U.S. patent application number 10/744856 was filed with the patent office on 2005-06-23 for paper product and method of making field.
This patent application is currently assigned to Weyerhaeuser Company. Invention is credited to Park, David W., West, Hugh.
Application Number | 20050133182 10/744856 |
Document ID | / |
Family ID | 34552858 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050133182 |
Kind Code |
A1 |
Park, David W. ; et
al. |
June 23, 2005 |
Paper product and method of making field
Abstract
Paper having improved curl and cockle properties for water
based, ink jet printing applications and a method of producing
them. The paper contains at least 50 pounds per ton of a material
that is water soluble, that can be highly concentrated during
application, has low viscosity and low hygroscopicity. The paper
has a maximum Cockle Value of 0.25. Certain of the materials also
provide water fastness.
Inventors: |
Park, David W.; (Puyallup,
WA) ; West, Hugh; (Seattle, WA) |
Correspondence
Address: |
WEYERHAEUSER COMPANY
INTELLECTUAL PROPERTY DEPT., CH 1J27
P.O. BOX 9777
FEDERAL WAY
WA
98063
US
|
Assignee: |
Weyerhaeuser Company
|
Family ID: |
34552858 |
Appl. No.: |
10/744856 |
Filed: |
December 22, 2003 |
Current U.S.
Class: |
162/158 ;
162/175 |
Current CPC
Class: |
D21H 17/24 20130101;
D21H 23/24 20130101; D21H 17/15 20130101; D21H 17/07 20130101 |
Class at
Publication: |
162/158 ;
162/175 |
International
Class: |
D21H 017/24; D21H
017/28 |
Claims
What is claimed is:
1. A method of manufacturing uncoated paper comprising forming a
wet web of cellulosic fibers, applying to the web at least 50
pounds of a material per ton of paper, said material being water
soluble, able to be highly concentrated during application, having
low viscosity at the high concentrations and having low
hygroscopicity, drying the web to provide an uncoated paper having
a maximum Cockle Value of 0.25.
2. The method of claim 1 wherein said material is applied to the
web prior to it being dried by heat.
3. The method of claim 1 wherein said material is a
disaccharide.
4. The method of claim 3 wherein the disaccharide is applied to the
web in a solution having 20 to 50% disaccharide by weight.
5. The method of claim 3 wherein the disaccharide is sucrose.
6. The method of claim 3 wherein the disaccharide is maltose.
7. The method of claim 1 wherein said material is a
monosaccharide.
8. The method of claim 1 wherein the monosaccharide is applied to
the web in a solution having 20 to 50% monosaccharide by
weight.
9. The method of claim 8 wherein the monosaccharide is glucose.
10. The method of claim 8 wherein the monosaccharide is
mannose.
11. The method of claim 1 wherein the material is corn syrup.
12. The method of claim 1 wherein the material is urea.
13. The method of claim 12 wherein the urea is applied to the web
in a solution having 20 to 50% urea by weight.
14. The method of claim 1 wherein the material is a salt of citric
acid.
15. The method of claim 14 wherein the salt of citric acid is
applied to the web in a solution having 20 to 50% salt of citric
acid by weight.
16. The method of claim 1 wherein the material is applied to the
web in a solution having 20 to 50% material by weight.
17. A method of claim 1 wherein said material is applied in an
amount of 50 to 300 pounds per ton of paper.
18. The method of claim 17 wherein said material is applied in an
amount of 75 to 250 pounds per ton of paper.
19. A method of manufacturing uncoated paper comprising forming a
wet web of cellulosic fibers, applying to the web at least 50
pounds of a disaccharide per ton of paper, drying the web to
provide an uncoated paper having a maximum Cockle Value of
0.25.
20. The method of claim 19 wherein said material is applied to the
web prior to it being dried by heat.
21. The method of claim 19 wherein the disaccharide is applied to
the web in a solution having 20 to 50% disaccharide by weight.
22. The method of claim 19 wherein the disaccharide is sucrose.
23. The method of claim 19 wherein the disaccharide is maltose.
24. A method of manufacturing uncoated paper comprising forming a
wet web of cellulosic fibers, applying to the web at least 50
pounds of a monosaccharide per ton of paper, drying the web to
provide an uncoated paper having a maximum Cockle Value of
0.25.
