NO300021B1 - Slurry of particulate calcium carbonate - Google Patents
Slurry of particulate calcium carbonate Download PDFInfo
- Publication number
- NO300021B1 NO300021B1 NO931216A NO931216A NO300021B1 NO 300021 B1 NO300021 B1 NO 300021B1 NO 931216 A NO931216 A NO 931216A NO 931216 A NO931216 A NO 931216A NO 300021 B1 NO300021 B1 NO 300021B1
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- Norway
- Prior art keywords
- calcium carbonate
- weight
- paper
- cationic
- particulate calcium
- Prior art date
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- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 title claims description 36
- 229910000019 calcium carbonate Inorganic materials 0.000 title claims description 17
- 239000002002 slurry Substances 0.000 title description 7
- 239000002245 particle Substances 0.000 claims abstract description 18
- 239000007787 solid Substances 0.000 claims abstract description 17
- 238000009826 distribution Methods 0.000 claims abstract description 10
- 239000007900 aqueous suspension Substances 0.000 claims abstract description 8
- 239000011248 coating agent Substances 0.000 claims description 13
- 238000000576 coating method Methods 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 9
- 239000000725 suspension Substances 0.000 claims description 9
- 229910010272 inorganic material Inorganic materials 0.000 abstract description 5
- 239000011147 inorganic material Substances 0.000 abstract description 5
- 125000002091 cationic group Chemical group 0.000 description 24
- 239000011230 binding agent Substances 0.000 description 13
- 239000000049 pigment Substances 0.000 description 12
- 229920000867 polyelectrolyte Polymers 0.000 description 11
- 229920001448 anionic polyelectrolyte Polymers 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- 239000000945 filler Substances 0.000 description 7
- 239000004579 marble Substances 0.000 description 7
- 125000000129 anionic group Chemical group 0.000 description 6
- 150000003863 ammonium salts Chemical class 0.000 description 5
- 239000000835 fiber Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- 229910052783 alkali metal Inorganic materials 0.000 description 4
- 150000001340 alkali metals Chemical class 0.000 description 4
- 150000002894 organic compounds Chemical class 0.000 description 4
- 229920000098 polyolefin Polymers 0.000 description 4
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 3
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 229920002125 Sokalan® Polymers 0.000 description 3
- 235000011941 Tilia x europaea Nutrition 0.000 description 3
- 239000008199 coating composition Substances 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
- 239000002270 dispersing agent Substances 0.000 description 3
- 239000004571 lime Substances 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 239000004584 polyacrylic acid Substances 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- BRLQWZUYTZBJKN-UHFFFAOYSA-N Epichlorohydrin Chemical compound ClCC1CO1 BRLQWZUYTZBJKN-UHFFFAOYSA-N 0.000 description 2
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 description 2
- 229920002845 Poly(methacrylic acid) Polymers 0.000 description 2
- 229920002873 Polyethylenimine Polymers 0.000 description 2
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical group [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- 125000000217 alkyl group Chemical group 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 229920001577 copolymer Polymers 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000012065 filter cake Substances 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 2
- 238000007645 offset printing Methods 0.000 description 2
- 229920000371 poly(diallyldimethylammonium chloride) polymer Polymers 0.000 description 2
- 229940088417 precipitated calcium carbonate Drugs 0.000 description 2
- 125000001453 quaternary ammonium group Chemical group 0.000 description 2
- 238000000518 rheometry Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- 229920002472 Starch Polymers 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- -1 aliphatic secondary amine Chemical class 0.000 description 1
- 125000005210 alkyl ammonium group Chemical group 0.000 description 1
- 229920006318 anionic polymer Polymers 0.000 description 1
- CJZGTCYPCWQAJB-UHFFFAOYSA-L calcium stearate Chemical compound [Ca+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O CJZGTCYPCWQAJB-UHFFFAOYSA-L 0.000 description 1
- 239000008116 calcium stearate Substances 0.000 description 1
- 235000013539 calcium stearate Nutrition 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 125000002843 carboxylic acid group Chemical group 0.000 description 1
- 239000005018 casein Substances 0.000 description 1
- BECPQYXYKAMYBN-UHFFFAOYSA-N casein, tech. Chemical compound NCCCCC(C(O)=O)N=C(O)C(CC(O)=O)N=C(O)C(CCC(O)=N)N=C(O)C(CC(C)C)N=C(O)C(CCC(O)=O)N=C(O)C(CC(O)=O)N=C(O)C(CCC(O)=O)N=C(O)C(C(C)O)N=C(O)C(CCC(O)=N)N=C(O)C(CCC(O)=N)N=C(O)C(CCC(O)=N)N=C(O)C(CCC(O)=O)N=C(O)C(CCC(O)=O)N=C(O)C(COP(O)(O)=O)N=C(O)C(CCC(O)=N)N=C(O)C(N)CC1=CC=CC=C1 BECPQYXYKAMYBN-UHFFFAOYSA-N 0.000 description 1
- 235000021240 caseins Nutrition 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000001805 chlorine compounds Chemical group 0.000 description 1
- 239000002734 clay mineral Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000007334 copolymerization reaction Methods 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 235000013312 flour Nutrition 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 238000007646 gravure printing Methods 0.000 description 1
- XMBWDFGMSWQBCA-UHFFFAOYSA-N hydrogen iodide Chemical compound I XMBWDFGMSWQBCA-UHFFFAOYSA-N 0.000 description 1
- 125000004356 hydroxy functional group Chemical group O* 0.000 description 1
- 239000011256 inorganic filler Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000001023 inorganic pigment Substances 0.000 description 1
- 239000004816 latex Substances 0.000 description 1
- 229920000126 latex Polymers 0.000 description 1
- 239000006194 liquid suspension Substances 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 150000007530 organic bases Chemical class 0.000 description 1
- 229920001495 poly(sodium acrylate) polymer Polymers 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 235000011164 potassium chloride Nutrition 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000005488 sandblasting Methods 0.000 description 1
- 238000005549 size reduction Methods 0.000 description 1
- 235000017557 sodium bicarbonate Nutrition 0.000 description 1
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 1
- NNMHYFLPFNGQFZ-UHFFFAOYSA-M sodium polyacrylate Chemical compound [Na+].[O-]C(=O)C=C NNMHYFLPFNGQFZ-UHFFFAOYSA-M 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- 239000008107 starch Substances 0.000 description 1
- 235000019698 starch Nutrition 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical compound [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 description 1
- 239000003115 supporting electrolyte Substances 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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
- D21H19/385—Oxides, hydroxides or carbonates
-
- 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
- D21H21/50—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 form
- D21H21/52—Additives of definite length or shape
Abstract
Description
Foreliggende oppfinnelse vedrører en vandig suspensjon av den art som er angitt i krav l's ingress. The present invention relates to an aqueous suspension of the type specified in claim 1's preamble.
