Note: Descriptions are shown in the official language in which they were submitted.
`` 1316957
PRESSURE SENSITIVE RECORD M~TERIAL
The invention relates to paper for carbonless copy
paper sets and to copy paper sets made up using it.
BACKGROUND
Carbonless copy paper sets consist of a top sheet known
as the Cs (coated back) shee'cl a back sheet known as the CF
(coated front) sheet, and optionally one or more
intermediate sheets known as CFs ~coated front and back)
sheets. The coatings of the back of the CB sheet, of the
front and back of the CFB sheets if any, and of the front of
the CF sheet contain materials that when brought into
association with each other develop a coloured image.
When the front of the CB sheet is typed on or otherwise
pressure imaged , material is transferred between the back
of one sheet and the front of the next through the set to
give rise to the copies required. Usually, a solution of a
dye precursor or "colour former" carried on the sheet as
isolated droplets each confined within a pressure rupturable
barrier is transferred from the back of one sheet -to the
front of the next after rupture of the barrier by the
applied pressurel and interacts with a "colour developer"
present there to give the image.
All of this is very well known and requires no detailed
description.
PIGMENT IN CB-SHEET FRONT COATINGS
The present invention has arisen from a requirement, in
40440-1 l 31 6957
the highest grade products, for a pigment-containing coating
on the front face of CB sheets, improving them in appearance
and in printability~
THE_INVENTION
ThP invention provides record material ~omprising a
paper sheet having on its front a printable pigment coating
and on its back isolated droplets of colour former solution
each confined within a pressure rupturable barrier, wherein
the pigment coating comprises a binder for the pigment
together with a synthetic reactive sizing agent or a coating
structure ayent or both, the sizing agent being for example
an alkyl ketene dimer, alkenyl succinic anhydride, or other
neutral reactive size, or a polyurethane size and the
coating structure agent being ~or example a carboxy methyl
~: cellulose, a soya or other protein, an alginate, or other
hydrophilic polymer. The relative amounts o~ components in
the coating are desirably by weight 60 - 95 parts pigment,
20 10 - 30 parts binder, 0.5 - 10 parts size where present and
0.5 - 5 parts coating structure where present. Within these
: ranges, for example i~ without coating structure agent, the
relative amounts of pigment binder and size are respectively
. 60 - 95 parts, 16 - 22 parts and 0.5 - 10 part~ or ii)
without size the relative amounts of pigment, binder and
coating structure are respectively 75 85 parts, 12 - 22
parts and 0.5 to 5 parts. When size is pxesent in
compositions of these last proportions it may be 1 5 parts
for example.
. ~ .
The coating mixe9 themselve~, besides their use, axe
new and an aspect of the invention.
1 31 6q57
The binder is present to hold the pigment in a non-
dusting, printable coatiny, and to enable enough binder to
be used for that purpose it must be a material that when
tested at 40 weight ~ in water gives a fluid preparation
mixable with pigment to give a coatable dispersion.
Normally it will be a latex binder but for example
hydroxyalkyl ether derivatives of starches are suitable.
Auxiliary binder materials may also be included.
The size, as discussed further below, is used to hold
off latex-based or other edge-padding adhesives to allow
form sets to be fanned.
The coating structure agent, as also discussed further
below, is a hydrophilic polymer that provides a Bendtsen
porosity of the finished i.e. CB coated sheet of not less
than 25 ml/min, preferably more. Such porosities reflect
porosities before CB coating of around 30 ml/min or more
allowing economic application of the CB coating. Suitable
materials are believed to act by gelling the pigment coating
in the course of drying~ preventing it from compacting into
an impermeable layer, and all are materials that when tested
; in water at 25 we~ght ~ or more give a gel-like preparation
not mixable with pigment to give a coatable dispersion.
It will be understood that as the intention is to
improve appearance as well as printability, the pigment
coating should not have any significant colour developing
.,
properties. Such properties would give rise to edge
staining after slitting or sheeting, and possibly other
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1 31 6q57
marking arising from capsule rupture and release of colour
former solution.
