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
  • D21H23/76—Processes or apparatus for adding material to the pulp or to the paper characterised by choice of auxiliary compounds which are added separately from at least one other compound, e.g. to improve the incorporation of the latter or to obtain an enhanced combined effect
  • D21H23/765—Addition of all compounds to the pulp
• • 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
  • D21H21/06—Paper forming aids
  • D21H21/10—Retention agents or drainage improvers
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/37—Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylates
  • D21H17/375—Poly(meth)acrylamide
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/41—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups
  • D21H17/42—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups anionic
  • D21H17/43—Carboxyl groups or derivatives thereof
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/41—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups
  • D21H17/44—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups cationic
  • D21H17/45—Nitrogen-containing groups
  • D21H17/455—Nitrogen-containing groups comprising tertiary amine or being at least partially quaternised
• • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments

Definitions

• the present invention is in the technical field of papermaking and more particularly in the technical field of wet-end additives to papermaking furnish.
• aqueous cellulosic suspension or slurry is formed into a paper sheet.
• the cellulosic slurry is generally diluted to a consistency (percent dry weight of solids in the slurry) of less than 1 percent and often below 0.5 percent ahead of the paper machine, while the finished sheet must have less then 6 weight percent water.
• a consistency percent dry weight of solids in the slurry
• the dewatering method of the least cost in the process is drainage, and thereafter more expensive methods re used for, for instance vacuum, pressing, felt blanket blotting and pressing, evaporation and the like, and in practice a combination of such methods are employed to dewater, or dry the sheet to the desired water content. Since drainage is both the first dewatering method employed and the least expensive, improvement in the efficiency of drainage will decrease the amount of water required to be removed by other methods and hence improve the overall efficiency of dewatering and reduce the cost thereof.
• a papermaking furnish contains generally particles that range in size from about the 2 to 3 millimeter size of cellulosic fibers, to fillers at a few microns, and to colloids. Within this range are cellulosic fines, mineral fillers (employed to increase opacity, brightness and other paper characteristics) and other small particles that generally, without the inclusion of one or more retention aids, would in significant portion pass through the spaces (pores) between the cellulosic fibers in the fiber mat being formed during papermaking and the forming fabric.
• a coagulant/flocculant system added ahead of the paper machine.
• a coagulant for instance a low molecular weight cationic synthetic polymer or a cationic starch
• a flocculant generally reduces the negative surface charges present on the particles in the furnish, particularly cellulosic fines and mineral fillers, and thereby accomplishes a degree of agglomeration of such particles, followed by the addition of a flocculant.
• the flocculant is anionic, the coagulant also provides anchoring sites of attachment for the flocculant.
• Such flocculant generally is a high molecular weight anionic synthetic polymer which bridges the particles and/or agglomerates, from one surface to another, binding the small particles into large agglomerates or attaching them to the large fibers.
• the presence of such large agglomerates in the furnish as the fiber mat of the paper sheet is being formed increases retention.
• the agglomerates are filtered out of the water onto the fiber web, where unagglomerated particles would to a great extent pass through such paper web.
• the shearing generally is provided by one or more of the cleaning, mixing and pumping stages of the papermaking process, and the shearing breaks down the large flocs formed by the high molecular weight polymer into microflocs, and further agglomeration then ensues with the addition of the bentonite clay particles.
• Another system uses the combination of cationic starch followed by colloidal silica to increase the amount of material retained on the web by the method of charge neutralization and adsorption of smaller agglomerates.
• This system is described in United States Patent No. 4,388,150, inventors Sunden et al., issued June 14, 1983.
• Sheet uniformity or formation may be determined by the variance in light transmission within a paper sheet, and a high variance is indicative of poor formation.
• retention increases to a high level, for instance a retention level of 80 to 90 percent, the formation parameter generally abruptly declines from good formation to poor formation. It is at least theoretically believed that as the retention mechanisms of a given papermaking process shift from filtration to adsorption, the deleterious effect on formation, as high retention levels are achieved, will diminish, and a good combination of high retention with good formation is attributed to the use of bentonite in U. S. Patent No. 4,913,775.
