EP1365993A1 - Procede de blanchiment reducteur de carbonates de metal alcalino-terreux - Google Patents

Procede de blanchiment reducteur de carbonates de metal alcalino-terreux

Info

Publication number
EP1365993A1
EP1365993A1 EP02714877A EP02714877A EP1365993A1 EP 1365993 A1 EP1365993 A1 EP 1365993A1 EP 02714877 A EP02714877 A EP 02714877A EP 02714877 A EP02714877 A EP 02714877A EP 1365993 A1 EP1365993 A1 EP 1365993A1
Authority
EP
European Patent Office
Prior art keywords
calcium carbonate
earth metal
alkaline earth
aqueous slurry
weight
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Withdrawn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
EP02714877A
Other languages
German (de)
English (en)
Inventor
Christopher R.L. Golley
Deborah Susan Thrale
Mark Daniel Mortimer
Desmond Charles Payton
Florangel D. Perez
Mark Windebank
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
Application filed by Imerys Minerals Ltd filed Critical Imerys Minerals Ltd
Publication of EP1365993A1 publication Critical patent/EP1365993A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/18—Carbonates
    • C01F11/185—After-treatment, e.g. grinding, purification, conversion of crystal morphology
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/60—Preparation of carbonates or bicarbonates in general
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/18—Carbonates
    • C01F11/182—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by an additive other than CaCO3-seeds
    • C01F11/183—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by an additive other than CaCO3-seeds the additive being an organic compound
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/24—Magnesium carbonates
    • 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
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 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 reductively bleached alkaline earth metal carbonate products, their preparation, and their use.
  • the invention is concerned with a process for preparing improved calcium carbonate products to be used in compositions for paper making and coating, paints, plastics, rubber, and the like.
  • Producers of paper, paper coatings, plastic compositions, rubber compositions, and non-aqueous surface coatings such as paints and film laminates use mineral materials such as calcium carbonate as property enhancing pigments or fillers in these and like products.
  • mineral materials such as calcium carbonate
  • the importance of the appearance of these products is significant, especially in the finer grades of printing and writing papers, plastics employed in consumer goods, and decorative surface coatings.
  • whiteness and brightness are key appearance factors and the majority of these products require a calcium carbonate having the highest degree of whiteness and brightness.
  • PCC precipitated calcium carbonate
  • GCC ground calcium carbonate
  • PCC is generally prepared by a process in which calcium carbonate is calcined to produce calcium oxide, or "quicklime," the quicklime is then "slaked” with water to produce an aqueous suspension of calcium hydroxide, and finally, the calcium hydroxide is carbonated with a carbon-dioxide- containing gas to produce the precipitated calcium carbonate.
  • GCC may comprise a ground naturally occurring calcium carbonate from sources such as marble, limestone, chalk and the like.
  • PCC may also be ground.
  • Various methods for improving the brightness of PCCs and GCCs are known in the art. For example, U.S. Patent No. 4,793,985 discloses the oxidative bleaching of calcium carbonate using ozone. U.S. Patent No. 5,188,814 discloses the oxidative bleaching of calcium carbonate using hydrogen peroxide.
  • reductive bleaching agents such as sodium dithionite (hydros), also known as sodium hydrosulfite, and formamidine sulfinic acid (FAS), also known as thiourea dioxide
  • hydros sodium dithionite
  • FAS formamidine sulfinic acid
  • U.S. Patent Nos. 4,900,533, 4,239,736, and 4,824,653 disclose the use of hydros to bleach calcium carbonate products, but require either a chelating agent, a flocculating agent, or substantially pure carbon dioxide to achieve measurable brightness increases.
  • composition of matter comprising an alkaline earth metal carbonate aqueous slurry combined with an amount of formamidine sulfinic acid sufficient to achieve reductive bleaching of the alkaline earth metal carbonate aqueous slurry.
  • alkaline earth metal carbonate compositions may be produced having an enhanced brightness.
  • the present invention provides a novel process that utilizes reductive bleaching agents to improve the brightness of alkaline earth metal carbonate products, a product produced thereby, and a composition, for use in paper, polymer, rubber and plastic production, paints coatings, films and the like, incorporating such a product.