_GE PADDING
A well known use of copy paper sets is in the
production of multiple sets or "form sets". In these,
repeats of the sequence of sheets, CB, optionally one or
more CFB and CF, that constitute an individual set are made
up as a stack. An adhesive, known as an edge padding
adhesive, is applied down one side of the stack, its
characteristic being that it is attracted to the coating of
the back of the CB ~and any CFB) sheets, or to the coating
of the front of the CF (and any CFB) sheets, or to both, to
a greater extent than to what are, conventionally, uncoated
faces of the sheets in the stac~, which are the fronts of
the CB sheets and the backs of the CF sheets. Thus there is
only a weak bond between CB sheets and adjacent CF sheets
above them and individual sets can be separated from each
other by "fanning" without the sheets within the sets coming
apart from each other.
However a CB front face pigment coating would be
thought of as incompatible with edge padding, the coating
attracting the edge padding adhesive in the same way as the
coatings within the sets. The invention, in the aspect in
which a size is present, overcomes such problems. While of
course the use of sizes in paper general]y is known, and so
is pigment coating and the use of binders to retain the
3 ~ pigment on the paper, there has been no reason to size a
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1~16957
pigment coating as such. Indeed a pigment would normally be
thought of as incompatible with size, using a lot of it to
no purpose, and the success of the combination is
surprising.
USE OF HIGH PIGMENT COAT WEIGHTS
Separate from questions of edge padding is a
desirability of high pigment coat weights for the best
properties of printability and appearance.
The requirement however conflicts with ready
application of CB coatings. These, containing colour former
in relatively fragile (usually encapsulated) form, must in
practice be applied after the coating of the front of the
sheet. Application involves use of driving rolls run at
high speed with the paper tensioned over them and if air is
not to be entrained between paper and roll the paper must
have enough permeability for the alr to escape. Without it
the paper is liable to "hover" on a layer of air over the
roll with loss of control of t~e process and variation in
the product. Running the coater at a lower speed to avoid
the ~problem is unacceptable for production efficiency.
Increasing the tension to exclude the air is possible in
theory but risks damage to the product, e.g. by more
frequent breaks and/or curling or inferior aspect.
In conventional pigment coated printing paper, the
plgment coating is typically highly consolidated to give a
smooth surface. The~use of these highly consolidated
coatings means that the sheet porosity of the paper is very
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1316957
low. We have however surprisingly found both good binding
and permeability, even though the invention uses a high
content of binder such as would in itself be expected to
give an entirely impermeable coating. The adverse effects
of this high content of binder are overcome by the presence
in the coating mix of the coating structure agent,
sufficient permeability for successful subsequent
application of CB coatings being obtained.
The inclusion of the coating structure agent ln the
coating mix promotes the generation of a relatively porous
coating. We believe that this arises because as the coating
mix dries, the coating structure agent helps the mix to set
or gel before all the water is removed, and that the set or
gelled structure is, at least in part, preserved through
drying to give a relatively bulky and thus porous coating.
That this effect generates a porous coating even at the high
binder levels typically used in this invention is very
sur~prising as such binder levels would ordinarily be
expected to "blind" the coating.
The reason for the success of the invention appears,
though such theory is not to be taken as a limitation of the
.
nvention ltself; to lie in a microporosity arising from
early setting or gelling of the coating as re~erred to
above, without excessive loss of binder into the paper,
followed by drying out of the water content of the coating
; without loss of the structure. It does not appear to arise
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~ by a multiple micro-cracking of the coating such as is seen
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1316957
in the colour-developer clay coatings used in CF sheets or
the CF face of CFB sheets.
PIGMENTS
The pigments are, generally, conventional paper coating
pigments, in particular inorganic or mineral-derived
particulate materials. Calcium carbonate especially is
economic and suitable, giving good whiteness and purity and
having good printing characteristics. It may be
supplemented with coating clays such as china clay (kaolin),
although with large amounts of clay care will be necessary
in formulation to achieve satisfactory rheology and
stability for successful coating, as will be appreciated by
those skilled in the art.
Other suitable pigments besides china clay include
cal.cined clays, tltanium dioxide, finely divided silica and
talc.
