U.S. patent application number 11/155411 was filed with the patent office on 2005-11-10 for paper products and method of making.
Invention is credited to Dougherty, Michael J., Neogi, Amar N., Park, David W..
Application Number | 20050247421 11/155411 |
Document ID | / |
Family ID | 34556644 |
Filed Date | 2005-11-10 |
United States Patent
Application |
20050247421 |
Kind Code |
A1 |
Dougherty, Michael J. ; et
al. |
November 10, 2005 |
Paper products and method of making
Abstract
A method for making coated or uncoated paper that has small
sized calcium carbonate on its surface. The calcium carbonate is
placed on the paper web at the size press, by a spray or at a
coating operation. The calcium carbonate can have a maximum mean
average size of 200 nm. Another embodiment has a maximum mean
average size of 100 nm. Another embodiment has a maximum mean
average size of 50 nm. Different weight levels may be place on the
paper.
Inventors: |
Dougherty, Michael J.; (Roy,
WA) ; Neogi, Amar N.; (Kenmore, WA) ; Park,
David W.; (Puyallup, WA) |
Correspondence
Address: |
WEYERHAEUSER COMPANY
INTELLECTUAL PROPERTY DEPT., CH 1J27
P.O. BOX 9777
FEDERAL WAY
WA
98063
US
|
Family ID: |
34556644 |
Appl. No.: |
11/155411 |
Filed: |
June 17, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11155411 |
Jun 17, 2005 |
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10823950 |
Apr 13, 2004 |
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10823950 |
Apr 13, 2004 |
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10744926 |
Dec 22, 2003 |
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10823950 |
Apr 13, 2004 |
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10744861 |
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Current U.S.
Class: |
162/181.2 ;
162/135 |
Current CPC
Class: |
D21H 23/28 20130101;
D21H 23/50 20130101; D21H 19/385 20130101; D21H 21/52 20130101 |
Class at
Publication: |
162/181.2 ;
162/135 |
International
Class: |
D21H 023/22; D21H
017/66; D21H 017/67 |
Claims
What is claimed is:
1. A method of forming paper comprising: forming a wet web of
cellulosic fibers; removing water from said web; drying said web;
placing calcium carbonate on said web; said calcium carbonate
having a maximum mean average size of 200 nm.
2. The method of claim 1 in which said calcium carbonate is placed
on said web by a size press and thereafter performing said drying
step.
3. The method of claim 1 in which said calcium carbonate is placed
on the web by a spray and thereafter performing said drying
step.
4. The method of claim 1 in which said drying step is performed and
thereafter said calcium carbonate is placed on the web by a coating
apparatus.
5. The method of claim 1 in which said calcium carbonate is applied
in the amount of 0.1 to 300 pounds per ton of base paper.
6. The method of claim 5 in which said calcium carbonate is applied
in the amount of 5 to 150 pounds per ton of base paper.
7. The method of claim 1 in which said calcium carbonate has a
maximum mean average size of 100 nm.
8. The method of claim 7 in which said calcium carbonate is placed
on said web by a size press and thereafter performing said drying
step.
9. The method of claim 7 in which said calcium carbonate is placed
on the web by a spray and thereafter performing said drying
step.
10. The method of claim 7 in which said drying step is performed
and thereafter said calcium carbonate is placed on the web by a
coating apparatus.
11. The method of claim 7 in which said calcium carbonate is
applied in the amount of 0.1 to 300 pounds per ton of base
paper.
12. The method of claim 11 in which said calcium carbonate is
applied in the amount of 5 to 150 pounds per ton of base paper.
13. The method of claim 1 in which said calcium carbonate has a
maximum mean average size of 50 nm.
14. The method of claim 13 in which said calcium carbonate is
placed on said web by a size press and thereafter performing said
drying step.
15. The method of claim 13 in which said calcium carbonate is
placed on the web by a spray and thereafter performing said drying
step.
