Note: Descriptions are shown in the official language in which they were submitted.
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HYDROPHOBIC POLYMERS AND THEIR USE IN PREPARING CELLULOSIC
FIBER COMPOSITIONS
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application No.
60/684,816, filed May 26, 2005, the entire content of which is herein
incorporated by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the use of hydrophobic polymers and
copolymers in the preparation of cellulosic fiber compositions. The present
invention
further relates to cellulosic fiber compositions, such as paper and
paperboard, which
incorporate the water compatible hydrophobic polymers or copolymers.
BACKGROUND OF THE INVENTION
[0003] The making of cellulosic fiber sheets, particularly paper and
paperboard, includes the following: 1) producing an aqueous slurry of
cellulosic fiber;
which may also contain inorganic mineral extenders or pigments; 2) depositing
this
slurry on a moving papermaking wire or fabric; and 3) forming a sheet from the
solid
components of the slurry by draining the water.
[0004] The foregoing is followed by pressing and drying the sheet to further
remove water. Organic and inorganic chemicals are often added to the slurry
prior to
the sheet-forming step to make the papermaking method less costly, more rapid,
and/or to attain specific properties in the final paper product.
[0005] The paper industry continuously strives to improve paper quality,
increase productivity, and reduce manufacturing costs. Chemicals are often
added
to the fibrous slurry before it reaches the papermaking wire or fabric, to
improve the
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method drainage/dewatering and solids retention; these chemicals are called
retention and/or drainage aids.
[0006] As to drainage/dewatering improvement, drainage or dewatering of the
fibrous slurry on the papermaking wire or fabric is often the limiting step in
achieving
faster machine speeds. Improved dewatering can also result in a drier sheet in
the
press and dryer sections, resulting in reduced steam consumption. In addition,
drainage and dewatering is the stage in the papermaking process that
determines
many final sheet properties.
[0007] With respect to solids retention, papermaking retention aids are used
to
increase the retention of fine furnish solids in the web during the turbulent
method of
draining and forming the paper web. Without adequate retention of the fine
solids,
they are either lost to the mill effluent or accumulate to high levels in the
recirculating
white water loop, potentially causing deposit buildup. Additionally,
insufficient
retention increases the papermakers' cost due to loss of additives intended to
be
adsorbed on the fiber to provide paper opacity, strength, or sizing
properties.
[0008] High molecular weight (MW) water-soluble polymers with either
cationic or anionic charge have traditionally been used as retention and
drainage
aids. Recent developments of inorganic microparticles in combination with high
MW
water-soluble polymers have shown superior retention and drainage efficacy
compared to conventional high MW water-soluble polymers. U.S. Patent Nos.
4,294,885 and 4,388,150 teach the use of starch polymers with colloidal
silica. U.S.
Patent No. 4,753,710 teaches flocculating the pulp furnish with a high MW
cationic
flocculant, inducing shear to the flocculated furnish, and then introducing
bentonite
clay to the furnish. U.S. Patent Nos. 5,274,055 and 5,167,766 disclose using
chemically cross-linked organic microparticies or micropolymers as retention
and
drainage aids in the papermaking process.
[0009] Copolymers are also used to control deposition of contaminants or
organic deposits in papermaking systems. Organic deposit(s) is a term used to
describe tacky, water insoluble materials in the papermaking system that are
detrimental to the production of paper. Such materials derived from trees
during the
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pulping and papermaking process are termed pitch or wood pitch, while the term
stickies is used to describe contaminants that are derived from adhesives
introduced
into the papermaking process as a contaminant of recycled fiber. One strategy
for
eliminating these materials is to agglomerate the organic deposits into
larger, non-
tacky particles that can be removed from the papermaking stock or incorporated
into
the sheet without causing deposits in the papermaking system or defects in the
sheet. Chemicals that are able to interact with organic deposits and mitigate
their
negative impact include surfactants and polymers. The polymers can be ionic or
nonionic, and includes materials used as flocculants, coagulants and
dispersants.
[0010] The efficacy of the polymers or copolymers used will vary depending
upon the type of monomers from which they are composed, the arrangement of the
monomers in the polymer matrix, the molecular weight of the synthesized
molecule,
and the method of preparation.
[0011] It has been found, unexpectedly, that hydrophobic polymers or
copolymers provide unanticipated retention and drainage activity and can
function
as contaminant control aids in applications including papermaking applications
Although the synthesis methods employed are generally known to those skilled
in
the art, there is no prior art suggesting that the unique physical
characteristics would
result in the unanticipated activity observed.
SUMMARY OF THE INVENTION
[0012] The present invention is directed to water compatible hydrophobic
polymers and copolymers and cellulosic fiber compositions containing the
hydrophobic polymers and copolymers, particularly a cellulosic sheet such as
paper
or paperboard. The invention is also directed to a method for making the
hydrophobic polymers and copolymers and the cellulosic fiber compositions.
[0013] In another aspect, the present invention provides a method of making a
cellulosic fiber composition comprising adding, to a cellulosic pulp slurry, a
water
compatible polymer or copolymer that contains a hydrophobic group.
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[0014] The invention further relates to cellulosic fiber compositions,
including
an aqueous slurry of cellulosic pulp, containing such water compatible
polymers and
copolymers. As used herein, the term copolymer is understood to be polymer
compositions consisting of two or more different monomeric units.
[0015] Additionally, a composition comprising water compatible hydrophobic
polymers and copolymers and cellulose fibers and optionally, a siliceous
material is
disclosed.
[0016] In accordance with the present invention, it has been unexpectedly
discovered that certain water compatible hydrophobic polymers and copolymers
exhibit unique physical characteristics and provide unanticipated activity as
retention
and drainage aids.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention provides for enhanced retention and/or drainage
in a papermaking process by addition of a water compatible hydrophobic polymer
or
copolymer to a papermaking slurry.
[0018] The present invention also provides for a composition comprising a
water compatible hydrophobic polymer or copolymer and cellulose fiber.