Det er kjent å dispergere uorganiske pigmenter og fyll-stoffer slik at partiklene har en total positiv ladning. Slike kationisk dispergerte suspensjoner er nyttige ved papirfremstilling (EP-0278602A) og papirbelegning. It is known to disperse inorganic pigments and fillers so that the particles have a total positive charge. Such cationically dispersed suspensions are useful in papermaking (EP-0278602A) and paper coating.
Det er nu funnet at rheologien for en kationisk dispergert suspensjon av kalsiumkarbonat kan forbedres ved å anvende mineral med en spesiell partikkelstørrelsesforde-ling. It has now been found that the rheology of a cationically dispersed suspension of calcium carbonate can be improved by using mineral with a particular particle size distribution.
Således er det i henhold til oppfinnelsen tilveiebragt en høyfaststoffholdig, vandig suspensjon av kationisk dispergert partikkelformig kalsiumkarbonat som er særpreget ved at det partikkelformige kalsiumkarbonat har en par-tikkelstørrelsesfordeling slik at ikke mer enn 10 vektprosent av partiklene har en ekvivalent sfærisk diameter (esd) mindre enn 0,25/zm, slik som angitt i krav' 1' s ka-rakteriserende. Et ytterligere trekk fremgår av krav 2. Høyfaststoffsuspensjonen bør fortrinnsvis inneholde minst 60 vektprosent faststoffer. Thus, according to the invention, a high-solids, aqueous suspension of cationically dispersed particulate calcium carbonate is provided, which is characterized by the particulate calcium carbonate having a particle size distribution such that no more than 10 percent by weight of the particles have an equivalent spherical diameter (esd) smaller than 0.25/zm, as indicated in claim 1's characterisation. A further feature appears in claim 2. The high-solids suspension should preferably contain at least 60% solids by weight.
Det er foretrukket at kalsiumkarbonatet, når det er malt til en partikkelformig masse, eksisterer i form av jevne, tilnærmet sfæriske partikler med et lavt midlere partik-kelaspektforhold. Således kan kalsiumkarbonatet foreligge i enhver form, syntetisk eller naturlig. Spesielt foretrukket er malt marmor, selv om utfelt kalsiumkarbonat (PCC) og kalk fungerer. It is preferred that the calcium carbonate, when ground into a particulate mass, exists in the form of uniform, approximately spherical particles with a low average particle aspect ratio. Thus, the calcium carbonate can be present in any form, synthetic or natural. Particularly preferred is ground marble, although precipitated calcium carbonate (PCC) and lime work.
Fortrinnsvis har kalsiumkarbonatet et spesifikt overfla-teareale, målt ved BET N2-metoden på mindre enn ca 7,5-m<2>/g, mere foretrukket mindre enn 6,5 m<2>/g, og fortrinns- Preferably, the calcium carbonate has a specific surface area, measured by the BET N2 method, of less than about 7.5 m<2>/g, more preferably less than 6.5 m<2>/g, and preferably
vis minst 2m<2>/g. show at least 2m<2>/g.
Det partikkelformige karbonat bør også fortrinnsvis ha en diameterfordeling slik at ikke mere enn 10% av partiklene har en esd større enn 10/zm og minst 65% har en esd mindre enn 2/xm. The particulate carbonate should preferably also have a diameter distribution such that no more than 10% of the particles have an esd greater than 10/zm and at least 65% have an esd less than 2/xm.
Kalsiumkarbonatet kan males, før dispersjon, til den ønskede partikkelstørrelsefordeling. Malebetingelsene kan justeres på i og for seg kjent måte til å gi materiale med varierende fordelinger. The calcium carbonate can be ground, before dispersion, to the desired particle size distribution. The milling conditions can be adjusted in a manner known per se to produce material with varying distributions.
