Note: Descriptions are shown in the official language in which they were submitted.
1089273
TREATING CHEMICALLY DELIGNIFIED A~D FIBERIZED
CEL~ULOSIC PULP FOR PULP PROPERTY IMPROVE~IENT
Background of the Invention
Field of the Invention
This invention relates to a process for mechanically treating
chemically delignified and ~iberized cellulo~ic pulp and to the
pulp product of improved properties resulting therefrom.
De3cription of the Prior Art
In the manufacture of paper, strength properties in two areas
must be satisfied: Those affecting machine runability and those
affecting final product strength. Overall, three areas of fiber
characteri~tics are critical: (a) their contribution to the stren-
eth requirements, (b) t~elr contributlon to brightness, density,
smoothnes~, opacity, and other propertles related to product re-
quire~ents; and (c) their co~t~
There are essentially three papermaking ~iber types: (a)
~roundwood (which i9 least expensive and weakest), (b) short chem-
ical fiber (which is intermediately expensive and strong), and (c)
long chemical fiber (which i8 most expensive and strongest). To
achieve the physical property balances required, a substantial pro-
portion of long chemical fiber conventionally is blended with gr-
oundwood or short chemical ~iber. The lone fiber portion of theseblends adversely a~fects the furnish costs and some product quality
aspects.
To minimize the requirements for the relatively expensive long
chemical fiber and to improve the product quality of the blends,
it is common practice to refine cellulosic ~ibers mechanically pr-
ior to final papermaking utilization. This treatment causes a
change in the specific surface area and/or shape, size and charac-
teristics of the individual pulp fibers, designed to satis~y st-
rength properties in the two areas referred to above, viz., the
properties affecting machine runability and final product strength.
Specifically, pulp properties sought to be improved are app-
-1- ~
10~9Z1~3
arent density, burst factorJ tear ~actor, fold, tensils strength,
elongation, internal bond and opacity.
The problem has been that the application of treatments which
successfully improve the pulp with respect to certain of these
properties deteriorates the pulp with respect to others. It i9
di~ficult to devise a mechanical treatment which materially impro-
ves the properties of the pulp in any given respect, while still
maintaining a satisfactory balance of the other important pulp pr-
operties.
The most common mechanical fiber treatment practiced in the
papermaking field i9 low consistency beating or re~ining. In these
operations the pulp, in the ~orm o~ a slush or slurry in water,
having a consistency ~rom about 0.3~ to about 5.0~, is sub~ected
to mechanical treat~ent in a beater, a disc re~iner, a con~cal re~
~iner or related equipmenk. This action improves some strength
properties of the resultant paper, notably tensile strength and
burst strength, However, these strength improvements are achieved
at the expenss o~ other desirable properties such as tear strength,
tensile energy absorption and pulp ~reeness.
Since low-consistency beating or re~ining procedures induce
~iber damage or fracturing, other techniques o~ processing cellulo-
sio pulp have been devised.
In one such process, Hill U.S. 2,516,384 and 3,028,632, as
reported in PaPer Trade Journal, Vol. 128, No. 9, pages 17-22
(March 3, 1949~ and Vol. 128, No. 11~ pages 19-27 ~March 17, 1949),
fibers are worked at high consistency between two opposed relatively
gyrating working elements whils under atmospheric pressure condi-
tions.
Although the application o~ this atmospheric pressure procedure
improvss some properties9 i.e. tear, opacity and rreeness, it dr-
astically reduces the bonding properties o~ the pulp below accept-
able limits. Accordingly, this proce~s has not gained widespread
commercial acceptance.
~89273
Leask U.S. 3,661,328 defiberizes wood chips and other raw
cellulosic material, rather than chemically delignified and fiber-
ized cellulo3ic pulp, in a mechanical defiberizer wherein the lig-
nocellulose is worked in an atmosphere of steam and accordingly
utilizes the high temperature of the ~team to soften the lignin in
the raw wood. However, the Leask process does not address itself
to the problem toward which the pre~ent invention i5 directed, viz.,
the problem of the properties of delignified cellulosic pulp, and
his product i8 not the same as, nor directed toward the same end
purpose, as is the product of our invention. Leask defiberizes
raw wood chips to produce lignooellulosic pulp. We refine deligni-
fied cellulosic fiber to produce a cellulosia pulp o~ improved
properties .
Henderson et al U.8. 3,382,140 describe~ a ~igh conslstoncy
refin1ng process for papermaking pulp. This process is termed
hereln the "HCR" proces~ to distinguish it from the process of our
invention which i~ a high consistency, high temperature refining
process, termed herein the "HCTR" process.
While the pulp product of Henderson et al may be converted to
a papermaking web having physical properties improved in certain
respects, its application is attended by serious disadvantA~es
whlch limit its commercial application. For example, even with the
refinine power input at its lowest stipulated level, the Henderson
process produces pulps of higher density than are desired for the
manufacture of fine or publication grade~ of paper. In fact, the
~enderson et al proce~s densifies the pulp so rapidly that as a
practical matter it is not possible to control densi~ication to the
desired range. As a result, certain papers made from the pulp are
commercially unacceptable becauqe of high density and insurficient
opacity.
In summary, while the prior art procedures for mechanically
refining cellulosic pulps have found wide application in the paper-
lOl~9Z73
making industry, nevertheless their effectiveness~ has~not been such as to enable reducti~on of the ~equired
proportion of the long chemical fiber content of the
papermaking furnish significantly below-its current
level. This disappointing result derives from the
ever-present pulp property deficits which accompany
the property advantages of the refined pulp. Specifi-
cally, high tear, stretch, tensile, bonding and
opacity at low-power input and low apparent density
are not simultaneously achievable by any of the pro-
cesses known to the prior art.
Objects of the Inventi~on
It accordingly is the general object of the
pr~sent invention to provide a process or treatincJ
chcmically delignified and fiberized cel:Luloslc pulp
for improvement of its strength and other papermaking
properties.
It is another object of the present i,nvention
to provide a process for mechanically treating cellulosic
pulp to produce a pulp product having an enhanced balance
of properties .
