Title of Invention

A PAPER OR PAPERBOARD HAVING IMPROVED BULK AND STIFFNESS .

Abstract The invention provides a throe layer reprographic paper having i mproved strength, stiffness and curl resistance properties and a method for making same. The paper has a central core layer (12) made largely of cellulose and bulked with a bulking with a bulking agent such as a diamide salt. A starch-based metered size presscoating is pressed on both sides of the core layer wherein the starch has a high solid content. The coating (14) forms a three layered paper having an I-beam arrangement with high strength outer lavers (14) surrounding a low-density core.
Full Text PAPER WITH IMPROVED STIFFNESS AND BULK AND
METHOD FOR MAKING SAME
A PAPER OR PAPERBOARD HAVING IMPROVED BULK
AND STIFFNESS
FIELD OF THE INVENTION
The invention relates to the papermaking arts and, in particular, to the manufacture of
paper substrates. This invention also relates to articles manufactured from the substrates of
this invention such as printing paper and paperboard articles.
RELATED APPLICATION
This application claims the benefit of United States Provisional Application Serial No.
60/410,666, filed September 13, 2002..
BACKGROUND OF THE INVENTION
The contemporary work and home offices use a multitude of paper products
including, but not limited to reprographic paper grades and paperboard., such as writing
papers, printing paper, copy paper, and forms paper. Unfortunately, such paper and
paperboard products exhibit one or more disadvantages. For example, some of these
products have relatively low basis weights or are not sufficiently stiff in bending or durable to
sustain a full run through a copy machine. Thus, within the industry there is a constant aim to
produce reprographic papers at lower basis weights, but at equal stiffness properties, in order
to save raw materials and to be able to increase productivity. Other important properties of
reprographic papers are curl, i.e.. out-of-plane movement, and hygroexpansivity, i.e.
expansion and contraction of the paper with varying relative humidities. A low curl is
required during stacking of paper in copier machines and for correct feeding. A low
hygroexpansivity is required because curl is a. function of the hygroexpansivity, and of the
material distribution in the sheet (see e.g. Carlsson, L.: A Study of the Bending Properties of
Paper and their Relation to the Layered Structure, Doctoral thesis, Chalmers University of
Technology, Department of Polymeric Materials, Gothenburg, Sweden, 1980, ISBN 91-7032-
003-9). The hygroexpansivity and curl are also a function of the paperrnaking process,
especially during drying of a fibrous web (see e.g. Handbook of Physical Testing of Paper,
2nd Edition, Vol. 1, Chapter 3, page 115-117, ISBN 0-8247-0498-3 by T. Uesaka:
Dimensional Stability and Environmental Effects on Paper Properties). The bending stiffness
Sb of paper is a function of the elastic modulus E and the thickness t, such that Sb is
proportional to Et3. This means that the most effective means to increase the bending stiffness
is by increasing the paper thickness. However, the thickness normally must be retained within
specifications. An even more efficient way to increase bending stiffness is to create an I-
beam effect, i.e. strong dense outer layers and a lower density core. Mathematical expressions
of a three-layered structure show that the I-beam effect creates considerably higher bending
stiffness compared to a homogeneous structure if all other parameters are kept constant (see
e.g. Handbook of Physical Testing of Paper, 2nd Edition, Vol. 1, Chapter 5, page 233-256,
ISBN 0-8247-0498-3 by C. Fellers and L.A. Carlsson: Bending Stiffness, with Special
Reference to Paperboard). This knowledge has been reduced to practice in multi-ply
paperboard as well as for low basis weight printing papers, such as reprographic papers (see
e.g. Haggblom-Ahnger, U., 1998, Three-ply office paper, Doctoral thesis, Abo Akademi
University, Turku, Finland, 1998).
Modem size-press units of paper machines produce reprographic paper grades
commonly having metered size-presses. These units enable the application of size-press
starch (and/or other strengthening components) to other layers of the sheet. This technology
has been demonstrated in the published literature (see e.g. Lipponen, J. et al.: Surface Sizing
with Starch Solutions at High Solids Contents, 2002 Tappi Metered Size Press Forum,
Orlando, FL, May 1-4, 2002, Tappi Press 2002, ISBN 1-930657-91-9). The authors
concluded a significant bending stiffness improvement running the starch solution at the size-
press at 18 % solids compared to lower solids (8, 12 and 15 %).
There are also flooded-nip (also called pond or puddle) size-press units in common
use. In this instance the potential for application of starch solutions to the outer layers is not
the same as for metered size-press units due to inherent deeper penetration into the sheet in
the flooded-nip. However, results in the literature suggest that an increase in starch solids can
also cause less penetration with potential for improved bending stiffness (see e.g. Bergh, N.-
O.: Surface Treatment on Paper with Starch from the Viewpoint of Production Increase, XXI
EUCEPA International Conference, Vol. 2, Conferencias nos. 23 a 43, Torremolinos, Spain,
page 547-, 1984). There is, however, room for considerable improvement in bending stiffness
over the results reported in the literature and to receive other benefits such as stated above.
Accordingly, there exists a need for improved paper and paperboard products that
reduce or eliminate one or more of these disadvantages while being able to produce
paperboard and reprographic paper grades at considerably lower basis weights, at higher
production rates, and, consequently, at lower manufacturing costs. Such an improvement
would benefit from increased bulk of the paper web before the size-press application (n.b. the
large influence of paper thickness on bending stiffness) in combination with high solids
starch solutions including viscosity modifiers and/or crosslinkers to increase the strength of
the size-press coating and to increase hold-out attachment of the surface to the applied layer.
Further, it is the object of this invention to provide these benefits within a single-ply paper,
thereby eliminating the costs associated with the additional machinery required for paper
having multiple cellulosic layers.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to provide a paper or paperboard having
improved bulk and stiffness having a three layered single-ply I-beam structure with a top
layer, a central layer and a bottom layer, wherein the central layer is a cellulosic core layer,
and the top and bottom layers are starch based, size-press applied coating layers that cover an
upper and lower surface of the central layer with minimal penetration into the central layer,
and a bulking agent interpenetrated within the cellulosic core layer.
It is a further object of the invention to provide a paper or paperboard having
improved bulk and stiffness having a three layered single-ply I-beam structure having a top
layer, a central layer and a bottom layer, wherein the central layer is a cellulosic core layer,
and the top and bottom layers are starch based, size-press applied coating layers that cover an
upper and lower surface of the central layer, the top and bottom layer have starch coat
weights in the range of 2-10 gram per square meter, and a bulking agent interpenetrated
within the cellulosic core layer.
It is an additional object of the invention to provide a method for making a paper or
paperboard comprising the steps of providing a furnish including cellulosic fibers and a
bulking agent, forming a fibrous web from the papermaking furnish, drying the fibrous web
to form a dried web, size-press treating the dried web with a high strength starch based size-
press solution to form top and bottom coating layers on a top and bottom side of the fibrous
web, and drying the fibrous web after the size-press treatment to form a three layered single-
ply having an I-beam structure.
Other objects, embodiments, features and advantages of the present invention will be
apparent when the description of a preferred embodiment of the invention is considered in

