Note: Descriptions are shown in the official language in which they were submitted.
~7~4~17
This invention relates to a process or treating
lignocellulosic pulp fibres of ei~her softwoods or
hardwoods to provide pulps of improved properties. In
particular this invention is directed to the treatment
of mechanical pulps and high-yield chemical pulps to
improve and retain the properties oE such pulp5.
Newsprint traditionally has been manufactured from
a furnish consisting of a mixture of a mechanical pulp
and a chemical pulp. Mechanical pulp is used because
it imparts certain desired properties to the furnish:
namely, its high light scattering coefficient contri-
butes to paper opacity and allows the use of a thinner
sheet; its high oil absorbency improves inX acceptance
during printing.
Chemical pulps are used because they impart
propertie~ to the furnish which improve its run-
nability. Runnability refers to properties which allow
the wet-web to--be transported at high speed through the
forming, pressing and drying sections of a paper-
machine and allows the dried paper sheet to be reeled
and printed in an acceptable manner. Runnability con-
tributes to papermachine and pressroom efficiency.
It is believed that improved runnability in chemi-
cal pulp is due to high wet-web strength and drainage
rate. Wet and dry stretch are important because they
are believed to contribute to preventing concentrations
of stress around paper defects, thereby minimizing
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breaks. High drainage rates lower the water content
and are believPd to yield a less fragile web.
Mechanical pulps including stone grounc1wood (SG)
and pressurized stone groundwood (PSG) can be made to
provide wet stretch but only at the expense of poor
drainage. Higher quality mec'nanical pulps are obtained
by manufacture in open discharge refiners, to produce
refiner mechanical pulp (RMP) and in pressurized
thermomechanical pulp (TMP). Still further upgraded
mechanical pulps were provided by chemical pretreatment
of the wood chips prior to refining to provide chemi-
mechanical pulp (CMP or CTMP).
U.S. Patent 3,446,699 issued May 27, 1965 to
Asplund et al. provided a method for producing mechani-
cal and chemimechanical or semichemical pulps from
lignocellulose-containing material, in order to provide
what was alleged to be improved quality of the ibres
with improved defibration.
U.S. Patent 3,55~,428 issued Jan. 26, 1971 to
Asplund et al. provided a method for manufacturing
chemimechanical pulps involving heating and defibrating
the same in an atmosphere of vapour at elevated temper-
atures and under corresponding pressure of the impreg-
nated chips to provide a more rapid and effective
impregnation.
U.S. Patent 4,116,758 issued Sept. 26, 1978 to
M.J. Ford provided a process for producing high-yield
chemimechanical pulps from woody lignocellulose materi-
al by treatment with an aqueous solution of a mixture
of sulfite and bisulfite, to provide a pulp which can
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be readily defibered by customary mechanical means to
provide a pulp having excellent strength characteris~
tics.
Today's papermaker is ~aced with the problems of
decreasing forest resources, an increasing demand for
paper products and stringent environmental laws. Low-
yield chemical pulps, e.g. sulphite and kraft pulps,
contribute highly to such problems~
The fibres of low-yield chemical pulps are known
for their desirable dry- and wet-web strength proper-
ties. Observations of low-yield chemical fibres in a
formed paper sheet indicate that these tend to have a
kink and curl which is said to contribute, in an advan-
tageous way, to the papermachine runnability and to
certain physical properties. Mechanical pulps lack the
desirable strength properties to replace, in whole or
in part, low-yield chemical pulps, e.g. kraft or sul-
phite pulps, in linerboard, newsprint, tissue, printing
grades and coated-base grade of paper. Consequently,
it has been an aim of the art to improve the physical
properties of mechanical and high-yield chemical pulps,
so that such improved pulps would be used to replace
low-yield chemical pulps.
A number of mechanical devices have been built to
produce curled chemical and mechanical fibres in order
to improve certain physical properties. Two such
mechanical fibre-curling devices are disclosed in H.S.
Hill, U.S. Pat. 2,516,384 and E.F. Erikson U.S. Pat.
3,054,532.
H.S. Hill et al. in Tappi, Vol. 33, No. 1, pp.
76~4~7
36-44, 1950, described a "Curlator" designed to produce
curled fibres. The process consisted of rolling fibres
into bundles at a consistency of around 15%-35%,
followed by dispersion. Advantages claimed were higher
wet-web stretch, improved drainage, and higher tear
strength and stretch of the finished product. These
advantages were at -the expense of certain other proper-
ties, notably tensile strength.
