U.S. patent application number 10/704687 was filed with the patent office on 2005-05-12 for method of controlling tackiness in papermaking.
Invention is credited to Mah, Thomas C.C..
Application Number | 20050098287 10/704687 |
Document ID | / |
Family ID | 34552178 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050098287 |
Kind Code |
A1 |
Mah, Thomas C.C. |
May 12, 2005 |
METHOD OF CONTROLLING TACKINESS IN PAPERMAKING
Abstract
To reduce the problem of tackiness caused by contaminants in
recycled paper, effective amounts of talc and a terpene such as
D-limonene are added to paper stock in conjunction with chemical
fixing agents and retention aids. The terpene increases the
affinity of the contaminants for the talc, thus increasing
detackification of the contaminants and improving the productivity
of the papermaking process.
Inventors: |
Mah, Thomas C.C.; (Ontario,
CA) |
Correspondence
Address: |
CLARK & BRODY
1090 VERMONT AVENUE, NW
SUITE 250
WASHINGTON
DC
20005
US
|
Family ID: |
34552178 |
Appl. No.: |
10/704687 |
Filed: |
November 12, 2003 |
Current U.S.
Class: |
162/173 ;
162/147; 162/169; 162/181.6; 162/181.7; 162/199 |
Current CPC
Class: |
D21H 21/02 20130101;
D21H 11/14 20130101 |
Class at
Publication: |
162/173 ;
162/199; 162/169; 162/181.6; 162/181.7; 162/147 |
International
Class: |
D21H 017/74 |
Claims
What is claimed is:
1. In a method of making paper from raw materials containing
contaminants that use talc or bentonite as an additive to detackify
contaminants in paper stock, the improvement comprising adding
effective amounts of a terpene to increase affinity of the
contaminants to the talc or bentonite.
2. The method of claim 1, wherein the terpene is one or D-limonene
or turpentine oil.
3. The method of claim 1, wherein a chemical fixing agent is added
either before or after addition of the terpene, the chemical fixing
agent added in an effective amount to fix the contaminants and the
talc or bentonite to fibers and fines in the paper stock.
4. The method of claim 1, wherein an effective amount of a
retention aid is added during the papermaking method, addition of
the retention aid following the steps of adding the talc or
bentonite and terpene.
5. The method of claim 3, wherein an effective amount of one or
more retention aids are added during the papermaking method,
addition of the retention aid following the steps of adding the
talc or bentonite, terpene, and chemical fixing agent.
6. The method of claim 3, wherein the chemical fixing agent is
added prior to addition of the terpene.
7. The method of claim 3, wherein the chemical fixing agent is
added after addition of the terpene.
8. The method of claim 5, wherein the chemical fixing agent is
added prior to addition of the terpene.
9. The method of claim 5, wherein the chemical fixing agent is
added after addition of the terpene.
10. The method of claim 1, wherein the method of making paper uses
substantially all recycled paper as raw material.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to a method of controlling
tackiness during papermaking, and in particular to a method that
employs talc and a terpene such as d-limonene during the
papermaking process to reduce tackiness of contaminants and enhance
the papermaking process productivity.
BACKGROUND ART
[0002] The method of making paper is well known in the art.
Generally, recovered papers are first defiberized in a pulper with
the additions of chemicals in the recycle pulp mill. Then the pulp
is subjected to various ink and contaminant removal treatments. In
these steps, the majority of the contaminants present in the
recovered papers are removed.
[0003] After the pulp mill, the cleaned and de-inked pulp is pumped
to the paper machine system. In this system, the pulp is further
treated with different types of chemicals at the wet end before
being fed to the paper machine for paper making. One example of an
additive is a retention aid which is designed to increase the
retention efficiency of fine materials in the paper formulation.
One example of a retention aid is a high mass copolymer of
acrylamide. Another additive used is a chemical fixing agent, which
is primarily intended to attach contaminants to the paper product.
