Note: Descriptions are shown in the official language in which they were submitted.
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DescriRtion
STABILIZED MICROFIBRILLAR CELLULOSE
FIELD OF THE INVENTION
The present invention relates to stabilized microfibrillar cellulose. More
specifically, the present invention relates to microfibrillar cellulose that
is
electrostatically stabilized by cationic groups.
BACKGROUND OF THE INVENTION
Polysaccharides are often found in nature in forms having fibrous
morphology. Polysaccharides which are not found in nature in fibrous form can
often be transformed into fibrous morphologies using fiber-spinning
techniques.
Whether the fibrous morphology is of natural or artificial origin, the
polysaccharide will often be present in such a form that the fibers can be
reduced
to fibrillar and microfibrillar sub-morphologies through the application of
energy.
1 S Fibrillar and microfibrillar cellulose obtained in this manner have been
considered for use in applications, including use as additives to aqueous-
based
systems in order to affect rheological properties, such as viscosity. The use
level
of these materials in aqueous systems is often on the order of about 2% by
weight, below which these materials have a tendency to poorly occupy volume,
and to exhibit gross inhomogeneities in distribution.
Microfibrillated cellulose and its manufacture are discussed in U.S. Patent
Nos. 4,500,546; 4,487,634; 4,483,743; 4,481,077; 4,481,076; 4,464,287;
4,452,722; 4,452,721; 4,378,381; 4,374,702; and 4,341,807, the disclosures of
which are hereby incorporated by reference thereto. These documents, in part,
purport to describe microfibrillated cellulose in stable, homogenous
suspensions,
characterized as useful in end use products including foods, cosmetics,
pharmaceuticals, paints, and drilling muds.
Cellulose nanofibrils are characterized in WO 98/02486
(PCT/FR97/01290), WO 98/02487 (PCT/FR97/01291), and WO 98/02499
(PCT/FR97/01297), the disclosures of which are hereby incorporated by
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reference. Nanofibrils are characterized as having diameters in the range of
about 2 to about 10 nanometers.
EP 845495 discusses cationic cellulose particulate which is characterized as
insoluble, positively charged, and used in water treatment, specifically to
treat
water in a paper manufacturing plant. In papermaking this cationic particulate
is
said to remove anionic trash from the water. The particles are obtained by
milling, which is stated to reduce particle size uniformly such that particles
are
typically round as described by a length/diameter ratio of approximately 1.
Particle size is stated to be 0.001 mm (i.e., 1 pm), and preferably 0.01 mm
(10
Vim).
EP 859011 ("EP '0l 1 ") is directed to a process for obtaining cationic
cellulose microfibrils or their soluble derivatives. The process is described
as
including making a cationic cellulose derivative and processing the derivative
through a high-pressure homogenizer to form transparent gels. The product can
be dehydrated and rehydrated. Viscosity measurements are reported on the
product at a concentration of 2% in water. EP '0l 1 indicates that the degree
of
substitution ("DS") of the cellulose can range from 0.1 to 0.7, with a DS of
between 0.2 and 0.7, 0.3 and 0.6, and 0.5 and 0.6 characterized as
representing
increasing orders of preference. The examples show cellulose with a DS ranging
from a low of 0.24 up to 0.72. Gelling is reported to occur above a
microfibril
concentration of 10 g/L, or above 1 %, in water. EP '0l 1 defines gelling as
occurring when G' > G", where G' is the dynamic storage modulus and G" is the
dynamic loss modulus.
Microfibrillated chitosan is reported to form uniplanar, oriented sheets upon
drying by H. Yokata, J. Polymer Sci., Part C: Polymer Letters, 24:423-425
( 1986). This article mentions that at a level of 4% chitosan in water, a gel
is
formed having a viscosity of 26,600 cps (Brookfield, 20° C, rotor #7, l
Orpm).
The microfibrillated chitosan is made by homogenization of commercial chitosan
flakes in a Gaulin homogenizer. The commercial chitosan is deacetylated using
sodium hydroxide.
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JP 59 [1984]-84938 discusses a method for producing a chitosan
suspension. Commercial chitosan separated and purified from crabs and lobsters
is pulverized to pieces having maximum length of about 1-2 mm. The pieces are
then suspended in water at up to 15% chitosan, and are run in multiple passes
through a high-pressure homogenizer at between 3,000 and 8,000 psi.
It would be desirable to obtain microfibrillar cellulose capable of forming a
gel at concentrations of 1 % or less, thereby providing economy and ease of
formulation, while still providing necessary rheological behavior and
homogeneity of distribution.
In addition, there is a continuing need in industry to improve the stability
of
commercial emulsions, such as paper sizing emulsions. At present, one method
for stabilizing such emulsions is the addition of charged materials, such as
cationic starches, which may be added in amounts equal to 10-20% by weight of
the size component. Interaction with anionic components, such as sulfonates,
can
also improve stability. However, emulsion failure still takes place in such
emulsions, either through density-driven separation, also referred to as
creaming,
or through gellation. It would accordingly be desirable to develop a material
that
could be added to emulsions to provide long-term stability.
SUMMARY OF THE INVENTION
The present invention is directed to a derivatized microfibrillar cellulose
which is derivatized to include a substituent that provides cationic charge
and is
capable of forming a gel in water at a concentration of less than 1%. The
cellulose used to prepare the derivatized microfibrillar cellulose may be
obtained
from any suitable source, including but not limited to chemical pulps,
mechanical
pulps, thermal mechanical pulps, chemical-thermal mechanical pulps, recycled
fibers, newsprint, cotton, soybean hulls, pea hulls, corn hulls, flax, hemp,
jute,
ramie, kenaf, manila hemp, sisal hemp, bagasse, corn, wheat, bamboo, velonia,
bacteria, algae, fungi, microcrystalline cellulose, vegetables, and fruits.
Preferably the cellulose is obtained from purified, optionally bleached wood
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pulps produced from sulfite, kraft, or prehydrolyzed kraft pulping processes;
purified cotton linters; fruits; or vegetables.
The substituent which provides cationic charge to the derivatized
microfibrillar cellulose may be, or include, an amine. A quaternary amine is
particularly preferred.
The derivatized microfibrillar cellulose may form a gel in water throughout
the concentration range of between about 0.01 % and about 100%, or throughout
the concentration range of between about 0.01 % and about 50 %, in water.
Moreover, the derivatized microfibrillar cellulose may form a gel at a
concentration of less than about 1 % in water, and preferably forms a gel at
least
one point in the concentration range of from about 0.05 % up to about 0.99% in
water.
The derivatized microfibrillar cellulose of the present invention may
include a solvent in which the derivatized microfibrillar cellulose is
substantially
insoluble. Suitable solvents include water, alcohol, or oil, with water being
preferred.
The derivatized microfibrillar cellulose may have a degree of substitution of
less than about 0.5, or of less than about 0.35, or of less than about 0.2, or
of less
than about 0.18, or of less than about 1.15. Preferably the degree of
substitution
is between about 0.02 and about 0.5, and more preferably between about 0.05
and
about 0.2.
A particularly preferred embodiment of the present invention is
microfibrillar 2-hydroxy-3-(trimethylammonium chloride) - propylcellulose
having a degree of substitution of less than about 2.0, preferably of less
than
about 0.35, more preferably of between about 0.02 and about 0.20, and most
preferably between about 0.1 and about 0.2.
The derivatized microfibrillar cellulose may form part of a comestible
composition of matter, including but not limited to a low fat, reduced fat, or
fat-
free mayonnaise, or a salad dressing. When it forms part of a comestible
composition of matter, the derivatized microfibrillar cellulose may include a
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pharmaceutically active ingredient, and may at least partially provide for the
controlled, sustained, or delayed release of the pharmaceutically active
ingredient.
Alternatively, the derivatized microfibrillar cellulose may form part of a
non-comestible composition of matter, such as, by way of non-limiting example,
a wound care product. Suitable wound care products include, without
limitation,
wound dressings and ostomy rings. In another embodiment, the non-comestible
composition of matter may be a skin care lotion or cream, a sunscreen lotion
or
cream, or an oral care composition, such as a toothpaste.
