Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/04—Addition to the pulp; After-treatment of added substances in the pulp
  • D21H23/06—Controlling the addition
  • D21H23/08—Controlling the addition by measuring pulp properties, e.g. zeta potential, pH
  • D21H23/10—Controlling the addition by measuring pulp properties, e.g. zeta potential, pH at least two kinds of compounds being added
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/02—Agents for preventing deposition on the paper mill equipment, e.g. pitch or slime control

Definitions

• This invention relates to pitch control in both pulping and papermaking operations, especially, and for the first time in a commercially successful manner, in furnishes made by mechanical pulping processes which contain groundwood pulp in amounts greater than about 10% by weight based on the total dry weight of pulp in the furnish.
• This invention also relates to pitch control in mills which utilize other kinds of furnishes, e.g., ones containing bleached or unbleached sulfate or Kraft pulp, or bleached or unbleached sulfite pulp, and especially furnishes in which groundwood pulp is present in amounts greater than about 10% by weight.
• this invention relates to preventing the buildup of nuisance deposits caused by resinous materials such as pitch and pitch colloids on papermaking equipment and to the dispersion of such materials in the paper being made in the form of tiny, non-harmful aggregated or agglomerated particles instead of larger, harmful globs.
• This invention also relates to particular combinations of substances for use in pitch control processes carried out in accordance with this invention and to methods of preparing such combinations.
• Wood is pulped to produce papermaking fibers by any of several different processes, each of which is designed to take maximum advantage of the characteristics of the
• EHST ⁇ particular type of wood fibers obtained in the paper ultimately produced.
• Paper used as newsprint or in other printing applications need not have the same degree of strength as packaging and container papers. Consequently, the mechanical pulping processes used to make furnishes for newsprint and like papers, including groundwood, thermomechanical (TMP) and chemical thermomechanical (CTMP) pulp processes, are designed to give higher yields of fibers of shorter average lengths, and more fines, than are obtained using typical chemical pulping processes. And while papermaking fibers obtained by mechanical pulping have certain properties that are in general undesirable -low brightness, color reversion with time and high resin contents - this is usually tolerated because of the cost savings achievable using these high yield pulping processes.
• TMP thermomechanical
• CMP chemical thermomechanical
• Pulps or furnishes used in continuous processes for making paper generally consist of fibers, fines, fillers and chemicals suspended or dissolved in water. It is desirable to retain the fines in the paper produced, not onl for purposes of pollution control but also to insure the greatest possible utilization of the wood being pulped and the other substances added and hence increase profitability.
• Such fines suspensions may contain pitch colloids not retained initially in the fiber mat, cellulose fines and hemicellulose, recirculated talc, kaolin or other fillers and pigments, and water soluble materials such as alum. Fines create a number of manufacturing problems, chiefly due to the difficulty of separating water used to make paper from the papermaking fibers while retaining fines with the fibers.
• Fines not retained with the fibers recirculate with the process water, and increasingly large concentrations of fines in the process water adversely affect drainage and paper formation. Reduced drainage can slow papermaking speed and increase the cost of making the paper. Poor paper formation reduces the quality of the manufactured sheet, causes production losses, or both, and thus can also increase manufacturing cost. The inability to incorporate fines in the paper and consequently the waste of this material, and particularly the paper fines portion of the pulp product, will further increase costs.
• Fines retention does not necessarily mean retention of all the fines present.
• Prior art processes typically used to make the more expensive fine papers focus on the retention of fillers and pigments in the paper while maintaining wet strength and adequate filler loading.
• Newsprint is relatively inexpensive in comparison to finer grades of paper. Additives such as fillers and retention aids are not normally used in newsprint, since to do so would greatly increase its cost.
• papermaking pulps are usually made in one of three ways: by chemical, semichemical, or mechanical pulping processes.
• chemical pulps e.g., by the Kraft or sulfate and sulfite processes
• cellulose fibers constituting the pulp are separated from other wood components by chemical reagents.