25. The method of claim 24 wherein said monosaccharide is applied
to the web prior to it being dried by heat.
26. The method of claim 24 wherein the monosaccharide is applied to
the web in a solution having 20 to 50% monosaccharide by
weight.
27. The method of claim 26 wherein the monosaccharide is
glucose.
28. The method of claim 26 wherein the monosaccharide is
mannose.
29. A method of manufacturing uncoated paper comprising forming a
wet web of cellulosic fibers, applying to the web at least 50
pounds of a corn syrup per ton of paper, drying the web to provide
an uncoated paper having a maximum Cockle Value of 0.25.
30. A method of manufacturing uncoated paper comprising forming a
wet web of cellulosic fibers, applying to the web at least 50
pounds of a urea per ton of paper, drying the web to provide an
uncoated paper having a maximum Cockle Value of 0.25.
31. A method of manufacturing uncoated paper comprising forming a
wet web of cellulosic fibers, applying to the web at least 50
pounds of a salt of citric acid per ton of paper, drying the web to
provide an uncoated paper having a maximum Cockle Value of
0.25.
32. A method of manufacturing uncoated paper comprising forming a
wet web of cellulosic fibers, applying to the web at least 50
pounds of a salt of citric acid per ton of paper, drying the web to
provide an uncoated paper having water fastness.
Description
FIELD
[0001] The present invention is directed to paper having reduced
cockle and water induced curl, and the method of making this
paper.
BACKGROUND
[0002] 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 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. 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 dried to remove more water.
[0003] Starch, optical brightener additives and surface size may be
placed on surface of the sheet in a surface sizing step at the size
press. Some of the materials may enter into the web if the pressure
of the nip at the press is great enough.
[0004] Thereafter the web of fiber, wet end chemicals and other
materials is dried by heat, calendered and rolled into rolls. The
resulting product is referred to as an uncoated or lightly coated
paper sheet or web.
[0005] The uncoated sheet may be 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 coating
station and a second drying station. It may pass through a second
calendering operation. The resulting product is referred to as a
coated paper sheet or web.
[0006] Uncoated or coated printing paper has a basis weight of from
16 to 180 pounds per 3300 square feet.
[0007] The application of high speed, variable printing is
experiencing tremendous growth in the printing industry, displacing
conventional offset printing for many applications. A digital
printing technology such as web-fed ink jet printing presents new
and different challenges for the paper maker as the optimum surface
physics and chemistry of paper for these printers are very
different than those required for conventional offset inks.
[0008] High speed, ink jet printing is exceptionally challenging
because it employs aqueous inks and a great deal of water is placed
on the paper surface during the printing process. In the process,
these water based inks may be applied at high coverage at paper
speeds of 500-1,000 ft. per minute. It is difficult to completely
dry the paper before the paper leaves the printer. If uncoated
paper is used, the water from the ink penetrates the sheet and
disrupts the bonding between the paper fibers. This creates a
deformation of the paper surface, which results in unacceptable
curling, cockling, or puckering of the printed paper.
[0009] Standard desk top ink jet printers are increasing in speed
and some of the same challenges are found when printing with these
printers because of the water placed on the paper and the
difficulty of completely drying the paper before it leaves the
printer.
[0010] Wide printers have similar challenges because of the amount
of ink and water placed on the paper.
[0011] Because of these factors, special papers are used when the
print job requires high levels of ink coverage. These special
papers are coated with water-absorbent silica or swellable gel
materials such as polyvinyl pyrilodone, or combinations of these
materials. Typically, these materials are applied by an off-line
coating operation. The price of these materials and the off-line
application significantly increases the cost of paper for these
applications.
[0012] The optical density of the printed image is also of primary
concern for many print jobs as high levels of ink are required to
provide vivid, robust colors. This is known as high optical
density. Uncoated papers are limited in the amount of ink they can
tolerate because of their tendency to curl and cockle. Thus more
expensive coated papers are generally required when high optical
densities are needed.
