U.S. patent application number 10/509181 was filed with the patent office on 2005-08-11 for white pitch deposit treatment.
Invention is credited to Blazey, Matthew Anthony, Chen, Gordon Cheng I., Edmonds, Christian Bruce, Grimsley, Swindell Allen, Williams, Stephanie Caine.
Application Number | 20050173088 10/509181 |
Document ID | / |
Family ID | 28792045 |
Filed Date | 2005-08-11 |
United States Patent
Application |
20050173088 |
Kind Code |
A1 |
Grimsley, Swindell Allen ;
et al. |
August 11, 2005 |
White pitch deposit treatment
Abstract
The present invention relates to a deposit control system,
consisting of an inorganic or organic (natural or synthesized)
coagulant and a microparticulate material (synthetic or
naturally-occurring) such as bentonite clay, cross-linked polymer,
colloidal silica, polysilicate, for pulp containing white
pitch/stickies.
Inventors: |
Grimsley, Swindell Allen;
(Chesapeake, VA) ; Blazey, Matthew Anthony;
(Suffolk, VA) ; Edmonds, Christian Bruce;
(Smithfield, VA) ; Williams, Stephanie Caine;
(Suffolk, VA) ; Chen, Gordon Cheng I.;
(Chesapeake, VA) |
Correspondence
Address: |
CIBA SPECIALTY CHEMICALS CORPORATION
PATENT DEPARTMENT
540 WHITE PLAINS RD
P O BOX 2005
TARRYTOWN
NY
10591-9005
US
|
Family ID: |
28792045 |
Appl. No.: |
10/509181 |
Filed: |
September 23, 2004 |
PCT Filed: |
April 3, 2003 |
PCT NO: |
PCT/EP03/03487 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60370653 |
Apr 8, 2002 |
|
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Current U.S.
Class: |
162/199 ;
162/147; 162/158; 162/164.1; 162/164.6; 162/168.2; 162/168.3;
162/181.1; 162/181.6; 162/181.7; 162/181.8 |
Current CPC
Class: |
D21H 17/66 20130101;
D21H 23/765 20130101; D21H 21/02 20130101; D21H 17/68 20130101;
D21H 11/14 20130101; D21H 17/455 20130101; D21H 17/56 20130101 |
Class at
Publication: |
162/199 ;
162/158; 162/164.1; 162/181.1; 162/181.8; 162/181.7; 162/181.6;
162/168.3; 162/168.2; 162/164.6; 162/147 |
International
Class: |
D21H 021/02; D21H
023/76; D21H 017/68; D21H 017/44; D21H 017/54; D21H 017/66; D21H
011/14 |
Claims
1. A process for making paper comprising adding to a paper stock an
effective amount for reducing the deposition of white pitch of at
least one cationic coagulant polymer or an inorganic coagulant and
followed by the addition of a microparticle material, wherein the
paper stock contains pulp derived at least in part from recycled
paper products.
2. A process according to claim 1 wherein the microparticle
material is selected from the group consisting of swellable clay
materials, cross-linked polymer, colloidal silica, borosilicate or
a suspension of microparticulate anionic material selected from
bentonite, colloidal silica, polysilicate microgel, polysilicic
acid microgel and crosslinked microemulsions of water soluble
monomeric material and mixtures thereof.
3. A process according to claim 2 wherein the microparticle
material is an anionic material.
4. A process according to claim 2 wherein the microparticle
material is a swellable clay from the smectite family.
5. A process according to claim 4 wherein the microparticle
material is a mineral selected from the group consisting of
bentonite, montmorillonite, saponite, hectorite, beidilite,
nontronite, fullers' earth and mixtures thereof.
6. A process according to claim 5 wherein the microparticle
material is a mineral composed primarily of bentonite.
7. A process according to claim 1 wherein the cationic coagulant
polymer is a homopolymer containing recurring cationic groups or a
copolymer of at least 80% by weight cationic monomer and 0 to 20%
by weight acrylamide or other non-ionic monomer.
8. A process according to claim 7 wherein the cationic groups are
derived from the group consisting of diallyl dimethyl ammonium
chloride and dialkylaminoalkyl (meth)-acrylates or
dialkylaminoalkyl (meth)-acrylamides or quaternary ammonium salts
thereof.
