Document bVbKQYB765pqEe30E037XOD1

BROOKES & MARTiN CHARTERED RATENT AGENTS TRADE MARK AGENTS EUROPEAN PATENT ATTORNEYS RICHARD C. MARTIN, r a x imm. DAVID C. WOOOCfiATT, a.s*.,(CHM C.ERIC BARNARD, C.ta.lMI.K.C^e.OiftA.r. JOHN F. SYMONOS. LL.B.Lc-9. BOUOTOH JOHN H. BLAKE, B.Se(eMiH) HUGH R. WRIGHT, ma o mn . PETER C. SANDERS. tt.Be. DONALD J. ATTFlELD, tt.*a.c.CM. h .*.i .c .Iipmin o h a m) ABWSTCD mv. TIMOTHY M. A. RICKARD, tt Be. Ph -O. GRAHAM F. MATTHEWS, B. A., C.e*o. F. I.S.E. (CON5ULTAHf } H. NICHOLAS MATTHEWS, M.iww.T, M.A. (CONSULTANT) GEOFFREY E. BROOME (CONSULTANT) OFftCB MABAaen AJ. JELLY AceauNTs*M*a e. GLSIN1A 10 September 1991 RECEIVED SEP 16 1991 pat ik t r bc o sds CEifSfig E.I. Du Pont de Nemours & Company Legal Department, Patent Records Center, 1007 Market Street, Wilmington, Delaware 19898, U.S.A. TELEPHONES 10711 242 9831 INTERNATIONAL +44 7t 842 9631 f a c s imil e (071) 031O5B6 IKTENNATIOKAL+44 7f 831 0566 T.I e* 267541 BROOKMAR G HIGH HOLBORN HOUSE 52/54, HIGH HOLBORN LONDON,WC1V 6SE JR/ OUN NET CHI 371 TOUR NET REC /ED SP25 iiftM DJG. For the attention of Mr. David J. Gould Dear Sirs, European Patent No. 0244180 We have pleasure in enclosing the Certificate of Grant of European Patent No. 0244180, granted on Application No. 87303681.8, together with a copy of the published patent specification. Publication of the grant took place on 7 August 1991 and the patent will be open to opposition for a period of nine months from that date. The patent will remain in force for a term of 20 years from the application filing date, i.e. from 27 April 1987 subject to the payment of annual renewal fees in each of the designated states in which it has been registered, I.e. Belgium, Germany, France, United Kingdom, the Netherlands and Spain. The patent may be maintained in all or any of these designated states. The Associates in each of these countries have been instructed to attend to the payment of the first renewal fee after grant and also to forward the certificate of renewal and their debit notes direct to Du Pont. We have entered the European Patent (UK) on our maintenance system. As you know the European (U.K.) Patent can be extended by registration to several overseas territories including Hong Kong (within 5 years of grant), and Singapore (within 3 years of grant). A }{{ /Hours faithfully, We can deal with these if you wish. FILE CHECKED Miss Jill Routh u BROOKES & MARTIN SEP 2 5 1991 TUNSRIOOE WELLS: I BOYNE PARK. TUNBRIDGE WELLS, KENT. TN4 6EL. TEL.IOS92) BI0800 TELEX 9*7078 FACSIMILE IOS92I SIOS6S BIRMINOHAM: PRUDENTIAL BUILOINOS, B ST. PHILIP'S PLACE. BIRMINGHAM, S3 2AF. TEL. 1021) 236 8282 TELEX 33S38I FACSIMILE (021) 20CIAT3 MUNICH: IS ZWEISHUCKEKSTRASSE. 8000 MUNICH 22. TEL. (0) 22 20 10 N 30946 Europaisches European Office europeen b Patentsmt Patent Office des brevets Urkunde Certificate Certificat Es wird hiermit bescheinigt, daS fur die in der beigefugten Patentschrift bescbriebene Erfmdung ein europaisches Patent fur die in der Patentschrift bezeichneten Vertragsstaaten erteilt worden ist. It is hereby certified that a European patent has been granted in respect of the invention described in the annexed patent specifi cation for the Contracting States designated in the specification. II est certifte qu'un brevet europeen a 6t6 dSlivrd pour I'invention ddcrite dans le fascicule de brevet ci-joint, pour les Etats contractants ddsignSs dans le fascicule de brevet. Europaisches Patent Nr. European Patent No. Brevet europeen ii 0244180 Patentinhaber Proprietor of the Patent Titulaire du brevet E.I. DU PONT DE NEMOURS AND COMPANY 1007 Market Street Wilmington Delaware 19898/US t Munchen, den Fa^tT^Munioh, le 07-08.91 EPA/EPO/OEB Form 2031 02.91 Paul Braendti President des Europaischen Patentamts President of the European Patent Office President de ('Office europeen des brevets N 30946.01 DUP050449494 V. Europaisches