ADDITIVE FOR PAPER MAKING, ITS PREPARATION AND USE

Abstract: The object of the invention is an additive composition, which can be used for instance in paper making, the preparation and use of this additive in paper making, e.g. as a pulp chemical chemical or as a surface size. The composition provides improvements i.a. in the printing properties of paper and/or board.

Description: Additive for paper making, its preparation and use 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. In addition to binding agents and fillers, 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. As intermediate agents in the calcium stearate dispersions urea, 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, are generally used to adjust the hydrophobic properties of paper, whereby these sizes are bonded to the fibres with the aid of alum. As the making of neutral paper has become common, 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. As the printing methods develop the surface properties of particularly wood- containing papers - newsprint, SC paper and LWC paper - have become ever more important in multi-colour printing. The surface properties can be adjusted for instance with mineral and micro wax dispersions. These problems arise due to the melting point of the waxes, which is close to the temperature of the paper machine's water circulation. The wax dispersion tends to form agglomerates which impair the runnability of the paper machine and increase the need to clean the rolls, wires, etc. These dispersions also impair the paper's strength properties. 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. As examples of 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. In this application it is thus not possible to make the mixture more cationic without increasing the amount of the cationic surfactant, and thereby increasing the hydrophility of the mixture. Also the strength properties of the paper may decrease due to the cationic surfactant. Said patent further states that oleic acid salts of alkali earths, particularly calcium, are not suitable for said purpose. 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. In order to attain the above-mentioned objects the additive according to the invention is characterised in what is defined in the characterising part of the first claim presented below. Thus 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. Thus 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. In an embodiment according to the invention the 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. Thus in the solution according to the invention 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. In the cationic dispersions 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. In this invention 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. It seems that the sufficiently large size of the cationic polymer molecules is of importance to the desired printing properties of paper, board or the like, which are obtainable with the dispersions according to the invention. 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. Advantageously 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. Generally it can be said, that by bringing the charge of the starch to a sufficiently high level, for instance over 0.7 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. Particularly advantageous are neutral emulgators. 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. Advantageously 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. Advantageously 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. In the following examples the invention is described in more detail. The percentages and proportions are calculated as mass percentages and mass proportions, and the charges are calculated per dry matter, if nothing else is stated. Example 1. Preparation of Ca stearate dispersion improved by a cationic polymer C 18/C 16 oleic acid (60 % / 40 %) 436 parts Ca(OH) 2 62 parts KOH 1 part Oleic acid etoxylate, HLB-value > 10 33 parts Polyethylene glycol 29 parts Water 439 parts Cationic starch, 1.2 mEkv/g, dry matter 20 % 1000 parts The raw materials are well admixed in a heated reactor, in the order of the recipe, and dispersed until a homogenous dispersion is obtained. Analysis: Dry solids content 35 %, charge 0.34 mEkv/g, viscosity 1800 mPas, particle size 8.11 μm (volume average), 0.239 μm (number average). Example 2. Preparation of Ca stearate dispersion improved by a cationic polymer C18/C16 oleic acid (60 % / 40 %) 436 parts Ca(OH) 2 62 parts KOH 1 part Oleic acid etoxylate, HLB-value > 10 33 parts Polyethylene glycol 29 parts Water 439 parts Cationic starch, 2.7 mEkv/g, dry contents 40 % 1000 parts The materials were dispersed in the same manner as in example 1. Analysis: Dry solids content 45 %, charge 1.2 mEkv/g, viscosity 1900 mPas. Example 3. Preparation of Ca stearate dispersion improved by a cationic polymer C18/C16 oleic acid (60 % / 40 %) 85 parts Ca(OH) 2 12 parts KOH 0.2 part Oleic acid etoxylate, HLB-value > 10 6.6 parts Polyethylene glycol 5.8 parts Water 90.4 parts Cationic starch, 1.1 mEkv/g, dry matter 20 % 1800 parts Analysis: Dry solids content 23.2 %, cationicity 0.86 mEkv/g, viscosity 2050 mPas. According to the examples 1 to 3 it is possible to prepare in a stepless fashion different combinations of calcium stearate or other metal carboxylates and a cationic polymer. The stability of the products is typically over 6 months, without any substantial separation. Example 4. Preparation of dispersions containing different cationic polymers and calcium salt of the oleic acid 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. In the example it is seen that with synthetic polymers cationic dispersions containing a metallic salt of oleic acid can be prepared, which dispersions correspond to those prepared by using a starch polymer. 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. As chemical a product according to example 1 was used, whereby the amounts of the added product were calculated as dispersion dry matter per paper dry matter. As a reference a corresponding paper was used without the dispersion according to the invention. The results show clearly that the hydrophobicity of the paper increased when using the dispersion according to example 1. Similarly, a lower friction was obtained and a clearly smaller amount of printing ink for obtaining the target density was used. 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. The results of the measurements made with a Hercules size tester show that, compared to the zero sample, a pure cationic polymer provides a slight increase in the sizing, but that surprisingly the cationic calcium carboxylate dispersions of the examples 1 and 3 have a greater effect on the paper's hydrophobicity. This can be considered this to explain the substantially reduced amount of ink for the desired density in the test run described in example 5. 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. Measurement liquids: water and ethyleneglycol Total surface energy and the polar component: water = 72.8 / 51 mJ/m z ethyleneglycol = 48.0 / 19 mJ/m 2 Samples: 1 = The cationic polymer of the example 1 as such (dry matter 20 %) 2 = The dispersion according to the invention prepared in example 1 3 = Conventional surface size starch 4 = 95 % strongly oxidised potato-based surface size starch + 5 % AKD wax 5 = 90 % surface size starch + 10 % AKD 6 = ASA size stabilised by starch (in mass proportions 1 :4) As reference points the conventional surface size starch, the surface size improved by AKD, and the surface size improved by ASA were used. The best hydrophobicity properties were obtained with the dispersion according to the invention (sample 2), which provided a clearly lower total surface energy value than all other tested surface sizes. The invention is not intended to be limited to the embodiment examples presented above, but the invention is intended to be applied within the scope of the inventive idea defined in the claims presented below.

