U.S. patent application number 11/686742 was filed with the patent office on 2007-09-20 for method for making a low density multi-ply paperboard with high internal bond strength.
This patent application is currently assigned to Weyerhaeuser Co.. Invention is credited to Daniel T. Bunker, Donald D. Halabisky, Shahrokh A. Naieni.
Application Number | 20070215301 11/686742 |
Document ID | / |
Family ID | 38283737 |
Filed Date | 2007-09-20 |
United States Patent
Application |
20070215301 |
Kind Code |
A1 |
Bunker; Daniel T. ; et
al. |
September 20, 2007 |
Method for making a low density multi-ply paperboard with high
internal bond strength
Abstract
Methods for improving the internal bond strength of paperboard
with greater than 25 percent crosslinked fiber in at least one ply
are described. In the methods, additives are added to the slurry in
various combinations and order while maintaining the ionic demand
of the slurry at less than zero. Paperboard with high ZDT, Scott
Bond and Taber Stiffness is obtained.
Inventors: |
Bunker; Daniel T.; (Seattle,
WA) ; Halabisky; Donald D.; (Tacoma, WA) ;
Naieni; Shahrokh A.; (Seattle, WA) |
Correspondence
Address: |
WEYERHAEUSER COMPANY;INTELLECTUAL PROPERTY DEPT., CH 1J27
P.O. BOX 9777
FEDERAL WAY
WA
98063
US
|
Assignee: |
Weyerhaeuser Co.
Federal Way
WA
|
Family ID: |
38283737 |
Appl. No.: |
11/686742 |
Filed: |
March 15, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60783624 |
Mar 17, 2006 |
|
|
|
Current U.S.
Class: |
162/146 ;
162/129; 162/142; 162/157.6; 162/158; 162/175 |
Current CPC
Class: |
D21H 17/28 20130101;
D21H 27/30 20130101; D21H 23/08 20130101; D21H 17/29 20130101; D21H
11/10 20130101; D21H 17/54 20130101; D21H 23/10 20130101; D21H
11/20 20130101; D21H 21/18 20130101; D21H 27/38 20130101; D21H
17/44 20130101; D21H 17/66 20130101 |
Class at
Publication: |
162/146 ;
162/175; 162/158; 162/142; 162/157.6; 162/129 |
International
Class: |
D21H 11/10 20060101
D21H011/10; D21H 11/20 20060101 D21H011/20; D21H 17/28 20060101
D21H017/28 |
Claims
1. A method for forming at least one ply of a paperboard comprising
the steps of: forming a slurry of cellulose fibers comprising
crosslinked fibers; adding mechanically refined fiber; adding an
anionic starch subsequent to adding said mechanically refined
fiber; adding a cationic fixative subsequent to adding said anionic
starch; wherein, after each addition step, the slurry ionic demand
is less than zero; depositing said slurry on a foraminous support;
forming a fibrous web layer by withdrawing liquid from said slurry;
drying said web to form a paperboard.
2. The method of claim 1 wherein said crosslinked fibers are
present at a level from 25 to 80 percent of the total fiber weight
in at least one ply of said paperboard.
3. The method of claim 1 wherein the total starch level is 50 to
120 lb/t.
4. The method of claim 1 wherein the mechanically refined fiber has
a CSF of less than 125 CSF, a curl index of 1/3 or less of the
unrefined fiber and a kink angle of 1/2 or less of the unrefined
fiber.
5. The method of claim 1 wherein the cationic fixative has an
anionic demand of greater than zero but less than 1 meq/g.
6. The method of claim 1 wherein the cationic fixative has an
anionic demand of from 1 meq/g to 10 meq/g.
7. The method of claim 1, wherein said paperboard is at least a
two-ply board, said at least one ply containing said crosslinked
fibers.
8. The method of claim 1, wherein said paperboard is at least a
three-ply board, said at least one ply containing said crosslinked
fibers.
9. A method for forming a paperboard comprising the steps of:
forming a slurry of cellulose fibers comprising crosslinked fibers;
adding mechanically refined fiber, adding a cationic fixative and
mixing with said slurry; adding an anionic starch subsequent to
adding said cationic fixative; wherein, after each addition step,
the slurry ionic demand is less than zero; depositing said slurry
on a foraminous support; forming a fibrous web layer by withdrawing
liquid from said slurry; drying said web to form a paperboard.
10. The method of claim 9 wherein said crosslinked fibers are
present at a level from 25 to 80 percent of the total fiber weight
in at least one ply of said paperboard.
11. The method of claim 9 wherein the total starch level is 50 to
120 lb/t.
12. The method of claim 9 wherein the mechanically refined fiber
has a CSF of less than 125 CSF, a index of 1/3 or less of the
unrefined fiber and a kink angle of 1/2 or less of the unrefined
fiber.
13. The method of claim 9 wherein the cationic fixative has an
anionic demand of greater than zero but less than 1 meq/g.
14. The method of claim 9 wherein the cationic fixative has an
anionic demand of from 1 meq/g to about 10 meq/g.
15. The method of claim 9, wherein said paperboard is at least a
two-ply board, said at least one ply containing said crosslinked
fibers.
16. The method of claim 9, wherein said paperboard is at least a
three-ply board, said at least one ply containing said crosslinked
fibers.
17. A method for forming at least one ply of a paperboard
comprising the steps of: forming a slurry of cellulose fibers
comprising crosslinked fibers; adding mechanically refined fiber;
adding an anionic starch subsequent to adding said mechanically
refined fiber; adding a first cationic fixative subsequent to
adding said anionic starch; adding a second cationic fixative
subsequent to adding said first cationic fixative; wherein, after
each addition step, the slurry ionic demand is less than zero;
depositing said slurry on a foraminous support; forming a fibrous
web layer by withdrawing liquid from said slurry; drying said web
to form a paperboard.
18. The method of claim 17 wherein said crosslinked fibers are
present at a level from 25 to 80 percent of the total fiber weight
in at least one ply of said paperboard.
19. The method of claim 17 wherein the total starch level is 50 to
120 lb/t.
20. The method of claim 17 wherein the mechanically refined fiber
has a CSF of less than 125 CSF, a curl index of 1/3 or less of the
unrefined fiber and a kink angle of 1/2 or less of the unrefined
fiber.
21. The method of claim 17 wherein the first cationic fixative has
an anionic demand of from 1 meq/g to 10 meq/g.
22. The method of claim 17 wherein the second cationic fixative has
an anionic demand of greater than zero but less than 1 meq/g.
23. The method of claim 17, wherein said paperboard is at least a
two-ply board, said at least one ply containing said crosslinked
fibers.
24. The method of claim 17, wherein said paperboard is at least a
three-ply board, said at least one ply containing said crosslinked
fibers.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Application No.