It is another object of the present invention to
provide a process ~or treating chemically delignified and
fiberized cellulosic pulp to enhance its balance of phyi-
cal characteristics beyond levels available with conven-
tional refining.
In summary of the above, therefore, the above
objects are met by the present invention which provides
the process for treating cellulosic pulp for property
improvement which comprises:providing a quantity of
chemicallv delignified and fiberized cellulosic pulp characterized
by: a TAPPI K number of from 0 to about 30, a ~onsistency
,,, _ a~ --
~()89273
of from about 10% to about 50~ by weigh~, a temperature
corresponding to the temperature of saturated steam at
a pressure from about 0 to about 60 psig, and mechan-
ically refining the pulp at said consistency under a
steam pressure of from about 10 to about 60 psig,
substantially continuously, at a feed rate and under
refining conditions determining an energy input into
the pulp of from about 0.5 to about 10 net horsepower
days per ton.
Description of the Drawings
The four figures of the drawings consist respective-
ly, of graphs illustrating the efect on pulp properties
of applying a typical high consistency, high temperature
reining procedure ~CTR) oE our invention to chemically
delianified and fiberized cellulosic pulps, as compared
to the effect of applying the conventional high consis-
tency refining (HCR) procedure thereto.
Fig. 1 is a graph of apparent density vs. energy in-
put for the two procedures. The energy input is express-
ed ~s horsepower days per ton (HPD/T). (TAPPI StandardReference No. T-220.)
Fig 2 is a plot of elongation vs. energy input.(TAPPI
Standard Reference No. T-457.)
Fig. 3 is a plot of tear factor vs. energy input.
(TAPPI Standard Reference No. T-220 . )
Fig. 4 is a plot of Scott internal bond vs. energy
input. (TAPPI Standard Reference No. RC-308.)
General Statement of the Invention
Generally stated, the presently described process
comprises mechanically refining chemically delignified,
fiberized, preheated
-- 5 --
1(~8~273
cellulo~ic pulp in an environment Or high pres~ure ~team but under
a condition Or low refining power con~umption.
Stated more specifically, the hereinde~cribed process for
treating chemically delignified, fiberized, cellulo~ic pulp compri-
ses providing a quantity of the pulp characterized by: (1) a TAPPI
"K" number o~ from 0 to about 30; (2) a con~listency of from about
10~ to about 50~ by weight; and (3) a temperature corre~ponding to
the temperature of saturated steam at a pre~sure of from about 10
to about 60 psig. The pulp thus characterized is mechanically re-
fined at the stated consistency under a steam pressure ~rom about10 to about 60 psig, sub~tantially oontinuously, at a feed rate and
under re~ining conditions predetermined to re~ult in an energy input
into the pulp o~ from about 0.5 to about 10 net horsepower dAys
pcr ton.
It i~ to be notsd that the procedure Or the invention as out-
lined above is directly contrary to the teachings o~ the prior art.
It would be expected that mechanically rerining chemically delig-
ni~ied and riberized cellulosic pulp in the presence of high pres-
sure steam would oause d~gradation of the cellulose, a le9~ of
brightness, and deterioration of other pulp propsrtie~. Ample au-
thority is available in support o~ this conclusion, the following
being illustrative:
Meohanioal Treatment o~ Chemical Pulps by M. D. FaheyJ Tappi,
Vol. 53, No. 11, November, 1970. At Page 2053, first complete
paragraph of column 1. See also Page 2062, column 1, fourth com-
plete paragraph thereof as well as Page 2063, column 1, third
co~plete paragraph and page 2064, column 1, la~t sentence of the
fi~th complete paragraph.
West, et al. U.S. 3,445,329, Column 2, at line 65 and ~ollow-
ing; column 3, at line 10 and following and lines 27-47 inclusiv0
thereof.
Hill U,S. 2,660,097, column 3, line~ 43-47 inclu3ive.
~089Z73
"The Curlator" Its Application to Hi~h Yield Newsprint Sul-
phite, Frank P. Silver - Papsr presented at Annual Meeting of the
Technical Section of the Canadian Pulp & Paper Association, Montreal,
Quebec, January 26-28, 1949. See the Abstract published in Pulp &
Paper Magazine o~ Canada, Convention Issue, 1949 at page 196; page
199, column 1, first incomplete paragraph thereof, last sentence.
Development o~ 65 Per Cent Yield Sulphiite ~or Newsprint Fur-
nish~ Pulp & PaPer Ma~azine of Canada, Convention Issue, 1953; Ab-
stract at Page 215; column 1, first complete paragraph at page 218,
column 1, fourth complete paragraph at page 219.
Surprislngly, we have discovered that, contrary to t;he teach-
ings of the above and other referenc~ sources, where the pro¢edure
i~ carried out under the conditions di~closed and claimed herein,
mechanically re~ining chemically deligni~ied and riberized cellu-
lo~ic pulp at high consi~tency and in a hlgh pres~ure ste~m environ-
ment actually improves its papermaking qualities to a significant
degree and in important re~pect~, without significantly degrading
the cellulose~
Speci~ically, mschanically refining such a pulp under the st-
ated conditions improves signirioantly its properties o~ tear, el-
ongation, bond, and tensile energy absorption while maintainin~
its apparent density at the desired value and its other papermaking
properk~es at satis~actory levels.
The accuracy o~ this conclusion is clearly portrayed in the
four figures of the drawings which are, respectively, plots of
power con~umption ~horsepower days per ton) vs. apparent density,
elongation, tear, and Scott internal bond. An inspection of these
plots indicates at once the very greatly improved properties of the
pulp produced by the herein described high consistency~ high temp-
erature refining procedure (HCTR pulp) as compared with that pro-
duced by the high consistency re~ining procedure o~ the prior art
(HCR pulp). Fig. 1 indicates, furthermore, that these propertie~
are achieved while mRintaining the apparent density of the pulp
1~139273
at the desired commercially acceptable level chosen from a wide
range of values.
