Note: Descriptions are shown in the official language in which they were submitted.
1309~2
CHEMIMECHANICAL PULPING PROCESS EMPLOYING
SODIUM CARBONATE AND SODIUM SULPHll'E
Back~round of the invention
The present invention relates to a process for the production of a high
yield, high strength chemimechanical (CMP3 pulp from wood or other
lignocellulosic materials. More particularly, this invention relates to a chemi-mechanical pulping process employing sodium carbonate and sodium sulphite in
the cooking liquor to chemically soften the wood chips or other lignocellulosic
materials prior to mechanical defibration.
In recent years there has been increased use of high yield
chemimechanical pulps in the manufacture of papers and, particularly, printing
papers. These pulps have relatively high strength as compared to the pure
mechanical pulps such as groundwood pulps and refimer pulps.
Traditionally newsprint is manufactured from a furnish consisting of about
three parts mechanical pulp, such as g~oundwood or refiner pulp and one part
chemical pulp. Groundwood, manufactured by pressing logs against a revolving
abrasive stone, is obtained in yields approaching 100%, whereas the refiner pulps,
such as the refiner mechanical pulp (RMP~ and thermomechanical pulp (TMP~ are
obtained by refining wood chips or other lignocellulosic materials in a disc refiner,
under atmospheric or elevated pressure, respectively. The RMP and TMP are
obtained in yields of 95% or more. Pollution problems associated with the
manufacture of mechanical pulps are minimal. HoweveF, the mechanical pulp
~lbers, containing almost all the lignin present in the wood, are relatively stiff and
produce papers of comparatively low strength because of their poor interfiber
bonding capacity. The lignin, concentrated in the intercellular layer known as the
rruddle lamella, cements the cellulose fibers to each other.
$~
1309a62
The main pulpose of chemical pulping processes, such as sulphate (kraft)
or sulphite pulping, is to dissolve the middle lamella so that the wood structure
breaks down into individual fibers without the use of substantial mechanical action.
This is accomplished by cooking the wood chips at high chemical concentrations
S and high ternperatures (about 120C to 180 C~ for a prolonged period of time (up
to 5 hours or rnore) and results in low yields based on the dry chips because a
substantial amount of the wood, particularly lignin, is removed. The chemical pulp
component is usually manufactured by either the kraft or sulphite process in yields
ranging from 45% to 65%.
Chemical pulps have many advantages due to their cleanliness, high
strength, and ease of bleaching, but they are expensive, make heavy demands on
the mill's wood resources, and entail formidable pollution problems. The presenttrend in newsprint manufacture, therefore, is towards reduction in the use of
chemical pulps.
The semichemical and chemimechanical pulping processes fall midway
between the chemical and mechanical processes in these respects.
The increasing world-wide demands for pulp, paper and other forest
products and the decreasing availability of fiber are creating an increasing need for
the use of higher yield pulps. The present invention produces a high yield pulp
that can replace some types of chemical or semichemical pulp in many products.
One attempt which has been made tO improve the yield of sulphite pulps,
which is relevant from the standpoint of the present invention, involves pre-treating
the chips with an alkaline solution for a period of time. Exarnples of such
sulphite pulping processes are described in U.S. patent 3,177,110 to Ogait and U.S.
patent 3,354,030 to Williams et al. However, these processes remain essentially
chemical pulping processes which rely upon the removal of most of the lignin
from the wood and do not provide high overall yields. For example, the yields il-
lustrated in the Ogait patent only range from about 55 to 65%. By contrast, the
major portion of the lignin is retained in CMP and (~TMP processes due to ~le
1~09~2
use of much milder conditions in the chemical treatments.
It is known that the ~eatment of wood chips with relatively small
amounts of sulphite and bisulphite, at near neutral pH, and under relatively rnild
cooking conditions ~100 C - 150 C, for 2-25 minutes) produces a softening effect
on the chips which makes them easier to de~lber and generally produces a cleanerand better draining pulp than can be produced by mechanical means alone. See
Uschmann U.S. patent 3,607,618; Aitken et al. U.S. patent 3,013,934; and Asplundet al. U.S. patent 3,558,428.
However, the pulps produced by such processes, while being superior to
conventional mechanical pulps in terms of cleanliness and drainage properties, do
not have sufficiently good physical properties to justify their increased cost of
production relative to the conventional mechanical pulps.