SUMMARY
[0013] The present invention is directed to an uncoated paper
usable with ink having a water content and which has a maximum
Cockle Value of 0.25. The Cockle Value is used to determine the
amount of cockle or water induced curl in the paper. An embodiment
of the invention is an uncoated paper having a paper basis weight
of 16 to 60 pounds per 3300 square feet and a maximum Cockle Value
of 0.25.
[0014] An embodiment of the invention is a paper that has been
treated with at least 50 pounds per ton of paper with a material
that is capable of being added at the size press, blade coater or
by a spray before the heated drying section. The material is water
soluble, is highly concentrated during application, has low
viscosity and low hygroscopicity. Water soluble means a compound
that is soluble to concentrations of 20-50% of the total weight of
the solution at room temperature or at temperatures of 50.degree.
C. or less. Highly concentrated means the weight or concentration
of the material is 20-50% of the weight of the solution. Low
viscosity means viscosities of 200 centipoises (cps) or less when
the weight or concentration of the material is 20-50% of the weight
of the solution. Low hygroscopicity means the dried material will
take up only a small amount of water in high humidity conditions.
Another embodiment is a paper that has been treated with at least
75 pounds of the material per ton of paper. Another embodiment is a
printing paper that has been treated with up to 250 pounds of the
material per ton of paper. Another embodiment is a paper that has
been treated with up to 300 pounds of the material per ton of
paper.
[0015] In one embodiment of the invention the material is a
disaccharide. In another embodiment of the invention the material
is a monosaccharide. In another embodiment of the invention the
material is a urea. In another embodiment of the invention the
material is a mono-citrate or di-citrate.
[0016] In another embodiment of the invention the material is
combined with starch, latex, polyvinyl alcohol, styrene acrylic
acid or an ester and the low viscosity of the additive can be
maintained.
BRIEF SUMMARY OF THE DRAWINGS
[0017] FIGS. 1-2 are digital Images of untreated commercial paper
using LANDCO Low Angle Light:
[0018] FIGS. 3-4 are digital Images of sucrose treated paper using
LANDCO Low Angle Light:
[0019] FIGS. 5-10 are digital images of treated and untreated pape
from the second side cockle test method.
[0020] FIG. 11 is a graph showing the coefficient of variation of
treated and untreated samples.
[0021] FIG. 12 is a drawing of the work station for carrying out
the second side cockle test method.
[0022] FIG. 13 is a schematic diagram of a paper machine.
DETAILED DESCRIPTION
[0023] The present invention is directed to an uncoated or lightly
coated paper which may be used for printing on ink jet printers and
which has a maximum Cockle Value of 0.25 after such printing. It is
also directed to an uncoated or lightly coated wide printing paper
used with ink jet printers which has a maximum Cockle Value of
0.25.
[0024] A quantitative test has been developed to determine the curl
and cockle of paper. It replaces the subjective test of viewing the
paper to determine whether there was curl and cockle and the amount
of curl and cockle. This prior subjective test also determined
whether a sheet of paper had sufficient treatment. The quantitative
test is the second side cockle test method.
[0025] The second side cockle test method is used to evaluate the
amount of cockle that an inkjet print, at an ink application level
of 5.9 grams/square meter, produces in the unprinted or second side
of a paper printed with a block print. The present test used a
Scitex Test Cockle Form Print. The unprinted side of the inkjet
print is illuminated using low angle (15.degree.) lighting. A
digital image is made of the cockled area on the unprinted side
associated with a 3.5 by 3.5 inch half-tone printed square on the
printed side of the sample. The image is then evaluated to
determine the amount of second side cockle.
[0026] The apparatus used for the second side cockle test method is
shown in FIG. 12. It includes a test platform 10, a Kodak.RTM.
megaplus 8-bit digital camera 12, and a Dedolight.RTM. light 14.
The camera 12 is mounted above surface 16 of the test platform 10
and at 90.degree. to the surface 16 of the test platform 10. The
camera is aimed directly at the center of the surface 16 of the
platform. The Dedolight light 14 is mounted at an angle of
15.degree. to the surface 16 and also aimed at the center of the
surface 16. Mathworks, Inc. Matlab.RTM. computer software is used
to analyze the images.
