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
  • D21H17/12—Organo-metallic compounds

Definitions

• the object of the invention is an additive defined in the preambles of the independent claims presented below, which additive can be used for instance in paper making, the preparation of this additive and its use in paper making, for instance as a pulp chemical agent and surface sizing agent.
• the object is to provide improvements i.a. to the printing properties of paper and/or board with the aid of the additive.
• lubricants are widely used as a component of the coating slip in the coating of paper and board.
• the lubricants are intended for improving the coating's properties regarding linting, flexibility and calendering after drying.
• Different wax emulsions, mixtures of soy lecithin and oleic acid, and water dispersions of metal soaps are generally used as such lubricants.
• the metal soaps are primarily water dispersions of alkali earths, such as calcium stearate.
• polyethylene-glycol and its oleic acid esters and sugars can be used, which in themselves also possess lubricating properties, but which are also used in order to increase the dry matter content of the calcium stearate dispersion.
• Different lubricants and their use, as well as the prior art regarding their use as an additive in the coating of paper and board is thoroughly discussed in the book Paper Coating Additives, A Project of the Coating Additives Committee of the Coating and Graphic Arts Division, Robert J. Kane, Task Group Chairman, Atlanta, Georgia, TAPPI Press, 1995, p. 69 - 88.
• Sizing agents such as resin sizes
• Sizing agents are generally used to adjust the hydrophobic properties of paper, whereby these sizes are bonded to the fibres with the aid of alum.
• reactive sizing agents such as ASA and AKD sizes have been taken into use, which react with the OH groups of the glucose units of cellulose.
• These sizing agents provide a so-called hard sizing (Cobb ⁇ 20), but their use in the sizing of wood-containing papers has proven problematic.
• US 5 800 677 mentions the use of a mixture of zinc salt of a higher oleic acid and a cationic surfactant in the pitch control in a paper machine, and it also mentions that the use of the mixture increases the sizing effect in the paper.
• cationic surfactants for instance the condensate of tall oil oleic acids and pentaethyle- nehexamine or aminoethylethanolamin can be mentioned, which typically are small molecules.
• Cationic surfactants have a disadvantage in that they are known to increase the surface energy of the mixture, whereby the paper will become more hy- drophilic.
• the object of this invention is to provide an improved additive which can improve or otherwise in a desired manner modify the printing properties and/or the properties obtained by sizing of paper, board and/or the like.
• the additive according to the invention comprises typically a dispersion of a cationic polymer and a metal carboxylate.
• Dispersion means in the description of the invention a liquid phase which contains material particles in a non-dissolved form of some other matrial, if nothing else is stated.
• the invention relates to a new cationic metal carboxylate dispersion containing a cationic polymer.
• This dispersion is useful as an additive in the manufacturing of paper, board and/or a the like product.
• the cationic property of the dispersion can be adjusted in a stepless fashion by adjusting the amount of the cationic polymer(s).
• the amount of the cationic polymer can be 0.1 to 99.9 %, advantageously it is 1 to 99 %, and more advantageously 10 to 90 % of the dry matter of the dispersion.
• the proportion of the metal carboxylate, i.e. the metallic salt of an oleic acid, of the dry matter of the dispersion may vary between 0.1 and 99.9 %, advantageously it is 1 to 99 %, and more advantageously 10 to 90 %.
• Metal means in this application typically a metal which is selected from the group alkali earth, such as calcium, magnesium and barium, zinc, aluminium, or a mixture of these.
• alkali earths are advantageous due to their crystalline form.
• Calcium is particularly advantageous as it forms plate-like crystals.
• Zn is also advantageous, because it provides a particularly good sizing effect.
• Carboxylate means in this invention a salt formed from an oleic acid containing more than 6 carbon atoms, i.e. a monocarboxyl acid.
• the oleic acids can be either unsaturated or saturated, and they can be either straight-chained or branched, and their carbon chain can typically contain 8 to 24 carbon atoms, advantageously 14 to 18 carbon atoms.