The non-comestible composition of matter may further be or include an
agricultural composition, such as a fertilizer, herbicide, fungicide, or
pesticide.
The derivatized microfibrillar cellulose may provide at least partially for
the
controlled, sustained, or delayed release of the fertilizer, herbicide, or
pesticide.
In an alternative embodiment, the non-comestible composition of matter
may be a drilling fluid.
In another embodiment, the present invention is directed to a paper
composition which contains the derivatized microfibrillar cellulose described
herein.
The present invention further includes a method for producing the
derivatized microfibrillar cellulose described herein, which involves at least
one
of the following steps:
(a) a derivatizing step of treating a microfibrillar cellulose to
obtain a derivatized microfibrillar cellulose;
(b) a microfibrillizing step of treating a derivatized non-
microfibrillar cellulose to produce a derivatized microfibrillar
cellulose; or,
(c) microfibrillizing and derivatizing a non-microfibrillar
cellulose substantially simultaneously.
In the above method, the derivatized microfibrillar cellulose is derivatized
to include a substituent that contains cationic charge, as for example by the
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presence of amine groups. Preferably the derivatizing step involves
derivatizing
the cellulose with a quaternary amine reagent, such that the derivatized
microfibrillar cellulose includes quaternary amine functionalized cellulose.
The derivatizing step of the above method may include contacting a non-
microfibrillar cellulose with a swelling agent. This contact may occur under
alkaline conditions, and the swelling agent may be an anionic reagent.
Moreover,
the alkaline conditions may include contacting the cellulose with the anionic
reagent in the presence of an alkaline reagent which is at least one of sodium
hydroxide, an oxide or hydroxide of an alkali metal or alkaline earth metal,
an
alkali silicate, an alkali aluminate, an alkali carbonate, an amine, ammonium
hydroxide, tetramethyl ammonium hydroxide, or combinations thereof. The
derivatizing step may further take place at high solids.
In a preferred method, the derivatized microfibrillar cellulose is obtained
by:
I S (a) derivatizing cellulose with 3-chloro-2-hydroxypropyl
trimethylammonium chloride under alkaline conditions to produce 2-
hydroxy-3-(trimethylammonium chloride) - propylcellulose;
(b) suspending the 2-hydroxy-3-(trimethylammonium chloride) -
propylcellulose in water to form a suspension; and
(c) homogenizing the suspension to produce microfibrillated 2-hydroxy-
3-(trimethylammonium chloride) - propylcellulose.
The microfibrillizing step of the above method may include applying
energy to the cellulose under conditions sufficient to produce microfibrillar
cellulose, and the cellulose may be treated with enzyme prior to
microfibrillizing.
Any suitable approach may be used to apply sufficient energy to the cellulose
to
obtain microfibrillar cellulose, including, without limitation, one or more of
homogenization, pumping, mixing, heat, steam explosion, pressurization-
depressurization cycle, impact, grinding, ultrasound, microwave explosion, and
milling. Use of a homogenizer is preferred, and preferred homogenization
conditions include passing the non-microfibrillar cellulose through a pressure
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differential of at least about 3,000 psi, and more preferably passing the non-
microfibrillar cellulose through the homogenizer at least three times.
Preferably, the derivatized microfibrillar cellulose obtained by the above
methods forms a gel throughout a concentration range of from about 0.01 % to
about 100% in water, and more preferably throughout a concentration range of
between about 0.01 % and about 50 % in water. Alternatively, the derivatized
microfibrillar cellulose should form a gel at at least one point in the
concentration
range of from about 0.05 % to about 0.99% in water. In a particularly
preferred
embodiment, the derivatized microfibrillar cellulose forms a gel at a
concentration of about 0.9% in water.
The present invention extends to derivatized microfibrillar cellulose
produced by the above-described method, including it's the described
variations
of the method.
In yet another embodiment, the present invention includes a method of
modifying the rheological properties of a composition of matter by
incorporating
the derivatized microfibrillar cellulose into the composition of matter, which
may
be a liquid, such as water. The derivatized microfibrillar cellulose may be
used
in an amount which is effective to provide scale control and/or corrosion
control.
Alternatively, the derivatized microfibrillar cellulose may be used to modify
one
or more of the viscosity, suspension stability, gel insensitivity to
temperature,
shear reversible gelation, yield stress, and liquid retention of the
composition of
matter. Compositions whose rheological properties may be modified in this
manner include foods, pharmaceuticals, neutraceuticals, personal care
products,
fibers, papers, paints, coatings, and construction compositions. More
specifically, possible compositions include oral care products; creams or
lotions
for epidermal application, including moisturizing, night, anti-age, or
sunscreen
creams or lotions; food spreads, including reduced fat, low fat, or fat free
food
spreads (for example, mayonnaise); and drilling fluids.
Alternatively, the derivatized microfibrillar cellulose may be incorporated
into a coating composition in order to improve its physical and/or mechanical
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properties. Those properties may include one or more of film forming,
leveling,
sag resistance, strength, durability, dispersion, flooding, floating, and
spatter.
The derivatized microfibrillar cellulose may further be incorporated into the
manufacture of paper and paper products in order to improve at least one of
sizing, strength, scale control, drainage, dewatering, retention,
clarification,
formation, absorbency, film formation, membrane formation, and polyelectrolyte
complexation during manufacture. Microfibrillated quaternary amine
functionalized cellulose is particularly preferred for use in this method.
In one embodiment of this method, the microfibrillated quaternary amine
functionalized cellulose may be used to increase the rate of drainage and/or
dewatering during paper manufacture. In another embodiment, the
microfibrillated quaternary amine functionalized cellulose may be used for
retention of organic and/or inorganic dispersed particles in a sheet of paper
during its manufacture. Representative dispersed particles which may be
retained
in this manner include pulp fines, fillers, sizing agents, pigments, clays,
detrimental organic particulate materials, detrimental inorganic particulate
materials, and combinations thereof. In a yet further embodiment, the
microfibrillated quaternary amine functionalized cellulose may be used in a
papermaking machine to improve the uniformity of formation of a sheet of paper
during its manufacture. Additionally, the microfibrillated quaternary amine
functionalized cellulose may be used in a papermaking machine to improve the
strength of a sheet of paper produced on a paper machine.
In each of the embodiments described in the above paragraph, the
microfibrillated quaternary amine functionalized cellulose may be used in the
presence of one or more of the following: colloidal silica; colloidal aluminum-
modified silica; colloidal clay, derivatives of starch containing carboxylic
acid
functionality; derivatives of guar gum containing carboxylic acid
functionality;
natural gums or derivatized natural gums containing carboxylic acid
functionality; polyacrylamides containing carboxylic acid functionality; and
combinations thereof.
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The derivatized microfibrillar cellulose may further be used in a method for
improving the stability of an emulsion, dispersion, or foam system, by
including
the derivatized microfibrillar cellulose in the system. Where the system being
treated is an emulsion, the emulsion may be produced by processing of an
emulsion formulation, in which case the derivatized microfibrillar cellulose
may
be added to the emulsion formulation prior to completion of processing of the
emulsion formulation. In one variation, a non-microfibrillated derivatized
cellulose is added to the emulsion formulation prior to completion of
processing,
and the emulsion formulation is then processed under conditions sufficient to
microfibrillate the non-microfibrillated derivatized cellulose. In another
variation, a microfibrillated non-derivatized cellulose is added to the
emulsion
formulation prior to completion of processing, and the emulsion formulation is
then processed under conditions sufficient to derivatize the microfibrillated
non-
derivatized cellulose. In yet a third variation, a non-microfibrillated, non-
derivatized cellulose is added to the emulsion formulation prior to completion
of
processing, and the emulsion formulation is further processed under conditions
sufficient to both microfibrillate and derivatize the non-microfibrillated,
non-
derivatized cellulose.
Emulsion systems which may be treated in this manner include water-in-oil
and oil-in-water emulsions. The present invention includes the system produced
by the above method.
