Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD TO REDUCE BACK TRAP OFFSET PRINT MOTTLE
BACKGROUND OF THE INVENTION
In offset printing, paper is run through from one to ten or more printing
nips. Typically,
the heatset web offset (HSWOS) process used for weekly national magazines has
four process
colors and at least one Pantone, high-light or special color such as the dark
blue color on the
cover of "Newsweek" magazine, which makes a series of five printing units or
offset print nips.
Higher quality sheet offset litho printing normally has at least six or more
printing units in series.
The offset printing process, especially in perfecting presses, has the
capability of simultaneously
printing both sides of a paper web at speeds as high as 3000 fpm (ft./min.).
The "offset printing
process" gets its name from the fact that "images" are formed on lithography
plates then
transferred (offset) to a rubberized printing blanket stretched around a
cylinder. The inked part
of the lithography plate that is also stretched around a cylinder forms the
image that gets
transferred to the offset blanket then in turn to the paper. The non-image
areas of the
lithographic plate are hydrophilic and are protected against ink adherence by
fountain solution
(water, gum arabic, surfactant, and acid). On perfecting offset presses, the
image is offset from
the top lithography plate to the paper by the offset blanket. To get
sufficient pressure for transfer
of the ink from the top offset blanket, an identical unit "perfects" or
contacts the moving paper
web from the bottom thus printing both sides simultaneously. At the successive
perfecting offset
blanket nips (unit 2, 3, 4, etc), ink is transferred to the web or wet-trapped
onto the paper either
to previous inked image areas or to non-image areas. This is called wet trap
in that non-image
areas of the offset blanket transfer a very thin layer of fountain solution to
the paper along with
ink in the image areas. The ink forming the image on the paper from the
previous printing
station (unit) has the possibility to re-split or "back trap" from the paper
to the next offset
printing blanket and so on. This phenomenon is known as back trap mottle
(BTM). Back trap
mottle is an undesired result from offset printing because a non-uniform print
image is created.
Printers desire to reduce or eliminate back trap mottle so uniform ink
densities result whether
they are "solids", "quarter tones", "half-tone" or "3/a-tones" or any ink
density range in between
or transition points within an image.
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SUMMARY OF THE INVENTION
The invention relates to a paper and paperboard material comprising a paper or
paperboard substrate, a basecoat layer on at least one surface of substrate
and topcoat on a
surface of the basecoat, said topcoat comprising one or more pigments
dispersed in one or more
binders and said basecoat comprising low density thermoplastic particles low
density
thermoplastic particles dispersed in one or more binders. This invention also
relates to a method
of preparing the material of this invention comprising: applying a basecoat
composition
comprising low density thermoplastic particles dispersed in one or more
binders to a paper or
paperboard substrate and applying a topcoat composition comprising one or more
pigments
dispersed in one or more binders over the basecoat.
This invention provides one or more advantages that are believed to result
from inclusion
of the low density thermoplastic particles in the basecoat. These advantages
include reduced 2'a
cyan mottle, enhanced sheet gloss and print gloss and/or enhanced Sheffield
and Parker Print
smoothness as compared to a similar material having the same characteristics
except for the
presence of low density thermoplastic particles in the basecoat.
BRIEF DESCRIPTION OF FIGURES
The above and other aspects and advantages of the invention will now be
further
described in conjunction with the accompanying drawings in which:
Figure 1 is a schematic representation of an embodiment of the paper or
paperboard of
this invention.
Figure 2 is a graph of 2 d Cyan Tobias mottle versus basecoat solids for
various preferred
paper or paperboard materials of this invention.
Figure 3 is a graph of 2 d Cyan Tobias mottle versus parts of plastic pigment
added to the
basecoats for various preferred paper or paperboard materials of this
invention.
Figure 4 is a graph of 2nd Cyan Tobias mottle versus 2"d Cyan scanner mottle.
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DETAILED DESCRIPTION
As used throughout, ranges are used as a short hand for describing each and
every value
that is within the range. Any value within the range can be selected as the
terminus of the range.
As depicted in Fig. 1, one aspect of this invention relates to coated paper or
paperboard material
10. Material 10 comprises a paper or paperboard substrate 12, basecoat 14 and
topcoat 16. Base
coat 14 comprises low density thermoplastic particles dispersed in a polymeric
matrix.