Better properties can be achieved by cooking under more severe
conditions such as increased temperatures in the 160 C - 240 C range, but the
strength improvement is always accompanied by a loss in yield. Instead of yieldsof over 90%, the yields are reduced to about 70-85%. See the above patents and
Richardson U.S. patent 2,962,412; Zimmerman U.S. patent 1,821,198; Cederquist
U.S. patent 3,078,208; Asplund et al. U.S. patent 3,44~,699; Von Hamzburg U.S.
patent 2,949,395; Olson U.S. patent 3,003,909; and Rasch et al. U.S. patent
2,847,304.
Mild sulphite treatments have been used in chernirnechanical pulping
processes to chemically soften the wood fibers and thereby facilitate mechanicaldefibration. It is known that sul~onation renders lignin more hydrophillic or less
hydrophobic so that the fibers swell in the sulphite liquor and the chips becomeeasier to defibraee. These chernimechanical processes produce higher yields thanchemical or semi-chemical processes, but the pulp strength is not as good.
Typically they are also more effective with softwoods than hardwoods.
U.S. patent ~,116,758 to Ford et al. describes a process which is specially
suited to softwood pulps whereby wood chips are softened prior to defibration by
1309~62
sulfonating the lignin with-out substantially removing it from the wood. This istypically accomplished by maintaining the wood chips in a solution containing 50-
180 g/L sodium sulphite at 100 - 140 C for approximately 30 - 60 minutes
without an alkaline pre-treatment and is followed by disc refining.
U.S. patent 3,016,324 to Textor also discloses a chemi-mechanical pulping
process wherein wood chips may be impregnated with sodium sulphite liquor by
squeezing the chips in a screwpress and spraying the chips emerging from the
press with sulphite liquor and then defibrated.
Chemimechanical pulping processes in which the chips are impregnated
with aLkaline liquors are also known.
One proposed mechanism by which the use of alkali, such as caustic soda
or sodium hydroxide, increases the strength of mechanical pulps is by increasingthe number of acidic groups in the wood. ~See publication of Katz et al. "A
Mechanism for the Alkali Strengthening of Mechanical Pulps", TAPPI, Vol. S4,
No. 7, pp. 97-100, July, 1981). The counter-ions of these acidic groups are saidto draw additional water into the cell wall and the accompanying swelling and
plasticization enhance the ability of the fibers to bond and the overall strength o
the pulp improves.
U.S. patents 3,479,249; 3,617,435; and 4,795,574 to Kalisch describe a
semi-chemical sulphite pulping process which is accomplished by impregnating
wood chips with sodium hydroxide or sodium carbonate and, thereafter, cooking
the chips in an aqueous solution of sulphur dioxide for 2 to 3 hours. In the latter
treatment, the sodium hydroxide or sodium carbonate in the chips reacts with
sulphur dioxide to produce bisulphite in the chips which reacts with the lignin to
solubilize it in a known manner. A~ter cooking, the chips are defibrated by
passing them through a disc refiner. The yields reported in the patent are about75% or less.
U.S. patent 4,486,267 to Prusas discloses a high yield chemither-
momechanical (CTMP) process wherein hardwood chips are subjected to a two-
1309562
stage chemical treatment prior to defibration, the first consisting of chip
impregnation and reaction with an aL~aline liquor followed by a second stage
treatment with sulphite and/or bisulphite. This process produces high strength
hardwood pulps, but the pulp brightness (22 - 40%) and yields (79 - 85%) are
greatly reduced.
U.S. patent 4,187,141 to Ahrel describes a process for producing bleached
chemimechanical pulp wherein screwpressed wood chips are subjected to a two-
stage impregnation with an alkaline peroxide solution, in which the impregnated
chips are introduced into a pressure vessel and ground in a disc refiner. This
process provides a pulp having high brightness but relatively low strength.
While sodium hydroxide has been used in the production of
chemimechanical and chemithermomechanical pulps in the past to improve pulp
strength, it has not maintained high b~ightness and high yield. It is ~nown thatsodium hydroxide darkens the pulp and solubilizes the hemicelluloses in known
manners. We have now made the surprising discovery that both the pulp yield
and brightness can be increased by replacing the sodium hydroxide by sodium
carbonate in the sulphite cooking of chips carried out prior to refining.
It has been found that, as the reaction in chemical treatment of chips
proceeds, the pH of the medium drops, probably as a result of hydrolysis of acetyl
groups on the chip. If the pH drops below 3, there is risk of damaging the fibrethrough hydrolytic action with consequent loss of strength. Wood fiber which hasbeen subjected to mechanical action, such as refining, is particularly susceptible to
acidic degradation. It is therefore a common industrial practice to add aLkali, such
as sodium hydroxide or sodium carbonate to the cooking li~uor as a buffer. It iswell known that sodium hydroxide solubilizes hemicelluloses, resulting in yield
loss.