[0019] The present invention also provides for a composition comprising a
hydrophobic polymer or copolymer, a siliceous material and cellulose fibers.
[0020] The present invention also provides for the use of water compatible
polymer(s) and copolymer(s) that interact or associate, via non covalent
bonding to
form an aggregation of two or more polymer chains. The driving force for the
molecular association can be electrostatic or hydrophobic in nature. Preferred
are
molecular associations driven by hydrophobic forces.
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[0021] The use of multi-component systems in the manufacturing of paper and'
paperboard provides the opportunity to enhance performance by utilizing
materials
that have different effects on the process and/or product.
[0022] The polymer is described to be water compatible. For the purposes of
the present invention, "water compatible" means that the polymer can be water
soluble or water swellable or water dispersible.
[0023] The term water soluble is used to indicate that the polymer will
dissolve
in the solvent, with no visible solid material remaining in the solvent.
Solubility of a
polymer in a solvent occurs when the free energy of mixing is negative.
Examples of
water soluble materials include, but are not limited to, exudates or gum,
extractives,
natural materials, modified natural materials, or synthetic material. One
example of
exudates or gum is gum tragacanth. One example of extractives is pectin. One
example of natural materials is guar. One example of modified natural
materials is
derivatized cellulose such as methylcellulose. One example of synthetic
material is
poly(acrylic acid). The synthetic polymers can be comprised of one or more
monomers selected to provide specific properties to the final polymer.
[0024] Water swellable polymers are those that can imbibe the aqueous solvent
and swell to a limited extent. Water swellability can be influenced by a
number of
factors including, but not limited to, crosslinking and electrostatic
interactions. Thus,
the interactions between polymer and solvent are limited. Although a visible
homogeneous solution may be obtained, it is not a uniform molecular
dispersion.
One example of a water swellable polymer is a crosslinked polymer. Cross
linked
polymers can be water compatible and water dispersible: In contrast, a
branched
polymer can be soluble.
[0025] Water dispersible materials are those that are not soluble in water,
but
do not phase separate. Typically, these materials have a modified surface that
allows them to remain as discrete particulate material that is suspended in
water, or
can be made dispersible by the addition of other materials. Examples include
latex
particle, oil-in-water emulsions, and dispersed clays or pigments.
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[0026] Hydrophobic substances are generally defined as substances that are
readily soluble in many nonpolar solvents, but are incapable of completely
dissolving
in water. Hydrophobic materials resist association with water and tend to
cluster
together in aqueous environment. A hydrophilic material, in contrast, is
soluble in
water, but only sparingly soluble in most nonpolar solvents. Hydrophilic
materials are
hydrated by water, resulting in solutions of the hydrophilic material in
water.
[0027] An amphiphilic compound is one that has both a hydrophobic and
hydrophilic segment. Thus, it is comprised of both a polar water soluble group
(hydrophilic segment) and a nonpolar water insoluble group (hydrophobic
segment).
For example, a surfactant is an amphiphilic compound. The amphiphilic nature
of
the materials are such that they will migrate to interfaces, be it liquid/gas,
liquid/liquid
or liquid/solid.
[0028] The hydrophobic polymers of the present invention are amphiphilic in
nature in that they have regions that are more hydrophobic in nature and
regions that
are more hydrophilic in nature. The relative extent of hydrophobicity and
hydrophilicity will determine the solubility of the material. In practice, the
materials
that are, overall, more hydrophobic will be relatively more. water insoluble
and oil
soluble. Conversely, the more hydrophilic materials will be relatively more
water
soluble and oil insoluble.
[0029] Polymers useful in the present invention are typically copolymers. The
term copolymer is understood to be a polymeric molecule that contains two or
more
different monomers. They can be copolymers of more than one monomer or
polymers where a fraction of the monomers are chemically derivatized.
[0030] A hydrophobic monomer is, as defined here, an amphiphilic compound.
A segment of the molecule is hydrophobic. Hydrophobicity is a relative
property.
For example, an ethylenically unsaturated monomer can be water soluble.
Examples are acrylamide and acrylic acid. Modification can make the monomer
more hydrophobic. Methacrylamide and methacrylic acid are less water soluble
due
to the methyl group. Ethyl acrylate would be even less soluble as it has a
larger
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hydrophobic group. Butyl acrylate, by virtue of its even larger alkyl chain,
is even
more hydrophobic.
[0031] Materials having utility in the present invention are known in the art
by
a number of terms including, but not limited to, hydrophobic polymers,
amphiphilic
polymers, hydrophobically modified polymer, and polymeric surfactants.
[0032] These materials can be made by a number of processes, including, but
not limited to, synthesis of polymers from one or more monomers,
derivatization of
existing polymer or grafting; grafting can occur either concurrent with or
subsequent
to polymerization.
[0033] A hydrophobic polymer of utility in the present invention is a
copolymer
wherein at least one of the monomers is hydrophobic in nature. The hydrophobic
monomer is, on a molar basis, less than 50% of the monomers, preferably less
than
10%, more preferably less than 5% and most preferably less than 2%.
[0034] Hydrophobic polymers, more commonly referred to as hydrophobically
modified polymers, are water compatible polymers onto which hydrophobic groups
are chemically attached, either at the ends of the chain (telechelic or end-
capped) or
randomly along the polymer chain (comb-like or pendant). A polymer with
hydrophobic group can undergo intermolecular association with another chain,
forming a network mediated by self-association of the hydrophobes. That this
association occurs without the formation of covalent bonds is an important
facet of
the invention. This network formation results in, amongst other unique
properties, a
strong viscosifying or thickening effect. A molecule with at least two
hydrophobes on
a single chain can also undergo intra-molecular association, altering the
structure of
the molecule in solution and hence, its viscosity.
[0035] Associative forces between hydrophobic groups occur due to the well
known phenomenon that is termed "the hydrophobic effect". Hydrophobic
substances are materials that are soluble in many nonpolar solvents, but can
be
sparingly soluble in water. There is an attraction between hydrophobic
materials
(i.e., oil) and water; this is, however, not nearly as strong as the
attraction that water
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has for itself. Hydrogen bonding between water molecules induces segregation
of
hydrophobic materials, effectively. resulting in hydrophobe-hydrophobe
association.