Patentamt European Patent Office Office europeen dee brevets Publication number: 0 244180 B1 EUROPEAN PATENT SPECIFICATION it, Date of publication of patent specification: 07.08.91 Int.CIS: C09C 1/36, C09C 3/06, C09C 3/08, C09D 7/12 Application number: 87303681.8 Date of filing: 27.04.87 Titanium dioxide pigment coated with cerium cations, selected acid anions, and alumina. Priority: 30.04.86 US 857325 Date of publication of application: 04.11.87 Bulletin 87/45 Publication of the grant of the patent: 07.08.91 Bulletin 91/32 Designated Contracting States; BE DE ES FR GB ML References cited: GB-A- 1 580 882 US-A- 2 512 079 US-A- 3 513 007 @ Proprietor: E.I. DU PONT DE NEMOURS AND COMPANY 1007 Market Street Wilmington Delaware 19898(US) Inventor: Jacobson. Howard Wayne 2009 Longcome Drive Wilmington Delaware 1981Q(US) Representative: Woodcraft, David Charles et al BROOKES & MARTIN High Holborn House 52/54 High Holborn London, WC1V 6SE(GB) EP 0 244 180 B1 Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid (Art. 99(1) European patent convention). Rank Xerox (UK) Business Services N 30946.02 DUP050449495 EP 0 244 180 B1 Description BACKGROUND OF THE INVENTION 6 The present invention relates generally to pigments composed of coated Ti02 particles, and particularly to Ti02 pigments having coatings comprising cerium cations, selected acid anions, and an outer coating of alumina. TiCfe has a high refractive index for its density, which renders it a superior pigment for use in coatings, e.g., paints. However, Ti02 is photoactive; exposure to ultraviolet radiation results in generation of free 10 radicals on the surface of Ti02 particles. Thus, where a Ti02 pigment is employed in a paint exposed to sunlight, free radicals are generated which can migrate to the film-forming component of the paint, resulting in coating degradation or failure. Therefore, minimizing free radical migration is desirable in order to provide lightfast and stable pigments for coating use. Heretofore, the majority of commercial TiOa pigments have been coated with rs dense silica or densitied alumina to provide lightfastness. However, some patent references have disclosed use of cerium in association with TiC>2 pigments to promote lightfastness. Lederer, U. S. Patent 3,513,007, discloses Ti02 particles having coatings formed from dispersions containing water-soluble hydrolyzable compounds of silicon, titanium, zirconium, or phosphorus, to which water-soluble hydrolyzable compounds of aluminum, cerium, and or calcium and alkali are added. 20 Barnard, U.S. Patent 4,239,548, discloses pigments having inner coatings comprising cerium and phosphate radicals and outer coatings comprising aluminum and phosphate radicals and optionally hydrous alumina. Jacobson, U.S. Patent 4,460,655, describes pigments of TiOz particles associated with compounds selected from the group consisting of Na7CesF3i, K7Ce6F31, Li7Ce$F3i, and(NHt)7Ces F31. 25 Jacobson, U.S. Patent 4,461,810, discloses pigments of TiOz particles, the surfaces of which are associated with cerium cations and sulfate, phosphate, or silicate anions. The particles are also provided with an outer coating of alumina. Newiand et al., U.S. Patent 4,022,632, describes TiC>2 pigments treated with carboxylate salts of cobalt, cerium or manganese. 