Det er funnet at en kationisk oppslemming fremstilt i henhold til foreliggende oppfinnelse kan formes til en oppslemming med en gitt viskositet ved høyere faststoffinnhold enn en oppslemming i hvilken det uorganiske materiale har en bredere partikkelstørrelsesfordeling. It has been found that a cationic slurry produced according to the present invention can be formed into a slurry with a given viscosity at a higher solids content than a slurry in which the inorganic material has a wider particle size distribution.
Når kalsiumkarbonatmaterialet er et pigment eller fyllstoff som bærer en nøytral eller positiv ladning, såsom marmor, kan partiklene av materialet dispergeres med anvendelse av et dispergeringsmiddel omfattende en kombinasjon av en anionisk polyelektrolytt og en kationisk polyelektrolytt, idet den kationiske polyelektrolytt anvendes i en mengde tilstrekkelig til å gjøre partiklene kationiske. Selv om kalkpartikler, i rå tilstand, ikke bærer noen positiv ladning på grunn av naturlige anioniske bestanddeler absorbert på partiklenes overflate, kan kalk underkastes en kraftig bevegelse/omrøring for å strippe av slike anioniske bestanddeler og gjøre materialet istand til å la seg effektivt dispergere ved høye faststoffer, under anvendelse av en kombinasjon av en anionisk polyelektrolytt og en kationisk polyelektrolytt. When the calcium carbonate material is a pigment or filler bearing a neutral or positive charge, such as marble, the particles of the material may be dispersed using a dispersant comprising a combination of an anionic polyelectrolyte and a cationic polyelectrolyte, the cationic polyelectrolyte being used in an amount sufficient to to make the particles cationic. Although lime particles, in their raw state, carry no positive charge due to natural anionic constituents absorbed on the surface of the particles, lime can be subjected to vigorous agitation/stirring to strip off such anionic constituents and enable the material to be effectively dispersed by high solids, using a combination of an anionic polyelectrolyte and a cationic polyelectrolyte.
Den vandige, høyfaststoffsuspensjon ifølge oppfinnelsen kan "bringes ned" til en papirbelegningsblanding ved fortynning (om nødvendig) til en faststoffkonsentrasjon på minst 45 vektprosent ved tilsetning av et bindemiddel, som bør være av ikke-ionisk eller kationisk natur. The aqueous, high solids suspension of the invention can be "brought down" to a paper coating composition by dilution (if necessary) to a solids concentration of at least 45 percent by weight by the addition of a binder, which should be nonionic or cationic in nature.
En full diskusjon av bestanddelene av papirbelegningsblandinger og fremgangsmåter for påføring av slike blan-dinger på papir er gitt i kapittel XIX, volum III i den andre utgave av boken av James P. Casey med tittelen "Pulp and Paper: Chemistry and Technology". En ytterligere diskusjon er gitt i "An Operator<x>s Guide to Agueous Coating for Paper and Board", redigert av T.W.R. Dean, The British Paper and Board Industry Federation, London, 1979. A full discussion of the constituents of paper coating compositions and methods of applying such compositions to paper is given in Chapter XIX, Volume III of the second edition of the book by James P. Casey entitled "Pulp and Paper: Chemistry and Technology". A further discussion is given in "An Operator<x>'s Guide to Aqueous Coating for Paper and Board", edited by T.W.R. Dean, The British Paper and Board Industry Federation, London, 1979.
Den vandige suspensjon ifølge oppfinnelsen bør fortrinnsvis underkastes en kraftig blanding før eller efter dispergering. Typisk bør den kraftige blanding være tilstrekkelig å tilveiebringe minst 10kJ energi pr. kg uorganisk materiale og fortrinnsvis ikke mere enn ca. 50kJ/kg. Normalt vil energitilførselen ligge i område 18-36kJ/kg uorganisk materiale. Papirbelegningsblandinger kan anvendes ved en fremgangsmåte for belegning av ark-elementer. Det således dannende belagte papir er spesielt egnet for resirkulering. The aqueous suspension according to the invention should preferably be subjected to vigorous mixing before or after dispersion. Typically, the powerful mixture should be sufficient to provide at least 10kJ of energy per kg of inorganic material and preferably no more than approx. 50kJ/kg. Normally, the energy input will be in the range 18-36kJ/kg inorganic material. Paper coating mixtures can be used in a method for coating sheet elements. The coated paper thus formed is particularly suitable for recycling.
Malt marmor for anvendelse ifølge oppfinnelsen er fortrinnsvis dannet ved knusing av satser av marmor i en vandig suspensjon i fravær av et kjemisk dispergeringsmiddel under anvendelse av et partikkelformig malemedium. Ground marble for use according to the invention is preferably formed by crushing batches of marble in an aqueous suspension in the absence of a chemical dispersant using a particulate grinding medium.
