Method to determine light scattering efficiency of pigments

• US 6,236,460 B1
• Filed: 01/11/2000
• Issued: 05/22/2001
• Est. Priority Date: 01/29/1999
• Status: Expired due to Term

• Current Assignee: The Chemours Company FC, LLC (The Chemours Company)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Johnson, Robert William
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Punnoose, Roy M.
• Application Number:
  US09/481,326
• Time in Patent Office: 497 Days
• Field of Search: 356/432, 356/436, 356/441, 356/336, 356/338, 356/339, 356/337, 106/436, 106/437
• US Class Current: 356/436
• CPC Class Codes: B29C 41/003 characterised by the choice of material
• CPC Class Codes: B29K 2105/0097 Glues or adhesives, e.g. hot melts or thermofusible adhesives
• CPC Class Codes: B29K 2105/16 Fillers
• CPC Class Codes: B29K 2995/0059 Degradable
• CPC Class Codes: G01N 21/532 with measurement of scattering and transmission
• CPC Class Codes: G11C 11/41 forming static cells with positive feedback, i.e. cells not needing refreshing or charge regeneration, e.g. bistable multivibrator or Schmitt trigger
• CPC Class Codes: G11C 2207/104 Embedded memory devices, e.g. memories with a processing device on the same die or ASIC memory designs
• CPC Class Codes: G11C 29/1201 comprising I/O circuitry

Abstract

A method for determining light scattering efficiency and a method to determine undertone of pigments or mixtures containing white pigments are described. The methods are based on measuring total transmittance of pigment slurries at a wavelength of at least 600 nm. Transmittance measurements can be used to calculate light scattering efficiencies and undertone which correlate with performance in end-use applications.

Claims

1. A method to determine light scattering efficiency of a mixture containing at least one light scattering component, comprising:

(a) preparing a dilute slurry of the mixture in a continuous liquid medium having a known concentration, where concentration is the concentration of mixture solids in the slurry;

(b) measuring the total transmittance (T) of the slurry at a wavelength (λ

) of at least 600 nm;

(c) converting the transmittance measurement (T) to optical density (OD) by the equation

2. The method of claim 1 wherein the continuous medium is selected from the group consisting of water, organic solvents, and paint resins.

3. The method of claim 2 wherein the continuous medium is water.

4. The method of claim 1 wherein the light scattering component is selected from the group consisting of white pigment, plastic pigment, latex polymer particles, clay and mixtures of these.

5. The method of claim 4 where white pigment is selected from the group consisting of rutile titanium dioxide, anatase titanium dioxide, zinc oxide, silica, calcium carbonate, calcium sulfate and clay, and mixtures thereof.

6. A method to determine undertone of a mixture containing at least one light scattering component, comprising:

(a) preparing a dilute slurry of the mixture in a continuous medium having a known concentration (C), where concentration is the concentration of the mixture solids in the slurry;

(b) measuring total transmittance (T₁) of the slurry at a wavelength, λ

₁, between 500 and 650 nm;

(c) measuring total transmittance (T₂) of the slurry at a wavelength, λ

₂, between 650 and 1000 nm;

(d) converting the transmittance measurements to optical densities (OD) by the equation

7. The method of claim 6 wherein the degree of change in OD/C is calculated according to the equation:

$\mathrm{undertone}=-\frac{\left[\ln <br><br>\frac{{\mathrm{OD}}_1/C<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{at}<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\lambda <br><br>}}_1}{{\mathrm{OD}}_2/C<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{at}<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\lambda <br><br>}}_2}\right]}{\left[\ln <br><br>\frac{{\mathrm{\lambda <br><br>}}_1}{{\mathrm{\lambda <br><br>}}_2}\right]},$

wherein OD₁/C at λ

₁ is the optical density calculated from the transmittance measurement at wavelength λ

₁, divided by the concentration of mixture solids in the slurry and OD₂/C at λ

₂ is the optical density calculated from the transmittance measurement at wavelength λ

₂, divided by the concentration of the mixture solids in the slurry.

8. The method of claim 6 wherein the degree of change in OD/C is calculated according to the equation:

$\mathrm{undertone}=-\frac{\left({\mathrm{OD}}_1/C<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{at}<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\lambda <br><br>}}_1-{\mathrm{OD}}_2/C<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{at}<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\lambda <br><br>}}_2\right)}{{\mathrm{\lambda <br><br>}}_1-{\mathrm{\lambda <br><br>}}_2},$

wherein OD₁/C at λ

₁ is the optical density calculated from the transmittance measurement at wavelength λ

₁, divided by the concentration of mixture solids in the slurry and OD₂/C at λ

₂ is the optical density calculated from the transmittance measurement at wavelength λ

₂, divided by the concentration of the mixture solids in the slurry.

9. A method for characterizing a mixture containing at least one light scattering component comprising comparing the of light scattering efficiency of the mixture calculated according to Equations 1 and 2 herein to the undertone of the mixture calculated according to Equation 3 or 4 herein.