EP1196503A1 - Produits du kaolin, leur preparation et leur utilisation pour la production de papier ou d'un revetement - Google Patents

Produits du kaolin, leur preparation et leur utilisation pour la production de papier ou d'un revetement

Info

Publication number
EP1196503A1
EP1196503A1 EP00929693A EP00929693A EP1196503A1 EP 1196503 A1 EP1196503 A1 EP 1196503A1 EP 00929693 A EP00929693 A EP 00929693A EP 00929693 A EP00929693 A EP 00929693A EP 1196503 A1 EP1196503 A1 EP 1196503A1
Authority
EP
European Patent Office
Prior art keywords
suspension
clay mineral
oba
coating composition
treatment
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00929693A
Other languages
German (de)
English (en)
Inventor
John Claude Husband
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Imerys Minerals Ltd
Original Assignee
Imerys Minerals Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GBGB9911393.8A external-priority patent/GB9911393D0/en
Priority claimed from GBGB9911396.1A external-priority patent/GB9911396D0/en
Application filed by Imerys Minerals Ltd filed Critical Imerys Minerals Ltd
Publication of EP1196503A1 publication Critical patent/EP1196503A1/fr
Withdrawn legal-status Critical Current

Links

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
    • D21H19/00—Coated paper; Coating material
    • D21H19/36—Coatings with pigments
    • D21H19/38—Coatings with pigments characterised by the pigments
    • D21H19/40—Coatings with pigments characterised by the pigments siliceous, e.g. clays
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/40—Compounds of aluminium
    • C09C1/42—Clays
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/60—Optical properties, e.g. expressed in CIELAB-values