9. A process according to claim 8 wherein the cationic groups are
dimethylaminoethyl acrylate or methacrylate quaternary ammonium
salt.
10. A process according to claim 1 wherein the cationic coagulant
polymer is a dicyandiamide polymer, a polyamine or a
polyethyleneimine.
11. A process according to claim 1 wherein the inorganic coagulant
is selected from the group consisting of alum, lime, ferric
chloride, polyaluminum chloride, ferrous sulfate and mixtures
thereof.
12. A process according to 1 wherein the cationic coagulant polymer
is a polyalkylenepolyamine prepared by the reaction of an alkylene
polyamine with a difunctional alkyl halide.
13. A process according to claim 1 wherein the cationic coagulant
polymer is a cationic polyelectrolyte that is a poly(diallyl
di(hydrogen or lower alkyl) ammonium salt having a number average
molecular weight greater than 300,000 but less than 2,000,000.
14. A process according to claim 13 wherein the microparticle
material is a mineral composed primarily of bentonite.
15. A paper product made according to the process of claim 1.
16. A paper product made according to the process of claim 6.
17. A paper product made according to the process of claim 14.
Description
BACKGROUND
[0001] Organic deposits in the papermaking system can cause losses
in productivity and reduce the quality of the finished paper by
forming spots, holes and breaks. These organic deposits are the
result of naturally occurring pitch in the wood itself or from
synthetic materials, such as adhesive, hot melt or latex, found in
recycled pulps. These components are hydrophobic and accumulate in
the process water. These deposits can agglomerate and stick onto
papermaking machine surfaces or in the paper sheet. Deposits
originating from wood are called "wood pitch" where as deposits
from man-made materials are called "stickies" or "white pitch".
White pitch is specific to coating binder lattices such as styrene
butadiene rubber (SBR) and polyvinyl acetate.
[0002] Paper manufacture, in the simplest sense, involves producing
a pulp from wood, slurrying the pulp and water, and forming a pulp
mat, which is pressed and dried to form paper. In the critical
forming step, the pulp/water slurry (furnish) is formed as a mat on
the wire web of the paper machine. Excess water and fines (white
water) pass through the mat on the wire and are recycled. The
formed web goes forward into the press and dryer section of the
machines where the mat becomes paper.
[0003] Broke paper is the term used in the paper industry to
describe the paper, which does not meet specifications, and for
that reason could not be sold. This paper is usually recycled
internally at the mill to recover fibers but it may also be sold to
other mills as a source of fiber. The broke paper may be coated,
the coating being applied to the base sheet of paper as it is
manufactured. The broke paper, which is coated, is referred to as
coated broke paper. Waste paper is the term used in the paper
industry to describe paper, which has been utilized by a consumer.
It is often termed "post consumer waste." This paper is often
collected and recycled at a mill to recover fibers. The waste paper
may be coated, the coating being applied to the base sheet of paper
as it is manufactured. The waste paper, which is coated, is
referred to as coated waste paper. Coated paper that is recycled
can be broke or wastepaper. In recent years many paper mills have
experienced problems with the recycling of coated paper because the
coatings introduce materials that normally would not be present in
the original stock of fibers used to manufacture the base paper
sheet.
[0004] The coatings normally comprise various pigments and binders.
Typical pigments used include many types of clay, calcium
carbonate, titanium dioxide, and other specialty fillers. The
problems of white pitch are thought to be mainly caused by the
binders, which include latex polymers derived from
styrene-butadiene and polyvinyl acetate resins and natural binders
such as starch.
[0005] White pitch problems have been known for some time in the
paper producing industry. White pitch is sticky, light gray
substance which is found as a deposit on metal surfaces in the
wet-end, forming press, or dryer sections of the paper machine. It
is termed "white" to distinguish it from the brown or black pitch,
which results from materials contained in the wood. White pitch is
also found in the white water system. At times the pitch deposits
carbonize to give black deposits in the dryer section of the paper
machine. The white pitch problem has been shown to be caused by the
relatively high use of coated paper in the furnish of mills
experiencing the problem. When coated paper is re-pulped, the clay
or minerals and the latex in the coatings do not readily disperse
into the pulp but form agglomerations, which result in white pitch.
