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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/03—Non-macromolecular organic compounds
  • D21H17/05—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only
  • D21H17/17—Ketenes, e.g. ketene dimers
• • 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
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/23—Lignins

Definitions

• This invention relates to active sizes containing a reactive sizing agent and a dispersant.
• paper is used in this specification to mean any form of paper, paperboard and related products, the manufacture of which involves the action of a sizing agent upon cellulosic or other fibres.
• Previous ketene dimer sizes have contained, as dispersant, cationic components such as starches, polyamines, polyamides and polyacrylamides. These emulsifiers and dispersants are homogenised in situ with the ketene dimer to form cationically stabilised emulsions.
• the present invention provides an active sizing composition which comprises an aqueous emulsion of a reactive sizing agent and an anionic dispersant and/or emulsifier serving to stabilise the emulsion, the reactive sizing agent comprising at least one compound according to the formula wherein R1 and R2 are, independently of each other, hydrocarbon radicals having at least six carbon atoms, more preferably alkyl, alkenyl, cycloalkyl, aryl, aralkyl or alkaryl radicals.
• Sizing agents of the invention can offer advantages especially in systems where cationic charged fillers e.g., precipitated calcium carbonates are present or in systems using cationic components e.g., retention aids of polyacrylamide, polyamine, PEI, etc. in furnishes consisting of groundwood, thermomechanical pulps or chemical thermomechanical pulps where limited hydroxyl (OH ⁇ ) sites are available for AKD attachment and reactivity.
• cationic charged fillers e.g., precipitated calcium carbonates are present
• cationic components e.g., retention aids of polyacrylamide, polyamine, PEI, etc. in furnishes consisting of groundwood, thermomechanical pulps or chemical thermomechanical pulps where limited hydroxyl (OH ⁇ ) sites are available for AKD attachment and reactivity.
• compositions of the invention are particularly suitable for use as an internal size in sizing operations carried out at the wet end of a paper-making process.
• R1 and R2 are, independently of each other, C12 to C22 alkyl groups, C14 to C19 alkyl groups being especially preferred.
• the compounds in which R1 and R2 are each C14H29 or C16H33 are most highly preferred and are referred to hereinafter as "palmitic-stearic dimer".
• active sizing compositions according to the invention can be effective in their sizing properties, particularly when used in highly-cationic environments, such as those encountered in wet-end sizing in the manufacture of liquid packaging papers and photographic papers as mentioned above, and those, also mentioned above, when the active size is used in connection with fluorescent whitening agents.
• papers using cationic fillers such as precipitated calcium carbonate can be sized efficiently using an anionically charged alkyl ketene dimer size of the present invention.
• compositions of the invention can be effective sizing agents is the more surprising because it has previously been supposed in the art that an anionically stabilised sizing agent would lack the necessary affinity with the hydroxyl groups of the cellulose and that a cationically stabilised emulsion was necessary to provide the necessary retention of the sizing agent by reaction with the hydroxyl groups.
• the dispersant and/or emulsifier stabilising the emulsion can be any suitable anionic dispersant or emulsifier.
• Sodium lignosulphonate, calcium lignosulphonate and the sodium salt of naphthalene sulphonic acid, and mixtures thereof, are examples of suitable dispersants.
• the dispersant and/or emulsifier is preferably used in a total amount of 0.5% to 10% based on the weight of the reactive sizing agent, the actual amount used in any particular composition being that which imparts a desired anionic charge to the dispersed sizing agent.
• the anionic charge density in the sizing compositions of the invention can be extended or modified using components such as anionic polyacrylamides, anionic starch or colloidal silica as emulsifiers.
• the sizing agent is preferably present in the sizing composition in an amount of 5% to 20% by weight, more preferably 10% to 15% by weight, of the sizing composition.
• the sizing compositions may be used in conjunction with effective quantities of material such as retention aids, dry strength agents and drainage aids, for example alum which acts both as a drainage aid and as a scavenger for anionic colloidal debris.
• material such as retention aids, dry strength agents and drainage aids, for example alum which acts both as a drainage aid and as a scavenger for anionic colloidal debris.