60/783,624 filed Mar. 17, 2006.
FIELD
[0002] The present application relates to a method for increasing
the bond strength in a multi-ply paperboard that has high
crosslinked cellulose fiber present in at least one of the
plies.
SUMMARY
[0003] This application is directed to a method improving the
internal bond strength of paperboard with greater than 25 percent
crosslinked fiber in at least one ply. In the method, additives are
added to the slurry in various combinations and order while
maintaining the ionic demand of the slurry at less than zero.
Paperboard with high ZDT, Scott Bond and Taber Stiffness is
obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a schematic diagram of the pilot line.
DESCRIPTION
[0005] In single or multi-ply paperboard where the inner plies
contain greater than approximately 25 percent crosslinked cellulose
fiber the density of the stratum will drop below 0.4 g/cc. As a
result, the internal bond strength can drop so low as to not only
be well below levels required for converting the paperboard into
packaging products but also below the level where conventional
methods of increasing the internal strength cannot provide enough
increase to meet minimum levels needed for converting. This effect
can occur either in the entire structure or some fraction within
the structure. The present application provides a method for
increasing the internal bond of low density paperboard back into
the range which is useable for converting.
[0006] In this application, the use of high concentrations of wet
end additives have been demonstrated while producing low density
paperboard.
[0007] A distinguishing characteristic of the present application
is that at least one ply of the paperboard, whether a single-ply or
a multiple-ply structure, contains crosslinked cellulose fibers and
strength enhancing additives such as mechanically refined fiber,
anionic and cationic starches and other additives to offset the
board strength lost by adding the crosslinked cellulosic fibers.
The crosslinked cellulosic fibers increase the bulk density of the
insulating paperboard characteristics of the board. The paperboard
also contains chemical pulp fibers. As defined herein, chemical
pulp fibers useable in the present application are derived
primarily from wood pulp. Suitable wood pulp fibers for use with
the application can be obtained from well-known chemical processes
such as the kraft and sulfite processes, with or without subsequent
bleaching. Softwoods and hardwoods can be used. Details of the
selection of wood pulp fibers are well known to those skilled in
the art. For example, suitable cellulosic fibers produced from
southern pine that are useable in the present application are
available from a number of companies including Weyerhaeuser Company
under the designations C-Pine, Chinook, CF416, FR416, and NB416. A
bleached Kraft Douglas Fir pulp (D. Fir), and Grande Prairie
Softwood, all manufactured by Weyerhaeuser are examples of northern
softwoods that can be used. Mercerized fibers such as HPZ and
mercerized flash dried fibers such as HPZ III, both manufactured by
Buckeye Technologies, Memphis Tenn., and Porosinier-J-HP available
from Rayonier Performance Fibers Division, Jessup, Ga. are also
suitable for use in the present application when used with
crosslinked cellulose fibers. Other non crosslinked cellulose
fibers include chemithermomechanical pulp fibers (CTMP), bleached
chemithermomechanical pulp fibers (BCTMP), thermomechanical pulp
fibers (TMP), refiner groundwood pulp fibers, groundwood pulp
fibers, TMP (thermomechanical pulp) made by Weyerhaeuser, Federal
Way, Wash., and CTMP (chemi-thermomechanical pulp) obtained from
NORPAC, Longview, Wash., sold as a CTMP NORPAC Newsprint Grade, jet
dried cellulosic fibers and treated jet dried cellulosic fibers
manufactured by the Weyerhaeuser Company by the method described in
U.S. application Ser. No. 10/923,447 filed Aug. 20, 2004. These
fibers are twisted kinked and curled. Additional fibers include
flash dried and treated flash dried fibers as described in U.S.
Pat. No. 6,837,970,
[0008] Suitable crosslinking agents for making crosslinked fibers
include carboxylic acid crosslinking agents such as polycarboxylic
acids. Polycarboxylic acid crosslinking agents (e.g., citric acid,
propane tricarboxylic acid, and butane tetracarboxylic acid) and
catalysts are described in U.S. Pat. Nos. 3,526,048; 4,820,307;
4,936,865; 4,975,209; and 5,221,285 The use of C.sub.2-C.sub.9
polycarboxylic acids that contain at least three carboxyl groups
(e.g., citric acid and oxydisuccinic acid) as crosslinking agents
is described in U.S. Pat. Nos. 5,137,537; 5,183,707; 5,190,563;
5,562,740; and 5,873,979.
[0009] Polymeric polycarboxylic acids are also suitable
crosslinking agents for making crosslinked fibers. These include
polymeric polycarboxylic acid crosslinking agents are described in
U.S. Pat. Nos. 4,391,878; 4,420,368; 4,431,481; 5,049,235;
5,160,789; 5,442,899; 5,698,074; 5,496,476; 5,496,477; 5,728,771;
5,705,475; and 5,981,739. Polyacrylic acid and related copolymers
as crosslinking agents are described U.S. Pat. Nos. 5,549,791 and
5,998,511. Polymaleic acid crosslinking agents are described in
U.S. Pat. No. 5,998,511 and U.S. Pat. No. 6,582,553. CHB405, a
citric acid crosslinked cellulose fiber and CHB505, a polyacrylic
acid crosslinked cellulose, both commercially available from
Weyerhaeuser Company, Federal Way, Wash. were used in this
work.
[0010] In single or multi-ply paperboard construction a mixture of
wood pulp fibers and crosslinked cellulose fibers are used. In one
embodiment the crosslinked cellulosic fibers are present in at
least one layer at a level of 25 to 80 percent by total fiber
weight of the ply. In another embodiment the crosslinked fibers are
present at a level of 40 to 75 percent by total fiber weight of the
layer and in yet another embodiment they are present at a level of
50 to 70 percent by total fiber weight of the layer.
Ionic Demand Balance
[0011] The technology relies on the ability to balance the ionic
demand in the wet end of the paper machine such that 1) anionic
polymeric materials can be retained on the fibers and fines without
excess remaining in the water system, 2) the fibers and system do
not pass through the zero charge point which destabilizes retention
and drainage 3) since pulp fibers are anionic, some cationic
material can be added, however, adding too much cationic material
without balancing the excess anionic demand will either cause the
fibers to flocculate reducing formation and/or cause the drainage
to drop, impacting the runnability.
[0012] Each of the components used in the paperboard containing
crosslinked fiber in this disclosure has a specific charge density
typically measured by ionic demand titration. A Mutek PCD--Titrator
was used for the particle charge titration coupled with the PCD 02
Particle Charge Detector for measuring the ionic demand of the
component or fiber furnish. The method was performed according to a
procedure from A.E. Staley Manufacturing, a subsidiary of Tate and
Lyle, Decatur, Ill. The method is as follows.