W.B. West in Tappi, Vol. 47, No. 6, pp. 313-317,
1964, describes high consistency disc refining to pro-
duce the same action.
D.H. Page in Pulp Paper Mag. Canada, Vol. 67, No.
1, pp. T2-12, 1966, showed that the curl introduced was
both at a gross level and at a fine level which he
called "microcompressions". Both types of curl w~re
advantageous.
J.H. De Grâce and D.H. Page in Tappi, Vol. 59, No.
7, pp. 98-101, 1976, showed that curl could be produced
adventitiously during bleaching of pulps, by the
mechanical action of pumps and stirrers at high con-
sistency.
R.P. ICibblewhite and D. Brookes in Appita, Vol.
28, No. 4, pp. 227-231, 1975, claimed that this adven-
titious curl could have advantages for practical run-
nability of papermachines.
High-consistency mechanical defibration of wood
chips is known to produce curled, kinked and twisted
fibres. Kinked fibres are known to be particularly
effective in developing extensibility in wet webs if
the kinks are set in position so that they survive the
7e~7
action of pumps and agitators at low consistency and
retain their kinked and curled state in the formed
sheet. This ensures enhancement of the wet-web stretch
and certain other physical properties.
A number of chemical treatment methods have been
reported to enhance and retain fibre curl in a refined
pulp. In one, Canadian Patent No. 1,102,969 issued
June 16, 1981 to A.J. Kerr et al., improvement in tear-
ing strength of the pulp is alleged by the treatment of
delignified lignocellulosic or cellulose pulp derived
from a chemical, semichemical or chemimechanical pulp-
ing process at a pressure of at least one atmosphere,
with sufficient gaseous ammonia to be taken up by moist
pulp in an amount greater than 3% by weight to weight
of oven dried pulp.
In another, Canadian Patent ~o. 1,071,805 issued
Feb. 19, 1980 to A.J. Barnet et al., a method of treat-
ment of mechanical wood pulp is provided by cooking the
pulp with aqueous sodium sulphite solution containing
sufficient alkali to maintain a pH greater than about 3
during the cooking. The cooklng was effected at an
elevated temperature for a time sufficient to cause
reaction with the pulp and to increase the drainage and
wet stretch thereof, but for a time insufficient to
cause substantlal dissolution of liquor from the pulp,
and insufficient to result in a pulp yield below about
90~. A minimum concentration of sodium sulphite was 1%
since, below 1% sodium sulphite improvements were said
to be too small to justify the expense of treatment.
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-: During the process of papermaXing, most of the
curl in both high-consistency refined mechanical and
hi~h-yield sulphi~e pulp is lost in the subsequent
steps of hanaling at low consistency and high tempera-
tures. This is also taught in the article by H.W.H.
Jones in Pulp Paper Mag. Canada, Vol. 67, No 6, pp.
T2~3-291, 1966. Jones showed that when mechanical pulp
fibres which are curled during high consistency refin-
ing are subjected to mild mechanical action in dilute
suspension at a temperature of arouna 70C the curl
tends to be removed. The increased tensile and burst
strengths produced by removal of curl was seen as
advantageous. Thus, curl in such pulps is normally
removed in ~apermachine operation, since auring practi-
cal papermaking, pulps are always subjected to mild
mechanical action ln dilute suspension at temperatures
of the order of 70C.
High-yleld and ultra high-yield sulphite pulps are
used as reinforcing pulps for manufacture of newsprint
and othe~ groundwood-containing papers. Although they
~ay be subjected to high-consistency refining, their
fibres are in practice substantially straight because
the curl introduced in high-consistency refining is
lost in subsequent handling.
Accordingly an object of one aspect of this inven-
tion is to provide a process for imparting and render-
ing permanent, the physical properties of such mechani-
cal and high-yield chemical pulps in order to improve
their papermachine runnability and pressroom effici-
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An object of another aspect of this invention is to providea non-chemical process of treating higher-yield pulps ta improve and
retain certain physical properties so that the pulp can be used to
replace in whole or in part, the low-yield chemical pulps.
It is an object of yet another aspect of the present inven-
tion to render permanent, by non-chemical means, the curl imparted
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to the fibres of high-consistency mechanically treated, mechanical
and high-yield chemical pulps.