  • paper embraces products which are of paper, board, card and the like.
  • the novel process of the present invention provides an improved alkaline earth metal carbonate product by the steps of (a) preparing an aqueous slurry of an alkaline earth metal carbonate material and adding to the slurry an amount of formamidine sulfinic acid (FAS) sufficient to achieve reductive bleaching of the alkaline earth metal carbonate material.
  • FAS formamidine sulfinic acid
  • the alkaline earth metal carbonate preferably is chosen from at least one of a calcium carbonate such as PCC or GCC, and a magnesium containing carbonate, such as dolomite. Most preferably, the alkaline earth metal carbonate is a calcium carbonate. In the description that follows, the description of parameters relating to calcium carbonate also apply to other suitable alkaline earth metal carbonates and vice versa.
  • the calcium carbonate may be a naturally occurring calcium carbonate such as the marble, limestone, or chalk derived products used by the paper industry for coating and filling compositions. And/or the calcium carbonate may be a PCC, such as scalenohedral, rhombohedral, aragonitic, or vateritic PCC's used by the paper industry for coating and filling compositions.
  • the calcium carbonate may be a GCC (ground naturally occurring calcium carbonate material), a ground PCC, or mixtures thereof.
  • step (a) may comprise further step(s) for synthesizing the precipitated calcium carbonate.
  • the further step(s) may be well-known to a person skilled in the art and may comprise a step of slaking calcium oxide (quicklime) to produce slaked lime and carbonating the slaked lime with a carbon dioxide containing gas so as to produce the precipitated calcium carbonate.
  • slaking calcium oxide quicklime
  • the method of the invention comprise an intermediate grinding or milling step (especially where the calcium carbonate product is to be used in a paper coating composition) in which the aqueous suspension of calcium carbonate from step (a) is ground to a desired particle size prior to addition of the reductive bleaching agent according to step (b).
  • Formamidine sulfinic acid the reductive bleaching agent used in the first aspect of the present invention, may also be referred to by the names thiourea dioxide or FAS.
  • FAS may be added to the aqueous calcium carbonate suspension of step (a) in solid form, or in the form of a solution, or in suspension.
  • the reductive bleaching agent FAS may be added during step (a), or after step (a) and before and/or after the grinding step.
  • the reductive bleaching agent FAS may be added during the PCC synthesis of step (a), which comprises (1) a calcium oxide slaking step and (2) a slaked lime carbonation step, or after step (a).
  • the FAS is preferably added during the carbonation step.
  • the FAS may also be added before or after the grinding step, or both before and after the grinding step.
  • the calcium carbonate product produced by the method of the present invention may advantageously have a brightness which has been enhanced by in the range of from about 2 to about 10 units.
  • the calcium carbonate product may have an ISO brightness on the order of from about 85 to about 98 units.
  • the brightness of the products produced by the process of the present invention can be measured by means of standard methods known to those of ordinary skill in the art. Two such standard methods are the TAPPI and the ISO standard test methods. 2000-2001 TAPPI test methods for brightness are available via ISBN No. 1-930657-500-1 , which is incorporated herein by reference in its entirety.
  • TAPPI/GE brightness for paper T 525 om-92 Diffuse brightness of pulp (d/0°):ISO brightness for paper T 646 om-94 Brightness of clay and other mineral pigments (45°/0°): TAPPI/GE brightness for pigments
  • the calcium carbonate materials of the present invention have a mean particle size d 5 o, as measured by a SedigraphTM 5100 machine (supplied by Micrometrics Corporation), of from about 5 microns ( ⁇ m) to about 0.1 microns with respect to both GCC and PCC, preferably from about 2 micron to about 0.2 microns and where the product may be used in a paper coating composition, from about 0.8 microns to about 0.3 microns.
  • the SedigraphTM 5100 machine provides measurements, and a plot of the cumulative percentage by weight of particles having a size, referred to in the art as the "equivalent spherical diameter" (esd), less than the given esd values.
  • the mean particle size, d 50 is the value determined in this way, of the particle esd at which there are 50% by weight of particles which have an esd less than that d 50 value.
  • the calcium carbonate product produced by the method of the invention has a particle size distribution (psd) such that at least 50% by weight of the particles have a particle size ⁇ 2 microns; more preferably, at least 60% by weight have a particle size ⁇ 2 microns.