This water-induced attraction is termed a hydrophobic interaction. Thus, the
hydrophobic effect occurs only in an aqueous environment.
[0036] The assembly of hydrophobic molecules requires the removal of water
from the regions between them. Thus, association of polymer bound hydrophobes
results in a region not solvated by water molecules. In an aqueous solution,
these
aggregates are not free draining and can act as small water insoluble
(particulate)
regions. Without being bound by theory, it is believed that this is the
mechanism by
which the polymers of the present invention provide their performance
properties.
[0037] One approach to producing a hydrophobic polymer is by direct
polymerization of monomers, which includes a least one hydrophobic monomer, to
form a copolymer. Polymerization may be done by any method known in the art,
including solution, dispersion and inverse emulsion polymerization.
[0038] The polymers can comprise, in addition to the hydrophobic monomers,
one or more anionic, cationic and/or nonionic monomers. The anionic, cationic
and
nonionic monomers can be used at any desired ratio. The polymer can contain 0
to
80% anionic monomers, 0 to 80% cationic monomers and 0 to 100% nonionic
monomers. Preferred compositions are 0 to 60% anionic monomers, 0 to 30%
cationic monomers and about 10 to 100% nonionic monomers.
[0039] Exemplary nonionic monomers include, but are not limited to,
acrylamide; methacrylamide; N-alkylacrylamides, such as N-methylacrylamide;
N,N-
dialkylacrylamides, such as N,N-dimethylacrylamide; methyl acrylate; methyl
methacrylate; acrylonitrile; N-vinyl methylacetamide; N-vinyl formamide; N-
vinyl
methyl formamide; vinyl acetate; N-vinyl pyrrolidone; alkyl acrylates; alkyl
methacrylates; alkyl acryamides; alkyl methacrylamides; and alkyloxylated
acrylates
and methacrylates such as alkyl polyethyleneglycol acrylates, alkyl
polyethyleneglycol methacrylates; mixtures of any of the foregoing and the
like.
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[0040] Exemplary anionic monomers include, but are not limited to, the free
acids and salts of acrylic acid; methacrylic acid; maleic acid; itaconic acid;
acrylamidoglycolic acid; 2-acrylamido-2-methyl-l-propanesulfonic acid; 3-
allyloxy-2-
hydroxy-1-propanesulfonic acid; styrenesulfonic acid; vinylsulfonic acid;
vinylphosphonic acid; 2-acrylamido-2-methylpropane phosphonic acid; mixtures
of
any of the foregoing and the like.
[0041] Exemplary cationic monomers include, but are not limited to, the free
bases and salts of cationic ethylenically unsaturated monomers such as the
diallyldialkylammonium halides, such as diallyidimethylammonium chloride; the
(meth)acrylates of dialkylaminoalkyl compounds, such as dimethylaminoethyl
(meth)acrylate, diethylaminoethyl (meth) acrylate, dimethyl aminopropyl
(meth)acrylate, 2-hydroxydimethyl aminopropyl (meth)acrylate, aminoethyl
(meth)acrylate, and the salts and quaternaries thereof; the N,N-
dialkylaminoalkyl(meth)acrylamides, such as N,N-dimethylaminoethylacrylamide,
and the salt and quaternaries thereof and mixture of the foregoing and the
like.
[0042] The hydrophobic monomer can be any monomer that has a
hydrophobic moiety as an integral part of its structure. The hydrophobic
moiety may
be linear or cyclic, aliphatic or aromatic. Preferred hydrophobic moieties are
typically
alkyl groups such as, but not limited to, propyl, butyl, hexyl, octyl, decyl,
dodecyl
(lauryl), cetyl, stearyl and behenyl groups.
[0043] Exemplary hydrophobic monomers include, but are not limited to,
ethylenically unsaturated monomers having hydrophobic moieties. The
hydrophobic
groups include hydrophobic organic groups, such as those having hydrophobicity
comparable to one of the following: aliphatic hydrocarbon graups having at
least six
carbons (preferably from CB to C22 alkyls and preferably from C6 to C22
cycloalkyls);
poly-nuclear aromatic hydrocarbon groups such as benzyls, substituted benzyls
and
naphthyls; alkaryls wherein alkyl has one or more carbons; haloalkyls of four
or more
carbons, preferably perfluoroalkyls; polyalkyleneoxy groups wherein the
alkylene is
propylene or higher alkylene and there is at least one alkyleneoxy unit per
hydrophobic moiety. The preferred hydrophobic groups include those having at
least
3 carbons or more per hydrocarbon group, preferably at least 6 carbons or
more.
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Also preferred are those hydrophobic groups having C6 to C22 alkyl groups or
those
having at least 6 carbons or more per perfluorocarbon group, such as the C6F13
-
C22F45. Particularly preferred are the C8 -C20 alkyl groups.
[0044] Suitable hydrocarbon groups containing ethylenically unsaturated
monomers include the esters of amides of the C6 and larger alkyl groups.
Particularly suitable esters include, but are not limited to, dodecyl
acrylate, dodecyl
methacrylate, tridecyl acrylate, tridecyl methacrylate, tetradecyl acrylate,
tetradecyl
methacrylate, octadecyl acrylate, octadecyl methacrylate, nonyl-a/pha-phenyl
acrylate, nonyl-a/pha-phenyl methacrylate, dodecyl-a/pha-phenyl acrylate, and
dodecyl-a/pha-phenyl methacrylate. The C10 -C20 alkyl esters of acrylic and
methacrylic acid are preferred. Of these, dodecyl acrylate and methacrylate
are
particularly preferred.