Sodium carbonate has been used in semichemical pulping experiments,
such as the neutral sulphite semichemical ~NSSC) processes. Conflicting results of
the influences of sodium carbonate on pulping ha7/e been reported. See the
1309~62
following publications: Upadhyaya et al., "Studies on Neutral Sulphite
Semichemical Pulping of Cajanus cajan", ABCP Congr. Anual l9th (Sao Paulo),
Nov. 24-28, 1986, pp. 177-188; ~Ialhotra et al., "Neutral Sulphite Sernichemical(NSSC) High-Yield Pulps from Eucalyptus globulus", Holzforsch. Holzverwert.
Vol. 33, No. 3, pp. 51-52, 1981; Cameron et al., "Response of Pines and
Eucalyptus to NSSC-AQ Pulping", SPCI Internatl. Symp. Wood & Pulping Chem.
Preprints, Vol. 2, 64-71 (June 9-12, 1981); Janci et al., "Production of
Semiehemieal Pulp Using Green Liquor from NSSC Chemieal Recovery ~ystem",
Papir Celluloza Vol. 34, No. 10, pp. 289-292 (1979); and Keller, "Is Caustic Soda
Suitable for Buffering NSSC Digestions?", Southern Pulp Paper Mfr. Vol. 32, No.
5, pp. 32, 34, 36 (May, 1969).
It has now been surprisingly found that physical properties of sulphite
chemimeehanieal pulps ean be significantly improved and their yields can be
maintained near 90% level, by an addition of sodium carbonate to the sulphite
liquor.
In aecordance with the present invention, there is provided a process of
produeing ehemimechanieal pulps which eomprises cooking the ehips with aqueous
sodium sulphite solution containing suf~leient sodium earbonate. The eooking is
effeeted at an elevated temperature for a time suffieient to eause reaetion with the
ehip and increase the swelling or the flexibility of the fibers but for a time
insufficient to eause substantial dissolution of wood components, such as ligninand hemicellulose from the ehip and insuffieient to result in a pulp yield belowabout 85%.
The improvement in strength properties aehieved by the present invention
permits use of the resultant pulps as either replacement or reinforcement
eomponent for the low yield, high eost chernieal pulps in papers, partieularly the
printing grades.
The proeedure of the present invention may be carried out on any types
of wood chips or other lignocellulosic materials, and the improvement in physieal
~309562
properties is achieved on each of these materials.
It is, accordingly, an object of the present invention to provide a high
yield chemimechanical pulping process for producing high strength pulp from
wood chips and other lignocellulosic materials.
It is also object of the invention to provide a two-stage process of
producing high yield chemimechanical pulp from wood chips whereby the chips
are impregnated with an aqueous solution of sulphite and sodium carbonate
followed by either liquid phase or vapour phase cooking and thereafter defibrating
the chips by a disc re~mer to provide a pulp having excellent strength charac-
teristics.
Other objects will be apparent to those skilled in the art from the present
description.
1~ Genera! Descri~tion of the invention
The process of the invention is an improved two-stage process for
producing high yield chemimechanical pulps from wood or other lignocellulosic
material, whereby in the first stage, the wood or other lignocellulosic material is
subjected to treatment with an aqueous solution of sulphite and sodium carbonate,
wherein sufficient sulphite is present to provide an amount of at least about 3% by
weight, based on weight of wood or other lignocellulosic materials and wherein
sufficient sodium carbonate is present to provide an amount to maintain a pH of
the liquor of about 7 to 1(), the cooking being at a temperature of between 100 C
and 200 C for between about 2 and 120 minutes, without reducing the pulp yield
2~ to below about 85%; and whereby in the second stage, the resulting treated wood
or other lignocellulosic material is subjected to mechanical defibration.
In the first stage of chemical treatment of the process of the present
invention, the cooking of the chemically trcated wood or other lignocellulosic
material may be carried out either in liquid phase or vapour phase.
~309~2
In liquid phase cooking, the chemically treated wood or other
lignocellulosic material is cooked in a heated sulphite/carbonate solution under the
specified conditions, prior to being subjected to mechanical defibration.
Cooking of the chemically treated wood or other lignocellulose material
may also be carried out in vapour phase, whereby the wood or other
lignocellulosic material is first impregnated with a sulphite-carbonate solution by
means of steeping or press impregnation of wood or other lignocellulosic material
and whereby the impregnated wood or other lignocellulosic material is subjected to
steam cooking, and thereafter to mechanical defibration.