White pitch can coat the equipment or form defects in the paper if
it travels into the paper machine with the pulp. High machine
downtime, frequent cleaning, paper sheet defects such as holes, and
increased number of sheet breaks are costly problems associated
with white pitch deposits. Equipment clean up is quite involved
because deposits can be found on the foils, table rolls, vacuum
boxes, dryer cans and dryer felts, and throughout the press
felts.
[0006] Various solutions have been suggested for dealing with the
white pitch problem. Several deposit control chemicals are
currently being used or evaluated by the paper industry. By
trapping and dispersing the small latex particles in the sheet, the
white pitch problem can be controlled. More specifically, the latex
particles should be attached to the fibers immediately passing
through the re-pulper. At this point the latex particles are small
and anionic, and therefore, they can exit the system as part of a
sheet. Due to the anionic character of both the latex particles and
the fibers, an additive having low molecular weight and high
cationic charge is best suited for this purpose. However, the
additive alone may not be sufficient to contain the latex particles
in the paper sheet and the use of a retention aid compatible with
the additive may be important for successful control of white
pitch.
[0007] Synthetic polymers are the most successful known
antideposition additives for white pitch. They are highly cationic,
enabling them to create a strong electrostatic bond between the
fibers, the latex particles and the additive. Once bonded, the
fiber will carry the latex particles through the mill, with the
help of a retention aid, and the particles will become part of the
finished paper. Medium molecular weight polyglycol, amine/glycol or
polyethyleneimine polymers have been shown to be useful in reducing
white pitch.
[0008] Some of the methods for treating white pitch problems are
described in documents below.
[0009] U.S. Pat. No. 5,131,982 (Michael R. St. John) describes the
use of DADMAC containing polymers and copolymers to treat cellulose
fibers recycled from coated broke recovery to make them suitable
for making paper.
[0010] U.S. Pat. No. 4,997,523 (Pease et al) describes the use of a
tetrafunctional alkoxylated diamine in combination with a phosphate
compound, phosphonate compound or phosphoric acid to minimize the
deposition of white pitch on paper making equipment.
[0011] U.S. Pat. No. 4,643,800 (Maloney et al) describe the use of
an oxyethylene glycol nonionic surfactant in which one end hydroxyl
group has been substituted with an aliphatic or alkylaromatic group
and the other end hydroxyl group has been replaced with a
polyoxypropylene group or a benzyl ether group in combination with
a medium molecular weight (500-50,000) polyelectrolyte dispersant
to remove and disperse contaminants from secondary fiber during
re-pulping.
[0012] There are several disadvantages of the use of polymers to
control white pitch. Polymers are not generally cost efficient. For
example, polyethyleneimine (PEI), a tertiary amine polymer, is an
effective white pitch control additive yet it is quite costly to
use.
[0013] There are other solutions used for control of white pitch.
Talc was commonly used in the past and is still sometimes used to
control deposits. As a surface-active filler, talc acts to control
deposits by detackifying the area around the pitch particle so that
it cannot attach to the paper making equipment. However, this
offers only a temporary solution to the pitch problem that
reappears as the process continues. Talc does not bind the latex
particles to the fibers, and therefore when exposed to shear, new
tacky areas appear causing deposits. Also, additives which react
with the surface of the pitch particle to render it less tacky
(detackifiers) offer temporary solution to controlling white pitch.
Published U.S. patent application 2001/0023751 describes a process
for reducing sticky contaminants using polyvinyl alcohols and
bentonite. The polyvinyl alcohol acts as a masking agent for the
particles. The problem relates to the need to use excess quantities
of polyvinyl alcohols. The bentonite absorbs excess polyvinyl
alcohol.
SUMMARY OF THE INVENTION
[0014] The present invention is a deposit control system,
consisting of an inorganic or organic (natural or synthesized)
coagulant and a microparticulate material (synthetic or
naturally-occurring) such as bentonite clay, cross-linked polymer,
colloidal silica, polysilicate, or borosilicate for pulp containing
white pitch/stickies. The order of addition of these two components
is essential to secure the benefits of reduced white pitch in a
papermaking process. Coagulant can be added to the pulper or thick
stock chest and the microparticulate may be added at the exit of
the pulper or chest prior to stock dilution.