A mixture of calcium carbonate and china clay,
particularly calcined china clay, is preferred. Calcium
carbonate contributes good whiteness and brightness, and
high print deflnition, but on its own tends to give dusting
on the surface and may not give good ink receptivity. Clay
or talc contribute to a good surface finish and give good
ink receptivity without dusting but give a less white
,
appearance. Ground calcite as the calcium carbonate has
high purity (to give whiteness etc. as compared with ground
limestone or chalk) without the very high surface of
; preaipitated carbonates, which can be used but are not
8 1 31 69S~
preferred because of high binder demand arising from small
particle size.
It will be understood that the pigment in the coatings
is not such as to have colour developing properties. To
this end the inclusion as pigments oE specific colour
developer materials, such as the clays that are used as the
active constituents of many CF coatings, will be avoided.
Kaolin has been mentioned in the literature as a colour
developer but in unmodified form is not so used or suitable,
and papercoating grades are essentially non-colour
developing. The use of high levels of binder reduces even
further or eliminates any minor residual colour developing
activity of the raw material.
i ~ The particle size of the pigment is important. The
finer the particles are the more effective the pigment is in
terms of brightness but, equally, the more the coating is
consolidated (thus reducing porosity) ~and also the more
dlfflcult any requlred sizing is. Particularly in a sizing
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context, a balance is desirable and the range of 1 to 10
.
~microns, advantageously 2 to 5 microns, is preferred.
,
Such~particle sizes are as measured by a laser particle
sizer such as the standard Malvern 3600 E Type. For
particles of~broadly the same dimensions in any direction,
such as those of calcium carbonate, such sizes approximate
actual sizes; for flat or elongated particles such as those
i~ ~
of coating clays the particle sizes as measured are nominal.
The laser instrument assesses particle size by measuring the
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9 1316q~7
interference pattern arising from diffraction of the laser
light illuminating a sample suspension e.g. in water, of the
particles. The pattern is manlpulated by a computer to give
results as particle size by volume, e.g. the volume itself
or the diameter of spheres of equal volume.
Amounts of pigment are given earlier, but a
particularly convenient range when size is not being used is
76 - 80 wt.~ of which preferably:-
75 - 88~ CaCO3
12 - 25% China clay, native or
calcined, or talc
Small quantities say up to 10~ of specialist pigments, for
example TiO2 whitener, can conveniently be included.
BINDERS
W~ithin the constraints above~, the binder may be
selected from among those conventional in themselves in
paper coating technology. In particular it may be a
synthetic rubber latex such as styrene butadiene latex
(normally a carboxylated grade to give good dispersibility
and stability in water) or styrene acrylic latex. It is
also however possible for it to be example an ether
derivative of starch, as already mentioned, and these are
not conventional in the sense of being in wide use.
SIZING AGENTS
The size will typically be~a neutral reactive size such
as an alkyl ketene dimer or alkenyl succinic anhydride with
the alkyl or alkenyl groups from C8 upwards, generally from
Cl2 upwards, with C~5-Cl8 ~ypical and the upper limit
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lo 1316957
determined, for example C24, by mix workability and
suitability of the final coating for printing. Such sizes,
in which "neutral" connotes eEfectiveness as sizes at
neutral coating mix pH, are effective in small quantities
and readily provide acceptable rheology in the coating
process, for example blade, roll or slot ~extrusion) coating
as known ~er se. Other synthetic sizes such as polyurethane
slzes may however be used. Amounts within the ranges given
earlier are typically 1 to 5% dry weight of the coating but
more usually 1 to 2~ will be used.
Suitability of sizes will be in terms of water
repellency of the coating in an edge padding context. The
water repellency of the coating is defined in terms of the
contact angle taken up by a water droplet on the surface of
the coated paper, measured within the drop, which ~or a size
to be suitable is~above 70 and advantageously above 90 or
100.
A convenient method of determining the contact angle
depends on measurement of the observed height and contact
width of a droplet of known volume applied to the paper, in
particular ;in ~a Lorentzen & Wettre No. 28 surface
wettability tester. The method;is as follows:-
i) A drop of water (initial diameter 4 mm volume ca.
