CA1051618A - Method of producing high yield chemimechanical pulps - Google Patents
Method of producing high yield chemimechanical pulpsInfo
- Publication number
- CA1051618A CA1051618A CA252,642A CA252642A CA1051618A CA 1051618 A CA1051618 A CA 1051618A CA 252642 A CA252642 A CA 252642A CA 1051618 A CA1051618 A CA 1051618A
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- lignocellulosic material
- aqueous solution
- woody lignocellulosic
- sulfite
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21B1/00—Fibrous raw materials or their mechanical treatment
- D21B1/02—Pretreatment of the raw materials by chemical or physical means
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C3/00—Pulping cellulose-containing materials
- D21C3/04—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides
- D21C3/06—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites sulfites
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Paper (AREA)
Abstract
Abstract of the Disclosure An improved process for producing high yield chemi-mechanical pulps from wood or other lignocellulosic materials, such as chips, whereby the material is first sulfonated to at least about 85% of the maximum level of sulfonation, as defined, for such material without reducing the pulp yield to below 90%
and subjecting the resulting sulfonated wood to mechanical defibration.
and subjecting the resulting sulfonated wood to mechanical defibration.
Description
METHOD OF PRODUCING ~IIGH YIELD
CHEMIMECHANICAL P~LPS
Background of the Invention _ This invention relates to the production of chemi-mechanical pulps from woody lignocellulosic materials, such as chips, shavings and sawdust, with ultra high yields and with improved strength properties. More particularly, this invention relates to the production of such pulps by means of the sulfonation of the lignin in the wood, using aqueous sulfite or bisulfite solutions, followed by mechanical defibering.
The pulp and paper and related industries use many processes to produce pulp from wood chips and other lignocellu-losic materials. These processes can be classified, for purposes of discussion, into four groups, shown below with the represen-tative yields:
Chemical Pulps - up to 60% yield Semichemical Pulps - 60 - 80% yield Chemimechanical Pulps - 80 - 95% yield Mechanical Pulps - at least 90% yield The yield ranges shown are approximate only.
Chemical pulps are prepared by cooking the wood chips (or other lignocellulosic material) at elevated temperatures and pressures with various chemical agents which dissolve the lignin and some carbohydrate material to leave relatively pure cellulose fibers at the 40-45% yield level or cellulose plus some residual ~
lignin at somewhat higher yield levels (45-55%). ~ -Mechanical pulps at the other extreme use mechanical means such as grindstones to defiber logs or disc refiners to defiber wood chips into pulp. These processes use water for cooling and dilution purposes so that the approximately 5% of the wood substance that is water soluble is lost for a net yield of about 95%.
~" ~
- 1 .
. ' .,, ' ~. : ' ~ ,' ~, , : , . . ; , .
OS~L618 Chemical pulps have many advantages due to their cleanliness, hicJh streng-~h, and ease of bleaching, but they are expensive to produce due to the low yield. Their dissolved solid and gaseous waste products give rise to many environmental problems.
Mechanical pulps are much cheaper to produce due to their high yield and constitute an efficient use of forest resources. Such processes offer no gaseous pollution and rela tively little BOD5 (biochemical oxygen demand, five-day test) discharge compare~-to che~i~al 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 resource based products are creating an increasing . need for the us~ of higher yield pulps due to the decreasing availability of fiber. The present invention produces a hiyh yield pulp that can replace some types of chemical or semichemical pulp in many products.
It is known that the treat~ent of wood chips with relatively small amounts of sulphite and bisulphite, at near neutral pH, and under relatively mild conditions (100-150C., for 2-15 minutes) produces a softening effect on the chips which makes them easier to defiber and generally produces a cleaner and better draining pulp than can be produced by mechanical means alone. See "Ultrahigh Yield NSCM Pulping", by C. A.
Richardson, Tappi, Vol. 45, No. 12, pp. 139A-142A (1962);
Richardson et al., "Supergroundwood from Aspen", Tappi, Vol. 48, No. 6, pp. 344-346 (1965); Chidester et al. "Chemimechanical Pulps from Various Softwoods and Hardwoods", Tappi, Vol. 43, No. 10, pp. 876-880 (1960); Uschmann U. S. patent 3,607,618;
.
- ~Q5~
Aitken et al. U. S. patent 3,013,93~; and Asplllnd et al. U. S.
patent 3,558,428.
However, the pulps produced by such processes, while being superior to conventional mecha.nical pulps in terms of cleanliness and drainage properties, do not have sufficiently good physical properties to justify their increased cost of production re].ative to the conventional mechanical pulps.
Better properties can be achieved by cooking under more severe conditions such as increased temperatures in the 1Ø 16Ø-240C.. range, but the strength improvement is always accom-panied by a loss in yield. Instead of yields of over 90~, the yields are reduced to about 70-85~. . See most of the above -:
publications and 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 3,446,699; Von Hamzburg U. SO patent 2,949,395; Oison U. S. patent 3,003,909; and Risch e~ al. U. S. patent 2,847,304. . .
Considerations of cost and environmental protection make the maintenance of yields in exGess of 90% highly desirable.
CHEMIMECHANICAL P~LPS
Background of the Invention _ This invention relates to the production of chemi-mechanical pulps from woody lignocellulosic materials, such as chips, shavings and sawdust, with ultra high yields and with improved strength properties. More particularly, this invention relates to the production of such pulps by means of the sulfonation of the lignin in the wood, using aqueous sulfite or bisulfite solutions, followed by mechanical defibering.
The pulp and paper and related industries use many processes to produce pulp from wood chips and other lignocellu-losic materials. These processes can be classified, for purposes of discussion, into four groups, shown below with the represen-tative yields:
Chemical Pulps - up to 60% yield Semichemical Pulps - 60 - 80% yield Chemimechanical Pulps - 80 - 95% yield Mechanical Pulps - at least 90% yield The yield ranges shown are approximate only.
Chemical pulps are prepared by cooking the wood chips (or other lignocellulosic material) at elevated temperatures and pressures with various chemical agents which dissolve the lignin and some carbohydrate material to leave relatively pure cellulose fibers at the 40-45% yield level or cellulose plus some residual ~
lignin at somewhat higher yield levels (45-55%). ~ -Mechanical pulps at the other extreme use mechanical means such as grindstones to defiber logs or disc refiners to defiber wood chips into pulp. These processes use water for cooling and dilution purposes so that the approximately 5% of the wood substance that is water soluble is lost for a net yield of about 95%.
~" ~
- 1 .
. ' .,, ' ~. : ' ~ ,' ~, , : , . . ; , .
OS~L618 Chemical pulps have many advantages due to their cleanliness, hicJh streng-~h, and ease of bleaching, but they are expensive to produce due to the low yield. Their dissolved solid and gaseous waste products give rise to many environmental problems.
Mechanical pulps are much cheaper to produce due to their high yield and constitute an efficient use of forest resources. Such processes offer no gaseous pollution and rela tively little BOD5 (biochemical oxygen demand, five-day test) discharge compare~-to che~i~al 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 resource based products are creating an increasing . need for the us~ of higher yield pulps due to the decreasing availability of fiber. The present invention produces a hiyh yield pulp that can replace some types of chemical or semichemical pulp in many products.
It is known that the treat~ent of wood chips with relatively small amounts of sulphite and bisulphite, at near neutral pH, and under relatively mild conditions (100-150C., for 2-15 minutes) produces a softening effect on the chips which makes them easier to defiber and generally produces a cleaner and better draining pulp than can be produced by mechanical means alone. See "Ultrahigh Yield NSCM Pulping", by C. A.
Richardson, Tappi, Vol. 45, No. 12, pp. 139A-142A (1962);
Richardson et al., "Supergroundwood from Aspen", Tappi, Vol. 48, No. 6, pp. 344-346 (1965); Chidester et al. "Chemimechanical Pulps from Various Softwoods and Hardwoods", Tappi, Vol. 43, No. 10, pp. 876-880 (1960); Uschmann U. S. patent 3,607,618;
.
- ~Q5~
Aitken et al. U. S. patent 3,013,93~; and Asplllnd et al. U. S.
patent 3,558,428.
However, the pulps produced by such processes, while being superior to conventional mecha.nical pulps in terms of cleanliness and drainage properties, do not have sufficiently good physical properties to justify their increased cost of production re].ative to the conventional mechanical pulps.
Better properties can be achieved by cooking under more severe conditions such as increased temperatures in the 1Ø 16Ø-240C.. range, but the strength improvement is always accom-panied by a loss in yield. Instead of yields of over 90~, the yields are reduced to about 70-85~. . See most of the above -:
publications and 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 3,446,699; Von Hamzburg U. SO patent 2,949,395; Oison U. S. patent 3,003,909; and Risch e~ al. U. S. patent 2,847,304. . .
Considerations of cost and environmental protection make the maintenance of yields in exGess of 90% highly desirable.
2~ It is well lcnown that the physical properties of wood .
pulps are strongly influenced by the flexibility of the indivi~
dual fibers -which flexibility permits the fibers to be brought into closer contact with each other during the pressing stages of the paper-making process, which in turn leads to better bonding and improved strength. Natural wood fibers are rendered relatively infle~ible by the presence of large amounts (20-30~
by weight) of lignin which is a relatively rigid material at - :
moderate temperatures (less than 100~C.). Fiber flexibility is ~
improved in conventional chemical or semichemical pulping pro- .:
. .: .
cesses by removing, chemically, at least part and in some cases nearly all of the lignin.
,,. . . , ':
,; ,, . ,. ' , . , . . ' :' . ~' ;, The present invention modifies the lignin by sulfo-nating it sufficiently to produce a marked change in the physical and chemical properties of the lignin, but not enough to render it soluble in water or in the cooking liquor, so it is not sub-stantially removed from the wood fiber, and yields are consistent with those of purely mechanical pulps (90-95%).
Many softwood species such as spruce can be sulfonated up to about 0.65% (expressed as combined sulfur on wood and measured by the test method, below), usually without reducing `
the yield below 90%. Conventional high yield chemimechanical pulping processes such as those reported by the Richardson and Chidester et al. publications and Asplund et al. patent, supra, achieve a level of about 0.3 to 0.35~ sulfur (on spruce) or only about 50% of the maximum level of sulfonation that can be reached without reducing the yield below about 90~ (see comparative prior art Example 9 below). This low level of sulfonation achieves some softening of the lignin, which permits the chips to be more .
readily defibered than untreated chips, but the individual fibers so produced are still relatively stiff and do not give strong pulps. The stiffness of the fibers also makes them prone to damage (cutting) in the refining stages and the consequent pro-duction of fines and debris -- although not to the same extent as untreated fibers.
It is, accordingly, an object of the present invention to provide a high yield chemimechanical process for producing pulp from wood chips and other woody lignocellulosic materials, including shavings and sawdust, and which . .
.
, .
provides a pulp having excellent strength characteristics.
In accordance with one aspect of the present invention, a method for the production of high yield chemimechanical pulp from woody lignocellulosic material comprises treating this material with an aqueous solution of a mixture of sulfite and bisulfite having a pH of between about 6.0 and about 8.5 at a temperature of between about 100C. and about 15~C. for a period of between about 10 and about 90 minutes, the aqueous solution being of sufficient strength to sulfonate the material to at least about ;
85% of the maximum level of sulfonation that can be achieved on the material without reducing the yield of pulp below about 90%
by weight. The resulting sulfonated material is subsequently subjected to mechanical defibration.