In a yet further embodiment, the present invention extends to a system
comprising an emulsion, dispersion, or foam containing a the derivatized
microfibrillar cellulose.
In another embodiment, the present invention includes a polyelectrolyte
complex containing the derivatized microfibrillar cellulose.
The derivatized microfibrillar cellulose of the present invention may also be
used in a method for treating wastewater, which includes the step of adding,
to
the wastewater, a amount of the derivatized microfibrillar cellulose
sufficient to
treat the wastewater. Materials being treated by this method in the wastewater
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may include, by way of non-limiting example only, anionic contaminants and
color bodies.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 shows the dynamic mechanical spectra of Sample 1 from Table 4.
Fig. 2 shows the dynamic mechanical spectra of Sample 2 from Table 4.
Fig. 3 shows the dynamic mechanical spectra of Sample 3 from Table 4.
Fig. 4 shows the dynamic mechanical spectra of Sample 4 from Table 4.
DETAILED DESCRIPTION OF THE INVENTION
The present invention comprises stabilized microfibrillar cellulose. Sources
of cellulose for use in this invention include the following: (a) wood fibers,
such
as from chemical pulps, mechanical pulps, thermal mechanical pulps, chemical-
thermal mechanical pulps, recycled fibers, newsprint; (b) seed fibers, such as
from cotton; (c) seed hull fiber, such as from soybean hulls, pea hulls, corn
hulls;
(d) bast fibers, such as from flax, hemp, jute, ramie, kenaf; (e) leaf fibers,
such as
from manila hemp, sisal hemp; (f) stalk or straw fibers, such as from bagasse,
corn, wheat; (g) grass fibers, such as from bamboo; (h) cellulose fibers from
algae, such as velonia; (i) bacteria or fungi; and (j) parenchymal cells, such
as
from vegetables and fruits, and in particular sugar beets, and citrus fruits
such as
lemons, limes, oranges, grapefruits. Microcrystalline forms of these cellulose
materials may also be used. The cellulose may be used as is, or spinning may
be
used to generate or improve fibrous structure. Preferred cellulose sources are
(1)
purified, optionally bleached, wood pulps produced from sulfite, kraft
(sulfate),
or prehydrolyzed kraft pulping processes; (2) purified cotton linters; and,
(3)
fruits and vegetables, in particular sugar beets and citrus fruits. The source
of the
cellulose is not limiting, and any source may be used, including synthetic
cellulose or cellulose analogs.
Cellulose is found in nature in several hierarchical levels of organization
and orientation. Cellulose fibers comprise a layered secondary wall structure
within which macrofibrils are arranged. Macrofibrils comprise multiple
microfibrils which further comprise cellulose molecules arranged in
crystalline
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and amorphous regions. Cellulose microfibrils range in diameter from about 5
to
about 100 nanometers for different species of plant, and are most typically in
the
range of from about 25 to about 35 nanometers in diameter. The microfibrils
are
present in bundles which run in parallel within a matrix of amorphous
hemicelluloses (specifically xyloglucans), pectinic polysaccharides, lignins,
and
hydroxyproline rich glycoproteins (includes extensin). Microfibrils are spaced
approximately 3-4 nm apart with the space occupied by the matrix compounds
listed above. The specific arrangement and location of the matrix materials
and
how they interact with the cellulose microfibrils is not yet fully known.
Further
background on the structure, functions, and biogenesis of native cellulose may
be
found in Haigler, C.H., Cellular Chemistry and Its Applications, Nevell, pp.
30-
83 ( 1985), the entirety of which is hereby incorporated by reference.
For purposes of the present invention microfibrils refer to small diameter,
high length-to-diameter ratio substructures which are comparable in dimensions
to those of cellulose microfibrils occurring in nature. By way of non-limiting
example, cellulose microfibrils may have diameters in the range of about 5 to
about 100 nanometers, combined with lengths providing high aspect ratios, such
as in excess of 100, in excess of 500, or in excess of 1,000. While the
present
specification and claims refer to microfibrils and microfibrillation, the
scope of
the present invention also includes nanofibrils, and the rheology
modification,
stabilization, and other properties that may be obtained with microfibrils by
practicing the present invention may also be obtained using nanofibrils,
either
alone or in combination with microfibrils.
The derivatized microfibrillar cellulose of the present invention is
characterized by being in microfibrillar form, and by the presence of cationic
substituents that provide electrostatic functionality. The amount of
substituent
present may be quantified by the degree of substitution, or DS. The degree of
substitution, which will vary with the molecular weight of the cellulose, is
the
average number of substituted hydroxyl groups per anhydroglucose unit, while
the molar substitution is the average number of substituent groups added per
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anhydroglucose unit. The DS determines the solubility of the derivatized
cellulose, and may be readily adjusted to obtain a derivatized cellulose that
is
substantially insoluble in the environment of use, whether aqueous or non-
aqueous. While the environment of use will frequently be aqueous, the
derivatized microfibrillar cellulose of the present invention has utility in
applications having other solvents or liquid carriers, such as paints,
coating,
lacquers, oil-rich foods, inks (including but not limited to ink jet inks),
and
water-in-oil emulsions.
Any suitable method may be used to obtain the derivatized microfibrillar
cellulose. In particular, the steps of microfibrillation and derivatization to
impart
electrostatic functionality to the cellulose may be carried out separately or
combined to arrive at the end result. Therefore, a non-microfibrillar
cellulose
starting material may be derivatized with cationic groups and then
microfibrillated, or may first be microfibrillated and then derivatized.
Alternatively, if the starting material is microfibrillar cellulose, only the
derivatizing step would be necessary, whereas if the starting material is a
cellulose that has already been properly derivatized with cationic groups,
only the
microfibrillation step is required.
The degree of substitution of the cellulose should be sufficiently low so that
the derivatized microfibrillar cellulose will be substantially insoluble in
the
solvent or carrier that is present in the intended environment of use. In many
applications the solvent or carrier will be water, and in such applications
the
degree of substitution should be such that the derivatized microfibrillar
cellulose
is substantially insoluble in water. However, in other applications a polar
solvent
or carrier (such as an alcohol) may be used having different solubility
characteristics, or a non-polar solvent or carrier (such as an oil) may be
used, and
in such cases the degree of substitution should be adjusted to obtain a
derivatized
microfibrillar cellulose that is substantially insoluble in the solvent or
carrier
used in the application of interest, which, for purposes of convenience, will
hereafter be referred to as the "solvent of use". Functionally, the
derivatized
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microfibrillar cellulose should be sufficiently insoluble in the environment
of use
to provide the desired properties in the intended application.
The presence of substantially insoluble material may be confirmed by
observation of a 1-5% suspension of the material in question in the solvent or
carrier of use under a light microscope at sufficient magnification to see
insoluble
material. A size determination may be made by preparing a suspension of the
material under consideration at approximately 0.1-0.01% in a liquid non-
solvent
which is effective in dispersing microfibrils. This suspension is then dried
on a
transmission electron microscope (TEM) grid; the sample is coated to protect
it
from electron beam damage, and examined at sufficient magnification and focus
to observe structure in the 1-1000 nanometer range. If microfibrillar elements
are
present they can be detected under these conditions, and the combination of
insolubility under the light microscope and microfibrillar structure under the
TEM will indicate the presence of substantially insoluble microfibrillar
material.
For purposes of simplicity, unless specifically indicated otherwise the term
"substituents" shall be used herein to mean chemical species that provide
electrostatic functionality to the cellulose through cationic charge. In
addition,
"electrostatic" means cationic charge. "Derivatization" refers not only to
chemical reactions resulting in covalent bonds, but to any process whereby the
substituents become sufficiently associated with the cellulose to provide the
rheological and other benefits of the present invention, and may include, for
example, adsorption. However, "derivatized" does not include the naturally-
occurring, de minimis presence of groups that would only provide the
electrostatic functionality required by the present invention at
concentrations
higher than those found in nature.
