U.S. patent application number 14/226872 was filed with the patent office on 2014-10-02 for paper coating formulation.
This patent application is currently assigned to Dow Global Technologies LLC. The applicant listed for this patent is Dow Global Technologies LLC. Invention is credited to Vivek Kalihari, John A. Roper, III.
Application Number | 20140295173 14/226872 |
Document ID | / |
Family ID | 50241266 |
Filed Date | 2014-10-02 |
United States Patent
Application |
20140295173 |
Kind Code |
A1 |
Kalihari; Vivek ; et
al. |
October 2, 2014 |
PAPER COATING FORMULATION
Abstract
The present invention relates to a laminate comprising coated or
uncoated paperboard coated with a film that comprises a polymeric
binder, TiO.sub.2, and tetrapotassium pyrophosphate. Paper or
paperboard coated with a film containing tetrapotassium
pyrophosphate shows excellent optical properties.
Inventors: |
Kalihari; Vivek; (Midland,
MI) ; Roper, III; John A.; (Midland, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dow Global Technologies LLC |
Midland |
MI |
US |
|
|
Assignee: |
Dow Global Technologies LLC
Midland
MI
|
Family ID: |
50241266 |
Appl. No.: |
14/226872 |
Filed: |
March 27, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61805638 |
Mar 27, 2013 |
|
|
|
Current U.S.
Class: |
428/335 ;
427/372.2 |
Current CPC
Class: |
B32B 2260/046 20130101;
Y10T 428/264 20150115; D21H 19/385 20130101; D21H 19/64 20130101;
D21H 21/08 20130101; D21H 19/44 20130101; B32B 5/16 20130101 |
Class at
Publication: |
428/335 ;
427/372.2 |
International
Class: |
D21H 19/64 20060101
D21H019/64; D21H 19/38 20060101 D21H019/38 |
Claims
1. A laminate comprising coated or uncoated paperboard; and a 5- to
35-.mu.m thick layer of a film adhered to the coated or uncoated
paper or paperboard; wherein the film comprises a) from 3 to 25
weight percent of a polymeric binder; b) from 5 to 35 weight
percent TiO.sub.2; and c) from 0.05 to 2 weight percent
tetrapotassium pyrophosphate; wherein the polymeric binder
comprises vinyl acetate, vinyl-acrylic, styrene-acrylic, or
styrene-butadiene polymer, and blends thereof; and wherein the
weight percentages are all based on the weight of the film.
2. The laminate of claim 1 wherein the polymeric binder contains
less than 0.05 weight percent of phosphate and phosphonate groups,
based on the weight of the binder.
3. The laminate of claim 2 wherein the concentration of
tetrapotassium pyrophosphate is from 0.1 to 0.8 weight percent,
based on the weight of total solids in the film.
4. The laminate of Claim 1 wherein the film further includes a clay
or calcium carbonate or both.
5. The laminate of claim 1 wherein the binder is a vinyl acetate
polymer.
6. The laminate of claim 1 wherein the binder is a styrene-acrylic
polymer.
7. The laminate of claim 1 wherein the binder is a
styrene-butadiene.
8. The laminate of claim 1 wherein the film comprises one or more
additives selected from the group consisting of rheology modifiers;
hollow sphere pigments; natural binders; optical brightening
agents; lubricants; antifoamers; crosslinkers; and polyacrylic
acid.
9. A method comprising the step of applying a 5- to 35-.mu.m thick
layer of a composition to paper or paperboard, wherein the
composition comprises an aqueous dispersion of a) from 3 to 25
weight percent polymeric binder particles; b) from 5 to 35 weight
percent TiO.sub.2; and c) from 0.05 to 2 weight percent of
tetrapotassium pyrophosphate; wherein the polymeric binder
particles comprise vinyl acetate, vinyl-acrylic, styrene-acrylic,
or styrene-butadiene polymer particles and blends thereof; and
wherein the weight percentages are all based on the weight of total
solids of the composition.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a pigmented paper coating
with improved brightness.
[0002] Titanium dioxide (TiO.sub.2) is used as a pigment in
paperboard coatings on darker substrates such as recycled board and
unbleached Kraft board to improve the optical properties such as
brightness, opacity, and appearance. In addition, TiO.sub.2 is used
in lightweight coated paper to improve opacity, or in premium
coated paper grades to improve the brightness and appearance.