Definitions

  • the present invention relates to kaolin products and their preparation and use in paper making and coating.
  • the invention is concerned with improved kaolin products to be used in compositions for paper making and especially for paper coating in which an optical brightening agent is employed.
  • Kaolin particulate materials are one of a number of kinds of mineral material employed as property enhancing fillers in compositions for making paper and like products and as property enhancing pigments in compositions for coating paper and like products.
  • OBAs optical brightening agents
  • One purpose of the present invention is to provide a kaolin particulate material which shows enhanced fluorescence when used in compositions containing an OBA.
  • a method for the preparation of a kaolin product for use in paper filling or pigment coating applications in the presence of an optical brightening agent which includes the steps of (a) preparing an aqueous suspension of a clay mineral comprising a kaolin particulate material; and (b) treating the clay mineral by addition of a treatment agent which reduces the harmful effect of metal ions present in the clay mineral on the activity of the OBA, the treatment agent being substantially free of multivalent cations and comprising (i) a complexing agent or (ii) formamidine sulfinic acid (FAS) .
  • paper filling or coating compositions may be produced as demonstrated later which show improved fluorescence brightness compared with clay minerals treated in accordance with prior art methods .
  • ⁇ paper' embraces products which are of paper, board, card and the like.
  • complexing agents have been used in the prior art to improve the whiteness and brightness of a natural white mineral material they have not been used to enhance the fluorescence produced by an OBA in the presence of a clay mineral pigment or filler by preventing the quenching effect of metals such as iron on an OBA.
  • WO-9707076-A1 relates to a method of producing whitened layer silicates using formamidine sulfinic acid as a bleaching agent.
  • a clay mineral bleached with FAS will exhibit less of a quenching effect on the fluorescence produced by an OBA.
  • complexing agents produce good gains in the fluorescence that may be produced by an OBA compared to a conventional reductive bleaching agent such as sodium hydrosulfite which gives only slight gains. The improvement in fluorescence when an OBA is used with a clay mineral treated in this way could not have been expected.
  • the treatment agent comprises a complexing agent
  • the complexing agent may comprise one or more known chelating agents for metal ions, especially ions of transition metals such as iron.
  • the complexing agent may comprise one or more of triethanolamine
  • the treated kaolin product produced in step (b) may be treated, prior to OBA addition, to remove impurities, such as iron, solubilised by the addition of the treatment agent.
  • the treatment to remove impurities may include the steps of dewatering and optionally washing, e.g. diluting with water and reconcentrating.
  • the dewatering step and washing and reconcentrating steps may be carried out in a well known manner, for example by sedimentation, decantation, centrifugation or by the use of a filtration membrane.
  • the impurities solubilised by the treatment in step (b) especially where the treatment agent comprises TEA, mayu be retained in the suspension and the suspension may subsequently be employed in an OBA-containing composition, e.g. for paper making or paper coating.
  • the clay mineral which is used in this invention may have considerable iron staining in its untreated state but in its pure state it may be substantially free of any such staining.
  • the clay mineral may contain at least 50% by weight kaolinite.
  • most commercially important china clays and kaolin minerals contain greater than 75% by weight kaolinite and may contain greater than 90%, in some cases greater than 95% by weight of kaolinite.
  • the clay mineral for use in the invention may be treated by one or more other processes which are well known to those skilled in the art, for example by known refining or remediation steps.
  • the clay mineral may be bleached with a reductive bleaching agent, such as sodium hydrosulfite, prior to step (b) and optionally prior to step (a) .
  • a reductive bleaching agent such as sodium hydrosulfite
  • the bleached clay mineral may optionally be dewatered, and optionally washed and again optionally dewatered, after the sodium hydrosulfite bleaching step.
  • the clay mineral used in step (a) of the first aspect of the invention may be untreated in the form of a solid or as an aqueous suspension and after treatment in step (b) with FAS or a complexing agent it may optionally undergo further refining and benefication steps, for example bleaching with a reductive bleaching agent, such as sodium hydrosulfite, prior to its use in an OBA containing composition.
  • a reductive bleaching agent such as sodium hydrosulfite
  • a paper making or coating composition containing a kaolin product produced in accordance with the method of the first aspect of the invention and also an OBA allows paper products of improved fluorescence to be obtained. Such products are brighter in daylight and this is a highly desirable property, particularly in high quality papers. Furthermore the effect of the improved fluorescence may be shown by a kaolin product which may or may not be made significantly brighter by further bleaching.
  • a wide variety of organic molecules containing delocalised ⁇ electrons can be used as optical brightening agents though for economic reasons the OBAs generally used are dye molecules which are derivatives of 4 : 4 x -bistriazinyl aminostilbene-2 : 2 " -disulfonic acid which has the generalised structure shown below;
