US3301745A

US3301745A - Pulp processing method for mixed cellulosic materials

Info

Publication number: US3301745A
Application number: US275857A
Authority: US
Inventors: Coppick Sydney; Brown Ralph
Original assignee: Scott Paper Co
Current assignee: Kimberly Clark Tissue Co
Priority date: 1963-04-26
Filing date: 1963-04-26
Publication date: 1967-01-31
Anticipated expiration: 1984-01-31

Description

Jan. 31, 1967 s. COPPICK ETAL PULP PROCESSING METHOD FOR MIXED CELLULOSIC MATERIALS 3 Sheets-Sheet 1 Filed April 26, 1963 $52; 11 0M 4 mcEuo E o 8.

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PElSOJm mwkwwgo mmElrOzx mmCwam AGENT Jan. 31, 1967 p ETAL 3,301,745

PULP PROCESSING METHOD FOR MIXED CELLULOSIC MATERIALS Filed April 26, 1963 3 ShQGtS-Shfib 2 Combined Primary 8 Secondary AccepTs INVENTORS SYDNEY COPPICK BY RALPH BROWN AGENT Jan. 31, 1967 s, COPPICK ET AL 3,301,745

PULP PROCESSING METHOD FOR MIXED CELLULOSIC MATERIALS 3 Sheets-Sheet :5

Filed April 26, 1963 SYDNEY COPPICK RALPH BROWN kc. L

AGENT United States Patent 3,301,745 PULP PROCESSING METHOD FOR MIXED CELLULOSIC MATERIALS Sydney Coppick, Ridley Park, Pa., and Ralph Brown,

Glastonbury, Conn., assignors to Scott Paper Company,

Philadelphia, Pa., a corporation of Pennsylvania Filed Apr. 26, 1963, Ser. No. 275,857 4 Claims. (Cl. 162-55) This invention pertains to a novel method of pulp and paper utilization, more specifically, this invention involves a novel method of operating pulp and paper mills, as well as pulp converting facilities, designed to process pulp and produce papers of various kinds from mixed sources of cellulose containing materials and cellulose containing growth species pulped according to different pulping techniques.

The prior art pulp to paper processes, wherein the pulp was cooked according to the various techniques, produced pulps having characteristics of the species of wood cooked or the aggregate characteristics of the various species cooked. If the pulp to paper method incorporated pulp obtained from different processes, such as, kraft or sulfate and the sulfite, the composite characteristics of the two pulps often had unwanted properties in the final paper product. Consequently, heretofore, papers of various qualities and types had to be tailored starting with the wood species, the cooking process, the processing of pulps, such as, beating, bleaching, thickening and washing, and finally the paper sheet forming. Moreover, the prior art wood species to final paper route was predicated upon the use of the type of wood or cellulose containing material and the pulping and processing had to be tailored for the desired end result.

The present invention is an improvement in the cellulose containing material pulp to paper route in that the novel process allows great variation in the use of the cellulose containing material species and mixtures of species in the pulp to paper route. According to the present process, significantly greater pulp and paper processing latitude is achieved, not only in the type of cellulose containing material or wood or species of Wood mixtures to be used, but also in the pulping and pulp processing operations, as well as in the final tailoring of the various papers desired.

The present invention is accomplished by a novel method of operating a cellulose pulping to paper web producing route comprising the steps of:

(A) processing at least one species of cellulose containing material to be pulped in at least one type of pulping process;

(B) pulping the cellulose containing material according to at least one pulping process in at least one pulping zone;

(C) obtaining a screened pulp from said pulping zone;

(D) separating the various fractions of said cooked and screened pulp by means capable of separating pulp fractions;

(1) the separating step being characterized by:

(a) separating a fraction of the screened pulp in a first pulp fraction separating zone,

(b) taking the first fraction and processing it for a first cellulose Web producing zone,

(c) taking the remainder of the pulp stream and processing it to at least one subsequent pulp fraction removing zone having optional recycle streams, and having at least one final reject stream,

(d) taking at least one of the subsequent fraction streams and processing it for at least one additional cellulose web producing zone;

(2) said separating step being characterized by the selected pulp fraction possessing the selected different physical and chemical properties when said pulp fraction is further subjected to subsequent pulp processing steps;

(3) said separating step being further characterized by the said selected pulp fraction possessing the selected properties when said pulp fraction is incorporated in the final paper web;

(E) the pulp fraction separating step being readjusted according to the operating conditions of said pulp processing route; and

(F) the pulp fraction separating step being readjusted in combination with the pulp processing route according to the selected properties desired in the paper web.

In order to accomplish the most effective separating of the pulp fractions, as well as the operation of pulp processing and papermaking route, liquid cyclone means are used in practicing the invention. Liquid cyclones, such as, centricleaners, are suitable, other cyclones are equally efficient, however, in all cases, the reject orifices of the cyclones must possess means that may be changed to allow a gradiation of opening sizes to permit the ready adjusting of the varying conditions and demands in the pulp processing and papermaking route.

