistant at the
temperature of operation within the refiner. Typically, treatment
to increase abrasion resistance sould be to chemically treat the
material with a flurocarbon compound, and treatment to increase
creep resistance would be to fill the material with glass fibers.
The preferred embodiment material is preferably plastic, ideally a
thermoplastic, but not a thermosetting plastic.
In FIG. 1, a plastic refiner disk 10 is illustrated on which a
plurality of grooves 12 are cut at an angle 14 with an imaginary
line extending radially from the center axis of rotation 16.
Grooves 12 define a plurality of blades 18 which fibrillate and
refine the stock as it passes radially outwardly between two such
refiner disks in refiner such as shown and described in U.S. Pat.
Nos. 2,968,444; 3,118,622 and 3,323,732, all owned by the assignee
of this application. The disks are attached to the refiner by cap
screws through holes 20.
In FIG. 4, a substantially cylindrical shaped beater 30 is shown
rotatably mounted in a tank 32. The individual blade elements 10a,
also shown in FIG. 5, are shaped like a rectangular prism and
extend radially from the axis of rotation 36 of beater 30. Stock
travels in a continuous path about the tank and is refined as it
passes between the beater blades 10a and the similarly constructed
blades 10b mounted in the tank.
FIG. 6 illustrates the type of refiner 40 in which the disk 10
shown in FIG. 1 would typically be mounted. The stock travels
inwardly axially at 42 and is refined between disks 10, 10' as it
travels radially outwardly to outlet 44.
The blade elements 10d shown in the conical beater wall 51 in FIGS.
7 and 8, are in a spiral configuration, but they can also extend in
a straight line in a plane coextensive with the beater's axis of
rotation 52 as the blade elements 10c shown on rotor plug 50 in
FIG. 9. Stock travels axially along the periphery of the conical
beater plug 50 where it is subjected to varying degrees of refining
intensity between the blade elements 10c on rotating plug 50 and
blades 10d mounted on the inner conical wall 51 of the beater as it
travels from the small end to the larger diamter end.
The construction and operation of all of these beater, disk and
conical types of stock refiners is well known in the paper
industry.
Naturally, the refiner materials described can also be used with
corresponding results when made into, or formed upon, the blade
elements for conical and beater type refiners. Thus, only the pulp
contacting portions of refiner disk could be made of, or coated
with, plastic to lower costs of manufacture and replacement. A more
rigid material, such as steel or cast iron, could provide the
support for the plastic covering on a plastic coated blade
element.
Thus, a set of parameters has been disclosed for a material to be
used as a paper pulp refiner blade element which provides
unexpectedly good results and achieves the objects, features and
advantages set forth. While a preferred embodiment has been
discussed in detail, it is understood that other specific materials
which meet the described parameters can be used and they also fall
within the spirit and scope of the attached claims. Also, while
wood constitutes the raw material commonly used for pulp, other
materials, such as cotton and bagasse, are used and are intended to
be within the scope of the invention.
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