In the preferred embodiments of this invention, the material exhibits superior
2nd Cyan
scanner mottle. Scanner mottle is determined using the following procedure:
Representative
samples are selected from pigment coated paper or paperboard printed under
controlled
conditions typical of commercial offset litho production with the cyan process
ink at a reflection
density of 1.35::L0.05. A 100 percent solid cyan print reflective image is
digitally scanned and
transformed through a neural network model to produce a print mottle index
number between
zero (perfectly uniform ink lay with no mottle) to ten (visually noticeable,
objectionable and
likely rejectable because of print mottle, a random non-uniformity in the
visual reflective density
or color of the printed area). Data from this 2"d Cyan scanner mottle system
can be correlated to
subjective visual perception (using the zero-to-ten guideline) or can be
transformed into
equivalent mottle values as measured with a Tobias mottle tester from Tobias
Associates using
the following equation:
Tobias=Scanner Mottle*8.8 + 188
that was determined from the graph in Figure 4. The data used in Figure 4 was
obtained by
measuring mottle of representative substrates using the scanner mottle systems
and the Tobias
mottle test and plotting the data to provide a means for converting mottle
data between these two
systems.
In these preferred embodiments, the 2nd cyan scanner mottle is less than about
6,
preferably less than about 5, more preferably less than about 4 and most
preferably from about 2
to about 3. In these preferred embodiments, the 2 d cyan scanner mottle is
preferably 20% lower
and the 2 d Cyan Tobias mottle is preferably 5% lower, the 2"d cyan scanner
mottle is more
preferably 40% lower and the 2 nd Cyan Tobias mottle is more preferably 10%
lower and the 2 nd
cyan scanner mottle is most preferably 60% lower and the 2d Cyan Tobias mottle
is most
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preferably 15% lower than that of a similar material having the same
characteristics except for
the presence of the low density thermoplastic particles in the basecoat.
Coated material 10 preferably has a smoothness of less than 2 as measured
using TAPPI
test method for Parker Print Surface: T 555 om-99. In the preferred
embodiments of this
invention, the coated paper has Parker Print Surface preferably less than
about 1.5. The Parker
Print Surface is more preferably less than about 1.3 and most preferably less
than about 1.2. In
the einbodiments of choice, the Parker Print Surface is more preferably less
than about 1. In
these preferred embodiments, the Parker Print Surface is preferably 10% lower,
more preferably
20% lower and most preferably 30% lower than the Parker Print Surface of a
similar material
having the same characteristics except for the presence of the low density
thermoplastic particles
in the basecoat.
Coated material 10 preferably has a Sheffield smoothness of less than about 25
as
measured by the procedure of TAPPI test method T5380m-1. In the preferred
embodiments of
this invention, the coated paper has Sheffield smoothness preferably less than
about 20. The
Sheffield smoothness is more preferably less than about 15 and most preferably
less than about
12. In these preferred embodiments, the Sheffield smoothness is preferably 10%
lower, more
preferably 20% lower and most preferably 30% lower than the Sheffield
smoothness of a similar
material having the same characteristics except for the presence of the low
density thermoplastic
particles in the basecoat.
As one essential component material 10 comprises a paper or paperboard
substrate 12.
Any conventional paper or paperboard web having a wide variety of porosities,
basis weights,
densities, calipers and the like can be used to make substrate 12. Such webs
and methods and
apparatus for their manufacture are well known in the art. See for example
"Handbook For Pulp
& Paper Technologies", 2"d Edition, G.A. Smook, Angus Wilde Publications
(1992) and
references cited therein. For example, the paper and paperboard substrate can
be made from pulp
fibers derived from hardwood trees, softwood trees, or a combination of
hardwood and softwood
trees prepared for use in a papermaking furnish by any known suitable
digestion, refining, and
bleaching operations as for example known mechanical, thermo mechanical,
chemical and semi
chemical, etc., pulping and other well known pulping processes. In certain
embodiments, at least
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a portion of the pulp fibers may be provided from non-woody herbaceous plants
including, but
not limited to, kenaf, hemp, jute, flax, sisal, or abaca although legal
restrictions and other
considerations may make the utilization of hemp and other fiber sources
impractical or
impossible. Either bleached or unbleached pulp fiber may be utilized in the
process of this
invention. Recycled pulp fibers are also suitable for use.