The sequence of steps used to arrive at the derivatized microfibrillar
cellulose of the present invention is not critical. Therefore, the starting
material
used to make the derivatized microfibrillar cellulose may be in microfibrillar
or
non-microfibrillar form. Similarly, the starting material may already be
derivatized with electrostatic substituents, or not. If the starting material
is non-
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microfibrillar, substituents may be placed on the cellulose followed by
microfibrillation, or the microfibrillation may be carried out first, followed
by the
placement of the substituents onto the resulting microfibrils. It is also
acceptable
to process cellulose into fibrils, place the substituents on the fibrils, and
then
further process the fibrils into microfibrils. Similarly, any non-
microfibrillar
form of cellulose which already contains such substituents may be processed
into
microfibrillar form. Moreover, derivatization and microfibrillation may be
carried out simultaneously.
It will be understood that most, if not all, cellulose will contain some
quantity of both microfibrillar and non-microfibrillar structure both before
and
after processing, and that the ratio between the two structures may range from
cellulose that is substantially completely microfibrillar, to cellulose that
is
substantially completely non-microfibrillar. As used herein, the terms
"microfibrillar", "microfibrillated", and the like include celluloses that are
substantially completely microfibrillated, and those which may be
substantially
microfibrillated while containing minor but significant amounts of non-
microfibrillar structure, provided the cellulose is sufficiently
microfibrillated to
confer the benefits afforded by the present invention.
Processes which minimize the energy needed to produce microfibrils from
non-microfibrillar starting material, and/or which reduce the amount of water
extracted during the process or at its end, are preferred. In this regard, it
should
be noted that while the derivatized microfibrillar cellulose of the present
invention can be made by derivatizing a microfibrillated cellulose, the
microfibrillation process generally requires less energy, and/or is more
efficient,
if the cellulose has already been derivatized. Without being bound by theory,
this
may be because the presence of electrostatic functionalities on the cellulose
'loosens' the structure of fibril bundles.
The ability to use less energy not only offers cost savings, but results in
less
breakage of the cellulose microfibrils. Therefore, microfibrillating a
cellulose
that has already been derivatized may result in a derivatized microfibrillar
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cellulose with relatively longer microfibrils as compared to effecting
derivatization after microfibrillation. This is particularly significant
because the
energy required for microfibrillation can be significantly reduced by amounts
of
derivatization which are below the level that would render the resulting
S derivatized microfibrillar cellulose freely soluble in water. For example,
derivatization of cellulose resulting in a DS on the order of 0.1 or 0.2 will
'loosen'
the fibril bundles enough to permit microfibrillation using conventional
shearing
devices such as a homogenizer, impingement mixer, or ultrasonicator. These low
DS cellulose microfibrils have diameters on the order of 50 nanometers
combined with lengths of up to 500 microns, resulting in aspect ratios in
excess
of 1,000. While the low DS allows microfibrillation, it is too low to allow
the
resulting material to be fully soluble in the solvent or carrier of use at the
concentrations of interest. Without being bound by theory, the presence of
insoluble regions in the fibers may explain the data showing maximum gel
formation at low DS's. These gels may be strengthened by weak association of
the more hydrophobic unsubstituted regions.
The stabilization or derivatization is accomplished by the generation or
placement of substituents onto the fibril and/or microfibril. It appears that
the
substituents become associated predominantly with the surface regions of the
fibrils or microfibrils. Regardless of the precise mechanism, in functional
terms
microfibril-microfibril contact is inhibited by electrostatic mechanisms or
forces.
The presence of the substituents also causes the microfibrils to occupy more
volume than when they are not derivatized, possibly due to inhibition of
contact
along at least part of the length of the microfibrils. Rheological performance
of
the resulting derivatized microfibrillar cellulose is enhanced at low
concentration
since volume is better occupied and the materials are distributed more
homogeneously.
Without being bound by theory, the surfaces of the derivatized microfibrils
appear to have some areas free of the substituents such that some limited
interaction between microfibrils still takes place. Limited interaction may
even
CA 02402181 2002-09-06
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be necessary to facilitate network formation, and may be a cause of the
rheological attributes of interest such as yield stress, shear reversible
gelation,
and insensitivity of the modulus to temperature. It also appears that the
length/diameter ratio, or aspect ratio, of the fibrils and microfibrils also
contributes to the performance of the materials of the present invention.
Any suitable process may be used to generate or place the substituents on
the cellulose. For convenience, the possible processes will generally be
referred
to collectively as "derivatization" herein; however, within the context of
this
invention, derivatization is used to mean any process which results in a
cellulose
(including fibrillar and microfibrillar cellulose ) having the substituents
sufficiently associated with the cellulose to provide the desired benefit(s),
and
includes not only chemical reactions resulting in covalent bonding, but also
physical adsorption. In addition, the present application will refer both to
"derivatization" and to "stabilization". Chemically, both terms refer to the
same
1 S type of process, namely, the placement or generation of substituents on
the
cellulosic substrate. Functionally, "derivatization" is generally the broader
term,
as "stabilization" implies a functionality which is usually observed primarily
or
exclusively when the cellulose is in microfibrillar form.
Possible derivatization processes include any synthetic methods) which
may be used to associate the substituents with the cellulose. More generally,
the
stabilization or derivatization step may use any process or combination of
processes which promote or cause the placement or generation of the
substituents. For example, the conditions for treating non-microfibrillar
cellulose
should generally include both alkalinity and swelling of the cellulose, in
order to
make the surface of the fibrils more accessible to the placement or generation
of
the substituents. Alkalinity and swelling may be provided by separate agents,
or
the same agent may both provide alkalinity and cause swelling of the
cellulose.
In particular, alkaline agents often serve multiple purposes, in that they may
catalyze the reaction between the cellulose and the substituent, optionally de-
16
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protonate the derivative, and swell open the cellulose structure to allow
access of
the reagents to carry out the derivatization.
Specific chemical methods which may be used to achieve the present
invention include but are not limited to generation of cationic groups, such
as
quaternary amine and/or amine, on or near the surface of the particulate
cellulose.
Alkaline conditions are preferably obtained by using sodium hydroxide. Any
material that functions as a swelling agent for the cellulose may be used, and
alternative alkaline agents include alkali metal or alkaline earth metal
oxides or
hydroxides; alkali silicates; alkali aluminates; alkali carbonates; amines,
including aliphatic hydrocarbon amines, especially tertiary amines; ammonium
hydroxide; tetramethyl ammonium hydroxide; lithium chloride; N-methyl
morpholine N-oxide; and the like. In addition to catalytic amounts of alkaline
agent, swelling agents may be added to increase access for derivatization.
Interfibrillar and intercrystalline swelling agents are preferred,
particularly
swelling agents used at levels which give interfibrillar swelling, such as
sodium
hydroxide at an appropriately low concentration.
These derivatization reactions, if carried out on the original fibrous
cellulose structure, may require specific conditions to maximize the
efficiency of
location of the derivatization onto the surface of the cellulose. For example,
in
the case of cellulose from wood pulp the concentration of the swelling agent
used
appears to have an effect on the performance of the final cellulose. In
particular,
in using sodium hydroxide it has been determined that the level of the sodium
hydroxide can have a significant effect on the rheological performance.
It is preferred that derivatization of these fibrous celluloses be performed
in
a manner which limits the formation of microfibrils which are soluble in the
intended end use composition, as these may not contribute significantly to the
desired rheological performance. This typically limits the degree of
derivatization which can be made where derivatization at higher levels would
make the cellulose soluble in the end use composition. Specific limits may be
readily determined based on the application in question, but as a matter of
17
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general guidance it is preferred that the degree of substitution (DS) be below
about 0.5, or below about 0.35, or below about 0.2, or below about 0.18, or
below
about 0.15.
The derivatization may be carried out in any suitable manner, including but
not limited to suspension in water; in organic solvent, either alone or in
mixtures
with water; in solution; and in high solids, either with water alone or with
water
and a minor amount of organic solvent. (For purposes of the present
disclosure,
"high solids" refers to a polysaccharide content of greater than about 25%.