DETAILED DESCRIPTION
[0015] Results of a number of turbidimeter measurements are shown
in FIG. 1. Turbidity of the backwater (filtrate) is an indicator of
colloidal retention of latex emulsion particles or cleanliness.
Using polyamine as a single component, a reduction in turbidity is
achieved compared to not treating the coated broke. However, the
addition of microparticle material with the coagulant provides a
significant reduction in water turbidity. This data indicates that
more white pitch/stickies particles are staying with the stock
rather than re-circulating in the papermaking system. These lab
results demonstrate that the coagulant/microparticulate system
significantly reduces the accumulation of white pitch/stickies in
the papermaking system.
[0016] The present invention is a deposit control system,
consisting of an inorganic or organic (natural or synthesized)
coagulant and a microparticulate material (synthetic or
naturally-occurring) such as bentonite clay, cross-linked polymer,
colloidal silica, polysilicate, or borosilicate for pulp containing
white pitch/stickies.
[0017] The coagulant can be inorganic or organic (natural or
synthetic) material. Examples of suitable organic coagulants are a
lower molecular weight, high charge density, polymer, which is
usually a homopolymer of recurring cationic groups or a copolymer
of at least 80% by weight cationic monomer and 0 to 20% by weight
acrylamide or other non-ionic monomer. The cationic groups can be
derived from diallyl dimethyl ammonium chloride and
dialkylaminoalkyl (meth)-acrylates and -acrylamides (generally as
quaternary ammonium or acid addition salts). Dimethylaminoethyl
acrylate or methacrylate quaternary ammonium salt is often
particularly preferred. Alternatively the coagulant can be a
condensation polymer such as a dicyandiamide polymer, a polyamine
or a polyethyleneimine. Inorganic coagulants (such as alum, lime,
ferric chloride, and ferrous sulfate) can be used.
[0018] The cationic coagulant materials, which may find use in this
aspect of the invention, include well-known commercially available
low-to mid molecular weight water-soluble polyalkylenepolyamines
including those prepared by the reaction of an alkylene polyamine
with a difunctional alkyl halide. Materials of this type include
condensation polymers prepared from the reaction of
ethylenedichloride and ammonia ethylene dichloride, ammonia and a
secondary amine such as dimethyl amine,
epichlorohydrin-dimethylamine,
epichlorohydrin-dimethylamine-ammonia, polyethyleneimines, and the
like. In certain cases cationic starch may be employed as the
coagulant. Inorganic coagulants, e.g., alum and polyaluminum
chloride, may also be used in this invention. The usage rate of
inorganic coagulants is typically from 0.005 to 1% by weight based
on the dry weight of fiber in the furnish.
[0019] The preferred coagulant is a cationic polyelectrolyte that
is a poly(diallyl di(hydrogen or lower alkyl) ammonium salt having
a number average molecular weight greater than 300,000 but less
than 2,000,000.
[0020] The microparticle materials can be synthetic or naturally
occurring. Examples of suitable microparticle materials are
swellable clay materials, cross-linked polymer, colloidal silica,
borosilicate or a suspension of microparticulate anionic material
selected from bentonite, colloidal silica, polysilicate microgel,
polysilicic acid microgel and crosslinked microemulsions of water
soluble monomeric material.
[0021] Microparticle materials are widely used in the papermaking
industry as retention aids, particularly for fine paper production.
One such system employs swellable clays to provide an improved
combination of retention and watering is described in U.S. Pat.
Nos. 4,753,710 and 4,913,775, the disclosures of which are
hereinafter incorporated by reference into this specification. In
the method disclosed in Langley et al., a high molecular weight
linear cationic polymer is added to the aqueous cellulosic
papermaking suspension before shear is applied to the suspension,
followed by the addition of a swellable clay, such as bentonite,
after the shear application. Shearing is generally provided by one
or more of the cleaning, mixing and pumping stages of the
papermaking process, and the shear breaks down the large flocs
formed by the high molecular weight polymer into microflocs.