The present invention is further accomplished by a continuous pulp to paper web producing route comprising the steps of:

(A) taking a screened pulp comprising of at least one species of wood pulped by at least one pulping process, containing various fractions of pulp having different chemical and physical properties;

(B) separating the various fractions of said screened pulp by means capable of separating pulp fractions;

(1) the separating step being characterized by:

(3) said separating step being further characterized by said pulp fraction possessing the'selected properties when said pulp fraction is incorporated in the final paper web;

(C) the pulp fraction separating step being readjusted according to the operating conditions of said pulp processing r-oute when said route is changed by the varying pulp fractions being obtained from different sources of screened pulp in step (A);

(D) the pulp fraction separating step being readjusted in combination with the pulp processing route according to the selected properties desired in the paper web.

The invention as accomplished above is further amplified that in the method, the separating step, characterized by the pulp processing properties, is operated producing pulp fractions of same bleachability; and the separating step is further characterized by the final paper web product of the first paper producing route being of im proved strength and printing characteristics, and the final paper web product of a second paper web producing route being of improved softness, hand feel and absorbency.

The present invention is still further accomplished by a novel continuous method of operating a pulp to paper web producing route comprising the steps of:

(A) pulping at least one species of cellulose containing material possessing various fractions of cellulose pulp of different chemical and physical properties associated with each species of cellulose containing m-aterial and its growth cycle;

(B obtaining a screened pulp consisting of mixed fractions of pul p (C) separating the various fractions by:

(l) introducing the screened pulp in a first liquid means pulp fraction separating zone,

(2) taking a portion of pulp from the first liquid means pulp fraction separating zone for further pulp processing and use in a first paper web producing route,

(3) taking the remainder of pulp from the first liquid means pulp fraction separating zone and introducing said remainder into a second liquid means pulp fraction separating zone,

(4) taking a part of the second liquid means pulp fraction separating zone accept effluent obtained by:

(a) combining the accept efiiuent recycled to said second zone from a third liquid means pulp fraction separating zone accept effluent which, in turn, has been made up of a fourth liquid means pulp fraction separating zone accept efliuent combined and introduced into the third zone with the reject efiluent from said second liquid zone, and

(b) the said remainder of pulp from said first zone, and further processing this pulp and using it in a second paper web producing route;

(5) said first, second, third and fourth liquid pulp fraction separating zones being characterized by the obtained pulp fractions possessing the preselected differing physical and chemical properties when said pulp fractions are further subjected to subsequent pulp processing steps;

(6) the said first, second, third and fourth liquid pulp fraction separating zones being further characterized by said pulp fractions possessing the selected properties when said pulp fractions are incorporated in the final paper web.

The method above again may be modified to be adjusted according to the needs of the pulp processing and papermaking route as outlined above.

The invention, as accomplished immediately above, is further amplified that in the method, the separating step, characterized by the pulp processing properties, is operated producing secondary accept fraction containing a reduced amount of parenchyma cells in respect to the total amount of parenchyma cells present in the wood pulped, and requiring less bleach chlorine for given brightness level in respect to the bleach chlorine for the unfractioned pulp; and the separating step is further characterized by the final paper web product of the second paper producing route being of improved absorbency properties. Again, the variations outlined in respect to the different facets of the accomplished invention may be incorporated in the other variations outlined above. It is to be understood that the flexibility of the invention is in no way hampered by the particular route followed if the liquid cyclone means are readily adjustable to accomplish the corresponding variations in the operating conditions. Thus, it is understood that the liquid cyclone separating 4 means are fully responsive to the operating conditions both upstream and downstream of the process route.

In another aspect, this invention is accomplished by a novel continuous method of operating a pulp to paper web producing route comprising the steps of (A) pulping at least one species of cellulose containing material possessing various fractions of cellulose pulp of different chemical and physical properties associated with each species of cellulose containing material and its growth cycle;

(B) obtaining a screened pulp consisting of mixed fractions of pulp;

(C) separating the various pulp fractions by:

(l) introducing the screened pulp into a first liquid means pulp fraction separating zone,

(2) taking a portion of a pulp fraction from the first liquid means pulp fraction separating zone and combining it with the accept fraction from a second liquid means pulp fraction separating zone for further pulp processing and use in a first paper web producing route,

(3) taking the reject fractions from the second liquid zone and introducing said fractions into the third liquid means pulp fraction separating zone,

(4) taking a portion of a pulp fraction from the third liquid means pulp fraction separating zone and combining it with the accept fractions from the fourth liquid means pulp fnaction separating zone for further pulp processing and use in a first paper web producing route,

(5) taking the reject fraction from the third liquid zone and introducing said fraction into the said fourth liquid means pulp fraction separating zone,

(6) said first, second, third and fourth liquid pulp fraction separating zones being characterized by the obtained pulp fractions possessing the preselected differing physical and chemical properties when said pulp fractions are further subjected to subsequent pulp processing steps,

(7) the said first, second, third and fourth liquid pulp fraction separating zones being further characterized by said pulp fractions possessing the selected properties when said pulp fractions are incorporated in the final paper web.