Motivated by the high cost of TiO.sub.2, papermakers are looking
for ways to either reduce its usage or improve its efficiency or
both.
[0003] In the absence of modifiers such as dispersants, TiO.sub.2
particles will crowd, leading to inefficient hiding. However, even
with well dispersed TiO.sub.2 there can be crowding of TiO.sub.2
particles as the level of TiO.sub.2 is increased. Furthermore, it
is known, for example, (2001 TAPPI Coating Conference Paper by
Imerys on "Optimum Dispersion In Blade Coating Operations;" also,
Chapter 3 on "Inorganic Salt Dispersants" in Practical Dispersion:
A Guide to Understanding and Formulating Slurries by R. F. Conley,
Wiley Press) that over-dispersing of a coating will cause pigment
particles to flocculate, which can lead to an improvement in
coating brightness on the order of 0.5 to 1.5 points. This
improvement in brightness, however, is attributed to an increase in
the porosity of the coating, which increases the amount of light
scattering from air voids, and not to the increased efficiency of
TiO.sub.2 dispersion in the coating. Furthermore, the brightness
advantage realized from using high levels of dispersants is greatly
reduced after calendaring to less than 1 point because the voids
created upon the addition of the dispersant are removed during the
calendaring process.
[0004] U.S. Pat. No. 8,043,476 discloses a paper or paperboard
coating formulation with improved viscosity stability comprising a
phosphate or phosphonate functionalized acrylic polymer binder,
TiO.sub.2, and a polyphosphate dispersant. Although the phosphate
or phosphonate functionality is known to enhance adsorptivity of
the binder to the TiO.sub.2, thereby improving the efficiency of
its usage, the presence of phosphates or phosphonates often
adversely affect viscosity stability of the binder and water
sensitivity of the coating. Moreover, latexes prepared with the
commonly used phosphate monomer, phosphoethyl methacrylate (PEM),
invariably contain impurities that are of concern to governmental
regulatory agencies (e.g., the FDA) that regulate products that may
come in contact with food. Accordingly, it would be an advance in
the art of paper and paperboard coating formulations to design a
coating with enhanced brightness that does not require the presence
of phosphate and phosphonate functionalized binders.
SUMMARY OF THE INVENTION
[0005] The present invention addresses a need in the art by
providing a laminate comprising coated or uncoated paperboard; and
a 5- to 35-.mu.m thick layer of a film adhered to the coated or
uncoated paper or paperboard; wherein the film comprises a) from 3
to 25 weight percent of a polymeric binder; b) from 5 to 35 weight
percent TiO.sub.2; and c) from 0.05 to 2 weight percent
tetrapotassium pyrophosphate; wherein the polymeric binder
comprises vinyl acetate, vinyl-acrylic, styrene-acrylic, or
styrene-butadiene polymer, and blends thereof; and wherein the
weight percentages are all based on the weight of the film.
[0006] In another aspect, the present invention is a method
comprising the step of applying a 5- to 35-.mu.m thick layer of a
composition to paper or paperboard, wherein the composition
comprises an aqueous dispersion of a) from 3 to 25 weight percent
polymeric binder particles; b) from 5 to 35 weight percent
TiO.sub.2; and c) from 0.05 to 2 weight percent of tetrapotassium
pyrophosphate; wherein the polymeric binder particles comprise
vinyl acetate, vinyl-acrylic, styrene-acrylic, or styrene-butadiene
polymer particles, and blends thereof; and wherein the weight
percentages are all based on the weight of total solids of the
composition.
[0007] The potassium pyrophosphate containing film shows improved
brightness with a variety of binders and grades of TiO.sub.2 as
compared with films containing other ostensibly similar
dispersants.
DETAILED DESCRIPTION OF THE INVENTION
[0008] The present invention addresses a need in the art by
providing a laminate comprising coated or uncoated paperboard; and
a 5- to 35-.mu.m thick layer of a film adhered to the coated or
uncoated paper or paperboard; wherein the film comprises a) from 3
to 25 weight percent of a polymeric binder; b) from 5 to 35 weight
percent TiO.sub.2; and c) from 0.05 to 2 weight percent
tetrapotassium pyrophosphate; wherein the polymeric binder
comprises vinyl acetate, vinyl-acrylic, styrene-acrylic, or
styrene-butadiene polymer, and blends thereof; and wherein the
weight percentages are all based on the weight of the film.