Further agglomeration then ensues with the addition of the
bentonite clay particles.
[0022] Other microparticle programs are based on the use of
colloidal silica as a microparticle in combination with cationic
starch such as that described in U.S. Pat. Nos. 4,388,150 and
4,385,961, the disclosures of which are hereinafter incorporated by
reference into this specification, or the use of a cationic starch,
flocculant, and silica sol combination such as that described in
both U.S. Pat. Nos. 5,098,520 and 5,185,062, the disclosures of
which are also hereinafter incorporated by reference into this
specification. U.S. Pat. No. 4,643,801 claims a method for the
preparation of paper using a high molecular weight anionic water
soluble polymer, a dispersed silica, and a cationic starch.
[0023] A still further microparticle is derived from borosilicates,
preferably aqueous solutions of colloidal particles of borosilicate
have a molar ratio of boron to silicon of from 1:1000 to 100:1 and
generally from 1:100 to 2:5. The microparticle retention aid can be
a colloid of borosilicate having a chemistry similar to that of
borosilicate glass. This colloid is generally prepared by reacting
an alkali metal salt of a boron-containing compound with silicic
acid under conditions resulting in the formation of a colloid. The
borosilicate particles may have a particle size over a wide range,
for example from 1 nm (nanometer) to 2 microns (2000 nm), and
preferably from 1 nm to 1 micron.
[0024] The microparticle may be inorganic, for instance colloidal
silica (such as described in U.S. Pat. No. 4,643,801), polysilicate
microgel (such as described in EP-A-359,552), polysilicic acid
microgel (such as described in EP-A-348,366), aluminum modified
versions thereof. In particular systems can be used as described in
U.S. Pat. Nos. 4,927,498, 4,954,220, 5,176,891 and 5,279,807 and
commercialized under the trade name Particol by Ciba Specialty
Chemicals and Dupont.
[0025] Anionic organic microparticulate materials can be used also.
For instance, anionic organic polymeric emulsions are suitable. The
emulsified polymer particles may be insoluble due to being formed
of a copolymer of, for instance, a water-soluble anionic monomer
and one or more insoluble monomers such as ethyl acrylate, but
preferably the polymeric emulsion is a cross-linked microemulsion
of water-soluble monomeric material, for instance as described in
U.S. Pat. Nos. 5,167,766 and 5,274,055 and commercialized under the
trade name Polyflex by Ciba Specialty Chemicals.
[0026] The particle size of the microparticulate material is
generally below 2 m, preferably below 1 m and most preferably below
0.1 m.
[0027] The amount of microparticle material (dry weight based on
the dry weight of the cellulosic suspension) is generally at least
0.03% and usually at least 0.1%. It can be up to for instance 1.6
or 2% but is generally below 1%.
[0028] The preferred microparticle material is a swellable clay,
particularly a swellable clay from the smectite family. Preferred
members of the smectite family of clays include bentonite,
montmorillonite, saponite, hectorite, beidilite, nontronite,
fullers' earth and mixtures thereof. A swellable clay component
containing primarily bentonite is particularly preferred. It is
necessary that the bentonite should be in a highly swollen,
activated, form and in practice this means that it should be in the
form of a monovalent salt of bentonite such as sodium bentonite.
Although there are some naturally occurring sources of sodium
bentonite, most natural bentonites are alkaline earth bentonites,
generally calcium or magnesium bentonites. The normal practice is
to activate the alkaline earth bentonite by ion exchanging the
calcium or magnesium for sodium or other alkali metal or ammonium
ion. Generally this is done by exposing the bentonite to an aqueous
solution of sodium carbonate, although some other activating
materials are known. Swellable clays are naturally occurring
substances and commercially available.
[0029] Suitable fibers for the production of the pulps are all
qualities conventionally used for this purpose, for example
mechanical pulp, bleached and unbleached chemical pulp and paper
stocks from all annual plants. Mechanical pulp includes, for
example groundwood, thermomechanical pulp (TMP),
chemothermomechanical pulp (CTMP), pressure groundwood,
semichemical pulp, high-yield chemical pulp and refiner mechanical
pulp (RMP). Examples of suitable chemical pulps are sulfate,
sulfite and soda pulps. The unbleached chemical pulps, which are
also referred to as unbleached kraft carrier pulp, are preferably
used. Suitable annual plants for the production of paper stocks
are, for example, rice, wheat, sugarcane and kenaf. Pulps are
produced using waste paper alone or as a mixture with other fibers.
