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
  • 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
  • D21H21/14—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 characterised by function or properties in or on the paper
  • D21H21/16—Sizing or water-repelling agents
• • 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
  • D21H17/14—Carboxylic acids; Derivatives thereof
  • D21H17/15—Polycarboxylic acids, e.g. maleic acid
  • D21H17/16—Addition products thereof with hydrocarbons
• • 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

Definitions

• the present invention relates to a sizing composition usable for the neutral sizing of paper or board.
• the invention additionally relates to a process for the manufacture of paper or board.
• alkyl ketene dimer or alkenyl succinic acid anhydride (ASA) is commonly used as a size in order to enhance the water repellence (hydrophobicity) of paper or board. Both of these molecules are deemed to react with cellulose fiber. The reaction occurs most rapidly in particular in alkaline or slightly basic conditions.
• AKD and ASA are added to an aqueous dispersion which contains fiber and additives (e.g. fillers, retention agents, anti-foaming agents, pH control agents), and from which an effort is made to separate the solids onto the wire as effectively as possible, i.e. the aim is as high a retention as possible.
• the water used for the dispersion is commonly circulation water and pure raw water added to it, in which case the water used for the dispersing usually contains, for example, approx. 200 ppm of alkaline earth metals: calcium and magnesium ions.
• pulps which contain calcium carbonate which is used for increasing the brightness of paper, consume more hydrophobification chemicals than do pulps without carbonate.
• Carboxyl groups on the surface of cellulose generate a negative charge in the fibers.
• the magnitude of the charge depends on the surrounding pH. In alkaline conditions the carboxyl group becomes protolyzed, and therefore the quantity of negative charges increases.
• the sizes used for purposes of hydrophobification are prepared by emulsifying the water-repellent substance in a cationically charged starch.
• the starch surrounds the water-insoluble hydrophobification agent, whereupon a dispersion evenly distributed in the water is formed. Owing to the starch the dispersion particles are cationic. They tend to adhere to negatively charged surfaces, for example cellulose fibers.
• bivalent alkaline earth metal ions such as Ca 2+ ions, and also other multivalent ions
• Ca 2+ ions neutralize the carboxyl groups of cellulose fibers, and consequently the negative charge of the fibers respectively decreases.
• a size particle formulated using a cationic starch attaches to the fiber surface by means of charges
• the presence of surface charges both in the size particle and the fiber is important in terms of retention.
• Ca 2- ions neutralize the surface charge, and consequently the retention of cationic size particles weakens.
• the adherence of cationic retention agents to fiber also depends on the surface charge of the fiber.
• a sizing composition which contains a sizing agent capable of reacting with cellulose and an organic complexing agent.
• the size is preferably alkyl ketene dimer (AKD) or alkenyl succinic acid anhydride (ASA).
• ALD alkyl ketene dimer
• ASA alkenyl succinic acid anhydride
• chelating agent is also used for complexing agents.
• Suitable complexing agents which can be used in accordance with the invention include
• the complexing agents cited above may be in the form of an acid or a salt.
• Suitable salts include alkali metal salts and ammonium salt.
• Sodium and potassium salts are preferred salts.
• Preferred complexing agents of group a) include aminopolycarboxylic acids having the following general Formula I.
• EDTA ethylene diamine tetra-acetic acid
• DTPA diethylene triamine penta-acetic acid
• NTA nitrilotriacetic acid
• Preferred complexing agents of group b) include N-bis- or tris-[(l,2-dicarboxylethoxy)ethyl]amines having the general Formula II where
• Especially preferable complexing agents in Formula II include the following compounds according to Formulae A, B and C:
• Preferred complexing agents of group c include phosphonic acids having the general Formula III where
• the amount of the organic complexing agent may be 0.1-50 % by weight, preferably 0.1-20 % by weight, and especially preferably 0.2-3 % by weight, of the amount of the size.
• the sizing composition according to the invention is preferably in the form of a dispersion, in which case it additionally contains a dispersion stabilizing agent.
• the stabilizing agents of AKD dispersions include starch, cationic starch and other polymers, such as polyethylene imine, polyepiamine, a polydiethyl diallyl or dicyandiamide compound, polyacrylamide or polyacrylic acid, or salts of these.
• starch or other polymers such as water-soluble cellulose derivatives, e.g. hydroxyethyl or hydroxypropyl, methyl hydroxypropyl ethyl hydroxyethyl cellulose, carboxymethyl cellulose, gelatin, guar gum, xanthan gum or polyvinyl alcohol.
• the amount of complexing agent may be 0.2-20 % by weight, preferably 0.2-10 % by weight, and especially preferably 1-5 % by weight, of the amount of the stabilizing agent.
• the complexing agent may be incorporated into the size or it may be dosed at the same location in the paper or board machine as the size.
• the invention additionally relates to the use of the sizing composition defined above for the neutral sizing of paper or board.
• the complexing agent binds to the starch layer, from which it detaches in dilution and forms a complex with Ca 2+ ions.