30 Bramekamp, U.S. Patent 3,506.466, discloses T1O2 pigment particles coated with inorganic oxides, where the inorganic oxide bears on its surface an amine salt of an oxycarboxylic acid selected from the group consisting of lactic, citric, malic, tartaric and glycolic acids. GB-A-1580882 describes a method of making a coated inorganic pigment which performs adequately in terms of gloss and dispersibility both organic and aqueous-based paint media. The inorganic pigment 35 particles, which are preferably Ti02 are coated with alumina and then contacted with one or more organic hydroxy acids or salts or with a water-soluble reaction product of one or more di- or polyhydric alcohols and one or more di- or poly-basic organic hydroxy acids. It has now been found that pigments of Ti02 particles treated with cerium cations in association with certain polyfunctional water-soluble acid anions or borate ions, and then topcoated with alumina, exhibit 40 excellent lightfastness, gloss and dispersion characteristics. SUMMARY OF THE INVENTION The present invention provides a pigment consisting essentially of rutile Ti02 particles bearing coatings 45 of alumina or alumina-silica, the particle surfaces having associated therewith 0.05-2%, by weight of the TiOz, of cerium cations and an associated quantity of borate anions or polyfunctional organic acid anions having a solubility in water of at least 10 grams per liter at 25* C. DETAILED DESCRIPTION OF THE INVENTION 50 The pigments of the present invention are composed of rutile TiOz particles treated with cerium cations in association with selected polyfunctional organic acid anions such as citrate anions, and then topcoated with alumina or alumina-silica. Optionally, the acid anions can be borate. In extreme lightfastness exposures, the pigments of this invention provide performance equivalent to T1O2 coated with 6% by weight silica and 55 2% by weight alumina. It is believed that cerium citrate in association with the TiOz particle surfaces provides recombination centers for electron/hole pairs produced when pigments containing such particles are exposed to actinic radiation. Quenching of eiectron/hole pairs eliminates free radical production which might otherwise degrade a paint film or other organic materials in proximity to pigment particles. 2 i j DUP050449496 EP 0 244 180 B1 The TiC>2 used to prepare the pigment of the invention can be of the conventional rutile variety, prepared by either the chloride or sulfate process. Associated with the particle surfaces of the T1O2 are cerium cations and selected acid anions. "Associated with the particle surfaces" means that the ions are bound to the TO2 particles by a chemical 5 or physical attraction. The acid anions associated with the cerium cations are borate anions or polyfunctional organic acid anions having water solubilities greater than 10 grams per liter at 25 C. Exemplary of such organic acid anions are citrate, succinate, fumarate, adipate, tartrate, and maleate ions. Of the foregoing, citrate ions are preferred. 10 The cerium cations can be supplied by any water-soluble cerium sait, e.g,, ceric sulfate or ceric nitrate, which are added to rutile slurries at pH 2-7. Polyfunctional organic acid anions are supplied by addition of the appropriate acid. Borate anions are supplied by addition of NazB204. The cerium ion content of the pigment can be determined by ion plasma chromatography. The polyfunctional organic acid anion content can be determined using a Leco or other total carbon analyzer. 15 The amount of alumina or aiumina-siiica which the particles bear as coatings can be varied depending primarily upon the pigment's intended use. Ordinarily, the alumina coating will constitute 0.5-10% of the total weight of the particles. Preferably, the alumina coating constitutes 1 -6%, and most preferably, 2-4%, of the total weight of the pigment particles. The amount of alumina the particles bear as coatings, expressed as percent by weight, is calculated by first determining, by ion plasma spectroscopy, the alumina content of 20 the coated pigment. The alumina content of the uncoated rutile Ti02 is similarly determined, and the alumina content attributable to the coating is determined by computing the difference between coated and uncoated alumina contents. The pigment of the present invention can be prepared from an aqueous slurry containing 200-450 grams per liter Ti02. This slurry is brought to 45*-70*C and is held at that temperature throughout the 25 preparation procedure. The slurry is adjusted to a pH at which added cerium ions will remain in solution by addition of mineral acid, e.g., HCI, and then sufficient cerium sait is added to provide a cerium ion concentration in the slurry of 0.05-2%, by weight of the T1O2. For example, if cerium ions are supplied by addition of ceric nitrate, pH should be adjusted to 2-4; if cerium ions are added in the form of ceric sulfate, pH should be adjusted to the range 2-7. 