Optional derivatizations or functionalities which may also be placed on the
cellulose include but are not limited to short chain aliphatic and other
hydrophobic-type substitutions; oligomeric and polymeric substitutions;
uncharged substitutions, as for example short chain ethylene and propylene
glycols; other associative-type functionality; surfactant-like functionality;
methyl; ethyl; propyl; and combinations of these. These substitutions are
optional in that they may not be intended for stabilization of the cellulose,
and
will instead provide additional functionality such as surface activity,
emulsification power, adsorption characteristics, and the like.
The method for processing a non-microfibrillar form of cellulose into the
microfibrillar form may be carried out before, during, or after the
derivatization
reaction. The preferred method involves the use of a homogenizes on a dilute
suspension of the non-microfibrillar cellulose in an aqueous medium. The
aqueous medium optionally may have additives such as swelling agents, in
particular interfibrillar and/or intercrystalline swelling agents, for example
sodium hydroxide, to aid in improving the ease of microfibril generation. A
more preferred method of micro~brillation involves the use of mechanical
energy
on an aqueous suspension of derivatized cellulose which has not been dried.
Other microfibrillation processes include, by way of non-limiting example, use
of
an impingement mixer; heat; steam explosion; pressurization-depressurization
cycle; freeze-thaw cycle; impact; grinding (such as a disc grinder); pumping;
mixing; ultrasound; microwave explosion; and milling. Combinations of these
18
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may also be used, such as milling followed by homogenization. Essentially any
method of reducing particle size may be used, but methods for reducing
particle
size while preserving a high aspect ratio in the cellulose are preferred. As
described previously, the degree of substitution of the cellulose also affects
the
ease of processing the cellulose to microfibrillar form.
The process to generate the particulate may either be run by the consumer
in the final application such that the particulate is generated in situ, or be
run as
described above in aqueous media, the material dehydrated, and the resulting
particulate dried. The dried particulate of this invention, hereafter referred
to as
the ready-to-gel or RTG form, can be rehydrated readily in polar solvents to
obtain the desired rheological attributes. Dehydration can be accomplished by
displacing water with less polar solvents and drying.
In terms of general properties, applications where the derivatized
microfibrillar celluloses of the present invention have particular utility
include
those where the desired rheological attributes include at least one of yield
stress,
shear reversible gelation, and a modulus which is insensitive to temperature.
The
ability to provide the rheological attributes described herein also makes it
possible to provide stabilization of mixtures of liquids and solids having
different
densities; gel-like properties; pumpable gels; stabilization at elevated
temperatures; and, control of hydration and diffusion.
In terms of more specific applications or fields of use, the utility of the
present derivatized microfibrillar cellulose includes, without limitation,
foods,
personal care products, household products, pharmaceuticals, neutraceuticals,
paper manufacture and treatment, coating compositions, water and wastewater
treatment, drilling fluids, agriculture, construction, and spill control
and/or
recovery. Use in food applications is also possible, subject to satisfactory
resolution of any concern regarding introduction of cationic materials into
substances intended for consumption.
In food applications, the derivatized microfibrillar celluloses of the present
invention may be useful as rheology modifiers; as stabilizers, such as by
19
WO 01166600 CA 02402181 2002-09-06 pCT/USO1/03458
inhibiting creaming or settling in suspensions; and as non-digestible dietary
fiber.
They may also be used to control ice crystal growth during, for example, ice
cream manufacture and storage.
In personal care products, the derivatized microfibrillar cellulose may be
used to stabilize emulsions, dispersions, suspensions, and foams, and may find
use in creams, lotions, gels, and pastes, including those intended for
epidermal
application (it should be noted that the derivatized microfibrillar cellulose
of the
present invention has substantivity to biological surfaces, including but not
limited to skin, hair, and nails). Representative but not exhaustive examples
include sunscreens; moisturizing or anti-aging creams and lotions; cleaning
soaps
or gels; antiperspirants and deodorants, including those in stick, pump spray,
aerosol, and roll-on form; fragrance releasing gels; lipsticks, lip glosses,
and
liquid makeup products; oral care products, including toothpastes, tooth
polishing
and whitening agents, and denture care products such as cleaners and
adhesives,
1 S and further including use in sorbitol, sorbitol-water mixtures, and
glycerol-water
mixtures; products where controlled, sustained, or delayed release of an
ingredient would be desirable; wound care products, such as ointments
(including
anesthetic, antiseptic, and antibiotic ointments), dressings, and products
such as
ostomy rings where good liquid retention is desirable; and absorbent products,
such as diapers. The present invention may have particular utility, not only
in
personal care products but in other applications, with products dispersed by a
pumping action. The shear-reversible gelation exhibited by the derivatized
microfibrillar cellulose is well suited for pump dispensing, and may be
advantageously combined with its ability to stabilize emulsions, dispersions,
and
foams to improve the uniform delivery of product.
In the area of household products, the rheological properties of the present
derivatized microfibrillar celluloses, and their ability to stabilize
emulsions,
dispersions, and foams, provide utility in areas such as detergents, shampoos,
cleaners, and air fresheners. Specific examples include, without limitation,
laundry products (including detergents, pre-spotting cleaners, and fabric
WO 01/66600 CA 02402181 2002-09-06 pCT/US01/03458
treatment compositions, such as softeners); rug and upholstery shampoos;
toilet
bowl cleaners (particularly those dispensed in liquid or gel form); air
fresheners;
and general purpose cleaning agents, including liquids, gels, pastes, and
foams
used in cleaning and/or disinfecting household surfaces.
In pharmaceutical applications, the derivatized microfibrillar cellulose may
have utility in controlled, sustained, or delayed release formulations
(including
epidermal patches used for slow and/or prolonged release of one or more active
ingredients); as disintegrants; as dietary fiber; in wound care, particularly
in
applications (such as ostomy rings) where liquid-holding ability is important;
and
as rheology modifiers.
In the area of paper manufacture and treatment, the derivatized
microfibrillar cellulose of the present invention has utility in emulsion
modification and/or stabilization; sizing; retention; clarification;
absorbence;
drainage; formation (such as by functioning as a flocculation aid); deposit or
scale control (by inhibiting the formation and/or growth of inorganic
deposits);
water and wastewater treatment; dewatering; film and membrane formation;
polyelectrolyte cross-linking; removal of detrimental organic and/or inorganic
materials; in paper coatings; and in improving properties such as stiffness,
wet
strength, absorbancy, softness, toughness, tear resistance, and fold
resistance.
In the context of paper manufacture, scale control refers to the prevention
of calcium carbonate and calcium oxalate deposits forming during the pulping
process. Scale control can be achieved by dispersion of salt crystals in the
medium to prevent growth and deposition, inhibition of nucleation, or
modification of the crystal growth mechanism to prevent the formation of
crystal
forms that will lead to deposits. The use of derivatized microfibrillar
cellulose
having micron and smaller particle size, stabilized with appropriate
functional
groups, would serve to control scale deposit because such microcarriers
inhibit
the crystal growth which leads to deposition. Moreover, cellulosic materials
would be easier to recover from the pulping process due to their organic
nature.
Preferred functional groups would include amines. Alternative functional
groups
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WO 01/66600 PCT/USO1/03458
and appropriate use levels may be readily determined by those of ordinary
skill in
the art, based on the particular environment of use.
The derivatized microfibrillar cellulose may also be used in a
papermaking machine to increase the rate of drainage and/or dewatering
during paper manufacture; to retain organic and/or inorganic dispersed
particles (such as pulp fines, fillers, sizing agents, pigments, and/or
clays);
to retain detrimental organic and inorganic particulate materials; to improve
the uniformity of formation of a sheet of paper; and to improve the strength
of a sheet of paper. With particular regard to drainage, drainage aids are
additives that increase the rate at which water is removed from a paper
slurry on a paper machine. These additives increase machine capacity, and
hence profitability, by allowing faster sheet formation. Charged
microfibrillar cellulosic derivatives are capable of greatly increasing
drainage, either alone or in combination with other charged polymers.