16. The method of claim 13 in which said drying step is performed
and thereafter said calcium carbonate is placed on the web by a
coating apparatus.
17. The method of claim 13 in which said calcium carbonate is
applied in the amount of 0.1 to 300 pounds per ton of base
paper.
18. The method of claim 17 in which said calcium carbonate is
applied in the amount of 5 to 150 pounds per ton of base paper.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of patent
application Ser. No. 10/823,950, filed Apr. 13, 2004, which is a
continuation-in-part of patent applications Ser. Nos. 10/744,926
and 10/744,861 both filed Dec. 22, 2003, and now abandoned.
FIELD
[0002] The present invention is directed to printing paper, and to
compositions and methods for making it.
BACKGROUND
[0003] Hardwood and softwood wood pulp fibers are used in the
manufacture of printing paper and newsprint. These fibers are
produced in a chemical pulping process, either sulfate or sulfite,
or in a mechanical pulping process. Mechanical processes would
include thermomechanical and chemithermomechanical. To form the
printing paper or newsprint, these hardwood or softwood wood pulp
fibers and wet end chemicals are mixed with water in the headbox of
the paper machine to form a suspension of fibers and chemicals. The
wet end chemicals may include fillers such as calcium carbonate and
clay. Both of these chemical would have a mean average diameter of
one micron or more. Other wet end chemicals would be internal
sizes, opacifiers, brighteners, and dyes.
[0004] The suspension of fibers and chemicals flow from the headbox
onto a wire. The water is removed from the fibers and chemicals by
both gravity and vacuum to form a wet web of pulp fibers into which
the chemicals are incorporated. The chemicals are throughout the
sheet. The sheet may be pressed and/or dried to remove more
water.
[0005] Starch, optical brightener additives and surface size may be
placed on the surface of the sheet in a surface sizing step at the
size press The materials that can be placed on the web at the size
press must have a viscosity which allows the transfer of the
material onto the web. Some of the materials may enter into the web
if the pressure of the nip at the press is great enough.
[0006] Thereafter the web of fiber, wet end chemicals and other
materials is dried by heat and calendered and rolled into rolls.
The resulting product is referred to as an uncoated paper sheet or
web.
[0007] The uncoated sheet is coated in another application of one
or more coating layers placed on the sheet in an off-line coating
operation. The uncoated sheet passes through a second coating
station and a second drying station. This paper sheet or web is
referred to as a coated paper sheet or web.
[0008] Uncoated or coated printing paper has a basis weight of from
16 to 500 grams per square meter of paper. Although the higher
weights are normally denoted as paperboard or linerboard, the term
"paper" will be used throughout the application to denote paper,
paperboard or linerboard within this weight range.
[0009] The paper may be printed with either aqueous inks or thermal
or toner inks. With either ink there is a concern about gloss
variation and print variation of the ink, and the density of the
ink on the paper. It is desired that the printing ink be evenly
coated and have an even gloss. It is also desired that each of the
different colored inks have an even density. It is also desired
that the thermal toner adhere to the paper and not be easily
removed.
[0010] In offset printing, ink from an ink roll is transferred to a
printing plate. The printing plate has been treated so that ink is
transferred to the plate in the printing regions of the plate and
not transferred to the plate in the unprinted regions of the plate.
The ink is transferred from the plate to a printing blanket which
in turn transfers the ink to the paper. During the process of
transferring ink from the blanket to the paper, fibers from the
paper may attach and transfer to the blanket. This is called
Tinting or picking. This is a problem because there is an unprinted
section or void in the printed images following the transfer of the
fiber to the blanket because no ink is transferred where the fiber
is attached to the blanket. The standard solution to the void
problem is to stop the printing press at intervals during the press
run and clean the blanket to remove the fibers. Many size press
formulations have been tried to prevent Tinting or picking. These
formulations have provided limited improvement.
