Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-12-26
2004-11-02
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C523S305000, C524S401000, C524S502000, C524S539000
Reexamination Certificate
active
06812278
ABSTRACT:
This invention relates to an aqueous tinting composition containing a pigment and a select dispersing resin. The aqueous tinting composition is useful for tinting an aqueous base paint to prepare an aqueous coating composition. A method is also provided for improving the viscosity stability of an aqueous coating composition upon the addition of the aqueous tinting composition.
A classic problem in paints is a decrease in the paint viscosity, in particular, a decrease in mid-shear viscosity (Krebs-Stormer viscosity), when colorants that contain high levels of surfactant are added. This is especially problematic when the paint is tinted to a deep tone because a high level of surfactant generally accompanies the colorant. Besides surfactants, the colorants also contain other low molecular materials such as dispersants. The addition of colorants thus provides a source of low molecular weight materials to the paint base. The properties of coatings prepared from paints may be adversely affected by the presence of low molecular weight materials, for example, the films may become water sensitive.
Many paints are formulated with associative thickeners. Associative thickeners are water-soluble or water-swellable polymers that have chemically attached hydrophobic groups. The associative thickeners operate to thicken systems to which they are added by the non-specific associations, such as adsorption on surfaces and aggregation in solution akin to micellization, between the hydrophobic groups on the thickener molecules and moieties on the other components in the system, similar to the non-specific associations of conventional surfactants. Paints formulated with associative thickeners are especially sensitive to the problem of a decrease in viscosity upon the addition of colorants containing high levels of surfactant.
WO 00/22050 discloses an universal tinting concentrate containing an organic acid having no more than 70 carbon atoms. The disclosed tinting composition is suitable for water based paints. The addition of this tinting concentrate adds the organic acid having no more than 70 carbon atoms to the paint. This organic acid is a low molecular weight material and may adversely affect film properties.
Colorants are added to paints in units of milliliter of colorant per liter of paint (hereinafter referred to as “ml/liter”) or ounces of colorant per gallon of paint (hereinafter referred to as “oz/gal”). Light-tint (pastel) paints typically contain no more than 31.2 ml/liter (4 oz/gal of colorant). Mid-tone paints typically contain from greater than 31.2 ml/liter (4 oz/gal of colorant) to 62.5 ml/liter (8 oz/gal) of colorant. Deep tone paints typically contain at least 62.5 ml/liter (8 oz/gal) of colorant.
Generally, it is possible to formulate a light tint base at a high enough mid-shear viscosity that colorants added to it will not depress the viscosity to an unacceptable degree. Combinations of associative thickeners have been found to be less sensitive to colorant addition than the individual thickeners alone, in some cases. However, neither of these solutions is completely satisfactory because they either require tedious reformulation, added cost or both, particularly in deep tone paints.
Many conventional tinting machines employ twelve different colorants to mix the large palette of colors typically offered for most paint lines. Thus, it would be highly desirable to tailor the viscosity stability of an aqueous formulation based on the type and level of colorant component to be added, in particular, without the introduction of low molecular weight materials which may materially affect film properties. The compositions and methods of the present invention provide such a solution.
The first aspect of this invention provides a method of improving the viscosity stability of an aqueous coating composition upon the addition of an aqueous tinting composition, including the steps of: providing an aqueous base paint containing at least one polymer binder and at least one rheology modifier; and adding to the aqueous base paint, the aqueous tinting composition containing at least one pigment and at least one select dispersing resin having a Hansch parameter in the range of 2.1 to 6 and an acid number in the range of 65 to 150.
The second aspect of this invention provides an aqueous tinting composition containing from 2 to 70 weight % of at least one pigment, and from 0.1 to 40 weight % of at least one select dispersing resin having a Hansch parameter in the range of 2.1 to 6 and an acid number in the range of 65 to 150, based on the weight of the aqueous tinting composition.
As used herein, the term “(meth)acrylate” refers to either acrylate or methacrylate and the term “(meth)acrylic” refers to either acrylic or methacrylic.
As used herein, pigment volume concentration (referred to herein as “PVC”) is a measure of how “binder-rich” a formulation is. It is calculated herein by the following formula:
PVC
=
100
%
×
(
volume
of
pigments
(
s
)
+
volume
of
extender
(
s
)
)
(
volume
of
pigments
(
s
)
+
volume
of
extender
(
s
)
+
volume
of
binder
(
s
)
)
As used herein, volume solids content (“VS” herein) is the dry volume of pigment(s) plus the dry volume of extender(s) plus the dry volume of binder(s). It is calculated herein by the following formula:
VS
=
100
%
×
(
dry
volume
of
pigments
(
s
)
+
dry
volume
of
extender
(
s
)
+
dry
volume
of
binder
(
s
)
)
(
total
volume
of
formulation
)
If additives are present, their volume is not included in determining the total dry volume.
As used herein, “KU” shall mean Krebs unit and is a measure of the mid-shear viscosity as measured by a Krebs-Stormer viscometer.
As used herein, “viscosity stability” shall mean the ability of a composition to resist change in viscosity as measured by KU upon the addition of surfactant or a composition containing surfactant. A preferred viscosity stabilizer for latex paints must provide KU viscosity changes of less than about 10 units upon the addition of up to 93.7 ml/liter (12 oz/gal) of colorant. A more preferred viscosity stabilizer for latex paints must provide KU viscosity changes of less than about 5 units upon the addition of up to 93.7 mi/liter (12 oz/gal) of colorant.
As used herein, a “volatile organic compound” (VOC) is defined herein as a carbon containing compound that has a boiling point below 280° C. at atmospheric pressure, compounds such as water and ammonia being excluded from VOCs. A volatile organic compound (VOC) may be added to an aqueous coating composition to improve the film properties or to aid in the application properties of the aqueous coating composition. Examples of such compounds include solvents and coalescents such as glycol ethers, organic esters, aromatic compounds, ethylene and propylene glycol, and aliphatic hydrocarbons.
The aqueous tinting composition of this invention contains at least one pigment and at least one select dispersing resin. The pigment is dispersed in the aqueous medium of the tinting composition.
The pigment is any organic or inorganic dry powder that imparts color to another substance or mixture. Examples of suitable pigments include titanium dioxide white, carbon black, lamp black, black iron oxide, red iron oxide, yellow iron oxide, brown iron oxide (a blend of red and yellow oxide with black), phthalocyanine green, phthalocyanine blue, organic red pigment (such as naphthol red, quinacridone red and toulidine red), quinacridone magenta, quinacridone violet, DNA orange, organic yellow pigment (such as Hansa yellow), and combinations thereof. Another type of pigment is a “metal effect agent”, which imparts metallic-type luster and ass
Eichman Henry Jude
Friel John Michael
Harris Jerome Michael
Jamasbi Homayoun
Lorah Dennis Paul
Greenblatt Gary D.
Niland Patrick D.
Rohm and Haas Company
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