The substrate may also include other conventional additives such as, for
example, starch,
mineral and polymeric fillers, sizing agents, retention aids, and
strengthening polymers. Among
the fillers that may be used are organic and inorganic pigments such as, by
way of example,
minerals such as calcium carbonate, kaolin, and talc and expanded and
expandable microspheres.
Other conventional additives include, but are not restricted to, wet strength
resins, internal sizes,
dry strength resins, alum, fillers, pigments and dyes.
As another essential component, material 10 comprises a basecoat 14 on a
surface of
substrate 12. Basecoat 14 comprises low density thermoplastic particles
dispersed in a polyineric
binder. As used herein, " low density thermoplastic particles" are particles
formed from
thermoplastic or elastic polymers having a density of less than 1.2 Kg/Liter
in a dry state
including the void air volume. The density is preferably less than 0.8
Kg/Liter, more preferably
less than 0.6 Kg/Liter and most preferably from about 0.3 Kg/Liter to about
0.6 Kg/Liter. The
low density thermoplastic particles preferably are not expandable and more
preferably have a
diameter less than about 3 microns, more preferably less than about 2 micron
and most
preferably from about 0.6 to about 1.5 microns. While we do not wish to be
bound to any theory,
it is believed that inclusion of the low density thermoplastic particles makes
the basecoat more
compressible and enhances the beneficial properties of the material 10.
Improved properties
include reduced 2"d cyan scanner mottle, enhanced sheet and print gloss and/or
enhanced
Sheffield and Parker Print smoothness as compared a similar material having
the same
characteristics except for the presences of the low density thermoplastic
particles in the basecoat.
While we do not wish to be bound by any theory, it is also believe that the
amount of
coating thickness and compressibility (range of compaction) load versus
decrease in coating
height needed to reduce back trap offset print mottle is directly proportional
to the Z-direction
non-uniformity of the base paper board's formation at offset printing
pressures. For example,
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offset printing pressures are typically in the range of about 10 kg/sq cm that
has been
standardized as R (rubber) 10 kg/sq cm of Parker Print Surface roughness (PPS,
microns). If
these load range is employed, the compressibility of basecoat at the employed
load range should
"float or cushion" the Z-direction hard fiber to fiber cross-over points to
prevent or reduce point
to point printing pressure variations. Where present, these variations lead to
further variations in
ink film transfer initially and in subsequent print units thus unevenly back
trapping part of the
ink film to subsequent offset blankets (impression cylinder).
Low density thermoplastic particles that can be used may vary widely and
include, but
are not limited to, hollow polymer plastic pigments and binders having a
particle size that is at
least about 175nm. Examples of these are ROPAQUE HP1055 and AF1353 from Rohm
and
Haas and the HS 2000NA and HS 3000NA plastic pigments from Dow Chemical
Company. The
amount of low density thermoplastic particles present in the basecoat may vary
widely but is
preferably in an amount less than about 30% by weight of the basecoat
composition. More
preferably, they are present in an amount from about 1 to about 15 % by weight
of the basecoat
composition most preferably in amount from about 2 to about 10% by weight of
the basecoat
composition and in amount from about 3 to about 7% by weight of the basecoat
composition in
the embodiments of choice.
As another essential component basecoat 14 includes one or more polymeric
binders.
Illustrative of useful are those which are conventionally used in coated
papers as for example
styrene butadiene rubber latex, styrene acrylate, polyvinyl alcohol and
copolymers, polyvinyl
acetates and copolymers, vinyl acetate copolymers, carboxylated SBR latex,
styrene acrylate
copolymers, styrene/butadiene/acrylonitrile,
styrene/butadiene/acrylate/acrylonitrile polyvinyl
pyrrolidone and copolymers, polyethylene oxide, poly (2-ethyl-2-oxazoline,
polyester resins,
gelatins, casein, alginate, cellulose derivatives, acrylic vinyl polymers, soy
protein polymer,
hydroxymethyl cellulose, hydroxypropyl cellulose, starches, ethoxylated,
oxidized and enzyme
converted starches, cationic starches, water soluble gums, mixtures of water
soluble and water-
insoluble resins or polymer latexes, and the like may be used. Preferred
polymeric binders are
carboxylated SBR latexes, polyvinyl alcohol, polyvinyl acetate,
styrene/acrylonitrile copolymer,
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styrene/butadiene copolymer, styrene/acrylate copolymer, and vinyl acetate
polymers and
copolymers.