1. Turn the Mutek on using the power switch on the back of the
instrument.
[0013] 2. Place 10 mL of a well mixed sample in the sample vessel.
Insert the plunger and washer into the vessel. The sample
consistency should be no more than 0.83. Thick stock samples should
be diluted. 3. With the instrument turned on, the plunger should
move up and down and a mV potential should be displayed. The sign
of the potential (+ or -) indicates whether the sample is cationic
(+) or anionic (-). 4. Titrate the sample with the appropriate
titrant until the mV potential reads 0 mV (PolyDADMAC is the
cationic polymer and is used to titrate anionic samples; PVSK or
PESNa are the anionic polymers used to titrate the cationic
samples). A buret or syringe can be used to deliver the titrant to
the sample. Titration should not be conducted with more than 4 mL
of titrant since higher volumes will give inaccurate measurements.
If the sample requires more than 4 mL of titrant, the sample should
be diluted or more concentrated titrant should be used. 5. Record
the amount of titrant used to titrate the sample. To calculate the
demand of the system, use the following equation:
"Ionic Demand" (ueq/L)=(mL titrant).times.(% titrant
dilution).times.(sample dilution)
[0014] Ionic Demand refers to the amount of anionic or cationic
charge required to neutralize the counter ion charge and is
expressed in meq/g or ueq/kg. For example, an additive with an
ionic demand of +2.2 meq/g has an anionic demand of 2.2 meq/g; an
additive with an ionic demand of -1.8 meq/g has a cationic demand
of 1.8 meq/g. Specific components whose ionic demand was measured
by the Mutek method are noted in Table 1, other component values
are from suppliers.
TABLE-US-00001 TABLE I Component Ionic Demand Fully bleached
Softwood kraft pulp ~-0.015 meq/g total Fully bleached Softwood
kraft pulp ~-0.0015 meq/g available CHB405 ~-0.43 meq/g total
CHB405 ~-0.015 meq/g available Kymene .RTM. 557H ~+2.2 meq/g
Hercobond .RTM. 2000 ~-1.8 meq/g STA-LOK .RTM. 300 ~+0.3 RediBOND
.RTM. 3050 ~-0.19 meq/g RediBOND .RTM. 2038 ~+0.24 meq/g STA-LOK
.RTM. 330 ~+0.41 meq/g PPD M-5133 ~+16 meq/g GALACTASOL .RTM.
SP813D ~+2.3 meq/g
[0015] With reference to the table, the difference between the
total and available ionic demand represents the amount of charge
that is internal to the fiber that is not accessible to polymers of
molecular weight above 300,000 g/mole. For papermaking, the
available ionic demand is more representative of the results
obtained in practice than the total ionic demand.
[0016] The situation is further complicated in a paper machine
wet-end where dilution water from outside sources and/or wash water
from pulp mill bleaching stages contain ionic materials, (both
dissolved and dispersed), is used to control consistency of the
pulp slurry. In integrated mills where excess ionic materials are
present, materials added to the pulp slurry to increase internal
bond strength can be consumed by the excess ionic materials. Also,
the available ionic sites on pulp wilt also depend on how much
refining has been done and on the basic fiber morphology, i.e. the
smaller the fiber or partial fiber the higher available surface
area, and therefore the higher available ionic demand.
[0017] In general it may be stated that the fiber slurry is anionic
to start with and should remain anionic through the paper making
process i.e. the ionic demand of the slurry should less than
zero.
[0018] Mechanically refined fiber can be added to the slurry to
increase the strength of the paperboard. In one embodiment the
mechanically refined fiber has a Canadian Standard Freeness of less
than 125 mL CSF, a curl index of 1/3 or less of the unrefined fiber
and a kink angle of 1/2or less of the unrefined fiber.
[0019] In one embodiment mechanically refined fiber is added to the
slurry followed by the addition of an anionic starch and then
followed by addition of a cationic fixative. After each addition
step the slurry ionic demand is less than zero. The slurry is
deposited on a foraminous support, dewatered forming a web and
dried to form a paperboard.
[0020] In one embodiment the total starch level on dry fiber is
from 50 to 120 lb/t. In another embodiment the total starch level
on dry fiber is from 60 to 100 lb/t. In yet another embodiment the
total starch level is 80 to 90 lb/t.
[0021] Cationic fixatives such as cationic starch (e.g.
STA-LOK.RTM. 300, STA-LOK.RTM. 330 and RediBOND.RTM.2038) have a
low anionic demand i.e. less than 1 meq/g. Other cationic additives
such as Kymene.RTM.557H have a high anionic demand (+2.2 meq/g). In
one embodiment the cationic fixative has an anionic demand of
greater than zero but less than one meq/g. In another embodiment
the cationic fixative has an anionic demand of from 1 meq/g to 10
meq/g.
[0022] The paperboard of the present application may be one of
several structures. In one embodiment the paperboard is a single
ply structure, in another the paperboard is a two-ply structure and
in yet another embodiment the paperboard is a multi-ply
structure.
[0023] In the method, the addition order of the additive can vary.
As stated earlier, in one embodiment, mechanically refined fiber is
added to the slurry followed by the addition of an anionic starch
and then followed by addition of a cationic fixative. After each
addition step the slurry ionic demand is less than zero. The slurry
is deposited on a foraminous support, dewatered forming a web and
dried to form a paperboard. In another embodiment mechanically
refined fiber is added to the slurry followed by the addition of a
cationic fixative and then followed by addition of an anionic
starch. After each addition step the slurry ionic demand is less
than zero. The slurry is deposited on a foraminous support,
dewatered forming a web and dried to form a paperboard. In yet
another embodiment, mechanically refined fiber is added to the
slurry followed by the addition of an anionic starch and then
followed by addition of first cationic fixative, followed by adding
a second cationic fixative. After each addition step the slurry
ionic demand is less than zero. The slurry is deposited on a
foraminous support, dewatered forming a web and dried to form a
paperboard. In each case, the first cationic fixative may have an
anionic demand of from 1 meq/g to 10 meq/g and the second fixant
may have an anionic demand of greater than zero but less than
1.
Mechanically Refined Fiber and High Levels of Starch
[0024] Fiber and polymer binders were applied to low density board
so that internal bond strength increases by 100% or more with 10%
or less increase in density. The effect of refining on freeness and
ionic demand is shown in Table 11.
TABLE-US-00002 TABLE II Effect Of Refining On Ionic Demand Kink
Ionic CSF, Curl angle, Demand,* #Test Fiber Description mL Index
.degree./mm meq/g 1 LV Lodgepole Pine - 720 0.25 92 -0.0008
Unrefined 2 LV Lodgepole Pine - EW 550 0.10 46 -0.0069 3 LV
Lodgepole Pine - EW 275 0.07 31 -0.0118 4 LV Doug. Fir - Unrefined
675 0.23 64 5 LV Doug. Fir - EW 85 0.07 28 -0.0114 6 LV Lodgepole
Pine - EW 65 0.05 18 -0.0167 7 LV Lodgepole Pine 33 0.05 21 -0.0114
*Fiber only LV, Longview EW, Escher Wyss VB, Valley Beater
Each of the following Examples were generated as follows: [0025] 1.