SUMMARY
[0011] In one embodiment the calcium carbonate has a mean average
size of 200 nanometers (nm) or less. In another embodiment the
calcium carbonate has a mean average size of 100 nm or less. In
another embodiment the calcium carbonate has a mean average size of
15 to 50 nm.
[0012] Small sized calcium carbonate may be in several physical
forms. These are particles, rods, needles and flakes. The particles
have the mean average size across the particle noted above. The
rods and needles have a a diameter in the same size ranges as the
mean average size of the particle. The rod has a length of 1 to 2
microns and the needle has a length of 1 to 3 microns. The flakes
have a thickness in the same size ranges as the mean average size
of the particle. The length or width of the flake is in the range
of 1 to 5 microns. For the purposes of this application, the term
"mean average size" means the size across the particle, the
diameter of the rod or needle and the thickness of the flake.
[0013] In one embodiment the small sized calcium carbonate can be
placed on the web in amounts ranging from 0.1 to 300 pounds per ton
of base paper. In another embodiment the small sized calcium
carbonate can be placed on the web in amounts ranging from 5 to 150
pounds per ton of base paper. In another embodiment the small sized
calcium carbonate would be placed on the web in amounts ranging
from 15 to 80 pounds per ton of base paper. These weights would be
divided between the two sides of paper. If the small sized calcium
carbonate is applied to only one side of the sheet then the weights
would be from 2.5 to 75 pounds per ton of base paper, or 7.5 to 40
pounds per ton of base paper, or up to 150 pound per ton of base
paper.
[0014] In one embodiment of the invention the small sized calcium
carbonate is applied at the size press or by a spray head before
the dryer.
[0015] In another embodiment of the invention the small sized
calcium carbonate is applied on an off-line coater.
[0016] In one embodiment the small sized calcium carbonate may be
applied with a binder such as starch, modified starch or synthetic
polymers or copolymers.
[0017] The attributes of the paper will depend on the use to which
the paper is put.
[0018] In one embodiment of the invention a printing paper sheet or
web having a small diameter calcium carbonate applied to its
surface will have less Tinting or picking than a sheet that does
not have such calcium carbonate on its surface. This will allow
more impressions to be made before the press is stopped and the
printing plate cleaned and reduces the cost and time of
printing.
[0019] In another embodiment of the invention a printing paper
sheet or web having a small diameter calcium carbonate applied to
its surface will be stiffer than a sheet of the same weight that
does not have such calcium carbonate on its surface. This will
allow a sheet to be used where paper stiffness is required for post
printing and conversion operations.
[0020] In one embodiment of the invention a printing paper sheet or
web having a small diameter calcium carbonate applied to its
surface will better toner adhesion than a sheet that does not have
such calcium carbonate on its surface. The print will not be
removed during use of the paper.
[0021] In another embodiment of the invention a printing paper
sheet or web having a small diameter calcium carbonate applied to
its surface will have less print variance than a sheet that does
not have such calcium carbonate on its surface. The print will look
better.
[0022] In another embodiment of the invention a printing paper
sheet or web having a small diameter calcium carbonate applied to
its surface will have less gloss variance than a sheet that does
not have such calcium carbonate on its surface. The print will look
better.
[0023] In another embodiment of the invention a printing paper
sheet or web having a small diameter calcium carbonate applied to
its surface will have better color density than a sheet that does
not have such calcium carbonate on its surface. The print will look
better.
[0024] In another embodiment of the invention an uncoated paper
sheet or web having a small diameter calcium carbonate applied to
its surface will have many of the attributes of a coated paper web
or sheet that does not have such calcium carbonate on its surface.
This will provide a less costly paper.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a schematic diagram of a paper machine for
uncoated paper.
[0026] FIG. 2 is a schematic diagram of a paper machine for coated
paper.
[0027] FIG. 3 is a schematic cross sectional diagram of apparatus
for obtaining a digital photograph for running the gloss variance
and print variance tests.