conjunction with the annexed drawings, Avhich should be construed in an illustrative and not
limiting sense.
ACCOMPANYING
BRIEF DESCRIPTION OF THE FIGURES/DRAWINGS
Fig. 1 is a schematic illustration of the three layered paper of the invention, achieved
by bulking the base sheet and using high solids starch including viscosity
modifiers/fillers/cross-linkers.
Fig. 2 is a schematic illustration of a paper machine process.
DETAILED DESCRIPTION
A paper 10 in accordance with one embodiment of the invention is shown in Fig. 1,
wherein the term "paper", as used herein, includes not only paper and the production thereof,
but also other web-like products, such as board and paperboard and the production thereof. A
flat, bulked cellulosic core layer 12 is coated on both sides by a high strength starch based
size-press coating 14. The cellulosic fibers are formed from a chemical pulp furnish having a
mixture of hardwood and softwood fibers with additional fillers such as precipitated calcium
carbonate or other fillers known in the art. The fibers may also be interspersed with
surfactants, retention agents or other additives typically added to paper products. The precise
ratio of softwood to hardwood fibers can vary within the scope of the invention. Ideally, the
ratio of hardwood to softwood fibers varies between 3:1 and 10:1. However, other
hardwood/softwood ratios or other types of fibers can be used, such as fibers from chemical
pulp such as sulphate, and sulphite pulps, wood-containing or mechanical pulp such as
fhermomechanical pulp, cherno-thermomechanical pulp, refiner pulp and groundwood pulp.
The fibers can also be based on recycled fibers, optionally from de-inked pulps, and mixtures
thereof.