An example of this type of fixing agent is a cationic polyamine or
cationic starch. These additives can be added at various locations
in the papermaking process. Retention aids are often added
downstream of the pressure screen and the fixing agents can be
added to thick or thin stock. The fixing agents are added at
various locations as well, e.g., before or after the fan pump or
into a thick stock stream or chest.
[0004] The paper machine consists of three sections--the forming,
pressing and drying sections. Through these three sections, the
pulp is first drained into wet sheet, then pressed and finally
dried into paper in the dryers.
[0005] The daily paper machine production and efficiency is
affected by many factors, one of these being the unexpected down
time due to breaks occurring during papermaking. The breaks could
be caused by mechanical defects and/or contaminant deposition in
the paper machine.
[0006] One particular problem in recycling paper is the use of
different grades of recovered papers as the feedstock for pulp
preparation. These recovered papers are generally contaminated with
different types of undesirable materials. Examples of contaminants
are: plastic bags and bottles; box board and old corrugated
containers (OCC), metal cans, envelops with glues, coating
materials of magazines, different types of adhesives, and hot melt
bindings of books and magazines.
[0007] The plastic and heavy metal materials can be effectively
removed in the recycle plant without any difficulty. Unfortunately,
not all the glues, adhesives and coating materials can be
removed.
[0008] It was found that after pulping, some of the glues,
adhesives and coating materials present in the recovered paper
become very fine particles (estimated to be between 5-50 um) and
are trapped in the pulp being sent to the paper machine. Most of
these materials were found to be polyvinyl acetate or PVAc-based
contaminants.
[0009] PVAc is one of the common synthetic polymers used in the
commercial glues and latex applications (other common synthetic
polymers being styrene butadiene rubber or SBR and polyacrylate).
Latex is also widely used as binder in coated paper manufacturing.
The problem with PVAc is that they are sometimes fine in size and
difficult to remove using pressure screens.
[0010] Most of these PVAc-contaminant particles are not very tacky
at the paper machine wet end temperature (115-120 degree F.), and
they passed through the forming and pressing sections without
causing deposition problem. However, once in the dryer section
where the temperature reach up to 265 degree F., the PVAc particles
becomes very tacky, depositing on dryer fabrics and dryer cans.
This can result in frequent dry end breaks that adversely affect
the paper machine production and efficiency.
[0011] As such, a need exists to improve the performance of
papermaking processes by reducing or eliminating the adhesive
affect of the contaminants, particularly during the drying phase of
the papermaking process.
[0012] One technique that has been proposed in the prior art to
reduce the tackiness or "stickies" problem is the addition of talc
or bentonite to the papermaking system. However, this technique has
not proven to be entirely successful and the stickies still
represent a major challenge to the papermaking industry.
[0013] The present invention responds to this need by providing an
improved papermaking process which reduces the affect of the
adhesive or tacky qualities of PVAc particles during the
papermaking process, especially the dryer phase.
SUMMARY OF THE INVENTION
[0014] It is a first object of the present invention to provide an
improved papermaking process.
[0015] Another object of the present invention is a papermaking
process that controls the tackiness of PVAc particles to reduce or
eliminate production slowdowns and disruptions dues to unwanted
adhesion caused by the PVAc particles.
[0016] Yet another object of the present invention is a method of
making paper which uses effective amounts of talc and a terpene
such as d-limonene for control of the tackiness of PVAc particles
during papermaking.
[0017] Other objects and advantages of the present invention will
become apparent as a description thereof proceeds.
[0018] In satisfaction of the foregoing objects and advantages, the
present invention is an improvement in the method of making paper,
particularly papermaking techniques that involve recycled paper,
high levels of contaminants, and those that use talc or bentonite
to treat the contaminants. The invention entails adding an
effective amount of a terpene prior to the addition of the talc or
bentonite. The use of the terpene enhances the affinity between the
contaminants and the talc or bentonite. The terpene can be any
terpene but is preferably an orange oil such as D-limonene or a
turpentine oil.