In a preferred embodiment of the invention, the amount of sulphite used
is in the range of 10 and 25% by weight based on weight of wood, although
lower concentrations down to about 1 % may be used with reduced bene~lcial
effect. Similarly improvements are observed with sulphite charges up to about 50%
by weight of the wood, but the additional cost is not justified by the small
additional improvement. Generally, therefore, a sulphite charge of between about1% and about 50% by weight, preferably between 10% and about 25% by weight
based on weight of wood is used.
The sodium carbonate charge may range from about 2% to about 25% by
weight of wood or other lignocellulosic material, preferably between 5 and 10%~
although lower concentrations down to about 1% may be used with reduced
beneficial effect. Similarly improvements in pulp properties are observed with
sodium carbonate charges up to about 30% by weight of the wood, but the
additional cost is not justified by the substantial loss in yield.
It is preferred to carry out the impregnativn of wood with a liquor-to-
wood ratio ranging from about 4 to about 6, preferably around 5. Lower ratios
may not permit uniform impregnation of wood, but higher ratios increase energy
costs as in liquid phase cooking, and decrease reaction rate because of dilution of
the reactants, necessitating longer reaction times.
1~03 ~2
The time and temperature of reaction may be vaned over a wide range.
The essential requirements are that the reaction must be allowed to effect an
increase in physical properties and must not be allowed to proceed far enough toyield substantial dissolution of lignin and hemicellulose, as it would decrease
substantially pulp yield and increase pollution problems. Practically, the application
of our invention is restricted to pulp yield in excess of about 85% by weight
based on starting wood chip. The minimum reaction time to yield beneficial results
is about 2 rninutes at 200 C, with longer times being used at lower temperatures.
In the practice of the invention, ~he wood or other lignocellulosic material is
exposed to a minimum degree of cooking corresponding to 2 minutes at 200 C,
and a maximum degree of cooking corresponding to a pulp yield of about ~5% by
weight.
The pulps made from this invention may be used in such products as
newsprint, coated papers, hook papers, sanitary tissues, corrugating medium,
linerboard, paper towelling, diaper fluff, miLk carton board, etc.
Specific DescriPtion of the Invention
In order to disclose more clearly the nature of the present invention, the
following examples illustrating the invention are given. It should be understood,
however, that this is done solely by way of example and is intended neither to
delineate the scope of the invention nor limit the ambit of the appended claims.
EXAMPLE 1
This example compares the effec~ of sodium carbonate to that of sodium
hy~roxide in alkaline sulphite treatment of black spruce.
Pulps were prepared using a 300-mL reactor provided with live steam, a
1309~62
4-L Waring blender and a PFI mill. Black spruce chips were impregnated with a
solution containing sodium sulphite, or sodium sulphite/sodium hydroxide, or
sodium sulphite/sodium carbonate, under vacuum at ambient temperature for 16
hours. The liquor concentration was 100 g/L, which contained 100, 90, 80, and 70g of sodium sulphite, the balance was made up of either sodium hydroxide or
sodium carbonate. A liquor-to-wood ratio of 5 was used. The impregnated chips
were drained and steamed at 190 C for 9 minutes.
The cooked chips were first defibrated in a Waring blender for 2 minutes
at 3% consistency, and then refined in a PFI mill at 10% consistency to yield
several freeness levels. Physical properties were measured on handsheets prepared
from the unscreened pulps after the removal of latency. The properties are shownin Tables lA to lG below.
It can be seen from the results of Tables lA to 1(3 that using of sodium
carbonate instead of sodium hydroxide in sulphite pulping can maintain a pulp
yield near 90% or above 86%, while improving substantially the physical
properties, particularly the breaking length and burst index. Using sodium
carbonate causes only a relatively small drop in pulp brightness, while using ofsodium hydroxide can bring about substantial loss in both pulp yield and
brightness.
EXAMPLE 2
This example illustrates the effect of addition of sodium carbonate to the
sulphite liquor and the effect of co~king time on pulp properties.
A mixture of softwood chips (2-4 mm thick) containing approximately
70% black spruce and 30% balsam fir were impregnated wi~h sulphite liquor
containing about 0, 9, 17, and 33% of sodium carbonate. A liquor-to-wood ratio of
5 was used. The impregnation of chips was carried out under vacuum, a~ ambient
1309~62
temperature for 16-18 hours. The impregnated chips were drained and steamed at
180 C for 7, 10 and 13 minutes.
The cooked chips were first defibrated in a Waring blender for 2 minutes
at 3% consistency and then refined in a PFI mill at 10% consistency to obtain
various degrees of freeness. Physical properties were measured on handsheets
prepared from the unscreened pulps after the removal of latency. The properties
are shown in Tables 2A to 2D.
