Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2000-04-19
2002-06-25
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S491000, C106S483000, C106S490000, C523S216000, C427S407100, C427S419500
Reexamination Certificate
active
06409814
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to pigment preparations suited for the preparation of water-borne effect base coats (i.e., base coats that provide a desired effect to the coated article, as opposed to merely providing color), a process for preparing the pigment preparations and water-borne effect base coats prepared therewith.
In a vehicle coating production line the coating supply of the spray-coating devices proceeds from coating supply reservoirs via circulation lines connected thereto. Heavy shearing strains affect the liquid coating material while it is conveyed within a circulation line. These shearing strains can lead to alterations of the effect and color shade of the coating materials, for example, water-borne effect base coats. Good effect and color shade constancy is however a key property of a suitable production line operation.
It is known from WO 99/57204 and A. Kiehl and K. Greiwe, “Encapsulated aluminum pigments”, Progress in Organic Coatings 37 (1999), pages 179 to 183, that pigments coated with a silicon-oxygen-matrix are in particular suitable for preparing water-borne effect base coats having a good shear stability.
It is an object of the invention to provide pigment preparations which can be used for preparing water-borne effect base coats having an excellent shear stability with respect to effect and color shade stability.
SUMMARY OF THE INVENTION
The present invention provides pigment preparations having a solid content of 10 to 60 wt-%, which are obtainable by mixing together, in the presence of water-miscible organic solvents:
a) pigments coated with a silicon-oxygen-matrix
b) at least one resin having carboxyl groups sufficient to provide an acid value of 10 to 100 mg KOHJg resin and having a number average molecular mass of 500 to 5000
c) wherein, the weight ratio of pigments to resin is in the range of 1:0.3 to 1:10.
Detailed Description of the Embodiments
The pigment preparations according to the invention contain one or more pigments, the surface of which is coated with a silicon-oxygen-matrix. The silicon-oxygen-matrix can be linked to the surface of the pigments by covalent bonds. Such pigments and their preparation are known for example from WO 99/57204, U.S. Pat. No. 5,332,767 and from A. Kiehl and K. Greiwe, “Encapsulated aluminum pigments”, Progress in Organic Coatings 37 (1999), pages 179 to 183.
Pigments coated with a silicon-oxygen-matrix can be prepared by subjecting monosilanes, having at least two hydrolyzable groups, to hydrolysis and condensation in the presence of the pigments. The monosilanes having at least two hydrolyzable groups are in particular bisalkoxy, trisalkoxy and tetraalkoxy monosilanes. Preferred alkoxy substituents are C1-C4 alkoxy groups, in particular methoxy and ethoxy groups. The monosilanes having at least two hydrolyzable groups can carry, apart from the hydrolyzable groups, further non-hydrolyzable organic radicals on the silicon atom. For example alkyl groups or preferably radicals with reactive functional groups or reactive functional groups such as for example vinyl, amino, isocyanate, epoxy or in particular (meth)acryloyl groups may be present.
Examples of monosilanes to be hydrolyzed in the presence of the pigments are vinyl trimethoxysilane, aminopropyl triethoxysilane, isocyanatopropyl triethoxysilane, 3-glycidyloxypropyl trimethoxysilane, 3-(meth)acryloxypropyl trimethoxysilane, 3-(meth)acryloxypropyl triethoxysilane.
Examples of pigments, in the presence of which the hydrolysis of the monosilanes can be carried out, are metallic pigments, for example of aluminum, copper or other metals; interference pigments such as, e.g., metal oxide-coated metallic pigments, e.g., titanium dioxide- or iron oxide-coated aluminum, coated mica such as, e.g., titanium dioxide-coated mica and graphite-like effect-giving pigments, metal oxide flake or non-metal oxide flake, e.g. iron oxide flake or silicon oxide flake. Preferred are metallic pigments, in particular of aluminum. The pigments may not be pretreated, for example not passivated.