[0045] Also the following hydrocarbon group-containing ethylenically
unsaturated monomers may be used: N-alkyl ethylenically unsaturated amides,
such as N-octadecyl acrylamide, N-octadecyl methacrylamide, N-octyl
acrylamide,
'N,N-dioctyl acrylamide and similar derivatives thereof; a/pha-olefins, such
as 1-
octene, 1-decene, 1-dodecene, and 1-hexadecene; vinyl alkylates wherein the
alkyl
has at least eight carbons, such as vinyl laurate and vinyl stearate; vinyl
alkyl ethers,
such as dodecyl vinyl ether and hexa-vinyl alkyl ethers, such as dodecyl vinyl
ether
and hexa-decyl vinyl ether; N-vinyl amides, such as N-vinyl lauramide and N-
vinyl
stearamide.
[0046] The hydrophobic monomer is present in the hydrophobic copolymer in
an amount up to about 10 mole percent, preferably up to 5 mole percent and
even
more preferably up to 2 mole percent. It is preferred that the hydrophobic
monomer
be present in an amount from at least about 0.01, preferably at least 0.1 mole
percent. It is preferred that the hydrophobic monomer be present in an amount
from
about 0.01 to about 2 mole percent and most preferred that the hydrophobic
monomer be present in an amount from about 0.1 to about 1 mole percent.
Preferred hydrophobic monomers are octylacrylamide and lauryl acrylate.
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[0047] The molar ratio of the hydrophobic, anionic, cationic and nonionic
monomer can be varied to contain any relative amount of the monomers necessary
to achieve the desired solubility.
[0048] Preferably the water compatible hydrophobic polymers and copolymers
useful in the present invention are prepared by an inverse (water-in-oil)
emulsion
polymerization technique. Such processes are known to those skilled in the
art, for
example see U.S. Pat. No. 3,284,393, and Reissue U.S. Pat. Nos. 28,474 and
28,576, the entire contents of each is herein incorporated by reference.
Preparation
of an aqueous solution from the emulsion polymer may be affected by inversion
by
adding the emulsion polymer to water, wherein the emulsion or water may also
contain a breaker surfactant. Breaker surfactants are additional surfactants
that are
added to a polymer emulsion to promote inversion. The resulting copolymers may
also be further isolated by precipitating in an organic solvent such as
acetone and
dried to a powder form. The powder can be easily dissolved in an aqueous
medium
for use in desired applications.
[0049] In general, an inverse emulsion polymerization process is conducted
by 1) preparing an aqueous solution of the monomers, 2) adding the aqueous
solution to a hydrocarbon liquid containing appropriate surfactant or
surfactant
mixture to form an inverse monomer emulsion, 3) subjecting the monomer
emulsion
to free radical polymerization, and 4) optionally adding a breaker surfactant
to
promote the inversion of the emulsion when added to water.
[0050] Polymerization of the emulsion may be carried out in any manner
known to those skilled in the art. Initiation may be effected with a variety
of thermal
and redox free-radical initiators including, but not limited to, azo compounds
such as
azobisisobutyronitrile and the like. Polymerization may also be effected by
photochemical irradiation processes, irradiation or by ionizing radiation with
a 60Co
source.
[0051] Preferred initiators are oil soluble thermal initiators. Typical
examples
include, but are not limited to, 2,2'-azobis-(2,4-dimethylpentanonitrile);
2,2'-
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azobisisobutyronitrile (AIBN); 2,2'-azobis-(2,-methylbutanonitrile); 1,1'-
azobis-
(cyclohexanecarbonitrile); benzoyl peroxide and lauroyl peroxide.
[0052] Any chain transfer agents known to those skilled in the art may be used
to control the molecular weight. Those include, but are not limited to, lower
alkyl
alcohols such as isopropanol; amines; mercaptans such as mercaptoethanol,
phosphites; thioacids; allyl alcohol; and the like.
[0053] The aqueous solution typically comprises an aqueous mixture of
monomers. The aqueous phase may also comprise such conventional additives as
are desired. For example, the mixture may contain chelating agents, pH
adjusters,
initiators, chain transfer agents as described above, and other conventional
additives. For the preparation of the water-compatible hydrophobic copolymer,
the
pH of the aqueous solution is below 12 and is preferably equal to or greater
than 2,
more preferably the pH is about 4 to about 6.
[0054] The hydrocarbon liquid typically comprises straight-chain
hydrocarbons, branched-chain hydrocarbons, saturated cyclic hydrocarbons,
aromatic hydrocarbons, or mixtures thereof.
[0055] The surfactants or surfactant mixtures used in the invention are
generally oil soluble. One or more surfactants can be used. Exemplary
surfactants
include, but are not limited to, sorbitan fatty acid esters, ethoxylated
sorbitan fatty
acid esters, ethylene oxide and/or propylene oxide adducts of long chain fatty
acids
or alcohols, ethylene oxide and/or propylene oxide adducts of alkyl phenols,
alkanolamides, mixed ethylene oxide/propylene oxide block copolymers, diblock
and
triblock copolymers based on polyester derivatives of fatty acids and
poly(ethyleneoxide), diblock and triblock copolymers based on
poly(ethyleneoxide)
and poly(propyleneoxide), diblock and triblock copolymers based on
polyisobutylene
succinic anhydride and poly(ethyleneoxide), mixtures of any of the foregoing
and the
like. Specific surfactants include sorbitan monooleate, sorbitan sesquioleate,
sorbitan trioleate, polyoxyethylene sorbitan monooleate, and surfactants sold
by
BASF under the Pluronic trade name and surfactants by Uniqema under the
Atlasne
and Arlacel trade names.
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[0056] Polymerization of the inverse emulsion may be carried out in any
manner known to those skilled in the art, for example see Allcock and Lampe,
Contemporary Polymer Chemistry, (Englewood Cliffs, New Jersey, PRENTICE-
HALL, 1981), chapters 3-5.
[0057] An alternative mechanism to prepare a hydrophobic polymer is
grafting. One example is copolymerization of ethylenically unsaturated
monomers,
such as acrylic acid with block copolymers of ethylene oxide and propylene
oxide.