[0028] FIG. 4 is a schematic diagram of apparatus for obtaining a
digital image used for the gloss variance values.
DETAILED DESCRIPTION
[0029] In one embodiment calcium carbonate having a mean average
size of 200 nm (0.2 .mu.m) or less is applied to the surface of a
paper product. In another embodiment calcium carbonate having a
mean average size across of 100 nm (0.1 .mu.m) or less is applied
to the surface of a paper product. In another embodiment the
calcium carbonate having a mean average size across the particle of
15 nm (0.015 .mu.m) to 50 nm (0.05 .mu.m) is applied to the surface
of a paper product. Throughout this application the term "small
sized calcium carbonate" is used. The term refers to the above
embodiments of calcium carbonate.
[0030] Small sized calcium carbonate may be in several physical
forms. These are particles, rods, needles and flakes. The particles
have the mean average size across the particle noted above. The
rods and needles have a a diameter in the same size ranges as the
mean average size of the particle. The rod has a length of 1 to 2
microns and the needle has a length of 1 to 3 microns. The flakes
have a thickness in the same size ranges as the mean average size
of the particle. The length or width of the flake is in the range
of 1 to 5 microns. For the purposes of this application, the term
"mean average size" means the size across the particle, the
diameter of the rod or needle and the thickness of the flake.
[0031] In one embodiment the small sized calcium carbonate is
applied at the size press of a paper machine. It has been found
that small sized calcium carbonate has the appropriate viscosity to
be placed on the paper web at the size press. A portion of the
small sized calcium carbonate may enter the web because of the nip
pressure of the size press but much will remain on the surface of
the web.
[0032] In another embodiment the small sized calcium carbonate can
be sprayed on the web prior to the dryer. The majority of this
material will remain on the surface of the web.
[0033] In one embodiment the small sized calcium carbonate can be
placed on the web in amounts ranging from 0.1 to 300 pounds per ton
of base paper. In another embodiment the small sized calcium
carbonate can be placed on the web in amounts ranging from 5 to 150
pounds per ton of base paper. In another embodiment the small sized
calcium carbonate would be placed on the web in amounts ranging
from 15 to 80 pounds per ton of base paper. These weights would be
divided between the two sides of paper. If the small sized calcium
carbonate is applied to only one side of the sheet then the weights
would be from 2.5 to 75 pounds per ton of base paper, or 7.5 to 40
pounds per ton of base paper, or up to 150 pound per ton of base
paper.
[0034] In one embodiment the small sized calcium carbonate may be
applied with a binder such as starch, modified starch or synthetic
polymers or copolymers.
[0035] FIG. 1 is a schematic drawing of a paper machine. Wood pulp
fiber furnish and wet end chemicals are mixed with water in a
headbox 10 to form a slurry. The slurry exits the headbox through a
slice 12 onto a wire 14. The water in the slurry drains from the
wire. A vacuum chest 16 is also used to draw water from the slurry
to form a wet paper web. The web is carried through press rolls 18
and a drier 20 that remove additional water.
[0036] Additional size press chemicals or materials are placed on
the wet paper web at the size press 22. The size press may be a
horizontal type with the rolls horizontally aligned, or a vertical
type with the rolls vertically aligned. The materials may be placed
on the web from the rolls or from a puddle between the rolls. The
web may, in some instances, be coated with material by the spraying
apparatus 24. The materials described in the various embodiments in
the present application would also be applied at the size press 22
or the spraying apparatus 24.
[0037] The paper web then passes through a drying section 26. The
drying is usually done by steam heated drier cans through which the
paper web is threaded. The paper is then calendered by calender
rolls 28 and rolled into paper rolls at the winder 30. The
resulting product is known as uncoated paper.
[0038] In the present invention the small sized calcium carbonate
is added at the size press 22 or at the spraying apparatus 24. The
resultant paper has better attributes than paper that is not coated
with small sized calcium carbonate.