The monosilanes are hydrolyzed in the presence of the pigments. This can be carried out, as is known from U.S. Pat. No. 5,332,767, in the presence of organic solvents that are not miscible with water, while adding a small amount of water, which is required for the hydrolysis. Preferred pigments coated with a siliconoxygen-matrix are however obtained when the hydrolysis is carried out in the presence of water-miscible solvents while adding water and alkaline catalysts, for example amines, as is known from WO 99/57204 and A. Kiehl and K. Greiwe, “Encapsulated aluminum pigments”, Progress in Organic Coatings 37 (1999), pages 179 to 183. After the hydrolysis, the pigments coated with a silicon-oxygen-matrix can be isolated by filtering off and drying. During the hydrolysis of the hydrolyzable groups of the monosilanes, silanol groups are formed, which condense to siloxane bridges while forming a silicon-oxygen-matrix. If for example solely silanes having four hydrolyzable groups are used, in particular tetraalkoxysilanes, the densest possible silicon-oxygen-matrix (SiO
2
) is created. The density of the silicon-oxygen-matrix is dependent on the choice of the kind and the amount of the individual monosilanes to be hydrolyzed, for example a monosilane mixture. The lower the average number of the hydrolyzable groups of the monosilanes, the less dense is the obtained silicon-oxygen-matrix. Preferably bisalkoxy and/or trisalkoxy monosilanes, optionally in combination with tetraalkoxy silanes, are hydrolyzed in the presence of the pigments. Thereby particular preference is given to the use of bisalkoxy and/or trisalkoxy monosilanes having reactive functional groups.
The monosilanes can be added and hydrolyzed in one or more steps. In a step after the hydrolysis and condensation the reactive functionality, introduced into the silicon-oxygen-matrix, can preferably be used for the build-up of a polymer, for example a three-dimensionally cross-linked polymer. The polymer can be linked to the silicon-oxygen-matrix located on the surface of the pigment in the manner of a resin coating. Suitable functionalised organic compounds of low molecular weight can for example be converted to a polymer with the reactive groups on the silicon-oxygen-matrix by polycondensation, polyaddition or radical polymerization. Epoxy groups on the silicon-oxygen-matrix can for example be converted to a three-dimensional polymer with polyamines such as ethylene diamine and triethylene tetraamine. It is preferred to have (meth)acryloyl groups as the reactive functional groups on the silicon-oxygen-matrix and to radically copolymerize these with radically polymerizable, in particular multiply olefinically unsaturated compounds, such as for example hexanediol diacrylate and trimethylolpropane tri(meth)acrylate.
Examples of commercially available aluminum pigments coated with a silicon-oxygen-matrix are the aluminum pigments characterized and sold by the company Eckart-Werke under the name “STAPA IL Hydrolan” as belonging to one product family.
The pigment preparations according .to the invention contain, apart from the pigments coated with a silicon-oxygen-matrix as explained above, carboxyl-functional resin and water-miscible organic solvents.
The carboxyl-functional resin(s) possess carboxyl groups sufficient to provide an acid value of 10 to 100 mg KOH/g resin, preferably of 20 to 50 mg KOH/g resin and have a number average molecular mass of 500 to 5000, preferably of 1000 to 5000. The carboxyl groups are not neutralized. Apart from the carboxyl groups, the polymers carry no further acid groups. Examples are carboxyl-functional (meth)acrylic copolymer, polyurethane and preferably polyester resins. The carboxyl-functional polymers can have a hydroxyl value of up to 100 mg KOH/g resin solids.
Examples of water-miscible organic solvents contained in the pigment preparations are N-methylpyrrolidone, C1-C4 alcohols and, in particular, glycol ethers such as, for example, isopropyl glycol, butyl glycol, methyl digl
Bosch Werner
Cuddemi Georg Antonio
Mueller Frank
Taschner Marco
Deshmukh Sudhir G.
E. I. du Pont de Nemours and Company
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