  • the calcium carbonate product may be used as a pigment in a paper coating composition and in which case it may be especially preferred that at least 80% by weight of the calcium carbonate particles have a particle size ⁇ 2 microns.
  • the present invention provides a novel process for producing an improved alkaline earth metal carbonate product comprising the steps of:
  • the phrase "carbon dioxide containing gas that is not substantially pure carbon dioxide” means a gas containing no more than about 50% carbon dioxide by volume.
  • the gas may contain from about 8% to about 30% carbon dioxide, it preferably will contain from about 10% to about 25% carbon dioxide.
  • the reductive bleaching agent may be FAS or hydros, preferably it is hydros.
  • the alkaline earth metal carbonate may be ground prior to or subsequent to reductive bleaching.
  • the hydros is added to the alkaline earth metal hydroxide slurry prior to carbonation of the slurry.
  • the hydros may be added to the slurry in solid form, or in the form of a solution, or in a suspension.
  • the alkaline earth metal carbonate slurry to which the reductive bleaching agent is added may have a solids content in the range of from about 10% by weight to about 80% by weight; preferably the solids content may be in the range of from about 15% by weight to about 78% by weight.
  • the present invention is effective in both high solids slurries and low solids slurries.
  • the solids content of the slurry to which the reductive bleaching agent is added should be in the range of from about 60% by weight to about 80% by weight.
  • the solids content of the slurry to which the reductive bleaching agent is added should be in the range of from about 15% by weight to about 40% by weight.
  • the slurry is dewatered after said reductive bleaching step, which may be before and/or after grinding.
  • the bleaching agent FAS or hydros
  • the calcium carbonate suspension in conditions such that the pH level is relatively high, above about pH 7.
  • the pH is preferably in the range of from about pH 7 to about pH 13, most preferably from about pH 8 to about pH 12.
  • the temperature of the slurry during the bleaching step should be relatively high, at least about 50°C.
  • the temperature of the slurry during the bleaching step is from about 50 Q C to about 100 9 C, most preferably from about 70°C to about 75°C.
  • the time of the reductive bleaching step should be in the range of from about 5 minutes to about 60 minutes, preferably from about 5 minutes to about 10 minutes.
  • the amount of the reductive bleaching agent, FAS or hydros, to be added to the alkaline earth metal carbonate slurry or alkaline earth metal oxide should be from about 0.01 % to about 1.0% (about 0.1 kg per tonne to 10 kg per tonne) by weight of the dry alkaline earth metal carbonate product, irrespective of the point in the process at which the reductive bleaching agent is added.
  • the amount of reductive bleaching agent is preferably in the range of from about 0.020% to about 0.3% (about 0.20 kg per tonne to about 3 kg per tonne) by weight of the dry alkaline earth metal carbonate product.
  • the bleaching agent provided by the method of the invention may cause enhanced brightness of a calcium carbonate material, for example, by a redox reaction.
  • Iron-containing impurities which may be present in a calcium carbonate, or, which may be displaced from the material of the grinding apparatus into a calcium carbonate suspension during grinding, may undesirably be present in the form of the +3 oxidation state (i.e. Fe 3+ ).
  • the beneficial effect of adding a bleaching agent comprising sodium dithionite or FAS to a calcium carbonate suspension may advantageously be caused by reducing the +3 oxidation state of the iron-containing impurities to the +2 oxidation state (i.e. Fe 2+ ) and thereby bleaching the calcium carbonate particles.
  • the process of the present invention may also include the addition of an effective amount of a phosphate additive which may function as a fixative to maintain the reduced iron-containing impurities in the Iron" state and thereby inhibit reversion to the Iron" 1 state.
  • the amount of phosphate additive may be in the range of from about 0.1 kg per tonne to about 4 kg per tonne of calcium carbonate.
  • Such a further step may preferably be applied to the bleached calcium carbonate suspension.
  • a suitable phosphate additive may be a calcium hydrogen phosphate (CaHP0 4 ).
  • the method of the invention may comprise further step(s) of, for example, dewatering, washing and drying the alkaline earth metal carbonate slurry, which processes may be applied by known techniques.
  • dewatering for example, is disclosed in GB Application No. 9828514.1 , which is incorporated herein by reference in its entirety.