The mechanicaI pulps or high-yield chemical pulps included
within the ambit of various aspect~s of this inventlon can be produced
by either mechanical deflbration of wood, e.g. in stone groundwood
(SG), pressurized stone groundwood (PSG), refiner mechanical pulp
(RMP) and thermomechanical pulp (TMPj production or by mechanical
defibration, at high~consistency, followed or preceded by a chemical
:. , : . .
treatment of wood chips~and pulps e.g.~in the production of ultra-
high-yield sulphite pulps (UHYS, yie;lds~ in the range 100-85%), high-
: : : : :
yield sulphlte~pulp~s (HYS, yields ln the range 85-65%),~chemi-thermo-
mechanical (C1`MP), high-yield chemimechanical (CMP), lnterstage~ ~
thermomechanical and chemically~post-treated mechanical pulp (MPC)
- or~thermomechanical~pulps (TMPC)
By~ a broad aspect of this invention`, a process is provided
for treating pulps, that havè already;been curled, in order to im-
~prove at least some~of the following physical properties: drainage,
:
wet-ueb stretch, wet-web work-to-rupture, and dry-sheet tear strength
and stretch,~which process comprises: sobjecting the curled pulp
.
fibres to a heat treatment while said pulp is at a high consistency ~ ;
in the form of nodules or entangled mass, without appreciable drying
of the pulp, the heat treatment being at an elevated temperature and
for a time sufficient to render the curl permanent to subsequent
~mechanical action, which process comprises: subjecting the curled
pulp to a heat treatment, e.g., at a treatmcnt of at least 100 C,
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preferably 100C-170C, for a sufficient length of time, e.g., between 60
minutes and 2 minutes, inversely dependent on the temperature while curled
pulp is at a high consistency, e.g., at least 15%, preferably 15% to 35%,
in the form of nodules or entangled masses, thereby to render the curl per-
manent to subsequent mechanical action.
The present invention in its broad aspects is a process which fol-
lows the mechanical action that the already made the fibres curly in either
mechanical, ultra high-yield or high-yield pulps. Such a mechanical action
generally takes place at high consistency (15%-35%), and may typically be
a high-consistency disc refining action, e.g. as is generally used io pulp
manufacture. ~ ;
The process of aspects of this invention thus consists of a simple
heat treatment of the pulp in the presence of water while it is retained in
the form of nodules or entangled mass at a high consistency. The process
preferably involves temperatures ahove;100 C, ln which case a pressure vessel
is required.
Wh~le the inven~tion is not to be limited to any theory, it is
believed that the process sets~the curl in place e~ther by relief of stresses
in the Eibre or by a cross-linking~mechanism, so that~upon subsequent pro-
cessing during papermaking, the~fibres retain their curled form. ,~
This curled form has particular advantàges for the propertibs~of~
,
the wet web, so that the runnability of the papermachine is improved. In
addition, the toughness of the finished produce is increased.
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ln gcncral tcr~s~ thc pr3C~ss b~ins ~it}, a p~llp tl~a~ has becn
converted to the curly state by mechanical action at hi~h consistency, and
in whichthe fibres are held in a curly s~ate in the or~, of nodules or en-
tangled mass. The pulp may be either purely mechanical, e.g, stone ground-
wood, pressurized stone groundwood, refiner mechanical, thcrnlomechanlcal,
or a chemimechanical pulp, e.g., ultra high-yield sulphite pulp or high-yield
sulphite pulp. Conversion to a curly state is generally achie~ed naturally
in the high-consistency refining actionthat is normally used for refiner
mechanical, theremomechanical and ultra high-yield sulphite pulp. For stone
groundwood, pressurized stone groundwood and high-yield sulphite pulp, it
would be necessary to add, to the normal processing, a step that curls the
.- fibres. This may be for example by use of a machine~known by the Trade Mark
of CURLATOR or high-consistency disc refining, or by use of a machlne known
by the Trade Mark FROTAPULPER (See E.F. Erikson, U.S. Pat. 3,054,532).
`~ The pulp fibres may be lignocellulos~c fibres produced by mechanlcal
, defibratlon, or by refining, or by refin~ng in a disc ref~ner at high consis-
tency, or by mechanical deflbratlon at high consistency of wood chips, or
by mechanical defibration at hlgh consistency of wood chips followed or
preceded by a chem~cal t~reatment, or by a slngle stage~refining~, or after
two successive~refinings, or between two~successive refinings. They may~ ;
alternatively be pulp fibres commercially~produced under the designation o~f
refIner mechanical pulp, pressurized~reflner meGhanicalpulp ànd thermo-
-
.