  • the identity of the groups x, y, w and z vary and are known to affect the substantivity of the molecule to the substrate.
  • molecules contain at least 4 and sometimes 6 sulfonic acid groups.
  • the OBA used in in conjunction with the kaolin product produced by the method of the first aspect of this invention may comprise one or more OBAs known in the art, for example it may comprise one or more molecules containing between 2 and 6 sulfonate groups, e.g. one or more substituted stilbenes.
  • solutions of commercially available OBAs sometimes contain one or more additives, e.g. a stabiliser such as urea.
  • An activator (or carrier) may be used in conjunction with the OBA. This interacts with the OBA molecules and allows greater levels of fluorescence to be achieved. Self activating OBA are also commercially available in which an activator has been combined with an OBA.
  • the aqueous clay mineral suspension employed in step (a) of the method according to the first aspect of the invention may have a solids content of between 10% and 70% by weight, e.g. from 12% to 50%, especially from 15% to 30% based on the total weight of the suspension. Mixing of the suspension may be for a period of time e.g. 2 to 30 minutes, especially 5 to 15 minutes to help to attempt to form a homogenous suspension.
  • the process of forming a suspension of the required solids content is well known to those skilled in the art .
  • a gas may be bubbled through the clay mineral suspension before and during the treatment process of step (b) to help to minimise the reversion of the iron to the oxidised ferric state which causes the undesirable discolouration of the clay mineral and quenches the fluorescence produced by the OBA when the OBA is added to the clay mineral.
  • the gas may be a non-oxidising gas, especially an inert gas, e.g. nitrogen.
  • the addition of the gas before the treatment step may be carried out during the formation of the suspension described earlier or as a separate step once the suspension is formed and is relatively homogenous. If it is added once the suspension is formed it may be added with the suspension still being mixed.
  • the addition of gas prior to the treatment process of step (b) may last for a period of time e.g.
  • the suspension may also be stirred during the treatment in step (b) of the first aspect of the invention as well as before and during the addition of the gas.
  • the OBA added to the kaolin product or suspension containing it may be added either alone or together with other ingredients, e.g. in the preparation of a pigment coating composition to incorporate the kaolin product as a pigment ingredient. The preparation of coating compositions is described later. If the OBA is used with other ingredients these may be added to the coating composition either before or after the OBA or they may be combined with the OBA prior to its addition into the pigment coating composition.
  • the OBA itself may be in solution, for example in an aqueous solution, which may contain other additives such as urea.
  • the OBA could alternatively be added in a dry form.
  • the other ingredients added before, with, or after the OBA or combined with it may include one or more ingredients selected from binders, activators, dispersants and other ingredients commonly used in coating compositions.
  • the treatment agent used to treat the kaolin product produced by the method according to the first aspect of the invention may be either (i) a complexing agent or (ii) FAS.
  • Step (b) may involve adding the treatment agent and leaving the suspension for a period of time to allow the reaction with impurity species provided by the treatment to take place. The suspension may be stirred during this time.
  • treatment agent is (i) a complexing agent the following conditions may be used.
  • the complexing agent may be added in dry form or in an aqueous solution. If an aqueous solution of the complexing agent is used this may be adjusted to a suitable pH before it is added to the clay mineral suspension and once the complexing agent is added the pH of the clay mineral suspension may then be adjusted to the pH required for the reaction.
  • the complexing agent may be added in an active amount of up to 80 kg.t -1 , e.g. in an amount from O.lkg.t -1 to 30kg. t "1 especially
  • the treatment of the clay mineral suspension with the complexing agent may be carried out for between 10 minutes and 5 hours, e.g. from 30 minutes to 4 hours, especially from 45 minutes to
  • the suspension may be mixed by stirring during this time.
  • Treating with the complexing agent may be carried out at a temperature of between 10°C and
  • 80°C e.g. between 20°C and 70°C, especially between 40°C and 65°C.
  • the pH of the clay mineral suspension is preferably adjusted during or immediately after the addition of the complexing agent.
  • the most beneficial pH for the reaction depends on the complexing agent used although it may be in the range of between pH 1.5 and 9, especially between pH 2 and 7.5. With EDTA the best results have been achieved at a low pH of between 2 and 3.
  • the pH adjustment of the clay mineral suspension may be carried out using dilute solutions of an acid, such as a 5% to 15% solution of sulfuric acid, or dilute solutions of a base, such as a 5% to 15% solution of sodium hydroxide. If the complexing agent is used as an aqueous solution, the pH of this may be adjusted in the same manner.
  • the suspension may preferably be dewatered, preferably using filtration to remove the complexed impurities, especially the complexed iron impurity, from the clay mineral.
  • the clay mineral may be filtered at the pH of the reaction.
