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Publication numberUSRE32320 E
Publication typeGrant
Application numberUS 06/737,501
Publication dateDec 30, 1986
Filing dateMay 24, 1985
Priority dateApr 4, 1983
Fee statusPaid
Publication number06737501, 737501, US RE32320 E, US RE32320E, US-E-RE32320, USRE32320 E, USRE32320E
InventorsHoward W. Jacobson
Original AssigneeE. I. Du Pont De Nemours And Company
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
TiO2 pigment bearing a coating with cerium cations and sulfate-, phosphate- or silicate anions and laminate and coating containing same
US RE32320 E
Abstract
A pigment of TiO2 particles coated with alumina, whose particle surfaces have associated with them cerium cations and sulfate-, phosphate or silicate anions, can be used to prepare paper laminates having a high degree of lightfastness.
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Claims(3)
I claim:
1. A pigment of rutile TiO2 particles bearing coatings consisting of alumina or alumina-silica, the particle surfaces having associated therewith .[.0.5-2%,.]. .Iadd.0.17-2%, .Iaddend.by weight of the TiO2, of cerium cations and a stoichiometric amount of sulfate-, phosphate or silicate anions.
2. A paper laminate comprising paper and a pigment according to claim 1, in a rigid matrix.
3. A coating composition comprising
(a) a pigment according to claim 1,
(b) a film-forming material, and
(c) a liquid carrier.
Description
DESCRIPTION Technical Field

This invention relates to pigment composed of coated TiO2 particles. More particularly, it relates to a pigment of TiO2 particles coated with alumina and having cerium cations and sulfate-, phosphate or silicate anions associated with them.

BACKGROUND AND SUMMARY OF THE INVENTION

Paper laminates are products widely used in the construction industry for making counter tops and the like. They are ordinarily composed of paper impregnated with TiO2 pigment and imbedded in a polymer matrix. Such laminates have an unfortunate tendency to discolor on exposure to ultraviolet light, and this detracts from their value because in many uses they are necessarily exposed to such radiation.

The pigment of the present invention is highly resistant to discoloration on exposure to ultraviolet light, and, when used in making a paper laminate, gives a product with significantly better lightfastness than one made with conventional TiO2 pigment.

The pigment of the invention is composed of rutile TiO2 particles conventionally coated with alumina or with alumina-silica. The coating ordinarily constitutes 1-8%, by weight, of the pigment. Associated with the pigment particle surfaces are cerium cations (preferably Ce+4 ions), at a concentration of .[.0.5-2%,.]. .Iadd.about 0.17-2%, .Iaddend.by weight, and a stoichiometric amount of sulfate-, phosphate or silicate anions. "Associated with the particle surfaces" means that the ions are bound to the TiO2 particles by a chemical or physical attraction.

The ion content of the pigment may be determined by ion plasma chromatography.

The amount of alumina the TiO2 particles bear as coatings, expressed as percent by weight, is calculated by first determining, by ion plasma spectroscopy,

(a) the alumina content of a pigment of the invention, and

(b) the alumina content of the raw TiO2 from which the pigment is made,

and then computing the alumina coating content of the pigment by difference.

The cerium cations may be supplied by any water-soluble cerium salt, preferably cerium sulfate, and even more preferably ceric sulfate: when the anion is sulfate, this will also supply the sulfate ion. When the anion of choice is phosphate or silicate, it is supplied by using phosphoric acid or sodium silicate solution during preparation of the pigment, as will be described.

The TiO2 used to prepare the pigment or the invention can be of the conventional rutile variety, prepared by either the chloride or the sulfate process.

The pigment of the invention can be made by first preparing an aqueous slurry containing 200-400 grams per liter of TiO2. This slurry is brought to 45-70 C. and is held there during the rest of the preparation procedure. To the slurry is then added, with stirring, enough of a cerium salt to give a cerium ion concentration in the slurry of .[.0.5-2%,.]. .Iadd.0.05-2%, .Iaddend.by weight of the TiO2. If one desires a phosphate anion or a silicate anion to be associated with the pigment, he also adds a stoichiometric amount of phosphoric acid or sodium silicate. In any case, the slurry is then stirred for 1-15 minutes.

Alumina is then precipitated on the TiO2 particles by slowly adding enough sodium aluminate to the slurry to give a concentration of about 2-8%, by weight of the TiO2. Acid, ordinarily 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 the aluminate is complete, the slurry is allowed to cure, with stirring, for 15-30 minutes.

The resulting pigment is then separated from the liquid by filtration or centrifugation, is washed with water and then dried.

The pigment thus prepared may be used to prepare a paper laminate in any of the customary ways typically by mixing the pigment with paper pulp and then making paper of it in the usual way, impregnating this paper with resin, ordinarily a melamine-formaldehyde or urea-formaldehyde resin, and then curing the mixture with heat. These procedures are set forth in greater detail in U.S. Pat. No. 4,239,548, which is incorporated into this specification to show such procedures.

Coating compositions may be prepared with the pigments of the invention in any of the conventional ways, by blending the pigment with a film-forming component and a liquid carrier.