Selection of the polymerization conditions will impact the structure of the
polymer
and, hence, its utility. These polymers, are known in the art, to associate
via
hydrophobic forces, to form aggregates.
[0058] Exemplary polymers prepared by grafting includes, but are not limited
to, polymers with poly(ethylene oxide) (PEO) arms and a core consisting of
hydrophobic triisocyanate or tetraisocyanate that were shown to possess
associative
properties when the PEO arms were modified with hydrophobic nonylphenoxy end
groups, hydrophobically modified ethoxylated urethane (HEUR) polymers,
fluorocarbon-containing polymers, end capped poly(ethylene oxide) such as
hexadecyl-terminated poly(ethylene oxide) and the like and mixtures thereof.
[0059] Yet another material is a graft copolymer of acrylic acid and a
monoamino-terminated surfactant. The surfactant is grafted via an amide bond
using dicyclocarbodiimide as a coupling agent.
[0060] Yet another method for preparation of hydrophobic water compatible
polymer is by derivatizing an existing synthetic polymer. This can be achieved
by a
number of technical approaches, which include but are not limited to, the
grafting of
a hydrophobic amine via the Mannich reaction.
[0061] Yet another method for preparation is the use of a water dispersible
macromer, sometimes referred to as polymerizable surfactant, such as
nonylphenoxy poly(ethylene oxide) acrylate that can be copolymerized with an
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ethylenically unsaturated monomer to a self-assembling hydrophobically
modified
polymer.
[0062] Yet another method for preparation is to modify an already prepared
polymeric backbone. This method implies either utilization of an aprotic
solvent
common for the polymer and a hydrophobic entity to be grafted upon the
polymer, or
selective hydrophilization of a hydrophobic water insoluble block copolymer.
[0063] Hydrophobically modified alkali-swellable emulsion, or HASE, are also
useful in the present invention. These materials are hydrophobically modified
acrylate copolymers. An example would be a copolymer of methacrylic acid,
ethylacrylate and a third monomer termed an associative macromonomer. An
example of associative macromonomer is an ethylenically unsaturated monomer
with a pendant hydrocarbon of more than 6 carbons linked to the monomer by an
ethylene oxide chain. Key variables are the chemistry of the hydrocarbon and
the
length of these ethylene oxide chains.
[0064] Additional polymers useful in the present invention are hydrophobically
modified polymers based on natural occurring polymers such as proteins and
polysaccharides. Derivatized natural materials, including starch and cellulose
derivatives can also be used. Exemplary based polymers include, but are not
limited
to, hydroxyethyl cellulose and cationic starch. Preferred are nonionic water
soluble
cellulose ether can be used as the cellulose ether substrate used to form the
products of this invention. Thus, e.g., hydroxyethyl cellulose, hydroxypropyl
cellulose, methyl cellulose, hydroxypropyl methyl cellulose, ethyl
hydroxyethyl
cellulose, and methyl hydroxyethyl celluose can all be modified. The amount of
nonionic substituent such as methyl, hydroxyethyl or hydroxypropy; does not
appear
to be critical so long as there is sufficient to assure that the ether is
water soluble.
[0065] The preferred cellulose ether substrate is hydroxyethyl cellulose
(HEC).
Accordingly, control of the modification process and control of the properties
of the
modified product can be more precise with this substrate. Hydrophilicity of
the most
commonly used nonionic cellulose ethers varies in the general direction:
hydroxyethyl>hydroxypropyl>hydroxypropyl>methyl.
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[0066] Long chain alkyl modifier can be attached to the cellulose ether
substrate via an ether, ester or urethane linkage. Preferred is the ether
linkage as
the reagents most commonly used to effect etherification are readily obtained,
the
reaction is similar to that comrrionly used for the initial etherification,
and the
reagents are usually more easily handled than the reagents employed for
modification via the other linkages. The resulting linkage is also usually
more
resistant to further reactions.
[0067] Methods of preparing mixed ethers of cellulose, i.e., products having
more than one etherifying modifier attached to the same cellulose molecule are
known to the art. The products of this invention can be prepared via
essentially the
same methods. Briefly, the preferred procedure for preparing the mixed ethers
of
this invention comprises slurrying the nonionic cellulose ether in an inert
organic
diluent such as a lower aliphatic alcohol, ketone, or hydrocarbon and adding a
solution of alkali metal hydroxide to the resultant slurry at a low
temperature. When
the ether is thoroughly wetted and swollen by the alkali, a C10 to C24 epoxide
is
added and the reaction is continued, with agitation, until complete. Residual
alkali is
then neutralized and the product is recovered, washed with inert diluents, and
dried.
The etherification can also be effected with a C10 to C24 halide or
halohydride but
these are sometimes less reactive, less efficient and more corrosive so it is
preferred
to use epoxide.
[0068] Substantially the same procedure is used to attach the hydrocarbon
modifier via the ester or urethane linkage. Conventional slurry methods of
reacting
this type of modifier with cellulose ethers, i.e., without the alkali, are
ineffective. The
alkali step is required in order to assure that the cellulose ether is swollen
to the
point that the modifier can react substantially uniformly on all cellulose
ether
molecules throughout. If reaction is not substantially uniform throughout the
cellulose
ether mass, the improved performance properties are not realized.
[0069] Optionally, siliceous materials can be used as an additional component
of a retention and drainage aid used in making paper and paperboard. The
siliceous
material may be any of the materials selected from the group consisting of
silica
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based particles, silica microgels, amorphous silica, colloidal silica, anionic
colloidal
silica, silica sols, silica gels, polysilicates, polysilicic acid, and the
like. These
materials are characterized by the high surface area, high charge density and
submicron particle size.
[0070] This group includes stable colloidal dispersion of spherical amorphous
silica particles, referred to in the art as silica sols. The terms sol refers
to a stable
colloidal dispersion of spherical amorphous particles. Silica gels are three
dimensional silica aggregate chains, each comprising several amorphous silica
sol
particles, that can also be used in retention and drainage aid systems; the
chains
may be linear or branched. Silica sols and gels are prepared by polymerizing
monomeric silicic acid into a cyclic structure that result in discrete
amorphous silica
sols of polysililcic acid. These silica sols can be reacted further to produce
a three-
dimensional get network. The various silica particles (sols, gels, etc.) can
have an
overall size of 5-50 nm. Anionic colloidal silica can also be used.