The practical aspects of this improvement are Or the greatest
importance.
As will be shown hereinafter9 by the practice of the present
invention it i9 possible to substitute without sacrifice of paper
properties a low cost pulp such a~ a hardwood kraft pulp or a me-
chanical pulp ~or a substantial proportion of the high cost, long
fiber pulp heretofore required to pruduce papers of certain grades.
In a typical lO00 ton per day paper mill, such a substitution can
result in a raw material cost saving o~ over l~ million dollars per
year, depending upon the cost and availability of the long riber
pulp. Multiply this savin~ by a ~actor corre~ponding to the number
Or paper mills making simllQr paper products and the total econo~ic
saving made possible by the application of the process o~ our in-
vention 19 indeed significant.
In addition, for integrated older mills, which represent the
ma~ority of North American paper mills, the present invention makes
other substantial prorit opportunities available. For example,
if the mill ha~ limited digester capacity which limits pulp pro-
duction, use Or the present proce~s can reduce the requirements ~or
low yield, long riber pulp, and th0reby increase ~ubstantially the
digesters~ effective productivity by using the digester capacity
~or making higher yield pulp.
The same opportunity is present in a mill having limited re-
covery facilities. By reducing the need for long cellulosic fibers,
the production Or which i9 attended by the production o~ an incr-
eased amount Or black liquor to be cycled to recovery, the strain
on the recovery unit is relieved,
In addition, the present process leads to the procluction of
a pulp, and hence Or a paper, which provides a higher profit margin
because of its increased use Or lower cost pulp, while maintaining
9273
commercial produ¢t properties.
DESCRIPTION OF PREFERRED EMBODIMENTS
OF THE INVENTION
As ~tated above, the pulp treating process o~ our invention
essentially comprises mechanically refining chemically deligni~ied
and fiberized cellulosic pulp in a preheatedl condition, at high
consistency, at high temperature~ in an environment of superheated
steam, under a condition of low power consumption.
The chemically delignified cellulosic pulp employed as the
starting material may comprise any chemically delignified pulp in
fiberized conditlon, e.g. softwood or hardwood pulps or mixtures
thereof, wherein the fibers are in the condition of ~ubstantially
individual ~ibers.
The pulp8 may be bleached or unb~ea¢hed. Pre~0rably they com-
prise the chemio~lly dellgniried ~ulp~ rererred to in the art as
"full ohemioal pulp8" . In the manufacture of ~uch pulps, a variety
of pulping liquors are employed, for example those employed in the
conventional kraft, soda or other alkaline systems; in the sulph-
ite, bisulphite or okher acid systemq; in the neutral sulphite Sy9-
tems; and the like.
In many chemical pulping operationq the wood is both deligni-
rled and ~iberized. In such ca~ss the re~ultant pulp i9 well suit-
ed for feeding at the proper ¢onsistency to the refining process
of this invention.
On the other hand, it i9 possible to subject wood chips to
chemical delignification under conditions whereby, although sub-
stantially delignified, the pulp i9 not fully fiberized. In ~uch
caqes the delignified pulp may be sub~ected to fiberizing operations
under mild conditions which do not adversely affect fiber length.
The re~qultant delignified and fiberized pulp then i5 suitable for
employment as a starting material for the proceqq o~ this invention.
In contradiqtinction to lignocellulosic pulps produced by the
~echanical defiberi~ation of wood, the pulps which are ~uitable
_9_
2~3
ror our purposes are largely cellulosic in character and contain
but a small proportion of lignin. B~ de~inition, a pulp suitable
for our purposes mu3t have a lignin content such as to be charac-
terized by a permanganate number ("K number"), as measured by
TAPPI Standard T-214 t3-50, of from 0 to about 300 Pulps having
K numbers hi~her than 30 contain too much lignin to be treated
satisfactorily by our process.
The pulp to be treatad must be of high consistency~ i.e. a
consistency Or broadly from about 10% to about 50%, preferably
rrom about 30 to about 45% by weight. A pulp Or this consistency
is obtained by feeding the contents Or the digester in which it is
produced into a washer where it is slurr~ed or otherwi3e washed to
remove chemical~ and 3~parated lignin. Therea~ter the pulp i~ de-
watored in a suitable dewaterin~ system, such as a twin roll presQ,
a screw press, a piston press, a vacuum filtsr, or vacuum flashing
apparatu~.
The pulp product of any Or the foregoing devices has a con-
sistency o~ broadly from about 10 to about 50~. To make it more
easily handled, the dewatered pulp prererably is pa~sed through a
shredder or similar device which breaks it down into chunks or
pieces having cro~s sectional dimen3ions Or the order o~ less than
onc in¢h. Pieoes Or this size are be~t suited ~or conveying, hand-
ling, steaming and refining under the conditions Or the presently
described process.
The ribrous raw material may, if de~ired, contain a proportion
Or any of the well known pulping and papermakin~ additives such as
alum or caustic ror pH control, polyelectrolytes ror zeta potential
control, peroxides ror bleachin~, pigments ror optical control~
resins ror ~izing control, etc.
To achieve the purposes o~ the present invention it is neces-
sary that the ribrou3 stock be at a temperature level corresponding
to the temperatur0 Or saturated steam at a pre~sure Or ~ro~ about
_ln_
~89273
10 to about 60 p9ig~ pre~erably from about 30 to about 50 p~ig.
Stated otherwiseJ the temperature of the ribrous stock should be
at a value of from about 116 to about 153 degrees Centigrade.
Concievably, this condition could be achisved by employing a
high consistency pulp the di~ester heat cont;ent o~ which has been
preserved. In other words, it is possible t;o feed a high consist-
ency, chemically deligniried and fiberizsd pulp into the process
flow of the invsntion under conditions whereby it i~ already hot as
~t comes from the digestion process in which it was produced.
Mors practically, however, undsr ths condition~ usually pre-
~ailing in the average pulp mill, it i8 nece~sary to heat the high
consistency pulp to the pro¢e~sing temperature.