In still another aspect, this invention may be accomplished by a novel continuous method of operating a pulp to paper web producing route comprising the steps of:

(A) pulping at least one species of cellulose containing material possessing various fractions of cellulose pulp of different chemical and physical properties associated with each species of cellulose containing material and its growth cycle;

(B) obtaining a screened pulp consisting of mixed fractions of pulp;

(C) separating the various pulp fractions by:

(l) introducing the screened pulp into a first liquid cyclone means pulp fraction separating zone,

(2) taking a portion of a pulp accepts fraction from the first liquid cyclone means pulp fraction separating zone and combining it with the accepts fraction from a second liquid cyclone means pulp fraction separating zone, wherein said second zone further is separating the rejects from said first zone, and using the two combined fractions for further pulp processing and use in a first paper web producing route,

(3) taking the reject fraction from the second zone and introducing said fractions into a third liquid cyclone means pulp fraction separating zone wherefrom the tertiary accepts are used for further pulp processing and use in a second paper web producing route,

(4) taking the reject fractions from the third zone and introducing said fraction into a fourth liquid cyclone means pulp fraction separating zone wherefrom the quaternary accepts are used for further pulp processing and use in a third paper web producing route,

(5) said first, second, third and fourth liquid pulp fraction separating zones being characterized by the obtained pulp fractions possessing the pre-selected differing physical and chemical properties when said pulp fractions are further subjected to subsequent pulp processing steps,

With the foregoing in mind, the present invention can be comprehended more readily by reference to the attached drawings wherein the same reference characters are used to indicate the corresponding zones and streams and wherein:

FIGURE 1 illustrates as an example of the invention, the diagrammatic flow sheet of the disclosed operation;

FIGURE 2 illustrates as an aspect of the invention another diagrammatic flow sheet of the liquid means pulp fraction separating zone;

FIGURE 3 illustrates as an aspect of the invention a still further diagrammatic flow sheet of the liquid means pulp fraction separating zone depicting thereby the various fraction separating arrangements possible;

FIGURE 4 depicts a mix of fibers in southern pine, magnified 950 times and containing springwood and summerwood;

FIGURE 5 depicts a fraction of southern pine magnified 950 times and containing a predominant portion of summerwood;

FIGURE 6 depicts a fraction of southern pine magnified 950 times and containing a predominant portion of sprin-gwood.

In reference to FIGURE 1, the novel process is carried out as follows: Area 1 represents the holding zone of cellulose containing material, such as, chips, straw, bagasse, or other known pulp yielding cellulose containing material. These materials are prepared according to the peculiar practices required for each species of starting material, as well as the type of pulping process used.

Area 2 represents another holding zone containing a species of cellulose containing material different from the material in Area 2. Of course, Areas 1 and 2 can represent holding zones having the same type of cellulose starting material. The digest-er 3 represents the pulping operation generally associated with either one or two stage sulfite operation or the kraft operation. The blowpit 4 represents a generally well-known step in any pulping operation and so does the knot removing zone 5. The washing zone 6 likewise depicts the final liquor removing step. The washed pulp is then introduced into a washed pulp holding zone 7 from which the pulp is subjected to the screening operation 8, well-known in the art. The screening operation is used to separate the unacceptable contaminants. Generally, these screening operations are insufiicient for some types of paper and the pulp must be further refined in order to remove the contaminants. Most prior art pulp mills have resorted to water cyclones to separate the final rejects from the pulp after the pulp has been screened. Consequently, dirt, shives and pitch particles often are removed by further processing of the screened pulp accumulated in a holding or storage zone, such as, 9.

However, in the present process, as depicted in FIG- URE 1, liquid separating means I", II,=-III and IV (such as, cyclones, continuous centrifuges, or other separatingmeans designed to take advantage of physical properties of pulp) are used to effect an integral function in the novel process in an entirely different manner, than previously used in the art. In the present process,

the preferred liquid cyclone separating means are used to obtain the natural, mechanical and chemical fractions of the pulp to separate the fractions according to their properties and to use the pulp fractions most suited for particular pulp processing steps or most suited as pulp material for papers having the particular paper properties associated with the particular pulp fraction.

In practicing the invention, the pulp fractions are separated by regulating the pressure of inlet water in the cyclone, the water velocity and the orifice opening. The particular combination of conditions which gives the desired result is found by test or trial runs for a given mix of cellulose starting materials or a given mix of pulp obtained from various sources. The important fact is that the pulp fractions as run are adjusted to suit the most economical and efficient operation of the mill to give the desired or pre-selected end results, which the varying pulp fractions afford because of their physical and chemical properties associated with the cellulose material and its growth cycle. By the same token, the novel method allows the use of a mixture of pulps in an optimum manner as well as the optimum use of each in dividual pulp fraction as it suits a certain pulp processing route or certain paper producing route.

Further, in reference to FIGURE 1 and the liquid separating means 1, 11, 111, and IV, it is obvious that various arrangements may be used to obtain the proper mix of fractions suitable for particular uses. For example, additional liquid means may 'be used in series or in parallel with various recycle arrangements. The.

particular arrangement may give highly refined pulp fractions directed to particular end uses in specialty papers. The various arrangements may also separate fractions which may be highly desirable for use in printing papers, while the remaining functions may be processed without additional steps and used in bag or kraft papers.

Obviously, the operating flexibility, the optimum use of the pulp and wood, and the pulping chemicals are \only some of the facets of this invention which characterize the novel process.