[0071] The siliceous material can be added to the cellulosic suspension in an
amount of at least 0.05 Kg per metric ton based on dry weight of the
cellulosic
suspension. The amount of siliceous material may be as high as 5 Kg per metric
ton. Preferably, the amount of siliceous material is fro m about 0.05 to about
25 Kg
per metric ton. Even more preferably the amount of siliceous material is from
about
0.25 to about 5 Kg per metric ton based on the dry weight of the cellulosic
suspension.
[0072] The components of a retention and drainage system may be added
substantially to the cellulosic suspension. The term retention and drainage
system is
used here to encompass two or more distinct materials added to the
papermaking.
slurry to provide improved retention and drainage. For instance, the
components
may be added to the cellulosic suspension separately either at the same stage
or
dosing point or at different stages or dosing points. When the components of
the
inventive system are added simultaneously any two or more of the materials may
be
added as a blend. The mixture may be formed in situ by combining any two or
more
of the materials at the dosing point or in the feed line to the dosing point.
Alternatively the inventive system comprises a preformed blend of the any two
or
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more of the materials. In an alternative form of the invention the components
of the
inventive system are added sequentially. A shear point may or may not be
present
between the addition points of the components. The components can be added in
any order.
[0073] The inventive system is typically added to the paper process to affect
retention and drainage. The inventive system may be added to the thick stock
or
thin stock, preferably the thin stock. The system may be added at one feed
point, or
may be split fed such that the inventive system is fed simultaneously to two
or more
separate feed points. Typical stock addition points include feed points(s)
before the
fan pump, after the fan pump and before the pressure screen, or after the
pressure
screen.
[0074] The amount of siliceous material in relationship to the amount of
associative polymer.copolymer used in the present invention can be about 100:1
to
about 1:100 by weight, or from about 50:1 to 1:50 or about 10:1 to 1:10.
[0075] Yet another additional components that can be part of the inventive
system are aluminum sources. such as alum (aluminum sulfate), polyaluminum
sulfate, polyaluminum chloride and aluminum chlorohydrate.
[0076] The copolymers useful in the invention can be used in papermaking
systems and processes. The copolymers are useful as drainage and retention
aids
as well as contaminant control aids. In commercial papermaking, a slurry of
cellulosic fibers or pulp is deposited on a moving papermaking wire or fabric.
The
slurry may contain other chemicals, such as sizing agents, starches, deposit
control
agents, mineral extenders, pigments, fillers, organic or inorganic coagulants,
conventional flocculants, or other common additives to paper pulp. As water
from
the deposited slurry is removed, a sheet forms. Ordinarily the sheets are then
pressed and dried to form paper or paper board. The copolymers of the
invention
are added to the slurry before it reaches the wire to improve the drainage or
dewatering and the retention of the fiber fines and fillers in the slurry.
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[0077] As a contaminant control aid, the polymers of the present invention
inhibit the deposition of pitch and stickies from the virgin or recycled pulp
stock on
the papermaking equipment. The aid is added to the pulp slurry where it
interferes
with the agglomeration of the pitch and stickies that would otherwise
detrimentally
affect the paper, paper making equipment or paper making processes. A method
of
inhibiting deposition of pitch and stickies comprises adding a hydrophobic
polymer to
a cellulosic pulp slurry.
[0078] Suitable cellulosiC fiber pulps for the method of the invention include
conventional papermaking stock such as traditional chemical pulp. For
instance,
bleached and unbleached sulfate pulp and sulfite pulp, mechanical pulp such as
groundwood, thermomechanical pulp, chemi-thermomechanical pulp, recycled pulp
such as old corrugated containers, newsprint, office waste, magazine paper and
other non-deinked waste, deinked waste, and mixtures thereof, may be used.
[0079] The copolymers useful in the invention may be provided to the end use
application in a number of physical forms. In addition to the original
emulsion form,
the inventive copolymer may also be provided as an aqueous solution, dry solid
powder, or dispersion form.
[0080] The hydrophobic polymer is typically diluted or inverted at the
application site to produce an aqueous solution of 0.1 to 1% active polymer.
Alternatively, a dried material is dissolved in water to produce an aqueous
solution.
[0081] The present invention provides for a method of improving retention and
or drainage of a cellulosic pulp slurry wherein the method comprises adding
hydrophobic polymer to a cellulosic pulp slurry to improve drainage.
[0082] This dilute solution of the copolymers used in the invention is added
to
the paper process to affect retention and drainage. The inventive copolymer
may be
added to the thick stock or thin stock, preferably the thin stock. The
copolymer may
be added at one feed point, or may be split fed such that the copolymer is fed
simultaneously to two or more separate feed points. Typical stock addition
points
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include feed point(s) before the fan pump, after the fan pump and before the
pressure screen, or after the pressure screen.
[0083] The copolymers useful in the invention are employed in a proportion of
from about 0.005 kg to about 5 kg of active polymer per metric ton of
cellulosic pulp,
based on the dry weight of the pulp. The concentration of copolymer is
preferably
from about 0.025 kg to about 2.5 kg of active polymer per metric ton of dried
cellulosic pulp. The concentration of copolymer is more preferably from about
0.1 kg
to about 1 kg of active polymer per metric ton of dried cellulosic pulp.
[0084] The present invention will now be further described with reference to a
number of specific examples that are to be regarded solely as illustrative and
not
restricting the scope of the present invention.
EXAMPLES
[0085] The following materials are used in the preparation of the examples
provided.
[0086] Atlas G-946 is sorbitan monoleate marketed by Uniqema, New
Castle, DE.
[0087] Hypermer B246SF is triblock polymeric surfactant marketed by
Uniqema, New Castle, DE.