Binder latex particles having a sufficient particle size also provide an
initial bulking when
included with inorganic or organic bulking pigments. Latex particles in
general have a particle
size from about 100 to about 300 nm for paper coating applications. Latex
particles having
sufficient size to provide compressibility generally have a particle size that
is at least 175 nm.
The size of the latex that provides compressibility is directly proportional
to the average size of
the inorganic and organic pigments used in basecoats. Typically, a source of
ground calcium
carbonate (GCC) used in paperboard basecoats is HYDROCARBO 60 (from OMYA).
This
ground calcium carbonate is a wet ball milled product having 60% of its
particles less than 2
microns. Conversely, 40% of the particles are equal to or larger than about 2
microns.
Preferably, the latex particle size is at least 175 nm for basecoats composed
mainly of
HYDROCARBO 60 calcium carbonate or similar products. More preferably, the
latex particle
size is at least 185 nm, and even more preferably, the latex particle size is
at least 190 nm.
In the more preferred embodiments of the invention, additional pigment or
fillers are
employed to improve the properties of the coated paper and paperboard. These
additional
pigments may vary widely and include those inorganic pigments typically used
in the coated
paper and paperboard such as silica, clay, calcium sulfate, calcium silicate,
activated clay,
diatomaceous earth, magnesium silicate, magnesium oxide, magnesium carbonate
and aluminum
hydroxide. To add additional initial coating bulk, inorganic particles such as
precipitated
calcium carbonate having bulky structures such as a rosette crystal can also
be included. In the
most preferred einbodiments of the invention, inorganic pigments having a
rosette or other bulky
structure can be included in the basecoat to make the basecoat have greater
initial bulk or
thickness. The rosette structure provides greater coating thickness, thus
improved coating
coverage for a given coat weight. This allows for the dried coating to more
easily move in the Z-
direction when compressed by the hot soft gloss calenders on coated SBS
paperboard machines,
and thus to form a level coated surface with a reduced number of low spots.
Preferred inorganic
pigments include, but are not limited to, precipitated calcium carbonate,
mechanically or
chemically engineered clays, calcined clays, and other pigment types that
function to lower the
average density of the coating when dry. These pigments do not provide
compressibility to dried
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basecoats. They synergistically lower average coating density and, raise
average coating
thickness at a given coat weight so compressible materials, such as larger
size binders and
hollow plastic spheres, become more efficient in cushioning the Z-direction
non-uniformity of
the base paperboard's formation from creating point to point variations in
printing pressure in the
offset printing nip.
Coat weight of the basecoat can vary widely and any conventional coat can be
used.
Basecoats are generally applied to paper substrates in an amount from about 4
to about 20gms.
The coat weight of the basecoat is preferably from about 6 to about 18gms and
more preferably
from about 7 to about l5gms. The thickness of the basecoat can vary widely and
any thickness
can be used. Generally, the thickness of the basecoat is from about 1.8 to
about 9.0 gm at a
minimum, which is figured on the average density and weight ratio of each
component in a
coating. The thickness of the basecoat is preferably from about 2.7 to about
8.1 gm and more
preferably from about 3.2 to about 6.8 m. When packing factors to dissimilar
shapes are taken
into account, the average thickness when applied to an impervious surface
would be significantly
greater than the theoretical values given here. However, because of the rough
nature of
paperboard in general and the application and metering system used to apply
and meter basecoats
at an average coat weight of 12 g/rn2, the coating thickness at the rough high
spots in the paper
may be as low as 2-3 microns while valleys between large surface fiber may
have coating
thickness as great as 10+ microns. Stiff blade metering of the basecoat
attempts to provide a
level surface to which a very uniform topcoat is applied.
As depicted in Figure 1, the third essential component of material 12 is
topcoat 16.