[0027] The samples of paper to be tested are printed on one side
with a Scitex Test Cockle Form using an inkjet printer and inkjet
ink. In the following tests a Hewlett Packard ink jet printer
HP560C was used. The ink used was Scitex Ink 2002 and the ink
application level was 5.9 g/square meter. The ink should be a water
based ink. The paper was handled carefully so as not to crease or
wrinkle the paper because creases or wrinkles would be analyzed as
cockle.
[0028] The settings of the camera 12 were adjusted to a pixel
resolution of 100 microns/pixel and an f-stop of F8. The camera
control was on Fixed and the image centering was at 127. The
Dedolight light 14 was adjusted for uniform low angle lighting. All
lighting was from the Delolight light 14. Other room lights were
turned off.
[0029] The paper sample 18 was placed on the surface 16 of the test
stand 10 with the unprinted side of the paper turned to the camera
and facing up. The 3.5 by 3.5 inch cockle area was centered in the
camera field of view with the light aimed at the center of the
cockle area. The camera's exposure was adjusted until the average
image pixel value was 127. The image was collected and saved to a
disk.
[0030] This process was repeated for each sample.
[0031] The images were analyzed using the Mathworks, Inc.
Matlab.RTM. computer software. Version 6, release 13 was used. The
image is read into the program and smoothed with a 5.times.5 median
filter to remove high frequency noise. The mean, standard deviation
and coefficient of variation were calculated for each row and
column. The larger of the maximum row coefficient of variability
and maximum column coefficient of variability is taken as the
sample Cockle Value. The program is evaluating the differences
between the light and dark areas of the image and determining the
variability.
[0032] Cockle Value means the cockle value determined by this
test.
[0033] An embodiment is an uncoated paper that has been treated
with at least 50 pounds per ton of paper with a material that is
water soluble, is highly concentrated during application, has low
viscosity and low hygroscopicity to reduce curl, cockle or other
deformation after printing with high levels of ink jet ink as
compared to uncoated paper. The maximum Cockle Value of the treated
printing paper is 0.25. A ton is defined here as 2000 pounds. Water
soluble means a compound that is soluble to concentrations of
20-50% of the total weight of the solution at room temperature or
at temperatures of 50.degree. C. or less. Highly concentrated means
concentrations of 20-50% of the weight of the solution. Low
viscosity means viscosities of 200 centipoises or less at
concentrations of 20-50% of the weight of the solution. Low
hygroscopicity means the dried material will not take up water in
high humidity conditions.
[0034] In another embodiment of the invention at least 75 pounds of
material per ton of paper is used. In another embodiment of the
invention as much as 300 pounds of the material per ton of paper
may be used. In another embodiment as much as 250 pounds of the
material per ton of paper may be used.
[0035] The material is applied at the size press or the blade
coater. It may be applied using a puddle, gate roll or metered size
press, or a knife or blade coater. In one embodiment the material
may be applied in a solution containing at least 20% by weight of
material. In another embodiment the material may be applied in a
solution containing 20 to 50% by weight of the material.
[0036] In one embodiment of the invention disaccharides may be used
as the material. Disaccharides such as sucrose and maltose can be
used. Any disaccharide having the properties noted above can be
used. Many disaccharides have viscosities below 200 centipoise
(cps.) at concentrations 20 to 50% of the weight of the
solution.
[0037] Another embodiment of the invention may use monosaccharides.
Monosaccharides such as glucose or mannose can be used. Many
monosaccharides have viscosities below 200 centipoise (cps.) at
concentrations 20 to 50% of the weight of the solution.
[0038] A material such as corn syrup may also be used.
[0039] Hygroscopicities and solubilities of certain polyols are
listed in table 1. From this table it can be seen that malitol,
lacitol monohydrate and erythritol have the desired
characteristics.
1TABLE 1 Solubility at 25.degree. C. Degree of hygroscopicity
Polyol g/100 g H.sub.2O % ERH @ 20.degree. C. Mannitol 22 g very
low Malitol 175 g low Lacitol monohydrate 140 g low Anhydrous
isomalt 39 g very low Erythritol 61 g very low sucrose 185 g low
maltose 70 g medium
EXAMPLE 1
[0040] Paper containing sucrose, starch, and surface size:
[0041] The percentages in this example are weight percentages.
