Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1026—Other features in bleaching processes
  • D21C9/1036—Use of compounds accelerating or improving the efficiency of the processes
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/08—Removal of fats, resins, pitch or waxes; Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1063—Bleaching ; Apparatus therefor with compounds not otherwise provided for, e.g. activated gases
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1026—Other features in bleaching processes
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1026—Other features in bleaching processes
  • D21C9/1042—Use of chelating agents
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/16—Bleaching ; Apparatus therefor with per compounds
  • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
• • 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
  • D21H17/68—Water-insoluble compounds, e.g. fillers, pigments siliceous, e.g. clays
• • 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
  • D21H21/02—Agents for preventing deposition on the paper mill equipment, e.g. pitch or slime control
• • 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
  • D21H21/32—Bleaching agents

Definitions

• the present invention relates to compositions for use in the bleaching of pulps.
• the compositions are suitable for use as additives for adjustment of pH and/or control of unwanted substances within a pulp slurry during a pulp bleaching step.
• the use of said compositions for example the use of said compositions in a pulp preparation or a papermaking process, as well as bleaching methods for pulps using said compositions.
• kits of ingredients for forming the compositions according to the invention, or for use in a method according to the invention are also part of the present invention.
• alkaline hydrogen peroxide As a bleaching agent.
• hydrogen peroxide and a water soluble alkaline compound such as sodium hydroxide and/or water glass are introduced into the pulp in order to improve whiteness and/or brightness of a wood pulp, a recycled paper pulp or any other chemical or mechanical pulp, such as a pulp for papermaking processes.
• chelating agents like EDTA to remove some of the metal ions from the pulp prior to adding peroxide allows the peroxide to be used more efficiently.
• Magnesium salts and sodium silicate may also be added to improve bleaching with alkaline peroxide. Magnesium salts typically are also used to protect cellulose fibres from too much degradation and therefore strength loss during delignification and bleaching process steps.
• alkaline earth metal hydroxides and/or alkaline earth metal oxides have been employed to replace sodium hydroxide and water glass, and to reduce the need for chelating agents and sodium silicate (see for example as disclosed in Li et al., Pulp & Paper Canada 106:6 (2005), pages T125 to T129 “Using magnesium hydroxide (Mg(OH) 2 ) as the alkali source in peroxide bleaching at Irving paper”).
• WO 2014/195478 A1 discloses the use of pitch control additives in combination with Mg(OH) 2 and/or MgO in paper bleaching pulps, in order to avoid the formation of magnesium based fatty acid salts and resins in paper pulps.
• Alkaline earth metal hydroxides and alkaline earth metal oxides are only sparingly soluble in aqueous solutions, which may lead to a reduction in bleaching efficiency and reduced efficiency in fibre protection.
• MgSO 4 in paper bleaching pulps as a radical scavenger and a slurry stabilising agent. MgSO 4 is expensive and difficult to store, due to its hygroscopic properties.
• Pulp viscosity is a measurement that indicates the strength of the fiber.
• the set-up of pulp processing plants, such as for example pulp bleaching plants, is notably designed to maintain the pulp viscosity while achieving desired bleaching result. Variation of pulp viscosity can therefore be problematic.
• the present invention is embodied by a composition for use in an aqueous pulp bleaching process, the composition comprising (i) one or more alkaline earth metal oxides and/or one or more alkaline earth metal hydroxides; (ii) one or more alkaline earth metal salts; and (iii) optionally, one or more pitch control additives.
• the alkaline earth metal may be selected from magnesium, calcium, or a mixture of magnesium and calcium.
• the alkaline earth metal salt is an alkaline earth metal sulphate, such as for example calcium sulphate or magnesium sulphate.
• the pitch control additive is selected from talc, bentonite, zeolite, diatomaceous earth, cationic mica, hydrophobic carbonates, resin-decomposing enzymes, cationic polymers designed to capture and immobilise resins or resinous components on fibre surfaces, aluminium sulphate, polyaluminium chloride, and dispersing agents specifically designed for the dispersion of resins and resinous components, and mixtures thereof. It was found that these pitch control agents lead to a reduction in fatty acid salts and resins in paper pulps.
• the pitch reduction agent is talc, such as for example micronized talc, bimodal talc, cationic talc, or mixtures thereof.
• the pitch control additive is bentonite, such as an activated bentonite.