The pulp accordingly is charged through a sealing devlce such
a~ a pocket valv~ or tapered ~crew to a pre~teamer wherein it i9
sub~ected in a ~ealed environment to a pressurized atmosphere oom-
prising stsam at superatmospheric pressurss of from about 10 to
about 60, preferably from about 30 to about 50 psig, and correspond-
ing te~perature~ for ~aturated steam.
If desired, the steam may be admixed with air and/or one or
more well known pulping and paper~aking agents such as chlorine,
chlorine monoxide, chlorine dioxide, oxygen, ozone, etc., provided
only that the partial pre~sure Or the steam i8 maintained at at
least about 10 psig.
The ribrous feed i9 treated in the presteamer for a time suf-
ficient only to heat the fibers to the indicated temperature levelO
In a typical instance, this will require from about 0.2 to about 5
minutes, pre~erably from about 0.5 to about 3 minutes.
Immediately artsr the fibrous charge has reached the indicated
temperature, it i~ mechanically refined. It is of critical import-
ance to the success of the instant process that the pul;p not besubjected to a presteaming operation for a period of time substan-
tially longer than that required to bring it to temperature. As
~(~89;~3
discussed at length above, to do so would subject it to the efrect
of high temperature steam ror an unduly long period of time and
result in the degradation o~ the pulp and the undesirable reduction
of its critical papermaking property values~,
Accordingly, the pulp is passed immediately from the presteam-
er into the device wherein it is mechanically refined.
The term ~'mechanically refining" as used hereln denotes Q
procedure in which the pulp is introduced under superatmospheric
steam pressure into an atmospherically closed reEion between two
working surfaces in relative rotation to each other, which are
maintained a sufficient distance apart to prevent surface contact
under empty running condition~.
The relative motion between these work~n~ ~ur~aces sub~0cts
the pulp to both inter~iber and intra~lber ~riction. Without com-
mitment to any particular theory, it is believed the mechanical
working and resultant ~rictional forces applied to the hot, ~uper-
atmospheric pressurized and high consistency pulp cause3 the pre-
steamed and delignified fibers to become micro-compressed, kinked,
ribrillated and extremely M exible, but without experienclng ex-
tensive zone ~racturine. The shapes o~ the ~ibers arter treatmentare such that they lie in more than one plane. These characteris-
tics are advantag~ous in developing desirable pulp physical prop-
erties. They are achieved in unique balance in the practics o~ our
invention by the expedient of presteaming the ~ibers and re~ining
them at low horsepower consumption while they are still hot ~rom
the presteamîng operation.
The mechanical refining device employed may be any suitable
apparatus wherein working sur~aces with relative rotary motion are
closely spaced and the working ~pace is maintained under super-
atmospherlc steam pres~ure. Pre~erably the refining space withinthe atmospherically closed mechanical re~iner contain~ opposed disc-
like working sur~aces relatively rotatable around a common axis.
-12-
~3892t73
Steam pressurized double-revolving di~c refiners in which the
di~cs rotate in oppo~ed direction~ are most preferred.
An exe~plary refining device i9 the pressuri2ed, double-re-
volving-disc refiner illustrated ~nd described in U.S. Patents
3,765,611 and 3,765,613 (e.g., double di~c pressurized re~iners
Nos. 418, 420 and 485 o~ the Bauer Brothers Company). However,
other type~ such as pressurized single disc re~iner (available
from various manufacturers, including for example the l'Ra~inator"
Series RLP 50/54 S of American Defibrator Inc.; Sprout Waldron
Models 36 and 42 ICP: and many others), will perform satisfactorily
in some applications o~ the process Or this invention.
As in the case Or the pre-~teamer in which the pulp i9 brought
to tempera~ure, the pres~urlzed re~iner provides a steam pres~ur-
iæed environment for the high conslstency pulp. In most ca3es the
steam prossure and temperature ¢onditions in the pre-steamer and
refiner are ~imilar. In fact, it is preferred that the two appar-
atus unit~ oommunicate with each other. As a result, the steam
pressure within both the pre-steamer and the refiner will vary from
about 10 to about 60 psig., preferably from about 30 to about 50
20 p9ig., with the temperature being the oorrespondlng temperature ~or
saturated steam.
T~us, as the hot, high oon3i~tency, ohemically dellgnified
and fiberized pulp i9 ~ed into the inlet of the presxurized refiner
and between the spaoed apart, opposed working surface~ thereof, it
i3 continuously under superatmospherio steam pressure.
In the usual pressurized double-revolving disc refiner, suoh
as the 8auer referred to above, the opposed working surfaces are
relatively rotatable about a common axis. The spacing between the
working surfaces (orten called "plate clearance") is in the range
Or from about 0.002 to about 0.070 inch, typically from about
0.015 to about 0.05 inch, and preferably from about Q.02 to about
0.04 inch. This 3pacing is ad~ustable. The surface~ ordinarily
~ rrad~ rk
-13-
1~89~3
are of a somewhat textured or rough character to minimi~e pulp
~lippageO
When using such a refiner in accordance with the proce3s of
this invention, the opposed working surfaces are rotated at a rel-
ative tangential velocity in the range Or from about 10,000 to
about 40,000 ft/min., and preferably from about 20,000 to about
40,000 ft/min. The speciric set of operating conditions for the
pressurized reriner will vary somewhat depending upon a number of
ractors such as the type, size and design of the refiner used, the
nature and consistency of the pulp being processedJ and khe rate
of pulp throughput in the system. Such factors can be ascertained
and optimiæed readily in any given situation.
Ordinarily the hlgh oon~istency pulp as it pa~ between the
worklng ~urrace~ Or the re~iner 1~ prim~rily in chunky, padded
form. In other words, in tho practice of this invention it is not
necessary to maintain the working space between the working surraces
packed with a continuous sheet of high consistency pulp.