Topcoat 16 comprises one or more inorganic pigments dispersed in one or more
polymeric
binders. Polymeric binders and inorganic pigments are those typically used in
coatings of coated
paper and paperboard. Illustrative of useful pigments and binders are those
used in basecoat 14.
Coat weight of topcoat 16 can vary widely and any conventional coat can be
used.
Topcoat 16 is generally applied to paper substrates in amount from about 4 to
about 20gms. The
coat weight of the basecoat is preferably from about 6 to about 18gms and more
preferably from
about 7 to about 15gms. The thickness of topcoat 16 can vary widely and any
thickness can be
used. Generally, the thickness of the basecoat is from about 1.8 to about 9.0
m at a minimum,
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which is figured on the average density and weight ratio of each component in
a coating. The
thickness of the basecoat is preferably from about 2.7 to about 8.1 m and
more preferably from
about 3.2 to about 6.8 m at a minimum, which is figured on the average
density and weight
ratio of each component in a coating. The point at which the void volume is
filled by binder and
additives among all pigments is referred to as the "critical void volume". In
the paint industry
this point is referred to as the transition from matte to gloss paints.
The paper or paperboard of this invention can be prepared using known
conventional
techniques. Methods and apparatuses for forming and applying a coating
formulation to a paper
substrate are well known in the paper and paperboard art. See for example,
G.A. Smook
referenced above and references cited therein all of which is hereby
incorporated by reference.
All such known methods can be used in the practice of this invention and will
not be described in
detail. For example, the mixture of essential pigments, polymeric or
copolymeric binders and
optional components can be dissolved or dispersed in an appropriate liquid
medium, preferably
water.
The percent solids of the top and basecoat coating formulation can vary widely
and
conventional percent solids are used. The percent solids of the basecoat
coating formulation is
preferably from about 46% to 69 % because within range excellent scanner
mottle characteristics
are exhibited by the material with increased drying demands. The percent
solids in the basecoat
coating formulation is more preferably from about 57 to 69% and is most
preferably from about
60% to about 68%. The percent solids in the basecoat coating formulation in
the embodiments of
choice is from about 63% to 67%.
The coating formulation can be applied to the substrate by any suitable
technique, such as
cast coating, Blade coating, air knife coating, rod coating, roll coating,
gravure coating, slot-die
coating, spray coating, dip coating, Meyer rod coating, reverse roll coating,
extrusion coating or
the like. In addition, the coating compositions can also be applied at the
size press of a paper
machine using rod metering or other metering techniques. In the preferred
embodiments of the
invention, the basecoat coating formulation is applied using blade coaters and
the topcoat coating
formulation is applied using a blade coater or air knife coater. In the most
preferred embodiments
the basecoat is applied using a stiff blade coater and the topcoat is applied
using a bent blade
coater or an air knife coater.
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The coated paper or paperboard substrate is dried after treatment with the
coating
composition. Methods and apparatuses for drying paper or paperboard webs
treated with a
coating composition are well known in the paper and paperboard art. See for
example G.A.
Smook referenced above and references cited therein. Any conventional drying
method and
apparatus can be used. Consequently, these methods and apparatuses will not be
described herein
in any great detail. Preferably after drying the paper or paperboard web will
have moisture
content equal to or less than about 10 % by weight. The amount of moisture in
the dried paper or
paperboard web is more preferably from about 5 to about 10 % by weight.
After drying the paper or paperboard substrate may be subjected to one or more
post drying steps
as for example those described in G.A. Smook referenced above and references
cited therein. For
example, the paper or paperboard web may be calendered to improve the
smoothness and other
properties of the paper as for example by passing the coated paper through a
nip formed by a
calender. Gloss calenders (chromed steel against a rubber roll) or hot soft
gloss calenders
(chromed steel against a composite polymeric surface) are used to impart gloss
to the top coated
paper or paperboard surface. The amount of heat and pressure needed in these
calenders depends
on the speed of the web entering the nip, the roll sizes, roll composition and
hardness, specific
load, the topcoat and basecoat weights, the roughness of the under lying rough
paperboard, the
binder strength of the coatings, and the roughness of the pigments present in
the coating. In
general, topcoats contain very fine particle size clays and ground or
precipitate calcium
carbonate, binder, rheology aids, and other additives. Typically hot soft
calenders are 1 m and
greater in diameter and are heated internally with very hot heat transfer
fluids. The diameter of
the heated steel roll is directly dependent on the width of the paper machine.