  • the pH may be lowered, e.g. to between pH 3 and 6, especially to between pH 3.5 and 4.5, preferably using a dilute solution of an acid, such as a 5% to 15% solution of sulfuric acid. This process allows the complexing agent to be used at a pH of above 7 without the disadvantage of the clay mineral deflocculating on filtering.
  • treatment agent used to treat the clay mineral in step (b) according to the first aspect of the invention is (ii) FAS the following conditions may be used:
  • FAS may be used in an amount of up to 40kg. t “1 especially from O.lkg.t “1 to 20kg. t '1 , e.g. from lkg. t “1 to 10kg. t “1 .
  • the treatment may be carried out for up to 1.5 hours, e.g. for between 10 minutes and 1 hour, especially for between 20 and 50 minutes.
  • Treatment with FAS may be carried out at a temperature of between 10°C and 90°C, e.g. between 15°C and 70°C, e.g. between 20°C and 60°C.
  • the clay mineral suspension may have its temperature adjusted to that required for the reaction prior to the addition of the FAS.
  • FAS is a reductive bleaching agent and works via the typical reaction of
  • a base such as sodium hydroxide must therefore be present in an amount of at least a 1:1 molar ratio with the FAS, in order to use the FAS most effectively, when FAS is used to treat the clay mineral.
  • a considerably higher molar ratio of base: FAS of 9:1 gives superior results and when low doses of FAS are used the molar ratio of base: FAS used may be as high as 70:1.
  • the base: FAS molar ratio may therefore be between 1:1 and 70:1, e.g. between 2:1 and 35:1, especially from 4:1 to 15:1.
  • the base may be sodium hydroxide.
  • the sodium hydroxide in a solution of between 10% and 40% by weight e.g. from 15% to 25%.
  • an aqueous clay mineral suspension and to form a solution of the FAS and an alkali such as sodium hydroxide which is added to the clay mineral suspension to give a suspension with a suitable solids content during the treatment process.
  • the solids content of the clay mineral suspension during the treatment process may be between 10% and 70% by weight, e.g. from 12% to 50%, especially from 15% to 30%.
  • the solid FAS or an aqueous solution of FAS alternatively be added separately to the clay mineral suspension without first forming a solution of FAS with alkali such as sodium hydroxide, the alkali being added separately.
  • the pH of the suspension may be lowered to between pH 3 and 6, e.g. to between pH 3.5 and 4.5, for example using an acidic solution, e.g. an aqueous solution of sulfuric acid, e.g. a 5 to 15% solution, although more concentrated solutions could also be used.
  • the suspension may then preferably be dewatered, for example by filtration.
  • the treated clay mineral produced in step (b) of the method according to the first aspect of the invention using either (i) a complexing agent or (ii) FAS as the treatment agent, has been dewatered it may optionally be resuspended at a solids level similar to that used for the treatment process e.g. between 10% and 70% by weight, e.g. from 12% to 50%, especially from 15% to 30% and mixed for a period of time, e.g. from 1 to 30 minutes, especially from 10 to 20 minutes before it is again optionally dewatered to remove any remaining impurities.
  • the filter cake so formed may be washed through with water whilst on a filter rather than by being re-suspended and again dewatered in the process previously described.
  • the dewatered clay mineral cake produced by either of the methods above may then be dried, e.g. thermally dried. Thermal drying may be carried out at a temperature of at least 60°C, especially at least 80°C for a period of time, e.g. 1 to 10 hours especially for 2 to 6 hours,
  • the dry treated clay mineral may optionally then be ground or milled to give a fine powder suitable for use in paper filling or pigment coating applications .
  • the dewatered kaolin product may also be used in a paper making or coating composition without the drying step,
  • the kaolin product may be used as a wet solid after the initial dewatering step or after the optional washing and reconcentrating/dewatering steps and water may be added to it after dewatering to form an aqueous suspension.
  • the amount of water removed in either of the dewatering stages may be controlled so that the solids content of the aqueous suspension is adjusted to that required for use in the application, e.g. coating composition.
  • the kaolin product could also be used without any dewatering or washing but it is usual to carry out the initial dewatering.
  • the application suspension in which the kaolin product is used may comprise a paper making composition, e.g.
  • the composition in which the kaolin product is used, together with an OBA may comprise a coating composition, e.g. for coating paper products.
  • the other components of the composition may be conventional.
  • the composition for coating may contain a dispersant, for example one of the well known dispersants employed in the art.
  • the dispersant may be a polyelectrolyte, e.g. a polyacrylate dispersant, e.g. sodium polyacrylate .
  • compositions for coating paper or the like which composition comprises : (A) an aqueous suspension of pigment material; (B) a binder; and (C) an OBA; wherein the pigment material comprises a kaolin product produced by steps (a) and (b) of the method according to the first aspect.
  • the kaolin product produced by the method according to the first aspect of the present invention may be the sole component of the pigment material. Alternatively the kaolin product may be blended with one or more additional pigment materials well known to those skilled in the art.