In general, the pressurized refiner is operated under condit-
ions suitable for causing the high consistency pulp to be mechan-
ically worked under superatmospheric steam pressure and temperature~o that the fiber~ retain their length and are refined to yield a
pulp product which can be made into Yheet~ of paper having signi~i-
cantly hi~her tear factor, elongation and Scott internal bond and
acceptable apparent density, as compared to sheet~ of paper made
rrom pulp produced ~rom the same kind Or chemically delignified and
riberized pulp which has been merely beaten to equal burst strength
in lieu of being subJected to the process of this invention.
It is a particular reature of the present invention that in
the refiner the power input, i.e. the work done on the pulp, is
controlled within stipulated limits in order to develop the desired
pulp properties. These limits are well below the power input app-
lied to pulps in the conventional procedures rererred to above.
-14;
-` :1089Z73
The power input, as determined by such factors as the ~eed
rate o~ the pulp, the pulp consistency, and the clearance of the
re~iner plates, is maintained at from about 0.5 to about 10 net
horsepower days per ton ~HPD/T), preferably from about 1 to about
5 net horsepower days per ton. By definitic,n horsepower days per
ton is the horsepower applied to the pulp divided by the tons per
day output of the same.
Increasing theenergy input to the pulp above 10 net horsepower
days per ton has the disastrous e~fect, from the standpoint Or the
present invention, of increasing the apparent density o~ the pulp
product to unacceptable values. See Fig. 1.
In particular, it raises the apparent density of the pulp to
level at which the paper made ~rom the pulp i9 too th~n, too
ea~y to ~oar, and too light-transmissive ~or satlsfaotory commerc-
iAl use ~,
A~ter re~ining, the pulp in a hot condition is discharged fromthe refiner and worked up in a suitable manner.
Accordingly, it may be diluted (quenched) in any apparatus
having a design calculated to bring the hot, refined pulp into con-
tact with water or other appropriate cooling liquids. Therea~terthe pulp is slurried with water to a consistency wh1ch is conven-
ient ror use in papermaking, and used in the ~urnish o~ a paper
making system~
Although the pulps o~ this invention when used per se as the
entire cellulosic pulp content o~ the furnish make paper suitable
for some purposes, it is generally advantageous to use them in com-
bination with one or more conventional pulps. So doing can result
in large pulp cost savings, as is discussed at length supra.
More particularly, the refined pulps o~ this invention may be
transferred to a suitable pulp mixer and therein slurried or other-
wise mixed in suitable proportions with one or more types of con-
ventional pulps to provide a pulp blend which therea~ter may be used
-15-
89Z~3
in the rurnish to the paper making systemO
EXAMPLES
The process of the invention and tha pulp products thereof are
illustrated in the following examples:
A ~eries of semi-work trials utilizing a Bauer Brothers No~
418 pre3surized double-revolving disc refiner was conducted. The
refiner had counter-rotating plates 36 inches in diameter which
operated at the normal factory preset speed of 1200 rpm, each plate.
The plates were textured (Manufacturer's plate design numbers 36325
and 36326) with a taper Or 0.001 inch.
All pulp~ u~ed in these trials were prepared from mixed North-
ea~tern U. SO softwood~ or mixed Northeastern U. S. hardwood~, all
Or the type conventlonally employed in New England paper mills.
The teQt~ performed on the pulp8 involved ln these exampleQ,
and the paper made therefrom, were conducted using standard TAPPI
methods (except where otherwise noted). Abbreviations used in the
exampleq are as rOllOws:
HCTR = High consistency, high temperature re~ining
(Qteam pressurized)
HCR = High consistency refining (no applied stsam
pre 9 gure )
VIB = Valley Iron Beater (laboratory)
HWK = Eardwood kraft
SWK = Softwood kraft
GWD = Groundwood
The units used for the operating conditionq and properties
presented in the examples are as follows unless otherwise indicated:
Consistency: dry weight percent of pulp in a slurry
Plate Clearance: inches
Feed Rate (pulp to Bauer No. 418 refiner): tons/clay
VIB Beating Time: minutes
Freeness (CSF): cc
~0892~3
Drainage Time: seconds
Apparent Density: lb/25" x 38" x 500/mil
Burst Factor: (lbs/in2/bs. wt.) x 100
Tear Factor: (grams to tear 16 sheets/bs~ wt.) x 100
Fold: NoO of double folds under 1 kg load
Tensile: km o~ web supportable by own skrength
Elongation: % at rupture
Scott Internal Bond: ft. - lb. x 10-3
Opacity (TAPPI): B & L %
Tensile Energy Absorption: g - cm/cm2 for
L~O lb/3300 ~t2 handsheets
In the ensuing tables, N/A i8 used to signi~y that the particular
oondit~on or property i~ not applioable. Dashe~ ) are used to
~ignl~y the absence o~ the particular determLnatlon or mea3urement.
HPD/T signif'ies net horsepower da~Js per ton of pulp (correcked f'or
horsepower wa~ted during idling of the refiner).
EXAMPLE 1
-
This example illustrates the characteristic changes in the
physical properties of bleached (85% Gardner brightness) so~twood
kra~t pulp produced by various conditions of' the process o~ this
invention (HC~R) a~ compared to those produced by a conventional
laboratory beater (VIB).
Conventional Qof'twood kra~t pulp was dewatered ~n an Impco~
twin roll press and wa~ continuously fed to a steam pressurized
Bauer Brothers re~ining system, which provided ~or a 2.8 minute re-
tention under 50 psig saturated steam pressure prior to ~eeding the
pulp under the same pressure through the above described Bauer
Brothers No. 418 counter-rotating double disc pressurized ref'iner.
The ref'ined pulp was discharged via a cyclone into a hydrapulper
for quenching and dilution. For comparison, ~amples of' the same
pulp, but without rerining, were beaten in a Va:Lley Iron laboratory
beater (VIB). Table I presents ~urther operating conditions and
m~r
-17
~89~:73
the re~ults of the operations.
From the results, it can be seen that handsheetq made from
HCTR treated pulp exhibit increases in tear strength, elongation,
Scott internal bond, and wet web tensile energy absorption co~pared
to hand~heets made from pulp treated in the Valley Iron beater,
while suffering losse~ only in opacity and very slight burst and
tensile deficits.