The derivatized microfibrillar cellulose of the present invention may also be
used in coated papers, where cellulose derivatives may be used to control the
rheology of the color coating and to provide water retention, thereby
controlling
the amount of liquid that permeates into the base sheet.
In coating compositions, such as paints and inks, the derivatized
microfibrillar cellulose can provide rheology modification, improving
properties
such as spatter, leveling, sag resistance, flooding, and floating, and may
have
particular utility in gel paints. It may also improve pigment dispersion
and/or
stabilization, and function as charge control or flow control agents,
including in
inks, such as ink jet inks.
In the area of water treatment, the derivatized microfibrillar cellulose of
the
present invention can provide scale control, that is, inhibiting the formation
and/or growth of inorganic deposits in aqueous systems; clarification;
flocculation; sedimentation; coagulation; charge delivery; and softening.
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In drilling fluids, the present derivatized microfibrillar cellulose can
provide rheology modification, reduce or prevent fluid loss, and improve
secondary oil recovery.
In agricultural applications, the derivatized microfibrillar cellulose of the
S present invention can be used in soil treatment, and may provide moisture
retention, erosion resistance, frost resistance, and controlled, sustained, or
delayed release of agricultural materials such as fertilizers, pesticides,
fungicides,
and herbicides. It may also be used for crop protection, such as to minimize
or
prevent frost damage.
In construction, derivatized microfibrillar cellulose can be used in dry wall
muds, caulks, water-soluble adhesives, and board manufacture.
In other areas, derivatized microfibrillar cellulose can be used for control
and cleanup of liquid spills; as absorbents for oil; as stabilizers for
emulsions,
dispersions, and foams (including but not limited to oil-in-water and water-in-
oil
emulsions); and for emulsification. Stability of commercial emulsions, such as
paper size emulsions, is a recurring issue in industry. Current commercial
emulsions include those which generally consist of an oil, waxy, or rosin
phase
dispersed in water. These dispersions are generally stabilized by the addition
of
charged materials such as cationic starches, sodium lignin sulfonate, and
aluminum sulfate. Such materials are generally added in amounts equal to about
10-20% by weight of the size component. The resulting dispersions are
typically
0.2 to 2 micron particles, thought to be stabilized by charge repulsion, for
example, with the positively charged starches on particle surfaces repelling
each
other.
One cause of emulsion failure is density-driven separation. This can be
limited by increasing viscosity, or internal structure within the fluid. For
example, an emulsion which maintains a viscosity of less than about 20
centipoise throughout a standard aging test might have its viscosity increased
initially by as much as 100 centipoise through addition of a viscosifier to
the
23
WO 01/66600 PCT/USO1/03458
formulation, and still be within acceptable commercial viscosity, provided
that
the viscosity did not then increase over time to exceed acceptable limits.
One method to accomplish this result would be to use a viscosifying agent
that does not cause a substantial increase in viscosity when first added to an
emulsion formulation, but which does provide an increase in viscosity during
normal processing of the emulsion formulation to produce the emulsion. This
can be accomplished by including, as an additive to the emulsion formulation,
cellulose that has been derivatized as described herein but not yet
microfibrillated. When the emulsion formulation is then subjected to energy,
typically high shear, during the processing used to turn the emulsion
formulation
into an emulsion, the shear will also microfibrillize the derivatized
cellulose,
resulting in the derivatized microfibrillar cellulose of the present
invention,
which will be present as part of the emulsion. The gel produced by the
derivatized microfibrillar cellulose will then thin under shear stress but re-
form
when shear stops. Moreover, the insolubility of such low DS cellulose may
cause
it to concentrate at the oil/water interface of oil-and-water emulsions,
rather than
the aqueous bulk phase, which may be desirable.
Effectively the same result may be achieved by adding the derivatized
microfibrillar cellulose of the present invention to an emulsion formulation,
or to
the final emulsion, or at any point during production of the emulsion. Further
variations would include introducing derivatized cellulose that is only
partially
microfibrillated into the emulsion-making process at a point where subsequent
processing would provide sufficient energy to complete the microfibrillation.
It
may also be possible to accomplish some or all of the derivatization as part
of the
emulsion production process; for example, the emulsion formulation may include
a charged species that will adsorb onto the cellulose microfibrils, or such a
species may be added during processing of the emulsion formulation, separately
or in combination with the cellulose. Therefore, the derivatized
microfibrillar
cellulose of the present invention may serve as a stabilizing additive to
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WO 01/66600 PCT/USO1/03458
emulsions, with several process routes being available to accomplish this end
result.
While the choice of method may cause some variation in the properties of
the resulting emulsion, the basic benefit of improved emulsion stability
should be
achieved by any procedure which has, as its final result, the presence of the
derivatized microfibrillar cellulose of the present invention in the final
emulsion.
Commercially, it may be desirable to supply customers with derivatized, non-
microfibrillated cellulose as a powder which, when added to a formulation and
subjected to high shear or other appropriate forms of energy, will
microfibrillate
and yield the derivatized microfibrillar cellulose of the present invention.
This improved emulsion stability may enable use of emulsion formulations
which would not perform satisfactorily in the absence of the derivatized
microfibrillar cellulose. Other benefits may include improved retention in
paper,
improved drainage of water from paper systems due to association of fillers
and
pulp fines with the retained microfibrils, and resistance to emulsion breakage
in
the presence of high salt concentrations.
The subject electrostatically derivatized materials of this invention have
also been discovered to provide rheology to aqueous systems over a wide range
of pH and ionic strength. This insensitivity to pH and ionic strength
facilitates
use in areas where low pH and high salt conditions exist, such as in personal
care
creams and lotions, food products, and the like.
In addition to the above, the derivatized microfibrillar cellulose of the
present invention represent a vehicle for providing cationic charge to a given
environment. This may include utility in water and wastewater treatment, where
charged particles may be used to remove color bodies and to flocculate
particulates and other contaminants. Thus, by way of non-limiting example, a
suitable amount of the derivatized microfibrillar cellulose may be added to
water
(or to an aqueous system) that is contaminated with anionic material and/or
color
bodies; allowed to bind or complex with the contaminants, optionally with
mixing and/or heating; and physical, chemical, and/or other conventional
CA 02402181 2002-09-06
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separation techniques may then be used to separate the bound or complexed
cellulose/contaminant combination from the water. While any amount of
derivatized microfibrillar cellulose would facilitate removal of some amount
of
contaminant from the water, in order to have the most effect the amount of
derivatized microfibrillar cellulose should preferably be at least equal to
the
stoichiometric equivalent necessary to bind or complex with the measured or
estimated concentration of the contaminant whose separation or removal is
desired.
The following examples indicate various possible methods for making and
using the derivatized microfibrillar cellulose of the present invention. These
examples are merely illustrative, and are not to be construed as limiting the
present invention to particular compounds, processes, conditions, or
applications.
Throughout this description, "gelling" is defined to occur when G'>G", where
G'
is the dynamic storage modulus and G" is the dynamic loss modulus. This is the
functional definition used in EP '011; for general background, see Ferry,
J.D.,
Viscoelastic Properties of Pol,~, John E. Wiley & Sons, NY, 1980.
The following examples indicate various possible methods for making and
using the derivatized microfibrillar cellulose of present invention. These
examples are merely illustrative, and are not to be construed as limiting the
present invention to particular compounds, processes, conditions, or
applications.
Example 1
Preparation Of A Quaternary Amine Functionalized Cellulose (QAC).
Isopropanol (IPA) and deionized (DI) water were charged to a nitrogen
sparged, jacketed resin kettle equipped with an air driven stirrer, stainless
steel
agitator, two pressure equalizing addition funnels, a reflux condenser,
nitrogen
inlet, vacuum line and thermocouple. Bleached sulfate wood pulp
(approximately 400 pm length, 5.2% moisture)(Wayerhauser Company) was
added to the reactor, the mixture slurry was agitated for 10 minutes, after
which
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the mixture was nitrogen sparged for 1 hour while cooling the slurry
temperature
to 15°C.