[0009] Preferably, the weight percent of the binder, based on the
weight of total solids of the composition, is from 5 to 25 weight
percent. The binder may contain up to 8 weight percent phosphate or
phosphonate groups but preferably comprises a substantial absence
of these groups. As used herein, the term "substantial absence of
phosphate or phosphonate groups" means that the binder particles
contain, based on the weight of the binder, less than 0.05 weight
percent, preferably less than 0.01 weight percent, more preferably
less than 0.001 weight percent, and most preferably 0 weight
percent phosphate and phosphonate groups.
[0010] The aqueous composition preferably comprises from 5 to 25
weight percent, more preferably to 20 weight percent, and most
preferably to 15 weight percent TiO.sub.2, based on the weight of
total solids of the composition; the TiO.sub.2 can be rutile or
anatase TiO.sub.2 and may be untreated, or treated with inorganic
silica or alumina or zirconia or a combination thereof.
[0011] The tetrapotassium pyrophosphate is preferably present in
the composition at 0.1 to 0.8 weight percent, based on the weight
of the composition.
[0012] The composition of the present invention advantageously
includes other additives including auxiliary pigments, such as
clays and calcium carbonate; rheology modifiers; hollow sphere
pigments, such as ROPAQUE.TM. AF-1055 Hollow Sphere Pigment (A
Trademark of The Dow Chemical Company or its Affiliates); natural
binders, such as proteins and starch; optical brightening agents;
lubricants; antifoamers; crosslinkers; and other dispersants, such
as polyacrylic acid based dispersant. The particle size of
auxiliary pigments useful for the composition of the present
invention is preferably finer than 2 .mu.m, more preferably 80% to
100% by weight finer than 2 .mu.m, as measured using Sedigraph.
This preferred size range is considerably smaller than what is
typically used in paint formulations.
[0013] The film thickness is preferably in the range of from 5
.mu.m, more preferably from 10 .mu.m, to 35 .mu.m, more preferably
to 20 .mu.m, which is about one-third to one-tenth the film
thickness of typical paint coatings.
[0014] In a second aspect, the present invention is a method
comprising the step of applying a 5- to 35-.mu.m thick layer of a
composition to paper or paperboard, wherein the composition
comprises an aqueous dispersion of a) from 3 to 25 weight percent
polymeric binder particles; b) from 5 to 35 weight percent
TiO.sub.2; and c) from 0.05 to 2 weight percent of tetrapotassium
pyrophosphate; wherein the polymeric binder particles comprise
vinyl acetate, vinyl-acrylic, styrene-acrylic, or styrene-butadiene
polymer particles, and blends thereof; and wherein the weight
percentages are all based on the weight of total solids of the
composition. The binder particles preferably have a volume average
particle size in the range of from 50 nm, more preferably from 80
nm, to 500 nm, more preferably to 300 nm.
[0015] It has surprisingly been discovered that the laminate of the
present invention imparts brightness to the paper or paperboard
without additional loadings of TiO.sub.2, and preferably using
binder that contains a substantial absence or complete absence of
phosphate and phosphonate groups. Moreover, as the following
examples demonstrate, it has surprisingly been discovered that
paper or paperboard coated with pigmented films containing TKPP
consistently provide superior brightness compared to films
containing ostensibly similar dispersants (TSPP or KTPP). This
trend of superiority was generally observed across a variety of
binders and TiO.sub.2 types.
Abbreviations
TABLE-US-00001 [0016] Product Name Abbreviation Kaomax Clay Clay
RPS Vantage TiO.sub.2 RPS TiO.sub.2 Kronos 2063 TiO.sub.2 2063
TiO.sub.2 Ti-Pure R-746 TiO.sub.2 R-746 TiO.sub.2 POLYCO .TM. 3960
Vinyl Acrylic Vinyl Acrylic Latex latex RHOPLEX .TM. NW-1715K
Styrene Acrylic Styrene Acrylic Latex latex RHOPLEX .TM. RM-232D
RM-232D HASE Rheology Modifier ROPAQUE .TM. AF-1055 AF-1055 Hollow
Sphere Pigment Tetrasodium Pyrophosphate TSPP Tetrapotassium
Pyrophosphate TKPP Potassium Tripolyphosphate KTPP
POLYCO, RHOPLEX, and ACUMER are all Trademarks of The Dow Chemical
Company or its Affiliates.