• Kraft and bleached pulps contain minor amounts of pitch, present as saponified pitch or pitch soap.
• Semichemical processes usually used on deciduous wood species, involve a mild chemical action followed by mechanical attrition.
• Mechanical pulps are prepared by grinding whole logs, without prior debarking, and thus the pulp obtained contains all of the constituents of the log, including pitch.
• Mechanical pulps such as groundwood and thermomechanical pulps commonly used in newsprint mills, sulfite mills and like operations are typically prepared from nondeciduous wood species such as Sitka Spruce, Norway Pine and the like.
• the large amounts of pitch found in mechanical pulps cause severe pitch problems in papermaking facilities using them, and yet despite extensive studies no completely satisfactory method for pitch control in processes used to make newsprint has been developed prior to this invention.
• Groundwood pulp contains large amounts of completely non-saponified pitch in the form of colloidal dispersions whose particles generally range in size from about 0.2 to about 2 ⁇ m and normally have an electronegativity of from about -10 to about -35 mV.
• Thermomechanical pulps contain the same types of pitch found in groundwood pulps but generally in greater amounts.
• Resins carried over from wood or bark pulped to make papermaking furnishes are complex mixtures of organic compounds which, because they are insoluble in water, will deposit on the fibers in the furnish and on the papermaking equipment. Aggregations of these resinous materials of larger than colloidal dimensions will interfere with the manufacture of high quality paper. Such resinous materials will, for simplicity's sake, be referred to collectively hereinafter as pitch or pitch colloids.
• Pitch colloids found in pulp generally are oleophilic, water insoluble, low molecular weight, relatively non-polar coagulable resins which are usually made up of at least several of the following components: fatty acids and resin acids having ionizable hydrophilic groups, esters of these acids, sterols, diglycerides, triglycerides, terpenes, waxes and various alcohols, hydrocarbons, and neutral compounds associated with these resins.
• the degree of fluidity of these resins is governed by the ratio of fatty acids to resin acids, the age of the wood, and the degree of oxidation or polymerization of the pitch. These factors determine the resins' deposition tendencies.
• such resins are present on the surfaces of the fibers in the form of thin patches and droplets, inside parenchyma cells, as soluble soaps, and in the form of colloidal droplets dispersed in the process liquid among the fibers.
• Pitch particles have been physically removed from papermaking systems by methods such as pulp fractionation, which involves removing a substantial portion of the colloidal pitch present together with a portion of the pulp fines. Such methods are prohibitively expensive, since they significantly increase the amount of pulp needed to make a given quantity of paper and pulp fines removed in the process are lost.
• alum-based pitch controlled systems in which alum is used alone or together with a base such as sodium hydroxide attempt to control pitch deposition by first dispersing the pitch, if it is not already sufficiently dispersed, and then flocculating it. Microscopic examination of this floe shows very little of the pitch actually attached to the papermaking fibers. Instead, the pitch is largely attached to itself as agglomerates consisting of many pitch particles clustered together. These clusters are small enough to pass through the wire of a newsprint mill and get into the Whitewater system, resulting in pitch buildup. Additionally, alum is extremely corrosive, necessitating rigorous pH control, in high concentration causes drainage and retention aid losses, and in some papers may also contribute to a loss of brightness, or yellowing, with age accompanied by loss of strength.
• Talc per se such as Mistron Vapor talc produced by Cyprus Industrial Minerals Company, has been used to control pitch in pulp and paper mills, usually Kraft or sulfite mills operating at a high enough pH to cause any pitch present to be partially saponified.
• the dispersed pitch particles are adsorbed on the faces of the talc particles and then retained in the paper. Attempts have been made to increase pitch adsorption by increasing the talc's surface area.
• too finely ground talc loses crystallinity and all ability to adsorb pitch; talc's pitch adsorption efficiency appears to peak at a surface area of about 15 square meters per gram.