It can be seen from the results of Tables 2A to 2D that the addition of
sodium carbonate can maintain the pulp yield in the neighbourhood of 90%,
depending on the cooking tirnes. Meanwhile the physical properties of handsheet
are improved particularly those of the pulp produced with 7-minute cooking time.It appears that the advantage of sodium carbonate decreases slighdy when the
cooking time was prolonged beyond 7 minutes.
EXAMPLE 3
This example compares the influences of sodium hydroxide and sodium
carbonate in sulphite pulping of softwoods, at semi-industrial scale.
Softwood chips containing approximately 85% black spruce and 15%
balsam fir were cooked in a liquor at 170 C for 20 minutes. The concentration of
the liquor was 50 g/L, in which sodium sulphite represented 45, 40 and 35 g, andthe balance was made up with either sodium hydroxide or sodium carbonate. In
other words, the sodium hydroxide or sodium carbonate represented, respectively,10, 20 and 30% of the total chemical applied. Ihe liquor-to-wood ratio used was
6. After cooking, the chips were washed and refined, under atmospheric pressure,using a Sunds De~lbrator 300CD re~mer. Physical properties were measured on
handsheets pr~pared from the unscreened pulps after the removal of latency. The
properties are presented in Tables 3A to 3F.
13 0 9 3 6 2
It can seen from the results in Tables 3A to 3F, that there is a substantial
gain, from about 3 to about 13 percentage points, in pulp yield by using sodium
carbonate instead of sodium hydroxide. It also can be noted that sodium carbonate
did noe darkened the pulp as much as sodium hydroxide. The freeness of the
carbonate pulps as shown in Tables 3D, 3E and 3F was quite high because much
less specific refining energy was applied in comparison with the caustic pulps as
indicated in Tables 3A, 3B and 3C. In spite of their high freeness, the carbonate
pulps yielded properties which were comparable to those of the caustic pulps.
EXAMPLE 4
This example compares the effect of sodium carbonate to that of sodium
hydroxide in sodium sulphite cooking of hardwood.
Trembling aspen chips were cooked in three different liquors; the first
contained 100% sodium sulphite, the second 90% sodium sulphite and 10% sodium
hydroxide,and the third contained 90% sodium sulphite and 10% sodium carbonate.
The concentration of the liquor was 100 g/L. A liquor-to-wood ratio of 6 was
used. In each pulping liquor, the chips were cooked at 150~ C and at three
different retention times, that is 8, 13 and 18 minutes in order to produce pulps at
different degrees of pulp yield.
The cooked chips were first defibrated in a Waring blender for 2 rninutes
at 3% consistency, and then refined in a PFI mill at 10% consistency tO obtain
various levels of freeness.
It can be seen from Figure 1 that partial replacement of sodium sulphite
by sodium carbonate resulted in considerable increase in pulp yield about 4%
points when compared with sulphite pulps. On the other hand, the replacement of
sodium sulphite by sodium hydroxide reduced the pulp yield by about 2% points.
Figure 2 indicates that the tensile strength of handsheet was improved by
130~g2
the presence of sodium carbonate in the cool~ing liquor. Sodium hydroxide was
also effective in improving the fiber bonding strength but it caused impor~nt yield
loss. In fact the tensile strength of sulphite-carbonate pulps was quite comparable
to that of sulphite-caustic pulps, but the pulp yield of the former was much higher
than that of the latter, which is a significant advantage. It was also observed that
using sodium carbonate maintained a high pulp brightness of about 55% (56% for
sulphite pulps, 45% for sulphite-caustic pulps). The tearing resistance of aspenpulps are shown in Figure 3 which indicates the advantages of sulphite-carbonatepulps which had high tear index at high yield levels.
The terms and expressions which have been employed are used as terms
of description and not of limitation, and there is no intention in the use of such
terms and expressions of excludin~ any equivalents of the features shown and
described or portions thereof, but it is recognized that various modifications are
possible within the scope of the invention claims.