Waste paper includes coated waste, which owing to the content of
binders for coatings and printing inks, gives rise to white pitch.
The stated fibers and pulps can be used alone or as a mixture with
one another. The adhesives originating from pressure-sensitive
adhesive labels and envelopes and adhesives from the gluing of book
spines as well as hotmelts give rise to the formation of
stickies.
[0030] The present invention is particularly suited for papermaking
systems that utilize a pulp derived from a significant amount of
recycled or broke paper. The meaning of a significant amount will
vary by system and by the type of recycled or broke paper utilized
but will be characterized by the presence of sufficient white pitch
in the process streams to materially effect operating conditions.
In general, at least 10% of the pulp must be derived from recycled
or broke paper products to generate material amounts of white
pitch.
[0031] The deposit control system is introduced into a papermaking
system by addition to the thick or thin stock system of the
papermaking process. An important aspect of this process is the
timing of addition for each component. The process requires the
addition of cationic coagulant, followed by the anionic
microparticle. Without being bound by theory, it is believed that
the prior addition of cationic coagulant improves the adsorption of
white pitch by the anionic microparticle. It is further believed
that the cationic coagulant is absorbed onto the pitch (wood, white
and stickies), which are predominantly anionic or non-ionic,
rendering them at least partially cationic. The bentonite now
having adsorbed increased amounts of pitch is retained in the paper
during formation. The result is reduced amounts of white pitch in
the effluent. In a preferred embodiment, coagulant is added to the
pulper or thick stock chest, while the microparticulate material is
added at the exit of the pulper or chest prior to stock
dilution.
[0032] The invention is further described by the following
non-limiting example(s). The examples illustrate the invention,
which is defined solely by the accompanying claims.
EXAMPLE 1
[0033] Coated paper sheets are re-pulped in a laboratory
disintegrator. A 400 ml aliquot of the 1% consistency stock is
mixed at 1000 rpm. A polyamine coagulant and bentonite
microparticle is added in one-minute intervals during mixing.
Polyamine is added at 1, 1.5 or 2 pounds per ton as received with
bentonite following at 4, 6 or 8 pounds per ton. After treatment,
the stock is filtered through a 100-mesh screen and the filtrate is
measured for turbidity. Each filtrate sample is prepared to a 1:14
dilution with deionized water. A portable turbidimeter Hach 2100P
is used in testing and the results recorded in NTUs (Nephelometric
Turbidity Units). The results are shown in FIG. 1.
EXAMPLE 2
[0034] Coated paper sheets are re-pulped in a laboratory
disintegrator. A 400 ml aliquot of the 2.5% consistency stock is
mixed at 1000 rpm. Either a polyamine, polyDADMAC or polyaluminum
chloride (PAC) coagulant and bentonite microparticle are added in
one-minute intervals during mixing. Coagulant is added at 1 pound
per ton as received with bentonite following at 4, 6 or 8 pounds
per ton. Coagulant is also added as a single component at 1 or 2
pounds per ton as received. After treatment, the stock is filtered
through a 100-mesh screen and the filtrate is measured for
turbidity. Each filtrate sample is prepared to a 1:14 dilution with
deionized water.
[0035] A portable turbidimeter is used in testing and the results
recorded in NTUs (Nephelometric Turbidity Units).
[0036] Results
[0037] The results of the turbidimeter measurements for each
treatment are shown in FIG. 2. Turbidity of the backwater
(filtrate) can be an indicator of colloidal retention of latex
emulsion particles or cleanliness. By using polyamine or polyDADMAC
as a single component at 1 or 2 pounds per ton, a reduction in
turbidity is achieved compared to not treating the coated broke.
However, the addition of bentonite with the various coagulants
provides a reduction in water turbidity. A significant reduction in
turbidity is noted when comparing 1 pound per ton as received
polyamine or PAC coagulant plus bentonite to 2 pounds per ton as
received coagulant.
* * * * *