Handsheets formed using typical handsheet making equipment with an
extension to reduce the forming consistency. [0026] 2. 250 gsm OD
fiber. [0027] 3. 60% CHB405 (crosslinked fiber), dispersed
independently; several methods were used interchangeably (Valley
beater with no load, lab disk refiner with 1-2 amps over no load
and a pilot scale deflaker. Mechanical dispersion was done to
improve formation. [0028] 4. 40% Douglas Fir refined to 400 ml CSF;
pH was adjusted to 7. [0029] 6. 4 #/t Aquapel sizing agent. [0030]
7. 5 #/t Kymene.RTM.557H. [0031] 8. 25 #/t cationic starch,
(STA-LOK.RTM. 300)
The above formulation serves as a control; adjustments to the
chemistry are noted in each Example.
[0032] As defined herein, mechanically refined fiber (MRF) is
mechanically refined wood pulp for example, Lodgepole Pine having a
Canadian Standard Freeness <125 mL, a index 1/2 or less of
unrefined starting fiber and a kink angle of 1/2 or less of the
unrefined starting fiber. Curl Index and kink angle were determined
using a Fiber Quality Analyzer (FQA) as published in the Journal of
Pulp and Paper Science 21(11):J367 (1995). Mechanically refined
fiber can be generated to meet these criteria by different refining
methods which have different impact on conventional fiber
properties. Table III shows the effect on Z-direction tensile and
density of various formulations with mechanically refined fiber.
ZDT was determined by TAPPI 541.
TABLE-US-00003 TABLE III Effect Of Mechanically Refined Fiber
Addition On Strength Properties Den- sity Change in ZDT, .DELTA.
ZDT, Description g/cc Density kPa % 100% D. Fir 0.628 138 498 1138
Control (as above) 0.264 40.22 10% valley beater mechanically 0.292
10.6% 95.38 137 refined fiber replacing 10% D. Fir 5% Escher Wyss
mechanically 0.274 3.7% 78.14 94 refined fiber replacing 5% D. Fir
5% Escher Wyss mechanically 0.274 3.7% 110 174 refined fiber
replacing 5% D. Fir 5% Escher Wyss mechanically 0.259 -1.9% 52.86
31.4 refined fiber replacing 5% D. Fir Control 0.232 24.8 5% Escher
Wyss mechanically 0.238 2.5% 68.95 178 refined fiber replacing D.
Fir 5% mechanically refined fiber 0.242 4.3% 85.5 244 replacing D.
Fir (double disk refined) Control 0.255 40.22 5% Valley Beater
mechanically 0.265 3.9 69.81 73.5 refined fiber replacing D. Fir 5%
Valley Beater mechanically 0.256 0.4 80.15 99.3 refined fiber
replacing D. Fir .DELTA. indicates "change in"
Internal bond strength can be increased by replacing some of the
cationic starch with a higher ionic strength molecule such as
Kymene.RTM. as shown in the following example.
50% CHB405.
50% Lodgepole Pine refined to 400 mL CSF.
[0033] 10 #/t Kymene.RTM. 557H from Hercules. 10 #/t Stalok 400
cationic starch from Staley.
Mechanically refined Lodgepole pine fiber refined at 50 ml CSF
using an Escher Wyss laboratory refiner.
[0034] In this formulation the level of the Kymene.RTM.557H with an
ionic demand of +2.2 meq/g was doubled and the STA-LOK.RTM. 300
cationic starch with an ionic demand of +0.3 meq/g was reduced by
60%. As noted from the table, significant increases in ZDT bond
strength and Scott Bond can be obtained by this method
TABLE-US-00004 TABLE IV Effect On Strength Of Partial Replacement
Of Cationic Starch With A Higher Ionic Demand Polymer Mechanically
Scott refined fiber Density % ZDT % Bond % % by wt. g/cc Increase
kPa Increase J/m.sup.2 Increase 0% 0.222 23 98 10% 0.234 +5.4% 62
+170% 135 +38% 20% 0.260 +14.6% 125 +443% 173 +76.5%
[0035] A third technology is use of a starch excess. The general
approach was to overcome the normal limits of effective wet-end
starch, balancing the charge in the wet-end by adding excess
anionic starch and fixing it to the fibers by adding cationic
starch or other high charge density cationic polymers thus
balancing the system to near neutral charge density. The
neutralization was important to prevent excessive flocculation and
large impacts on drainage.
[0036] Specifically, total starch content added to the wet can be
increased to 2% to 5% based on dry fiber. Anionic starch such as
RediBOND.RTM. 3050 supplied by National Starch & Chemical or
Aniofax.RTM. AP25 supplied by Carolina Starches can be used.
Cationic fixatives include common cationic starches like
STA-LOK.RTM. 300 supplied by Staley Corp., Poly Aluminum Chloride
(PAC) like Nalco ULTRION.RTM. 8187 or high charge density cationic
polymers like M5133 and M5134, GALACTAOL.RTM. SP813D (anionic guar)
and Kymene.RTM. 557H supplied by Hercules Corp. and Nalco
NALKAT.RTM. 62060 (branched EPEDMA) Nalco NALKAT.RTM. 2020 (poly
DADMAC). As used herein, a high ionic demand is represented by a
polymer that has an ionic demand of 1 meq/g to 17 meq/g, either as
an anionic demand or as a cationic demand. For example,
Kymene.RTM.557H has an anionic demand of 2.2 meq/g and
Hercobond.RTM.2000 has a cationic demand of 1.8 meq/g.
[0037] The level of anionic starch needed to obtain high strength
development depends on the charge density and more importantly on
the retention. Typically, 2% to 5% addition level based on dry
fiber is adequate. The amount of cationic fixative depends entirely
on the size of the polymer and the cationic charge density. As
defined herein, a fixative is a charged polymer that ionically
bonds to a molecule of the opposite charge. In general the higher
the charge density the smaller the amount required and for equal
charge density the larger the polymer the smaller the amount
required.
[0038] The following data was based on laboratory handsheets of the
following formulation: [0039] 1. Handsheets formed using typical
handsheet making equipment with an extension to reduce the forming
consistency. [0040] 2. 250 gsm OD fiber. [0041] 3. 60% CHB405,
dispersed independently; several methods were used interchangeably,
(Valley Beater with no load, lab disk refiner with 1-2 amps over no
load condition, and a pilot scale deflaker). Mechanical dispersion
is done to improve formation. [0042] 4. 40% Douglas Fir refined to
400 ml CSF. [0043] 5. pH adjusted to 7. [0044] 6. 5#/t Kymene.RTM.