14
1 309~62
TABLE lA
CHEMICAL COMPOSITION: 100 g Na2SO3 per liter
Pulp Yield: 89.5%
Properties
Freeness, mL 520 408 306 220 176
Density, g/cm3 0.39 0.41 0.45 0.47 0.48
Breaking Length, km S.l 5.8 6.2 6.5 6.6
Burst Index, kPa.m2/g2.7 3.0 3.3 3.6 3.9
Tear Index, mN.mVg 7.6 7.2 6.6 6.4 6.2
Brightness, % 46 45 45 46 46
Opacity, % 94 94 94 93 93
Light Scat. Coef. m2/kg 37 38 36 37 36
Light Abs. Coef., cm2/g 48 47 41 42 45
TABLE lB
CHEMICAL COMPOSITIONo 90 g Na2SO3 + 10 g NaOH per liter
Pulp Yield: 81.5%
Properties
Freeness, mL 546 412 312 274 148
Density, g/cm2 0.47 0.50 0.S2 0.54 0.56
Breaking Length, km 6.6 7.2 7.6 7.8 8.4
Burst Index, kPa.m2/g4.0 4.4 4.9 S.l 5.6
Tear Index, mN.mVg 8.4 7.4 7.2 7.0 6.5
Brightness, % 33 33 33 33 33
Opacity, % 97 96 96 96 96
Light Scat. Cbef., m2/kg 33 32 33 33 34
Light Abs. Coef., cmVg 83 82 82 83 81
1 309~62
TABLE lC
CHEMICAL COMPOSITION: 80 g Na2SO3 + 20 g NaOH per liter
Pulp Yield: 79.4%
Properties
Freeness, mL 540 392 266 196
Density, g/cm3 0.50 0.52 0.55 0.56
Breaking Length, km 7.7 7.9 8.4 8.8
Burst Index, kPa.m2/g4.8 5.2 5.8 6.1
Tear Index, mN.m2/g 8.6 8.0 7.9 7.4
Brightness, % 29 30 30 29
Opacity, % 97 97 97 97
Light Scat. Coef., m2/kg 32 32 33 33
Light Abs. Coef., cm2/g 105 102 104 104
TABLE lD
CHEMICAL COMPOSITION: 70 g Na~SO3 ~ 30 g NaOH per liter
Pulp Yield: 79.4%
ProDerties
Freeness, mL 533 380 240 160
Density, g/cm3 0.48 0.54 0.56 0.57
Breaking Length, km 7.8 8.3 8.7 9.2
Burst Index, kPa.m2/g4.7 5.6 5.8 6.2
Tear Index, mN.mVg 8.8 8.1 7.5 7.3
Brightness, % 28 27 27 27
Opacity, % 98 98 98 98
Light Scat. Coef., m2/kg 33 31 32 33
Light Abs., Coef., cm2/g 122 120 124 124
lS
1309~2
TABLE lE
CHEMICAL COMPOSmON: 90 g Na~SO3 + 10 g Na2CO3
Pulp Yield: 89.1%
Properties
Freeness, mL 387 290 280 230 174
Density, g/cm3 0.47 0.49 0.49 0.50 0.52
Breaking Length, km 7.2 7.6 7.7 7.8 8.1
Burst Index, kPa.m2/g4.0 4.4 4.5 4.7 4.9
Tear Index, mN.m2/g 7.2 6.9 6.9 6.8 6.4
Brightness, % 41 41 41 41 39
Opacity, % 94 94 94 94 94
Light Scat. Coef., m2/kg 35 34 34 34 31
Light Abs. Coef., cm2/g 56 52 51 52 57
TABLE lF
CHEMICAL COMPOSlTION: 80 g Na2SO3 + 20 g Na~C03 per liter
Pulp Yield: 86.9%
Properties
Freeness, mL 430 356 266 187
Density, g/~m3 0.51 0.52 0.54 0.56
Breaking Length, km 7.4 8.1 8.3 8.4
Burst Index, kPa.m2/g 4.4 4.9 5.1 5.4
Tear Index, mN.mVg 7.2 7.0 7.S~ 6.9
Brightness, % 36 36 35 35
Opacity, % 95 95 95 95
Light Scat. Coef., m2/kg 33 32 32 31
Light Abs., Coef., cmVg 68 68 71 67
.