• the saturated and/or branched oleic acids containing more than 8 carbon atoms are particularly advantageous in applications according to the invention. Particularly advantageous are such oleic acid mixtures which contain one or more oleic acids. Stearic acid, isostearic acid, palmitinic acid and/or myristinic acid can be mentioned as particularly advantageous.
• An oleic acid mixture containing at most 60 %, advantageously 5 to 50 % of branched oleic acids provides a particu- larly advantageous additive, which can provide smooth and/or glossy surfaces with a good hydrophobicity.
• the oleic acid or the oleic acid mixtures are advantageously selected so that at least a part of the oleic acid(s) remain as a salt, i.e. in a non-dissolved form, also at the place of application. If the carboxylate dissolves it can not yield the sizing effect desired of this material for instance in paper, or the desired surface property on the paper's surface.
• the cationic polymer and the metal carboxylate advantageously form such a dispersion, where at least a part of the metal carboxylate is in a non-dissolved form. Typically about 5 to 100 %, advantageously 30 to 100 % of the carboxylate contained in the additive is in the non-dissolved form.
• the melting point of the metallic salt of the oleic acid is typically over 70 °C, and most typically over 80 °C, so that no essential agglomeration occurs in the temperatures of the water circulation in the paper machine.
• the melting point is advantageously in the region 80 to 200 °C, and more advanta- geously in the region 120 to 180 °C. Therefore it is particularly advantageous to use for instance calcium stearate as the metallic salt of the oleic acid.
• Typically > 30 %, advantageously > 50 % of the metallic salt can be calcium stearate.
• a cationic polymer means cationic polymers generally applicable in the paper making, such as for instance a condensate polymer of synthetic epichloro- hydrin and dimethylamine (epiDMA), polydiallyldimethyl ammonium chloride (pDADMAC), polyethylene imine (PEI) and/or polyacrylamide copolymerised with cationic components (PAM-based cationic polymer) and a half-synthetic starch- based cationic polymer, and the mixtures of these.
• the cationic polymer is advanta- geously in the form of a solution, due to its ease of use.
• the molecule size of cationic polymers is mainly typically over 40,000 daltons.
• the synthetic cationic poly- mers are typically in the region 40,000 to 200,000, and the half-synthetic are typically over 500,000, advantageously between 1 and 1.5 millions.
• a starch-based cationic polymer is particularly advantageous in applications according to the invention, as it is able to form stable dispersions.
• Particularly suitable is a cationic starch polymer in the form of a solution.
• the starch can be a cationic starch obtained from any source, and it can be either degraded or undegraded.
• the charge of the starch can be higher than 0.1 mEkv/g, as calculated per dry matter.
• it is in the region 0.14 to 3.5 mEkv/g, more advantageously 0.36 to 3.5 mEkv/g, and even more advantageously 0.7 to 3.5 mEkv/g.
• the dispersion according to the invention will be much better attached to the paper fibre and the desired effects can be brought about much more effectively.
• the dispersion according to the invention provides a good retention of the metal carboxylate to the paper fibre. Due to the cationic polymers, particularly the cati- onic half-synthetic starch polymers, it is also possible to increase the strength of the paper in an advantageous way.
• the charge of a useful dispersion may be more than 0.05 mEkv/g, as calculated per dry matter of the dispersion, even up to 6 mEkv/g. If starch is used as the cationic polymer, the charge is advantageously between 0.05 and 3.5 mEkv/g, more advantageously between 0.1 and 3.0 mEkv/g, typically about 0.7 mEkv/g.
• the dry solids content of the dispersion can be advantageously between 10 and 55 %, more advantageously in the region 20 to 45 %, so that its viscosity remains at a level where the dispersion can be pumped with relative ease.
• the invention relates also to a method for the preparation of a dispersion containing a cationic polymer and a metallic salt of the oleic acid.
• the metallic salt of the oleic acid can be prepared in a known way, for instance directly from metal oxide or metal hydroxide and the oleic acid, or indirectly by precipitating by a salt of the de- sired metal, typically for instance by chloride or acetate, from an alkali salt of the corresponding oleic acid.
• the dispersion can be prepared by mixing efficiently the metallic salt of the oleic acid and the cationic polymer in an aqueous base. Additives, for instance emulgators, can be added in order to form the dispersion and stabilise it.