Wherever in this specification, including the claims, reference is made to the maximum level of sulfonation that can be achieved on a particular material, this means the maximum level for that material determined by the test described on page 23 -and under the conditions of the test, i.e. heating at 140C. for ;;
30 minutes. This maximum level is determined without reference to yield. Thus, in accordance with the invention, the liquor strength is chosen to be sufficient to give the 85% sulfonation level, while at the same time being low enough that it does not reduce the yield below about 90% by weight.
The sulfonated woody lignocellulosic material may be `~
pressed prior to mechanical defibra-tion to remove spent aqueous solution, the spent solution being recycled and used to treat fresh material. The volume of spent aqueous solution produced in this way may be equal to that which, after refortification with fresh sulfite and bisulfite, is applied to the fresh material to provide a system in which there is no excess flow of used aqueous solution.
. ~.
~' ; ) _5_ ;., --: -, In accordance with another aspect of the invention, a method for the production of high yield chemimechanical pulp from woody lignocellulosic material derived from softwoods com-prises treating this woody lignocellulosic material with an aqueous solution of a mixture of sodium sulfite and sodium bisulfite having a pH of between about 6.0 and about 8.5 and having a strength between about 100 g/l and about 200 g/l as sodium sulfite at a temperature of between about 120C. and about 140C for a period of between about 20 and about 60 minutes, and subsequently subjecting the resulting sulfonated material to mechanical defib-ration.
The term "softwoods" as used herein means wood from coni-ferous trees, for example spruce, balsam and pine.
Yet another aspect of the invention provides a similar pro-cess but using woody lignocellulosic material derived from poplar, in which the material is treated with an aqueous solution of a - -mixture of sodium sulfite and sodium bisulfite having a strength of between about 90 g/l and about 115 g/l as sodium sulfite, the other conditions and steps of the process being as recited above for softwoods.
A preferred method for carrying out the invention will be described with reference to the accompanying drawings, in which~
Figures la through le are a series of five graphs where five physical properties of pulps produced in accordance with Examples 1 and 2, infra, are plotted against freeness (CSF, ml.).
These properties are breaking length (Fig. la), burst factor (Fig.
lb), tear factor (Fig. lc), bulk (Fig. ld) and wet web strength (Fig. le).
Figures 2 through 7 are graphs of % yield of pulp and sulfur content of the pulp vs. liquor concentration (grams per liter) of Na2SO3 for a series of six woods, as follows:
5a--, 169~3 Fig. 2 - Spruce Fig. 3 - salsam Fig. 4 - Jack Pine Fig. 5 - Southern Pine Fig. 6 - Maple Fig. 7 - Poplar -Figure 8 is a graph showing the relationship of pulp yield and sulfur content for maple wood chips carried out under identical conditions for various time periods as in Example 16, infra. ;
General Description of the Invention In the process of the present invention, the wood is sulfonated to at least about 85% (0.55% sulfur for spruce) and preferably to about 90% or more (0.58% sulfur for spruce) of the maximum level of sulfonation for that wood as described, and under the conditions of the te:t given on p23, ~ , , ,,:
. .
~ -5b-~5~i3L8 infra. This level of sulfonation permits the wood chips to be readily mechanically defibered into individual fibers which have a flexibility more similar to low yield chemical pulp fibers than to conventional 90%-plus yield chemimechanlcal fibers.
Indeed, we have discovered that in accordance with the present invention, the higher the degree of sulfonation of the pulp, the greater the strength properties of the pulp. This increase in strength improves dramatically with increase in sulfur content of the pulp. This effect is shown in Examples 10, 11, 12, 13, 14 and 15, infra, and Table 2, below, where the cooking liquor strength is varied from 50 g/l (grams per liter) Na2SO3 to 180 g/l Na2SO3 in a series of labora~ory cooks all carried out at 140C. for 30 minutes. The best strength levels were not reached until at least about 120 g/l Na2SO3 liquor wasused, which achieved a level of sulfonation of 0.6% sulfur. Increasing the liquor strength (and hence the degree of sulfonation) beyond 120 g/l Na2SO3 did not produce substantial further strength improve-ments. `
The conventional chemimechanical pulp made by a process reported by C.A. Richardson (Example 9) has inferior strengths -compared to the pulps of Examples 13, 14 and 15 which employ the process of the present invention.
Since the nature and content of lignin in wood varies from species to species, so does the actual sulfur content that must be achieved in each case. However, in all cases the sul-fonation level must always be at least about 85% and preferably about 90% or more of the maximum sulfonation that can be achieved, the process conditions being also such as do not reduce the yield below about 90%. Higher sulfur yields can always be achieved by increasing time or temperature, however this will usually lead to yields below 90%. The .. ~. .~
t ! .~,J
,' ' .~ ~, ' ~3S~6~
following table illustrates the typical levels of sulfonation that must be achieved for a selection of commonly used wood species. These values were obtained using the test procedures for maximum level of sulfonation, l ra.
Wood Species Ma~imum 85% of Maximum ~ S % S ' ' ' Spruce 0.65 0.55 Balsam 0.70 0.60 Jack Pine 0.75 0.64 10 Southern Pine 0.65 0.55 Poplar 0.36 0.31 Maple 0.33 0.28 In order to achieve the 85% level of sulfonation while maintaining yields in excess of about 90%, it is desirable to carry out the reaction at temperatures not higher than 150C.
and preferably not higher than 140C., but at least about 100C.
The preferred range is between about 120 and 140C. These moderate temperatures also help to maintain good brightness.
In order to achieve reasonably short reaction times, e.g., 60 minutes or less, high chemical application levels are used; ;
typically a concentration of at least 120 g/l Na2SO3 in the -cooking liquor, with a cooking liquor to wood ratio of 3.3:1 [392 kg/t ~kilograms per metric tonne) Na2SO3 on oven dry wood].
The pH of the cooking liquor should be between about 6.0 and 8.5, preferably between about 7.2 and 8Ø
The process of the present invention is applicable ; -:, ~ . ....
to woods of all types, both hardwoods and softwoods, particularly the latter.
Table 1, below, illustrates the properties of some pulps that have been made using the process of the invention.
,~ . .
, ~ 7-~OSil 6~8 Examples of the pxoperties of a mechanical pulp ~refiner mec~ha-nical pulp, Example A) and a chemlcal pulp (semibleached kraft, Example B) have been included for comparison purposes~
Pulps made by this invention may be bleache~ by such known reagents as sodium hydrosulfite, hydrogen peroxide, or various co~inations of th~ two~ For example, a pulp (Example No. 7) with an initial brightness of 52.7 Elr~pho was bleached as follows:
Bleach Chemical Final Br~ tness 1~ sodium hydrosulfite 61r3% Elrepho 1~ hydrogen peroxide 65.7~ Elr@pho 1% hydrogen peroxide followed by 69.0% Elrepho 1% sodium hydrosulfite Since the attainment of the high levels of sulfonation required by the process of the invention will generally involve the use of relatively high concentrations of cooking chemicals and relatively heavy applications of cooking liquor on the wood, it is anticipated that for economic considerations in successful commercial application of the process o~ the invention, recycling of the unreacted sulfite from the cooked chips is desirable.
This may be achieved by pressing the cooked chips to remove the liquor from them and adding fresh chemicals to the liquor to return it to its original concentration be~ore reuse when recycled in the process. Recycling also assists in automatically control-ling the liquor pH to about 7-8, a desirable value. Substantially lower pH values tend to result in lower yields.
As long as the conditions ~or sufficient sulfonation are adhered to, the cook can be carried out in a variety of different ways. In Example 1~ below, a liquid phase process is used with no pre-impregnation with cooking liquor prior to the cook. Example 2, belo~, shows a liquid phase process with a 15-minute impregnation prior to the cook. In Examples 3 and 4, ~: .
.
. .
~ O 5~ 6~ ~
low, the chips were impregnated for 60 minutes prior to a vap~r phase ~ook. In each case, the pulps produced were sub-stantially similar in physical properties. These exampIes show that the process of the invention can be carried out using conventional and readily available liquid or vapor phase cooking equipment.
Example 4, below, illustrates the effect of cooking at a temperature (148C.) somewhat higher than the optimum 140C. While the strengths are excellent, the brightness, at 47% Elrepho, is lower than the 52-54~ Elrepho that can be achieved at 1~0C.
The present invention can produce good quality pulps from a wide variety of raw materials. Examples 5, 6, 7 and 8, belo~, show the use of southern pine, northern softwoods plus 32% poplar, 55~ northern softwoods and 45% northern hardwoods, and northern softwood sawdust.
Pulp made by this invention has excellent properties over a wide freeness range (100-600 ml.~. This is shown in ....
Figures la through le, where a number.of physical properties are plo~ted against freeness. These regression curves were taken from over one hundred pulp samples made as in Exzmples 1 and 2. The ability of this pulp to perform well over such a wide freeness range, serves to distinguish it from mechanical and conventional chemimechanical pulps which, typically, are only useful at relatively low freeness levels--usually below 3Q0 ml. In this respect, the pulp made by this invention is more comparable to low yield chemicàl pulps. As used in Figures la through le and throughout the present disclosure, freeness is referr~d to in terms of Canadian Standard Freeness ~CSF) as defined in Tappi Standard - T 227 (M~58). Freeness is a measure of the rate at which a dilute suspension of pulp may be dewatered.
3L05~6~13 Example 16, below, shows the effect of increasing the cooking time. In this e~ample, a very strong cooking liquor was used to illustrate the upper limit of sulfonation. Such a strong liquor could not be used in a commercial plant if liquor recycling was practiced, due to the solubility limit of Na2SO3 in spent liquor. It can be seen that the yield drops rapidly as the time is increased, and falls below 90% at about 90 minutes.
The operating pH range of this process is governed by two considerations. A pH substantially below 7.0 would be environmentally undesirable on a commercial level due to the presence o free sulfur dioxide. Due to the high concentration of the liquor, and paxticularly when recycled liquor is used, the pH does not drop substantially during the cook (see Example 1).
Nevertheless, it is important to maintain the spent liquor no lower than about pH 6.5 so as to keep the process essentially odorless.
It is well known that in most cooking processes a pH
substantially greater than about 8.0 will tend to degrade the liynin and hemicellulose and lead to reduced yield. This is shown by Example 17 (results in Table 3, below) where it can be seen that an increase in pH produced a substantial decrease in yield. It is also well known that a pH substantially above about 8.0 will tend to produce a discolored pulp which would be unacceptable in a wide range of products. Thus, this pH con-sideration would be significant on a commercial scale operation.In the laboratory, under carefully controlled conditions, the present process may be carried out at any pH over the about 6.0 to 8.5 range without producing odor, discolored pulp, or too low a yield. However, in a commercial plant, the control would not be as satisfactory, so that a practical minimum of above about 7.0, and preferably a pH range of from about 7.2 to 8.0 would be advisable.
.