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mechanical pulp either from a single stage or two-stage
refining, or commercially produced under the designa-
tion of -ul~ra high-yield pulps, high-yield pulps, high-
yield chemimechanical pulps, interstage thermomechani-
cal pulps an~ chemically post-treated mechanical or
.
thermomechanical pulps, or may be part of the furnish,
e.g. the' refined re~ects in mechanical pulp production
or may be whole pulps.
. .
The process consists of taking the curled pulp at
1,0 high consistency (say 15-35~) in the form of noaules or
entangled mass and- subjecting it to heat treatment
: ,
without appreciable drying of the pulp. The tempera-
ture and duration of the heat treatment controls the
extent to which the curl in the fibres is rendered
permanent,~ and this may be ,adjusted to match the a~van-
~tages sought. ~
This process may be carried out as a batch p.rocess
in a ~digester or as a~continuous p~roce~ss~ t~rough a '' ,'
s~'eaming tube maintained at high pressure. ; '
The process may also include the step of incorpora-
:
ting a brlg~tening agent during heat trea;tment, to
upgrade the brightness while retaining the improved
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pulp properties; or the subsequent steps of brightening
or bleaching sequences to upgrade the brightness of the
pulps while m~intaining the improved pulp properties;
or indeed may be carried out in brightened pulps there-
by also to maintain adequate~ brighkness after heat
treatment.
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Nowhere in the prior art is there disclosed a process in which a
separate and sole heat treatment at high consistency and high temperature is
given to curled pulp fibres in order to achieve the desired changes in the
properties of the wood pulp being treated.
Among the advantages of the process of aspects o this invention
in settling in fibre curl in high-yield pulps and mechanical pulps is to
provide a means of controlling pulp properties in order to impart high wet-
web stretch, work-to-rupture and increased drainage rates. In the case of
high-y1eld pulps, in addition to the above wet-web properties, higher dry-
sheet tear strength and stretch are also obtained.
Thus, by aspects of this invention, it has been discovered thatwhen lignocellulosic pulp fibres, that have already been made curly, are
heat treated at (a) consistencies ~from 10% to 35%, (b) temperatures from
100 C~to 170 C using steam at correspond1ng pressures of 5 psig to 105 psig,
(c) for a period of time from 2 minutes to 60 minutes, fibre curl permanently
sets 1n place, and the çurl is made resistant to removal in subsequent
mechanical action experienced by fibres in the papermaking process. The
process of aspects of this~1nvention improves drainage, wet-web stretch,
wet-web work-to-rupture and dry-sheet tear strength~and stretch.
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.
In one variant, the pr~cess is to take a pulp that
has been made curly by high-consistency (20-35%) refin-
ing, and to set in the curl (and perhaps microcompres-
sions) by subjecting it at a high consistency to an
elevated temperature te.g. llO~C - 160C) for a brief
time (eOg. 1 minute to 1 hour). This set-in curl is
resistant to removal by the hot disintegration experi-
enced during papermaking. The advantages of such a
pulp are: 1. higher wet-web stretch; 2. higher tearing
strength; and- 3. better drainage.
The process j may be a batch process, i.e. if the
pulp is-placed in a pressure vessel~e.g. a closed re-
action vessel -or digester, or it may be a continuous
process~e.g through a steaming tube maintaining high
pressures. ~ ~-~
The~ temper~ture and duration of the heat treatment
- . :
controls the extent to which the curl in the fibres is
rendered permanent, and this may be adjusted to match
r
the advantages sought. Preferred conditions are as
follows: temperatures of from above 100 to 170 with
.
corresponding stsam pressures of 5 psig to 105 psig and
~for periods from 2 minutes to 60 minutes.
The trsatment according to aspects of this invsn-
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^` 1.~704~7
tion has been observed to render fibre curl permanent
including fibre twists, kinks and microcompressions~
Either during or after completion of the heat
treatment the pulp may then be brightened in accordance
with any of the well-known conventional brightening
sequences.
In general, pulp fibres obtalned after refininy at
high consistency are very curly. For mechanical pulps,
if a mlld disintegration treatment at room temperature
is made on these pulps, the fibres retain substantially
their curliness so as to produce wet webs with high
wet-web stretch, work-to-rupture ~and fast drainage.
However, in the~ papermaking~process, pulps receive
mechanical action at high temperatures and low consis-
tencies so ~that ~their curliness~ls lost. ~ ~It ~is
believed that pulps which are~ given standard hot dis-
integration~treatment in the 1 aboratory ~at low cansi~s-
tency experience similar conditions dur~ing which the
carll~ness~is ~lost and the wet-web~ properties~deteri~
orate.