30 At this point, a sufficient quantity of a selected anion species (i.e, organic acid or borate) is added to the slurry to provide a concentration of added anion ranging from 100% to 300% of the cerium ion concentration. As a result, cerium will precipitate upon the surfaces of the TiOz particles in association with the added anion. Alumina is then precipitated on the TiOa particles by slowly adding enough sodium aluminate to the 35 slurry to provide a concentration of about 2-8% by weight of the TiC>2. Acid, normally sulfuric or hydrochloric, is added at the same time to maintain the pH of the slurry within the range 6-9 during the precipitation step. After addition of aluminate is complete, the slurry is allowed to cure, with continuous stirring, for 15-30 minutes. The resulting pigment is then separated from the liquid by filtration or centrifugation, washed with water, 40 and dried. Coating compositions can be prepared with the pigments of the invention in conventional ways, e.g., by blending the pigment with a film-forming component and a liquid carrier. The following examples illustrate particular aspects of the present invention. In the examples, all parts and percentages are by weight and all degrees are Celsius unless otherwise indicated. 45 Example 1 In a large plastic vessel equipped with stirring apparatus and a pH probe, 11,000 parts water are mixed with 5000 parts rutile Ti0250 The resulting slurry is heated to 60*, and the pH is adjusted to about 3.0 by addition of HCI. 42 parts of a 1.5 M CefNCb)* solution are then added, followed by 40 parts citric acid. The resulting mixture is then stirred for a period of about 5 minutes, and then the pH is increased to about 7.5 by addition of NaOH. A coating of 2% hydrous alumina is then deposited on the pigment by simultaneously adding 250 mL NaAIC>2 solution (containing the equivalent of 400 g AI2O3 per liter solution) and HCI, such that the pH of 55 the slurry is continuously maintained from about 7.0 to about 7.5. The resulting coated pigment is cured by holding for about 30 minutes at 60* and pH 7.5. The pigment is then filtered from the slurry, washed free of salts with deionized water, and air-dried. The pigment is then micronized, using 3 lbs. superheated steam per lb. pigment. The resulting pigment, containing about 0.2% 3 DUP050449497 EP 0 244 180 B1 Ce02 as Ce3(CsHs07)4, and a 2.0% alumina coating, is suitable for use in paint systems. Example 2 5 A mill base is made by mixing Pigment of Example 1 387 parts alkyd resin 70 {Syntex &3145; Celanese Coatings Co.) 149.6 parts n-butanol 9.4 parts 75 xylol 79 parts. This mixture is sand ground, and then the sand is filtered from the mill base. A paint is made by mixing 100 parts of the mill base with the following: 20 xylol 1.4 parts alkyd resin 25 {Syntex 3145; Celanese Coatings Co.) 71.8 parts melamine resin solution (Cymel 248-8, 55% 30 solids, American Cyanamid Co.) 38.5 parts. 35 Claims 1. A pigment consisting essentially of rutile Ti02 particles bearing a coating of alumina or alumina-silica, the Ti02 particle surfaces having bound therewith 0.05-2%, by weight of the V1O2, of cerium cations 40 and an associated quantity of borate anions or polyfunctional organic add anions having a solubility in water of at least 10 grams per liter at 25'C, said coating of alumina or aluminasilica forming a top coat on the Ti02 particles. 