EXAMPLES

In the following examples, all parts are by weight.

EXAMPLE 1

Three thousand parts of rutile TiO2 were dispersed in 7500 parts of distilled water, to give a slurry with a pH of 3.6. The slurry was then heated to and held at 50 C., and to it were added, over a 5-minute period, 145 parts of a solution of 85.5 parts of ceric sulfate in 1000 parts of water. The slurry at this point had a pH of 1.5. The slurry was then stirred for 10 minutes at 50 C.

To the slurry were then added, over a 30-minute period and with stirring at 50 C., 400 parts of an aqueous solution of sodium aluminate (containing an equivalent of 350 parts of Al2 O3 per 1000 parts of water). During this addition, the pH of the slurry was held at about 6.5 by adding sulfuric acid.

When addition of the sodium aluminate was finished, the slurry was stirred for 30 minutes at 50 C. The TiO2 was then filtered off, washed with water, dried and micronized.

The resulting pigment was composed of TiO2 particles coated with alumina and having cerium and sulfate anions associated with them.

EXAMPLE 2

Three thousand parts of rutile TiO2 were dispersed in 7500 parts of distilled water, to give a slurry with a pH of 3.6. The slurry was then heated to and held at 50 C., and to it were added, over a 5-minute period, 140 parts of a solution of 85.5 parts of ceric sulfate in 1000 parts of water.

When addition of the ceric sulfate was finished, 24 parts of concentrated H3 PO4 were added and the slurry stirred for 10 minutes at 50 C.

To the slurry were then added, over a 30-minute period and with stirring at 50 C., 343 parts of an aqueous solution of sodium aluminate (containing an equivalent of 350 parts of Al2 O3 per 100 parts of water). During this addition, the pH of the slurry was held at about 7.5 by adding sulfuric acid.

When the addition of the sodium aluminate was finished, the slurry was stirred for 30 minutes at 50 C. The TiO2 was then filtered off, washed with water, dried and micronized.

The resulting pigment was composed of TiO2 particles coated with alumina and having cerium cations and phosphate anions associated with them.

EXAMPLE 3

Two hundred parts of rutile TiO2 were dispersed in 500 parts of distilled water, to give a slurry with a pH of 3.8. The slurry was then heated to and held at 50 C., and to it were added, over a 5-minute period, 9.4 parts of a solution of 85.5 parts of ceric sulfate in 1000 parts of water.

When the addition of the ceric sulfate was finished, 5 parts of an aqueous sodium silicate solution (containing an equivalent of 400 parts of SiO2 per 1000 parts of water) were added and the slurry stirred for 10 minutes at 50 C.

To the slurry were then added, over a 10-minute period and with stirring at 50 C., 22.9 parts of an aqueous solution of sodium aluminate (containing an equivalent of 350 parts of Al2 O3 per 100 parts of water). During this addition, the pH of the slurry was held at about 7.5 by adding sulfuric acid.

When the addition of the sodium aluminate was finished, the slurry was stirred for 30 minutes at 50 C. The TiO2 was then filtered off, washed with water, dried and micronized.

The resulting pigment was composed of TiO2 particles coated with alumina and having cerium cations and silicate anions associated with them.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3513007 *Jul 14, 1966May 19, 1970British Titan ProductsMixed coating process
US3767455 *Jan 8, 1971Oct 23, 1973Laporte Industries LtdTreatment of oxide pigments
US3804655 *Mar 30, 1972Apr 16, 1974British Titan LtdPigments
US3960589 *May 27, 1975Jun 1, 1976Stanford Research InstituteStabilized pigment and method for producing the same
US4239548 *Dec 6, 1979Dec 16, 1980Tioxide Group LimitedTitanium dioxide pigment
GB1023590A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5730796 *Jan 16, 1997Mar 24, 1998Kerr-Mcgee Chemical CorporationDurable pigmentary titanium dioxide and methods of producing the same
US5777001 *Aug 4, 1997Jul 7, 1998Kerr Mcgee Chemical Corp.Addition polymers with inorganic oxide pigments formed by solution polymerization
US5851652 *Aug 22, 1996Dec 22, 1998E. I. Du Pont De Nemours And CompanyLightfast T102 pigment
Classifications
U.S. Classification428/530, 524/493, 428/342, 428/328, 106/439
International ClassificationC09C1/36, D21H27/28, D21H17/69, B32B27/42
Cooperative ClassificationC09C1/3661, C01P2004/84, D21H27/28, D21H17/69
European ClassificationD21H17/69, C09C1/36D6B, D21H27/28
Legal Events
DateCodeEventDescription
Dec 28, 1995FPAYFee payment
Year of fee payment: 12
Dec 9, 1991FPAYFee payment
Year of fee payment: 8
May 30, 1990FPAYFee payment
Year of fee payment: 4
Nov 27, 1987FPAYFee payment
Year of fee payment: 4
Oct 25, 1985ASAssignment
Owner name: E. I. DU PONT DE NEMOURS AND COMPANY, WILMINGTON,
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:JACOBSON, HOWARD W.;REEL/FRAME:004471/0203
Effective date: 19851017