[0042] A 60 gm./m.sup.2 unsized paper was used for each of the
samples in this example.
[0043] A control sample of paper was coated in a laboratory size
press with ethylated starch at 12% concentration. Both side of the
paper were coated to a coat weight of 40 pounds of starch per ton
of paper per side. This is typical of most uncoated paper grades
(Formula I).
[0044] One sample of paper was treated in a lab size press with a
solution containing a concentration of 35% sucrose, 5% ethylated
starch and 1% surface size (Hercules IJP). Both side of the paper
were coated to a coat weight of 105 pounds of material per ton of
paper per side (Formula II). The amount of sucrose was about 90
pounds per ton of paper per side.
[0045] A second sample was prepared with a solution containing a
concentration of 40% sucrose, 5% ethylated starch and 1% surface
size (Hercules IJP). Both sides of the paper were coated to a coat
weight of 112.5 pounds of material per ton of paper per side
(Formula III). The amount of sucrose was about 98 pounds per ton of
paper per side.
[0046] Each of the sheets were then dried and conditioned at 50%
R.H.
[0047] One set of the sheets was printed using an HP 560 printer
and Scitex High Speed ink jet ink. The image was a 3".times.3"
square, printed at 60% density, using Corel Draw, Version 10.
[0048] The printed sheets were then placed in a darkroom, face down
and viewed under a LANDSCO triple-bulb, low angle light. The degree
of curl and cockle were then visually estimated. The results are
given in Table 2. 100% is the base case for a starch control. The
others were judged against the starch control.
2 TABLE 2 Degree of Curl/ Cockle: Formula Scitex ink Formula I 100%
Formula II <10% Formula III <5%
[0049] Two commercial paper products A and B, printed with a HP 560
printer using Scitex high speed ink jet ink were digitally recorded
with a SONY Mavica digital camera, under low angle light. These
photographs are FIGS. 1 and 2. The Formula II and Formula III
sheets from Example 1 were also digitally recorded with a SONY
Mavica digital camera, under the same low angle light. These
photographs are FIGS. 3 and 4. FIG. 3 shows the Formula II sheet
from Example 1; FIG. 4 shows the Formula III sheet from Example 1.
The reduction in curl and cockle with high levels of sucrose is
easily observed by comparing FIGS. 1 and 2 with FIGS. 3 and 4.
[0050] Another embodiment of the invention may use urea as the
material. This material has the desired characteristics.
EXAMPLE 2
[0051] 60 gm./m2 unsized paper was used as the base paper for the
sheets in this example.
[0052] The percentages in this example are weight percentages.
[0053] The Formula 1 control samples from Example 1 were also used
as the control samples in this example.
[0054] A sample of paper was treated in a lab size press with a
solution containing a concentration of 40% urea, 5% ethylated
starch and 1% surface size (Hercules IJP). Both side of the paper
were coated to a coat weight of 101.5 pounds of material per ton of
paper per side (Formula IV). The amount of urea was about 88 pounds
per ton of paper per side.
[0055] The sheets were then dried and conditioned at 50% R.H.
[0056] The sheets were printed using an HP 560 printer and Scitex
High Speed ink jet ink. The sheets were then evaluated for curl and
cockle, using the same technique as in Example 1.
[0057] The results are shown in Table 3.
3 TABLE 3 Degree of Curl/ Cockle: Formula Scitex ink Formula I 100%
Formula IV <5%
[0058] Another embodiment of the invention uses a salt of citric
acid as the material.
EXAMPLE 3
[0059] 60 gm./m2 unsized paper was used as the base paper for the
sheets in this example.
[0060] The percentages in this example are weight percentages.
[0061] The Formula 1 control samples from Example 1 were also used
as the control samples in this example.
[0062] A sample of paper was treated in a lab size press with a
solution containing a concentration a 25% of the monosodium salt of
citric acid (monosodium citrate), heated to 50 degrees C. Both side
of the paper were coated to a coat weight of 37.5 pounds of
material per ton of paper per side (Formula V).
[0063] The sheets were then dried and conditioned at 50% R.H.
[0064] The sheets were printed using an HP 560 printer and Scitex
High Speed ink jet ink. The sheets were then evaluated for curl and
cockle, using the same technique as in Example 1. The sheets were
also tested for water fastness via submersion in water for 60
seconds and the ink dye was completely immobilized by the salt.