The~ followlng; examples are~ given to ~ lustrate
more clearly var~ious embodiments~of the invention. ~In
the following examples, the tests were conducted in the
following standard~ way:
Wet-web results were obtained following the pro-
cedure~ des~crlbed;by ~R.5. Seth,~ M.C. Bsrbe,~ J.C.R.
Williàms and D.H. Page in ~Tappi, Vol. 65, ~o. 3, pp.
:
135-138, 1982. ~ ~
Wet-web~percent solids, tenslle strength, stretch
and work-to-rupture were obtained on webs prepared by
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~1709~7
applying 0.7 kPa and 103 kPa wet-pressing pressures.
The percent stretch to-break was obtained for wet-
webs pressed so as to give a breaking length of 100
meters. It is considered that this value is a measure
of the "toughness" of the wet-web and is an iDdication
of the runnability of the pulp on a papermachine.
Changes in drainage rates are given by the measure
of Canadian Standard Freeness.
Hot disintegration was done accordlng to the pro-
cedure of C.W. Skeet and R.S. Allan in Pulp Paper Mag.
Canada, Vol. 69, ~o. 8, pp. T222-22~;, April l9,1968.
The extent of fibre~curliness has been quantified
by an Image Analysls method as described by B.D. Jordan
and D.H.~ Page ln the~Proceedlngs of the TAPPI Inter-
national Paper Physics Conference, Harrison Hot
Sprlngs, B.C.~ (1979~ Hlgh values~ of curl indices
reflect curlier~fibres.
In the examples following, two parameters have ;
been used~to follow~the progress of the heat treatment ~ ~
effect. ~ -
First the curliness of the fibres has been
measured, after a standard hot disintegration treatment
at low consistency, that simulates the subsequent
treatment that the pulp will~receive in ths papermaking
process. ~ ~
Secondly, the ~advantags of this new pulp (after
hot disintsgration) has been determined in terms oE the
extensibility (percent stretch-to-break) of wet webs
prepared from the pulp pressed so as to give a breaking
length of 100 metres. It is considered that t~is value
. :
37
is a measure of the "toughness" of the wet sheet, and
is an indication of the runnability of ~he pulp on a
papermachine.
EXAMPLE 1
This example is intended to illustrate that when
pulp fibres are given a heat treatment, as described
for aspects of this invention, they remain curly even
after standard hot disintegration.
In this example pulp fibres were treated in a
digester at 150C and at about 22~ consistency for
approximately 60 minutes.
The results obtalned after the above treatment on
a variety of mechanical, chemlmechanical~and chemical
:
wood pulp fibres are reproduced below in Table I.
From the results, it is seen that the heat treat-
.
ment produces the desired effects, on wet-web stretch
and drainage, for all the lignocelluloslc pulp fibres,
e.g., mechanical pulp and high-yield sulphite pulp
:
fibres. The treatment has no~effect on cellulosic pulp
fibres which~contain llttle or no lignin.
EXAMPLE 2
This example illustrates the effec~ o~ the temper-
ature of the treatment.
:: :
Lignocellulosic pulp fibres were treated in a
digester at temperatures of 110, 130, 150 and 170C for
60 minutes and at approximately 22~ consistency. The
results reproduced in Table II were obtained after a
standard hot disintegration.
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-- 18 --
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-- 19 -- ~
~ J7~ t7 .
EXAMPLE 3
r
This example illustrates the efect of the time
for the treatment.
Lignocellulosic pulp fibres at approximately 22%
consistency were treated in a digester at 150C for 2,
lO and 60 minutes respectively. The results reproduced
in Table III were obtained after a standard hot dis-
integration.
It can be seen that the time,~ as well as the
temperature (Example 2), control the extent to which
the curl in ~the fibres is rendered ~permanent. Both
variables can be adjusted to yield pulp with the re~
quired properties sought.
In addition to the ~time~to~ maintain the desired
properties of curIy ~fibres and temperature ~of the
treatment described above,~ the~extent to which;fibre
curl i~s present, after heat treatment~and hot dislnte-
gration also~depends on the state of the fibres immedi-
ately after~refinlng. In Table~ it can be seen that
for two 70%-yield sulphite pulps, ~the one re~ined at
30% consistency, i.e., containing more curly;fibres,
.
will~requir~e~a~shorter heat treatment and/or a treat- -
ment at a lower temperature~to achieve the same wet-web
strength properties~as that `for the pulp~refined at 9%
-.
consistency.
EXAMPLE 4
:
This example illustrates the effect of the con- ~
:'
sistency of the pulp fibres~when submitted to heat
treatment.