• European pulp and paper mills are known to use a dual filler retention system in which a naturally occurring cationic bentonite is introduced into the headbox after the last point of high shear, followed by the addition of a high molecular weight anionic polymeric flocculant.
• Bentonite mined from specific deposits has been demonstrated to exhibit a moderate degree of pitch control in addition to filler retention properties. Attempts to replace these specific bentonites with bentonites from other deposits, however, or with mica or
• Modified bentonite clays have also been used as cationic scavengers in mill process water to neutralize fiber fines and other anionic trash.
• Chemical dispersants generally anionic or nonionic in nature, have been used to maintain pitch colloids in a dispersed state in papermaking systems - in the pulp, stock, furnish and Whitewater - to prevent pitch deposition within the system. These dispersants function by charge or steric repulsion phenomena.
• Anionic dispersants for example, impart a still higher electronegative charge to pitch colloid particles, keeping them from touching and flocculating. Some dispersants may also tend to soften and dissolve those pitch deposits already formed.
• chemical dispersants do not attach the pitch to the papermaking fibers, they have proven to be inadequate in solving severe pitch problems, such as those found in groundwood pulp (newsprint) mills. Their use in fact can result in a buildup of pitch in the mill's tightly closed recirculated water system.
• Retention aids usually polymeric in nature, have been used to control pitch to a certain extent by flocculating the dispersed pitch resins.
• pulps containing large amounts of pitch such as groundwood pulps
• anionic trash or "pernicious objectionable ⁇ ” consume large quantities of the added retention aid, thus rendering them ineffective.
• To obtain good flocculation it becomes necessary to add still larger amounts of retention aid, which is at best marginally cost effective.
• the addition of too much retention aid results in overflocculation, adversely affecting the formation of acceptable paper.
• Pelton et al "A Survey of Potential Retention Aids for Newsprint Manufacture,” Paprican, July 1978, notes that retention aids may reduce pitch problems in newsprint mills by flocculating colloidal pitch onto fibers and fines and subsequently incorporating these pitch-coated particles into the paper sheet.
• Pelton et al observed a decrease in the concentration of colloidal pitch when 1 lb/ton of PEO was added to the headbox stock.
• PEO retention aids are, however, of limited applicability, since they are sensitive to shear and thus can be used only at locations in the papermaking process at which relatively low hydrodynamic shear forces are found. PEO is also very sensitive to depolymerization by trace amounts of chlorine and hence cannot be used with chlorine bleached pulps.
• U.S. Patent No. 4,313,790 discloses adding a Kraft lignin or modified Kraft lignin and polyethylene oxide to a mechanical pulp papermaking furnish to increase fines retention and decrease pitch deposition.
• the addition of the Kraft lignin derivative and/or polyethylene oxide is said to decrease the concentration of colloidally dispersed wood resin particles in the white water from 88 x 10 6 to as low as 5 x 10 6 particles per cm 3 .
• Very high molecular weight organic polymers such as PEO used as filler retention aids have not proven effective for flocculating bleached, groundwood or thermomechanical pulp.
• U.S. Patent No. 2,795,545, issued June 11, 1957 to Gluesenkamp discloses adducts prepared by reacting: ". . .inorganic solids that are gel- forming in water and/or that possess ion exchange like properties, e.g., clays [including kaolinite and montmorillonite] , . . . " with:
• polycations see, e.g., column 3, lines 44-61; column 4, lines 9-38; column 5, lines 49-66, column 6, lines 12-39 and column 8, line 32-column 9, line 4. Such "polycations” can then be used:
• Polymers or polymer/filler conglomerates for use as filler or pigment retention aids have also been disclosed in the following patents: acrylamide polymers, U.S. Patent No. 3,052,595; cationic ⁇ tarch-g-poly(N,N' ⁇ methylenebisacrylamide-co-amine) copolymers, U.S. Patent No. 4,278,573; cationic starches, U.S. Patent No. 4,643,804; cationic latexes, U.S. Patent No.