Cellulosic core layer 12 is a low density core bulked up by a bulking agent, thus
achieving increased thickness. The preferred embodiment uses a diamide salt based bulking
agent such as mono- and distearamid.es of animoethylethalonalamine, commercially known
as Reactopaque 100, (Omnova Solutions Inc., Performance Chemicals, 1476 J.A. Cochran
By-Pass, Chester, SC 29706, USA and marketed and sold by Ondeo Nalco Co., with
headquarters at Ondeo Nalco Center, Naperville, IL 60563, USA) in about 0.025 to about
0.25 wt% by weight dry basis. However, various chemical bulking agents known in art can
be used, such as quaternized imidazoline or microspheres, wherein the microspheres are
made from a polymeric material selected from the group consisting of methyl methacrylate,
ortho-chlorostyrene, polyortho-chlorostyrene, polyvinylbenzyl chloride, acrylonitrile,
vinylidene chloride, para-tert-butyl styrene, vinyl acetate, butyl acrylate, styrene, methacrylic
acid, vinylbenzyl chloride and combinations of two or more of the foregoing. Core layer 12
may contain other materials, such as surfactants, retention agents and fillers known in the art.
The use of retention agents are generally preferred if microspheres are utilized as the bulking
agent. In the preferred embodiment utilizing diamide salt, no retention agents are required.
In the preferred embodiment, starch based coating layers 14 cover both surfaces of the
core layer. The high density coatings cover an upper and lower surface of the lower density
bulked cellulose core, creating an I-beam effect that is a three-layered single-ply paper
product. In other embodiments, only one side of the cellulosic core layer may be coated with
a starch size press coating. The high strength coatings are formed from starch based
solutions in a solids range of 6-20 %, but preferably more starch strength than a typical paper
yet low enough to prevent excessive penetration of the coatings into the core layers.
Commercial embodiments of the present invention generally use solid content of about 6-
12%. However, in other preferred embodiments, high stiffness can be achieved with starch
solids of about 18%.
The coating penetrates the cellulose core layer minimally or not at all. As a result,
starch can be substantially absent from the cellulose core. The control of the penetration is
ideally achieved with a metered size press coating, such that the thickness of the outer film
can be closely monitored. In preferred embodiments, the ratio of the film thicknesses of the
starch coating layers to the paper as a whole is between 1:50 and 1:1.1. The porosity levels
of the paper also effects coating penetration. Controlling the thickness and penetration is key
to create three separate adjacent layers that form the I-beam structure having high strength
outer coatings around a lower density core.
The starches used in the coating can be any starch typically used in a coating,
preferably a hydroxy ethylated starch, oxidized starch, cationically modified or enzymatically
converted starch from any regularly used starch source, such as from potato, corn, wheat, rice
or tapioca. The coating may further contain viscosity modifiers, cross-linkers and pigments
such as polyvinyl alcohols, ammonium zirconium carbonate, borate chemicals, glyoxal,
melamine formaldehyde, ground and precipitated calcium carbonates, clays, talc, TiO2, and
silica.
As completed, the basis weight of paper 10 is generally in the range of 59-410 g/m2
and the coating has a basis weight between 2 and 10 g/m2
Figure 2 depicts a schematic that is one embodiment of a method used for formulating
the paper of Figure 1. Numerous types of papermaking machines are known, many with
variants of a typical wet-end/dry end type machine. Thus, the present invention is not limited
to a specific type of paper making machine such as the one represented in the schematic of
Fig. 2.
A bulking agent 20 is added to a furnish during the wet-end of the paper making
machine, wherein the furnish may further comprise additives including fillers, retention aids,
surfactants, and other substances typically added to wet end paper furnished that are known
in the art. In the present embodiment, the preferred bulking agent is a diamide salt based
product (Reactopaque 100). However, other bulking agents may be used within the spirit of
the invention.
The wet-end further comprises a refiner 22 for mechanical treatment of the pulp, a
machine chest 32, a headbox 24 that discharges a wide jet of the furnish onto a wire section
to form a fibrous paper web, a wire section 26 having a moving screen of extremely fine
mesh, a press section 28, and a dryer section 34 comprising a plurality of support rolls that
dries the fibrous web and conveys it to the size press.
A starch based coating is mixed in a mix-tank 30. The starch used is preferably a
hydroxy ethylated starch, oxidized starch, cationically modified or enzymatically converted
starch from any regularly used starch source, such as from potato, com, wheat, rice or
tapioca. In the present embodiment, starch is cooked and added to the mix-tank with
viscosity modifiers, cross-linkers and fillers such as one or more of the following: polyvinyl
alcohols, ammonium zirconium carbonate, borate chemicals, glyoxal, melamine
formaldehyde, ground and precipitated calcium carbonates, clays, talc, TiO2, and silica.. The
starch may be cooked with a borate chemical in a starch cooker 38 prior to entry into the mix-
tank. The mixed coating is conveyed to a size press tank and then size pressed onto the paper
web, coating one or both sides of the web. The starch based coating preferably has starch
solids in the range of 6-20% by weight. The coating layers may be added simultaneously or
in series in accordance with one of two techniques typically used in the industry. The paper's
thickness, weight, stiffness and curl resistance are largely the same with either technique.
The size press-treatment used is preferably a metered size-press application. Due to
the nature of the metered size press, application of starch solids can be controlled and
normalized. As a result, penetration of the starch coating into the cellulosic core layer is
minimal, maintaining the I-beam effect of the three-layer single ply structure. Even so, other