[0088] OA is t-octylacrylamide obtained from Monomer-Polymer & Dajac
Labs, Inc., Feasterville, PA.
[0089] COPS1 is Sipomer COPS1, a sodium alkylhydroxypropyl sulfonate
monomer marketed by Rhodia, Inc., Cranbury, NJ.
[0090] BEM-25 is Sipomer BEM-25, a behenyl polyethoxymethacrylate
monomer marketed by Rhodia, Inc., Cranbury, NJ.
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[0091] SEM-25 is Sipomer SEM-25, a tristyriphenol polyethoxymethacrylate
monomer marketed by Rhodia, Inc., Cranbury, NJ.
[0092] 5010 is Maxemul 5010, an alkenyl functional non-ionic surfactant
marketed by Uniqema, New Castle, DE.
[0093] Acrylic acid was obtained from Rohm and Haas, Philadelphia, PA.
[0094] Acrylamide was obtained from Cytec, Inc., Mobile, AL
Example 1
[0095] To a suitable reaction flask equipped with an overhead mechanical
stirrer, thermometer, nitrogen sparge tube, and condenser, charge an oil phase
of
paraffin oil (135.0g, Escaid 110 oil, Exxon - Houston, TX) containing
surfactants
(4.5g Atlas G-946 and 9.Og Hypermer B246SF), to which 1.77g of OA (t-
octylacrylamide) is added. The temperature of the oil phase is adjusted to 37
C.
[0096] An aqueous phase is prepared separately which comprises 53-wt. %
acrylamide solution in water (126.5g), acrylic acid (68.7g), deionized water
(62.12g),
and Versenex 80 (Dow Chemical) chelant solution (0.7g). The aqueous phase is
then adjusted to pH 5.4 with the addition of ammonium hydroxide solution in
water
(33.1g, 29.4-wt. % as NH3). The temperature. of the aqueous phase after
neutralization is 39 C.
[0097] The aqueous phase is then charged to the oil phase while
simultaneously mixing with a homogenizer to obtain a stable water-in-oil
emulsion.
This emulsion is then mixed with a 4-blade glass stirrer while being sparged
with
nitrogen for 60 minutes. During the nitrogen sparge the temperature of the
emulsion
is adjusted to 50t1 C. Afterwards, the sparge is discontinued and a nitrogen
blanket
implemented.
[0098] The polymerization is initiated by a 3 wt% solution of lauroyl peroxide
(LP) in toluene at a level of 20 molar ppm LP on a total monomer molar basis
to start
the polymerization, 10 molar ppm LP on a total monomer molar basis after one
hour
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of polymerization, and 10 molar ppm LP on a total monomer molar basis after
four
hours of polymerization.
[0099] The batch is then cooled to room temperature and the product
collected.
[0100] The molar ratio of acrylic acid to acrylamide to OA is 50: 49.25: 0.75.
Example 2 - 5
[0101] Examples 2-5 were prepared as described in example 1 except that the
molar composition of monomer was as shown in Table 1.
TABLE 1
Monomer I Monomer 2 Monomer 3
Example Monomer a %(b) Monomer a % Monomer a %
2 Acrylic Acid 50.00 Acrylamide 49.75 COPS1 0.25
3 Acrylic Acid 50.00 Acrylamide 49.60 BEM-25 0.40
4 Acrylic Acid 50.00 Acrylamide 49.90 SEM-25 0.10
Acrylic Acid 50.00 Acrylamide 49.70 5010 0.30
(a) Monomer(s) used in the example.
(b) Mole % of monomer, based on total monomer
[0102] Prior to inverting the emulsions of Examples 1 to 5 for analysis or
use,
-2 wt. % of a breaker surfactant, for example a 80:20 by weight mixture of
Tergitol
15-S-9 (Dow, Midland, MI) and Aerosol-OT-S (Cytec Industries, West Patterson,
NJ),
was added. The pH of the inverted water-soluble anionic copolymers was then
adjusted to a minimum of 7.0 with aqueous sodium hydroxide or ammonium
hydroxide, as required.
Examples 6-10
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[0103] Example 6 is PerForm 9232 Retention and Drainage Aid (Hercules
Incorporated, Wilmington, DE)
[0104] Example 7 is Acrysol TT-935 a HASE material marketed by Rohm
and Haas Company, Philadelphia, PA.
[0105] Example 8 is a copolymer of butylacrylate and acrylic acid, monomer
molar ratio at 50:50, obtained from Polysciences, Inc., Warrington; PA.
[0106] Example 9 is poly(N-isopropylacrylamide) obtained from Scientific
Polymer Products, Inc., Ontario, NY.
[0107] Example 10 is poly(N,N-dimethylacrylamide) obtained from Scientific
Polymer Products, Inc., Ontario, NY.
PERFORMANCE TESTS
[0108] The technique of paper sheet formation and retention/drainage is well
know in the art; for example, see Handbook for Pulp and Paper Technologist,
G.A.
Snook, ed., (TAPPI Press, Atlanta, GA, 1989) and PULP AND PAPER, Chemistry
and Chemical Technology, 3rd edition, J. P. Casey, ed., (Wiley-Interscience,
New
. York, 1981).
[0109] To evaluate the performance of the water-soluble hydrophobic
polymers and copolymers examples of the present invention, a series of
retention
tests and/or drainage tests were conducted. PerForm SP9232 retention and
drainage aid, a product of Hercules Incorporated, was used as a comparative
example (Example 6) for examples 1 to 5. Unless otherwise stated, all
percentages,
parts, etc., are by weight.
[0110] The furnish employed in this series of tests is a synthetic alkaline
furnish. This furnish is prepared from about 70% by wt of hardwood and 30% by
wt
of softwood dried market lap pulps, and from water and further materials.
First the
hardwood and softwood dried market lap pulp are separately refined in a
laboratory
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Valley Beater (Voith, Appleton, WI). These pulps are then added to an aqueous
medium.
[0111] The aqueous medium utilized in preparing the furnish comprises a
mixture of local hard water and deionized water to a representative hardness.