6~ ~
Subsequent to the sulfonation of the ~ood chips, they are subjected to mechanical defibration by any oE the conventional mechanical grinding or refining techniques.
These techniques are well known to those skilled ln the art of mechanical and chemimechanical pulping. One such suitable treat- -ment is the use of double-disc refinerb whereby tlle sulfonated chips are passed het~-een rotating grooved discs to apply work to the chips and thereby defibrate them. The sulfonated chips may be passed through one or more refiners until the desired freeness is achieved.
., 11 .
: - ~7~
~5~6~
h O ~ ~ ~D ,~, /J~ O U~ O r-- ul N
.F:~ 3 ~ O c:~ r_l I
00 ~ ~ ~ O ,~ N~ ~ N N
~ ~ ',3 ~) U) N ~D N N
U) O O (~ , ~
~ ~ Z U~ U~ . 1' '3 ~ ~ .. . r :~ ~ u7 U) ~ lLi . ~
~,~ h O h 0 - ~ (1~ ~O
a) ~ ~ o ~ o o oo u~
S~ 3 ^ S~ 3 ~ O O N I
~ ~1 1~ C~ N1~ N u~ o~ N O
:~ h 4~ Ln )~ h Lr) ~ m Nc~ N t~f) U7 ~ 0~ ~ ~rl I¢
~ O O U~ O :~ ~ U~
1:~ N Zi U~--z ~ ~_ h ~ t~
rtrJ~ .
U~ rt S
PJ I ~r~J c~ SrJ~ ~rl E~
,1 h O N ~ 0 rt ~1 a) O ~ ~( O ~ U~ U~ X
d rl S 3 ~O Ir) O I , ~d 1~ 0 ~ ~ ~J 111 r~l O rt rt ~D ~ O N ~P
~rl h h 41 ~ ~ ~ ~7 Ct~N ~r 1~ UlCi~~1 0 ~ ~
Q1 (1) O 0 ~1 0 ~, 1 0 .
o Q) C,.) ~ . ~
F~ h . ~ a ~a o ~ ~ O ~ U~ r~ ~ O
U~ ~ ~ ~ o 1~ ~ I
~rl Ir~ ~ au N ~ O O ~ 00 0 N 1 4! o,~ ~) ~r N rt ~J N ~`~ Ul O ~: 0 U) pl - G) ~ t ~ t t~rl ~a *
h O ~ -~1 ~ Q) O h O u:~ ~ri ~ a) rt a) O .~: 3 :~o o ~ I *
O ~ ~ q~l X N 1~ m ~ rt ~r~~r ~ cr~ ~: ~; X
rt . $-1 H z O ~ .IJ
~ . ~ Z
m ~ a ~ ~ .
~ ~ O o a~ ~ u~ ~ ~ h~
rt ~) ~ ~ O LO Q ~) oU'~ N N ~r ~ rt ,~
h 4~ X ~ ~D ~ 0~ ~1 ~ t~u~~n D ~ t) h X
O o-~l ~ n~
Z U~ ~ ~ a ~ ~Irt X t~
~ ~ r~
'd . ,~ ~ h ~0~ ~::ro . Sl O P~ * ~ O O O
- rt * ~ 3 1 o o o In h 41 o t~
~1 ~ a~ 9 . o u~ In ~ u) ~ h o o,,XJu) ~D ~ rt rt U~ ~ ~ h rt u~ ~;; Z u~ ~ 0 41 'd O 0 h O ~:: Q ,~
rt ~
V ~ ~O rt h h~t S~ O O co O U
~ 0 # S 3 ~ ~ 'O 'O h U
r~ 5~ ~ ~ ~ ~) ~ O O U~ O U~ r ~l O O
v~ U rt h 4~ ~, rt ~) r-l ~D~ N ~ ~ ~ UJ h h O ,~ ~
'd rt rt O h .~ ,J, 0 rd h rt ~r l ~r~
O t~ d h V~ h h a) rO
e~ ~ O ~ ~ h ~ ~ ~ * o ~
O ~1 ~ O ~ ~ R .~ N ~ O O ,~
z a) ~ o I~ u u ~ ~ u~
In t:n d U ~ aJ .c rA ~ a~
vd U R * F~ f~, rt ~3 ~ ~ O h ro * ~ # tri ): :
.Y OO ~ ~,t ~ * # ~ *
a) O sl 0 ,t ~ ~ ~ ~ ~ ~
X O h h ~ ~h rJ # #
~1 ~ ~ m ~ ~ ~ m ~ ~ ~ ~
.
," : . .
, ' ;
~L 13S~L6~8 - /3 :
. ~
.
U~ . .
a~
. .
.
~ W
U~ ~ ~; o C
~ _ O CO C~' O ~ . . ~' .. . ~D . S-~
E~ ~ co. o ~ o ~ ~ o . ~ ~ ~ . ~ ~ ~ ~ V
Z ,t ,~ ~ O cn ~ ~
. . ~ V ,; ~U o ~, . o ~ U~ i:
D c~ r:~ $
~ o o~ o o C~ ~ ~ ` ~ O
.P~ ~ o ~ o ~ ~ ~~ O o ~lC ~ 1 1~ ~ rl ~ ~r ~I f--N rl It- ~ O ~ 1~ 0 ~ ,~
~ . ~ V d) P~ . R~ s E~ o ~J ~ ~ o ~ ~ o co o oo o o r ~ D O ~ a) ~
t~ t~ ~ o ~ o Lr~ ~N ~ ~ E~ o O ~ o co ~ ~ ~ O
1~ 0 0 ~ O
. ' . ~ r . ~ .
Z; , * o t~ ~ CO It) ~' ~ D ~ ~ Q~ O
* ~o o o ~1 U~ Ln ~:1 ~ O ~r o ~ ~ ~ ~ ~
2, ., .
~n . . .
P~ . . a)~
D ~: o ~ ~ ` .;~
P- *CO O O 1~ U) ~1 ~ r~ ~
~1 0 o ~ o 5: ~ o . r~ u) I ~ 0 0 . ~ ~ ~1 1~ t` ~ ~-1 tr~ N r l Ir) C5~ 0 1-- S~
~ ' C`~ . . O aJ-rl ~ ,1~ . , U~ . . .~ )~P:; O
E~ ~ . .Id~ V a) ~ ,. -O ~ o ~ ` O ~ rl * CO O O N ~ ~ I` ~ ~ ~ ~ ~ O
U~ O O O ~ C~ Ir) r-l r-l Il') ~I ~' ~ a~
~ ~I Ln ~~1 r l 1` N ~1 IS) Cl~ O ~ -1 0 C.) -~
E-~ . . ~ ) h ~ , .
. ~ . . . ~-~ IQ O 1~
~ O 1` ~ D ~ ~ ~ ~ ~ O ~ 3 O ~o c~ ~ - O U~ O u~
O h~ h C
~ a)~ la~1 ~ : -U~
* . ~ 0~ V ~ `.-~ O ~ r~~rl ~ 5 X '-o q-~
0 i3 t~ P~ O N ~ 'X ~ ::
U~ U~ 0 0 rl 'F ~ .~ ~ ~s~ o .~ o S~ ~
O ~I Z ~rl G) ~ ~ 0 ~ O ~ ~1 C ~ ~ ` Q) ' - z ~ r4 E~ E~` U ~ u~ ~ ~1o ~ o u~
h ~ 1 .C a~ R::1 X
Q~ O O ~ rl X~ ~
~a ~ ~ o o (I~ ~ C ~1 ~ ul X 2) X ~ rl O O h h ~ aJ ~1 O aJ a~ 0 Q
m a: ~ m ~ m ~ ~ h ~
1 ~1 U
~ oJ u~
0 ~ O
C ~ X ~ ~
~ *
:
~5~L61~
T~BLE 3 The E~fect of p~-l; from Example 17, below.
% Yield ~ Sulfur 6.0 94.27 0.662 7.0 93.01 0.585 8.0 92.26 0.521 g.0 90.97 ~ 0.670 The pulps made from this invention are useful in such p~oducts as ~e~sprint, coated papers, book papers, sanitary tis-sues, corrugating medium, linerboard, paper toweling, diaperfluff, milk carton board, etc.
Speci~ic 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 l-imit the ambit of the appended claims. In the examples which follow, and through-out the specification, the quantities of material are expressed 20. in terms of parts by weight, unless otherwise specified.
In Example 1, below,the wood chips were digested in a continuous (3-tube Bauer M and D) digester. This type of digester is described in Paper Trade Journal, pages 36-37, (September 5~ 1960) in an article by Van Derveer, entitled "Unique New Continuous Digesters Improve Operations at Two Mills"; also Pulp and Paper International, May 1971, pages 55 . . .
and 56. The chips pass through the tubes of the continuous digester by means of a conveyor.
In Example 1 the refiner employed on the chips after ;~
sulfonation was a double-disc refiner manufactured by Bauer Bros. (now C-E Bauer) ~nown as Model 400. This double-disc - ,, ,, , ,~. . . :
~5~
refiner employs 36 inch diameter grooved discs and two 110 kilowatt (150 horsepower) motors. Type 36161 plates were used in the first stage, and 36106 or 36104 plates were employed in the second stage of the refiner. The feed rate through the refiner was between two and four tons per day.
In order to reach a final freeness of 400 milliliters CSF, a refiner power of about 2.5 megajoules per kilogram (35.2 horsepower days per air-dried ton) was applied in the ~irst stage of the refiner and 2.2 megajoules per kilogram (31.0 horsepower days per air-dried ton) in the second.
Examples 9 through 15, inclusive, represent a series of controlled experiments which demonstrate a comparison of the results obtained by the prior art (Example 9) and a series -of experiments with all conditions the same except that the concentration of the Na2SO3 in the digestion liquor is gradually -increased (Examples 10 through 15, inclusive). In all of Examples 9-15, the same source of wood chips was employed. As demonstrated by Examples 10-15, at the temperature and cooking time conditions employed, it was not until the liquor strength was increased to about 120 g/l Na2SO3 that the desired at least -about 85% of maximum sulfonation was achieved.
.,: .
The following method was used to produce pulp at the rate of about 4 tons per day in a pulping pilot plant.
A mixture of northern softwood chips containing approx-imately 42% black and white spruce, 35% balsam fir, and 23%
jack pine was presteamed for about 10 minutes, then metered -into a 3-tube M and D continuous digester along with cooking liquor at a liquor to wood ratio of 3.3:1 (wt./wt. of dry chips). The cooking liquor was initially prepared by mixing sodium hydroxide and sulfur dioxide in a tank to produce _ 15_ ,,, i' ~, . , ' ;': i ,,. , , "~, ,~, ,;,j ;,~""", ,~ " , ~, "
. ~ , , , ~ , , ~
~Ot516~L8 ~ concentration of 120 g/l as Na2SO3 at a pH o~ 7.8. As the run progressed, sp~nt liquor, still containing some unreacted sodium sulfite, was extracted from the last quadrant of the M
and D tube, fortified with additional sodium hydroxide and sulfur dioxide to readjust the original liquor concentrations, and reused. During the course of the run (several weeks) the liquor concentration varied rom about 115 g/1 to about 125 g!l as Na2SO3 and the pH varied from about 7.5 to about 8Ø The pH
of the spent liquor covered the range 7.0 to 7.4.