• the bentonite is activated by the alkaline earth metal oxide and/or alkaline earth metal hydroxide and/or the alkaline earth metal salt.
• Bentonite may bind heavy metals in the paper bleaching composition and reduce their interference with the bleaching process, for example by degrading the peroxide responsible for the bleaching process.
• the composition may be a dry particulate composition, or the composition may be an aqueous slurry, or the composition may be present as a constituent of an aqueous slurry comprising other components, such as for example, the composition may be present as a constituent of an aqueous paper bleaching pulp.
• a particulate composition according to the invention may be mixed with water in order to prepare an aqueous slurry, which is also a part of the present invention.
• the composition may be an aqueous slurry having a solids content of up to 75 wt.-%, such as for example 10 to 75 wt.-%, on the basis of the total weight of the slurry.
• the weight ratio of (i) the alkaline earth metal oxide and/or the alkaline earth metal hydroxide on the one hand and (ii) the alkaline earth metal salt on the other hand is from 1:10 to 100:1. It was found that the advantageous effects according to the present invention were best obtained if the components are present in such proportions.
• the said weight ratio may be in the range of 1:5 to 50:1, such as for example in the range of 1:2 to 25:1, or from 1:1 to 10:1, such as for example about 2:1, or about 70:30 or about 80:20, or about 90:10.
• the composition may further comprise one or more of the following additives: dispersants; fillers; surfactants; bleaching agents; chelating agents; and pH-buffering agents.
• a kit of ingredients comprising a first container comprising an alkaline earth metal oxide and/or an alkaline earth metal hydroxide, and either one or both of a second and a third container, the second container comprising an aqueous mineral acid solution and the third container comprising sulphur dioxide or carbon dioxide.
• the aqueous mineral acid is aqueous sulphuric acid.
• compositions of the present invention including a step of mixing an alkaline earth metal oxide and/or an alkaline earth metal hydroxide with an acid such as a mineral acid, such as sulphuric acid, or sulphur dioxide, or carbon dioxide, or an alkaline earth metal salt, such as for example an alkaline earth metal sulfate or an alkaline earth metal carbonate, optionally in the presence of one or more pitch control agents.
• an acid such as a mineral acid, such as sulphuric acid, or sulphur dioxide, or carbon dioxide
• an alkaline earth metal salt such as for example an alkaline earth metal sulfate or an alkaline earth metal carbonate, optionally in the presence of one or more pitch control agents.
• the alkaline earth metal may be selected, for example, from magnesium, calcium and mixtures thereof.
• the said method may be carried out in situ within an aqueous pulp bleaching composition. It was found that the alkaline earth metal oxide and/or alkaline earth metal hydroxide efficiently reacted in situ with an acid such as a mineral acid, such as sulphuric acid, and/or sulphur dioxide or carbon dioxide to form a mixture of alkaline earth metal oxide and/or alkaline earth metal hydroxide with alkaline earth metal salt, such as an alkaline earth metal sulphate, in situ.
• an acid such as a mineral acid, such as sulphuric acid, and/or sulphur dioxide or carbon dioxide
• the method according to the present invention may be performed by addition of a mineral acid, such as for example sulphuric acid, or carbon dioxide, or sulphur dioxide to a paper bleaching pulp comprising the alkaline earth metal oxide and/or the alkaline earth metal hydroxide.
• a mineral acid such as for example sulphuric acid, or carbon dioxide, or sulphur dioxide
• the method according to the present invention may be performed by addition of the alkaline earth metal oxide and/or alkaline earth metal hydroxide with an acidic pulp composition (e.g. wherein the only acid present in the acidic pulp composition is acid that is naturally present in the pulp composition (i.e. derived from the wood) or no external acid is added).
• the method may include a step of mixing an alkaline earth metal hydroxide with a mineral acid, wherein the base-acid normality, i.e. the molar ratio of hydroxide ions in the alkaline earth metal hydroxide and the hydrogen cations in the mineral acid is between 10:1 and 1:5, such as for example about 10:1, or about 5:1, or about 4:1, or about 3:1, or about 2:1, or about 1.5:1, or about 1:1, or about 1:1.5, or about 1:2, or about 1:5.
• Corresponding acid/base ratios shall be employed in the case of alkaline earth metal oxide, and carbon dioxide or sulphur dioxide, for example.