The reactor was then inerted, and aqueous NaOH (50% NaOH) was slowly
added to the reactor while maintaining the mixture slurry's temperature at or
below 15°C. The slurry was agitated for 1 hour after completion of
caustic
addition. Dow Quat 188 (3-chloro-2-hydroxypropyl trimethylammonium
chloride, Dow Chemical Company, Midland, MI) (65% in water) was slowly
added to the reactor by addition funnel while maintaining reaction slurry
temperature at 15° C. After Dow Quat addition, the reaction slurry was
heated to
70° C and held for 1 hour. The reaction slurry was cooled down to below
30° C
and then aspirator vacuum filtered with a sintered glass funnel and a rubber
dam.
The wetcake was slurried in 565g of 80% methanol for 15 minutes using an air
driven stirrer and a grounded stainless steel beaker and then aspirator vacuum
filtered with a sintered glass funnel and a rubber dam. This was repeated two
more times.
The wetcake obtained from the previous three washes was slurried in 1000g
of pure methanol using an air driven stirrer and a grounded stainless steel
beaker
for 15 minutes to dehydrate and then aspirator vacuum filtered with a sintered
glass funnel and rubber dam. The final wetcake was broken into small particles
using a rubber spatula and then dried in a Lab-Line fluidized bed dryer (model
number 23852) for 35 minutes. (Air-dry for 5 minutes, heat-dry at 50° C
for 10
minutes and heat-dry at 70° C for an additional 20 minutes). The
product was
ground using a Retsch Grinding Mill (model 2M 1 ) with a 1 mm screen.
Table 1: OAC Recipes
f all weights in r_g,. ams)
Quaternary
Amine
Functionalized
Cellulose
SampleCelluloseWt. CelluloseWt. Wt. Wt. 50% Wt. DS
# Length (dry wt. IPA H20 NaOH (aq)Dow Quat
Basis) 188
(65% aq.
Soln)
1 400 ~m 65 750 110 18.46 58.02 0.02
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Quaternary
Amine
Funetionalized
Cellulose
SampleCelluloseWt. CelluloseWt. Wt. Wt. 50% Wt. DS
# Length (dry wt. IPA H20 NaOH (aq)Dow Quat
Basis) 188
(65% aq.
Soln)
2 400 pm 65 750 110 13.84 43.52 0.03
3 400 ~m 65 750 110 23.07 72.53 0.03
4 200 ~m 65 750 110 18.46 58.02 0.07
200 pm 65 750 110 18.46 58.02 0.08
6 200 pm 65 750 110 23.07 72.53 0.11
7 400 pm 65 750 110 23.07 72.53 0.11
8 400 ~tm 65 750 110 23.07 72.53 0.11
9 400 um 65 750 110 23.07 72.53 0.12
400 ~m 65 750 I 23.07 72.53 0.13
10
11 200 pm 65 750 110 23.07 72.53 0.14
12 -400 65 750 110 N/A N/A 0.25
~m
Slurry preparation: An 800 g 1 % slurry was made from each Sample in
Table 1 using the following materials:
Weight W i ht°
5 QAC 8.00 grams 1.0 ~
0.06%
Germaben ~ II biocide 4.00 grams 0.5%
(Sutton Laboratories, New Jersey)
Deionized water 788.00 grams 98.5 ~
10 Q.06%
Total 800.00 grams
The container was closed and shaken to wet and disperse the QAC solids. The
solids will settle if left standing, so the container was shaken just prior to
pouring
the slurry into the homogenizer.
Homogenization of QAC slurries: The suspension was processed in the
homogenizer equipped with an agitated feed pot as follows: the homogenizer was
turned on before the slurry was loaded. An 800-gram slurry was processed for
about 20 minutes at about 3000 psi by recycling the discharged stream from the
homogenizer to the feed pot. Pressure was monitored and appropriate
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WO 01/66600 PCT/USO1/03458
adjustments made to the primary stage handwheel to keep the total pressure at
about 3000 psi. After the processing was completed, the discharge tube was
redirected so that the sample was collected and stored in a capped jar.
Rheological testing of microfibrillated QAC: each microfibrillated QAC
sample prepared in Example 1 was then tested for rheological properties. Data
was collected on a Bohlin CS Rheometer (Bohlin Instruments, Cranbury, New
Jersey). Dynamic mechanical properties were measured including the dynamic
storage modulus, the dynamic loss modulus, complex viscosity, and yield
stress.
Rheometer Test Conditions
Temperature Sweep: Measuring System: PP 40; 25° C - 65° C;
Shear Stress:
automatic; Frequency: 1 Hz; Temperature Ramp Rate: 5° C/60 seconds;
Measurement Interval: 20 seconds; Gap: 1 mm.
Yield Stress Test: Measuring System: CP 4/40; Stress: 6.0E-02 - 1.0E+02; Sweep
Time: 60.0 seconds; Number of Steps: 30; Temperature: Manual (25°
C); No of
measurements: 1; Measurement Interval: 5 seconds.
Stress Sweep Test: Measuring System: PP 40; Temperature: Manual (25
°C);
Number of Measurements: 1; Gap: 1 mm; Measurement Interval: 5 seconds;
Frequency: 1 Hz.
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Table 2: Rheologv of Microfibrillated OAC
SampleCelluloseDS of YIELD G' @ G' @25 Aomogenizer
# Length Quat- STRESS(Pa)5.75 C/50 C(Pa)Processing
Cellulose Pa(Pa) Time(minutes)
1 400 0.02 NONE 20
pm
2 400 0.03 NONE 20
pm
3 400 0.03 NONE 20
pm
4 200 0.07 38.0 572 619/633 25
pm
200 0.08 44.7 489 468/450 30
pm
6 200 0.11 51.4 480 505/530 25
pm
7 400 0.11 38.0 622 621/646 15
pm
8 400 0.11 34.7 482 20
~m
9 400 0.12 68.0 500 488/487 20
pm
400 0.13 18.1 420 20
~m
11 200 0.14 21.4 497 577/592 15
~m
12 400 0.25 51.4 106 119/131 30
~m
l
Example 2
Ready-To-Gel(RTG) Process For Quaternary Amine Cellulose
5 Gels are made as described in the "Slurry preparation" and
"Homogenization of QAC Slurries" steps in Example 1. The gels are then
processed as follows:
The following description pertains to Sample #1 in the data table. A similar
procedure was used for all of the other samples.
10 Approximately 2800 ml of IPA was added to a grounded 12-quart stainless
steel (SS) beaker. The IPA was stirred at the top speed of an overhead stirrer
driven by house air. A SS cowls blade on an SS shaft was used to stir the IPA.
Next, approximately 1400 grams of 1 % QAC gel was slowly added to the stirring
IPA. The material ratio is 2 ml IPA/1 gram gel. The beaker was covered with
Saran Wrap and the slurry was stirred for ten minutes.
When ten minutes had passed, the slurry was filtered through a synthetic
straining cloth. The slurry was filtered using gravity. The slurry was covered
with
Saran Wrap during the filtration to reduce IPA evaporation. Occasionally the
gel
on the cloth was stirred with a plastic spatula to help speed filtration. When
it
WO 01/66600 CA 02402181 2002-09-06 pCTNS01/03458
appeared that the filtration had gone about as far as it could, the wet cake
was
transferred back to the 12 quart SS beaker.
A fresh amount of approximately 2800 ml IPA was added to the beaker and
the slurry was again stirred for ten more minutes with the cowls blade/air
stirrer.
The slurry was then filtered on a 20 cm Buchner funnel with #415 VWR filter
paper. The wet cake was transferred to a glass crystallization dish. The dish
containing the wet cake was placed into an 80° C oven under vacuum
overnight
for drying. The sample was dried to constant weight, and the solids were
ground
in a blaring Blender.
The dehydrated gels were examined by rehydration as follows: a premix of
deionized water and Germaben II was prepared.
Weight W i ht°
Deionized water 788.00 grams 99.49%
Germaben II biocide 4.00 grams 0.51
The water/Germaben II solution was then weighed into a small blaring blender
cup along with the ready-to-gel dry QAC.