[0065] The results are shown in Table 4.
4 TABLE 4 Degree of Curl/ Cockle: Water Formula Scitex ink Fastness
Formula I 100% Poor Formula V <5% Excellent
[0066] It is believed that both the mono or di salts of citric acid
provide water fastness.
[0067] Water fast means the ability of ink to remain intact when
exposed to water or moisture. Water fast inks do not bleed. Water
based inks must be treated to be water fast.
[0068] Water fastness is typically obtained with a
nitrogen-containing organic compound of a cationic nature and
functions by precipitating the dye in the ink, rendering it
immobile, when exposed to moisture after printing. Unfortunately,
these types of materials are incompatible with anionic fluorescent
whitening agents, optical brighteners, which are typically applied
at the size press to brighten paper. As such, these types of
additives reduce the overall paper brightness, often times to
levels below customer acceptance.
[0069] Monosodium citrate maintains the brightness of the paper
while providing water fastness.
EXAMPLE 4
[0070] Samples were also evaluated using the second side cockle
test method.
[0071] The percentage shown are weight percentages.
[0072] 60 gm./m2 unsized paper was used as the base paper for the
sheets in this example.
[0073] The Formula 1 control samples from Example 1 were also used
as the control samples in this example.
[0074] A second sample was prepared with a solution containing a
concentration of 44% sucrose, 5% ethylated starch and 1% surface
size (Hercules IJP). Both sides of the paper were coated to a coat
weight of 105 pounds of material per ton of paper per side. The
amount of sucrose was 92.4 pounds per ton of paper per side.
[0075] A third sample of paper was treated in a lab size press with
a solution containing a concentration of 35% urea, 5% ethylated
starch and 1% surface size (Hercules IJP). These percentages are
weight percentages. Both side of the paper were coated to a coat
weight of 101.5 pounds of material per ton of paper per side. The
amount of urea was about 87 pounds per ton of paper per side.
[0076] A fourth sample of paper was treated in a lab size press
with a solution containing a concentration a 25% of the monosodium
salt of citric acid, heated to 50 degrees C. This percentage is a
weight percentage. Both side of the paper were coated to a net coat
weight of 37.5 pounds of material per ton of paper per side. The
amount of citrate was 37.5 pounds per ton of paper per side.
[0077] Two commercial papers were added to the study.
[0078] The samples were evaluated both visually and using the
second side cockle test method. The image evaluation test
correlated well with the visual observation. The results are given
in Table 5 and in FIG. 11.
5TABLE 5 Sample Visual Cockle Formula Designation Rank Subjective
Value Value 5% Starch, 1-2 Acceptable 0.2060 44% Sucrose 5% Starch,
1-2 Acceptable 0.2127 35% Urea 25% mono sodium 3 Acceptable 0.2296
salt of citric acid 12% Starch control 4 Unacceptable 0.2658 First
Choice .TM. 5 Unacceptable 0.2851 CI-2000 .TM. 6 Unacceptable
0.3211
[0079] It was determined that paper sheets having Cockle values of
0.25 or less were acceptable.
[0080] FIG. 13 is a schematic drawing of a paper machine. Wood pulp
fiber furnish and wet end chemicals are mixed with water in a
headbox 20 to form a slurry. The slurry exits the headbox through a
slice 22 onto a wire 24. The water in the slurry drains from the
wire. A vacuum chest 26 is also used to draw water from the slurry
to form a wet paper web. The web is carried through press rolls 28
and a drier 30 that remove additional water.
[0081] Additional size press chemicals or materials are placed on
the wet paper web at the size press 32. The size press may be a
horizontal type with the rolls horizontally aligned, 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 34. The materials described in the various embodiments in
the present application would also be applied at the size press 32
or the spraying apparatus 34.
[0082] The paper web then passes through a drying section 36. 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 38 and rolled into paper rolls at the winder 40. The
resulting product is known as uncoated paper.
[0083] This is the product of the present invention. Additional
expensive off-machine coatings would not be required to provide a
paper that has a maximum Cockle Value of 0.25.
[0084] 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.
* * * * *