• the method may be performed by admixing the ingredients of the kit according to one aspect of the present invention into a paper bleaching pulp. It was found that the said kit was easily transported, stored and applied for use in the method of the invention.
• Also part of the present invention is the use of the composition, the method or the kit as described according to the present invention in a pulp bleaching process. It was found that the pulp bleaching process could be rendered more simple, efficient and less expensive by the use of the present invention, while at the same time reducing the need for expensive raw materials or complex procedures.
• the composition, the method or the kit according to the present invention may be used in a process to reduce pitch in a pulp and/or in a process to protect the pulp from depolymerisation and/or degradation of pulp (e.g., resulting in the formation of stickies).
• methods for reduction of depolymerisation and/or degradation of a pulp and/or for protecting pulp from the formation of degradation products are also part of the present invention.
• the depolymerisation or degradation occurs due to attack of the bleaching chemicals on the cellulose molecules causing reduction of polymer chain length and consequently lower strength properties of the pulp. Very often this degradation is measured as fibre viscosity. Lower chain length by depolymerisation or degradation leads to lower viscosity values and hence lower strength properties which reduced the value of the produced pulp.
• composition or the product of the method or one or more of the components of the kit according to embodiments of the present invention are added to the pulp to be bleached, prior to an addition of any other alkaline bleaching agents, such as water glass, NaOH, sodium silicate, and/or hydrogen peroxide.
• the present invention according to the appended claims provides improvements for paper pulping processes, including bleaching, such as oxygen bleaching, peroxide-oxygen bleaching, oxygen-peroxide bleaching or oxygen delignification, for example.
• bleaching such as oxygen bleaching, peroxide-oxygen bleaching, oxygen-peroxide bleaching or oxygen delignification, for example.
• the improvements can be obtained by the products and kits as defined in the appended claims, as well as by their application according to the methods and uses as defined in the appended claims.
• alkaline earth metals hydroxides and/or alkaline earth metal oxides together with certain alkaline earth metal salts and optionally pitch control agents provides an array of advantages over the state of the art.
• One advantage is the reduction of the formation of harmful deposits in the pulp. This is achieved by the use of, on the one hand, the combination of alkaline earth metal oxide and/or alkaline earth metal hydroxide with the alkaline earth metal salt, and on the other hand by the presence of certain pitch control agents.
• radicals may lead to the formation of unwanted side products, e.g., from depolymerisation and/or degradation of pulp such as pitch, or “stickies”, which may lead to clotting of the slurry, and damage to the downstream paper treatment installations.
• the presence of certain alkaline earth metal salts leads to a stabilising of the pulp viscosity and improvement of the pulp strength properties. This is important for the usability of the pulp in paper and board production and other pulp end uses.
• the viscosity stability is obtained by the use of the compositions or kit of the invention, and leads to a maintenance of viscosity or to a reduction of the decrease in viscosity.
• the use of the compositions or ingredients of the kit leads to a change in viscosity which is no more than 10%, such as for example no more than 5%, or no more than 4%, or no more than 3%, or no more than 2%, or no more than 1%, or no more than 0.5%, or which essentially leads to no measurable change in viscosity.
• alkaline earth metal salts in the present invention allows to adapt the pH-value of the pulp bleaching preparation. Due to the presence of alkaline earth metal oxide and/or alkaline earth metal hydroxide, an alkaline slurry is normally obtained, with an elevated pH of 10 or more, or 11 or more. According to the present invention, the use of alkaline earth metal salt leads to a control of the alkalinity in the pulp bleaching preparation, and it is possible to reduce the pH to a value of between 7 and 10.5, such as for example about 8.5. It is advantageous to work in pH region below 10 or the near neutral region of pH value, in order to protect the equipment from alkali degeneration and evidently for safety reasons.
• the lower pH leads to better bleaching performance and/or reduction in pulp depolymerisation and/or degradation. Accordingly, the loading of alkaline earth metal hydroxide and/or alkaline earth metal oxide in the papermaking pulp may be reduced according to the present invention.
• the said alkaline earth metal salt is obtained by the combination of an alkaline earth metal oxide and/or an alkaline earth metal hydroxide with a mineral acid, or with sulphur dioxide or carbon dioxide in situ before or during a bleaching process.
