Classifications

• • 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
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/08—Removal of fats, resins, pitch or waxes; Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching
  • D21C9/086—Removal of fats, resins, pitch or waxes; Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching with organic compounds or compositions comprising organic compounds
• • 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

• the present invention relates to methods for inhibiting the deposition of organic contaminants. More particularly, it relates to inhibiting such deposition from pulp in pulp and papermaking systems and from secondary fiber during repulping.
• pitch can be used to refer to deposits composed of organic constituents which may originate from these natural resins, their salts, as well as coating binders, sizing agents, and defoaming chemicals which may be found in the pulp.
• pitch frequently contains inorganic components such as calcium carbonate, talc, clays, titanium, and related materials.
• Stickies is a term that has become increasingly used to describe deposits that occur in systems using recycled fibre. These deposits often contain the same material found in "pitch” deposits in addition to adhesives, hot melts, waxes, and inks. All of the aforementioned materials have many common characteristics including: hydrophobicity, deformability, tackiness, low surface energy, and the potential to cause problems with deposition, quality, and efficiency in the process. Diagram 1 shows the complex relationnship between pitch and stickies discussed here.
• Pitch Stickies Natural Resins (fatty and resin acids, fatty esters, insoluble salts, sterols, etc.)
• X X Defoamers (oil, EBS*, silicate, silicone oils, ethoxylated compounds, etc.)
• X X Sizing Agents (Rosin size, ASA*, AKD*, hydrolysis products insoluble salts, etc.)
• X X Coating Binders PVAC*, SBR*
• X Inks X Hot Melts
• X Contact Adhesives (SBR*, vinyl acrylates, polyisoprene, etc.)
• Organic contaminants can be detrimental to the efficiency of a pulp or paper mill causing both reduced quality and reduced operating efficiency.
• Organic contaminants can deposit on process equipment in papermaking systems resulting in operational difficulties in the systems.
• the deposition of organic contaminants on consistency regulators and other instrument probes can render these components useless.
• Deposits on screens can reduce throughput and upset operation of the system. This deposition can occur not only on metal surfaces in the system, but also on plastic and synthetic surfaces such as machine wires, felts, foils, Uhle boxes and headbox components.
• Pitch control agents of commerce have historically included surfactants, which when added to the system, can stabilize the dispersion of the pitch in the furnish and white water. Stabilization can help prevent the pitch from precipitating out on wires and felts.
• Mineral additives such as talc have also found use and can reduce the tacky nature of pitch by adsorbing finely dispersed pitch particles on their surfaces. This will reduce the degree to which the particles coagulate or agglomerate.
• Polyphosphates have been used to try to maintain the pitch in a finely dispersed state.
• Alum has also been widely used to reduce deposition of pitch and related problems.
• Non-chemical approaches include furnish selection, screening and cleaning, and thermal/mechanical dispersion units.
• Chemical treatment techniques for stickies control include dispersion, detackification, wire passivation and cationic fixation. Chemicals used included talc, polymers, dispersants and surfactants.
• anionic polymers and copolymers of anionic monomers and hydrophobic monomers have been used extensively to prevent pitch deposition of metal soap and other resinous pitch components. See “Pulp and Paper”, by James P. Casey, Vol. II, 2nd Edition, pp.1096-7.
• USA- 3 992 249 discloses the use of certain anionic vinyl polymers carrying hydrophobic-oleophilic and anionic hydrophilic substituents when added prior to the beating operation in the range of about 0.5 parts to 100 parts by weight of the fibrous suspension to inhibit the deposition of adhesive pitch particles on the surfaces of pulp-mill equipment.
• US-A- 4 781 794 (Moreland, November 1988) teaches methods for detackifying adhesive materials contained in secondary fibre.
• the methods comprise adding an unsubstituted methyl ether cellulose derivative to the secondary fibre.
• Methyl cellulose is a representative compound.
• a method for inhibiting the deposition of organic contaminants from pulp in pulp and papermaking systems which comprises treating the pulp and papermaking systems with a hydrophobically modified associative polymer.