• the aforementioned particulate composite pitch control substances used together with a relatively high molecular weight alkylene oxide polymer, such as a polyethylene oxide having a molecular weight, as determined by intrinsic viscosity measurements, of at least about 500,000 and up to about 12,000,000, can provide further improvements in pitch control and fines retention in all types of pulping and papermaking proces ⁇ es, but once again particularly in ones using mechanical furnishes.
• a relatively high molecular weight alkylene oxide polymer such as a polyethylene oxide having a molecular weight, as determined by intrinsic viscosity measurements, of at least about 500,000 and up to about 12,000,000
• pitch control systems comprising alum and the aforementioned particulate composite pitch control substances, with or without a relatively high molecular weight alkylene oxide polymer, can provide still further improvements in pitch control and fines retention in all types of pulping and papermaking processes, and once again particularly in ones using mechanical furnishes. It i ⁇ therefore an object of thi ⁇ invention to control pitch in pulp and papermaking facilities.
• a further object of thi ⁇ invention is to provide a novel pitch control method which also improves fines retention and drainage and lowers waste treatment costs in all types of pulping and papermaking processes.
• a still further object of this invention is to provide novel combinations including particulate composite pitch control substances for use in practicing this invention.
• Another object of this invention is to provide pitch control, fines retention-improving and drainage-improving compositions comprising such combinations including particulate composite pitch control substances and a relatively high molecular weight alkylene oxide polymer.
• Yet another object of this invention is to provide pitch control, fines retention-improving and drainage- improving compositions comprising alum and the aforementioned particulate composite pitch control substances, with or without a relatively high molecular weight alkylene oxide polymer.
• FIG. 1 is a graphic representation comparing the amounts of pitch removed from a newsprint furnish by talc alone (Sample A) , a cationic talc pitch control substance prepared in accordance with this invention (Sample B) and cationic kaolin, cationic kaolin/alum, cationic kaolin/PEO and cationic kaolin/alum/PEO pitch control sub ⁇ tances also prepared in accordance with this invention (Samples C-H, inclusive) .
• FIGS. 2 and 3 are graphic representations comparing pitch reduction in a groundwood pulp accomplished by the addition of a cationic polymer itself without kaolin (FIG. 2) and by the same polymer added as a pre-adsorbed particulate composite on kaolin (FIG. 3) .
• FIGS. 4 and 5 are computer-generated graphic representations illustrating the effect on pitch content in a groundwood pulp achieved by adding a cationic polymer as a pre-adsorbed particulate compo ⁇ ite on kaolin, adding the same composite plus alum, and adding alum alone.
• the water ⁇ oluble cationic polymer is first dissolved in water and contacted with the es ⁇ entially water insoluble particulate substrate. This results in the polymer being irreversibly ad ⁇ orbed onto the ⁇ urface of the ⁇ ub ⁇ trate, thereby rendering the polymer insoluble and immobile. While we do not wish to be bound by any theory or mechanism advanced to explain the operation of this invention, it appears that the strongly electropositive surface of the thus- obtained stable, water dispersible, three dimensional particulate composite pitch control substance, which results from the adsorbed polymer's cationic charge, attracts negatively charged pitch or pitch colloid and adsorbs it onto the particulate composite's surface.
• the resulting discrete pitch-containing particulate aggregate formed in the furnish whether because of electropositive ⁇ urface charge remaining after adsorption of pitch or pitch colloid onto the particulate composite's surface, the size or dimensions of the aggregate formed, or some other factor, will be retained in finely dispersed form within the paper sheet ultimately produced.
• the particulate composite substances of thi ⁇ invention have been found to be many times more efficient in controlling pitch than the cationic polymer components thereof used by themselves; see Example XI hereinbelow.