557H. [0045] 7. 4#/t Aquapel 625 sizing agent. [0046] 8. 25#/t
cationic starch (STA-LOK.RTM. 300)
Adjustments to the chemistry are noted in each Example.
EXAMPLE 1
[0047] The above described handsheet is the control. The following
adjustments were made to the non-fiber portion of the furnish, 80
lbs/t (4%) Aniofac.RTM. AP25 was mixed with the fibers, followed by
20 lbs/t cationic starch STA-LOK.RTM. 300. Then Kymene.RTM.557H was
added and the amount increased to 10 lbs/t. Last, before sheet
making a blend of cationic starch STA-LOK.RTM. 300 and Aquapel 625
were added, the cationic starch was reduced to 20 lbs/t and the
Aquapel was kept constant at 4 lbs/t. Handsheets were evaluated for
density, ZDT and Scott Bond the results are in Table V.
TABLE-US-00005 TABLE V Density ZDT Scott Bond Description g/cc kPa
J/m.sup.2 Control 0.243 45 80 4% Anionic Starch Example 1 0.273 204
119 (Aniofac .RTM. AP25)
EXAMPLE 2
[0048] The control handsheet as described above was adjusted as
follows to the non-fiber portion. 40 lbs/t Aniofax AP25 was mixed
with the fibers, followed by 20 lbs/t STA-LOK.RTM. 300 cationic
starch. Kymene.RTM. 557H at 5#/t was added and the same combination
of Stalok 300 and Aquapel 625 as in Example 1, i.e. 20 lb/t and 4
lb/t, respectively. Handsheets were evaluated for density, ZDT and
Scott Bond; the results are in Table V1 combined with the results
from Example 1.
TABLE-US-00006 TABLE VI Density ZDT Scott Bond Description g/cc kPa
J/m.sup.2 Control 0.243 45 80 4% Anionic Starch* Example 1 0.273
204 119 2% Anionic Starch* Example 2 0.262 85 113 *Aniofac .RTM.
AP25
EXAMPLE 3
[0049] The handsheet formulation described in Example 2 was altered
to contain mechanically refined fiber fibers so that the fiber
portion of the furnish is:
60% CHB405.
35% Fully Bleached D. Fir refined to 400 mL CSF.
5% Valley beater mechanically refined fiber--fully bleached kraft
Lodgepole Pine at .about.50 mL CSF.
The remainder of the additives are the same as in Example #2. The
results are shown in Table V11.
TABLE-US-00007 [0050] TABLE VII Density ZDT Scott Bond Description
g/cc kPa J/m.sup.2 Control 0.243 45 80 4% Anionic Starch* Example 1
0.273 204 119 2% Anionic Starch* Example 2 0.262 85 113 Control +
5% 0.274 78 106 Mechanically refined fiber 2% anionic starch + 5%
Example 3 0.283 122 148 mechanically refined fiber *Aniofac .RTM.
AP25
EXAMPLE 4
[0051] Adjustments were made to the non-fiber portion of the of the
handsheet formulation described in Example 3 (containing
mechanically refined fiber) as follows: 100 lb/t Aniofax.RTM. AP25
(was blended with the fibers followed by 90 lb/t Nalco 8187 PAC,
then 5 lb/t Kymene.RTM. 557H, 5 lb/t STA-LOK.RTM. 300 and 4 lb/t
Aquapel 625. The results are shown in Table VIII.
TABLE-US-00008 TABLE VIII Density ZDT Scott Bond Description g/cc
kPa J/m.sup.2 Control 0.243 45 80 Control + 5% mechanically 0.274
78 106 refined fiber 5% Anionic starch* + 4.5% Example 4 0.304 142
214 PAC *Aniofac .RTM. AP25
EXAMPLE 5
[0052] Adjustments were made to the non-fiber portion of the of the
handsheet formulation described in Example 3 (containing
mechanically refined fiber) as follows: 50 lb/t Aniofax.RTM. AP25
was blended with the fibers followed by 8 lb/t Nalco 62060 poly,
then 5 lb/t Kymene.RTM. 557H, 5 lb/t STA-LOK.RTM. 300 and 4 lb/t
Aquapel 625. The results are shown in the Table IX.
TABLE-US-00009 TABLE IX Density ZDT Scott Bond Description g/cc kPa
J/m.sup.2 Control 0.243 45 80 Control + 5% Mechanically 0.274 78
106 refined fiber 5% Anionic starch* + 4.5% Example 4 0.304 142 214
PAC 2.5% Anionic starch* + 0.4% Example 5 0.284 109 138 Poly DADMAC
*Aniofac .RTM. AP25
EXAMPLE 6
[0053] Adjustments were made to the non-fiber portion of the of the
handsheet formulation described in Example 3 (containing
mechanically refined fiber) as follows: 100 lb/t Aniofax.RTM. AP25
was blended with the fibers followed by 6 lb/t Nalco 2020 poly,
then 5 lb/t Kymene.RTM. 557H, 5 lb/t STA-LOK.RTM. 300 and 4 lb/t
Aquapel 625. The results are shown in Table X.
TABLE-US-00010 TABLE X Density ZDT Scott Bond Description g/cc kPa
J/m.sup.2 Control 0.243 45 80 Control + 5% Mechanically 0.274 78
106 refined fiber 5% Anionic starch* + 4.5% Example 4 0.304 142 214
PAC 2.5% Anionic starch* + 0.4% Example 5 0.284 109 138 Poly DADMAC
5% Anionic Starch* + 0.3% Example 6 0.279 218 215 Poly *Aniofac
.RTM. AP25
[0054] Single-ply handsheets designed to simulate the mid-ply of
low density multi-ply paperboard were made. A 0.015 percent to
0.035 percent consistency slurry was used in these studies.
Handsheet making equipment was standard 8''.times.8'' sheet mold
modified with an extended headbox so that twice the normal volume
of stock was used. This modification was necessary to improve
handsheet formation when using materials designed to generate high
bulk (e.g. crosslink fiber such as CHB405 and CHB505). Fiber
weights are expressed as a weight percent of the total fiber dry
weight; additives are based on weight of dry fiber.
[0055] A series of handsheets were made using different levels of
wet-end additives, different addition order and some changes in
fiber furnish to demonstrate the level of internal bond strength
that could be generated by starch loading the web. The additives
were added to the slurry in the order across each sample row and
the slurry stirred after each addition.
Series 1.
[0056] The Table XI below shows the conditions and formulations
used when making the series of handsheets
TABLE-US-00011 TABLE XI-A Handsheet Formulation And Addition Order.