The liquox in each of the three tubes in the digester was maintained at a temperature of 135C. (range 132-138C.) at a pressure of 410 kPa (range of from 400 to 500 kPa) (kPa refers to kilopascals). The residence time of chips in the digester - was 30 minutes (10 minutes per tube).
The cooked chips were discharged from the digester into a blow tank at atmospheric pressure, then transferred to a double-disc refiner. Sufficient water was added to the chips just before entering the refiner to reduce the consistency to about 15%. The pulp leaving the refiner had a freeness range of 650-720 ml., typlcally.
The pulp was diluted to about 2% consistency and pumped to a horizontal belt washer where it was washed with hot water to remove residual cooking chemicals and waste pro-ducts. The pulp left the washer at a consistency of about 15~ and was fed to a second double-disc refiner, at that con-sistency, where the freeness was reduced to about 350 ml.
After leaving the second refiner, the pulp was diluted to about 2% consistency and heated by direct steam injection to at least 75C. (not exceedin~ 100C.) and held above 75C. for at least 20 minutes, for latency removal. The pulp was then further diluted to about 0.8~ and passed th~ough a pressure screen ~(:3S~L6~8 ,~entriSCree~l) and centrifut3al cleaners before heing ~hic~ened on a lap machine to about 25% consistency.
The properties oE a typical pulp made in this manner are shown in Table 1, supra.
A quantity of this pulp was conveyed to a newsprint manufacturin~ mill, slurried with water and mixed with other pulps in the following proportions:
25~ pulp of this example 2% refined semibleached kraft ~5% stone groundwood ' 28~ refiner mechanical pulp This mixture was run over a fourdrinier paper machine twith vacuum pickup) and converted into newsprint with basis weight avera~ing 4g.8 g/m2. Operation of the machine was normal ';
compared to operation using a conventional pulp mixture containing ~ ' 18~ semibleached kraft except that drainage at the wet end was a little faster than normal. The newsprint was subsequently printed at the printing plant of a large metropolitan newspaper with ', excellent results. '' ' " ' . .
~XP~PLE 2 This example is substantially similar to Example 1, except that the chips were allo~ed to impregnate in the first ;' tube of the M and D digester for 15 minutes at a temperature of a,bout 75C., followed by a 30-minute cook (15 minutes in each of the next two tubes) at about 135C. The pulp produced by this technique was substantially similar to that made~in Example 1. This pulp was also used for newsprint production trials as in Example 1 and with substantially similar results.
~.
EXP~PLE 3 This example is similar to Example 2 except that the chips wexe impregnated in the first tube for 60 minutes at 345 kPa using sodium sulfite, bisulfite liquor with a concentration f 154 g /1 (as Na2SO3), and that liquor was removed from the last quadrant of the impregnating tube of the digester at a sufficient rate so as to prevent liquor from overflowing into the second tube. The chips, which entered the second tube sub~
stantially free of surface liquor wexe cooked at a temperature of 132~C. for 30 minutes using direct injection of steam to a pressure of 240 kPa. The pulp had properties similar to those of Example 1.
Example 3 was repeated, except that the chips were impregnated with 156 g /1 liquor then cooked at a temperature of 148C. using a pressure of 327 kPa. This pulp has properties as shown in Table 1, supra.
Example 2 was repeated, except that southern pine chips were used. This pulp had properties as shown in Table 1, supra.
:
Example 2 was repeated, except that the chips had ~0 the following average composition:
.
Red Spruce 32.9%
Balsam Fir 9.5%
Red Pine 15.9%
White Pine 9.7%
Poplar 32.0~ .
The pulp produced had the properties shown in Table 1, supra. Approximately 17 tons wexe made and shipped to a paper mill where the pulp was slurried and bleached using 1.5~ sodium hydrosulfite and 0.25% sodium tripolyphosphate, to a final bright-ness of 58.8 to 61.0 (a~erage 59.3) G. E. The pulp was then blended with other pulps in the following proportions: `
- 1 8-- :
;~
1C~5~6~8 35% pulp of this e~:ample 35% bleaciled, re~ined, softwood kraft 30~ stone groundwood This mixture was converted into 65 g/m2 (grams per square meter) coated publication yrade paper (base sheet weight 40.7 g/m2) using a fourdrinier paper machine with two on~machine coaters (appxoximately 12.2 g/m2 of clay coating per side being applied~. The sheet was supercalendered. All phases of the manufacturing process were normal compared to operation with the normal furnish of 52% bleached, refined softwood kraft and 48% -stone groundwood, and the sheet performed well on commercial - printing presses.
XA~SPLE 7 -Example 1 was repeated, except that a mixture of lS northern softwoods and hardwoods with the following approximate composition was used:
Spruce 34.8%
Balsam 12.5%
. Red and White Pine 8.3 Poplar 19.8~
Beech 5.1%
Maple 10.0~
Ash 3.6%
~lm 5.2%
Basswood 0.8~
Sufficient quantities for small scale investigations only were made. The pulp had the properties shown in Table 1, ;
supra.
EXA~PLE 8 `
Example 2 was repeated, except that mixed northern softwood sawdust was used and the liquor heating was substan-tially supplemented by direct steam. All spent liquor was allowed to discharge into the blow tank with the cooked sawdust.
Sufficient quantities only for small scale investigations were made. The pulp had properties sho~m in Table 1, supra.
-.. . . : ~ .
~5~6~
X~MPI,E 9 This is a comparative exa~ple illustrating fhe prior art.
800 g. (dry basis) of a mixture of northern softwood chips containing approximately 42% black and white spruce, 35%
balsam fir, and 23~ jack pine were placed in a 10-liter laboxa-tory digester to which was added 6 liters of a liquor consisting of a sodium sulfite/bisulfite solution with a concentration of 56 g /1 as Na2SO3, and had a pH of 6.8. The digester and contents were heated, using indirect steam, to a tempe~ature of 138C., pressurized to 585 kPa with nitrogen and held there for 15 minutes. After the cook, the chips were drained and defibered into pulp using three passes through a 50 HP, 12-inch diameter, Sprout 1~7aldron laboratory refiner using consis-tencies of about 159~. The pulp was screened ~hrough a 0.0152 cm. slotted screen, then given a 30-minute, 80C., latency treatment before testing. The pulp had properties as shown in Table 2.
These cooking conditions sirnulate those reported by C. A. Richardson in Tappi, December 1962, Vol. 45, No. 12 page 141A.
, This is a comparative control example.
Example 9 was repeated, except that the li.quor con-centration was 50 g/l as Na2SO3 at a pH of 7.8, and the cooking conditions were 140C. for 30 minutes, at self-generated pressure only.
The pulp had properties as shown in Table 2.
, This is a comparative control example.
Example 10 was repeated, except that the liquor con- ;-centration was 70 g/l as Na2S3 ~OSl~
The pulp had properties as shown in Table 2.
EXA~5P ~ 12 This is a comparative control example.
Example 10 was repeated, except that the liquor con-centration was 90 g /1 as Na2SO3.
The pulp had properties as shown in Table 2.
EX~MPLE 13 Example 10 was repeated, except that the liquor con-centration was 120 g /1 as Na2SO3.
The pulp had properties as shown in Table 2.
EX~IPLE 14 Example 10 was repeated, except that the liquor con-centration was 150 g /1 as Na2SO3.
The pulp had properties as shown in Table 2. .
..
EX~MPLE 15 Example 10 was repeated, except that the liquor con-centration was 180 g /1 as Na2~O3.
The pulp had pxoperties as shown in Table 2.
EXAMPLE 16 ;;
Maple chips were cooked in small bombs using a tech-nique substantially similar to that described in the sulfona~
tion test except that the cooking liquor strength was held constant at 200 g ,/1 Na2SO3 and a series of cooks were carried .
out at various times between 30 minutès and 8 hours.
The results are plotted in Figure 8 of the drawings.
. , - EX~5PLE 17 Mixed softwood chips similar to those used in Example 1 were cooked in small bombs using a technique sub-stantially similar to that described in the sulfonation test ,, , .
,: .
S~611~
`~cept that the coo~iny liquor strength was held constant at 120 g/l and the pll was varied from 6.0 to 9Ø
The xesults are set forth in Table 3, supra~
' .
' . 22 -` ~L0~ 8 l~est Procedure for Determining thc Maximum Level of Sulfonation that can be Achieved for Various ~ood Species --_ . _ . .. .. .. ... __ 2 ky. (dry basis) of screened wood chips are carefully mixed and 1 kg. is removed and dried to provide an accurate mois-ture deter~ination. The balance is divided into 100 g. (~ethasis) aliquots and each is carefully weighed. Each aliquot of chips is placed in a small bomb (capacity 540 ml.) to which is added sufficient sodium sulfite/bisulfite liquor to just cover the chips. A series of liquors are used, each being prepared by adding gaseous SO2 to a solution of sodium sulfite to reduce the pH to 7.8. The liquors have the following concentrations:
(w/v as Na2SO3) 50, 70, 90, 120, 150, and 180 g/l. At least two cooks are carried out at each liquor strength. The bombs-are sealed and placed in an oil bath which has been heated to 140C. The bom~s are mounted on a rotating device that upends the bombs 2 or 3 times per minute in order to provide some agitation to the mixture of chips and liquor. The bombs are removed after 30 minutes.
When each bomb is removed from the oil bath, it is immediately plunged into cold water to produce rapid cooling.
The cooked chips are removed from the bomb as soon as possible, the liquor is drained off and discarded, and the chips are defibered in cold water using an industrial blender (Waring or Osterizer type) for 15 minutes or until the chips are well defibered. The pulp is then fiitered, on a filter paper, care~
fully washed with a large volume of cold water, then dried in an oven and weighed and the yield calculated. After ~eighing, a sample of pulp is taken and its sulfur content is determined.
The yield and sulfur content data are plotted against liquor strength as illustrated in Figures 2 to 7 of the drawings.
These graphs show the customary scatter of clata points, xegres-sion curves were calculated in order to show ~he trend. For , . , . . ,.. ~ : . . ..
~5~
many species the sulfur content will tend to reach a m~ximum (or plateau) at 15~18% Na2SO3, and usually this maximum will be reached without reducing the yield below 90%. In the case of softwoods (Figures 2 to 5) it is probable that the sulfur content could be increased a little beyond that reached at 18%
Na2SO3 liquor, but higher liquor concentrations are not prac-tical, particularly when recycled liquors are used due to the solubility limit of Na2SO3 in the presence of dissolved organic materials.
10For each of the typical woods to which Figs. 2 to 7 relate, the graphs may be used to determine suitable ranges of liquor concentration, making reference to the figures for sul-fonation of the various woods given on page 7. Thus, for spruce, page 7 shows that 0.55%S is required to provide the desired level of 85% of maximum sulfonation, and Fig. 2 shows that a concentration of above about 100 g/l Na2SO3 is required to produce this sulfur content; this and higher levels up to ak least about 200 g/l will not reduce yield below 90%. Figs. 3 to 7 likewise give the fol- ;
lowing approximate results for the various woods~
g/l Na2SO
Wood %S equivalent to Graph Min. for Max. for 85% maximum sul-85% sul- at least fonation (from p7)fonation 90% yield `
salsam .60 Fig.3100 over 200 Jack Pine .64 Fig.4100 over 200 Southern Pine .55Fig.5 100 over 200 r~aple .28 Fig.6105 over 200 Poplar .31 Fig.7 95 115 Accordingly, it may be seen that for the softwoods (balsam, jack pine, southern pine) a range of about 100 to about 200 g/l is suitable; for poplar the suitable range is about 90 g/l to about 115 g/l.