EXAMPLES
Example 1
Preparation of Coating with Vinyl Acrylic Latex and TKPP
[0017] RPS TiO.sub.2 (10.5 parts by weight, 70.58% solids) was
added to Clay (89.5 parts by weight, 68.24% solids), followed by
addition of Vinyl Acrylic Latex (20 parts by weight, 49.8% solids),
then TKPP (0.3 parts by weight, 5% solids). Additional DI water was
added to adjust percent solids to 45%. The pH was then adjusted to
8-8.5 with NaOH followed by addition of RM-232D (0.6 parts by
weight, 28.27% solids).
Comparative Example 1
Preparation of Vinyl Acrylic Latex Coating without Dispersant
[0018] RPS TiO.sub.2 (10.5 parts by weight, 70.58% solids) was
added to Clay (89.5 parts by weight, 68.24% solids), followed by
addition of Vinyl Acrylic Latex (20 parts by weight, 49.8% solids).
Additional DI water was added to adjust percent solids to 45%. The
pH was then adjusted to 8-8.5 with NaOH followed by addition
RM-232D (0.6 parts by weight, 28.27% solids).
Comparative Example 2
Preparation of Vinyl Acrylic Latex Coating with TSPP
[0019] The method of Example 1 was used except that TSPP (0.3 parts
by weight, 5% solids) was used as the dispersant instead of
TKPP.
Comparative Example 3
Preparation of Vinyl Acrylic Latex Coating with KTPP
[0020] The method of Example 1 was used except that KTPP (0.3 parts
by weight, 5% solids) was used as the dispersant instead of
TKPP.
Example 2
Preparation of Coating with Styrene Acrylic Latex and TKPP
[0021] RPS TiO.sub.2 (10.5 parts by weight, 70.58% solids) was
added to Clay (89.5 parts by weight, 68.24% solids), followed by
the addition of Styrene Acrylic Latex (20 parts by weight, 46.5%
solids), then TKPP (0.8 parts by weight, 5% solids). Additional DI
water was added to adjust solids to 45%. The pH was then adjusted
to 8-8.5 with NaOH followed by addition of RM-232D (0.2 parts by
weight, 28.27% solids).
Comparative Example 4
Preparation of Styrene Acrylic Latex Coating without Dispersant
[0022] RPS TiO.sub.2 (10.5 parts by weight, 70.58% solids) was
added to Clay (89.5 parts by weight, 68.24% solids), followed by
addition of Styrene Acrylic Latex (20 parts by weight, 46.5%
solids). Additional DI water was added to adjust solids to 45%. The
pH was then adjusted to 8-8.5 with NaOH followed by addition of 0.2
parts of RM-232D (28.27% solids).
Comparative Example 5
Preparation of Styrene Acrylic Latex Coating with TSPP
[0023] The method of Example 2 was used except that TSPP (0.8 parts
by weight, 5% solids) was used as the dispersant instead of
TKPP.
Comparative Example 6
Preparation of Styrene Acrylic Latex Coating with KTPP
[0024] The method of Example 2 was used except that KTPP (0.8 parts
by weight, 5% solids) was used as the dispersant instead of
TKPP.
[0025] Example 3 and Comparative Examples 7-9 use the Vinyl Acrylic
Latex binder with the 2063 TiO.sub.2 which has a lower purity of
TiO.sub.2 and a higher concentration of inorganic alumina surface
treatment compared to the RPS TiO.sub.2.
Example 3
Preparation of Coating with Vinyl Acrylic Latex, 2063 TiO.sub.2,
and TKPP
[0026] 2063 TiO.sub.2 (10.5 parts by weight, 77.8% solids) was
added to Clay (89.5 parts by weight, 68.24% solids), followed by
addition of Vinyl Acrylic Latex (20 parts by weight, 49.8% solids),
then TKPP (0.3 parts by weight, 5% solids). Additional DI water was
added to adjust percent solids to 45%. The pH was then adjusted to
8-8.5 with NaOH followed by addition of RM-232D (0.6 parts by
weight, 28.27% solids).
Comparative Example 7
Preparation of Vinyl Acrylic Latex and RPS TiO.sub.2 Coating
without Dispersant
[0027] 2063 TiO.sub.2 (10.5 parts by weight, 77.8% solids) was
added to Clay (89.5 parts by weight, 68.24% solids), followed by
addition of Vinyl Acrylic Latex (20 parts by weight, 49.8% solids.