Ytterligere størrelsesreduksjon oppnås ved avyanning av suspensjonen av malt marmor, eksempelvis ved filtrering i fravær av et flokkuleringsmiddel og deretter tørke pigmentet og pulverisere det tørkede produkt i en konvensjonell mølle. Det partikkelformige pigment dispergeres med kombinasjon av en anionisk polyelektrolytt og en kationisk polyelektrolytt. Fortrinnsvis er den anioniske polyelektrolytt en vannoppløslig vinylpolymer, et alkalimetall- eller ammoniumsalt derav eller et alkalimetall-eller ammoniumsalt av polykiselsyre. Mest foretrukket er den anioniske polyelektrolytt en polyakrylsyre, en polymetakrylsyre, en substituert polyakrylsyre eller en substituert polymetakrylsyre, eller et alkalimetall- eller et ammoniumsalt av enhver av disse syrer. Den substituerte polyakrylsyre kan være en delvis sulfonert polymer. En spesielt effektiv anionisk polyelektrolytt er et alkalimetall- eller ammoniumsalt av en kopolymer av akrylsyre og et sulfonert syrederivat av akrylsyre, i hvilken ande-len av den sulfonerte syrederivatmonomer fortrinnsvis er 5-20% av det totale antall monomere enheter. Further size reduction is achieved by deaeration of the suspension of ground marble, for example by filtration in the absence of a flocculant and then drying the pigment and pulverizing the dried product in a conventional mill. The particulate pigment is dispersed with a combination of an anionic polyelectrolyte and a cationic polyelectrolyte. Preferably, the anionic polyelectrolyte is a water-soluble vinyl polymer, an alkali metal or ammonium salt thereof or an alkali metal or ammonium salt of polysilicic acid. Most preferably, the anionic polyelectrolyte is a polyacrylic acid, a polymethacrylic acid, a substituted polyacrylic acid or a substituted polymethacrylic acid, or an alkali metal or an ammonium salt of any of these acids. The substituted polyacrylic acid may be a partially sulfonated polymer. A particularly effective anionic polyelectrolyte is an alkali metal or ammonium salt of a copolymer of acrylic acid and a sulphonated acid derivative of acrylic acid, in which the proportion of the sulphonated acid derivative monomer is preferably 5-20% of the total number of monomeric units.
Den tallmidlere molekylvekt av den anioniske polyelektrolytt er fortrinnsvis 500, og fortrinnsvis ikke større enn 100000. Den anvendte mengde ligger generelt i området 0,01-0,5 vektprosent, beregnet på vekten av tørt pigment, fortrinnsvis i området 0,1-0,2 vektprosent. The number average molecular weight of the anionic polyelectrolyte is preferably 500, and preferably not greater than 100,000. The amount used is generally in the range 0.01-0.5 weight percent, calculated on the weight of dry pigment, preferably in the range 0.1-0, 2 percent by weight.
Den kationiske polyelektrolytt kan være at vannoppløslig, substituert polyolefin inneholdende kvatenære ammoniumgrupper. De kvarenære ammoniumgrupper kan være i den lineære polymerkjede eller kan være i forgreninger av den polymere kjede. Den tallmidlere molekylvekt for det substituerte polyolefin er fortrinnsvis minst 1500 og fortrinnsvis ikke større enn 1000000 og ligger mere foretrukket i området 50000-500000. Den nødvendige mengde ligger generelt i område 0,01-1,5 vektprosent, regnet på vekten av tørt pigment. Fordelaktige resultater er erholdt når det substituerte polyolefin er et polydial-lyldihydrogen eller lavere -alkylammoniumsalt. De lavere alkylgrupper som kan være like eller forskjellige, kan eksempelvis inneholde opptil 4 karbonatomer, og hver er fortrinnsvis metyl. Ammoniumsaltet kan eksempelvis være et klorid, bromid, jodid, HS04", CH3S04" eller nitritt. Fortrinnsvis er saltet et klorid. Mest foretrukket er den kationiske polyelektrolytt polydiallyldimetylammonium-klorid. Alternativt kan det vannoppløslige substituerte polyolefin være produktet erholdt ved kopolymerisering av epiklorhydrin og et alifatisk sekundært amin, hvilket produkt har formelen The cationic polyelectrolyte can be that water-soluble, substituted polyolefin containing quaternary ammonium groups. The quaternary ammonium groups can be in the linear polymer chain or can be in branches of the polymer chain. The number average molecular weight for the substituted polyolefin is preferably at least 1,500 and preferably not greater than 1,000,000 and is more preferably in the range 50,000-500,000. The required amount is generally in the range of 0.01-1.5% by weight, calculated on the weight of dry pigment. Advantageous results have been obtained when the substituted polyolefin is a polydiallyl dihydrogen or lower alkylammonium salt. The lower alkyl groups, which may be the same or different, may for example contain up to 4 carbon atoms, and each is preferably methyl. The ammonium salt can, for example, be a chloride, bromide, iodide, HS04", CH3S04" or nitrite. Preferably, the salt is a chloride. Most preferably, the cationic polyelectrolyte is polydiallyldimethylammonium chloride. Alternatively, the water-soluble substituted polyolefin may be the product obtained by the copolymerization of epichlorohydrin and an aliphatic secondary amine, which product has the formula
hvori R og R', som kan være like eller forskjellige, er hver hydrogen eller en lavere alkylgruppe med 1-4 karbonatomer, fortrinnsvis metyl eller etyl, og X er Cl", Br", I", HS04", CH3S04" eller nitritt. Den foretrukne tallmidlere molekylvekt for dette epiklorhydrinprodukt ligger i området 50000-300000. wherein R and R', which may be the same or different, are each hydrogen or a lower alkyl group of 1-4 carbon atoms, preferably methyl or ethyl, and X is Cl", Br", I", HSO 4 ", CH 3 SO 4 " or nitrite The preferred number average molecular weight for this epichlorohydrin product is in the range of 50,000-300,000.