[0019] Another aspect of the invention for solving the problem of
stickies is the use of a chemical fixing agent as an additive in
conjunction with the terpene and talc/bentonite additions. The
chemical fixing agent can be any of the known types that are
cationic starches or cationic polyamine, and it is added either
before or after the terpene addition.
[0020] One or more retention aids can be added as are
conventionally done in papermaking processes after the talc or
bentonite has been added.
[0021] The process is particularly adapted for papermaking that
employs recycled paper as its raw material source, i.e.,
substantially all of its raw material is derived from recycled
paper, since it is these operations that suffer the most from
contaminants such as PVAcs.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The present invention offers significant improvements in
methods of making paper, particularly papermaking processes which
derive their starting materials from recycled paper stock. This
stock is typically laden with impurities and contaminants that can
be very disruptive to the papermaking process, and reduce
productivity and increase costs. The present invention solves an
important problem by detackifying PVAc-particles and contaminants
carrying these types of particles. By detackifying these
contaminants, the interruptions in the drying phase of papermaking
are vastly reduced. While these materials were extremely sticky or
tacky at the temperatures typically used during drying, the
inventive method essentially detackifies these contaminants so that
they cannot disrupt the papermaking process.
[0023] In its broadest embodiment, the invention involves an
improvement in the papermaking process to effectively control the
problem of stickies created by contaminants found in the raw
materials used for papermaking. The invention comprises a novel and
unique sequence of adding an effective amount of a terpene,
preferably d-limonene, to paper stock followed by the addition of
an effective amount of talc or bentonite. The use of the terpene
enhances the affinity between the contaminants contained in the
stock, e.g., PVAcs, and the talc or bentonite. With this affinity,
the talc is better able to detackify the PVAcs, which then results
in an improved papermaking operation.
[0024] In a preferred mode, the talc/bentonite and terpene addition
are used in conjunction with chemical fixing agents and retention
aids. In one mode, the terpene and talc/bentonite are added between
additions of one or more fixing chemical agents and retention aids.
In another mode, the fixing chemical agent(s) are added after the
terpene addition and prior to the talc/bentonite addition. There
are no defined limits for the amount of terpene since the amount
could vary with each papermaking process. However, the amount is
considered to be a sufficient or effective amount to enhance the
affinity of the contaminants to the talc/bentonite to produce
effective detackification.
[0025] While preferred sequences are disclosed wherein the
placement of the chemical fixing agent varies as being before or
after the addition of the terpene, the addition of the terpene
should precede the addition of the talc or bentonite and the
terpene, chemical fixing agent and talc/bentonite additions should
precede the retention aid addition.
[0026] Based on plant trials, preferred amounts of the terpene
addition are believed to range between about 0.2 to up to about 1.0
lbs./ton of pulp. Preferred amounts of the talc/bentonite addition
range between 10-50 lbs./ton pulp.
[0027] The chemical fixing agents intended for use in the invention
are those fixing agents that are commonly used in papermaking
processes for attaching contaminants to fines and fibers. The
chemical fixing agent helps bind the talc/bentonite--PVAc
contaminants to the fines and fibers in the stock. Likewise,
retention aids as are commonly used in papermaking can be selected
from any of the known agents that are typically used in papermaking
for fixing and strength purposes, and retention purposes. Preferred
fixing agents are cationic types, either starches or polyamines,
and poly-DADMAC. Retention aids can be high molecular weight
polyacrylamides. Preferred ranges for these additives include
1.0-3.0 lbs./ton pulp for the cationic polyamines, and 4-10
lbs./ton pulp for the cationic starches. Retention aid amounts also
vary depending on the type used; 1-4 lbs./ton pulp for coagulants,
and 0.5-2.5 lbs/ton pulp for flocculants.