Anionic Cationic Anionic Cationic PVOH Starch Starch Starch Starch
Target Celanese Mechanically Avebe STA- Avebe STA- Basis D. Celvol
Refined Aniofax LOK .RTM. Aniofax Kymene .RTM. LOK .RTM. Aquapel
wt. CHB405 Fir 165SF Fiber* AP25 300 AP25 557H 300 650 Code
g/m.sup.2 % % % % #/t #/t #/t #/t #/t #/t 1 250 60% 30% 5% 5% 0 0 0
5 25 4 2 250 60% 35% 0% 5% 0 0 0 5 25 4 3 250 60% 40% 0% 0% 40 20 0
5 20 4 4 250 60% 35% 0% 5% 40 20 0 5 20 4 5 250 60% 35% 0% 5% 0 20
40 5 20 4 6 250 60% 35% 0% 0% 80 20 0 10 10 4 7 250 60% 35% 0% 5%
80 20 0 10 10 4 8 250 60% 35% 0% 5% 0 10 80 15 10 4 9 250 60% 40%
0% 0% 0 0 0 5 25 4 *Lodgepole Pine refined with Valley Beater to 33
CSF
TABLE-US-00012 TABLE XI-B Calculated Ionic Demand As Chemical
Additions Are Made In Table XI-A Ionic Ionic Ionic Ionic strength
Ionic Ionic Ionic strength demand, strength with strength strength
strength with Ionic Ionic Ionic Ionic total with STA- with with
with STA- Aquapel demand demand demand demand pulp and Aniofax
.RTM. LOK .RTM. Aniofax .RTM. Kymene .RTM. LOK .RTM. 650 - end
CHB405 D. Fir PVOH MRF particles AP25 300 AP25 557H 300 point Code
ueq/g ueq/g ueq/g ueq/g ueq/g ueq/g ueq/g ueq/g ueq/g ueq/g ueq/g 1
-9 -0.45 0 -0.57 -10.02 -10.02 -10.02 -10.02 -4.52 -0.89 -0.89 2 -9
-0.53 0 -0.57 -10.1 -10.1 -10.1 -10.1 -4.60 -0.97 -0.97 3 -9 -0.6 0
0 -0.96 -14.2 -11.3 -11.3 -5.8 -2.9 -2.9 4 -9 -0.53 0 -0.57 -10.1
-14.7 -11.8 -11.8 -6.3 -3.40 -3.40 5 -9 -0.53 0 -0.57 -10.1 -10.1
-7.20 -11.8 -6.3 -3.40 -3.40 6 -9 -0.53 0 0 -9.53 -18.7 -15.8 -15.8
-4.8 -3.38 -3.38 7 -9 -0.53 0 -0.57 -10.1 -19.3 -16.4 -16.4 -5.4
-3.94 -3.94 8 -9 -0.53 0 -0.57 -10.1 -10.1 -0.86 -0.86 -1.34 0.11
0.11 9 -9 -0.6 0 0 -0.96 -0.96 -0.96 -0.96 -4.1 -0.48 -0.48
[0057] Each handsheet was then coated with Polyvinyl Alcohol (PVA)
coating, Celvol V24203 supplied by Celanese Ltd. The total coat
weight was about 50 g/m.sup.2 and was divided equally between each
side of the sheet. The coating was added to the surface to
facilitate testing Z-direction tensile (ZDT) and internal Scott
Bond because low density structures without the coating tend to
separate at the tape instead of the within the sheet.
[0058] Each sheet was evaluated for several physical properties
including basis weight, caliper, ZDT, internal Scott Bond and Taber
Stiffness (15.degree.). Scott Bond and Taber Stiffness were
determined by TAPPI T 569 om-00 and T 489 om-04, respectively.
Table XII below shows the results for these key characteristics
TABLE-US-00013 TABLE XII Physical Characteristics of Laboratory
Handsheets as Described in Table XI Basis Z-direction Scott Taber
Weight Density Tensile Bond Stiffness Sample g/m.sup.2 g/cm.sup.3
kPa J/m.sup.2 g cm 1 297 0.267 124 158 375 2 296 0.274 78 106 316 3
306 0.262 85 113 433 4 303 0.283 122 147 387 5 303 0.281 121 142
388 6 305 0.273 204 119 403 7 301 0.284 179 128 374 8 303 0.284 140
116 394 9 301 0.264 40 67 364
[0059] Samples 1, 2 and 9 can be considered the controls for this
experiment. Sample number 9 is a fiber formulation designed to
deliver low density paper and uses typical wet end chemistry (i.e.
cationic starch and Kymene.RTM.557H). The result is a very low
Scott Bond, but typical Taber Stiffness. Sample 2, incorporates
mechanically refined fiber in an effort to increase the internal
bond and, by itself, results in an increase in ZDT and Scott Bond,
but not enough to reach the targets needed for converting multi-ply
paperboard. It is estimated the minimum necessary ZDT needed for
converting is about 175-190 kPa.
[0060] Sample 1 incorporates mechanically refined fiber with a
particle PVOH--known as a good binder but is hindered by issues
with retention, cost and process reliability impacts. The increase
in ZDT and Scott Bond for sample 1 begins to approach the amount
needed for converting paperboard. Samples 3 and 4 show that by
adding 4% total starch to the furnish the ZDT and Scott Bond
essentially double. Adding mechanically refined fiber, Sample 4,
gives an increase of about the same magnitude as it did to the
original structure, Sample 2 v. Sample 4 and Sample 3 v. Sample
9.
[0061] Sample 5 shows reversing the order (i.e. adding cationic
starch first then anionic starch) in which the cationic and anionic
starch are added makes no difference to the strength
development
[0062] Samples 6 and 7 are a case where the amount of anionic
starch is doubled while the cationic starch remains constant.
Kymeme.RTM. 557H, a higher charge density cationic polymer, is used
to balance the additional anionic charge. The result is further
increase in internal bond, increasing ZDT by 500%, (Sample 6) over
the control and Scott Bond is unaffected by the additional starch
and Kymene.RTM. 557H. Sample 7 shows that by adding mechanically
refined fiber the effect on ZDT is negative in this case, yet the
Scott Bond increases.
[0063] Sample 8 adjusts the source of cationic charge further,
increasing the amount of Kymene.RTM.557H and decreasing the amount
of cationic starch. In Table XI-B the ionic demand of the system
crosses from negative to positive at the last point of cationic
starch addition and from Table XII the corresponding ZDT and Scott
bond are further reduced indicating that when the ionic demand
exceeds zero the effectiveness of the ionic binding system is
reduced.
