Patent Application
20070295247
The present invention is directed to a pigment extender that can be used in combination with a pigment to improve the properties of a covering agent such as a paint. The pigment extender is particularly useful in latex paints and will be described in detail hereinafter with reference to latex paints; however, it will be appreciated that the pigment extender can be used in other types of paints and/or covering agents.
The pigment extender is formulated to be used as a partial or full substitute for other types of extenders. One non-limiting type of prior extender that can be partially or fully substituted by the pigment extender of the present invention is calcined diatomaceous earth (e.g., Celatom MW 27, etc.). Calcined diatomaceous earth is a well known extender that is used in a number of latex paints. Two representative formulations of a flat white latex paint that include calcined diatomaceous earth are set forth below. In each of these examples, a Dow Ucar emulsion system (vinyl-acrylic emulsion) was used as a standard formulation. This emulsion system forms a good quality interior latex paint.
The principal function of each of the components of the paint above is set forth as follows; however, it will be appreciated that one or more of these components may have other secondary functions. AMP 95 is a pH adjuster offered by Angus Chemical Co. Celetom MW 27 is an extender and flatting agent formed of calcined diatomaceous earth that is offered by Eagle-Pitcher. Celite 499 is also a calcined diatomaceous earth that can be used as a partial or full substitute of Celetom MW 27. Colloid 226/25 is a dispersant offered by Rhone-Poulenc AG. Drewplus L-475 is a defoamer offered by Ashland Specialty Chemicals. Duramite is calcium carbonate that is used as a filling agent and extender. Minex 3 is a filler and flatting agent (sheen reducing pigment) formed of nepheline syenite that is offered by Unimin Inc. Optiwhite is a pigment of calcined kaolin offered by Burgess Pigment Co. Propel GXL is dipropylene glycol that is used as a preservative and offered by Zeneca AG. Propylene Glycol is a solvent. Rhodoline 643 is a defoamer offered by Rhodia. Snowflake PE is a filler of calcium carbonate offered by IMERYS. Tamol 1124 is a dispersant offered by Rohm & Haas. Tergitol Np-9 is a surfactant offered by Dow Chemical. Tipure R-902 is a white pigment of rutile offered by DuPont. Triton X-902 is a surfactant offered by Dow Chemical. Ucar Polyphobe 102 and 107 is a rheology modifier and thickener offered by Union Carbide. Ucar Filmer IBT is a solvent offered by Union Carbide. Ucar Latex 379G is a vinyl-acrylic latex offered by Union Carbide. Water is a solvent.
The pigment extender of the present invention is formulated so as to be used as a partial or full substitute for previously used extenders such as calcined diatomaceous earth and/or calcined clay. The pigment extender of the present invention is formulated so as to be used as a partial or full substitute for previously used fillers such as calcium carbonate. The pigment extender of the present invention has been found in some paint formulations to reduce the cost of the raw materials of the paint without adversely affecting the properties of the paint. In some formulations, the pigment extender of the present invention increases the hiding power of the paint, reduces the sheen of flat paints, and improves the matting properties of the paint.
One novel formulation of the pigment extender is a combination of nepheline syenite and silica coated calcium fluoride. One non-limiting source of nepheline syenite is Minex 3 or Minex 4 offered by Unimin Inc. One non-limiting source of silica coated calcium fluoride is also offered by Unimin Inc. by the name UNI-05-1. The silica coated calcium fluoride generally has an average particle size of no larger than about 170 mesh; however, larger or smaller particles sizes can be used. The composition of the silica coated calcium fluoride was about 15-25 weight percent silica and about 75-85 weight percent calcium fluoride. The weight ratio of the silica coated calcium fluoride to nepheline syenite is generally about 0.1-1:1. As can be appreciated, other weight ratios can be used. Minex was used to at least partially replace calcium carbonate. The silica coated calcium fluoride was used to at least partially replace Celatom MW-27 and/or calcined clay. The use of Minex 3 and the silica coated calcium fluoride in the paint was found to closely match Celatom MW-27 with regard to paint color, resulting sheen of the paint and the resulting hiding power of the paint.