The primary pulp accepts in FIGURE 1 designated as stream A are further processed in the thickener 11e designated as thickener A and bleacher 12a designated as bleacher A. The pulp fraction, after the bleaching step, possesses different chemical properties and thus reacts difiFerently under identical pulp processing conditions. Some of this and other pulp fraction behavior is further illustrated by the examples. The other processing steps, such as, washing 13, are self-explanatory and the particular operation of a paper machine 14 is also self-explanatory. However, it is important to understand that the operation of the paper machines Will be different if the pulp fraction separating step will produce pulp fractions that have properties which do not require particular steps heretofore associated with the presently used mixed fraction pulps.

FIGURE 2, thus, shows a further arrangement of the 7 liquid means for separating pulp fraction. The primary,

secondary, tertiary and quaternary accepts produce a source of starting pulp material for the use in further pulp processing and final paper web producing routes designated as streams A and B respectively. Example V shows this particular operation.

FIGURE 3 again depicts a particular cyclone arrangement with the pulp fractions being separated into three streams for use in the various pulp processing steps and paper web making operations associated with the utilization of the particular pulp fractions. Example VIII further illustrates this particular operation.

FIGURE 4 depicts a collection of actual pulp fractions consisting of flat, flexible, predominantly ribbon-like springwood 1a; and 1b represents the rod-like, stiff summerwood fibers. The figure is a reproduction from a photograph of sample fibers taken from a representative batch of unfractionated southern pine pulp. The fibers are oriented under a microscope and embedded lengthwise in it. The solidified polymer is then transferred to the microtone and cross-sections of the fiber strands are cut transversally across the axis and photographed with a reproduced magnification of 95 times.

FIGURE depicts a collection of fibers in an actual pulp fraction used in the novel method. This fraction consists of predominantly rod-like, stifl summerwood fibers, designated as 1b and having most of springwood 1a removed. FIGURE 5 is obtained according to the same procedure use-d in obtaining the mixed fraction depicted in FIGURE 4. The fibers in FIGURE 5 have been magnified 950 times.

FIGURE 6 depicts a collection of pulp fibers in an actual pulp fraction used in the novel method. This fraction consists of predominantly ribbon-like, flexible, large surface area springwood fibers, designated as 1a and having most of the summerwood 1b fraction removed from the mixed starting pulp. The fibers in FIGURE 6 have been magnified 950 times and photographed as in FIG- URE 4.

Other wood cells, such as, parenchyma cells, are likewise separated from the desire-d pulp fractions and the pulp fractions are used for their pre-selected purpose. By the same token, the novel method also incorporates the use of pulp fractions of fibers of diiferent lengths or different geometrical configuration, as well as different chemical properties. For example, mixed and pulped species of Wood, such as, a mixture of:

Picea gluca: Canadian Spruce Pz'cea mariana: Black Spruce Pinus banksiana: Jack Pine Tsugd canadensis: Eastern Hemlock Pop ulus tremuloides: Quaking Aspen Populus grandidental'a: Bigtooth Aspen contains a mixture of anatomic constituent cells having the following representative pulp fractions:

Springwood tracheids Summerwood tracheids Springwood vessels Summerwood vessels Springwood fibers Summerwood fibers Longitudinal parenchyma} Radial parenchyma The appended examples more fully illustrate the process and are intended only to illustrate but not to limit the present invention.

} from the conifers from the hardwoods from the conifers and hardwoods.

northeastern hardwoods 2 (beech, birch and maple) werecooked together in an acid sulfite pulping digester 3 in the proportions of four parts of softwood to one part of hardwood.

On completion of the digestion, the combined delignified fibers were discharged to blow-pit 4 and the residual knots removed at 5. The deknotted pulp was washed free from spent cooking liquor on washer 6, and substantially freed from fiber bundles, shives, small splinters and residual bark by a series of screens 8 to produce screened pulp 9.

The screened pulp at 0.5% consistency was pumped through a series of liquid cyclones 10 arranged as in FIG- URE l with the primary accepted stock separated to stream A. The primary rejected stock was fed to the secondary cyclones together with accepted stock recycle from the tertiary cyclones. The rejected stock from the tertiary cyclones was fed to the quaternary cyclones and the quaternary accepted stock recycled to the feed of the tertiary cyclones. The final rejects from the quaternary cyclones, containing dirt particles, small bark specks and residual Wood shives, which constituted 1.27% of the original stock, was discarded. The secondary accepted pulp was directed to stream B.

The cyclones were 3-inch maximum periferal diameter, and operated with 45 p.s.i.g. feed inlet pressure and 5 p.s.i.g. accept outlet pressure, with a flow of 30 gallons/ minute for each cyclone. The reject tip orifices of the cyclones was 45 inch, so that the reject rate of the primary cleaners was about 20% of the feed rate. The flow rates and pressures of the subsequent stages were adjusted such that the final rejects from the fourth stage containing inorganic dirt, shives and bark particles were directed to the sewer and constituted 1.27% by weight of the primary feed pulp.

The production and pulp analysis data is shown in Table I. It is apparent that pulps of entirely different fiber characteristics are produced with regard to fiber length, hardwood content and proportions of spring and summerwood fibers, but with the same bleachability (permanganate number).