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3.35 micro11tres~) lS placed on a test strip of
paper
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ii) The drop height (h~ and ~idth of contact of thedrop on the paper (w) are measured on a projected
image of the drop using a graticule
iii) The contact angle is calculated as
~ = 2 tan~l (2h/w)
Since the paper will absorb the water slowly the
contact angle is taken as that measured 2 seconds after the
drop is placed on the paper.
COATING STRUCTURE AGENTS
The coating structure agents that are suitable include
in particular carboxy methyl cellulose such as is used in
coating technology as a dewatering control. Other suitable
materials are proteins, such as soya protein, and alginates
such as sodi~um alginate, their essential characteristlc
belng to provide the desired porous coating structure at the
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low amounts specified. The amounts used, within the overall
range, depend on the nature of the material~ ~enough to be
; effective but not so much as to increase viscosity or modify
the rheology to make the mix uncoatable.
Amounts are typically, weight % on coating:-
Carboxy methyl cellulose high mol.wt. 0.5 - 1.5%
medium mol.wt. 1 - 2 %
low mol.wt~ 2 - 3
Sodium algin~ate ~ 0.7 - 1.5
.oy~ proto~n ~ i.5 - 4
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12 131~957
OTHER COMPONENTS
Other agents, known in themselves may also be present
in the mix, for example sodium hydroxide or other alkalis
such as potassium hydroxide or ammonia for pH adjustment,
and further components of the final coating such as optical
brightening agents, dispersants for the pigments, lubricants
(e.g. calcium stearate) or antifoams.
COAT WEIGHTS
Coat weights may conveniently be 2 to 20 g/m2,
advantageously 3 to 15 g/m2. Papers of reduced substance
compared to normal, in terms of fibre weight per square
metre, may be used compensating in part for the extra cost
of the coatings.
POROSITY
For high speed, high quality (good curl : good aspect)
CB coating the Bendtsen porosity of the final product is
n~ot less than 25 ml/min and preferably not less than 30
:
ml/min with (for this product) a typical range of 35 - 50
ml/min. "High speed" is ca.500 m/min or above and a
preferred lower limit 400/450 m/min. A typical range is ca.
60~0 ~ 900 m/min~ and higher speeds e.g. up to;1500 m/min are
possible.
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SOLIDS OF TOPCOAT MIX
Widest convenient range 25 - 75~ solids, more usual 30
- 70%, advantageously 50 - 65~. Lower solids give a wetter
mix and greater drying requirement which restricts machine
speed; higher solids may give mix viscosity/rheology
problems.
DETAILED PREFERENCES
The invention is described broadly above, but in the
edge padding context most desirably provides a CB sheet with
a printable front coat at 2 - 20g/m2 comprising an inorganic
or mineral derived pigment and a latex-derived binder
together wi.th a siz.ing agent, the sizing agent being an
alkyl ketene dimer or alkenyl succinic anhydride or other
reactive neutral size giving a contact angle of 90 or more.
Preferred proportions of components by weight are pigment 60
- 95 parts, binder 5 - 30 advantageously 16 - 22 and size
0.5 - 10 parts.
:
: In the context wherein edge padding is not an
~: essential, the invention most desirably provides a CB sheet
for carbonless copy paper sets carrying in addition to a CB
:coating a front coating at 3 - 15 y/m2 comprising pigment 75
82~parts,; latex-derived binder 15 ;-~22 parts, and coating
structure:agent 0.5 - 5 parts, all by weight, such that the
finished sheet has a Bendtsen porosity of 25 ml/min or more.
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131695~
14
EX~MPLES
The invention is illustrated in the following examples,
of which Examples 1 and 2 show the use of a coating structure
agent in the absence of size.
Example 1
A coating material was prepared from the following
components 48.2~ solids in water, final pH 9.5.
Material Parts by wt.