[0028] The inventive control technique for stickies can be applied
to any recycled paper mill operation confronted with a paper
machine stickies deposition problem. It could potentially make all
the existing stickies detackification processes more versatile and
effective. The inventive process is particularly valuable to mills
that use recycled paper as their sole source of raw material, and
those using recycled paper to produce high brightness specialty
sheets. Because of the recycled paper raw material, these mills are
plagued with PVAc-related deposition problems. By instituting the
inventive stickies control scheme, these mills would be able to
operate with less dryer deposition problem and improved
productivity.
[0029] The locations in the papermaking process where the additives
are added to the paper stock can vary depending on the exact layout
and equipment used in the process. One example of locations would
be adding the chemical fixing agent at the stock storage after
pulping. The terpene could be added before the machine chest with
the talc or bentonite added at the machine chest. The retention
aids would be added as typically done in a papermaking process.
When using a two component retention aid system, the coagulant
would be added before the cleaner, and the flocculant before or
after screening.
[0030] The invention is a great improvement over processes that
used talc alone because talc is only effective in detackifying
stickies (i.e. pressure sensitive adhesives), which are tacky under
normal paper machine wet end process temperatures. By practicing
the invention, stickies control is broadened significantly in the
recycled paper mill operations, and enhanced business opportunities
are created for the talc and/or bentonite suppliers.
[0031] As part of the effort to solve the problem of stickies in
papermaking, plant trials were conducted using fixing agents and
retentions aids. More specifically, a scheme was proposed that
involved two steps. First, the PVAc contaminants were fixed onto
fines and fiber with a fixing agent. Then, the PVAc-containing
fines and fibers were retained onto sheet with retention aids, thus
removing from the papermaking machine system. The intent of this
(fixing chemical/retention aid) addition sequences was to remove
the PVAc particles with the sheet, thereby reducing their content
in the paper machine system and minimizing their tendency to
agglomerate into bigger aggregates and deposit in paper
machine.
[0032] This scheme, however, was only partially effective as the
fine PVAc particles retained on the sheet still become tacky at
high temperature in the dryer cans. As a result, the mill continued
to be confronted with paper machine deposition and break
problem.
[0033] An alternative approach was designed to overcome the problem
by the use of talc and/or bentonite. Talc and bentonite are known
hydrophobic minerals, which are widely used in the paper industries
for stickies control. Two trials with talc and bentonite were
conducted with the first trial using talc only. Talc was added to
the pulp before the retention aid addition and no fixing chemical
was added (i.e. the talc/retention aid sequence). In the second
trial using bentonite, bentonite was added to the machine chest
after a chemical fixing agent addition and this was followed by the
retention aid addition (i.e. the fixing
chemical/bentonite/retention aid sequence). Both trials, however,
were not successful and their additions did not help to reduce the
paper machine deposition and breaks. A potential reason for the
failures was thought to be that the PVAc particles were not tacky
at the paper machine wet end temperature (115-120 degree F.). As a
result, there was little affinity between the talc and PVAc
particles and most of the PVAc particles during the trials could
remain uncoated and undetackified.
[0034] Another trial was conducted embodying the invention. In this
trial, an orange oil based dispersant (commercially availably as
Dyasol, a mix of 30% D-limonene, 1% surfactant and the balance
water) was added to the pulp before the talc addition. The oil
component of Dyasol would attach to the PVAc particle surfaces
making them highly hydrophobic and more readily coated with talc
and detackified.
[0035] Two addition sequences were tried in two different paper
mills. In each sequence, a fixing chemical or agent and retention
aids were added with the D-limonene addition.
[0036] In Mill No. 1, the sequence of addition was fixing
chemical/Dyasol/talc/and retention aids. The fixing chemical was a
cationic polyamine (Bufloc 384 from Buckman), the retention aid was
a single component cationic polyacrylamide from Versa Chemical. The
chemical fixing agent rate of addition was 1.5-2.5 lbs./ton pulp.