The pulp from stream A was directed to a paper machine producing tabulating card stock where paper was prepared with improved strength and printing characteristics, while that from stream B was directed to a tissue machine manufacturing creped towel with improved softness, handfeel and absorbency.

The fiber length fractionation data was obtained via the Bauer McNett method as per TAPPI standards.

TABLE I Unbleached Bleached Thickener 'Ihickener Washer Washer A B A B 14 Mesh, Fraction Percent 28 Mesh, Fraction Percent.-- Hardwood, Percent Pulp Production, tons/noun. Percent of Total Pulp-. Pennanganate No Brightness (photo-volt) Ratio, Summerwood/Springwood Fibers EXAMPLE II In another sulfite pulp and paper operation similar to Example I, the chip proportions fed to the digester were changed such that the wood blend contained about 30% hardwood. The operation was conducted as in Example I and depicted in FIGURE 1. The results were as fol- It is further apparent from the above that the pulp has been separated into streams with widely differing fiber characteristics. For example, the chlorine demand of stream A is different from the chlorine demand of stream B. This property of the pulp fraction is useful in adjusting the operating conditions of the pulp processing as well as the papermaking route.

EXAMPLE III In a sulfite operation employing 25% hardwood and 75% softwood similar to that of Example II, the pulp 9 was separated into st-mains A and is as in FIGURE 1. The results were 'as follows:

It is apparent that at essentially the same freeness, the two pulps A and B have entirely different fiber length characteristics. In stream A, there is a wide distribution of long, medium and short fibers; while in stream B, the fibers are predominantly of the medium length varieties.

EXAMPLE IV In a Mitscherlich type acid sulfite pulping operation similar to that depicted in FIGURE 1, a single hardwood species; i.e., populus tremuloids, was digested and the pulp processed as in Example I to produce the screened pulp. This stock was pumped at 0.5% consistency to the 3-inch primary liquid cyclones equipped with a /2 inch reject discharge orifice, such that the accepts constituted about 10% by weight of the feed, while the primary rejects contained the remaining 90% of the feed stock. These primary rejects were processed through three further stages of liquid cyclones as in Example I, with recycle as shown in FIGURE 1. The secondary, tertiary and quaternary cyclones were equipped with A; inch reject orifices as in Example I, to culminate finally with a waste reject discharge of dirt and shives of 1.4% of the original pulp.

The primary accepted pulp of stream A was processed as in FIGURE 1, and utilized for a component of a papermaking furnish to produce a packaging grade of paper. The secondary accepted stock of stream B was processed separately as in FIGURE 1 to produce a pulp which was utilized as the major component in a soft absorbent tissue.

The properties of'the predominant fraction are compared with those of the whole pulp in Table IV. It was noted by microscopical examination of the B stream thata substantial reduction in the number of radial parenchyma cells had taken place during the cyclone fractionation, and were present predominantly in the stream A. Moreover, on staining with Sudan II (manufactured by The Matheson Company, Inc., East Rutherford, New Jersey) and examining microscopically, it was observed that the pitch was for the most part contained within these radial parenchyrna cells.

This is substantiated in Table IV, where the pitch, by alcohol-benzene extraction, is considerably reduced in stream B, with a corresponding improvement of the aged absorbency characteristics. These data were obtained by the accelerated aging of the paper sheets for 10 minutes at 300 F. and determining the time in seconds for the 10 complete absorption of 0.1 cc. of water added to the surface of the sheets as per TAPPI specifications. It is to be noted also that the bleaching requirements have been changed by the cyclone fractionation.

EXAMPLE V In another Mitscherlich acid sulfite pulping operation similar to Example IV, midwestern poplar wood was pulped and processed to screened pulp as in FIGURE 1. Thereafter, the pulp was fractionated in a series of liquid cyclones arranged as in FIGURE 2.

The cyclones were 3-inch diameter and operated with a /2-inch reject discharge orifice to produce the fractional proportions of Table V.

The primary and secondary accepts were combined to produce stream A (FIGURE 2) while the tertiary and quaternary accepts were combined to form stream B of FIGURE 2.

Stream A was thickened, bleached and washed as in FIGURE 1 and fed as a component furnish to a paper machine producing a wax base stock for the manufacture of wax paper, while stream B was separately processed as in FIGURE 1 to produce a component of a furnish for a paper machine producing tissue stock for paper dinner napkin manufacture.

It is apparent from the data of Table V that the absorbency characteristics of the fractions constituting stream B are greatly improved over those of the original pulp. Moreover, the fractions constituting stream A were observed microscopically to contain the majority of the radial parenchyma cells containing resinous materials which contributed to the water resistant characteristics of this pulp stream and accordingly directed its advantageous use in wax base stock paper.

EXAMPLE VI In an alkaline pulping operation of the kraft or sulfate type, southern pine was pulped, deknotted, washed and screened as in FIGURE 1. The pulp was then fractionated through a series of liquid cyclones as in Example V according to the arrangement of FIGURE 2. The primary and secondary accepts were combined to produce stream A while the tertiary and quaternary accepts were combined to produce stream B. These streams were thickened, bleached and Washed as in FIGURE 1, and bleached stream A was directed as a component furnish to a paper machine producing a strong notion bag paper, while the bleached stream B was directed to a paper machine producing a printing grade of specialty paper.