- 20 -
1:
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- 21 -
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. .,
-- 22 -- l
Lignocellulosic pulp fibres were treated in a
digester at 150C for 60 minutes at consistencies of 5,
10, 20, and 25%. For the purposes of this specifica-
tion, the term "% consistency" means the percenta~e of
oven-dried weight of pulp fibres to the total weight of
pulp fibres plus water. The results reproduced in
Table IV were obtained after a standard hot disin-tegra-
tion.
The effect of the treatment is greater, the higher
the consistency of the pulp flbres. The treatment has
no effect on pulp fibres at low consistency, typically
lower than 5%.
: `
EXAMPLE 5
This ~example illustrates the effect of the heat
treatment on the wet-web ~and~dry-handsheet properties
of high-yield pu~lps.
The lignocellulosic pulp fibres were heat ~treated
in a digester at 150C and at about 20% consistency for
approximately 60 minutes. For~the pulp fibres, in the
high-yield~range, the heat treatment improves, in addi-
tion to the wet-web stretch and work to rupture, ~the~
dry~handsheet tear strength and stretch (Table V).
EXAMPLE 6
This example illustrates the effect of the pH of
the pulp fibres during the~heat treatment. A 70% yield
sulphite pulp~ at a pH of 3.2 was heat treated in a
digester at 150C and at about 20% consistsncy for
approximately 60 minutes. Another sample of the same
.... ..
- 23 -
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-- 24 --
,
.
11~7(~ 7
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0 ~ n ~o ~ `D ~ ~n W P Pn~ ~ C~ ~q :
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-- 25 ~
~, ,.
- -: - . :
- ~ , . , " : :
- ~ .:. :
:
pulp was sprayed with a solution of sodium carbonate to
increase its pH to lO.0 and was also given a heat
treatment at the same conditions.
Both heat treated pulps show remarkable improve-
ment in wet-web properties and dry;tear strength and
stretch over the untreated sample (Table VI). The~puIp
heat treated at high pH has higher tear strength due to
the proteotive~action of the alkali which reduces the
loss in fibre strength through acid hydrolys1s.
,~
EXAMPLE 7
This example illustrates the effect of pulp
bleaching or brightening agents on the wet-web and dry-
~handsheet strength of heat tre~ted~pulp~s.
~ A 70~ yield sulphite pulp was ~bleached~by a con-
ventional hydrogen peroxide ~treatment following the
heat treatment~at 150C for 60~minutes and 20~ consis-
tency. Results are~given ~in Table~ VII for the~pulps
after treatment ~wlth dlfferent~;peroxide charges and
after a~standard hot disintegration~. The pulp after
bleaching ~6till possesses ~all the~ clalmed ~superior
properties ~(with the ~exception of~drainage) resulting
from the heat treatment done under the conditions dis-
: .
closed~in this invention.
EXAMPLE 8 ~ ~
As a further example pulps have been heat treatedin the~ way descrlbe~d earller, with the additicn cf a
brightening~agent during the heat treatment~stage.
~A thermomechanical pulp and a 70%-yield sulphite
- 26 -
1,
'~ ' , ' ' ,
TABLE VI
,
THE EFFECT OF THE PULP ~IBRE H DURING HEAT TREATMENT
P