[0064] The ZDT is reduced further, indicating that higher charge
density polymer is less effective than cationic starch in adding
internal bond strength. In general the impact of the starch loading
on Taber Stiffness at 15.degree. is small. For single ply
handsheets this is reasonable because caliper is the dominating
variable effecting bending stiffness. The impact of the starch
loading on density is small enough that the increase in elastic
modulus of the sheets due to the starch loading compensates for the
small changes in caliper. In a multi-ply web the same response
would be expected.
Series 2
[0065] A second set of handsheets was produced to determine the
impact of using high charge density cationic polymers to retain
additional anionic starch. It is thought that using higher charge
density polymers less total starch would be necessary to achieve
the same strength due to better retention. The result would reduce
the risk of affecting drainage and formation by adding excess
starch. Table XIII shows the formulations used in the
experiments.
TABLE-US-00014 TABLE XIII Handsheet Formulation and Addition Order
Anionic Cationic Cationic D. Fir @ Avebe STA- STA- CHB 500 ml
Aniofax .RTM. LOK .RTM. Nalco Nalco Nalco Kymene .RTM. LOK .RTM.
405 CSF MRF AP25 300 8187 62060 2020 557H 300 Code Wt. % Wt. % Wt.
% #/t #/t #/t #/t #/t #/t #/t 1 60 35 5 80 20 5 5 2 60 35 5 50 25 5
5 3 60 35 5 50 40 5 5 4 60 35 5 100 60 5 5 5 60 35 5 100 90 5 5 6
60 35 5 50 4 5 5 7 60 35 5 50 8 5 5 8 60 35 5 100 6 5 5 9 60 35 5
100 12 5 5 10 60 35 5 50 4 5 5 11 60 35 5 50 8 5 5 12 60 35 5 100 6
5 5 13 60 35 5 100 12 5 5 14 0 100 0 5 25 All Codes at 250
g/m.sup.2 target; all additives are on a dry fiber wt. basis
Aquapel 650 at 4 #/ton was used in all the studies (dry fiber
weight basis) MRF: Mechanically refined Fiber
[0066] Each handsheet was then coated with Polyvinyl Alcohol (PVA)
coating, Celvol V24203 supplied by Celanese Ltd. The total coat
weight was about 50 g/m.sup.2 and was divided equally between each
side of the sheet. The coating was added to the surface to
facilitate testing Z-direction tensile (ZDT) and internal Scott
Bond, because low density structures without the coating tend to
separate at the tape instead of the within the sheet.
[0067] Each sheet was evaluated for several physical properties
including basis weight, caliper, ZDT, Internal Scott Bond, Taber
Stiffness (15.degree.) and other. The table below shows the results
for these key characteristics
TABLE-US-00015 TABLE XIV Physical Characteristics Of Laboratory
Handsheets As Described In Table XIII Z-direction Taber Basis
Weight Density Tensile Scott Bond Stiffness Code g/m.sup.2
g/cm.sup.3 kPa J/m.sup.2 g cm 1 306 0.287 186 132 392 2 317 0.285
107 137 408 3 314 0.278 83 130 394 4 311 0.287 118 164 388 5 320
0.304 142 214 400 6 303 0.286 87 122 373 7 309 0.284 109 138 392 8
304 0.272 107 104 380 9 306 0.276 118 141 389 10 305 0.281 100 112
384 11 308 0.282 103 141 394 12 308 0.279 218 215 390 13 307 0.276
122 109 394 14 270 0.628 498 329 116 From Table XII - control with
normal strength additives, as a reference. 9 301 0.264 40 67
364
[0068] Sample code 9 from Tables X1 and XII above is the base
case.
[0069] The impact of using PAC such as Nalco 8187 (codes 2-5) to
retain the anionic starch in the presence of mechanically refined
fiber is less than that of using cationic starch on ZDT, however
the impact on Scott Bond is greater, suggesting that the PAC
improves the retention of the mechanically refined fiber giving
greater shear strength to the board.
[0070] For codes 6-9 using NALKAT.RTM.62060 a branched EPEDMA
cationic polymer as a fixative, the impact at 2.5% anionic starch
addition is roughly the same as the PAC Nalco 8187) but
significantly less ZDT development relative to the cationic starch,
Code 1. At the 5% anionic starch addition level there was no
further significant gain
[0071] Use of the polyDADMAC (codes 10-13) as a fixative shows more
promise than the other two cationic polymers at the 5% added starch
dose where it exceeded (Code 12) the cationic starch in ZDT and
Scott Bond development vs Code 1
[0072] The last code in Tables XIII and XIV, Code 14, is that of a
normal density board, included for comparison. The higher ZDT and
Scott Bond come at the expense of bending stiffness.
[0073] In general, at equal total starch levels it appears that
more ZDT is developed when using combination of anionic and
cationic starch than when using higher charge density cationic
polymers in combination with anionic starch. However, both methods
develop significant ZDT. Scott Bond has the opposite result. The
shear strength appears to increase at a greater rate than the ZDT
when using higher charge density cationic polymers in combination
with anionic starch.
[0074] Finally, the impact of the starch loading, independent of
the cationic fixative has little effect on the product density and
therefore little impact on the bending stiffness.
Pilot Trial
[0075] The disclosure was further explored using a pilot paper
machine where dynamic drainage and white water re-circulation could
be used to improve the simulation of commercial application on a
paper machine.
[0076] The fiber furnish used in all of the following examples was
the same, only the chemical additives and the order of addition
were changed. The fiber components were:
60% Weyerhaeuser CHB405
[0077] 35% Weyerhaeuser fully bleached kraft D. Fir wet lap refined
to .about.500 mL CSF
5% Douglas Fir refined to 85 ml CSF (Escher Wyss refined)
[0078] The chemical components were combinations of some or all of
the following, levels and addition order are shown in Table XV.
Kymene.RTM. 557H supplied by Hercules Incorporated (cationic wet
strength resin)
Aquapel.RTM. 650 supplied by Hercules Incorporated (AKD sizing
agent)
Hercobond.RTM. 2000 supplied by Hercules Incorporated (anionic
polyacrylamide, retention aid)
RediBOND.RTM. 3050 supplied by Hercules Incorporated (anionic
starch)
RediBOND.RTM. 2038 supplied by Hercules Incorporated (cationic
starch)
PPD M-5133 supplied by Hercules Incorporated (cationic high charge
density polymer)
GALACTASOL.RTM. SP813D supplied by Hercules Incorporated (cationic
guar gum)
[0079] The pilot paper machine was a standard Fourdrinier type
single ply former. The design is such that there are several
chemical addition points so that wet end additive effects can be
studied. FIG. 1 shows the basic unit operations with the chemical
addition points. indicated as lower case letters as in Table XV.
The addition points have been labeled and should be used as a
reference for the formulations shown in Table XV.