It is obvious from the data of Table VI that the components of stream A contain a considerably larger proportion of long fibers than do those of stream B, and hence their papermaking characteristics are quite different.

1 1 EXAMPLE VII In a kraft sulfate operation pulping southern pine, the stock was processed according to the flow diagram of Bleached stream B was directed to the paper manufacture of a bag stock with particular stifiness qualities.

Microscopical examination of the cross-section of the fibrous components of the original feed pulp in FIG- BR fi fi i. onfice i 25232: g 2 5 URE 4 are compared with the cross-sections of the fibrous was 21m so a ep lmarya 6p components in pulp fractions in streams A and B in Ofthetotal feedh A FIGURE 6 and FIGURE 5, respectively.

.Streams A and B Well? bleached. and Strean The widely differing pulp characteristics are manidlrected to paper machme Producing a g assme e tested in these photomicrographs and testify to the imof P 1 f Stream B Was directed to a mac me 10 proved utility of this process for different papermaking producing mrmeograph paper. T Propemes of the purposes Pulps are shownm Table The original pulp contains a mixture of both spring- TABLE VII wood and summerwood fibers, stream A contains predominantly the ribbon-like, flexible, large surface area Breaking Length (meters) springwood fibers; while Stream B contains predominantly the rod-like, stiff summerwood fibers. The relative pro- B a ing T (m 0 5 15 25 35 45 duction rates of the various fractional components of these streams are shown in Table VIII. l eed Pulp (Operation 9) 3, 500 5, 600 7, 500 s, 400 9, 000 9, 400 9, 600 TABLE VIII Stream A s, 600 8,400 8,800 9, 300 9, 500 9, 700 9,900 Percent of stream B 3, 200 5,000 6,400 7,500 8, 300 8,9 9,300 Pulp; original f d Screened Pulp (Operation 9) 100 It is apparent from Table VII that th r fi g Chaf- Primary Accepts 5.7 acberistics of the tWO pulps are entirely iff Stream Primary Rejects 94.3 A is an easy beating pulp With rapid Streng development Secondary Accepts 6.1 and resembles somewhat a Slllfi e pulp- HOWBVEF, Stream Secondary Rejects 88.2 B is a typical hard kraft ulp with parti l rly slow Tertiary Accepts 72.0 strength development. It is obvious t at th p p i g Tertiary Rejects 16.2 qualities of these tWO pulps diff r gre ly- It is also Quaternary Accepts 14.6 obvious that these properties ar us f l in the P p P E- Qua-ternary Rejects (to sewer) 1.6 paring, as well as papermaking process to adjust t e processing conditions to achieve the most effective use EXAMPLE IX of the various pulp fractions. Depithed 'bagasse was digested in a two stage alkaline pulping process, the first stage of which was similar to EXAMPLE VIII that depicted in FIGURE 1. After the first pulping stage, In a kraft operat n digesting gi p as i the partially digested fiber was screened as in FIGURE 1, URE 1, th screened ulp from operation 9 was proc ss d and the insufiiciently pulped screenings were subjected to through a series of liquid cyclones according to the flow a d stage lk li digestion Th Screened pulp diagram of FIGURE 3.- The cyclones W re 3-in h di mfrom the first digestion stage was rocessed through a eter and the primary, secondary units had /2-inch reject 40 series of liquid cyclones as in FIGURE 1, with the priorifices while the tertiary and quaternary units had a mary cyclones equipped with As-inch reject orifices. /s-inCh orifice. The inlet pressures to all of the cyclones Similar experimental fractionation runs were made with were maintained at 40 p.s.i.g., the primary and secondary the primary reject orifice set at inch and A inch. The accepts were combined to produce stream A, the quaterresults were as follows:

TABLE IX Bauer McNett Classification Primary Reject Percent Total Freeness, Breaking Spec. vol, Orifice (inches) Pulp From- Pulp on 150 Mesh Thm 150M651), cc. cc./gr. Mullen, lb.

percent percent Stream Au- 57.4 54.8 45. 104 5, 604 1.38 18,5 Stream B 42. 6 77. 4 22. 6 596 2, 435 2. 00 3.8 34 Stream A 50.8 68.5 31.5 119 4, 631 1.60 1 .0 Stream B 49. 2 84. 3 15. 7 549 2, 203 2.18 a. 5 M Stream 37.7 48.0 52.0 67 4, 433 1.41 Stream B 62.3 86. 0 14. 0 49s 2, 530 1.80 7. 0

nary accepts formed stream B, while the tertiary accepts formed stream C.

Each of these streams was processed separately as in FIGURE 1 to result in three pulps, two entirely different; i.e., streams A and B and a third intermediate pulp, stream C, somewhat similar in properties to the whole original pulp.

Streams A and B were bleached separately, while stream C was processed unbleached and utilized for the production of a brown wrapping paper.

Bleached stream A was directed to a paper machine and utilized as a component of a furnish producing a grade of ofiset paper with particular printing qualities such that fiber flexibilities enhanced the surface bonding of the sheet and reduced substantially the collection of fibers transferred from the sheet to the printingrolls.