In general, a wider
paper machine of 400" as compared to 300" or 250" wide machines requires much
larger
diameter rolls so that the weight of the roll does not cause sagging of the
roll in the center.
Hydraulically, internally loaded, heated rolls that are crown compensating are
used. Surface
temperatures typically used range from 100 to 200 C. The preferable range is
130 C to 1 85 C
with nip loads between 20 kN/m and 300 kN/m.
The coated paper or paperboard of the present invention can be used for
conventional
purposes. For example, specific uses of the paper and paperboard include, but
are not limited to
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use in the formation of Bristol, folding carton, aseptic paperboard, double
coated free sheet, and
any other type of product made from coated paper or paper board.
The invention is further described in the following examples. In the example,
all amounts
are parts per one hundred parts of pigment except as expressly indicated
otherwise. The
examples are merely illustrative and do not in any way limit the scope of the
invention as
described and claimed.
EXAMPLE 1
A. Preparation of Coating Formulations:
Preformed aqueous slurries of the pigments and low density thermoplastic
particles are
added to a high shear mixer. Then dispersant, binder and viscosity modifier
are added to the
slurry under shear to form a coating formulation having the desired Brookfield
viscosity. The
viscosity of the basecoat coating formulation is about 1000 centipoises (cps)
spindle 4 at 100
revolutions per minute. The viscosity of the topcoat coating formulation is
about 700 to 800
centipoises (cps) spindle 4 at 100 revolutions per minute. After final mixing,
the coatings are
ready for casting.
Controls were made using the same basecoat and topcoat formulations, except
that there
was no hollow pigment in the basecoat.
The coating formulations are set forth in the following Table 1.
Table 1
Basecoat 1 Basecoat 2 Basecoat 3 Basecoat 4 Basecoat 5 Basecoat 6 Basecoat 7
Topcoat 1 Topcoat 2 To coat 3
Hydrocarb 60 100.0 85.0 60.0 100.0 100.0 100.0 95.0
Ro a ue HP-1055 15.0 30.0 5.0
H dra loss 91 40.0 40.0 40.0
Hydrocarb 90 60.0 60.0 60.0
Ca im NP 10.0
Acronal 5-866 14.0 14.0 14.0 14.0 15.0 14.5
Acronal S-728 14.0 14.0 14.0 15.0
Dis ex N-40 0.2 0.2 0.2 0.4 0.4 0.2 0.4
Sterocol FD 0.3 0.5 1.0 0.3 0.3 0.35 0.5
Acumer 9300 0.09 0.09 0.38
L-229 0.43 0.43 0.09
Calcium Sterate 1.0 1.0 2.0
Solids68.5 57.0 46.0 68.5 56.0 68.5 64.8 64.0 63.0 66.2
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The identity and source of the materials listed in Table 1 are set forth in
the following Table
2.
Table 2
Coating Component Description Manufacturer
Hydrocarb 60 Fine Ground Calcium Carbonate Omya
Ropaque HP-1055 Hollow Sphere Plastic Pigment Rohm and Haas
Hydragloss 91 Number 1 Glossing Clay Huber
Hydrocarb 90 Ultrafine Ground Calcium Carbonate Omya
Capim NP Engineered Clay Imerys
Dispex N-40 Dispersant Allied Colloids
Acumer 9300 Pol ac lic Dispersant Rohm and Haas
Acronal S-866 Styrene Acrylic Acrolonitrile binder BASF
Acronal S-728 Styrene Acrylic binder BASF
Sterocoll FD Acrylic Viscosity Modifier BASF
Alcogum L-229 Acrylate Viscosity Modifier ALCO Chemical
Sunkote 450 Calcium Stearate Lubricant Omnova
B. Preparation of Coated Paper:
The paperboard substrate having a basis weight of 255 gsm was coated using a
flooded
nip blade coater to first form the basecoat followed by coating to form the
topcoat. A bent blade
was used to coat the topcoat and a stiff blade was used to form the basecoat.