Coating structure agent0.8
Sodium hydroxide (first batch) 0.2
Calcium carbonate pigment 60.1
China clay pigment 20.0
Latex binder 16.0
Optical brightener 0.8
Sodium hydroxide (remainder) 0.1
Mlx Procedure
Place water in a high speed mlxing vessel
Add the dry coating structure agent ~and stir for 15
mlnutes at high speed
Add first batch of NaOH (40% solids)
. ~ ,
Add calcium carbonate and china clay and stir for 30
minutes at high speed
Check pH~and adjust to approximately 10.0 with some
of the remaining NaOH
Reduce the stirring speed to slow, add the binder and
stir for~l0~minutes
Add the optical brightener
Bring final pH to 9.5-with NaOH.
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1 31 6957
Materials
i) The coating structure agent is a medium molecular
weight carboxymethyl cellulose~
ii) The calcium carbonate pigment is a ground calcite,
desirable as high-white material economic in cost.
Its median particle size is 2.8 microns.
ili) The china clay is a fine, white, commercially
available coating clay, median partlcle size 3.3 microns.
It acts as a white pigment accordlngly, whlle preserving the
advant~ages o~f clay coatings generally in terms of ~coat
adhesion and printing characteristlcs. It gives no
unacceptable reduction in the brightness of coating given by
the calcium carbonate.
iv) The binder is a conventional carboxylated styrene-
butadiene ~synthetic latex giving the coating the necessary
adhesion as~a whole ~ ;
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1316957
16
The coating mix so prepared was applied using trailing
blade metering to standard base paper of 48 g/m2 substance
for 'Idem' (Trade Mark) CB sheet to give coat weights of 3
to 7 g/m2. The coated paper was then calendered and its
porosity checked and found to be at a suitable figure. It
was CB coated at 800 m/min using a 3 roll coater head,
solids of the coating mix ca. 24~, constitution of solids:-
- 70~ capsules conventional gelatin-based capsules,
black-copy colour former formulation
in solvent, formed by coacervation
encapsulation
- 20% stilt cellulose floc, ungelatinised starch
particles or mixture.
- 10% binder maize starch
and dried to give ca 4.5 g/m2 coat weight (dry). A steam
shower was used to remove/reduce curl otherwise present from
paper wetting during coating.
The resulting CB sheets had ex~cellent printing
characteristics and~improved visus~1 appes1 and feel in terms
of formation~and roughness.
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1 31 6957
17
Example 2
Similarly to Example 1, a coating material was prepared
from the following components, made up to 3308 Kg with water
Component Dry_we~ A~rox.~_of dry
(Kq) welqht
'Dispex' N 40 540% in water) 3.6 0.2
dispersing agent
'Hydrocarb' 70 calcium1275 64.5
carbonate pigment
Sodlum hydroxide 2.4 0.12
(30% in water)
'Alphatex' calcined kaolin 300 15.2
(china clay) pigment
Carboxymethyl cellulose 24 1.2
coating structure agent
'Revinex' 98 F10 latex360 18.2
(50% solids in water)
'Nopcote' C 104 (50~ in 10 0.5
water) calcium stearate
Revinex 98 F10 latex is a carboxylated SBR latex ex
Doverstrànd :Limited 'Dispex', ~'H~ydrocarb', 'Alphatex',
'Revinex' and 'Nopcote' are trade marks.
;This coating was applied to a conventional CB base
paper containing 'Leucophor' (Trade Mark) LN optical
brightener which after checking porosity was given a CB
coating as before. ~A CB paper:of excellent printability was
given without problems in the CB coating process.
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1 3 1 6957
18
Examples 3 and 4
Examples 1 and 2 were repeated with respectively 2
parts by weight and 24 Kg of 'Aquapel' ~Trade Mark) 360 X 3
neutral C16 alkyl ketene dimer size (the level used being
such as to give a final coating contact angle of 110.
Papers of excellent printability and, further, edge paddable
with 1002i fanning were obtained.