2. A pigment according to claim 1, wherein the alumina or alumina-silica coating constitutes 0.5-10% of 45 the total weight of the Ti02 particles. 3. A pigment according to claim 2, wherein the alumina or alumina-silica coating constitutes 1-6% of the total weight of the Ti02 particles. 50 4. A pigment according to claim 3, wherein the alumina or alumina-silica coating constitutes 2-4% of the total weight of the TI02 particles. 5. A pigment according to any one of the preceding claims wherein the associated anions are borate ions. 55 6. A pigment according to claim 1, wherein the associated anions are polyfunctional organic acid anions having a solubility in water of at least 10 grams per liter at 25 C. 7. A pigment according to any one of claims 1 to 4, wherein the associated anions are citrate, succinate, 4 i / DUP050449498 EP 0 244 100 B1 fumarate, adipate, tartrate or maleate ions. 8. A coating composition comprising a pigment according to any one of claims 1 to 7, a film-forming material, and a liquid carrier. 5 9. A method of producing coated TiOa pigment particles which comprises (a) forming an aqueous slurry containing 200 to 450 grams per litre of HO2 and having a pH at which cerium ions will remain in solution, (b) adding sufficient cerium salt to provide a cerium ion concentration in the slurry of 0.05 to 2% by weight of 7102, (c) adding a sufficient quantity of a source of borate or polyfunctional organic 10 acid anions to provide a concentration of said anions of from 100 to 300% of the cerium ion concentration thereby causing the cerium ions to precipitate onto the surfaces of the Ti02 particles in association with the said borate or polyfunctional organic acid anions and (d) depositing an alumina or silicaalumina coating on the treated Ti02 particles. is 10. A method according to claim 9 wherein in step (d) alumina is precipitated onto the treated T1O2 particles by adding enough sodium aluminate to the slurry to provide a concentration of abut 2 to 8% by weight of the T1O2 and adjusting the pH to within the range of 6 to 9 during the precipitation step. Revendicatfons 20 1. Un pigment constitue essentiellement de particules de TiOa de la variete rutile portant un enrobage d'aiumine ou d'alumine-silice, les surfaces das particules de Ti02 comportant 0,05 a 2 %, par rapport au poids du Ti02, de cations cerium qui leur sont lies ainsi qu'une quantite associee d'anions borate ou d'anions d'acide organique poiyfonctionnel ayant une solubilite dans I'eau d'au moins 10 grammes par 25 litre a 25 C, ledit enrobage d'aiumine ou d'alumine-silice formant une couche superieure sur les particules de TiOz. 2. Un pigment selon la revendication 1, dans lequel I'enrobage d'aiumine ou d'alumine-silice constitue 0,5 a to % du poids total des particules de Ti02. 30 3. Un pigment selon la revendication 2, dans lequel I'enrobage d'aiumine ou d'alumine-silice constitue 1 A 6 % du poids total des particules de TiC>2. 4. Un pigment selon la revendication 3, dans lequel I'enrobage d'aiumine ou d'alumine-silice constitue 2 & 35 4 % du poids total des particules de Ti02. 5. Un pigment selon I'une quelconque des revendications prdcedentes, dans lequel les anions associes sent des anions borate. ' 40 6. Un pigment selon la revendication 1. dans lequel les anions associes sont des anions d'acide organique poiyfonctionnel ayant une solubilite dans I'eau d'au moins 10 grammes par litre a 25 C. 7. Un pigment selon I'une quelconque des revendications t a 4, dans lequel les anions associes sont des ions citrate, succinate, fumarate, adipate, tartrate ou malSate. 45 8. Une composition de revetement comprenant un pigment selon i'une quelconque des revendications 1 & 7, une matiere filmogene et un vehicule liquide. 