• the sizing compositions of the invention can be made by any convenient process, but preferably are made by homogenising the reactive sizing agent in liquid form (if necessary after heating to melt the material) with the dispersant and/or emulsifier and the appropriate amount of water to form an aqueous emulsion.
• the dispersant and/or emulsifier is dissolved in water at 65 to 80°C to which is added molten ketene dimer premelted at 65 to 80°C.
• the resultant mix is homogenised at 2500 to 3500 psi to form a stable emulsion.
• the sheets were then dried by passing them four times around a photographic drum dyer operated at 105°C, giving a residence time of 3.3 minutes, followed by 5.0 minutes in a forced-draught oven at 105°C. After cooling for at least 10 minutes, the sheets were roughly cut, laminated and finely cut to a final size of 5.0 cm x 12.5 cm.
• Examples 5 to 10 are comparison examples employing cationically-stabilised AKD sizing agents.
• Keydime SP1 is a dispersant containing sodium lignosulphonate and the sodium salt of naphthalene sulphonic acid. It is available from Albright & Wilson Limited. Keydime D10 and Keydime D125 are cationically stabilised AKD sizing agents containing, on a dry weight basis, 10% AKD (the palmitic-stearic compound mentioned above) and, respectively, 2.5% and 1.25% cationic polymer. Keydime D10 and Keydime D125 are also available from Albright & Wilson Limited.
• the AKD was added together with the Keydime SP1 (in examples 1 to 4) and as a component of the Keydime D10 or D125 (in examples 5 to 10), an AKD-Keydime SP1 emulsion having been formed by melting the AKD at 65 to 80°C, dissolving the molten AKD in water at 65 to 80°C and homogenising the mixture with Keydime SP1 at 2500 to 3000 psi.
• Examples 1 to 4 when compared with Examples 5 to 10, show fluid pick-ups (edgewick) with anionic agents comparable to or better than those of cationic agents. Examples 4 and 8 show that better results can be attained with recirculation which most realistically simulates the papermaking process.
• the sheets were dried at 105°C for 8 minutes then oven cured for 5 minutes.
• Lactic acid immersion tests were carried out on the sheets.
• the sheets were coated with tape and cut to 12.5cm x 5cm strips. These strips were weighed before immersion in 2.5cm of 1% lactic acid for 16 hours. The strips were then reweighed and the pickup calculated in grams. The average of 3 results was taken for each sizing composition.
• Example 16 is a comparison example using Keydime D10.
• composition 1 2 3
• Additive/Dispersant Naphthalene Sulphonic Acid 1.25 1.25 1.25 Na Lignosulphonate 4.5 4.5
• the process water was acidified prior to the addition of dispersants.
• the mixture was heated to 70°C before addition to a laboratory homogenizer which was preheated to the same temperature. Homogenization pressure was adjusted to 3500 psig (24 M Pa) (ideally 2500 to 5000 psig (17 to 34 M Pa)). Molten alkyl ketene dimer wax was added at 70°C and allowed three theoretical passes plus one to discharge. Upon discharge, the product was passed through a 200 mesh filter and the temperature rapidly reduced to below 20°C.
• the precipitated calcium carbonate used for this work was a commercially available grade Albacar HO made at 20% solids with no dispersant added. Particle size averaged 2.7 microns with a Zeta potential of +5 mV.
• the size test employed in this work was a 2-minutes Cobb test under standard conditions.
• Anionic size composition (1) of Example 11 was tested against a competitive, cationically stabilized size, Aquapal C348 supplied commercially by Hercules Powder Co. Sizing was measured to a standard 1-min. Cobb test. Machine Furnish on 60g/m2 Wove grade Fibrous - Chemithermal mechanical pulp 50% White Offcuts 17% White Letter Waste 17% White Waste Rejects 8% Own Broke 8%
• Retention Aid - Cationic Polyacrylamide Nalfloc 4662 commercially available from Nalco Ltd. Fillers - Calcium carbonate addition to a specified sheet ash of 23% w.o.f. Size Type Size Addition % as Received Retention Acid Addition g/tonne % Sheet Ash Sizing/mm Cobb Oven Cured 3 min at 105°C Aquapel C348 3.7 257 23.4 17.7 Composition(1) 1.6 257 22.9 16.9

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Cited By (27)

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Citations (1)

• 1989
  • 1989-09-11 GB GB898920456A patent/GB8920456D0/en active Pending
• 1990
  • 1990-09-10 CA CA002024975A patent/CA2024975A1/en not_active Abandoned
  • 1990-09-10 EP EP90309876A patent/EP0418015A1/en not_active Withdrawn
  • 1990-09-10 NO NO90903926A patent/NO903926L/no unknown
  • 1990-09-10 AU AU62317/90A patent/AU6231790A/en not_active Abandoned
  • 1990-09-10 FI FI904444A patent/FI904444A0/fi not_active Application Discontinuation
  • 1990-09-11 ZA ZA907216A patent/ZA907216B/xx unknown
  • 1990-09-11 BR BR909004518A patent/BR9004518A/pt unknown
  • 1990-09-11 JP JP2239152A patent/JPH03167391A/ja active Pending

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