_ _ 70% yie ~d sulphite pulp
Heat treated pulp at 150C
Untreatedfor 60 minutes and 20%
pulp hotconsistency followed by
disintegrated hot disintegration
-- : _: : ::
pH of heat treatment ~ ~ 3.2 10.0
- ~ - _ - ~
Pulp and fibre proper~ies ;~
Curl index 0.135 0.237 0.253
~ CSF (ml) ~ 643~ ~ ~ 610 ~ 672
0.7 kPa~ solids (%) 25.4 ~ ~ 22.1 ~ 26.7
l tensile (m) 103 ~89.5 ~ 67.8
¦~stretch~(%) ~ 2.67 -15.8 7.38 ~ -
~ l work to rupture ~ R~ . 29.1 ~; ; ;~157 ~ 52.6
103 kPa ~ solids ~(%) 29.0 ~ ~ 28.2 ~ ~ 29.4
tPnsilè ~(m)~ ~ 169 ~ ~ 141 ~ 103
~ ~ ~stretch (%? :~ : ~: 2.54 ~ ~ 9.61 6.19
~work to rupture~ ~ 34~.4 ~ ~ ~ 142~ ~ ~ ~ ~67.0
: ~ ~ : ~ : :'
Wet'Web~stretch st~ ~ 2.89 ~ ~ ~ 13.5 ~ ~ ~ 6.24
100 m breaking~length
Dry~handsheet~propertles~ ~ ~ ~ ~ ~
Bulk (cm3~/g)~ 1.72 ~ ~ 1.54~ ~ ~ 1.78
Burst index (kPa.m2/g) 6.70 ~ 4.71 3.43 ~ -
Téar index (mN.m2/g~ 8.15 ~ ~9.78 16.41
Breaking length~(m) ~ 9924 ~ ~ 7383 ~ ~ ~5547
% stretch` ~ ¦ ~ ~2~.89 ~ ~ 3.03 ~ ~ 2~99
Toùghnèss index (mJ)~ 167 ~ 137 107
Zero-span b.~l. tkm)~ 16.38 14.95 ~ 14.35
Scattering coeff.~;(cm2/g) 205~ ` 209 263
Tappi opacity~(%)~ ; 74.6 74.9 ;~93.7
Iso-brightness (%)~ ~ ~ 44.4 43.0 21.5
~Absorption~coeff.~(cm2/g)~ ~ 14.86 ~ ~ ~ 15.22 i ~30-50
--: --: :
1 Refined at O.99~mJ/kg and 18% consistency ~
~:
:: : : ~ ::
27
7(~ 7
TABLE VII
THE EFFECT OF BLEACHING HEAT-TREATED PULPS
70% Yield Sulphite Pulp1 -
After heat treatment at 150~C for
Before Heat60 minutes and 20% conslstency
Treatmentfollowed by peroxide bleaching
Weight of Peroxide on Pulp (%) - O 0-5 1.0 2.0
Pulp and Fibre Properties
.
Curl Index 0.138 0.227 0.216 0.209 0.204
CSF (ml)~ 662 607 583 533 524
Wet-Web Properties
0.7 kPa . Solids~(%) 27.4 23.3 22.9 25.0 22.7
TensiIe (m) 91.8 87.7 92.2 93.7 95.9
Stretch (%) 2.19 15.1 12.8 1k.0 16.5
~ Work to rupture ~19.0 ~ 150 131 165 210
103 kPa . ,Solids (~) ~ 31.8 29.0 28.I 32.8 25.3
Tensile (m) 158 133 139 180 151
Stretch (%) 2.34 9.31 9.26 8.95 8.48
~Work to rupture ~36.4 ~ 148~ 150 171 162
Wèt'Web stretch at 2.34 ~ 13.02 12.82 13.82 15.0
100 m breaking~ length (~
Dry Handsheet Properties~
Bulk (cm3/gj ` ~ 1.74 ~ 54 1.53 ~ ~ 1.47 ~ 1.49
Burst Index (kPa.m2lg) 6.73 ~ 4.~50 ~ 4.70 5.23 5.18
Tear Index (mN-m2/g) ~ ~ ~ 8.26 10.40 10.75 10.64 10.04
Breaking Length~(m3 ~ 9422 6754 6814 ~ 7389 ~ 7302 i;~ ;
Stretch (X)~ ~ ~ 2.79 ~ 3.26 ; 3.43 3.50 3.48
Toughness Inde~ (mJ) ~ 159 ~ 143 148 170 163
Zero-span b.l.~(km) ~ ~ I6.12 ~ 14.38 ~ 14.42 ~ 14.48 14~.98
Scattering Coeff.~(cm2/g) ~ 208 211 ; 206 ; ~ 196~ 198
Tappi Opacity (~%) ~ 76.3 76.8 61.5~ 68.7 ~ 66.4
Iso-Brightness (%)~ 44.8 42.1 49.3 52.9 56.6
Absorption Coeff. (~cm2/g) 14.88 ~ 16.36 7.02 5.23 4.03
Visual Efficièncy (%) 56.0 53.6 63.5 67.0 70.5 -~
Printing Opacity (~j ~ 86.0 86.6 69.6 77.0 73.7
1 Refined at 0.78 MJ/kg and 24% consistency
:: : :~
:
:
:; :
- 28 -
I
. .
,
pulp at about 30~ consistency were sprayed with a solu-
tion of 2% H202, 0.4~ EDTA, 3% Na2SiO3, 0.005% g 4
to bring it to 19% consistency. The pulps were treated
at 150C for 10 minutes.
Results are given in Table VIII. Both pulps are
higher in visual efficiency than the control and
possess all the other desired superior properties.