Alternativt kan den kationiske polyelektrolytt være en vannoppløslig organisk forbindelse med et antall basiske grupper og av fortrinnsvis en tallmidlere molekylvekt på minst 10000 og fortrinnsvis ikke større enn 1000000. Mest foretrukket er den tallmidlere molekylvekt på minst 50000. Disse vannoppløslige, organiske forbindelser kan beskrives som polysure organiske baser og er fortrinnsvis forbindelser bare av karbon, hydrogen og nitrogen og er frie for andre funksjonelle grupper, såsom hydroksy-eller karboksylsyregrupper, som ville forøke deres opp-løslighet i vann og således øke sjansen for at de absor-beres fra leiremineralet i en vandig suspensjon. Fortrinnsvis er den organiske forbindelse polyetylenimin (PEI) med en tallmidlere molekylvekt i området 50000-1000000. Et ytterligere eksempel på en vannoppløslig organisk forbindelse som kan anvendes er polyetylendiamin som kan være en kopolymer av etylendiamin med et etylendihalo-genid, eller med formaldehyd. Alternatively, the cationic polyelectrolyte can be a water-soluble organic compound with a number of basic groups and preferably of a number average molecular weight of at least 10,000 and preferably not greater than 1,000,000. Most preferably, the number average molecular weight is at least 50,000. These water-soluble, organic compounds can be described as polyacids organic bases and are preferably compounds only of carbon, hydrogen and nitrogen and are free of other functional groups, such as hydroxy or carboxylic acid groups, which would increase their solubility in water and thus increase the chance of their being absorbed from the clay mineral in a aqueous suspension. Preferably, the organic compound is polyethyleneimine (PEI) with a number average molecular weight in the range of 50,000-1,000,000. A further example of a water-soluble organic compound that can be used is polyethylenediamine, which can be a copolymer of ethylenediamine with an ethylene dihalide, or with formaldehyde.
Den kationiske polyeletrolytt anvendes i en mengde tilstrekkelig til å gjøre kalsiumkarbonatpartiklene kationiske. Forsøk har vist at zeta-potensialet for partiklene normalt vil være minst +20mV efter behandlingen, typisk i området +3 0-+40mV og vanligvis ikke større enn +50-+60mV. Disse potensialer er målt under anvendelse av en fortynnet (0,02 vektprosentig) faststoffsuspensjon under anvendelse av en støtteelektrolytt, såsom kaliumklorid (10"<4>M) med et "Pen Kem Laser Z" -meter. The cationic polyelectrolyte is used in an amount sufficient to make the calcium carbonate particles cationic. Experiments have shown that the zeta potential of the particles will normally be at least +20mV after treatment, typically in the range +3 0-+40mV and usually not greater than +50-+60mV. These potentials are measured using a dilute (0.02% by weight) solids suspension using a supporting electrolyte such as potassium chloride (10"<4>M) with a "Pen Kem Laser Z" meter.
Det anvendte vektforhold mellom kationisk polyelektrolytt og anionisk polyelektrolytt ligger fortrinnsvis innen området 2:1 til 20:1, og mere foretrukket i området 2:1 til 10:1. The weight ratio between cationic polyelectrolyte and anionic polyelectrolyte used is preferably within the range of 2:1 to 20:1, and more preferably in the range of 2:1 to 10:1.
Ved fremgangsmåten ved fremstilling av oppslemmingen ifølge oppfinnelsen er det vanlige tilfelle at råpigmen-tet mottas som en filterkake med et relativt høyt fast-stoff innhold. Til denne tilsettes dispergeringsmidlet for å gi dispergert høyfaststoffoppslemming (45- 80 vektprosent faststoffer) som deretter kan underkastes kraftig blanding. In the process for producing the slurry according to the invention, it is usually the case that the raw pigment is received as a filter cake with a relatively high solids content. To this, the dispersant is added to give a dispersed high-solids slurry (45-80% solids by weight) which can then be subjected to vigorous mixing.
Når pigmentet skal dispergeres under anvendelse av en kombinasjon av en anionisk og en kationisk polyelektrolytt, blir pigmentet først blandet med den anioniske polyelektrolytten før blanding med den kationiske polyelektrolytt. Dette synes å muliggjøre erholdelse av en mer flytende suspensjon med en høyere faststoffkonsentrasjon. When the pigment is to be dispersed using a combination of an anionic and a cationic polyelectrolyte, the pigment is first mixed with the anionic polyelectrolyte before mixing with the cationic polyelectrolyte. This appears to enable obtaining a more liquid suspension with a higher solids concentration.
Når den vandige suspensjon skal anvendes for papirbelegning kan den også innbefatte andre tilsetningsmidler for en papirbelegningsblanding, såsom et uoppløsliggjørende middel (eksempelvis en melaminformaldehydharpiks), et smøremiddel, såsom kalsiumstearat, og en katalysator for å katalysere en fornetning av en eventuelt tilstedeværen-de kationisk latex: en egnet slik katalysator er nat-riumbikarbonat. Mengdene av disse hjelpemidler som er When the aqueous suspension is to be used for paper coating, it may also include other additives for a paper coating composition, such as an insolubilizing agent (for example, a melamine formaldehyde resin), a lubricant, such as calcium stearate, and a catalyst to catalyze a cross-linking of any cationic latex present : a suitable such catalyst is sodium bicarbonate. The amounts of these aids that are
nødvendige er kjente for fagmannen. necessary are known to the person skilled in the art.