-18-
~089273 . - .
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9Z73
EXAMPLE 2
This example illu~trates the characteristic changes in the
physical properties Or bleached hardwood kraft pulp produced by
various conditions Or the process of this invention.
Convent~onal hardwood kraft pulp bleached to 85~ Gardner br-
ightness was treated in the ~ame refining sgstem as that described
in Example 1. The operating conditions of the system were the ~ame
as in Examp~e 1 except as otherwise indicated in Table II. Com-
parison of the HCrrR-treated pulp with the untreated but VIB beaten
pulp can be made from the data in Table II.
TABLE Il
Processin~ and Perrormance of ~leached Hardwood Kraft PU1P
Untreated
Pulp HCTR
; (VIB) Treated Pulp
Consisten¢y N/A 24 28 40
Plate Clearance N/A .o25 .015 3
Feed Rate N/A 12.~ 7.7 14.5
VIB Beating Time 20 None None None
Freeness (C~F) 251 290 255 284
Drainage Time 5.2 4.3 4.8 4.4
Apparent Den~ity 13.6 13.3 13.8 13.8
Burst ~actor 82 84 92 82
Tear Factor 87 97 100 101
Fold 71 44 107 95
Tensile 6.1 5.5 6.0 5.6
Elongation 3.2 4.2 4.7 4.7
Scott Internal Bond 126 135 151 175
Opacity (TAPPI) 75.0 75,0 72.3 72.0
EIPD/T -- 1.2 2.0 1.1
Theqe results indicate that bleached hardwood kraft pulp sub-
~ected to the HCTR proce~s produces handsheets having increases
in the same phyqical properties a~ found in the hand~heet~ produced
from bleached ~oftwood kraft pulp of Example 1.
EXAMPLE 3
This example illustrates that the changes characteristic o~
the process can be produced by treating an unbleached pulp. Fur-
thermore, it ~hows that these characteristic 9 can be ~naintained
even after bleaching the treated pulp.
Conventional unbleached sortwood kraft pulp having a perman-
--20 -
9273
ganate number of 20 was treatad at 32% consistency and .050 inch
plate clearance in the same manner a~ that clescribed in Example 1
using a feed rate Or 8.8 ton~/day. Another portion Or the ~ame
initial unbleached pulp was processed in the VIB in lieu of HCTR.
Subsequently, ~ampleQ of the unbleached treated pulp and the un-
treated but VIB beaten pulp were blsached in the laboratory by the
CEHD sequence to 85% brightness. The results are presented in
Table III.
TABLE III
Processing of Unbleached SWK Pulp and Performance
With and Without Subsequent Bleachin~
Unbleached Pulp~ Bleachad Pulp~
Untreated Treated Untreated Treated Before
(VIB) ~ (VIB) Bleachln~ (HCTR)
VIB Beating Tlmo 10None 4 None
~roen~s~ (CS~) 626613 625 633
Drainage Time 4.24.o 4~1 4.o
Apparent Density 13.012.9 13.2 13.2
Burst Factor 140115 140 112
Tear ~actor 161235 163 265
Fold 15001000 1000 800
Tensile 8.56.5 7.8 6.1
Elongation 3.24.8 3.8 4.8
Scott Internal
Bond 94 124 95 116
Opacity (TAPPI) ~ 71.1 69.8
HPD/T -~ -7 ~~ -7
EXAMPLE 4
~he procedure o~ Example 3 was sub~tAntially ~ollowed in tr-
eating conventional unbleaohed fIWK pulp having a permanganate
number of 11, at 34~ consistency at a refiner feed rate of 9.4
tons/dAy and at a refiner plate clearance of 0.020 inch (Table IV)
and then bleaching by CEHD to 85~ brightne~.
-21-
9Z'73
TABL~ IV
Processing of Unbleached HWK Pulp arld Performance
With and Without Subsequent Ble~
Unbleached Pulp~ Bleached Pulps
Untreated Treated Untre~ated Treated Before
(VIB) (HCTR) (VIB) Ble~ohing (HCTR)
VIB Beating Time30 None 25 None
Freeness (CSF)208 196 3 293
Drainage Time 9.0 5.7 6.0 5.1
Apparent Den~ity14.3 14.4 14.1 14.1
Burst Factor 112 117 102 109
Tear Factor 97 113 102 11~
Fold 270 600 ~20 190
Tensile 7~6 7~3 7~1 6~7
Elongation 3~2 5.0 2a8 5.1
Scott Internal
Bond 197 208 152 179
Opacity (TAPPI) -- -- 73~9 71~5
Wet Web TEA -- -- 2~1 2.9
HPD/T -- 1.6 -- 1~6
The forcgoing re~ults (Examples 3 and 4) indicate that the
HCrrR proce~s oan be utilized on both unbleaohed and bleach0d kraft
pulp~ wlth simllar improvements in lmportant physical properties.
It i~ al~o demonstratod that bleaching after HCTR treat~ent does
not materially adversely affect the important physical properties
o~ paper made from HCTR treated pulp.
EXAMPLE 5
This example illustrates clear~y the advantages of the high
consistency re~lning at elevatecl temperatures (HCTR) over the high
consiatency rerlnlng wlthout steam pressurization (HCR).
Bleached SWK pulp was treated at 25~ and at 40% consistency
in the above Bauer Brothers No. 418 refiner system with and without
applied stea~ pressure. In the HCTR run~ the pulp Wa3 held under
s~eam at 50 p~ig for 2.8 minutes and then fed into the refiner
whioh was likewlse maintalned under 50 p9ig steam pressurization.
In the HCR runs air at a pressure of 50 to 60 psig was u~ed instead
of ~team in the operation of the refiner system. Thi~ e~perimenk
verified that HCTR of~ers better control than HCR in the densi~i-
cation of the pulp. Within a range o~ 2 to 12 HPD/T, the HCR tr-
eaked pulps wsre always excessively densified (apparent density in
9Z73
excess of 14.5 lbs/mil), while the HCTR pulp8 had an acceptableapparent density (below 13.8 lbs/mil). Table V shows the property
change cau~ed by HCR or HCTR, expressed a~ percent deviation ~rom
the corresponding properties of the untreated pulp (VIB) beaten to
equal burst ~trength.
