Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
1995-06-06
2001-08-07
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S600000, C106S628000, C106S635000, C106S426000, C106S428000, C106S431000, C106S434000, C106S435000, C106S438000, C106S442000, C106S444000, C106S446000, C106S454000, C106S457000
Reexamination Certificate
active
06270566
ABSTRACT:
This invention relates to a process for coloring building materials with inorganic pigments in the form of microgranulates.
If building materials bound with cement and lime, such as plaster, calcareous sandstone, cement fibreboards or concrete slabs and especially roof tiles and paving stones and slabs are required to be colored, color is generally imparted by means of inorganic pigments. It is customary in the building industry to use iron oxides or iron hydroxides as red, black, brown or yellow pigments, manganese oxides as blackish brown pigments, chromium oxides as green pigments and titanium dioxides as white pigments. Further, carbon blacks may be used as black pigments, nickel and chromium rutiles may be used as yellow pigments, spinels containing cobalt may be used as blue and green pigments, spinels containing copper may be used as black pigments and the mixed crystals of barium sulphate and barium manganate may be used as blue pigments.
For coloring concrete materials, the pigments are normally used in a pulverulent form. As milled pigments they have the advantage of being easily dispersible. Completely homogenous distribution of such pigment powders in concrete mixtures can be completed within a short time of up to a few minutes. The disadvantage of these fine powders, however, is that they do not pour well but frequently cake together and agglomerate as lumps when kept in storage. Accurate dosing of the powders is then difficult. Another disadvantage of some powders is that they tend to throw up dust.
It is known that these disadvantages can be avoided when pigmenting concrete parts by using aqueous pigment suspensions instead of dry pigment powders. The use of such pastes or slurries containing 30 to 70% by weight of pigment has, however, only slowly become established since the additional water content may considerably increase the cost of transport, depending on the distance between the site of manufacture and the building site. Moreover, the large quantity of water present in the paste or slurry cannot be absorbed in all concrete mixtures.
The building industry has therefore mainly kept to the use of dry pigment powder. Pigments in the form of microgranulates such as are used in the plastics and lacquer industry have not hitherto been used because it was believed that such granulates with diameters from 25 to 600 &mgr;m would be difficult to disperse in concrete mixtures. Pigment agglomerates which are difficult to disperse require much longer mixing times. In the short mixing times conventionally used in the building industry, specks, streaks and nests of color occur on the surface of the concrete due to imperfect distribution of the pigment. The full intensity of color of the pigment then cannot develop and larger quantities of pigment are therefore required for obtaining a given intensity of color in the concrete workpiece.
Pigment granulates consisting substantially of pigment and one or more binder(s) for promoting dispersion of the pigment in concrete are described in DE-C 36 19363 for coloring concrete ware. The following are the binders mentioned in the said document for facilitating dispersion in concrete: Alkyl benzene sulphonate, alkyl naphthalene sulphonate, lignin sulphonate, sulphated polyglycol ether, melamine formaldehyde condensates, naphthalene formaldehyde condensates, gluconic acid, salts of low molecular weight, partially esterified styrene/maleic acid anhydride copolymers and copolymers of vinyl acetate and crotonic acid. The proportion in the pigment should preferably be from 2 to 6% by weight.
The above-mentioned dispersing agents act as liquefiers in the concrete mixtures. They influence the ratio of water to cement and affect the consistency of the concrete.
In the inorganic pigment itself, the binders added are organic substances which constitute foreign bodies.
It is an object of the present invention to provide free-flowing, non-dusting inorganic pigment microgranulates which are free from the above-described disadvantages of the state of the art for coloring building materials.
This problem has been solved by a process for coloring building materials with inorganic pigments in the form of microgranulates consisting of one or more pigments and of compounds of boron, aluminum, silicon, titanium, zinc and/or tin. The microgranulate inorganic pigments according to this invention can be mixed with building materials such as plaster, calcerous sandstone, cement or concrete, or other settable materials prior to curing. A completely homogeneous distribution of the pigment results when the microgranulates are mixed with the building materials in standard mixing units. The pigment disperses within the building materials in a short time, comparable to or better than that for pigment powders and slurries. This process is the subject matter of the present invention.
It has surprisingly been shown that these pigment microgranulates containing purely inorganic additives are comparable in their properties of dispersion in concrete preparations to pigment granulates containing substances which act as liquefiers in concrete preparation although they contain no organic substances.
Pigment microgranulates or bead granulates are granulates which are obtainable from pigment suspensions by spray drying. They may be produced in the spray drier by means of slowly rotating centrifugal atomizers or by pressure nozzles (one-material nozzles) or two-material nozzles having a low air/liquid ratio.
Whereas two-material nozzles give rise to particles with diameters of up to 200 &mgr;m, the atomizer disc can be used for the production of larger particles with diameters of up to 300 &mgr;m. The coarsest individual particles, measuring up to 600 &mgr;m and having a relatively narrow grain size distribution, are obtained when pressure nozzles are used. Secondary agglomerates with diameters larger than those mentioned above may be obtained by using spray driers with an integrated fluidized bed.
The compounds added according to the invention are preferably in the form of oxides and/or hydroxides but may consist of borates, aluminates, silicates, titanates, zincates and/or stannates which are added to the pigments either in the form stated or as substances which give rise to these compounds. Thus, for example, compounds which decompose in the manufacturing process to form oxides may be used, such as titanic acid esters or silicic acid esters.
In one particular embodiment of the process according to the invention, the compounds added are silica sol or waterglass. These are substances which are in any case present as components of concrete.
The quantity of compound added according to the invention may amount to 0.05 to 5.0% by weight, preferably from 0.1 to 1% by weight, calculated as oxide and based on the quantity of pigment. Smaller quantities are ineffective while larger quantities may give rise to difficulties in dispersion. The compounds may be used in the form of their solutions, as colloids, or as suspensions during the whole process of manufacture of the granulates or they may have already been added at the stage of pigment formation as such.
It has been found that the granulates according to the invention should not exceed a particular particle size, which depends on the pigment used. This particle size depends mainly on the bulk weight of the granulate, which in turn is a measure of the porosity of the particles. The porosity is in turn dependent on the solids content of the pumpable starting suspension before it is dried. This solids content of the suspension may vary according to the particle size and particle form of the pigment. The compacted bulk density or compacted bulk weight defined in DIN 53 194 of August 1957 is used as a measure of the bulk density. The pigment granulates according to the invention are distinguished by the fact that they do not decompose when the compacted bulk density is determined. The granulates according to the invention preferably have a compacted bulk density of from 0.5 to 2.5 g/ml, most preferably from 0.8 to 1.5 g/ml.
The
Rademachers Jakob
Teichmann Gunther
Bayer AG
Connolly Bove & Lodge & Hutz LLP
Koslow C. Melissa
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