EXAMPLE 9
This example illugtr~ates the effect of the heat
treatment on bleached or brightened pulps.
A 70% yield sulphi~e ~palp ~and a thermomechanical
pulp at about 30% ~consistency were sprayed with a solu-
tion of 2% ~22~ 0-4% EDTA, 3% Na25103 and 0.005% MgS04
to bring it~to~l9% consistency.~The pu1ps reacted with
the`chemicals for one hour at ~60C. Afterwards, the
pulps were~heat treated at 150C for 10 mlnutes.
Results~ are glven in Table ~IX~for the orl~ginal
pulps before~ heat~treatment,~the brightened~ pulps and
for both pulps~ after ~heat treatmen~t. The heat treat~
ment~ done~under the condltions~disclosed~herein;on the~
brightened pulp~compared to; the~ orig1nal pulp gaye~
similar~properties while it had higher visual effici-
ency.
,.
:
;
- 29 -
, . , , ~ , , . :
-- . :. : : . . .: . ,
7~
TABLE VIII
.
THE EFFECT OF THE ADDITION OF A BRIGHTENING AGENT
TO PULP DURING THE HEAT TREATMENT
. .
:
70% YIELD SULPHITE PULP1 TMp2
Heat Treatment at Heat Treatment at~
150C, 10 minj 19% 150C, 10 min, 19%
consistency with consistency with
Before No 0.4% EDTA BeforeNo 0.4% EDTA
Heat Bleaching 3% Na2SiO3 HeatBleaching 3% Na2SiO3
Treatment Chemicals 0.005% MgS04 Treatment Chemicals 0.005% MgS04
Pulp and Fibre Pr perties
Curl Index 0.148~ 0.187 0.209 0.106 0.177 0.163
CSF ~(mI) 673 651 685 175 312 293
t Wet'Web Properties
0.7 kPa ~ Solids (%) 26.1 26.5 25.1 20.6 25.9 23.4
¦ TensiIe~(m) 82.8 92.4 ~ 80.1 110 86.1 96.1
Stretch ~(%) ~ 2.38 3.32 ~5.045.02 10.1 iO.l
Work to rupture 20.3 ~ 32.0 ~ 43.7~ 68.4 117 122
I03 kPa ~ Solids (%) ~29~1 32.5 ~ 32.1 ~25.0 ~ 32.3 29.3
Tensile (m) i ~ 143 147 ~ ~ 127~ 167 ~144 150
Stretch (%3 ~ ~ 1.95 ~ 2.~53 ~ 3.49 4.42 8.22 ~ 7.24
: Work to rupture~;27.3 38~ 44.7 ~ 86.8 ~ 159 144
Wet-Reb stretch at
~100 m breaking;length ~(%) ~ ~2.23 ;2.90~ ~ 4.05 ~5.22~ ~ 9.61 ~8.93 ~;
Dry Handsheet Properties
:~:: : ~:
Bulk ~cm3/gj ~ ~ ~ 1.81 1.65 1.79~ ~ 2.79 3.10~ 2.;96
Burst Index (kPa.m21g) ~ ~ 6.24 5.78 4.38 2.02 1.~36 ~ ~1.50
Tear Index (mN.m2/g)~ 8.22 7.84 7.84 ~ ~ 8.72 8.27 ~8.94
Breaking Length (m) ~ 9704 9251 ~ 7361 ~ 3625 2469 ~2792
Stretch (X) ~ 2.63; ;2.71~ 2~.32 ~ ~ 2.15~ ~ 2~05~ 2.07
Toughness Index (mJ)~ 150 156 ~ 113 ~ 45 ~ 32~ 37~
2ero-span b.l. (km)~ 16.45 16.23 13.96 11.20 ~ 9.78~ 10.47
Scattering Coeff. (~cm2-/g)~ 219 ;~ 203 238 ~ ~568 568 581 ~ ;
Tappi Opacity (~%)~ 77.2~ 76.1 79.7 93.8 95.1 ~93.3
Iso-Brightness (%) ~ ~ 45.3 ~ 41.7 42.8 ~ 56.0 ~ 50.9 55.8
Absorption Coeff. `(cm2/g)~ 14.68 ~ 15.10 9.22 ~20.23 20.49 9.83
Vlsual~Efficiency~(%)~ 56.6~ 54.3 60.4~ 67.3 ~ 64~4~ 71.2 ;~
Refined at 0.57 MJ/kg~and~ 9% consistency
2 Refined at 8.52 MJ/kg and~35%~consistency afeer second stage
: ~:
~
.
.
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