Weight W i ht°
water/Germaben 29.70 grams 99.0%
Ready-to-gel QAC 0.30 grams 1.0%
The blender cup was covered and the sample was mixed until it appeared to be
homogeneous. The resulting gel was transferred to a glass jar. It was then
shaken
on a vortex mixer.
Rheological testing: Same as described in example 1.
Table 3: Rheologv of RTG OAC
Sample DS of YIELD STRESS G' @ 5.75
Pa
# QAC (Pa) (Pa)
1 0.09 61.4 385
Rheological properties as a function of concentration: a series of gels were
prepared from a 1 % QAC (DS 0.09) by diluting with DI water.
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Table 4: Rheologv of RTG OAC by Concentration
Sample QAC G' @ 5.75
# Concentration Pa
(wt%) (Pa)
1 1 246
2 0.5 35.6
3 0.25 0.475
4 0.1 0.136
G' > G" in all samples ( 1 - 4); see Figures 1 to 4, respectively.
Stable water/oil emulsions containing QAC: cetyl trimethyl ammonium
S bromide was mixed with deionized water. The CTAB solution was added to 1%
quaternary amine (DS=0.15) functionalized microfibrillated cellulose gel
prepared as in Example 1. The mixture was stirred in a blaring Blender for 3
minutes on high speed. The sample remained a gel. This gel was processed
through a Gaulin homogenizer, 1 pass at 4000 psi. Ten percent ( 10%) miglyol
emulsions were prepared from the gels by adding miglyol and deionized water to
the gel and mixing with a rotary mixer for 4 minutes. The resulting emulsions
were aged in a 50° C oven.
Table S: Stability of Water/Oil Emulsions
10% Miglyol Emulsion Stability at 50 C
0.45% QAC/0.008% CTAB > 3 weeks
0.90% QAC/0.016% CTAB
> 3 weeks
Use in paper sizing compositions: the following examples relate to use of QAC
as made in example 1 having a DS of about 0.10 in connection with compositions
used in paper sizing.
Example 3
A 600 ml beaker was used to combine 66.0 grams of Precis~ 787 ketene
dimer (available from Hercules Incorporated, Wilmington, Delaware; Precis is a
registered trademark of Hercules Incorporated), 1.5g of QAC, and 232.5 grams
of
deionized (DI) water. The mixture was stirred, and then passed through a
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WO 01/66600 PCT/USO1/03458
Microfluidics Corporation Model M 110 Series impingement mixer
(Microfluidics Corp.) with its pressure set at 5000 PSI. The emulsion was
collected, and a second pass was made. The second pass product was collected
in
a clean jar, a stir bar was added, the jar was capped, and then cooled in a S
to 15°
C water bath.
Example 4
Three grams of QAC were dispersed in 465g of DI water for 5 minutes
using a Tekmar Ultra-turax SD45 rotor-stator high shear mixer (Tekmar
Company, Cincinnati, Ohio) at a power setting of 50. The resulting materials
was then given three passes through the impingement mixer at 5000 psi. As in
Example 3, 66.0 g of Precis were combined with 234.0 g of QAC in DI water gel,
stirred using the high shear mixer at a power setting of 50, then given two
passes
through the impingement mixer at 5000 psi and cooled in a 5 to 15° C
water bath.
Example 5.
Four (4.0) grams of QAC was dispersed in 400g of DI water for 5 minutes
using the high shear mixer at a power setting of 50, then given three passes
through the impingement mixer at 5000 psi to create a gel. A 44% emulsion of
Precis ketene dimer was made by combining 176.0 grams of Precis 787 ketene
dimer with 224.0 grams of DI water in a wide mouth jar; the pre-mix was
sheared
in a high shear mixer for 5 minutes at a power setting of 50, the resulting
material
was quickly poured into the feed chamber of the impingement mixer, and, with
mechanical stirring set at about 250 RPM, the premix was passed twice through
the impingement mixer set at 5000 psi. Next, 150.0 g of the QAC gel was
combined with 150.0 g of the Precis ketene dimer 44% emulsion and stirred for
5
minutes using the high shear mixer at a power setting of 50.
The following table provides testing results for the sample emulsions using
TAPPI standard Method T560:
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WO 01/66600 PCT/USO1/03458
Table 6: Surface Sizing of Example 3 through Example 5 Size Emulsions
(formulation weight in grams)
Pre-shear
Desi nation MF e1 MF e1
Exam 1e 3 4 5
Precis 787 66.00 66.00 66.00
AC 1.50 1.50 1.50
DI Water 232.50 232.50 232.50
Total 300.0 300.0 300.0
Tekmar Shearin cond. 2 min. 2 min. 2 min.
SO 50 50
Microfluidizer shearin2X Sk 2X Sk si
si
Tekmar Gel Shearin 5 min. 5 min.
50 50
Microfluidizer Gel 3X Sk si 3X Sk si
Shear
Calc. % Actives 22.00 22.00 22.00
IRA % Actives NA 14.9 NA
H 2.42 2.60 2.75
tem 20.7 21.0 26.80
Particle size 0.75 0.97 Failed
Particle size Sonicated0.70 0.63 Failed
Zeta Potential -58.3 -57.9 Failed
Brookfield Visc. Failed 119.3 Failed
"Failed"
means
emulsion
broke
prior
to
testin
.
Drainage Aids in Paper Manufacture: the following examples
demonstrate the effectiveness of derivatized microfibrillar cellulose as a
drainage-improvement aid.
Drainage measurements were performed on a Canadian Standard Freeness
(CSF) tester, using a bleached kraft pulp consisting of 70% hardwood and 30%
softwood. All freeness testing was performed in hard water having a pH of 7.95-
8.05, alkalinity of 50 ppm (as calcium carbonate), and hardness of 100 ppm (as
calcium carbonate) using TAPPI method T 227 om-92. A pulp consistency of
0.3% was used. Higher CSF values indicate better (faster) drainage.
The following results were obtained using microfibrillated quaternary
amine cellulose (MFQAC), alone and in combination with microfibrillar
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carboxymethyl cellulose (MFCMC). The preparation of MFCMC is described in
U.S. patent application serial number 09/248,246, filed February 10, 1999, the
disclosure of which is hereby incorporated in its entirety by reference
thereto.
The MFQAC had a degree of substitution of about 0.09, while the MFCMC had a
degree of substitution of about 0.17 charge group per anhydroglucose unit. All
loadings are calculated as percent of additive (dry basis) relative to pulp.
Example 6
MFQAC alone.
% MFOAC ~,~F
0.00 211
0.05 264
MFOAC ~,~F
0.10 315
0.20 388
0.30 451
0.40 491
0.50 509
Example 7
MFQAC (0.2% loading) with Hercules Reten~ 1523H anionic polyacrylamide resin:
Reten~1523H ~,SF
0.000 464
0.003 464
0.006 503
0.009 513
0.012 526
WO 01/66600 CA 02402181 2002-09-06 pCT/USO1/03458
Example 8
MFQAC with MFCMC
CSF VALUES
MFQAC 0% 0.05%
abased on pull MF MC MF M
0.00 211 N/A
0.10 315 432
0.20 388 518
0.40 491 612
In addition to the examples provided above, QAC may be produced with a
range of alternative cellulose sources, including Avicel~ pH-lOINF (-90);
Solka~ Floc (grade 300 FCC), which may be obtained from Fiber Sales &
Development Corp., Urbana, Ohio; and Bleached CTMP (Chemical
Thermomechanical Pulp) Fluff, which may be obtained from SCA Graphic
Sundsvall AB, Timra, Sweden.
The present invention has of necessity been discussed herein by reference
to certain specific methods and materials. The enumeration of these methods
and
materials was merely illustrative, and in no way constitutes any limitation on
the
scope of the present invention. It is to be expected that those skilled in the
art
may discern and practice variations of or alternatives to the specific
teachings
provided herein, without departing from the scope of the present invention.
36