130~2
TABLE lG
CHEMICAL COMPOSITION: 70 g Na2SO3 + 30 g Na2CO3 per liter
Pulp Yield: 86.5%
Properties
Freeness, mL 420 316 236 172
Density, g/cm3 0.49 0.51 0.52 0.54
Breaking Length, km 6.9 7.4 7.9 7.9
Burst Index, kPa.m2/g 4.0 4.5 4.7 4.8
Tear Index, mN.m2/g 7.2 6.9 6.7 6.6
Brightness, % 36 36 35 35
Opacity, % 95 95 95 96
Light Scat. Coef., m2/kg 33 33 33 34
Light Scat. Abs., cm2/g 69 69 68 71
TABLE 2A
CHEMICAL COMPOSlTION: 100 g Na2SO3 per liter
P~o~erties Cookin Time, min
7 10 13
Pulp Yield, % 92.9 91.6 89.6
Freeness, rnL 280 190 140 340 230 170 350 260 190
Density, g/cm3 0.45 0.45 0.49 0.46 0.51 0.55 0.52 0.54 0.56
Breaking Length, km6.2 6.4 6.7 6.3 7.3 8.0 7.5 7.9 8.2
13urst Index, lcPa.mVg 3.3 3.3 3.7 3.6 4.3 4.5 4.6 4.6 4.8
Tear Index, mN. m2/g 7.0 6.8 6.4 7.5 6.7 6.1 7.1 6.8 6.7
Brightness, % 51 51 51 49 49 48 46 46 46
Opacity, % 90 90 90 90 89 89 90 90 90
L. Scat. Coef., m2/~g 34 35 35 32 32 31 31 30 30
L Abs. Coef., cm2/g33 33 31 33 34 33 38 38 38
13~93~2
TABLE 2B
CHEMICAL COMPOSITION: 100 g Na2SO3 + 10 g Na2CO3 per liter
Properhes Cookin Time~ min
7 10 13
Pulp Yield, % 92.4 89.6 88.2
Freeness, mL 280 200 150 340 240 190 300 220 160
Density, g/cm3 0.46 0.46 0.46 0.45 0.47 0.47 0.44 0.48 0.48
Breaking Length, k}n 6.9 7.4 7.6 7.1 7.6 7.7 7.1 7.6 7.9
Burst Index, kPa.m2/g 3.9 4.0 4.1 4.0 4.2 4.4 4.1 4.3 4.4
Tear Index, mN. m2/g 7.4 6.8 6.6 8.1 7.2 7.0 7.8 7.5 6.7
Brightness, % 45 45 44 45 44 44 44 44 44
Opacity, % 91 90 90 90 90 89 90 90 90
L. Scat. Coef., m2/kg 32 32 32 31 31 31 31 30 30
L Abs. Coef., cm2/g38 37 37 35 37 36 37 39 38
-
TABLE ~2C
CHE~MICAL COMPOSITION: 100 g Na2SO3 + 20 g Na2CO3 per liter
Properties Cookin~ Time. min
7 10 13
Pulp Yield, % 92 89 88
Freeness, mL 280 210 140 420 280 180 420 280 180
Density, g/cm3 o~so 0.52 0.53 0.48 0.49 0.53 0.46 0.47 0.48
Breaking Length, km8.0 8.1 8.5 7.4 7.9 8.5 7.1 7.7 8.1
Burst Index, kPa.m2/g 4.5 5.0 5.3 4.5 4.9 5.1 4.2 4.6 4.6
Tear Index, mN. m2/g 7.5 7.0 6.4 7.7 7.3 6.6 8.3 7.4 6.8
Brightness, % 41 40 40 40 39 40 40 40 39
Opacity, % 91 91 90 91 91 91 91 91 91
L. Scat. Coef., m2/kg 31 30 29 30 29 29 30 30 29
L Abs. Coef., cm2lg41 42 43 45 46 47 44 44 46
19
130~ 2
TABLE 2D
CHEMICAL COMPOSITION: 100 g Na2SO3 ~ 30 g Na2CO3 per liter
Properties Cookin~ Time min
7 10 13
Pulp Yield, % 89.5 87.5 87.3
Freeness, mL 378 264 188 376 256 182300 200126
Density, g/cm3 0.48 0.500.53 0.45 0.47 0-490.52 0.530.55
Breaking Length, km 7.0 7.8 8.0 7.1 7.4 7.87.9 8.79.1
Burst Index, kPa.m2/g4.1 4.3 4.6 3.9 4.2 4.45.3 5.25.4
Tear Index, mN. m2/g 7.8 7.5 6.9 7.6 7.1 7.07.9 7.47.1
Brightness, % 38 38 37 39 38 38 37 36 36
Opacity, % 93 93 93 93 93 92 93 93 93