It is again apparent that the process has separated the original pulp into two streams with entirely different fiber lengths, drainage characteristics, strengths. and bulks. Stream A was utilized as a component in a. papermaking furnish for corrugated packaging media, while stream B was used in a paperboard for impregnating purposes.

EXAMPLE X TABLE X Breaking Bauer-McNett Sample Percent of Freeness, Length, TAPPI Tear Mullen, lb. Spec. vo1.,

Feed cc. meters Factor cc./g.

Feed 740 3, 520 178 18.0 1. 91 69. 3 16. 6 8.0 1st run Accepts 7. 2 560 6, 680 188 40. 3 1. 62 83. 5 8. 9 3. 8 2nd run Accepts 54. 8 690 3, 280 178 19. 5 1. 83 72. 4 15. 2 7. 3rd run Accepts. 31. 5 729 3, 240 138 14. 0 1. 94 69. 6 11. 2 11. 2 3rd run Rejects 6. 5 747 2, 670 117 11. 9 2. 00 55. 0 25. 1 13. 7

From the above data, it is obvious that pulps of differ- C.C.S.F. and run to make an 18 lb./ream flat sheet. The

ent characteristics may be processed at different conditions before the pulps are used in a papermaking machine.

The data also show that the same species of wood yields pulps having entirely different properties and uses. Moreover, the high throughput operations commonly encountered in pulp and paper mills are compatible with the present invention as any size of mill can be converted to the novel method of operation.

EXAMPLE XI A. Fractionation properties of the paper are given in the following table.

TABLE XII.-MACHINE PAPER OF NORTHEASTERN 80% SOFTWOOD AND 20% HARDWOOD PULP FRACTIONS Accepts Rejects Percent of Original Pulp 54. 6 45. 4 C.C.S.F 449 420 Breaking Length (MD/CD), meters- 7, 710/4, 780 6, 990/3, 630 Burst (Mullen), lbs- 12.8 8.9 TAPPI Tear Factor (MD/CD) 52/43 44/38 Specific Volume, cc./g .4 1.36 1. 30 Opacity, percent- 45. 1 41. 9 Brightness, G.E 76. 0 78. 2 Basis Weight, lbs/ream 18. 8 17. 9

The paper machine run data show that the accepts pulp fraction gives a stronger sheet than the rejects pulp fraction with respect to breaking length, tear factor and Mullen even when both sheets are beaten to the same freeness. The opacity of the accepts fraction is slightly more than that of the rejects. The brightness of the accepts is 2 points below that of the rejects due to the presence of larger amount of parenchyma cells which makes the pulp more difiicult to bleach.

TABLE XI.BEATER RUNS OF FRACTIONS OF UNBLEACHED PULP FROM 80% SOFTWOOD/20% HARDWOOD CHIPS RUN 169.6/30.4ACCEPTS/REJECTS PULP FRACTION RATIO C.C.S.F.* Breaking Length, Mullen Factor, lbs. TAPPI Tear Specific Volume, Basis Weight, Beating Time meters Factor cc./g. g./M

(Minutes) A R A R A R A R A R A R RUN 254.6/45.4-ACCEPTS/REJECTS PULP FRACTION RATIO '*Canadian Standard Freeness, cc. A=Accepts Stream Fraction.

B. Paper machine runs The two fractions obtained in the run with 54.6% accepts and 45.4% rejects were bleached and run under sub stantially identical conditions on a 10 paper machine. Both fractions were given a single stage hypochlorite bleach at 10% consistency with 100% chlorine demand and bleached to trace residual according to TAPPI stand- R= Rejects Stream Fraction.

ards. The two fractions were beaten to between 400-450 75 vice versa.

Further, from the above examples, it is readily apparent that the various chemical and physical properties of the pulp fractions may be used to adjust the operating rates, conditions and demands both upstream, e.g., in the chip preparing stages, digesting stages, etc., as well as downstream, e.g,, the bleaching, beating and paper producing and also finally, in final paper product utilization. The flexibility obtained by the novel method is one of the improvements over the heretofore rather inflexible pulp and papermaking processes.

We claim:

1. A continuous method of operating a pulp to paper Web producing route comprising the steps of:

(A) pulping at least two species of cellulose containing material possessing various fractions of cellulose pulp of different chemical and physical properties associated with each species of cellulose containing material and its growth cycle, thereby obtaining a screened pulp consisting of mixed fractions of pulp;

(B) separating the various fractions by:

(1) introducing the screened pulp in a first liquid means pulp fraction separating zone,

(a) combining the accept effiuent recycled to said second zone from a third liquid means pulp fraction separating zone accept effiuent which, in turn, has been made up of a fourth liquid means pulp fraction separating zone accept effluent combined and introduced into the third liquid zone with the reject eflluent from said second liquid zone, and

(b) the said remainder of pulp from said first zone and further pulp processsing and use in a second paper web producing route;

2. A continuous method of operating a pulp to paper web producing route comprising the steps of:

(B) separating the various pulp fractions by:

(1) introducing the screened pulp into a first liquid means pulp fraction separating zone,