Examples 5 and 6
These are further Examples with coating structure agent
and size together, mixes as below, with water to total 3630
parts, i.e. solids of mix = 55~
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19 131~57
Example 5 Example 6
Component Wet Dry ~Wet Dry
Parts Parts Parts Parts
'Hydrocarb'701275 1275 63.81259 125g 63.0
calcium carbonate
'Alphatex' calcined 300 300 15 300 300 15
kaolin
'Dispex' N40 9.1 3.6 0.18 9.1 3.6 0.18
; dispersing agent
CMC (med mol.wt.) 24 24 1.240 40 2.0
coating structure agent
'Aquapel' 360 X 3322.5 24 1.2322.5 24 1.2
size
'Revinex' 98F10 720 360 18 - - -
latex binder
i Dow 620 latex - - - 720 360 18
I binder
: :
'Nopcote' C104 20 10 0.520 10 0.5
calcium stearate
;Procedures for preparation of the coating mix and its
application arè as in Examples 1 and 2. Measured porosities
:
~ ~ (Bendtsen) are: ;
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Ex. 5 Ex. 6
Before CB coat40.2 ca.40
After ~ 35.4 ca.35
and, generally, similarly successful results to Examples 1
and 2 are obtained.
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1 3 1 6957
Example 7
The following is again of the use of a coating
structure agent and size together, and is in effect six
examples in one ~three mixes each coated at two levels).
The formulations were made and coated as in Example 11
the calcium carbonate being of 4 microns median particle
size, at 3 and 6 g/m2,on the rougher side of 'Idem' base
: paper as used in Example 1.
: Material Dry parts
Mix 1 Calcium carbonate100
Binder 22 Total
Coating structure agent 1 55~ solids
Size 2.5 pH 9.5
Optlcal brightener
Mix 2 Calcium carbonate75
China clay ~ ~ 25 ; : Total
Binder ~ 20~ 50% solids
Coatl~ng structure agent 1 pH 9.5
Slze ~ 2.5
Optlcal b~rlghtener
Mix;~3 Calclum carbonate~ ~ 50~
China~clay 50;~ Total
Blnder~ 20~ 47~ solids
Coating~structure agent ~ 1: pH 9.5
Size ~ : 3.7
: Optical:brightener
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21 1316957
The pairs of samples, all of which showed satisfactory
porosities, were subjected to physical testiny, in
comparison to the uncoated base itself, on a number of
criteria significant to CB sheet performance.
a) Rouqhness
Lower values ( of rate of passage of air) indicate improved
smoothness
Base 220 ml/min
3 g/m2 samples 170 ml/min
6 q/m2 samples 140 ml/min
b) Contact Angle
Base 118
Mix 1, both samples 117
Mix 2, both samples 116
Mix 3, both samples 111
These are all very good values of above 110 and, it may be
noted,~do not~vary wlth the coatlng welght.
c) Cobb
Lower~Cobb values (of water uptake) represent improvement.
Base ~ ; 19.0 g/m2/min
Other samples 15.5 - 17.0 " " `~
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22 1 31 6q57
d ) Whiteness/Briqhtness
A . E 1 r epho
Values calculated using filters 9, 10, 11, the brightness
being given by the filter 11 value.
BriqhtnessLiqhtness a b
Base 87.3 96.96 15.85 -8.81
Coatings 88.5 to 89.1 96.24 16.16to 16.42 -9.29 to -9.83
+ a = redder + b = yel lower
- a = greener - b = bluer.
B. Macbeth IC System.
Results were taken with the U.V. in. Significant
improvement was seen in reflectance at 440 nm.
Sampl e Coat 440 nm L a b
weight
g/m Ref lectance D65 D65 D65
Base ~ - 88.95 ~95.54 -0.05 0.32
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Run 1 3 91.19 95.19 0.24 -0.67
Run 2 6 92.64 95.60 0.39- 0.74
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Run 3 3 91.43 95.31 0.19 -0.65
Run ~4 6 92.14 95.61 0.32 -0.52
Run 5 3 ~ 91.03 95.85 0.20 0.27
'~ Run 6 6 91.30 95.78 0.29 0.11
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23 1316957
e) I G T Pick
Using Spring A (35 Kgf) and medium oil, Mix 1 and Mix 2 show
improvements on the base and Mix 3 approximately equal
values to the base, all satisfactory.