  • the benefits provided by the method of the invention may advantageously permit the use of low-grade lime sources containing a significant amount of iron- containing impurities which lime sources are normally considered unusable.
  • the present invention also provides a composition of matter comprising an alkaline earth metal carbonate aqueous slurry combined with an amount of formamidine sulfinic acid sufficient to achieve reductive bleaching of the alkaline earth metal carbonate aqueous slurry.
  • the application suspension, or slurry, in which the calcium carbonate product is used may comprise, among other things, a paper making composition, e.g., a dilute aqueous suspension of cellulose fibers, the calcium carbonate being used as a filler material optionally with other materials.
  • the composition in which the calcium carbonate product is used may also comprise a coating composition, e.g., for coating paper products.
  • the calcium carbonate slurries of the present invention may also contain other conventional components.
  • Convention components include, by are not limited to, biocides, suspension aides, dispersants, binders/adhesives, other pigments, lubricants, brightening agents, viscosity modifiers and water retention chemicals.
  • the composition may contain a dispersant.
  • a dispersant may be a polyelectrolyte, preferably, a polyacrylate dispersant. More preferably, the dispersant is a sodium polyacrylate having a molecular weight ⁇ 10,000.
  • An aqueous suspension of an Italian limestone was prepared having a solids content of 15% by weight of limestone.
  • the limestone suspension was introduced into a grinding apparatus using sand as the grinding medium; the suspension was ground until the limestone particles had a particle size distribution such that 88% by weight of the particles had a particle size less than 2 ⁇ m.
  • the ground suspension was heated to a temperature of 50 9 C and 8 kg/T of sodium dithionite (hydros), based on the weight of the limestone, was added followed by addition of 4 kg/T of calcium hydrogen phosphate, based on the weight of the limestone.
  • the reaction was carried out for 60 minutes; the limestone suspension was then filtered, washed and dried.
  • the ISO brightness of the limestone was then measured at 91.3% brightness.
  • the measured ISO brightness of the limestone sample was found to be 88.1 % brightness.
  • the ISO brightness of the bleached limestone sample compared to the unbleached limestone sample has been raised by over 3.0%.
  • a paper making or paper coating composition incorporating such a calcium carbonate produced by the method of the invention may exhibit an enhanced brightness.
  • a ground calcium carbonate product having 95 wt.% of the particles less than 2 ⁇ m and at 72 wt.% solids was treated with dry FAS bleach at 72°C. Dose and brightness data are shown in Table 1 below.
  • a ground calcium carbonate product having 93 wt.% of the particles less than 2 ⁇ m and at 75 wt.% solids was treated with dry FAS bleach at 40°C. Dose and brightness data are shown in Table 2 below.
  • a coarse GCC suspension was bleached with 0.10 wt.% FAS prior to grinding at 72 wt.% solids to a final particle size distribution of 96 wt.% less than 2 ⁇ m.
  • the brightness increased from 92.0 to 93.1 (ISO).
  • a ground calcium carbonate product having 85 wt.% of the particles less than 2 ⁇ m and at 25 wt.% solids was treated with FAS at a dose rate of 0.15 wt.%.
  • the brightness increased from 91.9 (ISO) to 92.7 and further increased to 93.1 after centrifugal dewatering.
  • a 0.15 wt.% FAS solution was applied to the final grinder of a cascade during the production of a 93 wt.% less than 2 ⁇ m GCC.
  • the brightness increased from 91.9 to 93.4 (ISO).
  • a rhombohedral PCC sample having a d 50 of 0.60 ⁇ m was bleached with 0.200 wt.% FAS after comminution and prior to dewatering.
  • the product brightness increased from 96.5 to 98.2 (TAPPI).
  • a ground aragonitic PCC sample having a d 50 of 0.35 ⁇ m was bleached with FAS prior to dewatering. Dose and brightness data are shown in Table 3 below.
  • PCC pigments from Example 7 above were coated onto a wood- free base using a lab coater in a formulation comprising 44 parts no.1 coating kaolin, 35 parts PCC, 9 parts specialty pigment additives and 12 parts binder at a coat weight of 10 gsm.
  • the sheet brightness for the control sheet was 81.8 while the sheet coated with FAS bleached PCC had a brightness of 82.2. (TAPPI)
  • the process of the invention also takes into account the change in the various components comprising the aqueous slurry after combination with one another. Accordingly, the invention also relates to a product produced by the process of the invention.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
  • Paper (AREA)