size-presses known in the art. such as a flooded-nip size-press application, may be used. In
this instance the potential for application of starch solutions to the outer layers is not the same
as for metered size-press units due to inherent deeper penetration into the sheet in the
flooded-nip.
The coated paper web is then conveyed to the size-press treatment in the dry end 36 of
the paper making machine, wherein the dry end typically comprises a multiplicity of steam
heated, rotating cylinders under a heat confining hood structure in proximity to the paper web
traveling route to further dry the paper after size press application.
The resultant paper substrate exhibits one or more enhanced properties as compared to
substrates that do not include the bulking additive and/or the high solids starch size-press in
combination with viscosity modifiers and/or cross-linkers. For example, for some
embodiments of this invention, the substrate exhibits improved Sheffield Smoothness (TAPPI
538om-88)) on both wire side and felt side of the substrate in contrast to the same substrate
without the above mentioned ingredients, thus enabling less calendering with retained bulk.
Further, the paper exhibits improved curl resistance, a property of greatest importance
for end-user performance of reprographic grades, improved hygroexpansivity, and enhanced
Lorentzon & Wettre Bending Resistance. Other benefits of the invention include a more
closed sheet and/or an enhanced possibility to target a certain porosity of the paper, resulting
in higher Gurley numbers (TAPPI T460 om-96). This is beneficial as reprographic papers are
usually fed through copier machines using vacuum suction to lift the sheets.
The following non-limiting examples illustrate various additional aspects of the
invention. Unless otherwise indicated, temperatures are in degrees Celsius, paper basis
weight is in grams per square meter and the percent of any pulp additive or moisture is based
on the oven-dry weight of the total amount of material.

Example 1
A series of trials were made on a paper machine equipped with a flooded-nip size-
press. Paper was made from a mixture of about 9 parts hardwood and 1 part softwood and
containing 19 % filler (precipitated calcium carbonate). A standard AKD size was added as
internal size and a standard surface size was added to the size-press together with the starch
solution. The trial commenced with addition of Reactopaque 100 to the hardwood pulp chest
before refining. The addition rate was ramped up to 0.15 % and the size-press coating having
enzymatically converted corn starch was changed to contain starch at higher solids (10 %
instead of the standard 8 %) in combination with 5 parts based on starch of glyoxal (Sequarez
755, Omnova Solutions Inc., SC, USA) and 25 parts based on starch of ground calcium
carbonate, (Omyafil OG, Omya, Inc., Alpharetta, GA, USA). One condition was run at these
settings, then the size-press coating was switched back to starch without glyoxal and filler
while maintaining the higher solids. The last condition maintained these settings but
decreasing the paper basis weight in order to evaluate the impact of bending stiffness. Table 1
gives the results in Lorentzon & Wettre bending resistance (bending stiffness), paper caliper
and Bendtsen porosity as compared to a control without a bulking agent and standard starch
solids. Condition 2 shows an increase over the control in caliper and in bending stiffness and
a decrease in the porosity number. Condition 2 also showed a smoother surface as determined
from the Bendtsen smoothness number, which decreased from 225 / 210 ml/min (wire/felt
side) to 205 / 195 ml/min (wire/felt side). This and the decreased porosity for condition 2 can
be attributed to the filler closing the surface and creating a smoother surface. The most
important finding is when comparing Condition 2, 3 and 4 with Condition 1 (control). The
caliper increases Avith addition of Reactopaque and the bending stiffness goes up as a result of