[0039] The small sized calcium carbonate, however, may also be
placed on the paper web or sheet at the coating station of a
machine for making coated paper.
[0040] FIG. 2 is a schematic diagram of a paper machine for making
coated paper. The reference numerals in FIGS. 1 and 2 are the same
for the same elements. In FIG. 2 there is an additional off machine
coating operation. The web goes from the dryer 26 to the coating
operation and passes through a coating station 32. Coating station
32 is shown as rolls but any type of coating equipment may be used.
The web may then pass through a dryer 34 and calender rolls 36. In
some installations there are calender rolls before and after the
coating station 32. The paper web is then wound into rolls 38.
[0041] The small sized calcium carbonate may be placed on the web
at the coating station 32 instead of size press 22 or spray head
24. In some instances the small sized calcium carbonate may be
placed on the web at the size press 22 or spray head 24 and the
coating station 32.
[0042] In one embodiment the application of small sized calcium
carbonate reduces the voids that are found in the print surface.
The following test is used to determine this.
[0043] Void Count Test
[0044] The void count test was run using a Diddie offset web press.
A printing plate having a solid printing area of approximately 12.6
in.sup.2 is used. It has a 0.9 ink density and a uses a 40% screen.
A void is an area which should be printed but is not printed. It is
caused by fibers coming off the sheet surface and depositing on the
printing plate or other printing surface and blocking further
printing where it is deposited. This is called picking or
linting.
[0045] A paper roll containing the equivalent of at least 6000
81/2".times.11" paper sheets are run through the press using the
same printing plate. The number of voids in the 12.6 in.sup.2 solid
printed area of the sheet are counted on the 1000.sup.th,
2000.sup.th, 4000.sup.th 6000.sup.th and 8000.sup.th sheet.
[0046] In another embodiment the application of small sized calcium
carbonate increases the stiffness of paper. The following test is
used to determine this.
[0047] Cross Direction Gurley Stiffness
[0048] Cross direction Gurley stiffness of a paper sheet is
determined using Tappi test method T-543 om-94. The bending
resistance of paper is determined by measuring the force required
to bend a sample under controlled conditions.
[0049] Toner Adhesion Test. This test method is used to determine
the toner adhesion of papers imaged on a Xerographic copy machine,
folded and creased. A computerized image analysis is made of the
crease in the solid image area. An average pixel width is
calculated and converted to width in mm.
[0050] The equipment required for the test is a roller of specific
weight and dimensions, cotton pads and a test sled.
[0051] The paper to be tested is conditioned at 50% relative
humidity.
[0052] The copy machine is warmed up by running one ream of copy
paper through the machine. 5% text is used.
[0053] A 5 block test pattern is used for the test. There is a pair
of blocks at the top and a pair of blocks at the bottom of the test
sheet. Each of the blocks is 3.8 mm.times.3.8 mm. There is a single
block at the center of the test sheet. This block is 3.8
mm.times.7.5 mm. The copy machine is tested by printing 50 sheets
with the test pattern and checking the density of the ink using a
Gretag densitometer. The ink density should be between 1.50 and
1.54. If the density is in the target range of 1.50 to 1.54 then
the samples can be printed. The samples should be in a 50% relative
humidity environment during printing. The ink density should be
monitored. If the density falls below 1.50 then printing of the
sample sheets should be stopped. Additional copy paper should be
printed until the density is above 1.50 and then printing of
samples can be resumed.
[0054] The samples should be reconditioned at 50% relative humidity
for 24 hours after printing.
[0055] A sample is folded in the machine direction so that a crease
line will fall in the middle of the sample. The sample is gently
pressed in the folded area without creasing the sample. The
weighted roller is rolled gently over the folded area to create a
crease. Use only the weight of the roller and a uniform and
continuous movement in one direction to form the crease.