• any essentially water-insoluble particulate organic or inorganic sub ⁇ tance can be employed a ⁇ the ⁇ ub ⁇ trate, phyllo ⁇ ilicate mineral ⁇ : kaolin, talc, mica, montmorillonite, chlorite, p ⁇ eudolayer silicates, etc.; see U.S. Patents Nos. 4,391,733 and 4,391,734, issued July 5, 1983 to Lamar et al and Ferreira et al, respectively, and especially kaolin, are particularly preferred a ⁇ the essentially water-insoluble particulate sub ⁇ trate onto which a cationic polymer is adsorbed to produce the particulate composite pitch control substances of this invention.
• Kaolin is a naturally hydrophilic clay mineral consisting es ⁇ entially of hydrous aluminum silicates in the form of alternating silicon-oxide and al minum- hydroxyl layers or ⁇ heets having an approximate composition of A1 2 0 3 »2H 2 0. In its natural state kaolin has a strong negative zeta potential and little or no tendency to adsorb pitch.
• essentially water-insoluble particulate inorganic substrates which can be used in practicing this invention include materials such as titanium dioxide, aluminum hydrate, hydrated silica, serpentine, calcite (calcium carbonate) , and the like.
• Essentially water- insoluble particles suitable for use as substrates in practicing this invention can range in particle size from fine, about 0.1 ⁇ m, to coarse, about 40 ⁇ m.
• e ⁇ entially water-insoluble particles are made cationic for u ⁇ e in practicing this invention by adsorbing on the particles* surfaces a cationic polymer.
• Suitable cationic polymers will be ones which exhibit the ability to change the zeta potential of the particulate substrate, whether negative or ⁇ omewhat po ⁇ itive, to a zeta potential ⁇ ufficiently po ⁇ itive to provide effective pitch control in accordance with the teachings of this invention.
• kaolin in its natural state has a zeta potential of about -40 mV.
• Useful cationic polymers for this purpose include, but are not limited to, salts, such as quaternary ammonium salts and acid salts, of aminoacrylates and salt ⁇ , ⁇ uch as quaternary ammonium salt ⁇ and acid salts, of diallylamines which may contain substituents such as carboxylate, cyano, ether, amino (primary, secondary or tertiary) , amide, hydrazide and hydroxyl groups, and the like, whose zeta potentials are ⁇ ufficiently positive to provide particulate composite sub ⁇ tance ⁇ having zeta potentials of at lea ⁇ t about +30 mV, and preferably from about +60 to about +80 mV (about +0.06 volt to about +0.08 volt) or above.
• cationic polymers are poly- fa Iky ltr imethy lammonium chlorides) , poly- f a Iky ltr imethy lammon ium bro
• dialkyldiallylammonium halides such as poly (diallyl- dimethylammonium chloride) and poly (diallyldi- methylammonium bromide) , poly ( ethacryloyloxy- ethyltrimethylammonium methyl sulfate) , poly-
• Another class of cationic polymers useful in practicing this invention includes naturally occurring polymers such as casein, chitosan and derivatives thereof.
• a particularly preferred cationic polymer is poly(diallyldimethylammonium chloride) , which contains the repeating unit:
• n is from about 600 to about 3500, i.e., poly(diallyldimethylammonium chloride) polymers having an average molecular weight, as determined by intrinsic viscosity measurements, of from about 100,000 to about 500,000.
• the addition of the cationic polymer to the substrate particles will generally be carried out at room temperature (about 25°C) , although addition can be carried out at any suitable temperature which will facilitate adsorption of the polymer onto the substrate particles' surfaces. Moderate stirring, e.g., at from about 100 to about 1000 rpm, will also facilitate adsorption.
• the amount of cationic polymer added will be, first of all, that amount sufficient to provide particulate composite pitch control sub ⁇ tance ⁇ having a zeta potential of at least about +30 mV, and preferably a zeta potential of from about +60 to about +80 mV.
• the resulting aqueous slurry of cationic particulate composite pitch control substance will have a solids content ranging from about 40% to about 70%, and preferably from about 50% to about 60%.