The terms and expressions which ha~e 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 excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifi-cations are possible within the scope of the invention claimed.
. ' ' ' ` ~ ', ` :,
pulps are strongly influenced by the flexibility of the indivi~
dual fibers -which flexibility permits the fibers to be brought into closer contact with each other during the pressing stages of the paper-making process, which in turn leads to better bonding and improved strength. Natural wood fibers are rendered relatively infle~ible by the presence of large amounts (20-30~
by weight) of lignin which is a relatively rigid material at - :
moderate temperatures (less than 100~C.). Fiber flexibility is ~
improved in conventional chemical or semichemical pulping pro- .:
. .: .
cesses by removing, chemically, at least part and in some cases nearly all of the lignin.
,,. . . , ':
,; ,, . ,. ' , . , . . ' :' . ~' ;, The present invention modifies the lignin by sulfo-nating it sufficiently to produce a marked change in the physical and chemical properties of the lignin, but not enough to render it soluble in water or in the cooking liquor, so it is not sub-stantially removed from the wood fiber, and yields are consistent with those of purely mechanical pulps (90-95%).
Many softwood species such as spruce can be sulfonated up to about 0.65% (expressed as combined sulfur on wood and measured by the test method, below), usually without reducing `
the yield below 90%. Conventional high yield chemimechanical pulping processes such as those reported by the Richardson and Chidester et al. publications and Asplund et al. patent, supra, achieve a level of about 0.3 to 0.35~ sulfur (on spruce) or only about 50% of the maximum level of sulfonation that can be reached without reducing the yield below about 90~ (see comparative prior art Example 9 below). This low level of sulfonation achieves some softening of the lignin, which permits the chips to be more .
readily defibered than untreated chips, but the individual fibers so produced are still relatively stiff and do not give strong pulps. The stiffness of the fibers also makes them prone to damage (cutting) in the refining stages and the consequent pro-duction of fines and debris -- although not to the same extent as untreated fibers.
It is, accordingly, an object of the present invention to provide a high yield chemimechanical process for producing pulp from wood chips and other woody lignocellulosic materials, including shavings and sawdust, and which . .
.
, .
provides a pulp having excellent strength characteristics.
In accordance with one aspect of the present invention, a method for the production of high yield chemimechanical pulp from woody lignocellulosic material comprises treating this material with an aqueous solution of a mixture of sulfite and bisulfite having a pH of between about 6.0 and about 8.5 at a temperature of between about 100C. and about 15~C. for a period of between about 10 and about 90 minutes, the aqueous solution being of sufficient strength to sulfonate the material to at least about ;
85% of the maximum level of sulfonation that can be achieved on the material without reducing the yield of pulp below about 90%
by weight. The resulting sulfonated material is subsequently subjected to mechanical defibration.
Wherever in this specification, including the claims, reference is made to the maximum level of sulfonation that can be achieved on a particular material, this means the maximum level for that material determined by the test described on page 23 -and under the conditions of the test, i.e. heating at 140C. for ;;
30 minutes. This maximum level is determined without reference to yield. Thus, in accordance with the invention, the liquor strength is chosen to be sufficient to give the 85% sulfonation level, while at the same time being low enough that it does not reduce the yield below about 90% by weight.
The sulfonated woody lignocellulosic material may be `~
pressed prior to mechanical defibra-tion to remove spent aqueous solution, the spent solution being recycled and used to treat fresh material. The volume of spent aqueous solution produced in this way may be equal to that which, after refortification with fresh sulfite and bisulfite, is applied to the fresh material to provide a system in which there is no excess flow of used aqueous solution.
. ~.
~' ; ) _5_ ;., --: -, In accordance with another aspect of the invention, a method for the production of high yield chemimechanical pulp from woody lignocellulosic material derived from softwoods com-prises treating this woody lignocellulosic material with an aqueous solution of a mixture of sodium sulfite and sodium bisulfite having a pH of between about 6.0 and about 8.5 and having a strength between about 100 g/l and about 200 g/l as sodium sulfite at a temperature of between about 120C. and about 140C for a period of between about 20 and about 60 minutes, and subsequently subjecting the resulting sulfonated material to mechanical defib-ration.
The term "softwoods" as used herein means wood from coni-ferous trees, for example spruce, balsam and pine.
Yet another aspect of the invention provides a similar pro-cess but using woody lignocellulosic material derived from poplar, in which the material is treated with an aqueous solution of a - -mixture of sodium sulfite and sodium bisulfite having a strength of between about 90 g/l and about 115 g/l as sodium sulfite, the other conditions and steps of the process being as recited above for softwoods.
A preferred method for carrying out the invention will be described with reference to the accompanying drawings, in which~
Figures la through le are a series of five graphs where five physical properties of pulps produced in accordance with Examples 1 and 2, infra, are plotted against freeness (CSF, ml.).
These properties are breaking length (Fig. la), burst factor (Fig.
lb), tear factor (Fig. lc), bulk (Fig. ld) and wet web strength (Fig. le).
Figures 2 through 7 are graphs of % yield of pulp and sulfur content of the pulp vs. liquor concentration (grams per liter) of Na2SO3 for a series of six woods, as follows:
5a--, 169~3 Fig. 2 - Spruce Fig. 3 - salsam Fig. 4 - Jack Pine Fig. 5 - Southern Pine Fig. 6 - Maple Fig. 7 - Poplar -Figure 8 is a graph showing the relationship of pulp yield and sulfur content for maple wood chips carried out under identical conditions for various time periods as in Example 16, infra. ;
General Description of the Invention In the process of the present invention, the wood is sulfonated to at least about 85% (0.55% sulfur for spruce) and preferably to about 90% or more (0.58% sulfur for spruce) of the maximum level of sulfonation for that wood as described, and under the conditions of the te:t given on p23, ~ , , ,,:
. .
~ -5b-~5~i3L8 infra. This level of sulfonation permits the wood chips to be readily mechanically defibered into individual fibers which have a flexibility more similar to low yield chemical pulp fibers than to conventional 90%-plus yield chemimechanlcal fibers.
Indeed, we have discovered that in accordance with the present invention, the higher the degree of sulfonation of the pulp, the greater the strength properties of the pulp. This increase in strength improves dramatically with increase in sulfur content of the pulp. This effect is shown in Examples 10, 11, 12, 13, 14 and 15, infra, and Table 2, below, where the cooking liquor strength is varied from 50 g/l (grams per liter) Na2SO3 to 180 g/l Na2SO3 in a series of labora~ory cooks all carried out at 140C. for 30 minutes. The best strength levels were not reached until at least about 120 g/l Na2SO3 liquor wasused, which achieved a level of sulfonation of 0.6% sulfur. Increasing the liquor strength (and hence the degree of sulfonation) beyond 120 g/l Na2SO3 did not produce substantial further strength improve-ments. `
The conventional chemimechanical pulp made by a process reported by C.A. Richardson (Example 9) has inferior strengths -compared to the pulps of Examples 13, 14 and 15 which employ the process of the present invention.
Since the nature and content of lignin in wood varies from species to species, so does the actual sulfur content that must be achieved in each case. However, in all cases the sul-fonation level must always be at least about 85% and preferably about 90% or more of the maximum sulfonation that can be achieved, the process conditions being also such as do not reduce the yield below about 90%. Higher sulfur yields can always be achieved by increasing time or temperature, however this will usually lead to yields below 90%. The .. ~. .~
t ! .~,J
,' ' .~ ~, ' ~3S~6~
following table illustrates the typical levels of sulfonation that must be achieved for a selection of commonly used wood species. These values were obtained using the test procedures for maximum level of sulfonation, l ra.
Wood Species Ma~imum 85% of Maximum ~ S % S ' ' ' Spruce 0.65 0.55 Balsam 0.70 0.60 Jack Pine 0.75 0.64 10 Southern Pine 0.65 0.55 Poplar 0.36 0.31 Maple 0.33 0.28 In order to achieve the 85% level of sulfonation while maintaining yields in excess of about 90%, it is desirable to carry out the reaction at temperatures not higher than 150C.
and preferably not higher than 140C., but at least about 100C.
The preferred range is between about 120 and 140C. These moderate temperatures also help to maintain good brightness.
In order to achieve reasonably short reaction times, e.g., 60 minutes or less, high chemical application levels are used; ;
typically a concentration of at least 120 g/l Na2SO3 in the -cooking liquor, with a cooking liquor to wood ratio of 3.3:1 [392 kg/t ~kilograms per metric tonne) Na2SO3 on oven dry wood].
The pH of the cooking liquor should be between about 6.0 and 8.5, preferably between about 7.2 and 8Ø
The process of the present invention is applicable ; -:, ~ . ....
to woods of all types, both hardwoods and softwoods, particularly the latter.
Table 1, below, illustrates the properties of some pulps that have been made using the process of the invention.
,~ . .
, ~ 7-~OSil 6~8 Examples of the pxoperties of a mechanical pulp ~refiner mec~ha-nical pulp, Example A) and a chemlcal pulp (semibleached kraft, Example B) have been included for comparison purposes~
Pulps made by this invention may be bleache~ by such known reagents as sodium hydrosulfite, hydrogen peroxide, or various co~inations of th~ two~ For example, a pulp (Example No. 7) with an initial brightness of 52.7 Elr~pho was bleached as follows:
Bleach Chemical Final Br~ tness 1~ sodium hydrosulfite 61r3% Elrepho 1~ hydrogen peroxide 65.7~ Elr@pho 1% hydrogen peroxide followed by 69.0% Elrepho 1% sodium hydrosulfite Since the attainment of the high levels of sulfonation required by the process of the invention will generally involve the use of relatively high concentrations of cooking chemicals and relatively heavy applications of cooking liquor on the wood, it is anticipated that for economic considerations in successful commercial application of the process o~ the invention, recycling of the unreacted sulfite from the cooked chips is desirable.
This may be achieved by pressing the cooked chips to remove the liquor from them and adding fresh chemicals to the liquor to return it to its original concentration be~ore reuse when recycled in the process. Recycling also assists in automatically control-ling the liquor pH to about 7-8, a desirable value. Substantially lower pH values tend to result in lower yields.
As long as the conditions ~or sufficient sulfonation are adhered to, the cook can be carried out in a variety of different ways. In Example 1~ below, a liquid phase process is used with no pre-impregnation with cooking liquor prior to the cook. Example 2, belo~, shows a liquid phase process with a 15-minute impregnation prior to the cook. In Examples 3 and 4, ~: .
.
. .
~ O 5~ 6~ ~
low, the chips were impregnated for 60 minutes prior to a vap~r phase ~ook. In each case, the pulps produced were sub-stantially similar in physical properties. These exampIes show that the process of the invention can be carried out using conventional and readily available liquid or vapor phase cooking equipment.