The coat weight of
the topcoat was 8 gsm and the coat weight of the basecoat was 10 gsm. Controls
were made
using the control basecoat and topcoat formulations that did not include
hollow pigment in the
basecoat. At the line speed of the coater applying the topcoat, a single hot
soft calender nip was
used to impart gloss. The operating temperature of the metal roll surface was
185 C; nip load
was varied, but sufficient to reach 60% sheet gloss (TAPPI Method, T480, 75
angle meter).
Substrate 1 identified in Table 3 below required 75 kN/m to obtain a 60% sheet
gloss while
Substrate 2 identified in Table 3 below only required 65 kN/m to reach 60%
sheet gloss.
Substrate 6 required a calendering pressure of 50kN/m to obtain a 60% sheet
gloss while
Substrate 7 required a calendering pressure of 4lkN/m to reach 60% sheet
gloss.
The combinations of topcoat and base coat of the coated paperboard substrates
are set
forth in the following Table 3.
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Table 3
Substrate 1 Substrate 2 Substrate 3 Substrate 4 Substrate 5 Substrate 6
Substrate 7
Base ToR Base ToR Base Top Base T~ Base ToR Base T~ Base Toi)
Coat Coat Coat Coat Coat Coat Coat Coat Coat Coat Coat Coat Coat Coat
1 1 2 1 3 1 4 2 5 2 6 3 7 3
C. Testingof the Coated Pqper
The coated substrates identified in Table 3 were evaluated to determine their
scanner
mottle using a unit 2 cyan solid print from a 6-color offset press. The
scanner mottle results
were transformed into equivalent mottle values as measured with a Tobias
mottle tester from
Tobias Associates using the following equation:
Tobias = Scanner Mottle*8.8 + 188
that was determined from the graph in Figure 4. The data used in Figure 4 was
obtained by
measuring mottle of representative substrates using the scanner mottle test
and the Tobias mottle
test and plotting the data to provide a means for converting mottle data
between these two
systems. Lower 2nd cyan scanner and Tobias mottle values indicate a more
uniform print. The
results are set forth in Figures 2 and 3.
Substrate 1 and Substrate 2 were tested for mottle on a mottle tester from
Tobias
Associates, Inc using a unit 2 cyan solid print from a 6-color offset press.
Substrate 1 had a
rating of 246, and the Substrate 2 had a rating of 208.
EXAMPLE 2
Using the procedure of Example 1, coating fonnulations were prepared. The
coating
formulations used are set forth in the following Table 4.
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Table 4
Properties/Components Basecoat 8 Basecoat 9 Topcoat 4
Hydrocarb 60 100 95 -
Ropaque AF-1353 - 5.0 -
Hydragloss 91 - - 40
Hydrocarb 90 - - 60
Acronal S-866 14.0 14.0 15.0
Acumer 9300 0.09 0.09 0.38
L-229 0.43 0.4.3 0.09
Calcium Stearate - - 2.0
Solids (%) 68.5 64.5 64.0
Using the procedure of Example 1, Substrate 8 and Substrate 9 coated
substrates were
prepared. Substrate 8 identified in Table 5 was calendered at 185 C and with
sufficient load to
achieve 60% gloss measured at 75 and Substrate 9 was calendered under the same
calendering
conditions as Substrate 8.
Table 5
Substrate 8 Substrate 9
Basecoat 8 Top coat 4 Basecoat 9 Topcoat 4
The coated substrates identified in Table 5 were evaluated to determine their
2 cyan solid
print gloss at 60 from a 6-color offset printing press as measured by the
procedure of TAPPI test
method T480, sheet gloss at 75 as measured by the procedure of TAPPI test
method T480, sheet
gloss Parker Print Surface as measured by the procedure of TAPPI test method:
T555 and
Sheffield smoothness as measured by the procedure of TAPPI test method T538.
The results are
set forth in the following Table 6.
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WO 2006/033952 PCT/US2005/032881
Table 6
Pro er Substrate 8 Substrate 9
Sheffield Smoothness 20 11
Parker Print Surface 1.76 1.35
Sheet Gloss 75 56 64
2nd Cyan Print Gloss 60 38 49
It should be appreciated that the present invention is not limited to the
specific
embodiments described above, but includes variations, modifications and
equivalent
embodiments defined by the following claims.