  • the other pigment materials may for example comprise a mineral selected from kaolinite containing minerals, calcined kaolin, titania, talc, so called plastic pigment, calcium sulphate, silica, mica or calcium carbonate. If calcium carbonate is used as the additional pigment material it may be either a natural ground calcium carbonate or a synthetic precipitated calcium carbonate. If the kaolin product of the method according to the first aspect of the present invention is blended with one or more other pigment materials then it may be present in an amount of between 1% and 99% by weight in the blended pigment material. For example the blended pigment material may contain between 10% and 90%, especially between 25% and 75%, by weight of the kaolin product.
  • the solids content of the coating composition according to the second aspect may be from 40% to 90%, e.g. 50% to 80%, in many cases from 60% to 75% by weight.
  • the binder may be added, on an active basis, in an amount of up to 30% by weight based on the dry weight of the pigment material. Usually, the active binder content will be less than 10% by weight, e.g. from 4% to 6% by weight based on the dry pigment weight .
  • Such a composition could be prepared by any person skilled in the coating art in a known manner and may also contain other known additives.
  • the OBA in the composition according to the second aspect may be added, on an active basis, in an amount of up to 2% by weight, e.g. from 0.01% to 1%, especially 0.05% to 0.5%, more especially 0.1% to 0.2% by weight based on the dry weight of the kaolin product present in the suspension.
  • the OBA could be added to a dry powder of the clay mineral. It may though be found most convenient to add the OBA to an aqueous suspension formed from the dried kaolin product which is to form a coating composition as previously described.
  • Known additives may be associated with the OBA.
  • a known activator or carrier
  • the OBA may be self activating.
  • the OBA may comprise one or more OBA compounds known in the art, for example it may comprise one or more stilbene compounds containing between 2 and 6 sulfonate groups.
  • the activator may comprise a polyvinyl alcohol (PVOH) and the binder may comprise a latex binder, although other OBAs, water-borne binders and activators known in the art may be used.
  • an activator may be used in conjunction with the OBA, as previously described, in the pigment coating composition.
  • Coating pigments and latex binders, with the exception of PVA latices do not act as OBA activators so, in order to achieve the required levels of fluorescence, an activator may be present within the coating composition.
  • Suitable activators are water soluble polymers such as polyvinyl alcohol (PVOH) , sodium carboxymethyl cellulose (NaCMC) starch, or proteins.
  • PVOH polyvinyl alcohol
  • NaCMC sodium carboxymethyl cellulose
  • PVOH low molecular weight polyethylene glycol
  • Most of these polymers also function as cobinders, thickeners and possibly water retention aids.
  • the coating composition according to the second aspect may be prepared in a known manner by first forming an aqueous suspension. This may be done by dispersing the dry kaolin product into a solution of water and dispersant. Alternatively, dispersant and if necessary additional water may already have been added to the wet clay mineral at some point prior to the end of step (b) and the wet dispersed product may be employed.
  • the dispersant may be used, on an active basis, in amounts of up to 3% by weight, e.g. from 0.01% to 2% by weight, e.g. from 0.05% to 1%, especially 0.1% to 0.5% based on the dry weight of the pigment material in the coating composition.
  • the pH of this coating composition may be adjusted, e.g. to between pH 6 and 10, especially to between pH 7.5 and 8.5. This may be done using an aqueous solution of a base such as sodium hydroxide, especially a dilute solution, which may be a 5% to 15% solution.
  • the pigment coating composition may also optionally contain other well known additives additional to those hereinbefore described to control other properties of the composition, in a well known manner .
  • a coating composition was prepared from an untreated
  • English kaolin clay which had a particle size distribution such that about 70% by weight consisted of particles smaller than 2 ⁇ m and a powder brightness of 77.1 ISO brightness units.
  • the coating composition was made using 50g of the dry clay, 0.3% by weight, on an active basis, of sodium polyacrylate dispersant based on the dry weight of the pigment material and 22.5g of water to which about 0.5cm 3 of a 10% solution of NaOH and a small amount of water were added to produce a lump free suspension. These were all mixed together using an impeller with the clay added slowly to the water and dispersant solution. The suspension of pigment material was weighed so that reagents could be added in the correct concentrations.
  • Latex sold under the trade name Dow 950 in an amount of 5%, on an active basis, by weight based on the dry weight of the pigment material was added.
  • the pH was adjusted to between 7.8 and 8.0 and then the coating composition was screened using a 53 ⁇ m screen before after which it was coated onto an impervious, non fluorescent plastics substrate made of material sold under tha trade name Synteape using wire wound hand draw down rods.
  • the pigment which had a powder brightness of 77.1 ISO brightness units, produced a coating with a fluorescence of 2.46 ISO brightness units at a coat weight of lOg.m .
  • All measurements of powder brightness given in this specification were carried out using a reflectance spectrophotometer calibrated using an ISO level 2 standard, using a barium sulfate tablet, as the primary reference.
  • All measurements of the paper brightness which were used to determine the fluorescence of the coated paper were carried out using a reflectance spectrophotometer calibrated with ISO method 2469 (Methods for determining optical properties of pulp, paper and board) level 3 reference standards and fluorescence reference standards.