Example 4, below, illustrates the effect of cooking at a temperature (148C.) somewhat higher than the optimum 140C. While the strengths are excellent, the brightness, at 47% Elrepho, is lower than the 52-54~ Elrepho that can be achieved at 1~0C.
The present invention can produce good quality pulps from a wide variety of raw materials. Examples 5, 6, 7 and 8, belo~, show the use of southern pine, northern softwoods plus 32% poplar, 55~ northern softwoods and 45% northern hardwoods, and northern softwood sawdust.
Pulp made by this invention has excellent properties over a wide freeness range (100-600 ml.~. This is shown in ....
Figures la through le, where a number.of physical properties are plo~ted against freeness. These regression curves were taken from over one hundred pulp samples made as in Exzmples 1 and 2. The ability of this pulp to perform well over such a wide freeness range, serves to distinguish it from mechanical and conventional chemimechanical pulps which, typically, are only useful at relatively low freeness levels--usually below 3Q0 ml. In this respect, the pulp made by this invention is more comparable to low yield chemicàl pulps. As used in Figures la through le and throughout the present disclosure, freeness is referr~d to in terms of Canadian Standard Freeness ~CSF) as defined in Tappi Standard - T 227 (M~58). Freeness is a measure of the rate at which a dilute suspension of pulp may be dewatered.
3L05~6~13 Example 16, below, shows the effect of increasing the cooking time. In this e~ample, a very strong cooking liquor was used to illustrate the upper limit of sulfonation. Such a strong liquor could not be used in a commercial plant if liquor recycling was practiced, due to the solubility limit of Na2SO3 in spent liquor. It can be seen that the yield drops rapidly as the time is increased, and falls below 90% at about 90 minutes.
The operating pH range of this process is governed by two considerations. A pH substantially below 7.0 would be environmentally undesirable on a commercial level due to the presence o free sulfur dioxide. Due to the high concentration of the liquor, and paxticularly when recycled liquor is used, the pH does not drop substantially during the cook (see Example 1).
Nevertheless, it is important to maintain the spent liquor no lower than about pH 6.5 so as to keep the process essentially odorless.
It is well known that in most cooking processes a pH
substantially greater than about 8.0 will tend to degrade the liynin and hemicellulose and lead to reduced yield. This is shown by Example 17 (results in Table 3, below) where it can be seen that an increase in pH produced a substantial decrease in yield. It is also well known that a pH substantially above about 8.0 will tend to produce a discolored pulp which would be unacceptable in a wide range of products. Thus, this pH con-sideration would be significant on a commercial scale operation.In the laboratory, under carefully controlled conditions, the present process may be carried out at any pH over the about 6.0 to 8.5 range without producing odor, discolored pulp, or too low a yield. However, in a commercial plant, the control would not be as satisfactory, so that a practical minimum of above about 7.0, and preferably a pH range of from about 7.2 to 8.0 would be advisable.
.
6~ ~
Subsequent to the sulfonation of the ~ood chips, they are subjected to mechanical defibration by any oE the conventional mechanical grinding or refining techniques.
These techniques are well known to those skilled ln the art of mechanical and chemimechanical pulping. One such suitable treat- -ment is the use of double-disc refinerb whereby tlle sulfonated chips are passed het~-een rotating grooved discs to apply work to the chips and thereby defibrate them. The sulfonated chips may be passed through one or more refiners until the desired freeness is achieved.
., 11 .
: - ~7~
~5~6~
h O ~ ~ ~D ,~, /J~ O U~ O r-- ul N
.F:~ 3 ~ O c:~ r_l I
00 ~ ~ ~ O ,~ N~ ~ N N
~ ~ ',3 ~) U) N ~D N N
U) O O (~ , ~
~ ~ Z U~ U~ . 1' '3 ~ ~ .. . r :~ ~ u7 U) ~ lLi . ~
~,~ h O h 0 - ~ (1~ ~O
a) ~ ~ o ~ o o oo u~
S~ 3 ^ S~ 3 ~ O O N I
~ ~1 1~ C~ N1~ N u~ o~ N O
:~ h 4~ Ln )~ h Lr) ~ m Nc~ N t~f) U7 ~ 0~ ~ ~rl I¢
~ O O U~ O :~ ~ U~
1:~ N Zi U~--z ~ ~_ h ~ t~
rtrJ~ .
U~ rt S
PJ I ~r~J c~ SrJ~ ~rl E~
,1 h O N ~ 0 rt ~1 a) O ~ ~( O ~ U~ U~ X
d rl S 3 ~O Ir) O I , ~d 1~ 0 ~ ~ ~J 111 r~l O rt rt ~D ~ O N ~P
~rl h h 41 ~ ~ ~ ~7 Ct~N ~r 1~ UlCi~~1 0 ~ ~
Q1 (1) O 0 ~1 0 ~, 1 0 .
o Q) C,.) ~ . ~
F~ h . ~ a ~a o ~ ~ O ~ U~ r~ ~ O
U~ ~ ~ ~ o 1~ ~ I
~rl Ir~ ~ au N ~ O O ~ 00 0 N 1 4! o,~ ~) ~r N rt ~J N ~`~ Ul O ~: 0 U) pl - G) ~ t ~ t t~rl ~a *
h O ~ -~1 ~ Q) O h O u:~ ~ri ~ a) rt a) O .~: 3 :~o o ~ I *
O ~ ~ q~l X N 1~ m ~ rt ~r~~r ~ cr~ ~: ~; X
rt . $-1 H z O ~ .IJ
~ . ~ Z
m ~ a ~ ~ .
~ ~ O o a~ ~ u~ ~ ~ h~
rt ~) ~ ~ O LO Q ~) oU'~ N N ~r ~ rt ,~
h 4~ X ~ ~D ~ 0~ ~1 ~ t~u~~n D ~ t) h X
O o-~l ~ n~
Z U~ ~ ~ a ~ ~Irt X t~
~ ~ r~
'd . ,~ ~ h ~0~ ~::ro . Sl O P~ * ~ O O O
- rt * ~ 3 1 o o o In h 41 o t~
~1 ~ a~ 9 . o u~ In ~ u) ~ h o o,,XJu) ~D ~ rt rt U~ ~ ~ h rt u~ ~;; Z u~ ~ 0 41 'd O 0 h O ~:: Q ,~
rt ~
V ~ ~O rt h h~t S~ O O co O U
~ 0 # S 3 ~ ~ 'O 'O h U
r~ 5~ ~ ~ ~ ~) ~ O O U~ O U~ r ~l O O
v~ U rt h 4~ ~, rt ~) r-l ~D~ N ~ ~ ~ UJ h h O ,~ ~
'd rt rt O h .~ ,J, 0 rd h rt ~r l ~r~
O t~ d h V~ h h a) rO
e~ ~ O ~ ~ h ~ ~ ~ * o ~
O ~1 ~ O ~ ~ R .~ N ~ O O ,~
z a) ~ o I~ u u ~ ~ u~
In t:n d U ~ aJ .c rA ~ a~
vd U R * F~ f~, rt ~3 ~ ~ O h ro * ~ # tri ): :
.Y OO ~ ~,t ~ * # ~ *
a) O sl 0 ,t ~ ~ ~ ~ ~ ~
X O h h ~ ~h rJ # #
~1 ~ ~ m ~ ~ ~ m ~ ~ ~ ~
.
," : . .
, ' ;
~L 13S~L6~8 - /3 :
. ~
.
U~ . .
a~
. .
.
~ W
U~ ~ ~; o C
~ _ O CO C~' O ~ . . ~' .. . ~D . S-~
E~ ~ co. o ~ o ~ ~ o . ~ ~ ~ . ~ ~ ~ ~ V
Z ,t ,~ ~ O cn ~ ~
. . ~ V ,; ~U o ~, . o ~ U~ i:
D c~ r:~ $
~ o o~ o o C~ ~ ~ ` ~ O
.P~ ~ o ~ o ~ ~ ~~ O o ~lC ~ 1 1~ ~ rl ~ ~r ~I f--N rl It- ~ O ~ 1~ 0 ~ ,~
~ . ~ V d) P~ . R~ s E~ o ~J ~ ~ o ~ ~ o co o oo o o r ~ D O ~ a) ~
t~ t~ ~ o ~ o Lr~ ~N ~ ~ E~ o O ~ o co ~ ~ ~ O
1~ 0 0 ~ O
. ' . ~ r . ~ .
Z; , * o t~ ~ CO It) ~' ~ D ~ ~ Q~ O
* ~o o o ~1 U~ Ln ~:1 ~ O ~r o ~ ~ ~ ~ ~
2, ., .
~n . . .
P~ . . a)~
D ~: o ~ ~ ` .;~
P- *CO O O 1~ U) ~1 ~ r~ ~
~1 0 o ~ o 5: ~ o . r~ u) I ~ 0 0 . ~ ~ ~1 1~ t` ~ ~-1 tr~ N r l Ir) C5~ 0 1-- S~
~ ' C`~ . . O aJ-rl ~ ,1~ . , U~ . . .~ )~P:; O
E~ ~ . .Id~ V a) ~ ,. -O ~ o ~ ` O ~ rl * CO O O N ~ ~ I` ~ ~ ~ ~ ~ O
U~ O O O ~ C~ Ir) r-l r-l Il') ~I ~' ~ a~
~ ~I Ln ~~1 r l 1` N ~1 IS) Cl~ O ~ -1 0 C.) -~
E-~ . . ~ ) h ~ , .
. ~ . . . ~-~ IQ O 1~
~ O 1` ~ D ~ ~ ~ ~ ~ O ~ 3 O ~o c~ ~ - O U~ O u~
O h~ h C
~ a)~ la~1 ~ : -U~
* . ~ 0~ V ~ `.-~ O ~ r~~rl ~ 5 X '-o q-~
0 i3 t~ P~ O N ~ 'X ~ ::
U~ U~ 0 0 rl 'F ~ .~ ~ ~s~ o .~ o S~ ~
O ~I Z ~rl G) ~ ~ 0 ~ O ~ ~1 C ~ ~ ` Q) ' - z ~ r4 E~ E~` U ~ u~ ~ ~1o ~ o u~
h ~ 1 .C a~ R::1 X
Q~ O O ~ rl X~ ~
~a ~ ~ o o (I~ ~ C ~1 ~ ul X 2) X ~ rl O O h h ~ aJ ~1 O aJ a~ 0 Q
m a: ~ m ~ m ~ ~ h ~
1 ~1 U
~ oJ u~
0 ~ O
C ~ X ~ ~
~ *
:
~5~L61~
T~BLE 3 The E~fect of p~-l; from Example 17, below.
% Yield ~ Sulfur 6.0 94.27 0.662 7.0 93.01 0.585 8.0 92.26 0.521 g.0 90.97 ~ 0.670 The pulps made from this invention are useful in such p~oducts as ~e~sprint, coated papers, book papers, sanitary tis-sues, corrugating medium, linerboard, paper toweling, diaperfluff, milk carton board, etc.
Speci~ic 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 l-imit the ambit of the appended claims. In the examples which follow, and through-out the specification, the quantities of material are expressed 20. in terms of parts by weight, unless otherwise specified.