[0056] The paper is unfolded and a cotton pad is placed on the
crease at one end of the crease. A sled having a weight of 305
grams is placed on top of the pad and both are pulled the entire
length of the crease in one continuous motion. The other side of
the pad is placed on the crease at the other end of the crease. The
sled is placed on the pad and both are pulled along the crease I in
the opposite direction.
[0057] A computerized image analysis is made of the crease in the
solid image area. An average pixel width is calculated and
converted to width in mm.
[0058] In the following examples, the small sized calcium carbonate
was supplied by NanoMaterials Technology Pte Ltd (NMT). It is a
precipitated calcium carbonate made using the high gravity reactive
precipitation (HGRP) technology platform.
EXAMPLE 1
[0059] In this example, calcium carbonate having a mean size of 40
nm was applied to the surface of the paper with the use of starch
(Penford Gum-290). Formulations were made using 80-100 pounds
ethylated starch (Penford Gum-290) per ton of paper and 0.5-180
pounds calcium carbonate per ton of paper. The amounts were pounds
per ton based on the total weight of the paper and calcium
carbonate. Two types of calcium carbonate were used. One was a
standard coating grade of calcium carbonate having a mean averages
diameter of 1 micron. The other was a calcium carbonate having a
mean average diameter of 40 nm. The formulations were applied to a
paper substrate using a laboratory two-roll press.
[0060] The substrate was a 70 pound per 3300 square feet paper web
without size press starch and additives. The paper was prepared
from a furnish including a blend of hardwood and softwood fibers
and standard papermaking additives such as wet end starch, sizing,
calcium carbonate, optical brighteners and retention aids.
EXAMPLE 2
[0061] The papers from Example 1 were tested for Gurley stiffness
using TAPPI Method T543-om94. The results are summarized in Table
1.
1TABLE 1 ethylated 1 micron 40 nm Cross- starch starch CaCO.sub.3
CaCO.sub.3 direction Change lbs/T lbs/T lbs/T lbs/T Gurley Change
over 1 column paper paper paper paper stiffness over A % micron % A
80 119.1 B 80 15 116.9 80 15 139.2 +16.8 +19.1 C 80 40 120.2 80 40
140.6 +18.1 +16.9 D 80 80 124.3 80 80 137.2 +15.2 +10.4 E 80 100
130.2 80 100 176.1 +47.9 +35.3 F 80 150 132.0 80 150 167.7 +40.8
+27
[0062] It can be seen that paper sheets coated with small sized
calcium carbonate had an increase in cross-direction Gurley
stiffness over the control sheet at even at low levels of
application, and increased greatly at higher levels of
application.. It can also be seen that small sized calcium
carbonate had a higher cross-direction stiffness than conventional
coating calcium carbonate at all levels of application.
EXAMPLE 3
[0063] In this example, calcium carbonate (NPCC-112) having a mean
average size of 40 nm was applied to the surface of a paper web
without the use of a binder such as starch, polyvinyl alcohol, or
latex. Typically, a binder is required to attach calcium carbonate
to the paper. The minimum ratio is 1 part binder to 1 part calcium
carbonate.
[0064] The calcium carbonate was applied to the paper at 47 percent
solids in a two-roll laboratory pond size press. The resulting
paper had much of the calcium carbonate on its surface. The amount
of calcium carbonate attached to the paper was at least 250 pounds
per ton of paper.
EXAMPLE 4
[0065] Size press formulations were made using 40 pounds of
ethylated starch (Penford Gum-290) per ton of paper per side. The
formulations were applied to a paper substrate using a 2 roll size
press and a gate roll.
[0066] The substrate was a 35 pound per 3300 square feet paper web
without size press starch and additives. The paper was prepared
from a furnish including a blend of hardwood and softwood fibers,
and standard papermaking additives such as wet end starch, sizing,
standard calcium carbonate, optical brighteners and retention
aids.