• the dispersion can be prepared in situ by admixing the components, or the different materials can be added during the mixing, either in one or more batches. It is also possible to prepare separately a dispersion containing the metallic salt of the oleic acid, and then this is admixed to the cationic polymer.
• the cationic polymer is already present in an aqueous solution or as a dispersion, before the final dispersion is pre- pared.
• the dispersion can be prepared by conventional means in a heated reactor, in such conditions where the oleic acid is in a molten form.
• the cationic metal carboxylate dispersion according to the invention is prepared so, that the metallic salt of the oleic acid and the cationic polymer are dispersed in a heated reactor in an aqueous base, in the presence of any possible additives.
• the dispersion can be made directly at a useful concentration, or it can be diluted at a later stage before the use in the making of paper, board or the like.
• the invention relates also to a method for making paper, board and/or the like by using a dispersion containing a cationic polymer and a metallic salt of the oleic acid as additive.
• the dispersion can be added to the pulp stock. The addition can be made at different stages and in pulps of different qualities having a thickness, which can vary between 0.1 and 10 %. In wet end applications the dispersion can be added in amounts of 0.1 to 10 kg/ton paper (calculated as dry matter/dry matter). Alternatively the dispersion can be added at the size press like a conventional surface sizing agent. The dispersion can be added as such, or it can be added when admixed to the surface size.
• the added amounts in the surface sizing applications can vary between 0.1 and 20 kg/ton paper (dry matter/dry matter).
• the invention relates also to the use of a dispersion containing a cationic polymer and a metallic salt of the oleic acid as a pulp chemical in order to improve the printability and/or formability and/or to adjust the friction and/or hydrophobicity properties of the surface of paper, board and/or the like, and in order to improve the strength and/or hydrophobicity of paper, board and/or the like in surface sizing.
• the invention relates also to paper, board and/or the like, which are manufactured by using a dispersion containing a cationic polymer and a metallic salt of the oleic acid, of which thus a part is in a non-dissolved form.
• the dispersion can act as a pulp chemical agent or as a surface sizing agent.
• the cationic polymer which also acts as a protective colloid, i.e. as an agent strengthening the dispersion in dispersions according to the invention, provides good retention properties for a metal carboxylate particle, particularly for a calcium stearate particle, whereby the plate-like calcium stearate particle according to the invention attaches evenly on the surface of the fibre so that it makes it possible to obtain the most advantageous surface properties for each quality of paper, board or the like.
• the raw materials are well admixed in a heated reactor, in the order of the recipe, and dispersed until a homogenous dispersion is obtained.
• a C18/C16 oleic acid mixture (60 % / 40 %) was used as the oleic acid.
• the oleic acid, Ca(OH) 2 and emulgators were used in the same proportions as described in example 1.
• the dry solids content of the cationic polymers and the formed Ca carboxylate were adjusted so, that they corresponded to the values given in the table.
• the dispersions were prepared by mixing until homogenous compositions were obtained. The dispersions remained in good condition at least one week without any substantial separation.
• Example 5 The use of a cationic calcium carboxylate dispersion as pulp chemical in the making of paper
• the test run was made in a pilot newsprint machine.
• the pulp composition was 80 % groundwood pulp (TMP) and 20 % cellulose and in addition 15 % reject.
• TMP groundwood pulp
• Example 6 The use of cationic calcium carboxylate dispersions as a pulp chemical in the making of paper. Laboratory sheets were made by using pulp of recycled paper, grammage 150 g/m 2 , pH 6.0. As the zero sample a corresponding pulp without the dispersion according to the invention was used, and as a second reference sample only cationic polymer was used.
• Example 7 The use of the dispersion prepared in example 1 in the surface sizing of LWC base paper
• the surface sizing was made on LWC base paper (50 g/m 2 ) in an Endupap device with the aid of a rod, the target amount being 4 g/m 2 .
• the measurements were made with a surface energy measuring device (manufacturer Fotocomp).
• the results present the dispersive and the polar components of the surface energy calculated according to the traditional angle, as well as the total surface energy and the contact angles for the measurement liquids.

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