• a composition comprising magnesium hydroxide and magnesium sulphate may be obtained within a pulp bleaching preparation by introducing magnesium hydroxide and an acid such as sulphuric acid, according to the following reaction:
• Acids such as aqueous sulphuric acid are readily available and easy to store in large quantities over prolonged time at a papermaking site.
• alkaline earth metals salts such as for example magnesium sulphate, are often expensive to procure and store and difficult to handle, due to their low durability or hygroscopic behaviour.
• the methods and kits according to the present invention therefore lead to the formation of the composition according to the present invention, and they also form part of the present invention, and present additional advantages over the prior art.
• the alkaline earth metal hydroxide or alkaline earth metal oxide may be selected from magnesium hydroxide, calcium hydroxide, magnesium oxide and calcium oxide, or mixtures thereof. If an alkaline earth metal oxide is used, this acts in the same way as an alkalinity agent by formation of the corresponding alkaline earth metal hydroxide in aqueous medium. These compounds have a low solubility in water and are therefore released into the pulp only at the rate they are being consumed during the bleaching process. According to the present invention, control of pH is improved as it can be regulated by the addition of alkaline earth metal salt, or acid, in accordance with the embodiments of the invention.
• the alkaline earth metal hydroxide may be magnesium hydroxide.
• the magnesium hydroxide may be crystalline (e.g., brucite). In other embodiments, the magnesium hydroxide may be an amorphous form.
• magnesium hydroxide, calcium hydroxide, and mixtures thereof may be provided by dolomitic limestone being converted to dolomitic lime, which is then converted to magnesium hydroxide, calcium hydroxide, and mixtures thereof.
• Such embodiments including magnesium hydroxide and calcium hydroxide may provide the pulp bleaching benefits described herein as well as a reduction in deposits (e.g., calcium oxalate deposits) and/or a higher availability of soluble hydroxide ions.
• the ratio of magnesium hydroxide to calcium hydroxide in such embodiments may range from 10:1 to 1:10, such as for example from 5:1 to 1:5, such as for example in the range of 1:2 to 2:1.
• the alkaline earth metal salt for use in the present invention may for example be an alkaline earth metal sulphate, such as for example magnesium sulphate.
• an alkaline earth metal sulphate such as for example magnesium sulphate.
• Magnesium sulphate is a hygroscopic particulate salt.
• the use of the alkaline earth metal salt helps to adjust the pH of the slurry, and may also stabilise the slurry.
• magnesium chloride or magnesium nitrate may be used.
• the pitch control agent for use in the composition according to certain embodiments of the present invention may be talc, a natural magnesium silicate with a platy structure.
• the pitch control agent for use in the composition according to certain embodiments of the present invention may be bentonite, an absorbent aluminium phyllosilicate including montmorillonite.
• the bentonite may be activated by the alkaline earth metal hydroxide or alkaline earth metal oxide (e.g., Mg(OH) 2 or Mg(OH)).
• the bentonite may act as an ion exchanger for heavy metals such as Mn, Cr, Fe, and/or Ni, which provides the benefit of rendering these ions less available to disturb the bleaching process.
• the bentonite may stabilize the peroxide used in bleaching and/or reduce the silicate content.
• the pitch control agent may be a blend of talc and bentonite.
• the ratio of talc to bentonite in such embodiments may range from 10:1 to 1:10, such as for example from 5:1 to 1:5, such as for example in the range of 2:1 to 1:2.
• This blend of the two different pitch control agents shows the benefit of treating a wider variety of detrimental substances in the process as both substances have different adsorption properties.
• the hydrophobic surface of talc preferentially adsorbs hydrophobic materials while bentonite has more attraction for hydrophilic substances.
• the compositions for use in bleaching of pulps may be present as an aqueous slurry.
• Aqueous slurries are commonly used, for example in papermaking, for introducing solids into a pulp.
• a composition according to certain embodiments of the present invention in the form of an aqueous slurry may be introduced into the pulp in order to support hydrogen peroxide bleaching.
• the aqueous slurries comprising the composition according to certain embodiments of the present invention have a solids content of 10 wt.-% or higher, on the basis of the total weight of the slurry, such as 30 wt.-% or higher, or 30 wt.-% or higher, or 40 wt.-% or higher, or 45 wt.-% or higher, or 50 wt.-% or higher, or even 60 wt.-% or higher, such as up to 70 wt.-%, or 72 wt.-%, or 75 wt.-%.
• the slurries may also comprise further components such as fillers, surfactants, bleaching agents, pH-buffering agents, or other additives.
• the compositions have the form of dry particulate powders.
• the compositions may be transported as dry powders and slurries be formed only at the site of use of the compositions in a bleaching process.
• the said dry particulate powders may be obtained, for example, by use of a spray-drying process.
• Spray-dried particulate compositions may have a low or a very low moisture content, such as for example 5 wt.-% moisture or less, based on the total amount of solids in the spray-dried particulate powder, or 4 wt.-% moisture or less, or 3 wt.-% moisture or less, or even 2 wt.-% moisture or less, such as for example about 1 wt.-% moisture or 0.5 wt.-% moisture.
• the dry compositions may also comprise further components such as dispersants, fillers, surfactants, bleaching agents, chelating agents, pH-buffering agents, or other additives.
• the compositions are in the form of pellets.
• the pellets may have a moisture content from 0.1 wt.-% to 25 wt.-%, based on the total weight of the composition, such as for example from 2 wt.-% to 20 wt.-% or from 5 wt.-% to 15 wt.-%, such as for example about 15 wt.-%.
• the pellets may comprise from 2 wt.-% to 50 wt.-% pitch control additive and from 98 wt.-% to 50 wt.-% particulate alkaline earth metal oxide or alkaline earth metal hydroxide or mixtures thereof, based on the total solids content of the pellets.
• the compositions for use in bleaching of pulps may have a weight ratio of the alkaline earth metal oxides and/or alkaline earth metal hydroxides on the one hand, and the alkaline earth metal salt on the other hand in the range of 1:1 to 100:1, such as for example from 2:1 to 50:1, such as for example in the range of 3:1 to 25:1, or from 5:1 to 10:1, such as for example about 70:30 or about 80:20, or about 90:10.
• the kit of ingredients may include such amounts of ingredients that a weight ratio as described above may be obtained. It is understood by the skilled person in the art that such weight ratio as a result of the reaction of, for example, magnesium hydroxide with sulphuric acid to obtain magnesium sulphate, as described above, may depend on many factors, such as concentration, temperature, relative amounts of ingredients, acidity/alkalinity prior to the reaction, etc. According to certain embodiments of the present invention, the method for obtaining a composition according to the invention may be carried out in such a way that a weight ratio as described above may be obtained.
• the weight ratio of the alkaline earth metal oxides, alkaline earth metal hydroxides and the alkaline earth metal salt on the one hand, and the pitch control agent on the other hand may be ranging from 1:9 to 9:1, such as for example between 3:7 and 7:3, such as for example ranging from 2:3 to 3:2, for example at a weight ratio of 1:2, or 1:1, or 2:1.
• the compositions for use in bleaching of pulps may comprise the one or more particulate alkaline earth metal oxides or alkaline earth metal hydroxides in an amount of 10 wt.-% to 90 wt.-% of the total solids content of the composition, such as for example in an amount of 30 wt.-% to 70 wt.-% of the total solids content of the composition, such as for example in an amount of 40 wt.-% to 60 wt.-% of the total solids content of the composition, such as for example in an amount of 50 wt.-% of the total solids content of the composition.
• the compositions for use in bleaching of pulps may comprise the alkaline metal salt in an amount of 0.1 wt.-% to 50 wt.-% of the total solids content of the composition, such as for example in an amount of 1 wt.-% to 30 wt.-% of the total solids content of the composition, such as for example in an amount of 5 wt.-% to 15 wt.-% of the total solids content of the composition, such as for example in an amount of 10 wt.-% of the total solids content of the composition.
• the compositions for use in bleaching of pulps may comprise one or more pitch control additives in an amount of 1 wt.-% to 90 wt.-% of the total solids content of the composition, such as for example in an amount of 10 wt.-% to 70 wt.-% of the total solids content of the composition, such as for example in an amount of 20 wt.-% to 60 wt.-% of the total solids content of the composition, such as for example in an amount of 50 wt.-% of the total solids content of the composition.
• compositions or kits of ingredients according to certain embodiments of the present invention in the bleaching process of pulps, such as in the bleaching process of pulps for papermaking.
• the compositions according to certain embodiments of the present invention may be used in combination with other additives such as hydrogen peroxide, complexing agents, water glass, or others, in a bleaching process of pulp in a paper making process.
• compositions according to the present invention may fully or partially replace known alkaline compositions, such as NaOH.
• NaOH may be fully omitted as the alkaline agent in a H 2 O 2 -bleaching process, or the amount of NaOH may be reduced by simultaneous addition of a composition according to the present invention.
• an additional aspect of the present invention is the use of a composition obtained by separately introducing one or more (e.g. all) of the components of a composition into a papermaking pulp, or by separately introducing one or more (e.g. all) of the components of a kit of ingredients into a papermaking pulp, thereby forming the composition within a pulp during the bleaching of said pulp.
• the composition or the kit of ingredients according to certain embodiments of the present invention may be introduced into the pulp in such an amount that the amount of the one or more particulate alkaline earth metal oxides or alkaline earth metal hydroxides or mixtures thereof in the pulp is from 0.1 wt.-% to 8 wt.-% of the total solids content of the pulp during the bleaching, such as from 0.2 wt.-% to 4 wt.-% of the total solids content of the pulp during the bleaching, such as from 0.5 wt.-% to 2.5 wt.-% of the total solids content of the pulp, such as for example 1 wt.-% or 2 wt.-% of the total solids content of the pulp, and that the amount of the one or more alkaline earth metal salts in the pulp is from 0.01 wt.-% to 5 wt.-% of the total solids content of the pulp during the bleaching, such as from 0.02 wt.-% to 1 w
• the composition or the ingredients of a kit of ingredients for use in bleaching of a papermaking pulp may be included in said pulp for example during the bleaching stage, or at the beginning of the bleaching stage, or prior to the bleaching stage. It also may be included during or prior to the delignification stage.
• the composition for use in bleaching of a papermaking pulp may be included in said pulp as early as the grinding stage during which the pulp components are ground, or at any time between the grinding stage and the bleaching stage.
• the various components of the composition according to certain embodiments of the present invention may also be added to the papermaking pulp at separate stages, such as for example during the grinding stage and or just prior initiation of the bleaching step or the delignification step.
• the composition or the ingredients of a kit of ingredients for use in bleaching of a papermaking pulp may be introduced into a pulp to be bleached prior to the introduction of any alkaline bleaching agents, such as NaOH, waterglass, sodium silicate, and/or hydrogen peroxide.
• any alkaline bleaching agents such as NaOH, waterglass, sodium silicate, and/or hydrogen peroxide.
• the alkaline earth metal oxide or the alkaline earth metal hydroxide has been activated by the presence of alkaline earth metal salt (such as earth metal sulphate), and/or organic acids of wood origin present in the pulp mixture, and/or the mineral acid prior to the beginning of the bleaching process.
• the alkaline earth metal hydroxide and/or alkaline earth metal oxide is added to an acidic pulp mixture (e.g. wherein the only acids present are those naturally found in the pulp and/or no external acid is added) prior to the beginning of the bleaching process and/or prior to the addition of any alkaline bleaching agents.
• an acidic pulp mixture e.g. wherein the only acids present are those naturally found in the pulp and/or no external acid is added
• composition of ingredients or the ingredients of a kit of ingredients may be added at an earlier step, such as during an acidic bleaching step, during the addition of chelating agents such as EDTA or chlorine dioxide.
• This embodiment includes all uses of the composition of ingredients or the ingredients of a kit of ingredients in a bleaching step which occurs at a pH of 7 or below.
• a composition for use in a pulp bleaching process comprising one or more alkaline earth metal oxides and/or one or more alkaline earth metal hydroxides; one or more alkaline earth metal salts; and optionally, one or more pitch control additives.
• said pitch control additive is selected from talc, bentonite, zeolite, diatomaceous earth, cationic mica, hydrophobic carbonates, resin-decomposing enzymes, cationic polymers designed to capture and immobilise resins or resinous components on fibre surfaces, aluminium sulphate, polyaluminium chloride, and dispersing agents specifically designed for the dispersion of resins and resinous components, and mixtures thereof.
• a composition according any of the previous numbered sentences wherein the alkaline earth metal is selected from magnesium, calcium, and mixtures thereof. 4.
• a composition according to any of the previous numbered sentences which is an aqueous slurry.
• a composition according to numbered sentence 6 wherein said aqueous slurry has a total solids content of from 10 to 75 wt.-%, on the basis of the total weight of the slurry.
• composition according to any of the previous numbered sentences wherein the weight ratio of (i) an alkaline earth metal oxide and/or an alkaline earth metal hydroxide and (ii) an alkaline earth metal salt is from 1:2 to 100:1.
• a composition according to any of the previous numbered sentences further comprising at least one of the following additives: (a) dispersants; (b) fillers; (c) surfactants; (d) bleaching agents; (e) chelating agents; and (f) pH-buffering agents. 10.
• a kit of ingredients comprising, an alkaline earth metal oxide and/or an alkaline earth metal hydroxide stored in a first container, and either one or both of a second and third container with an aqueous mineral acid solution stored in the said second container and sulphur dioxide and/or carbon dioxide stored in the said third container.
• a method according to numbered sentence 11 when performed within an aqueous pulp bleaching composition. 13.
• a method according to numbered sentence 12 wherein the step of mixing is performed by addition of sulphuric acid or sulphur dioxide or carbon dioxide to a paper bleaching pulp comprising the alkaline earth metal oxide and/or the alkaline earth metal hydroxide.
• a method according to any one of numbered sentences 11 to 13 comprising the step of admixing the ingredients of the kit of numbered sentence 10 into a paper bleaching pulp or a delignification pulp.
• a use according to numbered sentence 15 in a process to reduce pitch in the pulp. 17.
• pulp viscosity was measured in accordance with TAPPI T 230 om-08. Furthermore, as used herein, the kappa value indicating the residual amount of lignin in the pulp was measured in accordance with ISO-302:2012.
• magnesium hydroxide as an additive was compared to the use of magnesium hydroxide in combination with mineral acid, as well as in combination with mineral acid and EDTA as a chelating agent.
• Pulp testing was performed to the usual standards according to German Thünen Institute (Hamburg, Germany). The viscosity was determined according to ISO 5351 using a copper ethylenediamine (cuen) solution. The results are shown in Table II.
• Example 3 making use of EDTA in addition to the combination Mg(OH) 2 /H 2 SO 4 , does not substantially modify the expected technical properties of the pulps.
• Pulp mixtures shown in Table III were prepared by first mixing the additive components together and then adding this mixture to an aqueous pulp.
• the bleaching was carried out in plastic bags, put in a preheated water bath of 70° C. with the bag opening outside the water to avoid additional water getting into the bag during the bleaching.
• the total reaction time was about 2 hours in each case.
• magnesium hydroxide can be used to replace sodium hydroxide in the bleaching process when using an acidic pulp mixture. Even at relatively low substitution rates of NaOH by Mg(OH) 2 , a significant drop in COD values can be observed. This is advantageous for pulp yield since each kg produced COD is lost pulp yield. It also has a positive effect on the COD in the waste water, which thus provides an improved environmental impact.
• Pulp mixtures shown in Table V were prepared by either mixing the additive components and then adding this mixture to aqueous pulp, or, where the magnesium hydroxide was added to the pulp first, adding the magnesium hydroxide to the aqueous pulp and mixing the pulp mixture by hand for around 1 minute, then mixing the remaining additive components and adding this mixture to the magnesium hydroxide and pulp mixture.
• the bleaching was carried out in plastic bags, put in a preheated water bath of 70° C. with the bag opening outside the water to avoid additional water getting into the bag during bleaching. The total reaction time was about 80 minutes in each case.
• Pulp mixtures shown in Table VII were prepared by either mixing the additive components and then adding this mixture to aqueous pulp, or, where the magnesium hydroxide was added to the pulp first, adding the magnesium hydroxide to the aqueous pulp and mixing the pulp mixture by hand for around 1 minute, then mixing the remaining additive components and adding this mixture to the magnesium hydroxide and pulp mixture.
• the bleaching was carried out in plastic bags, put in a preheated water bath at 70° C. with the bag opening outside the water to avoid additional water getting into the bag during bleaching. The total reaction time was about 80 minutes in each case.
• the present invention may comprise any combination of the features and/or limitations referred to herein, except for combinations of such features which are mutually exclusive.
• the foregoing description is directed to particular embodiments of the present invention for the purpose of illustrating it. It will be apparent, however, to one skilled in the art, that many modifications and variations to the embodiments described herein are possible. All such modifications and variations are intended to be within the scope of the present invention, as defined in the appended claims.

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