• additives that can be delivered to the paper machine without undue problems.
• An additive that is difficult to dissolve, slurry or otherwise disperse in the aqueous medium may require expensive equipment to feed it to the paper machine.
• the additive is often maintained in aqueous slurry form by virtue of high energy input equipment.
• additives that are easily dissolved or dispersed in water require less energy and expense and their uniformity of feed is more reliable.
• the claimed invention comprises a papermaking process comprising forming an aqueous cellulosic papermaking slurry, adding to the slurry a mineral filler, adding to the slurry after the addition of the mineral filler a cationic polymeric coagulant, then adding to the slurry an effective flocculating amount of a high molecular weight anionic polymer selected from the group consisting of acrylamide/sodium acrylate copolymers and copolymers of acrylamide and acrylamido methyl propyl sulfonate (AMPS), adding a low molecular weight anionic polymer selected from the group consisting of polyacrylic acid and methacrylic acid, draining the slurry to form a sheet, and drying to form a paper sheet.
• a high molecular weight anionic polymer selected from the group consisting of acrylamide/sodium acrylate copolymers and copolymers of acrylamide and acrylamido methyl propyl sulfonate
• a water soluble polymer is added to a cellulosic slurry before the formation of a paper product.
• the water soluble polymer should become substantially dispersed within the slurry before formation ofthe paper product.
• the low molecular weight anionic polymer of the invention is added after the addition of a cationic polymeric coagulant and a high molecular weight anionic polymer.
• the addition of the low molecular weight anionic polymer in an aqueous medium for instance as a water solution or disbursing, facilitates the dispersion of the polymer into the slurry.
• the polymer is added to the cellulosic slurry before the processing steps of draining and forming the paper sheet.
• the cationic coagulant may be chosen from among the following compounds: epi-DMA (dimethyl acrylate), ammonia crosslinked epi-DMA, DADMAC (Diallyl dimethyl ammonium chloride) and copolymers of DADMAC and acrylamide or acrylate, polyethylene imines, polyamido amides, cyanoguanidine and condensation derivatives of various amines.
• epi-DMA dimethyl acrylate
• DADMAC Diaallyl dimethyl ammonium chloride
• copolymers of DADMAC and acrylamide or acrylate polyethylene imines
• polyamido amides polyamido amides
• cyanoguanidine condensation derivatives of various amines.
• the high molecular weight of the invenion is chosen from among copolymers of acrylamide and sodium acrylate and copolymers of acrylamide and AMPS.
• the charge densities of these copolymers vary between 0.7 to 1.7 meq(milliequivalents) per gram of polymer.
• the molecular weight of the copolymers is preferably greater than 1 million daltons. Most preferably, the molecular weight is greater than 10 million daltons.
• the present process is believed applicable to all grades and types of paper products, and further applicable for use on all types of pulps including, without limitation, chemical pulps, including sulfate and sulfite pulps from both hard and soft woods and acid pulps, thermo-mechanical pulps, mechanical pulps and ground wood pulps, although it is believed that the advantages of the process ofthe present invention are best achieved when the pulp employed is of the chemical pulp type, particularly alkaline chemical.
• the filler used in the cellulosic slurry is anionic, or at least partially anionic when present in the furnish.
• Other mineral, or inorganic, fillers may however, be used, or used in part, such as titanium dioxide, kaolin clay and the like.
• the amount of inorganic filler generally employed in an alkaline papermaking stock is from about 10 to about 30 parts by weight of the filler, as CaCO 3 , per hundred parts by weight of dry pulp in the slurry, but the amount of such filler may at times be as low as abut 5, or even about 2, parts by weight, and as high as about 40 or even 50 parts by weight, same basis.
• the amount of high molecular weight anionic polymer that may be used in the process of the present invention may be within the range of from about 0.01 to about 1.5 parts by weight per hundred parts by weight of dry solids in the cellulosic slurry, including both pulp and filler solids.
• the polymer is used in the amount of from about 0.05 to about 0.5 parts by weight per hundred parts by weight of dry solids in the cellulosic slurry.
• the level of such polymer may also be correlated with the amount of filler in the cellulosic stock.
• the polymer used may be within the range of from about 0.01 to about 20 parts by weight per hundred parts by weight of the filler, as CaCO3, and preferably will be in the range of from about 0.1 to about 10 parts by weight, and more preferably form about 0.1 to about 2.5 parts by weight, same basis. with latex polymers.

Landscapes

• Paper (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=24408106

Family Applications (1)

Country Status (2)

Cited By (11)

Citations (2)

• 1997
  • 1997-02-14 EP EP97300969A patent/EP0790351A3/fr not_active Withdrawn
  • 1997-02-14 DE DE1997300969 patent/DE790351T1/de active Pending

Patent Citations (2)

Also Published As

Similar Documents

Legal Events