• diallyldimethylammonium chloride of 100,000 molecular weight was found to require a polymer: substantially water insoluble substrate ratio of 5 wt.% to give the same effectiveness in combining with pitch particles as the composite of Example I, infra, in which a counterpart polymer of 400,000 molecular weight is present in a polymer: ⁇ ub ⁇ trate ratio of 2.5 wt.%.
• a preferred ratio of polymer to substantially water insoluble particulate substrate can easily be determined experimentally.
• a slow but steady increase in the effectivenes ⁇ of the composite substance in combing with pitch particles Effectiveness becomes more dramatic as this ratio continues to be increase,d until the point is reached where effectivenes levels off, at which point further additions of cationic polymer to the substrate produce no further increase ⁇ in effectiveness.
• a cationic polymer: substrate ratio of 2.5% was found to be effective.
• Poly(diallyldimethylammonium chlor:-.5e) is known to have a low affinity for cellulosic materials; Winter, et al. , J.Colloid and Interface Science, Vol. Ill, No. 2, June, 1986, pp. 537-543.
• Low affinity for cellulosic materials, including papermaking fibers may be an important reason for the effectiveness of the particulate composite pitch control ⁇ ub ⁇ tances of this invention, since if the polymer employed in such substances had a strong affinity for cellulosic fibers, the composite sub ⁇ tance, in ⁇ tead of combining with pitch particle ⁇ , would in ⁇ tead combine with the overabundance of cellulosic fiber and fines in the furnish.
• Slurries of cationic particulate composite pitch control sub ⁇ tances useful in practicing this invention can also be prepared by continuously adding an aqueous solution of the cationic polymer, for example poly(diallyldimethylammonium chloride) , to a flowing aqueous slurry of the sub ⁇ trate particles and then passing the resultant aqueous cationic slurry through a static mixer, from which the slurry can then be fed to the wet end of a papermaking machine.
• an aqueous solution of the cationic polymer for example poly(diallyldimethylammonium chloride)
• the relatively high molecular weight alkylene oxide polymers which can be used in conjunction with the above- described cationic .particulate composite pitch control substance ⁇ in practicing thi ⁇ invention are nonionic high molecular weight polymer ⁇ with a molecular weight of at least about 500,000, as determined by intrinsic viscosity measurement ⁇ , and preferably a molecular weight of from about 1,000,000 to about 12,000,000.
• Repre ⁇ entative of ⁇ uch alkylene oxide polymers are ethoxylates, propoxylates and ethoxylate/propoxylates, such as polyethylene glycols ( polyoxyethylenes ) , polypropylene glycols
• polyoxypropylenes polyoxyalkylene ethylene glycol and propylene glycol condensates, tridecyloxypoly-
• Ethylene oxide polymers preferred for use in practicing this invention are represented by the formula: --(-- CH 2 CH 2 0—)— n wherein n 1 is a number such that those polymers will have an average molecular weight of at least about 500,000 up to about 12,000,000.
• the relatively high molecular weight alkylene oxide polymers used in practicing this invention may be supplied as true solution ⁇ in water, as solid products or as dispersion ⁇ in a carrier oil, but in all ca ⁇ e ⁇ they should be dis ⁇ olved in water and added a ⁇ dilute aqueous solution ⁇ during the pulping or papermaking process.
• the cationic particulate composite pitch control substance or a mixture of such sub ⁇ tance ⁇ will ordinarily be added to papermaking pulp (furni ⁇ h) in amounts ranging from about 5 to about 200 lbs., and preferably from about 10 to about 80 lbs., by weight, per short ton (2000 lbs.) of dry paper pulp in the furni ⁇ h.
• the alkylene oxide polymer When a relatively high molecular weight alkylene oxide polymer i ⁇ used together with a cationic particulate composite pitch control substance in practicing this invention, the alkylene oxide polymer will be used in amount ⁇ ranging from about 0.05 to about 2, and preferably from about 0.10 to about 0.50, lbs. per short ton, based on the dry weight of paper pulp in the furnish.