In a printing trial, mix 1, 2 and 3 papers, which had
been CB coated with production black copy formulation with
control samples from normal production CB, were printed on a
Muller-Martini webb offset printing machine using 'Irlam
T11392' (Trade Mark) black ink and a speed of 670 rpm (250
m/mln). The Mix 1, 2 and 3 papers all showed Iow dust, with
good ink density/intensity, very little set off, and IGT
pick very low or not visible.
In an edge padding trial, form sets were made up using
a latex-based adhesive with CB, 2 x CFB, and CF sheets, the
CFB and CF sheets being standard 'Idem' production and the
CB~sheets being either standard 'Idem' production base, for
comparison, or the Mix 1, 2 and 3 papers above. All sets
fanned apart 100%.~ Bonding strengths within sets, on a
subjective 1 to 5 scale ~too weak, ~slightly weak, optimum,
slightly strong, too~strong) were acceptable throughout, the
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CB-CF bond in particular, though a little less strong with
the Mix 1, 2 and 3 papers than with the base, giving no
problem through the presence of the front coating.
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24 1 31 6957
Example 8
In a further multi-part example the formulation below
was made up as before, first as sho~n (Example 8-C) then
with the following changes, substitutions being weight for
weight:-
Example 8-2 Mistron Vapour 3 P (Trade Mark) talc as
pi.gment replacing the kaolin clay
Example 8-5 Solfarex A 55 ~Trade Mark) starch
hydroxyalkyl ether as binder replacing
latex
Example 8-7 Cyclopal A (Trade Mark ) anionic modified
polyurethane as size replacing the
: 'Aquapel'
Example 8-10 CMC coating structure agent omitted
Example 8-11 Procote 400 (Trade Mark) soy protein as
;coating structure agént replaclng the CMC
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1 31 6q 57
Formulation
Example 8-C
Components are given in the order, pigment, binder,
other components, not the order of addition used in mix
preparation.
Material Description % (w/w)
Hydrocarb 70 Calcium carbonate pigment 63.9
Alphatex Calcined kaolln clay pigment 15.0
Dow 620 Styrene butadiene latex binder 18.0
Aquapel 360X Alkyl ketene dimer size 1.2
Finfix 5 Carboxy methyl cellulose coating 1.2
structure agent
Nopcote C104 Calcium stearate lubricant 0.5
Dispex N40Sodium polyacrylate dispersing agent 0.18
Sodium Hydroxide - 0 04
Leucophor LNOptical brightening agent ~ -
Solids = 55%
The formulations were coated onto base paper as ln
Example 1, the machine speed being 400 m/min,~and
measurements made of important properties. The following
table shows the~mix viscosity~ of the coating mix, together
with porosity before and after application of the CB coat,
contact angle~, and Bendtsen roughness.
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Test Results - Example 8
Example Coat Mix Porosity Porosity Contact Roughness
Vlscosity Before CB After CB Angle (Bendtsen)
(cPs) (ml/min) (ml/min) (Degrees
after 2
seconds)
8-C 520 31.5 25.0 77.6 119.0
8-2 505 38.3 13.0 79.0 100.0
8-5 800 25.2 26.0 108.9 125.0
8-7 525 27.3 26.5 79.1 132.0
8-10 195 55.2 60.4 89.8 150.0
8-11 102 25.0 23.0 95.8 146.0
In addition to the above tests edge padding trials
were carried out as before, with bond strengths found normal
or slightly low ~but still within-specification) CB-CFB and
CFB-CF and 100% fan apart. Printing trials, again carried
out as before, gave good results, the ink on this occasion
being B;onsfield Constat Black 308:62 (Trade Mark). Ink
density was good (:slightly light in the absence of the
coatlng structure agent), p:iling was absent, dusting
acceptable throughout ~and in the ;mix with starch ether
binder~exceptionally low.
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Example 9
In a further example a eoat mix was made up as an
Example 8-C but with the Aquapel 360X replaced by 3.6 parts
by weight of 'Fibran 71' (Trade Mark) from National Stareh &
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Chemical Co., which is an alkenyl succlnic anhydride size,
the other components being in relative parts by weight as
shown there, and coated as before. A satisfactory eoating
was given, the measured eontact angle in particular being
:104, well suited to edge padding.
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