TABLE ~
Comparison Between HCTR and HCR With SWK Pulp
at Two Di~ferent Consi~tencies
HCR _ HCTX HC~ HCTR
o con~i~tency % 2~ 25 40 4
Plate Clearance .o30 .o45 .035 to .062
.095
Feed Rate 8.1 9.4 -- 10.6
Steam Pres~ure Applied p~ig 0 50 0 50
Drainage Time Deviation % 4 0 -5 -2
Apparent Density " ~ 6 0 3 3
Burst ~ %
Tear " ~ 1 35 15
~B (Fold) ll ~ 2 2 -10
Ten8il0 " ~ 3 9 2 -1
Elongation 1l % 7 33 ~33 25
Soott Int. Bond " % 22 56 60 75
Opa¢ity 11 Points-3.4 -2.2 -2.5 -3.8
Brightness " Point 8-3 -10 0 -9
Wet Web TEA 11 ~ 32 38 __ __
HPD/T 5.6 5.6 __ __
It will be noted that HCR of~ers no tear advantage when com-
pared to untreated pulp at equal burst while HCTR offers ~igni~i-
cantly higher tear, elongation (and thererore TEA), and higher in-
ternal bond. It will also be noted that the hlgher temperatures
employed in the HCTR treatment oause a substantially higher bright-
nes~ 10~9. Although this disadvantage o~ HCTR can be avoided if
desired by treating the pulp before bleaching, it will, in some
cases, be of little concern in papermaking when a~sociated with only
a small portion o~ the ~urnish, as shown below.
The following two examples illu~trate the unique opportunity
to reduce the expensive long fiber portion of a papermaking ~urnish
by taking advantage of the charaoteristics of pulps produced by the
process of this invention.
EXAMPLE 6
About 12 tons o~ bleaohed SWK pulp were treated by HCTR in the
-23-
39Z73
above refining syste~ at 40% consistency and at 2-3 HPDjT (Plate
Clearance .040 inch; Feed Rate 16 tons/day; 50 psig steam; 2.8
minutes o~ preconditioning under 50 p9ig st3am), and the pulp was
used in a paper machine trial to make 38 pounds continuou~ bond.
The HCTR fiber, substituted for conventionally re~ined SWK, allowed
the reduction of SWK in the furnish from a regular 27~ SWK - 73~
HWK to as low as 12~ SWK - 88% HWK. Paper machine runability rem-
ained excellent even at the loweqt SWK level.
Paper properties indicated that a 30~ reduction in the amount
of SWK is possible while achieving all paper specifications. The
re~ultq of these experi~ents are ~ummarized in Table VI.
-24-
- l~ssz7a. --
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-25 -
~Q89Z73
EXAMPLE 7
This example illustrates, again via a production paper machine
trial9 the ability to reduce the amount o~ SWK and increase corre~-
pondingly the amount of GWD in a publioation coated grade by ~ub-
~tituting HCTR treated SWK for conventional:Ly re~ined SWK. About
22 tons of the HCTR treated SWK prepared in a manner similar to
that described in Example 6 (Feed Rate 11 tons/day; 38~ average
consi~tency; Plate Clearance varied to keep power input constant)
allowed the reduction o~ SWK in the rurnish from a normal level o~
o 45-50% to as low a~ 24% without su~ering any uncoated stock run-
ability problems. Table VII show~ some o~ the paper propertie~
which were obtained. To maint~in eood perrormance on machine
coater runability) the HCTR-SWK levels had to be kept above 30 per-
cenb .
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-27- 1()89Z73
~q,~8~273
From a consideration of the results set ~orth in several of
the above Example~ it can be appreciated that the pulp produced
pursuant to this invention produces paper which, as compared to
paper made from pulp produced from the same kind o~ chemically
delignified and fiberized pulp beaten to equivalent burst strength
in3tead of being refined in accordance with the process of this in-
vention, possesses each of the following advantageous properties:
-- higher tear ~trength
-- higher internal bonding strength
-- higher elongation or stretch
-- higher wet and dry tenslle energy absorption
(o~ten termed "TEA")
Although the magnitude Or these dl~rerence~ will vary dependin~
upon the type and ~peoie~ Or wood u~ed in maklng the pulps, the
~peciric type and conditions Or the chemical pulping process em-
ployed and the specific HCTR conditions utilized, these dif~erences
are all significant. They translate into the ability to provide
paper having a balance of desirable propertie~ unavailabla from any
previously known proce3s.
In order to still ~urther appreciate these improvements ef~-
ectcd by the process o~ this invention, there are presented in
Table VIII a ~eries Or comparisons between handsheet~ made ~rom
variou~ pulps o~ this invention produced a~ described in several o~
the above Examples and handsheets made ~rom a portion of the same
original chemical pulp which was beaten to equivalent burst strength
instead o~ being sub~ected to the process of this invsntion. Table
VIII also set3 forth, for further comparative purposes, the cor-
responding physical property characteristics of the corresponding
original unrerined chemical pulps themselves. The estimated TEA
values given in Table VIII are not measurements but rather calcula-
ted values based on the elongation and tensile determinations.
-28-
~t~89273
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-29-
~ 39Z73
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-30-
1~89~73
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--31--
~0~9273
The next two examples ~how that it is po~sible to utilize
HCTR in combination with conventional refining processes, such as
beating.