Abstract

L'invention concerne un procédé permettant d'améliorer la brillance d'un carbonate de métal alcalino-terreux au moyen d'acide sulfinique de formamidine ou de dithionite de sodium comme agent de blanchiment réducteur. Si le carbonate de métal alcalino-terreux est un carbonate de calcium, on ajoute l'agent de blanchiment réducteur à une suspension aqueuse de carbonate de calcium avant, pendant ou après la formation du carbonate, choisi parmi au moins un carbonate de calcium précipité et un carbonate de calcium naturel.
EP02714877A 2001-02-13 2002-02-13 Procede de blanchiment reducteur de carbonates de metal alcalino-terreux Withdrawn EP1365993A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB0103500 2001-02-13
GBGB0103500.5A GB0103500D0 (en) 2001-02-13 2001-02-13 Calcium carbonate products
PCT/US2002/004168 WO2002064505A1 (fr) 2001-02-13 2002-02-13 Procede de blanchiment reducteur de carbonates de metal alcalino-terreux

Publications (1)

Publication Number Publication Date
EP1365993A1 true EP1365993A1 (fr) 2003-12-03

Family

ID=9908627

Family Applications (1)

Application Number Title Priority Date Filing Date
EP02714877A Withdrawn EP1365993A1 (fr) 2001-02-13 2002-02-13 Procede de blanchiment reducteur de carbonates de metal alcalino-terreux

Country Status (4)

Country Link
EP (1) EP1365993A1 (fr)
CA (1) CA2438039A1 (fr)
GB (1) GB0103500D0 (fr)
WO (1) WO2002064505A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10211292A1 (de) * 2002-03-14 2003-09-25 Basf Ag Verfahren zur Herstellung von gefälltem Calciumcarbonat mit hohem Weißgrad
US10590003B1 (en) 2017-08-24 2020-03-17 Mississippi Lime Company Method of brightening ground calcium carbonate
CN111017944A (zh) * 2019-12-31 2020-04-17 濮阳宏业环保新材料股份有限公司 一种水磨高岭土研磨漂白工艺

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2520850A (en) 1944-02-12 1950-08-29 Minnick Leonard John Process of whitening alkaline earth carbonates
EP0844988A1 (fr) 1995-08-16 1998-06-03 Gebrüder Dorfner GmbH & Co. Kaolin- und Kristallquarzsandwerke KG Procede de production de mineraux eclaircis
US6211400B1 (en) 1997-10-02 2001-04-03 L. Bruggemann Kg Sulphinic acid derivatives, method for producing them, and their use

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US4900533A (en) * 1981-02-24 1990-02-13 English Clays Lovering Pochin & Company Alkaline earth metal carbonates
JPS58151326A (ja) * 1982-02-25 1983-09-08 イングリツシユ・クレイズ・ラヴア−リング・ポチン・アンド・コムパニ−・リミテツド アルカリ土類金属炭酸塩に関する改良法
US4824653A (en) * 1988-09-29 1989-04-25 Franklin Industries, Inc. Method of bleaching limestone
JP3223589B2 (ja) * 1992-07-20 2001-10-29 王子製紙株式会社 軽質炭酸カルシウムの製造方法
CA2237960A1 (fr) * 1997-06-18 1998-12-18 Goldcorp Inc. Production de carbonate de calcium precipite a couleur amelioree, sous forme cristallisee stable

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2520850A (en) 1944-02-12 1950-08-29 Minnick Leonard John Process of whitening alkaline earth carbonates
EP0844988A1 (fr) 1995-08-16 1998-06-03 Gebrüder Dorfner GmbH & Co. Kaolin- und Kristallquarzsandwerke KG Procede de production de mineraux eclaircis
US6211400B1 (en) 1997-10-02 2001-04-03 L. Bruggemann Kg Sulphinic acid derivatives, method for producing them, and their use

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO02064505A1

Also Published As

Publication number Publication date
CA2438039A1 (fr) 2002-08-22
WO2002064505A1 (fr) 2002-08-22
GB0103500D0 (en) 2001-03-28

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