(2) taking a portion of a pulp fraction from the 'first liquid means pulp fraction separating zone and combining it with the accept fraction from a second liquid means pulp fraction separating zone for further pulp processing and use in a first paper web producing route,

(3) taking the reject fractions from the second liquid zone and introducing said fractions into 16 the third liquid means pulp fraction separating zone, (4) taking a'portion of a pulp fraction from the third liquid means pulp fraction separating zone 5 and combining it with the accept fractions from the fourth liquid means pulp fraction separating zone for further pulp processing and use in a first paper web producing route,

3. A continuous method of operating a pulp to paper 25 Web producing route comprising the steps of:

(B) separating the various pulp fractions by:

(1) introducing the screened pulp into a first liquid cyclone means pulp fraction separating zone,

(2) taking a portion of a pulp accepts fraction from the first liquid cyclone means pulp fraction separating zone and combining it with the accepts fraction from a second liquid cyclone means pulp fraction separating zone, wherein said second zone further is separating the rejects from said first zone and using the two combined fractions for further pulp processing and use in a first paper web producing route,

(5) said first, second, third and fourth liquid pulp fraction separating zones being characterized by the obtained pulp fractions possessing the preselected differing physical and chemical properties when said pulp fractions are further subjected to subsequent pulp processing steps,

4. The method of claim 1 wherein the separating step (B), characterized by the pulp processing properties, is operated producing secondary accept fraction containing a reduced amount of parenchyma cells in respect to the total amount of perenchyma cells present in the wood pulped, and requiring less chlorine demand for given brightness level in respect to the chlorine demand for the unfractionated pulp; and the separating step is further characterized by the final paper web product'of the sec- 0nd paper producing route being of improved absorbency 2,913,362 11/1959 Cusi 162-55 properties. 2,972,171 2/ 1961 Heritage 1 6255 X 3,085,927 4/1963 Pesch 16255 References Cited by the Examiner UNITED STATES P 5 DONALL H. SYLVESTER, Primary Examiner.

1,809,312 6/1931 Richter 162--55 HOWARD CAINE, Examiner-

Claims

1. A CONTINUOUS METHOD OF OPERATING A PULP TO PAPER WEB PRODUCING ROUTE COMPRISING THE STEPS OF; (A) PULPING AT LEAST TWO SPECIES OF CELLULOSE CONTAINING MATERIAL PROCESSING VARIOUS FRACTIONS OF CELLULOSE PULP OF DIFFERENT CHEMICAL AND PHYSICAL PROPERTIES ASSOCIATED WITH EACH SPECIES OF CELLULOSE CONTAINING MATERIAL AND ITS GROWTH CYCLE, THEREBY OBTAINING A SCREENED PULP CONSISTING OF MIXED FRACTIONS OF PULP; (B) SEPARATING THE VARIOUS FRACTIONS BY; (1) INTRODUCING THE SCREENED PULP IN A FIRST LIQUID MEANS PULP FRACTION SEPARATING ZONE, (2) TAKING A PORTION OF PULP FROM THE FIRST LIQUID MEANS PULP FRACTION SEPARATING ZONE FOR FURTHER PULP PROCESSING AND USE IN A FIRST PAPER WEB PRODUCING ROUTE, (3) TAKING THE REMAINDER OF PULP FROM THE FIRST LIQUID MEANS PULP FRACTION SEPARATING ZONE AND INTRODUCING SAID REMAINDER INTO A SECOND LIQUID MEANS PULP FRACTION SEPARATING ZONE, (4) TAKING A PART OF THE SECOND LIQUID MEANS PULP FRACTION SEPARATING ZONE ACCEPT EFFLUENT OBTAINED BY: (A) COMBINING THE ACCEPT EFFLUENT RECYCLED TO SAID SECOND ZONE FROM A THIRD LIQUID MEANS PULP FRACTION SEPARATING ZONE ACCEPT EFFLUENT WHICH, IN TURN, HAS BEEN MADE UP OF A FOURTH LIQUID MEANS PULP FRACTION SEPARATING ZONE ACCEPT EFFLUENT COMBINED AND INTRODUCED INTO THE THIRD LIQUID ZONE WITH THE REJECT EFFLUENT FROM SAID SECOND LIQUID ZONE, AND (B) THE SAID REMAINDER OF PULP FROM SAID FIRST ZONE AND FURTHE PULP PROCESSING AND USE IN A SECOND PAPER WEB PRODUCING ROUTE; (5) SAID FIRST, SECOND, THIRD AND FOURTH LIQUID PULP FRACTION SEPARATING ZONES BEING CHARACTERIZED BY THE OBTAINED PULP FRACTIONS POSSESSING THE PRESELECTED DIFFERING PHYSICAL AND CHEMICAL PROPERTIES WHEN SAID PULP FRACTIONS ARE FURTHER SUBJECTED TO SUBSEQUENT PULP PROCESSING STEPS; (6) THE SAID FIRST, SECOND, THIRD AND FOURTH LIQUID PULP FRACTION SEPARATING ZONES BEING FURTHER CHARACTERIZED BY SAID PULP FRACTIONS POSESSING THE SELECTED PROPERTIES WHEN SAID PULP FRACTIONS ARE INCORPORATED IN THE FINAL PAPER WEB.