Bindemidler som anvendes ved fremstilling av en papir-beledningsblanding bør være ikke-ionisk eller være et kationisk bindemiddel. Disse bindemidler anvendes i mot-setning til de anioniske bindemidler, som normalt anvendes ved papirbelegningsblandinger hvori pigmentene er anioniske. Således kan kationisk kasein og kationiske stivelsebindemidler anvendes såvel som kationiske eller ikke-ioniske latexer. Slike kationiske og ikke-ioniske bindemidler er lett kommersielt tilgjengelige. Det spesielt anvendte kationiske eller ikke-ioniske bindemiddel vil eksempelvis være avhengig av den trykkeprosess som skal anvendes, eksempelvis offsettrykk krever at bindemidlet er vannuoppløselig. For papir som skal anvendes ved offsett-trykketeknikken, bør mengden av bindemiddel fortrinnsvis være 7-25 vektprosent, regnet på vekten av pigmentet, men for dyptrykningspapir bør bindemidlet anvendes i en mengde på 4-15 vektprosent, regnet på pig-mentets vekt. Den eksakte mengde nødvendig bindemiddel vil være avhengig av bindemidlets natur og materialet som skal belegges, men dette kan lett bestemmes av en fag-mann. Binders used in the production of a paper-coating mixture should be non-ionic or be a cationic binder. These binders are used in contrast to the anionic binders, which are normally used in paper coating mixtures in which the pigments are anionic. Thus, cationic casein and cationic starch binders can be used as well as cationic or non-ionic latexes. Such cationic and nonionic binders are readily available commercially. The particular cationic or non-ionic binder used will, for example, depend on the printing process to be used, for example offset printing requires that the binder is water-insoluble. For paper to be used in the offset printing technique, the amount of binder should preferably be 7-25 percent by weight, calculated on the weight of the pigment, but for gravure printing paper, the binder should be used in an amount of 4-15 percent by weight, calculated on the weight of the pigment. The exact amount of binder required will depend on the nature of the binder and the material to be coated, but this can easily be determined by a person skilled in the art.
Belegningblandingen kan belegges på et ark under anvendelse av normalt papirbelegningsmaskineri og under norma-le belegningsbetingelser. Det er funnet at belegning med den kationiske blanding i henhold til foreliggende oppfinnelse generelt gir tilsvarende resultater som dem som erholdes med konvensjonelt anionisk system. The coating mixture can be coated on a sheet using normal paper coating machinery and under normal coating conditions. It has been found that coating with the cationic mixture according to the present invention generally gives similar results to those obtained with a conventional anionic system.
Det belagte papir som kan anvendes ved utøvelse av foreliggende oppfinnelse, er fordelaktig ved at det kan anvendes som "skrap" eller resirkulert- papir i papirfrem-stillingsprosessen. Vanligvis blir store mengder papir resirkulert på fremstillingsstedet av en eller annen grunn, og fordelen med papiret ifølge oppfinnelsen ved resirkulering er av største betydning for papirfabri-kanten. En slik fremgangsmåte for sirkulering av papir innbefatter trinnet å redusere papiret til en fibrøs resirkulerbar tilstand og innarbeider fibrene i papirfremstillingsmassen. En slik papirfremstillingsmasse kan innbefatte konvensjonell papirfremstillingsmasse, såsom en bleket sulfittmasse og typisk vil vrakfibrene og mas-sen anvendes i et mengdeforhold fra 10:90 til 60:40. The coated paper that can be used in the practice of the present invention is advantageous in that it can be used as "scrap" or recycled paper in the paper-making process. Generally, large quantities of paper are recycled at the manufacturing site for one reason or another, and the advantage of the paper according to the invention in recycling is of the greatest importance to the paper manufacturer. One such method of recycling paper includes the step of reducing the paper to a fibrous recyclable state and incorporating the fibers into the papermaking stock. Such a papermaking pulp can include conventional papermaking pulp, such as a bleached sulphite pulp, and typically the scrap fibers and the pulp will be used in a ratio of 10:90 to 60:40.
Innbefattende i papirfremstillingsblandingen vil også være et fyllstoff, eksempelvis et kalsiumkarbonatfyllstoff og også et retensjonshjelpemiddel. Da avfallsfib-rene vil omfatte et kalsiumkarbonat fra belegget, er det mulig å nedsette mengden av kalsiumkarbonatfyllstoff som anvendes for å gi en total mengde fyllstoff i området 5-20 vektprosent av den totale papirfremstillingsblanding. Vekten av det tilsatte tørket vrak (fiber og fyllstoff) bør fortrinnsvis ligge i området 5-30 vektprosent regnet på fibrene. Included in the papermaking mixture will also be a filler, for example a calcium carbonate filler and also a retention aid. As the waste fibers will comprise a calcium carbonate from the coating, it is possible to reduce the amount of calcium carbonate filler used to give a total amount of filler in the range of 5-20% by weight of the total papermaking mixture. The weight of the added dried scrap (fibre and filler) should preferably be in the range of 5-30% by weight calculated on the fibres.