  • a coating composition was prepared according to the procedure described in Example 1 using a kaolin clay mineral which had been bleached with sodium hydrosulfite in a concentration of 2.5 kg.t -1 relative to the dry weight of the clay mineral.
  • For the hydrosulfite bleaching an aqueous suspension was prepared containing 20% by dry weight of the same feed clay as used in Example 1. The suspension was mixed by stirring using an impeller for 20 minutes to achieve a homogeneous suspension in a water bath at 20°C and then the pH was lowered to 2.3 with a 10% solution of sulfuric acid.
  • a commercially available phosphate was added in an amount of 1 kg.t -1 relative to the dry weight of the clay mineral. The suspension was stirred for a further 15 minutes. Sodium hydrosulfite was then added in an amount of 2.5 kg.t -1 relative to the dry weight of the clay and the suspension was stirred for 20 minutes to help to ensure complete and homogenous bleaching.
  • the pH of the suspension was raised to pH 4 with a 10% solution of sodium hydroxide and then dewatered by filtering using a Buchner funnel.
  • the wet clay mineral cake so produced was washed by re- suspension in clean water to give a suspension of approximately 20% solids which was stirred for 20 minutes to give a homogenous suspension. This was then further dewatered by filtering using a
  • the coating composition was prepared and applied to a substrate, and the brightness and fluorescence of the coated substrate was measured, as described in Example 1.
  • An aqueous suspension was prepared using 150g of dry kaolin clay and 600g of distilled water to produce a suspension containing 20% by dry weight of the same feed clay as used in
  • Example 1 The suspension was mixed by stirring using an impeller for 20 minutes to achieve a homogeneous suspension and the suspension was then stirred for a further 15 minutes while nitrogen gas (oxygen free) was bubbled through it to exclude oxygen. This was carried out in a sealed reaction vessel equipped with a nitrogen inlet tube to bubble nitrogen into the clay suspension and an outlet hole in the top of the vessel equipped with a condenser through which the nitrogen could leave the reaction vessel.
  • nitrogen gas oxygen free
  • Ethylenediaminetetra-acetic acid (EDTA) in the form of its disodium salt was then added to the suspension in an amount of 1 kg.t -1 relative to the dry weight of the clay mineral and the pH was adjusted using a 10% solution of sulfuric acid to give a pH of 2.3.
  • the reaction vessel was resealed and then immersed in a water bath at 60°C and left for a nominal reaction period of four hours with continual stirring. Nitrogen was passed through the suspension during this period.
  • the suspension was dewatered by filtering using a Buchner funnel and the wet clay mineral cake so produced was washed by re-suspension in clean water to form a suspension of approximately 20% solids and this was stirred for 20 minutes until it was homogeneous.
  • the suspension was then further dewatered by filtering using a Buchner funnel and left overnight to dry.
  • the clay mineral cake produced was placed in an oven at a temperature of 80°C for a period of 4 hours to produce a bleached clay mineral of approximately 98% solids content. This product was ground using a pestle and mortar ready for incorporation in a coating composition and for testing.
  • a coating composition was prepared and applied to a substrate, and the brightness and fluorescence of the coated paper were measured, as described in Example 1.
  • Example 3 The procedure of Example 3 was repeated using an EDTA dose of 10kg. t -1 and the same feed clay as used in Example 1 which had first been bleached with sodium hydrosulfite in a concentration of 2.5 kg.t -1 relative to the dry weight of the clay mineral.
  • the hydrosulfite bleaching was carried out according to the process of Example 2 except that after the suspension was washed and dewatered by filtering using a Buchner funnel, the wet clay mineral cake produced was left on the funnel for 2 days to produce a relatively dry cake of around 80% solids which was crumbled by gentle grinding ready for treatment with EDTA.
  • An aqueous suspension was prepared using 150g of dry clay and 500g of distilled water to produce a suspension containing 23% by dry weight of the same feed kaolin clay as used in Example 1.
  • the suspension was mixed by stirring using an impeller for 20 minutes to achieve a homogeneous suspension and the suspension was then stirred for a further 15 minutes whilst nitrogen gas (oxygen free) was bubbled through it.
  • nitrogen gas oxygen free
  • DTPA diethylenetriaminepentacetic acid
  • the suspension was dewatered by filtering using a Buchner funnel and the wet clay mineral cake so produced was washed by re-suspension in clean water to form a suspension of approximately 20% solids and this was stirred for 20 minutes.
  • the suspension was homogenous it was further dewatered by filtering using a Buchner funnel and left overnight to dry.
  • the clay mineral cake produced was placed in an oven at 80°C for 4 hours to produce a treated clay mineral of approximately 98% solids content. This was then ground using a pestle and mortar ready for incorporation in a coating composition and for testing.
  • the coating composition was prepared, and a substrate was coated using the composition and the brightness and fluorescence of the coated substrate were measured, as described in Example 1.
  • Table IV shows that high levels of fluorescence can be produced independently of a significant improvement in powder brightness using DTPA. Similar improvements can be obtained by coating papers.
  • An aqueous suspension was prepared containing 20% by dry weight of the same feed clay as used in Example 1.