9. Un proeddd de production de particules de pigment de TiC>2 enrobees, qui consist & (a) former une 50 suspension aqueuse contenant 200 a 450 grammes par litre de Ti02 et ayant un pH auquel les ions cerium restent en solution, (b) ajouter une quantite suffisante de sel de c4rium pour obtenir une concentration d'ions cerium dans la suspension de 0,05 a 2 % par rapport au poids de Ti02, (c) ajouter une quantite suffisante d'une source d'anions borate ou d'anions d'acide organique poiyfonctionnel pour obtenir une concentration desdits anions qui soit de 100 & 300 % de la concentration des ions 55 cerium, pour fairs ainsi precipiter les ions cerium sur les surfaces des particules de T1O2 en association avec lesdits anions borate ou d'acide organique poiyfonctionnel et (d) deposer un enrobage d'aiumine ou de silice-alumina sur les particules de Ti02 traitees. 5 DUP050449499 EP 0 244 180 B1 10. Un procede selon la revendication 9, dans lequei, dans I'etape (d). on fait prgcipiter de I'alumine sur les particules d T1O2 traitees en ajoutant suffisamment d'aluminate de sodium a la suspension pour obtenir un concentration d'environ 2 & 8 % par rapport au poids du Ti02 et en ajustant le pH dans I'intervalle de 6 a 9 pendant I'etape de precipitation. s Patentansprti che 1. Pigment, das im wesentlichen aus Rutil-Ti02-Teilchen mit einer Beschichtung aus Aluminiumoxid Oder Siliciumaluminiumoxid besteht. wobei die Oberfiachen der TKVTeilchen 0,05 bis 2 %, bezogen auf 10 das Gewicht des TiOa, Cerkationen und eine assoziierte Menge Boratanionen Oder poiyfunktionelle organische Saureanionen mit einer Loslichkeit in Wasser von wenigstens 10 g/l bei 25 C aufweisen und wobei die Beschichtung aus Aluminiumoxid Oder Siliciumaluminiumoxid eine Deckschicht auf den Ti02-Teilchen bildet. 15 2. Pigment nach Anspruch 1, worin die Aluminiumoxid- Oder Siliciumaiuminiumoxidbeschichtung 0,5 bis 10 % des Gesamtgewichts der Ti02-Teilchen ausmacht. 3. Pigment nach Anspruch 2, worin die Aluminiumoxid- Oder Siliciumaiuminiumoxidbeschichtung 1 bis 6 % des Gesamtgewichts der Ti02-Teilchen ausmacht. so 4. Pigment nach Anspruch 3, worin die Aluminiumoxid- Oder Siliciumaluminiumoxidbeschichtung 2 bis 4 % des Gesamtgewichts der TiOa-Teilchen ausmacht. 5. Pigment nach einem der vorstehenden Anspruche, worin die as30ziierten Anionen Barationen sind. 25 6. Pigment nach Anspruch 1, worin die assoziierten Anionen poiyfunktionelle organische Saureanionen mit einer Loslichkeit in Wasser von wenigstens 10 g/l bei 25*C sind. 7. Pigment nach einem der AnsprUche 1 bis 4, worin die assoziierten Anionen Citrat-, Succinat-, Fumarat-, 30 Adipat-, Tartrat- Oder Maleationen sind. 8. Uberzugszusammensetzung, welche ein Pigment nach einem der AnsprOche 1 bis 7, ein filmbiidendes Material und einen flUssigen Trager umfaflt. 35 9. Verfahren zur Herstellung von beschichteten Ti02-Pigmentteilchen durch (a) Bilden einer wassrigen Aufschlammung mit 200 bis 450 g/l Ti02 und einem pH-Wert, bei dem Cerionen in Losung bleiben. (b) Zugeben von ausreichend Cersalz zur Bereitstellung einer Cerionenkonzentration in der Aufschlam mung von 0,05 bis 2 % des Gewichts des T1O2, (c) Zugeben einer ausreichenden Menge einer Quelle von Boratoder polyfunktionellen organischen Saureanionen zur Bereitstellung einer Konzentratlon dieser 40 Anionen von 100 bis 300 % der Cerionenkonzentration, wodurch die Cerionen zur Niederschlagung auf den Oberfiachen der TiOj-Teilchen in Assoziation mit den Borat- Oder polyfunktionellen organischen Saureanionen veranlaflt werden, und (d) Aufbringen einer Aluminiumoxid- Oder Siliciumaluminiumoxidbeschichtung auf den behandelten Ti02-Teilchen. 45 10. Verfahren nach Anspruch 9, worin in Schritt (d) Aluminiumoxid auf den behandelten TiCVTeitchen niedergeschlagen wird, indem genOgend Natriumaluminat zur Aufschlammung zugegeben wird, um eine Konzentration von etwa 2 bis 8 % des Ti02-Gewichts bereitzustellen, und der pH-Wert innerhalb des Bereiches von 6 bis 9 wahrend des Ausfallungsschritts eingestellt wird. 50 55 6 DUP050449500