Det er funnet at når de anvendte vrakfibre er avledet fra et belagt papir i henhold til foreliggende oppfinnelse, vil dette muliggjøre at mengden av retensjonshjelpemiddel som anvendes i papirfremstillingsmassen kan nedsettes. It has been found that when the scrap fibers used are derived from a coated paper according to the present invention, this will enable the amount of retention aid used in the papermaking pulp to be reduced.
Den vandige oppslemming ifølge oppfinnelsen er også spesielt egnet som papirfyllstoff, og i denne anledning hen-vises det til EP-278602A. The aqueous slurry according to the invention is also particularly suitable as a paper filler, and on this occasion reference is made to EP-278602A.
Oppfinnelsen skal illustreres ved hjelp av de følgende eksempler: The invention shall be illustrated by means of the following examples:
EKSEMPEL EXAMPLE
To kalsiumkarbonatpigmenter ble fremstilt ved lavfast-stoffsandmaling av marmormel. Justering av malebetingelsene tillot sammenligning av produkter med forskjellige fordelingsbredder. Sedigrafdata ble erholdt som vist i tabell 1 nedenfor (prosentandeler er gitt i vektprosent <%>) <:>Two calcium carbonate pigments were produced by low-solids sandblasting of marble flour. Adjustment of the grinding conditions allowed comparison of products with different distribution widths. Sedigraph data was obtained as shown in table 1 below (percentages are given in weight percent <%>) <:>
Begge prøver ble filtrert til å gi en filterkake med 70-75% faststoffer. En slik kake ble deretter kationisk dispergert ved anvendelse av en forbehandling med nat-riumpolyakrylat (molekylvekt 4000) efterfulgt av tilsetning av større doser polydadmac (det vil si et polydi-allyldimetylammoniumklorid) med molekylvekt 500,000, efterfulgt av en ytterligere tilsetning av en større dose av polydadmac. Vektforholdet mellom kationisk til anionisk polymer holdt 3,2-3,5:1. Suspensjonen ble fortynnet med vann inntil viskositeten, målt ved 100 omdr/min under anvendelse av et "Brookfield Viscometer" på ca 600 mPa.s ble nådd og faststoffinnholdet av suspensjonen bestemt. Som det fremgår av eksempelet gir malt marmor med den videre størrelsesfordeling ca 4 enheter lavere tørrstoff for en gitt rheologi, når den dispergeres kationisk. Both samples were filtered to give a filter cake with 70-75% solids. Such a cake was then cationically dispersed using a pretreatment with sodium polyacrylate (molecular weight 4000) followed by the addition of larger doses of polydadmac (ie a polydiallyldimethylammonium chloride) of molecular weight 500,000, followed by a further addition of a larger dose of polydadmac. The weight ratio of cationic to anionic polymer was kept at 3.2-3.5:1. The suspension was diluted with water until the viscosity, measured at 100 rpm using a "Brookfield Viscometer" of about 600 mPa.s was reached and the solids content of the suspension determined. As can be seen from the example, ground marble with the wider size distribution gives approx. 4 units lower dry matter for a given rheology, when it is dispersed cationically.
Claims (2)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9026362A GB2251254B (en) | 1990-12-04 | 1990-12-04 | Calcium carbonate slurry |
| PCT/GB1991/002110 WO1992010609A1 (en) | 1990-12-04 | 1991-11-28 | Inorganic material slurry |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| NO931216D0 NO931216D0 (en) | 1993-03-31 |
| NO931216L NO931216L (en) | 1993-08-03 |
| NO300021B1 true NO300021B1 (en) | 1997-03-17 |
Family
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| NO931216A NO300021B1 (en) | 1990-12-04 | 1993-03-31 | Slurry of particulate calcium carbonate |
Country Status (13)
| Country | Link |
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| JP (1) | JP2919970B2 (en) |
| AT (1) | ATE157415T1 (en) |
| AU (1) | AU654514B2 (en) |
| BR (1) | BR9107142A (en) |
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| DE (1) | DE69127458T2 (en) |
| DK (1) | DK0560813T3 (en) |
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| GB (1) | GB2251254B (en) |
| NO (1) | NO300021B1 (en) |
| WO (1) | WO1992010609A1 (en) |
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| US5731034A (en) * | 1990-12-04 | 1998-03-24 | Ecc International Limited | Method of coating paper |
| US5169443A (en) * | 1991-11-13 | 1992-12-08 | Engelhard Corporation | Paper coating kaolin pigments there preparation and use |
| GB2275876B (en) * | 1993-03-12 | 1996-07-17 | Ecc Int Ltd | Grinding alkaline earth metal pigments |
| US5755930A (en) * | 1994-02-04 | 1998-05-26 | Allied Colloids Limited | Production of filled paper and compositions for use in this |