• alum aluminum sulfate or one or more double ⁇ ulfates of trivalent metals such as aluminum and, e.g., a univalent metal such as potassium or sodium, including potassium aluminum sulfate, ammonium aluminum sulfate, and the like
• a cationic particulate composite pitch control substance with or without a relatively high molecular weight alkylene oxide polymer, it will be used in amounts ranging from about 10 to about 80 lbs., and preferably from about 35 to about 50 lbs., per short ton of dry paper pulp in the furnish, and can be added as early in the papermaking system as pos ⁇ ible, e.g., at the grinder ⁇ .
• a cationic particulate compo ⁇ ite pitch control ⁇ ubstance e.g., cationic kaolin
• a cationic particulate compo ⁇ ite pitch control ⁇ ubstance e.g., cationic kaolin
• the relatively high molecular weight alkylene oxide polymer cause ⁇ the formation of a floe in which pitch particle ⁇ adsorbed onto the cationic particulate composite pitch control particles and fine ⁇ are held in the paper sheet in a finely dispersed and innocuous state, preventing their entering into the white water system or beyond.
• the alkylene oxide polymer solution is ideally added after the last point of high shear prior to sheet formation, typically at or close to the headbox but in any event after the refiners. This avoids excessive shear which can adversely impact the alkylene oxide polymer's retention/drainage properties and also en ⁇ ure ⁇ good mixing.
• the pitch control ⁇ ystems of this invention also demonstrate markedly reduced temperature sensitivity compared to PEO used alone, and in fact cationic kaolin/alkylene oxide polymer pitch control sy ⁇ tems prepared in accordance with thi ⁇ invention have been found to exhibit ⁇ lightly increased pitch adsorption capabilities with increased temperatures.
• the following examples are set forth. These example ⁇ are given solely for the purpo ⁇ e of illu ⁇ trating the invention, and should not be considered as expres ⁇ ing limitations unless so set forth in the appended claims. All parts and percentages are by weight, unless otherwise stated.
• An aqueous slurry of cationic kaolin was prepared by mixing at room temperature (about 25°C) with ⁇ tirring at about 1500 rpm for 30 minute ⁇ :
• the thus-obtained slurry was stable, non-settling, non-foaming and sufficiently fluid for easy handling and pumping. It had a total solids content of 60%, contained 50 parts of pol (diallyldimethylammonium chloride) per 2000 parts of kaolin, and exhibited the following properties: Brookfield viscosity (No. 2 spindle) : at 1 rpm 18,200 cp ⁇ at 100 rpm 1,262 cps
• Thixotropic index (determined by dividing vi ⁇ co ⁇ ity at 1 rpm by vi ⁇ co ⁇ ity at 100 rpm) 14.4 Zeta potential (measured using a Laser-Zee Meter) +71.4 mV
• Example III The same groundwood pulp used in Example III above was first treated with 35 lbs. of papermakers' alum/ton of fiber and then with the cationic kaolin slurry of Example I above in the amounts shown in Table III below. Pitch counts were again determined using the dynamic drainage jar. Table III Sample Contents Pitch Counts A Control (35 lbs./ton alum) 77 x 10° particles/cm
• thermomechanical pulp was first treated with 35 lbs. of papermakers' alum/ton of fiber and then with the cationic kaolin slurry of Example I above in the amounts shown in Table IV below. Pitch counts were again determined using the dynamic drainage jar.
• Example VI Pitch counts were determined, using the dynamic drainage jar, for a sample of newsprint furnish, first as- i ⁇ at pH 6.5, next adju ⁇ ted to pH 4.5 with papermaker ⁇ ' alum, and then in the pre ⁇ ence of varying levels of the cationic kaolin slurry of Example I above by itself or together with 0.10 lb ⁇ ./ton of polyethylene oxide (PEO) having a molecular weight of 6.0 x 10°. The re ⁇ ult ⁇ of these runs are given in Table V below. Table V
• Example VII The procedure of Example VII above was repeated in every detail except for the following. Brass plates were substituted for steel (steel and bras ⁇ are prominent among the metal ⁇ urface ⁇ commonly exposed to pitch-containing pulps in pulp and paper mills) . No runs were made using "Mistron Vapor" talc. The amount ⁇ of the cationic kaolin slurry of Example I above which were u ⁇ ed and the amount ⁇ of pitch depo ⁇ ited in each run are given in Table VII below.