the increased caliper in combination with increased starch located to the surface layers. The
overall starch content in the sheet also increased as a result of the more open sheet (higher
Bendtsen porosity number). Condition 4 compared to Condition 1 is especially important as it
shows that the increased bending stiffness allows for the basis weight to be decreased while
maintaining almost the same stiffness as the control.
Example 2
A series of papers were evaluated in metered size-press trials. A test base paper was
produced at 90 gram per square meter without Reactopaque 100. Control CI using this base
paper was given a size press coating of 2 g/m2, control C2 was given a size press coating of 5
g/m2, and control C3 was given a size press coating of 8 g/m2. The controls were run in side-
by-side comparisons on a metered size-press unit with a series of test papers produced with
88 gram per square meter with 0.18 % Reactopaque 100 added before hardwood refining.
The test base papers were given a size-press coating containing hydroxy ethylated corn starch
(Ethylex 2035 from A.E. Staley Manufacturing Co., Decatur, IL, USA) at higher solids (18 %
instead of the standard 8 %) in combinatic; with glyoxal and a filler (ground calcium
carbonate). The size-pressed coated papers were tested for bending stiffness, smoothness and
porosity. In order to summarize the results, bending stiffness was plotted as a function of
smoothness and results evaluated at a Sheffield smoothness of 120 after steel to steel
calendering. Gurley porosity and Sheffield smoothness numbers are given for the un-
calendared papers. The coefficient of hygroexpansion was evaluated on paper strips in
machine and cross-machine direction using a Varidim hygroexpansivity tester (Techpap,
Grenoble, France). Hygroexpansion was measured between 15 and 90 % relative humidity
from which the coefficient of hygroexpansion was calculated.
Different additives for the starch solutions were selected from the list below:
• Sodium tetraborate pentahydrate, borax (Neobor from US Borax, CA, USA) added in
0.25 % on starch before the starch was cooked.
• Glyoxal (Sequarez 755, Omnova Solutions Inc., SC, USA) added in 5 % on starch in
combination with precipitated calcium carbonate added in 50 % based on starch
(Megafil 2000, Specialty Minerals, PA, USA)
• Polyvinyl alcohol (Celvol 325 from Celenese Chemicals, TX, USA) added in 5 % on
starch.
Table 2 shows the results. The combination of high starch solids and viscosity
modifier/filler/cross-linker increases bending stiffness by over 20 % over the control. High
starch solids alone also give some benefit but the surprising result is the overall impact on
several important paper properties by the bulking and size-press application.. The; size-press
application gives a more closed sheet as seen from the increasing Gurley porosity numbers,
the base paper containing the bulking additive is smoother and the coefficient of
hygroexpansion is significantly lower for the conditions with the combination of high starch
solids and viscosity modifier/filler/cross-linker.
Example 3
A series of papers were formed from a mixture of 8 parts Northern hardwood pulp
and 2 parts Northern softwood pulp and having 20 % filler, precipitated calcium carbonate
(Megafil 2000) from Specialty Minerals. The pulps were refined together and having a
Canadian Standard Freeness of about 450 ml. A standard AK.D size (Hereon 70) from
Hercules was added in the wet-end to give the base sheet a Hercules size test number of 50-
100 seconds. Reactopaque 100 at 0.17 wt%) was added before refining at a temperature of
the pulp of 54 C (130 F) to achieve the bulking effect. The papers were tested for heated curl
with a proprietary instrument developed for such measurements at assignee's International
Paper's research center. The results are given in Table 3. It is shown that the addition of
Reactopaque 100 to the base sheet gives a significant reduction in the curl number (a
difference in 5 units is considered to be a significant difference.)
Although the invention has been described with reference to preferred embodiments,
it will be appreciated by one of ordinary skill in the art that numerous modifications are
possible in light of the above disclosure. For example, the optimum amount of bulking agent
used with different types and ratios of cellulosic fibers may vary. All such variations and
modifications are intended to be within the scope and spirit of the invention as defined in the
claims appended hereto.
We Claim:
1. A paper or paperboard having improved bulk and
stiffness comprising: a three layered single-ply
I-beam structure having a top layer, a central
layer and a bottom layer, wherein the central
layer is a cellulosic core layer, and the top and
bottom layers are starch based, size-press
applied coating layers that cover an upper and
lower surface of the central layer with minimal
penetration into the central layer, and a bulking
agent such as herein described interpenetrated
within the central layer.
2. The paper or paperboard as claimed in claim 1,
wherein the ratio of the thickness of the central
layer compared to the thickness of the paper or
paperboard is between 1:50 and 1:1.1.
3. The paper or paperboard as claimed in claim 1,
wherein the basis weight, of the paper is
between 59 g/m3 and 410 g/m2 and the basis weight
of each of the top and bottom coating layers are
between 2 and 10g/m2.
4. The paper or paperboards as claimed in claim 1,
wherein the top and bottom layers have starch
application controlled with a metered size press.
5. The paper or paperboards as claimed, in claim 1,
wherein the top and bottom layers are formed from
a starch coating solution having starch solids