  • the suspension was mixed by stirring using an impeller for 20 minutes to achieve a homogeneous suspension and the suspension was then stirred for a further 15 minutes while nitrogen gas (oxygen free) was bubbled through it to exclude oxygen.
  • nitrogen gas oxygen free
  • the clay mineral cake produced was placed in an oven at a temperature of 80°C for a period of 4 hours to produce a treated clay mineral of approximately 98% solids content. This was then ground using a pestle and mortar ready for incorporation in a coating composition and for testing.
  • the coating composition was prepared and applied, and the brightenss and fluorescence of the coated substrate were measured, as described in Example 1.
  • the experiment was repeated using varying amounts of TEA and a clay that had been treated by bleaching with sodium hydrosulfite.
  • the hydrosulfite bleaching was carried out according to the process described in Example 2 except that after the suspension was washed and filtered using a Buchner funnel it was left on the funnel for 2 days to produce a relatively dry cake of around 80% solids which was crumbled by gentle grinding using a pestle and mortar ready for treatment with TEA.
  • the experiment was also repeated using a hydrosulfite bleached clay and a temperature of
  • Example 2 An aqueous suspension was prepared containing 20% by dry weight of the same feed clay as used in Example 1 which had been bleached with sodium hydrosulfite.
  • the sodium hydrosulfite bleaching was carried out according to the process of Example 2 except that after the suspension was washed and filtered using a
  • the suspension was mixed by stirring using an impeller for 20 minutes to achieve a homogeneous suspension and the suspension was then stirred for a further 15 minutes while nitrogen gas (oxygen free) was bubbled through it to exclude oxygen.
  • nitrogen gas oxygen free
  • the suspension was dewatered by filtering using a Buchner funnel and the wet clay mineral cake so produced was washed by re-suspension in clean water to form a suspension of approximately 20% and this was stirred for 20 minutes. Once the suspension was homogenous it was again dewatered by filtering using a Buchner funnel and left overnight to dry.
  • the clay mineral cake produced was then placed in an oven at a temperature of 80°C for a period of 4 hours to produce a treated clay mineral of approximately 98% solids content. This was then ground ready for incorporation in a coating composition and for testing.
  • the coating composition was prepared and applied to a substrate, and the fluorescence of the coated paper was measured, as described in Example 1.
  • Table VI shows that the use of citric acid can give significant improvements in the fluorescence of a clay mineral that has been bleached with sodium hydrosulfite and may also further improve the powder brightness.
  • An aqueous suspension was prepared using 150g of dry clay and 550g of distilled water to give a suspension containing 21.5% by weight of the same feed clay as used in Example 1.
  • the suspension was mixed by stirring using an impeller for 20 minutes to achieve a homogeneous suspension and the suspension was then stirred for a further 15 minutes while nitrogen gas (oxygen free) was bubbled through it to exclude oxygen.
  • nitrogen gas oxygen free
  • the vessel was immersed in a water bath at 15°C during the whole of this time.
  • Formamidine sulfinic acid (FAS) in an amount of 2 kg.t -1 relative to the dry weight of the clay, was weighed into a beaker and distilled water was added to this along with a sufficient amount of a 20% solution of sodium hydroxide so that the sodium hydroxide would be present in the suspension in an amount of 50 kg.t -1 relative to the dry weight of the clay.
  • the mass of this solution was adjusted with distilled water so that when it was added to the suspension it produced a suspension of total mass 680g with a solids content of 18.3%.
  • the reaction vessel was again resealed and was still immersed in a water bath at a temperature of 15°C and left for a period of 30 minutes during which the reaction continued. The suspension was stirred throughout with nitrogen bubbled through the suspension.
  • the pH of the suspension was reduced to pH 4 with a 10% solution of sulfuric acid and then the suspension was dewatered by filtering using a Buchner funnel.
  • the wet clay mineral cake so produced was washed by re-suspension in clean water to form a suspension of approximately 18% solids and this was stirred for 20 minutes until it was homogeneous.
  • the suspension was homogenous it was further dewatered by filtering using a Buchner funnel and left overnight to dry.
  • the clay mineral cake produced was placed in an oven at a temperature of 80°C for a period of four hours to produce a treated clay mineral of approximately 98% solids content. This was then ground using a pestle and mortar ready for incorporation in a coating composition and for brightness testing.
  • the coating composition was prepared and applied to a substrate, and the fluorescence of the coated substrate was measured, as described in Example 1.
  • a pigment coating composition was prepared using a clay mineral which had been bleached using 2.5kg.t -1 of sodium hydrosulfite according to the method of Example 2.
  • a coating composition was made using 50g of the dry clay mineral, 0.3% by weight, on an active basis, of sodium polyacrylate dispersant, based on the dry weight of the pigment material, and 22.5g of water to which about 0.5cm 3 of a 10% NaOH solution and a small amount of water were added to produce a lump free suspension. These ingredients were all mixed together using an impeller with the clay added slowly to the water and dispersant solution. An amount of 5%, on an active basis, by weight of Dow 950 Latex was added, based on the dry weight of the pigment material.

