Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
1999-10-25
2002-02-19
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S448000, C106S449000, C106S018320, C106S018350, C516SDIG005, C514S561000, C562S553000, C562S574000
Reexamination Certificate
active
06348092
ABSTRACT:
This invention relates to surfactant treated particulate titanium dioxide and other pigments. More particularly, this invention is concerned with surfactant treated titanium dioxide and other particulate materials readily employable in coating compositions, plastic molding compositions, reinforced plastic composite compositions, and paper making compositions.
Industrial pigment particles agglomerate or cake together into hard packed clusters during the drying operation near the end of the manufacturing process. Forces holding pigment clusters together are not large in many cases but are yet large enough that the pigment user, those who incorporate industrial pigments into their products such as paints and plastics and the like, are required to subject industrial pigments to a milling operation in which the agglomerates are sheared under stress into particles of suitable smallness and homogenized into the matrix or product which incorporates them. The process is dispersion.
Pigment dispersion is a bottleneck, a limiting requirement, and the most expensive operation in terms of energy and time in manufacturing processes which employ pigments. This present invention is concerned with the employment of surfactants for the surface treatment of pigments during the pigment manufacturing process in order to provide pigments of improved dispersibility in subsequent manufacturing processes and in some cases, to provide improvements in certain important aspects of products incorporating these surface treated pigments.
Titanium dioxide pigments present a special case. Uncoated titania pigments are extremely difficult to disperse. In addition, their employment in pigmented plastics, coatings, papers, and fiber compositions induces a photoactivity which results in oxidative degradation which is destructive of the materials of which they are a part. As a consequence, most titanium dioxide pigments are provided with some form of surface coating during manufacture to promote dispersibility and to reduce photoactivity. Two materials in widespread use at present are silica and alumina. These materials are coated onto the surfaces of pigment particles in the range of three to ten percent by weight of TiO
2
.
The surface treatment of pigments can provide the following beneficial primary effects:
1. The total number of agglomerates is reduced.
2. Any agglomerates that are present are more easily broken up since their mechanical strength is reduced.
3. Pigment particle wettability is improved due to a lowering of the interfacial tension between the pigment surface and the application medium
4. Wettability of the pigment particles is also improved due to the liberation of the free energy of solution of the coating agent on the pigment surface. (Surface Treatment of Organic Pigments; K. Merkle and H. Schafer, Pigment Handbook, page 158, Vol. III; John Wiley and Sons, Inc., 1973.)
Pigments, their preparation and properties are described in volumes I, II and III of the book “Pigment Handbook” published by John Wiley & Sons, Inc. The uses, preparation and characterization of pigments is further described in the various units of “The Federation Series on Coating Technology” published by the Federation of Societies for Coating Technology.
German Pat. Nos. 889,042 and 930,998 teach the use of surface-active substances as emulsifiers together with oils in the manufacture of water-insoluble azo-dyestuffs having a soft grain.
U.S. Pat. No. 3,120,508 discloses that water-insoluble azo-dyestuffs having a particularly high tinctorial strength can be prepared by adding during the coupling cationic surface-active compounds without simultaneously using oils.
U.S. Pat. No. 3,437,502 teaches improvement of opacity and dispersibility of titanium dioxide through surface treatment with silica and alumina. U.S. Pat. No.3,658,566 teaches the production of titanium dioxide of improved properties by treatment with oxides of silicon and aluminum U.S. Pat. No. 4,599,114 discloses improvement of pigmentary properties for a variety of pigments through surface treatment of pigment filter cakes.
Cationic surface-active compounds are described in the book “Surface-Active Agents and Detergents” by A. M. Schwartz, J. W. Perry and J. Berch, vol. II (1958), pages 103 to 119.
U.S. Pat. Nos. 4,599,114, 4,741,780 and 4,909,852 disclose compositions having surfactants consisting of the reaction product of a diamine, a carboxylic acid and a fatty acid. U.S. Pat. No. 5,808,118 discloses a composition which is the reaction product of a diamine, a sulfonic acid and a fatty acid.
British Patent No. 1,080,115 discloses the use of primary long chain alkyl amines for treating pigments improving their dispersibility.
Suitable cationic surface-active substances are, for example, long-chained aliphatic amino compounds that contain about 10 to 18 carbon atoms, or the salts of such nitrogen compounds with carboxylic acids, such as for example, formic acid, acetic acid, oleic acid, tallow fatty acid, lactic acid or mineral acids, for example, hydrochloric acid. Fatty amines are for example, coconut oil amine, oleyl amine, stearyl amine, and tallow fat amine, as well as the secondary and tertiary amines or quaternary ammonium compounds derived therefrom that may carry as substituents aliphatic, aromatic or oxethylated radicals, for example, alkyldimethyloxyethyl ammonium chloride. Oxethylated fatty amines in their secondary, tertiary or quaternary form are also suitable. Also useful are the condensation products of long-chained, in some cases also unsaturated, carboxylic acids with amines, in particular alkylenediamines, alkylenetriamines, or alkylenepolyamines containing alkylene radicals of low molecular weight, for example, ethylene diamine, diethylene triamine, etc., as well as the secondary, tertiary or quaternary amines formed by alkylation of the condensation products, especially in the form of their water-soluble salts with the above-mentioned acids. Further, there may be used fatty acid amides and esters of long-chained carboxylic acids with alkylol amines, for example, triethanolaminoleate, stearate, and the like, further also cyclical, nitrogen-containing compounds, for example, long-chained derivatives of morpholine, imidazoline, piperidine, piperazine or pyridine. The above-mentioned amino compounds are used preferably in the form of their carboxylic or hydrochloric salts.
There is described herein the use of surfactants which have the capability of increasing the dispersibility of titanium dioxide and other pigments to which they are applied.
Titanium dioxide is an established pigmentary material which can also be employed as a reinforcing filler, albeit an expensive one. It is commonly made by two processes, the chloride process and the sulfate process. The chloride process is dry process wherein TiCl
4
is oxidized to TiO
2
particles. In the sulfate process titanium sulfate, in solution, is converted by a metathesis reaction to insoluble and particulate titanium dioxide. In both processes, particle formation can be seeded by aluminum compounds. Thereafter, the processes are essentially the same. The TiO
2
particles in a water slurry are put through multiple hydroseparations to separate out the large particles and the further refined pigment in slurry form is passed to a treating tank where the particles may be treated with an aluminum compound and/or silicon compound, such as aluminum triethoxide, sodium aluminate, aluminum trichloride, aluminum sulfate, ethyl silicate, sodium silicate, silicon tetrachloride, trichlorosilane, and the like. By pH adjustment, the pigment is flocculated and precipitated with its coating of alumina and/or silica, or without any coating. It is then made into a filter cake by a vacuum drying and further dried in an oven, generally of a vibrating type. The optimum average particle size can range from about 0.05 to about 0.35 microns with a range of about 0.1 to about 0.25 more preferable.
One feature of the dispersion promoters of this invention is that they alter the surface characteristics of the titanium d
Green Anthony
Hanegan, Esq Herbert M.
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