| DE19529661C1 (en) * | 1995-08-11 | 1997-04-03 | Ctp Papierhilfsmittel Gmbh | Coating slip for paper |
| US5827398A (en) * | 1996-02-13 | 1998-10-27 | Allied Colloids Limited | Production of filled paper |
| FI104502B (en) | 1997-09-16 | 2000-02-15 | Metsae Serla Oyj | A method of making a paper web |
| FI105840B (en) | 1997-09-16 | 2000-10-13 | Metsae Serla Oyj | A method for coating a web of material |
| FI108950B (en) | 1998-03-13 | 2002-04-30 | M Real Oyj | A process for making coated wood-free paper |
| FI111649B (en) | 1998-05-11 | 2003-08-29 | M Real Oyj | The use of calcium carbonate is made from calcium oxalate as pigment |
| WO2002066393A1 (en) * | 2001-01-10 | 2002-08-29 | Florida State University Research Foundation, Inc. | Method of controlling the viscosity of a cementitious mixture using oppositely-charged polyelectrolytes |
| US7261771B2 (en) | 2002-01-09 | 2007-08-28 | Nanostrata Inc. | Method of controlling the viscosity of a cementitious mixture using oppositely-charged polyelectrolytes |
| US8017014B2 (en) | 2005-06-01 | 2011-09-13 | Nalco Company | Method for improving flux in a membrane bioreactor |
| FR2910480B1 (en) * | 2006-12-21 | 2012-10-19 | Kabongo Isaac Mulumba | PRINTING PROCESS WITH NATURAL PRODUCTS; POWDER OF STONES, SANDS AND OTHER NATURAL PRODUCTS HAVING THE PROPERTIES CLOSE TO THE PRODUCTS CITED, WITH PRINTING MACHINES EXISTING AS TRADITIONAL INKS. |
| EP3245269B1 (en) | 2015-01-15 | 2020-05-20 | Imertech Sas | Foam forming compositions comprising a particulate inorganic material |
| TR201802411T4 (en) * | 2015-02-27 | 2018-03-21 | Omya Int Ag | High solids PCC with cationic additive. |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1308143A (en) * | 1969-04-21 | 1973-02-21 | Ici Ltd | Manufacture of paper |
| GB1505641A (en) * | 1974-04-19 | 1978-03-30 | Grace W R & Co | Process of preparing a filler composition for paper |
| FR2468688A1 (en) * | 1979-10-29 | 1981-05-08 | Omya Sa | Paper coating compsn. contg. calcium carbonate - as sole pigment, at high concn. producing rapid drying |
| DE3316949C3 (en) * | 1983-05-09 | 1995-03-23 | Pluss Stauffer Ag | calcium carbonate |
| US4738726A (en) * | 1985-05-06 | 1988-04-19 | Engelhard Corporation | Treatment of clays with cationic polymers to prepare high bulking pigments |
| US4816074A (en) * | 1985-07-12 | 1989-03-28 | E.C.C. America Inc. | Kaolinite aggregation using sodium silicate |
| US4799964A (en) * | 1985-07-29 | 1989-01-24 | Grain Processing Corporation | Preparation of filler compositions for paper |
| JPS62223396A (en) * | 1986-03-24 | 1987-10-01 | 三菱製紙株式会社 | Production of filler internal added paper |
| GB8701491D0 (en) * | 1987-01-23 | 1987-02-25 | Ecc Int Ltd | Aqueous suspensions of calcium |
-
1990
- 1990-12-04 GB GB9026362A patent/GB2251254B/en not_active Expired - Fee Related
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1991
- 1991-11-28 DE DE69127458T patent/DE69127458T2/en not_active Expired - Fee Related
- 1991-11-28 CA CA002088515A patent/CA2088515A1/en not_active Abandoned
- 1991-11-28 BR BR919107142A patent/BR9107142A/en not_active Application Discontinuation
- 1991-11-28 WO PCT/GB1991/002110 patent/WO1992010609A1/en active IP Right Grant
- 1991-11-28 DK DK91920520.3T patent/DK0560813T3/en active
- 1991-11-28 AT AT91920520T patent/ATE157415T1/en not_active IP Right Cessation
- 1991-11-28 JP JP4500472A patent/JP2919970B2/en not_active Expired - Lifetime
- 1991-11-28 AU AU89399/91A patent/AU654514B2/en not_active Ceased
- 1991-11-28 ES ES91920520T patent/ES2104735T3/en not_active Expired - Lifetime
- 1991-11-28 EP EP91920520A patent/EP0560813B1/en not_active Expired - Lifetime
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1993
- 1993-03-31 NO NO931216A patent/NO300021B1/en not_active IP Right Cessation
- 1993-05-31 FI FI932475A patent/FI932475A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| AU8939991A (en) | 1992-07-08 |
| CA2088515A1 (en) | 1992-06-05 |
| ES2104735T3 (en) | 1997-10-16 |
| NO931216D0 (en) | 1993-03-31 |
| EP0560813A1 (en) | 1993-09-22 |
| DE69127458T2 (en) | 1998-01-02 |
| AU654514B2 (en) | 1994-11-10 |
| JP2919970B2 (en) | 1999-07-19 |
| WO1992010609A1 (en) | 1992-06-25 |
| GB2251254B (en) | 1994-06-29 |
| FI932475A0 (en) | 1993-05-31 |
| ATE157415T1 (en) | 1997-09-15 |
| DE69127458D1 (en) | 1997-10-02 |
| GB9026362D0 (en) | 1991-01-23 |
| FI932475A (en) | 1993-05-31 |
| DK0560813T3 (en) | 1998-04-06 |
| NO931216L (en) | 1993-08-03 |
| EP0560813B1 (en) | 1997-08-27 |
| GB2251254A (en) | 1992-07-01 |
| BR9107142A (en) | 1993-11-03 |
| JPH06503127A (en) | 1994-04-07 |
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