Inorganic salts are added in amounts so as to provide this medium with a total
alkalinity of 75 ppm as CaCO3 and hardness of 100 ppm as CaCO3.
[0112] To prepare the furnish, the hardwood and softwood are dispersed into
the aqueous medium at typical weight ratios of hardwood and softwood
(typically
about 70:30). Precipitated calcium carbonate (PCC) is introduced into the
furnish at
25 weight percent, based on the combined dry weight of the pulps, so as to
provide a
final furnish comprising 80 % fiber and 20 % PCC filler.
[0113] To the pulp slurry, a cationic potato starch, Stalok 400 (A.E. Staley,
Decatur, IL), is added at a level of 5 kg per metric ton, based on dry pulp,
and then
alum, (aluminum sulfate octadecahydrate available as a 50% solution from Delta
Chemical Corporation, Baltimore, MD), is added at a level of 2.5 kg per metric
ton.
Next, a cationic flocculant, (Perform PC 8138, Hercules Incorporated) is
added at a
level of 0.25 kg/metric ton, based on dry pulp.
[0114] For examples 1 to 5, copolymers were then added at a level of 0.4 kg
of active component / metric ton of furnish solids. The vaccum drainage time
of the
water compatible hydrophobic copolymers and the comparative copolymer (example
6) were measured. The control is the pulp composition described above but
without
the water compatible hydrophobic copolymers.
[0115] The following is a description of the test procedures.
[0116] The Britt jar retention test (Paper Research Materials, (nc.; Gig
Harbor,
WA) is known in the art. In the Britt jar retention test a specific volume of
furnish is
mixed under dynamic conditions and an aliquot of the furnish is drained
through the
bottom screen of the jar, so that the level of fine materials which are
retained can be
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quantified. The Britt jar utilized for the present tests is equipped with 3
vanes on the
cylinder walls to induce turbulent mix, and a 76 pm screen in the bottom
plate.
[0117] A series of drainage tests were also conducted utilizing a vacuum
drainage test (VDT) developed to differentiate the activity between the
microparticle
technology and conventional linear flocculants. The results of this testing
demonstrate the ability of the VDT to differentiate drainage aids in both CPAM
and
APAM programs by the magnitude of the drainage time.
[0118] The device setup is similar to the Buchner funnel test as described in
various filtration reference books, for example see Perry's Chemical
Engineers'
Handbook, 7tn edition, (McGraw-Hill, New York, 1999) pp.18-78. The VDT
consists
of a 300-m1 magnetic Gelman filter funnel, a 250-m1 graduated cylinder, a
quick
disconnect, a water trap, and a vacuum pump with a vacuum gauge and regulator.
The VDT test is conducted by first setting the vacuum to the desired level,
typically
inches Hg, and placing the funnel properly on the cylinder. Next, 250g of 0.5
wt.
% paper stock is charged into a beaker and then the required additives
according to
treatment program (e.g., starch, alum, and testing flocculants) are added to
the stock
under the agitation provided by an overhead mixer. The stock is then poured
into
the filter funnel and the vacuum pump is turned on while simultaneously
starting a
stopwatch. The drainage efficacy is reported as the time required to obtain
230 ml of
filtrate.
[0119] The principle of the VDT is based on the cake filtration theory, for
reference see L. Svarovsky, editor, Solid-Liquid Separation, 3rd edition
(London,
Butterworths, 1990), Chapter 9. Initially, the solids in the slurry are
deposited on a
relative thin filter medium that serves to support the filter cake. The
successive
deposits of solids layer to form the filter cake, or mat. The rate of filtrate
passing
through the filter cake (or mat) is dependent on floc density, floc size
distribution in
the mat, and levels of residual polymeric materials in the aqueous phase. A
flocculant that forms dense and uniform-sized flocs and has low residual level
in
water (i.e., good formation characteristics) will demonstrate good drainage in
the
VDT test, and vice versa.
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[0120] The data set forth in Table 2 illustrates the retention and drainage
activity of the water-compatible hydrophobic copolymers.
TABLE 2
PERFORMANCE DATA
Example Retention (a) Drainage
(%) (sec.)
Control 40.7 34.0
1 95.7 13.4
2 94.4 16.8
3 92.2 16.4
4 93.7 13.4
96.1 15.3
6 93.4 15.3
(a) First pass fine retention as measured by Britt Jar test
(b) Drainage as measured by the vacuum drainage test
[0121] The data in Table 2 demonstrate that the. water-soluble hydrophobic
polymers and copolymers of the present invention provide a significant
improvement
over the control material.
[0122] The drainage test data for examples 7 to 10 are shown in Table 3.
Note that the use levels of these copolymers was 0.25 kg of active polymer per
metric ton of furnish solids.
TABLE 3
PERFORMANCE DATA
Example Amount Added Drainage (a)
(kg/MT) (Sec)
Control - 40.0
7 0.25 36.8
8 0.25 38.4
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9 0.25 39.9
0.25 37.6
(a) Drainage is measure by the vacuum drainage test
[0123] These data indicate that these materials provide an improvement in
drainage compared to the control.
[0124] It is noted that the foregoing examples have been provided merely for
the purpose of explanation and are in no way to be construed as limiting of
the
present invention. While the present invention has been described with
reference to
an exemplary embodiment, it is understood that the words that have been used
herein are words of description and illustration, rather than words of
limitation.
Changes may be made, within the purview of the appended claims, as presently
stated and as amended, without departing from the scope and spirit of the
present
invention in its aspects. Although the present invention has been described
herein
with reference to particular means, materials and embodiments, the present
invention is not intended to be limited to the particulars disclosed herein.
For
example, cationic and/or amphoteric copolymers prepared per the preferred
polymerization conditions may also exhibit activity in papermaking
applications. The
water-soluble anionic copolymers of the present invention may also exhibit
activity in
other applications such as coagulants and/or flocculants in wastewater
treatment
applications, or as rheology modifiers in paints, coatings, drilling fluids
and/or cement
processing applications.
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