L. Scat. Coef., m2/kg32 32 31 32 31 30 30 29 29
L Abs. Coef., cm2/g 54 54 56 53 54 52 57 61 59
TABLE 3A
CHEMICAL COMPOSITION: 45 g Na2SO3 + 5 g NaOH per liter
Pulp Yield: 87.1%
Properties
Specific Energy, m~cg 8.9 9.8 10.5 14.6
Freeness, mL 613 502 413 147
BuL~c, cm3/g 2.53 2.54 - 2.26 2.02
Brightness, % 39 39 39 38
Opacity, % 98 97 96 95
Porosity, mL/min 3464 2527 1213 69
Brealcing Length, km 4.4 4.6 5.4 6.7
Stretch, % 2.12 2.39 2.63 3.17
Burst Index, kPa.m2/g 2.4 2.8 3.4 4.2
Tear Index, rnN.mVg 11.6 11.2 10.9 9.8
~30~2
TABLE 3B
CHEMICAL COMPOSITION: 40 g Na2SO3 + 10 g NaOH per liter
-
Pulp Yield: 80.9%
Properties
Specific Energy, mJ~g 12.1 12.6 13.3 13.7
Freeness, mL 254 136 88 62
Bulk, cm3/g 2.12 1.99 1.89 1.79
Brightness, % 34 34 34 34
Opacity, % 98 98 98 98
Porosity, rnIlmin166 61 24 16
Breaking Length, km5.8 6.4 6.6 6.7
Stretch, % 3.10 3.30 3.24 3.22
Burst Index, kPa.mVg 3-9 4-3 4-5 4-4
Tear Index, mN.m2/g9.5 9.2 7.8 7.5
TABLE 3C
CHEMICAL COMPOSITION: 35 g Na2SO3 + 15 g NaOH per liter
Pulp Yield: 74.8%
Properties
Speci~lc Energy, mJ~g 12.9 13.2 14.0 14.5
Freeness, mL 251 207 105 59
Bulk, cm3/g 2.17 2.08 2.02 1.93
Brightness, % 32 32 32 32
Opacity, % 99 99 99 99
Porosity, mL/min 201 111 46 17
Brealdng Length, km5.4 5.7 6.2 6.7
Stretch, % 2.98 3.27 3.49 3.58
Burst Index, kPa.m2/g 3.4 3.7 4.3 4.8
Tear Index, mN.m2/g11.410.8 9.0 8.8
~ 3 ~ 2
TAI~LE 3D
CHEMICAL COMPOSITION: 45 g Na2SO3 + 5 g Na2CO3 per liter
Pulp Yield: 89.9%
Properties
Specific Energy, mJ/kg 5.2 5.3 6.2 6.4
Freeness, rnL 695 670 521 470
Bulk, cm3/g 3.53 3.38 3.04 2.64
Brightness, % 45 45 45 45
Opacity, % 94 94 94 94
Porosity, mL/min4696 4212 2424 582
Breaking Length, km4.0 4.2 5.0 5.2
Stretch, % 1.89 1.96 2.36 2.37
Burst Index, kPa.m2/g 2.2 2.5 2.9 2.8
Tear Index, mN.m2/g14.814.1 10.6 9.2
TABLE 3E
CHEMICAL COMPOSlTION: 40 g Na2SO3 + 10 g Na2CO3 per liter
Pulp Yield: 88.8%
Properties
Specific Energy, mJ~cg 6.2 7.7 7.7 7.8
Freeness, mL 485 475 470 457
Bulk, cm3/g 309 2.95 2.55 2.32
Brightness, % 41 41 41 41
Opacity, % 95 95 95 95
Porosity, mL/min4224 3352 2224 446
Breaking Length, km4.6 5.2 5.5 5.7
Stre~ch, % 2.14 2.30 2.43 2.51
Burst Index, kPa.m2/g 2.7 3.0 3.3 3.4
Tear Index, mN.m2/g14.113.1 12.3 10.1
22
13095~2
TABLE 3F
CHEMI(:AL COMPOSITION: 35 g Na2SO3 + 15 g Na2CO3 per liter
Pulp Yield: 88~6%
Properties
Speci~lc Energy, mJlkg 6.7 6.9 7.0 9.3
Freeness, mL 490 480 475 403
Bulk, cm3/g 2.82 2.74 2.50 2.15
Brightness, % 38 38 38 38
Opacity, % 96 96 96 96
Porosity, mL/min3680 3052 1520 277
Breaking Length, km4.9 5.2 5.7 6.5
Stretch, % 2.27 2.42 2.55 2.7g
Burst Index, kPa.m2/g 2.9 3.1 3.5 4.0
Tear Index, mN.m2/g15.212.7 12.0 9.1