Claims: Claims 1. An additive useful in paper making, characterised in that it comprises a dispersion of a cationic polymer and a metal carboxylate. 2. An additive according to claim 1, characterised in that the amount of the cationic polymer is 0.1 to 99.9 % of the dry matter in the dispersion. 3. An additive according to claim 1 or 2, characterised in that the cationic polymer is selected from the group epiDMA, pDADMAC, polyethylene-imine, a PAM-based cationic polymer, a starch-based cationic polymer, and mixtures of them. 4. An additive according to claim 3, characterised in that the cationic polymer is a starch-based cationic polymer. 5. An additive according to claim 4, characterised in that the charge state of the starch-based cationic polymer is over 0.1 mEkv/kg. 6. An additive according to any of the previous claims 1 to 5, characterised in that the amount of the metal carboxylate is 0.1 to 99.9 % of the dry matter in the dispersion. 7. An additive according to any of the previous claims 1 to 6, characterised in that the metal is selected from the group alkali earth, such as calcium, magnesium or barium, zinc, aluminium, and mixtures of these. 8. An additive according to claim 7, characterised in that the metal is calcium. 9. An additive according to any of the previous claims 1 to 8, characterised in that the acid part of the metal carboxylate contains more than 6 carbon atoms, and advantageously it is one or more selected from the group C8-C24 oleic acids, more advantageously one or more selected from the group C14-C18 oleic acids. 10. An additive according to claim 9, characterised in that the oleic acid is a saturated straight or branched oleic acid. 11. An additive according to claim 9 or 10, characterised in that the oleic acid is a mixture, which contains at most 60 %, advantageously 5 to 50 %, saturated branched oleic acids. 12. An additive according to any of the previous claims 1 to 12, characterised in that the metal carboxylate comprises calcium stearate and/or calcium palmitate. 13. An additive according to any of the previous claims 1 to 11, characterised in that the cationic polymer comprises cationic starch having a charge state of over 0.7 mEkv/kg. 14. A method for preparing the additive according to any of the previous claims 1 to 13, characterised in that the metal carboxylate and the cationic polymer are dispersed in a heated reactor in an aqueous base in the presence of any possible additives. 15. A method for making paper, board or the like, characterised in that an additive according to any of the previous claims 1 to 13 is used in the making. 16. A method according to claim 15, characterised in that the additive is used as a pulp chemical. 17. A method according to claim 15, characterised in that the additive is used as a surface size or as a component of the surface size. 18. The use of an additive according to any of the previous claims 1 to 13 as a pulp chemical admixed to the pulp stock in order to yield better printing properties, hydrophobic properties and/or friction properties to paper, board and/or the like. 19. The use of an additive according to any of the previous claims 1 to 13 as such, or as an additive to the surface size in the surface sizing of paper, board and/or the like, in order to provide better hydrophobic properties. 20. A paper, board and/or the like, characterised in that an additive according to any of the previous claims 1 to 13 is used in the making of it.

Inventors: LUUKKONEN KARI, NIINIVAARA VEIKKO, VIHERVAARA TAPIO, LUUKKONEN, KARI, NIINIVAARA, VEIKKO, VIHERVAARA, TAPIO
Applicants: LUUKKONEN KARI, NIINIVAARA VEIKKO, RAISIO CHEM LTD, VIHERVAARA TAPIO, LUUKKONEN, KARI, NIINIVAARA, VEIKKO, RAISIO CHEMICALS LTD, VIHERVAARA, TAPIO
Application year: 2001
Main classification: D21H21
IPC codes: D21H17, D21H21