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  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Organic Chemistry (AREA)
  • Paper (AREA)
  • Pigments, Carbon Blacks, Or Wood Stains (AREA)

Abstract

L'invention concerne un procédé et la préparation d'une composition pouvant être utilisée dans des compositions de production de papier ou de revêtement pigmentaire contenant également un azureur optique (OBA). Le procédé consiste à: a) préparer une suspension aqueuse d'un minéral des argiles réfractaires contenant une matière particulaire du kaolin; et b) traiter le minéral des argiles réfractaires par adjonction d'un agent de traitement pouvant réduire l'effet nocif des ions métalliques présents dans le minéral des argiles réfractaires sur l'action de l'azureur optique. Ledit agent de traitement est sensiblement exempt de cations polyvalents et comprend: i) un complexant ou ii) un formamidine de l'acide sulfinique (FAS).
EP00929693A 1999-05-18 2000-05-17 Produits du kaolin, leur preparation et leur utilisation pour la production de papier ou d'un revetement Withdrawn EP1196503A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
GBGB9911393.8A GB9911393D0 (en) 1999-05-18 1999-05-18 Improved pigment coating composition
GB9911396 1999-05-18
GB9911393 1999-05-18
GBGB9911396.1A GB9911396D0 (en) 1999-05-18 1999-05-18 Clay mineral compositions and their preparation and use in coating compositions
PCT/GB2000/001800 WO2000069977A1 (fr) 1999-05-18 2000-05-17 Produits du kaolin, leur preparation et leur utilisation pour la production de papier ou d'un revetement

Publications (1)

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EP1196503A1 true EP1196503A1 (fr) 2002-04-17

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EP00929693A Withdrawn EP1196503A1 (fr) 1999-05-18 2000-05-17 Produits du kaolin, leur preparation et leur utilisation pour la production de papier ou d'un revetement

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EP (1) EP1196503A1 (fr)
AU (1) AU754382B2 (fr)
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Publication number Priority date Publication date Assignee Title
AU2005227634A1 (en) 2004-03-23 2005-10-13 Imerys Pigments, Inc. Effective reductive bleaching of mineral slurries
SE530020C2 (sv) * 2006-06-15 2008-02-12 Holmen Ab Förfarande för stabilisering av vitheten hos i ytbehandlingslim/smet för papper ingående fluroescerande vitmedel (FWA) och hos av detta/dessa formade ytbehandlingsskikt
CN102245719B (zh) 2008-12-08 2014-01-29 惠普开发有限公司 用于喷墨介质的表面涂料组合物
CN114195161B (zh) * 2021-12-16 2024-01-23 中国有色桂林矿产地质研究院有限公司 一种提高滑石浆渣白度的方法

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Publication number Priority date Publication date Assignee Title
US4935391A (en) * 1989-03-31 1990-06-19 Fmc Corporation Process for preparing a purified mineral coating
GB2268484B (en) * 1992-07-06 1995-10-11 Ecc Int Ltd Improving the brightness of white minerals

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Title
See references of WO0069977A1 *

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AU4769700A (en) 2000-12-05
WO2000069977A1 (fr) 2000-11-23
AU754382B2 (en) 2002-11-14
BR0010630A (pt) 2002-02-19

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