• the complexing ion detaches from a fiber, the fiber becomes more anionic and the size particle adheres to the fiber.
• the equilibrium constant of cellulose fiber with respect to the complexing of Ca 2+ ions is approx. 3.
• the sizing composition works in particular in pulps which are made in hard waters and in machines the retention of which is otherwise poor.
• the performance of the invention is not affected by the other chemicals, such as starch and calcium carbonate, used in the making of the paper, or by the quality of the pulp. Also, the order in which the chemicals are added in the paper machine or the other running parameters of the paper machine do not affect the performance of the invention.
• the amount of complexing agent used in the sizing formulation may be 0.1-50 % by weight of the amount of AKD or ASA and 0.2-20 % by weight of the total amount of starch or other polymer stabilizing the formulation.
• These compounds can be used as such in acid form or in the form of their alkali or ammonium salts. If the agent is used in the form of a salt thereof, the cation of the said salt does not have a substantial effect on the performance of the invention.
• AKD emulsions are physically stable and usable for several weeks.
• concentration of AKD in the products may be 0.5-30 % by weight.
• Various starches are commonly used for the formulation of AKD. They are generally cationated either with quaternary amines, in which case the starch retains its cationic charge also in alkaline conditions, or with primary, secondary or tertiary amines, the charge of which is dependent on the pH.
• the amount of starch may be 0.1-10 times the proportion AKD.
• AKD wax For the dispersing of AKD wax there are generally used various anionic chemicals, such as lignosulfonates, aliphatic or aromatic sulfonates, nonionic surfactants such as fatty acid or fatty alcohol ethoxylates, or cationic surfactants such as fatty acid amines or imidazolines.
• anionic chemicals such as lignosulfonates, aliphatic or aromatic sulfonates, nonionic surfactants such as fatty acid or fatty alcohol ethoxylates, or cationic surfactants such as fatty acid amines or imidazolines.
• polymers such as polyethylene imine, polyepiamine, polydimethyl diallyl or dicyandiamide compounds, polyacrylamide or polyacrylic acid and its salts. It is commonly known that the amount of stabilizing chemicals is 1-200 % by weight of the amount of AKD.
• polymers it is possible not only to improve the stability of the product but also to affect the performance
• ASA is dispersed at the paper or board mill by using apparatus installed for this purpose.
• the prepared dispersion is run immediately to the paper or board machine.
• a surfactant such as dioctyl sulfosuccinate, octyl phenoxy polyethoxy ethanol, and polyethylene oxy dinonyl phenyl phosphate, polyethylene oxy sorbitane trioleate.
• ASA dispersions starch or other polymers, such as water-soluble cellulose derivatives, e.g. hydroxy ethyl and hydroxy propyl, methyl hydroxy propyl and ethyl hydroxy ethyl cellulose, carboxy methyl cellulose, or gelatin, guar gum. xanthan gum, polyvinyl alcohol, etc.
• the drop size of the dispersion is in general on average 0.2-3 ⁇ m.
• the complexing agents can be added to ASA-based commonly known compositions.
• the sizing composition according to the invention is suitable for use for chemical pulps, mechanical pulps, chemimechanical pulps, and mixtures of these.
• compositions which are the object of the present invention are illustrated with the following examples.
• the percentages are percentages by weight, unless otherwise indicated.
• a mixture of pine and birch sulfate pulps at a ratio of 50:50 was dispersed in ion exchange water and was ground to a Schopper number of 20°.
• the pulp was filtered and redispersed to a consistency of 1 % a) in ion exchange water and b) in ion exchange water which contained 0.1 % DTPA as an Na salt.
• the pulps were stirred for approx. 1 hour.
• the pulps were washed with ion exchange water at pH 7.
• the charge of the fiber was determined using polydiallyl dimethyl ammonium chloride and its back titration with a Na salt of polyethylene sulfonate by a Mütek apparatus.
• a pulp the composition of which was 40 % chemical birch pulp, 40 % chemical pine pulp and as the filler 20 % calcium carbonate and pulp starch 5 kg/t.
• a dispersion of AKD was prepared in a 2% starch, the concentrations of Complexing Agents 1 and 2 in the dispersion being 0.6 % of the amount of AKD.
• the AKD dose used was 1 kg/t, in which case the amount of active ingredient forming the complex was 6 g/t.
• Test sheets having a grammage of 80 g/m 2 were prepared from the pulp according to the instructions by Scan-C 26:76. Cobb 60 min was determined from the sheets immediately and after 10 min of curing at 105 °C.
• the pulp used in the pilot machine was 35 % chemical pine pulp and 65 % chemical birch pulp.
• the filler used was calcium carbonate 23 % of the dry pulp.
• the rate of AKD used was 1 kg/t.
• the AKD size contained Complexing Agent 1 in an amount of 0.3 % of the amount of AKD.

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Cited By (7)

Citations (2)

• 1998
  • 1998-09-04 FI FI981893A patent/FI109218B/fi not_active IP Right Cessation
• 1999
  • 1999-08-20 ES ES99660129T patent/ES2226321T3/es not_active Expired - Lifetime
  • 1999-08-20 PT PT99660129T patent/PT984101E/pt unknown
  • 1999-08-20 AT AT99660129T patent/ATE271160T1/de active
  • 1999-08-20 DE DE69918621T patent/DE69918621T2/de not_active Expired - Lifetime
  • 1999-08-20 EP EP99660129A patent/EP0984101B1/de not_active Expired - Lifetime

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