EXAMPLE 5
[0067] Size press formulations were made using 80 pounds ethylated
starch (Penford Gum-290) per 3300 square feet of paper per side of
and two weights of calcium carbonate having a mean average size of
40 nm. The calcium carbonate weights were 20 pounds per 3300 square
feet of paper per side and 40 pounds per 3300 square feet of paper
per side. The formulations were applied to a paper substrate using
a 2 roll size press.
[0068] The substrate was a 35 pound per 3300 square feet paper web
without size press starch and additives. The paper was prepared
from a furnish including a blend of hardwood and softwood fibers,
and standard papermaking additives such as wet end starch, sizing,
standard calcium carbonate, optical brighteners and retention
aids.
EXAMPLE 6
[0069] Size press formulations were made using 80 pounds of
ethylated starch (Penford Gum-290) per ton of paper per side. The
formulations were applied to a paper substrate using a 2 roll pond
size press.
[0070] The substrate was a 60 pound per 3300 square feet paper web
without size press starch and additives. The paper was prepared
from a furnish including a blend of hardwood and softwood fibers,
and standard papermaking additives such as wet end starch, sizing,
standard calcium carbonate, optical brighteners and retention
aids.
EXAMPLE 7
[0071] Size press formulations were made using 80 pounds of
ethylated starch (Penford Gum-290) per ton of paper per side and
various weights of calcium carbonate having a mean average size of
40 nm. The calcium carbonate weights were 7.5 pounds per ton of
paper per side, 20 pounds per ton of paper per side, and 40 pounds
per ton of paper per side. The formulations were applied to a paper
substrate using a laboratory 2 roll pond size press.
[0072] The substrate was a 60 pound per 3300 square feet paper web
without size press starch and additives. The paper was prepared
from a furnish including a blend of hardwood and softwood fibers,
and standard papermaking additives such as wet end starch, sizing,
standard calcium carbonate, optical brighteners and retention
aids.
EXAMPLE 8
[0073] The papers from example 4, 5, 6, and 7 were tested for void
count and cross-machine Gurley stiffness. The results are
summarized in Table 2.
2 TABLE 2 Cross small direction sized Gurley paper starch
CaCO.sub.3 Void Void Stiffness Lbs lbs/T lbs/T 6K 8K mg 35 80 46.5
35 80 40 4.0 35 80 80 7.0 60 80 47.0 127 60 80 15 15.0 138 60 80 40
7.0 10 165 60 80 80 12.0 13 172
[0074] It can be seen that void count was reduced with the
application of small sized calcium carbonate. It can also be seen
that cross machine Gurley stiffness increased.
EXAMPLE 9
[0075] In this example, calcium carbonate having a mean size of 40
nm was applied to the surface of the paper with the use of starch
(Penford Gum-290). Formulations were made using 80 pounds ethylated
starch (Penford Gum-290) per ton of paper and 0, 15, 40 or 80
pounds small sized calcium carbonate per ton of paper. The amounts
were pounds per ton based on the total weight of the paper and
calcium carbonate. The starch and calcium carbonate were evenly
divided on both sides of the paper. The formulations were applied
to a paper substrate using a laboratory two-roll press.
[0076] The substrate was a 80 pound per 3300 square feet paper web
without size press starch and additives. The paper was prepared
from a furnish including a blend of hardwood and softwood fibers
and standard papermaking additives such as wet end starch, sizing,
calcium carbonate, optical brighteners and retention aids.
EXAMPLE 10
[0077] The samples from Example 9 were printed and tested using the
toner adhesion test. The results are given in Table 3.