The retention aid addition was 0.5-1.0 lbs./ton pulp. The Dyasol
addition rate was 0.3-0.5 lbs./ton pulp. The talc addition rate was
30-45 lbs./ton pulp.
[0037] In Mill No. 2, the sequence of addition was Dyasol/fixing
chemical/talc/retention aids. The chemical fixing agent was a
modified starch with a cationic charge (Raisabond from Raiso
Chemical), two retention aids were used, a coagulant and a
flocculant. The coagulant was a cationic polyamine (Bufloc 5132
from Buckman) and the flocculant was a cationic polyacrylamide from
Buckman. The fixing chemical rate of addition was 1.5-2.5 lbs./ton
pulp. The coagulant addition was 5.0-8.0 lbs./ton pulp. The
flocculant addition was 1.0-2.0 lbs./ton pulp. The Dyasol addition
rate was 0.25-0.4 lbs./ton pulp. The talc addition rate was 25
lbs./ton pulp.
[0038] Both chemical addition sequences were found to work very
well and significantly reduced the paper machine deposition and
breaks. As a result, the paper machines in both mills were able to
operate with fewer breaks and improved efficiencies.
[0039] These trials clearly demonstrated that the Dyasol was indeed
effective in enhancing the affinity between PVAc particles and
talc--a condition required for the successful detackification of
PVAc with talc.
[0040] It should also be noted that trials conducted at Mill No. 1
used sequences of adding Dyasol/talc/retention aids. While these
trials showed that the use of the D-limonene with the talc improved
the operation in terms of stickies and the trials were somewhat
effective, better performance should still be sought. In another
trial, the sequence of adding fixing chemical/talc/retention aids
resulted in very poor results, and clearly showed that talc alone
was ineffective for stickies control. The reason optimum
performance was obtained when using the chemical fixing agents was
that the detackified contaminants, e.g., the PVAcs treated with the
terpene and talc are effectively bound or attached to the fines and
fibers by the fixing agent so that they would be retained on the
paper sheet and kept out of the paper machine system. Thus, fixing
chemical plays an important role in optimizing the success of these
PVAC control schemes, although the fixing agents could be optional
if the levels of contaminants were such that the terpene and talc
would effectively eliminate the stickies problem. As noted above,
the fixing agents attach the detackified PVAc particles onto fines
and fibers and allowed them to be more easily retained onto sheets
with the retention aid addition. As a result, there were less free
PVAC contaminants being recycled around in the paper machine
system. This minimized the PVAc particles agglomeration
problem--another factor to increased paper machine deposition.
[0041] While D-limonene in the form of Dyasol has been found to be
effective in reducing the stickies problem in papermaking, it is
believe that since D-limonene is a terpene, that other terpenes
could also be employed in place of D-limonene as an effective
additive with the talc, e.g., turpentine oil. As mentioned above,
it is also believe that while certain levels of the various
additives worked in conjunction with the mill trials, other amounts
could also prove effective in treating the stickies problem faced
by the papermaking industry. Thus, it is believed that the amount
of terpene, talc, fixing chemicals and retention aids are added in
amounts that are effective for stickies control, and this amount
may vary depending on the particularities of the papermaking
process being used. For example, the two mill trials show that each
mill is different in the amount of fixing chemical, retention aid
and talc, and the invention does not require absolute amounts of
the various additives for it to be effective.
[0042] As such, an invention has been disclosed in terms of
preferred embodiments thereof, which fulfills each and every one of
the objects of the present invention as set forth above and
provides a new and improved method of making paper, particularly
methods using recycled paper stock.
[0043] Of course, various changes, modifications and alterations
from the teachings of the present invention may be contemplated by
those skilled in the art without departing from the intended spirit
and scope thereof. It is intended that the present invention only
be limited by the terms of the appended claims.
* * * * *