Several examples of the novel pigment extender of the present invention used in a flat white latex paint is set forth below. In each of these examples, a Dow Ucar emulsion system (vinyl-acrylic emulsion) was used as a standard formulation.
Several physical properties of the formulated paints containing the novel pigment extender were compared to the formulated paint that included Celetom MW 27. The results of these comparisons is set forth in Table 1.
As set forth above, the formulations in Example 1 and Examples C-D illustrate similar paint formulations except for the type of pigment extender that is included in the paint. Likewise, Example 2 and Examples A and B illustrate similar paint formulations except for the type of pigment extender that is included in the paint.
As illustrated in Table 1, the use of the pigment extender of the present invention forms a flat white latex paint that is either comparable or superior to a flat white latex paint that includes the extender Celatom MW 27. The pigment extenders of the present invention all result in a flat white paint having a sheen value at 85° of less than 1.8. Several of the pigment extenders of the present invention result in a flat white paint having a sheen value of about 1-1.2. The sheen of the paint samples was tested after a two day drying period. Six mil coatings were used to test the sheen, color, gloss and brightness of each paint sample. Low sheen is desirable by painters to hide imperfections on the substrate surface. The pigment extenders of the present invention can be successfully used to reduce the sheen value of paints.
The pigment extender of the present invention not only can function as a flatting agent to reduce the sheen of the paint, the use of the pigment extender resulted in a paint having equivalent or superior hiding power as compared to a paint that included Celatom MW 27. The pigment extender of the present invention also resulted in a high contrast ratio for the paint. The contrast ratio was determined by measuring the light reflected over a white surface versus the amount of light reflected over a black surface multiplied by 100. The higher the reflectance over a black surface, the greater the contrast ratio or hiding power of the paint. The contrast ratio for each paint sample was measured after a two day drying period. A paint thickness of three mils was used for each contrast ratio test.
The cost of using the pigment extender for each sample was either comparable or less expensive than to a paint that included Celatom MW 27.
The pigment extenders illustrated in Examples C and D were shown to function as a partial substitute for Duramite (calcium carbonate). The pigment extenders illustrated in Examples E-H were shown to function as a full substitute for Duramite (calcium carbonate) and a partial substitute for Optiwhite (calcined clay). As such, the pigment extender of the present invention exhibited properties not only related to hiding power, the pigment extender also exhibited properties relating to a paint filler and a matting agent. The versatility of the pigment extender of the present invention thereby resulted in less need for more expensive components thereby reducing the cost of raw materials to form the paint.
The test results of the paint formulations revealed that silica coated calcium fluoride can be used as both a flatting agent and an extender. The silica coated calcium fluoride was found to increase the Stormer and ICI viscosity of the paint due to the high oil absorption properties of the silica coated calcium fluoride. The silica coated calcium fluoride was thus found to be a good full or partial substitute for calcined clay (an extender) without loss in the contrast ratio of the paint. Indeed in several paint formulations, the silica coated calcium fluoride increased the contrast ratio of the paint. The silica coated calcium fluoride was found to cause the L* and brightness of the paint to diminish only slightly when the content of the silica coated calcium fluoride exceeded about 3.0 gallons. The test results revealed that the best balance for matting efficiency, cost, and color was a pigment extender that included about 160-190 lbs. Minex 3 and about 70-90 lbs. silica coated calcium fluoride. This formulation of the pigment extender provided a good substitute for Celatom MW-27 in the paint. As can be appreciated, for different paint formulations, the best balance for Minex 3 and silica coated calcium fluoride in the paint may vary.
These and other modifications of the discussed embodiments, as well as other embodiments of the invention, will be obvious and suggested to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the present invention and not as a limitation thereof.