In Example 1, below,the wood chips were digested in a continuous (3-tube Bauer M and D) digester. This type of digester is described in Paper Trade Journal, pages 36-37, (September 5~ 1960) in an article by Van Derveer, entitled "Unique New Continuous Digesters Improve Operations at Two Mills"; also Pulp and Paper International, May 1971, pages 55 . . .
and 56. The chips pass through the tubes of the continuous digester by means of a conveyor.
In Example 1 the refiner employed on the chips after ;~
sulfonation was a double-disc refiner manufactured by Bauer Bros. (now C-E Bauer) ~nown as Model 400. This double-disc - ,, ,, , ,~. . . :
~5~
refiner employs 36 inch diameter grooved discs and two 110 kilowatt (150 horsepower) motors. Type 36161 plates were used in the first stage, and 36106 or 36104 plates were employed in the second stage of the refiner. The feed rate through the refiner was between two and four tons per day.
In order to reach a final freeness of 400 milliliters CSF, a refiner power of about 2.5 megajoules per kilogram (35.2 horsepower days per air-dried ton) was applied in the ~irst stage of the refiner and 2.2 megajoules per kilogram (31.0 horsepower days per air-dried ton) in the second.
Examples 9 through 15, inclusive, represent a series of controlled experiments which demonstrate a comparison of the results obtained by the prior art (Example 9) and a series -of experiments with all conditions the same except that the concentration of the Na2SO3 in the digestion liquor is gradually -increased (Examples 10 through 15, inclusive). In all of Examples 9-15, the same source of wood chips was employed. As demonstrated by Examples 10-15, at the temperature and cooking time conditions employed, it was not until the liquor strength was increased to about 120 g/l Na2SO3 that the desired at least -about 85% of maximum sulfonation was achieved.
.,: .
The following method was used to produce pulp at the rate of about 4 tons per day in a pulping pilot plant.
A mixture of northern softwood chips containing approx-imately 42% black and white spruce, 35% balsam fir, and 23%
jack pine was presteamed for about 10 minutes, then metered -into a 3-tube M and D continuous digester along with cooking liquor at a liquor to wood ratio of 3.3:1 (wt./wt. of dry chips). The cooking liquor was initially prepared by mixing sodium hydroxide and sulfur dioxide in a tank to produce _ 15_ ,,, i' ~, . , ' ;': i ,,. , , "~, ,~, ,;,j ;,~""", ,~ " , ~, "
. ~ , , , ~ , , ~
~Ot516~L8 ~ concentration of 120 g/l as Na2SO3 at a pH o~ 7.8. As the run progressed, sp~nt liquor, still containing some unreacted sodium sulfite, was extracted from the last quadrant of the M
and D tube, fortified with additional sodium hydroxide and sulfur dioxide to readjust the original liquor concentrations, and reused. During the course of the run (several weeks) the liquor concentration varied rom about 115 g/1 to about 125 g!l as Na2SO3 and the pH varied from about 7.5 to about 8Ø The pH
of the spent liquor covered the range 7.0 to 7.4.
The liquox in each of the three tubes in the digester was maintained at a temperature of 135C. (range 132-138C.) at a pressure of 410 kPa (range of from 400 to 500 kPa) (kPa refers to kilopascals). The residence time of chips in the digester - was 30 minutes (10 minutes per tube).
The cooked chips were discharged from the digester into a blow tank at atmospheric pressure, then transferred to a double-disc refiner. Sufficient water was added to the chips just before entering the refiner to reduce the consistency to about 15%. The pulp leaving the refiner had a freeness range of 650-720 ml., typlcally.
The pulp was diluted to about 2% consistency and pumped to a horizontal belt washer where it was washed with hot water to remove residual cooking chemicals and waste pro-ducts. The pulp left the washer at a consistency of about 15~ and was fed to a second double-disc refiner, at that con-sistency, where the freeness was reduced to about 350 ml.
After leaving the second refiner, the pulp was diluted to about 2% consistency and heated by direct steam injection to at least 75C. (not exceedin~ 100C.) and held above 75C. for at least 20 minutes, for latency removal. The pulp was then further diluted to about 0.8~ and passed th~ough a pressure screen ~(:3S~L6~8 ,~entriSCree~l) and centrifut3al cleaners before heing ~hic~ened on a lap machine to about 25% consistency.
The properties oE a typical pulp made in this manner are shown in Table 1, supra.
A quantity of this pulp was conveyed to a newsprint manufacturin~ mill, slurried with water and mixed with other pulps in the following proportions:
25~ pulp of this example 2% refined semibleached kraft ~5% stone groundwood ' 28~ refiner mechanical pulp This mixture was run over a fourdrinier paper machine twith vacuum pickup) and converted into newsprint with basis weight avera~ing 4g.8 g/m2. Operation of the machine was normal ';
compared to operation using a conventional pulp mixture containing ~ ' 18~ semibleached kraft except that drainage at the wet end was a little faster than normal. The newsprint was subsequently printed at the printing plant of a large metropolitan newspaper with ', excellent results. '' ' " ' . .
~XP~PLE 2 This example is substantially similar to Example 1, except that the chips were allo~ed to impregnate in the first ;' tube of the M and D digester for 15 minutes at a temperature of a,bout 75C., followed by a 30-minute cook (15 minutes in each of the next two tubes) at about 135C. The pulp produced by this technique was substantially similar to that made~in Example 1. This pulp was also used for newsprint production trials as in Example 1 and with substantially similar results.
~.
EXP~PLE 3 This example is similar to Example 2 except that the chips wexe impregnated in the first tube for 60 minutes at 345 kPa using sodium sulfite, bisulfite liquor with a concentration f 154 g /1 (as Na2SO3), and that liquor was removed from the last quadrant of the impregnating tube of the digester at a sufficient rate so as to prevent liquor from overflowing into the second tube. The chips, which entered the second tube sub~
stantially free of surface liquor wexe cooked at a temperature of 132~C. for 30 minutes using direct injection of steam to a pressure of 240 kPa. The pulp had properties similar to those of Example 1.
Example 3 was repeated, except that the chips were impregnated with 156 g /1 liquor then cooked at a temperature of 148C. using a pressure of 327 kPa. This pulp has properties as shown in Table 1, supra.
Example 2 was repeated, except that southern pine chips were used. This pulp had properties as shown in Table 1, supra.
:
Example 2 was repeated, except that the chips had ~0 the following average composition:
.
Red Spruce 32.9%
Balsam Fir 9.5%
Red Pine 15.9%
White Pine 9.7%
Poplar 32.0~ .
The pulp produced had the properties shown in Table 1, supra. Approximately 17 tons wexe made and shipped to a paper mill where the pulp was slurried and bleached using 1.5~ sodium hydrosulfite and 0.25% sodium tripolyphosphate, to a final bright-ness of 58.8 to 61.0 (a~erage 59.3) G. E. The pulp was then blended with other pulps in the following proportions: `
- 1 8-- :
;~
1C~5~6~8 35% pulp of this e~:ample 35% bleaciled, re~ined, softwood kraft 30~ stone groundwood This mixture was converted into 65 g/m2 (grams per square meter) coated publication yrade paper (base sheet weight 40.7 g/m2) using a fourdrinier paper machine with two on~machine coaters (appxoximately 12.2 g/m2 of clay coating per side being applied~. The sheet was supercalendered. All phases of the manufacturing process were normal compared to operation with the normal furnish of 52% bleached, refined softwood kraft and 48% -stone groundwood, and the sheet performed well on commercial - printing presses.
XA~SPLE 7 -Example 1 was repeated, except that a mixture of lS northern softwoods and hardwoods with the following approximate composition was used:
Spruce 34.8%
Balsam 12.5%
. Red and White Pine 8.3 Poplar 19.8~
Beech 5.1%
Maple 10.0~
Ash 3.6%
~lm 5.2%
Basswood 0.8~
Sufficient quantities for small scale investigations only were made. The pulp had the properties shown in Table 1, ;
supra.
EXA~PLE 8 `
Example 2 was repeated, except that mixed northern softwood sawdust was used and the liquor heating was substan-tially supplemented by direct steam. All spent liquor was allowed to discharge into the blow tank with the cooked sawdust.
Sufficient quantities only for small scale investigations were made. The pulp had properties sho~m in Table 1, supra.
-.. . . : ~ .
~5~6~
X~MPI,E 9 This is a comparative exa~ple illustrating fhe prior art.
800 g. (dry basis) of a mixture of northern softwood chips containing approximately 42% black and white spruce, 35%
balsam fir, and 23~ jack pine were placed in a 10-liter laboxa-tory digester to which was added 6 liters of a liquor consisting of a sodium sulfite/bisulfite solution with a concentration of 56 g /1 as Na2SO3, and had a pH of 6.8. The digester and contents were heated, using indirect steam, to a tempe~ature of 138C., pressurized to 585 kPa with nitrogen and held there for 15 minutes. After the cook, the chips were drained and defibered into pulp using three passes through a 50 HP, 12-inch diameter, Sprout 1~7aldron laboratory refiner using consis-tencies of about 159~. The pulp was screened ~hrough a 0.0152 cm. slotted screen, then given a 30-minute, 80C., latency treatment before testing. The pulp had properties as shown in Table 2.
These cooking conditions sirnulate those reported by C. A. Richardson in Tappi, December 1962, Vol. 45, No. 12 page 141A.
, This is a comparative control example.
Example 9 was repeated, except that the li.quor con-centration was 50 g/l as Na2SO3 at a pH of 7.8, and the cooking conditions were 140C. for 30 minutes, at self-generated pressure only.
The pulp had properties as shown in Table 2.
, This is a comparative control example.
Example 10 was repeated, except that the liquor con- ;-centration was 70 g/l as Na2S3 ~OSl~
The pulp had properties as shown in Table 2.
EXA~5P ~ 12 This is a comparative control example.
Example 10 was repeated, except that the liquor con-centration was 90 g /1 as Na2SO3.
The pulp had properties as shown in Table 2.
EX~MPLE 13 Example 10 was repeated, except that the liquor con-centration was 120 g /1 as Na2SO3.
The pulp had properties as shown in Table 2.
EX~IPLE 14 Example 10 was repeated, except that the liquor con-centration was 150 g /1 as Na2SO3.
The pulp had properties as shown in Table 2. .
..
EX~MPLE 15 Example 10 was repeated, except that the liquor con-centration was 180 g /1 as Na2~O3.
The pulp had pxoperties as shown in Table 2.
EXAMPLE 16 ;;
Maple chips were cooked in small bombs using a tech-nique substantially similar to that described in the sulfona~
tion test except that the cooking liquor strength was held constant at 200 g ,/1 Na2SO3 and a series of cooks were carried .
out at various times between 30 minutès and 8 hours.
The results are plotted in Figure 8 of the drawings.
. , - EX~5PLE 17 Mixed softwood chips similar to those used in Example 1 were cooked in small bombs using a technique sub-stantially similar to that described in the sulfonation test ,, , .
,: .
S~611~
`~cept that the coo~iny liquor strength was held constant at 120 g/l and the pll was varied from 6.0 to 9Ø
The xesults are set forth in Table 3, supra~
' .