between 6% and 20% weight.
6. The paper or paperboard as claimed in claim 1,
wherein the bulking agent is a diamide salt
based product.
7. The paper or paperboard as claimed in claim 1,
wherein the bulking agent is made from a
polymeric material in form of microspheres
selected from the group consisting of methyl
methacrylate, ortho-chlorostyrene, polyortho-
chloroatyrene, poly-vinylbenzyl chloride,
acrylonitrile, vinylidene chloride, para-tert-
butyl styrene, vinyl acetate, butyl acrylate,
styrene, methacrylic acid, vinylbenzyl chloride
and combinations of two or more of the
foregoing.
8. The paper or paperboard as claimed in claim 7,
wherein the central layer optionally comprises
a retention agent such as herein described.
9. The paper or paperboard as claimed in claim 1,
wherein the central layer optionally comprises
an additive selected from the group consisting
of fillers, surfactants, sizing agents, or a
combination thereof.
10. The paper or paperboard as claimed in claim 1,
wherein the starch is selected from the group
consisting of hydroxy ethylated starch,
oxidized starch, cationically modified or
enzymatically converted starch from any
regularly used starch source, such as from
potato, corn, wheat, rice or tapioca.
11. The paper or paperboard as claimed in claim 1,
wherein the top and bottom layers optionally
comprise a cross linking agent.
12. The paper or paperboard as claimed in claim 1,
wherein the top and bottom layers optionally
comprise a viscosity modifier,
13. The paper or paperboards of claim 1, wherein
the top and bottom layers optionally comprise a
pigment.
14. The paper or paperboard as claimed in claim 1,
optionally comprising additives selected from
the group consisting of polyvinyl alcohols,
ammonium zirconium carbonate, borate chemicals,
glyoxal, melamine formaldehyde, ground and
precipitated calcium carbonates, clays, talc,
TiO2, and silica, or a combination thereof.
15. A paper or paperboard having improved bulk and
stiffness comprising: a three layered single-ply
I-beam structure having a top layer, a central
layer and a bottom layer, wherein the central
layer is a cellulosic core layer, and the top
and bottom layers are starch based, size-press
applied coating layers that cover an upper and
lower surface of the central layer, a starch
coat weights of each of the top and bottom
coating layers being between 2 and 10 g/m2, and
a bulking agent interpenetrated within the
cellulosic core layer.
16. A method for making a paper or paperboard
comprising the steps of:
a) providing a furnish including cellulosic
fibers and a bulking agent,
b) forming a fibrous web from the papermaking
furnish,
c) drying the fibrous web to form a dried web,
d) size-press treating the dried web with a high
strength starch based size-press solution to
form top and bottom coating layers on a top and
bottom side of the fibrous web, and
e) drying the fibrous web after the size-press
treatment to form a three layered single-ply
having an I-beam structure.
17. The method as claimed in claim 16, wherein the
ratio of the thickness of the fibrous web
compared to the thickness of the paper or
paperboard is between 1:50 and 1:1.1.
18. The method as claimed in claim 16, wherein the
basis weight of the paper is between 59 gsm and
410 gsm and the basis weight of each of the top
and bottom coating layers are between 2 and 10
gsm.
19. The method as claimed in claim 16, wherein no
substantial levels of starch from the top and
bottom coating layers are in the fibrous web.
20. The method as claimed in claim 16, wherein the
top and bottom coating layers have starch
solids less than 20% weight.
21. The method as claimed in claim 16, wherein the
size-press treatment uses a metered size-press.
22. The method as claimed in claim 16, wherein the
bulking agent is a diamide salt based product.
23. The method as claimed in claim 16, wherein the
furnish optionally contains an additive
selected from the group consisting of: fillers,
surfactants, or a combination thereof.
24. The method as claimed in claim 17, wherein the
starch is chosen from a group comprising of :
hydroxy ethylated starch, oxidized starch,
cationically modified or enzymatically
converted starch from any regularly used starch
source, such as from potato, corn, wheat, rice
or tapioca.
25. The method as claimed in claim 16, wherein the
size-press solution optionally contains an
additive selected from the group consisting of:
polyvinyl alcohols, ammonium zirconium
carbonate, borate chemicals, glyoxal, melamine
formaldehyde, ground and precipitated calcium
carbonates, clays, talc, TiO452, and silica, or
a combination thereof.
26. The method as claimed in claim 17, wherein a
starch solution of the high strength starch
based size-press solution, is pre-cooked with a
borate chemical prior to the size-press
treatment.
27. The paper of paperboard as claimed in claim 1,
wherein the top and bottom layers are formed
from a starch coating solution having starch
solids from 6 to 12wt%.
28. The method as claimed in claim 16, wherein the
high strength starch based size-press solution
contains from 6 to 12 wt.% starch solids.
The invention provides a throe layer reprographic paper having i mproved strength, stiffness and curl resistance
properties and a method for making same. The paper has a central core layer (12) made largely of cellulose and bulked with a
bulking with a bulking agent such as a diamide salt. A starch-based metered size presscoating is pressed on both sides of the core
layer wherein the starch has a high solid content. The coating (14) forms a three layered paper having an I-beam arrangement with
high strength outer lavers (14) surrounding a low-density core.