• a method for inhibiting the deposition of organic contaminants from secondary fiber during repulping which comprises treating the secondary fiber with a hydrophobically modified associative polymer.
• These associative polymers act to inhibit the deposition when adsorbed onto contaminants or contaminant prone surfaces.
• Common organic contaminants include constituents which occur in the pulp (virgin, recycle or combinations) having the potential to deposit and reduce paper machine performance or paper quality.
• This will include natural resins such as, for example as fatty acids, resin acids, their insoluble salts, fatty esters, sterols and other organic constituents, like ethylene bis-stearamide, waxes, sizing agents, adhesives, hot melts, inks, defoamers, and latexes that may be found to deposit in papermaking systems.
• hydrophobically associative polymer relates to polymers which have two or more hydrophobic regions giving them the capacity to form associative networks by the attraction/interaction of the hydrophobic regions.
• Hydrophobically associating water-soluble polymers possess unusual rheological characteristics which are thought to arise from the intermolecular association of neighbouring hydrophobic substituents.
• the hydrophobic substituents are incorporated onto the polymer through chemical grafting or a suitable co-polymerization procedure.
• the hydrophobic groups are incorporated to a level so as to not render the final modified polymer water insoluble.
• Associative thickeners are water-soluble polymers containing hydrophobic groups which are capable of non-special hydrophobic association, similar to surfactants. See Polymers as Rheology Modifiers, Chapter 12. page 207, Systems Approach to Rheology Control, P.R.Howard, E.L. Leafure, S.T. Rosier and E.J. Schaller.
• hydrophobically modified associative polymers are the hydrophobically modified hydroxyethyl cellulose associative polymers. These polymers are available from Aqualon Company as Natrosol Plus 330 and Plus 430 and previously from Hercules as WSP-D-330. (Natrosol is a Trade Mark.) The hydrophobically modified hydroxyethyl cellulose associate polymers are described by K.G. Shaw and D.P. Liepold, Journal of Coatings Technology 57, No. 727, pp. 63-72 (August, 1985).
• hydrophobically modified associative polymers are the hydrophobically modified associative water-soluble anionic polymers which are derived from ethylenically unsaturated acids such as acrylic acid and methyacrylic acid; ethylenically unsaturated monomers such as 2-acrylamido-2-propane sulfonic acid(AMPS) and 1-allyloxy-2-hydroxypropyl sulfonate and unsaturated acid monomers in general.
• AMPS 2-acrylamido-2-propane sulfonic acid
• Acrylate-based monomers are the preferred monomers in deriving these polymers.
• Alcogum SL70 is thought to be a terpolymer of methacrylic acid, ethyl acrylate, and a nonionic monomeric surfactant.
• the nonionic surfactant monomer consists of a poly(oxyethylene) compound and an alkyl hydrocarbon segment. The components are consistent with the patent literature in an approximate ratio of 40:50:10.
• the Alcogum 296W polymer is the sodium salt of poly(acrylic acid) prepared by the hydrolysis of poly(methyl acrylate) and was found to contain approximately 16 mole percent residual methyl acrylate units.
• the modified associative polymers are hydrophobically substituted acrylamide copolymers. These copolymers result from substitution of an acrylamide monomer to some extent to result in a copolymer. These copolymers can possess the comonomers other than acrylamide with the following structures:
• Other representative modified polymers used in the present invention are hydrophobically substituted polyethylene oxide polymers. These multihydrophobically substituted polymers indicate that two or more hydrophobic groups are desirable for optimum efficiency. These polymers can have hydrophobic groups which are combined to the polyethylene oxide polymer by ester linkages.
• Preferred polyethylene oxide polymers include polyethylene oxide dioleate esters. Mapag 6000 available from PPG/Mazer is a representative polyethylene oxide polymer. (Mapag is a Trade Mark).
• hydrophobically associative thickener polymers based on modified ethylene oxide are also effective deposition control polymers as defined for use in the present invention.
• Pluracol TH922 and TH916 available from BASF are polymers useful in accordance with the present invention.
• a further embodiment of the present invention utilizes associative water-soluble urethane polymers. These polymers have alternating blocks of hydrophobic groups and hydrophilic groups. These polyethylene glycol/ethylene oxide based urethane block polymers may have molecular weights in the range of (10,000 to 2,000,000) and are disclosed in US-A- 4 079 028 and US-A-4 155 892 as paint thickeners. Commercial formulations of these copolymers are available as Acrysol RM-825 and Acrysol RM-1020 from Rohn and Haas. These polymers comprise urethane block copolymers in different carrier fluids.
• Acrysol RM-825 is a 25 percent solids grade of polymer in a mixture of 25 percent butyl carbitol (a diethylene glycol monobutyl ether) and 75 percent water. Similar copolymers are available from Union Carbide Corporation as UCAR SCT 200 and UCAR SCT 275. These compounds are discussed in US-A- 4 496 708. Similar compounds are also available from Henkel Corporation under the trade names DSX 1514 and DSX 1550. These compounds are discussed in US-A- 4 438 225.
• the polymers used in the present invention are effective at controlling the deposition of organic contaminants in papermaking systems. This may include Kraft, acid sulfite, mechanical pulp and recycled fiber systems. For example, deposition in the brown stock washer, screen room and decker system in Kraft papermaking processes can be controlled.
• the term "papermaking system” is meant to include all pulp processes. Generally, it is thought that these polymers can be utilized to prevent deposition on all surfaces from the beginning of the pulp mill to the reel of the papermachine under a variety of pH values and conditions. More specifically, these polymers effectively decrease the deposition not only on metal surfaces but also on plastic and synthetic surfaces such as, for example, machine wires, felt, foils, Uhle boxes and headbox components.
• the polymers may be added to the papermaking system along with other papermaking additives. These can include other polymers, starch and sizing aids.
• the polymers used in the present invention can be added to the pulp at any stage of the papermaking system. They may be added directly to the pulp furnish or sprayed on wires, felts, press rolls or other deposition-prone surfaces. They may be added to the papermaking system neat, as a powder, slurry or in solution; the preferred primary solvent being water but is not limited to such. They may be added specifically and only to a furnish identified as contaminated or may be added to blended pulps. The polymers may be added to the stock at any point prior to the manifestation of the deposition problem and at more than one site when more than one deposition site occurs. Combinations of the above additive methods may also be employed by way of feeding the pulp millstock, feeding to the papermachine furnish, and spraying on the wire and felt simultaneously.
• the effective amount of these polymers to be added to the papermaking system depends on a number of variables, including the pH of the system, hardness of the water, temperature of the water, additional additives, and the organic contaminant type and content of the pulp. Generally, 0.5 parts per million to about 150 parts per million is added to the paper making system. Preferably, from about 10 parts per million to about 50 parts per million is added to the system.
• pitch natural resins, etc.
• pitch could be made to deposit from a 0.5% consistency fiber slurry containing approximately 2000 parts per million of a laboratory pitch preparation by placing the slurry into a metal pan suspended in a laboratory ultrasonic cleaner water bath.
• the slurry contained 0.5% bleached hardwood Kraft fiber, approximately 2000 parts per million of the potassium salt of a fatty acid blend, approximately 200 parts per million calcium from calcium chloride and approximately 300 parts per million sodium carbonate.
• the slurry was maintained at 50 o C and at a pH of 11.
• hydrophobically modified associative polymers are more efficient deposit inhibitors than the unmodified polymers of a related type.
• the polymers used in the present invention are effective at controlling deposition on metal surfaces and under alkaline conditions and specifically referred to typically as "pitch".
• Hydrophobically modified ethylene oxide polymers were also tested according to the procedure described in respect of Table I. The results of this testing appear in Table V. TABLE V Treatment Agent % Control 50 ppm 10 ppm Hydrophobically modified Associative Ethylene Oxide1 Copolymer 95 88 Hydrophobically Modified Associative ethylene oxide2 Copolymer 95 86 1 Available commercially as Pluracol TH922 2 Available commercially as Pluracol TH916 (Pluracol is a Trade Mark)
• water-soluble urethane polymers synthesized using a wide variety of reactive isocyanates, water-soluble dios, branching agents, and terminating groups.
• These polymers constitute polyethylene oxide/polyethylene glycol polymers with urethane linkages. They are synthesized utilizing isocyanate compounds such as, for example, hexamethylene, diisocyanate, toluene diisocyanate, isophorone diisocyanate, and other dihydroxyl reactive materials.
• These polymers are also synthesized utilizing water-soluble diol compounds and can be selected from polyethylene glycol compounds with molecular weights from about 400 to about 1450 and ethylene oxide/propylene oxide block copolymers.
• the isocyanates included hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate and other dihydroxyl reactive materials.
• the water-soluble diols included PEG (Polyethylene Glycol) 400, PEG 600, PEG 1000, PEG 1450, Pluronic L-35 and Pluronic 10R5. (Pluronic is a Trade Mark).
• the branching agents included glycerol and pentaerythritol.
• the terminating groups (monohydroxy compounds) included 2-ethyl hexanol, nonyl phenol, nonyl phenol ethoxylates with 40 and 70 moles E0, and secondary alcohol ethoxylates with 30 moles E0.
• the stickie coupon can be fabricated from any type of adhesive tape that will not disintegrate when placed in water.
• tapes made from a styrenebutadiene rubber and vinylic esters were used. Both of these potential organic contaminants are known to cause problems "stickies" in secondary fiber utilization.
• a second coupon was fabricated from polyester film such as the product marketed as MYLAR by the DuPont Chemical Company. This material was chosen because papermachine forming fabrics are frequently made of polyester which is susceptible to considerable problem caused by stickies.
• the average peel strength of the bond formed between the tape coupon and the polyester coupon was measured with an Instron tensile tester.
• the peel strength of the bond formed between the stickie tape coupon and the polyester coupon was interpreted as a measure of the tendency for an organic contaminant to attach to components of a paper-machine and cause runnability or product quality problems. More specifically, this indicates the tendency of a stickies deposit to form on a plastic surface.
• Table VIII further support the efficacy of the present invention (examples 6-9 of Table VIII) for deposit control on plastic surfaces. They showed better efficacy relative to prior art deposit control agents (examples 1-5 of Table VIII). This demonstrates the effectiveness of nonionic polymers used in the present invention for stickies deposition control.
• Papermaking consists of various processes which can be affected by sudden changes in pH, temperature, dilution (i.e., concentration), shear force, etc. Severe changes in these parameters can cause system shock which adversely impact paper production.
• Deposit control agents that can strongly adsorb onto the organic contaminant surface and resist the desorbing effects of dilution are highly desirable. Not only will deposition control be improved, but also the required dosage will be reduced, while negative side effects, such as forming and wet-end interferences, will be reduced or eliminated.
• Table VIII was modified to examine the effect of dilution on deposition control. Dilution was accomplished by immersing the adhesive tape and MYLAR in distilled water for 30 minutes after the initial immersion. This can be repeated as many times as desired.
• the associative polymers used in the present invention (samples 5-8 of Table X) in this test were very effective after the fourth dilution. They showed better performance relative to prior art deposit control agents (samples 1-4 of Table X). This demonstrates a strong adsorbing power and good resistance to the desorbing effects of dilution.

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• 1993
  • 1993-03-09 CA CA002091272A patent/CA2091272A1/en not_active Abandoned
  • 1993-03-31 NO NO93931206A patent/NO931206L/no not_active Application Discontinuation
  • 1993-04-06 AU AU36743/93A patent/AU663170B2/en not_active Ceased
  • 1993-04-19 EP EP93303007A patent/EP0568229A1/en not_active Ceased
  • 1993-04-28 FI FI931912A patent/FI931912A/fi not_active Application Discontinuation

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