' . 22 -` ~L0~ 8 l~est Procedure for Determining thc Maximum Level of Sulfonation that can be Achieved for Various ~ood Species --_ . _ . .. .. .. ... __ 2 ky. (dry basis) of screened wood chips are carefully mixed and 1 kg. is removed and dried to provide an accurate mois-ture deter~ination. The balance is divided into 100 g. (~ethasis) aliquots and each is carefully weighed. Each aliquot of chips is placed in a small bomb (capacity 540 ml.) to which is added sufficient sodium sulfite/bisulfite liquor to just cover the chips. A series of liquors are used, each being prepared by adding gaseous SO2 to a solution of sodium sulfite to reduce the pH to 7.8. The liquors have the following concentrations:
(w/v as Na2SO3) 50, 70, 90, 120, 150, and 180 g/l. At least two cooks are carried out at each liquor strength. The bombs-are sealed and placed in an oil bath which has been heated to 140C. The bom~s are mounted on a rotating device that upends the bombs 2 or 3 times per minute in order to provide some agitation to the mixture of chips and liquor. The bombs are removed after 30 minutes.
When each bomb is removed from the oil bath, it is immediately plunged into cold water to produce rapid cooling.
The cooked chips are removed from the bomb as soon as possible, the liquor is drained off and discarded, and the chips are defibered in cold water using an industrial blender (Waring or Osterizer type) for 15 minutes or until the chips are well defibered. The pulp is then fiitered, on a filter paper, care~
fully washed with a large volume of cold water, then dried in an oven and weighed and the yield calculated. After ~eighing, a sample of pulp is taken and its sulfur content is determined.
The yield and sulfur content data are plotted against liquor strength as illustrated in Figures 2 to 7 of the drawings.
These graphs show the customary scatter of clata points, xegres-sion curves were calculated in order to show ~he trend. For , . , . . ,.. ~ : . . ..
~5~
many species the sulfur content will tend to reach a m~ximum (or plateau) at 15~18% Na2SO3, and usually this maximum will be reached without reducing the yield below 90%. In the case of softwoods (Figures 2 to 5) it is probable that the sulfur content could be increased a little beyond that reached at 18%
Na2SO3 liquor, but higher liquor concentrations are not prac-tical, particularly when recycled liquors are used due to the solubility limit of Na2SO3 in the presence of dissolved organic materials.
10For each of the typical woods to which Figs. 2 to 7 relate, the graphs may be used to determine suitable ranges of liquor concentration, making reference to the figures for sul-fonation of the various woods given on page 7. Thus, for spruce, page 7 shows that 0.55%S is required to provide the desired level of 85% of maximum sulfonation, and Fig. 2 shows that a concentration of above about 100 g/l Na2SO3 is required to produce this sulfur content; this and higher levels up to ak least about 200 g/l will not reduce yield below 90%. Figs. 3 to 7 likewise give the fol- ;
lowing approximate results for the various woods~
g/l Na2SO
Wood %S equivalent to Graph Min. for Max. for 85% maximum sul-85% sul- at least fonation (from p7)fonation 90% yield `
salsam .60 Fig.3100 over 200 Jack Pine .64 Fig.4100 over 200 Southern Pine .55Fig.5 100 over 200 r~aple .28 Fig.6105 over 200 Poplar .31 Fig.7 95 115 Accordingly, it may be seen that for the softwoods (balsam, jack pine, southern pine) a range of about 100 to about 200 g/l is suitable; for poplar the suitable range is about 90 g/l to about 115 g/l.
The terms and expressions which ha~e 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 excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifi-cations are possible within the scope of the invention claimed.
. ' ' ' ` ~ ', ` :,
Claims (17)
1. A method for the production of high yield chemi-mechanical pulp from woody lignocellulosic material which comprises treating said woody lignocellulosic material with an aqueous solution of a mixture of sulfite and bisulfite having a pH of between about 6.0 and about 8.5 at a temperature of between about 100°C. and about 150°C. for a period of between about 10 and about 90 minutes, said aqueous solution being of sufficient strength to sulfonate said woody lignocellulosic material to at least about 85% of the maximum level of sulfonation that can be achieved on said woody lignocellulosic material without reducing the yield of pulp below about 90% by weight, and subsequently subjecting the resulting sulfonated material to mechanical defibration.
2. A method according to Claim 1, wherein the aqueous solution is of sodium sulfite and sodium bisulfite.
3. A method according to Claim 1, wherein the pH is between about 7 and about 8.
4. A method according to Claim 1, wherein the pH is between about 7.2 and about 8Ø
5. A method according to Claim 1, wherein the temperature is between about 120 and about 140°C.
6. A method according to Claim 1, wherein the period of treatment with aqueous solution is between about 20 and about 60 minutes.
7. A method according to Claim 1, wherein the woody lignocellulosic material is sulfonated to at least about 90%
of the maximum level of sulfonation that can be achieved on said material without reducing the yeild of pulp below about 90%
by weight.
of the maximum level of sulfonation that can be achieved on said material without reducing the yeild of pulp below about 90%
by weight.
8. A method according to Claim 1, wherein the woody lignocellulosic material is wood chips.
9. A method according to Claim 1, wherein the woody lignocellulosic material is sawdust.
10. A method according to Claim 1, wherein the sul-fonated woody lignocellulosic material is pressed prior to mech-anical defibration to remove spent aqueous solution and the spent aqueous solution is then adjusted to initial strength with regard to concentration of sulfite and bisulfite and is recycled and used to treat fresh material.
11. A method according to Claim 10, wherein the pressing of said sulfonated woody lignocellulosic material pro-duces a controlled volume of spent aqueous solution, said volume being substantially equal to that which, after refortification with fresh sulfite and bisulfite, is applied to fresh woody lignocellulosic material to provide a system in which there is no excess flow of used aqueous solution.
12. A method for the production of high yield chemi-mechanical pulp from woody lignocellulosic material derived from softwoods, which comprises treating said woody lignocellulosic material with an aqueous solution of a mixture of sodium sulfite and sodium bisulfite having a pH of between about 6.0 and about 8.5 and having a strength between about 100 g/l and about 200 g/l as sodium sulfite at a temperature of between about 120°C and about 140°C. for a period of between about 20 and about 60 minutes, and subsequently subjecting the resulting sulfonated material to mechanical defibration.
13. A method according to Claim 1 or Claim 12 wherein the strength of the aqueous solution is at least about 120 g/l as sodium sulfite.
14. A method for the production of high yield chemi-mechanical pulp from woody lignocellulosic material derived from poplar, which comprises treating said woody lignocellulosic material with an aqueous solution of a mixture of sodium sulfite and sodium bisulfite having a pH of between about 6.0 and about 8.5 and having a strength of between about 90 g/l and about 115 g/l as sodium sulfite at a temperature of between about 120°C.
and about 140°C. for a period of between about 20 and about 60 minutes, and subsequently subjecting the resulting sulfonated material to mechanical defibration.
and about 140°C. for a period of between about 20 and about 60 minutes, and subsequently subjecting the resulting sulfonated material to mechanical defibration.
15. A method according to Claim 12 or Claim 14, wherein the pH is between about 7 and about 8.
16. A method according to Claim 12 or Claim 14, wherein the pH is between about 7.2 and about 8Ø
17. A method according to Claim 12 or Claim 14, wherein the conditions of the treatment with respect to time, temperature, and sulfite concentration are such as not to reduce the yield of pulp below about 90% by weight.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA252,642A CA1051618A (en) | 1976-05-14 | 1976-05-14 | Method of producing high yield chemimechanical pulps |
| NZ18405177A NZ184051A (en) | 1976-05-14 | 1977-05-09 | Production of high yield chemi-mechanical pulp |
| US05/838,837 US4116758A (en) | 1976-05-14 | 1977-10-03 | Method of producing high yield chemimechanical pulps |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA252,642A CA1051618A (en) | 1976-05-14 | 1976-05-14 | Method of producing high yield chemimechanical pulps |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1051618A true CA1051618A (en) | 1979-04-03 |
Family
ID=4105968
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA252,642A Expired CA1051618A (en) | 1976-05-14 | 1976-05-14 | Method of producing high yield chemimechanical pulps |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1051618A (en) |
| NZ (1) | NZ184051A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017215877A1 (en) * | 2016-06-17 | 2017-12-21 | Andritz Ag | Method for producing a fibrous material |
-
1976
- 1976-05-14 CA CA252,642A patent/CA1051618A/en not_active Expired
-
1977
- 1977-05-09 NZ NZ18405177A patent/NZ184051A/en unknown
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017215877A1 (en) * | 2016-06-17 | 2017-12-21 | Andritz Ag | Method for producing a fibrous material |
| RU2704362C1 (en) * | 2016-06-17 | 2019-10-28 | Андриц Аг | Fibrous material manufacturing method |
| US11535983B2 (en) | 2016-06-17 | 2022-12-27 | Andritz Ag | Method for producing a fibrous material |
Also Published As
| Publication number | Publication date |
|---|---|
| NZ184051A (en) | 1979-11-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4152197A (en) | Process for preparing high-yield cellulose pulps by vapor phase pulping an unpulped portion of lignocellulosic material and a partially chemically pulped portion | |
| US4116758A (en) | Method of producing high yield chemimechanical pulps | |
| CA1226705A (en) | Chemithermomechanical pulping process employing separate alkali and sulfite treatments | |
| EP0764225B1 (en) | A light drainability, bulky chemimechanical pulp that has a low shive content and a low fine-material content | |
| Leatham et al. | Biomechanical pulping of aspen chips: energy savings resulting from different fungal treatments | |
| EP0434692A1 (en) | Supercritical delignification of wood | |
| US4087317A (en) | High yield, low cost cellulosic pulp and hydrated gels therefrom | |
| US4211605A (en) | High yield chemimechanical pulping processes | |
| US4552616A (en) | Pulping process pretreatment using a lower alkanolamine in the presence of ammonium hydroxide | |
| FI73473C (en) | FRAMEWORK FOR FRAMSTAELLNING AV FIBERMASSA. | |
| AU2002244309B8 (en) | Method for producing pulp | |
| US4190490A (en) | Impregnation and digestion of wood chips | |
| AU2002244309A1 (en) | Method for producing pulp | |
| US20190211508A1 (en) | Paper Processing Composition and Process of Production | |
| CA1051618A (en) | Method of producing high yield chemimechanical pulps | |
| FI83238C (en) | FOER FARING FRAMSTAELLNING AV CELLULOSA. | |
| US3013931A (en) | Printing paper and process of making the same | |
| EP0030778B1 (en) | Process for the formation of refiner pulp | |
| CA1232109A (en) | Pulping process | |
| FI57454C (en) | FRAMSTAELLNING AV FOERBAETTRAD HOEGUTBYTESMASSA | |
| US4534397A (en) | Method for producing chemimechanical high yield pulp using an oxygen alkali treatment followed by an oxygen mechanical defibration | |
| GB1595719A (en) | Method of applying one or more layers of surface stock to the web of base pulp in fibreboard manufacture by the wet-lay system | |
| CA1162358A (en) | Process and apparatus for the deresination and brightness improvement of cellulose pulp | |
| JPH0114357B2 (en) | ||
| CA1057007A (en) | Impregnation of wood particles |