Additional DI water was added to adjust percent solids to 45%. The
pH was then adjusted to 8-8.5 with NaOH followed by addition of
RM-232D (0.6 parts by weight, 28.27% solids).
Comparative Example 8
Preparation of Coating with Vinyl Acrylic Latex, 2063 TiO.sub.2,
and TSPP
[0028] The method of Example 3 was used except that TSPP (0.3 parts
by weight, 5% solids) was used as the dispersant instead of TKPP
dispersant.
Comparative Example 9
Preparation of Coating with Vinyl Acrylic Latex, 2063 TiO.sub.2,
and KTPP
[0029] The method of Example 3 was used except that KTPP (0.3 parts
by weight, 5% solids) was used as the dispersant instead of TKPP
dispersant.
[0030] Example 4 and Comparative Examples 10-12 use the Vinyl
Acrylic Latex binder with R-746 TiO.sub.2, which is an alumina- and
silica-surface treated TiO.sub.2 of reduced purity compared to RPS
TiO.sub.2.
Example 4
Preparation of Coating with Vinyl Acrylic Latex, R-746 TiO.sub.2,
and TKPP
[0031] R-746 TiO.sub.2 (10.5 parts by weight, 76.81% solids) was
added to Clay (89.5 parts by weight, 68.24% solids), followed by
addition of Vinyl Acrylic Latex (20 parts by weight, 49.8% solids),
then TKPP (0.3 parts by weight, 5% solids). Additional DI water was
added to adjust percent solids to 45%. The pH was then adjusted to
8-8.5 with NaOH followed by addition of RM-232D (0.6 parts by
weight, 28.27% solids).
Comparative Example 10
Preparation of Vinyl Acrylic Latex and R-746 TiO.sub.2 Coating
without Dispersant
[0032] R-746 TiO.sub.2 (10.5 parts by weight, 76.81% solids) was
added to Clay (89.5 parts by weight, 68.24% solids), followed by
addition of Vinyl Acrylic Latex (20 parts by weight, 49.8% solids).
Additional DI water was added to adjust percent solids to 45%. The
pH was then adjusted to 8-8.5 with NaOH followed by addition of
RM-232D (0.6 parts by weight, 28.27% solids).
Comparative Example 11
Preparation of Coating with Vinyl Acrylic Latex, R-746 TiO.sub.2,
and TSPP
[0033] The method of Example 4 was used except that TSPP (0.3 parts
by weight, 5% solids) was used as the dispersant instead of TKPP
dispersant.
Comparative Example 12
Preparation of Coating with Vinyl Acrylic Latex, R-746 TiO.sub.2,
and KTPP
[0034] The method of Example 4 was used except that KTPP (0.3 parts
by weight, 5% solids) was used as the dispersant instead of TKPP
dispersant.
Example 5
Preparation of Coating with RPS Ti0.sub.2, AF-1055, and TKPP
[0035] RPS TiO.sub.2 (9 parts by weight, 70.58% solids) and AF-1055
(2.16 parts by weight, 26.61% solids) were added to Clay (88.6
parts by weight, 68.24% solids), followed by addition of Vinyl
Acrylic Latex (20 parts by weight, 49.8% solids), then TKPP (0.24
parts by weight, 5% solids). Additional DI water was added to
adjust percent solids to 45%. The pH was then adjusted to 8-8.5
with NaOH followed by addition of RM-232D (0.6 parts by weight,
28.27% solids).
Comparative Example 13
Preparation of Coating with RPS TiO.sub.2 and AF-1055 without
Dispersant
[0036] RPS TiO.sub.2 (9 parts by weight, 70.58% solids) and AF-1055
(2.4 parts by weight, 26.61% solids) were added to Clay (88.6 parts
by weight, 68.24% solids), followed by addition of Vinyl Acrylic
Latex (20 parts by weight, 49.8% solids). Additional DI water was
added to adjust percent solids to 45%. The pH was then adjusted to
8-8.5 with NaOH followed by addition of RM-232D (0.6 parts by
weight, 28.27% solids).
