Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2001-01-26
2003-04-08
Wood, Elizabeth D. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S438000, C106S442000, C106S445000, C106S447000, C106S450000, C106S481000, C106S483000
Reexamination Certificate
active
06544328
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for preparing improved inorganic pigment having enhanced dispersibility in paints and plastics concentrates as determined by the time or energy required to achieve dispersal.
2. Description of the Prior Art
Inorganic pigments such as titanium dioxide, zinc sulfide, zinc oxide and the like are used in paint, plastics and other products. Such pigments have heretofore been difficult to disperse in paints and plastics concentrates, i.e., the pigments have required long time periods and/or high levels of energy to achieve dispersal. Inorganic pigments are generally in the form of a finely divided powder which has been jet-milled or micronized as a final step in their production.
More recently, processes have been developed and used for preparing low-dusting, free-flowing pigment which requires less energy to disperse in paints and plastics concentrates. For example, U.S. Pat. No. 5,733,365 issued to Halko et al. on Mar. 31, 1998 and its related U.S. Pat. No. 5,908,498 issued to Kauffman et al. on Jun. 1, 1999 disclose a process for preparing improved low-dusting, free-flowing pigments which have not been subjected to final micronizing treatments. The process is comprised of the steps of providing an inorganic pigment material which has not been micronized, providing a source of water, forming a fine, well dispersed slurry of the pigment and water, milling the slurry, adjusting the pH of the slurry, depositing a treating agent having the formula ROOCCHSO
3
MCH
2
COOR′ wherein R and R′ are monovalent alkyl radicals having from about 2 to about 20 carbon atoms and M is a metallic monovalent cation on the slurried milled pigment, and then drying the pigment material having the treating agent deposited thereon. The presence of the treating agent makes the pigment produced more readily dispersible in paints and plastics concentrates.
While the pigments produced in accordance with the teachings of the above described patents constitute a major improvement as compared to prior pigments, the dispersal of the pigments in paints and plastics concentrates still requires considerable mixing time, energy and expense.
Thus, there is a continuing need for a process for preparing improved pigments which are more easily dispersed in paints and plastics concentrates.
SUMMARY OF THE INVENTION
The present invention provides a process for preparing improved pigment which is more readily dispersible in paints and plastics concentrates, and therefore, meets the need described above and overcomes the deficiencies of the prior art. The process of this invention basically comprises the steps of: (a) mixing a particulate pigment with water to form a slurry of the pigment and water; (b) mixing a surface active agent with the slurry of step (a) so that the pigment is coated therewith, the surface active agent being selected from the group consisting of alkyl alcohols ethoxylated with from about 4 to about 14 ethylene oxide groups and wherein the alkyl groups have from about 6 to about 16 carbons atoms, ethoxylated sorbitan derivatives having HLB values in the range of from 1 to about 20, a mixture of non ethoxylated mono and diglycerides and ethoxylated mono and diglycerides having HLB values in the range of from 1 to about 20 and mixtures of said ethoxylated sorbitan derivatives, said non-ethoxylated mono and diglycerides and said ethoxylated mono and diglycerides; and (c) drying the pigment coated in accordance with step (b).
Another process of this invention for preparing improved pigment which is highly dispersible in paints and plastics concentrates comprises the steps of: (a) mixing a particulate pigment with water to form a slurry of the pigment and water; (b) milling the slurry formed in step (a) to produce a pigment particle size in the range of from about 0.1 micron to about 1 micron; (c) mixing a surface active agent with the slurry of step (b) so that said pigment is coated therewith, said surface active agent being selected from the group described above; and (d) drying the pigment coated in accordance with step (c).
It is, therefore, a general object of the present invention to provide a process for preparing improved pigments which are more readily dispersible in paints and plastics concentrates.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
DESCRIPTION OF PREFERRED EMBODIMENTS
As mentioned, it has heretofore been difficult to disperse particulate pigment in paints and plastics concentrates or melts. The pigments utilized in paints and plastics concentrates include, but are not limited to, white opacifying pigments such as titanium dioxide, basic carbonate white lead, basic sulfate white lead, basic silicate white lead, zinc sulfide, zinc oxide, composite pigments of zinc sulfide and barium sulfate, antimony oxide and the like, white extender pigments such as calcium carbonate, calcium sulfate, china and kaolin clays, mica, diatomaceous earth and colored pigments such as iron oxide, lead oxide, cadmium sulfide, cadmium selenide, lead chromate, zinc chromate, nickel titanate, chromium oxide and the like. Of the foregoing pigments, inorganic pigments are preferred with titanium dioxide being the most preferred.
The pigments produced by the present invention are more readily dispersed in paints and plastics concentrates and require less time and/or energy to disperse than prior art pigments. The treated pigments produced by this invention can be low-dusting and free-flowing non-micronized pigments or the treated pigments can optionally be micronized.
The process of the present invention for preparing improved pigment which is more readily dispersible in paints and plastics concentrates is basically comprised of the following steps: (a) mixing a particulate pigment with water to form a slurry of the pigment and water; (b) mixing a surface active agent with the slurry of step (a) so that the pigment is coated therewith; and (c) drying the pigment coated in accordance with step (b).
The particulate pigment utilized in step (a) of the above process is preferably pigment which has not been milled or micronized. The preferred non-treated titanium dioxide pigment for use in the process of this invention can be of either the anatase or rutile crystalline structure or a combination thereof. The titanium dioxide pigment can be produced by a commercial process which is well known to those skilled in the art such as the sulfate process or the vapor phase chloride oxidation process.
The surface active agents which can be utilized in accordance with the present invention include alkyl alcohols ethoxylated with from about 4 to about 14 ethylene oxide groups and wherein the alkyl groups have from about 6 to about 16 carbon atoms, ethoxylated sorbitan derivatives having hydrophile-lipophile balances (HLB values) in the range of from about 1 to about 20, a mixture of non-ethoxylated mono and diglycerides and ethoxylated mono and diglycerides having HLB values in the range of from about 1 to about 20 and mixtures of said ethoxylated sorbitan derivatives, said non-ethoxylated mono and diglycerides and said ethoxylated mono and diglycerides.
Of the foregoing surface active agents, a mixture of ethoxylated sorbitan derivatives having HLB values in the range of from about 2 to about 15, non-ethoxylated mono and diglycerides having HLB values in the range of from about 2 to about 15 and ethoxylated mono and diglycerides having HLB values in the range of from about 2 to about 15 is preferred. The ethoxylated sorbitan derivatives are preferably present in the mixture in an amount in the range of from about 5% to about 100% by weight of the mixture with the non-ethoxylated mono and diglycerides and ethoxylated mono and diglycerides making up the remainder of the mixture. A more preferred mixture of the ethoxylated sorbitan derivatives, non-ethoxylated mono and dig
Elliott Jeffrey D.
Hoskins Ronnie L.
Palmer Bruce R.
Roberts Bruce L.
Dougherty, Jr. C. Clark
Hailey Patricia L.
Kerr-McGee Chemical LLC
McAfee & Taft
Wood Elizabeth D.
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