• Turbidity in these dynamic drainage jar filtrates is caused by the presence of pitch colloid, fiber fines and other colloidal anionic trash; increase ⁇ in percent transmittance correspond to reductions in turbidity.
• the cationic kaolin ⁇ lurry of Example I is effective in tying up and consequently retaining all such fine particle ⁇ ize material.
• Example X The substances listed in Table IX below were used in the amounts indicated and at the indicated pH's (pH 6.5 was the initial pH of the furni ⁇ h; adju ⁇ tments to pH 4.5 were made using papermaker's alum) to remove pitch from a newsprint furnish containing 50% thermomechanical pulp, 30% groundwood pulp and 20% bleached Kraft pulp. Pitch removal efficiency was determined by passing the pulp slurry through a dynamic drainage jar, examining the filtrate microscopically, and counting pitch colloid particle ⁇ using a hemocytometer.
• Example XI demonstrates that simply adding a cationic polymer itself to a pitch-containing paper pulp is not nearly as effective in controlling pitch as first adsorbing the polymer onto the surfaces of kaolin particles and then adding this substance to the pulp.
• pitch removal was determined by the dynamic drainage jar method.
• FIG. 2 shows that only 1.22 lbs. of the polymer will remove 47% of the pitch present when the polymer is first adsorbed on kaolin.
• FIG. 3 also shows that levels of pitch removal approaching 100% are achievable simply by adding more kaolin-adsorbed polymer.
• Example XII With reference first to computer-generated FIG. 4, the effect on pitch content obtained by adding to pitch- containing groundwood pulp:
• FIG. 4 illustrates still another type of respon ⁇ e ⁇ urface having contours of equal pitch content (i ⁇ opitche ⁇ ) .
• FIG. 5 illustrates still another type of respon ⁇ e ⁇ urface having contours of equal pitch content (i ⁇ opitche ⁇ ) .
• this level of pitch control (a pitch count of approximately 3.0) can be obtained using either 100 lbs./ton of cationic kaolin slurry plus 16 lbs./ton of alum or 7 lbs./ton of cationic kaolin slurry plus 35 lbs./ton of alum.
• the third contour line from the bottom of FIG. 5 shows that this level of pitch control (a pitch count of approximately 5.0) can be obtained using either 100 lbs./ton of cationic kaolin ⁇ lurry and no alum or 5 lbs./ton of cationic kaolin slurry plus 35 lbs./ton of alum. This gives the papermaker great latitude in his selection of a pitch control system embodying this invention as well a ⁇ in the alum (or pH) level at which he choo ⁇ e ⁇ to operate.

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• 1989
  • 1989-01-05 NZ NZ22752689A patent/NZ227526A/en unknown
  • 1989-01-06 JP JP50164589A patent/JPH03502591A/ja active Pending
  • 1989-01-06 WO PCT/US1989/000025 patent/WO1989006294A1/en not_active Application Discontinuation
  • 1989-01-06 BR BR898904545A patent/BR8904545A/pt not_active Application Discontinuation
  • 1989-01-06 AU AU29373/89A patent/AU616237B2/en not_active Ceased
  • 1989-01-06 EP EP19890901770 patent/EP0374196A4/en not_active Withdrawn
  • 1989-01-07 ES ES8900056A patent/ES2010072A6/es not_active Expired
  • 1989-09-06 FI FI894197A patent/FI894197A0/fi not_active IP Right Cessation
  • 1989-09-06 DK DK441289A patent/DK441289A/da not_active Application Discontinuation

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