[0080] Other unit operations were changed to maximize the bulk, for
example, lowering the amount of vacuum on the forming table suction
boxes, lifting the Dandy rolls away from the web using only one wet
press, a normal drying profile, no size press (typical solids
entering dryer 32-36%) no calendaring and finally, samples were
taken for evaluation at the reel (eliminating effect of reel
tension)
[0081] For each different formulation, the machine was run 10 to 15
minutes after making adjustments and insuring the basis weight was
on target. In this way, the white water was completely turned over
and reach equilibrium with the new chemistry. Target basis weight
was 200 g/m.sup.2.
[0082] Each sample was then coated with Polyvinyl Alcohol (PVA)
coating, Celvol V24203 supplied by Celanese Ltd. The total coat
weight was about 22 g/m.sup.2 and was divided equally between each
side of the sheet. The coating was added to the surface to
facilitate testing Z-direction tensile (ZDT) and Internal Scott
Bond, because low density structures without the coating tend to
separate at the tape instead of the within the sheet.
TABLE-US-00016 TABLE XV Wet End Additives for Pilot Paper Machine
Starch Loading Trials. Code b c d e g h 1 5 #/t Kymene .RTM. 2 #/t
Hercobond 10 #/t RediBOND 2038 4.5 #/t Aquapel 650 557H 2000 2 20
#/t 20 #/t RediBOND 5 #/t 2 #/t Hercobond 10 #/t RediBOND 2038 4.5
#/t Aquapel 650 RediBond2038 3050 Kymene .RTM. 2000 557H 3 20 #/t
RediBond 20 #/t RediBOND 5 #/t 10 #/t RediBOND 2038 4.5 #/t Aquapel
650 2038 3050 Kymene .RTM. 557H 4 30 #/t RediBond 40 #/t RediBOND 5
#/t 2 #/t Hercobond 10 #/t RediBOND 2038 4.5 #/t Aquapel 650 2038
3050 Kymene .RTM. 2000 557H 5 20 #/t RediBond 60 #/t RediBOND 10
#/t 2 #/t Hercobond 10 #/t RediBOND 2038 4.5 #/t Aquapel 650 2038
3050 Kymene .RTM. 2000 557H 6 20 #/t RediBond 10 #/t Kymene .RTM.
20 #/t 2 #/t Hercobond 10 #/t RediBOND 2038 4.5 #/t Aquapel 650
2038 557H RediBOND 2000 3050 7 30 #/t RediBond 10 #/t Kymene .RTM.
40 #/t 2 #/t Hercobond 10 #/t RediBOND 2038 4.5 #/t Aquapel 650
2038 557H RediBOND 2000 3050 8 40 #/t RediBond 20 #/t RediBOND 5
#/t 10 #/t RediBOND 2038 4.5 #/t Aquapel 650 2038 2038 Kymene .RTM.
557H 9 40 #/t 2 #/t 8.2 #/t 10 #/t RediBOND 2038 4.5 #/t Aquapel
650 RediBOND 3050 M-5133 Hercobond 2000 10 5 #/t Kymene .RTM. 2 #/t
Hercobond 10 #/t RediBOND 2038 4.5 #/t Aquapel 650 557H 2000 11 30
#/t 10 #/t Kymene .RTM. 40 #/t 2 #/t Hercobond 10 #/t RediBOND 2038
4.5 #/t Aquapel 650 RediBOND 2038 557H RediBOND 2000 3050 12 30 #/t
5 #/t 40 #/t 2 #/t Hercobond 10 #/t RediBOND 2038 4.5 #/t Aquapel
650 RediBOND 2038 Kymene .RTM. 557H RediBOND 2000 3050 13 30 #/t
2.5 #/t Kymene .RTM. 40 #/t 2 #/t Hercobond 10 #/t RediBOND 2038
4.5 #/t Aquapel 650 RediBOND 2038 557H RediBOND 2000 3050 14 30 #/t
40 #/t RediBOND 5 #/t 2 #/t Hercobond 10 #/t RediBOND 2038 4.5 #/t
Aquapel 650 RediBOND 2038 3050 Kymene .RTM. 2000 557H 15 8 #/t 40
#/t RediBOND 5 #/t 2 #/t Hercobond 8 #/t GALACTASOL 4.5 #/t Aquapel
650 GALACTASOL 3050 Kymene .RTM. 2000 SP813D SP813D 557H 16 40 #/t
20 #/t RediBOND 5 #/t 4 #/t GALACTASOL 4.5 #/t Aquapel 650 RediBOND
3050 2038 Kymene .RTM. SP813D 557H Lower case letters refer to the
additive addition points in FIG. 1
Codes number 1 and 10 are controls for two different running days,
code 14 is a repeat of code 4 on a different day and code 11 is a
repeat of code 7 on a different day. The physical characteristics
of the resultant paper are shown in Table XV.
TABLE-US-00017 TABLE XVI Physical Characteristics of Pilot Paper
Machine Samples in Table XV Geometric Geometric Basis Z-direction
Mean Scott Mean Taber Weight Density Tensile Bond Stiffness Code
g/m.sup.2 g/cm.sup.3 kPa J/m.sup.2 g cm 1 228 0.271 161 198 135 2
256 0.273 194 242 163 3 251 0.283 204 258 161 4 245 0.274 219 252
166 5 237 0.284 265 236 147 6 236 0.276 241 227 146 7 239 0.279 232
236 146 8 262 0.288 199 246 190 9 236 0.260 134 189 156 10 231
0.271 192 227 140 11 230 0.295 350 354 127 12 229 0.290 360 340 131
13 234 0.288 319 323 131 14 244 0.292 339 340 144 15 228 0.288 305
297 134 16 243 0.273 269 345 146
Pilot Machine Versus Control
[0083] The effect of starch loading is basically the same, it is
estimated that the target internal bond strength that would be
enough for performance during converting is about 2.times. of the
control samples. For the pilot trial ZDT doubled and Scott Bond
increased 75%.
[0084] By loading the wet-end with between 2% and 4% total starch
(anionic and cationic), ZDT can be increased by approximately 25%
to 85% relative to the same furnish with conventional levels of
cationic starch (Codes 2-8, 11-14).
[0085] Loading up to 2% anionic starch into the wet-end and using
high charge density cationic polymer (code 9) to retain the starch
little or no gain in ZDT or Scott Bond was achieved.
[0086] Loading the wet-end with up to 2% anionic starch and using
cationic guar gum (codes 15 and 16) to improve retention as a
substitute for cationic starch about 40%-50% increase in ZDT was
obtained.
[0087] When changing the order of addition, indications were that
adding the anionic starch after the cationic material resulted in
better strength efficiency.
[0088] Starch loading resulted in an increase in density of <10%
in all cases and had no significant impact on stiffness.
* * * * *