Preparation of Coated Samples
[0037] The coatings were manually applied to a Leneta paint scrub
panel substrate using a wire wound rod #12 and then were dried at
83.degree. C. for 3 min. Brightness measurements were performed
using Technidyne Micro S-5 Brightmeter. Brightness calibration was
done using a standard (84.7 brightness reading) before
measurements. Five measurements per sample were recorded and the
median values reported in Table 1. The brightness data for Examples
1-2 and Comparative Examples 1-6 (C1-C6) are shown in Table 1:
TABLE-US-00002 TABLE 1 Brightness Comparison for Coatings
Containing RPS Vantage TiO.sub.2 and Vinyl Acrylic Latex (VA) or
Styrene Acrylic Latex (SA) Ex. # 1 C1 C2 C3 2 C4 C5 C6 Binder VA VA
VA VA SA SA SA SA Dispersant TKPP None TSPP KTPP TKPP None TSPP
KTPP B.sub.Med 65.1 59.4 63.4 65.4 66.1 59.7 63.1 64.5 stdev 0.3
0.3 0.7 0.3 0.3 0.4 0.2 0.3
[0038] The results show that the films containing TKPP (Examples 1
and 2) exhibits superior brightness as compared with the films
containing TSPP (C2 and C5); the results further show that TKPP is
better than KTPP for the styrene acrylate binder. The TKPP coatings
(Ex 1 and 2) show about 5-6 point improvement in brightness
compared to the coating with no dispersant (C1 and C4) while the
TSPP coatings show only about a 3-4 point improvement in
brightness.
[0039] To compare the effects of a modified TiO.sub.2 on the
performance of the coating, coated substrates were prepared using
two types of surface treated TiO.sub.2: an alumina treated
TiO.sub.2 (2063) and a silica and alumina treated TiO.sub.2 (R
746). 2063 TiO.sub.2 based coatings were made with a) TKPP (Example
3); b) no dispersant (C7); c) TSPP (C8); and d) KTPP (C9). R-746
TiO.sub.2 based coatings were made with a) TKPP (Example 4); b) no
dispersant (C10); c) TSPP (C11); and d) KTPP (C12).The results are
summarized in Table 2.
TABLE-US-00003 TABLE 2 Brightness Comparisons for Coatings with VA
and 2063 TiO.sub.2 or R-746 TiO.sub.2 Ex. # 3 C7 C8 C9 4 C10 C11
C12 TiO.sub.2 type 2063 2063 2063 2063 R-746 R-746 R-746 R-746
Dispersant TKPP None TSPP KTPP TKPP None TSPP KTPP B.sub.med 67.9
65.1 65.4 66.6 66.6 62.7 65.3 65.5 stdev 0.3 0.2 0.3 0.5 0.6 0.5
0.3 0.4
[0040] The data show that the film containing TKPP dispersant and
alumina-treated TiO.sub.2 (2063) (Example 3) exhibits brightness
superior to the comparative films. The film containing TSPP (C8)
exhibits no improvement in brightness compared to the film with no
dispersant (C7), while the film containing KTPP (C9) exhibits about
a 1 point increase in brightness. By comparison the TKPP film
exhibits about a 3 point increase in brightness with this
alumina-modified TiO.sub.2.
[0041] A similar trend is observed in alumina and silica surface
treated TiO.sub.2 (R-746) where the film containing TKPP shows
brightness superior to the comparative films. The film containing
TKPP dispersant (Example 4) shows about a 4 point increase in
brightness compared to the film with no dispersant (C10). By
comparison, the films containing TSPP (C11) and KTPP (C12) show
about a 3 point increase in brightness.
[0042] To compare the effects of TKPP in films containing TiO.sub.2
and hollow spherical pigment, two coatings were prepared: a) a
coating containing RPS TiO.sub.2, AF-1055 and TKPP (Example 5) and
b) a coating containing RPS TiO.sub.2 and AF-1055 (C13). The
results in Table 3 indicate a superior brightness performance of
coatings containing TKPP (Example 3) over the coatings without TKPP
(C13). Specifically, the film containing TKPP exhibits a brightness
increase of about 4 points over the film without TKPP.
TABLE-US-00004 TABLE 3 Brightness Comparison for Coatings
Containing Hollow Spherical Pigment AF-1055 with and without TKPP
Ex. # 5 C13 Hollow sphere pigment type AF-1055 AF-1055 Dispersant
TKPP None B.sub.med 65.3 61.3 stdev 0.5 0.3
[0043] It has surprisingly been discovered that paper or paperboard
coated with pigmented films containing TKPP consistently provided
superior brightness compared to films containing ostensibly similar
dispersants. This trend of marked superiority was generally
observed across a variety of binders and TiO.sub.2.
* * * * *