EXAMPLE 8
A typical unbleached sortwood kraft pu:Lp having a permangan-
ate number of 21 was treated at 38% consistency and .030 inch
plate clearance in the above pressurized re~iner system. In this
operation the pulp was subJected to 50 psig steam ~or a period Or
2.8 minutes and thereupon eontinuously introduced at a ~eed rate
o~ 10:4 tons/day to the pres~urized refinsr in which 50 p9ig steam
pre~sure wa~ likewise maintained. Upon release rrom the pressurized
re~lner the pulp wa~ discharged ViEl a oyclone into a hydrapulper
~or quenchlng and dilution. The HCTR-treated pulp was ble~ched
u~lng the C~HD sequence to a brightncs~ Or over ~0~0 and a portion
o~ the bleached HCTR-pulp was then beaten in the Valley Iron beater.
Table IX ~how~ the properties Or paper samples made from this
bleached HCTR/VIB pulp and those made from the same kind of initial
sortwood kra~t pulp which was bleached in the same ~a~hion and re-
rined solely by beating in the Valle~ Iron beater (no HCTR).
TABLE IX
Porformance Or SWK Pulp Rerined by HCTR Followed
by Bleachin~ and Conventional Beatin~
Control Treated
(no HCTR) (HCTR)
VIB Beating Time 2.0 4.0
Freeness (CSF) 649 421
Drainage Time 4.0 4.6
Apparent Density 12.9 14.2
Burst Factor 122 150
Tear Factor 173 182
Fold 1000 1800
Ten~ile 7.4 8.6
Elongation 3.7 5.1
Scott ïnternal Bond 88 165
~pacity (TAPPI) 72.8 6l~.7
HPD/T -- 11.6
EXA~IPLE 9
The procedure Or Example 8 was applied to unbl~ached hardwood
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kra~t having a permanganate number of 12. In this case the pulp
was fed to the pressurized refiner at a consistency of 34% and
at a ~eed rate of 9.4 tons/day. The plata clearance was .020 inch.
The pulp was then bleached by CEHD to a brightness of over 80%
and a portion thereof beaten in the Valley Iron beater. Table X
~ets forth the properties o~ paper ~amples made from the resultant
pulp as well as the properties of paper samples made from pulp
produced by bleaching the same kind of initial hardwood kra~t by
CEHD also to a brightness o~ over 80% and then beating the bleached
pulp in the Valley Iron beater (no HCTR).
TABLE ~
Per~ormance of HWK Pulp Refined by HCTR Followed
by Bleaching and Conventional Beating
Control Treated
(no HCTR)
~IB Beatine Time 20 10
Freeness (CSF) 350 209
Drainage Time 5.2 6.2
Apparent Density 13.7 14.7
Burst Factor 96 120
Tear Factor 104 106
Fold 120 490
Tensile 6.8 7.3
Elongation 2.9 4 .7
Scott Internal Bond 130 211
Opacity (TAPPI) 75.0 69.3
Tensile Energy Absorption 2.0 3.0
HPT/T -- 1.6
Example 10 illustrates the results obtained pursuant to thls
invention when exposing high consistencg pulp to presteaming for a
relatively short period Or time before re~ining in the steam pres-
~urized re~iner.
EXA~PLE 10
In this operation a typical unbleached SWK pulp having a per-
manganate number of 21 was subjected to HCTR under the :~ollowing
conditions:
Consistency: 32%
Presteaming Time: 1 minute
Feed Rate: 8.8 tons/day
1~8~Z73
Plate Clearance: .OL~O inch
Steam Pressurization: 50 psig
(Steaming Vessel and Refiner)
Table XI presents the properties of hand3heets made from this
HCTR pulp and the properties of handsheets mada from the same kind
of pulp which was treated in the VIB beater (no HCTR).
TABL~ XI
Per~ormance of Unbleached SWK Pulp Refined by HCTR
Untreated Treated
(VIB) (HCTR)
VIB BeatinE Time 1 Non~
Freeness ~CSF) 679 595
Drainage Ti~e 3.9 )~.0
Apparent Density 12.0 13.3
Burst Factor 90 122
Tear Factor 210 212
Fold 600 1100
T~nsile 6.o 7.0
Elongation 2.7 5.
Soot,t Internal ~ond 68 141
HPT/D -- 1.8
EXAMPLE 11
Using the general prooedure of Example 5, bleached SWK was
re~ined under HCTR and HCR oonditions, using selected values o~
energy input (not HPD/T) over ~ range Or such values up to 12
HPD/T. This study had for its purpose determination o~ the erfect
of varying the enerey input on the apparent den~ity, elongation,
tear, and Scott Bond Or the HCTR and HCR pulps. The results, whioh
have been discussed supra, are given in Table XII below, as well as
in Figs. 1-4 Or the drawing~.
TABLE XII
HCTR _ HCR
HPD/T (nst) 1.9 3.7 5.6 12.0 2.5 3.1 5.6 12.0
Apparent Density 13.7 13.813.9 14.8 14.6 14.6 lL~.6 14.5
E~ongation 5.0 5.5 5.7 5.2 4.6 4.4 l~.5 4.5
Tear 195 219 198 173 158 138 139 130
Scott Bond 163 197 206 227 183 153 177 212
Fro~ the foregoing, it can be seen that the high consistenoy,
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high temperature, high pressure re~ining process of the present
invention, when applied to chemically delignified and fiberized
pulp8~ produces treated pulps which have signifi¢antly improved
propertie~ making them particularly ~uitable ~or uæe in blending
with lower grade, short ~iber, mechanically and/or chemically de-
rived pulps for the production of fine papers. Among the physical
properties of papers which are improved by utilizing pulps treated
according to the prooe~ of the present invention are tear strength,
stretch and bonding ~trength. These improvements in physical
properties are achieved without signiricant reduction Or the other
de~irable paper properties. Long fiber, chemically deligniried and
fiberized pulp treated aecording to tha proce~ of the present in-
vention i~ particularly u~erul in blending with conventionally re-
rined, shorter riber length cellulo3ic pulp~ to produoo the rine
paper~ u~ed in book and magazine printingl ledger papers, bu~iness
~orms, and other conventional rine paper products. It has been
~ound that the pulps produced by the present invention permit a
reduction Or 20 to 50 percent in the long ~iber portion o~ the blends
conventionally used in preparing ~ine grade paper ~tock without
introducing any serious product or performance dericiencies.