3 TABLE 3 Toner Adhesion Crack paper starch CaCO.sub.3 Width Lbs
lbs/T lbs/T mm 60 80 -- 0.521 60 80 15 0.280 60 80 40 0.247 60 80
80 0.248
EXAMPLE 11
[0078] FIG. 3 shows the cross section of an apparatus used to
obtain prints which are used for the print variance values. Print
variance is also known as print mottle. The device 20 creates
diffuse illumination using an integrating sphere 22 onto which
lights 24 shine. The diffuse light shines onto a flat surface 26
holding the sample 28 centrally of the sphere 22. A digital camera
30 is aligned perpendicular to the sample surface to capture a
reflected light print image. A Kodak Megaplus digital area camera
with a 52 mm lens was used in this example. The field of view for
this evaluation is 51.2.times.51.2 mm. The full digital image is
captured in a single frame as an area image. The light level is set
by setting the camera F-stop and adjusting the shutter speed until
the average pixel intensity is approximately 127.
[0079] FIG. 4 shows an apparatus 40 used to obtain digital images
which are used for the gloss variance values. Gloss variance is
also known as gloss mottle. A sample 42 is placed onto a flat
surface 44. The apparatus creates directional illumination using a
light 46 oriented at an angle to the surface of sample 42. The
directional light shines onto a flat surface of the sample 42. A
digital camera 48 is on the side of the sample 42 opposite the
light 46 and aligned with the light 46. The camera 48 captures the
reflected light gloss image from the sample surface. The camera 48
is oriented at the same angle as light 46 so that the illumination
and detection angles are equal. As an example, both the light 46
and camera 48 would be oriented at a 60.degree. angle to the sample
surface. An EG&G Reticon digital line camera with a 105 mm lens
was used in this example. The field of view for this evaluation was
51.2.times.51.2 mm. The sample is moved linearly under convergence
of the light beam and camera field so that the camera 48 captures
individual lines which are reconstructed into an area image. The
light level is set by setting the camera f-stop and adjusting the
scanning speed until the average pixel intensity is approximately
120.
[0080] The images of the print and gloss samples are then used to
determine print mottle and gloss mottle, respectively. The pixel
intensity for each of the pixels on the photo is read and stored.
If necessary, an 8.times.8 order polynomial regression is applied
to the print images and a 1.times.4 polynomial regression is
applied to the gloss images. The mean intensity for the entire
regressed image is calculated. The mean intensity is subtracted
from the individual regressed data to provide intensity difference
image data. The intensity difference image data is multiplied by
the pixel resolution in millimeters to scale the variance results.
The autocovariance function of the intensity difference image data
is calculated. The circular footprint Hanning window extending to
the Nyquist frequency is also calculated. A windowed autocovariance
function is calculated by multiplying the autocovariance function
by the Hanning window extending to the Nyquist frequency. The full
power density matrix is extimated from the windowed autocovariance
function using a Fast Fourier Transform.
[0081] The image power is calculated by summing up the elements of
the Fast Fourier Transform array. The image power is given in Table
4. The variance was better when small sized calcium carbonate was
used.
4TABLE 4 Gloss Print Var. Var. paper starch CaCO.sub.3 Image Image
Lbs lbs/T lbs/T Power Power. 60 80 -- 4.17 0.190 60 80 15 3.40
0.135 60 80 40 3.08 0.150 60 80 80 2.72 0.160
EXAMPLE 11
[0082] Paper samples was printed with black, cyan, magenta and
yellow using an HP 990C printer. The density of the colors was
evaluated using a Gretag densitometer. The results are shown in
Table 5. Density increased with increasing amounts of small sized
calcium carbonate.
5TABLE 5 HP HP HP HP 990C 990C 990C 990C Gretag Gretag Gretag
Gretag paper starch CaCO.sub.3 Densi. Densi. Densi. Densi. Lbs
lbs/T lbs/T Black Cyan Magenta Yellow 60 80 -- 1.04 1.01 0.89 0.75
60 80 15 1.42 1.02 0.97 0.76 60 80 40 1.35 1.06 1.01 0.78 60 80 80
1.36 1.09 1.05 0.81
[0083] Those skilled in the art will note that various changes may
be made in the embodiments described herein without departing from
the spirit and scope of the present invention.
* * * * *