Documents:

627-KOLNP-2005-(05-01-2012)-CORRESPONDENCE.pdf

627-KOLNP-2005-(05-01-2012)-OTHER PATENT DOCUMENT.pdf

627-KOLNP-2005-(05-01-2012)-PA-CERTIFIED COPIES.pdf

627-KOLNP-2005-CORRESPONDENCE.pdf

627-KOLNP-2005-FORM 1.pdf

627-KOLNP-2005-FORM 27.pdf

627-KOLNP-2005-FORM-27.pdf

627-kolnp-2005-granted-abstract.pdf

627-kolnp-2005-granted-assignment.pdf

627-kolnp-2005-granted-claims.pdf

627-kolnp-2005-granted-correspondence.pdf

627-kolnp-2005-granted-description (complete).pdf

627-kolnp-2005-granted-drawings.pdf

627-kolnp-2005-granted-examination report.pdf

627-kolnp-2005-granted-form 1.pdf

627-kolnp-2005-granted-form 13.pdf

627-kolnp-2005-granted-form 18.pdf

627-kolnp-2005-granted-form 3.pdf

627-kolnp-2005-granted-form 5.pdf

627-kolnp-2005-granted-gpa.pdf

627-kolnp-2005-granted-reply to examination report.pdf

627-KOLNP-2005-OTHERS.pdf

627-KOLNP-2005-RECEIPT.pdf


Patent Number 226476
Indian Patent Application Number 627/KOLNP/2005
PG Journal Number 51/2008
Publication Date 19-Dec-2008
Grant Date 17-Dec-2008
Date of Filing 12-Apr-2005
Name of Patentee INTERNATIONAL PAPER COMPANY
Applicant Address 400 ATLANTIC STREET, STAMFORD, CT
Inventors:
# Inventor's Name Inventor's Address
1 SWERIN AGNE 53 ECHO LANE, WARWICK, NY 10990
2 SONG JAY C 7 YALE DRIVE, HIGHLANDS MILLS, NY 10930
3 HERMAN MICHAEL 6 VAN KEUREN COURT, MONROE, NEW YORK 10959
4 LEE PETER F ONE FOX STREET PARNELL, P.O. BOX 50
5 BED NARIK LADISLAV 6201 PINTAIL COURT, LOVELAND, OHIO 45140
6 YANG SEN 32 TERRACE AVENUE, NANUET, NY 10954
PCT International Classification Number D21H 19/84
PCT International Application Number PCT/US2003/029216
PCT International Filing date 2003-09-12
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA